Transfer parameters and internal dose assessment for polonium-210 in Canadian freshwater biota.

Polonium-210 (210Po) is a naturally occurring radioisotope that can bioaccumulate in aquatic organisms, contributing substantially to internal radiation dose. However, empirical transfer parameters for freshwater ecosystems remain limited, constraining accurate dose assessments. This study presents a comprehensive assessment of 210Po transfer and internal dose rates across 38 freshwater systems spanning non-mine and mine-impacted environments in Canada. Site-specific 210Po activity concentrations in water, sediment, whole organisms and fish tissues were used to derive empirical sediment-water partition coefficients, bioaccumulation factors, and internal dose rates. Bioaccumulation factors followed clear organism-level patterns, with benthic invertebrates exhibiting the highest uptake and macrophytes the lowest. Among fish, northern pike had the greatest whole-body exposure, and viscera consistently received the highest tissue-specific dose. Bioaccumulation factors for fish exceeded international reference values and measured internal dose rates across organisms were frequently higher than published background benchmarks for naturally occurring radionuclides. Together, these findings improve current understanding of 210Po transfer and internal dose in Canadian freshwater systems and provide empirically derived parameters that can support ecological risk assessments where site-specific data are unavailable. The results also highlight the importance of organism group, tissue type and local site conditions when applying transfer parameters to freshwater dose assessments.