Cycling of redox-sensitive trace metals in barrier island freshwater lenses.
Cycling of redox-sensitive trace metals in barrier island freshwater lenses.
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DOI：
10.1016/j.scitotenv.2021.144964
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发表时间：
2021-05
期刊：
影响因子：
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通讯作者：
Anja Reckhardt;Stephan L. Seibert;T. Holt;J. Ahrens;M. Beck;G. Massmann;H. Brumsack
中科院分区：
文献类型：
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作者：
Anja Reckhardt;Stephan L. Seibert;T. Holt;J. Ahrens;M. Beck;G. Massmann;H. Brumsack
淡水透镜体通过岛屿边缘的地下水排放连接陆地和海洋领域，并作为饮用水资源。我们研究了氧化还原敏感的金属U，Mo，V，和Tl沿着的氧化还原梯度的新鲜地下水透镜体Spiekeroog岛，北方德国。地下水溶质浓度与地下水年龄和氧化还原特性有关。我们进一步量化的降水，海喷雾，含水层基质的地下水金属浓度的贡献，并评估的汇和源功能的含水层在好氧和还原conditions.We发现，地球化学过程改变了微量金属的浓度。在年轻的，氧气硝酸盐还原区，含水层基质代表了地下水的主要金属来源。对于T1，雨水是一个额外的重要（人为）来源。在锰和铁的氧化物硫酸盐还原条件下，U和Tl是敏感的氧化还原依赖的去除，而Mo和V的还原沉淀/吸附的影响较小。详细地，与来自较少还原区的值相比，99%的溶解的Tl、88%的U、66%的Mo和44%的V被去除到固相。施皮克鲁格岛西部淡水透镜的大部分是缺氧的。因此，通过淡水地下水排放向海洋输送含水层衍生金属的情况似乎有限。在斯皮克鲁格岛东部目前发育的新生淡水透镜中观察到较高的U、Mo、V和TI浓度。这表明，减少地下水透镜体可能是这些金属到邻近的海滩/沿海海水的来源。特别是对于V，桑迪沿海含水层的淡水排放可能是重要的，因为在好氧和缺氧条件下地下水浓度超过海水浓度。关于淡水作为饮用水的适宜性，所有测得的痕量金属浓度均被归类为非关键性。
Freshwater lenses connect the terrestrial and marine realm via groundwater discharge at the edges of islands and serve as drinking water resources. We studied the redox-sensitive metals U, Mo, V, and Tl along the redox gradient of fresh groundwater lenses on Spiekeroog Island, northern Germany. Groundwater solute concentrations were linked to groundwater age and redox characteristics. We further quantified the contribution of precipitation, sea spray, and aquifer matrix to the groundwater metal concentrations and evaluated the sink and source function of the aquifer under oxic and reducing conditions.We found that biogeochemical processes altered the concentrations of the trace metals. In young, oxygen to nitrate reducing zones, the aquifer matrix represented the major metal source to the groundwater. For Tl, rain was an additional important (anthropogenic) source. Under manganese and iron oxide to sulfate reducing conditions, U and Tl were sensitive to redox dependent removal, whereas Mo and V were less affected by reductive precipitation/adsorption. In detail, 99% of dissolved Tl, 88% of U, 66% of Mo, and 44% of V were removed to the solid phase in comparison to values from less reducing zones. Large parts of the western freshwater lens on Spiekeroog were anoxic. For this reason, the delivery of aquifer derived metals to the ocean via fresh groundwater discharge appeared to be limited. Higher U, Mo, V, and Tl concentrations were observed in the presently developing young freshwater lens in the east of Spiekeroog Island. This suggests that less reducing groundwater lenses may be a source of these metals to the adjacent beach/coastal seawater. Especially for V, freshwater discharge from sandy coastal aquifers may be important, as groundwater concentrations exceeded seawater concentration under oxic as well as anoxic conditions. Regarding the suitability of the freshwater as drinking water, all measured trace metal concentrations were classified as uncritical.