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Environmental fate & pathways

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According to the REACH legislation Annex VIII 9.3.1 a study on the adsorption/desorption behaviour does not need to be conducted if the substance and its relevant degradation products decompose rapidly. Therefore, data on the adsorption/desorption behaviour of LAS-IPA are not required.

Assuming full and rapid dissociation of LAS-IPA in aqueous environments, data on the adsorption/desorption behaviour of LAS-Na and IPA can be used to describe the adsorption and desorption behaviour of LAS-IPA. Both LAS-Na and IPA decompose rapidly as well, and therefore no data on the adsorption/desorption behaviour of LAS-Na and IPA is required, however, the following information is available:

IPA:

Adsorption:  Koc = 15 (Podsol)

Koc = 105 (Alfisol)

Koc = 107 (limnic soil/sediment)

Adsorption was reversible to great extent: the mass balance resulted in a recovery of > 80 %.

LAS-Na:

The adsorption-desorption behaviour of LAS in activated sludge was determined in batch experiments. The Kp for commercial LAS was 2,500 L/kg, with a log Kp of 3.4.

Fugacity modeling of LAS was done using several different models: Mackay level I, II, and III, the ChemCAN model, and the WW-TREAT, GRiDS, and ROUT models.Based on these findings, the dominant fate processes are degradation rates in water and soil, and water-sediment transfer.

The HAZCHEM derived from Mackay type level III model was used to calculate the distribution of LAS in the environment. Results show that most of the LAS partitions to soil, with relatively little in water or air. However, the amount in soil may be overpredicted as the model did not take into account degradation in soil.