"user manual"
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1. ayDIdN 21120 Sununssp oq dq pup ypidn aaisspd Sununssp Jup d Hit uonngqisiq JD aypjdn 241190 Sununssp OAG g 2ypnidn aaisspd Sununssp 4 t dsolqg Ul uo1l nq14 siq V p1JOnuo1ppa p p numoop ABVIJUBIAI Z p 4n51 w L Q Q Q Q Q Q ie Q CO CO CO CO CO CO CO CO CO CO T T T T T T T T T T 3 CO CO N N N N cO N GA ech cO N GA l l l l l l Z 1de I oo PIO Was PIO je 7 PIO oozi was Ier fleegt E Je1 UIN snuunH Jeu JURId d V VV VV NUMM UY OL co pil9nuoipei p e nuin55v LO pi j9nuolpei p e nuin55V OOL m ul l O O O O O O O O O O O KG KG KG KG KG KG KG KG KG KG KG T T T T T T T T T T T Ceo Co Co N N N N N Te N Q ech Te N o Q I I I La be I 2 l I I 0 he S x SS TE d 5 O g c I 3 WW my Ser d i LO o lt a a Le a i 9 1 8 I E 9 gt 5 c Ore Q OO PIO W3 S PIO Je PIO o Joo TERTS yeoq tl 0 Regen E Ob a 02 O OV OS 09 je OUIIN 02 snuny 08 19 I7 06 JUBId OoL apljonuoipes payejnunsoy 18 The plant uptake using active uptake was not only higher it showed also more within years variation This can be explained by the differences in allocation within the plant Using passive uptake most of radionuclide was allocated in o2. where Cuer Grain 1S the flux of carbon from leaves to grain TE ars the ratio of trace element and leaf carbon TE reaf TE mg TE gC 2 5 rLeaf Leaf where TE a 18 the trace element content of leaves and Creat 1s the carbon content of leaves The transfers of tracers from roots to grain TEk Grain and from stem to grain TEstem Grains are calculated analogously For applications north of equator every 1 of January the amount of trace elements of the current year pool TE ap TEstem and TEpoos are transferred to pools for old plant material 1 e TEotateats TEoidstem and TEoaroots For applications south of the equator this is done on 1 of July every year 12 Trace element fluxes in litter formation and decomposition Trace element fluxes with litterfall from leaves stem grain and roots are calculated in the same manner as trace element fluxes to grain 1 e in proportion to carbon fluxes and the ratio of trace element and carbon content of the respective plant source pool Trace elements originating from above ground plant parts accumulate in the surface litter TEsurfaceLitter mg TE m From the surface litter there is a constant flux of trace elements into the litter pool in the uppermost soil compartment TE itte z1 mg TE m calculated as de Suma sasana z l p r E SurfaceLitter mg TE day 2 6 where lu is a rate coefficient day that is assumed similar as for carbon and nitrogen Below gro
3. Passive uptake means in this study that the root uptake rate of a radionuclide 1s governed by water uptake Normal mechanism for the passive water uptake is the convective flux of water from the soil to the plant An example of element taken up passively is Ca Active plant uptake is in this model defined as the root uptake rate of a radionuclide that is governed by carbon assimilation 1 e photosynthesis and plant growth The actively taken up element can for example be an element essential to plant but not available in high enough concentration by passive uptake alone like the major nutrients N and P or an element that very well resembles a plant nutrient like Cs resembles K Active uptake of trace element may occur alone or in addition to passive uptake Normal mechanism for the active uptake is molecular diffusion from the soil solution to the roots or via any other organism living in symbiosis with the roots like the mychorrhiza Also a model approach describing adsorption was introduced CoupModel Jansson and Karlberg 2004 dynamically couples and simulates the flows of water heat carbon and nitrogen in the soil plant atmosphere system Any number of plants may be defined and are divided into roots leaves stem and grain The soil is considered in one vertical profile that may be represented into a maximum of 100 layers The model is the windows successor and integrated version of the DOS models SOIL and SOILN which have been widely
4. ooje Jea C 0 Uu0l 961 Olle Je9 0 UO 30e Je9 lt 4o 5eJ BUILDS sAissegd 40 9e Bugs aaissed 10 9e Buile5s aAisseg S1 0 SCH S O oICn SCH 32 569 0 30 32 0 Sc 0 S10 SZ9 0 S O Gin on 0 0 0 o g o gt OL gt OL gt OL gt O oO O ot 3 Sb 3 GL 3 E D E T 3 a oz Oc a oz 3 y SZ 6 IC SE gt E 2 oe oe oe o D o Ge Se Ge A d d wu L u d p jooy wu 0 u d p jooy wu 0 u d p Joo 20 JJ1qp 1papolq JO sJ 42 pup s lp uuussp fba UOGADI PUD p1iJoOnuo1pD4 ODA WNUIXDU uo1jOD4 uoydiospo Juasaffip aof ypidn BAIIV BUISN APIINUOCIPDA p p numno2D ABVIUZII f p AANGL 6 51 6wg Jeaj0 4 L 6 4 1 6wgz Je o 3 L FO 96 41 6w Je o 31 ae 6 41 6wg 0 Je9 o 31 96 3 16w 0 4299 3 L lt 6w Ayiliqe eAeolg 5w Ayiqejeaeorg G0 500 1 90 300 L 0 300 S0 300 L 90 300 L Z0 300 L S0 300 L 90 300 L 20 3004 oe oe oe 6w Apjiqeyeaeoig so se gt gt gt S 2 O ce e GE g CC 2 3 3 3 c E s D v S D 2 gt N o ra Q S S ur 2 gt S S Gy GY GV 0 uol diospv 0Z UOl diospy 0 uondiospv 21 5 Conclusions We conclude that the Introduced module was able to simulate different dynamic plant uptake processes and hydrological conditions We also demonstrated how the model could be used to simulate potential long term incorporation of a radionuclide in the biosphe
5. day 2 3 where z is the relative depth thickness z of the root zone r TE aug 1s the concentration ratio of trace elements actively taken up and calculated as follows L L tE AZ T u z mi 2 1 i P 4urLeaf mg TE gC P AUcBio where Paucpio reflects the bioavailability i e a threshold concentration of the trace element in the soil solution Above this threshold concentration is the trace element uptake ratio equal to the maximum ratio of trace element and new carbon assimilates of respective plant compartment denoted with DA ent Paurstem and Paurroot mg TE gC for new leaf stem and roots assimilates respectively Analogous equations are used to calculate the active uptake to stem TEmin stem and roots TEmin gt rootse by exchanging DA et est tO Paurstem OF PAurRoots and Ca Leaf to Ca Stem or Ca Root respectively The total active uptake of trace elements TEaumin piants 18 the sum TE Aen TEmin gt stem and TEmin roots z after integration over the different soil layers Allocation of trace elements to the grain and old plant pools Allocation of trace elements to the grain pool from roots leaves and stem is proportional to the carbon fluxes and the ratio of trace element and carbon content of the respective plant source pool For example the transfer of trace elements from leaves to grain TEL Gran 1S calculated as TE Leaf Grain C Leaf Grain TE rear Mg TE day 2 4
6. e g TEsurtacetitters T Erite and TExqumus and mineral pool TEyin including both dissolved in soil solution and adsorbed to soil in each soil layer were included Figure 2 1 Trace elements can enter the soil plant air system either as an initial concentration in the soil layers TE mg TE l or as a constant groundwater TE flux qrrin mg TE day by means of a constant water flow qsoa mm day with a constant concentration TEconcsoriow mg I in a specific soil layer z m It can leave the system by deep percolation qreap or drainage qrea mm day The description of trace element fluxes between one state variable to another have much in common with those of nitrogen Fluxes due to uptake allocation to grain and old plant parts decomposition and mineralization are described in detail in following sections 10 SrTEoIqdStem A Z He Stes T S TELeaf QTE in S TERoots S TELitter QTE ar QTE dp Figure 2 1 The storage and fluxes of trace elements in the model Passive plant uptake Passive uptake of a trace element denoted with PU is governed by plant water uptake Wap mm day the trace element concentration in soil water denoted with subscript c TE mg I in the root zone denoted with r and a dimensionless scaling factor represent ing degree of convective transport Ppuscate Where zero means no convective uptake and one full convective uptake The uptake is calc
