7-9 OFF LOCKTitle DT50 電装配線図 Created Date 7/2/2018 6:47:25 PM
3.2 Substance parameters - Uni Koblenz-Landau · Substance parameters DegT50, DT50 Time taken for a...
Transcript of 3.2 Substance parameters - Uni Koblenz-Landau · Substance parameters DegT50, DT50 Time taken for a...
Substance parameters–
Degradation in soilDegradation in water/sediment
Sorption
SubstanceSubstance parametersparameters
SubstanceSubstance parametersparameters
E-Fate Parameter
• Degradation / dissipation DegT50, DT50
� derived from kinetic evaluations of soil degradation / field dissipationstudies or from water-sediment studies
• Sorption Kfoc, 1/n
� estimated from batch-equilibriumstudies
• Phys-chem data
SubstanceSubstance parametersparameters
DegT50, DT50
Time taken for a 50% decline in mass or concentration of a substance to occur from
• degradation -> DegT50
• dissipation processes -> DT50� does not distinguish between transfer or
degradation processes� summarizes diff. processes such as degradation,
volatilization, photolysis, leaching etc.
Recommendations on how to derive endpoints that can be used inenvironmental fate models were provided by the
FOCUS Working Group on Degradation Kinetics*
Recommendations regarding
• Data issues• Kinetic models• Quality criteria for kinetic fits• Procedure to derive endpoints• Recommendations on the selection of endpoints
* FOCUS (2006). “Guidance document on Estimating Persistence and Degradation Kinetics from
Environmental Fate Studies on Pesticides in EU Registration. EC Document Reference SANCO/10058,
version 2.0, June 2006.
SubstanceSubstance parametersparameters
Kinetic models
• SFO single first order model
• FOMC first order multi compartment model
• DFOP double first order in parallel model
• HS hockey stick model or Gustafson-Holden model
SubstanceSubstance parametersparameters
Single first order (SFO) kinetic model
kdDT
)2ln()(50 =
tkeCC ⋅−⋅= 0
C concentration at time t C0 concentration at time 0 (mg/kg)k degradation rate (1/d)t time
SubstanceSubstance parametersparameters
FOMC
First Order Multi Compartment Modell
HSHockey Stick Modell
DFOPDouble First Order in Parallel
DT50 (FOMC) Pseudo-SFO
DT50: DT90/3.32Two consecutive SFO DT50:
slow phase and fast phase
Two parallel SFO DT50:
slow phase and fast phase
Plots of bi-phasic and multi-compartment models
SubstanceSubstance parametersparameters
SFO
one single dissipation process
FOMC
several parallel dissipation processes
HS (bi-phasic)two consecutive dissipation processes
DFOP (bi-phasic)
two parallel dissipation processes
Concepts of different kinetic models
SubstanceSubstance parametersparameters
Assessment of thegoodness of fit by
• Chi² test• Visual assessment
Assessment of thereliability of theparameter estimate by
• t-test (significance test)
SubstanceSubstance parametersparameters
Example of a pathway fit (parent + metabolite) conducted using the KinGui tool
Tools:
• ModelMaker• KinGUI• others
Results:
• k-rates (dissipation rates),• other model parameters in case of non-SFO models
from which DegT50/DT50 values can be calculated
SubstanceSubstance parametersparameters
Normalisation of degradation rates (temperature, soil moisture)
Temperature and soil moisture have an influence on the degradation rate (warm temperature and maximum soil moisture represent optimum conditions for degradation)
Surface water and groundwater tools correct degradation rates according to the temperature profile of the scenario.� DegT50/DT50 at reference conditions are needed as model input
Reference conditions used in the groundwater and surface water models: Temperature = 20°CSoil moisture = 100% FC (field capacity)
� DT50 values from experimental data need to be normalised to these reference conditions.
