Occurrence and hydrogeochemical characteristics of high-fluoride groundwater in Xiji County, southern part of Ningxia Province, China

Abstract

High-F(-) groundwater is widely distributed in Xiji County, which endangers the safety of drinking water. In order to evaluate the key factors controlling the origin and geochemical mechanisms of F(-) enrichment in groundwater at Xiji County, one hundred and five groundwater samples and sixty-two sediment samples were collected. Fluoride concentration in the groundwater samples ranged from 0.2 to 3.01 mg/L (mean 1.13 mg/L), with 17 % exceeding the WHO drinking water guideline value of 1.5 mg/L and 48 % exceeding the Chinese drinking water guideline value of 1.0 mg/L. High-F(-) groundwaters were characterized by hydrochemical types of Na-HCO3 and Na-SO4·Cl, which were found in Quaternary sediment aquifer and in Tertiary clastic aquifer, respectively. Conditions favorable for F(-) enrichment in groundwater included weakly alkaline pH (7.2-8.9), low concentration of Ca(2+), and high concentrations of HCO3 (-) and Na(+). Calcite and fluorite were the main minerals controlling F(-) concentration in groundwaters. The hydrolysis of F-bearing minerals in aquifer sediments was the more important process for F(-) release in Tertiary clastic aquifer, which was facilitated by long residence time of groundwater, in comparison with Quaternary sediment aquifer. Cation exchange would also play important roles, which removed Ca(2+) and Mg(2+) and led to more free mobility of F(-) in groundwater and permitted dissolution of fluorite, especially in Tertiary clastic aquifer. However, evapotranspiration and competing adsorption of B and HCO3 (-) were the more important processes for F(-) enrichment in Quaternary groundwater. Groundwater in Lower Cretaceous aquifer had relatively low F(-) concentration, which was considered to be the potential drinking water resource.

Assessment of processes controlling the regional distribution of fluoride and arsenic in groundwater of the Western Jilin Province, Northeast China

“…10a). In some aquifers, the content of F and Ca 2+ in the groundwater were negatively correlated, re ecting the limiting effect of uorite mineral dissolution on the F content (Yan et al, 2020;Currell et al, 2011;Wei et al, 2016). However, all the samples in the study area were in an unsaturated state relative to uorite (Fig.…”

“…It has high TDS and pH values, and is rich in Na + and poor in Ca 2+ ; that is, carbonate dissolution and cation exchange occur, promoting the enrichment of F and As in the groundwater. Owing to the loss of dissolved components and CO 2 , evaporation causes an increase in TDS and pH values (Wei et al, 2016). The higher TDS (1740-2080 mg/L) and pH value (7.9-8.3) of the shallow groundwater samples indicated that evapotranspiration could be another factor leading to an increase in F and As concentrations in shallow groundwater.…”

Synergic Origin and Evolution of TDS, Mg and Fluoride in Groundwater as Relative to Chronic Kidney Disease of Unknown Etiology (CKDu) in Sri Lanka

“…Hence, cation exchange is calculated by subtracting the equivalent concentration of HCO 3 − and SO 4 2− from Ca 2+ and Mg 2+ , ([(Ca 2+ + Mg 2+ ) − (HCO 3 − + SO 4 2− )]. Na + and K + come from desorption and can be calculated by subtracting an equivalent concentration of Cl − from Na + + K + [(Na + + K + ) − Cl − ] [59]. Almost all groundwater samples collected from both seasons were plotted near the line with a slope of −1, indicating the presence of alternating cation adsorption in both CKDu endemic and control areas (Figure 5f).…”

Characteristics and mechanism of spatial-temporal changes of fluorosis in typical high fluoride areas of Northwest China over the past 40 years

“…Sodium and bicarbonate in the water environment have an important impact on the enrichment of uoride. In recent years, the researches mainly focuse on the origin and geochemistry of high uoride groundwater (Wei et al 2016; Kashyap et al 2020), geochemical processes controlling uoride concentration in groundwater (Ra que et al 2015; Wang et al 2021) and health risk assessment of high uoride groundwater (Ahada and Suthar 2017; Xiao et al 2022). In China, high uoride groundwater is widely distributed in the north, northeast and northwest part, mainly in shallow groundwater (He et al 2020).…”