Natural and artificial radioactivity in volcanic ash soils of Jeju Island, Republic of Korea, and assessment of the radiation hazards: importance of soil properties

摘要

In this study, we investigated the activity concentrations of natural (Ra-226, Th-232, K-40) and artificial (Cs-137) radionuclides of soils in Jeju Island, and radiation hazard indices arising from the activity concentrations. The activity concentrations of Th-232 and K-40 based on soil color were in the order of black volcanic ash soils (BVAS) < very dark brown volcanic ash soils (VDBAS) < dark brown soils, but Cs-137 was highest in BVAS, and Ra-226 was lowest in VDBAS. The radiation hazard indices calculated from the activity concentrations were negligible. In terms of annual outdoor effective dose rate (AEDR(out)), the contribution of radionuclides to the soils was Cs-137 (5.1%) < K-40 (24.7%) < Ra-226 (29.0%) < Th-232 (41.3%), i.e., dominated by natural radionuclides, but contributions were dependent on soil properties.