7. organic matter Adsorbed tracer element should not be confused with trace elements internal parts of litter and humus TE ouer and TEgumus The amount of adsorbed tracer element originates from mineralization and or groundwater contamination while the amounts of trace element part of litter and humus originate from litter production and humification The soil water TE concentration of a certain soil layer TE can be estimated by dividing the TE storage in the soil layer TEs reduced with the layer specific absorbed fraction Lama With the soil moisture storage Az 0 z of that layer TE TE I z Jaare DI o 2 ege mg TE ml 2 10 13 3 Model application and sensitivity analysis The fate of an unknown radioactive element introduced by groundwater was illustrated by simulating a mature Spruce forest stand in central Sweden on a loamy soll for a 20 years period The simulated period started 1 April 1970 and continued in 20 years Daily weather records of temperature precipitation wind speed humidity and global radiation of Uppsala were used as driving variables The N deposition corresponded to 5 kg N ha year in average The initial groundwater table was set to at 0 8 m depth It was assumed that the contamination with unknown radionuclide occurred as a single pulse at simulation start with a radionuclide concentration of 10 mg 1 between 40 and 95 cm depth That resulted into a total contamination of 1 400 mg m at
8. s 0 001 mg Mn g C We set the optimum concentration to 0 001 A certain minimum concentration of the element is needed so that uptake reaches maximum efficiency We keep this at the default value of 110 Abiotic parameter tables The maximum root depth of this Plant is assumed to be 1 m Adsorption is assumed to be related to soil organic matter content and therefore decrease exponential with depth Salt tracer to reflect a single pulse contamination originating from groundwater the initial is 10 mg l between 30 and 100 cm and 0 at other depths Please note that the Adsorption distribution fraction should be interpreted as solution fraction 1 e an adsorption fraction of 0 7 means that 70 of salt storage is in solution and 30 adsorbed Soil physical characteristics are strongly site specific and differ very much between agri cultural clay and a forest till For this exercise we will use soil properties from Skogaby Check under Soil hydraulics that the Brook Corey is adjusted to measured values of Skogaby profile The soil profile should be divided into 15 layers with increasing thickness Organic layer 0 5 cm and mineral soil layers 5 15 15 25 25 35 35 50 50 70 etc down to 630 cm To CoupModel is added a soil database see under the File menu to Read from database select Current document Here you can select the Soil properties chapter of the database and view a list of soil profiles Forest soils are found under numbers hi
9. sandy soils Water Resources Research 35 95 103 Stahli M Nyberg L Mellander P E Jansson P E Bishop K 2001 Soil frost effects on soil water and runoff dynamics along a boreal forest transect 2 Simulations Hydrological Processes 15 927 941 Svensson M 2004 Modelling soil temperature and carbon storage changes for Swedish boreal forests Licenciate Thesis TRITA LWRLIC 2018 Underwood E J 1977 Trace elements in human and Animal nutrition 4 Ed Academic press New York 26 Appendix 1 Model exercise Accumulation of water solutes in biosphere By Annemieke Gardenas and Per Erik Jansson 2003 12 10 SLU Uppsala Sweden A 1 Plant uptake of water solutes This exercise deals with the accumulation of an element or compound in an ecosystem after a single pulse groundwater contamination Three scenarios will be compared the first one excluding plant uptake the second one including passive plant uptake and the third one including both passive and active plant uptake It is assumed that the user has completed the other tutorials especially the ones about carbon and nitrogen balances of arable and forest ecosystems If this is not the case it is recommended to review these sections In the manual or to run some of the other tutorials before going through this one Make use of the Help buttons whenever you need to see the theory and the processes governed by a specific switch or parameter It is also assumed th
10. used on different ecosystems and climate regions during 25 years time period To this soil plant atmosphere model were introduced a module describing accumula tion of a radionuclide in the biosphere originating from groundwater contamination The radioactive element is represented as a state variable in different plant parts stem leaves roots and grain and in soil layers as attached to soil organic matter fractions litter and humus solved in soil water solution and adsorbed to soil particles The importance of the different plant uptake models and their parameterization for accumulation of radio nuclides in the biosphere was demonstrated by a model application of a mature boreal forest for a 20 years period with an initial single pulse groundwater contamination The passive uptake approach was used to demonstrate importance of root depth allocation to leaves and different scaling to the water uptake rate The active uptake approach was used to demonstrate the importance of adsorption fraction bioavailability and optimum ratio of leaf carbon and radionuclide After 20 years 9 of the originally added radionuclide had accumulated in the biosphere when assuming no plant uptake Corresponding numbers for passive and active uptake were 12 37 and 35 44 respectively The percentages accumulated using passive uptake was most sensitive to tested range of rooting depth and ones using active uptake to tested range of optimum ratio of leaf ca
11. A model of accumulation of radionuclides in biosphere originating from groundwater contamination Annemieke G rden s Department of Soil Sciences Swedish University of Agricultural Sciences Per Erik Jansson Louise Karlberg Department Land and Water Resources Royal Institute of Technology March 2006 R 06 47 Svensk K rnbr nslehantering AB Swedish Nuclear Fuel and Waste Management Co Box 5864 SE 102 40 Stockholm Sweden Tel 08 459 84 00 46 8 459 84 00 Fax 08 661 57 19 46 8 661 57 19 ISSN 1402 3091 SKB Rapport R 06 47 A model of accumulation of radionuclides in biosphere originating from groundwater contamination Annemieke Gardenas Department of Soil Sciences Swedish University of Agricultural Sciences Per Erik Jansson Louise Karlberg Department Land and Water Resources Royal Institute of Technology March 2006 This report concerns a study which was conducted for SKB The conclusions and viewpoints presented in the report are those of the authors and do not necessarily coincide with those of the client A pdf version of this document can be downloaded from www skb se Abstract The objective of this study is to introduce a module in CoupModel Jansson and Karlberg 2004 describing the transport and accumulation in the biosphere of a radionuclide origi nating from a ground water contamination Two model approaches describing the plant uptake of a radionuclide were included namely passive and active uptake
