Analysis of hydrochemical characteristics and their controlling factors in the Fen River of China

Water shortage and pollution are threatening the sustainability of cities and society, and it is thus fundamental to analyze the water chemistry and quality in regions subject to water shortages. This study collected surface and groundwater samples from the Fen River of China in the wet seasons of 2015 and 2017, and analyzed the water chemistry, quality and their controlling factors using ternary diagrams, Gibbs diagrams, a fuzzy membership function, correlation analysis, and a forward model. The overall water type was Na + HCO3 and Ca + HCO3 in 2015 and 2017, respectively. HCO3- accounted for 48%-56% of the total anions, while Ca2+ and Na+ accounted for 43%-57% and 18%-27% of the total cations, respectively. Concentrations of HCO3- and Ca2+ decreased along the direction of flow, while the concentrations of other ions increased. Of the surface water and groundwater samples, 63% and 95% complied with environmental quality standards, respectively, in 2015, but only 88% and 44% were compliant in 2017. The dissolved solutes mainly came from rock weathering, to which evaporite dissolution contributed 38%-43%, silicate weathering 7%-34%, and carbonate weathering 17%-44%. Atmospheric and anthropogenic inputs were shown to exert minor effects on the hydrochemistry. Ion exchange and mineral deposits also affected the spatiotemporal hydrochemistry