SubstanceSubstance parametersparameters
Temperature correction (Arrhenius approach)
Moisture correction (Walker-equation)
10/)20(
1050)20(50CT
QDegTCDegT°−
⋅=°
7.0
Θ
Θ=
ref
f
Θ soil moisture during the experimentΘref reference soil moisture at 100% field capacity
SubstanceSubstance parametersparameters
Temperature and
moisture
normalisationequations
Q10 = 2.58 (EFSA, 2007)
Example temperature correction:
DT50 measured at 25°C: 50 dayscorrection factor: 1.61DT50 normalised to 20°C: 80.5 days
Example moisture correction:
DT50 measured: 50 daysSoil moisture during study: 17%Soil moisture at 100% FC: 30%correction factor: 0.67DT50 normalised to 100% FC: 33.5 days
SubstanceSubstance parametersparameters
P-I levelone-compartment approach
�DT50 water�DT50 sediment�DegT50 total system
P-II level
two-compartment approach
�DegT50 water
�DegT50 sediment
Kinetic concepts of parent disappearance in water-sediment
SubstanceSubstance parametersparameters
M-I levelone-compartment approach
�DT50 water
�DT50 sediment�DT50/DegT50 total system
Kinetic concepts of metabolite disappearance in water-sediment
M-II levelTwo-compartment approach
Theoretically comprising
water and sediment forparent and metabolite (includingbacktransfer from sediment to water)
Not recommended by FOCUS
due to high level of complexity
SubstanceSubstance parametersparameters
Modelling endpoints vs. persistence endpoints
Modelling endpoint:SFO or Pseudo-SFO DT50 to be used in surface water (and groundwater) models
Persistence endpoint:best fit DT50 to determine whether further studies are triggered
If best fit is FOMC � use pseudo DT50 = DT90/3.32 for modellingIf best fit is DFOP � use slow phase DT50 for modelling
SubstanceSubstance parametersparameters
Recommendation for the use of modelling endpoints for
parent compounds
FOCUS (2006)
SubstanceSubstance parametersparameters
Recommendation for the use of persistence endpoints
for parent compounds
FOCUS (2006)
SubstanceSubstance parametersparameters
Sorption behaviour
• Adsorption/desorption: substance reversibly binds to soil compounds (clay, organic carbon)
• Ads/des is measured in batch equilibrium studies (OECD 106) � Kd values(distribution of a substance between the equilibrium solution (water) and soil / sediment particles)
� Sorption depends on
• Soil properties (organic carbon content, pH, texture etc.)
• Substance properties
Groundwater and surface water models generally require an organic carbon related sorption value for a substance as model input.
� Koc values
SubstanceSubstance parametersparameters
Sorption behaviour: Koc
• high Koc (eg 200 mL/g) = strong sorption to soil or sediment particles
low risk of leaching to groundwater or drainage systems
higher risk of runoff loss
• low Koc (eg 20 mL/g) = low sorption to soil or sediment
high risk of leaching to groundwater or drainage systems
low risk of runoff loss
SubstanceSubstance parametersparameters
Sorption behaviour: Freundlich exponent
The Freundlich exponent (1/n) describes the linearity of the sorptionbehaviour
• 1/n = 1 � linear sorption
• 1/n < 1 ���� non-linear sorption
usually 1/n values are in a range of 0.7 to 1
Current default values used for modlling in the absence of Freundlich sorption data:
1 if only one concentration was measured
0.9 if non-linearity can be expected
SubstanceSubstance parametersparameters
OC
KK F
FOC =
OC organic carbon (-) OM organic matter
n
eqFS CKC/1
⋅=
724.1
FOC
FOM
KK =
CS concentration adsorbed (kg/kg)Ceq concentration in the solution (kg/L)
1/n Freundlich exponentKF Freundlich sorption coefficient (L/kg)
Freundlich sorption isotherm
SubstanceSubstance parametersparameters
Phys. – chem. Parameters
• Molar mass (g/mol)
• Solubility in Water (g/L)
• Henry Constant (Pa x m3 / mol)
• Vapor pressure (Pa)
SubstanceSubstance parametersparameters
Data selection
• Degradation data � geometric mean values
� default in the absence of reliable data: 1000d
• Sorption data � arithmetic mean values
� default 1/n: 0.9
1 in case of linear sorption
• Phys-chem data � as reported
� for metabolites: estimated data (EPI WIN)
parent data
SubstanceSubstance parametersparameters
SubstanceSubstance parametersparameters
PEC actual and time weighted
Regulatory Assessment Endpoints
E-Fate Parameters necessary for calculation
Study Types
PECsoil
TERs of soil organisms
- Half Lives in soil - formation fraction of metabolites - incubation conditions
- DT50/DT90 (rate studies) - aerobic soil metabolism - field dissipation - field leaching . . .
PECsw TERs of water organims
- Half in water phase - formation and dissipation rates in the water phase - dissipation rates by aqueous photolysis
- Water/Sediment - aqueous photolysis - sensitized photolysis - mesocosm . . .
PECsediment TERs of sediment organims
- formation/binding onto and dissipation rates in the sediment
- Water/Sediment Study - mesocosm . . .
PECgroundwater 0.1 µg/l level on an annual basis
see PECsoil - Sorption
see PECsoil - lysimeter - adsorption/desorption . . .