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GROUNDWATER SAMPLING - Water Research Commission

1. x O oe cO a 14 Measure the water level see chapter 10 Measure the borehole depth Then height of water column borehole depth depth to water level Calculate the standing volume of water in litres by substituting in the formula V Tr x d x h 4000 where V Volume of standing water in litres d diameter of borehole in mm h Height of water column in metres or from the information in table 13 1 Install the pump with the inlet close to the static water level for a high yielding borehole For a low yielding borehole see section 13 3 The pump must always be installed above the main water strike to avoid cascading Set up the EC meter the pH meter and the Eh or DO meter Start pumping Measure pumping rate in L sec Using the calculated well volume of step 4 calculate the pumping time needed to remove three volumes Take continuous readings of pH temp EC and either Eh or DO If the field chemistry stabilizes before three volumes are pumped use the time for three volumes as the purge time at that pumping rate If the field parameters have not stabilized this is uncommon continue pumping until they stabilize This will be the purge time at that pumping rate Record all the above for the Monitoring Programme Guide Chapter 7 so that succeeding sampling runs can follow this established routine Note that subsequent sampling runs should not measure
2. In those cases where it may be relevant to know how much precipitated iron or manganese is present in the form of suspended colloids in the groundwater an unfiltered sample needs to collected and the result reported as total iron The Fe level of the filtered sample is reported as dissolved iron The difference between the two measurements gives the concentration of colloidal iron It is also possible to measure the different redox states of iron separately i e Fe II and Fe III This is important for investigations where iron clogging is a problem or in groundwater affected by acid mine drainage In such cases Eh and pH data are also required for proper understanding Because Fe II is oxidised to Fe III in the presence of oxygen it is necessary to conduct the analyses as soon as possible after collecting the sample or even preferably to analyse the iron species in the field if a field colorimeter is available Test kits are available for Fe II and total iron determinations at various concentration ranges and levels of accuracy from suppliers such as Hach or Merck The analysis is based on a colorimetric technique using reagents that form a coloured complex with Fe Stookey 1970 APHA 1998 Two samples are used one analysed directly for ferrous iron Fe and the other digested and treated with a reducing agent then analysed for total iron Ferric iron Fe is calculated by subtracting th
3. A list of critical spare parts which should be on hand A plan for periodic assessment of data accuracy precision and completeness 7 3 REFERENCES ANZECC 2000 Australian guidelines for water quality monitoring and reporting National water quality management strategy No 7a published by the Australian and New Zealand Environment and Conservation Council and the Agriculture and Resource Management Council of Australia and New Zealand URL http www deh gov au water qualityynmnwqms monitoring html last accessed on 17 October 2006 Sanders T G R C Ward J C Loftis T D Steele D D Adrian and V Yevjevich 1983 Design of networks for monitoring water quality Water Resources Publications Littelto Colorado ISBN 0 918334 51 9 106 CHAPTER 8 SAMPLE RECORDS AND CHAIN OF CUSTODY 8 1 INTRODUCTION The Monitoring Program Guide Chapter 7 describes in detail the information needed by staff to collect samples consistently from one sampling run to the next Complementary to this Guide is the requirement to keep a record during each of these sampling runs This is the first of two important field record forms and is called the Field Record Sheet The second of these forms is the Chain of Custody form These two forms when filled in for a sampling run comprise the written record which documents the sample identity from collection to analytical result In sampling programs related to legal actions proper ch
4. John M C Weaver Lisa Cave A Siep Talma GROUNDWATER SAMPLING Second Edition TT 303 07 Water Research Commission GROUNDWATER SAMPLING A COMPREHENSIVE GUIDE FOR SAMPLING METHODS Prepared for the Water Research Commission by John M C Weaver Lisa Cave and A Siep Talma Groundwater Sciences CSIR South Africa WRC Report No TT 303 07 March 2007 Obtainable from Water Research Commission Private Bag X03 GEZINA 0031 The publication of this report emanates from a project entitled Groundwater Sampling Manual Revision of the 1992 Guide WRC Project No K8 532 DISCLAIMER This report has been reviewed by the Water Research Commission and approved for publication Approval does not signify that the contents reflect the views and policies of the Water Research Commission nor does mention of trade names or commercial products constitute endorsement or recommendation for use ISBN 978 1 77005 545 2 Set 1 874858 46 2 Printed in the Republic of South Africa ACKNOWLEDGEMENTS Writing and publishing of both the first and the second edition were funded by the Water Research Commission of South Africa The reference group responsible for this project consisted of the following persons whom we thank for their inputs Dr K Pietersen Water Research Commission Chairman Dr G Tredoux CSIR Mr B Cowan CSIR Dr S Adams University of the Western Cape Ms C Colvin CSIR Dr B Usher
5. 3 4 4 3 Volatile Organic Compounds VOC This group is also referred to as Purgeable Organic Compounds POC as they can be purged from water in an air stripping tower In such a tower the water is broken up into fine droplets and allowed to fall through up flowing air The VOCs evaporate and are thus removed from the water Petroleum derived compounds see section 3 4 3 3 are included in this group Please read this section before continuing Other compounds falling into this category are solvents and degreasers Follow the sampling methodology as 37 described under section 3 4 3 3 Note that for each sample point you must collect two samples a duplicate Consult the analytical laboratory before going into the field to confirm the methodology If it is known beforehand what contaminants are present specific preservatives may be recommended in addition to keeping cool at 4 C For an accurate assessment of subsurface conditions the suitable pump is an all metal piston pump or a positive displacement pump made from PVC Pumps made from the more adsorptive polymers see section 18 3 are difficult to decontaminate A submersible pump is not suitable for accurate assessment as the negative pressure of the centrifugal pumping action will tend to reduce the concentration of VOCs However for a rapid assessment one may use a submersible but regard the results with due caution 3 4 4 4 Semi Volatile Organic Compounds SVOC These or
6. e Check the batteries of all the meters Do you have a spare set packed with the meter It is not much use having the spare set in the cupboard of your office e For the various field meters in the carrying case do you have a set of precise step by step instructions and are the instructions water protected e The carrying cases for the various meters should be water proof but make sure that when you return from the field that the cases are left with the lid open so they can properly dry out If you leave the water proof cases shut tight any dampness will condense both on and inside the meter and you will end up with corroded electronics and a faulty meter e Are your buffer solutions still usable and do you have enough Have you tested your electrodes e Do you have a completely equipped toolbox so that you can carry out any necessary repairs in the field 2 8 REFERENCES ANZECC 2000 Australian Guidelines for Water Quality Monitoring and Reporting National water quality management strategy No 7a published by the Australian and New Zealand Environment and Conservation Council and the Agriculture and Resource Management Council of Australia and New Zealand URL http www deh gov au water quality nwqms monitoring html last accessed on 17 October 2006 12 CHAPTER 3 DETERMINAND SELECTION AND SAMPLING 3 1 INTRODUCTION Modern chemistry allow for a wide range of determinands that can be analysed in water sometimes at consid
7. 71 Clean the electrode with water and place it in saturated KCI for approximately one hour When cleaning a combination electrode keep the O ring moist Remove salt precipitates KCI from the filling solution from the outside wall or tip of the probe by flushing with deionised water The filling solution chamber should also be flushed out from time to time To clean the porous pin on combination electrodes after Kokholm remove protein with 5 minute soaking in 5 v v hypochlorite solution or soak in a strong pepsin solution in 0 1 M HCl for some hours Rinse with deionised water remove oil and grease with acetone Rinse with deionised water remove insoluble compounds e g AgCl by polishing the porous pin gently with a mild abrasive remove sulphide contamination by sealing the KCI filling hole and soaking the electrode for 24 hours in a solution of thio urea in 0 1 M HCI Rinse with deionised water 4 4 5 REFERENCES FOR Eh MEASUREMENTS APHA 1998 Standard Methods for the examination of water and wastewater 20 ed Am Public Health Assoc Washington DC Appelo C A J and D Postma 1996 Chapter 7 Redox processes 239 295 In Geochemistry Groundwater and Pollution Balkema Rotterdam Hostettler J D 1984 Electrode electrons aqueous electrons and redox potentials in natural water systems Am J Sci 284 734 759 Kokholm G Not dated REDOX measurements their theory and technique revised editi
8. Dissolved gas O2 CO and N gt solubility is temperature dependent e The temperature of groundwater increases with depth and temperature can therefore provide a first indication of depth of water interception Temperature gradients in southern Africa range between 1 and 3 C 100m 4 1 1 EQUIPMENT FOR TEMPERATURE MEASUREMENT A digital thermometer of the right range typically 0 50 C and precision 0 1 C or else two mercury thermometers that can be read to 0 2 C and that have been 47 calibrated one is a spare as they are prone to breakage Digital thermometers are generally accurate and are often incorporated in pH meters Mercury in equipment is being phased out for health reasons nowadays so it is better to invest in a good digital thermometer for field work Calibration of the meter should be done at least once a year Wilde 2006 This should be done using available local facilities which are quite common nowadays when ISO and other standards are generally enforced The chemical analytical lab is likely to have facilities being applied of follow the USGS procedure 4 1 2 FIELD PROCEDURE FOR TEMPERATURE MEASUREMENT 1 Rinse the thermometer with flowing sample water if available else use distilled water 2 Immerse the thermometer in the sample 3 Wait for the temperature to equilibrate Allow sufficient time for any pipes to equilibrate if the pump has just been switched on 4 Read and record the temperature to
9. Investigations requiring field alkalinity measurements will include 1 Hydrogeochemical studies in aquifers with high carbonate e g dolomite and coastal quaternary sands 2 Water stabilization investigations including water softening water conditioning to reduce cement aggressiveness water conditioning to reduce cast iron and mild steel aggressiveness iron and manganese removal management of carbonate encrustation 3 Certain pollution investigations 4 Sampling for radiocarbon isotopes The formal definition of the alkalinity of water is its acid neutralising capacity Total alkalinity is the sum of all titratable bases in the sample APHA 1998 For most groundwaters with pH between 6 and 8 total alkalinity essentially represents the bicarbonate concentration For this reason alkalinity titration with acid is used to approximate bicarbonate levels in order to complete the ion balance of water samples High levels of borates phosphates and silicates can also contribute to alkalinity and in such cases suitable adjustments have to be made to achieve proper ion balance The practical implementation is that a sample is titrated to a designated pH value generally the equivalence point between pH 4 and 5 of the weak acid base carbonate system CO HCO CO Loewenthal et al 1986 When the pH of the water sample is above pH 8 3 alkalinity titrations are conducted to two endpoints e The first en
10. Turbid water is the enemy of proper groundwater sampling If a turbid water sample is acidified then levels of metals will be overestimated Filtration is a method of rectifying the problem except that filtration can introduce other errors such as removal of potentially mobile particles such as colloids It is far better to be able to collect a water sample that is not turbid thus avoiding the need to fix the problem of turbid water Thus after drilling a new borehole make sure that it is thoroughly cleaned before the contractor is allowed off site or make sure that a borehole cleaning program is in place and has been completed before you arrive to collect groundwater samples for analysis Newly drilled boreholes also affect the groundwater chemistry as the fresh surfaces of rock are exposed to water This must be reduced to a minimum by ensuring that all particles of rock are removed from the borehole by adequate cleaning of the borehole The drilling fluids that are used to maximize drilling efficiency have a much bigger than appreciated effect on the natural geochemistry of the groundwater Drilling fluids contain a number of contaminants including sodium sulphate and carbon Also drilling fluid may dilute the natural geochemical makeup including chloride fluoride and silicon The most dramatic changes are seen with the carbon isotopes C and 14C Graham and Johnson 1991 calculated that when developing a newly drilled borehole
11. procedure Chapter 3 is a description of all the various laboratory measured determinands that a hydrogeologist would consider for determining groundwater quality For each determinand or group of determinands there is a brief description of the determinand and its characteristics followed by a detailed description of sample container type sampling routine and preservation Chapter 4 provides a detailed description of why and how the field measured determinands namely temperature electrical conductivity pH Eh dissolved oxygen and alkalinity must be collected Chapter 5 covers aspects of using down hole logging of field measured determinands Chapters 6 to 8 describe the documentation and procedures that must be prepared and followed during a sampling programme Chapters 9 to 19 describe various devices and procedures used or followed in a groundwater monitoring programme In order these are sample containers and sample preservation water level measurement sample collecting devices developing newly drilled boreholes purging the borehole filtering devices flow through cell multiple level sampling protective clothing decontamination and sampling of springs and seeps Chapter 20 is a list of websites of water quality guidelines In writing this manual we have tried to present the information in a logical and easily understood manner without compromising scientific integrity The style we have adopted is to us
12. URL http www phmeters com Islet_pH Information htm last accessed 17 October 2006 Shaver R B 1993 Field vs lab alkalinity and pH effects on ion balance and calcite saturation index Ground Water Monitoring Review 13 2 104 112 Wilde F D Busenberg E and Radtke D B 2006 pH U S Geological Survey Techniques of Water Resources Investigations book 9 chap A6 section 6 4 version 1 2006 Available from the URL http pubs water usgs gov twri9A6 last accessed on 22 November 2006 60 4 4 Eh OXIDATION REDUCTION POTENTIAL ORP OR REDOX POTENTIAL Oxidation and reduction redox reactions involve the transfer of one or more electrons between chemical elements that can exist in more than one oxidation state called multivalent elements Redox reactions exert important control on the distribution of species like O2 NOs Fe Mn SO H2S and CH in groundwater systems Since many redox reactions are catalysed by micro organisms redox potential also affects microbiological activity in groundwater Thus redox potential influences the fate and transport of many metals and the degradation of organic contaminants Appelo and Postma 1996 Redox reactions are often very slow in relation to other aqueous reactions which means that apart from equilibrium chemistry reaction kinetics also play a significant role When interpreting the measured Eh value it cannot be assumed that the redox species coexist in equilibrium
13. and Zn form ionic complexes and solid compounds with multivalent elements notably sulphur The concentrations of these heavy metals are therefore also influenced by DO in water Uranium selenium and arsenic are insoluble under reducing or anaerobic conditions Conversely iron and manganese are insoluble in aerobic water with a neutral pH The pH of the solution and the concentration of inorganic and organic complexing agents need also be considered in determining the fate of these species DO measurements are usually reported as concentration in mg L ppm which is an actual concentration Some geochemists prefer to use umole L 0 032 mg L For various applications where water is in contact with air it is more appropriate to express DO as saturation with respect to air which is a derived unit The conversion between mg L and saturation is described below 4 5 1 METHODS OF DO MEASUREMENT 4 5 1 1 Method selection The methods available for DO determination are e Winkler iodometric titration which is a cumbersome method that is seldom used anymore e Amperometric measurement through a membrane DO electrode which is the common field method This is the preferred method of analysis because of its simplicity e Spectrophotometric determination in which the sample is added to an ampoule of chemicals and the colour change is measured with a spectrophotometer or compared with tests samples or a colour chart The Rhodazine D techniq
14. conducted as accurately as possible Analytical results are only as good as the samples they are testing Sixteen items should be included in a QA plan and they can be grouped together as follows Keith and Wilson 1982 A Format 1 title page 2 table of contents B Project overview what is the purpose of the project 3 project description 4 project organization and responsibility C Data quality objectives what will be required 5 QA objectives for measurement data in terms of precision accuracy completeness representativeness and comparability D Measurement activities how will it be done data reduction validation and reporting internal quality control checks and frequency 12 preventive maintenance E Quality assurance can the results be trusted 13 performance and systems audits and frequency 14 specific routine procedures to be used to assess data precision accuracy and completeness of specific measurement parameters involved 15 corrective action 16 quality assurance reports to management 6 sampling procedures 7 sample custody 8 calibration procedures and frequency 9 analytical procedures 0 1 1 1 99 This grouping could be useful in at least a couple of ways For someone writing a QA plan particularly for the first time it might clarify the way in which the sixteen items relate to each and to the plan as a whole Additionally there are occasions particu
15. contamination of drinking water World Health Organization Report WHO SDE WSH 02 08 Available from the URL http www who int water_ sanitation health dwq wsh0208 en index html last accessed on 17 October 2006 Vogel A I 1951 Quantitative Inorganic Analysis Longmans Green London 918p 4 7 6 SUPPLIERS OF EQUIPMENT The authors do not claim that the supplier s list is complete nor can they guarantee the performance of the products Chemetrics http Awww chemetrics com last accessed on 17 October 2006 CSIR HeS Strip Test Ms M Franck CSIR Stellenbosch South Africa Ph 021 888 2581 Fax 021 888 293 mfranck csir co za Hach Pathoscreen test URL http www hach com hc search product details invoker PackagingCode 2859100 NewLinkLab el PathoScreen Field Kit last accessed on 17 October 2006 Hanna URL http www hannainst com last accessed on 17 October 2006 Merck URL http photometry merck de serviet PB menu 1168630 index htm last accessed on 17 October 2006 SOPAC H2S paper sirip test Institute of Applied Sciences University of the South Pacific Box 1168 Suva Fiji Ph 679 3212967 Fax 679 3300373 URL http www sopac org data virlib T R T R0373 pdf_ last accessed on 17 October 2006 Orion now part of the Thermo Corporation URL http www thermo com com CDA Category CategoryFrames 1 2213 248 00 html last accessed on 17 October 2006 Radiometer ion selective electrodes URL
16. o N oOo 12 12 13 14 14 15 15 16 16 16 17 17 19 19 20 20 21 22 22 23 23 24 3 4 3 5 3 3 5 CFCs and SF 3 3 6 Sulphur 34 and oxygen 18 in sulphates 3 3 7 Other isotopes and tracers 3 3 8 Radioactivity 3 3 9 Isotope references Organic compounds 3 4 1 Sample containers for organics 3 4 2 Sampling equipment for organics 3 4 3 More commonly encountered organic contaminants 3 4 3 1 Phenolic compounds 3 4 3 2 Pesticides 3 4 3 3 Petroleum derived compounds 3 4 4 General groups of organic compounds 3 4 4 1 Dissolved organic carbon DOC 3 4 4 2 Dissolved organic halogen DOX 3 4 4 3 Volatile organic compounds VOC 3 4 4 4 Semi volatile organic compounds SVOC 3 4 4 5 LNAPLs and DNAPLs 3 4 5 Organics references Microbiological Determinands 3 5 1 Introduction 3 5 2 General microbiological determinands 3 5 2 1 Heterotrophic plate count 3 5 2 2 Faecal coliform test 3 5 2 3 Bacteriophages 3 5 3 Sampling general microbiological determinands 3 5 4 Enteric viruses and parasites 3 5 5 Pitfalls for microbiology sampling 3 5 6 Microbiology references Chapter 4 Field Determinands 4 1 4 2 4 3 Temperature 4 1 1 Equipment for temperature measurement 4 1 2 Field procedure for temperature measurement 4 1 3 Temperature references Electrical Conductivity 4 2 1 Method of conductivity determination 4 2 2 Equipment for conductivity determination 4 2 3 Field procedure for conductivity determination 4 2
17. would be preferred as the brass may introduce contaminants The sonic water level meter mentioned in section 10 2 2 above has the advantage that using it will reduce the danger of cross contamination 117 CHAPTER 11 SAMPLE COLLECTING DEVICES 11 1 SAMPLE COLLECTING DEVICES The following article by Pohlmann and Hess 1988 is reprinted verbatim and with permission from Groundwater Monitoring Review Vol 8 No 4 Although nearly 20 years old the sampling tools have not changed significantly and this review paper is regarded as being comprehensive and complete The only notable changes in groundwater sampling technology are the concept of low flow sampling and the use of foot valve samplers These are discussed at the end of the reprint Some minor additional notes and comments have been added at the end of the reprint For this revised manual the units of the original article have been converted to S I units Generalized Ground Water Sampling Device Matrix by K F Pohlmann and J W Hess The sampling matrix was prepared by K F Pohlmann and J W Hess of the Water Resources Center Desert Research Institute University of Nevada System and submitted to the U S EPA as part of a cooperative research program The chart is based on a review of the literature and it illustrates general relations of ground water parameters to sampling devices There were 12 types of sampling devices and 14 ground water determinands including inorganic org
18. 0 1 to 10 mg L and is composed primarily of fulvic and humic acids Groundwater polluted from waste disposal sites can have DOC values over 1000 mg L most of which are fatty acids High levels of DOC will also be obtained if an organic drilling fluid was used and the borehole was not properly developed If the VOC fraction of DOC is not needed then the DOC measurement can be done on the water sample collected for major cation and anion analysis section 3 2 1 If the VOC content is needed then follow the procedure outlined under VOC section 3 4 4 3 3 4 4 2 Dissolved Organic Halogen DOX Dissolved organic halogen DOX is a measurement used to estimate the total quantity of dissolved halogenated organic material in a water sample This is similar to previous literature references to TOX The presence of halogenated organic molecules is indicative of synthetic chemical contamination Halogenated compounds that contribute to a DOX result include but are not limited to the trihalomethanes THMs organic solvents such as trichloroethylene tetrachloroethene and other halogenated alkanes and alkenes chlorinated and brominated pesticides and herbicides polychlorinated biphenyls PCBs chlorinated aromatics such as hexachloro benzene and 2 4 dichlorophenol and high molecular weight partially chlorinated aquatic humic substances Compouna specific methods such as gas chromatography typically are more sensitive than DOX measurements Th
19. 3 National Water Well Association Dublin Ohio USA Parker L V and Ranney T A 1997a Decontaminating materials used in groundwater sampling devices Cold Regions Research and Engineering Laboratory Special Report 97 24 URL http www crrel usace army mil techpub CRREL Reports reports SR97_24 pdf last accessed 20 September 2006 Parker L V and Ranney T A 1997b Decontaminating groundwater sampling devices Cold Regions Research and Engineering Laboratory Special Report 97 25 URL http www crrel usace army mil techpub CRREL_ Reports reports SR97_25 pdf last accessed 20 September 2006 TPH CWG 1998 Analysis of petroleum hydrocarbons in environmental media W Weisman ed Volume 1 Total Petroleum Hydrocarbon Criteria Working Group Series Amherst Scientific Publishers Massachusetts URL http www aehs com publications catalog contents Volume1 pdf last accessed 20 September 2006 Hydrocarbons recommended reading with web sites addresses Schwerko E M 1994 Sampling and Analytical methods for petroleum contaminated soil and groundwater An Overview BP Oil Environmental Technology NZ MoE 1999a Draft Sampling Protocols and Analytical Methods for Determining Petroleum Products in Soil and Water Oil Industry Environmental Working Group Published by the Ministry for the Environment PO Box 10362 Wellington New Zealand URL http www mfe govt nz publications hazardous sampling protocols oil may99 pdf las
20. 5 November 2006 http www dnr state wi us org water dwg qw pubs desk b pdf last accessed on 5 November 2006 US EPA OSWER 9950 1 This publication entitled the RCRA Ground Water Monitoring Technical Enforcement Guidance Document TEGD describes in detail what the United States Environmental Protection Agency deems to be the essential components of a groundwater monitoring programme Note this is a 10 MB document URL 109 http www epa gov Compliance resources policies civil rcra rcragwquiddoc rpt pdf last accessed on 5 November 2006 ANZECC 2000 Australian guidelines for water quality monitoring and reporting http www deh gov au water quality nwqms monitoring html last accessed on 5 November 2006 Chain of custody US Geological Survey This document deals with COC for geochemical samples not water nevertheless it contains some good descriptions and has a form http pubs usgs gov circ 1997 c1138 c1138 htm last accessed on 5 November 2006 The Minnesota Pollution Control Agency has a variety of COC forms on their website at http www pca state mn us water groundwater samplequide html last accessed on 5 November 2006 Cyto Labs http www cytoculture com sample 20info htm last accessed on 5 November 2006 http www cytoculture com generic 20AN 20CC doc last accessed on 5 November 2006 8 5 REFERENCES ANZECC 2000 Australian guidelines for water quality monitoring and reporting National water qual
21. 7 2 2 A description of the project and what aims of the project the sampling programme is likely to achieve The same information as described below for the Monitoring Programme Guide The field data sheets from previous sampling runs Copies of these are inserted into the Field guide MONITORING PROGRAMME FIELD GUIDE This is the document taken into the field by the sampling crew It is referred to at all times to check that the correct site is being sampled and is being sampled correctly It must include the following A detailed list of the equipment needed to carry out the sampling run See chapter 2 5 for a comprehensive sample equipment checklist Calibration and checks to field instruments that need to be done before departure from the base Safety information Map s showing the location of each borehole and or sampling site A detailed small scale map is often necessary for individual boreholes especially if there is more than one borehole at the site Where to obtain keys for gates and borehole locking caps Contact details about the owner and supervisor s of the site Contact details of the contact person who provides access to the site Local contact person in case there is a problem Depth and size of the borehole s to be sampled It is expensive to arrive at a site with a sampling pump too large to fit in the borehole Position of screens or fractures i e position for installing sa
22. Cool Chloroform or HSO 2 months Organic N 500 P G Cool 4 C 7 days Kjeldahl H2SO0 to pH lt 2 Oil amp grease 1000 G wide mouth Cool 4 C 24 hours calibrated H2SO to pH lt 2 28 days 5 0 20 P G 1 year Pesticides amp 1000 G S Amber TC Cool 4 C Dark 7 days 166 PCBs 40 days extracted Ph 50 P G Analyse on site 15 min Phenolics 500 G P TC Cool 4 C 28 days HSO to pH lt 2 PAHs 1000 G S Amber TC Cool 4 C Dark 7 days 40 days extracted Parasites Filtered on Filter stored in Cool 4 C 4 days site 100 to plastic 1000 L Phosphorus 100 P G Cool 4 C 28 days Total HS0 to pH lt 2 Orthophosphate 100 G A Filter on site 48 hours Cool 4 C Radioactivity Gross alpha gt 1000 P G HNO to pH lt 2 1 year Gross beta gt 1000 P G HNO to pH lt 2 1 year Radium 226 gt 1000 P G HNO to pH lt 2 1 year Radium 228 gt 1000 P G HNO to pH lt 2 1 year Radon 222 2x25 Special containers Cool 4 C 4 days Uranium gt 1000 P G HNO to pH lt 2 1 year Caesium gt 1000 P G HCI to pH lt 2 1 year Strontium gt 1000 P G HNO to pH lt 2 1 year lodine gt 2000 P G None 14 days Photon emitters gt 1000 P G HNO to pH lt 2 1 year Potassium 100 P G B Filter on site 6 months HNO to pH lt 2 Semi VOCs 1000 G S Amber TC Cool 4 C 7 days 40 days extracted Selenium 100 P A G A Filter on site 6 months HNO to pH lt 2 SFe 200 Special containers 2 months
23. Liquid Litres per second see note above Molar concentration mole L Cubic metres per day Cubic metres per hour milli equivalent litre mEq L milligrams milligrams per litre micrograms per litre millilitres millimetres micron micrometres micromho per centimetre microsiemen per centimetre milli siemen per metre unit of electrical conductivity Methyl tertiary butyl ether millivolts xi NO PAH PET POC POX ppb PPE ppm PTFE PVC QA QC RCRA SFe SHE SVOC TCE TDS THM TPC TPH TPH DRO TPH GRO UST VOCs WIG WRC Nitrogen oxides collective term Polycyclic Aromatic Hydrocarbon Polyethylene terephthalate Purgeable organic compounds Particulate Organic Halogens parts per billion ug kg Personal protective equipment parts per million mg kg Polytetrafluoroethylene commonly available as Teflon Polyvinyl chloride Quality Assurance Quality Control Resource Conservation and Recovery Act Sulfur hexafluoride Standard hydrogen electrode Semi volatile Organic Compound Trichloroethylene Total dissolved solids Trihalomethane Total Plate Count now known as HPC Heterotrophic plate count Total Petroleum Hydrocarbons Total Petroleum Hydrocarbons Diesel Range Organics Total Petroleum Hydrocarbons Gasoline Range Organics Underground Storage Tank Volatile organic compounds Wax impregnated graphite electrode Water Research Commission South Africa Equivalent Terms petrol gas
24. Silica 200 P PTFE or Cool 4 C 28 days quartz Do not freeze Sodium 100 P Cool 4 C 6 months Sulphate 100 P G Cool 4 C 28 days Sulphide 100 P G Cool 4 C 4 drops Zn 28 days acetate 100 mL NaOH to pH gt 9 Surfactants 250 P G Cool 4 C 48 hours 167 MBAS Temperature 50 P G Analyse on site 15 min Tritium 500 G None 1 year Turbidity 100 P G Cool 4 C Dark 24 hours THM 1000 G TC Cool 4 G 24 hours 2x25 G TC Cool 4 G 14 days TPH 1000 G TC Cool 4 C 28 days Add 5 ml 50 HCI Viruses 100 to Filtered on site Cool 4 C 4 days 1000 L Filter stored in plastic VOC 2x40 G TC Cool 4 C 14 days HCI to pH lt 2 A acid rinsed with 1 1 HNO3 B borosilicate glass S organic solvent rinsed reagent grade acetone or methylene chloride or baked TC Teflon lined cap 168
25. These are mainly faecal indicator bacteria and their presence or absence is used to interpret whether faecal contamination has occurred or has not Typically one will use these determinands when looking at groundwater fitness for use as a drinking water resource domestic or otherwise They will also be used when looking at groundwater contamination especially when sewage contamination is suspected Other than for health reasons micro organisms should also be looked at since they catalyze nearly all the important redox reactions occurring in groundwater The main source of energy for these bacteria is organic carbon At a typical pollution site with a high organic carbon load the groundwater rapidly changes from aerobic through anoxic to anaerobic conditions down the groundwater flow path With each of these changes there is a corresponding change in the bacterial population The identification of which bacteria are responsible for the degradation of which organic pollutants is receiving a lot of attention If the bacteria can be identified and cultured the commercial implications for groundwater pollution clean up programmes are vast Indeed bacteriological aided clean up methods and brews of bacteria are commercially available and applications are increasing What is briefly discussed above is a vast field and involves fairly specialised collection transport and analytical techniques As these techniques require a manual on their own and tec
26. a dirty electrode Short term storage Keep the electrode bulb of the glass electrode moist and capped when not in use and between sampling points Drying of the bulb will lead to slow response times Follow the manufacturer s instructions on storage solutions A small volume of pH 7 buffer solution is usually poured into the cap before covering the bulb Deionised water or concentrated KCI solutions should not be used to keep the glass bulb wet unless specified by the manufacturer Liquid filled electrodes should preferably be stored upright when not in use Wilde et al 2006 Long term storage Drain the filling solution from liquid filled electrodes that will not be used for several weeks or longer Cover the bulb with a protective cap filled with storage solution or electrolyte if recommended by the manufacturer Rinse the outside of the electrode with deionised water and store the electrode dry Wilde et al 2006 ISFET electrodes are more robust but care should still be taken not to damage the delicate sensor tip usually recessed into the probe Static electricity or other electrical charges should be avoided as they may damage the transistor For general use rinsing the probe in deionized water then wiping dry with a soft towel or tissue will be sufficient to clean the probe ISFET probes can also be cleaned with a toothbrush and mild detergent or soaked for not more than 3 minutes in 0 5 bleach solution 10 to 1 dilution of laundr
27. a few sets of borehole data can be recorded You do not need a separate sheet for each borehole e Sample ID recorded on bottle and on Chain of Custody form e Borehole physical data Any damage depth to water surface depth to bottom of borehole calculate water level above sea level e Sampling pump details Type depth of intake pumping rate required purging time to purge e Field determinands Temp EC pH Eh DO alkalinity you should have a few rows so that readings at various elapsed times since pumping started can be recorded e Sampler s observations on the pumped water Colour and colour changes during pumping odours DNAPLs or LNAPLs e Sample handling Filtering sample bottle type and size preservatives storage e Provide space for additional notes at the end of the sheet Many sampling programs will require the sampling of waters from sources other than boreholes These could include wells seeps springs rivers dams domestic water points reticulated water systems and more Devise a method of including these on the Field Record Sheet 83 CHAIN OF CUSTODY There will be occasions when the results of a groundwater monitoring program will be entered as evidence in a legal dispute To be admissible as evidence sample results must be traceable back through their collection storage handling shipment and analysis so that the court is satisfied how the sample results submitted as evidence were collected tran
28. and record it together with the temperature 8 Rinse the cell with distilled water and pack away wet Note Errors in reading will be made if the electrode is not fully immersed in the sample or air bubbles are present on the platinum electrodes 50 4 2 4 CONDUCTIVITY REFERENCES APHA 1998 Standard Methods for the Examination of Water and Wastewater 20 ed Am Public Health Assoc Washington DC Wood W W 1981 Guidelines for collection and field analysis of ground water samples for selected unstable constituents Techniques of Water Resources Investigation Chapter D2 US Geological Survey 43 pH pH is a measurement of the concentration of hydrogen ions in solution These concentrations in natural waters are generally very low and vary over many orders of magnitude which make it more convenient to report them on a logarithm scale rather than as absolute concentrations By definition pH logio H where H represents the hydrogen ion H concentration in moles per litre pH is one of the most important parameters affecting the chemical composition of groundwater Anything that changes the pH of a sample will likely affect other constituents as well Aeration oxidation mineral precipitation temperature changes and degassing of a sample can significantly alter its pH The pH of pure carbon dioxide free water at 25 C is 7 0 Above this pH samples are considered basic or alkaline and at pH less than 7 samples are cons
29. chapter 4 6 provides quite accurate results Simple kits are available that yield semi quantitative results that may be acceptable in some cases With titration one is not looking at intensity of colour as in the above examples but at a colour change when the equivalence point is reached Titrations basically require a fixed volume of sample an indicator and some sort of dispenser to control and measure the reagent added Light levels and water colour should be sufficient to observe the colour change at the equivalence point Different indicators with different colours are available Table 4 7 1 The HTH test kit commonly available in South Africa for swimming pool water testing uses bromo cresol green as indicator for alkalinity determination A sample volume of 16 mL is measured out in the supplied special plastic container Acid 0 06N is dispensed with a dropper each drop 0 05 ml and the colour change observed The alkalinity as mgCaCoO L is obtained by multiplying by 10 the number of acid drops used to reach the endpoint The precision of this method is hardly better than 20 but there may be occasions where this can be acceptable e g radiocarbon sampling where one needs to determine sample size see section 3 3 3 Table 4 7 1 pH indicators suitable for alkalinity determination from Vogel 1951 Indicator pH range Low pH colour High pH colour methyl orange 3 2 4 4 red Yellow bromocresol green 3 8 5 4 yell
30. checked in this way There are further internal Quality Control checks which are carried out by the laboratory and which do not form part of the field sampling methodology and thus are not included in this manual However the manager of a groundwater monitoring program must be aware of them especially should litigation occur Read about them in APHA 1998 and in Canter et al 1987 6 3 QUALITY ASSESSMENT Quality assessment is external QC This is a performance audit which is carried out periodically to determine the accuracy of the measurement system Modern rapid analytical techniques are capable of giving very precise results sometimes at the expense of accuracy It is not uncommon in a monitoring programme which samples boreholes at regular intervals over a period of time to encounter changes in groundwater chemistry when a change in analyst or laboratory occurs Quality assessment includes such items as performance evaluation samples performance audits and inter laboratory comparison samples In South Africa the South African National Standards SANS conducts a nation wide inter laboratory comparison study called SANS Water Check This programme is open to participation by all laboratories that analyse water and wastewater samples Use only a laboratory that regularly participates and is accredited Inter laboratory comparison for organic compounds is conducted by SANAS Isotope inter laboratory comparison surveys are conducted by IAE
31. constructed containment sites for the disposal of waste that is regarded as hazardous Such a site requires an impermeable membrane or a relative impermeable layer that will efficiently contain both the waste and the leachate in the site or in the immediate surroundings of the site Non hazardous waste sites will be where household and other general waste such as building rubble can be disposed Such a site will have been characterized to emit leachate very slowly and continuously The leachate is regarded as relatively harmless in terms of toxic compounds and will be located in a position that will not endanger an existing or future water resource If sampling groundwater at a hazardous waste site it is essential to wear personal protection equipment PPE At other sites do not be surprised to find that the explosimeter indicates dangerous conditions and that PPE should be worn when collecting groundwater samples Protective clothing must be sufficient to safeguard the health of the sampler Education and training of sampling personnel in correct procedural methods is required by law and can prevent accidents Safety Acts usually stipulate that personnel are made aware of the potential hazards and the need for precautions It is the responsibility of the Project Leader to ensure that proper safety equipment is 152 made available that the sampling personnel are trained in the use thereof and that the safety equipment and use thereof is spec
32. drinking water applications for humans and animals It is therefore usually required for analysis for supply purposes Sampling for fluoride Fluoride samples need no filtration or special preservation 3 2 1 5 Iron and manganese Iron levels in water above 0 5 mg L and manganese above 0 05 mg L may cause stains especially to clothing that has been washed A high iron concentration also imparts a metallic taste to water Soluble iron in groundwater is in the Fe state ferrous When this water comes into contact with air the iron is oxidised to Fe state ferric which is insoluble and precipitates as ferric hydroxide e g ferrihydrite which forms a slimy dark brown semi suspended material This process often takes place in the standing water in the borehole Manganese in groundwater behaves similarly to iron and thus the sampling procedure is the same Mn oxidises to Mn Sampling for iron and manganese In order to collect a representative water sample the borehole must be properly purged and the water sample filtered to prevent previously precipitated ferric hydroxide from ending up in the sample bottle The sample container can be glass or plastic To prevent solution of previously precipitated Fe or Mn use either new bottles or acid washed bottles prepared in advance Filter 0 45 micron the sample immediately it is discharged No preservative is needed but keep the samples cool 16
