Laboratoire d'Etudes Radioécologiques en milieu Continental et Marin (LERCM), Institut de Radioprotection et de Sûreté Nucléaire (IRSN), Saint-Paul-lez-Durance, France.
Laboratoire d'Etudes Radioécologiques en milieu Continental et Marin (LERCM), Institut de Radioprotection et de Sûreté Nucléaire (IRSN), Saint-Paul-lez-Durance, France.
Sci Total Environ. 2015 Jan 1;502:122-32. doi: 10.1016/j.scitotenv.2014.08.082. Epub 2014 Sep 25.
Delivery of suspended sediment from large rivers to marine environments has important environmental impacts on coastal zones. In France, the Rhone River (catchment area of 98,000 km(2)) is by far the main supplier of sediment to the Mediterranean Sea and its annual solid discharge is largely controlled by flood events. This study investigates the relevance of alternative and original fingerprinting techniques based on the relative abundances of a series of radionuclides measured routinely at the Rhone River outlet to quantify the relative contribution of sediment supplied by the main tributaries during floods. Floods were classified according to the relative contribution of the main subcatchments (i.e., Oceanic, Cevenol, extensive Mediterranean and generalised). Between 2000 and 2012, 221 samples of suspended sediment were collected at the outlet and were shown to be representative of all flood types that occurred during the last decade. Three geogenic radionuclides (i.e., (238)U, (232)Th and (40)K) were used as fingerprints in a multivariate mixing model in order to estimate the relative contribution of the main subcatchment sources-characterised by different lithologies-in sediment samples collected at the outlet. Results showed that total sediment supply originating from Pre-Alpine, Upstream, and Cevenol sources amounted to 10, 7 and 2.10(6)tons, respectively. These results highlight the role of Pre-Alpine tributaries as the main sediment supplier (53%) to the Rhone River during floods. Other fingerprinting approaches based on artificial radionuclide activity ratios (i.e., (137)Cs/(239+240)Pu and (238)Pu/(239+240)Pu) were tested and provided a way to quantify sediment remobilisation or the relative contributions of the southern tributaries. In the future, fingerprinting methods based on natural radionuclides should be further applied to catchments with heterogeneous lithologies. Methods based on artificial radionuclides should be further applied to catchments characterised by heterogeneous post-Chernobyl (137)Cs deposition or by specific releases of radioactive effluents.
从大河向海洋环境输送悬浮泥沙对沿海地区有着重要的环境影响。在法国，罗纳河（流域面积 98000 平方公里）是向地中海输送泥沙的主要河流，其年固体排放量在很大程度上受洪水事件的控制。本研究通过在罗纳河出口处常规测量一系列放射性核素的相对丰度，探讨了基于替代和原始示踪技术的相关性，以量化洪水期间主要支流供应的泥沙的相对贡献。洪水根据主要子流域（即海洋、塞文、广泛的地中海和广义）的相对贡献进行分类。2000 年至 2012 年，在出口处采集了 221 个悬浮泥沙样本，结果表明这些样本代表了过去十年中发生的所有洪水类型。三种地球成因放射性核素（即 (238)U、(232)Th 和 (40)K）被用作多元混合模型中的示踪剂，以估计出口处采集的泥沙样本中主要子流域源的相对贡献-具有不同的岩性。结果表明，源自前阿尔卑斯山、上游和塞文的总沉积物供应分别为 10、7 和 2.10(6)吨。这些结果强调了前阿尔卑斯山支流作为罗纳河洪水期间主要沉积物供应源（53%）的作用。其他基于人工放射性核素活度比（即 (137)Cs/(239+240)Pu 和 (238)Pu/(239+240)Pu）的示踪方法也进行了测试，并提供了量化泥沙再悬浮或南部支流相对贡献的方法。在未来，基于天然放射性核素的示踪方法应进一步应用于具有异质岩性的流域。基于人工放射性核素的方法应进一步应用于具有不均匀的切尔诺贝利后 (137)Cs 沉积或放射性废水特定排放的流域。
