Source apportionment and health risk prioritization of groundwater contamination in a coal-mining area: An integrated SOM-PMF-Monte Carlo framework

Groundwater quality in arid/semi-arid coal-mining areas is increasingly threatened by intensive human activities. However, quantitatively linking specific pollution sources to health risks and translating this into risk-based management priorities remains a critical challenge. This study addresses this gap by proposing an integrated framework combining self-organizing maps (SOM), positive matrix factorization (PMF), and Monte Carlo simulation to systematically decipher groundwater contamination sources and prioritize associated health risks, using the Huolingol mining area in Inner Mongolia, China, as a representative case. SOM analysis recognized three hydrochemical clusters: Cluster 1 (Na-HCO 3 /Ca-Na-HCO 3 type), influenced by cation exchange and silicate weathering under alkaline conditions, exhibited elevated F − and NH 4 + -N concentrations. Cluster 2 (Ca-Na-SO 4 /Ca-Na-HCO 3 type) was characterized by elevated TDS, TH, SO 4 2− , and NO 3 − , indicating significant anthropogenic impact. Cluster 3 (Ca-HCO 3 type) represented the natural background with minimal contamination. Source apportionment using PMF revealed that human-driven composite pollution is the main cause of water quality evolution, with the mixed source of coal mine drainage and industrial/domestic wastewater contributing the highest proportion (22.42%), highlighting the overwhelming impact of mining and industrial activities. Monte Carlo simulation showed children faced a 33.9% probability of exceeding the safe health threshold (HI > 1), 1.75 times higher than adults (19.4%). F − and SO 4 2− were the main risk drivers. Source-specific analysis indicated geogenic fluoride (Factor 1) contributes ∼48% of total health risk, followed by organic degradation (∼26%) and anthropogenic sulfate (∼23%). This framework quantitatively links sources to health risks and provides actionable guidance for groundwater management in water-stressed mining regions.