33. during the analysis e g the cations and anions do not balance and the analysis has to be repeated and the third bottle is stored for a few months after the analytical results have been posted in case of any queries concerning the analysis 113 CHAPTER 10 WATER LEVEL MEASUREMENT 10 1 INTRODUCTION When arriving at a borehole or well to collect a water sample the first measurement that must be taken is the water level and the second is the depth of the borehole However if you intend to use the low flow sampling method or down hole logging method then measure the depth after sampling is complete By lowering the dip meter probe to the bottom of the borehole you disturb sediment that has settled and this will create turbidity and thus require a longer purging time There are a number of reasons why the water level and the depth of the borehole must be measured amongst others If the water level measuring device cannot go down the borehole the sampling pump will also not be able to go down When sampling an unknown borehole the depth of installation of the sampling pump must be determined If the borehole has been sampled previously the depth measurement will indicate whether borehole collapse or silting has occurred The volume of water that must be purged see Chapter 13 must be calculated so that a representative sample can be collected Water levels are essential for calculating groundwater flow directions an
34. electrode in saturated KCI solution if recommended by the manufacturer Separate platinum metal electrodes can be stored in an oxygen scavenging solution of 0 2M sodium sulphide Long term storage Procedures vary and the manufacturer s instructions should be consulted Combination electrodes are usually stored dry after rinsing precipitates from the outside of the probe draining the filling solution chamber and flushing out with water 4 4 3 3 Eh reference solutions Eh reference solutions provide stable and known Eh values over a range of temperatures One of the drawbacks of reference solutions is that they do not cover the range of Eh values found in natural and polluted groundwater especially in the lower Eh range Reference solutions can be bought commercially or made up in the laboratory The composition of two common Eh reference solutions is given in Table 4 4 1 Use dried salts stored in a desiccator and weigh out accurately for Zobell s solution Zobell s solution should be stored in a dark plastic bottle in a refrigerator The solutions should be stable for approximately 3 months Do not use reference solutions after the manufacturer s expiry date or more than 90 days after preparation if made up in the laboratory Quinhydrone solution has the advantage that by using different pH buffers to make the solution you can cover a wide range of redox potential Quinhydrone solution is however less stable than Zobell s solution
35. especially above 30 C and its temperature dependence is less well defined Nordstr m and Wilde 2005 Table 4 4 1 Composition of Eh reference solutions Reference Preparation solution Quinhydrone buffer Dissolve quinhydrone crystals in a suitable acid base solution buffer solution pH 1 to 9 until saturation and then add a Ref Kokholm few more crystals The solution contains equal parts of undated the hydroquinone and quinhydrone redox couple Zobell s solution 1 4080 g K Fe CN s 3H gt O potassium ferrocyanide plus Ref APHA 1998 1 0975 g K3Fe CN potassium ferricyanide plus 7 4555 g KCI potassium chloride all dissolved in deionised water and made up to 1L at 25 C Store ina dark bottle and keep chilled Note Zobell s solution is toxic handle with care and dispose responsibly 65 Temperature dependence Eh is temperature dependant and temperature is therefore important for all measurements The Eh of the quinhydrone solutions are also pH dependent The temperature dependence of these reference solutions relative to the standard hydrogen electrode can be calculated from the following equations Quinhydrone buffer solution Eh in mV 700 0 1983x t 273 15 x pH Zobell s solution Eh in mV 428 2 2x t 25 where t is the temperature in degrees Celsius For ease of reference the same information for a range of temperatures commonly found in groundwaters is given in Append
36. for Eh measurements and the readings must be taken in the field Use an electrode system that has been tested for adequate performance see section 4 4 4 1 The steps for field measurement of Eh are as follows 68 9 Check that the reference electrode is filled with the correct filling solution and the platinum electrode is brightly polished Rinse the electrodes with deionised water and then with the sample water Set up the flow cell with the Eh electrode system and thermometer in place and allow groundwater to run for several minutes to purge air from the cell before taking En measurements Check that the connectors and ports for the sensors do not leak and that the groundwater fills the cell and flows gently eliminating all bubbles Switch on the Eh meter and allow it to warm up If the same meter is used for pH readings take the pH measurements first and then switch to the millivolt scale for Eh Allow the Eh electrode system to reach equilibrium with the groundwater Note that this may take 30 minutes or more The platinum electrode should be flushed with large volumes of water to obtain reproducible values Readings will tend to drift if the water has low concentrations of redox active species or if thermal equilibrium has not been reached Take millivolt and temperature readings every few minutes for the first 15 to 20 minutes Stop the flow while taking readings to avoid streaming potential effects Record the time temperature a
37. formula for phenol is CsH O Halogens Cl F Br and other functional groups such as nitro 32 groups and amino groups can substitute for H on the benzene ring All substituted phenols are referred to collectively as phenols Many halogenated phenols are common groundwater pollutants pentachloro phenol 2 4 dichlorophenol etc Chlorination of water can produce chlorophenols which impart bad taste and odour to the water which is of concern Generally toxicity limits for phenols are higher than the aesthetic limits DWAF 1996 Unfiltered water samples are collected in properly cleaned 1 L glass bottles Analytical grade sulphuric acid is added to achieve a pH lt 2 Note that H2SO is very corrosive so handle with due care Samples are kept cool and must be analysed within 28 days 3 4 3 2 Pesticides Pesticides include insecticides herbicides fungicides nematicides and molluscicides They vary widely in toxicity to humans so that for some pesticides a few grams can be lethal whereas for others e g sulphur many kilograms need to be ingested to be lethal Some pesticides can be absorbed through the skin eyes or lungs and can therefore be dangerous even though they are not swallowed Organo phosphorous compounds can condition the body upon repeated exposure to small doses to increasing susceptibility so that later exposure may suddenly cause acute poisoning Some pesticides have been shown to be teratogenic causing foetal malf
38. has laid down any regulations for dealing with the specific situation The bottles are usually glass or plastic of the right properties and need to be acid washed before sampling Radioactive elements are heavy metals see section 3 2 2 and therefore filtering may be required in some cases Radon however is a dissolved gas and its collection method must be one that reduces degassing and does not allow filtering 28 The sample container for radon is usually supplied by the laboratory and is one that can be inserted directly into the scintillometer 3 3 9 Isotope Cecil L D and Green J R 2000 Radon 222 In Cook P G and Herczeg A L eds Environmental Tracers in Subsurface Hydrology Kluwer Boston Clark I D and Fritz P 1997 Environmental Isotopes in Hydrogeology Lewis Publishers Boca Reton NY URL http www science uottawa ca eih last accessed on 17 October 2006 Cook P G and Herczeg A L eds 2000 Environmental Tracers in Subsurface Hydrology Kluwer Boston 529p DWAF 1996 South African Water Quality Guidelines Volume 1 Domestic use 2nd ed Department of Water Affairs and Forestry Pretoria 190p URL http www dwaf gov za Dir WQM docsFrame htm last accessed on 17 October 2006 Gat J R Mook W G and Meijer H A J 2001 Environmental Isotopes in the Hydrological Cycle Volume 2 Atmospheric water IHP V UNESCO Paris URL http www iaea or at programmes ripc ih volumes volume
39. http www radiometer analytical com news en electrode catalogue asp s go last accessed on 17 October 2006 Sigma Aldrich http www sigmaaldrich com Brands Fluka__ Riedel Home Analytical Analytical_Specialties A QUANAL reg html last accessed on 17 October 2006 93 CHAPTER 5 DOWN HOLE LOGGING FOR FIELD DETERMINANDS 5 1 INTRODUCTION Field measurements are usually taken from flowing boreholes using a bucket or flow through cell at the wellhead Thanks to the advances in sensor technology down hole logging instruments have been developed that can be used to take physical and chemical measurements inside the borehole These can be used for measuring unstable determinands in the aquifer with minimal disturbance since no pumping is required They are also useful for plotting vertical profiles of how determinands vary with depth which can be used to interpret contaminant plume movement water quality stratification or flow characteristics A very good understanding of how the borehole is constructed which sections are screened or open hole is essential when interpreting the data Geophysical wireline logging is a fairly well established practice which traditionally includes limited water quality determinands such as temperature or electrical conductivity Several other types of down hole sensors are now available These have expanded water quality logging capabilities to include pH dissolved oxygen Eh and even some
40. in groundwater e Mineralisation of soil organic nitrogen e Excess inorganic fertilizer transported from the soil into groundwater e Oxidation of nitrogen from manure and septic tanks that is transported to groundwater Each of these general categories of sources exhibits a distinct 5 N range of values which can be used to identify the sources of nitrogen in water Heaton 1986 Clark amp Fritz 1997 Sampling for N The samples need to be poisoned with acid chloroform or Hg gt Cl gt consult the laboratory or freezing the sample Store cool Sample size depends on the N content of the water 3 3 3 RADIOCARBON The radiocarbon C content actually refers to the ratio of C C in the dissolved inorganic carbon DIC or TIC CO2 HCO3 COs content of water This ratio is quite low in natural water 107 and is expressed in pmc percent modern carbon 100 pmc is the average activity of recent biological material and this is the concentration representing input into the groundwater system see for example Clark amp Fritz 1997 Mook 2000 23 14C is a radioactive isotope with a half life of 5730 years The ratio C C will therefore decrease by a factor two due to radioactive decay every 5730 years and this technique enables one to date water up to tens of thousands of years Water in contact with carbonate soils or aquifer material will react with this carbonate and thereby reduce its ratio of C C Thi
41. line filter or hand filter the next sample sets 5 8 Collect sample for dissolved trace metals filtered 5 9 Collect sample for phosphate iron and manganese filtered 6 Wrap up 6 1 Switch off the pump 6 2 Protect all samples from the sun during sampling 6 3 Ensure all the necessary forms are completed 6 4 Ensure all preservation procedures are complete 6 5 Clean all equipment thoroughly before putting it away rinsing with distilled water where indicated 6 6 Clean up the site Return the samples to the laboratory in time for analysis to be started before samples deteriorate When in a remote area prepare the samples for shipment to the various analytical laboratories ensuring refrigerated transport where necessary If the samples are to be transported by air determine whether depressurization will occur and affect the samples e g stoppers coming off gases lost evaporation of chloroform for pesticide extraction Such samples must travel in a pressurised hold NOTE Try to keep equipment as clean as possible Wash with distilled water after use to prevent contamination Sampling is susceptible to error and maintaining cleanliness keeps errors and contamination to a minimum 11 2 7 EQUIPMENT MAINTENANCE AND REPAIR It is much easier to repair your equipment in the office than in the field Refer to previous field trip notes and make sure that the necessary repairs have been done and broken equipment has been replaced
42. of three shallow boreholes and a suction cup over a distance of about 200 m perpendicular to the flow direction in an unconsolidated aquifer However in a shallow 6 m borehole in between the contaminated boreholes only 30 mg L of nitrate was observed rather than the 150 mg L which was expected This shallow borehole is adjacent to a deep 30 m borehole which allowed low nitrate groundwater to be displaced upwards from deeper in the aquifer The deep borehole acted as a short circuit with respect to the various pressure heads in different depths Before the borehole was equipped with stationary packers a large volume of up flowing low nitrate groundwater infiltrated the shallow aquifer Even after a long purging period using a temporary double packer system the original groundwater of the shallow aquifer was not intercepted Subsequent to the first sampling run a permanent also called stationary packer system was installed in the deep borehole This packer separated the lower from the upper aquifer After allowing the system to stabilise multilevel sampling took place and high levels of nitrate as expected were obtained in the shallow borehole as well as in the upper zones of the deep borehole R delsperger et al 1991 Short circuiting in boreholes allows water types to be transferred vertically in the aquifer causing changes in groundwater quality in the region of the borehole where 148 hydraulic head is lower The effect is
43. overlap as far as sampling methodology is concerned between the various groups of organic compounds and to go through the full potential range will be time consuming if not impossible For the purpose of this manual the more commonly encountered groups of organic compounds having an impact on groundwater will be looked at individually After that the general group in terms of sampling methodology will be described More commonly encountered organic compounds include phenolic compounds pesticides petroleum derived compounds General groups suites of compounds detected by an analytical method e dissolved organic carbon DOC e total organic carbon TOC e volatile organic compounds VOC e semi volatile organic compounds SVOC e light non aqueous phase liquids LNAPLs e dense non aqueous phase liquids DNAPLs 30 Note too that the analytical methods for organic matter in water are classified into two general types of measurements 1 Those that identify and quantify individual organic compounds and 2 Those that identify and quantify the total amount of organic compounds which have a common characteristic These methods are the scanning methods and are used when you suspect a problem but have not identified that there is a specific problem DOC is a relatively cheap parameter to have analysed costing between one and two times the price of sodium or chloride DOC is becoming a standard request in groundwater investig
44. own list that is specific for the project Add the equipment lists for specific field measurements as described in the various sections of chapter 4 The complete list will be part of your Monitoring Programme Guide See Chapter 7 Pack equipment in the vehicle taking into consideration the order in which it will be required 1 Borehole location 1 1 A copy of the Monitoring Programme Guide 1 2 Map or instructions for locating the sampling site or sites 1 3 Letter of introduction and visiting cards 1 4 Key to get into site and Q20 or oil to lubricate padlocks 1 5 GPS 2 Borehole operation 2 1 Water level recorder distilled water to clean recorder spare batteries 2 2 Tape measure as long as possible 2 3 Pump or purging device power compressor 2 4 Downhole logging equipment 2 5 Clear plastic bailer if you expect NAPL 2 6 Containers for purged water 2 7 Container to measure pumping rate 25 litre or 10 litre 2 8 Sample record sheets to identify sample and or sample sets and to record field measurements 2 9 Shovel 3 Toolbox 3 1 3 2 3 3 3 4 3 5 3 6 3 7 3 8 3 9 Torch Indelible ink fiber tip pen s pencils ballpoint field note book micro cassette recorder especially useful for recording field notes in the rain Protective clothing see Chapter 17 This includes rain gear cold weather gear warm clothing sun glasses and sun hat Camera plus film or memory chip First aid kit commerc
45. pH 6 and 10 alkalinity is therefore a fair measure of bicarbonate concentration 2 Figure 4 6 1 Distribution of CO2 HCO3 CO3 and alkalinity as a function of pH Loewenthal et al 1986 The y axis shows the relative concentration in mmol L and meq L for alkalinity A titration curve Fig 4 6 2 shows the pH response to the addition of acid to a sample Inflection points of the curve also called titration endpoints are the 83 characteristic pH value where the most rapid pH change occurs The first one is the point where all the carbonate has been converted to bicarbonate near pH 8 fig 4 6 2 and then again when all the bicarbonate has been converted to CO near pH 4 fig 4 6 2 APHA1998 method 2320B Rounds 2006 The aim of titration in the field is to perform the titration procedure with sufficient care and then to determine the inflection point s with the accuracy required for the task in hand pH slope carbonate alkalinity slope bicarbonate alkalinity ml acid added Fig 4 6 2 Typical titration curve of a somewhat alkaline unpolluted water sample The upper curve shows the pH change as function of quantity of acid added The lower curve shows the calculated slope ApH AV 4 6 2 TITRATION METHODS Alkalinity and acidity determinations involve the titration of a quantity of sample with acid or alkali for acidity in order to determine the quantity of acid necessary to reach
46. program accordingly Ayyenb seyem Hulyuup 10 spueujwazap piepue s y s pnioui ABoOjOIqoJOIW o suolue pue suopeo Jofew Jo siskjeue n4 uyfeQ pap100e q 0 sp u pue 1949W Hd y Wo qe i eAe Ajensn s ainyesodwia o J9y2 p sn S yey anjea 94 SI 93 Ayoyesoge au sny pue ayeinooe ss SOLUIJOWOS O12 SIB OLU DF p JOAOMOH Hul dwes e 10 p p10991 pue peunseew aq pinous OJ pial p nb sy p uinb sy Buuiolluoui uonnjjod 19 emnpunoi xoq Soq uve oad Hd uonnijod pajoedsns je1auey s onpoid uonepeiBap snid spunodwos uin jon d 6a seouejsqns p ljnu pi 90d LSN syue eHes0 s punosBHsapun ABojoiqos9Iw NOG uyAeD og yg Hd jesodsip sbemes ss oo4d au q poulwsajeq og yg Hd uolnyjod ajsem en snpu sjejow neay payluep uyAeD od ua Hd any eBeuresp ouu poy suoneBns Au uonnjjod uinissejod pue ej eujiu seplonsed 261e p ljlu pi oq uy Hd uoneujue uoo Apldiised sayempunoly 1s 1 lu JO SeoURISqNs 21x0 snid XOA 20A UYALI oq uy Hd s s jesods p ISP A xoq pue sjouayd ABojoiqoiolw OOdq uvAeoO Od 4g Hd 1 abreyoos eIoyly yoaloid Aq p uluu gl q yoaloid Aq p uluuugl q sp u zp fo d se slu ui aoe snid uyjAeD sp u 15 oi1d yeym snid uyAenD Ayuieyfe Oq Hd L ya Hd 93 L Ya Hd 93 L s do los Ayaoeolpey slu uui L Aulsiuu uoSoup u ofe SAOAANS 19 ApunoiB6 1OJ d1siuu u5o Boip H uW 8d uolsouioo uolg sn
47. radioactive isotope with a half life of 12 32 years As such it has the potential of being used to date groundwater ages in the order of decades The tritium levels in rainwater are extremely low and the unit used TU represents a H H ratio of 10 Before the advent of nuclear weapon tests rainfall tritium values were in the order of 3 to 5 TU During the period of nuclear weapon tests rainfall tritium levels reached 5000 TU in the northern hemisphere while it was never more than 100 TU in the southern hemisphere Present day rainfall tritium 24 levels in the southern hemisphere are down to the pre bomb values of 3 5 TU while the northern hemisphere still had about 80 to 100 TU in 2000 Clark amp Fritz 1997 Gat et al 2001 This major worldwide contamination event has afforded the possibility of using tritium as an indicator of recent post 1955 recharge indicator The tritium levels in groundwater remain intact underground and are only influenced by mixing with older water and radioactive decay Sampling for tritium Water should be collected in glass or plastic bottles with tightly fitting caps Fill bottles to the top Usually 0 5 1L samples are required 3 3 5 CFCs and SF Chlorofluorocarbons freons are a group of compounds that were invented during the twentieth century and that have had profound technological and environmental consequences The levels of gaseous CFCs in the atmosphere have increa
48. readings and estimate how long the logging is likely to take Try to take at least two readings at each depth before lowering the logger by the next increment to check the reproducibility of the results At the start of logging once the logger is submersed in the borehole hold it for a few minutes below the water table This is to allow time for the sensors to stabiles The response of the Eh and dissolved oxygen sensors in particular is sometimes sluggish and can give an inaccurate impression of the depth of aeration of the water if not allowed to equilibrate Lower the logger smoothly and slowly between measurements to avoid stirring up the water column Stop the logging at least 1 or 2 metres above the bottom of the borehole There is usually a sump constructed at the base of a 96 borehole which collects mud sand biofilm and other materials that form or fall into the hole These can cause unnecessary fouling or damage to the sensors We have found that readings taken when the logger is raised quickly out of the borehole often fail to agree with those from when slowly lowering the instrument Disturbance of the water column and inadequate equilibration times are possible reasons for this observation In general any data collected while pulling the logger out of the borehole should be rejected Pumping of the borehole before logging or pumping of nearby boreholes during logging can have a large impact on the ver
49. reasonably high rates The debate as to whether or not to filter was that these boreholes usually had a low turbidity and that water from these boreholes was often consumed directly Also filtering added an additional variable that could alter chemistry This last argument is essentially not applicable as proper field filtering procedures as described below virtually eliminates this effect As to the first two arguments if you suspect there may be a problem with the as delivered water then the proper approach is to collect both a filtered sample and an unfiltered sample Have both analysed and if the filtered sample is okay for consumption but the unfiltered is not acceptable then call in the water treatment experts to install an in line treatment facility to remove the offending suspended particles 14 3 FILTER APPARATUS There are two methods of filtering namely vacuum and pressure filtering Vacuum filtering speeds up all the chemical changes that require one to filter a sample in the first place Vacuum filtering is not recommended and will not be discussed here Pressure filter devices are either in line filters or syringe type filters An in line filter is one which is connected to the pump discharge line The advantage of this system is that the groundwater is filtered before coming into contact with oxygen and this is recommended There are two types a disposable in line filter or one which disassembles and takes a normal filter pa
50. samples for sensitive determinands Ensure that samples from the pilot sampling run were adequate and correctly preserved Generally iron out any potential problems before proceeding to the next step which is writing the Monitoring Programme Guide 2 4 COMPILE THE MONITORING PROGRAMME GUIDE The monitoring programme guide is a detailed document covering every possible aspect of the project see Chapter 7 Hydrological aspects of the aquifer should be considered when compiling this guide Sampling sequence must be worked out ina logical order visiting the least contaminated holes first to prevent cross contamination The guide should list all boreholes to be sampled For each borehole there must be details on its location dimensions purging requirements determinands to be analysed specific preservation and transportation procedures to be followed indeed all relevant data Note which sites are potentially hazardous and record any special precautions that need to be taken If the borehole diameter is unusual and special equipment required this must be highlighted in the programme monitoring guide Borehole home owners should be informed of the proposed frequency of sampling runs and a mutually satisfying arrangement reached Having compiled the Monitoring Programme Guide regular sampling runs may commence 2 5 CHECKLIST OF FIELD SAMPLING EQUIPMENT The following items may be of use for field sampling of groundwater Use this list to make your
51. sampling record forms and chain of custody forms References Sample Containers and Sample Preservation Sample Containers Sample bottle preparation Marking the sample bottle Sample preservation Sample size Chapter10 Water Level Measurement 10 1 Introduction 10 2 Water level measuring equipment 10 2 1 The dip meter 10 2 2 Measuring in a borehole equipped with a pump viii 91 92 92 92 93 94 95 96 97 98 99 100 101 101 103 104 104 105 106 107 107 108 110 111 111 111 112 113 114 114 114 115 10 3 Chapter 11 11 1 11 2 11 3 11 4 11 5 Chapter 12 12 1 12 2 12 3 Chapter 13 13 1 13 2 13 3 13 4 13 5 13 6 13 7 Chapter 14 14 1 14 2 14 3 14 4 14 5 14 6 14 7 Chapter 15 15 1 15 2 15 3 15 4 Chapter 16 16 1 16 2 Field procedure 10 3 1 Field procedure monitoring boreholes 10 3 2 Field procedure pollution monitoring boreholes Sample Collecting Devices Sample collecting devices Some additional comments and notes Low flow sampling Foot valve samplers References Newly Drilled Boreholes Turbid water and chemistry Microbiology and new boreholes References Purging the Borehole Introduction Field procedure Low yielding boreholes Turbid water Purging equipment To purge or not to purge The debate References Filtering Devices Introduction Sampling water supply boreholes Filter apparatus Filter materials and sizes General field proc
52. seriously questioned the validity of the flow though assumption using open boreholes in view of the fact that the effective hydraulic conductivity inside the borehole is infinitely larger than the hydraulic conductivity of any formation Any slight vertical hydraulic gradient in the aquifer around the borehole contributes to some degree of vertical movement and thus mixing inside the borehole Open boreholes are known to act as a short circuit allowing groundwater to flow from one aquifer layer to another Shapiro 2002 examined the theory conducted field experiments and concluded that It is recommended that open boreholes be permanently outfitted with borehole packers or borehole liners in instance where maintaining the hydraulic and chemical stratification in the aquifer is of importance Gravel packs are also usually of high permeability relative to the aquifer formation and can provide a short circuit along the outside the borehole even if flow is prevented in the borehole This vital point is occasionally overlooked when designing the borehole construction Make sure that the outside annulus between the casing and the undisturbed aquifer material is properly sealed thus isolating upper from lower aquifer zones An investigation by R delsperger et al 1989 R delsperger et al 1989 1991 provides proof of short circuiting in an unconsolidated aquifer with primary porosity Nitrate as NO3 at 150 mg L was found in a series
53. solutions and electrodes 161 Tables relevant to DO determination Oxygen solubility of water at different temperatures and pressures 162 Oxygen solubility of water at different temperatures and elevations 163 Correction factors to calculate the salinity effect on DO in water 164 Table C 1 Sample size preservation and holding times 165 Abbreviations and Acronyms The use of a capital L for abbreviating litre has been adopted throughout this report Alk amsl APHA ASTM BTEX Cat An CFC COC COD C CSIR DIG DNAPL DO DOC DOX DWAF EC Eh EPA GG HDPE HPC LDPE LNAPL L sec m d m hr meq L mg mg L ug L mL mm um umhos cm mS m MTBE mV Alkalinity elevation above mean sea level in metres American Public Health Association American Society for Testing and Materials Benzene Toluene Ethylbenzene and Xylenes Cations and anions Chloro fluoro carbon Chain of Custody Chemical Oxygen Demand Degrees Celsius centigrade Council for Science and Industrial Research South Africa Dissolved Inorganic Carbon Dense Non Aqueous Phase Liquid Dissolved Oxygen Dissolved Organic Compounds Dissolved Organic Halogens Department of Water Affairs and Forestry South Africa Electrical Conductivity Oxidation reducion potential Environmental Protection Agency USA Gas chromatography High density poly ethylene Heterotrophic plate count Infrared litre Low density poly ethylene Light Non Aqueous Phase
54. w 9 AIp 1e85 eyo si uo pawnsse SI spueuluu l p 1 lewpuno 6 x 2 r 1920 0 0 ww g yw ouf 4ajdwes 6uu s oyloads BulsAyeue u Ayiqeyins 10 payenjeaa q Pinoys 218 s ull ney B6uiqni Buipniou sjeleyew uononilsuoo saolnep Builduies w sa e q8uPA ww zL Huu ou 1J leq u do paesu A u ueuuu d ave yey Jonan wu aup n x uw z 0 wu 8g W 0SH _se6 dund uolsig uw St 0 WwW 0S w 09 10 01 19H lqisi tuuqns AINAWAOV1dSIC SAILISOd ajqeuen Ww ZL yu OU Jajreq 51nos luloq avy joe pate eq Jajoweig yidag ajdwes Buuoyuow nus ui z H leq_ 8 eudje mejoa se seB puoni4 se w suol SUINJOA Jo 3PH IeM Une pue sjem Buyopuow Wooo ssoio wnipey xoL DOL leloA __uon panossia ayen oeu sofew _xop u Hd Oa ___M ny q ejdwies Maa W eu xo ddv SS d Sunse Budwes 7019 3ALOVOIdVH JINY9HO SINVSYONI 10 s 914 p lqeluod L seuoBayeo om olu PAPIAIP 91 yeyo siy uo s olA p Bullduues SGNVNIWYSLAG YALVM GNNOYD Bueuo 0 1o qns si pue ainyesoy ajqeyrene Ajjuasino uo paseq si AjIgeyINS xuleuu u p uilino se s oiA p Huljdwes nys ul 104 e9 Aew si jinbe janan 10 S901 Paunjoes se YONS suonipuoo eINedS slisod p payepljosuooun u payjeysul sjam Buuolluouu Bullsix u asn 104 p uBis p ase papnjou s 3IA p ay JO IS
55. 3 7 2 7 0 6 9 6 8 6 6 6 5 6 3 6 2 6 0 5 9 5 8 34 7 1 7 0 6 8 6 7 6 5 6 4 6 3 6 1 6 0 5 8 5 7 5 6 36 6 9 6 7 6 6 6 5 6 3 6 2 6 1 5 9 5 8 5 7 5 5 5 4 38 6 7 6 5 6 4 6 3 6 1 6 0 5 9 5 7 5 6 5 5 5 3 5 2 40 6 5 6 3 6 2 6 1 5 9 5 8 5 7 5 6 5 4 5 3 5 2 5 1 162 780 11 2 10 6 10 1 9 6 9 1 8 7 8 3 7 9 7 6 7 3 7 0 6 7 6 5 6 2 6 0 5 8 5 6 5 4 5 3 5 1 4 9 Appendix B Table 2 Dissolved oxygen content of water in mg L at different temperatures and elevations in equilibrium with saturated air derived from Weiss 1970 Elevation m 0 200 400 600 800 1000 1200 1400 1600 1800 2000 Temp C 0 146 142 139 136 133 129 126 123 12 1 11 8 11 5 2 13 8 135 132 128 125 123 12 0 11 7 11 4 11 1 10 9 4 13 1 12 8 125 122 11 9 11 6 11 3 11 1 10 8 10 6 10 3 6 12 4 12 1 11 8 11 6 11 3 11 0 10 8 10 5 10 3 10 0 9 8 8 11 8 11 5 11 3 11 0 10 7 10 5 10 2 10 0 9 8 9 5 9 3 10 11 3 11 0 10 7 10 5 10 2 10 0 9 8 9 5 9 3 9 1 8 9 12 10 8 10 5 10 3 10 0 9 8 9 5 9 3 9 1 8 9 8 7 8 5 14 10 3 10 0 9 8 9 6 9 4 9 1 8 9 8 7 8 5 8 3 8 1 16 9 9 9 6 9 4 9 2 9 0 8 7 8 5 8 3 8 1 7 9 7 8 18 9 4 9 2 9 0 8 8 8 6 8 4 8 2 8 0 7 8 7 6 7 4 20 9 1 8 9 8 6 8 4 8 2 8 0 7 9 7 7 7 5 7 3 7 1 22 8 7 8 5 8 3 8 1 7 9 7 7 7 6 7 4 7 2 7 0 6 9 24 8 4 8 2 8 0 7 8 7 6 7 4 7 3 7 1 6 9 6 8 6 6 26 8 1 7 9 7 7 7 5 7 4 7 2 7 0 6 8 6 7 6 5 6 4 28 7 8 7 6 7 4 7 3 7 1 6 9 6 8 6 6 6 4 6 3 6 1 30 7 5 7 4 7 2 7 0 6 8 6 7 6 5 6 4 6 2 6 1 5 9 32 7 3 7 1 6 9 6 8 6 6 6 5 6 3 6 2 6 0 5 9 5 7 34 7 0 6 9 6
56. 6 Conductivity references pH 4 3 1 Method of pH measurement 4 3 2 pH measuring equipment and supplies 4 3 2 1 pH meter 4 3 2 2 Electrodes 4 3 2 3 pH buffers vi 25 26 26 28 29 30 31 32 32 32 33 34 36 36 36 37 38 38 39 41 41 42 42 42 43 43 44 45 45 47 47 48 48 48 49 50 50 50 51 52 52 53 53 56 4 4 4 5 4 6 4 7 4 3 2 4 pH equipment checklist 4 3 3 Field procedure for pH measurement 4 3 3 1 Calibration procedure 4 3 3 2 pH measurement 4 3 3 3 Trouble Shooting 4 3 4 pH References Eh Oxidation Reduction Potential or Redox Potential 4 4 1 Electrochemical theory 4 4 2 Method of Eh measurement 4 4 3 Eh equipment and supplies 4 4 3 1 Eh meter 4 4 3 2 Electrodes 4 4 3 3 Eh reference solutions 4 4 3 4 Equipment checklist for En measurement 4 4 4 Field procedure for En measurement 4 4 4 1 Equipment test procedure 4 4 4 2 Field measurements 4 4 4 3 Troubleshooting Eh measurements 4 4 5 Eh references Dissolved Oxygen DO 4 5 1 Methods of DO measurement 4 5 1 1 Method selection 4 5 1 2 DO electrodes 4 5 2 Equipment and supplies for DO 4 5 2 1 Sampling devices suitable for DO analysis 4 5 2 2 Checklist of DO equipment 4 5 3 Field procedure for DO measurement 4 5 3 1 Zero point calibration 4 5 3 2 High point calibration 4 5 3 3 Measurement of DO 4 5 3 4 Trouble shooting 4 5 4 DO references Alkalinity and Acidity 4 6 1 The carbonate system in water 4 6 2 Titration methods 4 6 3 Titration
57. 7 6 6 6 4 6 3 6 1 6 0 5 8 5 7 5 5 36 68 6 7 6 5 6 3 6 2 6 1 5 9 5 8 5 6 5 5 5 4 38 6 6 6 5 6 3 6 2 6 0 5 9 5 7 5 6 5 5 5 3 5 2 40 64 6 3 6 1 6 0 5 8 5 7 5 6 5 4 5 3 5 2 5 0 163 2200 11 2 10 6 10 1 9 6 9 1 8 7 8 3 7 9 7 6 7 3 7 0 6 7 6 5 6 2 6 0 5 8 5 6 5 4 5 2 5 1 4 9 Appendix B Table 3 Correction factors to calculate the salinity effect on DO in water in mg L derived from Weiss 1970 EC mS m 0 200 500 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 Temp C 0 1 00 099 0 98 0 96 0 92 0 88 0 84 0 80 0 76 0 72 0 68 0 63 0 59 2 1 00 0 99 0 98 0 96 0 92 0 88 0 84 0 80 0 76 0 72 0 68 0 64 0 60 4 1 00 0 99 0 98 0 96 0 92 0 89 0 85 0 80 0 76 0 72 0 68 0 64 0 60 6 1 00 099 0 98 0 96 0 93 0 89 0 85 0 81 0 77 0 73 0 69 0 65 0 61 8 1 00 0 99 0 98 0 96 0 93 0 89 0 85 0 81 0 77 0 73 0 69 0 65 0 61 10 1 00 099 0 98 0 96 0 93 0 89 0 85 0 81 0 77 0 73 0 69 0 66 0 62 12 1 00 0 99 0 98 0 96 0 93 0 89 0 85 0 81 0 78 0 74 0 70 0 66 0 62 14 1 00 0 99 0 98 0 97 0 93 0 89 0 86 0 82 0 78 0 74 0 70 0 66 0 63 16 1 00 0 99 0 98 0 97 0 93 0 89 0 86 0 82 0 78 0 74 0 70 0 67 0 63 18 1 00 0 99 0 98 0 97 0 93 0 90 0 86 0 82 0 78 0 75 0 71 0 67 0 63 20 1 00 0 99 0 98 0 97 0 93 0 90 0 86 0 82 0 79 0 75 0 71 0 67 0 64 22 1 00 0 99 0 98 0 97 0 93 0 90 0 86 0 83 0 79 0 75 0 72 0 68 0 64 24 1 00 0 99 0 98 0 97 0 93 0 90 0 86 0 83 0 79 0 76 0 72 0 68 0 65 26 1 00 0 99 0 98 0 97 0 94 0 90 0 87 0 83 0 79 0 76 0 72 0 69 0 65 28 1 00 099 0 98 0 97 0
58. 94 0 90 0 87 0 83 0 80 0 76 0 73 0 69 0 65 30 1 00 0 99 0 98 0 97 0 94 0 90 0 87 0 84 0 80 0 76 0 73 0 69 0 66 32 1 00 0 99 0 98 0 97 0 94 0 91 0 87 0 84 0 80 0 77 0 73 0 70 0 66 34 1 00 0 99 099 097 094 091 087 0 84 081 0 77 0 74 0 70 0 67 36 1 00 0 99 099 097 094 091 087 0 84 081 0 77 074 0 70 0 67 38 1 00 0 99 0 99 0 97 0 94 0 91 0 88 0 84 0 81 0 78 0 74 0 71 0 67 40 1 00 0 99 0 99 0 97 0 94 0 91 0 88 0 85 0 81 0 78 0 75 0 71 0 68 164 APPENDIX C Table 1 Sample size preservation and holding time for various determinands These details are mere guideline based on past experience of the authors In all cases consult the analytical laboratory prior to sampling and follow their recommendations Measurement Volume Container Preservation Maximum holding required plastic P or time ml glass G Acidity 100 P G Cool 4 24 hrs Alkalinity 200 P G Cool 4 24 hrs Aluminium 50 P A G A Membrane filter on site 6 months HNO to pH lt 2 Ammonium 500 P G Cool 4 C 24 hours H2SO to pH lt 2 7 days Arsenic 100 P A G A Filter on site 6 months HNO to pH lt 2 Boron 1000 P PTFE or HNO to pH lt 2 28 days quartz Bromide 100 P G Cool 4 C 28 days BTEX See VOCs Calcium 100 P A G A Filter on site 6 months HNO to pH lt 2 sc 100 P G NaN 3 months GC 20 100 litre P G Extract carbonate on site 1 year OG 200 G 6 months CFCs 100 Special containers 3 months COD 100 G preferred H2SO
59. 98 Noble metal electrodes can as last resort be cleaned with strong acid chromic acid or aqua regia Aqua regia make up fresh when required by mixing 1 volume concentrated nitric acid with 3 volumes concentrated hydrochloric acid Dilute by at least 50 with distilled water or Chromic acid dissolve 5 g potassium dichromate in 500 ml concentrated sulphuric acid Make up either of the acids and clean electrodes in a fume hood wearing appropriate safety gear REMEMBER add acid to water and NOT water to acid To clean the platinum electrode immerse in warm aqua regia 70 C for about one minute not longer or even the noble metal will also dissolve and then soak for several hours in tap water before use Nordstr6m and Wilde 2005 Note Chromic acid and aqua regia are toxic and highly aggressive handle with care and dispose responsibly Neutralise acids before disposal Combination electrodes should not be fully immersed in strong acid but the metal tip should still be cleaned and polished Disassembly of the electrode is not recommended for routine cleaning and should only be used when absolutely necessary Nordstr6m and Wilde 2005 A reconditioning procedure for the combination electrode after Kokholm is Rinse the surface of the platinum element with conc H SO4 Without contaminating the porous pin immerse the electrode surface for 10 to 20 minutes in warm 50 C 3 solution of K Cr O in 10 v v H2S0
60. A Performance audits should be carried out on field sampling techniques on an unscheduled basis The procedure involves using a check list to document the manner in which a sample is collected and delivered to the laboratory The goal is to detect any deviations from the standard operating procedures so that corrective action can be taken Design the audit for the monitoring programme and include in the QA plan Item 13 Chapter 6 1 For further reading see APHA 1998 and Canter et al 1987 6 4 REFERENCES APHA 1998 Standard Methods for the examination of water and wastewater 20 ed Am Public Health Assoc Washington DC Canter L W R C Knox and D M Fairchild 1987 Ground Water Quality protection Lewis Publ Michigan 101 Keith S J and L G Wilson 1982 Stacking the deck in ground water quality data Proceedings of the Arizona Section American Water Resource Association Ground Water Quality Symposium 102 CHAPTER 7 MONITORING PROGRAMME GUIDE 7 1 INTRODUCTION TO WATER QUALITY MONITORING Water quality monitoring is the systematic and careful collection and analysis of samples observations and in situ measurements with the aim of providing an information and knowledge about a water body ANZECC 2000 Fig 7 1 ANZECC 2000 shows the components of a monitoring programme The important point is that this is an interactive process so that at all times the objectives of the programme are kept in mind and the programm
61. Dissolved oxygen for example has been found to coexist with hydrogen sulphide methane or ferrous iron in many situations Nordstr m and Wilde 2005 This means that the measured Eh may not correspond with the Eh calculated from electrochemical theory using one of the redox active elements e g dissolved oxygen in the water Quantitative determinations of Eh using the platinum or other noble metal electrode method are valid only when the redox species are electro active and are present in solution at concentrations of about 10 molal and higher Nordstr m and Wilde 2005 Eh measurement is not a routine procedure and can not be measured unambiguously in most natural waters Eh readings are open to misinterpretation if the electrochemical theory behind the measurement and the practical limitations of the measurement are not clearly understood Although the determination of redox potential is fraught with difficulties and should not be considered a routine measurement there are some applications for which at least a relative measurement of the redox potential may prove extremely valuable and the effort may be justified Nordstr m and Wilde 2005 En measurements in conjunction with pH measurements are useful for qualitative insights on groundwater evolution qualitative delineation of strong redox gradients e g from artificial recharge or contaminant plumes qualitative estimates of the behaviour of multivalent elements in aqui
62. Envir Sci Techn 26 3 614 621 Puls R W and M J Barcelona 1996 Low flow minimal drawdown groundwater sampling procedures U S Environmental Protection Agency Groundwater issues report EPA 540 s 95 504 http www epa gov ahaazvuc download issue lwflw2a pdf last accessed on 5 November 2006 Saar R A 1997 Filtration of groundwater samples a review of industry practice Ground Water Monitoring Review 17 1 56 62 14 7 FILTER SUPPLIERS The authors do not claim that the supplier s list is complete nor can they guarantee the performance of the products Geotech brochures Geotech Environmental Equipment Inc 1441 West 46th Avenue Unit 17 Denver C080211 Millipore http www millipore com catalogue nsf home last accessed on 5 November 2006 QED brochures QED Groundwater Specialists P O Box 3726 Ann Arbor M1148106 134 Schleicher and Schuell Gmbh brochure Postfach 4 D 3354 Dassel Germany Available in South Africa from Laboratory and Scientific Co Pty Ltd Whatman http Awww whatman com last accessed on 5 November 2006 135 CHAPTER 15 FLOW THROUGH CELL 15 1 THE FLOW THROUGH CELL There are three factors that change when groundwater is removed from the aquifer and brought to the surface for analysis 1 the hydrostatic pressure certainly changes 2 the temperature may change 3 the sample comes in contact with the atmosphere There is not much the sampler can do to maintain pressure Tempe
63. METRE AND FRACTURED ROCK LEVEL AND Purge COLLECT THe WATER SAMPLE 128 Figure 13 1 Sketch showing the method of positioning the sampling pump in a borehole in order to avoid contaminating the water sample with stagnant water after Robin and Gilham 1987 13 3 LOW YIELDING BOREHOLES Some boreholes that are to be sampled may be low yielding and run dry when they are purged using the above normal pumping rates If one is surveying an area for general aquifer hydrogeochemistry leave the borehole to recover for a few hours When returning obtain as many measurements as possible for the water that is there as this is representative groundwater for stable ionic species but not for parameters susceptible to oxidation If the objective is to assess hydrogeochemical processes or groundwater contamination issues then consider using low flow sampling techniques Chapter 11 3 Low yielding boreholes pumped at high rates will give erroneous results for parameters that are affected by exposure to air 13 4 TURBID WATER Turbid water is the enemy of proper groundwater sampling Chapter 12 If the borehole water becomes turbid or silty the borehole must be re developed before the next sampling run Previously clear water turning turbid is usually caused by purging or sampling at a too rapid a pumping rate and causing turbulence in the aquifer Reduce the pumping rate to see whether turbidity reduces Record the revised pumping rate in the Monitor
