Fluoride in Groundwater: Mobilization, Trends, and Remediation
In many cases, the high-fluoride groundwater turns out to be undersaturated with respect to fluorite. Fluoride has a very narrow therapeutic spectrum—it protects against tooth decay at levels around 1 mg/L in drinking water but causes dental fluorosis at slightly higher levels, notably in warmer climates like India where the need for fluid is elevated and mostly satisfied by the locally available groundwater. The groundwater bears the sign of being concentrated by evaporation and evapotranspiration and enriched in sodium along with mobilization of fluoride. K. R. Reddy et al. and P. J. Sajil Kumar found a sizeable oversaturation in the groundwater with respect to dolomite, while fluorite was generally undersaturated even with a trend of larger undersaturation downslope, due to loss of calcium precipitated as calcrete. The extent of sodic soils was only 0.6 Mha in 1979. Along with promoting recharge, it is also necessary to remediate the alkalinity/sodicity of soils.