Department of Radiation Chemistry, Institute of Radiation Emergency Mediation, Hirosaki University, Hirosaki 036-8652, Japan.
College of Humanities and Sciences, Nihon University, Tokyo 156-8550, Japan.
Int J Environ Res Public Health. 2019 Oct 24;16(21):4094. doi: 10.3390/ijerph16214094.
The March 2011 earthquake and tsunami resulted in significant damage to the Fukushima Daiichi Nuclear Power Plant (FDNPP) and the subsequent release of radionuclides into the ocean. Here, we investigated the spatial distribution of strontium-90 (Sr) and cesium-134/cesium-137 (Cs) in surface seawater of the coastal region near the FDNPP. In the coastal region, Sr activity was high, from 0.89 to 29.13 mBq L, with detectable FDNPP site-derived Cs. This indicated that release of Sr from the power plant was ongoing even in May 2013, as was that of Cs and Cs. Sr activities measured at open ocean sites corresponded to background derived from atmospheric nuclear weapons testing fallout. The FDNPP site-derived Sr/Cs activity ratios in seawater were much higher than those in the direct discharge event in March 2011, in river input, and in seabed sediment; those ratios showed large variability, ranging from 0.16 to 0.64 despite a short sampling period. This FDNPP site-derived Sr/Cs activity ratio suggests that these radionuclides were mainly derived from stagnant water in the reactor and turbine buildings of the FDNPP, while a different source with a low Sr/Cs ratio could contribute to and produce the temporal variability of the Sr/Cs ratio in coastal water. We estimated the release rate of Sr from the power plant as 9.6 ± 6.1 GBq day in May 2013 on the basis of the relationship between Sr and Cs activity (Sr/Cs = 0.66 ± 0.05) and Cs release rate.
2011 年 3 月的地震和海啸对福岛第一核电站（FDNPP）造成了重大破坏，并随后将放射性核素释放到海洋中。在这里，我们调查了 FDNPP 附近沿海地区表层海水中锶-90（Sr）和铯-134/铯-137（Cs）的空间分布。在沿海地区，Sr 活性很高，为 0.89 至 29.13 mBq/L，可检测到源自 FDNPP 的 Cs。这表明，即使在 2013 年 5 月，工厂仍在持续释放 Sr 和 Cs。在开放海域测量的 Sr 活性与源自大气核武器试验沉降物的背景值相对应。源自 FDNPP 的 Sr/Cs 活性比在海水中的比值远高于 2011 年 3 月直接排放事件、河流输入和海底沉积物中的比值；尽管采样时间很短，但这些比值变化很大，范围从 0.16 到 0.64。源自 FDNPP 的 Sr/Cs 活性比表明，这些放射性核素主要来自 FDNPP 反应堆和涡轮机房的死水，而不同来源的 Sr/Cs 比值较低，可能会对沿海水中 Sr/Cs 比值的时间变化做出贡献并产生影响。基于 Sr 和 Cs 活性之间的关系（Sr/Cs = 0.66 ± 0.05）和 Cs 释放率，我们估计 2013 年 5 月该工厂 Sr 的释放速率为 9.6 ± 6.1 GBq 天。
