Bioconversion of alachlor in an anaerobic stream sediment

We incubated a stream sediment amended with 50 μg per ml of 14C-ring labeled alachlor, 2-chloro-2′,6′-diethyl- N -(methoxymethyl) acetanilide, anaerobically for 10 weeks at 28°C. After 10 weeks, only 50.5% of the 14C-label was extractable into 30% acetonitrile from a nonsterile sediment. Combustion of the soil pellets indicated that increasing amounts of the 14C-label became strongly adsorbed or bound to the sediment. Chromatographic analysis of the hexane extract of the aqueous phase showed that it contained 16% of the unchanged alachlor and 35% of a product which was determined to be the dechlorinated alachlor by mass spectral analysis (C.I. and E.I.). Only alachlor was found in the extract of sterilized samples, indicating that biological activity caused the formation of the dechlorinated product.