USING RADIOISOTOPE METHODS TO DATE Cs INFLOW TO BOTTOM SEDIMENTS OF THE YENISEI RIVER

Abstract

The long-term study of samples of bottom sediments (BS) of the Yenisei River revealed the presence of a unique set of artificial radionuclides (Co, Cs, Eu, Eu), which made it possible to combine different methods for calculating sedimentation rates for a retrospective assessment of river BS. Studies have been carried out to determine the sedimentation rates by various methods, using natural non-equilibrium Pb, the ratios of artificial isotopes Cs/Co and Eu/Eu, and marker Co, in several sections of the Yenisei River - downstream of the radioactive discharges of the Mining and Chemical Combine (MCC) of Rosatom near the villages of B. Balchug and Atamanovo, as well as upstream of the MCC discharges in the reference areas near the villages of Esaulovo and Shivera. Estimation of sedimentation rates using non-equilibrium Pb, Cs/Co and Eu/Eu isotope ratios, and marker Co for reference areas and the areas near villages located downstream of the MCC showed that their values lay in the range of 0.5-1.3 cm/year. A chronology of Cs influx into BS was constructed using different radioisotope methods, which demonstrated that the maximum Cs influx into BS in the reference regions of the villages of Esaulovo and Shivera and in areas of the village of B. Balchug was noted during the extreme flood of 1966. Cs maxima were also found in the BS layers whose dating coincided with the floods of 1988 and 1995-1997.