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UBC Theses and Dissertations

The interaction of sediment bacteria with arsenic compounds Jaafar, Jafariah


In general, bacteria are capable of biotransforming inorganic arsenic into methylarsenic acids and arsines. The microbial activity of lake sediments was examined with respect to the mobilization of mine tailings that have a high arsenic content. Aerobic and anaerobic mixed microbial populations were isolated from Kam Lake, Yellowknife, N.W.T. An aerobic microbial population from 5 cm sediment depth, the layer immediately above the contaminated mine tailings, was capable of transforming arsenicals. Speciation of arsenicals in the culture medium, determined by using hydride generation - gas chromatography - atomic absorption spectrometry (HG-GC-AAS) shows that this bacterial population is able to methylate arsenicals and subsequently demethylate the product. However, only methylation was observed in media containing dimethylarsinic acid. Anaerobic microbial populations, from all depths, produce a yellow precipitate upon incubation with arsenate for 10-14 days. The precipitate was identified as AS₂S₃ by microanalysis and scanning electron microscope + energy dispersive x-ray (SEM + EDX). The anaerobic microbial population, which should not contain sulfate-reducing organisms, appears to be arsenic tolerant; there is no evidence of methylation of arsenic.

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