Contrasting tissue-specific distributions of 210Po and 137Cs in three marine fish species from Korean coastal waters

In this study, we investigated the tissue-specific activities and accumulation patterns of the natural radionuclide 210 Po and the anthropogenic radionuclide 137 Cs in three marine fish species [red seabream ( Pagrus major ), john dory ( Zeus faber ), and olive flounder ( Paralichthys olivaceus )] collected from coastal waters off Busan and Jeju Island in May and June 2024. Five tissues (gill, liver, viscera, skin, and muscle) were analyzed using pooled samples to compare the tissue-specific distributions of the two radionuclides among the three species. 210 Po accumulated predominantly in digestive tissues, viscera and liver, whereas 137 Cs showed relatively high activity in muscle. Multidimensional scaling analysis suggests that the distributions of 210 Po (stress = 0.01, similarity = 80%) and 137 Cs (stress = 0, similarity = 90%) were separated primarily by tissue type. These contrasting tissue-specific distributions may be associated with differences in the physicochemical and biokinetic behavior of the two radionuclides, potentially involving differences in organic matter affinity, ionic transport, tissue retention, and metabolic processes.