Hydrogeochemical characteristics and water quality assessment of shallow groundwater: a case study from Linhuan coal-mining district in northern Anhui Province, China

Major ion and trace element concentrations in shallow groundwater of Linhuan coal-mining district, Northern Anhui Province, China, were analyzed to determine its hydrogeochemical characteristics and to assess drinking and irrigation water quality. The relative abundance of cations and anions was Na+ > Mg2+ > Ca2+ > K+ and HCO3- > SO42- > Cl- > NO3-, respectively. The concentrations of Nat HCO3-, NO3-, and total dissolved solids (TDS), and the electric conductivity (EC) values in some samples were higher than the permissible limits of the Water Health Organization (WHO). Gibbs diagrams showed that rock weathering mainly controlled the major ion chemistry of the groundwater, and the first aquifer of this study area had a weak hydraulic connection with atmospheric precipitation. The calculated sodium percentage (%Na) and sodium adsorption ratio (SAR) revealed that the slight sodium and high salinity hazards needed to be controlled before irrigation. According to the fuzzy comprehensive assessment, the groundwater samples were classified into four categories. The results showed that 92.86% of the groundwater samples were suitable for drinking use. For human health, the NO3- and Mn levels in the groundwater should be reduced before drinking, and treatment of the high salinity hazards is required before irrigation.