Chromium (VI) Bioreduction in Contaminated Soil using Bacterium Immobilized on Algae Biochar

The objective of this study was to eliminate chromium(VI) from a contaminated soil through reducing it to chromium(III) by immobilized Shewanella sp. bacteria on algae biochar and to investigate its accumulation in barley. A sandy loam soil was contaminated with 50 mg kg-1 Cr(VI) and incubated for two weeks. Then, the barley pot experiment in the contaminated soil was performed in the autumn of 1400 in the research greenhouse of University of Guilan in a completely randomized design with three replications. Treatments included Shewanella sp. (S), algae biochar (B), algae biochar + Shewanella sp. (BS), and immobilized Shewanella sp. bacteria on algae biochar (IB). Soil contaminated with Cr(VI) and non-contaminated soils were also included as positive (C+) and negative (C-) controls, respectively. After 30 days, the plant was harvested and dry weight of root and shoot were measured. Total chromium and Cr(VI) contents in the root and shoot of plant and also in the soil were measured. The Cr(III) content was calculated from the difference between the total chromium and the Cr(VI) contents. Growth ratio, Cr(VI) accumulation factor in roots and shoots and the transfer factor in plants were calculated. The highest and lowest amounts of Cr(III) in roots, shoots and soil were obtained in IB and C+ treatments, respectively. In Cr(VI) contaminated treatments, the highest and the lowest values of root and shoot dry weight were obtained in IB and C+ treatments, respectively. Cr(VI) reduction in soil in BS treatment was more than S and B treatments. The lowest and the highest plant growth ratios were obtained in C+ (23.8%) and IB (60%) treatments, respectively. The BS and IB treatments further reduced the transfer factor. Therefore, immobilized bacteria on biochar can be effective in remediation of chromium contaminated soils.