Schubert Michael, Knoeller Kay, Rocha Carlos, Einsiedl Florian
Department Groundwater Remediation, UFZ - Helmholtz Centre for Environmental Research, Leipzig, Germany,
Environ Monit Assess. 2015 Mar;187(3):105. doi: 10.1007/s10661-015-4274-3. Epub 2015 Feb 10.
Freshwater discharge into the coastal sea is of general interest for two reasons: (i) It acts as vehicle for the transport of contaminants or nutrients into the ocean, and (ii) it indicates the loss of significant volumes of freshwater that might be needed for irrigation or drinking water supply. Due to the large-scale and long-term nature of the related hydrological processes, locating and quantitatively assessing freshwater discharge into the sea require naturally occurring tracers that allow fast, inexpensive and straightforward detection. In several studies, the standard water parameters electrical conductivity (EC) and pH have proven their suitability in this regard. However, while distribution patterns of EC and pH in the coastal sea indicate freshwater discharge in general, a separation between discharging surface water and submarine groundwater discharge (SGD) is not possible with these alone. The naturally occurring radionuclide radon-222 has been shown to be useful in the quantification of SGD and its distinction from surface runoff. This study aimed to evaluate and compare the informative value of the three parameters-EC, pH and radon concentration-in detecting and quantifying SGD by carrying out a case study in a bay located in western Ireland. The results reveal that radon activity is the most sensitive parameter for detecting SGD. However, only the combined evaluation of radon, EC and pH allows a quantitative allocation of groundwater and surface water contributions to the overall freshwater discharge into the sea. This conclusion is independently supported by stable isotope data measured on selected samples.
淡水排入沿海水域受到广泛关注，原因有二：其一，它是污染物或营养物质进入海洋的载体；其二，它意味着大量可能用于灌溉或饮用水供应的淡水流失。由于相关水文过程具有大规模和长期性，要定位并定量评估排入海洋的淡水，就需要利用天然示踪剂，以便进行快速、廉价且直接的检测。在多项研究中，标准水参数电导率（EC）和pH值已证明在这方面具有适用性。然而，尽管沿海水域中EC和pH值的分布模式总体上表明有淡水排放，但仅靠这些无法区分排放的地表水和海底地下水排放（SGD）。天然存在的放射性核素氡-222已被证明在量化SGD及其与地表径流的区分方面很有用。本研究旨在通过在爱尔兰西部的一个海湾开展案例研究，评估和比较电导率、pH值和氡浓度这三个参数在检测和量化SGD方面的信息价值。结果表明，氡活度是检测SGD最敏感的参数。然而，只有对氡、EC和pH值进行综合评估，才能定量确定地下水和地表水对排入海洋的总淡水排放的贡献。这一结论得到了所选样本稳定同位素数据的独立支持。
