title: Uptake and translocation of radiocesium in cedar leaves following the Fukushima nuclear accident.
abstract: Cryptomeria japonica trees in the area surrounding Fukushima, Japan, intercepted (137)Cs present in atmospheric deposits soon after the Fukushima nuclear accident in March 2011. To study the uptake and translocation of (137)Cs in C. japonica leaves, we analyzed activity concentrations of (137)Cs and the concentration ratios of (137)Cs to (133)Cs ((137)Cs/(133)Cs) in old and new leaves of C. japonica collected from a forest on Mount Tsukuba between 9 and 15 months after the accident. Both isotopes were also analyzed in throughfall, bulk precipitation and soil extracts. Water of atmospheric and soil origin were used as proxies for deciphering the absorption from leaf surfaces and root systems, respectively. Results indicate that 20-40% of foliar (137)Cs existed inside the leaf, while 60-80% adhered to the leaf surface. The (137)Cs/(133)Cs ratios inside leaves that had sprouted before the accident were considerably higher than that of the soil extract and lower than that of throughfall and bulk precipitation. Additionally, more than 80% of (137)Cs in throughfall and bulk precipitation was present in the dissolved form, which is available for foliar uptake, indicating that a portion of the (137)Cs inside old leaves was presumably absorbed from the leaf surface. New leaves that sprouted after the accident had similar (137)Cs/(133)Cs ratios to that of the old leaves, suggesting that internal (137)Cs was translocated from old to new leaves. For 17 species of woody plants other than C. japonica, new leaves that sprouted after the accident also contained (137)Cs, and their (137)Cs/(133)Cs ratios were equal to or higher than that of the soil extract. These results suggested that foliar uptake and further translocation of (137)Cs is an important vector of contamination in various tree species during or just after radioactive fallout.
authors.affiliation: Center for Regional Environment Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan.
authors.forename: Tatsuhiro
authors.initials: T
authors.lastname: Nishikiori
authors.affiliation: Center for Regional Environment Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan. Electronic address: watanabe.mirai@nies.go.jp.
authors.forename: Mirai
authors.initials: M
authors.lastname: Watanabe
authors.affiliation: Center for Regional Environment Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan.
authors.forename: Masami K
authors.initials: MK
authors.lastname: Koshikawa
authors.affiliation: Center for Regional Environment Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan.
authors.forename: Takejiro
authors.initials: T
authors.lastname: Takamatsu
authors.affiliation: Center for Regional Environment Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan.
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Ishii
authors.affiliation: Center for Regional Environment Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan.
authors.forename: Shoko
authors.initials: S
authors.lastname: Ito
authors.affiliation: Center for Environmental Biology and Ecosystem Studies, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan.
authors.forename: Akio
authors.initials: A
authors.lastname: Takenaka
authors.affiliation: Center for Regional Environment Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan; Center for Environmental Science in Saitama, 914 Kamitanadare, Kazo, Saitama 347-0115, Japan.
authors.forename: Keiji
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: Center for Regional Environment Research, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba, Ibaraki 305-8506, Japan.
authors.forename: Seiji
authors.initials: S
authors.lastname: Hayashi
mesh_terms: D028203:Cedrus / Q000737:chemistry; D002588:Cesium Radioisotopes / Q000032:analysis*; D062406:Fukushima Nuclear Accident; D007564:Japan; D018515:Plant Leaves / Q000737:chemistry*; D011834:Radiation Monitoring; D011847:Radioactive Fallout; D012990:Soil Pollutants, Radioactive / Q000032:analysis*
chemical_list: D002588:Cesium Radioisotopes; D011847:Radioactive Fallout; D012990:Soil Pollutants, Radioactive
keywords: (137)Cs; Cryptomeria japonica; Foliar uptake; Fukushima; Translocation