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Environmental fate & pathways

Adsorption / desorption

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Description of key information

After 48 hours, the Kd values of 125.04, 287.62 and 294.47 were determined for Soil 2.3, 2.4 and 6S, respectively. The Koc values of 18663.4, 14526.5 and 17021.2 were determined for Soil 2.3, 2.4 and 6S, respectively, after 48 hours. An equivalent Koc value of 16648.7 was calculated from the three soils, and was then used to calculate partition coefficients for the substance to other environmental matrices in addition to soil (e.g. suspended sediment). The equivalent Koc value results in a Kd value of 333 for standard soil with 2 % organic carbon.

Key value for chemical safety assessment

Koc at 20 °C:
16 648.7

Additional information

In order to determine the adsorption/desorption of potassium dicyanoaurate a limited partitioning study with three soils was performed according to OECD 106 (Fraunhofer 2016). The approach was considered adequate for the information requirements.

Based on the results, the equilibrium time for potassium dicyanoaurate was visually reached for soil 2.3 after 16 h and for soil 2.4 and 6S after 48 h. At equilibrium time the Koc values of 16144.7, 14526.5 and 17021.2 were determined for Soil 2.3, 2.4 and 6S, respectively. The Kd values of 108.17, 287.62 and 294.47 were determined for Soil 2.3, 2.4 and 6S, respectively.

Whilst in the case of some of the soils equilibrium was considered to have been reached before 48 hours the results which have been used for the derivation of the PNEC values which are calculated by equilibrium partitioning have all used the value calculated after 48 hours for consistency. In the case of tests where equilibrium was reached earlier the result will not be significantly different between the time at which equilibrium was first reached and after 48 hours.

After 48 hours, the Koc values of 18663.4, 14526.5 and 17021.2 were determined for Soil 2.3, 2.4 and 6S, respectively. The Kd values of 125.04, 287.62 and 294.47 were determined for Soil 2.3, 2.4 and 6S, respectively, after 48 h. An equivalent Koc value of 16648.7 was calculated from the three soils, and was then used to calculate partition coefficients for the substance to other environmental matrices in addition to soil (e.g. suspended sediment). The equivalent Koc value results in a Kd value of 333 for standard soil with 2 % organic carbon and 1664.9 for suspended sediment with 10 % organic carbon.