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Environmental fate & pathways

Adsorption / desorption

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Description of key information

Only one study, reporting Kp values for solids-water in sediment ranging between 234 and 1820 L/kg dw, is judged reliable (Klimisch 2). The Kp values are based on the measurement of elemental Mg in river sediment and corresponding pore water. An average log Kp of 2.82 L/kg dw was selected for the chemical safety assessment.

Key value for chemical safety assessment

Other adsorption coefficients

Type:
log Kp (solids-water in sediment)
Value in L/kg:
2.82

Additional information

The selected Kp value for sediment is also used as a screening approach for the Kp in soils and suspended matter.

Kp values for sediment and soil were also estimated by comparing the typical median background concentration of Mg in European surface water, sediment and soil (7.1 mg Mg/L, 6918 mg Mg/kg dw and 3930 mg Mg/kg dw, respectively; van Nederkassel and Oorts, 2010), assuming that these median values are relevant for the compartments and represent a state of chemical equilibrium (surface water concentration used as estimate for pore water concentration in soil). This results in log Kp values of 2.99 and 2.74 L/kg dw for sediment and soil, respectively. These values are both very close to the selected log Kp value of 2.82 L/kg dw for these compartments and justify the use of this single value for these compartments in the chemical safety assessment. Kp values for suspended matter are generally higher than for sediment and the use of Kp sediment for suspended matter can therefore be considered as a conservative approach. The chemical safety assessment based on log Kp sediment of 2.82 L/kg dw indicates the absence of risk to soil and sediment organisms and it was concluded that the availability of measured data for Kp values in soil and suspended matter is not critical for the outcome of the risk assessment and therefore there is no need for new experimental data.

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