Fluoride enrichment in aquifers of the Thar Desert: controlling factors and its geochemical modelling

The groundwater is the only source of drinking water in the Jaisalmer district of Rajasthan, India. The study area is a part of the Thar Desert. It has low and scattered population and no industries; hence, the possibility of anthropogenic input of fluoride is almost negligible. Thus, the enrichment of fluoride is only possible due to geochemical processes taking place in the groundwater of the region. A total of 100 groundwater samples, 34 samples from Jaisalmer and 66 samples from the Pokharan administrative blocks, were collected. It was observed that the concentration of fluoride ranged from 0.08mg/l to 4.56mg/l in the groundwater of Jaisalmer and from 0.56mg/l to 6.60mg/l in the samples of the Pokharan block. The alkaline condition (average pH, 7.7 +/- 0.22 and 8.01 +/- 0.25 in Jaisalmer and the Pokharan administrative block, respectively) in the region favours fluorite dissolution. Ion exchange, dissolution of calcite, semi-arid climate, alkaline conditions and weathering are responsible for fluoride enrichment in the groundwater of the study area. Copyright (c) 2012 John Wiley & Sons, Ltd.