Temporal changes in the transfer of accidentally released 137Cs from tree crowns to the forest floor after the Fukushima Daiichi Nuclear Power Plant accident

Abstract

Forests in Fukushima and neighboring prefectures accumulated atmospheric fallout of radioactive materials after the Fukushima Daiichi Nuclear Power Plant accident. We investigated the initial behavior of 137Cs deposited in coniferous forest plantations. Furthermore, we conducted in-situ measurements of radioactivity in coniferous and broadleaf forest canopies. The results of this study demonstrated that more than 60% of the Fukushima reactor accident–derived radiocesium remained in coniferous forest canopies 5 months after initial deposition. Furthermore, in-situ measurements of radiocesium indicated that the radiocesium absorbed in forest canopies has been moving downward through the canopy to the forest floor. Keywords: