Geochemical appraisal of fluoride contamination of groundwater in the Nayagarh District of Orissa, India

The occurrence of high concentrations of fluoride in groundwater (> 1.5 mg/l) in the villages of Singhpur and Sagaragan in the Nayagarh District of Orissa and its relation with the fluoride-rich hot spring water (> 10 mg/l) located nearby have been studied. The composition of the hot spring water is very comparable to the other thermal waters of the world. Thermodynamic considerations show that more than 65% of the groundwater and hot spring water samples are oversaturated with calcite, and only four samples are oversaturated with fluorite. Fluoride concentration shows a positive relation to sodium, bicarbonate and PH, and a negative relation to calcium and magnesium in fluoride-rich groundwater and hot spring water. Principal component analysis shows that the fluoride-rich groundwater was produced due to a mixing of hot spring water with the surrounding groundwater. Studies of the saturation index of fluorite with log electrical conductivity also indicate mixing of hot spring water with the surrounding groundwater. The spatial distribution of fluoride in groundwater follows the topography of the area.