2020 Volume 62 Issue 1 Pages 17-27
Air dose rate is an important indicator that shows spatial distributions of radionuclides contaminations derived from Fukushima Daiichi nuclear power plant accident, however, studies which analyzed spatial and temporal patterns of air dose rates in forests in 2011, the initial stage of environmental radioactivity, were scarce. The spatial distributions and the temporal changes of the air dose rates among three types of forest stands (seed orchards, Japanese red pine and deciduous hardwood forests, Japanese cedar forests) at the height of 0.1 m and 1.0 m above the ground from June to November, 2011 in Koriyama city, Fukushima Prefecture, were investigated. In June 2011, the air dose rates were associated with the vegetation types (seed orchards > Japanese red pine and deciduous hardwood forest > Japanese cedar forest). It was suggested that the air dose rates influenced by canopy interceptions during the initial atmospheric fallout. The time-depended changes of air dose rates varied among three types of the forests from June to November, 2011, decrease rates of air dose were in the order of seed orchards, the Japanese red pine and deciduous hardwood forests and the Japanese cedar forests. Therefore, it was suggested that the time-depended changes of air dose rates were influenced by vertical migration processes of radionuclides such as above the ground and below the ground.