Electronic Supplementary Materials
Modelling the bioaccumulation of persistent organic pollutants in agricultural food chains for regulatory exposure assessment
Environmental Science and Pollution Research
KOKI. TAKAKI, ANDREW. J. WADE, CHRIS. D. COLLINS
Department of Geography and Environmental Science, School of Archaeology, Geography and Environmental Science, University of Reading, Reading. RG6 6DW
(1) model descriptions
Model descriptions are shown below. Default values are in brackets in italics.
Root uptake model for AgriCom 1
BCFroot=QKdQKrw+kg+km ρpVKrw=(W+LaKOWb)/ρp
Kd=KOCfOC
variable / description / value and unit / reference
Krw / partition coefficient between root and water
Q / transpiration stream flow rate / 1000 cm3/day / 2
W / root water content / 0.833 g/g / 3
L / lipid content / 0.005 g/g / 3
ρP / density of plant / 1 g/cm3 / 2
a / density correction factor between water and octanol / 1.22 / 2
b / correction coefficient for roots / 0.77 / 2
Kd / soil-water partition coefficient / cm3/g
fOC / fraction organic carbon in soil / 0.02 or measured value / 4
KOC / organic carbon-water partition coefficient (deduced by EPI SuiteTM) / cm3/g / 5
kg / first order growth rate constant (set for minimising the residual errors between the simulated and the observed root uptake) / 0.01 /day / 6
km / first order metabolism rate constant / 0 /day / 2
V / root volume / 1000 cm3 / 2
Root uptake model for AgriSim 3
BCFroot=Kroot-water∙PW/VSW ∙ρBS /ρRKroot-water=VRW+VL KOWb
PW=ZWVSW/(ZA∙VA+ZW∙VSW+ZS∙VS)
ZS=Kd ∙ρBS∙ZW/VS/1000 / (4)
Kd=fOCKOC
variable / description / value and unit / reference
Kroot-water / partition coefficient between root and water
PW / mass fraction soil moisture
VRW / volume fraction of root water / 0.833 / 3
VL / volume fraction of root lipid / 0.005 / 3
VA / volume fraction of soil air / 0.2 / 3
VSW / volume fraction of soil water / 0.3 / 3
VS / volume fraction of soil solid / 0.5 / 3
ρBS, / density of bulk soil / 1200 kg/m3 / 3
ρR / density of root / 1000 kg/m3 / 3
b / correction for differences between root lipids and octanol / 0.77 / 2
ZW / fugacity capacities of water / mol/m3Pa
ZA / fugacity capacities of water / mol/m3Pa
ZS / fugacity capacities of water / mol/m3Pa
Kd / partition constant soil-water / dm3/kg
fOC / fraction organic carbon in soil / 0.02 or measured value / 4
KOC / organic carbon-water partition coefficient (deduced by EPI SuiteTM) / dm3/kg / 6
Root uptake model for EUSES4,7
BCFroot=Kplant-water/Ksoil-water∙ρBS /ρRKplant-water=VPW+VL KOWb
Ksoil-water=VAKAW+VSW+VS∙Kd∙ρS
Kd=fOCKOC
KOC=1.26∙KOW0.81/1000
variable / description / value and unit / reference
Kplant-water / partition coefficient between plant and water
Ksoil-water / partition coefficient between soil and water
ρBS / density of bulk soil / 1700 kg/m3 / 4
ρR / density of root / 700 kg/m3 / 4
ρS / density of solid / 2500 kg/m3 / 4
VPW / volume fraction of root water / 0.65 / 4
VL / volume fraction of root lipid / 0.01 / 4
VA / volume fraction of root lipid / 0.2 / 4
VSW / volume fraction of root lipid / 0.2 / 4
VS / volume fraction of root lipid / 0.6 / 4
b / correction for differences between plant lipids and octanol / 0.95 / 4
Kd / solid to water partition coefficient in soil / m3/kg
