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Sediment toxicity

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Description of key information

No toxicity value can be derived for sediment as no testing information are available. However the hazard for the compartment can be assessed using marine and freshwater toxicity data plus equilibrium partitioning and calculation (see below discussion for PNEC derivations). 

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Sediment toxicity testing is not required for the aquatic compartment by the REACH Regulation (Annex VII-X), and for this substance an assessment of hazard for both freshwater and marine sediments can be derived using aqueous data and calculation methods such as equilibrium partitioning (table R16-9, and equation R16-6).

The Koc is converted to the partition coefficient for solid-water in suspended matter (Kpsusp) by multiplying by the fraction of organic matter in suspended matter (focsusp = 0.1, from Table R.16-9). This gives a Kpsusp of 10000; i.e. using the equation (R.16-6): Kpsusp = focsusp*Koc. This is then used to derive the partition coefficient between suspended matter and water using equation R.16-7: Ksusp-water = (Fwatersusp) + (Fsolidsusp * (kpsusp/1000)*RHOsolid), where (from Table R.16-9): Fwatersusp (fraction of water in suspended matter) = 0.9; Fsolid susp (fraction of solids in suspended matter) = 0.1; and RHO solid (density of solid phase) = 2500 kg/m3. From this, a Ksusp-water of 2500.9 is obtained. The PNEC is then calculated using equation R.10-2: PNECsed = (Ksusp-water/RHOsusp)*PNECwater*1000, where RHOsusp is density of suspended matter (1150 kg/m3) from equation R.16-16. This results in the PNECsed in mg/kg wwt. This figure then has to be multiplied by 4.6 to give the appropriate figure as mg/kg dwt. Using the freshwater PNEC aquatic value of 0.25 mg/L, a PNEC sed of 2500.9 mg/kg dwt is obtained assuming a Koc of 10000 mL/g.

The Koc is converted to the partition coefficient for solid-water in suspended matter (Kpsusp) by multiplying by the fraction of organic matter in suspended matter (focsusp = 0.1, from Table R.16-9). This gives a Kpsusp of 10000; i.e. using the equation (R.16-6): Kpsusp = focsusp*Koc. This is then used to derive the partition coefficient between suspended matter and water using equation R.16-7: Ksusp-water = (Fwatersusp) + (Fsolidsusp * (kpsusp/1000)*RHOsolid), where (from Table R.16-9): Fwatersusp (fraction of water in suspended matter) = 0.9; Fsolid susp (fraction of solids in suspended matter) = 0.1; and RHO solid (density of solid phase) = 2500 kg/m3. From this, a Ksusp-water of 2500.9 is obtained. The PNEC is then calculated using equation R.10-2: PNECsed = (Ksusp-water/RHOsusp)*PNECwater*1000, where RHOsusp is density of suspended matter (1150 kg/m3) from equation R.16-16. This results in the PNECsed in mg/kg wwt. This figure then has to be multiplied by 4.6 to give the appropriate figure as mg/kg dwt. Using the marine PNEC aquatic value of 0.024 mg/L, a PNEC sed of 240.1 mg/kg dwt is obtained assuming a Koc of 10000 mL/g.

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