Intake of Radionuclides in the Trees of Fukushima Forests 2. Study of Radiocesium Flow to Poplar Seedlings as a Model Tree

Shoko Aoki,Takahisa Hayashi,Tomoko Seyama,Rumi Kaida,Yoichi Sakata,Miki Nonaka,Iwao Uehara,Masaharu Tsubokura,Kei’Ichi Baba,Masateru Itakura,Chisato Yasukawa,Hiroya Ohbayashi,Teruaki Taji

doi:10.3390/f10090736

Shoko Aoki, Takahisa Hayashi + Show 11 more

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https://doi.org/10.3390/f10090736

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Abstract

After the nuclear power plant accident in Fukushima, radionuclides were deposited over a large area of local forest. However, almost nothing is known about radionuclide infiltration into trees. Here, we used poplar seedlings as a model to show that radiocesium can enter directly into leaves and bark, moving via ray cells through the symplastic pathways to the xylem and concentrating around the meristems, cork, and vascular cambium. During induced potassium incorporation and reduced seasonal growth, the radiocesium in the meristems of stems mainly passes into abscission tissues such as leaves and heartwood. There is no turnover of radiocesium after it enters the heartwood.

Highlights

The accident at the Fukushima-Daiichi nuclear power plant in Japan in March 2011 caused the dispersal of abundant radionuclides into the atmosphere and ocean [1]
This paper demonstrates model experiments on how radiocesium could move into forest trees during seasonal growth in the presence of high and low potassium levels in the soil
When radiocesium was placed on the surface of the stem, it was incorporated within 10 min, moving to the nearest leaves and higher stems in 30 min, and to the higher stems and the bases of the topmost leaves in 60 min

Summary

Introduction

The accident at the Fukushima-Daiichi nuclear power plant in Japan in March 2011 caused the dispersal of abundant radionuclides into the atmosphere and ocean [1]. The radionuclide moved from the surface bark to the inner xylem in tree samples obtained from September 2011 to November 2015, 6 to 51 months after the accident [5]. Through the forest tree analyses, we found that radiocesium could be incorporated into the surfaces of trees and could migrate throughout the tissues of the entire tree. Growing cells within the tree could be a target for the accumulation of the radionuclide, similar to that of potassium. Its turnover in a tree body occurs via transition to the dead cells, and it occurs in a forest field [5,6]. This paper describes a study on the immediate effects of radiocesium on trees

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