Statistical and Geochemical Evaluation of Fluoride-rich Groundwater from North Coastal Part of Odisha

Abstract

The chemistry of the groundwater of north coastal part of Odisha is primarily controlled by weathering of minerals present in basement rocks superimposed by anthropogenic activities and sea water intrusion. The water is hard and alkaline in nature, but most of the constituent ions excluding F^- are within permissible limits for human consumption. Four factors satisfying over 86% of the total variance and three clusters corresponding to geogenic, alkaline and anthropogenic processes have been identified. Ca²⁺, Mg²⁺, Na⁺, K⁺, F⁻, CO₃²⁻ and HCO₃⁻ are geogenic, contributed by the basement rocks and soils. Cl⁻, SO₄⁻ and NO₃⁻ are anthropogenic, derived from haphazard household waste disposal, overflows of septic tanks, return flow from irrigation, animal wastes, manures, soil conditioners and chemical fertilizers. K⁺ and F⁻ belong to both the categories while Na⁻ and Cl⁻ are contributed by saline intrusion to some extent. The pH, total alkalinity and F⁻ represent alkaline component, while HCO₃⁻ is derived from weathering of minerals and influence of atmospheric CO₂. Change of groundwater types from Ca-HCO₃ (fresh water) → Ca-Mg-Cl → Na-Cl (saline water) as well as increase of total dissolved solids in seaward direction indicates the effect of seawater intrusion in the study area. Sympathetic relationship of F” with total alkalinity, pH and Na⁺ as well as negative correlation with Ca²⁺ suggest the prevalence of alkaline environment that favors dissolution of fluoride minerals of the basement rocks. It is suggested to minimize the anthropogenic activities like haphazard waste disposal and excessive use of agrochemicals, adopt artificial recharge measures, take up regular groundwater quality check and aware the public for proper management of groundwater resource in the study area.