12. C Roots C Total PlantLitter CTOESOITOTG CTotSoilRespRate Figure A 2 Simulated flows of carbon in soil plant atmosphere system 33 A 5 3 Water Add the water budget of your simulation in terms of the flows in table below Flows are expressed per unit of days so you have to accumulate values PrecCorrected InterceptionActEva Transpiration Evapotranspiration SoilEvaporation SoilInfil SpoolRunoff Soil Water TotalDrainage p TotalRunoff Figure A 3 Simulated flows of water in soil plant atmosphere system 34 A 5 4 Nitrogen Add the nitrogen budget of your simulation in terms of the flows and changes of storage in table below Flows italic are expressed per unit of days so you have to accumulate the values to get annual flows N Tot Denitrification Deposition NH4 Rate Deposition NO3 Rate N Plant AboveG N Roots N Total PlantLitter N Total PlantUptake ee N Tot MinN Soil N Tot MinN Drainage Figure A 4 Simulated flows of nitrogen in soil plant atmosphere system 35 A 6 Acknowledgement The tutorial is an extension of tutorial for CN forest by Eckersten and Gardenas 2001 The parameterization is based on Eckersten et al 1999 Svensson 2004 and Gardenas et al 2003 A 7 Literature Berggren D Johansson M B Langvall O Majdi H Melkerud P A 2002 In Olsson M Ed Land use strategies for reducing net greenhouse gas emissions Mistra Programme Pro
13. age of added radio nuclide was tested A tutorial how to use the module is given in the appendix 2 Model description 2 1 General In CoupModel Jansson and Karlberg 2004 the flows of water heat carbon and nitrogen In the soil plant atmosphere system are dynamically coupled The nitrogen and carbon balances of an ecosystem strongly depend on the water and heat balances as processes like growth and decomposition depend on the soil temperature and moisture content The water and heat balances in turn are influenced by the carbon and nitrogen balances e g water uptake varies with growth rate and N fertilization CoupModel is the windows successor and coupling version of the DOS models SOIL Jansson and Halldin 1979 Jansson 1998 and SOILN Johnsson et al 1987 Eckersten et al 1998 which have been widely used on different ecosystems and climate regions during 30 years time e g Espeby 1992 Gardenas and Jansson 1995 Eckersten et al 1995 1999 Gustafsson et al 2004 It is a one dimen sional deterministic model with the partial differential equations of water and heat flow solved by using an explicit forward difference method called the Euler integration Plants are divided into compartments root leaves stem and grain and soils into a maximum of 100 internally homogenous layers with specified properties like hydraulic conductivity litter content and root density Jansson and Karlberg 2004 compromises a complete documentation of
14. at the user can analyze and plot results If this 1s not the case please refer to the Infill tutorial A 1 1 Purpose The purpose of this exercise is to demonstrate the importance of plant uptake for accumula tion and or residence time of elements or compounds in the biosphere originating from a single pulse in the groundwater Plant uptake of water solutes can be passive or both passive and active Passive plant uptake means that the uptake rate 1s governed by water uptake Examples of elements or com pounds which can be taken up passively are Cd and benzene Active plant uptake means that the uptake rate is governed by carbon assimilation i e plant growth The actively taken up element often resembles very well a plant nutrient like Cs resembles K Active uptake occurs in addition to passive uptake Adsorption of the element to soil organic matter and or soil particles 1s also taken into account The fate of the element introduced by groundwater will be illustrated simulating a mature coniferous forest stand in central Sweden Knottasen on a loamy soil for a 20 years period The importance of initial groundwater table variation of salt concentration and adsorption factor with depth will be analyzed After conducting this tutorial the user should have gained some knowledge about the proc esses and properties affecting accumulation of a contaminating element by groundwater in an ecosystem Furthermore you will get practi
15. ce in how to model these processes and properties with the CoupModel 21 A 1 2 Input files The following files in the directory C Program Files LWR KTH CoupModel Samples PlantTE will be used for this exercise ClimateU bin A Pgraph PG binary file with climate data for 40 years period of Uppsala Knotspruce SIM A simulation document file with input data used as a starting point for your simulation This file represents an application of CoupModel to spruce forest in central Sweden A 2 Description of the simulated system The forest you will model represents the coniferous forest in Knottasen In central Sweden see Berggren et al 2002 for general description The dominant tree species is Norway spruce The bedrock consists of older granites sediments and volcanic rocks The bedrock is covered by a sandy till soil except for a few outcrops The soil type is podzol FAO The soil hydraulic properties were taken from a similar loamy soil Skogaby Bergholm et al 1995 The soil C and N content were adjusted to measurements in Knottasen The stand was planted 1965 with two years old seedlings The site quality is 7 8 m ha and site index is G24 i e dominant height at age of 100 years is estimated to become 24 m When the forest was almost 40 years old the stem needle and root biomass were about 39 7 and 9 ton C ha respectively Typical leaf area index is 3 The total soil organic content of the whole profile down t
16. cribed with a first order rate coefficient and limited by the amount of soil organic matter in each fraction and the excess of available mineral N Soil organic matter is fractionated into a surface pool of fresh litter litter and humus Microbes may be described by a separate pool or considered as a part of the soil organic matter while mycorrhiza may be considered as incorporated into the root biomass pool The plants trees and ground vegetation are divided in roots leaves needles stems and grains The roots leaves and stems are divided into current year and old biomass Each pool in the soil layers and plant have an initial defined carbon and nitrogen content Especially the root depth and root distribution patterns are important feed back mechanism between the hydrological conditions and the dynamics of nitrogen and carbon Plant charac teristics like photosynthesis efficiency litter rate and allocation pattern between root shoot can be parameterized and changed to represent plant age species and or climatic region 2 4 Radionuclide model The model of cycling of a radioactive element is defined as a general model of a trace element cycling in the soil plant atmosphere system The trace element is denoted with the abbreviation TE throughout the model description State variables mg TE m of the tracer element in all plant parts e g TE ear TEceatoias TEstem TEstemotds TEroot TErootoia and TEGrain all soil organic matter fractions