KAW / air to water partition coefficient
fOC / fraction organic carbon in soil / 0.02 or measured value / 4
KOC / organic carbon-water partition coefficient / dm3/kg
Shoot uptake model for AgriCom 3,8
BCFshoot=βα/ρP/Csα=AREA ∙gKshoot-air∙V+kelim+kgrowth
Kshoot-air=Kplant-water/KAW
Kplant-water=VPW+VL KOWb
β=Cs∙ρBSPWVSW ∙TSCF∙QV+Ca+Caer∙g∙AREAV
Caer=Ca measured∙Fassaer(1-Fassaer) / (11)
PW=ZWVSW/(ZA∙VA+ZW∙VSW+ZS∙VS)
ZS=Kd ∙ρBS∙ZW/VS/1000 / (13)
Kd=fOCKOC
TSCF1=0.784∙exp(-logKOW-1.782/2.44)
TSCF2=0.7∙exp(-logKOW-3.072/2.78)
Fassaer =CONjunge∙SURFaer VP_L+CONjunge∙SURFaer
Ca=Dfs/VFp
Dfs=Da∙Csa/d
Da=0.03676/MW
variable / Description / value and unit / reference
α / sink term of different equation / /d
β / source term of different equation / kg/m3/d
Cs / concentration in soil / kg/kg
Ca / concentration in air (use maximum value between calculated and measured) / kg/kg
Caer / concentration in aerosol (use measured value prior to the calculated) / kg/kg
Csa / concentration in soil air / kg/kg
ρP / density of plant / 800 kg/m3 / 3
ρBS / density of bulk soil / 1200 kg/m3 / 3
Kshoot-air / partition coefficient between shoot and air
Kplant-water / partition coefficient between plant and water
AREA / leaf surface area / 5 m2 / 3
g / Conductance / 86.4m/d / 4
V / shoot volume / 0.002 m3 / 3
kelim / rate constant for elimination in plant by metabolism or photolysis / 0 /d / 3
kgrowth / rate constant for growth dilution / 0.035 /d / 3
KAW / air to water partition coefficient
VPW / volume fraction of shoot water / 0.65 / 3
VL / volume fraction of shoot lipid / 0.01 / 3
VA / volume fraction of soil air / 0.2 / 3
VSW / volume fraction of soil water / 0.3 / 3
VS / volume fraction of soil solid / 0.5 / 3
b / correction for differences between plant lipids and octanol / 0.95 / 3
TSCF / transpiration stream concentration factor (use the maximum value between TSCF1 and TSCF2)
Q / transpiration stream / 0.001 m3/d / 3
Fassaer / fraction of chemical associated with aerosol particles
PW / mass fraction soil moisture
ZW / fugacity capacities of water / mol/m3Pa
ZA / fugacity capacities of air / mol/m3Pa
ZS / fugacity capacities of solid / mol/m3Pa
Kd / solid to water partition coefficient in soil / m3/kg
fOC / fraction organic carbon in soil / 0.02 or measured value / 4
KOC / organic carbon-water partition coefficient / m3/kg
CONjunge / constant of junge / 0.4 / 3
SURFaer / surface area of aerosol particles / 0.00025 / 3
VP_L / vapour pressure pure product / Pa
Dfs / diffusion flux water-soil to surface level / kg/m2/h
VFp / dilution velocity plant / 84 m/h / 3
Da / diffusion coefficient in air / m2/h / 8
MW / molecular weight
d / boundary layer thickness / 0.005 m / 8
Shoot uptake model for AgriSim 9,2,6
BCFshoot=SCF ∙TSCF∙(ρsvw+ρsKOCfOC)SCF=100.95logKOW-2.05+0.82
TSCF1=0.784∙exp(-logKOW-1.782/2.44)
TSCF2=0.7∙exp(-logKOW-3.072/2.78)
SCF / stem concentration factor
TSCF / transpiration stream concentration factor (use the maximum value between TSCF1 and TSCF2) / 7
ρs / density of bulk soil / 1,200 kg/m3 / 2
vw / volume fraction of soil water / 0.3 / 2
fOC / fraction organic carbon in soil / 0.02 or measured value / 4
Shoot uptake model for EUSES 7,4
BCFshoot=βα/ρP/Csα=AREA ∙gKshoot-air∙V+kelim+kgrowth
