Groundwater fluoride contamination in Coimbatore district: a geochemical characterization, multivariate analysis, and human health risk perspective
P. J. Sajil Kumar
Abstract
Abstract In this paper, fluoride geochemistry and health risk of groundwater in Coimbatore district is studied. The order of dominance of ions were HCO 3 > Cl > SO 4 > CO 3 and Na > Ca > Mg > K. Alkaline groundwater and the dominance of HCO 3 and Na is favourable for the fluoride enrichment. Around 46% of the samples, N–NE regions, have F − higher than permissible limit of 1.5 mg/L. Pink granites, charnockite and gneisses in lithology is the possible origin of F − . However, NO 3 vs F plot shows positive trend in some samples, indicating anthropogenic inputs of F − . Correlation plots of F − was trending positive with pH, HCO 3 and Na and but negative for Ca, indicating the control of these ions in F − mobility. This result is supported by undersaturation of fluorite and supersaturation of carbonates. Four significant principal components were derived, which have explained 87% of the total variation. PC1 has high factor loadings for EC, Ca, Mg Na, Cl, SO 4 , NO 3 indicating both natural and anthropogenic influences. PC2, PC3 and PC4 have higher loading for pH and HCO 3 , K and HCO 3 and F − , respectively, indicating geogenic factors in the F − enrichment. Human health risk assessment (HHRA) by ingestion and dermal pathways were calculated using Hazard Quotient HQ and Hazard Index (HI). 27% of males, 36% of females and 39% of the children have HI > 1, posing noncarcinogenic risks.