Bioremediation of Hg-contaminated soil by combining a novel Hg-volatilizing Lecythophora sp. fungus, DC-F1, with biochar: Performance and the response of soil fungal community.

Reducing Hg contamination in soil using eco-friendly approaches has attracted increasing attention in recent years. In this study, a novel multi-metal-resistant Hg-volatilizing fungus belonging to Lecythophora sp., DC-F1, was isolated from multi-metal-polluted mining-area soil, and its performance in reducing Hg bioavailability in soil when used in combination with biochar was investigated. The isolate displayed a minimum inhibitory concentration of 84.5mg·L-1 for Hg(II) and volatilized >86% of Hg(II) from LB liquid medium with an initial concentration of 7.0mg·L-1 within 16h. Hg(II) contents in soils and grown lettuce shoots decreased by 13.3-26.1% and 49.5-67.7%, respectively, with DC-F1 and/or biochar addition compared with a control over 56days of incubation. Moreover, treatment with both bioagents achieved the lowest Hg content in lettuce shoots. Hg presence and DC-F1 addition significantly decreased the number of fungal ITS gene copies in soils. High-throughput sequencing showed that the soil fungal community compositions were more largely influenced by DC-F1 addition than by biochar addition, with the proportion of Mortierella increasing and those of Penicillium and Thielavia decreasing with DC-F1 addition. Developing the coupling of Lecythophora sp. DC-F1 with biochar into a feasible approach for the recovery of Hg-contaminated soils is promising.