Spatial distribution and controlling mechanisms of high fluoride groundwater in the coastal plain of Bohai Rim, North China

Fluoride enrichment in groundwater of coastal plains poses a potential health hazard to hundreds of millions of people. In the present study, 515 groundwater samples were collected from shallow and deep aquifers to investigate spatial distribution, quantify the dominant mechanisms and factors of F- enrichment in groundwater and assess potential health hazards of groundwater F-. Results showed that high F- groundwater was widely distributed in deep aquifers with chemical types of HCO3-Na and Cl-Na, and sporadically distributed in shallow aquifers. Based on the groundwater chemistry characterization and regression analysis, it was found that mineral dissolution and precipitation, cation exchange, desorption, evaporation and competitive adsorption jointly controlled groundwater F- enrichment in the study area, which contributes 61%, 15%, 11%, and 7% and 5%, respectively. The influence of seawater intrusion on groundwater F- enrichment was ignored. The results of health risk assessments indicated that more than 85% of deep groundwater samples posed potential health hazards to infants, children, and adult females and males, while approximately 55% of shallow groundwater samples posed potential health hazards to infants, followed by 27% to children, 22% to adult females, and 18% to adult males. This study provides a scientific basis for the effective management of high F- groundwater in coastal plains.