64. O suoleBils Au lis seA snopiezeu 104 ajqeyleae s oS A p Buljdwes sayempuno b jo sad jesouab y Jo uuos s uillno yeyo siy L 11 2 SOME ADDITIONAL COMMENTS AND NOTES Bladder pump As can be seen from the matrix table the bladder pump is suitable for sampling for all determinands The bladder pump has the advantage over the helical rotor which is the only other all rounder almost excepting for sampling coliform bacteria in that the bladder pump is easy to disassemble in the field for cleaning and repair The bladder pump is also relatively inexpensive The pump alone costs about 400 The complete set up which includes a surface pulse controller the pump and all air lines costs about 1000 The cost of the air supply is not included This could be an air compressor a set of SCUBA bottles or nitrogen gas bottles Point source bailer From the table this device appears to be suitable for most components However the major drawback is that it cannot be used to purge the well Using a bailer there is a high probability that stagnant water will be collected Also when collecting the sample there is a high probability that material such as iron hydroxide may be mechanically dislodged from the borehole or borehole casing wall which may interfere with the results if precautionary measures are not taken In general bailers should never be used for groundwater sampling The main and very useful occasion for using a bailer is when col
65. OR YOUR INSTRUMENT NOTE There are many types of pH meters on the market many with different features and operating procedures to those described in this manual It is very important to read the manufacturer s instructions on the correct calibration operation and maintenance procedures for your particular instrument Some of the equipment and procedures described here may not be applicable for your instrument If so make sure you understand the manufacturer s instructions and adapt the procedures below accordingly 57 4 3 3 1 Calibration procedure For manual calibration calibrate the pH meter as follows 1 2 10 11 Label beakers for pH 7 and pH 4 buffers with a waterproof marker If alkaline water is expected use pH 7 and pH 10 buffers Place containers of pH 4 and pH 7 buffers in a bucket with running groundwater for 5 minutes to equalise temperature Measure the temperature of the running water with a thermometer and set this temperature on the pH meter Step 2 is not needed if the instrument has automatic temperature compensation Ensure electrode is filled with filling solution if liquid filled and that the junction is not clogged Rinse the pH electrode with deionised water and blot dry with soft tissue Gently tap or shake to dislodge any trapped air bubbles inside the electrode From the container of pH 7 buffer decant fresh buffer solution into the clean labelled beaker Use enough buffer solution to cov
66. PTER 20 1 WATER QUALITY GUIDELINES WEBSITES The URL addresses below are listed because they have been providing useful information at various times and may still be useful in the future As with all websites be aware that they may become outdated and that more recent information may exists elsewhere South Africa http www dwaf gov za Dir WQM docsFrame htm last accessed on 17 October 2006 World Health Organisation http www who int water_ sanitation health dwq quidelines en index html last accessed on 5 November 2006 http www who int water_san itation health GDWQ PDF DOCS qdw3 pdf last accessed on 5 November 2006 USA www epa gov OGWDW mcl html last accessed on 5 November 2006 Australia and New Zealand http www mfe govt nz publications water anzecc water quality guide 02 last accessed on 5 November 2006 United Kingdom www dwi gov UK regs si1 147 index htm last accessed on 5 November 2006 European Union Council Directive 98 83 ED of 3 November 1998 European Union URL http eur lex europa eu LexUriServ LexUriServ do uriz CELEX 31998L0083 EN HTML last accessed on 5 November 2006 http ec europa eu environment enlarg handbook water pdf last accessed on 5 November 2006 159 APPENDIX A Tables relevant to Eh field determination chapter 4 4 Appendix A Table 1 Half cell potentials mV of silver silver chloride and calomel reference electrodes relative to the standard hydrogen e
67. PVC and poly tetra fluoro ethylene PTFE or Teflon for exposure to three VOCs plus a nitro aromatic and to four pesticides They established that e Stainless steel could be properly cleaned using a hot detergent wash e PVC could be properly cleaned using a hot detergent wash e PTFE LDPE and the more adsorptive polymers needed a hot detergent wash plus drying in a hot oven e a solvent rinse a recommended procedure in earlier protocols did not aid in the removal of VOCs from these latter materials A few rules that have been established for decontamination of sampling equipment at sensitive sites are e Avoid using adsorptive materials for sampling devices and any equipment that is in contact with the water prior to sample collection e Include a hot detergent wash and oven drying in the decontamination procedure e You can remove rinsing in a solvent as part of the decontamination procedure e The optimum will be to have dedicated sampling equipment for each sampling point If you are about to embark on a sampling program at a sensitive site you will need to obtain and study the ASTM procedure ASTM 2002 or obtain the USGS procedure Wilde 2004 18 4 REFERENCES ASTM 2002 Standard practice for decontamination of field equipment used at non radioactive waste sites Document D5088 02 URL hittp www astm org cgi bin SoftCart exe DATABASE CART REDLINE PAGES D5088 htm L mystore meyo0623 last accessed on 5 Novemb
68. University of the Free State Mr E van Wyk Department of Water Affairs and Forestry While writing this manual we had extensive and informative discussions with our colleagues in the Groundwater Group at CSIR which served to clarify our thoughts In particular we would like to acknowledge the assistance of Mike Louw Pannie Engelbrecht and Gideon Tredoux Table of Contents Abbreviations and Acronyms Unit conversion factors Chapter 1 1 1 1 2 1 3 1 4 1 5 Introduction Introduction What this manual is and is not Wise sayings A brief overview of the chapters References Chapter 2 Setting the scene and pre planning 2 1 2 2 2 3 2 4 2 5 2 6 2 7 2 8 Why sample groundwater What is to be tested Planning the sampling programme Compile the Monitoring Program Guide Checklist of field sampling equipment General groundwater sampling procedure Equipment maintenance and repair References Chapter 3 Determinand selection 3 1 3 2 3 3 Introduction Inorganic determinands 3 2 1 Cations and anions 3 2 1 1 Major ions 3 2 1 2 Ammonium and nitrate 3 2 1 3 Phosphate 3 2 1 4 Fluoride 3 2 1 5 Iron and manganese 3 2 1 6 Silica 3 2 2 Trace and heavy metals 3 2 2 1 Hexavalent chromium 3 2 2 2 Arsenic 3 2 3 Encrustation and corrosion 3 2 4 EC and TDS Total Dissolved Solids 3 2 5 Chemistry References Isotopes 3 3 1 Oxygen 18 and Deuterium 3 3 2 Nitrogen 15 3 3 3 Radiocarbon 3 3 4 Tritium xii ROWDY
69. Walton Day K D L Macalaudy M H Brooks and V T Tate 1990 Field measurement of ground water redox chemical parameters Groundwater Monitoring Review Fall 1990 Waterra 2003 The Sheffield LFC flow through cell URL http www waterrauk com pages SamplingAccessories asp Flow Through 20Cell last accessed on 5 November 2006 139 CHAPTER 16 MULTIPLE LEVEL SAMPLING 16 1 INTRODUCTION In a study of natural groundwater chemistry or contamination it is often important to obtain detailed information on the vertical distribution of the chemicals In all geological materials there are heterogeneities and especially so for hydraulic conductivities Figure 16 1 shows the effect of simple layered heterogeneities on chemical transport patterns Contaminant source Stream ta Steady water table a Divide K u go flow Divide Homogeneous Ko Ky 100 Figure 16 1 Effect of layers and lenses on flow paths in shallow steady state groundwater flow systems a Boundary conditions b homogeneous case c single higher conductivity layer d two lower conductivity lenses e two higher conductivity lenses Freeze and Cherry 1979 p 397 Level determined samples collected from known depth intervals in an aquifer are becoming increasingly important in hydrogeological studies They are valuable for studies where the focus is on detailed chemical transport processes or three dimensional characteris
70. ain of custody procedures are crucial To be admissible as evidence sample results must be traceable back through their collection shipment and analysis so that the court is satisfied as to how the sample results submitted as evidence were collected transferred and claimed This is accomplished by a written record which documents the sample identity from collection to introduction as evidence 8 2 FIELD RECORD SHEET The Field Record Sheet is where the sampler records each step that she he takes during the sampling of a specific borehole or water sampling point As each and every monitoring program will have varying conditions and aims so each field record sheet will vary Thus you must prepare these for the program There are a number of items that will appear regularly and these are listed below If you carry out a Google search you will locate numerous examples many if not most from the various Government Agencies from each of the States of the USA A few of these are included at the end of this chapter The contents of a field record sheet usually comprise the following General data e The header will include the organization logo addresses and the phrase page of pages e Project name e Date of sampling run e Any license or authorization details e Name of person s sampling e Weather conditions on the day of sampling 107 Sampling site data e Borehole name you can have a few columns so that on one sheet
71. alinity A 0 1 x 0 8 100 x 1000 x 50 40 mg CaCO L The second end point V1 is 8 0 8 7 2 ml Then Bicarbonate alkalinity A 0 1 x 7 2 100 x 1000 x 50 360 mg CaCO L Therefore Total alkalinity TA As Ap 40 360 400 mg CaCO L If we know that there are no other bases present then the carbonate content will be CO 40 mg CaCOs L 40 x 30 50 24 mg CO L and HCO3 360 mg CaCO L 360 x 61 50 439 mg HCO L In the course of time it will become evident which pH values are critical for endpoint determinations and only readings in restricted pH ranges need to be taken usually 9 8 and 5 4 Under some field conditions it may be difficult to work with a burette retort stand and stirrer An alternative method is to use two or more pipettes of different volume auto pipettes are easiest to deliver the acid Write down each time you add a measured volume of acid and record the pH after gently swirling the beaker by hand Start using the larger volume pipette e g 1 ml and then change to a smaller volume e g 0 1 ml as you approach the end point With this method it is very important to keep good track of the acid additions so that you can calculate the total volume added 4 6 4 2 Acidity titration The titration for acidity is usually done with sodium hydroxide solution following the same procedure The special requirement of sodium hydroxide solution is that it can absorb COs Keep the bottle stopp
72. amplers require some time to equilibrate after installation usually several days depending on the aquifer flow properties and are then sampled from the surface by a peristaltic pump or inertial hand pump When pumped at very low rates the bundled piezometer allows a large number of samples to be collected at relatively small depth intervals The bundled piezometer system can be installed as a removable sampler in fully screened boreholes or uncased hard rock boreholes It can also be installed as a permanent multilevel sampling system by inserting a casing supported bundle in an uncased auger hole in unconsolidated sediments In uncased boreholes it is necessary to sheath the intake area with a mesh or gauze sock fitted over the end of each the tube The size of the mesh should be chosen to prevent the aquifer sediments from entering the tube This method must be viewed with due caution The problem of vertical flow in the borehole and resultant ambiguous results for hydrogeochemistry is not resolved with this method Diffusive gradient gel dialysis membrane samplers These samplers work on the principle of diffusion or dialysis to accumulate dissolved species for chemical analysis No pumping is required Several diffusive gel units or 144 dialysis units may be installed at the desired sampling depths e g by suspension on a length of weighted fishing line or mounting at desired intervals in a rigid sampler inserted into an open bo
73. ampling errors and to develop a smooth running groundwater monitoring programme 7 2 MONITORING PROGRAMME GUIDE This is a very important part of any groundwater sampling programme as the guide describes in detail the information needed by staff to locate the correct groundwater sampling point and to collect the water sample in a manner that is exactly the same as the previous sampling run and exactly the same as the next sampling run This is done to ensure that the method of sample collection does not introduce an error in the analytical result If for some very valid reason there is a change of sample collecting procedure this must clearly be documented Such a procedural change may introduce a change in the analytical results and unless there is a clear record the observed change may be interpreted as a change in subsurface conditions The monitoring programme guide consists of three parts 1 The master guide which is kept in the office 2 The field file which has a set of relevant information which is needed in the field 3 Sample records and chain of custody forms this is dealt with in more detail in the next chapter 7 2 1 MONITORING PROGRAMME MASTER GUIDE This document is kept in the office so that if some mishap should occur to the field crew this document can be referred to and copied and a replacement sampling crew 104 can continue with the sampling programme with no interruption It will contain the following
74. analytical method measures DOX as a total without distinguishing one from the other It is however possible to quantify the volatile or purgeable organic halogen POX and or the non volatile or non purgeable organic halogen NPOX by a relatively simple modification to the analytical method with an increase in cost of course This knowledge will be of importance when groundwater pollution remedial engineering design has to be implemented For example if the bulk of the DOX is volatile POX then air stripping towers might be the only remedial action needed Sample containers are properly cleaned 50 mL amber glass or clear glass stored in darkness bottles with Teflon lined screw caps which have a hole in the centre The hole in the centre is so that the bottle does not have to be opened with consequent loss of volatiles The Teflon is merely pierced and the sample removed The sample bottle must be filled taking care to reduce any loss of volatiles by carefully filling the sample bottle without turbulence Preserve samples at pH lt 2 by acidifying with concentrated nitric or sulphuric acid and keep cool at 4 C Samples should be analysed within 7 days As volatiles are part of DOX the only suitable sampling pump is a positive displacement pump e g piston or bladder pump Chapter 11 Sample collection devices A syringe is suitable but cannot be used for purging Also the sample must NOT be filtered as this will cause loss of the volatile fraction
75. anic radioactive and biological considered and notes regarding sampling depths well diameters sample delivery rates and construction materials were included The matrix was prepared in response to ground water sampling research needs expressed by the U S EPA Regional and Program Offices and is one part of EMSL LV s continuing Comparative Testing of Ground Water Sampling Methods research project Description of Sampling Devices and Construction Materials Commonly Used Open bailer Open top Bottom sealed or fitted with foot valve Available in wide range of rigid materials Point source bailer Check valve at both top and bottom Valves are opened by cable operated from ground surface Available in wide range of rigid materials Syringe sampler Sample container is pressurized or evacuated and lowered into sampling installation Opening the container and or releasing the 118 pressure allows sample to enter the device Materials may include stainless steel 316 Teflon polyethylene glass Gear drive pump Electric motor rotates a set of Teflon gears which drives the sample up the discharge line Constructed of stainless steel 304 Teflon and Viton Bladder pump Flexible bladder within Device has check valves at each end Gas from ground surface is cycled between bladder and sampler wall forcing sample to enter bladder and then be driven up the discharge line Gas does not contact sample Materials may include
76. are collecting VOC samples take a trip blank with you e A trip blank is water known to contain no hydrocarbons placed in two of the sample bottles These are carried in the cooler bag in the field and returned to the laboratory with the samples The trip blank is analysed at the same time as the field samples This is to ensure that external VOCs did not contaminate the groundwater samples e When the same sampling pump is used for several pollution monitoring boreholes collect an equipment blank also called field blank Choose one of the boreholes showing the highest level of contamination decontaminate the sampling equipment Chapter 18 and then collect a sample of the final rinse water as an equipment blank e Ensure that quality control standards are used by the analytical laboratory A quality control standard is a typical sample of known constitution which is included with every set of samples that they analyse Most laboratories use quality control standards as part of their internal QC program If your laboratory does not have use a QC standard either change laboratory or prepare your own standard On the pilot sampling run fill a 20 L container 100 with groundwater from a borehole which is representative of the area Allow the sample to stabilise for 2 3 weeks filter and then include a sample from the drum with every set of samples submitted Obviously fragile parameters such as nitrate alkalinity many organics etc cannot be
77. at least 100 times the drilling fluid loss has to be removed before one can obtain reasonable hydrochemically representative samples For the carbon isotopes the volumes needed to be removed are even more So the rule is develop develop and then develop the new borehole a little bit more 12 2 MICROBIOLOGY AND NEW BOREHOLES Most water borehole drilling fluids for rotary drilling are organic based usually guar bean based These result in high COD levels for months GWMR Forum 1987 and up to a year after completion This high COD environment is a wonderful breeding ground for bacteria The levels of HPC E coli and total coliforms increase rapidly soon after drilling and then slowly the numbers reduce This occurs even with extensive purging and sterilization so be warned that if the water is to be used for drinking water supply closely monitor the bacterial levels and ensure the water is chlorinated before use Regard any microbiological monitoring program results with 124 due care understanding that the first year of monitoring data is probably not representative of the natural conditions 12 3 REFERENCES Graham D L and Johnson V G 1991 Effects of fluid rotary drilling on hydrochemical sampling results from deep boreholes in fractured Colombia River Basalt J Hydrol 128 171 212 GWMR Forum 1987 How drilling fluids and grouting materials affect the integrity of groundwater samples from monitoring wells Groundwater M
78. ation of pollution for design and evaluation of remediation systems Lerner and Teutsch 1995 140 16 2 METHODS OF CONSTRUCTION AND APPROACHES FOR MULTILEVEL SAMPLING Multilevel sampling installations are grouped into three methods of construction 1 Multiple monitoring boreholes at one site 2 Single monitoring borehole with multiple screens and piezometers installed 3 Single monitoring borehole with a single long screen flow through or open hole The description of sampling systems in this document is by no means exhaustive but covers a wide range of methods reported in the literature over the last few decades Although becoming more common in routine pollution investigations multilevel sampling is a specialised groundwater sampling activity and the approach taken is often designed or adapted to meet the specific requirements of a particular project or site The chapter on down hole logging chapter 5 and the section on low flow sampling chapter 11 3 should also be referred to Some of the more common multi level sampling approaches are illustrated in Fig 16 2 amp lla lla sign 3 X NXN 1 gt k _ S a N gt 2 4 3 Ny A F TE oni N x N y Taek eens PE eee a raia N Figure 16 2 Types of monitoring boreholes and sampling devices After UNESCO 1972 Version A This is a gr
79. ations COD chemical oxygen demand is a parameter used in investigations of heavily contaminated waters such as sewage waste water At the low levels of organic compounds usually encountered in groundwater COD is meaninglessly inaccurate and should not be analysed or requested unless serious contamination is known to occur Depending on the laboratory a COD analysis is two or more times the price of a DOC analysis 3 4 1 SAMPLE CONTAINERS FOR ORGANICS Many of the organic compounds are toxic or pose a threat at very low concentrations In some countries the drinking water standards for some specific organic compounds are in the 0 0001 to 0 01 mg t range 0 1 to 10 ppb At such very low detection levels bias by cross contamination is of particular concern and special care must be taken with the sample containers and with all other aspects of sample collection and transport Amber or brown to reduce UV degradation glass bottles and not plastic bottles must be used Depending on the compound and thus analytical method used the required sample volume varies between 25 mL and 2 L Some laboratories prefer wide mouthed bottles so that a stirrer can be inserted into the bottle in order to thoroughly mix an extractant with the sample water Bottle caps should be Teflon lined If Teflon lined caps cannot be obtained an alternative is to use Teflon coated woven fibreglass sheets These are cut into squares placed on the mouth of the bottle and th
80. between samples 4 5 3 1 Zero point calibration A deoxygenated water sample is produced by a solution of sodium sulphite 10g Na2S20 per litre plus a trace of cobaltous chloride The steps to determine this point are as follows 1 Pour a sample of the groundwater into a 250 mL plastic bottle Add several mL of the zero DO solution Replace cap and stir This is the de aerated sample 2 Prepare the DO meter for calibration according to manufacturer s instructions 3 Switch the meter to the DO reading position Insert the electrode in the de aerated sample of Step 1 The DO reading should be less 0 02 mg L 4 If the DO reading is greater than 0 02 mg L add saturated sodium sulphite in small increments until a reading lt 0 02 mg L is obtained Add an excess of several ml to ensure low DO in the water If this can not be achieved then clean the electrodes or replace the membrane before continuing 77 4 5 3 2 High point calibration The high end of the scale requires a measurement of water with a known DO concentration Make sure you understand the term automatic correction of of your instrument It may mean that the instrument is equipped with a sensor that detects the property in question temperature is an easy one and applies the required correction It may also mean that the user should enter the required value e g altitude barometric pressure and or salinity after which the instrument will do the requir
81. bilization of municipal waters Monograph Water Research Commission Pretoria Rounds S A 2003 Web based Alkalinity Calculator URL http or water usgs gov alk last accessed 17 October 2006 88 Rounds S A 2006 Alkalinity and acid neutralizing capacity version 3 0 U S Geological Survey Techniques of Water Resources Investigations book 9 chap A6 section 6 6 Available from the URL hittp pubs water usgs gov twri9A6 last accessed on 5 November 2006 Stumm W and Morgan J J 1981 Gran titration Appendix to Chapter 4 Aquatic Chemistry 226 229 J Wiley amp Sons New York 780p 89 4 7 FIELD TEST KITS AND OTHER SHORT CUT METHODS There are a number of simple test kits available on the market that can be used to test for specific determinands in water at the borehole and obtain immediate results The results may not always be very accurate but they do enable one to make a yes no decision in the field They are thus a very useful item as they can result in significant time and cost savings during pilot sampling or when large changes of a substance are expected in a monitoring project The methods employed range from various colour methods to drop titrations to field colour comparison and to electrometric methods The method of choice depends on the accuracy requirements anticipated frequency of use skills of the operator and cost Most of these methods are short cuts of established laboratory techniques and im
82. bsen R and Andesen L J 1995a Development and testing of active groundwater samplers J of Hydr 171 223 238 Nilsson B Luckner L and Schirmer M 1995b Field trials of active and multiport sock samplers in gravel packed wells J of Hydrol 171 259 289 R delsperger M J Kiefer and T Ball 1989 Fallstudien ber Stickstoffumsetzungen in Boden und Grundwasser in den Gebieten Bruchsal Karlsdorf Neuthard und Lobdengau Final report of projects 75 84 02 and PW 86 038 DVGW Forschungsstelle am Engler Bunte Institut Univ Karlsruhe R delsperger M U Rohmann and F Frimmel 1991 A stationary packer system for layer wise groundwater sampling in monitoring wells technique and results Wat Sci Tech 23 545 553 Ronen D Magaritz M and Levy 1986 A multi layer sampler for the study of detailed hydrochemical profiles in groundwater Water Research 20 311 315 150 Schirmer M Jones l Teutsch G and Lerner D N 1995 Development and testing of multiport sock samplers for groundwater J of Hydrol 171 239 257 Shapiro A M 2002 Cautions and suggestions for geochemical sampling in fractured rock Groundwater Monitoring amp Remediation 22 3 151 164 Taylor R G Barrett M H Baines O P Trowsdale S A Lerner D N and Thornton S F 2000 Depth variations in aquifer hydrochemistry using a low cost multilevel piezometer In Sililo et al editors Groundwater Past achievements and futur
83. ccessed on 22 November 2006 Rose S and A Long 1988 Monitoring dissolved oxygen in groundwater some basic considerations Ground Water Monitoring Review 8 1 93 97 Stumm W and J J Morgan 1996 Aquatic chemistry 3 ed John Wiley amp Sons New York Weiss R F 1970 The solubility of nitrogen oxygen and argon in water and seawater Deep Sea Research 17 721 735 White A F Peterson M L and Solbau R D 1990 Measurement and interpretation of low levels of dissolved oxygen in ground water Ground Water 28 4 584 590 Wood W W 1981 Guidelines for collection and field analysis of groundwater samples for selected unstable constituents Techniques of Water Resources Investigation Chapter D2 US Geological Survey 81 4 6 ALKALINITY AND ACIDITY If the investigation requires an understanding of the chemical equilibrium related to carbonate minerals it is essential to obtain accurate values of pH and the carbonate and bicarbonate concentrations of the groundwater In such cases either conducts a total alkalinity determination titration in the field or else measures the pH during sample collection and analyse the sample in a laboratory on the same day This last procedure is recommended and of course it makes the task of the field sampler easier In many cases particularly where there are substantial quantities of free CO involved it is better to do alkalinity determinations right at the borehole on a fresh sample
84. ce The pumps are not required if the water table is less than 9 metres below surface as the samples can then be retrieved by suction not if sampling for volatiles 143 16 2 2 Open hole multilevel sampling systems Purpose constructed boreholes Versions A B amp C above are expected to give the best confidence in the results Gillham et al 1983 but it is expensive to construct dedicated multilevel boreholes Several approaches have therefore been developed for multilevel sampling in open boreholes which are used for other purposes None of these are recommended for long term monitoring These are only to be used if the boreholes are used for other purposes and one wishes to gain an indication of sub surface conditions See Section 16 3 below Examples of open hole multilevel sampling systems include e Packer systems e Bundled piezometer systems e Diffusive gel dialysis membrane samplers e Depth specific samplers e Separation pumping e Baffle systems Bundled piezometer systems Bundled piezometers are similar in design to the multiple piezometer system shown in Figure 16 2 Version B Essentially the system consists of a number of narrow tubes installed to different depths in an open borehole The tubes may be bundled together e g Powell and Puls 1993 or strapped to the outside of a rigid support casing e g Taylor et al 2000 Holes may be punched in the bottom few centimetres of each tube to increase the intake area The s
85. cent technology Follow the manufacturer s instructions wherever these differ from the procedures described in this manual 63 4 4 3 1 The Eh meter Eh measurements require a high impedance potentiometer that can be read in millivolt A pH meter with added millivolt reading capability can double as an Eh meter The meter should have a scale readable to 1400 mV with a sensitivity of 0 1 mV An instrument with temperature probe and automatic temperature compensation would be an advantage 4 4 3 2 The electrodes The oxidation reduction indicator electrode is most commonly constructed of platinum although gold and graphite may also be used The wax impregnated graphite WIG electrode is more resistant to poisoning and is recommended for very turbid samples APHA 1998 This section will deal only with the platinum electrode Consult the manufacturer s documentation for specific instructions of other electrodes Eh is defined against the standard hydrogen electrode SHE but this is impractical for field use A reference electrode with a known stable potential relative to the hydrogen electrode is used as relative reference The reference electrode is either a silver silver chloride or a mercury mercury chloride calomel electrode These are available as liquid or gel filled electrodes with various types of liquid junction e g annular ceramic quartz or sleeve type Eh values are calculated by adjusting for the difference in potential b
86. cient water until the field chemistry parameters pH EC DO Eh temperature and turbidity remain stable For most cases this involves the removal of three to five times the volume of the standing water in the borehole is sufficient and a safe working procedure The usual order of stabilization is pH temp and EC which stabilize fairly rapidly followed by Eh DO and turbidity Puls and Barcelona 1996 The last three have been shown to fluctuate slightly even after protracted purging thus care must be taken not to be too prescriptive for parameter stabilization criteria especially for turbidity We suggest that for most cases as soon as pH temp EC and either Eh or DO are stable sampling can start Open hole constructed boreholes can give results that can be erroneously interpreted even when purging has been diligently carried out This will apply when there is pressure gradient between the various horizons intersected and vertical flow and short circuiting occurs This is discussed extensively in Section 16 3 Limitations of open borehole construction 126 13 2 FIELD PROCEDURE Prior to commencing purging examine the record sheet for the borehole An important aspect of purging is that the purging should not drop the dynamic water level below the main water intersection If the water level is dropped to below this level then cascading occurs oxygen is introduced gases and volatiles are lost thus leading to erroneous results
87. colour comparisons are made In these cases some indicator and or reagent is added to a quantity of sample water in a tube and it is compared to a colour chart This is the well known method for free chlorine and pH testing in swimming pool water Various levels of complexity are available that are useful for groundwater professionals e g Aquamerck Aquaquant and Microquant of Merck Chemets of Chemetrics Aquanal of Sigma Aldrich and 90 others The variations provide for longer path length to improve sensitivity or colour comparison to enable turbid or coloured waters to be analysed These methods require more experience cleanliness of work area good light and some cost for the purchase of indicators 4 7 1 3 Field Spectrophotometry Upscaling of the visual comparison of colours requires an instrument also called a colorimeter to measure colour intensity more reproducibly Small battery powered units exist into which a sample tube can be inserted for analysis Generally some standard is required and this has to be taken on site and the instrument calibrated before use Methods exist to accommodate coloured or turbid water Suppliers known to the authors are Merck Reflectoquant Hanna Chemetrics Sigma Aldrich Aquanal 4 7 2 FIELD TITRATIONS For some determinands e g hardness and alkalinity no colour tests exist and titrations in the field need to be done The field alkalinity method using a pH meter described in
88. concentrations in the environment BUT no single method measures the entire range Within this group there are methods directed towards lighter ends namely TPH GRO TPH gasoline range organics a GC method towards middle ends namely TPH DRO TPH diesel range organics a GC method and towards the heavier ends namely TPH an IR method If you have information on the TPH source you are investigating discuss this with the laboratory and they will then use a TPH method suited to your problem BTEX analysis Benzene Toluene Ethyl benzene and Xylenes This method looks at the lighter end of the hydrocarbon range but more importantly these are the compounds that have higher water solubilities than other compounds of this group Thus they can migrate quite some distance from the source PAH analysis Polyaromatic hydrocarbons also called polynuclear aromatic hydrocarbons This method is generally used for the middle ends diesel and kerosene Again they are important for groundwater as they deal with soluble compounds MTBE analysis Methyl tertiary butyl ether is an additive to gasoline It is soluble in water and can be used as an indicator of gasoline contamination Check that MTBE is actually used in the country in which you are working It has been banned in South Africa since 2006 Some countries use other additives check with the producers and tailor your investigation accordingly Sampling of boreholes for hydrocarbons i
89. cts the muddiness of the sample It is occasionally used during surface water quality sampling when information on contamination by transported solids or sediments is required So before requesting total metals ensure you understand why you are requesting this particular analysis and how you will actually use the results If a laboratory receives an unfiltered water sample and is requested to analyse for selected metals the standard practice is to let the sample stand for a few days or centrifuge the sample decant the clear solution filter and analyse This could be meaningless for groundwater interpretation purposes as by this stage most if not all of the metals will have either precipitated out or have been scavenged by iron and manganese Thus if trace and heavy metals are to be analysed for it is most important to filter the sample and to state so on the sample bottle label A good practice is to liaise with the analytical laboratory before going into the field and ensure that they know what you are doing and what you expect from them 3 2 2 1 Hexavalent chromium Hexavalent chromium is toxic To analyse groundwater for Cr is expensive and the holding time of the sample lt 24 hours is critical If hexavalent chromium is a possible pollutant first analyse for total chromium and if it is present in significant amounts then arrange a special sampling run for hexavalent chromium after you have liaised fully with the analytical laborato
90. cusses Sample Bottles and Appendix C 1 lists the determinands and typical volumes required container type preservation and maximum holding times Arrange access to springs wells boreholes and other sampling points This may involve having duplicate keys made or ensuring that a staff member accompanies you on the site Notify property owners of your intentions to sample and discuss possible security issues with them Consider the impact of sampling upon the environment disposal of pumped water and plan rehabilitation measures Establish from the client and or the property owner what the liabilities would be should any damage to property or the environment occur as a result of sampling Where feasible consider doing a pilot sampling run This is a reconnaissance exercise to establish the project sampling procedure and it should be flexible but well documented It is on this run that relevant data on each borehole is recorded This data ranges from information about access to a particular sampling point pump type diameter of the borehole purging rates turbidity of the water and anything of relevance which will facilitate efficient future sampling of the borehole Sampling procedures for the project as a whole are established from this pilot run More than one run may be necessary to test various methods Liaise with the laboratory again to finalise such things as sample delivery and what the latest day of the week is for receipt and analysis of
91. d seasonal changes of the aquifer 10 2 WATER LEVEL MEASURING EQUIPMENT 10 2 1 The Dip meter The apparatus of choice is a twin core cable mounted on a hand winch Figure 10 1 This tool is called a dip meter The end of each wire is bared so that the open contacts are 50 mm apart Figure 10 2 A weight is hung below the bared ends The weight must be stainless steel not lead or copper as these latter will introduce contamination At the top end the circuit is completed with an indicator such as an ohm or milli amp meter using a multi meter a buzzer or a light When the bared ends are submersed in the water either the ohm meter or amp meter needle deflects or the buzzer buzzes or the light lights up This system can quite easily be made up in a workshop They are also freely available from most suppliers of groundwater monitoring equipment 114 Figure 10 1 Hand winch and twin core Figure 10 2 Close up of the probe at the cable set up fitted with a voltmeter end of the cable showing the upper for water level measurement The 6 bared end and the lower end volt battery fitting for the voltmeter soldered to the metal weight is dangling next to the voltmeter To measure the depth to water level use one of the following three methods 1 Securely attach the zero of the measuring tape at the upper open contact and lower the tape with the twin core cable If the tape is to be leftas a permanent fixture on the water level measuri
92. d Polyethylene is preferred as less adsorption occurs on it than on PVC Plastic bottles are preferred to glass for general drinking water samples due to their resistance to breakage Plastic bottles must not be used for DO and for organic compound analyses Plastic bottles only should be used for silica and boron analyses 9 2 SAMPLE BOTTLE PREPARATION Sources of error could arise if sample bottles are not properly prepared before a sampling run New bottles must be rinsed filled with water and allowed to soak for several days to remove any water soluble compounds The bottled water industry uses food grade PET plastic bottles which are specially designed not to have leachable substances in the plastic With the world wide increase of consumption of bottled water over the past 10 years these bottles are freely available and as long as the bottles are new can be used without preparation for most sampling exercises For specialised analyses such as heavy metals and organic compounds the sample bottle preparation is more involved Each section of Chapter 3 Determinand Selection has a paragraph on sample bottle preparation which must be strictly and routinely adhered to in order to produce consistent results 9 3 MARKING THE SAMPLE BOTTLE Nothing is more frustrating than returning from a sampling trip to find that the sample number and field data have been washed off or rubbed off To prevent this happening the best method is to use a waterpr
93. d and substantially revised edition For this edition two additional authors have been co opted in order to increase the depth of the manual which reflects changes in the industry This revised edition incorporates a number of additional sections such as sampling for isotopes down hole logging etc Some chapters have been substantially revised to include advances in field instrumentation such as pH meter technology and increased attention to organic compounds Other chapters have undergone only minor changes since what was relevant in 1992 is today still relevant 1 2 WHAT THIS MANUAL IS AND IS NOT The purpose of the manual remains the same as the first edition and that is to provide consistent groundwater sampling techniques that will ensure that all groundwater quality data collected is representative of in situ groundwater quality Using these techniques will reduce sampling error to a minimum Groundwater quality data collected according to these described techniques can then reliably be used to evaluate hydrogeochemical conditions Groundwater sampling for many years has been directed towards evaluating water quality of aquifers for water supply purposes Closely allied to this objective has been the curiosity of hydrogeochemists who have wished to understand the natural processes that govern changes of groundwater chemistry over the distances and time of long groundwater flowpaths Gradually over the past twenty or so years and increa
94. d point around pH 8 3 is used to determine carbonate alkalinity phenolphthalein alkalinity The terms end point equivalent point and infection point used in titration discussions all have the same meaning 82 e The second end point around pH 4 5 gives bicarbonate alkalinity methyl orange alkalinity Acidity is the lesser used opposite parameter to alkalinity It is the quantitative capacity of water to react with a strong base to a designated pH value APHA 1998 Acidity is quantitatively linked to the corrosion potential of water It is sometimes reported as negative alkalinity The endpoint needs to be specified usually it is pH 8 or 9 4 6 1 THE CARBONATE SYSTEM IN WATER Carbon dioxide bicarbonate and carbonate in groundwater originate from a variety of sources atmosphere plants soil and aquifer material The reactions that relate these species to pH in natural waters are CO H2O lt gt H2CO3 lt gt HCO H lt gt CO 2H Lower H higher pH tends to shift both reactions to the right The equations can be used to show the distribution of the different carbonate species in water as affected by pH Fig 4 6 1 At pH lt 5 there is only dissolved CO2 in solution between pH 5 and 10 bicarbonate dominate and at pH gt 10 all of it is in the carbonate specie Alkalinity as sum of HCO CO only becomes significant above pH 4 and doubles in value beyond pH 9 Within the range of
95. de PVC polypropylene Pneumatic In situ devices generally utilize the same operating principles as syringe samplers a pressurized or evacuated sample container is lowered to the sampling port and opened allowing the sample to enter Materials may include PVC stainless steel polypropylene Teflon 119 ora srenazew jqeyns jo payonsjsuod s pue Alu doid payesado pue p ue s 9 p Buiwinsse uoleojdde 104 ajqeyins Ajjesoueb SI 9IA p SAPIIPUI S3HOIAAG 7 19 0 70 0 lqeod1dde jou yw OU onewneud ONMdANVS NLIS NI ajdwies y jo Buisse6 p 10 uone Ju A id 0 p llonuo2o nj 1eo q pinoys s lei seoinap ajqeuen ww Ge a qeuen Hi se9 Ie 404 uod Buidwes 0 uld p pue suonipuoo o1BojoaboupAy oe Burdugs UIT LL p0 0 wwz ug Ontelsu d Jo Ayoedeo pue azis uole je sul Buuolluouu JO 19 uuelp Jo uonoun e ale sayes Au AIl D P ww SZ wog nup se9 19 VH1NOO sv l4 NOILONS S3O9IA3GQ ONMIdWNVS 318V LdOd ayqeuen ww GZ JqeHeA Ie6niilueo pla 1e91d uo p seq sabues obesone ale s unioA pue s lei Aanijap BuiiduuesS uoneuuuiolul JEUOIIPPe 10 s 52u 1 J 1 S 1s J lu x UO spueuluu18 p 9y JO uolo8 p 104 a qeyins sjeyeyew Jo pejonsjsuoo x uw GZ 0 WW 8g w Odt duund 1 ppelg pue payje sul Ayedoid ae sjjam Buyoyuow Bunsix yey i uluu 72 0 WwW 0S
