Improvement of the model concept for volatilisation of pesticides
Contents
1. 0 5 Default value in PEARL OptTraRes Option for the description of Options are Laminar and Aerodynamic the volatilisation ThiAirBouLay Thickness of stagnant air 0 01 layer at soil surface m Default value in PEARL OptDspCrp Option for the description of Options are Lumped Specified Calculated the loss routes of parent If Calculated is selected then wash off volatilisation compound from the crop penetration and transformation are simulated surface DTS0DspCrp Half life for dissipation of the 1000000 parent compound at the crop surface d FacWasCrp Factor for the wash off of 0 0001 parent compound from the Default value in PEARL crop by rainfall or irrigation Not relevant because substance is applied to soil m RadGloRef Reference global radiation for Default value 500 W m2 the factor for the effect of 23 radiation on the pesticide on the plant W m 2 FacTraDepRex Factor for the effect of Range 0 0 to 1 0 If set to 1 0 then no effect of reduced restricted exposure of deposit exposure on transformation FacVolDepRex Factor for the effect of Range 0 0 to 1 0 If set to 1 0 then no effect of reduced restricted exposure of deposit exposure on volatilisation FacPenDepRex Factor for the effect of Range 0 0 to 1 0 If set to 1 0 then no effect of reduced restricted exposure of deposit exposure on penetrat2. 2 5 2 2 8 K u Pr This description has also been used by Asman 1998 to describe the ammonia fluxes to the atmosphere The Prandtl number can be set at 0 72 In combination with a value of 0 4 for the Karman constant Equation 2 2 8 can be simplified to 62288677 u r 2 2 9 D 2 3 Description of improved concept for volatilisation from plants The volatilisation of pesticides from plant surfaces can also be described using the concept of transport resistances Firstly the source has to be described because this determines the resistances for the transport between the source height or source layer and the atmosphere During spraying of arable crops spray droplets move downwards from the nozzles towards the plant surfaces Part of the droplets will deposit on the top leaves whereas others penetrate more deeply into the canopy Model concepts for the volatilisation may be developed on the basis of a canopy layer with a distribution of pesticide deposits or on the basis of an apparent source height at some level between the soil surface and the crop height For a description of the transport resistances within and above a plant canopy the displacement height has to be taken into account The displacement height is defined as the height of the plane for absorption of momentum The displacement height d for the crop is given by Van Dam et al 1997 d 2i 2 3 1 3 in which d displacement height m he hei
3. 20 0 7 1 54 pH independent 2075 207500 L 0 9 0 0042 20 4 3 20 27 95 0 0 0 0 20 0 0 5 0 0006 Calculated 1000000 0 330 1000000 0 433 500 0 RPNNNNO c lt N O G gt D oy EH DT50Ref_SUB1 d TemRefTra_ SUBI C ExpLiqTra SUBI CntLiqTraRef_SUB1 kg kg 1 MolEntTra_SUB1 kJ mol 1 OptCofFre SUBI KomEql_ SUBI L kg 1 KomEglMax_SUB1 L kg 1 ConLigqRef_ SUBI mg L 1 ExpFre SUBI PreVapRef_SUB1 Pa TemRefVap_SUB1 C SlbWatRef_SUB1 mg L 1 TemRefSlb_SUB1 C MolEntSlb_SUB1 kJ mol 1 MolEntVap_SUB1 kJ mol 1 CofDesRat_SUB1 d 1 FacSorNegEql_SUB1 MolEntSor_SUB1 kJ mol 1 TemRefSor_ SUBI C FacUpt_ SUBI ThiAirBouLay m OptDspCrp DT50DspCrp d DT50PenCrp d DT50VolCrp d DT50TraCrp d RadGloRef W m 2 FacWasCrp m 1 FacTraDepRex FacVolDepRex FacPenDepRex FacWasDepRex FraDepRex TemRefDif SUBI C CofDifWatRef_SUB1 m2 d 1 CofDifAirRef SUBI m2 d 1 28 Section 6 Management section Ap SUB1 ApplicationScheme T ZFoc m table Applications 01 May 2001 0000 AppCrpLAI 0 691 end table NoRepeat DelTimEvt a table VerticalProfiles end table table TillageDates end _ table No DepositionScheme table FilmDep kg ha 1 d 1 end_table x Section 7 Crop section x HAMB SUGARB
4. 26 1072 1079 18 Appendix 1 PARAMETERISATION OF PEARL Author Erik van den Berg Date 1 September 2004 Characteristics of the parameterisation Example run At run time the PEARL user interface produces two input files 1 X PRL containing all soil and substance input parameters with X as the run identification 2 Y MET containing meteorological input in which Y is the name of the meteorological station If the irrigation option is used there is a third input file 3 Z IRR containing irrigation input in which Z is the name of the irrigation scheme X PRL PARAMETER DESCRIPTION VALUE SOURCE amp COMMENTS Section 1 Control CallingProgram Release type Set to Alterra Model Version Version number of the model Set to 1 OptSys Option for system to be Set to All Options are Al and PlantOnly If simulated PlantOnly is selected then soil profile input data are not required 1 ScreenOutput Output to screen Yes TimStart Starting time of simulation 1 Jan 2001 Start of simulation period TimEnd End time of simulation 31 Dec 2002 End of simulation period AmaSysEnd Stopcondition kg ha 0 ThetaTol Maximum difference in water 0 001 content between iterations OptDelTimPrn Option to set output interval Set to Hour Options are Hour Day Month Decade Year Other For volatilisation studies select Hour DelTimPrn Print in
