Fluoride contamination in groundwater of the Shanmuganadhi River basin (south India) and its association with other chemical constituents using geographical information system and multivariate statistics

Contamination of fluoride in drinking water affects human health, and its reduction is essential for the safe utilization of groundwater for domestic and agricultural uses. Groundwater in the ephemeral (monsoonal) Shanmuganadhi River basin, situated at rain shadow of the Western Ghats (south India), is indiscriminately utilized for rural water supply and agricultural activities. Fluoride contamination in groundwater of the river basin was evaluated using geochemical characteristics of sixty-one groundwater samples collected from the observation wells. Groundwater quality evaluation was attempted by estimating pH, Total Dissolved Solids (TDS), Electrical Conductivity (EC), and concentrations of Ca2+ Mg2+, Na+, K+, HCO3-, Cl-, SO42-, NO3-, PO43- and F-. Multivariate statistical techniques helped to identify the factors responsible for fluoride enrichment. The fluoride ion ranges from 0.01 to 2.5 mg/l with 77 % of the samples having less than 1.5 mg/l. Groundwater samples (23 %) with more than 1.5 mg/l of F- are unsuitable for consumption. Fluoride vulnerable zones were mapped using the Geographical Information System (GIS) in which fourteen villages of the basin are with risk category for dental fluorosis among children. The multivariate statistical techniques (including correlation matrix) highlight the relationship among various geochemical parameters, and the cluster analysis apprehends the sources/processes contributing the chemical variables. Based on this study, it is recommended to adopt natural remediation technique like Managed Aquifer Recharge (MAR) for the enhancement of groundwater quality in this basin.