Geochemical and geostatistical appraisal of fluoride contamination: An insight into the Quaternary aquifer

Fluoride (F^-) in groundwater poses a severe public health threat in the Dwarka River Basin (DRB) of West Bengal, India, where many cases of fluorosis have been reported. This research evaluates the spatial distribution patterns of major cations and anions, delineates zones of high F^- concentrations within alluvial sediments of the DRB, and identifies both the sources and the geochemical processes responsible for the release of F^- to groundwater. A total of 607 groundwater samples were collected from shallow and deep tube wells located within the DRB, encompassing an area of 435 km² and including 211 villages. Fluoride levels range from 0.01 to 10.6 mg/L, and high concentrations (>1.5 mg/L) are restricted to isolated areas within the basin (occurring within nine of the villages and comprising 4.3% of the samples collected). The high-fluoride areas are characterized by mostly Na-HCO₃ type groundwater, where the abundance of cations and anions are Na⁺ > Ca²⁺ > Mg²⁺ > K⁺ and HCO₃^- > Cl^- > SO₄^2- > F^- > NO₃^- > Br^-, respectively. Analyses of the groundwater geochemistry and sediment mineralogy suggest that fluoride is released to groundwater primarily through the hydrolysis of albite and biotite; however, the resulting alkaline conditions are also favorable for release of fluoride from weathered biotite and clay minerals through anion exchange (OH^- in groundwater replacing F^- within the mineral structure). Multiple linear regression models show that fluoride concentrations can be predicted from the measures of other dissolved constituents with a high degree of accuracy (R² = 0.96 for high fluoride samples and R² = 0.8 for low fluoride samples).

Inferring the fluoride hydrogeochemistry and effect of consuming fluoride-contaminated drinking water on human health in some endemic areas of Birbhum district, West Bengal

This research work is carried out to evaluate fluoride (F) hydrogeochemistry and its effect on the population of two endemic villages of Birbhum district, West Bengal. Fluoride concentration in drinking water varies from 0.33 to 18.08 mg/L. Hydrogeochemical evolution suggests that ion-exchange mechanism is the major controlling factor for releasing F in the groundwater. Most of the groundwater samples are undersaturated with respect to calcite and fluorite. Health survey shows that out of 235 people, 142 people suffer from dental fluorosis. According to fluoride impact severity, almost 80 and 94 % people in an age group of 11-20 and 41-50 suffer from dental and skeletal fluorosis, respectively. Statistically drinking water F has a positive correlation with dental and skeletal fluorosis. Bone mineral density test reveals that 33 and 45 % of the studied population suffer from osteopenic and osteoporosis disease. IQ test also signifies that F has a bearing on the intelligence development of the study area school children. The existence of significant linear relationship (R (2) = 0.77) between drinking water F and urinary F suggests that consumption of F-contaminated drinking water has a major control over urinary F (0.39-20.1 mg/L) excretion.