5. T P Meyers R P Hosker and D R Matt 1987 A preliminary multiple resistance routine for deriving dry deposition velocities from measured quantities Water Air and Soil Pollut 36 311 330 Leistra M A M A van der Linden J J T I Boesten A Tiktak and F van den Berg 2000 PEARL model for pesticide behaviour and emissions in soil plant systems Description of processes Alterra report 13 RIVM report 711401009 Alterra Wageningen 107 pp Tiktak A F van den Berg J J T I Boesten M Leistra A M A van der Linden and D van Kraalingen 2000 Pesticide Emission Assessment at Regional and Local Scales User Manual of Pearl version 1 1 RIVM Report 711401008 Alterra Report 28 RIVM Bilthoven 142 pp Van Dam J C J Huygen J G Wesseling R A Feddes P Kabat P E V Van Walsum P Groenendijk and C A van Diepen 1997 Theory of SWAP version 2 0 Simulation of water flow solute transport and plant growth in the Soil Water Atmosphere Plant environment Report 71 Department Water Resources Wageningen Agricultural University Wageningen The Netherlands 167 pp Van der Molen J A C M Beljaars W J Chardon W A Jury and H G van Faassen 1990 Ammonia volatilization from arable land after application of cattle slurry 2 Derivation of a transfer model Netherlands J Agric Sci 38 239 254 Wang D S R Yates and J Gan 1997 Temperature effect on methyl bromide volatilization in soil fumigation J Environ Qual
6. The rate coefficient kp is set dependent on the intensity of solar irradiation L k pn k K onres 4 4 2 ref with lact actual solar irradiation intensity W m het reference solar irradiation intensity 500 W m Kphrer rate coefficient of phototransformation at reference irradiation intensity d The coefficient Kpnrer is one of the quantities to be calibrated in the computation on the basis of the measurements or it has to be derived from other studies on the pesticide Usually direct measurements on the phototransformation of a pesticide on plant surfaces are not available Types of information that may be available are 13 photolysis in water purified or natural phototransformation on artificial surfaces phototransformation on soil or other natural surfaces phototransformation in air These types of measurements give an indication whether phototransformation on plant surfaces may occur However translation of rates between such media does not seem to be possible yet The rate of phototransformation on plant surfaces may show a wide variation Possible factors are a the substances in the formulated product b the substances at the plant surface c the substances in the local air etc An attempt could be made to classify a pesticide in one of five classes of vulnerability to phototransformation on plant surfaces on the basis of available research data The following representative values
7. USA 26 Appendix 2 Example PEARL input file using option OptSys is PlantOnly x INPUT FILE for Pearl version 1 5 8 1 1 A1 x x Section 1 Control section x Consensus CallingProgram 3 ModelVersion 01 May 2001 TimStart 03 May 2001 imEnd 0 AmaSysEnd kg ha 1 No RepeatHydrology Automatic OptHyd PlantOnly OptSys Hour OptDelTimPrn Yes OptScreen No OptDelOutput Yes PrintCumulatives x Section 2 Soil section HAMB S_Soil SoilTypeID Hamburg Location x Section 3 Weather and irrigation section HAMB M MeteoStation Hourly OptMet Inp Laminar OptTraRes PenmanMonteith OptEvp 52 Lat 50 Alt m 100 LenFld m 0 01 LenRghMmtLcl m 10 TemLboSta C 10 0 ZMeaWnd m 2 0 ZMeaTem m Hicks OptResBou No OptIrr No IrrigationScheme 1 0 FacPre 1 50 FacTem 130 FacEvp x Section 4a Lower boundary flux x Section 4b Drainage infiltration section x No OptDra x Section 5 Compound section x SUB1 SubstanceName 27 table compounds SUB1 end_table 30355 table FraPrtDau end_table MolMas_SUB1 mol mol 1 g mol 1 OptimumConditions OptCntLiqTraRef_SUB1 table horizon FacZTra hor SUBI 1 2 1 3 O23 4 0 35 5 0 5 6 0 3 7 O 8 0 end_table table horizon FacZSor hor SUBI L 05 2 0 5 3 0 55 4 04 5 5 0 5 6 0 55 7 O45 8 0 5 end_table 67
8. the plant surface is given by M p Ce ps RT 2 3 6 where Caps concentration in the air at the plant surface kg m M molecular mass kg mol Ds saturated vapour pressure of the pesticide Pa R universal gas constant J K mol T temperature K The flux density of volatilisation from plant surfaces can be described by c s Cair Ja Cep Cuir 2 3 7 Fr r in which la aerodynamic resistance d m lb boundary layer resistance d m 3 Sorption to soil In FOCUS PEARL 1 1 1 and FOCUS PEARL 2 2 2 the sorption coefficient is assumed to be constant However an increase in this coefficient at low moisture contents in soil has been measured This increase in sorption to soil particles is expected to result in lower volatilisation flux densities at the soil surface A simple approach to take this effect into account is to specify a maximum sorption coefficient for air dry soil and a moisture content below which the sorption coefficient increases The increase in the sorption coefficient can be described using a linear or an exponential relation Assuming an exponential relationship the effect of the moisture content on the sorption coefficient can be described as follows K K max 2 for w lt Wiow 3 1 al and Kie Ka for w gt Wiow 3 1b in which K err Effective sorption coefficient L kg Ka max Maximum sorption coefficient L kg a coefficient w mois
9. theory do not seem to be available A major problem is that besides the physico chemical properties of the pesticide the substances in the formulation may have a great effect on penetration An attempt could be made to classify formulated pesticides into e g five classes with respect to their propensity to penetrate into the plants A representative rate coefficient could be assigned to each of the classes as a first approximation of the rate of penetration The following five main classes of penetration rate are distinguished 1 very fast penetration half life 0 04 d 1 h Kpen 17 d7 2 fast penetration half life 0 21 d 5 h Kpen 3 3 d 3 moderate penetration rate half life 1 0 d kpen 0 69 d 4 slow penetration half life 5 0 d kpen 0 14 d 5 very slow penetration half life 25 days kpen 0 03 d If the above classification is too rough one of the boundaries between the classes could be selected half life 0 13 d 3 h Kpen 5 5 d half life 0 63 d 15 h Kpen 1 1 d half life 3 0 d ken 0 23 d half life 15 d Kpen 0 05 d7 In this way the available empirical knowledge on penetration is translated into a rate coefficient The classification allows for penetration into the plants to be included in the computations as a process competing with volatilisation 4 3 Wash off The rate of pesticide wash off from the leaves by simulated rainfall is set
