Large amounts of anthropogenic radionuclides, such as 134Cs and 137Cs(radiocesium), were released into the atmosphere due to the Fukushima Daiichi Nuclear Power Plant (F1-NPP) accident and were transported into various environments. The soil accumulations of diffused radionuclides are marked by large differences in their horizontal distributions, and the vertical air dose rates vary depending on the topography, altitude and other factors. In this study, soil activity concentrations of eight islands in the Izu Islands, ~334-563 km south of the F1-NPP, were analyzed from both horizontal and vertical perspectives. Soil samples were collected over a 4-y period from 2012 to 2016, and their activity concentrations of radiocesium were measured. The activity concentrations in the soil were categorized for intervals of a 100-m altitude above sea level, and the relationship between the maximum activity concentration in each category and the distance from the F1-NPP was analyzed. The correlation was good at the lower altitudes.
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