Roles of nanoparticles in arsenic mobility and microbial community composition in arsenic-enriched soils.

Environmental effects of nano remediation engineering of arsenic (As) pollution need to be considered. In this study, the roles of FeO and TiO nanoparticles (NPs) on the microbial mediated As mobilization from As contaminated soil were investigated. The addition of FeO and TiO NPs restrained As(V) release, and stimulated As(III) release. As(V) concentration decreased by 94% and 93% after FeO addition, and decreased by 89% and 45% after TiO addition compared to the Biotic and Biotic+Acetate (amended with sodium acetate) controls, respectively. The maximum values of As(III) were 20.5 and 27.1 µg/L at 48 d after FeO and TiO NPs addition, respectively, and were higher than that in Biotic+Acetate control (12.9 µg/L). The released As co-precipitated with Fe in soils in the presence of FeO NPs, but adsorbed on TiO NPs in the presence of TiO NPs. Moreover, the addition of NPs amended with sodium acetate as the electron donor clearly promoted As(V) reduction induced by microbes. The NPs addition changed the relative abundance of soil bacterial community, while Proteobacteria (42.8%-70.4%), Planctomycetes (2.6%-14.3%), and Firmicutes (3.5%-25.4%) were the dominant microorganisms in soils. Several potential As/Fe reducing bacteria were related to Pseudomonas, Geobacter, Desulfuromonas, and Thiobacillus. The addition of FeO and TiO NPs induced to the decrease of arrA gene. The results indicated that the addition of NPs had a negative impact on soil microbial population in a long term. The findings offer a relatively comprehensive assessment of FeO and TiO NPs effects on As mobilization and soil bacterial communities.