10. to be linear or exponential Logarithmic Y axis 10 4 Dissipation processes on the plant After application to the plant the fate of the compound is influenced by different processes such as volatilisation penetration into the plant tissue transformation and wash off In FOCUS PEARL versions 1 1 1 and 2 2 2 an overall half life could be specified or values had to be specified for the half life for each of these processes Using this concept the effect of environmental factors such as solar radiation or air temperature could not be taken into account Therefore model concepts for each of these processes were developed 4 1 Volatilisation The saturated vapour concentration of the pesticide in the air at the deposit surface on the leaves is calculated from the vapour pressure by using the Gas Law as described in Eq 2 3 6 The potential rate of volatilisation of pesticide from the deposit leaf surface is calculated by similar to Eq 2 1 2 J pot k Cur 4 1 1 r with Jypot potential flux of volatilisation from the surface kg m d Cair concentration in the turbulent air just outside the laminar air layer kg m set at zero r resistance to transport from plant surface to atmosphere d m All the areic quantities such as fluxes are expressed per m field surface not plant surface The actual rate of pesticide volatilisation is described by taking into account the mass of pesticide on the plants Jy ac
11. EST and the volume fraction of liquid 0 7 Default value recommended by FOCUS CntLiqTraRef_PEST Reference content of liquid in transformation study from which DTS50Ref of PEST was Set to 1 Not relevant in this run derived kg kg MolEntTra PEST Molar activation enthalpy of 54 transformation of PEST Default value recommended by FOCUS kJ mol table horizon FacZTra Hor PEST Factor for influence of depth on transformation rate in soil as a function of soil horizon 0 1 using the format number of horizon Factor 1 1 2 0 5 3 0 11 4 0 5 0 OptCofFre Option to choose between pH dependent pH independent or user defined sorption Set to pH independent so the Freundlich sorption equation is used The sorption coefficient is calculated by multiplying the coefficient of sorption on organic matter and the organic matter content ConLiqRef PEST Reference liquid concentration for sorption coefficient of PEST mg L 1 ExpFre PEST Freundlich exponent of PEST 0 9 Default value in PEARL KomEql_ PEST Coefficient of equilibrium sorption of substance on organic matter Kom Set at 45 L kg Measured at temperature TemRefSor KomEqIMax_ PEST Coefficient of equilibrium sorption of substance on organic matter Kom under Set at 4500 L kg Measured at temperature TemRefSor 22 dry conditions MolEntSor_ PEST Molar enthalpy o
12. FlmLiqLbo print _FlvLiqEvpIntlrr print_FlvLigEvpIntPre print_FlvLigEvpSol print_FlvLigEvpSolPot print_FlvLigPre print_FlvLigTrp print_FlvLigqTrpPot print_FlvLiqGrw print_StoCap print_AvoLigErr print_DelTimPr 30
13. ITB SCP content organic matter kg kg pH table VanGenuchtenpar Table specifying the 1 0 599 0 06 0 06 0 06 1 5 0 3 1 VanGenuchten parameters for 2 0 355 0 01 0 06 0 06 1 2 00 l each horizon using the format 3 0 355 0 01 0 05 0 05 1 3 0 03 l horizon number 4 0 355 0 01 0 05 0 05 1 3 0 03 l ThetaSat 5 0355 0 01 0 05 0 05 1 3 0 03 l ThetaRes AlphaDry em AlphaWet cm Source Values obtained by fitting data as presented in n ITB HCU and ITB WRC files Ksat m d LO OptRho Option for input of bulk Input density data table horizon Rho Table specifying the Nr Rho kg m3 bulk density for each 1 1050 horizon 2 1700 number x La bulk density kg m3 5 1700 Source Data taken from ITB HCU ZpndMax Maximum thickness of 0 0 ponding water layer m OptSolEvp Option to select evaporation Set to Boesten reduction mPESTd FacEvpSol Coefficient for potential 1 evaporation from bare soil Source FOCUS 2000 CofRedEvp Coefficient for reduction of 0 63 evaporation from bare soil Default value in PEARL resulting from drying of top layer cm PreMinEvp Minimum rainfall to reset Set to 1 cm d reduction table horizon LenDisLiq Dispersion length of solute in 0 05 liquid phase m Default value in PEARL OptCofDifRel Option for tortuosity MillingtonQuirk Default in PEARL ExpDifLiqMilNom Exponent in nominator of 2 relation of Millington amp Default va
14. Improvement of the model concept for volatilisation of pesticides from soils and plant surfaces in PEARL Description and user s guide for PEARL 2 1 1 C1 F van den Berg M Leistra Version 1 1 23 September 2004 Contents A INTRODUCTION assises rentrent need E EE EEE 3 2Z MOlAtilISAtiON PRE danegcmeeecmsgumeascaetinaes 3 2 1 Description of current concept for volatilisation from bare soil 3 2 2 Description of improved concept for volatilisation from bare soil 4 2 3 Description of improved concept for volatilisation from plants 6 S SOPDUON tO SOI lens nn Re More le nent rende Sua 9 4 Dissipation processes on the plant 11 4 1 Volatilisation see 11 4 2 Penetration of substance into plant tissue 12 4 3 WaShi O fs sua oss dae s saa re tn Manet EE SES ESS TRE ASS 12 4 4 Transformations steel en lente au a aus San Guyana 13 4 5 Mass conservation equation on the plant surface 14 5 Getting started running the new PEARL model 15 IREIEKENCES sn tnt E Aym ua ku m u A e usut a aya 18 Appendix 1 PARAMETERISATION OF PEARL 19 Appendix 2 Example PEARL input file using option OptSys is PlantOnly 27 1 Introduction After spraying pesticide onto the soil surface various processes influence the subsequent fate of the pesticide De
