Geochemical appraisal of fluoride contaminated groundwater in the vicinity of a coal mining region: Spatial variability and health risk assessment

Abstract

The present study focuses on the geochemical characteristics and quality of potable groundwater in mining area, particularly with reference to fluoride (F−). Spatial variability in physicochemical parameters of groundwater samples (32) collected from Katras block coal mine area was analysed. Parameters such as total hardness, total alkalinity, calcium (Ca2+), sodium (Na+), bicarbonate (HCO3-) and concentration of fluoride (F−) were found to be exceeding the Bureau of Indian standard (BIS) guidelines. The contributions of major cations and anions were found to be in the order of Ca2+ (44 %) > Na+ (40 %) > Mg2+ (15 %) > K+ (1%) and HCO3- (50 %) > Cl− (34 %) > SO42- (14 %) respectively, and aggregates of minor anions such as nitrate and fluoride constituted approximately 2% respectively. Piper trilinear diagram suggested dominance of Ca-Mg-Cl, CaCl and NaCl type of water, resulting in hard brackish water. Alkaline pH and high bicarbonate concentration provide suitable conditions for release of fluoride from fluorite and fluorapatite. Water quality index (WQI) indicated that most of the samples (53 %) of the study area belonged to "poor water", 41 % to "good water" and one sample was categorized as "excellent" type of water. Moreover, only one sample was classified as "not suitable for drinking purposes" with WQI value of 322.94. Health risk assessment for ingestion and dermal routes were carried out for various age groups based on chronic daily dose and hazard quotient, and results indicated that fluoride uptake through ingestion was more severe. Infants (6−12 months) were found to be at a higher risk when compared to higher age group population. To improve the existing groundwater quality and reduce associated human risks, suitable water management measures is also recommended.