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Environmental fate & pathways

Adsorption / desorption

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Description of key information

No valid study fully compliant to the relevant guidelines is available. The studies performed on the adsorption and desorption of chloroform to soils indicate a rather weak sorption to organic carbon found in soils. Chloroform tends to be transported readily through soils, especially when the organic matter content is low.
Value used for CSA: KOC at 20°C: 185 L/kg

Key value for chemical safety assessment

Koc at 20 °C:
185

Additional information

Batch adsorption/desorption studies were carried out with chloroform on two aquifer solids (Uchrin and Mangels 1986) using 14C-labelled chloroform. The tests were in many aspects equivalent to those of the relevant guideline OECD No. 106, but with some restrictions. Both aquifer solids differed in their composition exhibiting different contents of organic carbon. The solid/liquid phase equilibrium partitioning was characterised using Freundlich isotherms. Based on the partitioning coefficient KP and the fraction of organic carbon in the soils, the Koc was determined. The mean KOC value was 190 and the S. D. was 151, showing that chloroform adsorption to soil material was rather weak. Desorption tests showed that the sorptive processes involving chloroform and the subject aquifer solids were somewhat reversible. The study by Wilson et al. (1981) indicated also rather low values for the partition coefficient KOC (log KOC < 2) and concluded that chloroform was transported readily through soil.

From the available data it can be concluded that especially ground waters underlying soils with low organic matter content are vulnerable to pollution by chloroform. The study by Gratwohl (1990) indicated that the sorption of chloroform to soils is depending to a large extent on the nature as well as on the percentage of organic matter found in the sorbent. Soils and recent sediments tended to have the lowest sorption coefficients (approximate log KOC = 1.44), whereas unweathered shales and mudrocks had clearly higher sorption coefficients (approximate log KOC = 2.79).