Local area distribution of fallout radionuclides from Fukushima Daiichi Nuclear Power Plant determined by autoradiography analysis

Sakamoto, Fuminori  ; Onuki, Toshihiko; Kozai, Naofumi   ; Igarashi, Shosuke*; Yamasaki, Shinya; Yoshida, Zenko; Tanaka, Shunichi*

The autoradiography analyses of plants and soils collected in Fukushima showed radioactive Cs was distributed on the branch and leaves of trees that were present at the accident and that only small fraction may be transported to new branch and leaves grown after the accident. Radioactive Cs was present on the grass and rice stubble on the soils, but not in the soils beneath the grass and rice stubble, indicating that the radioactive Cs was deposited on the grass and the rice plant. In addition the ratio of the radioactive Cs penetrated into soil layer by weathering was very small for two months after the accident. These results indicate that trees and plant would be the reservoir of the fallout Cs and function for retardation of the fallout Cs migration with rain water.