Bacteria-loaded biochar for the immobilization of cadmium in an alkaline-polluted soil

Abstract

The combination of biochar and bacteria is a promising strategy for the remediation of Cd-polluted soil.However, the synergistic mechanisms of biochar and bacteria for Cd immobilization remain unclear. In this study, the experiments were conducted to evaluate the effects of the combination of biochar and Pseudomonas sp. AN-B15, on Cd immobilization, soil enzyme activity, and soil microbiome. The results showed that biochar could directly reduce the motility of Cd by adsorption and formation of CdCO 3 precipitates, thereby protecting bacteria from Cd toxicity in the solution. Moreover, bacterial growth further induces the formation of CdCO 3 and CdS and enhances Cd adsorption by bacterial cells, leading to a higher Cd removal rate. Thus, bacterial inoculation signi cantly enhances Cd removal in the presence of biochar in the solution. Moreover, soil incubation experiments showed that bacteria-loaded biochar signi cantly reduced soil exchangeable Cd in comparison with other treatments by impacting soil microbiome. In particular, bacteria-loaded biochar increased the relative abundance of Bacillus, Lysobacter, and Pontibacter, causing an increase in pH, urease, and arylsulfatase, thereby passivizing soil exchangeable Cd and improving soil environmental quality in the natural alkaline Cd polluted soil. Overall, this study provides a systematic understanding of the synergistic mechanisms of biochar and bacteria for Cd immobilization in soil and new insights into the selection of functional strain for the e cient remediation of the contaminated environments by bacterial biochar composite.