15. Ku The height of the internal boundary layer Z at which the concentration in air is equal to the background concentration can be calculated iteratively using the equation derived by Van der Molen et al 1990 Under neutral conditions Z is given by ns X 2 2 4 Zom in which XF length of the treated field m In the new PEARL version neutral conditions are assumed and the aerodynamic resistance is calculated using Eqs 2 2 3 and 2 2 4 The resistance to the transport between the source height i e the soil surface and Z Zom Can be described with the boundary resistance r Different parameterisations have been given for this resistance Wang et al 1997 have described r by 1 4 1 2 e ea 2 2 5 d u in which Re roughness Reynolds number Sc Schmidt number a constant us friction velocity m d The constant a is taken to be 0 137 The roughness Reynolds number Re dimensionless is given by Zom Re 2 2 6 D in which v kinematic viscosity of air m d The Schmidt number is given by Go 2 2 7 D g where D diffusion coefficient of pesticide in air m d At sea level the value of vis 1 46 10 m s the temperature dependency of vand D is about the same so the quotient of the two variables is about constant i e 0 71 An alternative description of the surface boundary layer resistance r is given by Hicks et al 1987 2 3 r
16. T ET CropCalendar Yes RepeatCrops Fixed OptLenCrp table Crops 15 Apr 2001 08 Oct 2001 SUGARBEET1 end_table table CrpPar_SUGARBEET1 0 0 il 0 0 0 78 4 2 0 87 1 2 0 1 4 2 0 87 12 0 end_ table 0 765 FraCovCrpinp Od HgtCrpiInp m x x Section 8 Output control x None OutputDepths No OptDelOutFiles Air OptReport DaysFromSta DateFormat G12 4 RealFormat table OutputDepths m end_table Yes print_AmaAppCrp Yes print_AmaAppSol Yes print_AmaCrp Yes print_AmaCrpFex Yes print_AmaCrpRex No print_AmaHarCrp Yes print_AmaWasCrpFex Yes print_AmaWasCrpRex Yes print_AmaWasCrp Yes print_AmaPenCrpFex Yes print_AmaPenCrpRex Yes print_AmaTraCrpFex Yes print_AmaTraCrp Yes print_AmaPenCrp Yes print_AmaTraCrpRex Yes print_AmaVolCrpFex Yes print_AmaVolCrpRex Yes print_AmaVolCrp Yes print_AmrDspCrp Yes print_AmrWasCrp Yes print_AmrVolCrp No print_AmaHarCrp No print_DelTimPr Yes print_FacCrpEvp Yes print_FlmDepCrp Yes print_FraCovCrp 29 Yes Yes Yes Yes Yes Yes No No No Yes No Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes No No No No print_TemAir print_RstAer print_RstBou print_VelWnd print_RstAirLam print_VelFrilLcl print_LAI print_ZRoot print_GrwLev print_Tem print_PreHea print_FlmGas print_FlmGasVol print_FlmLig print _FlmLiqinf print _
17. dependent on rainfall intensity and a wash off coefficient R k W A 4 3 1 12 With Ry rate of pesticide wash off from the leaves kg m d ky coefficient for pesticide wash off mm W rainfall intensity mm d Various factors are known to affect pesticide wash off with rainfall from plants However no relationships are available for a mechanistic and quantitative description of this process Only a rough classification of wash off based on the experimental results seems to be possible at present It is proposed to classify wash off in a certain situation in one of the following five classes kw 0 09 mm e g 90 wash off with 10 mm rainfall kw 0 07 mm 70 with 10 mm kw 0 05 mm 50 with 10 mm kw 0 03 mm 30 with 10 mm kw 0 01 mm 10 with 10 mm If this classification is too rough a value at the boundary of two classes can be selected In this classification it is assumed that the crop is only sprayed if no rain is expected in the first period of e g 6 hours It should be noted that in some experiments rainfall was simulated to occur very soon after spraying which may result in very high wash off 4 4 Transformation The rate of pesticide transformation on the plant surface by solar irradiation is described by first order kinetics R Kon Ap 4 4 1 with Ron rate of phototransformation on the leaves kg m d Koh rate coefficient of phototransformation d
18. e dependency of the sorption coefficient and in Chapter 4 the model concepts for the dissipation processes on the plant surface is presented In Chapter 5 instructions are given how to execute runs with the new PEARL version and information is given on the modifications in the PEARL input and meteorological files 2 Volatilisation 2 1 Description of current concept for volatilisation from bare soil The volatilisation of the pesticide at the soil surface is described assuming a boundary air layer through which the pesticide has to diffuse before it can escape into the atmosphere This concept has been adopted in FOCUS_PEARL versions 1 1 1 and 2 2 2 Leistra et al 2000 Tiktak et al 2000 The transport resistance of this air boundary layer can be described as r saat 2 1 1 D T with lb resistance for transport through boundary air layer d m d thickness of boundary air layer m D T coefficient for diffusion in air m d at temperature T The volatilisation flux density depends on the concentration gradient of the pesticide across the boundary air layer and this flux density is described as JE Gas Cor 2 1 2 n with Jya volatilisation flux density through the boundary air layer kg m d Cg ss concentration in the gas phase at the soil surface kg m Cair concentration in the air kg m It is assumed that the concentration of the pesticide in the air is negligible compared to the concent
19. e laminar layer is equal to that specified in the input file if the temperature increases with height then atmospheric conditions are assumed to be stable and the value of the thickness of the laminar layer is set at 100 times the value specified in the input file RadGloRef Reference global radiation for the factor for the effect of radiation on the pesticide on the plant FraDepRex Fraction of applied mass to be put in deposit with reduced exposure If set at 0 then all mass applied is fully exposed FacTraDepRex Factor for the effect of restricted exposure of deposit on transformation FacVolDepRex Factor for the effect of restricted exposure of deposit on volatilisation FacPenDepRex Factor for the effect of restricted exposure of deposit on penetration FacWasDepRex Factor for the effect of restricted exposure of deposit on wash off In the Output section the following record is modified OptReport A new possible option has been added Air If set at Air then report on the volatilisation is generated with a hourly volatilisation losses during the first 24 h after application The volatilisation fluxes that are required by the EVA model are also generated A full list of records for the new PEARL version is given in Appendix 1 An example PEARL input file is given in Appendix 2 16 The format of the file with daily meteorological data is unchanged If the hourly option is used then the format of the meteorologica
