Restoration of environmental radioactivity in urban areas and its effects due to anthropogenic activities

市街地における環境放射能からの回復と人間活動の影響

吉村 和也  

Yoshimura, Kazuya

This study shows decreases in air dose rate and Cs activity on paved surface, which is a major radiation source in urban area, observed in urban areas 5-10 km far from the FDNPP. Air dose rate in Difficult-to-Return Zone, of which anthropogenic effects was ignorable, decreased faster in urban area than agricultural fields. The wash-off of radiocesium on paved surface was indicated to facilitate the decrease in air dose rate in urban area. The air dose rate in Specified Reconstruction and Revitalization Base Areas decreased faster than the other zones due to the decontamination, which reduced Cs activity on paved surface to less than about 20%. In areas where were not affected by decontamination, Residential Zone showed faster decreases in air dose rate and Cs activity on paved surface than the Difficult-to-Return Zone. This suggests that the anthropogenic effects other than the decontamination facilitate the decrease in air dose rate in urban areas.