Laboratory of Ion Beam Physics, ETH Zürich , CH-8093 Zürich, Switzerland.
Institute of Biogeochemistry and Pollutant Dynamics, Environmental Physics, ETH Zürich , CH-8092 Zürich, Switzerland.
Environ Sci Technol. 2017 Sep 5;51(17):9826-9835. doi: 10.1021/acs.est.7b03057. Epub 2017 Aug 11.
After the Fukushima Dai-ichi nuclear accident, many efforts were put into the determination of the presence of Cs, Cs, I, and other gamma-emitting radionuclides in the ocean, but minor work was done regarding the monitoring of less volatile radionuclides, pure beta-ray emitters or simply radionuclides with very long half-lives. In this study we document the temporal evolution of I, U, and Pu isotopes (Pu and Pu) in seawater sampled during four different cruises performed 2, 3, and 4 years after the accident, and we compare the results to Cs collected at the same stations and depths. Our results show that concentrations of I are systematically above the nuclear weapon test levels at stations located close to the FDNPP, with a maximum value of 790 × 10 at·kg, that exceeds all previously reported I concentrations in the Pacific Ocean. Yet, the total amount of I released after the accident in the time 2011-2015 was calculated from the I/Cs ratio of the ongoing Cs releases and estimated to be about 100 g (which adds to the 1 kg released during the accident in 2011). No clear evidence of Fukushima-derived U and Pu isotopes has been found in this study, although further monitoring is encouraged to elucidate the origin of the highest Pu/Pu atom ratio of 0.293 ± 0.028 we found close to FDNPP.
福岛第一核电站核事故后，人们投入了大量精力来确定海洋中 Cs、Cs、I 和其他γ放射性核素的存在，但对监测挥发性较低的放射性核素、纯β射线发射体或半衰期非常长的放射性核素的工作做得较少。在这项研究中，我们记录了在事故发生后 2、3 和 4 年期间进行的四次不同航次中采集的海水中 I、U 和 Pu 同位素（Pu 和 Pu）的时间演化，并将结果与在相同站位和深度采集的 Cs 进行了比较。我们的结果表明，在靠近 FDNPP 的站位，I 的浓度系统地高于核武器试验水平，最高值为 790×10 at·kg，超过了太平洋中以前报告的所有 I 浓度。然而，根据正在进行的 Cs 释放的 I/Cs 比值，从 2011 年至 2015 年事故发生后释放的 I 总量估计约为 100g（这增加了 2011 年事故中释放的 1kg）。尽管进一步的监测被鼓励以阐明我们在靠近 FDNPP 的地方发现的最高 Pu/Pu 原子比 0.293±0.028 的来源，但本研究中没有发现明显的福岛衍生 U 和 Pu 同位素的证据。
