Identification of the hydrochemical features, genesis, water quality and potential health hazards of groundwater in Dawen River Basin, North China

Groundwater resources fulfill a key role in socioeconomic development and residential water use in the Dawen River Basin (DRB). This study sampled and tested three types of groundwater in the DRB, including pore groundwater (PGW), fissure groundwater (FGW), and karst groundwater (KGW). Groundwater in the DRB was assessed for hydrochemical characteristics, quality, and hazards to human health by nitrate contents. Results identified the dominant groundwater anion and cation to be HCO3− and Ca2+, respectively, whereas groundwater was generally weakly alkaline hard-fresh water. The groundwater contents of main chemical components during wet season exceeded those in the dry season, with the rank of groundwater types by chemical component contents being: PGW > KGW > FGW. A Durov diagram indicated groundwater in the DRB to be mixed HCO3-Ca and HCO3·SO4–Ca·Mg types. Rock weathering (silicate and carbonate rocks) was found to be the predominant process regulating groundwater chemistry of the DRB, whereas human activities also had a significant impact, particularly for high NO3− related to agricultural activities. Groundwater quality of the DRB was relatively good overall, falling into the good and moderate classification grades, with that of the PGW the worst. Long-term human direct consumption or exposure to groundwater of DRB poses certain health risks due to groundwater nitrate, with the risk for children highest. The spatial variations in quality of groundwater and nitrate health hazard in the DRB were relatively consistent, with better quality and lower health risk of PGW and FGW in the east than in the west, and that of KGW better in the center than in the east and west. The present study can provide some reference for groundwater safety and protection management in DRB and other similar areas in the world.