Formation of high fluoride groundwater and associated health risks in the Cangzhou area of the North China Plain

Abstract

High fluoride (F⁻) groundwater poses a potential health hazard to hundreds of millions of people worldwide. As the largest agricultural growing area in China, the high F⁻ groundwater in the North China Plain is attracting more attention. In this study, a total of 76 groundwater samples were collected in Cangzhou City of North China Plain, to analyze the controlling mechanisms and their relative contribution on groundwater F⁻ enrichment, and evaluate the potential health hazards. Results showed that the exceedance rates of F⁻ in shallow groundwater (SG) and deep groundwater (DG) were 42% and 90%, respectively. Through the characterization of groundwater chemistry coupled with machine learning algorithm, it was found that mineral dissolution and precipitation, cation exchange, competitive adsorption, evaporation and seawater intrusion together control groundwater F⁻ enrichment in the study area, and their contributions were 42%, 34%, 12%, 7% and 5%, respectively. The high water table of SG was more susceptible to evaporation and seawater intrusion, while the geological environment of DG was more conducive to cation exchange and competitive adsorption. Results of health risk assessment showed that 52% of SG samples threatened the health of infants, while 37% and 33% of samples threatened the health of children and adult female. And among DG, more than 71% of samples threatened the health of adults, while 98% and 90% of them threatened the health of infants and children. This study identified the groundwater F⁻ enrichment process in agricultural areas, thereby enhancing our comprehension of the hydrogeochemical evolution groundwater F⁻.