17. ded by SKB 24 7 References Berggren D Johansson M B Langvall O Majdi H Melkerud P A 2002 In Olsson M Ed Land use strategies for reducing net greenhouse gas emissions Mistra Programme Progress report 1999 2002 http www lustra slu se rapportermm pdf utv pdf Bergholm J Jansson P E Johansson U Majdi H Nilsson L O Persson H Rosengren Brinck U Wiklund K 1995 Air pollution tree vitality and forest production The Skogaby project General description of a field experiment with Norway spruce in south Sweden In Nutrient Uptake and Cycling in Forest Ecosystems eds L O Nilsson R F Huttl U T Johansson P Mathy Ecosys Res Rep European Commission 21 69 87 ISBN 92 826 9416 X de Wit CT 1965 Photosynthesis of leaf canopies Agric Res Rep 663 1 57 PUDOC Wageningen Eckersten H Gardenias A Jansson P E 1995 Modelling seasonal nitrogen carbon water and heat dynamics of the Solling spruce stand Ecological Modelling 83 119 129 Eckersten H Jansson P E Johnsson H 1998 SOILN model user s manual Version 9 2 Swed Univ Agric Sci Dept Soil Sci Communications 98 6 113 pp Eckersten H Beier C 1998 Comparison of N and C dynamics in two Norway spruce stands using a process oriented simulation model Environmental Pollution 102 395 401 Eckersten H Beier C Holmberg M Gundersen P Lepist A Persson T 1999 Application of the nitrogen model to forested land In Nitrogen processe
18. er and heat conditions Description of the SOIL model Swed Univ Agric Sci Dept Soil Sci Communications 98 2 Jansson P E Halldin S 1979 Model for the annual water and energy flow in a layered soil In Comparison of forest water and energy exchange models Proc from an IUFRO workshop ed S Halldin 145 163 pp Jansson P E Karlberg L 2004 COUP model Coupled heat and mass transfer model for soil plant atmosphere system Dept of Civil and Environmental Engineering Royal Institute of Technology Johnsson H Bergstr m L Jansson P E Paustian K 1987 Simulated nitrogen dynamics and losses in a layered agricultural soil Agric Ecosyst Environ 18 333 356 Karlberg L 2002 Modelling transpiration and growth of salinity and drought stressed tomatoes Licentiate thesis TRITA LWR LIC 2008 Department of Land and Water Resources Engineering Royal Institute of Technology Stockholm Lohammar T Larsson S Linder S Falk S O 1980 FAST simulation models of gaseous exchange in Scots pine In Structure and Function of Northern Coniferous Forests An Ecosystem Study ed T Persson Ecol Bull 32 505 523 Stockholm Monteith J L 1965 Evaporation and environment In Fogg G E Editor The State and Movement of Water in Living Organisms 19 Symp Soc Exp Biol 205 234 pp Cambridge The Company of Biologists Stahli M Jansson P E Lundin L C 1999 Soil moisture redistribution and infiltration in frozen
19. g is reached and winter regulation is active In the forest Soil organic processes organic uptake and dissolved organic play a role The initial organic content decreases exponential with depth Under common abiotic responses you can define the temperature response to follow the Ratkowsky function Technical options Meteorological data is given in the ClimateU bin PG file The infor mation about climate that you have in the ClimateU bin 1s daily mean air temperature daily mean relative air humidity daily sums of global radiation daily sums of precipitation and daily mean wind speed The air humidity could be represented in different forms You have to specify that it is the relative air humidity that is given in the file Cloudiness and net 29 radiation have to be estimated The temperature conditions at the lower boundary of the soil profile are represented by an annual cycle The Abiotic driving variables for the C N sub model are all simulated by the water and heat sub model of the CoupModel except deep percolation input which is not used A 3 5 Parameter values In this section you will change parameters that are of importance for the accumulation of a contamination originating from groundwater in an ecosystem Some are specific for a certain element or compound as discriminating factor for uptake others are plant specific like root uptake close to saturation and others depend on weather conditions and soil h
20. gher than 100 30 Biotic parameters External N inputs to the forest occur by means of N deposttion We assume a yearly deposition of almost 3 kg ha y and that all deposition to be in wet form and that all reaches the soil surface This means that the N concentration of water infiltrat ing soil is about 0 5 mgNIl The fractions of NHu and NO are the same Several Plant Growth processes rates differ with plant species one very important is the radiation use efficiency for optimal water nitrogen and temperature conditions 2 3 g d w MJ the temperature range for optimum photosynthesis is 10 25 C and the maximum range for photosynthesis 2 28 C The minimum C N ratio of needles is higher than for crop leaves about 20 Spruce fall litter year around but more in the autumn therefore two leaf litter fall rate are used A 10 and 0 01 day Soil organic processes The specific decomposition rate for litter and humus they are 0 005 day and 4 10 4 day respectively Microbes are assumed to be a part of the litter pool Here this microbial C N ratio represents the C N ratio of decomposed material which in forest soils is about 20 Biotic parameter tables Twenty five percent of the assimilated carbon of the above ground biomass 1s allocated to the leaves The allocation to the roots depends on the C N ratio of the leaves At high N status of the leaves less carbon will be an allocated to the roots 0 4 Plant N uptake is re
21. graphics of your results 31 AAA Making a new simulation If you want to make a new simulation press the green arrow toolbar button The new simulation is created with the settings from the last simulation You can for example alter the initial groundwater table differ adsorption with depth alter root depth etc Before doing so save your final sim file under suitable name It is recommended that you analyze the salt water and carbon balances before making new simulations A 5 Results A 5 1 Salt tracer element Add the salt tracer element budget of your simulation in terms of the flows and changes of storage In table below Flows italic are expressed per unit of days so you have to accumu late the values to get annual flows Auxiliary variables denoted Acc may be useful here TE Total Plant TE Total Litterfall TE Total Plant Uptake TE Total Litter TE Total Mineral TE Total Humus TE Total Mineralization AccSaltOutput AccSaltInput Figure A 1 Simulated flows of salt in soil plant atmosphere system 32 A 5 2 Carbon Add the carbon budget of your simulation in terms of the flows and changes of storage in table below Flows italic are expressed per unit of days so you have to accumulate the values to get annual flows Auxiliary variables denoted with Acc may here be useful C LeafAtm C OldLeafAtm C AtmNewMobile C StemAtm C OldStemAtm C RootsAtm C Plant AboveG
