Chemical variability of sediment and groundwater in a Pleistocene aquifer of Cambodia: Implications for arsenic pollution potential
Chemical variability of sediment and groundwater in a Pleistocene aquifer of Cambodia: Implications for arsenic pollution potential
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DOI：
10.1016/j.gca.2018.11.008
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发表时间：
2019-01-15
影响因子：
5
通讯作者：
Polizzotto, Matthew L.
中科院分区：
文献类型：
--
作者：
Gillispie, Elizabeth C.;Matteson, Audrey R.;Polizzotto, Matthew L.
更新世含水层中的低砷（As）地下水很容易受到南亚和东南亚未来地质和外源砷污染的影响，威胁着数百万将其作为饮用水和灌溉水“安全来源”的人。这些含水层沉积物中铁和锰氧化物的丰度和化学反应性控制砷的发生和流动性。在本研究中，不同的沉积物样品中的As，Fe和Mn的含量从更新世含水层在柬埔寨干丹省。结合地下水分析的沉积物的实验室和光谱表征显示，沉积As的可用性和丰度在整个更新世含水层从孔隙到现场尺度各不相同。沉积物As浓度（0.47-7 μ g/g）与Fe浓度（R-2 > 0.66）的相关性比与沉积物钻井岩屑中Mn浓度（R-2 > 0.35）的相关性更强，并趋于在10 - 15 m之间达到峰值。化学提取和X-射线吸收光谱表明，大部分的As强烈吸附到含水层沉积物或共沉淀在氧化物中的As（V）的形式，但As（III）可以被发现在整个含水层的沉积物微环境。地下水化学和锰矿物学表明，更新世含水层是亚氧，平均溶解氧为1.9毫克/升（+/- 0.9毫克/升），氧化还原电位为0.155 V（+/- 0.097 V），和丰富的锰（III/IV）氧化物矿物。根据我们的研究结果，外源As的运输和地质As的释放将可能取决于本地化的地球化学过程，在一个范围内的尺度变化。总的来说，特定的Fe和Mn矿物学和含水层内的含量将最终管理作为污染的潜力，因此了解其多尺度分布和变异性是必不可少的，更好地预测未来的风险，目前低As含水层的井水质量。(C)2018爱思唯尔有限公司版权所有
Low-arsenic (As) groundwater from Pleistocene aquifers is vulnerable to future geogenic and allogenic arsenic pollution in South and Southeast Asia, threatening the millions who use it as a "safe source" of drinking and irrigation water. The abundance and chemical reactivity of iron and manganese oxides within these aquifer sediments control the occurrence and mobility of arsenic. In the present study, sediment samples varying in As, Fe, and Mn content were obtained from a Pleistocene aquifer in the Kandal Province of Cambodia. Laboratory and spectroscopic characterization of the sediment combined with groundwater analyses revealed that the availability and abundance of sedimentary As varied across a Pleistocene aquifer from the pore to field scales. Concentrations of sediment As (0.47-7 mu g/g) correlated more strongly with Fe (R-2 > 0.66) than with Mn (R-2 > 0.35) concentrations in sediment well cuttings and tended to peak between 10 and 15 m. Chemical extractions and X-ray adsorption spectroscopy indicated the majority of As was strongly adsorbed to aquifer sediments or coprecipitated in oxides in the form of As(V) but that As(III) could be found in sediment microenvironments across the aquifer. Groundwater chemistry and Mn mineralogy indicated that the Pleistocene aquifer was suboxic, with average dissolved oxygen of 1.9 mg/L (+/- 0.9 mg/L), redox potential of 0.155 V (+/- 0.097 V), and abundant Mn(III/IV) oxide minerals. According to our results, allogenic As transport and geogenic As release will likely be dictated by localized geochemical processes that vary over a range of scales. Collectively, the specific Fe and Mn mineralogy and content within aquifers will ultimately govern As pollution potential, so understanding their multi-scale distributions and variability is essential for better predicting future risks to well-water quality in currently low-As aquifers. (C) 2018 Elsevier Ltd. All rights reserved.