Department of Environmental Studies, Institute of Science, Visva-Bharati, Santiniketan, 731235, Birbhum, West Bengal, India.
Department of Environmental Studies, Institute of Science, Visva-Bharati, Santiniketan, 731235, Birbhum, West Bengal, India.
Environ Pollut. 2020 Mar;258:113646. doi: 10.1016/j.envpol.2019.113646. Epub 2019 Nov 22.
High concentration of fluoride (up to 20.9 mg/L) in groundwater with significant variation (p = 5.9E-128) among samples was reported from Birbhum district, an acknowledged fluoride endemic region in India. The groundwater samples (N = 368) were grouped based on their hydrochemical properties and aquifer geology for hydro-geochemical characterization. Friedman's test showed p < 0.0001 confidence level which indicates that fluoride concentration among geological groups and water groups are independent. Bland-Altman plot was used to study the inter-relationships among the groups through bias value (∂) and limit of agreement (LoA). Among the geological groups, laterites and granite-gneiss groups exhibited statistically significantly difference in fluoride geochemistry; whereas the younger and older alluvium groups displayed similar characteristics. The fluoride concentration was found to be in the order Lateritic > Granite-gneiss > Older alluvium ≥ Younger alluvium. Dissolution of minerals (such as fluorite, biotite) in laterite sheeted basalt, and granite-gneiss is the main source of groundwater fluoride in the region. Fluoride concentration is also influenced by depth of water table. Hydrochemical study indicated that fluoride concentration was higher in Na-HCO than in Ca-SO and Ca-HCO type of groundwater. The fluoride concentration were positively correlated with Na and pH and negatively correlated with the Ca and Mg signifying linkage with halite dissolution and calcite, dolomite precipitation. Geostatistical mapping of WQI through empirical bayesian kriging (EBK) with respect to regional optimal guideline value (0.73 mg/L) classified that groundwater in some parts of the district are unfit for drinking purpose. Health survey (N = 1767) based on Dean's criteria for dental fluorosis indicated presence of slight to moderate dental hazard. Besides, providing baseline data for management of groundwater quality in the study area, the study demonstrated the applicability of Bland-Altman analysis and empirical bayesian kriging (EBK) in delineation and interpolation of fluoride contaminated region.
在印度被公认为氟中毒流行地区的比尔邦（Birbhum）地区，报道了地下水中氟化物浓度高（高达 20.9mg/L），且样本间存在显著差异（p=5.9E-128）。根据其水文化学特性和含水层地质，将地下水样本（N=368）分为若干组进行水文地球化学特征描述。弗里德曼检验表明置信度水平 p<0.0001，这表明地质组和水样组之间的氟浓度是独立的。 Bland-Altman 图用于通过偏差值（∂）和一致性界限（LoA）研究组间的相互关系。在地质组中，红土和花岗岩-片麻岩组的氟地球化学特征存在统计学显著差异；而较年轻和较古老的冲积组则表现出相似的特征。氟浓度的顺序为红土>花岗岩-片麻岩>较老的冲积物>较年轻的冲积物。红土状玄武岩和花岗岩-片麻岩中的矿物（如萤石、黑云母）的溶解是该地区地下水氟化物的主要来源。地下水位深度也会影响氟浓度。水文化学研究表明，在 Na-HCO 型地下水的氟浓度高于 Ca-SO 和 Ca-HCO 型地下水。氟浓度与 Na 和 pH 呈正相关，与 Ca 和 Mg 呈负相关，这表明与岩盐溶解和方解石、白云石沉淀有关。根据区域最佳指导值（0.73mg/L），通过经验贝叶斯克里金（EBK）对水质指数（WQI）进行地质统计学绘图，将该地区部分地区的地下水分类为不适合饮用。根据 Dean 对氟斑牙的标准进行的健康调查（N=1767）表明，存在轻微到中度的牙齿危害。此外，该研究为该地区地下水质量的管理提供了基线数据，还证明了 Bland-Altman 分析和经验贝叶斯克里金（EBK）在氟污染区域的划分和插值中的适用性。