Kshoot-air=VA+Kplant-water/KAW
Kplant-water=VPW+VL KOWb
β=Cs∙ρBSPWVSW ∙TSCF∙QV+1-FassaergCaAREAV
Ksoil-water=VAKAW+VSW+VS∙Kd∙ρS
Kd=fOCKOC
KOC=1.26∙KOW0.81/1000
TSCF=0.784∙exp(-logKOW-1.782/2.44)
Fassaer =CONjunge∙SURFaer VP_L+CONjunge∙SURFaer
variable / Description / value and unit / reference
α / sink term of different equation / /d
β / source term of different equation / kg/m3/d
Cs / concentration in soil / kg/kg
Ca / concentration in air (deduced from the multimedia fugacity model) / kg/kg / 4
ρP / density of plant / 700 kg/m3 / 4
ρBS / density of bulk soil / 1700 kg/m3 / 4
ρS / density of solid / 2500 kg/m3 / 4
Kshoot-air / partition coefficient between shoot and air
Kplant-water / partition coefficient between plant and water
Ksoil-water / partition coefficient between plant and water
AREA / leaf surface area / 5 m2 / 4
g / Conductance / 86.4m/d / 4
V / shoot volume / 0.002 m3 / 4
kelim / rate constant for elimination in plant by metabolism or photolysis / 0 /d / 4
kgrowth / rate constant for growth dilution / 0.035 /d / 4
KAW / air to water partition coefficient
VPW / volume fraction of shoot water / 0.65 / 4
VL / volume fraction of shoot lipid / 0.01 / 4
VA / volume fraction of soil air / 0.2 / 4
VSW / volume fraction of soil water / 0.2 / 4
VS / volume fraction of soil solid / 0.6 / 4
b / correction for differences between plant lipids and octanol / 0.95 / 4
TSCF / transpiration stream concentration factor (This equation is used for log KOW -0.5 to 4.5 (outside this range the minimum or maximum KOW is used)) / 4
Q / transpiration stream flow rate / 0.001 m3/d / 4
Kd / solid to water partition coefficient in soil / m3/kg
fOC / fraction organic carbon in soil / 0.02 or measured value / 4
KOC / organic carbon-water partition coefficient / m3/kg
Fassaer / fraction of chemical associated with aerosol particles
CONjunge / constant of junge / 0.4 / 4
SURFaer / surface area of aerosol particles / 0.00025 / 4
Cattle transfer model for AgriCom10,11
BTFmilk=φg-b(φremgut+φg-b)∙φmilkφremblood+φmilk∙1-e-kfatt1+(φremblood+φmilk)/φbloodfat/MmilkBTFmeat=φg-b(φremgut+φg-b)∙flmeat∙KOWφremblood+φmilk∙(1-e-kfatt)
φg-b=(1QAW+1QAO∙KOW)-1
φremgut=kmet gutMwgut+Mlgut∙KOW+φwfec+φlfec∙KOW
kmet gut=ln23200∙e-2.16∙(BioWIN4 score) / (29)
φremblood=kmet cowMwcow+flavailable∙Mlcow∙KOW+φwurine +φg-b∙1-fabs / (30)
kmet cow=Averageln2half life of EPI , ln2half life of IFS / (31)
flavailable=0.8-0.8/9∙logKOW
φmilk=φwmilk+φlmilk∙KOW
kfat=1Mfat∙KOW∙11φbloodfat+1φremblood+φmilk / (34)
φbloodfat=φbloodwfat+φbloodlfat∙KOW
fabs=φg-bφremgut+φg-b
variable / Description / value and unit / reference
φg-b / flux of chemical from gut to blood / kg/d
φremgut / flux of removal from gut / kg/d
φmilk / flux of chemical in milk / kg/d
φwmilk / flux of water phase with milk / 21.16 kg/d / 10
φlmilk / flux of lipid phase with milk / 0.92 kg/d / 10
φremblood / flux of removal from blood / kg/d
φwfec / flux of water phase with faeces / 27.2 kg/d / 10
φlfec / flux of lipid phase with faeces / 0.48 kg/d / 10
φwurine / flux of water phase with urine / 13.6 kg/d / 10
φbloodfat / flux of blood through fat / kg/d
φbloodwfat / flux of blood through watter / 3233 kg/d / 10
, φbloodlfat / flux of blood through lipid / 6.8 kg/d / 10