22. gress report 1999 2002 http www lustra slu se rapportermm pdf utv pdf Bergholm J Jansson P E Johansson U Majdi H Nilsson L O Persson H Rosengren Brinck U Wiklund K 1995 Air pollution tree vitality and forest production The Skogaby project General description of a field experiment with Norway spruce m south Sweden In Nutrient Uptake and Cycling in Forest Ecosystems eds L O Nilsson R F H ttl U T Johansson P Mathy Ecosys Res Rep European Commission 21 69 87 ISBN 92 826 9416 X Eckersten H Gardenias A 2001 Carbon balance of forest ecosystem Effects of climate change Samples of CoupModel 21 pp Eckersten H Beier C Holmberg M Gundersen P Lepist A Persson T 1999 Application of the nitrogen model to forested land In Nitrogen processes in arable and forest soils in the Nordic countries Field scale modelling and experiments TemaNord 1999 560 Nordic Council of Ministers Copenhagen p 99 129 Gardenas A Eckersten H Lillem gi M 2003 Modeling long term effects of N fertilization and N deposition on the N balance of forest stands in Sweden 30 pages Emergo 2003 3 Shaw R H Pereira A R 1982 Aerodynamic roughness of a plant canopy a numerical experiment Agricultural Forest Meteorology 26 51 65 Svensson M 2004 Modelling soil temperature and carbon storage changes for Swedish boreal forests Licenciate Thesis TRITA LWRLIC 2018 A 8 Corresponding authors Per Erik Jansson Pey k
23. iving variable file ClimateU bin which is 19610101 19991231 Set simulation start to 19700401 and simulation end to 19900331 Since long periods will be simulated it 1s recommended to choose output for every ten days Check that number of iteration is 64 A 3 4 Model specific options Here you will set switches that configure the CoupModel the way you want it to represent a spruce forest With help of the switches you select which processes to be included in the model and how to represent the processes Use the help command for the single switches to make sure you understand what these switches do The information 1s valid for all scenarios unless marked as addition for scenario with passive alt passive and active uptake General options We assume the evaporation to be driven by radiation We also assume that groundwater table can fluctuate The forest is not irrigated and horizontal flows are neglected Soil water dynamics are simulated as well as heat and snow dynamics The C N model simulates the plant properties like leaf area and root depth dynamically interacting with the water dynamics The canopy of the forest must be represented by the big leaves approach although we will consider only one layer of vegetation in this exercise Salt mass balance and transport is taken into account but vapour dynamics not Abiotic options The Plant in the water and heat simulations should be represented by leaf area canopy height and ro
24. lant development in detail The CoupModel Jansson and Karlberg 2004 is such a model It s well known for its coupling of detailed descriptions of the water heat carbon and nitrogen balances in the plant soil atmosphere system and has a large number of applications both on natural and managed ecosystems within cold temperate climate and other climate regions e g Stahli et al 2001 Karlberg 2002 Gustafsson 2002 The aim of the study was to introduce a module in CoupModel Jansson and Karlberg 2004 describing the transport and accumulation in the biosphere of a radionuclide originating from a ground water contamination Two model approaches describing the plant uptake of a radionuclide were introduced namely a passive uptake governed by water uptake and b active uptake governed by carbon assimilation The radionuclide module was designed as a general tracer element module A radioactive or any other trace element was imple mented in the CoupModel as a state variable in different plant parts stem leaves roots and grain and in soil layers as part of soil organic matter fractions litter and humus solved in soil water solution and adsorbed to soil particles The model development was demonstrated with application of a mature boreal forest for a 20 years period with an initial single pulse groundwater contamination with a radionuclide The importance of the different plant uptake approaches and their parameterization for accumulated percent
25. lated amount of radioactive element resulting from a single pulse contamination mgl in the groundwater at simulation start was compared for three reference scenarios assuming 1 no uptake 2 passive uptake and 3 active uptake In all references scenarios the adsorption of the radionuclide was assumed to be strongly related to soil organic matter content 1 e it decreases with depth The adsorption fraction faste was set to 0 2 down to 0 55 m depth to 0 1 between 0 55 and 0 95 cm depth and to 0 05 between 0 95 and 1 25 cm depth In the reference scenario of passive uptake was the passive scaling factor ppuscaie Set to 0 5 meaning that the radionuclide concentration of water taken up by plants was only halve of that in the soil water solution of corresponding root zone layer It was assumed that most of the taken up radionuclide was allocated to the roots 60 of total uptake and 20 to both leaves and stem In the reference scenario of active uptake was the bioavailability threshold concentration Paucpio Set to 10 mgl The maximum ratio between radionuclide and new carbon assimilates were set to 1 1 and 0 1 mg TE g C for paurroots Dad est and Paurstem respectively Active uptake of trace element may be used in combination with passive uptake In this study we used active uptake and passive uptake approaches separately 15 The sensitivity of total accumulation in biosphere for different parameters describing active and
26. lated to carbon allocation The maximum N uptake 1s defined by the minimum C N ratios of plants which are 40 533 and 20 for roots stem and leaf respectively Lifetime of needles is 5 years and of plant 100 years Grains are neglected in this application therefore we set initial and minimum Growth Stage Index tol and maximum GSI to 2 No cutting or clearing harvest took place during the simulation period A 3 6 Driving variable file Make sure that the driving variable file 1s selected in the Model files Meteorological data If this file 1s not selected use the dialog menu to browse A 3 7 Outputs You should select outputs before making the simulation Select those that you find interest ing to study See in figures of fluxes of salt carbon water and nitrogen at pages 32 35 respectively which variables that are needed for checking the salt carbon water and nitrogen balances respectively In addition to this you have to select variables needed to show the explanation of the results e g driving variables Which variables to select depend on what to explain A 4 Running the model A 4 1 Start the simulation Press the red arrow toolbar button A 4 2 View the results Results from the simulation can be viewed in the result table which is opened from Configurations Document View The second alternative is to make use of the Graphic Server see View output menu which enables you to create
