Seasonal controls on uranium mobility and radiological risk in groundwater of U-bearing formations

Uranium (U), a naturally occurring radioactive material (NORM), is a major contributor to environmental radioactivity in groundwater systems. In U-bearing geological formations, its mobility and related radiological risk are strongly influenced by hydrogeological and biogeochemical processes, yet their seasonal variability and associated health risks remain poorly constrained. We investigated seasonal changes in groundwater chemistry, dissolved uranium, and microbial activity in a fractured aquifer hosted in U-rich bedrock. Groundwater samples were collected under contrasting hydrological conditions and analyzed for major ions, redox-sensitive species, uranium concentrations, and microbial community structure. Our results reveal pronounced seasonal variations in uranium mobility linked to shifts in redox conditions and groundwater recharge. Wet season recharge and enhanced microbial activity promoted reducing conditions and uranium immobilization, whereas dry season oxidizing conditions enhanced U(VI) mobilization, leading to elevated dissolved uranium concentrations and increased radiological exposure potential. These findings demonstrate that groundwater-biogeochemical interactions exert major control on uranium mobility and associated health risks, highlighting the need to jointly consider groundwater quality and radiological exposure in water resource management. Incorporating seasonal dynamics is therefore essential for reliable NORM-related groundwater risk assessment and the protection of drinking water resources in U-bearing aquifers.

[This abstract is based on the published paper: Kim, Jaeyeon, et al. "Seasonal variation of groundwater quality and potential risks in U-bearing formations revealed from hydrogeological-microbiological investigation." Environmental Research 276 (2025): 121544.]

[Acknowledgments: This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT) (No. 2022R1A5A1085103) and the Institute for Korea Spent Nuclear Fuel (iKSNF) and National Research Foundation of Korea (NRF) grant funded by the Korea Government (Ministry of Science and ICT, MSIT) (NRF-2021M2E1A1099413).]