Hydrogeochemical properties, source provenance, distribution, and health risk of high fluoride groundwater: Geochemical control, and source apportionment

Abstract

This study evaluated high fluoride (F-) levels, source distribution, provenance, health risk, and source apportionment in the groundwater of Sargodha, Pakistan. Therefore, 48 groundwater samples were collected and analyzed by ion-chromatography (DX-120, Dionex). The lowest concentration of F- was 0.1, and the highest was 5.8 mg/L in the aquifers. In this study, 43.76% of the samples had exceeded the World Health Organization's allowable limit of 1.5 mg/L. The hydrogeochemical facies in Na-rich and Ca-poor aquifers showed NaCl (66.6%), NaHCO3 (14.5%), mixed CaNaHCO3 (8.3%), CaCl2 (8.3%), mixed CaMgCl2 (2%), and CaHCO3 (2%) type water. Alkaline pH, high Na+, HCO3- concentrations, and poor Ca-aquifers promoted F- dissolution in aquifer. The significant positive correlations between Na⁺ and F- suggested cation exchange, where elevated Na⁺ occurs in Ca-poor aquifers. The cation exchange reduces the availability of Ca2+ would lead to higher F- concentrations. Meanwhile, the correlation between HCO₃- and F- indicates that carbonate minerals dissolution helps in increasing pH and HCO₃- as a result F- triggers in aquifers. Groundwater chemistry is primarily governed by the weathering of rock, water-rock interaction, ion-exchange, and mineral dissolution significantly control groundwater compositions. Cluster analysis (CA) determined three potential clusters: less polluted (10.4%), moderately polluted (39.5%), and severely polluted (50%) revealing fluoride toxicity and vulnerability in groundwater wells. Mineral phases showed undersaturation and saturation determining dissolution of minerals and precipitation of minerals in the aquifer. PCAMLR model determined that high fluoride groundwater takes its genesis from F-bearing minerals, ion exchange, rock-water interaction, and industrial, and agricultural practices. The health risk assessment model revealed that children are at higher risk to F- toxicity than adults. Thus, groundwater of the area is unsuitable for drinking, domestic, and agricultural needs.