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Radioactivity Dynamics in forests


How much radioactive cesium is released from forests? How much radioactive cesium flows into the sea?

Of the initial deposit of 137Cs in forests after the accident, which is approximately 370TBq, it is estimated that approximately 1TBq was released into the sea in one year (examples of the Ukedo and Takase rivers).

Fig.1 Map for air dose rate (Nov.7,2014) around Ukedo River system7)

【Forest investigation】Flow from forests: Amount of cesium flowing out with soil is on average about 0.1% in a year. (Map project1),2), F-TRACE, NIES3))
【Analysis of soil flow】Outflow from other than forests: Estimated from SACT (Soil (Sediment) and Cesium (Contaminants) Transport model) (F-TRACE 4))
【Analysis of migration in river systems】Amount of radioactive cesium flowing out from Ogaki-dam at high water level is lower than 10% of that from forests. (Data by Ministry of Agriculture, Forestry and Fisheries5), F-TRACE6))
【River investigation】Measured data under the Map Project in 20131)

Reference: 1) Project entrusted by Nuclear Regulatory Agency, Report on the project “Establishment of the Methods for Long-term Effect of Radioactive Materials Released form Fukushima Daiichi Nuclear Power Station, TEPCO” (2013).. 2) Yoshimura, K. et al., J. Environ. Radioact., 139, pp.362-369(2015). 3) T. Nishikiori et al., J. Jpn. Forest Soc. 97, 63-69 (2015). 4) A. Kitamura et al., Anthropocene, 5, 22-31(2014). 5) Tohoku Regional Agricultural Administration Office, Ministry of Agriculture, Forestry and Fisheries “Results for Investigation of Radioactive Cesium in Ogaki-dam” (September 18, 2014). 6) H. Kurikami, et al., J. Environ. Radioact., 137, 10-17(2014). 7) Map Zoom-in Site for Radiation Distribution/ The Geospatial Information Authority of Japan