Hydrochemical characteristics and quality evaluation of groundwater in terms of health risks in Luohe aquifer in Wuqi County of the Chinese Loess Plateau, northwest China

Groundwater is the main source of water for domestic and agricultural purposes in Wuqi County on the Loess Plateau. The present study was carried out to assess the hydrochemical characteristics and quality of groundwater in the Luohe aquifer, which is a crucial aquifer for water supply. For this study, 22 groundwater samples and 6 surface water samples were collected for analysis. Hydrochemistry and hydrochemical facies of groundwater were analyzed using statistical analysis and Tri-linear diagram. Gibbs diagram, correlation analysis and bivariate plots were used to investigate the natural evolution mechanisms of groundwater and surface water. Potential health risks of nitrate and Cr6+ through drinking water ingestion for adults and children were estimated. The results show that the major hydrochemical facies is ClSO4-Na, mixed ClSO4HCO3-Na and SO4Cl-MgNa types, and high concentration of Na+ is a remarkable feature of groundwater in the study area. Groundwater chemistry evolution is affected by rock weathering and evaporation. The high concentrations of Na+, SO42- and TDS suggest that groundwater is not suitable for irrigation purposes. According to WQI values, above 80% of the groundwater samples are fair quality water. It is also found that the groundwater of the study area is contaminated with nitrate and Cr6+. Children are at higher health risk than adults. Multiple measures such as establishing new centralized water supply sources and inter-basin water transfer projects have also been proposed in this study to guarantee the safety of sustainable groundwater supply.