Integrated Science Education and Research Centre (ISERC), Institute of Science, Visva-Bharati, Santiniketan, Birbhum 731235, West Bengal, India.
Department of Environmental Science, School of Earth, Biological and Environmental Sciences, Central University of South Bihar, Gaya 824236, Bihar, India.
Sci Total Environ. 2021 Sep 15;787:147657. doi: 10.1016/j.scitotenv.2021.147657. Epub 2021 May 9.
Prevalence of nitrate in different aquifer systems is a growing environmental and public health concern. Efforts were made for the first-time to achieve a higher accuracy in health risks characterization associated with the nitrate in groundwater of the diverse aquifer systems on the residents of a semi-arid rural tract of Lower Ganga Basin using Monte Carlo Simulations and Sobol Sensitivity analyses. The nitrate levels in groundwater varied between 0 and 508.3 mg/L with a mean of 19.79 ± 32.78 mg/L and 0-435.0 mg/L with a mean of 24.44 ± 35.15 mg/L during the pre-monsoon and post-monsoon periods, respectively. About 847.12-1000.25 km area of the survey area (total area 4545 km) exhibited nitrate concentrations (C) > the pre-intervention limits (45-50 mg/L). Minor populations, especially the infants from the granite gneiss, Rajmahal traps, laterite, recent alluvial and old alluvial aquifer zones under the Central Tendency Exposure (CTE) condition and all the aquifer zones (including the Gondwana supergroup aquifer zone) under Reasonable Maximum Exposure (RME) scenarios, were characterized as being at high risks of methemoglobinemia, primarily due to ingestion of untreated nitrate contaminated groundwater. Residents of the alluvial aquifer zones of the study area were found to the most vulnerable to the groundwater nitrate toxicity through oral and dermal exposures. The study validated the prediction accuracies of different interpolation methods including the Spline, Kriging, polynomial and Inverse Distance Weighted and revealed that Kriging predicted the Spatio-seasonal variations of groundwater nitrate of the district more accurately. Sobol Sensitivity analysis revealed C and the interaction effects of C and groundwater Ingestion Rate (IR), and C and Fraction of skin area contacted with groundwater (F) as the influential parameters for oral and dermal health risks exposure models. Therefore, the study recommends to residents of the study area to consume treated groundwater to mitigate nitrate related health morbidities.
不同含水层系统中硝酸盐的存在是一个日益严重的环境和公共卫生问题。本研究首次利用蒙特卡罗模拟和 Sobol 敏感性分析，对恒河下游半干旱农村地区不同含水层系统地下水硝酸盐相关健康风险进行了更准确的评估。在季风前和季风期间，地下水中的硝酸盐水平分别在 0 到 508.3 mg/L 之间，平均值为 19.79 ± 32.78 mg/L 和 0 到 435.0 mg/L，平均值为 24.44 ± 35.15 mg/L。调查区（总面积 4545 平方公里）约有 847.12-1000.25 平方公里的地区硝酸盐浓度（C）>干预前限值（45-50mg/L）。少数人群，特别是来自片麻岩、拉贾马哈尔陷阱、红土、近期冲积层和旧冲积层含水层带的婴幼儿以及在中央趋势暴露（CTE）条件下的所有含水层带（包括冈瓦纳超群含水层带）以及在合理最大暴露（RME）情景下的所有含水层带，都具有高铁血红蛋白血症的高风险，主要是由于摄入未经处理的受硝酸盐污染的地下水。研究发现，该地区冲积层含水层带的居民最容易受到地下水硝酸盐毒性的影响，通过口服和皮肤接触暴露。该研究验证了不同插值方法的预测精度，包括样条函数、克里金、多项式和反距离加权法，发现克里金法更能准确地预测该地区地下水硝酸盐的时空变化。Sobol 敏感性分析表明，C 以及 C 与地下水摄入率（IR）和 C 与与地下水接触的皮肤面积分数（F）的交互作用是口服和皮肤健康风险暴露模型的影响因素。因此，本研究建议研究区居民饮用处理后的地下水，以减轻硝酸盐相关的健康问题。