20. epth m content mg kg DepositionScheme Option for including No deposition table FlmDep Table defining the flux of empty deposition using the format date daily deposition rate kg ha d 24 Section 7 Crop RepeatCrops Option to repeat growth of No same crop each year OptLenCrp Option to make the length of Fixed the crop cycle dependent on temperature sum table Crops Table that specifies the crops Example and their emergence and 12 Jun 2001 10 Oct 2001 SUNFLOWERI harvest dates using the format 22 May 2002 30 Sep 2002 SUNFLOWER2 emergence date harvest date crop code table CrpPar cropl Table that specifies crop parameters of crop as a function of development stage using the format development stage which is 0 at emergence and at harvest Leaf Area Index crop factor for description of potential evapotranspiration rooting depth m crop height m For all three crops 0 0 1 0 0 04 4 0 7 0 3 3 1 4 0 7 0 3 3 table RootDensity_ cropl Table that specifies the root density distribution over the rooting depth using the format relative rooting depth i e depth divided by rooting depth relative root density For all crops 0 1 1 1 Default values from SWAP HLim1_ crop pressure head above which there is no water extraction cm 15 same value for other crop HLim2_ crop pressure head below which optimal
21. f sorption Describing the relation between the sorption coefficient of the substance and temperature Default value defined by FOCUS workgroup 0 kJ mol TemRefSor_ PEST Temperature of reference at which the sorption coefficient was measured In degrees Celsius KSorEql PEST Equilibrium sorption coefficient for soil of PEST L kg Only needed if OptCofFre set to user defined table horizon FacZSor Factor for influence of depth 1 1 Hor PEST on sorption in soil as a 2 0 66 function of soil horizon 0 1 3 0 37 using the format 4 0 26 number of horizon 5 0 26 Factor PreVapRef PEST Saturated vapour pressure of 4 0E 3 PEST Pa TemRefVap PEST Temperature of reference at 25 which the saturated vapour pressure of PEST was measured Celsius SlbWatRef_PEST Water solubility of PEST 90 mg L TemRefSlb_PEST Temperature of reference at 25 which the water solubility of PEST was measured C MolEntSlb_ PEST Molar enthalpy of the 27 dissolution of PEST kJ mol Default value in PEARL MolEntVap PEST Molar enthalpy of the 95 vaporization process of PEST Default value in PEARL kJ mol CofDesRat_PEST Desorption rate coefficient of 0 PEST d FacSorNeqEql PEST Factor relating coefficients for 0 0 equilibrium and non equilibrium sorption of PEST Not relevant because CofDesRat was set to zero FacUpt_PEST Coefficient for uptake by plant roots of PEST
22. ght of the crop m For a crop the roughness length for momentum Zom is given by Zom 4 h d 2 3 2 in which Zom roughness length for momentum m a coefficient dimensionless Substitution of Equation 2 3 1 in 2 3 2 gives Zom 4h 2 3 3 in which a coefficient dimensionless Van Dam et al 1997 have proposed a value for the coefficient a of 0 123 For the description of the volatilisation flux the aerodynamic transport resistance r for the substance is the resistance for transport from d Zom and the height of the internal boundary layer Z See chapter 3 The aerodynamic resistance for the transport from Z d Zom to Z Z is given by z d z d z In 22 bl Zom Zom vil L J vi L J r 2 3 4 Ku in which la aerodynamic resistance s m Zo height of the internal boundary layer m Ph stability correction for heat and substance dimensionless L Obukhov length m K Karman constant dimensionless u friction velocity m s Under neutral conditions Eq 2 3 4 simplifies to a Zn d Zom 2 3 5 Ku a The boundary resistance r to transport between the source height and z d Zom can be described by Eq 2 2 7 or 2 2 8 The concentration of the pesticide in the gas phase at the plant surface depends on its vapour pressure at the prevailing temperature Assuming perfect gas behaviour the maximum concentration in the air at
23. ion FacWasDepRex Factor for the effect of Range 0 0 to 1 0 If set to 1 0 then no effect of reduced restricted exposure of deposit exposure on wash off FraDepRex Fraction of applied mass to be put in deposit with rediced exposure TemRefDif_PEST Temperature of reference at 20 which diffusion coefficients were measured C CofDifWatRef_PEST Coefficient of diffusion of 0 43E 4 PEST in water m7 d Default value in PEARL CofDifAirRef PEST Coefficient of diffusion of 0 43 PEST in air m d Default value in PEARL Section 6 Management ApplicationScheme Name of application scheme App PEST Zfoc FOCUS target depth m 1 DelTimEvt Time difference in years NoRepeat between subsequent Implies that the application is not repeated each year applications table Applications Table defining the 01 May 2001 1100 AppCrpLAI 0 691 applications using the format The hour of application can be specified then format is dd date mmm yyyy hhmm type application rate kg ha table TillageDates data and depth of tillage Empty event using the format data e g 01 Jan 1999 depth m table interpolate Table defining the initial Empty CntSysEql content of parent compound in the equilibrium domain of the soil using the format depth m content mg kg table interpolate Table defining the initial empty CntSysNeq content of parent compound in the equilibrium domain of the soil using the format d