27. ld stem i e stem pool older than current year dotted light grey line Figure 4 2C while using active uptake most of radionuclide was allocated in the old leaves dotted black line Figure 4 2D The old leaves biomass varies within a year because losses by litterfall are concentrated to autumns and gains to transfer from current year leaves black line to old leaves dotted black line at the 1 of January The old stem biomass has a constant litterfall production throughout the year However the old stem biomass also accumulated a sustainable part when using active uptake This part seemed to be converting to the percentage accumulated in old leaves Moreover at the end of the simulation time the forest stand age 50 years is only half of its expected lifetime Thus when simulating a longer period like one or more rotation periods the old stem biomass could have accumulated a more important part During first year of simulation the accumulated amount 1s highest in current year roots dark grey line Figure 4 2C and D for both approaches and to decrease afterwards In this application the contamination was at simulation start When instead the contamination is continuous the percentage accumulated in roots can be expected to be more important 4 2 Sensitivity analysis The sensitivity of total accumulation in biosphere for different parameters describing passive and active uptake was tested as well as importance of adsorption pattern and ro
28. no plant uptake the radionuclide stayed in the mineral pool partly solved in soil water solution and partly adsorbed to soil particles and soil organic matter Assuming passive or active uptake the radionuclide was distributed in the ecosystem among plant litter humus and mineral pool Figure 4 2A and B Originally all radionuclide was in the mineral pool as the contamination came with groundwater and the soil water solution was considered to be part of to mineral pool After simulation of a 20 years period the remained percentage in the mineral pool was rather similar for both plant uptake approaches 7 6 and 6 8 for passive and active uptake respectively The differences in percentage accumulated between the two approaches depended on the higher plant uptake percentage using active uptake 14 compared with 10 for passive uptake and consequently higher transfer to litter 9 compared to 2 and humus 10 compared to 5 Figure 4 2A and B 100 No plant uptake e 90 Passive plant uptake 80 9 Active plant uptake Z 70 e 60 8 y 50 s 40 301 5 20 lt 104 x 0 E e LO N ka CO LO N O ce ee ee es oS fe se es a cs S amp S S G amp s amp amp amp Ge Ge G G Ge Ge G G G G G G Time Figure 4 I Pevcentage accumulated radionuclide assuming no plant uptake black line passive uptake light grey and active uptake dark grey line 17
29. o 100 cm depth was estimated at 2 3 ton N ha and 50 ton C ha You will make a simulation for a 20 years period using weather data from Uppsala 1971 1991 For Uppsala the mean air temperature is 5 3 C the annual precipitation 578 mm and the mean daily global radiation of 8 3 Mm The yearly N deposition was adjusted to Knottasen 4 kg N ha A 3 Model set up A 3 1 Configuration Go to the set up menu and choose User set up In the user set up specify the working directory to C Program Files LWR KTH CoupModel Samples PlantTE or your indi vidual path to the samples directory if different Also set the user level to experienced A 3 2 Files Start the open file dialog and choose the Knotspruce SIM file that should be shown in the dialog menu We will compare three scenarios one without plant uptake of the contaminat ing element one with passive and one with both passive and active You can run all three after each other or divide among you when you are a group Save your scenario without plant uptake as KnotspruceX sim passive uptake scenario as KnotspruceP sim and scenario with both uptake pathways as KnotspruceA sim Select the file with meteorological data ClimateU bin under Edit model files Click the View button to look at the data inside the driving variables file 28 A 3 3 Run options The dates for the start and end of the simulation should be within the period given in the dr
30. ot depth and Leaf Area Index LAI 1 e the number of leaf layers projected on ground surface are described as functions of plant biomass The canopy conductance is estimated according to the Lohammar equation Lohammar et al 1980 as a function of the global radiation saturation deficit and LAI The CoupModel is among water balance models well known for its details of describing the heat balance processes including freezing and thawing with high temporal resolution Stahli et al 1999 This is of great importance for correct modeling of N cycling of boreal forests e g N transport with high water flow after snowmelt and the effect of thawing on mineralization 2 3 Carbon and nitrogen model The nitrogen and carbon balances were modeled using the simulated daily variation in water and heat flows as driving variables The carbon and nitrogen balances strongly interact Photosynthesis C uptake is driven by global radiation cf de Wit 1965 and is limited by low needle nitrogen status cf Ingestad et al 1981 At the same time photosynthesis determines the plant N demand Available nitrogen for plant uptake depends on N deposi tion N fertilization N mineralization uptake of organic N by symbiosis with mycorrhiza and losses as N leaching N mineralization is determined by soil temperature and moisture microbial activity and biomass the C N ratio and the amount of soil organic matter Uptake of organic N by symbiosis with mycorrhiza is des
31. ot depth as simulated by the C and N sub model of CoupModel Albedo is defined by parameters The roughness length used for estimating Potential transpiration is calculated following Shaw and Pereira 1982 Interception is an important process in the forest however we consider all precipitation in this matter to be rain Soil evaporation and surface temperature are estimated using the energy balance As concerns Soil water flows preferential flow through cracks is not considered The initial water pres sure is uniform in the profile Drainage and deep percolation drainage is calculated using a simple linear model In the first scenario with Salt Tracer no plant uptake is considered but adsorption is considered The initial salt concentration 1s non uniformly spread in the soil profile No road salt is taken into consideration Passive uptake Salt tracer activate the trace element uptake option and both passive and active uptake options will become visible Mark the passive uptake option Active and passive uptake As for passive uptake but mark also the active uptake option Biotic options External N input is by means of deposition Plant growth is assumed to be proportional to the radiation absorbed by the canopy and the temperature response follows dio for the whole range The root allocation is linear related to the leaf N content No salinity stress on plant growth is considered Litterfall starts after the temperature sum for dorm in
32. oting depth The percentage accumulated using passive uptake varied between 12 and 37 of total added and was most sensitive to tested range of rooting depth Figure 4 3 It might be that rooting depth as such ts not the most important factor as well the distance between rooting depth and ground water table At simulation start when contamination occurred the groundwater table was assumed to be at 80 cm depth During simulation groundwater table varied between 0 5 and 1 7 m and was in average 1 1 m This means that the simula tions with 0 5 root depth the roots were all time above groundwater table and those with 1 5 m root depth most of simulation period within groundwater table With increasing rooting depth also the passive scaling factor and leaf allocation fraction gain importance as discriminating factor Using active uptake the accumulated percentages varied from 35 to 44 with the higher ones for maximum ratio between radionuclide and carbon leaf assimilates Dar and lower percentage adsorption Figure 4 4 Lower adsorption enabled higher plant uptake in first simulation year and thereby accumulated amount was higher for lower percentage adsorp tion The accumulated percentages were insensitive to tested bioavailability levels 19 40120f uo1 boo p fda pup AOJID Sul jpos adissod yjdap 1004 Juasaff ip aof ypidn a1sspd BUISN pljonuolpba PAJD NWNIIV 5pJu o242q F AANGL 9 0 UOIOEIL ooje Je 71 EPO uol o81J
