Background radioactivity of soil in Wakasa Bay area (southern Fukui Prefecture)

Soil samples of surface layer were collected in Wakasa Bay area which is composed of various geologic properties. Concentrations of background radionuclides in soil samples were determined by γ-ray spectrometry with a coaxial type and a planer type of Ge(Li) detectors. The spectra of soil samples obtained by X-ray diffraction analysis show the characteristic composition of minerals based on the geologic properties of their mother's rocks. The concentrations of 238U, 226Ra, 228Ra and 40K in soil roughly correspond to the geologic properties. The highest concentrations of these four nuclides are the soil collected from granitic zone and next comes the soil from paleozoic zone. For homologous soil from granite and paleozoic the 40K contents decrease with increasing surface area, respectively. A good correlation between the 137Cs contents and the unsupported 210Pb contents was found in the soil samples of surface layer. (author)