96. de approach to redox measurement and groundwater redox measurements read Whitfield 1974 Lindberg and Runnells 1984 Hostettler 1984 Thorstenson 1984 Stumm and Morgan 1996 or Appelo and Postma 1996 4 4 2 METHOD OF Eh MEASUREMENT An electrometric method is used to measure Eh Electro active oxidised or reduced species in solution donate or accept electrons from a redox electrode usually a platinum electrode creating a potential difference between the redox electrode and a reference electrode immersed in the same solution Ideally at redox equilibrium the potential difference between the two electrodes read from a millivolt meter is equal to the redox potential Eh of the system Reference solutions with known Eh at a particular temperature are used to check the accuracy of the Eh electrode system 4 4 3 Eh EQUIPMENT AND SUPPLIES An electrometric Eh measuring system consists of the Eh meter the measuring electrode the reference electrode Eh reference solution s The measuring electrode and reference electrode may be combined into one combination electrode or Eh probe Eh is temperature dependent so a means of measuring the temperature is also required NOTE There are several Eh electrodes and combination electrodes on the market which may require slightly different maintenance and operational procedures Some of the procedures described here may also be out of date if the equipment incorporates more re
97. determinands Section 3 2 e Major cations and anions e Minor cations and anions e Trace and heavy metals e Parameters controlling encrustation corrosion 13 Environmental isotopes Section 3 3 e Oxygen 18 and deuterium e Nitrogen 15 e Radiocarbon e Tritium e CFC and SFe e Radioactivity Organic compounds Section 3 4 can be subdivided into specific and general groups Specific groups Phenols Pesticides Petroleum derived compounds General groups Dissolved organic carbon DOC Dissolved organic halogens DOX Volatile organic compounds VOC Semi volatile organic compounds SVOC Light non aqueous phase liquids LNAPL and dense non aqueous phase liquids DNAPL Microbiological indicators Section 3 5 Heterotrophic Plate Count Faecal coliforms Bacteriophages Enteric viruses and parasites 3 2 INORGANIC DETERMINANDS 3 2 1 CATIONS AND ANIONS The ions termed major cations and anions are K Na Ca Mg SO Cl Alk potassium sodium calcium magnesium sulphate chloride alkalinity carbonate plus bicarbonate 14 Other species which are often included in the list for analysis and termed minor cations and anions are NH ammonium NO nitrate plus nitrite PO phosphate F fluoride Fe iron Mn manganese SiO silica 3 2 1 1 Major ions The major ions are the main sources of salinity in groundwater and determine the general character of t
98. dify before analysis With boreholes drilled into low permeability aquifers mostly at pollution monitoring sites the problem is often turbid water Thus the rate of pumping exceeds the rate of capacity of the aquifer to yield water drawdowns are excessive and turbulent flow 131 close to the borehole mobilizes formation material Low flow sampling Chapter 11 is an approach to resolve the issue and obtain low turbidity water Alternatively filtration should be applied Burger in Braids et al 1987 presented three case studies where filtered and unfiltered samples had been collected and analysed For all three sites the dissolved concentrations filtered samples of chemical analytes were significantly lower than the total concentrations unfiltered samples Sometimes turbid water is a result of poorly constructed or inadequately developed boreholes When these are encountered the proper solution is to replace or rehabilitate the borehole Filtering the water sample from such a well is poor practice i e trying to fix a problem that should not be there The paper by Saar 1997 provides a good overview of filtration of groundwater samples Braids et al 1987 and Puls and Barcelona 1996 should also be read 14 2 SAMPLING WATER SUPPLY BOREHOLES Two decades ago sampling was mostly done to determine water quality fitness for consumption Most of these boreholes and wells were completed in high yielding aquifers and were pumped at
99. dissolved ion concentrations such as ammonium chloride or nitrate in addition to temperature and electrical conductivity Hydrolab 1997 In simple down hole logging systems a long cable probe is lowered down the borehole connected to the meter and power source which remain at the surface This method has been in common use for electrical conductivity logging using a low loss or impedance matched cable It tends to be impractical however for working at depths of more than about 50 metres Modern down hole logging instruments usually combine four to six different sensors in one submersible multi probe The sensors are attached to a submersible data logger with on board power source The whole unit is watertight and pressure rated to 20 bar or more currently instruments up to 150 bar are available This allows the logger to be lowered down the borehole on a rope to depths of up to 200 or 300 metres below surface The data logger is programmed in advance to take readings at specified time intervals Data is then retrieved by downloading to a computer after retrieval from the borehole Systems are also available where data can be transmitted via telemetry For vertical profiling depth is measured by a pressure sensor below the water table or using graduations on the rope used to lower the logger Downhole logging offers a useful addition to routine and specialised groundwater investigations by adding information about the vertical dimensi
100. drocarbon Criteria Working Group Series TPH CWG 1998 The more common petroleum products are e Petrol Automotive petrol also called gasoline is a mixture of C4 to C42 Additives include methyl tertiary butyl ether MTBE alcohols and lead additives The variety and relative amounts of additives vary for different countries There may be more than 200 compounds in a petrol product e Napthas and solvents This is a term for a variety of products in the Ce to C12 range that are aromatics or mixtures with paraffins Napthas are used as diluents for paints solvents in dry cleaning softening asphalt and in extraction processes e Aviation gasoline This is a mixture of paraffins napthenes and aromatics with a high octane rating They are all leaded e Jet fuels Comprise paraffins and napthenes in Cs to C range e Paraffin Also called kerosene is in common use as illuminant It has the same C range as jet fuel e Diesel fuel There are 5 grades of diesel fuels for uses ranging from motor cars through trucks to railroad engines The lighter diesels are mainly Cio to C44 and the heavier Cio to Czo e Fuel oils Are heavier than diesel fuel and are used for heating or are re refined to lighter hydrocarbons e Lubricating oils Have a high boiling point They are mostly complex mixtures of hydrocarbons and additives The hydrocarbons range from Czo to Cas These products are ubiquitous in our lives and can be spilled into the env
101. e active voice verbs and personal pronouns 1 5 REFERENCES APHA 1998 Standard Methods for the Examination of Water and Wastewater 20 ed Am Public Health Assoc Washington DC Appelo C A J and Postma D 1993 Geochemistry Groundwater and Pollution A A Balkema Rotterdam 536p Domenico P A and Schwartz F W 1990 Physical and Chemical Hydrogeology John Wiley and Sons New York 824p Drever J I 1997 The Geochemistry of Natural Waters Prentice Hall Upper Saddle River 436p Fetter C W 1999 Contaminant Hydrogeology Prentice Hall Upper Saddle River 500p Hem J D 1992 Study and interpretation of the chemical characteristics of natural water 39 ed U S Geological Survey Water Supply Paper 2254 263p Weaver J M C 1992 Groundwater sampling a comprehensive guide for sampling methods Report TT 54 92 Water Research Commission Pretoria CHAPTER 2 SETTING THE SCENE AND PRE PLANNING 24 WHY SAMPLE GROUNDWATER Why sample for groundwater quality The answer to this important question will assist in the design of the sampling study and the field sampling program Groundwater is sampled for a variety of reasons e Probably the commonest is to assess the groundwater quality for fitness for use This fitness for use can be for irrigation for human consumption for use in a factory for livestock watering etc e Hydrochemical data is also used to understand the hydrogeology of an aquifer i e the recharge th
102. e adsorption pyrolysis titrimetric method for DOX measures only the total molar amount of dissolved organically bound halogen retained on the carbon adsorbent it yields no information about the structure or nature of the organic compound to which the halogens are bound or about the individual halogens present It is sensitive to organic chloride bromide and iodide but does not detect fluorinated organic compounds 36 DOX measurement is an inexpensive and useful method for screening large numbers of samples before specific and often more complex analyses for extensive field surveying for pollution by certain classes of synthetic organic compounds in natural waters for mapping the extent of organo halide contamination in groundwater for monitoring the breakthrough of some synthetic organic compounds in water treatment processes and for estimating the level of formation of chlorinated organic by products after disinfection with chlorine When used as a screening tool a large positive i e above background measurements DOX test result indicates the need for identifying and quantifying specific substances In saline or brackish waters the high inorganic halogen concentrations interfere with the analysis method The possibility of overestimating DOX concentration because of inorganic halide interference always should be considered when interpreting results APHA 1998 The DOX spectrum comprises both volatile and non volatile components The
103. e cap is screwed on All sample bottles must be thoroughly cleaned prior to sample collection The accepted cleaning procedure is to wash in hot detergent solution rinse in warm tap water rinse in dilute hydrochloric acid and finally rinse in distilled water The bottles are then put into an oven at 300 C overnight The Teflon lined caps are washed in detergent rinsed with distilled water and heated to 200 C overnight After heat treatment the bottles are capped 31 Use a strongly constructed case for transport of the glass bottles being large and made of glass they are susceptible to breakage 3 4 2 SAMPLING EQUIPMENT FOR ORGANICS The sampling device used to collect a groundwater sample for organic content analysis must be chosen with great care Many of the organic compounds are considered undesirable at low concentrations For example the maximum level for chloroform in drinking water is 0 1 mg L Thus any device which either introduces bias due to its construction materials or to its method of pumping should not be used when sampling groundwater for organic content analysis As many if not most organic compounds are either semi volatile or volatile any device which reduces pressure is not suitable i e suction lift pumps peristaltic pumps surface located centrifugal pumps and air lift pumps Gas driven piston pumps have limited suitability for volatile organic sampling An electric submersible is a centrifugal pump and
104. e challenges IAH2000 Conference Proceedings Balkema Rotterdam UNESCO 1972 Ground water studies UNESCO Press Paris Walton Day K D L Macalaudy M H Brooks and V T Tate 1990 Field measurement of ground water redox chemical parameters Groundwater Monitoring Review Fall 1990 Zhang H and Davison W 1999 Diffusional characteristics of hydrogels used in DGT and DET techniques Anal Chem Acta 398 329 340 151 CHAPTER 17 PROTECTIVE CLOTHING Protective clothing to protect the sampler may be required in some waste site investigations The degree of protection required depends upon the nature of the site being sampled and the physical chemical and biological properties of the water that will be handled In many cases the individual waste products are relatively harmless but when combined in the waste disposal site they can react to produce hazardous by products All countries will have legislation that lays down stringent guidelines as to safety equipment that must be worn at any site where hazardous materials may be found To assess the nature of the hazard a photo ionization meter or explosimeter can be used Lower the probe down the well take a reading record and then take appropriate action This should be done on the pilot sampling run and potential hazards noted Waste disposal sites can be split into two classes namely e Hazardous waste sites e Non hazardous waste sites Hazardous waste sites are specially
105. e constituents To evaluate the mobility of pollutants in the subsurface environment knowledge of the true in situ Eh is essential Dissolved oxygen DO concentration is affected by aeration of the water Thus DO needs to be measured using a flow through cell DO measurement is essential for groundwater pollution studies as the DO concentration together with Eh regulates the valence state of trace metals and constrains the bacteriological metabolism of organic compounds Alkalinity is measured in the field since degassing of CO could cause precipitation of carbonates If precipitation of carbonates occurs the laboratory analytical results will reflect a lower alkalinity than is actually found in the formation water Field alkalinity is important for carbonate rock hydrogeochemical studies and is essential for water stabilization investigations 41 TEMPERATURE Temperature is an important measurement because it affects many chemical and biological reaction rates Temperature measurements are often the easiest of all of the in field measurements but are still subject to error if not properly understood The following uses for temperature measurement can be cited e Species solubility is temperature controlled i e for most species the higher the temperature the more soluble they are The apparent exception is calcium carbonate deposition in kettles and boilers which is actually due to CO de gassing thereby causing carbonate deposition e
106. e ferrous iron concentration from the total iron concentration A method for direct determination of Fe using a selective complexing agent acetohydroxamic acid has also been developed which gives more accurate speciation results Bangthanh et al 1999 Using filtered and unfiltered samples the colloidal and dissolved fraction of each redox species of iron can also be determined 3 2 1 6 Silica Silica is sometimes required for determining the source rock of the aquifer for water quality analysis for boiler feed water and for some geochemical modelling The form that silica takes in groundwater samples can be quite complex and is not that well understood pH is a controlling factor Sampling for silica Silica can appear as large colloidal particles in which case even a 2 micron filter will remove some of these particles A 0 2 micron filter will have an even greater removal effect Thus determine what the needs of the project are and what filtering is required before sampling Analyses can be done on the same samples as taken for the major ions 3 2 2 TRACE AND HEAVY METALS Which of the many trace and heavy metals should one analyse This depends on what information is required from the groundwater monitoring or investigation programme 17 These metal ions are generally relatively immobile under normal groundwater flow conditions Low pH and or Eh cause the solubility of metals to increase When low pH and or Eh dev
107. e flow the water rock interactions and the discharge processes The ideal is to find convergence between hydrogeochemistry and the hydraulic flow data e Investigations for groundwater pollution require sampling This is both to identify and quantify the occurrence of the pollutants in groundwater and to investigate the processes around the pollution event s e Water quality monitoring is the systematic collection of samples and observations on a regular basis to identify changes in a water body ANZECC 2000 The quality of water resources have tended to decline worldwide due to pollution climate changes over exploitation of aquifers etc Regular checks are therefore required to identify future risks in time in order for remedial measures to be taken Whatever the intention of sampling groundwater it is important to do the sampling properly A properly collected sample is a water sample that in terms of physical and chemical properties is as close as possible to the groundwater in situ in the aquifer 2 2 WHAT IS TO BE TESTED The selection of determinands to be analysed depends on the purpose of the water quality survey as described above and needs careful consideration The sampling tree Table 2 1 is a reference table that can be used to determine what field determinands need measuring and what the laboratory needs to analyse Establish for what purpose you need to know the water quality then refer to Table 2 1 and design your field
108. e horizon with the higher of the hydraulic gradients will flow in the borehole and into the horizon with the lower pressure Collecting samples using temporary moveable packers will result in a correct sample for the one horizon but a mixed sample for the other horizon The correct method is to leave a permanent packer in the borehole and only collect the samples after the borehole has stabilised Multi port sock samplers A sock sampler consists of one or more elongated packer balloons or socks up to several tens of metres in length which are inflated with air or water after installation in the borehole Schirmer et al 1995 Jones and Lerner 1995 This displaces the water over a long section of the borehole and avoids vertical circulation Multiple sampling ports are created by tubing that runs down from the surface either inside the packer elements or between the packer and the borehole casing Multi port sock samplers may be used as removable devices or as semi permanent installations up to a maximum depth of around 100 metres Several modifications have been made to the multi port sock samplers since the original concept was proposed by Andersen 1982 Jones et al 1999 describe a double walled sock sampler filled with benthonite slurry Inlet ports at fixed depth intervals along the sock are connected by Teflon tubes to individual gas drive or bladder pumps inside the sock Each pump is sampled via an HDPE tube running to the surfa
109. e open borehole A water level measuring device that is useful for equipped boreholes which do not have such piezo tubes fitted is a sonic water level meter This can see past the riser main cabling and other fittings Its accuracy is about 0 2 of the depth to the water level but the readout accuracy is 0 025 m It is however a fairly expensive item compared to the dip meter costing about R7000 10 3 10 3 1 FIELD PROCEDURE Field procedure general monitoring boreholes Lower the sensor of the dip meter down the borehole or the piezo tube until the needle deflects the buzzer or light goes on Raise it until it stops deflecting or going off This is the water level Measure the water level depth using the datum point which should be marked on the casing usually the top of the casing Re check the water level and record Lower the weight until the bottom of the borehole is felt and record the depth Has siltation occurred since it was last measured Record the data Note that lowering to the bottom of the borehole will disturb the water column and dislodge particles that are loosely attached to the sidewall If the borehole is to be purged i e the borehole has a reasonable yield of water this may not affect the sample integrity However for low yielding boreholes for which purging may not be done then rather first collect the water samples and measure the depth of borehole after completion of sample collection Remov
110. e re assessed if necessary The objectives should never be cast in stone Conversely the monitoring programme should only be altered if there is a real and valid reason and the change will result in a better end result Program objectives Data analysis and interpretation Reporting and Information dissemination 103 Figure 7 1 Framework for a water quality monitoring programme from ANZECC 2000 This groundwater sampling manual is not intended to describe in fine detail the methods of developing a monitoring programme as in Fig 7 1 It is rather a description of the methods within the part of the programme described as field sampling methods in Fig 7 1 There are a number of documents discussing the design of monitoring programmes Amongst these the following two should be referred to Design of networks for monitoring water quality Sanders et al 1983 and Australian guidelines for water quality monitoring and reporting ANZECC 2000 Things to be considered by the designers of the monitoring programme are effective sampling significant parameters laboratory requirements cost time and efficiency Each programme should be specifically designed and on occasion deviate from normal sampling procedures to achieve a better end result Liaison with the laboratory is of paramount importance and the designer should work hand in hand with laboratory managers Pilot sampling runs are vital to detect possible initial s
111. e surface and measure the thickness of LNAPL film relating this thickness to the intake area of the bailer Decant the LNAPL sample into a properly cleaned glass bottle and seal with a Teflon lined screw cap Drop the bailer to the bottom of the borehole and collect the DNAPL sample measure the thickness of the layer relate this to the intake area of the bailer decant the DNAPL into a properly cleaned glass bottle and seal with a Teflon lined screw cap 38 Interface meters are a relatively new development on the market These are similar to dip meters in that the interface probe is lowered down the borehole with a special measurement tape The top and bottom of the NAPL is then measured and an accurate thickness of the immiscible layer is noted These are quite expensive items and are useful when regular measurement and monitoring of NAPL polluted sites are being done It must be noted that the thickness of the NAPL layer in the borehole is not a true reflection of the NAPL layer in the aquifer 3 4 5 ORGANICS REFERENCES APHA 1998 Standard Methods for the Examination of Water and wastewater 20 ed Am Public Health Assoc Washington D C DWAF 1996 South African Water Quality Guidelines Volume 1 Domestic use 2 ed Department of Water Affairs and Forestry Pretoria Freeze R A and Cherry J A 1979 Groundwater Prentice Hall New Jersey Lehr 1989 Toxicological Risk Assessment editorial Groundwater 30 1 2 and
112. e the cable and clean off any rust or oil Field procedure pollution monitoring boreholes If the borehole being sampled is a pollution monitoring borehole then due consideration must be taken as to the suitability of the materials that will come into contact with the contaminant water Can these be properly cleaned Refer to Chapter 11 for a detailed discussion on materials If each borehole is properly purged and sampled in order i e from least to most contaminated the risk of cross contamination will be minimized and there is no need to decontaminate your water level cable until the final borehole If not then clean it thoroughly before doing anything else If floating NAPLs such as hydrocarbons are present these will coat and prevent the simple electrical device as described above from working properly If LNAPLs are suspected to be present or are the reason for sampling then a specially designed water level meter must be used This 116 measures both the water level plus the thickness of the LNAPLs These can be purchased from specialist suppliers An alternate measuring device is a plopper This is a smallish cup shaped weight attached to the measuring tape This is lowered and when the down pointing cup touches the water or NAPL layer a plop is heard This is repeated a few times to be sure the correct liquid level is being measured A small brass bell with the clapper removed works well Stainless steel SS316
113. ected of being hazardous e g explosion or corrosion hazard special shipping procedures may be required by the courier Check with the courier for restrictions and procedures 4 Record field measurements and other important data on Field Record Sheet that meets site specific needs For legal purposes indelible ink should be used for recording all data Errors in field records should be crossed out with one line and initialled 5 When required or applicable use photographs to document sample locations pollution sources violations etc Preferably use a camera that print the date on which the photos were taken 6 Make sure that samples are safely packed so they do not break during transport If field blanks and or trip blanks are required include them in the same packing case Maintain physical possession of the collected samples until they are properly transferred to the laboratory custodian or the courier 7 Obtain a sample possession transfer receipt a copy of the dated and signed chain of custody record after transferring possession of the samples to the laboratory custodian or the courier 8 4 WEB ADDRESSES FOR FORMS Wisconsin Home site http www dnr state wi us org water dwq gcc Pubdwnld htm last accessed on 5 November 2006 Sampling document http www dnr state wi us org water dwg qw pubs field pdf last accessed on 5 November 2006 http www dnr state wi us org water dwg qw pubs desk_a pdf last accessed on
114. ed correction So please make sure you understand every button and knob on your instrument before leaving for the field This you do by reading and understanding the manufacturer s manual The usual high point calibration method is to place the electrode in a bottle with air at 100 moisture content Use sample water especially in high salinity cases Most DO instruments are supplied with an equilibration flask containing a sponge that can be wetted into which the electrode is inserted An alternative is to make a bottle of air saturated water by shaking water in the presence of air or having air bubbled through the water 1 Pour a sample of the groundwater into the equilibration flask and insert the electrode Alternatively use a 1 L plastic bottle and aerate for 15 minutes by shaking vigorously after which you should pour an aliquot of the aerated sample into a clean 250 mL plastic bottle and insert the electrode 2 Switch the DO meter to the DO setting position and allow the meter to settle If required set the pressure and temperature dials to the correct values 3 For a fully automated pressure and temperature meter calibration will now be complete and the setting can be stored The meter is now ready for use 4 For a non automated system you should calculate the DO concentration of the aerated sample by taking the water temperature the barometric pressure alternatively elevation and the salinity into account Follow
115. ed in the laboratory to ensure that all leachable material has been removed Analytical grade nitric acid must be added to the bottle before the filtered sample of groundwater is added The acid can be added to the bottle either in the laboratory or in the field If the bottle is pre acidified then acid loss can occur if the bottle is either over filled or rinsed out In the field acid is added either by using ampoules recommended or by buretting not recommended The ampoules contain the correct amount of acid for the sample bottle Their narrow necks with a cut groove are easy to break without spilling After pouring out the acid wash out the ampoule with plenty of water before disposing of it in a rubbish bag do not litter At all times when working with concentrated acid wear acid proof gloves and protective eye gear For low level trace metal sampling it is advisable to collect a field blank as well see section 6 2 When a water sample is not filtered suspended solids are collected in the sample bottle as well If this water sample is subsequently acidified and analysed for metals the results will reflect the muddiness of the water sample as metals will be leached by the acid from the clay particles and suspended solids Total metals is a determinand that is sometimes requested This involves the acidification of an unfiltered sample This is however a meaningless determinand for groundwater 18 quality as it merely refle
116. ed water for long periods of time as salts may leach from the electrode If the electrode becomes clogged it may help in some cases to place the electrode in warm water 60 C for a short time one minute or less to liquefy the salt gel and rejuvenate the junction Wilde et al 2006 54 Liquid filled electrodes require periodic refilling of the electrolyte solution Filling solutions are usually potassium chloride KCI but differ in concentration for different electrodes e g 1M 3M saturated solution Check the manufacturer s instructions for the correct solution for your electrode Remove salt crystal deposits from the outside of the electrode and membranes before use by rinsing it with deionised water Electrodes using saturated KCI may have some crystals inside the filling solution chamber which do not require dissolving Before using the electrode top up the filling solution so that it reaches the bottom of the fill hole on the side of the electrode When measuring pH always unplug the fill hole before use and replug afterwards If the electrode has not been used for some time it may need reconditioning by replacing the filling solution see manufacturer s instructions Use a syringe to drain out the old solution flush the chamber with deionised water several times if necessary to remove crystals and refill with the correct solution Cleaning solutions are available in the market that may extend the life of
117. edure References Filter suppliers Flow Through Cell The flow through cell The bottle and cork method The open bucket method References Multiple Level Sampling Introduction Methods of construction and approaches for multilevel sampling 16 2 1 Single hole multilevel sampling 16 2 2 Open hole multilevel sampling systems 16 2 3 Summary of multilevel sampling techniques 116 116 116 118 121 121 122 122 124 124 125 126 127 129 129 129 129 130 131 132 132 133 134 134 134 136 138 138 139 140 141 143 144 146 16 3 Limitations of open borehole techniques 148 16 4 Fractured rock considerations 149 16 5 Core volume sampling 149 16 6 References 150 Chapter 17 Protective Clothing 152 Chapter 18 Decontamination 18 1 18 2 18 3 18 4 Introduction 154 Basic Decontamination Routine 154 Decontamination at Sensitive Sites 155 References 155 Chapter 19 Sampling of Wetlands Springs Seeps Pits and Wells 19 1 19 2 19 3 19 4 19 5 Sampling wetlands 157 Sampling springs 157 Sampling groundwater seeps 158 Sampling riverbed pits 158 Sampling large diameter dug wells 158 Chapter 20 The Last Chapter 20 1 Appendix A A 1 A 2 A 3 Appendix B B 1 B 2 B 3 Appendix C Water Quality Guidelines Websites 159 Tables relevant to Eh determination Half cell potentials of reference electrodes 160 Temperature dependence of Eh for reference solutions 160 Redox potentials of reference
118. elop as is typical at a pollution site trace metal concentrations can rapidly increase i e the metals from the insoluble phase are mobilised Then again when the groundwater is brought to surface CO degassing and aeration occurs causing pH to rise and the Eh to tends towards oxidising conditions causing the valence state of some of these metals to change to less soluble phases causing them to precipitate onto the sample bottle In addition when iron or manganese precipitate they are strong scavengers adsorption that will remove many metals from the solution by co precipitation From a health point of view the important trace elements to guard against are cadmium mercury lead and arsenic the dangerous four since these have the most deleterious effects on humans Sampling for trace metals It is important to filter a sample for analysis as rapidly as possible after the groundwater has been brought to surface and with minimum exposure to the atmosphere The filtered water is acidified to pH lt 2 to keep the metals in solution Some laboratories request that the sample not be acidified in the field These laboratories prefer to control the acidification in the laboratory allowing sufficient time before analysis for any metals that may have precipitated to re dissolve The sample bottles can be either plastic or glass It is best to use new bottles as old bottles may have metals adhering to the sides The bottles must be acid rins
119. en permeable membrane The membrane polyethylene or fluorocarbon serves as a diffusion barrier against impurities but is transmissible to oxygen The rate at which oxygen diffuses through the membrane is proportional to the pressure differential across the membrane Since all the oxygen is immediately consumed at the cathode the current through the electrode system is then proportional to the oxygen diffusion rate through the membrane which is itself proportional to the absolute pressure of oxygen outside the membrane Suitable two point calibration procedures are used to convert this current to a DO measurement The critical parts of the electrode system are the membrane which can easily get damaged or fouled with contaminants and the electrodes which accumulate products from the oxygen consumption reaction Successful field measurements require proper sampling to ensure sample integrity stability of the instrument readings and proper calibration to convert instrument readings into meaningful DO results 75 4 5 2 EQUIPMENT AND SUPPLIES FOR DISSOLVED OXYGEN 4 5 2 1 Sampling devices suitable for DO analysis It is quite easy to introduce air and oxygen in water and therefore only some methods of collecting the water sample for DO testing from the borehole are acceptable Table 4 5 2 The rule is that no air should contact the sample and the least amount of suction to be applied to lift the sample to the surface The better pumping me
120. equipment 4 6 4 Procedure for alkalinity and acidity determination 4 6 4 1 Field titration 4 6 4 2 Acidity titration 4 6 4 3 Alkalinity and acidity units 4 6 5 Alkalinity and acidity references Field Test Kits and other short cut methods 4 7 1 Colour methods 4 7 1 1 Indicator strips 4 7 1 2 Visual colour comparisons 4 7 1 3 Field spectrophotometry vii 57 57 58 59 59 60 61 62 63 63 64 64 65 66 66 66 68 70 72 73 74 74 75 76 76 76 77 77 78 80 80 80 82 83 84 85 86 86 87 88 88 90 90 90 90 91 4 7 2 Field titrations 4 7 3 lon selective electrodes 4 7 4 H2S strip for coliforms 4 7 5 References 4 7 6 Suppliers of field equipment Chapter 5 Down hole logging for field determinands 5 1 5 2 5 3 5 4 5 5 Chapter 6 6 1 6 2 6 3 6 4 Chapter 7 7 1 7 2 7 3 Chapter 8 8 1 8 2 8 3 8 4 8 5 Chapter 9 9 1 9 2 9 3 9 4 9 5 Introduction Calibration and maintenance of logging equipment Helpful hints for operation of down hole loggers A cautionary note on down hole logging References Quality Assurance Introduction Quality control Quality assessment References Monitoring Programme Guide Introduction to water quality monitoring Monitoring programme guide 7 2 1 Monitoring Programme Master Guide 7 2 2 Monitoring Programme Field Guide References Sample Records and Chain of Custody Introduction Field record sheet Chain of Custody Web addresses for field
121. er 2006 Parker L V and Ranney T A 1997a Decontaminating materials used in groundwater sampling devices Cold Regions Research and Engineering Laboratory Special Report 97 24 URL http www crrel usace army mil techpub CRREL Reports reports SR97_24 pdf_ last accessed on 5 November 2006 155 Parker L V and Ranney T A 1997b Decontaminating groundwater sampling devices Cold Regions Research and Engineering Laboratory Special Report 97 25 URL http www crrel usace army mil techpub CRREL Reports reports SR97_25 pdf last accessed on 5 November 2006 Wilde F D 2004 Cleaning of Equipment for water sampling version 4 2004 U S Geological Survey Techniques of Water Resources Investigations book 9 chap A3 Obtainable from http oubs water usgs gov twri9A3 last accessed on 22 November 2006 156 CHAPTER 19 SAMPLING OF WETLANDS SPRINGS AND GROUNDWATER SEEPS 19 1 SAMPLING WETLANDS There is an increasing awareness of the role that springs seeps and wetlands play in the maintenance of various ecosystems and this area of groundwater science is called Groundwater Dependant Ecosystems As a consequence some sampling programs will include springs seeps and wetlands Many if not most wetlands are maintained by groundwater in flow In order to collect samples of this groundwater great care must be taken to ensure that the water being sampled is actually groundwater flowing into or towards the wetland and that i
122. er the bulb or the FET part of the pH electrode and the reference junction Immerse the electrode in the pH 7 buffer and agitate gently The bulb of a glass electrode should not touch the bottom or sides of the beaker Adjust the pH meter value to match that of the buffer pH Look up the adjusted pH of the buffer solution in the temperature correction tables if there is no temperature compensation on the instrument The tables are usually on the side of the buffer stock solution bottle Remove the electrode rinse with deionised water and blot dry From the container of pH 4 buffer decant fresh buffer solution into the next clean labelled beaker and immerse electrode as before Adjust the pH meter to read the second value temperature compensated if necessary The adjustment may either be made with the same knob button or screw as for the first buffer or with a separate one for buffer 2 slope adjustment or even the temperature knob Check the instrument manual Rinse the electrode blot dry and re check the value of the pH 7 buffer If the value is within 0 05 pH of the original proceed with step 11 If drift has occurred repeat steps 5 to 9 until two successive reading are obtained without needing further adjustment The pH meter is now calibrated Discard all used buffer solutions Note If the entire calibration procedure has to be repeated more than three times there is probably a problem with the pH meter elect
123. erable cost The selection of a set of suitable determinands depends on the purpose of the project Groundwater hydrochemical studies can be divided into three broad categories 1 Water quality surveys for the purpose of water consumption 2 Hydrochemistry surveys 3 Groundwater pollution investigations 4 Water quality monitoring Under each of these categories there are specific subdivisions each of which requires a different set of determinands These are summarized in the sampling tree Table 2 1 which can serve as a guideline for determinand selection The selection of determinands is very important for the effective planning of sampling and analytical protocols You must know what to do with the results before going into the field For exploratory efforts i e when you are not quite sure beforehand what the specific requirements will be it is better to obtain more chemical data than the immediate needs require A minimum in such a case would be field measurements a full major cation and anion analysis plus a DOC analysis Once the specific requirements are known later sampling runs can be more selective Bear in mind the cost implications since analysis costs can escalate rapidly with multiple samplings Useful determinands can be divided into five groups namely Field determinands Chapter 4 e Temperature e Electrical conductivity EC e pH e Oxygen reduction potential Eh e Dissolved oxygen DO e Alkalinity Inorganic
124. ered and discard used solution from the buret The pH endpoint is selected to fit the nature of the acid producing compounds in the water In natural waters where dissolved CO is the only acid present titration is carried to pH 8 3 and reflects the amount of CO dissolved in the water In polluted waters the required endpoint may be different A general practice is to titrate to pH 3 7 methyl orange endpoint and then to pH 8 3 phenolphthalein endpoint APHA 1998 method 2310B Results should be reported as acidity to pH and can be expressed in mgCaCO L or meq L Unpolluted water with high CO content low pH needs to be handled with care to minimize CO loss Water polluted by other acids is less fragile 87 4 6 4 3 Alkalinity and acidity units Alkalinity and acidity concentrations are usually reported as mgCaCO3 L This is an equivalent unit and equates all the contributors of the alkalinity as if they were CaCO which they usually are not This unit has developed in the water treatment industry and has become standard in the South African water supply industry The other equivalent unit is milli equivalent litre meq L which is more popular amongst chemists In other countries measured alkalinity results are reported as the individual bicarbonate HCO and carbonate CO components Carbonate is determined from the first endpoint and bicarbonate from the second endpoint Figure 4 6 2 The conversion formulae are as f
125. etween R10 R20 Sobsey and Pfaender 2002 reviewed many variations of the H2S strip test Genthe and Franck 1999 tested the method and its application in South African rural water supply projects and are now recommending the method and selling built up kits Mosley and Sharp 2005 describe the method and production of kits from common chemical supplies Although the kits are simple to make their version can also be purchased HACH chemical company make a H2S test called the Pathoscreen test It is described as Bacteria Hydrogen Sulphide Producing Method 10032 for the detection of Salmonella Citrobacter Proteus Edwardsiella Klebsiella Some spp Cost is R200 per test 4 7 5 REFERENCES Rundle C C 2006 A Beginners guide to ion selective electrodes URL http www nico2000 net Book Guide1 html last accessed on 22 November 2006 Genthe B and M Franck 1999 A tool for Assessing Microbial Quality in Small Community Water Supplies an H2S Strip Test Water Research Commission Report 961 1 99 Pretoria 33p 92 Mosley L M and Sharp D S 2005 The hydrogen sulphide H2S paper strip test A simple test for monitoring drinking water quality in the Pacific Islands South Pacific Applied Geoscience Commission SOPAC Technical Report 373 Suva Fiji URL http www sopac org data virlib T R T RO373 pdf_ last accessed on 17 October 2006 Sobsey M D and Pfaender F K 2002 Evaluation of the H2S method for the detection of fecal
126. etween the hydrogen electrode and the chosen reference electrode This half cell potential Eagagci OF ExgHgeci2 is dependent on the type of electrode filling solution concentration and temperature consult Appendix A 1 Combination electrodes which combine the Eh electrode and the reference electrode in one probe are commonly used for Eh measurements Before use non sealed reference or combination electrodes should be filled with the correct electrolyte solution to the level of the fill hole Make sure that the reference electrode junction is properly wetted Electrode performance Unlike the pH measuring system Eh electrodes cannot be calibrated The electrode is tested for accuracy using Eh reference solutions but the slope cannot be adjusted as for pH The electrode testing procedure with standard solutions is described in the following section Electrode maintenance and storage Platinum electrodes may be of foil wire ring or billet type APHA 1998 Keep the metal surface of the electrode brightly polished and clean of coatings or mineral deposits for good performance A billet tip is more easily cleaned than a wire tip on a platinum electrode Nordstr m and Wilde 2005 Short term storage Immerse the combination electrode in deionised water to above the reference junction and keep the fill hole plugged with a moistened rubber sealing ring or with paraffin film to reduce evaporation from liquid filled electrodes 64 Store the
