Teramage Mengistu T, Onda Yuichi, Patin Jeremy, Kato Hiroaki, Gomi Takashi, Nam Sooyoun
Center for Research in Isotopes and Environmental Dynamic, University of Tsukuba, Tennodai 1-1-1, Tsukuba shi, Ibaraki 305-8572, Japan.
Center for Research in Isotopes and Environmental Dynamic, University of Tsukuba, Tennodai 1-1-1, Tsukuba shi, Ibaraki 305-8572, Japan.
J Environ Radioact. 2014 Nov;137:37-45. doi: 10.1016/j.jenvrad.2014.06.017. Epub 2014 Jul 4.
This study deals with the description of the vertical distribution of radiocaesium ((137)Cs and (134)Cs) in a representative coniferous forest soil, investigated 10 months after the Fukushima radioactive fallout. During soil sampling, the forest floor components (understory plants, litter (Ol-) and fermented layers (Of)) were collected and treated separately. The results indicate that radiocesium is concentrated in the forest floor, and high radiocesium transfer factor observed in the undergrowth plants (3.3). This made the forest floor an active exchanging interphase for radiocesium. The raw organic layer (Ol + Of) holds 52% (5.3 kBq m(-2)) of the Fukushima-derived and 25% (0.7 kBq m(-2)) of the pre-Fukushima (137)Cs at the time of the soil sampling. Including the pre-Fukushima (137)Cs, 99% of the total soil inventory was in the upper 10 cm, in which the organic matter (OM) content was greater than 10%, suggesting the subsequent distribution most likely depends on the OM turnover. However, the small fraction of the Fukushima-derived (137)Cs at a depth of 16 cm is most likely due to the infiltration of radiocesium-circumscribed rainwater during the fallout before that selective adsorption prevails and reduces the migration of soluble (137)Cs. The values of the depth distribution parameters revealed that the distribution of the Fukushima-derived (137)Cs was somewhat rapid.
本研究描述了在福岛放射性尘埃沉降10个月后，对一片典型针叶林土壤中放射性铯（(137)Cs和(134)Cs）垂直分布的调查。在土壤采样过程中，对林地组成部分（林下植物、凋落物（Ol层）和发酵层（Of层））进行了分别采集和处理。结果表明，放射性铯集中在林地中，并且在林下植物中观察到较高的放射性铯转移因子（3.3）。这使得林地成为放射性铯的一个活跃交换界面。在土壤采样时，原始有机层（Ol + Of）含有福岛核事故后产生的52%（5.3 kBq m(-2)）的(137)Cs以及福岛核事故前(137)Cs的25%（0.7 kBq m(-2)）。包括福岛核事故前的(137)Cs在内，99%的土壤总存量位于上层10厘米，其中有机质（OM）含量大于10%，这表明后续分布很可能取决于有机质的周转。然而，在16厘米深度处福岛核事故后产生的(137)Cs所占比例较小，最有可能是由于在那次选择性吸附占主导并减少可溶性(137)Cs迁移之前的沉降过程中，放射性铯受限雨水的入渗所致。深度分布参数值表明，福岛核事故后产生的(137)Cs的分布有些迅速。
