Influence of Temperature Cycling and Ethanol Amendment on Arsenic Mobility in a Contaminated Northern Wetland
Pyritic tailings from legacy gold mines frequently leach elevated concentrations of sulfate, iron, and arsenic into surrounding environments, with mines in northern environments being subject to freeze-thaw cycling that can encourage further leaching. In this study, the effects of freeze-thaw cycling and ethanol amendment on an iron and arsenic contaminated wetland sediment were investigated. Sediment chemistry and aqueous element concentrations were monitored, while the microbial communities were probed using 16S gene analysis. In ethanol amended microcosms, greater proportions of arsenic were removed from solution and identified in sulfide associated sediment fractions, presumably because of ethanol stimulated microbial activity. Ethanol addition also stimulated the growth of Geobacter and other SRBs. Freeze-thaw cycling tended to cause a lag in microbial sulfate reduction. This implicates that loss of arsenic from wetlands may occur at the beginning of freeze-thaw cycling, until the function of the microbial community with respect to arsenic removal is restored.