title: Radiocesium contamination in living and dead foliar parts of Japanese cedar during 2011-2015.
abstract: Radiocesium (137Cs) activity concentrations, mainly derived from the Fukushima accident of March 2011, were measured in green foliar parts without separation by age (bulk green foliar parts; GL) and litterfall (LF) of Japanese cedar (Cryptomeria japonica) from 2011 to 2015. In all samples,137Cs concentrations decreased exponentially over time, but were always higher in LF (7.36-0.58 Bq g-DW-1) than in GL (2.10-0.06 Bq g-DW-1). The difference in the decreasing rate between GL and LF would reflect a difference in the dominant factor of the decrease between living and dead tissues (i.e., internal translocation and weathering, respectively). Over this same timeframe, potassium (K) concentrations in both GL and LF experienced repetitive periodical changes within a certain range (0.38-3.0 mg g-DW-1for LF and 2.08-4.77 mg g-DW-1for GL, respectively). Thus, there was no specific correlation between137Cs and K concentrations in LF and GL. However, analyses of the age classified green foliar parts (GL-S) and dead foliar parts still retained on trees (DL) could indicate another view. The annual changes in residual rates of both137Cs and K concentrations in GL-S demonstrated very similar two-phase reductions (i.e., a faster reduction in each expansion year than in the following years) and an obvious linear correlation between each other. Radiocesium concentration in DL were always higher than in any part of GL-S sampled at the same timing, but K concentrations showed the reverse relation. It is probable that137Cs is basically translocated from older parts to the developing parts (as long as the former are alive) via a seasonal nutritional flow of K; however, a part of137Cs translocation would cease considerably earlier than the cessation of K translocation.
authors.affiliation: Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan. Electronic address: yoshiha@criepi.denken.or.jp.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Yoshihara
authors.affiliation: Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan.
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Matsumura
authors.affiliation: Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan.
authors.forename: Shin-Nosuke
authors.initials: SN
authors.lastname: Hashida
authors.affiliation: Laboratory of Environmental Science, Central Research Institute of Electric Power Industry (CRIEPI), 1646 Abiko, Chiba 270-1194, Japan.
authors.forename: Ko
authors.initials: K
authors.lastname: Nakaya
mesh_terms: D002588:Cesium Radioisotopes / Q000032:analysis*; D032485:Cryptomeria / Q000737:chemistry*; D062406:Fukushima Nuclear Accident; D011834:Radiation Monitoring; D011848:Radioactive Pollutants / Q000032:analysis*
chemical_list: D002588:Cesium Radioisotopes; D011848:Radioactive Pollutants
keywords: Fukushima; Japanese cedar; Potassium; Radiocesium; Translocation