ABSTRACT
Arsenic behavior in paddy soils is known to couple with the redox process of iron (Fe) minerals. When soil is flooded, Fe oxides are transformed to soluble ferrous ions by accepting the electrons from Fe reducers. In this study, we tried to manipulate the Fe redox processes in paddy soils by deploying sediment microbial full cells (sMFC). The results showed that the sMFC bioanode can modulate soil porewater Fe and arsenic (As) concentrations. At the end of the experiment, Fe and As contents around sMFC anode were 65.0% and 47.0% of the control respectively. A similar trend was observed in the sMFC bulk soil, where the Fe and As contents were 67.0% and 89.0% of the control respectively. This decrease in Fe and As concentrations could be attributed to the enhanced organic matter (OM) removal by sMFC. In the vicinity of bioanode, OM removal efficiencies were 10.3% and 14.0% higher than the control for lost on ignition carbon and organic carbon respectively. Furthermore, sequencing of the 16S rRNA genes suggested that the change in microbial community structure was minimal. Moreover, during the experiment a maximum current and power density of 0.31mA and 12.0 mWm−2 were obtained, respectively. This study shows a novel way to make good use of As contaminated paddy soils, which is to simultaneously generate electricity and reduce the As mobility.