127. f determinands in the sub surface or any such geochemical processes Nor are there any descriptions of laboratory analytical methods For this type of information the reader must refer to the many excellent text books such as Hem 1992 Domenico and Schwartz 1990 Appelo and Postma 1993 Drever 1997 APHA 1998 and Fetter 1999 1 3 SOME WISE SAYINGS As with all activities there are a few wise sayings proverbs which seem to help one to reduce wasted time and effort and keep the job simpler Here are some wise sayings for groundwater sampling e There is no excuse for collecting a sample which due to its method of collection gives doubtful data e A properly collected borehole water sample is cheaper than having to return to site to re collect a sample poorly collected the first time e A practical on site demonstration of proper sample collecting techniques is better training than giving the sampler this manual to self train 1 4 A BRIEF OVERVIEW OF THE CHAPTERS Chapter 2 is a broad outline of the manual From Table 2 1 according to the field of investigation which is either groundwater consumption or groundwater hydrochemistry survey or groundwater pollution monitoring one can determine those field determinands and laboratory determinands that need to be measured The three remaining sections are Planning the sampling programme checklist of sampling equipment required in the field and general groundwater sampling
128. f electron transfer Positive values of Eh indicate more oxidised environments negative more reduced conditions Redox equilibria in solution are governed by the Nernst equation This means that Eh can theoretically be calculated from the activities of the dissolved redox active species For example using the oxidation of ferrous iron the simple half reaction Fe Fe e yields the following expression for Eh Eh E 2 303RT nF log aFe aq aFe aq where Eh is the equilibrium redox potential in volts E is the standard potential if all substances are present at unit activity at 25 C and 1 bar also in volts the number is usually looked up from a table n is the number of electrons in the half reaction in this case 1 F is Faraday s constant 96 42 kJ Volt gram equivalent R is the gas constant 8 314 x 10 kJ mol deg Kelvin T is the temperature in degrees Kelvin C 273 15 62 aFe and aFe are the thermodynamic activities of the free ions of reduced and oxidised iron in solution calculated from measured analytical concentrations using an aqueous speciation software program The problems of slow redox reactions non equilibrium conditions multiple redox couples and poor interaction of species with the platinum electrode means that the Nernst equation should be used cautiously when interpreting measured Eh For detailed discussions of the theory and significance of the electro
129. f the Monitoring Programme Guide Chapter 7 for pump type and installation depth 3 2 Install the flow through cell 3 3 Purge the hole Refer to the Monitoring Programme Guide for purging rates and times If the water in the hole is hazardous collect the purged water ina suitable container and dispose properly according to site protocol 3 4 Measure and record the following field parameters whilst purging the hole of stagnant water e temperature e EC e pH e DO 10 3 5 Check the pumping rate Record the rate of flow the time taken to fill a container of a known volume and record the quantity of water removed during purging 3 6 Whilst purging the borehole complete sampling record sheets log custody and label the sample bottles 4 Field measurements 4 1 When three borehole volumes have been removed from the borehole or the field parameters are stable note the final values of the field measurements 4 2 Titrate sample alkalinity 5 Sample collection 5 1 Collect unfiltered samples see individual section on types of equipment used methods etc Label sample sets as you go along 5 2 Collect samples for organic compounds unfiltered 5 3 Collect samples for pesticides unfiltered 5 4 Collect samples for sensitive non filtered inorganic compounds cyanide ammonia unfiltered 5 5 Collect sample for microbiology unfiltered 5 6 Collect sample of major cations and anions unfiltered 5 7 Attach in
130. f the water expressed by the relation E Eo S pH where Eo is a constant that depends on the electrode system and S is a temperature dependent constant that is theoretically known To determine these two constants one therefore requires two buffers i e solutions of known pH that are used to calibrate the electrode pair Electrochemical theory predicts that S 0 1984 273 15 t where t is the temperature in degrees Celsius In practice it has proved to be better to check this slope hence the introduction of the second buffer in the recommended procedure 4 3 2 pH MEASURING EQUIPMENT AND SUPPLIES An electrometric pH measuring system consists of the pH meter potentiometer 52 the measuring electrode the reference electrode usually built into the measuring electrode pH buffer solutions 4 3 2 1 pH meter For routine work use a pH meter accurate and reproducible to 0 1 pH unit with a range of 2 to 12 pH The instrument should preferably be equipped with a temperature compensation adjustment and should operate over a temperature range of 0 to 45 C The pH meter for field measurements should be portable a lightweight battery powered unit is recommended and come in a robust casing Waterproof models are highly recommended particularly for work in humid areas Many instruments have fully automated calibration routines This can improve their ease of use but can also restrict the choice of buffer solutions for cal
131. fer In turn bacteria can either decompose or in some cases produce organic contaminants as part of their metabolism For example most alkyl benzene and chloro benzene groups are probably biodegradable in aerobic water while they are stable in anaerobic water Conversely trichloroethylene TCE is stable in oxygenated water while possibly biodegradable in anaerobic water A detailed investigation of contaminant migration from landfills tailings piles and retention ponds should define a three dimensional DO profile within both the contaminant zone s and the surrounding region The often mapped parameters TDS and EC usually cannot be used to infer the presence or concentration of oxygen sensitive contaminants such as methane or hydrogen sulphide The dissolved organic carbon DOC concentration in landfill leachate is often hundreds of times higher than that in uncontaminated groundwater When groundwater becomes polluted to this degree DO is likely to be absent even at shallow depths However this assumption always requires site specific verification 73 Oxygen in large part influences the solubility of many naturally occurring polyvalent trace elements in groundwater Nine of the 16 inorganic constituents that have specified concentration limits in drinking water in the USA As Cr Fe Hg Mn Se U N S have multiple oxidation states and are therefore sensitive to DO concentration Other potentially hazardous heavy metals Ag Cu Cd
132. fers quantitative assessment of iron redox reactions especially in acid mine waters quantitative assessment of sulphide redox chemistry in waters undergoing sulphate reduction 61 Eh measurements are not useful for quantitative assessment of other redox active species such as methane bicarbonate nitrogen sulphate and dissolved oxygen These species are not sufficiently electro active to establish an equilibrium potential at the surface of the platinum electrode Nordstr m and Wilde 2005 4 4 1 ELECTROCHEMICAL THEORY DEFINITIONS Eh is a measure of the equilibrium potential relative to the standard hydrogen electrode developed at the interface between a noble metal electrode usually platinum and an aqueous solution containing electroactive redox species Nordstr m and Wilde 2005 ORP is a less specific term in which the measurements can be made relative to another reference electrode Voltage measurements obtained as ORP readings can be converted to Eh by adding or subtracting the offset voltage of the reference electrode relative to the standard hydrogen electrode In a redox reaction every loss of an electron oxidation half reaction is coupled to an electron gain by another species reduction half reaction Unlike protons electrons cannot exist in free or solvated Surrounded by water molecules form in aqueous solution Eh does not measure the concentration of electrons in solution but rather the intensity o
133. g making use of the inertia of the water column results in water being pumped These have been quite widely promoted as they are inexpensive and can be left in situ thus reducing potential cross contamination when sampling at a pollution site Foot valve samplers would have been the answer to keeping sampling costs low but they have a few drawbacks the rapid physical up and down movement in the borehole loosens deposits from the sidewall similarly aquifer material is loosened if the borehole has a large well volume you need to have a few very fit operators to ensure proper purging and operator variability reduces the repeatability of sampling procedure These foot valve samplers are useful for purging and cleaning newly drilled sampling wells and are recommended for this purpose They are not recommended for sampling programs 11 5 REFERENCES Pohlman K F and J W Hess 1988 Generalized ground water sampling device matrix Ground Water Monitoring Review 8 4 82 84 122 Puls R W and M J Barcelona 1996 Low flow minimal drawdown groundwater sampling procedures U S Environmental Protection Agency Groundwater issues report EPA 540 s 95 504 URL http www epa gov ahaazvuc download issue lwflw2a pdf_ last accessed on 5 November 2006 Stone W J 1997 Low flow groundwater sampling Is it a cure all Groundwater Monitoring Review 17 2 70 72 123 CHAPTER 12 NEWLY DRILLED BOREHOLES 12 1 TURBID WATER AND CHEMISTRY
134. ganic compounds are also known as either acid extractable organic compounds or base neutral extractable organic compounds This group includes fuel oils dye residues wood preservatives plasticisers coal tar PCBs and other priority pollutants Pesticides section 3 4 3 2 are included in this group The recommended sampling device is a positive displacement pump made of all metal or PVC however there is less danger of volatilization than for VOCs soa submersible centrifugal pump can be used if a suitable pump is not available Use 1 L or larger properly cleaned amber glass sample bottles with Teflon cap liners Do not filter the water Keep the sample cool at 4 C 3 4 4 5 Light Non Aqueous Phase Liquids LNAPLs and Dense Non Aqueous Phase Liquids DNAPLs LNAPLs are those organic compounds which do not dissolve in water and which float on groundwater most commonly petrol derived products and degreasers DNAPLs are those organic compounds which do not dissolve in water and sink to lower levels such as chloroform liquid chlorofluorocarbons CFC trichloroethylene TCE creosote polychlorinated biphenyls PCB Note that DNAPLs can move faster than groundwater These two classes of organic compounds will always be pollution related They are measured in the borehole by using a clear sided bailer collecting first the LNAPLs by lowering the bailer so that the water level corresponds to the middle of the bailer Bring the bailer to th
135. hat of air saturation Dissolved oxygen has a significant effect upon groundwater quality since it regulates the valence state and thus the solubility of many trace metals and by constraining the bacteriological metabolism of organic compounds in groundwater Domenico and Schwartz 1998 For these reasons the measurement of DO is important for groundwater quality investigations and especially so when dealing with polluted water The main characteristic of oxygen is its ability to oxidise that is accept electrons from other species in water Stumm and Morgan 1996 Both electrons and energy are transferred in biological and geochemical oxidation reduction redox reactions No other naturally occurring constituent of water is a more energetic or biologically reactive oxidant than molecular oxygen therefore aerobic bacteria utilize DO as part of their metabolism This results in the oxidation of organic carbon hydrogen sulphide ammonium and other reductants An important aspect of these biochemical redox reactions is their irreversibility Bacterial metabolism always consumes but never produces oxygen Dissolved oxygen concentration is a critical parameter in any investigation of groundwater contamination particularly those involving the migration of landfill leachates or mining wastes Oxygen in water often controls the fate of dissolved organic contaminants by constraining the types and numbers of micro organisms present within an aqui
136. he water Excessive ions can be detrimental to its use for many purposes Sampling for major ions Glass or plastic sample bottles can be used but plastic is preferable as glass can break more easily The rapid international growth of the bottled water industry has made PET bottles easily obtainable from the manufacturers at relatively low cost Make sure the sample bottle is clean For new bottles rinse at least three times with water from the sample site remember to include the cap before collecting the water sample If re using a sample bottle rinse with acid e g dilute hydrochloric acid solution and soak for a few days beforehand in deionised water Confirm with the laboratory how much sample is needed for the cation anion analysis as depending on the laboratory method especially for nitrate up to one litre may be required On site filtration is not needed for well purged borehole water Alkalinity needs to be measured on site if this is a critical determinand for the hydrochemical survey However for most purposes alkalinity is sufficiently stable that it can be measured in the laboratory Note that if phosphate is a critical determinand a filtered sample must be collected Keep the samples cool not specifically at 4 C but do not leave in the sun 3 2 1 2 Ammonium and nitrate The two nitrogen species are usually the products of pollution and most monitoring is directed to establish pollution levels Sampling for am
137. his is controlled by the levels of CO usually higher in the subsurface and O usually depleted in the subsurface The pH and Eh in turn control the solubility of metals including iron and manganese All hydrogeologists will sooner or later encounter the clear water sample that a few minutes hours or days later has an orange brown floc Some will have seen a water supply borehole that when switched on spews out a gush of orange brown ferric hydrous oxide precipitate This slowly decreases until a few minutes or tens of minutes later the water is clear These are the result of CO coming out of solution and pH rising and Oz dissolving and Eh rising the iron oxidising from the soluble Fe to the insoluble Fe which precipitates When this happens calcium and other metal ions can co precipitate and other ions can also decrease by adsorption or cation and anion exchange These can include phosphate molybdate silicate sulphate borate copper lead zinc and calcium Braids et al 1987 When iron is present in groundwater it is very important to filter as rapidly as possible to prevent contact with air If a sample with iron floc arrives at the laboratory what are they to analyse Decant and analyse the supernatant filter and analyse the filtrate or acidify and analyse the resultant clear solution Either of these will give an untrustworthy result Rather filter immediately on site and either acidify or instruct the laboratory to aci
138. hnology is rapidly developing only the four micro organisms most commonly used by the general hydrogeological practitioner for health purposes are discussed below Further information can be obtained from WHO 1996 2004 41 3 5 2 GENERAL MICROBIOLOGICAL DETERMINANDS The two main determinands are e Heterotrophic Plate Count Test section 3 5 2 1 e Faecal Coliform Test including Escherichia coli E coli section 3 5 2 2 In addition under certain circumstances one may also need to sample and analyse for e Bacteriophages section 3 5 2 3 e Enteric viruses and parasites section 3 5 4 3 5 2 1 Heterotrophic Plate Count test The Heterotrophic Plate Count HPC test previously known as the standard plate count or total plate count includes all micro organisms which produce a visible colony on a pour plate using a nutrient rich non selective medium after an incubation time of 48 hours at 35 to 37 C It excludes obligate anaerobes and acid fast bacteria which represent a significant proportion of viable bacteria in water The test gives an indication of the general microbiological quality of water For groundwater that is not contaminated you will expect HPC counts of between 20 and 200 per 1 millilitre Do not be unduly alarmed if the count is in the hundreds to thousands However when readings of tens to hundreds of thousands are obtained you will need to determine what is leading to these elevated counts The main applicatio
139. hole loggers by their very nature need to be used in boreholes that are open hole Thus the data must always be interpreted with due regard for the misleading results that can be introduced by vertical flow in the borehole This is discussed in more detail in section 16 3 Limitations of open borehole techniques 97 5 5 REFERENCES Hydrolab 1997 Datasonde 4 and MiniSonde Water Quality Multiprobes User s manual Revision D Hydrolab Corp Austin Texas Tredoux G Cav L C and Engelbrecht J F P In situ measurement of physico chemical parameters down a borehole as a tool for resource evaluation In Sililo et al eds Groundwater Past Achievements and Future Challenges Proceedings of the XXX IAH Congress Cape Town 26 Nov 1 Dec 2000 AA Balkema Rotterdam 667 672 98 CHAPTER 6 QUALITY ASSURANCE 6 1 INTRODUCTION Quality assurance QA is a set of operating principles which if strictly followed during sample collection and analysis will produce data of known and defensible quality That is the accuracy of the analytical result can be stated with a high level of confidence Included in quality assurance are quality control and quality assessment If the QA is good and correct the analytical results cannot be rejected as being invalid by a court of law Remember that sampling can be one of the most error prone sections of any monitoring programme Certain controls are necessary to ensure that sampling is
140. ially available kits Drop sheet some type of sheeting to protect instruments from contamination in the event of their falling to the ground Folding table or other work surface Calculator Personal equipment money driver s license identity card credit card food and drink etc 3 10 Decontamination kit sprays detergent buckets soap rinse water and PVC pipe 4 Field measurements 4 1 4 2 4 3 4 4 4 5 4 6 4 7 4 8 4 9 Flow through cell Thermometer Conductivity meter pH meter electrode and buffer solutions thermometer Eh meter electrode and buffer solution thermometer Spare batteries for the all meters DO meter plus reagents Wash bottle distilled water Extra distilled water 4 10 Titration kit for alkalinity acidity 5 Sample collection 5 1 5 2 5 3 5 4 5 5 5 6 5 7 Alcohol cotton wool and matches for flaming sampling taps for micro sampling Labels and transparent tape to cover them Chain of Custody sheets Sample bottles and caps plus foil and teflon inserts when necessary Refer to Chapter 9 for bottle size and type 5 4 1 Always take more bottles than necessary 5 4 2 Ensure bottles are cleaned and or sterilised by the laboratory as needed 5 4 3 For inorganic chemical analysis 5 4 4 For organic chemical analysis 5 4 5 For microbiological virological analysis 5 4 6 For isotope analysis Bottles or ampoules containing preservatives clearly labelled Material t
141. ibration in some cases Make sure the pH meter has millivolt reading capability if it is also to be used to measure Eh The pH meter should be tested before each sampling trip and properly cleaned and stored after use Check batteries for leakage every two months pH meters even the field models are sophisticated electronic equipment that require care in handling and operation Try to keep the instrument clean and dry by using a groundsheet and portable shelter during field work Make sure it is stored in a clean dry place away from temperature extremes The pH meter is usually supplied in a waterproof transport case Do not store the pH meter in this case with the lid closed as condensation may occur and damage the meter Avoid unnecessary jostling or sudden impacts which can damage fragile components or dislodge electronic connections 4 3 2 2 Electrodes Two electrodes are needed to measure pH 1 the measuring electrode either glass electrode or ISFET sensor 2 the reference electrode which provides an independent constant potential against which to measure the unknown pH The glass electrode consists of a bulb of special glass containing a fixed concentration of KCI or a buffered chloride solution in contact with an internal reference electrode When immersed in aqueous solutions the outer layer of the glass becomes a gel layer that allows hydrogen ions to diffuse in or out proportional to their concentration in solution This ca
142. idered acidic Temperature has a strong effect on pH measurements and must be taken into account for accurate field measurements For example neutral pH at 30 C is not 7 0 but 6 92 and at 0 it is 7 48 Wilde et al 2006 pH is usually reported on a scale that ranges from 0 to 14 Values above 14 and below 0 are possible in concentrated 1M solutions but not found in environmental waters For example during a water sampling project in the Western Cape of South Africa it was observed that CO degassing from low TDS groundwater from Table Mountain Group quartzite caused the measured pH to change from 4 9 to 7 1 In practical terms highly corrosive water became mildly corrosive If the pH had been measured in the laboratory and not on site pipeline design precautions might not have been taken pH is a parameter that controls the valence state solubility and hence mobility of many trace metal species which may be significant in environmental investigations Eh pH diagrams or geochemical models can be used to make predictions of whether a species is soluble and hence mobile in an aquifer These require an accurate measurement of the pH and temperature and Eh for multivalent species and cannot rely on pH analysis in the laboratory a few days later Shaver 1993 Since these parameters are unstable and will often change rapidly when groundwater is brought 51 to the surface the measurements must be taken in the discharge stream as close
143. ields values for dissolved solids closer to those obtained through summation of individually determined mineral species than the dissolved solids values secured through drying at the lower temperature APHA 1998 To ask for TDS measurement by drying and weighing by a laboratory is time consuming and expensive EC is rapid and cheap and gives a good indication of TDS The relationship between TDS and EC for most groundwaters is linear and TDS Ax EC The factor A is between 5 5 and 9 for TDS in mg L and EC in mS m A depends on the actual chemical composition of the sample The conversion factor of 6 4 is used by the CSIR water laboratory to report calculated TDS Of course if a full analysis of the major and minor constituents is made then TDS can be calculated by summation of the ions and correcting for CO loss from the carbonates 20 3 2 5 Chemistry references APHA 1998 Standard Methods for the Examination of Water and Wastewater 20 ed Am Public Health Assoc Washington DC Bangthanh T T Nordstr m D K Cunningham K M Ball J W and McCleskey R B 1999 New method for the direct determination of dissolved Fe III concentration in acid mine waters Env Sci amp Techn 33 807 813 Stookey L L 1970 Ferrozine a new spectrophotometric reagent for iron Anal Chem 42 779 781 21 3 3 ISOTOPES 3 3 1 OXYGEN 18 AND DEUTERIUM Oxygen 18 analysis refers to the high precision determination of the stable isoto
144. ified in the Monitoring Program Guide Some of the chemicals used on site and preservatives used to treat samples are themselves hazardous such as mercury from thermometers that may break ZoBell s solution nitric acid and sulphuric acid Due precaution must be taken when handling these materials 153 CHAPTER 18 DECONTAMINATION 18 1 INTRODUCTION Collecting groundwater quality samples is expensive in terms of both time and money Obtaining erroneous results through cross contamination of boreholes is unforgivable Following a few simple rules as set out in section 18 2 will significantly reduce potential errors of cross contamination If however a monitoring programme is designed where the possibility of cross contamination of samples and boreholes is critical to the credibility of chemical data the decontamination routine becomes more stringent and structured The degree of stringency of decontamination procedure is determined by the monitoring programme and the results required So it is up to you to determine what is needed to write it up in the Monitoring Programme Guide chapter 7 to ensure that the guidelines are adhered to and at intervals to carry out a performance audit chapter 6 as part of the Q A programme 18 2 BASIC DECONTAMINATION ROUTINE Basic decontamination procedures apply to monitoring programmes where the credibility of the chemical data is not a critical aspect of the monitoring programme This does not i
145. ing Programme Guide 13 5 PURGING EQUIPMENT Submersible and bladder pumps are suitable Chapter 11 Bailers grab samplers and syringe devices are not suitable because they cause disturbance and dislodge material from the borehole sidewall Inertial foot valve pumps are also suspect sampling equipment as the up and down movement will disturb fine material adhering to the sidewalls 13 6 TOPURGE OR NOT TO PURGE THE DEBATE When dealing with an aquifer with a reasonable permeability there should be no debate as to whether or not to purge The two possible reasons why a groundwater quality investigator promotes the idea that a borehole in such an aquifer should not be purged are 129 1 She he does not possess the equipment to sample groundwater properly Often the standard and only sampling equipment of these operators is a bailer and 2 She he is unwilling or too lazy to purge and sample the well properly Low flow sampling also called micro purging is a method that is widely used at contamination sites where the permeability of the aquifers is low to very low At the outset it must be clearly understood that low flow sampling does not equate to not purging Low flow sampling has evolved as a method of overcoming the problem of creating turbidity in low permeability formations when sampling using standard equipment The low flow pump 0 1 to 0 5 L min is positioned opposite the well screen or fracture and then purging takes place at
146. io9u9 Uye Ayuieiy 43 Hd OF abesn jeuisnpu Uolsooo uOITe sNsoua uW 8d UYALD Hd 94 uone uondwnsuo 10 pap dsns s wajqoid J SON pue 4 OS Hd 93 BulyuLp Y20 S9A17 uolrsouuooyuol sniou H a Ayyenb 191eM p p dsns s uu qoid e j slu ui 19470 pue u 24 ABoloiqo 91 N wUWAeO Hd 93 uonduinsuos p jou snoH A10 210qe u Ul p inse ui oq 0 spueurwa q lu ui inse ui Pjal4 uonesijddy uv 201 Buiriduies z lmlqe l 2 3 PLANNING THE SAMPLING PROGRAMME Possibly the most important step is to liaise with the analytical laboratory and have confidence in what they do Establish the standard of work produced by the laboratory by requesting their accreditation credentials for the specific methods Talk with other users of the same laboratory to find out how they experience the service Check what output the laboratory will provide within what time frame and cost If the laboratory does not appear to be of a sufficiently high standard for the particular project switch to another laboratory Discuss the aims of the project with the laboratory their input can be invaluable since they may have worked on similar problems already Time spent with the laboratory personnel can save many hours of unnecessary work Establish what determinands need to be analysed Discuss the laboratory s requirements in terms of sample quantities preservation techniques and time and day to submit sample for analysis Chapter 9 dis
147. ion flask 76 Checklist of dissolved oxygen equipment DO meter and electrode with spare membranes O rings and electrolyte Flow through cell preferred especially for low DO water Thermometer if not included in the DO meter Barometer if not included in the DO meter Two 250 mL plastic bottles One 1000 mL plastic bottle for aeration of reference sample or 7 Zero DO solution dissolve 12g sodium sulphite NazSO3 and a few crystals of cobaltous chloride CoClz in 100 ml of deionised water This is used to make up a zero DO solution Prepare a fresh solution for each sample trip 4 5 3 FIELD PROCEDURE FOR DISSOLVED OXYGEN MEASUREMENT The electrode only provides a relative DO reading and should be calibrated before each use The procedure consists of checking whether the zero point is correct and then calibrating the high DO end of the electrode by using a sample of known DO content air saturated with water The procedure below describes all the steps required to do this absolute calibration Modern instruments automate some of these steps It is essential for the user to understand the level of sophistication of his her instrument to avoid double correction to the measurements The diffusivity of a Teflon membrane changes by 3 per C The temperature at which the measurement is done is therefore crucial If your instrument electrode is not equipped with a temperature probe be scrupulous with the temperature settings
148. ion that contains water of a different quality Detection of an anomaly may indicate that more detailed sampling or re evaluation of the well is required If so the work can usually be done more economically at the time the original sample is collected rather than several weeks or months later e The EC of asample can change with time owing to the precipitation of minerals from the water once the sample is in the environment of the container A sample that has been acidified or otherwise treated will not yield an accurate representation of the EC of the water in the aquifer in some cases it may be better to obtain an accurate EC determination in the field on fresh water Wood 1981 4 2 1 METHOD OF CONDUCTIVITY DETERMINATION The temperature of the electrolyte affects the ionic velocities and consequently the specific conductance For example the specific conductance of potassium chloride KCI solutions changes about 2 percent per degree Celsius near 25 C Wood 1981 49 The standard temperature for reporting EC is 25 C Thus you must measure the temperature accurately in order to correct the measured EC value to give the EC at 25 C Fortunately modern conductivity meters all have temperature sensors built into the conductivity probe compensators and thus the EC can be read directly as mS m or uS cm or mS cm at 25 C On other meters there is a dial that has to be set to the water temperature The direct reading meter is recommended as
149. ios in the water For most of these processes O and deuterium variations occur in parallel resulting in a fixed relation of 8 between the deuterium and O isotope ratios in the water resulting in Global or else Local Meteoric Water Lines Evaporation of water from open water bodies such as lakes pans rivers and the like results in enrichment i e increase of both isotope ratios of the water remaining in the reservoir The rate of increase is different A plot of 5D versus 5 O will show a slope of 4 to 6 and by this means evaporating water can readily be identified Oxygen and hydrogen isotope labels are generally very conservative underground once the water has recharged beyond a few metres depth in an aquifer They 22 therefore form unique characteristic groundwater tracers for the surface water processes that occurred prior to recharge Sampling for O and deuterium Water should be collected in glass or plastic bottles with tightly fitting caps Fill bottles close to the top Usually 10 20 mt samples are sufficient 3 3 2 NITROGEN 15 The 5 N values representing deviations of the ratio of N N are reported relative to atmospheric air AIR The biogeochemistry of nitrogen in its path towards groundwater can be quite complex The most commonly observed occurrence on nitrogen in groundwater is as nitrate since ammonia is readily oxidized In general terms three sources of nitrogen contribute to nitrate
150. iosulphate in the field as this would be adding non sterile material and could introduce contamination When collecting from a sampling tap or any other pipe permanenily in place the orifice must be flame sterilised Using tweezers to hold the cotton wool dip some cotton wool in alcohol set alight and play the flames around the orifice DO NOT FILTER THE WATER When collecting the water sample from any source open the bottle and keeping the cap in one hand hold the bottle under the discharge pipe leave some air space and then replace the cap Do not rinse the bottle just fill it up and close it Be very careful not to touch the inside of the cap or the bottle Record the time and date of sampling on the sample bottle Store the filled bottles on ice 4 C and in darkness Ideally the sample should be plated out in the laboratory within 6 hours but within 24 hours is quite acceptable The maximum holding time for obtaining realistic results is 48 hours Table 3 5 1 Sample size requirement and holding time for HPC and FC A Sample Recommended Maximum Incubation Determinand i Holding I Volume Holding Time Period Time Heterotrophic Plate Count 48 hours Faecal coliforms Total 1 L 6 to 24 hours 2 days 24 hours Coliphages 8 24 hours 3 5 4 ENTERIC VIRUSES AND PARASITES Enteric viruses multiply in the gastro intestinal tract of warm blooded animals They include enteroviruses reoviruses adenoviruses and r
151. ious preservatives that may be used to retard changes in samples Preservative Action Applicable to Acidity alkalinity organic materials BOD colour odour organic P organic N Refrigeration Bacterial inhibitor I carbon etc biological organism coliform etc Dissol tals pr Acid HNOs issolves metals prevents Metals precipitation 112 Bacterial inhibitor Organic samples COD oil and grease Acid H SO Salt formation with organic organic carbon bases Ammonia amines Salt formation with volatile Alkali NaOH compounds Cyanides organic acids HgCl Bacterial inhibitor Nitrogen forms phosphorus forms Mercury compounds are being phased out as preservative because of the health hazard and the possibility of heavy metal contamination 9 5 SAMPLE SIZE The golden rule is to ask the analytical laboratory what volume of water sample they need before going into the field If you have omitted this detail rather collect twice as much as you think necessary it s a lot cheaper and less time consuming than having to go back for a top up sample It is also good practice to use a number of smaller sample bottles for one sampling site rather than one large bottle For example the chemical laboratory at CSIR used by the authors requests 3 x 330 mL bottles for the major cations and anions One bottle is used for the analysis the second bottle is used if there is a problem
152. ironment in a variety of ways overturned fuel tankers automobile and truck crashes spillage at the fuel pump leakage from storage tanks discarding sump oil the list is long Leakage from underground storage tanks USTs is probably the source which has the greatest impact on groundwater These leakages often go undetected for years and thousands ol litres of fuel can be discharged Some well written overview references on hydrodarbon site investigations are Schwerko 1994 and New Zealand Ministry of the Environment NZ MoE 1999a and NZ MoE 1999b Once hydrocarbons discharge into the environment the fuels start to weather Weathering is the term to describe the loss of the volatile component leaving behind the heavier fraction The rate of weathering varies thus gasoline spilled onto an impermeable surface exposed to the atmosphere shows changes in less than a day but if lost from a UST beneath an impermeable cover will weather very slowly Other weathering processes include chemical oxidation and microbial degradation 34 The heavier ends of the hydrocarbons weather slower than the light ends The best example of very slow weathering is the brittling of the tarmac seal on a road The analytical methods for hydrocarbon target various hydrocarbon ranges and or specific groups TPH analysis Total petroleum hydrocarbon typically looks at compounds in the Cg to Css range There are many analytical techniques that measure TPH
153. it saves time and more importantly reduces the chances of error With CO degassing CaCO may precipitate from sample water and alter the cell constant in the course of time If this happens immerse the cell in dilute HCI to clean Other materials that may precipitate or foul the electrode are iron and organic compounds 4 2 2 EQUIPMENT FOR CONDUCTIVITY DETERMINATION 1 EC meter Make sure that the EC meter you purchase can be calibrated otherwise it is a waste of money EC electrode usually included with the meter Thermometer graduated in 0 2 C if EC meter is not temperature compensated 1000 mL plastic beaker Flow through cell optional OW N O 4 2 3 FIELD PROCEDURE FOR CONDUCTIVITY DETERMINATION 1 Read the manufacturer s instructions for procedures specific for your instrument and adapt these instructions accordingly 2 Calibrate the instrument with standard EC solution usually KCl either in the field or in the laboratory before leaving for the field 3 Start pumping the borehole 4 Measure the water temperature 5 If necessary set the temperature dial to the observed groundwater temperature 6 Immerse the electrode in flowing water for a few minutes to equalize the temperature of the electrode and the water Move up and down a few times to remove any air bubbles that may be trapped in the electrode 7 Take the EC reading make sure it is in mS m or else converted
154. ity management strategy No 7a published by the Australian and New Zealand Environment and Conservation Council and the Agriculture and Resource Management Council of Australia and New Zealand http www deh gov au water quality nwqms monitoring html last accessed on 5 November 2006 Karklins S 1996 Groundwater sampling field manual PUBL DG 038 96 Bureau of Drinking Water and Groundwater Wisconsin Department of Natural Resources Madison Wisconsin http www dnr state wi us org water dwq qw pubs field pdf last accessed on 5 November 2006 110 CHAPTER 9 SAMPLE CONTAINERS AND SAMPLE PRESERVATION 9 1 SAMPLE CONTAINERS The container for collecting and storing the water sample must be selected bearing the following in mind resistance to solution and breakage efficiency of closure size shape availability and cost The two commonly used container materials are polyethylene or PVC plastic and borosilicate glass Glass This must be borosilicate glass and preferably a dark colour to reduce photo degradation of the sample and growth of biological matter Where possible polyethylene plastic bottles should be used as glass can break in transit or in the laboratory which means a repeat sampling trip Glass is not suitable for boron silica and sodium analyses Glass is the best container for organic constituents and the only container for DO analyses Plastic Either polyethylene or polyvinylchloride PVC plastic bottles can be use
155. ix A 2 The purpose of knowing the Eh potential of the reference solutions at various temperatures is so that you can immerse the container of reference solution in flowing groundwater equalise and measure temperature and then test the electrode and Eh meter performance all at the sample temperature 4 4 3 4 Equipment checklist for En measurements Eh meter or pH meter with millivolt scale 1 2 Eh combination electrode or platinum electrode and reference electrode 3 Eh reference solution Check expiry date 4 100 mL glass or plastic beaker to hold reference solution 5 Filling solution for reference electrode plus syringe 6 Electrode cleaning solutions and mild abrasive for polishing 7 Bucket for equalisation of the reference solution to the sample water temperature 8 Thermometer if the Eh meter does not have automatic temperature compensation Deionised water plus squeeze wash bottle Soft tissue to dry electrodes Flat table or working surface Flow through cell with connectors tubing and accessories essential Safety equipment and waste disposal containers for working with acid cleaning solutions and Zobell s solution 4 4 4 FIELD PROCEDURE FOR Eh MEASUREMENT 4 4 4 1 Equipment test procedure Testing of the performance of the Eh electrode system is time consuming and should preferably be done in the laboratory before and after deployment in the field If 66 possible work at 25 C as this is the standa
156. l to maintain the water flow rate through the cell to less than 1 litre minute to avoid turbulence and stream flow potential on the pH probe Some form of valve system with a bypass line is essential to control the flow rate through the cell This will aid in line filtration and sampling after the field measured parameters have stabilized An alternative design the Sheffield LFC cell allows the water flow in series through separate small cells each containing one electrode Waterra 2003 With this design 136 the sequence of probes is important since some probes e g DO can alter the water and a minimum flow rate needs to be maintained to minimize this alteration SIDE VIEW OF CELL TOP VIEW OF CELL Electrodes Nut of Gland Solid Plexiglass Block REDOX Electrodes y aS Outer body ____ 5 Diameter 5 diameter ane Ne ee ee plexiglass tube Elbow 7 2 a Probe Sus 3x Waste in well Teflon Tubing gt O N T Inline Teflon Filter Apparatus 0 4 uM Filters Unfiltered Samples LPE tubing valves and filters can be used when Teflon only doing inorganic Filter sampling Figure 15 1 Diagrammatic views of the essential features of the flow through cell Garske and Schock 1986 137 15 2 THE BOTTLE AND CORK METHOD An improvised cell has been made on occasion when measurements had to be taken and the right equipment was not available While it should no
157. laboratory 3 2 4 EC AND TDS TOTAL DISSOLVED SOLIDS TDS is a measure of the total mass of dissolved salts in a given mass of solution The experimental determination of the salt content by drying and weighing presents some difficulties due to the loss of some components The temperature at which the residue is dried has an important bearing on results because weight losses due to volatilization of organic matter mechanically occluded water water of crystallization and gases from heat induced chemical decomposition as well as weight gains due to oxidation depend on temperature and time duration of heating Residues dried at 103 C to 105 C may retain not only water of crystallization but also some mechanically occluded water Loss of CO will result in conversion of bicarbonate to carbonate Loss of organic matter by volatilization usually will be very slight Because removal of occluded water is marginal at this temperature attainment of constant weight may be very slow Residues dried as 180 2 C will lose almost all mechanically occluded water Some water of crystallization may remain especially if sulphates are present Organic matter may be lost by volatilization but not completely destroyed Loss of CO results from conversion of bicarbonates to carbonates and carbonates may be decomposed partially to oxides or basic salts Some chloride and nitrate salts may be lost In general evaporating and drying water samples at 180 C y
