Radiological behavior and health risk assessment of radon gas in Lake Nasser sediments, Egypt: implications for natural hazards

Abstract Radon, a naturally occurring radioactive gas, represents a critical environmental factor linked to natural hazards through its contribution to radiation exposure in both indoor and outdoor environments. Therefore, it is essential to conduct an in-depth assessment of its dynamics in regions like Nasser Lake, Egypt. Radon activity concentrations were measured using the ionization chamber AlphaGUARD PQ2000PRO, while gamma spectrometry was employed to determine radium content in sediment samples. The results show significant variations in radon activity concentrations across the lake, ranging from 9.59 ± 0.37 Bq/m 3 (lowest) to 66.24 ± 2.56 Bq/m 3 (highest). A positive correlation was observed between radium content and radon activity concentrations. Radium content ranged from 10.37 ± 0.40 to 71.65 ± 2.77 Bq/kg. Radon exhalation rates for mass and area showed variability. The mass exhalation rates (× 10⁻ 3 ) ranged from 1.18 ± 0.05 to 8.13 ± 0.31 Bq/kg h. The area exhalation rates (× 10⁻ 3 ) ranged from 20.82 ± 0.81 to 143.84 ± 5.56 Bq/m 2 h. The emanation coefficient (× 10⁻ 3 ) varied between 22.16 ± 0.86 and 214.98 ± 8.32, with an average value of 80.6 ± 3.12. These findings suggest a direct relationship between radium content and radon exhalation, emphasizing the role of sediment composition in radon release. The annual effective dose values, reflecting potential radiation exposure to residents and fishermen, ranged from 0.24 to 1.67 mSv/year, with an average of 0.57 mSv/year. These results fall mostly within the internationally accepted safety thresholds; however, certain locations near the High Dam showed elevated levels, indicating the need for continued monitoring in these areas. This study highlights the need for continuous environmental monitoring and risk mitigation strategies to reduce radon exposure. The findings enhance the understanding of radon dynamics in sediment-rich environments and support risk-informed decision-making frameworks related to environmental health and natural hazard mitigation.