Radiocesium distribution and fluxes in the typical Cryptomeria japonica forest at the late stage after the accident at Fukushima Dai- Ichi Nuclear Power Plant Vasyl Yoschenko a, * , Tsugiko Takase a , Alexei Konoplev a , Kenji Nanba a , Yuichi Onda b , Sergiy Kivva a , Mark Zheleznyak a , Natsumi Sato a , Koji Keitoku a a Institute of Environmental Radioactivity of Fukushima University, 1 Kanayagawa, Fukushima, Fukushima Prefecture, 960-1296, Japan b Center for Research in Isotopes and Environmental Dynamics, University of Tsukuba, Tsukuba, Ibaraki Prefecture, 305-8572 Japan article info Article history: Received 31 October 2015 Received in revised form 2 February 2016 Accepted 17 February 2016 Available online xxx Keywords: Fukushima accident Radiocesium Forest Radionuclide distribution Radionuclide fluxes abstract The Fukushima-derived radiocesium distribution in the typical Japanese cedar (Cryptomeria japonica D. Don) forest ecosystem was determined. In four years after the Fukushima accident, about 74% of the total radiocesium inventory was localized in soil, 20% was in the litter, and only 6% was associated with the aboveground biomass. Most of the radiocesium that was initially intercepted by the tree canopies has been already transported to the ground surface. The importance of the processes for removal of radio- cesium from the tree canopies decreased in the order litterfall > throughfall >> stemflow. Within the tree compartments, the largest radiocesium activity fraction, about 46%, was observed in old foliage, which indicates that the process of removal of the initial deposit from the tree crowns has not yet completed. The aggregate soil-to-wood transfer factor was 1.1, 10 3 m 2 kg 1 d.w., which is close to the geometric means of transfer factors recommended by IAEA for other coniferous tree species. Further studies in Fukushima forest are necessary to assess the variation of this parameter under various soil-landscape conditions. Presence of the residues of the initial deposits does not allow to obtain the accurate values of the annual radiocesium fluxes in the ecosystem. Based on the conservative assumptions, the ranges of the fluxes were estimated. Analysis of the flux structures shows that up to percents of the total radio- cesium activity in the ecosystem may be involved into biogenic cycling. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction On March 11th, 2011,14:46 JST, the Great East Japan earthquake of magnitude 9.0, the worldwide fourth largest earthquake recor- ded in history, occurred off Tohoku region of Japan. The earthquake and tsunami followed in 1 h trigged a sequence of events that finally led to the severe damage to Units 1e4 of Fukushima Daiichi Nuclear Power Plant (FDNPP) and to the release of large amounts of radionuclides into the environment (Atomic Energy Society of Japan, 2015). Shortly after, the International Atomic Energy Agency (IAEA) had rated the accident at the FDNPP as Level 7 ac- cording to the International Nuclear Event Scale (IAEA, 2011). Thus, the Fukushima accident is the second largest nuclear accident after the Chernobyl accident. Recent comparison of the two accidents (Steinhauser et al., 2014) presents the total radionuclides releases of 5300 PBq from Chernobyl and 340e800 PBq from Fukushima (excluding noble gases). In contrast to the Chernobyl accident, the accident at the FDNPP resulted mainly in release of gas phase radionuclides. The only long-lived radionuclide released in significant amount during the Fukushima accident was 137 Cs (T 1/2 ¼ 30.1 y), while the near zone of the Chernobyl accident contains large inventories of the long-lived fuel component radionuclides, such as 90 Sr, Pu isotopes and others (Kashparov et al., 2001, 2003). In general, the area contaminated by the Chernobyl accident is much larger than the area contaminated by the Fukushima accident (Steinhauser et al., 2014; United Nations, 2000; Ohta, 2011); however, it should be noted that the densities of the territory contamination with 137 Cs in the near zones of the two accidents are similar. Similarly to the Chernobyl zone, forests cover the main part (about 71%) of the whole area of Fukushima prefecture (Fukushima Prefecture, 2014). About 343,000 ha of the forests, or about 35% of * Corresponding author. E-mail address: r705@ipc.fukushima-u.ac.jp (V. Yoschenko). Contents lists available at ScienceDirect Journal of Environmental Radioactivity journal homepage: www.elsevier.com/locate/jenvrad http://dx.doi.org/10.1016/j.jenvrad.2016.02.017 0265-931X/© 2016 Elsevier Ltd. All rights reserved. Journal of Environmental Radioactivity xxx (2016) 1e11 Please cite this article in press as: Yoschenko, V., et al., Radiocesium distribution and fluxes in the typical Cryptomeria japonica forest at the late stage after the accident at Fukushima Dai-Ichi Nuclear Power Plant, Journal of Environmental Radioactivity (2016), http://dx.doi.org/10.1016/ j.jenvrad.2016.02.017