158. larly in small or short term projects when something less than a complete QA plan would be appropriate In these cases a smaller document organized around the major headings listed above might be in order Many of these items are also included in the Monitoring Programme Guide Chapter 7 which is an information file taken into the field by the sampler 6 2 QUALITY CONTROL Discussed in this section are the specific internal quality control methods that should be followed Section 6 3 Quality Assessment describes the external quality control methods For the field scientist collecting groundwater samples the following items must be considered e Use buffer and standard solutions which are the same temperature as the groundwater being sampled to calibrate field chemistry meters Calibrate before a field measurement and if possible after the field measurement is complete Make notes in your field notebook that these calibrations have been done e Send a duplicate sample with the set of samples to the laboratory Collect twice as much sample from the same borehole and decant into two different bottles Label these bottles differently Make sure they are recorded correctly on the sample record sheet A second set of duplicates can be sent to another laboratory for quality assurance external quality control e A laboratory blank is either a sample of deionised water or deionised water plus the reagents depending on the analytical method If you
159. lected LNAPLS In particular using a clear sided bailer enables one to visually see approximately how thick the layer of LNAPS is 11 3 LOW FLOW SAMPLING When sampling high permeability aquifers usually for water supply or hydrogeochemistry purposes sampling mostly takes place at fairly high flow rates Sampling at groundwater pollution sites however often has to take place in low permeability formations Using a normal sampling pump will often if not always rapidly lower the water level often to the pump intake This in turn induces much higher than natural rates of flow in the formation mobilisation of formation particles increased turbidity of sample and thus biased results Low flow sampling is the technique that has developed in response to these problems This involves using a pump that delivers 0 1 to 0 5 L minute The theory is that the pump is inserted opposite the screen or fracture pumps at a low rate that does not disturb the aquifer material thus keeping turbidity low induces laminar flow that does not cause mixing inside the borehole and thus enables collection of a representative groundwater sample The method has been widely adopted for use in the USA where it is recommended or prescribed by US EPA As a consequence there are a variety of commercially available pumping systems satisfying this method and these are actively being promoted by the sales staff The pumps can be peristaltic bladder electric submersible or ga
160. lectrode as a function of temperature and potassium chloride filling solution concentration adapted from Nordstrom and Wilde 2005 The linear regression equation for each Eh temperature relationship is also given for interpolation to other temperatures in this range Silver silver chloride Calomel Temp Saturated Saturated M KCl 5M KCI 4M KCl C 3M KCI 3 5M KCI KCI 3 C 3 5 C C KCI 10 220 215 214 260 256 255 254 15 216 212 209 259 254 252 251 20 213 208 204 257 252 249 248 25 209 205 199 255 250 246 245 30 205 201 194 253 248 244 241 35 202 197 189 251 246 241 238 40 198 193 184 249 244 239 234 E s 0 731 0 741 t 0 37 t 0 4 t 0 53 t 0 66 t i 227 223 224 264 260 260 261 Appendix A Table 2 Temperature dependence of Eh platinum electrode vs SHE for common reference solutions Temperature Quinhydrone Quinhydrone Zobell s C pH 4 mV pH 7 mV mV 5 479 314 472 10 475 307 461 12 474 304 457 14 472 301 452 15 471 300 450 16 471 299 448 18 469 296 443 20 467 293 439 22 466 290 435 24 464 288 430 25 464 286 428 26 463 285 426 28 461 282 421 30 460 279 417 35 456 272 406 40 452 265 395 160 Appendix A Table 3 Quick reference look up table for theoretical redox potentials of common Eh reference solutions relative to different types of
161. ly if the E coli count is low to re sample to confirm the presence of E coli If your sample has E coli then you must identify the source and process that has caused the groundwater to become contaminated and take appropriate action 3 5 2 3 Coliphages A bacteriophage also known as phage is a virus that infects bacteria E coliis the host bacterium for the group of bacteriophages called coliphages The survival rate of a coliphage is higher than that of all the indicator bacteria faecal coliforms including E coli Therefore the presence of coliphages combined with the absence of E coli indicates that E coli was present but that it has either died off or the pollution source is distant Their importance as a water pollution indicator test is that their presence indicates the potential presence of enteric viruses or other longer living pathogens The test is relatively inexpensive costing about R100 compared to greater than R1000 for enteric virus and parasite analyses 3 5 3 SAMPLING GENERAL MICROBIOLOGICAL DETERMINANDS Sample containers Sample containers can be glass or plastic as long as they can be sterilized at 121 C for 15 minutes in an autoclave or in an oven at 170 C for 120 minutes Plastic is preferred to glass since it is less prone to breakage The seal or cap must be able to close so that contamination cannot occur after sterilization The sampler should contact the analytical laboratory to supply
162. monium and nitrate Ammonium in a water sample if not chemically preserved will slowly be degraded by microbiological activity to nitrate The rate of conversion is variable For most purposes the rate of conversion is sufficiently slow that no special preservation is needed as long as the sample is analysed within a reasonably short space of time If the ratio of ammonium to nitrate is important or nitrogen isotopes are to be measured the bacterial activity must be inhibited by acidifying the water sample with 15 analytical grade concentrated HSO to pH lt 2 Ensure that the sample bottle is correctly marked 3 2 1 3 Phosphate Phosphate like nitrogen is a nutrient and is a critical parameter when determining eutrophication of open surface water Phosphate in the form of sodium phosphate is used to increase the cleaning power of household detergents The main source of phosphate is therefore from treated waste water Usually phosphate is not detected in groundwater as it readily adsorbs onto soil particles However under special circumstances phosphate may occur in the dissolved phase in groundwater Sampling for phosphate Phosphate readily precipitates out onto suspended sediment or onto the sides of the sample container Thus if phosphate is an important required determinand for the investigation an on site filtered sample must be collected 3 2 1 4 Fluoride Fluoride has severe health impacts for
163. more severe with stronger vertical gradients As a result there is potential ambiguity about the source of the water in multilevel sampling Vertical gradients can also spread contaminants to regions that were previously uncontaminated For a more detailed discussion on this phenomenon see Lerner and Teutsch 1995 Repeatability of the vertical profile of hydrochemical measurements from one sampling run to another also does not necessarily guarantee that the designed sampling method is accurate This merely shows that the water is sampled in a consistent manner rather than that the composition profile is undisturbed Gillham et al 1983 16 4 FRACTURED ROCK CONSIDERATIONS Boreholes drilled in secondary or hard rock aquifers also called basement or bedrock formations are usually completed as open hole construction Occasionally collapsing ground will require slotted casing Those boreholes with two or more water strikes are likely to be flow through boreholes as described above Thus the results of groundwater quality sampling conducted in these situations must be viewed with due caution Shapiro 2002 provides a detailed discussion of the ambiguities involved in sampling boreholes intersecting multiple fractures This article must be required reading for all hydrogeologists working in hard rock terrains In the initial exploratory phase flow through boreholes can be sampled in order to gain an initial understanding of the aquifer F
164. mpling pump and or packers Rate of discharge and pumping time to purge the borehole correctly Note that the first field sampling run will set the discharge and pumping times for subsequent sampling runs However the field sampler must still perform field measurements and if there is significant diversion from previous results then use discretion and purge accordingly This variation must be recorded and discussed with the program supervisor Field measurements to perform at each borehole Number and type of samples to collect at each borehole Procedure for preserving and sending samples to the laboratory Any other data however trivial that may be of importance e g distance to pollution source distance to nearest pumping borehole etc 105 A Monitoring Programme Guide should be a carefully compiled document which is the result of experimentation in the field and laboratory By spending time and effort designing a sampling programme a lot of unnecessary work can be avoided A Monitoring Programme Guide should also include A plan or chart of the project organisation showing the line of authority of key personnel Anticipated starting and completion dates Intended use of acquired data The name of the responsible person in the laboratory who is the sample custodian authorised to sign for incoming samples Schedule of preventative maintenance tasks which will ensure smooth running of sampling
165. mply that the results obtained will not be correct but rather that if the credibility of the chemical data must withstand legal scrutiny this basic decontamination routine is not acceptable and the procedure as detailed in section 18 3 must be followed When sampling for trace elements especially trace organic compounds which are measured at parts per 10 or 10 and also for trace metals the basic procedure might be inadequate 1 Use sampling equipment that is easy to clean and pumps that can easily be disassembled 2 Start sampling at the borehole with the LOWEST concentration of chemicals and end up at the borehole with the HIGHEST concentration of chemicals 3 Purge the borehole correctly i e follow the procedures of chapter 12 Following this procedure will ensure that the sample collected is not cross contaminated If there is some chemical carry over only the stagnant water will be affected 4 Dispose of the purged water safely so that cross contamination will not Occur 5 After the last borehole has been sampled clean your sampling equipment as follows Thoroughly rinse with phosphate free detergent solution Rinse with tap water 154 Give final rinse with distilled water Air dry 18 3 DECONTAMINATION AT SENSITIVE SITES Parker and Ranney 1997a 1997b carried out a series of investigations of the efficiency of various decontamination protocols They tested stainless steel polyvinyl chloride
166. n of the HPC method is for monitoring the efficiency of disinfection procedures in the treatment of drinking water supplies for evaluating the quality of water in bathing areas and for establishing after growth or secondary contamination in distribution systems Nevertheless as stated above it is a useful indicator of the general microbiological quality of water but must not on its own be used to determine whether that source of groundwater is fit for consumption This test is not an index of pathogen presence and thus there are no set upper limits for any health standards 3 5 2 2 Faecal Coliform test The Faecal Coliform Test is an indicator test of probable faecal pollution although some bacteria detected by this method may not be of faecal origin The bacteria that are able to ferment lactose at 44 to 45 C are known as thermo tolerant coliforms In most waters the predominant genus is Escherichia but some types of Citrobacter Klebsiella and Enterobacter are also thermo tolerant Escherichia coli can be differentiated from the other thermo tolerant coliforms E coli is present in very high numbers in human and animal faeces and is rarely found in the absence of faecal pollution although there is some evidence for growth in tropical soils Thermo tolerant coliform species other than E coli can include environmental organisms WHO 1996 2004 42 The presence of E coli indicates recent faecal contamination It is advisable especial
167. nd close consultation with the collaborating lab is necessary to obtain the right sample vessels and sampling instructions 3 3 6 SULPHUR 34 AND OXYGEN 18 IN SULPHATES Sulphates in groundwater can be derived from atmospheric pedospheric lithospheric or industrial origin The sources and processes by which sulphate is formed exhibit different isotope fractionations This results in characteristic isotope ratios S S and 80 O in dissolved sulphate Clark and Fritz 1997 Krouse and Mayer 2000 Sampling for sulphate isotopes If the sulphate content of the water is high enough and one litre of water will be sufficient for the lab then no processing or preservation needs to be done For low sulphate water precipitation of BaSO is required from an acidified sample according to the lab s instructions If sulphide is present in the water its oxidation to sulphate must be prevented and it must be separated from the sulphate A procedure with cadmium acetate has been developed to do this Clark and Fritz 1997 p280 3 3 7 OTHER ISOTOPES AND TRACERS A number of lesser known isotopes and gas tracers are known to provide useful information in specific cases Cook and Herczeg 2000 Chloride 36 is a radioactive isotope produced in the atmosphere and by nuclear weapons similar to C It has a longer half life than C and has been used to date groundwater up to a million years old and also to identify post 1960 recharge The com
168. nd potential about every ten minutes until at least 30 minutes have passed from the first measurement and the millivolt readings are within 10 mV of each other Record the reading to the nearest millivolt noting the plus or minus sign and the temperature of the groundwater at the time of measurement to the nearest 0 1 C Make a note of the reference electrode used Calculate the Eh relative to the hydrogen electrode by correcting the millivolt reading for the half potential of the reference electrode See below Rinse electrodes thoroughly with deionised water and blot dry before packing away Some natural groundwaters will not contain enough electro active species to give a stable Eh reading even with a flow through cell For these poorly poised systems the Eh reading is generally of little value as a quantitative measurement and the value of the measurement probably does not warrant spending hours waiting for the reading to stabilise To calculate Eh of groundwater The steps for Eh calculations are given below with a worked example 1 Using Eh meter with offset function when testing the instrument set Eh reading for reference solution relative to hydrogen electrode values in Appendix A 2 not relative to reference electrode in use The difference between the hydrogen electrode and the silver silver chloride or calomel 69 electrode will automatically be added to the readings Eh can then be read directly on the mete
169. ndard Reference Material Note that buffer solutions obtained for measurement of pH from 4 to 10 typically have high ionic strength For accurate work on dilute waters obtain low ionic strength buffers Note the expiry date of the buffer solutions and copy it onto any containers into which the buffer is transferred Discard buffers on their expiry date as the pH may have changed substantially due to carbon dioxide absorption evaporation or mould growth Always cap buffer bottles to minimise evaporation and contamination from atmospheric carbon dioxide Buffers are stable for the short exposure time during electrode calibration Sensitivity of buffers to CO contamination ranges from most sensitive for high pH to least sensitive for low pH i e pH 10 gt pH 7 gt pH 4 Never pour used buffer solutions back into the bottle Always decant a small amount for use and discard after calibration Never insert an electrode or other material into the buffer stock solution bottle Be careful not to contaminate the buffer with another buffer or other fluids Do not pour one buffer after another into a beaker Always use a clean container pH 4 buffer is the least sensitive to contamination Do not dilute buffers for example with water dripping from the electrodes pH 7 buffer is the most sensitive to dilution 56 Store buffer stock solution in a fridge when not in use Before using buffers bring them to the
170. nds are fulvic and humic acids DOC dissolved organic carbon analyses show the common range in uncontaminated groundwater to be from 0 1 mg L and up to 10 mg L From a water quality viewpoint the man made organic compounds and their impact on groundwater is of increasing concern Organics in groundwater is a field in which many questions are only partially answered or even remain unanswered Extensive work is being carried out especially in the USA and also Europe to understand these impacts These studies include developing analytical techniques refining sampling methodology understanding the subsurface behaviour of these organic compounds and understanding their effect on groundwater consumers One reason for concern is that a number of these compounds have been identified as being carcinogenic This latter aspect is quite an emotional matter and the reader is urged to obtain and read an editorial in Groundwater entitled Toxicological Risk Assessment Lehr 1989 The number of identified man made organic compounds now totals nearly 2 million and is growing at a rate of about 250 000 new formulations annually of which 300 500 reach commercial production More than 1200 individual man made organic substances have been identified in drinking water supplies This number is increasing rapidly as investigations of organic compounds in water supplies are intensified Freeze and Cherry 1979 As one can thus imagine there is considerable
171. ndwater sampling Memoirs of the 17 Congress of the International Association of Hydrogeologists Impact of agricultural activities on groundwater Novinar Prague p115 124 DGT Research 2003 Diffusive Gradient Thin film URL http www dgtresearch com last accessed 5 November 2006 Freeze R A and J A Cherry 1979 Groundwater Prentice Hall New Jersey Gillham R W M J L Robin J F Barker and J A Cherry 1983 Groundwater monitoring and sample bias Department of Earth Sciences University of Waterloo Waterloo Ontario Prepared for Environmental Affairs Department American Petroleum Institute Harper M Davison W and Tych W 1997 Temporal spatial and resolution constraints for in situ sampling devices using diffusional equilibration dialysis and DET Envir Sci Techn 31 3110 3119 Jones and Lerner D N 1995 Level determined sampling in an uncased borehole J of Hydrol 171 291 317 Jones l D N Lerner and O P Baines 1999 Multiple sock samplers A low cost technology for effective multilevel groundwater sampling Groundwater Monitoring Review Winter 1999 134 142 Powell R M and R W Puls 1993 Passive sampling of groundwater monitoring wells without purging multilevel well chemistry and tracer disappearance Journal of Contaminant Hydrology 12 51 77 Lerner D N and Teutsch G 1995 Recommendations for level determined sampling in wells J of Hydrol 171 355 377 Nilsson B Jako
172. ng equipment use a fibre glass tape as a steel tape will rust This is the method of choice 2 Permanently mark the cable at 1 m intervals and measure the final part of the last metre with a carpenter s tape This method is less preferred as the cable can stretch Also errors can be made when adding or subtracting the partial metre to or from the last noted whole metre 3 Mark the cable remove it from the borehole and measure the depth of the mark with a tape This method is not preferred as it requires two persons 10 2 2 Measuring in a borehole equipped with a pump When the borehole to be sampled is fitted with a production pump access to the water level must be open The pump riser main the electrical cabling and the safety rope for the pump usually create a tangled mess and if you try to lower the dip meter cable inevitably it will get stuck If this is a borehole that will be sampled on a regular basis then a piezo tube must be fitted in the borehole This is a small diameter pipe installed from well head to some distance below the expected lowest water level in the borehole This is securely attached to the riser main of the pump The diameter of the pipe can be 20 mm to 25 mm or similar size The piping usually used is class 4 or 6 HDPE irrigation tubing The pipe diameter must be able to take the dip meter 115 cable and the attached weight This pipe allows the water level to be accessed without danger of getting stuck in th
173. ng the behaviour of the curvature of the titration curve on either side of the inflection points Gran 1952 Stumm and Morgan 1981 Rounds 2006 2003 This approach is only recommended for special cases where alkalinity and or EC are low or where there are significant non carbonate interfering species present Establishment of the infection points with a pH meter is the recommended method for alkalinity determination Usually one needs to setup and calibrate the pH meter anyway for pH measurements With good care this method provides sufficient accuracy for most purposes and should be better than transporting samples to a laboratory for titration days or weeks later While it is better practice to analyse samples directly at the sampling point it is quite often acceptable to accumulate all the samples during the day keep them cool and do all the titrations in a field lab at the end of the day This is however not recommended for samples with either very low or very high pH because of possible CO interaction with air 4 6 3 TITRATION EQUIPMENT The equipment recommended for field titration is 1 pH meter buffers and glassware for pH measurement see chapter 4 3 1 2 25 mL burette 3 25 or 50 mL pipette 4 magnetic stirrer and stirrer bar 5 stands clamps beakers 6 hydrochloric acid 0 01 to 0 1M 7 sodium hydroxide solution 0 01 to 0 1M only for acidity determination 8 distilled or deionised water 9 a well padded s
174. o spike samples for quality control Trip blanks for VOC samples 5 8 Filter apparatus for field filtered samples including extra filters 5 9 Preservation equipment e g ice box cool box with cooling medium such as frozen ice bricks ice Foil to protect those samples sensitive to light 5 10 Paper towels rags plus plastic garbage bags for discards Before packing the equipment calibrate all the field measuring equipment to ensure that it is in working order 2 6 1 GENERAL GROUNDWATER SAMPLING PROCEDURE Borehole setup 1 1 Find the sampling site 1 2 Consult the Monitoring Programme Guide for specific details of the sampling site and ensure you are at the correct sampling site 1 3 Fill in sampling sheet i e weather conditions date time and sample number or set number 1 4 Put down drop sheet to avoid any contamination of equipment should it fall on the ground 1 5 Put on protective clothing as required by the site classification 1 6 Assemble sample kit at the wellpoint or borehole 1 7 Remove any seal on the monitoring point such as a locking cap or manhole cover Pre purging activities 2 1 Measure static pre pumped water level record the level and rinse the water level gauge 2 2 Perform downhole logging 2 3 Collect free phase hydrocarbon sample 2 4 Measure the borehole depth only after downhole logging is complete Purging 3 1 Install the pump in the borehole following the specifications o
175. o two components on either side of a water divide A flow meter is used to locate the position of the water divide and the sample pump is positioned at this depth Flow at the water divide is assumed to be horizontal i e pumping the sample pump at a very low rate less than 1 of the total rate allows a groundwater sample to be collected from the discrete depth in the aquifer where the water divide is located The position of the water divide can be manipulated by changing the pumping rate of the flow control pumps to enable sampling of a vertical chemical profile The method requires accurate prior knowledge of the aquifer transmissivity and specific capacity of the borehole and a high level of skill to operate It is also limited by the diameter of the borehole which may not be wide enough to accommodate the three pumps Nilsson et al 1995a b Jones and Lerner 1995 Baffle systems Baffle systems consist of a packer with an open ended inner tube of slightly smaller diameter than the borehole The function of the baffle is to guide the flow above the packer A purging pump is operated above the baffle element creating vertical flow inside the borehole through the baffle Horizontal radial flow should develop around the borehole This allows level determined samples to be collected just above the packer in the annulus between the baffle and the borehole screen The sample pump must be pumped at a lower flow rate than the rate of inflow through
176. oline in USA jet fuel aviation fuel paraffin fuel kerosene xii UNIT CONVERSIONS Alkalinity 1 meq alkalinity 50 mg CaCO 61 mg HCO 30 mg CO Atmospheric pressure 1 atmosphere 760 mm Hg 101 325 Pa 1013 hPa 1013 mBar Dissolved Oxygen 1 mg L 31 25 umole L Electrical Conductivity EC 1 mS m 10 uS cm 0 01 mS cm 1000 uS m Water flow rate 1 L sec 3 6 m hr 86 4 m d 951 US gallons hour 792 UK gallons hour More general conversion data can be found at the URLs http www chemie fu berlin de chemistry general units_en html last accessed on 5 November 2006 http www onlineconversion com last accessed on 5 November 2006 xiii xiv CHAPTER 1 INTRODUCTION 1 1 INTRODUCTION The first edition of this manual was written by the first author John Weaver in 1992 At that time he was motivated to write this manual after joining the Groundwater Research Group at the CSIR He realized that the lack of knowledge of groundwater sampling he had at that time was probably reflective of the whole industry both in South Africa and probably also elsewhere This first edition of the sampling manual Weaver 1992 proved to be one of the most popular manuals ever produced by the Water Research Commission The edition had a print run treble the normal one and the stock of the printed version was finished within 5 years after which only photo copied versions were available The present manual is the Secon
177. ollows 1 meq alkalinity 50mgCaCO3 61 mg HCO 30mgCO Many databases and chemical modelling software programs require the input of bicarbonate and carbonate species separately as mg L rather than the analysed alkalinity If the field pH of unpolluted water is below pH 8 0 the carbonate concentration is negligible see Figure 4 6 1 and the alkalinity can be taken as the bicarbonate concentration using the conversion factors above For alkaline waters pH gt 8 the alkalinity titration should be carried out to two end points The amount of acid added to reach the first end point nominally pH 8 3 gives an approximation of the carbonate concentration and the second endpoint nominally pH 4 5 the bicarbonate concentration For waters with pH between 4 and 9 carbonate and bicarbonate concentrations can be calculated from the pH and total alkalinity TA APHA 1998 method 4500 D If TA is expressed in mgCaCO L then B HCO mg L 61 50 TA 5 10 pH 10 1 0 94 104 pH 10 and C COs mg L 0 56 B 10 pH 10 Geochemical speciation models can be used for more detailed calculations 4 6 5 ALKALINITY AND ACIDITY REFERENCES APHA 1998 Standard Methods for the Examination of Water and Wastewater 20 ed Am Public Health Assoc Washington DC Gran G 1952 Determination of the equivalence point in potentiometric titrations Analyst 77 661 Loewenthal R E H N S Wiechers and G v R Marais 1986 Softening and sta
178. olution Switch the meter to the millivolt function Allow the reading to stabilise 5 mV fluctuation is fine and record the millivolt reading and temperature of the reference solution Look up or calculate the theoretical potential Eet for the reference electrode system see below at the system temperature and compare this to the measured value If the values are within 10 mV some instruments 20mV even the equipment is ready for field use If the values differ by more than that repeat steps 3 to 7 with a fresh portion of reference solution If it is still not in agreement troubleshooting is required see section 4 4 4 3 Note the type of reference electrode type of reference solution and theoretical Eh for the system at the working temperature in your Eh records Calculating the theoretical E of reference solution 1 Eh is the theoretical potential of the reference solution relative to the hydrogen electrode value from Appendix A 1 or calculated from one of the equations in section 4 4 3 3 at temperature t 67 2 Eagagc t OF Exggaci2 are the half cell potentials of the electrodes relative to the hydrogen electrode at temperature t from Appendix A 2 3 Eet is the theoretical potential of the reference solution for the system being tested where Eret t Et Eagiagci t or Erer t Eh t Ehgmg2ci2 t Appendix A 3 presents a quick reference for Ee values for commonly used electrodes and reference sol
179. on Radiometer A S Copenhagen Denmark Lindberg R D and D Runnells 1984 Ground water redox reactions an analysis of equilibrium state applied to Eh measurements and geochemical modelling Science 225 925 927 Nordstr m D K and F D Wilde 2005 Reduction oxidation potential electrode method U S Geological Survey Techniques of Water Resources Investigations book 9 chap A6 section 6 5 version 9 2005 Available from the URL http pubs water usgs gov twri9A6 last accessed on 22 November 2006 Stumm W and J J Morgan 1996 Chapter 8 Oxidation and reduction equilibria and microbial mediation In Stumm W and J J Morgan Aquatic Chemistry 3 ed John Wiley amp Sons New York 425 515 Thorstenson D C 1984 The concept of electron activity and its relation to redox potentials in aqueous geochemical systems U S Geological Survey Open File Report 84 072 45p Whitfield M 1974 Thermodynamic limitations of the use of the platinum electrode in Eh measurements Limnol Oceanogr 19 857 865 72 4 5 DISSOLVED OXYGEN The maximum quantity of oxygen that can dissolve in water is proportional to the local atmospheric pressure and inversely related to water temperature and salinity Figures 4 5 1 4 5 2 and 4 5 3 In low salinity water at sea level the dissolved oxygen DO content of water saturated with air is 9 mg L at 20 C Only in waters subject to high photosynthetic rates will the DO level ever exceed t
180. on in aquifers 94 5 2 CALIBRATION AND MAINTENANCE OF LOGGING EQUIPMENT Downhole logging instruments are sophisticated devices which are usually supplied with a comprehensive instruction manual as well as software for programming the data logger or downloading data for example Hydrolab 1997 In most respects the procedures for maintenance calibration and troubleshooting of the individual sensors are similar to those described in Chapter 4 on field measurements To identify possible problems check the sensor calibration in the office or laboratory on the day before heading out to the field Some suppliers provide a multipurpose standard solution which allows several parameters e g EC pH and Eh to be calibrated at once Electrical conductivity readings should be checked against a standard conductivity solution chapter 4 2 At least two pH buffer solutions should be used to calibrate the pH electrode with the buffers chosen to bracket the pH expected range of the groundwater e g pH 7 and pH 4 or pH 7 and pH 10 chapter 4 3 Calibration of the pH meter should be checked again once in the field by measuring the pH of the buffers and recalibrating if necessary immediately before logging Eh electrodes should be checked with a standard redox buffer solution see chapter 4 4 and the platinum electrode cleaned if the Eh reading is not in agreement with that of the standard Check that the dissolved oxygen membrane is n
181. one or both inflection points The main requirements are to prevent loss or gain of CO and to detect the endpoint precisely enough The simplest and classic endpoint determination is by using colour indicators that are used to show pH changes Table 4 7 1 In general indicator alkalinity determinations in the field are less precise than proper laboratory titrations even if done days later pH indicator titration is described as one of the short cut methods in chapter 4 7 The use of a pH meter to determine the endpoint is a more precise method because it allows better definition of the end points It is the method of choice for general field 84 practice Modern pH meters are robust enough to be used in the field see chapter 4 3 pH and together with a magnetic stirrer can provide accurate titration results The method would be either to read off the inflection point pH and note the corresponding acid volume or to use a graphic method to determine the inflection point Rounds 2006 The inflection method requires a set of regularly spaced additions and corresponding pH values The acid volume at which a maximum pH response per acid volume added is obtained indicates the inflection point Figure 4 6 2 This evaluation can be done in the field using manual or small spreadsheet methods There is even a web page available on which the required calculations can be done Rounds 2003 The Gran method of end point determination is based on usi
182. onitoring Review 7 1 33 38 125 CHAPTER 13 PURGING THE BOREHOLE 13 1 INTRODUCTION Stagnation of water in an unused borehole modifies the chemistry of the water to the extent that stagnant water samples may be totally unrepresentative of the formation water A borehole that has not been pumped must first be purged to remove stagnant water from the borehole so that the groundwater sample subsequently collected is representative of the groundwater drawn from the aquifer Stagnant water is modified by a number of processes e Leaching or adsorption of certain constituents from or onto the borehole casing or screen e Changes of redox potential and dissolved oxygen content due to gas exchange with the atmosphere e Changes of microbial population as contact with the atmosphere changes anaerobic environment to aerobic This will result in subsequent changes in pH and redox conditions and chemistry of the water e Precipitation or dissolution of certain metals due to changes in the concentration of certain dissolved gases such as oxygen and carbon dioxide e Loss of VOCs e Reaction of steel casing with hydrogen ions resulting in increasing pH and decreasing Eh e Depletion of heavy metal species precipitated by sulphide produced by the action of sulphate reducing bacteria commonly found in the stored water e Addition of foreign materials through the top of the borehole Purging of the borehole in practice involves the removal of suffi
183. oof felt tip pen to write on sample 111 bottle labels and then cover the writing with a clear adhesive tape 8M 72 mm wide transparent tape works well The bottle label should include the following Sample ID no Sample site and borehole number Date and time of sampling Field parameters pH Eh DO T and alk Whether filtered or not filtered Whether preservative has been added and what type of preservative 9 4 SAMPLE PRESERVATION Sample preservation methods are intended to retain the collected sample as close as possible to its original state in the underground environment Preservation methods are intended to retard biological activity retard chemical reaction reduce volatility Methods are limited to pH control chemical stabilizers HNO3 NaOH HgCl etc refrigeration freezing poisoning No matter which method is applied complete preservation is not possible and it is good practice to analyse as soon after sampling as is practical Confirm with the laboratory what the analysis turn around time is before submitting samples If the delay is too long consider changing laboratories Proper sample handling which includes preservation reduces sampling error which in turn increases the accuracy and thus effectiveness of groundwater monitoring Preservatives and their actions are detailed in Table 9 1 below Specific requirements are listed in Appendix C 1 Table 9 1 Var
184. or detailed follow up work either multiple wells completed at different depths or multiple piezometers with grout benthonite seals or semi permanent packers must be used Down hole logging techniques chapter 5 especially electrical conductivity and temperature logs are a useful way of detecting the target zones for multilevel sampling in fractured rock boreholes during the exploratory phase 16 5 CORE VOLUME SAMPLING The sampling methods above can all be categorised as flux samples i e they are all captured from flowing water whether by pumping grab sampling or chemical equilibration in a borehole drilled into the aquifer An alternative approach is to obtain a volume sample by coring a volume of saturated or partly saturated aquifer material and then centrifuging or leaching out the liquid fraction Volume samples capture the volume of water within an aquifer volume irrespective of its mobility while flux samples contain a mixture of flow streams in proportion to their velocities or aquifer permeabilities Lerner and Teutsch 1995 A flux sample may have a different composition depending on the pumping rate while the composition of a volume sample is fixed Volume sampling is often used to obtain hydrochemical 149 profiles in low permeability formations e g clay aquitards or for pollution investigations where the total mass of contaminant must be established 16 6 REFERENCES Andersen L J 1982 Techniques for grou
185. orehole is completed with one long screen for unconsolidated material or is open hole construction for hard rock For Version D an inflatable double packer system is moved to various positions and a sample is pumped from between the packers For Version E the depth specific grab sampler usually a Kemmerer sampler or syringe device is lowered to the required depth and a sample collected For Version F two or more pumps are used to simultaneously collect samples from different depths 142 16 2 1 Single hole multilevel sampling Multiple boreholes at one sampling point Version A and multi level piezometers systems Version B are expensive to construct Thus several approaches to modifying the single hole construction have been developed e Packer systems e Multi port sock samplers Packer systems Packer systems are used to isolate a specific zone in an open borehole for sampling The system involves lowering one of more inflatable packers to a desired depth in a borehole and then inflating the packers to seal off the flow of water at that depth The common configuration is either a double packer system with packers above and below a narrow pumped zone or a single packer separating an upper and a lower zone of the aquifer or separating two fractures This method must be used with caution The borehole creates a path of very high hydraulic conductivity Thus if there is the slightest hydraulic pressure gradient between two horizons th
186. ormation and others carcinogenic causing cancer Modern pesticides degrade when exposed to one or more of the variables water sunlight temperature pH and bacteria The rate of degradation is called the half life of the pesticide The degradation rate is variable depending on the combination of these factors Preservation methods are thus dark bottles keeping the sample cool and analysing as soon as possible The maximum holding time is regarded as 28 days For some pesticides acid is added to retard bacterial activity Know what pesticides to analyse for by conducting a usage survey Then consult your analytical laboratory for precise sampling instructions and sample bottles Some pesticides are volatile although most are semi volatile It is thus good practice to have no head space in the sample bottle Some pesticides require specific preservation methods If you know beforehand from a pesticide usage survey what pesticides are expected to occur in groundwater then use the preservation methods specific for those pesticides in addition to keeping the sample cool 33 3 4 3 3 Petroleum derived compounds Petroleum and petroleum derived products are complex mixtures mainly of hydrocarbons compounds of only carbon and hydrogen plus some other compounds of sulphur nitrogen and oxygen and a few additives The hydrocarbons range from the very volatile C up to the heavy end Cas This is well described in Total Petroleum Hy
187. ot fouled and that the probe can be calibrated before leaving for the field chapter 4 5 Dissolved oxygen calibration is sensitive to atmospheric pressure and the instrument must be recalibrated at the sampling site Most dissolved oxygen sensors require some agitation of the water sample e g flowing water and a stirrer is used on some loggers to fulfil this function Follow the manufacturer s instructions for calibrating ion sensitive electrodes if you are planning to use these on your logger Some instruments have pressure sensors to measure depth which should be zeroed under atmospheric pressure conditions at the sampling site Because logging devices are lowered down boreholes the probes tend to become more easily fouled than other field equipment and require proper cleaning after each sampling trip Use only the tools cleaning materials and detergents or solvents recommended by the manufacturer Periodic visual inspection of the instrument comparison of pre and post calibration results and monitoring of sensor response time can be used to decide when maintenance or servicing is required Regular maintenance procedures may include 95 Filling or replacing reference electrode filling solution Check that you use the correct concentration of KCI Replacing the dissolved oxygen membrane Cleaning the platinum Eh electrode Replacing components such as o rings for sealing the instrument Replacing worn ro
188. otaviruses as well as the hepatitis A and Norwalk viruses Polio echo and Coxsackie B are reported as enteroviruses These viruses can survive for some time in nature and can be transmitted via water The viruses of major concern in health aspects are the Coxsackie A adenoviruses hepatitis A rotaviruses and Norwalk viruses The parasites of concern are Giardia lamblia and Cryptosporidium parvum Sampling for enteric viruses and parasites Sampling for enteric viruses and parasites is complex The equipment required is a large container for water pumped from the borehole a pressure pump and a filter cartridge with sterile glass fibre filters Groundwater is pumped into the container so that a known volume can be filtered The volume filtered can vary between 100 to 1000 44 litres The enteric viruses and parasites are strained onto the filter which is then placed into a sterile bag kept on ice and despatched to the analytical laboratory As can be appreciated this is a fairly complex method and the equipment is specialised If the test needs to be done locate a method capable laboratory that will supply the sampling equipment will give detailed instructions and will train the sampler Table 3 5 2 Sample size requirement and holding time for enteric viruses and parasites Maxi Sample Recommended UU Incubation Determinand I Holding Volume Holding Time Period Time Enteric viruses 100 Lor 2 4 week
