AEROBIC AND ANAEROBIC DEGRADATION OF SEVERAL ARSENICALS BY SEDIMENTARY MICROORGANISMS

Two media (1/5 ZoBell 2216E and inorganic salt media) were used for degradation experiments. Each arsenical [arsenobetaine, trimethylarsine oxide (TMAO), dimethylarsinic acid (DMA), sodium methanearsonate, sodium arsenate and sodium arsenite] was added to 20cm3 of each medium (0.084% as As) in a 30‐cm3 Erlenmever flask. The mixtures were kept at 25°C in the dark for 91 days for aerobic cultivation. For anaerobic cultivation, about 5 cm3 of liquid paraffin was placed on the surface of each mixture. Under aerobic conditions, arsenobetaine was the only methylarsenical which was rapidly degraded, being converted to several metabolites. In contrast, under aerobic conditions, little or no arsenobetaine (ZoBell or inorganic salt‐media respectively) was converted to its metabolites, while all the methylarsenicals other than arsenobetaine were converted to less methylated compounds. The conversion of inorganic arsenic was observed only in the aerobically incubated ZoBell/arsenite mixture; arsenate was derived from it. A peculiar conversion pattern was observed in the aerobically incubated ZoBell/TMAO mixture; DMA derived from TMAO began to convert to TMAO after 14 days of incubation, and TMAO was the only arsenical in the mixture after 35 days. Copyright © 1990 John Wiley & Sons Ltd.