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    淮河流域高砷地下水的形成演化过程及其环境健康风险

    Hydrogeochemical processes and potential exposure risk of high-arsenic groundwater in Huaihe River Basin, China

    • 摘要: 砷(As)有确定的环境健康风险,饮用高砷地下水是人类遭受As暴露风险的主要途径,研究As在地下水中的分布、迁移、富集规律是世界范围的一个重要环境公共卫生问题。淮河流域是中国新发现的高砷地下水分布区域,本次以流域内典型高砷地下水域为天然实验场,通过分析地下水水文地球化学数据,解析高砷地下水的形成演化过程,追溯砷污染物的来源及溶出释放过程,评估其潜在污染风险。结果表明:As、F是影响研究区水质的主要无机化学物质,浓度分别为(5.75±5.42)μg/L、(1.29±0.40)mg/L,超过世界卫生组织饮用水推荐准则值的测试样品比例分别为23%、31%,呈现高暴露污染风险。根据水化学图解与矿物饱和指数计算,研究区地下水受蒸发作用、岩盐溶解、水岩相互作用等过程的共同影响。高砷地下水总碱度主要分布在400~700 mg/L,化学类型主要为HCO3-Na型,高砷地下水更大程度受到蒸发作用、阳离子交换作用的影响。高砷地下水的As可能源自含水层原生砷的溶出释放,含砷矿物氧化溶解与还原活化可能是高砷地下水形成的主要机制。

       

      Abstract: Arsenic (As) poses a danger to environmental health, and drinking arsenic-rich groundwater is a key exposure risk for humans. The study on distribution, migration, and enrichment of As in groundwater is an important worldwide environmental and public health problem. Huaihe River Basin is presently defined as a region of high-arsenic groundwater in China. In this study, a typical high arsenic groundwater area in the basin was selected as the natural experimental site to analyze the formation and evolution of high arsenic groundwater through the analysis of groundwater hydrogeochemical data, to trace the source and dissolution of arsenic pollutants, and evaluate the potential pollution risk. The results showed that As and F were the main inorganic chemical substances affecting the water quality in the study area, with concentrations of (5.75±5.42) μg/L and (1.29±0.40) mg/L respectively, the ratio of test samples exceeding the recommended drinking water standards of the World Health Organization by 23% and 31% respectively. According to the hydrochemical diagram and the calculation of mineral saturation indices, the groundwater in the study area underwent evaporation, halite dissolution, and water-rock interaction. The total alkalinity of high-arsenic groundwater ranged mainly between 400 and 700 mg/L, and the hydrogeochemical type was mainly of HCO3-Na. High-arsenic groundwater was largely affected by evaporation and cation exchange. Arsenic in high-arsenic groundwater derived from the dissolution and release of geogentic arsenic in aquifer. The oxidation dissolution and reduction activation of As-bearing minerals may be the main mechanism of the formation of high arsenic groundwater.

       

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