Occurrence and Formation Mechanisms of High-Fluoride Groundwater in Xiong’an New Area, Northern China

Abstract

While extant research has predominantly focused on elucidating the mechanisms of fluorine (F−) enrichment in groundwater within the North China Plain, the occurrence and formation mechanisms of high-F− groundwater in Xiong’an New Area remain unexplored. Consequently, 365 groundwater samples (172 from shallow groundwater, 193 from deep groundwater) were collected from Xiong’an New Area. Hydrochemical analysis, geochemical modeling, and statistical analysis were used to explore the occurrence and formation mechanisms of high-F− groundwater. The results reveal that the highest F− concentrations in shallow and deep groundwater were up to 3.22 mg/L and 1.79 mg/L, respectively. High-F− groundwater was primarily located at the eastern part of the study area. The distribution area of high-F− shallow groundwater was much greater than that of deep groundwater. F-bearing minerals dissolution and ion exchange were the principal formation mechanisms of high-F− groundwater in both shallow and deep aquifers. Moreover, competitive adsorption, evaporation, and the impacts of Ca2+ and Mg2+ dissolution equilibrium on F-bearing dissolution were crucial to the formation of high-F− groundwater in shallow aquifers. Desorption in an alkaline environment, evaporites dissolution and salt effects were vital to the formation of high-F− groundwater in deep aquifers. These findings can contribute to the support of local groundwater security and management.