Hydrogeochemical Characteristics and Water Quality Assessment of the Carboniferous Shanxi Formation Sandstone Water in the Huafeng Coal Mine Using an Integrated GTCWM-FCE-TOPSIS Framework

High Resolution Image Download MS PowerPoint Slide Groundwater in coal mining areas is extensively extracted to prevent coal roof water inrush, generating substantial volumes of mine water that must be properly managed and treated. Accurate hydrochemical assessment is therefore crucial for developing effective strategies for water resource protection and utilization. This study proposes an integrated groundwater quality assessment framework that synergistically combines the game theory combinatorial weighting method (GTCWM) with fuzzy comprehensive evaluation (FCE) and Order Preference by Similarity to an Ideal Solution (TOPSIS). Within this framework, GTCWM reconciles subjective weights derived from the analytic hierarchy process (AHP) with objective weights from the entropy weight method (EWM) through game theory optimization, providing a balanced weighting strategy for subsequent evaluation. FCE is then applied to classify water quality into discrete categories, while TOPSIS enables refined ranking of samples within the same quality class, thereby complementing the classification with finer differentiation. The framework was applied to assess the Carboniferous Shanxi Formation sandstone aquifer in the Huafeng coal mine. Results reveal severe groundwater quality degradation, with all samples exceeding Class V standards for TDS and 77.3% exceeding Class V for total hardness (TH). Na +, Cl – are identified as the predominant contaminants. Hydrochemical analysis indicates that water–rock interactions govern the hydrochemical evolution within this confined synclinal structure. The shallow southern aquifer receives lateral recharge and is influenced by silicate weathering, and halite/gypsum dissolution, whereas the deep northern aquifer exhibits stagnant conditions characterized by halite/gypsum dissolution, reverse cation exchange, and silicate weathering. GTCWM weight analysis identifies Cl –, TH, and Na + as the key water quality parameters and thus the primary targets for treatment and resource recovery. GTCWM-FCE classification demonstrates that 81.8% of samples fall into Class V, indicating widespread contamination that renders the groundwater unsuitable for direct use without treatment. GTCWM-TOPSIS ranking further reveals substantial spatial heterogeneity. WQRI values range from 0.011 to 0.489 (a 45-fold difference), and exhibit a 12-fold variability within Class V samples. These findings underscore the need for differentiated management strategies. Accordingly, a tiered management strategy is proposed: minimal treatment and direct reuse for the southern high-quality zone (Class III–IV); conventional treatment and industrial reuse for the treatment-oriented zone (Class V, WQRI <0.356); and salt resource recovery (NaCl and Na 2 SO 4 ) via membrane concentration and crystallization for the resource-oriented zone (Class V, WQRI >0.356). This dual-method framework provides a robust tool for groundwater quality evaluation in mining-affected areas, offering critical insights for targeted water treatment and resource utilization strategies that contribute to sustainable mining practices.