Multi-spectroscopy reveals coal-derived DOM fingerprints for mine-water source identification

Mine water source identification and water-inrush tracing in deep coal mines remain challenging due to the complex hydrogeological conditions. Coal-derived dissolved organic matter (Coal-DOM) has emerged as a potential organic tracer, yet its temperature-dependent release characteristics under deep mining conditions are poorly understood. This study investigates the release of Coal-DOM from coals of varying metamorphism (long flame coal, lean coal, anthracite) at 25 °C and 50 °C using DOC analysis, EEM spectroscopy, and FT-ICR MS. Results show that elevated temperature significantly enhances DOC release, most markedly in anthracite (from 9.1 to 13.5 mg-C/L). For low-rank coals, temperature promotes the release of polar, protein-like DOM, increasing molecular diversity (from 3,877 to 7,876 formulas) and oxidation state (O/C from 0.31 to 0.40). In contrast, anthracite releases DOM dominated by aliphatic compounds (>75%), a signature reinforced at higher temperatures. These rank-specific molecular fingerprints exhibit clear media-specificity, demonstrating their potential as supplementary organic tracers for discriminating mine water sources and tracing water-inrush pathways in complex deep mining environments.