24. l file is the following MSTAT HH DD MM YYYY RAD TAIR TAIRLow HUM WIN RAI ETREF ii ki m2 C C kPa m s mm mm KK KKK KK k ik KKK k ke e Heke e e Heke e He ke ke ke e keke e ke He e ke eke kek ke keke RH ke ke ke keke eke keke ke eke kek ke keke eke ke eke kk kek k keke ek ke kek RER kk k kk kk k kk kk kk k kk kk k kk kkk JUL M 1 11 5 1995 0 8 25 825 1 082 2 945 3 0 0 A new column specifying the hour during the day is added Further air temperatures at two heights can be specified If only measurements for one height are available then these measured values can be copied to the column with the header TAIRLow Measurements of the temperature at two heights are needed to assess the temperature gradient stable or unstable neutral To run the PEARL version create a bat file with the following command dir Pearl exe pearlmodel example After double clicking on the bat file pearlmodel exe will look for the input file example prl and if present in the same directory as the bat file the run will start It should be noted that the pearlmodel exe can be put in any directory The command line in the bat file should then specify the directory where the pearlmodel is located Further the swap209 exe must be in the same directory as the pearlmodel exe 17 References Asman W A H 1998 Factors influencing local dry deposition of gases with special reference to ammonia Atmos Environ 32 415 421 Hicks B B D D Baldocchi
25. lue in PEARL Quirk for diffusion in liquid phase 20 ExpDifLiqMilDen Exponent in denominator of 0 6667 relation of Millington amp Default value in PEARL Quirk for diffusion in liquid phase ExpDifGasMilNom Exponent in nominator of 2 relation of Millington amp Default value in PEARL Quirk for diffusion in gas phase ExpDifGasMilDen Exponent in denominator of 0 6667 relation of Millington amp Default value in PEARL Quirk for diffusion in gas phase Section 3 Weather and Irrigation MeteoStation Name of MeteoStation HAMB M OptEvp Option to select the type of Input data used by model OptMetInp Option to select the time Set to Hourly Options are Hourly and Daily resolution of meteo data Lat Latitude of the meteo station 2 12 Alt Altitude of the meteo station 55 12 m LenRghMmtLcl m LenFld m ZMeaWnd m ZMeaTem m OptResBou Set to Hicks Options are Hicks and Wang TemLboSta Initial lower boundary soil 7 temperature 20 40 C FacPre Correction factor for Set to 1 0 precipitation DifTem Correction for temperature Set to 0 0 FacEvp Correction factor for Set to 1 0 evapotranspiration Optlrr Option to choose between a No scenario with and a scenario without irrigation IrrigationScheme Identification of irrigation No scheme IrrigationData Name of file with irrigation The filename consists of the name of
26. n the Weather and Irrigation section the following records are added or modified OptMetinp This option gives the possibility to read hourly or daily meteorological data If OptOut SWAP is set at Hourly then OptMetInp should also be set at Hourly OptResBou This option is used to select either the parameterisation by Hicks et al 1987 to calculate the boundary resistance or that by Wang et al 1997 ZmeaWnd The height of the measurements of the wind speed 15 ZmeaTem The height of the measurements of the air temperature LenRghMmitLcl The roughness length of the soil or plant surface LenFld The length of the field upwind fetch In the Compound section the following records are added or modified KomEqlMax The maximum value for the sorption coefficient i e under very dry soil conditions OptTraRes This option gives the possibility to select either the concept of a laminar air boundary layer to calculate the volatilisation flux density Eq 2 1 1 or the concept of a combination of a boundary and aerodynamic resistances to calculate this flux Eq 2 2 3 2 2 5 Wang et al or 2 2 3 2 2 8 Hicks et al Options are Laminar and Aerodynamic If set to Laminar in combination with the option of hourly meteorological data then the thickness of the laminar air boundary layer depends on the sign of the temperature gradient If the temperature decreases with height than the value for the thickness of th
27. not be used to prepare input files However an input file made by the GUI of PEARL 2 2 2 can be taken as a starting point for the preparation of an input file that contains the correct records required by the new PEARL version In the following section the changes in the input file are described The PEARL input file contains the following sections Control Soil Weather and irrigation Lower boundary flux and drainage infiltration Compound Management Crop section Crop calendar and crop properties Output FN Oy 01 NS In the Control section the following records are added or modified CallingProgram Because the new version is not a FOCUS version the record CallingProgram should be set at Consensus ModelVersion The version number of the new PEARL consensus version is 1 OptSys If this option is set at PlantOnly then no input records are needed to describe the soil and the lower boundary and drainage conditions In this case only the processes on the plant are simulated If this option is set at All then the soil as well as the plant system is simulated and no records can be left out OptOutSWAP This option gives the possibility to run SWAP on an hourly or daily basis The options are Daily and Hourly OptDelTimPrn A new possible option has been added Hour If set at Hour then hourly output is generated If this option is used then OptOutSWAP should be set at Hourly I
