Identifying the Hydrochemical Characteristics, Genetic Mechanisms and Potential Human Health Risks of Fluoride and Nitrate Enriched Groundwater in the Tongzhou District, Beijing, North China

Abstract

Fluoride and nitrate enriched groundwater are potential threats to the safety of the groundwater supply that may cause significant effects on human health and public safety, especially in aggregated population areas and economic hubs. This study focuses on the high F^– and NO₃^– concentration groundwater in Tongzhou District, Beijing, North China. A total of 36 groundwater samples were collected to analyze the hydrochemical characteristics, elucidate genetic mechanisms and evaluate the potential human health risks. The results of the analysis indicate: Firstly, most of the groundwater samples are characterized by Mg-HCO₃ and Na-HCO₃ with the pH ranging from 7.19 to 8.28 and TDS with a large variation across the range 471–2337 mg/L. The NO₃^– concentration in 38.89% groundwater samples and the F^– concentration in 66.67% groundwater samples exceed the permissible limited value. Secondly, F^– in groundwater originates predominantly from water-rock interactions and the fluorite dissolution, which is also regulated by cation exchange, competitive adsorption of HCO₃^– and an alkaline environment. Thirdly, the effect of sewage disposal and agricultural activities have a significant effect on high NO₃^– concentration, while the high F^– concentration is less influenced by anthropogenic activity. The alkaline environment favors nitrification, thus being conducive to the production of NO₃^–. Finally, the health risk assessment is evaluated for different population groups. The results indicate that high NO₃^– and F^– concentration in groundwater would have the largest threat to children's health. The findings of this study could contribute to the provision of a scientific basis for groundwater supply policy formulation relating to public health in Tongzhou District.