Prediction and prevention of sulfate pollution from abandoned mines in the Taozao Coalfield

Coal mining has posed severe threats to groundwater resources, particularly in abandoned mines where mine water interacts with karst aquifers. Focusing on the Taozao Coalfield in Shandong Province, this study investigates the spatial distribution, evolution mechanisms, and migration pathways of sulfate pollution in post-mining groundwater systems. By integrating isotope tracing, Bayesian mixing models, hydrogeochemical analysis, and random forest regression, this study systematically identifies sulfate sources, transport dynamics, and future trends. Results show that pyrite oxidation is the dominant source of sulfate, intensified by mining-induced fractures that expose sulfide minerals to oxygen-rich conditions, while gypsum dissolution contributes locally. Mine water migrates into karst aquifers primarily through the Dalüxiang Fault and floor fractured zones. A random forest model predicts minor fluctuations in sulfate concentrations over the next decade, with total dissolved solids (TDS) as a key influencing factor. To mitigate pollution, this study proposes a "source–pathway–receptor" control framework involving shaft sealing, grouting barriers, and constructed wetlands for sulfate removal and water reuse. This work provides scientific insights and practical strategies for sustainable groundwater management in coal-mining regions.