Hydrogeochemical processes and potential exposure risk of high-arsenic groundwater in Huaihe River Basin, China

Arsenic (As) poses a danger to environmental health, and drinking arsenic-rich groundwater is a key exposure risk for humans. The study on distribution, migration, and enrichment of As in groundwater is an important worldwide environmental and public health problem. Huaihe River Basin is presently defined as a region of high-arsenic groundwater in China. In this study, a typical high arsenic groundwater area in the basin was selected as the natural experimental site to analyze the formation and evolution of high arsenic groundwater through the analysis of groundwater hydrogeochemical data, to trace the source and dissolution of arsenic pollutants, and evaluate the potential pollution risk. The results showed that As and F were the main inorganic chemical substances affecting the water quality in the study area, with concentrations of (5.75±5.42) μg/L and (1.29±0.40) mg/L respectively, the ratio of test samples exceeding the recommended drinking water standards of the World Health Organization by 23% and 31% respectively. According to the hydrochemical diagram and the calculation of mineral saturation indices, the groundwater in the study area underwent evaporation, halite dissolution, and water-rock interaction. The total alkalinity of high-arsenic groundwater ranged mainly between 400 and 700 mg/L, and the hydrogeochemical type was mainly of HCO₃-Na. High-arsenic groundwater was largely affected by evaporation and cation exchange. Arsenic in high-arsenic groundwater derived from the dissolution and release of geogentic arsenic in aquifer. The oxidation dissolution and reduction activation of As-bearing minerals may be the main mechanism of the formation of high arsenic groundwater.