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 Fe_(2)O_(3)and TiO_(2)nanoparticles(NPs)on the microbial mediated As mobilization from As contaminated soil were investigated.The addition of Fe_(2)O_(3)and TiO_(2)NPs restrained As(V)release,and stimulated As(Ⅲ)release.As(V)concentration decreased by 94% and 93% after Fe_(2)O_(3)addition,and decreased by 89% and 45% after Ti O_(2)addition compared to the Biotic and Biotic+Acetate(amended with sodium acetate)controls,respectively.The maximum values of As(Ⅲ)were 20.5 and 27.1μg/L at 48 d after Fe_(2)O_(3)and TiO_(2)NPs addition,respectively,and were higher than that in Biotic+Acetate control(12.9μg/L).The released As co-precipitated with Fe in soils in the presence of Fe_(2)O_(3)NPs,but adsorbed on TiO_(2)NPs in the presence of TiO_(2)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 Fe_(2)O_(3)and TiO_(2)NPs induced to the decrease of arr A 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 Fe_(2)O_(3)and TiO_(2)NPs effects on As mobilization and soil bacterial communities.