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Environmental fate & pathways

Adsorption / desorption

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Description of key information

Kp for solid particulate matter and water (Kpsusp): 130000 l/kg (log value: 5.1)
Kp for water and sediment (Kpsed); 10000 l/kg (log value: 4 )
Kd for marine waters is 617 l/kg (log value: 2.79)

Key value for chemical safety assessment

Other adsorption coefficients

Type:
log Kp (solids-water in suspended matter)
Value in L/kg:
5.1
at the temperature of:
20 °C

Other adsorption coefficients

Type:
log Kp (solids-water in sediment)
Value in L/kg:
4
at the temperature of:
20 °C

Other adsorption coefficients

Type:
other: marine waters
Value in L/kg:
2.79
at the temperature of:
20 °C

Additional information

For metals, the transport and distribution over the different environmental compartments e.g. the water (dissolved fraction, fraction bound to suspended matter), soil (fraction bound or complexed to the soil particles, fraction in the soil pore water,...) is described and quantified by the metal partition coefficients between these different fractions. The information on these partition coefficients is given under 5.6.

Partition coefficients for cadmium in freshwater have been reviewed in the EU risk assessment report (ECB 2008). Based on this experimental evidence, a partition coefficient for the distribution between solid particulate matter and water (Kpsusp) of 130 x 103l/kg has been defined for EU waters and was used throughout the RAR..

The Kp for the distribution between sediment and water (Kpsed) was estimated in the RAR from the ratio of the average sediment (1.32mg/kgDW) to average water Cd concentrations (0.14µg/l). This "best fit" Kd yields 10000L/kgDW (ECB 2008).

These partition coefficients have been used since then in other legislative processes in the EU (e.g. the water framework directive) and will also be used for REACH.

The marine Kd was derived based on data from several marine waters. the geomean value for cadmium in seawater is 617 l/kg