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Environmental fate & pathways

Biodegradation in soil

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The biodegradation in soil under aerobic conditions was studied in a simulation test with two soil samples (silt loam and sandy loam) in a seven day laboratory test using air dried soil samples (Anderson et al. 1991). The toxicity of the substance to soil microorganisms was first tested in a 7-day pre-test. An infrared gas analyser was used to measure CO2 efflux from incubated (20 °C) 50 g soil samples. Every 24 hours a flow of moist CO2-free air was passed through the incubation jars. Toxicity determinations were based on whether microbial respiration in the soil had returned to control levels by the end of the 7-day experiment. Chemical degradation of the substance was then tested with two soils in incubation jars which were fitted with charcoal traps to determine the amount of chemicals lost from soil to the headspace. Chemical solution was added to the soils which were adjusted to 80 % water holding capacity. The soils were afterwards incubated at 20 °C in the dark. Every 24 hours the jars were flushed with a stream of cleaned air to sample the charcoal traps and also to maintain aerobic conditions. The soil was extracted in toto from the jars on days 0, 2, 3, 6 and 7 and the test substances was extracted with methanol to monitor the degradation of 1,2,3-trichloropropane. The chemical was analysed by gas chromatography. The half-life for primary degradation in soil of 1,2,3-trichloropropane under aerobic conditions found in the two loam samples was about 2.7 days.