Geochemistry of Fluoride Bearing Groundwater from Nuzendla Mandal, Guntur District, Andhra Pradesh, India

The continuous consumption of groundwater carrying high amount of fluoride causes dental and skeletal fluorosis to humans. Excessive fluoride concentrations in groundwater have been reported in 25 nations including India where 14 states are facing fluoride problem. In view of this, an attempt has been made to find out the fluoride content in the groundwater and impact on the people. Nuzendla mandal, Guntur district is the present study area which is identified as one of the drought prone and fluoride incidence mandals of Andhra Pradesh. Groundwater samples from different hydro-geological set-up have been collected during pre- and post-monsoon seasons and determined for various physico-chemical parameters. About 62% and 68% of the samples collected respectively during pre-and post-monsoon seasons are exceeding the safe limit of 1.5 Mg/L of Fluoride. The chemical data of the groundwater shows positive correlation between F^- & pH; F^- & Na⁺; F^- & HCO₃^- whereas negative correlation is observed between F^- & Mg²⁺; F^- & Ca²⁺. Probable sources of fluoride are weathering and leaching of fluoride bearing minerals under the alkaline environment along with high rate of evaporation and longer residence time of water. Correlation matrix also supports the above observations.