TERRAPUB Geochemical Journal

Geochemical Journal, Vol. 52, 2018

Structures of radioactive Cs-bearing microparticles in non-spherical forms collected in Fukushima

Noriko Yamaguchi1*, Toshihiro Kogure2, Hiroki Mukai2, Kotone Akiyama-Hasegawa3, Masanori Mitome3, Toru Hara4, and Hideshi Fujiwara1

1Institute for Agro-Environmental Science, NARO, 3-1-3, Tsukuba, Ibaraki, 305-8604, Japan
2Department of Earth & Planetary Science, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
3International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan
4Research Center for Structural Materials, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047, Japan

(Received January 31, 2017; Accepted April 26, 2017)

Abstract: Structures and distribution of constituent elements of non-spherical radioactive microparticles collected in the Fukushima Prefecture were investigated mainly using scanning transmission electron microscopy (STEM) with energy-dispersive X-ray spectroscopy of high detection efficiency. An angulated radioactive microparticle collected as an aerosol in 2015 had a chemical composition similar to that of the spherical microparticles collected in 2011 but with a different distribution of Sn and alkali ions, which may have been caused by partial dissolution of the microparticle in the field. Other non-spherical microparticles collected from the atmosphere in 2013 contained Al as a constituent of silicate glass, which was not detected in the spherical microparticles. Chromium-oxide glass containing Fe, Zn and Sn was also present, coexisting intricately with silicate glass in one of the microparticles. Finally, a microparticle collected in 2015 from plant tissue was substantially an aggregate of fine particulates composed of Cs-bearing silicate glass that did not contain either Fe or Zn, which were common in the silicate glass forming the other radioactive microparticles. These results suggest that the radioactive microparticles emitted from the Fukushima Daiichi nuclear power plant are of a considerable variety and that their structures likely change with time in the field.
Key words: radioactive microparticle, cesium, silicate glass, Fukushima Daiichi nuclear power plant, scanning transmission electron microscopy

*Corresponding author E-mail: nyamag@affrc.go.jp

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