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Environmental fate & pathways

Adsorption / desorption

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Description of key information

Kd = 2.1-7.9 ml/g

Koc = 60 - 234 ml/g

Key value for chemical safety assessment

Koc at 20 °C:
234

Additional information

The adsorption characteristics of the substance were determined in three soils and two sediments at 20 ± 2°C according to OECD Guideline 106 and GLP. No deviation from the guideline was observed during the test. The soils and sediments were from the UK. The three soils used were SK961089 (clay loam), SK104691 (silty clay loam or silt loam) and SK566696 (loamy sand) and the two sediments used were Calwich Abbey sediment and Swiss Lake sediment. The three components of the substance studied were sodium monoisopropylnaphthalenesulphonate, diisopropylnaphthalenesulphonate and triisopropylnaphthalenesulphonate. These accounted for 75.1% of the total components of the substance. The test was performed in 0.01 M calcium chloride solution using plastic centrifuge tubes. Two soil (sediment) : solution ratios (chosen from 1:1, 1:5 or 1:25 w/v) and an equilibrium time of 24 h was used.

The components of reaction product of the test substance were found to be stable over the time scale of the test. The test material concentrations of 10 μg/ml were used to study adsorption characteristics.

The adsorption distribution coefficients Kd and KOC (Kd related to the percent organic carbon in the sample) were determined for each of the three components in each soil and sediment. The overall adsorption coefficients for the test substance were also calculated.

Distribution coefficients (Kd) for the three measured components of the test substance were within the range 0.4 to 31.3 ml/g and Koc values were in the range 23 to 992 mL/g. The monoisopropylnaphthalenesulphonate had high or very high mobility, the diisopropylnaphthalenesulphonate had medium to high mobility and the triisopropylnaphthalenesulphonate had low to medium mobility. Mobility therefore decreased in the order mono > di > tri. Overall, the components had low to very high mobility depending on component and soil, according to the McCall classification.

Distribution coefficients (Kd) for the test substance were in the range 2.1 to 7.9 ml/g and Koc values were in the range 60 to 234 ml/g. Depending on the soil, the test material was shown to be of ‘medium’ or ‘high mobility’ according to the McCall classification.