Hydrogeochemical Characteristics and Quality Assessment of Mine Water in Coalfield Area, Guizhou Province, Southwest China.

Coal resources are widely distributed in Guizhou province, China and environmental pollution caused by coal mining is becoming increasingly serious, especially mine drainage. A total of 120 mine water samples collected from different coalfields were analyzed to investigate the hydrogeochemical characteristics and assess the water quality for drinking, domestic, and irrigative purposes. Water samples had a pH of 1.90-9.12 and most of them were acidic or weakly acidic. Total dissolved solids (TDS) ranged from 254 to 13,944 mg/L and correlated closely with the electrical conductivity (EC). The coal mine drainage of Guizhou was characterized typically by low pH value, high Fe and SO concentration, which were mainly attributed to oxidative weathering of pyrite. The most dominant type for abandoned coal-mine drainage was Ca-Mg-SO, while that of the underground drainage for active mine were mainly Na-SO and Na-HCO because of high concentration of Na from the dissolution of evaporites and clastic rocks. High concentration of the TDS, SO, Fe, Mn, et al. made it unsuitable for drinking and domestic use, but part of the coal mine drainage could be used for irrigation at some sites.