Potentially toxic metal contamination and microbial community analysis in an abandoned Pb and Zn mining waste deposit

Bioindicators have been widely used to assess the contamination of lead/zinc (Pb/Zn) in smelter areas, mining waste disposal areas and in areas containing slags from Pb ore smelting. In this context, the analysis involving microorganisms has gained prominence as a complementary tool in studies aimed at assessing contaminated sites. Therefore, the objective of this study was to assess the contamination of Pb, Zn and cadmium (Cd) in an area where a PbZn smelter operated, using the integration of geochemical and microbial data. The experimental analysis was conducted to characterize the soil collected at three different sites (samples NS, EW and EP). The analysis conducted was physicochemical, metal concentration, metal speciation and analysis of the microbial community through high-throughput sequencing technique. Through the results it was observed that the high concentrations of metals altered the bacterial community present in the soil. Differences were noted between the microbial communities according to the sampling site, especially in sample EP, collected at the margin of the dirt road, which presented higher metal concentrations and microbial diversity. The main phyla detected in the samples were: Proteobacteria, Bacteroidetes and Acidobacteria. Bacteria tolerant to the presence of potentially toxic metals (PTM), such as Rhodoplanes, Kaistobacter, Sphingomonas and Flavisolibacter were identified in the analyzed samples. The phylogenetic groups identified in the study area are similar to those obtained in other studies in metal contaminated areas. The differences between the bacterial communities in each sample indicate that the concentration of PTM may have influenced the microbial community in the soil. Thus, it is noted the importance of the integration of geochemical and microbial data to evaluate the impact of the improper disposal of high PTM concentrated slags in natural soils.