Singh Chander Kumar, Mukherjee Saumitra
Department of Natural Resources, TERI University, New Delhi, 110070, India,
Environ Sci Pollut Res Int. 2015 Feb;22(4):2668-78. doi: 10.1007/s11356-014-3504-5. Epub 2014 Sep 9.
Fluoride-enriched water has become a major public health issue in India. The present study tries to evaluate the geochemical mechanism of fluoride enrichment in groundwater of western India. Total 100 groundwater samples were collected for the study spreading across the entire study area. The results of the analyzed parameters formed the attribute database for geographical information system (GIS) analysis and final output maps. A preliminary field survey was conducted and fluoride testing was done using Hach make field kits. The fluoride concentration ranges from 0.08 to 6.6 mg/L (mean 2.4 mg/L), with 63 % of the samples containing fluoride concentrations that exceed the World Health Organization (WHO) drinking water guideline value of 1.5 mg/L and 85 % samples exceeding the Bureau of Indian Standards (BIS) guidelines of 1 mg/L. The study also reveals high concentration of nitrate that is found to be above WHO standrads. The dominant geochemical facies present in water are Na-Cl-HCO3 (26 samples), Na-Ca-Cl-HCO3 (20 samples), Na-Cl (14 samples), and Na-Ca-Mg-Cl-HCO3 (11 samples); however, sodium and bicarbonate being the major component in all the water types of 100 samples, which in fact has a tendency to increase fluoride concentration in water by dissolving fluoride from fluorite. The thermodynamic considerations between the activities of calcium, fluoride, and bicarbonate suggest that fluoride concentration is being governed by activity of calcium ion. X-ray diffraction analysis of sediments reveals calcite and fluorite are the main solubility-control minerals controlling the aqueous geochemistry of high fluoride groundwater. The results indicate that the fluoride concentration in groundwater is mainly governed by geochemical composition of rocks, such as metamorphic granites and sedimentary rocks, alkaline hydrogeological environment, climatic conditions, high temperature and lesser rainfall, and geochemical processes such as weathering, evaporation, dissolution, and ion exchange.
富氟水已成为印度的一个主要公共卫生问题。本研究试图评估印度西部地下水中氟富集的地球化学机制。为开展该研究，在整个研究区域共采集了100个地下水样本。分析参数的结果构成了地理信息系统（GIS）分析的属性数据库和最终输出地图。进行了初步的实地调查，并使用哈希牌现场检测试剂盒进行了氟含量检测。氟浓度范围为0.08至6.6毫克/升（平均2.4毫克/升），63%的样本氟浓度超过世界卫生组织（WHO）饮用水指导值1.5毫克/升，85%的样本超过印度标准局（BIS）1毫克/升的指导值。该研究还揭示了硝酸盐浓度很高，超过了WHO标准。水中主要的地球化学相为Na-Cl-HCO3（26个样本）、Na-Ca-Cl-HCO3（20个样本）、Na-Cl（14个样本）和Na-Ca-Mg-Cl-HCO3（11个样本）；然而，钠和碳酸氢根是100个样本中所有水类型的主要成分，实际上它们有通过从萤石中溶解氟来增加水中氟浓度的趋势。钙、氟和碳酸氢根活度之间的热力学考量表明，氟浓度受钙离子活度控制。沉积物的X射线衍射分析表明，方解石和萤石是控制高氟地下水水地球化学的主要溶解度控制矿物。结果表明，地下水中的氟浓度主要受岩石的地球化学组成（如变质花岗岩和沉积岩）、碱性水文地质环境、气候条件、高温少雨以及风化、蒸发、溶解和离子交换等地球化学过程的控制。
