High-Arsenic Groundwater from Huaihe River Basin, China：Geochemistry and Hydrogeochemical Processes

Abstract Arsenic (As) poses a danger to environmental health, and drinking arsenic-rich groundwater is a key exposure risk for humans. The distribution, migration, and enrichment of As in groundwater is an important worldwide environmental and public health problem that requires research. Huaihe River Basin has been newly identified as a region of high-arsenic groundwater in China. This study aims to analyze the hydrogeochemical data of high-arsenic groundwater, trace its formation and evolution, and evaluate its potential pollution risks. 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-1 and 1.29±0.40 mg L-1, respectively, exceeding the recommended drinking water standards of the World Health Organization by 23% and 31%, respectively. The proportion of groundwater with a high As content presents a high exposure risk. 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 ranges mainly between 400–700 mg L-1, and the chemical type is mainly of HCO3-Na. High-arsenic groundwater is largely affected by evaporation and cation exchange. In an alkaline environment, As in high-arsenic groundwater derives from the dissolution and release of arsenic sulfide in aquifer sediments and poses a potential threat to human health through food and drinking water.