Mmilk / output flux of milk / 23 kg/d / 10
flmeat / lipid fraction in meat
t / time / 999 d
kfat / rate constant of reaction which steady state is reached in fat / /d
kmet gut / rate constant of , metabolic degradation in gut / /d
krem gut / rate constant of overall removal from gut / /d
kmet cow / rate constant of metabolic degradation in cow / /d
krem cow / rate constant of overall removal from cow / /d
QAW / diffusion transfer coefficient of water film / 13000000 kg/d / 11
QAO / diffusion transfer coefficient of octanol film / 0.65 kg/d / 11
Mwgut / mass of water in gut / 110 kg / 10
Mlgut / mass of lipid in gut / 11 kg / 10
Mwcow / mass of water In cow / 350 kg / 10
Mlcow / mass of lipid in cow / 63 kg / 10
Mfat / mass of ffat / 180 kg / 10
fabs / fraction absorbed from the gastro-intestinal tract into the blood
flavailable / the available fraction of the total fat / 0.01 / 3
BioWIN4 score / deduced by BioWIN model / 5,12
half life of EPI / Deduced by EPI-HL model and attained from EPI SuiteTM / 5,13
half life of IFS / deduced by IFS-HL model and attained from EPI SuiteTM / 14
Cattle transfer model for AgriSim11
BTFmilk=0.64∙log((kmet gut∙kmet cow)-1) - 4.37BTFmeat=0.78∙log(kmet gut∙kmet cow-1) - 3.95
Cattle transfer model for EUSES15,4
logBTFmilk= logKOW-8.1 3<logKOW<6.5 =-5.1 logKOW<3 =-1.6 logKOW>6.5logBTFmeat= logKOW-7.6 1.5<logKOW<6.5 =-6.1 logKOW<1.5 =-1.1 logKOW>6.5
Estimating milk concentration from BTF for AgriCom and AgriSim16,11,17
milk concentration (mg/kg)=BTFmilk∙chemical daily intake (mg/day)chemical daily intake = I∙fsoil∙Csvs+fgrass∙Convgrass∙0.8∙Cs∙BCFshoot+0.2∙Cs∙BCFroot+Gre∙Cair
I / daily intake of organic matter / 16 kg/d / 15
fsoil / fraction of soil ingestion / 0.06 / 18
fgrass / fraction of grass ingestion / 0.94
Cs / concentration in soil / mg/kg
Ca / concentration in air / mg/m3
vs / volume fraction of soil soild / 0.5 / 3
Convgrass / conversion factor from dry weight to wet weight for grass / 4 / 4
Gre / cattle respiration rate / 150 m3/day / 16
Estimating milk concentration from BTF for EUSES4
ICgrass / daily intake of grass / 16.9 kg/d / 4
ICsoil / daily intake of soil / 0.41 kg/d / 4
ICair / daily intake of air / 122 m3/d / 4
Cs / concentration in soil / mg/kg
Ca / concentration in air / mg/m3
Convgrass / conversion factor from dry weight to wet weight for grass / 4 / 4
CONVsoil / conversion factor from dry weight to wet weight for soil / 1.13 / 4
(2) Model simulations
a) polluted soil and air scenario
b) polluted soil scenario
c) highly polluted soil surface scenario
d) different elevations scenario
Figure S1 Observed and simulated POPs concentration in milk (black: experimental observation, grey: estimation by AgriCom, dot: estimation by AgriSim, white: estimation by EUSES) for four different scenarios: a) polluted soil and air scenario by McLachlan19, b) polluted soil scenario by Mamontova et al.20, c) highly polluted soil surface scenario by Batterman et al.21, d) different elevations scenario by Shunthirasingham et al.22
Figure S2 Observed and simulated concentration of α-HCH in milk in the different altitudes scenario. Two simulated concentration was expressed; one was estimated with using the simulated BTF of α-HCH and the other with using the observed BTF.