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Environmental fate & pathways

Biodegradation in soil

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Description of key information

In a study equivalent to OECD TG 307, the fate of14C-OTNE in agricultural soils was studied in microcosms according to protocols described in documents from the U.S. Food and Drug Administration of 1987(Envirogen, sponsored by IFF, 1999). Method: Samples were taken from an agricultural soil and a sludge amended agricultural soil from farms in New Jersey, USA. Sealed flasks with the soil, spiked with 10 µg test substance/g sediment dw (10 mg/kg) were incubated at laboratory ambient temperature for 12 weeks. Periodically the headspace was flushed for oxygen replenishment and the effluent gas was drawn through a train of scintillation fluids to capture volatile organics and CO2 to be determined by liquid scintillation counting. Periodically also flasks were sacrificed and exhaustively extracted with hexane/acetone. An aliquot of the solvent fraction was used for thin layer chromatography for analysis of the test substance and metabolites. The total 14C-mass balance was established for the parent and metabolites based on extraction. Results: Radiolabeled OTNE in soil is almost completely degraded after 6 weeks. After 6 weeks mineralisation (CO2 evolution) is circa 50%. After 1 to 2 weeks a range of more polar metabolites was found. After a lag time of approx. 7 days the initial rate of CO2 production was 1.4 - 1.8% /day in the sludge amended soil and in the agricultural soil, respectively. The half-life of the parent substance was estimated to be 4.2 days and 6 days in the sludge amended soil and in the agricultural soil, respectively. The half-life in agricultural soil converted to 12oC results in 11 days.

Key value for chemical safety assessment

Half-life in soil:
11 d
at the temperature of:
12 °C

Additional information

In a sludge amended soil the DT50 was slighly shorter: 4.2 days at 22oC and converted to 12oC this results in 7.7 days.