Hydrogeochemical Assessment to Explore the Extent, Nature and Source of Fluoride Contamination within the Groundwaters of the Panda River Basin, Sonbhadra District, Uttar Pradesh, India

Abstract

Significant amounts of fluoride are found in the abstracted groundwater of the southern part of the Upper Panda River basin, Sonbhadra district, Uttar Pradesh, India. Hence groundwater with high fluoride and water mixture patterns were studied in Panda River basin through hydrochemical interpretation from 65 groundwater chemical data information from different wells for both the seasons, premonsoon and postmonsoon. The chemical relationship and Gibbs diagram suggest that the groundwaters mainly belong to freshwater, alkali type and are controlled by rock dominance; due to influence of semi arid condition and water-rock interaction. Na-HCO₃ is dominated in most part (60 % of the total number of water samples for both the seasons) of the study area. The whole environment is favorable for the fluoride dissolution as the increasing Na concentrations are observed under alkaline conditions with a subsequent reduction in Ca concentration. Major rock types of the area are phyllites and granite gneissic rocks. Geochemical study reveals that Fluor-apatite and biotite mica in the granite gneissic rock is the main source of fluoride in the groundwater through water–rock interactions. Fluoride concentrations are in the range 0.4–5.6 mg/L in the pre-monsoon season and 0.1–6.7 mg/L in the post-monsoon season. Ion exchange, dissolution, semi-arid climate, alkaline conditions and weathering are responsible for fluoride enrichment in the groundwater of the study area.