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

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