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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): 110000 l/kg (log value: 5.04) (ECB 2008)
Kp for water and sediment (Kpsed); 73000l/kg ( log value:4.86) (ECB 2008)
Kd for marine waters is 6010 l/kg (log value: 3.78)
Kd for solids-water in soil is 158.5 l/kg (log value: 2.2)

Key value for chemical safety assessment

Additional information

For metals, adsorption/desorption translates in the distribution of the metals between the different fractions of the environmental compartment, 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,...).This distribution between the different compartments is translated in the partition coefficients between these different fractions. Study records on partition coeficients are given under IUCLID section 5.6.

Partition coefficients for zinc in freshwater has been reviewed in the RAR (ECB 2008). Based on the extensive experimental evidence, a partition coefficient for the distribution between solid particulate matter and water (Kpsusp) of 5.04 (log value) has been defined for EU waters and used throughout the RAR.

The Kp for the distribution between sediment and water (Kpsed) was estimated in the RAR from that for particulate matter, as follows: Kpsed= Kpsusp/ 1.5, based on the average difference in concentrations of zinc and other metals in both media. For zinc this results in a Kpsedof 73,000 l/kg. (ECB 2008)

The marine Kd was derived based on data from several marine waters. the geomean value for zinc in seawater is 6010 l/kg

For soil, a solids-water partitioning coefficient of 158.5 l/kg (log value 2.2) was determined experimentally on 11 American soils. This value was used in the RA Zinc.