Water quality in a worldwide coal mining city: A scenario in water chemistry and health risks exploration

In the face of increasing influences of coal industries on the water environment and water security, a deeper understanding of the chemistry of water and the eco-environmental health risks to human is needed to contribute. One of largest coal capital city of Yulin (NW of China) was chosen a scenario and case for further investigation. The distribution levels of multi-ions (F−, Cl−, HCO3−, NO3−, SO42−, Li+, K+, Ca2+, Na+, Mg2+, NH4+) and potentially toxic metals (PTMs) (Cd, Co, Cr, Cu, Mn, Ni, Pb, Sb and Zn) in drinking water, lake water and river water at the river catchment scale collected from study areas were determined by using ion chromatography and inductively coupled plasma mass spectrometer (ICP-MS). The water chemistry, health risks, sources and anthropogenic inputs were explored. The dominant ions in drinking, lake and river waters decreased as HCO3− > SO42− > Cl− in anions, and cations as Ca2+ > Na+ > Mg2+. The strong correlation between Na+ and Cl−, K+ and Cl−, Na+ and K+, Mg2+ and SO42− in surface waters (lake and river water) was controlled by rock weathering and with the hydrochemical type of SO42−·Cl−—Ca2+·Mg2+ illustrated by the Gibbs diagram. The concentrations of Cd, Co, Cr, Cu, Mn, Ni, Pb, Sb and Zn in drinking and surface waters were varied significantly, which was associated with coal mining and coal combustion activities. Although the non-carcinogenic risk of Cu, Mn, Ni, Pb, Sb and Zn in drinking water, lake and river water were acceptable, the carcinogenic risk caused by Cr in both drinking water and surface waters exceeded the values of 5.00E-05 and 1.00E-06 recommended by three international health organizations, respectively, which should be paid more attention to and monitored continuously in order to significantly understand the pollutants and the anthropogenic impact on water security and ecosystems, and also to ensure the sustainable clean energy and ecological coal exploitation in Yulin city.