Журнал наук о Земле и изменения климата

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Geochemical Appraisal of Fluoride Laden Groundwater in Suri I and II Blocks, Birbhum District, West Bengal

Shreya Das and SK Nag*

The present study has been carried out covering two blocks – Suri I and II in Birbhum district, West Bengal, India. The evaluation focuses on occurrence, distribution and geochemistry in twenty six water samples collected from bore wells spread across the entire study area homogeneously. Quantitative chemical analysis of groundwater samples collected from the present study area have shown that samples from two locations – Gangta and Dhalla contain fluoride greater than the permissible limit prescribed by WHO during both post monsoon and pre monsoon sampling sessions. Significant factor controlling geochemistry of groundwater has been identified to be rock – water interaction processes during both sampling sessions based on the results of Gibb’s Diagrams. Geochemical modeling studies have revealed that fluorite (CaF2) is indeed present as a significant fluoride bearing mineral in groundwaters of this study area. Calcite or CaCO3 is one of the most common mineral with which fluorite remains associated and saturation index calculations have revealed that the calcite – fluorite geochemistry is the dominant factor controlling fluoride concentration in this area during both post and pre monsoon. High fluoride waters have also been found to be of ‘bicarbonate’ type showing increase of sodium in water with decrease of calcium.