189. oup of monitoring boreholes at the same site Each borehole has a short length of screen at different depths This method is the safest way to ensure that cross contamination does not occur but is also the most expensive 141 The critical aspect of construction is that the annulus along the outside of the borehole casing must be carefully constructed to ensure that short circuiting does not take place along the space between the outside of the casing and the aquifer material Thus in borehole A3 the deeper of the 3 the screens are set at the bottom of the borehole On the outside opposite the screens must be installed the filter pack Above the filter pack on the outside must be installed a seal usually of benthonite that will prevent water from the upper horizons travelling down the annulus and producing incorrect answers for the sample collected Version B This method consists of multiple piezometers installed at different depths in a single borehole Each zone is sealed off from the adjacent zone using either a benthonite or a grout seal The critical aspect of this construction method is the integrity of the seal If a complete seal is not obtained vertical flow will be induced during sampling If the piezometric level is less than 8 metres from surface suction lift can be used to collect samples but is not suitable for gases and VOCs If greater than 8 metres then the piezometers will have to be 50 mm to 65 mm outer diameter in orde
190. ow Blue phenolphthalein 8 2 0 0 colourless Pink thymol blue 8 0 9 6 yellow Blue 91 The Merck system Aquamerck and the Hanna system both use droppers to add reagent into plastic vials The Chemetic system Titrets uses a syringe type holder with an ampoule of reagent 4 73 ION SELECTIVE ELECTRODES Electrodes have been developed that produce specific responses in mV for certain anions and cations in water Rundle 2006 Similarly to pH and Eh it is therefore possible to connect such an electrode to a pH meter or a special millivolt meter After calibration this yields the concentration of that determinand in water usually a logarithmic response to concentration These electrodes can be influenced by interfering substances and are fragile Orion Research were the pioneers in the development of ion selective electrodes but there are now other manufacturers as an internet search will show 4 7 4 H2S STRIP FOR COLIFORMS A simple method has been developed to indicate coliforms in water This consists of a treated material in a sterile plastic vial Water is added and the vial closed and left standing at room temperature for up to 72 hours A black colour indicates the presence of coliforms A limitation is that if H2S is present then a positive is always obtained Fortunately the human nose is extremely sensitive to H2S rotten egg so these false positives can mostly be avoided The kits are quite inexpensive b
191. p After inserting the spear allow a period of time for turbidity caused by inserting the spear to disappear If the monitoring program is to continue for a long period then temporary shallow piezometers should be installed Ensure the Monitoring Program Guide has detailed instructions and maps on how to access these wellpoint Wetlands are eco sensitive and random walking will cause damage 157 19 3 SAMPLING GROUNDWATER SEEPS If you plan to sample the seep only once dig a small pit in the seep zone let it flow until the water runs clear and sample as for a spring After sampling return the dug sods and restore the area If necessary install a temporary piezometer in the middle of the seep develop it and return the following day when the water has cleared If you are planning to sample the seep periodically then install a semi permanent piezometer A problem with seeps is that the rate of flow can be slower than the rate of volatilization of organic compounds and slower than the drift in pH Eh and of other parameters which depend to some extent on exposure to the atmosphere Results should be interpreted with care 19 4 SAMPLING RIVERBED PITS Sometimes pits dug in a dry riverbed need to be sampled These pits can be animal dug or a source of drinking water for a rural community or self dug in order to get a water sample These can be regarded as springs or seeps If the sampling program is to assess drinking water fitness for
192. pH Chapter 4 3 Eh Chapter 4 4 dissolved oxygen DO Chapter 4 5 alkalinity Chapter 4 6 They must consequently be measured at the borehole preferably using a flow through cell so that the sample is not subjected to the chemical or physical changes caused by exposing the groundwater to the atmosphere Temperature affects most chemical and biological reaction rates and equilibria Temperature can be easy to measure Phreatic water temperature is a reflection of groundwater recharge conditions and for confined water it can be a reflection of depth of flow Electrical conductivity is a simple indicator of all the salts in solution Thus physical or chemical changes caused by exposure of the groundwater sample to the atmosphere can affect it Yet it is a very helpful parameter during a reconnaissance sampling exercise 46 When groundwater is brought to surface degassing or absorption of CO can occur pH changes in the order of 2 units have been noted in some water samples Knowledge of the in situ pH is essential to reconstruct the potential mobility of constituents many chemical equilibria and encrustation and corrosion potential of the groundwater For monitoring groundwater pollution the use of a flow through cell is particularly important as in situ polluted groundwater often has Eh below zero Groundwater with a negative Eh when exposed to the atmosphere rapidly absorbs oxygen causing oxidation and precipitation of som
193. pe ratio of 80 O in the water molecule Deuterium hydrogen 2 analysis refers to the determination of the stable isotope ratio H H in the water molecule Because of the high precision with which these ratios are measured it has become customary to express the ratios as relative deviations from an agreed upon standard The symbol is used to denote this deviation and is defined as S80 a ad Pion O O standara The factor 1000 converts the ratio deviations to per mil parts per thousands abbreviated as o which ensures that the results are expressed in manageable numbers The identical expression is used for 5D or 5 H The standard globally used for water analyses is SMOW Standard Mean Ocean Water This universality means that although 6 is a relative measurement data from different laboratories are quite comparable and meaningful Both these pairs of isotopes are used to describe the processes to which the water has been subjected in the course of the hydrological cycle see for example Clark amp Fritz 1997 Mook 2000 In many mountainous areas there is a distinct altitude effect meaning that lower ratios more negative 5 are found in rainfall at higher altitudes In some areas there is a temperature effect derived from the fact that winter rainfall has lower isotope ratios than summer rainfall In arid areas there is usually an amount effect meaning that large rainfalls or high flood events have lower isotope rat
194. pe or damaged cables immediately Loggers tend to use more power than traditional field meters and replacing batteries or recharging the power supply is also a common maintenance activity Checking the power supply is the first option for troubleshooting Batteries should be removed when the logger is in storage If batteries or probes are replaced or any part of the logger is opened for some other reason be careful to ensure that the watertight seal is restored and all electronic components are protected against water leakage Water repellent grease such as silicone grease may be used to ensure a good seal if advised by the manufacturer 5 3 HELPFUL HINTS FOR OPERATION OF DOWN HOLE LOGGERS It is not possible to provide detailed step by step instructions on the use of down hole logging devices because there are several different instruments on the market which operate in different ways It should also be noted that at the time of writing down hole logging is a growing field in groundwater studies and the information in this manual may be out of date This section gives some general advice which should be applicable for down hole chemical logging of boreholes First check the water table by measuring with a water level probe and total borehole depth The borehole depth must be known from data sheets do not plumb the bore to measure depth as you will disturb stratification This allows you to determine an appropriate depth interval for
195. per that is replaced after each filtering event The advantage of the disposable version is that it is simple to use it is 132 available either standard size for normal groundwater or as high capacity for large volumes or highly turbid samples the disadvantage is that they are more expensive The hand held syringe system can be either a normal syringe or a syringe with a two way valve and a double piston cylinder The normal syringe type is used for low turbidity waters For more turbid waters additional pressure of the pump type is needed Water is drawn into the large cylinder by pulling out the plunger The valve is then turned to divert the water to the filter holder Then a pressure is created to force the water through the filter by pumping the pressure piston This device is acceptable for collecting filtered samples as although the water sample is exposed to oxygen the time span of less than 1 minute to filter the sample should cause no discernible bias 14 4 FILTER MATERIALS AND SIZES Filter membranes come in a variety of diameters the common sizes being 47 mm 90 mm 102 mm and 142 mm The 47 mm size is the most common If the water has abundant suspended sediment using the larger diameter filter means a slower rate of clogging and thus faster rate of filtering Taking into account the first paragraph of this chapter and accepting that filtering will always be considered the question is what filter size should use Fil
196. plications are that there is a production process underground and that dissolution of young chlorides may interfere with the atmospheric CI signal Analysis of Cl is by AMS 26 Helium 3 is produced from the decay of tritium H In some cases it can therefore be used to show the initial tritium content of the water and thereby expand the use of tritium analysis to that of a true dating tool Analysis of He is by high sensitivity mass spectrometry Helium 4 is produced by the radioactive decay of uranium thorium and its daughters the alpha particles produced by these materials are in fact He nuclei He content in groundwater is therefore proportional to the time that the water has resided underground the radioactivity of the aquifer material and some other factors Heaton 1984 It can therefore be employed as a relative dating tool Analysis of He is by high sensitivity mass spectrometry The concentrations of the noble gases neon krypton and xenon are dependent on the atmospheric concentrations the recharge temperature and the amount excess air that is co absorbed by the water during recharge Ne Kr and Xe concentrations have therefore found applications to calculate the recharge temperature of groundwater required for palaeo recharge studies Analysis of these low level noble gases is by high sensitivity mass spectrometry The concentration of the dissolved gases nitrogen and argon in groundwater can also be
197. ply that the user is not as well protected against interferences from other constituents as a proper accredited laboratory method will be Measurements made with these methods in the filed need to be backed up by proper laboratory analysis later 4 7 1 COLOUR METHODS Colour responses of combinations of chemicals are well known and actually form the backbone of many accredited standard laboratory methods The intensity of colour is related to concentration Some of these methods have been adapted for simple routine measurement 4 7 1 1 Indicator Strips Indicator papers also called test sticks are well known for pH measurement and used for quick checks Various papers are available covering different ranges and sensitivities down to 0 5 pH units Many other determinands in water can be analysed in a similar way with specific papers The paper is wetted with the water sample some time is allowed for development of the colour and it is then compared with a colour chart In some cases e g NH another reagent needs to be added first The papers are generally not suitable for low concentrations and may be influenced by other major constituents Merck supplies a wide range of papers trademarked Merckoquant Sigma Aldrich supplies Quantofix test sticks and there are other suppliers 4 7 1 2 Visual Colour Comparisons Accuracy and sensitivity of colour indicators are improved when the reaction takes place in a flask of sample and thereafter
198. r 2 Using Eh meter without offset function the meter is tested by checking Evet relative to the reference electrode used with the procedure outlined above The meter reading for the groundwater Emeasurea must be adjusted to account for the half cell potential of the reference electrode relative to the standard hydrogen electrode Calculate Eh as Eh Emeasured t Eagagcl it or Eh Emeasurea t EvgHg2ce t The subscript indicates that all values are unique for the temperature of the water being measured The values for Eagagc and Engrgect2 Can be looked up in Appendix A 1 for the working temperature of the system EXAMPLE A combination electrode comprising a coupled platinum and silver silver chloride reference electrode saturated KCI filling solution is used to measure Eh of a groundwater sample in a flow through cell After 30 minutes the temperature and millivolt readings stabilise at 22 C and 334 mV respectively The instrument does not have an offset function so the measured potential is relative to the silver silver chloride electrode and must be converted to Eh 334 mV 202 mV Appendix A 1 Using the equation 132 mV 22 224 gives 202 mV 4 4 4 3 Troubleshooting Eh measurements There are several reasons why an Eh measurement system may fail to give reproducible readings Some of the troubleshooting tips below or in the reference documents may help If the reference solution does not gi
199. r Table 2 to obtain the solubility of oxygen in water in mg L e f EC gt 200 mS m then read of the correction factor from Table 3 and multiply this with the solubility obtained above Example calculation of saturated DO At 22 C and 1400 masl and EC 4000 mS m DO of water saturated with air will be 7 4 0 86 6 4 mg L 199 umole L Appendix B Table 1 Dissolved oxygen content of water in mg L at different temperatures and pressures in equilibrium with saturated air derived from Weiss 1970 Pressure mBar 1020 1000 980 960 940 920 900 880 860 840 820 800 Temp C 0 14 7 144 141 138 135 133 130 12 7 124 121 11 8 11 5 13 9 136 134 13 1 128 125 123 12 0 11 7 114 11 2 109 4 13 2 129 12 7 124 12 1 11 9 11 6 11 4 11 1 109 106 10 3 6 125 123 120 11 8 11 5 11 3 11 00 10 8 10 6 103 10 1 9 8 8 11 9 11 7 11 4 11 2 11 0 10 7 10 5 103 10 0 9 8 9 6 9 3 10 11 3 11 1 10 9 10 7 10 5 102 10 0 9 8 9 6 9 3 9 1 8 9 12 10 8 106 104 10 2 10 0 9 8 9 6 9 3 9 1 8 9 8 7 8 5 14 10 4 102 10 0 9 8 9 5 9 3 9 1 8 9 8 7 8 5 8 3 8 1 16 9 9 97 95 9 3 9 1 8 9 8 8 8 6 8 4 8 2 8 0 7 8 18 9 5 9 3 9 1 9 0 8 8 8 6 8 4 8 2 8 0 7 8 7 6 7 5 20 9 1 9 0 8 8 8 6 8 4 8 2 8 1 7 9 7 7 7 5 7 3 7 2 22 8 8 8 6 8 4 8 3 8 1 7 9 7 7 7 6 7 4 7 2 7 1 6 9 24 8 5 8 3 8 1 8 0 7 8 7 6 7 5 7 3 7 1 7 0 6 8 6 6 26 8 1 8 0 7 8 7 7 15 7 3 7 2 7 0 6 9 6 7 6 5 6 4 28 7 9 7 7 7 5 7 4 7 2 7 1 6 9 6 8 6 6 6 5 6 3 6 2 30 7 6 7 4 7 3 7 1 7 0 6 8 6 7 6 5 6 4 6 2 6 1 6 0 32 7
200. r to accept a down the hole pump or 25 mm to accept a 19 mm bladder pump The number of piezometers that can be installed in a borehole with a water level deeper than 8 metres is thus dependent on the diameter of the drilled borehole and the practicalities of properly introducing the seal A 160 mm borehole will take two at most three piezometers and a 200 mm borehole will take three to four piezometers Version C This method consists of a single casing fitted with openings ports at different levels These are very useful in aquifers where the water table is at most 8 metres below surface as the samples can then be collected by suction lift Suction lift is not a suitable sampling method for gases and VOCs The usual construction is to use 3 mm silicone tubing to the sampling port If however you wish to obtain water levels at least 20 mm tubing should be used so that the water level gauge can be inserted into each piezometer tube The multi port sock sampler of Schirmer et al 1995 Jones and Lerner 1995 described later in this chapter is such an example Versions D E and F These methods are described here as they may be encountered in literature or the field None of versions D E or F are recommended for collection of groundwater samples from multi layered or multi fractured aquifers They are not recommended as short circuiting is quite likely to occur in such boreholes Later in this chapter this theme is expanded upon The b
201. rature can be controlled somewhat by pumping long enough so that the sampling equipment attains the groundwater temperature Contact with the atmosphere can cause loss or gain of various dissolved gases and can be avoided by using well designed flow through cells pH Eh DO are particularly sensitive to air contact and reliable measurements of these parameters require protection against air interaction A flow through cell is a closed container with groundwater flowing in at the bottom and out at the top in such a way that no air is trapped inside pH Eh and DO probes can be inserted into the flowing water through waterproof glands on one side of the container in order to take the field readings Many designs of flow through cells exist Walton Day et al 1990 and more can be found on the internet The recommended design Figure 15 1 is that of Garske and Schock 1986 The advantages of this design are Transparent sides so that the coating of electrodes with bubbles colloidal material or mineral precipitates can be observed A conical shape to minimise the trapping of air bubbles and to ensure laminar flow provided the flow rate is low enough The relatively large diameter which if combined with a slow rate of through flow reduces stream potential which might lead to erroneous pH readings An arrangement of probes with respect to the water flow direction so that interaction between probes is avoided It is essentia
202. rd temperature for which reference potentials are reported and will simplify any calculations In general field testing with reference solutions is not always required but will depend on the sampling purpose and accuracy requirements Eh reference solutions may react with dust small particles of iron from borehole infrastructure or other substances making field use difficult Test the equipment as follows 1 Set up the meter and connect the electrodes Switch on and allow the meter to warm up If you are working in the field immerse the container of reference solution in a bucket of flowing sample water to allow for temperature equilibration Unplug the reference electrode fill hole Check the filling solution level and top up to the level of the fill hole if necessary Shake the electrode gently to remove air bubbles Decant a portion of the reference solution into a clean beaker to a level high enough to cover the tip of the platinum electrode and the reference electrode junction Rinse the electrode s with deionised water and blot dry with soft tissue Immerse the combination electrode or both platinum and reference electrodes in the Eh reference solution Do not touch the bottom or the sides of the beaker with the electrodes Stir or swirl solution slowly and allow 15 to 30 minutes for the solution and electrodes to equilibrate Rinse the thermometer with deionised water wipe dry and measure the temperature of the reference s
203. reference electrodes This is a combination of tables 1 and 2 Quinhydrone pH Silver silver chloride Calomel 4 Temperature 3M 3 5M Sat 3M KCI 3 5M 4M KCI Sat KCI KCI KCI KCI KCI 10 255 260 261 215 219 221 221 15 255 259 262 213 217 220 220 20 254 259 263 210 215 218 219 25 255 259 265 209 214 218 219 30 255 259 266 207 212 216 219 35 254 259 267 204 210 215 218 40 254 259 268 203 208 213 218 Quinhydrone pH Silver silver chloride Calomel 7 Temperature 3M 3 5M Sat 3M KCI 3 5M 4M KCI Sat KCI KCI KCI KCI KCI 10 87 92 93 47 51 52 53 15 84 88 91 42 46 48 49 20 80 85 89 36 41 44 45 25 77 81 87 31 36 40 41 30 74 78 85 26 31 35 38 35 70 75 83 21 26 31 34 40 67 72 81 16 21 26 31 Zobell Silver silver chloride Calomel Temperature 3M 3 5M Sat 3M KCI 3 5M 4M KCI Sat KCI KCI KCI KCI KCI 10 241 246 247 201 205 206 207 15 234 238 241 192 196 198 199 20 226 231 235 182 187 190 191 25 219 223 229 173 178 182 183 30 212 216 223 164 169 173 176 35 204 209 217 155 160 165 168 40 197 202 211 146 151 156 161 161 APPENDIX B TABLES TO DETERMINE THE DISSOLVED OXYGEN CONTENT OF WATER To use these tables e Use the water temperature and either the air pressure in mBar or the site elevation amsl in metres from either Table 1 o
204. rehole The sampler is left for a period of time to allow the units to equilibrate with the dissolved species in the groundwater and then recovered for analysis of the accumulated solutes in each unit The accumulated concentrations of solutes in the dialysis cell or gel can be related back to the original concentrations in the groundwater at that depth The dialysis cell sampler is suitable for obtaining undisturbed groundwater samples over small vertical intervals Ronen et al 1986 used a dialysis cell sampler to measure multilevel electrical conductivity and major anion concentrations chloride nitrate sulphate at 3 cm intervals just below the water table in an open borehole The dialysis cells mounted on a PVC rod were filled with distilled water and left in the borehole to equilibrate for 30 days before analysing the equilibrated solutions A diffusive gradient thin film DGT is a method involving a gel disc or strip ina suitable holder Harper et al 1997 Zhang and Davison 1999 DGT Research 2003 The gels are designed to accumulate specific dissolved species from sediment pore waters Specific gels are available for sampling metals phosphorus sulphide or caesium There are also open pore diffusive gels for more general application and restricted pore size gels for labile inorganic species DGT samplers have been used in open water systems and may find future application in multilevel groundwater sampling This method must be viewed
205. relies on a pressure difference behind and in front of the impellor blades to pump water This pressure difference can introduce bias and for very sensitive projects will be unsuitable However for investigations where data accuracy is less stringent electric submersibles can be used Syringes are suitable but cannot be used to purge the borehole Bailers are unsuitable except in two specific cases when they are the method of choice These two cases are when either LNAPLs or DNAPLs are present i e floating organic compounds or sinking organic compounds In either case use a clear wall bailer so that you can get an indication of the thickness of the layer of organic compounds Other than in these two specific cases bailers have limited suitability The sampling pump of choice is a bladder pump section 11 1 Many of these are made of Teflon PTFE However Parker and Ranney 1997a 1997b see chapter 18 investigated decontamination of sampling equipment and showed that PTFE LDPE and the more adsorptive polymers tended to absorb higher levels of organic compounds than did stainless steel and PVC Consequently to avoid cross contamination these plastics need a hot detergent wash plus drying in a hot oven whereas stainless steel and PVC could be properly cleaned using only hot detergent wash 3 4 3 MORE COMMONLY ENCOUNTERED ORGANIC CONTAMINANTS 3 4 3 1 Phenolic compounds Phenol is a benzene ring attached to a hydroxyl group The empirical
206. ric pressure mBar saturated air as function of Figure 4 5 2 Correction factor to account temperature from Weiss 1970 for reduced atmospheric pressure on oxygen solubility lt PRE HH ARERR AEE Ei 1 1 21 1i 1412111 0o95 ES A o9 H 5 H 8 oss E n c Sos BS m go FS m 070 BS H 0 65 FE He HAHEI 0 60 Ei ELE Oe ls s az S mil ee sd ga 68 1 O 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 0 500 1000 1500 2000 2500 Elevation of sample site metre Electrical Conductivity mS m t Figure 4 5 4 Correction factor to account for salinity effects on oxygen solubility from Weiss 1970 Figure 4 5 3 Correction factor to accoun for reduced air oxygen solubility at higher elevations 79 4 5 3 3 Measurement of DO Actual DO measurement of the sample water can be done once the meter electrode system has been calibrated A well looked after electrode will remain stable during a day s work provided the water temperature remains constant It is nevertheless good practice to check the high point calibration at every site The analysis procedure with a Calibrated system is as follows 1 Place the sensor in the flow through cell Gently open the flow control valve 2 Measure the DO concentration at about 5 10 minute intervals until a stable reading is obtained Do not change the pressure or temperature dial on the meter after calibration It is important not to have too high a flo
207. rode or buffer solutions Abandon the calibration and measurements until the problem is found and corrected The third calibration buffer can be used to check the range The pH meter should read the value temperature adjusted if necessary to within 0 1 pH units otherwise the instrument should be recalibrated 58 Calibrate the pH meter immediately before the first measurement of the day and then check for calibration drift with the pH 7 buffer before each subsequent reading Check that the meter holds its slope by measuring the pH 4 or pH 10 buffer a few times during the day 4 3 3 2 pH measurement Always ensure the pH meter is properly calibrated even by measuring a third buffer before measure the pH of a groundwater sample The pH measurement should be taken as follows 1 Rinse a clean beaker several times with the water to be tested and collect a fresh sub sample from as close to the borehole outlet as possible Do not use a bailed sample Try to minimise aeration by using a low flow rate Do not shake or stir the sample vigorously and do not leave it standing in the sun Rinse the pH electrode with deionised water and gently blot dry Insert the electrode into the beaker and stir gently while waiting for the reading to stabilise Record the pH to the nearest 0 1 units Rinse the electrode blot dry and switch off O N O NOTE The tip of a glass electrode can easily be damaged due to scra
208. ry so that they are prepared for receiving and analysing the samples within the holding time 3 2 2 2 Arsenic Arsenic has been identified as an important natural contaminant of natural groundwaters especially from sedimentary formations Examples abound in the literature especially from the Indian sub continent of its behaviour and negative health effects Arsenic is toxic and even at low intake levels has been directly correlated to cancer in humans Arsenic in water occurs in two forms namely arsenate As and arsenite As with arsenite being the more toxic form Analytical methods APHA 1998 are available that can identify and determine the relative levels of total arsenic arsenite and arsenate Sampling for arsenic For total arsenic no special preservation methods are required If the relative amounts of As and As are required sampling must include in line filtering and sample collection and storage without contact with air to prevent oxidation that may change the oxidation state Analyse as quickly as possible after collection There is no universal preservation method 19 3 2 3 ENCRUSTATION AND CORROSION Untreated groundwater can lead to either encrustation or corrosion or can have no effect on the water distribution system In order to assess the potential of these determinands it is important to accurately measure pH in the field chapter 4 and the cations and anions section 3 2 1 in the
209. s Parasites more L s 2 3 days 3 5 5 PITFALLS FOR MICROBIOLOGY SAMPLING The microbiological population of a water sample is estimated by counting the number of colonies that develop when the water sample is cultured grown on a growth medium The sample is incubated for between 12 and 48 hours after which a population count is done Thus you must liaise with the laboratory when you plan to deliver the samples If you can only deliver on a Thursday or a Friday the laboratory technician will have to come in over the weekend This means that a you may have to pay more and b if you have not made prior arrangements and the technician is away for the weekend the sample will not be analysed and you will have to repeat the sample run So if you plan to have microbiological analysis done arrange the sampling programme to have the samples in the laboratory on Monday Tuesday or Wednesday if feasible Boreholes that have been drilled by the mud rotary method can give very high counts of micro organisms for up to a year after installation The drilling mud usually used is a biodegradable material such as Revert and this being made from organic material forms an ideal growth medium for micro organisms Take this into account when evaluating results 3 5 6 MICROBIOLOGY REFERENCES WHO 1996 Guidelines for Drinking water Quality 2 ed Volume 2 Health Criteria and other supporting information World Health Organisation Gene
210. s 95 504 URL http www epa gov ahaazvuc download issue lwflw2a pdf last accessed on 5 November 2006 Robin M J L and R W Gillham 1987 Field evaluation of well purging procedures Ground Water Monitoring Review 7 4 85 93 130 CHAPTER 14 FILTERING DEVICES 14 1 INTRODUCTION Groundwater samples brought to the surface will to varying degrees contain dissolved species colloids and suspended particles One of the aims of low flow sampling is to reduce but seldom eliminate the amount of larger colloids and suspended particles The truly dissolved phase has molecules or polymers that are much smaller than 0 1 micron 1 micron 1 um Colloids range in size from 0 1 um to 10 um Puls and Barcelona 1996 Saar 1987 Suspended particles are still larger Filters come in a variety of filter pore sizes commonly ranging from 0 1 um to 5 um Thus depending on the filter size used you can filter out some or most of the colloids and the suspended particles The question as to whether or not to filter the sample before analysis to some extent depends on the original question posed at the start of your groundwater sampling program What is the purpose of the sampling program As noted a few times in this manual the purpose of the program influences the contents of the Monitoring Program Guide which in turn prescribes the sampling procedures The pH and Eh of in situ groundwater is usually different to that same water at surface and t
211. s divided into two methods depending on the presence or absence of free phase hydrocarbons floating on the surface see also section 3 4 4 5 LNAPLs and DNAPLs 1 Lower a clear sided bailer and collect a sample at the water table Check for free phase Even a haze of hydrocarbon is regarded as free phase If no free phase is present go to 2 If a free phase is present go to 3 If no free phase is present measure the water level purge the borehole collect the water sample and preserve at 4 C If a free phase is present then the hydrocarbon must be identified Use a bailer and collect samples from the interface until about 500 mL has been collected Collect the floating product in a clean amber glass jar and preserve at 4 C An interface meter chapter 10 is a useful tool to have if one plans to measure many monitoring wells and regularly 35 3 4 4 GENERAL GROUPS OF ORGANIC COMPOUNDS 3 4 4 1 Dissolved Organic Carbon DOC DOC is an indicator of the total organic matter content of groundwater As such it is a very useful screening tool as it is a relatively cheap parameter costing between one and two times the price of a sodium or chloride determination In a groundwater sample the total organic carbon will comprise the dissolved DOC and insoluble or particulate organic carbon The DOC in turn comprises the volatile and the non volatile fractions The concentration range of DOC in most unpolluted groundwater is typically
212. s driven The most widely available are bladder pumps Peristaltic pumps must not be used for volatile organics An important aspect is that inserting pumps for a sampling causes mixing in the column and thus requires an 121 extended purging time Dedicated pumps left in the well are therefore preferred over any other system If you are designing a sampling program for a big issue pollution site and are considering low flow sampling then you must do considerable additional reading The influential paper strongly promoting the method by Puls and Barcelona 1996 is a must read while Stone 1997 discusses the pro s and con s Many other documents especially from the US EPA can be found by Googling WARNING 1 Make sure that a zone of high permeability on the outside of the casing caused by a poorly designed gravel pack or damaged formation does not allow vertical flow and short circuiting Doing low flow sampling in such a borehole will be fruitless and misleading WARNING 2 The pumped water flows slowly delivery pipe and thus will be affected by variable outside temperatures Thus collecting a groundwater temperature during low flow sampling is likely to be misleading 11 4 Foot valve samplers Foot valve samplers go under various names such as inertial foot valve samplers and tubing check valve samplers These are non return valves or foot valves fitted to the end of reasonably stiff tubing Rapid up and down movement of the tubin
213. s htm_ last accessed on 17 October 2006 Geyh M 2000 Environmental Isotopes in the Hydrological Cycle Volume 4 Groundwater IHP V UNESCO Paris URL http Awww iaea or at programmes ripc ih volumes volumes htm last accessed on 17 October 2006 Heaton T H E 1984 Sources of the nitrate in phreatic groundwater in the western Kalahari J of Hydrol 67 249 259 Heaton T H E 1986 Isotopic studies of nitrogen pollution in the hydrosphere and atmosphere a review Chem Geol 59 87 102 Kalin R M 2001 Radiocarbon dating of groundwater systems 111 144 In Cook P G and Herczeg A L ed Environmental Tracers in Subsurface Hydrology Kluwer Boston Krouse H R and Mayer B 2000 Sulphur and oxygen isotopes in sulphate 195 232 In Cook P G and Herczeg A L ed Environmental Tracers in Subsurface Hydrology Kluwer Boston Mook W G 2000 Environmental Isotopes in the Hydrological Cycle Volume 1 Introduction IHP V UNESCO Paris 280p URL http www iaea or at programmes ripc ih volumes volumes htm last accessed on 17 October 2006 Plummer L N and Busenberg E 2000 Chlorofluorocarbons 441 478 In Cook P G and Herczeg A L ed Environmental Tracers in Subsurface Hydrology Kluwer Boston 29 3 4 ORGANIC COMPOUNDS Organic compounds have primarily carbon hydrogen and oxygen as the main components of their structural framework In natural uncontaminated groundwater most dissolved organic compou
214. s measure and record the conductivity of the water sample The International System of Unit SI which is used by South Africa and most countries reports conductivity in millisiemen per metre mS m In many other countries the unit of measurement is micromhos per centimetre umhos cm Some instruments have various scales of sensitivity and unfortunately have named these scales in various fashions such as millisiemen per centimetre or microsiemen per centimetre All measurements must be reported in mS m It is not unusual to read a set of chemistry results that appear to be incorrect only to discover that the EC has been reported as shown on the meter read out face and thus with the incorrect units Conversion table for EC units 1 Siemen per cm x 100 000 1 millisiemen per metre 1 Millisiemen per cm x 100 1 millisiemen per metre 1 Microsiemen per cm x 0 1 1 millisiemen per metre 1 Micromho per cm x 0 1 1 millisiemen per metre There are several reasons for determining the EC of a sample in the field at the time of collection rather than waiting for a laboratory measurement e The field determination can be used as an aid in evaluating whether a sample is representative of water in the aquifer see Chapter 13 Purging the Borehole e An EC value that is markedly different from values obtained in nearby boreholes may indicate a different source of water such as induced recharge contamination from the surface or leakage from a format
215. s needs to be taken care of by assessing chemical change and the isotope ratio 9C 2C Clark amp Fritz 1997 Kalin 2000 Geyh 2001 Atmospheric nuclear weapons tests conducted between 1954 and 1962 have released large quantities of radiocarbon into the atmosphere and this has gradually found its way through photosynthesis of atmospheric CO into all living matter In the southern hemisphere atmospheric radiocarbon values peaked to 160 pmc and thereafter reduced to 110 pmc by the year 2000 The radiocarbon content of groundwater has followed suit and elevated C contents in groundwater are a clear indication of a contribution of recharge from the period after 1955 Sampling for radiocarbon lf fC analysis is done by conventional counting analysis then large quantities of water are required Some extraction method needs to be used to concentrate the dissolved inorganic carbon DIC into bottles that can practically be transported Field analysis of alkalinity will provide a good estimate of the DIC of the sample Consult the analytical laboratory for equipment and procedures If C analysis is done by accelerator mass spectrometry AMS the 0 5 to 1L water will be sufficient No extraction will be required Keep samples cool and in the dark If biological activity is expected preservation with NaN2 or HgCle is required Note that HgCls is poisonous and should be avoided when possible 3 3 4 TRITIUM Tritium or hydrogen 3 is a
216. s x duioo x duuoo x9 dwo9 ajduis Aaa 9uo l dus duts asn jo seg MoT MOT MOT 1e1 polN ayesapoy ayesapoy MOJ Ala MO MO s soo Buluuny 1e1 polN MO ayesapoyy MO MO MO MOJ A uBiu poyy uBiu poy s soo jeyide juawdinbZ Jaujo Aue ssieuuoo5 1 Buuolluouu Bunoyuow Buuolluouu aouessieu Jaujo Aue aouessieu JO BuuolluoNW 10 100d y 400d nq gy 400d Ing y 100d Ing IV uoo tJ BuuolluoW jo BuuolluolN ad uonsBi ls Au uoo tJ pano poys B6uidund uni sdund payyeysul Ayedoid aye su lps Bulxiw ou QUON SOWIJOWOS ON SOWIJOWOS J QUON 80U0 uoN SINDIO J QUON J au0N 8 Bumno sro uous u do u do p u sun yoed ou u do u do p u uiosun u do p leSip q p 1eoSip q ou uoq Jo d JUQWUOIIAUZ si 1l uioz ld si dues sji dues si uuoz ld si duies IBA nInuu yoos B6uidund sui ls s oyloods I A nInuu s ou ioq s s e1p 199 p jpung yod niny suu ls s ayjeg uoesedag JOYIed yydeq pelleysu JENplAlpu SI e19p 104 1X9 s G66 L YOS NE pue J8UI97 191JV s nbiuuo 1 Huljdwes 134eMmpuno jangjNjnw Jo s in1e j 1 9 AALL 16 3 LIMITATIONS OF OPEN BOREHOLE TECHNIQUES Open borehole methods whether in unconsolidated aquifers or in hard rock aquifers or in fractured rock aquifers carry the risk of obtaining poor or unrepresentative samples Lerner and Teutsch 1995 Shapiro 2002 Gillham et al 1983
217. se isotopes tend to settle in parts of the body where their radiation interferes with human processes Gamma radiation mainly from potassium readily passes through the body with very little absorption and is of little health significance Alpha particles are the main health hazards since their range in the body is short yet they have sufficiently high energy to cause DNA damage leading to increased cancer risk Beta emission is considered less dangerous since the energy levels are lower Analyses of gross beta and gross alpha radioactivity are used as a first screening technique to identify the presence of radioactive isotopes The actual permissible levels depend on the water use and the identification of the individual isotopes that may be present in the water DWAF 1996 Radon gas is quite soluble in water and since it is an emanation product of uranium is quite common in polluted and unpolluted groundwater where its level is mainly dependent on flow characteristics It is rapidly released from surface water and can therefore serve as indicator of groundwater inflow into surface water bodies Cecil amp Green 2000 Sampling for radioactive determinands When planning to carry out a radioactivity monitoring programme first consult the analytical laboratory for containers preservation reagents and procedures The lab will be able to advise whether the nuclear regulator in South Africa it is the National Nuclear Regulator
218. sed steadily at known rates since the 1950s Since the early 1990s the growth rates have dropped off significantly Plummer and Busenberg 2000 Three of these compounds CFC 11 CFC 12 and CFC 113 have proved very useful as hydrological tracers From the atmospheric levels and solubility in water it can be calculated what the different CFC levels in recent groundwater for each recharge year since 1960 would have been Given the good chemical stability of these compounds one therefore has an additional tool for dating and tracing of recent groundwater recharge Sulphur hexafluoride SF is also a man made compound exhibiting a steady increase in the atmosphere since 1960 It is also an inert gas used in various technical applications worldwide and there are no indications that its atmospheric level will decrease As with the CFCs SF can be used as tracer of recent groundwater recharge the advantage is its chemical inertia and steady input function the disadvantage is its much lower concentration in water which is due to its low solubility in water and lower atmospheric levels 25 Sampling for CFCs and SF Sampling for these gases requires complete isolation from the atmosphere during the transfer from underground to sample bottle The methods require some practice to obtain reliable results that can withstand the rigours of field work and transport Different techniques have been developed by the various analytical laboratories a
219. sferred and claimed This is accomplished by a written record documenting the sample identity from collection to introduction as evidence Karklins 1996 The Chain of Custody form often shortened to COC is the document that lists all the persons that have access to the samples Thus the sampler hands the samples and custody to the designated laboratory person who hands them and custody to the designated person s carrying out the various required analyses There may be a few persons in between such as the courier recipient the courier deliverer or a head office staff person All of these must sign the Chain of Custody form A sample is in custody Karklins 1996 if it is 1 In physical possession or 2 In view after being in physical possession or 3 Secured so that no one can tamper with it 108 The following Field Chain of Custody Procedures have been adapted from the Wisconsin Groundwater Sampling Manual Karklins 1996 1 Limit sample collection and handling to as few people as possible If sample transfers to another person are necessary use signed receipts of possession The chain of custody record must accompany the samples Keep a copy of the chain of custody record for your own records 2 If the samples are known or suspected of being hazardous give a receipt for each sample collected to the property or facility owner The property or facility owner may request split samples 3 If the samples are known or susp
220. singly rapidly in terms of volume of research undertaken papers published and funding provided attention has been directed towards contamination of groundwater With this attention the understanding of the complex hydrogeochemical and hydrogeological processes governing the fate and transport of these contaminants has increased and continues to increase Closely linked to this has been a proliferation of specialised sampling equipment complex sampling techniques and legislation governing sampling at pollution sites This manual does not pretend to be exhaustive and provide all the answers to groundwater sampling for all instances What this manual does provide is sufficient technical detail for hydrogeologists involved in water supply projects to collect proper samples and to conduct hydrogeochemical investigations of natural systems and forms the fundamental base for the majority of groundwater pollution investigations However if a highly complex or big issue groundwater pollution project is to be tackled then the Groundwater Sampling Project Leader will need to ensure that she he is up to date with the latest advances The bulk of published information used for this manual derives from the USA and in particular the US EPA and the USGS Most if not all of their information can be obtained by Googling or searching their websites namely http Awww epa gov and http www usgs gov This manual does not describe in any detail the behaviour o
