Biotransformation of the pesticide sodium arsenate

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Abstract
Biotransformation is an important parameter in assessing the environmental impact and fate of pesticides since metabolites produced may be either more or less toxic than the parent compound. Sodium arsenate (+5 inorganic), the wood preservative and insecticide, may be converted to both inorganic (+3) and organic compounds (‐3) by microorganisms in soil, sediment and water bodies. Bio‐transformation of sodium arsenate was studied in pure cultures of 5 bacterial species using a mineral salt and limited carbon source medium. Arsenate concentrations were 10 μg/ml and 100 μg/ml of arsenic respectively. The rate of biodegradation of the parent compound was described by a first order composite exponential equation of the form Ct = C1e‐k 1 t + C2e‐k 2 t. Rates of production of metabolites (arsenite, monomethylarsine, dimethylarsine and trimethylarsine) were described by a first order exponential equation of the form Ct = Co (1‐e‐kt).