Sakaguchi Aya, Tanaka Kazuya, Iwatani Hokuto, Chiga Haruka, Fan Qiaohui, Onda Yuichi, Takahashi Yoshio
Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526, Japan.
Institute for Sustainable Sciences and Development, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8530, Japan.
J Environ Radioact. 2015 Jan;139:379-389. doi: 10.1016/j.jenvrad.2014.05.011. Epub 2014 Jun 12.
The occurrence of (137)Cs in size fractionated samples in river water from the Abukuma River system, (the Kuchibuto and Abukuma Rivers, five sampling events for three sites) was studied from June 2011--approximately some three months after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident until December 2012. The total concentration of (137)Cs (mBq/L) in river water was generally high at the upper stream site in the Yamakiya District within the evacuation/off-limits zone. The (137)Cs concentration was about 1Bq/L for the first sampling campaign (June 2011) at all sites, but then decreased substantially to about one-tenth of that by the time of a second sampling campaign (November or December 2011). The (137)Cs in the <0.45 μm fraction was present exclusively as a dissolved species rather than as a species adsorbed on suspended solids or complexed with organic materials. The contribution of the dissolved fraction ranged from 1.2 to 48.9% (averaged 20%) of the total concentration of (137)Cs throughout the observation period. The maximum contribution of (137)Cs was found in the silt size fraction (3-63 μm), which can be explained by the relatively large Kd values and the suspended solids (SS) concentration of this size fraction. Although the concentration (Bq/g) of (137)Cs in each size fraction did not show any significant trends and/or variations for any of the sampling campaign, Kd values for each site increased with time. Furthermore, it was found that the Kd values decreased with distance from the headstream in the off-limits zone. Thus, the data acquired in this study give an overview of the radiological situation for Fukushima including temporal and spatial variation of radiocaesium in a natural riverine system, within a few years after the accident.
对阿武隈川河水系（久知太河和阿武隈河，三个采样点进行了五次采样）中不同粒径分级样品中¹³⁷Cs的出现情况进行了研究，研究时间从2011年6月（福岛第一核电站事故发生约三个月后）至2012年12月。撤离/禁区内山木谷地区上游采样点河水的¹³⁷Cs总浓度（mBq/L）通常较高。所有采样点在第一次采样（2011年6月）时¹³⁷Cs浓度约为1Bq/L，但在第二次采样（2011年11月或12月）时大幅下降至约十分之一。<0.45μm粒径级分中的¹³⁷Cs仅以溶解态存在，而非吸附在悬浮固体上或与有机物质络合的形态。在整个观测期内，溶解态部分对¹³⁷Cs总浓度的贡献范围为1.2%至48.9%（平均为20%）。¹³⁷Cs的最大贡献出现在粉砂粒径级分（3 - 63μm）中，这可以通过该粒径级分相对较大的分配系数（Kd）值和悬浮固体（SS）浓度来解释。尽管在任何一次采样中，各粒径级分中¹³⁷Cs的浓度（Bq/g）均未显示出任何显著趋势和/或变化，但各采样点的Kd值随时间增加。此外，还发现禁区内Kd值随离源头距离的增加而降低。因此，本研究获得的数据概述了事故发生后几年内福岛的放射性状况，包括天然河流系统中放射性铯的时空变化。
