STUDY OF HIGH FLUORIDES IN GROUNDWATER IN PARTS OF EASTERN INDIA: GEOCHEMICAL AND HEALTH IMPLICATIONS

The present study is undertaken to investigate the nature and distribution of high fluorides in groundwater and determine its probable source in two regions in eastern India. The endemicity of fluoride related problems in humans starts with mottling of teeth, disorder in skeletal and bone structures and later massive degeneration of bones with high consumption of fluoride from drinking water. This work involves study of remote sensing data coupled with field observations, to account for the source and pathway of fluoride migration in this region. Groundwater/Drinking water samples were collected from 75 hand pumped tube wells (covering~1000 km²area), with emphasis on the sectors previously reported to have high fluoride incidence. In the current study 13 locations are identified with high fluoride (mean~1.5mg/l) and varies from 0.25 to 5.4mg/l. The concentration of other elements in these waters (mg/l) associated with similar mineral phases that houses and controls fluoride distribution and mobility are Ca (10 to 346), Na (2.2 to 36), Mg (0 to 97), K (0.3 to 144), Fe (< 0.2 to 8), and HCO₃^- (45 to 530). The total hardness of these waters in terms of CaCO₃ varies from 60 to 1000 mg/l. The pH range is 6.8 to 8 and specific conductivity is in the range of 138 to 2640µs/cm. From this study it is emphasised that a combination of hydrogeochemistry, landuse pattern and structural orientation of the source rocks aid in the release and mobilization of fluoride from the granitic rocks/pegmatite to the deep groundwater (~60m). Low fluoride areas have also seen to cause fluorosis among adults due to chronic exposures of low concentration during high water intake in this dry arid climate.