Biochar and biochar-polylactic acid composite enhance biodegradation of hexachlorobenzene in soil by altering microbial community

Abstract

It is of great scientific and practical importance to explore the mechanisms of accelerated degradation of hexachlorobenzene (HCB) in soil. However, the response of microbial community composition and structure, and their links to anaerobic reductive dechlorination in paddy soils remains unclear yet. We examined impacts of biochar and biochar-polylactic acid composite addition on the diversity, composition, and structure of soil prokaryotic community and their different contribution to HCB anaerobic dechlorination. The results showed that both biochar and biochar-polylactic acid composite addition could promote HCB dechlorination in paddy soils. Soil prokaryotic community richness and diversity were not significantly impacted by biochar but were remarkably affected by biochar-polylactic acid composite amendment. Random forest analysis and structural equation models indicated that the relative abundance of indicator taxa, soil Eh, and Fe2+ content best explained (p < 0.01) the HCB dechlorination with biochar addition, while soil Eh, Fe2+ content, and microbial diversity were the most important predictors of HCB dechlorination with biochar-polylactic acid composite addition. Together, our findings suggest that biochar amendment promoted anaerobic dechlorination of HCB in paddy soils by increasing the relative abundance of specific bacterial genera, while biochar-polylactic acid composite promoted HCB dechlorination by enhancing microbial community diversity. Therefore, biochar and biochar-polylactic acid composite showed distinct effect on the composition and diversity of soil prokaryotic community and different contribution to HCB dechlorination. Overall, our results suggested that biochar-polylactic acid composite could be used as soil remediation material to efficiently accelerate dechlorination of HCB.