Role of microbes in controlling the speciation of arsenic and production of arsines in contaminated soils

The influence of microbes on the speciation of arsenic and production of arsines in contaminated soils was investigated under laboratory conditions. Microbes were able to carry out reactions that resulted in changes in the speciation of arsenic in soil. The transformation of soil dominating species, arsenate AsŽV. , under both aerobic and anaerobic conditions to arsenite AsŽIII. , monomethylarsonic acid MMAA , dimethylarsinic acid DMAA and to volatile trimethylarsine TMA was, however, less than 0.5%, of which the production of TMA represented 0.02 0.3%. The volatilization process was also verified in the field, in the soil of a dumping area. The ‘life-time’ of arsines in air was, however, short and they were rapidly converted back to water soluble species, AsŽV. and trimethyl arsine oxide ŽTMAO..