Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, Unité Mixte de Recherche 8212 (CEA-CNRS-UVSQ), Université Paris-Saclay, F-91198, Gif-sur-Yvette, France.
CEA, DAM, DIF, F-91297, Arpajon, France.
Environ Pollut. 2018 Sep;240:167-176. doi: 10.1016/j.envpol.2018.04.094. Epub 2018 May 4.
The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident resulted in a significant release of radionuclides that were deposited on soils in Northeastern Japan. Plutonium was detected at trace levels in soils and sediments collected around the FDNPP. However, little is known regarding the spatial-temporal variation of plutonium in sediment transiting rivers in the region. In this study, plutonium isotopic compositions were first measured in soils (n = 5) in order to investigate the initial plutonium deposition. Then, plutonium isotopic compositions were measured on flood sediment deposits (n = 12) collected after major typhoon events in 2011, 2013 and 2014. After a thorough radiochemical purification, isotopic ratios (Pu/Pu, Pu/Pu and Pu/Pu) were measured with a Multi-Collector Inductively Coupled Mass Spectrometer (MC ICP-MS), providing discrimination between plutonium derived from global fallout, from atmospheric nuclear weapon tests, and plutonium derived from the FDNPP accident. Results demonstrate that soils with the most Fukushima-derived plutonium were in the main radiocaesium plume and that there was a variable mixture of plutonium sources in the flood sediment samples. Plutonium concentrations and isotopic ratios generally decreased between 2011 and 2014, reflecting the progressive erosion and transport of contaminated sediment in this coastal river during flood events. Exceptions to this general trend were attributed to the occurrence of decontamination works or the remobilisation of contaminated material during typhoons. The different plutonium concentrations and isotopic ratios obtained on three aliquots of a single sample suggest that the Fukushima-derived plutonium was likely borne by discrete plutonium-containing particles. In the future, these particles should be isolated and further characterized in order to better understand the fate of this long-lived radionuclide in the environment.
福岛第一核电站（FDNPP）事故导致放射性核素大量释放，这些核素沉积在日本东北部的土壤中。在 FDNPP 周围采集的土壤和沉积物中检测到了痕量的钚。然而，对于该地区过境河流沉积物中钚的时空变化知之甚少。在这项研究中，首先测量了土壤（n=5）中的钚同位素组成，以研究初始钚沉积。然后，在 2011 年、2013 年和 2014 年发生的主要台风事件后，测量了洪水沉积物沉积物（n=12）中的钚同位素组成。经过彻底的放射化学纯化后，使用多收集器电感耦合质谱仪（MC ICP-MS）测量同位素比（Pu/Pu、Pu/Pu 和 Pu/Pu），可区分来自全球沉降、大气核武器试验和 FDNPP 事故的钚。结果表明，受福岛影响最大的钚存在于主要放射性铯羽流中，而洪水沉积物样本中存在来源多样的钚。2011 年至 2014 年间，钚浓度和同位素比普遍下降，反映了在洪水事件期间，受污染的沉积物在这条沿海河流中的逐渐侵蚀和输送。这种总体趋势的例外归因于去污工作的发生或台风期间受污染物质的再移动。从单个样本的三个等分样品中获得的不同钚浓度和同位素比表明，福岛产生的钚可能由离散的含钚颗粒携带。将来，应将这些颗粒分离并进一步表征，以更好地了解这种长寿命放射性核素在环境中的归宿。
