School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083, China.
School of Water Resources and Environment, China University of Geosciences (Beijing), Beijing 100083, China.
Water Res. 2022 Jul 1;219:118530. doi: 10.1016/j.watres.2022.118530. Epub 2022 May 1.
The mechanisms controlling arsenic (As) enrichment and mobilization associated with human health risk assessment of groundwater in the Longdong Basin, located in the southern part of the Loess Plateau, China, have been yet unexplained. This uncertainty is partly attributed to a poor understanding of groundwater arsenic management. To address this problem, this study investigated the occurrence and spatial distribution of As in unconfined groundwater (UG) and confined groundwater (CG) in the study area, integrated Self-Organizing Maps (SOM) and geochemical modeling to elucidate the mechanisms controlling As release and mobilization in groundwater, and conducted a health risk assessment of groundwater As. The results showed that 13.6% of UG samples (n = 66) and 22.4% of CG samples (n = 98) exceeded the WHO guideline limit of As (10 μg/L). The detailed hydrogeochemical studies showed that As-enrichment groundwater is dominated by Cl-Na type, and Gaillardet diagram indicated that evaporites weathering may contribute to As mobilization in CG. The SOM analysis combined with Spearman's correlation coefficient quantified the negative correlation between As and redox potential, dissolved oxygen, SO, NO, and the positive correlation between As and HCO, Mn in UG. In CG, As is positively correlated to pH and negatively to electrical conductivity, SO, Fe and Mn. The saturation indices of the mineral phases indicates an insignificant relationship between As and Fe. We conclude that under oxidizing conditions, evaporative controls and the desorption of Fe-oxides under alkaline and high salinity conditions are the dominant mechanisms controlling As release and mobilization in groundwater. In addition, exposure to groundwater As through drinking water posed potential risk of carcinogenic and non-carcinogenic effects on children and adults. This study contributes to groundwater As management and sustainable safe groundwater supply.
中国黄土高原南部的陇东盆地，其地下水中的砷（As）富集和迁移与人类健康风险评估相关的机制尚未得到解释。这种不确定性部分归因于对地下水砷管理的了解不足。为了解决这个问题，本研究调查了研究区无约束地下水（UG）和约束地下水（CG）中砷的存在和空间分布，综合自组织映射（SOM）和地球化学模拟来阐明地下水砷释放和迁移的控制机制，并对地下水砷进行了健康风险评估。结果表明，13.6%的 UG 样本（n=66）和 22.4%的 CG 样本（n=98）超过了世界卫生组织（WHO）规定的砷（10μg/L）指导限值。详细的水文地球化学研究表明，富砷地下水主要为 Cl-Na 型，Gaillardet 图表明蒸发岩风化可能导致 CG 中砷的迁移。SOM 分析结合 Spearman 相关系数定量描述了 UG 中砷与氧化还原电位、溶解氧、SO、NO 呈负相关，与 HCO、Mn 呈正相关。CG 中，砷与 pH 呈正相关，与电导率、SO、Fe 和 Mn 呈负相关。矿物相的饱和度指数表明砷与 Fe 之间的关系不显著。我们得出结论，在氧化条件下，蒸发作用控制和碱性高盐条件下 Fe 氧化物的解吸是控制地下水砷释放和迁移的主要机制。此外，通过饮用水接触地下水砷可能对儿童和成人造成致癌和非致癌影响的潜在风险。本研究有助于地下水砷管理和可持续安全地下水供应。
