Institute of Radiation Emergency Medicine, Hirosaki University, Hirosaki City 036-8564, Japan.
Center for Research in Isotopes and Environmental Dynamics, University of Tsukuba, Tsukuba City 305-8577, Japan.
Environ Sci Technol. 2022 Nov 15;56(22):15541-15551. doi: 10.1021/acs.est.2c03451. Epub 2022 Oct 14.
The March 2011 Fukushima Dai-ichi Nuclear Power Plant accident in Japan released 520 PBq of radionuclides compared to a total release of 5300 PBq from the Chornobyl Nuclear Power Plant accident. Both nuclear accidents resulted in deposition of radiocesium throughout the northern hemisphere, and a plethora of studies have been performed regarding radiocesium (Cs) behavior. However, few studies have assessed the impact of precipitation on Cs deposition in forests. Wide-scale environmental measurements from 2011 and 2016 were used to determine the differences in Cs deposition because of precipitation following the Fukushima accident. In areas where wet deposition processes were dominant, dense forests generally had lower ambient dose rates and levels of contamination on forest floors than other stands with fewer stems per hectare in 2011. Similar tendencies were not observed in areas that were primarily subject to dry deposition nor were any trends observed in 2016. Cs was retained in dense forest canopies for an extended period regardless of the deposition mode. Additionally, it was found that the initial retention of radionuclides by forest canopies is in general higher for areas with predominantly dry deposition. Incorporation of radiocesium into wood tissues was the same for both wet and dry deposition.
日本 2011 年 3 月福岛第一核电站事故释放了 520 PBq 的放射性核素，而切尔诺贝利核电站事故总共释放了 5300 PBq 的放射性核素。这两次核事故都导致放射性铯在整个北半球沉积，并且已经进行了大量关于放射性铯 (Cs) 行为的研究。然而，很少有研究评估降水对森林中 Cs 沉积的影响。利用 2011 年和 2016 年的广泛环境测量数据，确定了福岛事故后降水对 Cs 沉积的影响差异。在湿沉积过程占主导地位的地区，与其他每公顷茎数较少的林分相比，茂密森林的环境剂量率和森林地表污染水平通常较低。在主要受干沉积影响的地区，没有观察到类似的趋势，2016 年也没有观察到任何趋势。无论沉积模式如何，Cs 都在茂密的森林冠层中保留了很长时间。此外，发现对于以干沉积为主的区域，森林冠层对放射性核素的初始截留通常更高。放射性铯被纳入木材组织的情况在湿沉积和干沉积两种情况下是相同的。
