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Environmental fate & pathways

Biodegradation in soil

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Sulfolane can be degraded within the PBT criteria of 120 days for soils at environmentally relevant temperatures between 8-10°C under aerobic conditions in non-standard studies. The studies form part of a weight of evidence assessment on the persistence of sulfolane which is appended to the CSR in Section 13.

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There are no standard soil simulation studies for sulfolane. There are however non-standard studies that investigate the degradation of sulfolane in shake flasks and microcosm tests (Greene and Fedorak 2001; Saint Fort 2006). The studies suggest that sulfolane can be degraded within the PBT criteria of 120 days for soils at environmentally relevant temperatures between 8-10°C under aerobic conditions. Greene and Fedorak (2001) used soils from contaminated and non-contaminated sites. In shake flask tests degradation of sulfolane in non-contaminated topsoil took approximately 11.6 days at 22°C. In microcosms with topsoil dosed with 200 mg/kg sulfolane there was a lag time of 15 days before sulfolane degradation commenced at a rate of 0.56 mg/kg/h (Greene and Fedorak (2001). Greene and Fedorak (2001) report that degradation of sulfolane from contaminated sediments was slower than for the uncontaminated sediments. Nutrient enrichment improved biodegradation rates for both the contaminated and non-contaminated soils.Saint-Fort (2006) investigated biodegradation of sulfolane from soils obtained from a sour gas plant in microcosm tests. The soils from a depth of 0-0.2 meters and the samples from 0.2-0.91 m were able to biodegrade sulfolane completely within 85 days regardless of temperature (8 or 25°C) or N enrichment and these would therefore meet the ECHA criteria of <120 days for not persistent in soils. Degradation took longer in soils from greater depths indicated the requirement for aerobic soils. As the soils were taken from a sour gas plant there is expected to have been pre-exposure to sulfolane (Saint Fort 2006). The studies form part of a weight of evidence assessment on the persistence of sulfolane which is appended to the CSR in Section 13.