221. stainless steel 316 Teflon Viton polyvinyl chloride PVC Silicone Neoprene polycarbonate Delrin Helical rotor pump Water sample is forced up discharge line by electrically driven rotor stator assembly Materials may include stainless steel 304 ethylene propylene rubber EPDM Teflon Viton polypropylene Gas drive piston pump Piston is driven up and down by gas pressure controlled from the surface Gas does not contact sample Materials may include stainless steel 304 Teflon Delrin polypropylene Viton acrylic polyethylene Centrifugal pump Electrically driven rotating impeller accelerates water within the pump body building up pressure and forcing the sample up discharge line Commonly constructed of stainless steel rubber and brass Peristaltic pump Self priming vacuum pump is operated at ground surface and is attached to tubing which is lowered to the desired sampling depth Sample contacts vacuum Materials may include Tygon silicone Viton Neoprene rubber Teflon Gas lift devices Gas emitted from gas line at desired depth forces sample to surface through sampling installation Another method utilizes gas to reduce effective specific gravity of water causing it to rise Wide variety of materials available for tubing Gas drive devices Positive gas pressure applied to water within device s sample chamber forces sample to surface Materials may include polyethylene brass nylon aluminium oxi
222. steps 5 9 5 Use the water temperature to obtain the solubility of oxygen in water in mg L Figure 4 5 1 6 If a pressure reading on site is available read off the pressure correction factor Figure 4 5 2 otherwise use the site elevation in masl from Figure 4 5 3 7 If EC gt 200 mS m then read off the salinity correction factor from Figure 4 5 4 8 Multiply the solubility with the two correction factors to obtain the corrected value 78 9 Adjust the DO reading with the calibration control to the value obtained by step 8 Some instruments will allow you merely to set saturation to 100 The meter is now ready for use To get the pressure input correct note that 1 atmosphere 760 mm Hg 101 325Pa 1013hPa 1013 mBar To improve the calibration accuracy the tables of Appendix B 1 B 2 and B 3 can be used rather than figures 4 5 1 to 4 5 4 Example calculation of saturated DO At 22 C and 1400 masl and EC 4000 mS m DO of water saturated with air will be 8 7 0 845 0 86 6 3 mg L 198 umole L ATIT EO saaana Z73333 IILE F EEEE EED EEEE s Tr 2 o FECERAT Trt A eE esl aa a Sate HF os FeaT TETE CEER TEE 5 Prik PEETELI AREE L g L a k ee Li EI Leta LECIrial131131r1rrr Errciciiaq1irrrr sss 5 add bb cec EEEE 0 5 10 15 20 25 30 35 40 E eS ee ee E E eS Temperature oC 70 POE PT ae 750 800 850 900 950 1000 1050 Figure 4 5 1 Solubility of oxygen from Atmosphe
223. t accessed 20 September 2006 39 NZ MoE 1999b Guidelines for assessing and managing petroleum hydrocarbon contaminated sites in New Zealand Published by the Ministry for the Environment PO Box 10362 Wellington New Zealand URL http Awww mfe govt nz publications hazardous oil quide jun99 user quide jun99 pdf last accessed on 20 September 2006 40 3 5 MICROBIOLOGICAL DETERMINANDS 3 5 1 INTRODUCTION The subsurface environment both in the vadose zone and the saturated zone has a huge microbial population and a wide variety of micro organisms These range from health affecting species such as Giardia lamblia and Salmonella typhi typhoid fever to indicator bacteria such as faecal coliforms and to the large variety of species of bacteria that mineralise organic carbon Groundwater from virtually any source has living micro organisms present Living and viable micro organisms have been found in water at high temperatures in highly saline environments and even in water that is 100 000 s of years old The study of these organisms is specialised and requires a well trained microbiologist who will apply special sampling and preservation techniques in order to obtain representative samples It is in this latter sohere of activity that extensive and on going research is being conducted For the non specialist groundwater investigator there are various groups of micro organisms that are sampled and analysed called indicator bacteria
224. t be considered good practice these types of short cuts are occasionally necessary and can be quite effective provided they are used with caution The system requires a clear bottled water bottle a rubber bung and the necessary tubing through the bung to control the flow rate of the water Figure 15 2 Water is fed through the neck of the bottle to its bottom and led out through a short tube at the top The probe is held in position in the bottle through the rubber bung One could also use Prestik provided the internal pressure of the system can handle it It is essential to keep the water flow rate low and to ensure that all air bubbles are eliminated Prope WATER IN NV WATER ouT Figure 15 2 Sketch of improvised flow through cell The outlet tube should not protrude through the stopper into the bottle to ensure that all bubbles can readily be removed from the cell 15 3 THE OPEN BUCKET METHOD An even more primitive but practical solution is to feed the water to the bottom of a bucket and allow the bucket to overflow The electrodes should then be suspended in the bucket in such a way that the sensors do not touch the bottom yet are deep enough in the water for atmospheric air not to have an influence 138 15 4 REFERENCES Garske E E and M R Sch ck 1986 An inexpensive flow through cell and measurement system for monitoring selected chemical parameters in groundwater Groundwater Monitoring Review 6 3 79 84
225. t is not either surface water or groundwater that has already entered the wetland and which should now be regarded as surface water So ensure that the boreholes seepages or well points do in fact sample the water that they are intended to sample 19 2 SAMPLING SPRINGS For sampling purposes a spring should be treated similarly to a borehole except for two differences Firstly a spring flows continuously so there is no need to purge The second difference is a complication You must be very careful not to allow contamination of this inflowing water with standing water The best way to reduce contamination is to use the borehole sampling pump and put it in the flowing water as close to the spring outlet as possible Measure field parameters record results rinse sample bottles and collect samples as you would for a borehole Electrode measurements can be made from a little pool close to the spring outflow provided that the water velocity is not too great to cause distortion of the electrode readings Also be aware that it is easy to damage the sensitive parts of an electrode by touching the side of a water catchment A useful tool is a well pointing spear This is a short section of stainless steel well screen with a point at the end and connected to a length of metal casing The spear is pushed into the source the sampling pump lowered down the inside and a sample can be collected without problems of grit jamming or damaging the sampling pum
226. tching against the sides of a beaker or too vigorous drying before or after measurement Be extremely careful with the electrode it is expensive and breakage can ruin your field trip Where possible pH measurements should be made using a flow through cell Chapter 15 rather than using a groundwater sub sample for measurement 4 3 3 3 Trouble shooting pH meters and electrodes Do not let the glass electrode dry out Cover it with the cap or the rubber sleeve that is supplied with the electrode and fill with a few drops of storage solution Ensure the liquid filled glass electrode is filled with KCI solution and contains no trapped air bubbles Ensure that the electrode is clean If not clean glass electrodes by alternately immersing three times each in 0 1N NaOH and 0 1N HCI Clean ISFET electrodes with a toothbrush and mild detergent Use buffer solutions before their expiry date and decant a fresh portion for each calibration For further trouble shooting read Standard Methods APHA 1998 or Wilde et al 2006 Gel filled electrodes should always be stored with the bulb wetted with the manufacturer s solution never store wetted with dilute solutions 59 4 3 4 pH REFERENCES APHA 1998 Method 4 500 H Standard methods for the examination of water and wastewater 20 ed Am Public Health Assoc Washington DC IQ Scientific Instruments 2002 Frequently asked questions about ISFET FET pH technology
227. temperature of the sample solution e g by immersing sealed bottles in the sample water for five minutes Check for temperature correction factors usually printed on the side of the buffer bottle and set the pH meter to read the temperature corrected pH value for each buffer unless automatic temperature compensation is active For precise determinations the buffer temperatures should be within 1 C of the sample solution APHA 1998 4 3 2 4 pH Equipment Checklist 1 pH meter 2 pH combination electrode 3 pH buffer solutions of pH 4 pH 7 and pH 10 500 mL each 4 3 x 100 mL glass or plastic beakers to hold buffer solutions when calibrating the pH meter Use plastic beakers if using a glass pH electrode in order to reduce breakage Filling solution for electrode plus syringe Bucket to immerse buffer solution in order that the buffer solution and the groundwater are within 1 C 7 Thermometer if pH meter does not have automatic compensation 8 Deionised water plus squeeze wash bottle 9 Soft tissue to dry electrode 10 11 O Oo x N Table or flat working surface Flow through cell Chapter 14 desirable but not essential i NOTE Low salinity or low alkalinity water is usually badly buffered which means that the pH meter readings will not be steady A flow through cell will improve stability 4 3 3 FIELD PROCEDURE FOR pH MEASUREMENT READ THE MANUFACTURER S INSTRUCTIONS F
228. ters come ina variety of pore sizes ranging from 0 1 um to 5 um The industry standard size recommended is 0 45 um but this allows smaller colloids to pass through If you want to understand the dissolved phase only then use a 0 1 um filter At this pore size even bacteria will be removed This filter size usually clogs very quickly making it worthwhile to use a large diameter filter and to check the required sample size carefully If you do not have large diameter filters then use a sandwich of filters with a coarser 1 um or 2 um filter first then the finer filter If you want to understand the colloid phase matters become more complex Colloid composition and physical make up vary considerably Colloids range in size from 0 1 um to 10 um Puls and Powell 1992 showed that colloids up to about 2 um can move with groundwater but larger colloids tend not to move Colloids include large organic molecules such as humic and fulvic acids aluminium oxides iron hydroxides manganese oxides and secondary clay minerals They can have contaminants adhering to them and thus the smaller ones can increase the mobility of contaminants Thus if the monitoring program requires an understanding of colloid transport then add a second filtering program to ensure the colloid pollution load is included in the total contaminant loading For contaminant site monitoring highly turbid samples must be avoided by firstly ensuring the boreholes are properly cons
229. the depth of the borehole described in step 2 By measuring the depth you tend to disturb material settled in the sump and this will add to the turbidity Seeing as the purging volume has been established and recorded in the Monitoring Programme Guide the depth should only be checked once sampling of the borehole is complete Once the borehole has been purged with the pump still pumping lower the pump about 0 5 m and collect the water sample This is done so that contamination from the stagnant water which is above the pump inlet does not occur Figure 13 1 127 15 Collect the required groundwater samples 16 Ifthe site contains hazardous or potentially hazardous groundwater pollution make arrangements to safely dispose of the purged water which may or may not contain toxic substances Collect the purged water in the pre arranged containers and dispose safely 17 Measure the borehole depth to check that collapse has not occurred since the previous sampling run Table 13 1 Borehole volumes per metre depth for different borehole diameters Borehole diameter Borehole diameter Volume per metre depth inches mm litre 1 25 0 51 2 51 2 0 3 76 4 6 4 102 8 1 5 127 13 6 152 18 7 178 25 8 203 32 9 229 41 10 254 51 11 279 61 12 305 73 Please remove non standard diameters from the table EXISTING BORE HOLE INSTALL SAMPLING AFTER PURGING WITH SCREENS OR PUMP A FEW METRES LOWER PUMP OPEN HOLE WITH BELOW THE WATER OS
230. the nearest 0 2 C while the thermometer is immersed in the water do not pull the thermometer out of the water to read it in the air 5 Rinse the thermometer with distilled water and place it somewhere safe for future use 6 Do not measure the temperature in discharging water at the end of a long discharge pipe or if the flow is very low as the water will have been heated or cooled while travelling down the pipe and will not reflect in situ groundwater 4 1 3 TEMPERATURE REFERENCES Wilde F D 2006 Temperature version 6 2006 U S Geological Survey Techniques of Water Resources Investigations book 9 chap A6 section 6 1 Available from the URL http oubs water usgs gov twri9A6 last accessed on 22 November 2006 4 2 ELECTRICAL CONDUCTIVITY Conductivity is the ability of an aqueous solution to conduct an electric current The electric conductivity of water is measured as the reciprocal of the resistance measured between two parallel metal plates through an aqueous solution at a specified temperature The conductivity of water depends on the presence of ions their total concentration mobility valence and relative concentrations and on the temperature of measurement Solutions of most inorganic acids bases and salts are relatively 48 good conductors Conversely molecules of organic compounds that do not dissociate in aqueous solution are poor conductors if at all APHA 1998 Practical meters and electrode
231. the necessary sterile bottles Some laboratories supply glass bottles with glass stoppers A piece of paper or length of floss is used to prevent the stopper from permanently sticking Note that when collecting the water sample this paper floss must not be left in the bottle but must be discarded More information on sampling bottles is given in chapter 9 Sampling procedures For most investigations you will be assessing the microbiological quality of groundwater straight from the aquifer Therefore use a sample collecting device as described in Chapter 11 Purge the borehole properly On the other hand if the object is to determine the water quality available to the end user then sampling must be done right at the user s tap For some cases you will be trying to track down the cause or source of microbiological contamination in a reticulation system You will then sample at the well head and also 43 at various points along the reticulation network right up to the end user s When you collect water from a reticulation system the water will most likely have been chlorinated In order to understand whether this water is safe for consumption the free chlorine must be neutralised Free chlorine is neutralised by adding 1 mL of 30 m v sodium thiosulphate per 1 L of sample If this is part of the sampling program ensure that you take along sample bottles with sodium thiosulphate added prior to sterilisation Do not add sodium th
232. the screen Nilsson et al 1995a b Jones and Lerner 1995 16 2 3 Summary of multilevel sampling techniques Table 16 1 has been adapted from Lerner and Teutsch 1995 to summarise the features of various multilevel sampling techniques 146 AA joy 10q S A S A S A S A S A S A SO ON S A Jo asn asodindnynyy a qeue quos sebaq quos sebaq quos sebaq qios sebaq quos sebaq seb p Aen ajqeue ajqeue ajdwes uo yay uoN 100d uoN poor poop poog uoN poop poop Ayyiqe Buiysn 4 ews Ala poy yews 12 10 abe abe ayesapoy 12 S0 pon yews pon yews pejdwes uin joA molfeus mo feyus WOO gt d q d q d q d q d q d q yd p uinuixeN uonnios u XIU qix J lqix J s n u lqix ju lqix jU ulJ S A Aew nq s A S A Alaa SoA AJOA SoA MO e O SOA ON 1nq sod ing SO eyeinooe 9497 JULUHOH d s ou ioq duind Ajuo s ou ioq sdund slu uoduuoo s ou ioq usemjeq ajdwes j jjeq dwnd jdwes sjoyoed usemjeq jq s wqns paAow sduind aiqesodsip usamjeq juo luO 404 p p N JO Pp D N JOJ YNA p p N usn HIH p p N uolguluie1luo5 9q p p u ON ying swoy ying swoy ying swoy sduind ying swoy Burp Burjjp y nq woy yayddns oN ddns on ddns ON JeloJOWWOD Velose uUWOdD eloJOWWOD pasijeioeds piepuels iliqe ieAV Nenuwun yeySul Scuo p dx p u p dx pseu pa jeysul ajdwis a dwis a dui
233. the stirrer mixes the water gently and does not touch the pH sensor 7 Record the pH when a stable value has been reached 8 If the pH of the water is greater than 9 a two point titration will be required In that case follow step 9 to 13 to the end point at pH 8 and the repeat the same steps to end point pH 4 see figure 4 6 2 9 Add a small quantity of acid to the solution note the burette reading V and record the pH value when it has reached stability Repeat step 9 until the pH is below 3 Plot out the pH as function of the volume of acid added Fig 4 6 2 Determine the end point V1 by one of two methods Visually establish the value of V at which the pH changed most rapidly A more precise alternative to 13 is to calculate the slope ApH AV for each interval plot it against V as in Fig 4 6 2 and determine the points of maximum slope 15 The calculation of alkalinity is done by the following equation a Alk M x V V2 x1000 x 50 in mg CaCO L 16 Rinse the beaker and pipette Discard unused acid from the burette and pack everything away k sk ots OWN O wm rae veo YS a CALCULATION EXAMPLE 100 ml V2 sample was titrated with 0 1M HCI M1 The first endpoint was at 0 8 ml acid the second endpoint at a burette reading of 8 ml acid What are the different alkalinity values Use the equation 86 A M x V1 V2 x1000 x 50 For the first endpoint V 0 8 ml from which Carbonate alk
234. these very low pumping rates The theory of practice is that one does not need to evacuate 3 borehole volumes rather pumping at these low rates results in laminar flow within the borehole and mixing of fresh aquifer water with stagnant borehole water does not occur Puls and Barcelona 1996 describe the purging and sampling procedure in detail so if you have a contamination site with low permeability horizons ensure you read this document Occasions when purging should not be done are e When it is necessary to observe whether or not floating and or sinking organic compounds such as diesoline gasoline petrol etc are present For this purpose use a bottom entry bailer made of clear material so that the thickness of the floating organic compounds LNAPLs can be measured For sinking chlorinated solvents DNAPLs such as carbon tetrachloride CCl a clear bailer is used to collect a sample at the bottom of the monitoring borehole Note that neither of these two procedures gives a measurement of the degree of contamination but only gives a yes contamination is present or a no contamination does not appear to be present answer e When you are about to conduct down hole logging Chapter 5 do this first and then purge the borehole for sampling 13 7 REFERENCES Puls R W and M J Barcelona 1996 Low flow minimal drawdown groundwater sampling procedures U S Environmental Protection Agency Groundwater issues report EPA 540
235. thods are therefore all positive displacement devices The method of choice is a bladder pump which is also the method of choice for sample collection at pollution sites Table 4 5 2 Rose and Long 1988 Sampling pumps suitable for monitoring dissolved oxygen from Acceptability of Sampling method or Comment method recovery mechanism Bladder pump Acceptable Offers flexibility to select sampling depths I I Conditionally N M h itrogen displacement Aoceptable ay cause pressure changes Gas driven piston Conditionally May cause pressure changes pump acceptable Conditionally Sampling bottle should be held well below Natural spring bas acceptable the spring orifice Conditionally Intake level should be well below the Production well pump in place pumping acceptable as a method of last resort pumping water level turbulence and pressure changes can result Portable submersible pump Conditionally acceptable as a method of last resort Intake level should be well below the water level turbulence and pressure changes can result Bailer Unacceptable Transfer of sample can disturb dissolved gases Suction lift centrifugal pump Unacceptable Outgassing loss of oxygen is likely to occur Airlift pump Unacceptable Oxygenation of the sample will occur 4 5 2 2 oO N O O WS wae we we was wa manufacturer s aerat
236. tical profile data Stratification of water quality in the aquifer cannot be identified under such conditions Tredoux et al 2000 It is probably safest to allow at least one day with no pumping before trying logging the borehole Down hole logging devices are expensive and are exposed to unusual risks when lowered into the subsurface Protruding pieces of screen or casing along joints changes in casing diameter or foreign objects in the borehole can provide obstacles that damage the logger or cause it to become lodged in the borehole particularly in cases where boreholes are poorly constructed Sometimes borehole logs are also inaccurate for example the depth may not be properly recorded To minimise risks to the logger a dummy can be used This is simply a cylinder preferably of slightly bigger dimensions and greater mass than the logger which is lowered down on a rope to check the ease of access before logging especially in unfamiliar boreholes The time needed to stabilise after disturbance of the water column by the dummy must be weighed against the considerable expense of damaging or losing the logger A CAUTIONARY NOTE REGARDING DOWN HOLE LOGGING Down hole logging data can provide very useful insights to water quality variations with depth and this relation to either lithological changes or to fracturing Down hole loggers should be used more often in groundwater quality investigations A cautionary note is however raised Down
237. to the borehole as possible Although use of a flow through cell Chapter 15 is recommended for pH measurement it is not essential 4 3 1 METHOD OF pH MEASUREMENT pH can be determined by electrometric or colorimetric methods Electrometric methods use either a glass electrode or an ion sensitive field effect transistor ISFET Colorimetric methods use pH indicators e g litmus paper which change colour with a change in pH Colorimetric methods are only suitable for very rough pH estimates 2 units and are generally not recommended for groundwater investigations The glass electrode is the classical method of pH measurement pH is determined by measuring the electrical potential that develops across a glass membrane which is sensitive to hydrogen ions ISFET is a relatively new technology using a solid state sensor that responds to the hydrogen ion IQSI 2002 Both the glass electrode and the ISFET sensor are used in combination with a reference electrode of stable known electrode potential connected to electric potential measuring device high impedance voltmeter When the electrodes are immersed in liquid a circuit is completed through the meter and a voltage is produced that is related to the hydrogen ion activity in solution The measured value must be calibrated to one or more aqueous pH buffer solutions of known fixed pH The electrode system produces an electrical potential E in millivolt that is linearly related to the pH o
238. to pH lt 2 Cool 4 C 7 days Chloride 50 P G Cool 4 C 28 days Colour 500 P G Cool 4 C 48 hours Chromium total 100 P A G A Filter on site 6 months hexavalent 1000 P A G A HNO to pH lt 2 Unfiltered 24 hours Cool 4 C Cyanide 1000 P G NaOH to pH gt 12 14 days total Cool 4 C Dark 24 h if S present Deuterium 20 P G 1 year 165 Diesel Range 1000 G TC Cool 4 C 7 days Organics DRO 40 days extracted DO Winkler 300 G Fix on site 8 hours DOC 100 G preferred Cool 4 C Dark 7 days EC 500 P G None 28 days Fluoride 100 P G None 28 days Gasoline Range 40 x2 G TC Cool 4 14 days Organics Hardness 100 P G Cool 4 C 7 days HNO to pH lt 2 6 months lodine 500 P G Unfiltered Cool 4 C 24 hours Iron total 50 P A G A Filter on site 6 months Iron ferrous 50 P A G A HNO to pH lt 2 15 min Analyse on site Manganese 50 P A G A Filter on site HNO to pH lt 2 6 months Major cations amp 500 P G Cool 4 C 7 days anions Metals not Hg 1000 P A G A Filter on site 6 months or Cr VI HNO to pH lt 2 Mercury 500 G A P A Filter on site 28 days G HNO to pH lt 2 14 days P Cool 4 C Microbiology Coliforms 1000 G B P sterilized Cool lt 10 C during transit 24 hours Plate count 100 24 hours MTBE see VOCs Nitrate 100 P G Cool 4 C dark 1 2 days HSO to pH lt 2 Nitrite 100 P G Cool 4 C dark ASAP 5N 500 P G
239. torage box to prevent breakage of glassware Various concentrations of acid alkali can be used for the titration as long as the concentration is known accurately Use either standard hydrochloric acid solutions of certified concentration or ask the lab to standardise the solution For high alkalinity samples titrations will be quicker with a more concentrated acid e g 0 1M For low alkalinity samples a more dilute acid e g 0 02M will give more accurate results 85 This equipment is not easily obtained off the shelf If you intend to conduct such an investigation and need to titrate in the field acquire the necessary equipment and be sure to carry out a sufficient number of titrations in the laboratory under supervision before doing them in the field Conducting field alkalinity titrations is not difficult do not be put off by the apparent complexity but do stick to the rules 4 6 4 PROCEDURE FOR ALKALINITY AND ACIDITY DETERMINATION 4 6 4 1 Field titration The titration procedure is as follows 1 Set up the burette pH meter and magnetic stirrer 2 Calibrate the pH meter with buffers section 4 3 3 Rinse the burette with a small quantity of acid of molarity M1 4 Rinse a beaker and stirrer bar with distilled deionised water 5 Rinse the pipette with sample water and transfer a measured volume V2 of sample to the beaker x 6 Insert the pH sensor in the solution start the stirrer and monitor the pH Ensure that
240. tructed and secondly adopting low flow sampling techniques 133 Filters are made from a variety of material such as cellulose nitrate cellulose acetate polycarbonate glass fibre or PTFE Teflon For general purposes the first three are suitable for groundwater If expecting a specific pollutant in very high concentrations consult a compatibility chart e g Geotech 14 5 GENERAL FIELD PROCEDURE 1 When you are using a hand held pressure filter device first rinse it with deionized water 2 Insert the filter membrane correct side up usually the side with the printed grid 3 Connect the in line filter to the discharge pipe or draw up a sample into the pressure filter Discard the first 50 mL Collect the required amount of filtered sample Discard filter membrane or in line filter in a waste bag do not litter Disassemble filter apparatus and rinse clean with deionised water Make sure the filtering procedure is properly described in the Monitoring Program Guide and is adhered to for all sampling runs This important oa Nj Nm 00 O wer wa 14 6 REFERENCES Braids O C Burger R M and Trela J J 1987 Should groundwater samples from monitoring wells be filtered before laboratory analysis Groundwater Monitoring Review Summer 1987 58 67 Puls R W and Powell R M 1992 Transport of inorganic colloids through natural aquifer material implications for contaminant transport
241. ue are comparing this with the theoretical slope S Good working glass electrodes should give slopes better than 95 and this should remain constant A lower slope indicates that the electrode has deteriorated and maintenance or replacement is required Electrode manufacturers supply information on remediation procedures Electrodes with slopes less than 90 should not be used Some drift in the electrode potential does occur and 0 1 to 0 2 mV per hour drift is common for a properly functioning electrode Wilde et al 2006 The transistor in ISFET systems may be slightly sensitive to light and should not be used in direct sunlight Electrode maintenance and storage Electrodes may give many years of reliable service if they are carefully handled stored and maintained Glass electrodes especially are fragile and should be handled delicately Electrodes should be rinsed with deionised water and gently blotted with soft tissue before use and in between transferring the electrode from one solution to the next Do not touch the glass bulb with your fingers or wipe it roughly with paper towel Oily film or scratches on the bulb may affect the pH reading and static charge caused by wiping can lead to drifting or sluggish response Electrodes filled with gel or solid polymer in some newer models are easier to maintain than liquid filled electrodes Gel filled electrodes do not require filling Do not leave this in dilute solutions e g deionis
242. ue can have a lower detection limit than the electrode method Lewis 2006 White et al 1990 Table 4 5 1 shows a comparison of the merits of different DO analysis methods The electrode method will be described in detail Details of the spectrometric method can be found in the instrument suppliers literature and the USGS manual Lewis 2006 Details of some semi quantitative field methods are given in section 4 7 field test kits 74 Table 4 5 1 Comparison of DO methodologies White et al 1990 and Chemetrics 2006 Spectrophotometric Spectrophotometric DO electrode with field with colour spectrophotometer comparator Initial costs High Medium Low Running costs Low High High Level of Low if understanding sufficiently Medium Low required automated ne Or 0 1mg l 0 01mg l 0 01mg Calibration required for mg l Yes No No measurements In flow analyses Yes No No Interference HS Oxidizing agents Oxidizing agents 4 5 1 2 DO electrode method The detector of the DO meter is a polarographic system consisting of two metal electrodes surrounded by an electrolyte Wood 1981 APHA 1998 When a suitable polarizing voltage usually 0 8 volt is applied across the cell the consumption of oxygen at the cathode causes a current to flow through the cell This current is directly proportional to the oxygen consumption rate The electrode system is separated from the test solution by an oxyg
243. use then collect two samples Collect the initial sample using your specialized sampling equipment to assess the intrinsic quality of the groundwater and a second sample using the same equipment and method of use that the community uses to collect their water If the sample is for another purpose e g geochemical or isotopic work then purge the pit and collect the water sample from the fresh inflow water For this latter purpose the better method will be to use a metal well pointing spear and drive this into the sand close to the pit and collect the sample from this piezometer 19 5 SAMPLING LARGE DIAMETER DUG WELLS The preferred method is to use two pumps a larger capacity purging pump anda smaller capacity sampling pump Place the larger capacity pump midway in the well and start purging Observe the flow in the well and try to identify the inflow point Place the sampling pump at this point similar to spring sampling and collect water samples If you cannot observe an inflow point then assume the inflow is at the bottom of the well and place the sampling pump close to the bottom If the sampling program is to assess drinking water fitness for use then collect two samples Collect the initial sample using your specialized sampling equipment to assess the intrinsic quality of the groundwater and a second sample using the same equipment and method of use that the community uses to collect their water 158 CHAPTER 20 THE LAST CHA
244. used to determine the recharge temperature and excess air provided no other nitrogen source or sink is present Analysis is by gas chromatography Krypton 85 is produced when spent fuel rods from nuclear installations are processes The Kr content of the atmosphere has steadily increased since 1955 8SKr dissolves in groundwater at the water table and is inert underground It therefore serves as a dating tracer similar to SF and the CFCs Analysis of Kr is by fairly sophisticated low level counting and requires the sampling of some 300 litres of water The technique is therefore not often used Argon 39 is produced by cosmic radiation similar to tritium and radiocarbon Nuclear weapon testing does not produce any Ar and in contrast to fC H and Cl the input function of Ar dissolved in groundwater at the water table has remained constant in recent times Having a half life of 269 years Ar should be able to date young water quite well The difficulties of the method are that Ar is also produced by potassium decay enhanced by the presence of uranium and thorium Analysis requires some 10 m which severely limits the application of this technique 27 3 3 8 RADIOACTIVITY The radioactivity in water is due to the presence of nuclides emitting alpha a beta B and or gamma y radiation These are essentially contributed by the isotopes of uranium radon radium potassium and to a lesser extent thorium When ingested the
245. uses a potential difference measured in millivolts to develop between the inner buffer solution and the external sample The ISFET pH sensor consists of a silicon semiconductor substrate with two electrical contacts source and drain a small distance apart An electrical insulator gate is deposited on the substrate between the source and drain Hydrogen ions at or near the surface of the insulator cause a variable voltage potential between the insulator and the underlying semiconductor material IQSI 2002 For both types of pH 53 electrodes the potential developed is proportional to the relative concentration of hydrogen ions in the solution and is used to measure the pH The glass electrode system is preferred over the ISFET for high accuracy applications The advantages of ISFET sensors for environmental applications are their small dimensions rapid response times and robustness The reference electrode part of the pH measuring system is usually a silver silver chloride electrode or calomel electrode filled with electrolyte gel or solution An electrode junction ceramic polymer or direct contact allows for electrical contact between the internal electrolyte and the external solution For general field use a combination electrode is recommended which incorporates the measuring and the reference electrodes into a single probe available in a robust plastic envelope Electrode performance Instruments that report slope as a percentage val
246. ution combinations over a range of temperatures found in groundwater EXAMPLE Testing a platinum electrode calomel electrode combination with saturated KCI filling solution with Zobell s solution at 18 C gives a reading of 190 mV Is the electrode functioning The theoretical potential for the system is Ever Eh Eng gecie sat KCI Eh 443 mV for calomel electrode with 443 mV 249 mV saturated KCI at 18 C Appendix A 2 193 mV EnigHgecie 249 mV Appendix A 1 or E Hg Hg2Cl2 0 66 1 8 261 Appendix A 1 249 mV Erer is within 10 mV of the measured potential so the system appears to be working properly Some meters have a redox calibration function which requires the theoretical potential E er of the reference solution to be entered by the user Check whether the value entered is relative to the hydrogen electrode in which case the instrument automatically compensates for the half cell potential of the reference electrode to calculate Eh or whether it is relative to the silver silver chloride or calomel electrode in which case the ORP readings must be adjusted manually to calculate Eh see the next section Setting the reading relative to SHE may cause out of range errors on some meters 4 4 4 2 Field measurements Eh measurements are sensitive to reactions of dissolved gases and the use of an airtight flow through cell Chapter 15 is essential Groundwater samples cannot be preserved
247. va URL http www who int water_ sanitation health dwq guidelines en last accessed 22 September 2006 WHO 2004 Guidelines for Drinking water quality 3 ed Volume 1 Recommendations World Health Organisation Geneva URL http Awww who int water sanitation health dwq quidelines en last accessed 22 September 2006 45 CHAPTER 4 FIELD DETERMINANDS Analysis of some determinands on fresh water right at the well head during the sampling run are done for three reasons 1 to check the efficiency of purging see Chapter 13 2 to obtain reliable values of those determinands that will change in the bottles during transport to the laboratory 3 to obtain some values that may be needed to decide on the procedure or sampling sequence immediately during the sample run pH and EC and possibly DO and Eh are measured on a continuous basis to check on the efficiency with which the standing water in the boreholes has been replaced with fresh water from the aquifer If these determinands are stable for the duration of purging of one well volume then sample collection can start although it is safer to wait until three purge volumes have been removed see chapter 13 When groundwater is removed from its natural environment to surface several water quality determinands undergo changes due to aeration oxidation and degassing These determinands are temperature Chapter 4 1 electrical conductivity EC Chapter 4 2
248. ve the expected theoretical potential e check the calculations check the meter and electrodes as described below use a fresh aliquot of reference solution or make up a new reference solution If the millivolt reading does not stabilise check the meter replace the batteries use a shorting lead to check the zero reading check all plugs and connectors follow manufacturer s instructions for servicing 70 check the platinum electrode polish the platinum electrode with a mild abrasive recondition electrode by acid cleaning aqua regia or chromic acid as a last resort using the method described below Poisoned physically damaged or shorted out electrodes cannot be reconditioned and will need to be replaced check the reference electrode check that the recommended filling solution has been used check filling solution level drain and refill with fresh filling solution check for an air bubble in the electrode and release it by tapping electrode swinging by the lead or immerse in warm water to melt KCI crystals trapping bubbles clean the porous pin on combination electrodes Platinum electrodes can be cleaned with hydrogen peroxide and detergent washing use non phosphate laboratory grade detergent anodic activation or abrasive polishing Polish the electrode with a mild abrasive such as coarse cloth e g crocus cloth jeweller s rouge a hard eraser or 400 to 600 grit wet dry Carborundum paper APHA 19
249. w rate otherwise a pressure effect will be introduced which will give erroneous readings 3 Record the meter reading to the nearest 0 1 mg L 4 Dismantle and wash the equipment with distilled water 5 Store the electrode according to the manufacturer s instruction This usually means that the membrane tip of the electrode be kept moist ALWAYS measure Dissolved Oxygen in a flowing stream of water NEVER use discrete samples 4 5 3 4 Trouble shooting e Incase of malfunction first check the battery and the integrity of all the connections to the electrode e Re do both calibration steps e If the low point calibration value has shifted electrode cleaning is usually required e If the high point calibration value has changed then the fault usually lies with damage to the membrane Replace the membrane and recalibrate the electrode 4 5 4 DO REFERENCES APHA 1998 Standard Methods for the Examination of Water and Wastewater 20 ed Am Public Health Assoc Washington DC Chemetrics 2006 URL http Awww chemetrics com home himl last accessed on 17 October 2006 Domenico P A and Schwartz F W 1998 Physical and Chemical Hydrogeology 2nd ed John Wiley amp Sons New York 505p 80 Lewis 2006 Chapter 6 2 Dissolved Oxygen U S Geological Survey Techniques of Water Resources Investigations book 9 chap A6 section 6 2 version 6 2005 Available from the URL http oubs water usgs gov twri9A6 last a
250. with due caution The problem of vertical flow in the borehole and resultant ambiguous results for hydrogeochemistry is not resolved with this method Depth specific samplers These consist of a plastic or metal tube or vessel sometimes evacuated or over pressurised with an inert gas or air The sampler is lowered by rope or cable to the desired depth and an inlet valve opened to allow the borehole water to enter the sampling vessel The device is then recovered to the surface and the sample poured into a sampling bottle or delivered in the pressurised vessel to the laboratory The trigger for the valve system is usually operated electromagnetically One of the simplest and cheapest depth specific samplers is an open top bailer with a bottom ball valve When lowering the bailer the valve is open and groundwater moves through the bailer When the bailer is withdrawn the valve closes during upward movement trapping a sample of water from the maximum depth to which the device was lowered Although a common method of depth specific sampling this method is not very accurate This method is not recommended for proper sampling in multi layered aquifers 145 Separation pumping This system uses three pumps two flow control pumps are positioned one at the top and the other at the bottom of the borehole and one sample pump in the middle When both flow control pumps are in operation they separate the flow of water in the borehole int
251. y bleach in deionised water to remove protein build up An ISFET probe should be stored dry with a protective cap covering the probe tip IQSI 2002 55 4 3 2 3 pH buffers pH buffer solutions are used to calibrate the pH meter readings During calibration the electrodes are immersed in a buffer solution and the instrument adjusted according to the manufacturer s instructions so that the meter reads the correct pH value for that buffer Some instruments offer one two or three point calibration using up to three buffer solutions A minimum of two buffers is recommended for routine pH measurement work For two point calibration buffers should be selected that bracket the expected pH range of the samples to be measured usually with pH 7 0 buffer as one end of the bracketed range Single point calibration can be used in the field between boreholes to check that the instrument has not drifted between readings The pH of groundwater from quartzites is usually between 5 and 6 so select buffers pH 4 and pH 7 to calibrate the meter Limestone or dolomite aquifers typically have groundwaters of pH greater than 7 and buffers of pH 7 and pH 10 should be used for calibration Poor quality old or contaminated buffers will give at best inaccurate and at worst completely wrong pH readings Advice for using pH buffer solutions Wilde et al 2006 Use certified buffers that are traceable to an internationally accepted standard e g NIST Sta

GROUNDWATER SAMPLING - Water Research Commission

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