Abstract
Microorganisms are applied to remediate chromium (Cr)-contaminated soil extensively. Nevertheless, the microbial loss and growth inhibition in the soil environment restrain the application of this technology. In this study, a Cr(VI)-reducing strain named Bacillus cereus WHX-1 was screened, and the microbial aggregates system was established via immobilizing the strain on Enteromorpha prolifera biochar to enhance the Cr(VI)-reducing activity of this strain. The mechanism of the system on Cr(VI) transformation in Cr-contaminated soil was illuminated. Pot experiments indicated that the microbial aggregates system improved the physicochemical characteristics of Cr-contaminated soil obviously by increasing organic carbon content and cation exchange capacity, as well as decreasing redox potential and bulk density of soil. Moreover, 94.22% of Cr(VI) was transformed into Cr(III) in the pot, and the content of residue fraction Cr increased by 63.38% compared with control check (CK). Correspondingly, the physiological property of Ryegrass planted on the Cr-contaminated soil was improved markedly and the main Cr(VI)-reducing microbes, Bacillus spp., were enriched in the soil with a relative abundance of 28.43% in the microbial aggregates system. Considering more active sites of biochar for microbial aggregation, it was inferred that B. cereus WHX-1 could be immobilized by E. prolifera biochar, and more Cr(VI) was transformed into residue fraction. Cr stress was decreased and the growth of plants was enhanced. This study would provide a new perspective for Cr-contaminated soil remediation.
Highlights
Cr is the main heavy metal in polluted soil with two speciation of Cr(VI) and Cr(III)
The degrading curve of Cr(VI) by B. cereus WHX-1 conformed to firstorder kinetics equation and is shown in Supplementary Figure S5
A pot experiment was conducted to explore the effect of the microbial aggregates containing strain (B. cereus WHX-1) on Cr in soil, including the transformation of Cr(VI) and the change of Cr fraction
Summary
Cr is the main heavy metal in polluted soil with two speciation of Cr(VI) and Cr(III). The toxicity of Cr(VI) is about 300 times that of Cr(III). Cr(VI)-Reducing Bacteria Remediated Contaminated Soil remediation have been implemented (Yin et al, 2019; Xia et al, 2021). The biological technology was applied extensively for its simple process, low cost, and less secondary pollution. The microbial loss and growth inhibition in the soil environment limit the performance of this technology. Microbial immobilization technology should be implanted for the sake of reducing microbial loss and improving biodegradation efficiency (Luo et al, 2015; Tan et al, 2020b)
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