28. of the rate coefficient kpn rer are assigned to each of these classes 1 very fast phototransformation half life 0 04 d 1 h Kphrer 17 d7 2 fast phototransformation half life 0 21 d 5 h kpn ref 3 3 d 3 moderate rate of phototransformation half life 1 0 d Kpn rer 0 69 d 4 slow phototransformation half life 5 0 d kpn ret 0 14 d 5 very slow phototransformation half life 25 days Kprrer 0 03 d If the above classification is too rough one of the boundaries between the classes could be selected half life 0 13 d 3 h kohrer 5 5 d7 half life 0 63 d 15 h Kphyret 1 1 d half life 3 0 d konrer 0 23 d half life 15 d kpn rer 0 05 d If the rate of phototransformation at plant surfaces is critical in the environmental evaluation special measurements should be made 4 5 Mass conservation equation on the plant surface The equation for the conservation of mass of pesticide on the plant surface reads dA ve T er R pen R Rp 4 4 2 with t time d All areic quantities in this equation are expressed on the basis of m field surface The definition of the two deposit classes of a well exposed deposit and b poorly exposed deposit requires the use of two mass conservation equations one for each of these classes 14 5 Getting started running the new PEARL model As the new PEARL version requires new input records the GUI of FOCUS PEARL 2 2 2 can
29. pending on the physico chemical properties of the pesticide and the soil and weather conditions the relative contribution of processes such as leaching transformation and volatilisation to the overall fate will differ For an accurate description of the fate of the pesticide in the soil model concepts are needed that adequately describe the different processes involved So far the description of the volatilisation process has been rather simple and especially for soil surface applied pesticides reliable estimates on the course with time of the rate of emission into the air could not be made The description of the volatilisation process from soil and plant surfaces was improved Further a concept was developed to describe the effect of the soil moisture content on the coefficient for the sorption of pesticide to soil particles These improvements were implemented in PEARL 1 5 8 F2 the model version included in FOCUS PEARL 2 2 2 The resulting PEARL version is 2 1 1 C1 The character C stands for Consensus which means that this version of PEARL has been approved by both Alterra and RIVM In Chapters 2 3 and 4 first the model concepts used in FOCUS PEARL 1 1 1 and FOCUS PEARL 2 2 2 is described and this is followed by a description of the improved concept as included in the new PEARL version Chapter 2 gives a description of the model concepts for volatilisation from soil and plant surfaces Chapter 3 gives a description of the moistur
30. ration at the soil surface 2 2 Description of improved concept for volatilisation from bare soil The volatilisation flux density depends on physico chemical properties of the substance but also on moisture and meteorological conditions at the site of application The effect of the environmental factors can be taken into account with the concept of a resistance to transport of substance from the surface into the atmosphere Wang et al 1997 Asman 1998 Using this concept the flux density of volatilisation is given by Cox Cair Joa 2 2 1 F r in which la aerodynamic resistance d m lp boundary layer resistance d m The aerodynamic resistance is the resistance to transport between the roughness length for momentum Zom and the height of the internal boundary layer z into which the pesticide has mixed This height depends on the length of the sprayed field the roughness length and the stability conditions of the atmosphere see Van der Molen et al 1990 Hence the aerodynamic resistance is given by Ze Z yA In 2 yl 7 Zon 3 2 vil vil L J i 2 2 2 Ku in which Zo height of internal boundary layer m Zom roughness length for momentum m Ph stability correction for heat and substance dimensionless L Obukhov length m K Karman constant dimensionless us friction velocity m d Under neutral conditions Eq 2 2 2 simplifies to In 2L Zom r 2 2 3 a
31. re C HUM Air humidity kPa WIND Daily average wind speed m s RAIN Daily rainfall mm ETref Daily reference evapotranspiration mm Literature references Boesten JJTI 1986 Behaviour of herbicides in soil simulation and experimental assessment Doctoral thesis Institute for Pesticide Research Wageningen 263 pp Feddes R A Kowalik P J and H Zaradny 1978 Simulation of field water use and crop yield Pudoc Wageningen the Netherlands 188 pp FOCUS 2000 FOCUS groundwater scenarios in the EU review of active substances Report of the FOCUS Groundwater Scenarios Workgroup EC document Sanco 32 1 2000 rev 2 197 pp Available at http viso ei jre it focus gw Ritchie JT 1972 A model for predicting evaporation from a row crop with incomplete cover Water Resour Res 8 1204 1213 Tiktak A F van den Berg JJTI Boesten D van Kraalingen M Leistra and AMA van der Linden 2000 Manual of FOCUS Pearl version 1 1 1 RIVM Report 711401008 Alterra Report 28 RIVM Bilthoven 142 pp Tomlin C 1997 The Pesticide Manual British Crop Protection Council 11 ed Farnham UK 1606 pp Van Dam JC Huygen J Wesseling JG Feddes RA Kabat P Van Walsum PEV Groenendijk P amp Van Diepen CA 1997 Theory of SWAP version 2 0 Technical Document 45 DLO Winand Staring Centre Wageningen The Netherlands 167 pp Weast RC 1974 Handbook of chemistry and physics 55th edition CRC Press Cleveland
32. t Ts J 4 1 2 with Jya actual rate of pesticide volatilization kg m d fmas factor for the effect of pesticide mass on the plants The pesticide is assumed to be deposited on the leaves in spots of variable thickness The thinner the deposit at a certain place the sooner that place will be depleted by volatilisation The concept is that the volatilising surface decreases in proportion to the decrease in mass of pesticide in the deposit So A Snas 4 1 3 Ap ref with 11 Ap areic mass of pesticide on the plants kg m Aprr reference areic mass of pesticide on the plants 1 0 10 kg m 1 kg ha 4 2 Penetration of substance into plant tissue Pesticide penetration into the leaves is influenced by many factors but no quantitative relationships are known Therefore the description of the process in the plant module can be kept simple The rate of pesticide penetration into the leaves is calculated by R pen K pen Ap 4 2 1 with Roen rate of pesticide penetration into the leaves kg m d Kpen rate coefficient of penetration d The coefficient kpen is one of the quantities to be calibrated in the computation on the basis of the measurements or it is derived from other studies on pesticide and formulation Direct measurements on the rate of penetration of pesticides into plants are usually not available Quantitative predictions on such penetration on the basis of process
