Image analysis of radiocesium distribution in coniferous trees two years after the Fukushima Daiichi Nuclear Power Plant accident

For the investigation of the characteristics and behavior of fallout deposits of the accident at the Fukushima Daiichi Nuclear Power Plant (NPP) in March 2011, autoradiographic imaging was used to examine tree leaves, branches, and barks from locations at 10-60 km south of the Fukushima Daiichi NPP. The autoradiographs revealed particulate contamination in many old leaf samples; few contaminations were present in current-year leaves. Although no particulate contamination was observed on leaves that had grown after the accident, a relatively small amount of radiocesium had become incorporated in the upper leaves of the sampled branches.