Artificial radionuclides in sediment of the Yenisei River

Abstract

Releases from the nuclear facility Mining-and-Chemical Combine (MCC) located at Zheleznogorsk have contributed to the radionuclide contamination of the Yenisei River since operations commenced in 1958. The aim of this study was to assess the activity concentrations of artificial radionuclides and the strength of their binding in Yenisei River sediments. