@misc{oai:repo.qst.go.jp:00071258,
 author = {Zheng, Jian and Tagami, Keiko and Bu, Wenting and Uchida, Shigeo and 鄭 建 and 田上 恵子 and ト 文庭 and 内田 滋夫},
 month = {Sep},
 note = {Plutonium isotopes have been released into the environment mainly from the atmospheric nuclear weapons tests in last century, the discharges from nuclear fuel reprocessing facilities, and the nuclear accidents, such as the Chernobyl and the Fukushima Daiichi Nuclear Power Plant (FDNPP) accidents [1-3]. Accurate determination of Pu isotopic composition is important for the source identification of radioactive contamination in the environment since Pu isotopic composition is characteristic for various Pu sources. Among Pu isotopes (238Pu, 239Pu, 240Pu, and 241Pu) observed in the environment, the short-lived 241Pu (t1/2 = 14.4 y), a beta emitter, in a sensitive indicator for the identification of any new contamination of Pu isotopes resulted from nuclear power plant accident. For 241Pu originated from the global fallout, the activity 241Pu in the environment is quite low due to the dacay with time. The activity ratio of 241Pu/239+240Pu is ca. 1.2 in 2011 for the global fallout-sourced Pu isotopes. Therefore, higher activity ratio of 241Pu/239+240Pu in the environment will provide evidence of additional Pu input. 
Due to its short half life and beta emission, determination of 241Pu in environmental samples has been a great analytical challege. Conventional technique is the low level liquid scintillation counting, which requires tedious sample preparation and long measurement time (typically 13-24 h). In the past years, we have developed sensitive analytical method using inductively coupled plasma mass spectrometry for the determination of 241Pu in various environmental samples, such as atmospheric fallou material, marine sediments, seawater reference material [4-6]. In this work, we report the determination of 241Pu environmental samples, such as litter, soil and marine sediments collected in Fukushima Prefecture after the FDNPP accident in 2011. Fig. 1 shows the results of 241Pu activity in litter and surface soils collected in 20-30 km zone of the FDNPP, and in Cities of Mito, Kamagaya and Chiba. High activities of 241Pu ranging from 4.5 to 34.8 mBq/g were detected in samples of the J-Vilage surface soil (0-2 cm) of two litter samples. This finding of high 241Pu activities in environmental samples after the FDNPP accidnet provided evidence of the release of Pu isootpes from the accident., ５th Asia-Pacific Symposium on Radiochemistry (APSORC 13)},
 title = {Determination of short-lived 241Pu in environmental samples by inductively coupled plasma mass spectrometry},
 year = {2013}
}