Laboratoire de Radioécologie de Cherbourg-Octeville (LRC), IRSN, 50130 Cherbourg-Octeville, France; Université de Caen-Basse Normandie, Laboratoire M2C, UMR CNRS 6143, 14032 Caen, France.
J Environ Radioact. 2013 Dec;126:20-31. doi: 10.1016/j.jenvrad.2013.06.005. Epub 2013 Aug 7.
Sediment cores were collected at the outlet of the highly anthropogenized catchment of the Seine River at two contrasting sites: a flood plain of the lower Seine River and a quasi-permanently submerged harbour basin (or wet dock) in the upper tidal estuary. Analyses of artificial radionuclides ((137)Cs and plutonium isotopes), coupled with hydrological and bathymetric data, lead to a precise dating of the sediment cores collected at the two sites. (137)Cs signals originating from global fallout (early 1960s) and from the Chernobyl accident (1986) are identified, but at different levels due to the incomplete nature or variable continuity of the records. Anomalous (238)Pu concentrations found at both sites (1-2 Bq kg(-1)) are attributed to unknown industrial releases originating from upstream. Interpolating (137)Cs sediment activities under the assumption of a constant sediment rate, those releases were dated back to 1975 ± 1, thus providing a local but reliable time-marker. Age models have highlighted a very contrasting sediment filling dynamics in these two sites. This study presents the first sediment record of alpha- and gamma-emitting artificial radionuclides obtained at the outlet of the huge catchment area of the River Seine, over a period covering the last 50 years.
一个是下塞纳河的洪泛平原，另一个是上潮汐河口的准永久性淹没港池（或湿船坞）。对人工放射性核素（(137)Cs 和钚同位素）的分析，结合水文学和水深数据，对在两个地点采集的沉积物岩芯进行了精确的年代测定。确定了源自全球沉降（20 世纪 60 年代初）和切尔诺贝利事故（1986 年）的(137)Cs 信号，但由于记录的不完全性或可变连续性，其水平不同。两个地点都发现了异常的(238)Pu 浓度（1-2 Bq kg(-1)），归因于上游未知工业排放。在假设沉积速率恒定的情况下对(137)Cs 沉积物活动进行插值，这些排放可追溯到 1975 ± 1 年，从而提供了一个局部但可靠的时间标记。年龄模型突出了这两个地点沉积物填充动力学的非常不同。本研究首次提供了在过去 50 年期间，在塞纳河流域巨大集水区出口处获得的α和γ发射人工放射性核素的沉积物记录。
