Potential Transforming Pathway of Arsenic Species Mediated by Iron- and Sulfate-Reducing Bacteria During Ice-Bound Period

The biogeochemical cycle of arsenic (As) inherently associates with its species. Bacterially mediated redox reactions, such as those accomplished by dissimilatory iron-reducing bacteria (DFeRB) and sulfate-reducing bacteria (SRB), are regarded as the most important mechanisms affecting As species transformation and mobilization. The novelty of this study is that partial least squares (PLS) path model was used to explore the possible pathways of As species transformation mediated by DFeRB and SRB in sediments during an ice-bound period based on continuous As species monitoring of a sediment–water system. Results showed that the effects of DFeRB and SRB on the reduction of As(V) were 1.5 and 2.5 times those of the sterilized group, respectively. Additionally, the TAs and As(III) concentrations in the aqueous mediated by SRB were 1.4 and 1.5 times those of the DFeRB group on average, respectively. The discerned trends reveal that DFeRB and SRB retained their reduction capacity and efficiency during the ice-bound period, which influenced the As species transformation. The amount reduced from As(V) to As(III) and the endogenous release of As mediated by SRB was higher than that of DFeRB. DFeRB mediated the reduction and indirectly influenced the As species transformation through the reductive dissolution and re-distribution of Fe(III) oxyhydroxides and As-containing Fe(III) minerals, while SRB mediated the reduction process, the As in sediment-overlying water system was gradually transformed into a more stable sulfide binding state. This study provides information for redirecting the environmental effects of DFeRB and SRB in the biogeochemical cycle of As in lakes and soils located in cold regions. Graphical abstract