Effect of indigenous bacterial activity on arsenic mobilization under anaerobic conditions.

Batch biochemical leaching tests were carried out to investigate the mobility of arsenic from a contaminated soil collected from a French gold mining site. The specific objective of this research was to examine the effect of indigenous bacterial activity on arsenic mobilization under anaerobic conditions. In a first step, physical and chemical characterizations were performed to provide data concerning the liquid-solid partitioning and mobility of arsenic and other inorganic constituents. In a second step, batch bioleaching tests were conducted in shaker flasks to determine the effect of indigenous bacterial activity under different anaerobic conditions (i.e., addition of mineral nutrients and carbon sources) on arsenic mobilization. Results indicated that arsenic release during contact with deionized water was limited by its very low solubility in the interstitial solution and by the stability of the different arsenic compounds formed with the amorphous solid phases of the soil (mainly iron (oxy)hydroxides). However, an increased mobilization potential was observed over the long term under anaerobic conditions with indigenous bacterial activity enhanced by the addition of carbon sources.