Fluoride Hazard and Risk Enumeration of Hard Rock Unconfined Aquifers in the Extended Part of Chhota Nagpur Gneissic Complex

Abstract

Fluoride (F−) is the most electronegative and reactive micro nutrient and has no colour, taste and smell. WHO (1984) has set a range of 0.6–1.2 mg/l in drinking water. It is very essential element for strong teeth and bones in human being but beyond permissible limit, it is very harmful for human health. A field based scientific study was conducted in the year 2017 and 2018 in the district of Purulia, an extended part of Chhota Nagpur gneissic complex of North Singbhum craton. A total of 619 water samples were collected from various affected and non-affected villages and the important parameters like pH and Fe were tested within 24 hours in the laboratory. Around 1513 households with 4348 male and 3456 female from 320 villages spread over 20 blocks have been extensively surveyed, applying stratified random and quota sampling techniques. Furthermore, Likert method is applied to understand the scenario of vulnerability along with application of remote sensing and GIS techniques to prepare the digital maps. Besides, empirical equations are also computed to determine the magnitude of fluoride hazard, vulnerability and risk. The fluoride risk study (R=H+V) reveals that Puncha and Purulia II are the very high and high fluoride risk prone zone out of 20 blocks of Purulia district. Although the Singbhum craton is moderately fluoride hazard region but due to large degree of vulnerability in the recent years it has drastically changed into a high or very high fluoride risk category.