Radionuclide equilibria between the aquatic environment and fish tissues

Equilibrium conditions are often assumed in dose and risk calculations based on the simple linear concentration factor model, a commonly used model in the study of contaminant flow through ecosystems. It has been argued that by using a power function model to describe radionuclide retention in fish, equilibrium may never be achieved under natural conditions, thereby violating the equilibrium requirement in the concentration factor model. Our results demonstrate uranium-series radionuclide equilibria in a natural population of common white sucker (Catostomus commersoni). Concentration factors indicated that 226Ra, 232Th, 230Th, and 228Th preferentially deposited in bone over muscle. Although 226Ra had the highest concentration in bone, 228Th yielded the highest concentration factors for water-to-bone transfer. 232Th may not be in equilibrium because of a growth dilution effect.