Experimental assessment of 241Am accumulation in Carassius gibelio from amphipods.

Accumulation of dietary 241Am in freshwater omnivorous fish (Carassius gibelio) was studied aiming to estimate the distribution and retention of 241Am in the fish body. Amphipods labeled with 241Am served as a food item. From 0.4 to 0.6% of ingested 241Am was retained in the fish body after short courses of feeding and depuration, the trophic transfer factor of 241Am for whole organism level was about 2∙10-4.

Time-dependent trends of artificial radionuclides in biota of the Yenisei River (Siberia, Russia).

We investigated time-dependent trends of artificial radionuclides in aquatic moss, zoobenthos (amphipods and caddisfly larvae), and three abundant wild fish species (Northern pike, Arctic grayling, and Siberian dace) inhabiting the Yenisei River in the vicinity of the radioactive discharge site in 2007-2015, in a period before and after the shutdown of the last nuclear reactor plant at the Mining-and-Chemical Combine (MCC), which occurred in 2010. From our research, we learned that concentrations of short-lived radionuclides, whose discharges to the Yenisei either stopped or declined after the shutdown of the reactor plant at the MCC (24Na, 46Sc,51Cr, 54Mn, 58Co, 59Fe, 60Co, 65Zn, 103Ru, 141,144Ce, 152,154Eu, 239Np), decreased in biota samples as well. The ecological half-life (EHL) of 65Zn (0.4-0.7 y) was similar to the physical half-life of this isotope, the EHLs of 60Co (1.2-2.1 y) and 152Eu (1.8 y) were shorter than the physical half-lives of these isotopes. Concentration of 137Cs did not decrease significantly in biota of the Yenisei after the shutdown of the last reactor plant because the discharges of this radionuclide to the Yenisei continued at the same level. On a longer-term scale (since 1973 and since 1991), concentration of 137Cs in fish muscle had significantly decreased, following the decrease in annual discharges of this radionuclide to the Yenisei, and the EHL of 137Cs was estimated as 6.5-12.8 y. Statistically significant correlation with annual discharges of 137Cs was revealed for the concentration of this radionuclide in grayling (whole bodies and muscle); dace (muscle), and amphipods. Despite their ability to accumulate high concentrations of 137Cs, aquatic moss and caddisfly larvae (analyzed together with their stony casings) were not sensitive to interannual fluctuations in the releases of this radionuclide to the Yenisei. Among the analyzed fish species of the Yenisei, the highest activity concentration of 137Cs was revealed in pike (body and muscle), indicating biomagnification of this radionuclide in the top level of the trophic chain.

Use of the aquatic plant Elodea canadensis to assess toxicity and genotoxicity of Yenisei River sediments.

The toxicity, cytotoxicity, and genotoxicity of bulk sediments from the Yenisei River (Siberia, Russia) were estimated in laboratory bioassays based on several endpoints in the aquatic plant Elodea canadensis. The bottom sediment samples were collected in the Yenisei River upstream and downstream of the sources of chemical and radioactive contamination. The testing revealed different sensitivities of Elodea endpoints to the quality of the bottom sediment: weight of shoots < length of shoots < mitotic index < length of roots < percentage of abnormal cells. The response of the genotoxicity endpoint (percentage of cells with chromosome abnormalities in roots of Elodea) was the highest in sediments with chemical pollution, whereas the highest inhibition of toxicity endpoints (shoot and root length) occurred in sediments with the highest level of radioactive pollution. The extreme response of Elodea endpoints to the quality of certain sediment samples may be regarded as related to the possible presence of unknown toxicants. The results show that E. canadensis can be used as an indicator species in laboratory contact testing of bottom sediment. The responses of shoot and root length growth endpoints of Elodea can be recommended as basic sensitivity indicators of bottom sediment toxicity. Analysis of cells carrying abnormal chromosomes in the apical root meristem of Elodea can be performed optionally in the same test to assess the genotoxicity of sediments.