The presence of the toxic metalloid arsenic in ground- and drinking water is a global threat to humans. Microbial reduction leading to dissolution of As-bearing Fe(III) oxyhydroxide minerals was suggested to be the main mechanism responsible for mobilization of arsenic from As-containing minerals into groundwater. Surface-derived fresh biomass as well as older organic matter already present in the subsurface (e.g. from old peat lenses) has been suggested and in some cases even demonstrated to be involved as electron donor and energy source for microbial Fe(III) reduction in As-contaminated subsurface environments. In this presentation we will present hydrogeochemical, isotope and microbial community data from microcosm experiments performed with arsenic-bearing sediments obtained from a drilling campaign in Van Phuc village, near Hanoi/Vietnam. Our results demonstrate the importance of fermenting microorganisms for organic matter turnover leading to arsenic mobilization into the groundwater via microbially mediated anaerobic oxidation of both in-situ organic matter and methane coupled to reduction of As-bearing Fe(III) minerals.

Arsenic mobilization by iron(III) mineral reduction fueled by in-situ organic matter and methane

ACS Spring 2022

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