Most of the knowledge on the occurrence of Uranium (U) in groundwater comes from in-situ manipulation experiments in the field, computational modelling studies or from laboratory analyses where individual processes of U mobilization were studied in isolation. Because of Uranium's vital redox chemistry it interacts, often simultaneously, with many other element cycles (e.g., sulfur, carbon, iron, and manganese) making it difficult to predict U concentrations in natural environments. For the present study a large data set was analyzed to predict the occurrence of U in groundwater from basic hydrochemistry. The data set consists of more than 8000 chemical groundwater analyses (including Uranium concentrations) from more than 2000 sampling locations.A strong relation between U concentrations and electric conductivity as well as alkalinity was observed, suggesting that weathering of geogenic source material and desorption from mineral surfaces is the principle mechanism of U release. Except for aquifers with strongly reducing conditions this process leads to a slow but continuous accumulation of U in groundwater in most cases. Importantly, the occurrence of U is modulated by the prevailing redox conditions in an aquifer. Uranium concentrations were moderate under oxic conditions and highest under Manganese-und Nitrate-reducing conditions (heterotrophic as wells as autotrophic nitrate reduction). Only in iron- and sulfate-reducing groundwater the probability of U concentrations above 1 μg l⁻¹ was virtually zero, as these ground waters act as U sinks.The combination of mineral weathering (especially carbonates) with mobilization of U under manganese and nitrate reducing conditions results in the highest risk of detecting U. In contrast, a low risk is associated with low pH (<7) and low mineralization of groundwater, which is the case in granitic catchments, for example. Our results further provide evidence, that agricultural practices such as liming, fertilizer inputs and irrigation influence the occurrence of U in groundwater in multiple ways. Accurate management of aquifers underlying farmland will therefore become more and more important in the future. In summary, we find that the vulnerability of an aquifer to elevated U concentrations cannot be explained by a single factor. This complicates affords to target elevated U concentrations in groundwaters that are abstracted for drinking water production.

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地下水中的铀–基于大型水文地球化学数据集的概要

有关地下水中铀（U）发生的大多数知识来自现场的现场操作实验，计算模型研究或实验室分析，这些研究单独研究了铀动员的各个过程。由于铀的重要氧化还原化学作用，它经常与许多其他元素循环（例如，硫，碳，铁和锰）相互作用，因此很难预测自然环境中的U浓度。对于本研究，分析了一个大数据集，以预测基本水化学作用在地下水中U的发生。该数据集包含来自2000多个采样点的8000多种化学地下水分析（包括铀浓度）。铀浓度与电导率以及碱度之间存在很强的关系，这表明地源物质的风化和矿物表面的脱附是铀释放的主要机理。除了条件大大降低的含水层外，在大多数情况下，该过程都会导致U在地下水中缓慢而连续地积累。重要的是，U的发生受到含水层中主要的氧化还原条件的调节。在有氧条件下，铀浓度中等，在还原锰和减少硝酸盐的条件下（异养以及硝酸盐自养），铀的浓度最高。仅在还原铁和硫酸盐的地下水中，U浓度高于1μgl的可能性 这表明，地源物质的风化和矿物表面的解吸是铀释放的主要机理。除了条件大大降低的含水层外，在大多数情况下，该过程都会导致U在地下水中缓慢而连续地积累。重要的是，U的发生受到含水层中主要的氧化还原条件的调节。在有氧条件下，铀浓度中等，在还原锰和减少硝酸盐的条件下（异养以及硝酸盐自养），铀的浓度最高。仅在还原铁和硫酸盐的地下水中，U浓度高于1μgl的可能性 这表明，地源物质的风化和矿物表面的解吸是铀释放的主要机理。除了条件大大降低的含水层外，在大多数情况下，该过程都会导致U在地下水中缓慢而连续地积累。重要的是，U的发生受到含水层中主要的氧化还原条件的调节。在有氧条件下，铀浓度中等，在还原锰和减少硝酸盐的条件下（异养以及自养硝酸盐还原），铀的浓度最高。仅在还原铁和硫酸盐的地下水中，U浓度高于1μgl的可能性 U的存在受含水层中主要的氧化还原条件调节。在有氧条件下，铀浓度中等，在还原锰和减少硝酸盐的条件下（异养以及硝酸盐自养），铀的浓度最高。仅在还原铁和硫酸盐的地下水中，U浓度高于1μgl的可能性 U的存在受含水层中主要的氧化还原条件调节。在有氧条件下，铀浓度中等，在还原锰和减少硝酸盐的条件下（异养以及硝酸盐自养），铀的浓度最高。仅在还原铁和硫酸盐的地下水中，U浓度高于1μgl的可能性^-1几乎为零，因为这些地下水充当了U汇。矿物风化（尤其是碳酸盐）与在锰和硝酸盐还原条件下迁移U的结合，导致发现U的风险最高。相反，低风险与pH低（<7）和地下水矿化度低，例如在花岗岩集水区就是这种情况。我们的结果进一步提供了证据，证明诸如撒石灰，肥料输入和灌溉等农业实践会以多种方式影响地下水中U的发生。因此，在未来，精确管理底层农田的含水层将变得越来越重要。总而言之，我们发现含水层对U浓度升高的脆弱性无法用单个因素来解释。