Microbially facilitated incorporation of As(III) into bioreduced Fe-(hydr)oxide minerals

Ferric (oxyhydr)oxide minerals are widespread in the (sub)surface soils such as in agricultural fields, and arsenic compounds have been used widely in the production of pesticides, herbicides, and insecticides, which have caused potential As contaminations in the (sub)surface soils including Fe-(oxyhydr)oxides. Because one of the potential relationships between Fe-(oxyhydr)oxides and As was suggested above, scientists have been motivated to investigate the relationship between Fe-(oxyhydr)oxides and As. In the present study, a dissimilatory Fe(III)-reducing bacterium, Shewanella sp. HN-41 was employed to elucidate effect of microbial Fe(III) reduction on the relationship between Fe-(oxyhydr)oxides and As, and incubated with lactate and synthetic Fe(III)-oxyhydroxide as the electron donor and acceptor, respectively, in the presence of As(III). For comparison, abiotic incubations were performed under the same condition except for addition of the bacterial cells. By sequential chemical extraction of the incubation products, As(III) was determined to be incorporated into the bioreduced minerals at higher concentrations (∼14.4% of the total extracted As) than in the abiotic products (∼10.2%) that were aged for the same duration as the microbial incubation. The results of this study emphasized that bacterial Fe(III)-reduction of the initial synthetic Fe-oxyhydroxide, akaganéite, induced more As(III) incorporation into the structures of the final product minerals than the abiotic transformation of the initial As(III)-adsorbed Fe-oxyhydroxide in the control incubations. Thus, microbial Fe(III)-reduction-mediated incorporation of As(III) into biotransformed Fe-(oxy)(hydr)oxide minerals could be suggested as one of potential strategies for arsenic immobilization in anoxic soils and groundwater.