Seaborg Institute, Lawrence Livermore National Laboratory, Livermore, CA, 94550, United States.
Seaborg Institute, Lawrence Livermore National Laboratory, Livermore, CA, 94550, United States.
Chemosphere. 2022 Dec;308(Pt 1):136240. doi: 10.1016/j.chemosphere.2022.136240. Epub 2022 Aug 31.
Since 1952, liquid radioactive effluent containingPu, Am, Np, Cs, and Tc has been released with authorization from the Sellafield nuclear complex (UK) into the Irish Sea. This represents the largest source of plutonium (Pu) discharged in all western Europe, with 276 kg having been released. In the Eastern Irish Sea, the majority of the transuranic activity has settled into an area of sediments (Mudpatch) located off the Cumbrian coast. Radionuclides from the Mudpatch have been re-dispersed via particulate transport in fine-grained estuarine and intertidal sediments to the North-East Irish Sea, including the intertidal saltmarsh located at the mouth of the Esk Estuary. Saltmarshes are highly dynamic systems which are vulnerable to external agents (sea level change, erosion, sediment supply, and freshwater inputs), and their stability remains uncertain under current sea level rise projections and possible increases in storm activity. In this work, we examined factors affecting Pu mobility in contaminated sediments collected from the Esk Estuary by conducting leaching experiments under both anoxic and oxic conditions. Leaching experiments were conducted over a 9-month period and were periodically sampled to determine solution phase Pu via multicollector-inductively coupled plasma-mass spectrometry (MC-ICP-MS), and to measure redox indicators (Eh, pH and extractable Fe(II)). Microbial community composition was also characterized in the sediments, and at the beginning and end of the anoxic/oxic experiments. Results show that: 1) Pu leaching is about three times greater in solutions leached under anoxic conditions compared to oxic conditions, 2) the sediment slurry microbial communities shift as conditions change from anoxic to oxic, 3) Pu leaching is enhanced in the shallow sediments (0-10 cm depth), and 4) the magnitude of Pu leached from sediments is not correlated with total Pu, indicating that the biogeochemistry of sediment-associated Pu is spatially heterogeneous. These findings provide constraints on the stability of redox sensitive Pu in biogeochemically dynamic/transient environments on a timescale of months and suggests that anoxic conditions can enhance Pu mobility in estuarine systems.
自 1952 年以来，经授权，含有 Pu、Am、Np、Cs 和 Tc 的液态放射性废水已从塞拉菲尔德核设施（英国）排入爱尔兰海。这是整个西欧排放的钚（Pu）的最大来源，已排放了 276 公斤。在爱尔兰海东部，大部分超铀放射性物质已沉降到位于坎布里亚海岸附近的沉积物区（泥斑区）。来自泥斑区的放射性核素通过细颗粒港湾和潮间带沉积物中的颗粒输送再次分散到东北爱尔兰海，包括埃斯克河口的潮间盐沼。盐沼是高度动态的系统，容易受到外部因素（海平面变化、侵蚀、沉积物供应和淡水输入）的影响，在当前海平面上升预测和风暴活动可能增加的情况下，其稳定性仍不确定。在这项工作中，我们通过在缺氧和有氧条件下进行浸出实验，研究了从埃斯克河口采集的受污染沉积物中 Pu 迁移的影响因素。浸出实验进行了 9 个月，并定期取样，通过多接收电感耦合等离子体质谱法（MC-ICP-MS）测定溶液相中 Pu，并测量氧化还原指标（Eh、pH 和可提取的 Fe（II））。沉积物中的微生物群落组成也进行了表征，并在缺氧/有氧实验的开始和结束时进行了表征。结果表明：1）与有氧条件相比，缺氧条件下浸出的 Pu 浸出量增加了约三倍；2）随着条件从缺氧变为有氧，沉积物泥浆微生物群落发生变化；3）浅层沉积物（0-10cm 深度）中的 Pu 浸出量增加；4）从沉积物中浸出的 Pu 量与总 Pu 量没有相关性，表明与沉积物相关的 Pu 的生物地球化学性质在空间上是不均匀的。这些发现限制了在数月时间尺度上生物地球化学动态/瞬变环境中氧化还原敏感 Pu 的稳定性，并表明缺氧条件可以增强港湾系统中 Pu 的迁移能力。
