Concentration mechanism of fluorine, arsenic, and uranium in groundwater of the Hailar Basin, China

Abstract

Located in a semiarid region of the Hulun Buir League in China’s Inner Mongolia Autonomous Region, the Hailar Basin is a region with less precipitation, where groundwater is the most important water supply source. It is important to study groundwater characteristics and hydrogeochemical processes for the better management of groundwater resources. Fluorine (F), arsenic (As), and uranium (U) cocontamination currently exists in the groundwater of the Hailar Basin, China. To understand the concentration mechanism of F, As, and U in groundwater in the study area, groundwater samples were collected for detection and analysis. The results showed that the main hydrochemical types in the study area were Cl–Na, HCO3–Na, and HCO3–Ca. The median values of F, As, and U were 3.32 mg/L, 0.029 mg/L, and 0.066 mg/L, respectively, which all exceeded the World Health Organization (WHO) guidelines. Through a Gibbs diagram and endmember diagram, it can be seen that the groundwater in the study area is mainly affected by the hydrogeochemical effects of evaporative crystallization, rock weathering mechanisms, and the dissolution of silicate rock and evaporative salt rock minerals. Mineral dissolution, cation exchange, and weakly alkaline environments are important factors affecting F concentrations. Low NO3− and SO42− concentrations cause a reducing environment, and the competitive adsorption of HCO3− promotes As pollution. The concentrations of Ca2+, Mg2+, SO42−, and NO3− have a great influence on the concentration of U.