Gunma Prefectural Fisheries Experiment Station, Japan.
Gunma Prefectural Fisheries Experiment Station, Japan.
Sci Total Environ. 2018 May 1;622-623:1153-1164. doi: 10.1016/j.scitotenv.2017.12.017. Epub 2017 Dec 13.
Understanding ecosystem dynamics of radionuclides is necessary to ensure effective management for food safety. The Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident on March 11, 2011 released large amounts of radiocesium (Cs and Cs) and contaminated the environment across eastern Japan. In this study, we aimed to elucidate the temporal dynamics of Cs in the aquatic ecosystem of Lake Onuma on Mt. Akagi. The effective ecological half-life (T) of Cs in fishes, western waterweed (Elodea nuttallii), seston (phytoplankton and zooplankton), and lake water was estimated using survey data of Cs concentration collected from 2011 to 2016, and single- and two-component decay function models (SDM and TDM, respectively). The decay processes of Cs concentrations in wakasagi (Hypomesus nipponensis), pale chub (Zacco platypus), phytoplankton, and total Cs concentrations of the water column (WC) in the lake were well suited by the TDMs. The T in the fast component of the TDMs in these samples ranged from 0.49 to 0.74years. The T in the slow component of the TDMs could converge towards the physical half-life of Cs. Nearly five and a half years after the FDNPP accident, we concluded that Cs concentrations approached a state of dynamic equilibrium between some aquatic organisms (wakasagi, pale chub, and phytoplankton) and the environment (lake water). However, the decay processes of Cs concentrations in Japanese dace (Tribolodon hakonensis), western waterweed, zooplankton, and particulate- and dissolved-forms in the WC were better predicted for the SDM. The total Cs concentrations in inflowing river and spring waters were one to two orders of magnitude lower than lake water under normal flow conditions. However, particulate Cs contamination level in the river water was high after heavy rains. Overall, Cs contamination levels have significantly decreased in Lake Onuma, but monitoring surveys should be continued for further understanding of the reduction processes.
了解放射性核素的生态系统动态对于确保食品安全的有效管理是必要的。2011 年 3 月 11 日福岛第一核电站（FDNPP）事故释放了大量放射性铯（Cs 和 Cs），污染了日本东部的环境。在这项研究中，我们旨在阐明赤城山沼内湖水生生态系统中 Cs 的时间动态。使用 2011 年至 2016 年收集的 Cs 浓度调查数据，以及单组分和双组分衰减函数模型（SDM 和 TDM），估算了鱼类、西方水芹（Elodea nuttallii）、悬浮物（浮游植物和浮游动物）和湖水 Cs 的有效生态半衰期（T）。 wakasagi（Hypomesus nipponensis）、白腹鲦（Zacco platypus）、浮游植物和湖中总 Cs 浓度（WC）的 Cs 浓度衰减过程非常适合 TDM。这些样品中 TDM 快组分的 T 范围为 0.49 至 0.74 年。TDM 慢组分的 T 可收敛到 Cs 的物理半衰期。在 FDNPP 事故发生近五年半后，我们得出结论，Cs 浓度在一些水生生物（wakasagi、白腹鲦和浮游植物）和环境（湖水）之间达到了动态平衡状态。然而，日本七鳃鳗（Tribolodon hakonensis）、西方水芹、浮游动物以及 WC 中的颗粒态和溶解态 Cs 浓度的衰减过程更适合 SDM 预测。在正常流量条件下，流入河流和泉水的总 Cs 浓度比湖水低一到两个数量级。然而，大雨后河水的颗粒态 Cs 污染水平很高。总体而言，沼内湖的 Cs 污染水平显著降低，但应继续进行监测调查，以进一步了解减少过程。
