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Calculation of PNEC soil and sediment according to equilibrium partitioning method.

Additional information

PNEC calculation for sediment and soil based on aquatic toxicity data using the EPM (Equilibrium Partitioning Method)

The PNEC for freshwater sediment, marine sediment and soil was calculated according to the ECHA guidance “Guidance on information requirements and Chemical Safety Assessment, Chapter R.16: Environmental exposure assessment” and “Guidance on information requirements and chemical safety assessment, Chapter R.10: Characterisation of dose [concentration]-response for environment”.

The respective equations for freshwater sediment, marine sediment and soil R.10-2, R.10-3, R.10-5 in the ECHA Guidance R.10 were used:

PNECcomp= Kcomp-water/RHOcomp∙ PNECwater∙ 1000

where

comp = environmental compartment, e. g. freshwater sediment, marine sediment or soil;

PNECcomp= Predicted No Effect Concentration in wet comp, mg/kg of wet comp;

Kcomp-water= comp-water partitioning coefficient, m³/m³;

RHOcomp= bulk density of wet comp, kg/m³, from table R.16-8: Characterisation of environmental compartments)

RHOsoil: 1700 kg/m³,

RHOsediment: 1300kg/m³; and

PNECwater= Predicted No Effect Concentration in water (freshwater or marine), mg/L.

 

The unknown term in the above equation is the partitioning coefficient, Kcomp-water, which is derived from equation R.16-7 in the ECHA guidance Chapter R.16:

Kcomp-water= Faircomp∙ Kair-water+ Fwatercomp+ Fsolidcomp∙ (Kpcomp/1000) ∙ RHOsolid

where

Faircomp= fraction of air in comp, m³/m³ (only relevant for soil); given, from table R.16-8: Characterisation of environmental compartments

Fairsoil= 0.2 m³air/m³soil,

Kair-water= air-water partitioning coefficient; Kair-water = Henry’s Law Constant/(R ∙ T)

T = 285 K

R = gas constant = 8.314 Pa∙m3∙mol-1∙k-1

Fwatercomp= fraction of water in comp, m³/m³; given, from table R.16-8: Characterisation of environmental compartments

Fwatersed= 0.8 m³water/m³sediment,

Fwatersoil= 0.2 m³-water/m³soil,

Fsolidcomp= fraction of solid in comp, m³/m³; given, from table R.16-8: Characterisation of environmental compartments

Fsolidsed= 0.2 m³soild/m³sediment,

Fsolidsoil= 0.6 m³soild/m³soil,

Kpcomp= solid-water partitioning coefficient in comp, L/kg;

Kpcomp= Foccomp* Koc                  equation R.16-6

where,

Foccomp= weight fraction organic carbon in comp solid, kg oc/kg solid; from table R.16-8: Characterisation of environmental compartments,

Focsed= 0.05 kg oc/kg-solid

Focsoil= 0.02 kg oc/kg-solid

Koc = partitioning coefficient organic carbon-water (794322823 L/kg from substance data set))

RHOsolid= density of the solid phase, kg/m³ (= 2500 given; from table R.16-8: Characterisation of environmental compartments).

Compartment

PNECcomp

Kcomp-water

RHOcomp

PNECwater

Fair-comp

Kair-water

Fwater-comp

Fsolid-comp

Kpcomp

RHOsolid

Foccomp

Koc

HLC

VP

MW

water solubility

 Unit

mg/kg of wet comp

m3/m3

kg/m3

mg/L

m3/m3

 

m3/m3

m3/m3

L/kg

kg/m3

kg/kg

 

Pa∙m3/mol

Pa

g/mol

mg/L

freshwater sediment

76,461

993,997

1300

0.1

NA

NA

0.9

0.1

3971641

2500

0.05

79432823

 679.15

 

 

 

marine sediment

7,646

99,3997

1300

0.01

NA

NA

0.9

0.1

3971641

2500

0.05

79432823

 679.15

 

 

 

soil

140,205

140,205

1700

0.1

0.2

0.287

0.2

0.6

1588656

2500

0.02

79432823

679.15

6.51E-4

648.9

622

PNECfreshwater= 0.1 mg/L

PNECmarine water= 0.01 mg/L

Koc = 79432823 (average Koc of UVCB; calculation according to Koc values of percentage share of individual constituent)

MW = 648.9 g/mol (UVCB, component with highest MW)

water solubility = 622 mg/L

vapour pressure = 6.51*10-4Pa

HLC (Henry’s Law Constant) : (vapour pressure ∙ MW)/ water solubility = 679.15Pa∙m3/mol

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