Radiocesium was released to the North Pacific coastal waters by the accident at the Fukushima Dai-ichi Nuclear Power Plant (1FNPP) of the Tokyo Electric Power Company (TEPCO) in March 2011. Since the radiocesium in the sediment off Fukushima was suggested as a possible source for the transfer of this radionuclide through the benthic food chain, we conducted numerical simulations of 137Cs in sediments off the Fukushima coast by using a model which incorporates dynamic transfer processes between seawater and the labile and refractory fractions in sediment particles. This model reproduced the measured temporal changes of 137Cs concentration in seabed surface sediment off Fukusima coasts, by normalizing the radiocsium transfer between seawater and sediment according to the particle diameter sizes. We found that the 137Cs level in sediment decreased by desorption during the first several months after the accident, followed by a reduction in the labile fraction until the end of 2012. The apparent decrease of the total radiocesium level in surface sediment was estimated to occur at rates of approximately 0.2 y-1 within a 20 km distance from the 1FNPP. The comparison of 137Cs level decreases in the demersal fish and the simulated temporal labile fraction in fine sediment demonstrated that the consideration of radiocesium transfer via sediment is important for determining the 137Cs depuration mechanism in some demersal fish.

中文翻译：

---

福岛附近沉积物中放射性铯水平的重建：使用从观测到的137Cs浓度导出的参数对生物利用度进行模拟分析。

放射性铯是由于2011年3月东京电力公司（TEPCO）的福岛第一核电站（1FNPP）事故而释放到北太平洋沿海水域的。由于建议将福岛附近沉积物中的放射性铯释放出来作为这种放射性核素通过底栖食物链转移的来源，我们使用了一个模型，该模型结合了海水与沉积物颗粒中不稳定的和难熔部分之间的动态转移过程，对福岛沿岸沉积物中的137 Cs进行了数值模拟。该模型通过根据粒径大小归一化海水和沉积物之间的放射性铯迁移，再现了福岛沿岸海底表层沉积物中137 Cs浓度随时间的变化。我们发现，事故发生后的头几个月，泥沙中的137Cs水平通过解吸而降低，直到2012年底，其不稳定组分的含量均下降。据估计，地表沉积物中总放射性铯水平的明显下降出现在与1FNPP距离20公里以内的速率约为0.2 y-1。比较深海鱼类中137Cs含量降低和细沉积物中模拟的时间不稳定部分的结果表明，通过沉积物进行放射性铯迁移的考虑对于确定某些深海鱼类中137Cs的净化机理很重要。在距1FNPP 20 km的距离内，估计地表沉积物中总radio水平的明显下降发生的速率约为0.2 y-1。比较深海鱼类中137Cs含量降低和细沉积物中模拟的时间不稳定部分的结果表明，通过沉积物进行放射性铯迁移的考虑对于确定某些深海鱼类中137Cs的净化机理很重要。据估计，在距1FNPP 20 km的距离内，表面沉积物中总ces水平的明显下降发生的速率约为0.2 y-1。比较深海鱼类中137Cs含量降低和细沉积物中模拟的时间不稳定部分的结果表明，通过沉积物进行放射性铯转移的考虑对于确定某些深海鱼类中137Cs的净化机理很重要。