title: Forest type effects on the retention of radiocesium in organic layers of forest ecosystems affected by the Fukushima nuclear accident.
abstract: The Fukushima Daiichi nuclear power plant disaster caused serious radiocesium (137Cs) contamination of forest ecosystems over a wide area. Forest-floor organic layers play a key role in controlling the overall bioavailability of137Cs in forest ecosystems; however, there is still an insufficient understanding of how forest types influence the retention capability of137Cs in organic layers in Japanese forest ecosystems. Here we conducted plot-scale investigations on the retention of137Cs in organic layers at two contrasting forest sites in Fukushima. In a deciduous broad-leaved forest, approximately 80% of the deposited137Cs migrated to mineral soil located below the organic layers within two years after the accident, with an ecological half-life of approximately one year. Conversely, in an evergreen coniferous forest, more than half of the deposited137Cs remained in the organic layers, with an ecological half-life of 2.1 years. The observed retention behavior can be well explained by the tree phenology and accumulation of137Cs associated with litter materials with different degrees of degradation in the organic layers. Spatial and temporal patterns of gamma-ray dose rates depended on the retention capability. Our results demonstrate that enhanced radiation risks last longer in evergreen coniferous forests than in deciduous broad-leaved forests.
authors.affiliation: Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Ibaraki 319-1195, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Koarashi
authors.affiliation: Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Ibaraki 319-1195, Japan.
authors.forename: Mariko
authors.initials: M
authors.lastname: Atarashi-Andoh
authors.affiliation: Nuclear Science and Engineering Center, Japan Atomic Energy Agency, Ibaraki 319-1195, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Matsunaga
authors.affiliation: Fukushima Environmental Safety Center, Japan Atomic Energy Agency, Fukushima 975-0036, Japan.
authors.forename: Yukihisa
authors.initials: Y
authors.lastname: Sanada
mesh_terms: D002244:Carbon / Q000032:analysis; D002588:Cesium Radioisotopes / Q000032:analysis*; D065928:Forests; D062406:Fukushima Nuclear Accident; D009584:Nitrogen / Q000032:analysis; D012987:Soil; D013997:Time Factors; D014197:Trees / Q000737:chemistry
chemical_list: D002588:Cesium Radioisotopes; D012987:Soil; D002244:Carbon; D009584:Nitrogen