33. passive uptake was tested as well as importance of adsorption pattern and rooting depth For passive uptake was tested a three maximum rooting depth 0 5 1 and 1 5 m all with exponentionally decreasing root density b five passive scaling factors Pruscae 0 25 0 375 0 5 0 675 and 0 75 and c four allocation fraction to leaves frurear 0 0 2 0 4 0 6 For the active uptake approach were tested a five maximum ratio of radionuclide and new C leaf assimilates Paue 0 5 0 75 1 1 25 and 1 5 mg TE g O b five bioavailability thresh olds concentrations Paucpio 10 gt 310 10 310 and 10 mgl and c three adsorption fraction of the upper soil layer far 0 1 0 2 and 0 3 The adsorption fraction was assumed to decrease with depth as a function of soil organic matter content In total were included one reference scenario with no uptake 60 different scenarios with the passive uptake and 75 different scenarios with the active uptake approach 16 4 Results and discussion 4 1 General Without any plant uptake 9 of the originally added amount of radionuclide was left over In the ecosystem after 20 years Figure 4 1 Assuming passive and active uptake the corresponding percentages were 24 and 40 Thus active uptake resulted for this ecosystem application in four times higher accumulation than without plant uptake and almost double as much as the accumulation simulated using passive uptake By definition when assuming
34. rbon and radionuclide We conclude that the introduced module was able to simulate different possible plant uptake mechanisms and hydrological conditions Further dynamically modeling studies are important to analyze the effect of a continuous contamination on long term 10 000 years accumulation in biosphere for various specific radionuclides ecosystems and climatic conditions Contents 1 2 2A 22 Zi 2 4 3 4 4 1 4 2 5 6 7 Appendix 1 Model exercise Accumulation of water solutes in biosphere Introduction Model description General Water and heat model Carbon and nitrogen model Radionuclide model Model application and sensitivity analysis Results and discussion General Sensitivity analysis Conclusions Acknowledgement References O D sO xO 15 17 17 19 23 24 25 27 1 Introduction For a risk assessment of final deposit of radioactive fuel residues it s necessary to estimate the possible accumulation of a radionuclide in the biosphere from an eventual groundwater contamination The potential accumulation In the biosphere is often estimated by water uptake rate and concentration of a radionuclide in soil water here after called passive uptake It s known that a radionuclide can be taken up In higher concentration than can be explained by the convective water uptake In such a case the ultimate driving force may be the carbon assimilation and the typical mechanism for
35. re after a groundwater contamination Of the original added amount of radionuclide was accumulated after 20 years without uptake 9 assuming passive uptake 12 37 and active uptake 35 44 The percentages accumulated using passive uptake was most sensitive to tested range of rooting depth and ones using active uptake to tested range of optimum ratio of radio nuclide and leaf assimilates Further dynamically modeling studies are important to analyze the effect of a continuous contamination on long term 10 000 years accumulation and distribution in biosphere for various specific radionuclides Uptake of different radionuclides varies for the same plant species See overview by Greger 2004 Both radionuclides which are essential to plant and not essential should be included Furthermore an analysis of long term contamination on accumulation should be done for several ecosystems of interest with different hydrologi cal and climatic conditions Underwood 1977 concluded already in 1977 that accumula tion of radionuclide in biosphere depends on 1 genetic differences of plant 2 soil biotic and abiotic factors and 3 season and plant development stage The model presented in this study may be useful to demonstrate the importance and interaction of all these factors 23 6 Acknowledgement We wish to thank Ulrik Kautsky SKB Henrik Eckersten SLU and David Gustafsson KTH for valuable discussions and contributions The project was fun
36. s in arable and forest soils in the Nordic countries Field scale modelling and experiments TemaNord 1999 560 Nordic Council of Ministers Copenhagen p 99 129 Espeby B 1992 Coupled simulations of water flow from a field investigated glacial till slope using a quasi two dimensional water and heat model with bypass flow J Hydro 131 105 132 Greger M 2004 Uptake of nuclides by plants Swedish Nuclear Fuel Technical report TR 04 14 70 pp Gustafsson D 2002 Boreal land surface water and heat balance Modelling soil snow vegetation atmosphere behaviour TRITA LWR PHD 1002 Department of Land and Water Resources Engineering KTH Stockholm Sweden Gustafsson D Lewan E Jansson P E 2004 Modelling water and heat balance of the boreal landscape in Scandinavia Comparison of forest and arable land Journal of Applied Meteorology 43 1750 1767 G rden s A I Jansson P E 1995 Simulated water balance of Scots pine stands for different climate change scenarier Journal of Hydrology 166 107 125 G rden s A Eckersten H Lillem gi M 2003 Modeling long term effects of N fertilization and N deposition on the N balance of forest stands in Sweden 30 pp Emergo 2003 3 25 Ingestad T Aronsson A Agren G I 1981 Nutrient flux density model of mineral nutrition in conifer ecosystems In Understanding and predicting tree growth ed S Linder Stud For Suec 160 61 71 Jansson P E 1998 Simulation model for soil wat
37. simulation start The soil was divided into 15 layers 0 10 10 20 20 30 30 40 40 55 55 75 75 95 95 125 125 155 155 215 215 275 275 335 335 435 435 535 and 535 635 cm depth The soil hydraulic properties were taken from a loamy soil in Skogaby Bergholm et al 1995 The initial total soil C and N content were adjusted to measurements in Knottasen Berggren et al 2002 and were set to 58 ton C ha and 2 8 ton N ha respec tively Parameterization of plant properties like initial C and N contents and radiation use efficiency were taken from a model application on Knott sen coniferous forest stand by Svensson 2004 In addition were used parameterization by Eckersten and Beier 1998 Eckersten et al 1999 and G rden s et al 2003 The initial plant biomass was assumed to be 33 ton C ha and thereof 2 ton C ha was allocated to the roots The initial amounts N plant and N roots were 260 and 54 kg N ha respectively Please notice that with roots we mean fine roots biomass the coarse roots and trunk are supposed to be part of stem biomass The fine roots biomass is assumed to be relatively small and not to increase with time Maximum root depth was assumed to be 1 m depth with exponentially decreasing root density Leaf area index at start of simulation 1 April 1971 was 3 and at the end of simulation 4 31 March 1991 It was at most 4 7 Initial and final tree height were 13 m and 17 m respectively The accumu
