Radioactive particles in the Yenisei River floodplain (Russia): Characterization, leaching and potential effects in the environment.

The operation of the Mining-and-Chemical Combine (MCC), the largest producer of weapons-grade plutonium in Russia, has resulted in radioactive contamination of the Yenisei River floodplain. Investigations carried out in Novosibirsk and Krasnoyarsk institutes have shown that the floodplain of the Yenisei downstream of the MCC is contaminated by radioactive particles (RP) of various types and activities. Analytical characterization of the RP showed that most of them were fuel particles, which were carried into the Yenisei after incidents at the MCC reactors. The plutonium and caesium isotope ratios (238Pu/239,240Pu; 137Cs/134Cs) vary substantially between the particles, indicating different source terms and time intervals when the RP were formed. In addition to fuel RP, there were particles that contained activation radionuclides. The experiment on dissolution of RP using the model solution (the simulated stomach fluid) showed different cumulative extractions of radionuclides from the particles: 60Co and 137Cs extractions were the lowest, the extracted fractions of europium and americium isotopes were the largest, and plutonium occupied an intermediate position. High concentrations of radionuclides in RP are sources of exposure of organisms in aquatic and terrestrial ecosystems to low radiation doses. The plant bioassays of the effects of γ-radiation from RP showed the effect of low doses of γ-radiation on growth parameters of aquatic plant Elodea canadensis growing in the Yenisei River floodplain. The presence of RP from different sources in the Yenisei River floodplain makes this region a unique site for studying environmental effects of the particles.