title: Changes in radiocesium concentrations in epigeic earthworms in relation to the organic layer 2.5 years after the 2011 Fukushima Dai-ichi Nuclear Power Plant accident.
abstract: We reported previously that radiocesium ((137)Cs) concentrations in earthworms increased with those in litter and/or soil in Fukushima Prefecture forests 0.5 y after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. This study provides further results for 1.5 and 2.5 y after the accident and discusses temporal changes in (137)Cs concentrations and transfer factors (TF) from litter to earthworms to better understand the mechanisms by which (137)Cs enters soil food webs. The concentration of (137)Cs in accumulated litter on the forest floor rapidly decreased, and the concentration in soil (0-5-cm depth) increased over time from 0.5 to 1.5 y, but changed only moderately from 1.5 to 2.5 y. The concentration of (137)Cs in earthworms consistently decreased during the study period; values 2.5 y after the accident were 18.8-68.5% of those 0.5 y after the accident. The TFs from accumulated litter to earthworms decreased over time: 0.24 ± 0.08 (mean ± SD) at 0.5 y and 0.16 ± 0.04 at 2.5 y. This decrease may be a result of decreases in the bioavailability of (137)Cs in litter and the surface soil layer. Changes in (137)Cs bioavailability should be continuously tracked to determine any changes in the relationship between radiocesium concentrations in earthworms and that in accumulated litter or soil.
authors.affiliation: Forestry and Forest Products Research Institute, Tsukuba, Ibaraki 305-8687, Japan. Electronic address: motohiro@ffpri.affrc.go.jp.
authors.forename: Motohiro
authors.initials: M
authors.lastname: Hasegawa
authors.affiliation: Forestry and Forest Products Research Institute, Tsukuba, Ibaraki 305-8687, Japan. Electronic address: kanekos@affrc.go.jp.
authors.forename: Shinji
authors.initials: S
authors.lastname: Kaneko
authors.affiliation: Forestry and Forest Products Research Institute, Tsukuba, Ibaraki 305-8687, Japan. Electronic address: ikedas@ffpri.affrc.go.jp.
authors.forename: Shigeto
authors.initials: S
authors.lastname: Ikeda
authors.affiliation: Forestry and Forest Products Research Institute, Tsukuba, Ibaraki 305-8687, Japan. Electronic address: akama@ffpri.affrc.go.jp.
authors.forename: Akio
authors.initials: A
authors.lastname: Akama
authors.affiliation: Forestry and Forest Products Research Institute, Tsukuba, Ibaraki 305-8687, Japan. Electronic address: kopine@ffpri.affrc.go.jp.
authors.forename: Masabumi
authors.initials: M
authors.lastname: Komatsu
authors.affiliation: Surugadai University, Hanno, Saitama 357-8555, Japan. Electronic address: itooc@surugadai.ac.jp.
authors.forename: Masamichi T
authors.initials: MT
authors.lastname: Ito
mesh_terms: D000818:Animals; D002588:Cesium Radioisotopes / Q000032:analysis / Q000378:metabolism*; D062406:Fukushima Nuclear Accident; D007564:Japan; D009835:Oligochaeta / Q000378:metabolism*; D011834:Radiation Monitoring; D012990:Soil Pollutants, Radioactive / Q000032:analysis / Q000378:metabolism*
chemical_list: D002588:Cesium Radioisotopes; D012990:Soil Pollutants, Radioactive
keywords: Accumulated litter; Earthworm; Radiocesium; Soil; Transfer factor