Variation of terrestrial gamma radiation in Toki, Japan—comparison between gamma-ray spectrometry using Ge semiconductor and ICP-MS measurement

Abstract The cause of the spatial variation in external radiation levels in the Toki area in Japan was investigated by in-situ measurements of gamma-ray spectrum and by collections and measurements of soil samples. It was found that the radionuclide contents of topsoil largely governed the radiation level while land exploitation, gardening activities, and concrete-building constructions caused the variation in radiation there.