Iwagami Sho, Tsujimura Maki, Onda Yuichi, Nishino Masataka, Konuma Ryohei, Abe Yutaka, Hada Manami, Pun Ishwar, Sakaguchi Aya, Kondo Hiroaki, Yamamoto Masayoshi, Miyata Yoshiki, Igarashi Yasuhito
Center for Research in Isotopes and Environmental Dynamics, University of Tsukuba, Tsukuba 305-8577, Japan.
Department of Sustainable Environmental Studies, Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba 305-8572, Japan.
J Environ Radioact. 2017 Jan;166(Pt 3):458-465. doi: 10.1016/j.jenvrad.2015.03.025. Epub 2015 May 11.
The concentration of dissolved Cs in groundwater and stream water in the headwater catchments in Yamakiya district, located ∼35 km north west of Fukushima Dai-ichi Nuclear Power Plant (FDNPP), was monitored from June 2011 to July 2013, after the earthquake and tsunami disaster. Groundwater and stream water were sampled at intervals of approximately 2 months at each site. Intensive sampling was also conducted during rainstorm events. Compared with previous data from the Chernobyl NPP accident, the concentration of dissolved Cs in stream water was low. In the Iboishi-yama catchment, a trend was observed for the concentration of dissolved Cs in stream water to decline, which could be divided into two phases by October 2011 (a fast flush of activity as a result of rapid washoff and a slow decline as a result of soil fixation and redistribution processes). The highest Cs concentration recorded at Iboishi-yama was 1.2 Bq/L on August 6, 2011, which then declined to 0.021-0.049 Bq/L during 2013 (in stream water under normal water-flow conditions). During the rainfall events, the concentration of dissolved Cs in stream water increased temporarily. The concentration of dissolved Cs in groundwater at a depth of 30 m at Iboishi-yama displayed a decreasing trend from 2011 to 2013, with a range from 0.039 Bq/L to 0.0025 Bq/L. The effective half-lives of stream water in the initial fast flush and secondary phases were 0.10-0.21 and 0.69-1.5 y, respectively in the three catchments. The effective half-life of groundwater was 0.46-0.58 y at Koutaishi-yama and 0.50-3.3 y at Iboishi-yama. The trend for the concentration of dissolved Cs to decline in groundwater and stream water was similar throughout 2012-2013, and the concentrations recorded in deeper groundwater were closer to those in stream water. The declining trend of dissolved Cs concentrations in stream water was similar to that of the loss of canopy Cs by throughfall, as shown in other reports of forest sites in the Yamakiya district.
在福岛第一核电站（FDNPP）西北约35公里处的山木谷地区源头集水区，对地震和海啸灾害后2011年6月至2013年7月期间地下水中和溪水中溶解铯的浓度进行了监测。每个站点每隔约2个月采集一次地下水和溪水样本。暴雨期间也进行了密集采样。与切尔诺贝利核电站事故之前的数据相比，溪水中溶解铯的浓度较低。在伊保石山集水区，观察到溪水中溶解铯的浓度有下降趋势，到2011年10月可分为两个阶段（由于快速冲刷导致的快速活性冲刷阶段和由于土壤固定和再分配过程导致的缓慢下降阶段）。伊保石山记录到的最高铯浓度于2011年8月6日为1.2贝克勒尔/升，然后在2013年期间降至0.021 - 0.049贝克勒尔/升（正常水流条件下的溪水中）。降雨事件期间，溪水中溶解铯的浓度暂时增加。伊保石山30米深处地下水中溶解铯的浓度在2011年至2013年呈下降趋势，范围为0.039贝克勒尔/升至0.0025贝克勒尔/升。在三个集水区中，溪水在初始快速冲刷阶段和第二阶段的有效半衰期分别为0.10 - 0.21年和0.69 - 1.5年。在小太石山，地下水的有效半衰期为0.46 - 0.58年，在伊保石山为0.50 - 3.3年。在2012 - 2013年期间，地下水中和溪水中溶解铯浓度下降的趋势相似，较深层地下水中记录的浓度更接近溪水中的浓度。溪水中溶解铯浓度的下降趋势与山木谷地区其他森林站点报告中通过穿透雨导致的冠层铯损失趋势相似。
