Department of Radioecology, Institute for Environmental Sciences, 1-7 Rokkasho, Aomori 039-3212, Japan.
Tohoku Research Center, Forestry and Forest Products Research Institute, Shimo-Kuriyagawa, Morioka, Iwate 020-0123, Japan.
Radiat Prot Dosimetry. 2022 Sep 9;198(13-15):1131-1136. doi: 10.1093/rpd/ncac076.
Since the Fukushima Dai-ichi Nuclear Power Plant (FDNNP) accident in 2011, 134Cs had been detected in atmospheric deposition samples collected in Rokkasho and Aomori in Japan, located ~400-km north of the FDNNP, during March 2011-May 2015. To study the distribution of radiocesium (134, 137Cs) in a Japanese black pine tree forest, we measured the activity concentration of 134, 137Cs in whole black pine trees, including roots collected during 2017-19 along with soil samples in 2015 and 2017-19. The results show that most of the deposited 134Cs was retained in the forest floor in 2015, with depth distribution different from that of the weapon testing fallout. Proportions of the weapon fallout 137Cs in trunks, branches, needles and roots were 44, 17, 13 and 26%, respectively, indicating that >50% of 137Cs in above-ground part existed in the trunks. The total inventories of 134Cs and 137Cs in the forest were estimated to be 8.9 and 2.5·103 Bq m-2, respectively, and ~4.8% of 137Cs inventory was originated from the accident. Inventory of 134Cs in the forest-including the black pine trees-was 1.6 times larger than cumulative deposition outside of the forest due to the canopy effect.
自 2011 年福岛第一核电站（FDNNP）事故以来，在 2011 年 3 月至 2015 年 5 月期间，位于 FDNNP 以北约 400 公里的日本陆奥和十和田市采集的大气沉积样本中检测到了 134Cs。为了研究放射性铯（134、137Cs）在日本黑松林中的分布，我们在 2017 年至 2019 年期间测量了整棵黑松树（包括根）和土壤样本（2015 年和 2017 年至 2019 年）中 134、137Cs 的活度浓度。结果表明，2015 年大部分沉积的 134Cs 保留在林地上，其深度分布与武器试验沉降物不同。树干、树枝、针叶和根中的武器试验 137Cs 比例分别为 44%、17%、13%和 26%，表明地上部分 137Cs 的>50%存在于树干中。森林中 134Cs 和 137Cs 的总库存分别估计为 8.9 和 2.5·103 Bq m-2，其中~4.8%的 137Cs 库存来自事故。由于树冠效应，包括黑松树在内的森林中 134Cs 的库存是森林外累积沉降量的 1.6 倍。