33. terval d Only required if OptDelTimPrn is set to Other OptScreen Option to write output to Set to Yes screen RepeatHydrology Repeat the same hydrology No each year OptHyd Hydrology simulation option Automatic DelTimSwaMin Minimum time step 1 E 8 DelTimSwaMax Maximum time step 0 2 OptDelOutput Option to delete detailed No output PrintCumulatives Option to output cumulative Set to Yes Options are Yes and No data GWLTol Tolerance for groundwater Set to 1 m level MaxItSwa Maximum number of Set to 10000 iterations in SWAP OptHysteresis Option to include hysteresis Set to No PreHeaWetDryMin Minimum pressure head to Set to 0 2 Treated as a dummy switch drying wetting Section 2 Soil 19 SoilT ypelD Name of soil type HAMB SOIL Location Name of location HAMBURG table SoilProfile Table defining the soil 0 3 12 profile 0 3 12 specify for each horizon the 0 3 6 thickness m and the number 0 1 2 of numerical soil 15 15 compartments Comment the thickness of numerical layers is 2 5 cm in the top 0 6 m then 5 cm up to 1 0 m depth and 10 cm to 2 5m depth table SoilProperties Table specifying the soil 1 0 389 0 41 0 201 0 0172 8 4 composition for each horizon 2 0 4 0 398 0 202 0 0113 7 9 horizon number 3 039 0 449 0 161 0 0063 7 8 fraction sand kg kg 4 0 434 0 427 0 139 0 0045 8 fraction silt kg kg 5 0 434 0 427 0 139 0 0045 8 fraction clay kg kg Source file
34. the irrigation scheme data with the extension irr Section 4a Lower Boundary Flux ZgrwLevSta Initial depth of groundwater level m OptLbo Option for bottom boundary GrwLev condition table GrwLev Table containing daily values of groundwater level for the full experimental period using the format date e g 01 Jan groundwater level m Section 4b Drainage infiltration section 21 OptDra Default set to No OptSurDra Option to consider surface Default set to No drainage NumDraLev Number of drainage levels 0 Section 5 Substance PEST SubstanceName Name of substance PEST table Compounds List of names of parent PEST compound and metabolites table FraPrtDau Table containing fractions empty formed on amount of substance basis for all parent and metabolite combinations MolMas PEST Molar mass g mol of PEST 200 0 OptCntLiqTraRef PEST Option to use the moisture OptimumConditions content during the incubation study of PEST comment this implies that DTSORef has to be specified at matric suction of 100 hPa DTSORef PEST Half life for transformation of PEST in topsoil at reference temperature and a matric suction of 100 hPa 8 2 TemRefTra_PEST Temperature at which half life of transformation of PEST was measured C 25 ExpLiqTra_PEST Coefficient describing the relation between the transformation rate of P
35. ture content kg kg Wiow moisture content below which sorption coefficient increases kg kg The coefficient a can be calculated by substituting Ww for w and Ka for Kg ew in Eq 3 1a This gives K a l nf Kea 3 2 Wow d Substituting Eq 3 2 in Eq 3 1a results in w Kd max In 2 Wiow Kd 3 3 K K deff T d max The value of Wow is set equal to the water content at pF4 2 wilting point At pF values greater than 4 2 the relative humidity of the air in the soil pores is no longer 100 So in the new PEARL version the only new parameter needed to describe this effect is Ka max An example for both the linear and the exponential relation is given in Figures 1 and 2 Note that the data for Figures 1 and 2 are the same The only difference is that in Fig 1 sorption data are presented on a linear scale and in Fig 2 on a logarithmic scale Exponential Linear 20000 Sorption coefficient L kg 0 0 01 0 02 0 03 0 04 0 05 0 06 Moisture content kg kg Figure 1 The sorption coefficient as a function of the moisture content Increase in sorption coefficient taken to be linear or exponential Exponential Linear oO Oo oO el to t Sorption coefficient L kg o 10 0 0 01 0 02 0 03 0 04 0 05 0 06 Moisture content kg kg Figure 2 The sorption coefficient as a function of the moisture content Increase in sorption coefficient taken
36. water extraction starts cm 30 same value for other crop HLim3U_crop1 pressure head below which reduction starts when potential transpiration is high cm 325 same value for other crop HLim3L cropl pressure head below which reduction starts when potential transpiration is low cm 600 same value for other crop HLim4_cropl pressure head below which there is no water extraction cm 8000 same value for other crop RstEvpCrp_cropl Canopy resistance s m 70 same value for other crop Source Allen et al 1989 CofExtRad cropl Extinction coefficient for global radiation 0 39 same value for other 2 crops Source Feddes et al 19878 Ritchie 1972 CofintCrp cropl Interception coefficient cm 0 0001 same value for other crop This value implies zero interception in practice FraCovCrpInp Fraction of surface covered by crop Only required if OptSys is set to PlantOnly Otherwise read from SWAP output 25 HgtCrpInp m Only required if OptSys is set to PlantOnly Otherwise read from SWAP output File Y MET PARAMETER DESCRIPTION VALUE SOURCE amp COMMENTS Station Name of weather station HAMBURG DD Number of day MM Number of month YYYY Number of year RAD Daily global radiation kJ m Tmin Minimum air temperature C Tmax Maximum air temperatu
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