Nano-sized FeO/FeO facilitate anaerobic transformation of hexavalent chromium in soil-water systems.

The purpose of this study is to investigate the effects of nano-sized or submicro FeO/FeO on the bioreduction of hexavalent chromium (Cr(VI)) and to evaluate the effects of nano-sized FeO/FeO on the microbial communities from the anaerobic flooding soil. The results indicated that the net decreases upon Cr(VI) concentration from biotic soil samples amended with nano-sized FeO (317.1±2.1mg/L) and FeO (324.0±22.2mg/L) within 21days, which were approximately 2-fold of Cr(VI) concentration released from blank control assays (117.1±5.6mg/L). Furthermore, the results of denaturing gradient gel electrophoresis (DGGE) and high-throughput sequencing indicated a greater variety of microbes within the microbial community in amendments with nano-sized FeO/FeO than the control assays. Especially, Proteobacteria occupied a predominant status on the phylum level within the indigenous microbial communities from chromium-contaminated soils. Besides, some partial decrease of soluble Cr(VI) in abiotic nano-sized FeO/FeO amendments was responsible for the adsorption of nano-sized FeO/FeO to soluble Cr(VI). Hence, the presence of nano-sized FeO/FeO could largely facilitate the mobilization and biotransformation of Cr(VI) from flooding soils by adsorption and bio-mediated processes.