Evaluation of aqueous geochemistry of fluoride enriched groundwater: A case study of the Patan district, Gujarat, Western India

High fluoride (F⁻) groundwater causes fluorosis which might at severe stages lead to deformation of bones, bilateral lameness. The concentration of F⁻ ranged from 0.4 to 4.8 mg/L. This study suggests that high HCO₃⁻ and Na⁺ in alkaline medium along with water–rock interaction plays important role in enrichment of F⁻ in groundwater. Na-HCO₃ is the dominant water type followed by Ca-HCO₃ suggesting dominance of Na⁺, Ca²⁺ and HCO₃⁻ ions in groundwater. Factor analysis of water quality parameters suggests that four principal components account for 74.66% of total variance in the dataset. Factor 1 shows higher positive loading for pH, HCO₃⁻ negative loading for F⁻, Ca²⁺, SO₄²⁻ depicting ion-exchange and HCO₃ dominant water type responsible for F enrichment in groundwater. Saturation index for selected minerals suggests that most of the samples are oversaturated with calcite and undersaturated with fluorite. Calcite precipitation leads to the removal of Ca²⁺ from solution thus allowing more fluorite to dissolve. These released Ca²⁺ ions combine with CO₃²⁻ ions to further enhance the precipitation of CaCO₃.