Satoshi Sakurai, Hideki Ogawa
To elucidate the dynamics of radiocesium within tree trunks following the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, we investigated the 137Cs activity concentration in konara oak (Quercus serrata) trunks at three forest stands in Fukushima Prefecture. The vertical distributions of 137Cs activity concentrations between the trunks exposed to direct deposition from the atmosphere and those that regenerated and sprouted after the FDNPP accident were compared. Trees were felled and separated into components (outer bark, inner bark, sapwood, and heartwood), and 137Cs activity concentrations were measured using a germanium semiconductor detector. Our results indicated different patterns in the vertical distributions of 137Cs activity concentrations between the trunks exposed to direct deposition and those that regenerated and sprouted, particularly in outer bark. The vertical distribution of 137Cs activity concentration in the sapwood and inner bark was nearly uniform in both trunk types. In contrast, the vertical distribution of 137Cs activity concentration in the heartwood showed similar trends in both trunk types. These findings contribute to a better understanding of the long-term behavior of radiocesium within konara oak trunks and provide essential information for decision-making in log production and forest management.