Short-term bioconcentration studies of Np in freshwater biota.

Short-term laboratory exposures were conducted to determine the potential accumulation of Np in aquatic organisms. Concentration factors were highest in green algae. Daphnia magna, a filter-feeding crustacean, accumulated Np at levels one order of magnitude greater than the amphipod Gammarus sp., an omnivorous substrate feeder. Accumulation of Np in juvenile rainbow trout (Oncorhynchus mykiss) was highest in carcass (generally greater than 78% of the total body burden) and lowest in fillets. Recommended concentration factors for Np, based on fresh weight, were 300 for green algae, 100 for filter-feeding invertebrates, for nonfilter-feeding invertebrates, 10 for whole fish, and one for fish flesh.

Concentration factors used in the assessment of radiation dose to consumers of fish: a review of 27 radionuclides.

Concentration factors (CFs) for 27 radionuclides in marine and freshwater fish were reviewed, as were factors that may influence the dose commitment to man resulting from the consumption of fish. These factors include environmental partitioning, ecological trophic level discrimination and specific tissue accumulation (tropism). Our recommendations are based first on field data for radioisotopes of each element; second, on data for stable elements for which data on radioisotopes are lacking; and third, on the potential for bioaccumulation, which is influenced most by the established biological significance of the element or its chemical similarity to biologically active elements in the same chemical group. Only radionuclides of elements with known biological functions or their analogues accumulate to significant levels in fish tissue. The environmental data that exist for Cs, Sr, Co, Fe, Mn, I, P, Am, Cm, Np and Pu were used for adjusting CFs based on water quality or trophic status of fish. Separate CFs have been listed for particular groups of fish that showed a high propensity for certain radionuclides to accumulate in tissue at higher specific activity than that found in water.