Mapping natural radionuclide distribution and assessing radiological hazards in soils from an iron ore mine

Abstract Natural radionuclides such as 226 Ra, 232 Th, and 40 K are widely distributed in geological materials and may pose significant radiological risks when concentrated in mining environments. Iron ore mining activities can enhance the redistribution and accumulation of these radionuclides in surrounding soils, making their assessment essential for environmental safety and radiation protection. In this study, the natural radioactivity levels of soils collected from an Iranian iron ore mine were investigated using high-purity germanium (HPGe) gamma-ray spectrometry. Twenty soil samples were collected from a depth of 10–20 cm, prepared under standardized laboratory conditions, and analyzed to determine activity concentrations of 226 Ra, 232 Th, and 40 K. Radiological hazard indices, including radium equivalent activity (Ra Eq ), absorbed gamma dose rates, annual effective dose equivalent (AEDE), internal and external hazard indices (H In , H Ex ), annual gonadal dose equivalent (AGDE), and gamma index (I γ ), were calculated to evaluate potential health risks. The results showed that activity concentrations ranged from 10.5 to 246.7 Bq/kg for 226 Ra, 5.3 to 124.4 Bq/kg for 232 Th, and 20.8 to 399.7 Bq/kg for 40 K, indicating considerable spatial variability. The mean Ra Eq was 94.63 Bq/kg, while the maximum value reached 451.96 Bq/kg. Elevated absorbed dose rates and hazard indices were observed in two samples (#4 and #10), with indoor AEDE reaching up to 1.93 mSv/y and gamma index values up to 28.33, exceeding recommended safety limits. Strong positive correlation was observed between 226 Ra, 232 Th (r = 0.94), suggesting common geochemical origins. The study concludes that although most of the investigated area remains within internationally recommended safety limits, localized radiological hotspots exist, particularly in low-lying water-accumulation zones. These findings highlight the importance of targeted monitoring and risk management strategies in iron ore mining environments to minimize potential occupational and environmental radiation exposure.