Regulation mechanism of microbial Fe(III) reduction on heavy metals pollution in paddy soil

The objective of this study was to investigate influences of microbial Fe(III) reduction on biogeochemical transformations of different heavy metals in flooded paddy soil. Anaerobic slurry incubation was adopted with amendment of Cr(VI), As(V) and Cu(II) at different concentrations levels, respectively. Results showed that Cr(VI) was reduced to Cr(III) by Fe(II) which was the product of microbial Fe(III) reduction. Glucose and ferrihydrite significantly accelerated rate of Cr(VI) reduction indirectly. There was an equilibrium between arsenite and arsenate in flooded paddy soil with the ratio of 7:5, indicating the possible existence of arsenite oxidation bacteria in anaerobic environment. Exogenous iron oxide could promote the stabilization of copper which was presented as amorphous iron bound copper. The work highlights that it is possible to regulate Cr-, As- and Cu- pollution by microbial iron reduction.