Study on soil improvement and microbial diversity restoration in metals-contaminated mining areas

The ecological and environmental issues caused by uncontrolled mining in metal-rich areas have raised significant concerns, particularly regarding soil pollution, erosion, and hindered vegetation recovery. This study systematically assessed the impacts of individual and combined applications of lime, earthworm castings, and chicken manure on soil nutrient dynamics, enzymatic profiles, metals mobility, and bacterial microbiota in Pb-Zn contaminated mining soils. Results demonstrated that amendments significantly improved soil properties: pH, cation exchange capacity, total exchangeable base, organic matter, and nutrient levels (e.g., total nitrogen, phosphorus, potassium) increased by 41.3-2370.7%. The QY treatment (500 g kg^-1 of earthworm castings) most effectively enhanced urease (618.2%) and sucrase (274.1%) activities, while QYJF (325 g kg^-1 of earthworm castings + chicken manure) and QYJFSH (257.5 g kg^-1 of earthworm castings + chicken manure + lime) boosted nitrate reductase and catalase. Although total metals reductions were limited, QY decreased Hg, Ni, and As by 12.1-26.6%, whereas QYJFSH and QYSH (260 g kg^-1 of earthworm castings + lime) best reduced Pb and Zn. QYSH also increased bacterial diversity. Spearman correlation analysis and canonical correlation analysis (CCA) linked soil pH, organic matter, key nutrients, and enzyme activities to dominant phyla (e.g., Planctomycetes, Actinobacteria). In conclusion, amendments effectively restored soil quality and microbial communities, offering a scientific basis for ecological remediation in mining areas.