Correlating microbial diversity patterns with V and Cr in blast furnace slag contaminated soil

This study systematically investigated the vertical variations of physicochemical properties, toxic elements and bacterial communities in soils surrounding a 32-year operational blast furnace slag stockpile site in Panzhihua, southwest of China, to explore the response of bacterial communities to the harsh environmental conditions. Soil in the region is substantially contaminated with multiple toxic elements. Both V and Cr were found in the 60–80 cm soil profile with average concentrations of 175.64 mg kg⁻¹ and 566.87 mg kg⁻¹, respectively. Topsoil (0–20 cm) and subsoil (20–80 cm) displayed distinct microbial community compositions. The predominant phyla in the topsoil included Actinobacteriota, Proteobacteria, Acidobacteriota, Chloroflexi, and Gemmatimonadota, whereas the subsoil primarily consisted of Actinobacteriota, Gal15, and Methylmirabilota. The diversity of bacteria was positively related with Mn, V, Pb, Zn and V(V) but negatively associated with MC. The microbial diversity in the topsoil was influenced by Mn and V, while microbial communities in the subsoil were impacted by MC. Functional annotation based on PICRUSt2 and FAPROTAX showed organic carbon oxidation was their main energy acquisition strategy, OM, MC, Mn, V(V) and Fe were the main factors shaping microbial community structure, and trace metals were the core factors regulating metabolic networks. These results enhanced our understanding of distinct heterogeneity of microbial communities influenced by the presence of V and Cr in soil environments.