[Effects of Mercury Pollution on Soil Organic Carbon Stability and Carbon-fixing Microbial Communities]

To elucidate the effects of Hg pollution on soil organic carbon stability and autotrophic microbial carbon assimilation, the characteristics of soil CO₂ emission rate, organic carbon components, and cbbL and cbbM functional microorganisms before and after 29 d of Hg pollution were studied using indoor culture experiments and molecular biology techniques. The results showed that the effects of different levels of Hg pollution on soil CO₂ emission rates were different. High levels of Hg （S2,S3,and S5） inhibited soil CO₂ cumulative emissions, whereas low levels of Hg （S1,S4,and S6） promoted soil carbon emissions. Hg pollution affected the proportion of soil organic carbon components. The changes in SOC and MBC contents in different treatments were basically the same, with significant differences （P < 0.05）. EOC and DOC decreased with the increase in Hg content. Compared with that at 1 d, the qCO₂ of each treatment was significantly decreased at the end of culture （P < 0.05）. The effects of different levels of Hg pollution on the functional microbial communities of cbbL and cbbM were significantly different. Proteobacteria, Actinobacteria, and Acidobacteria were the dominant phyla shared by the two functional microorganisms. Cumulative soil CO₂ emissions and SOC were the main factors affecting the change in the cbbL community, and soil available Hg was the main factor affecting the change in the cbbM community. In summary, the results of this study can provide a theoretical basis for the carbon cycle and accumulation of Hg-contaminated regional ecosystems.