Elucidating effects of magnesium sulfate on chemical properties, enzyme activity and microbial community in rare earth ores extraction

Abstract The widespread use of ammonium-based leaching agents in rare earth mining has caused severe soil degradation and nitrogen pollution. Magnesium sulfate (MgSO4), an ammonium-free alternative, may reduce these effects while maintaining leaching efficiency, but its long-term effects on soil health remain unclear. This study examined ion-adsorption rare earth ore soils treated with 0–2% MgSO4 to assess changes in chemical properties, enzyme activities and microbial communities. MgSO4 application altered soil pH (0.56–0.86 units), reduced organic matter by 54–64% and caused greater than 95% nitrogen loss. Available phosphorus (AP) was depleted after eight days, and potassium declined by 19–30%. Cation exchange capacity (CEC) decreased by more than 10%. Enzyme responses varied: peroxidase increased, sucrase decreased and urease peaked at 2% Mg. Microbial diversity rose at less than or equal to 1% Mg but fell at higher concentrations. Excessive MgSO4 impaired nutrient retention and microbial diversity, indicating potential long-term ecological risks. Maintaining MgSO4 concentrations at or below 1% is recommended to mitigate environmental effects and support soil function in rare earth leaching operations.