@article{oai:repo.qst.go.jp:00046796,
 author = {鄭, 建 and 田上, 恵子 and ト, 文庭 and 内田, 滋夫 and 渡辺, 嘉人 and 久保田, 善久 and 府馬, 正一 and et.al and 鄭 建 and 田上 恵子 and ト 文庭 and 内田 滋夫 and 渡辺 嘉人 and 久保田 善久 and 府馬 正一},
 issue = {10},
 journal = {Environmental Science & Technology},
 month = {Apr},
 note = {Since the Fukushima Daiichi nuclear power plant (FDNPP) accident in 2011, intensive studies on the distribution of released fission products, in particular 134Cs and 137Cs, in the environment have been conducted. However, the release sources, that is, whether the damaged reactors or the spent fuel pools, have not been identified, which resulted in a great variation in the estimated amounts of 137Cs released. Here, we investigated heavily contaminated environmental samples (litter, lichen and soil) collected from Fukushima forests for the long-lived 135Cs (half-life, 2x106 y), which is usually difficult to be measured using decay-counting techniques. Using a newly developed triple quadrupole ICP-MS/MS we analyzed the 135Cs/137Cs isotopic ratio of the FDNPP-released radiocesium in environmental samples. We demonstrated that radiocesium was mainly released from the Unit 2 reactor. Considering the fact that the widely used tracer for the released Fukushima accident-sourced radiocesium in the environment, the activity ratio of 134Cs/137Cs, will become unavailable in the near future due to the short half-life of 134Cs (2.06 y), the 135Cs/137Cs isotopic ratio can be considered as a new tracer for source identification and long-term estimation of the mobility of released radiocesium in the environment.},
 pages = {5433--5438},
 title = {Cs135/Cs137 isotopic ratio as a new tracer of radiocesium released from the Fukushima nuclear accident},
 volume = {48},
 year = {2014}
}