Effects of heavy metals on variation in bacterial communities in farmland soil of tailing dam collapse area.

Heavy metals are commonly present in polluted soil in mining areas. In this study, we investigated 10 sites of farmland soil in the heavy metal tailing dam collapse area (TDCA) with the dominant phyla Acidobacteriota, Proteobacteria, Bacteroidetes, and Planctomycetes. The heavy metal dam collapse area is a composite contamination area of multiple heavy metals, with Cd, Pb and Zn being the most severely contaminated, and the levels of Hg and Cu exceeding the screening values at some of the sites. The Shannon, Chao1 and ACE indices revealed high microbial diversity but low relative abundance of microorganisms at the severely polluted TDCA1 and TDCA3 sites. The results of redundancy analysis (RDA) showed that Hg (Max = 4.31 mg/kg) and Cu (Max = 100 mg/kg) were important factors affecting soil microbial community in the TDCA compared to other heavy metals. Correlation analysis of heavy metals with microbial communities showed that RB41 (Acidobacteria) was more resistant to high concentrations of Cd, Pb, and Zn pollution. The genera of UTCFX1 (Chloroflxi) and norank_TRA3-20 had strong tolerance to the heavy metal Hg. Cu was significantly negatively correlated with norank_WD2101_soil_group (P < 0.05). Therefore these can be used as indicators for monitoring potential heavy metal contamination. The results can be used to predict the changes in the ecosystem of the mining area to maintain its ecological balance and health.