Assessment of potential hazards of fluoride contamination in drinking groundwater of an intensively cultivated district in West Bengal, India

We assessed the potential of fluoride (F) contamination in drinking groundwater of an intensively cultivated district in India as a function of its lithology and agricultural activities. Three hundred and eight groundwater samples were collected at different depths from various types of wells and analyzed for pH, EC, NO3-N load and F content. A typical litholog was constructed and database on fertilizer and pesticide uses were also recorded for the district. The water samples were almost neutral in reaction and non-saline in nature with low NO3-N content (0.02 to 4.56 mu g mL(-1)). Fluoride content in water was also low (0.01 to 1.18 mu g mL(-1)) with only 2.27% of them exceeding 1.0 mu g mL(-1) posing a potential threat of fluorosis. On average, its content varied little spatially and along depth of sampling aquifers because of homogeneity in lithology of the district. The F content in these samples showed a significant positive correlation (r = 0.12, P = a parts per thousand currency sign0.05) with the amount of phosphatic fertilizer (single super phosphate) used for agriculture but no such relation either with the anthropogenic activities of pesticide use or NO3-N content, pH and EC values of the samples was found. The results suggest that the use of phosphatic fertilizer may have some role to play in F enrichment of groundwater.