Sediments of the Yenisei River: monitoring of radionuclide levels and estimation of sedimentation rates

摘要

The Yenisei River, one of the largest rivers in the world, is contaminated with artificial radionuclides released by a Russian nuclear facility producing weapon-grade plutonium, which has been in operation for many years. Examination of Yenisei River sediment samples revealed the presence of artificial radionuclides typical of radioactive discharge from the Mining-and-Chemical-Combine (MCC) nuclear facility: isotopes of europium (~(152)Eu, ~(l54)Eu, and ~(l55)Eu), caesium (~(137)Cs and ~(134)Cs), ~(60)Co, ~(90)Sr, and transuranium elements. Maximum radionuclide concentrations in sediments remained high as far as 240 km downstream of the MCC. In sediment cores collected upstream of the MCC, γ-spectrometric measurements registered only one artificial radionuclide, ~(137)Cs, with a maximum activity of approx. 8 Bq kg~(-1) dry mass. Sediments of the Yenisei River also contain natural radionuclides. Sedimentation rates in several sections of the Yenisei River were determined using different approaches: the ~(210)Pb dating method and the ratios of artificial radionuclides - ~(137)Cs/~(60)Co and ~(152)Eu/~(154)Eu. With increasing distance downstream of the city of Krasnoyarsk, sedimentation rates increased from 0.88 cm year~(-1) to 1.30-1.51 cm year~(-1).