Faculty of Engineering, Information and Systems, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 Japan.
Faculty of Engineering, Information and Systems; Center for Research in Isotopes and Environmental Dynamics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 Japan.
Sci Rep. 2021 Oct 13;11(1):20336. doi: 10.1038/s41598-021-99667-1.
The Fukushima Daiichi Nuclear Power Plant accident also contaminates lakes in Japan. Especially in closed lakes, there is a problem of prolonged low-level [Formula: see text]Cs contamination because the activity concentration of [Formula: see text]Cs declines sharply immediately after the accident, but then begins to decrease slowly. In this paper, we derived a long-term prediction formula based on the fractional diffusion model (FDM) for the temporal variation in [Formula: see text]Cs activity concentrations of the water in Lake Onuma on Mt. Akagi, one of the closed lakes, and of pond smelt (Hypomesus nipponensis), a typical fish species inhabiting in the lake. The formula reproduced well the measured [Formula: see text]Cs activity concentration of the lake water and pond smelt for 5.4 years after the accident. Next, we performed long-term prediction for 10,000 days using this formula and compared it with the prediction results of the two-component decay function model (TDM), which is the most common model. The results suggest that the FDM prediction will lead to a longer period of contamination with low-level [Formula: see text]Cs than the TDM prediction.
福岛第一核电站事故还污染了日本的湖泊。特别是在封闭的湖泊中，由于[Formula: see text]Cs 的活度浓度在事故发生后立即急剧下降，但随后开始缓慢下降，因此存在长时间低水平[Formula: see text]Cs 污染的问题。在本文中，我们基于分数扩散模型（FDM），为位于赤城山的封闭湖泊之一的沼尻湖的湖水和栖息于该湖的典型鱼类日本七鳃鳗（Hypomesus nipponensis）中的[Formula: see text]Cs 活度浓度的时间变化推导了一个长期预测公式。该公式很好地再现了事故发生后 5.4 年的湖水和日本七鳃鳗的实测[Formula: see text]Cs 活度浓度。接下来，我们使用该公式进行了 10000 天的长期预测，并将其与最常用的双组分衰减函数模型（TDM）的预测结果进行了比较。结果表明，与 TDM 预测相比，FDM 预测将导致更长时间的低水平[Formula: see text]Cs 污染。