38. th se Annemieke Gardenas Annemieke Gardenas mv slu se 36
39. the CoupModel which is regular updated on webpage www wr kth se vara 20datorprogram CoupModel Below are given short descriptions of the water and heat and the carbon and nitrogen models and a full description of the introduced uptake models of a radioactive including its equations In the CoupModel documentation the uptake models are part of the salt tracer module see www wr kth se vara 20datorprogram CoupModel A tutorial for modeling uptake and transport of a water solute in the biosphere is given in Appendix 1 2 2 Water and heat model Water flow is estimated by combining Darcy s law for water flow with the law of mass conservation Analogue is heat flow estimated by combining Fourier s heat flow law and the law of energy conservation Soil physical properties may be defined with various degrees of vertical resolution and heterogeneity for a soil profile Typical characteristics are the water retention curve functions for the hydraulic conductivity heat capacity and water uptake response Water is lost through transpiration soil evaporation evaporation of intercepted water called interception deep percolation and surface run off Potential transpiration is modeled according to the Penman Monteith equation Monteith 1965 Records of air temperature precipitation wind speed relative humidity and global radiation are used as driving variables Plant development is described with a dynamic behaviour where height of plant ro
40. ulated separately for the leaf stem and roots compartment with for the compartment specific allocation fraction of the total passive uptake an zap fpustem and fruroot for leaf stem and root respectively all dimensionless For example passive trace element uptake from the mineral pool of one soil layer to the leaf Tat ent 18 calculated as TE vin gt Leaf z TE z W z P puscale J eoig mg TE day 2 1 Analogue equations are used to calculate the passive uptake to stem TEminstemz and roots TEmin gt roots by exchanging frureat tO fpustem OF fpuRco respectively The root fraction fpuroots 1S Set to ass PULeaf T J pUStem be 2 2 The total passive uptake of trace elements TEpumin_ pian mg day is the sum of the passive uptake to the leaves stem and roots The sum is also made over all the different layers from which a water uptake rate Wape 1s simulated 11 Active plant uptake Active uptake denoted with AU can take place in addition to passive uptake or alone Active uptake of a trace element to each plant compartment Is governed by the carbon assimilation of the respective plant compartment Ca Leaf Ca Stem and Ca Root g C day and the trace element concentration in the root zone TE min For example the active trace element uptake from a soil layer of the mineral pool to the leaf TEmin gt Leafz 18 calculated as TE vin Leaf z Z TE a Z i LL Cent mg TE
41. und litter production 1 e root litter goes directly to the litter compartment of same soil layer Decomposition of litter results in a flux of trace elements to humus and one to the mineral soil pool TEmin Both fluxes are a function of the total turnover i e decomposed material The turnover of litter TEpecomp 18 calculated as L pasas k f T f O TE sitter mg TE day 2 7 where k is a decomposition rate parameter day f T and f 0 are the dimensionless common response functions for temperature and soil water content The flux of trace elements from litter to humus TE itter tHumus mg TE day is subsequently calculated as TE pe amis Sni TE yeeompl mg TE day 2 8 where f is the fraction of the total turnover that is allocated to humus The remaining decomposed material is the fraction that is assumed to be mineralized Bee Min 1 z Jp e mg TE day 2 9 The decomposition of humus also results in a mineralization of trace elements TEqumus nins calculated by equation 2 7 by substituting k with ky and TE wer with TEpumus The mineral trace element pool TEmin 1s the sum of the amount of dissolved trace elements in soil solution and the adsorbed trace element to soil particles and dead soil organic matter Note that the amount of adsorbed material is not calculated explicitly Neither is a division made between adsorbed tracer element to mineral soil particles and those to soil
42. uptake may be the molecular diffusion In this model we call the uptake that is driven by the carbon assimilation active uptake Please be aware that active uptake might be somewhat different defined than commonly used in plant physiology The two uptake approaches of radionuclides can be combined to describe any specific radionuclide accumulation in biosphere originating from a groundwater contamination Estimation of uptake of a radionuclide also has to take into account the difference in function between the unsaturated and the saturated zone of the soil profile Many plants will have roots that will not survive in the saturated zone whereas others may take up water and nutrients both under unsaturated and saturated conditions The contamination with radioactive element is assumed to take place in the saturated zone Consequently it s important to understand how plant uptake may take place directly from the saturated zone and how radionuclides may be transported from saturated to unsaturated conditions in the soil The depth at which the saturated zone starts the so called ground water table fluctuates with season and topographical position in the landscape So can in a recharge area the groundwater table temporary rise into the normally unsaturated root zone and could contaminate the root zone with a dissolved radioactive These phenomena can be described and quantified using a dynamic deterministic model describing both soil hydrology and p
43. ydraulic properties Abiotic parameters Soil water flow the simulation starts early spring In wet profile with groundwater table at 0 8 m depth and initial pressure head of 60 cm Please observe differ ences In units Water uptake the roots can extract water close to saturation but at minimum air content of 10 volume is needed to avoid reduction in uptake with a reduction factor of 6 The critical threshold for reduction under dry conduction is 400 cm These parameters are typically plant specific Salt tracer The deposition of salt is set to the lowest possible value 1 10 to avoid confusion about sources of salt Passive uptake Salt tracer also when a plant take up an element passively with water uptake the element uptake flux can still be reduced compared to the soil water solute flux This defined by passive uptake scaling A value of 1 means that mass transport is fully convective For this exercise we set it to 0 8 After an element or compound has been taken up passively the major part will stay in the roots Allocation to leaves is therefore assumed to be 20 and to stem 10 of total uptake Active and passive uptake The plant will allocate the contaminating element in the differ ent plant parts leaf root and stem in the same nutrient carbon ratio as the nutrient it most resembles If we assume that our element resembles macronutrient K the optimum ratio in the needles stem and roots are 4 mg K g C for all For Mn it
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