title: (137)Cs distributions in soil and trees in forest ecosystems after the radioactive fallout - Comparison study between southern Finland and Fukushima, Japan.
abstract: The nuclear accidents at Chernobyl and Fukushima released large amounts of (137)Cs radionuclides into the atmosphere which spread over large forest areas. We compared the (137)Cs concentration distribution in different parts of two coniferous forest ecosystems (needle litter, stems and at different depths in the soil) over short and long term periods in Finland and Japan. We also estimated the change in (137)Cs activity concentrations in needle and soil between 1995 and 2013 in Southern Finland based on the back-calculated (137)Cs activity concentrations. We hypothesized that if the (137)Cs activity concentrations measured in 1995 and 2013 showed a similar decline in concentration, the (137)Cs activity concentration in the ecosystem was already stable in 1995. But if not, the (137)Cs activity concentrations were still changing in 2013. Our results showed that the vertical distribution of the (137)Cs fallout in the soil was similar in Hyytiälä and Fukushima. The highest (137)Cs concentrations were observed in the uppermost surface layers of the soil, and they decreased exponentially deeper in the soil. We also observed that (137)Cs activity concentrations estimated from the samples in 1995 and 2013 in Finland showed different behavior in the surface soil layers compared to the deep soil layer. These results suggested that the (137)Cs nuclei were still mobile in the surface soil layers 27 years after the accident. Our results further indicated that, in the aboveground parts of the trees, the (137)Cs concentrations were much closer to steady-state when compared to those of the surface soil layers based on the estimated declining rates of (137)Cs concentration activity in needles which were similar in 1995 and 2013. Despite its mobility and active role in the metabolism of trees, the (137)Cs remains in the structure of the trees for decades, and there is not much exchange of (137)Cs between the heartwood and surface layers of the stem.
authors.affiliation: University of Eastern Finland, Department of Environmental and Biological Sciences, P.O. Box 1627, 70211, Kuopio, Finland. Electronic address: jukka.pumpanen@uef.fi.
authors.forename: Jukka
authors.initials: J
authors.lastname: Pumpanen
authors.affiliation: School of Human Science and Environment, University of Hyogo, 1-1-12 Shinzaike-honcho, Himeji City, Hyogo, 670-0092, Japan. Electronic address: ohashi@shse.u-hyogo.ac.jp.
authors.forename: Mizue
authors.initials: M
authors.lastname: Ohashi
authors.affiliation: Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan. Electronic address: izok@fr.a.u-tokyo.ac.jp.
authors.forename: Izuki
authors.initials: I
authors.lastname: Endo
authors.affiliation: University of Helsinki, Department of Forest Sciences, P.O. Box 27 (Latokartanonkaari 7), FI-00014, Finland. Electronic address: pertti.hari@helsinki.fi.
authors.forename: Pertti
authors.initials: P
authors.lastname: Hari
authors.affiliation: University of Helsinki, Department of Forest Sciences, P.O. Box 27 (Latokartanonkaari 7), FI-00014, Finland. Electronic address: jaana.back@helsinki.fi.
authors.forename: Jaana
authors.initials: J
authors.lastname: Bäck
authors.affiliation: University of Helsinki, Department of Physics, P.O. Box 64, Gustaf Hällströmin Katu 2a, FI-00014, Finland. Electronic address: markku.kulmala@helsinki.fi.
authors.forename: Markku
authors.initials: M
authors.lastname: Kulmala
authors.affiliation: Biosphere Informatics Laboratory, Department of Social Informatics, Graduate School of Informatics, Kyoto University, Kyoto, 606-8501, Japan. Electronic address: nobu@bre.soc.i.kyoto-u.ac.jp.
authors.forename: Nobuhito
authors.initials: N
authors.lastname: Ohte
mesh_terms: D002588:Cesium Radioisotopes / Q000032:analysis*; D047852:Chernobyl Nuclear Accident; D032485:Cryptomeria; D005387:Finland; D062406:Fukushima Nuclear Accident; D007564:Japan; D028223:Pinus; D018515:Plant Leaves / Q000737:chemistry; D018547:Plant Stems / Q000737:chemistry; D011847:Radioactive Fallout; D012990:Soil Pollutants, Radioactive / Q000032:analysis*; D014197:Trees / Q000737:chemistry*
chemical_list: D002588:Cesium Radioisotopes; D011847:Radioactive Fallout; D012990:Soil Pollutants, Radioactive
keywords: Chernobyl; Coniferous forest; Fukushima Daiichi Nuclear Power Plant; Radiocesium; Soil; Steady-state concentrations