Remediation of soil contaminated with high levels of hexavalent chromium by combined chemical-microbial reduction and stabilization

[Display omitted] •Chemical-microbial method was used to restore Cr(VI) contaminated soil.•Microbial reduction reduces the risk of re-oxidation of Cr(III) to Cr(VI).•The reduction effect of microorganisms on Cr(VI) is stable.•The reduction process has great influence on the microbial community. In order to solve the problem of re-oxidation after chemical remediation of soil contaminated with high levels of hexavalent chromium (Cr(VI)), we investigated the use of chemical reduction combined with microbial stabilization to remediate soils contaminated with high Cr(VI) concentration. The leaching toxicity and microbial diversity of Cr(VI)-contaminated soil and the leaching toxicity of remediated soil oxidized by potassium permanganate (KMnO4) were measured. The results indicate that the conversion rate of Cr(VI) reached 97 %, and the concentration of Cr(VI) in toxic solutions leaching can be reduced by 95 % after 40 days of microbial stabilization. Sterilization experiments showed that the reduction of Cr(VI) by microorganisms is stable. The results of microbial diversity analysis indicate that bacterial community changed more than fungal community during the reduction process of Cr(VI), and the species abundance and species evenness of bacteria decreased. Bacillus spp. and Halomonas spp. were the dominant species in this study.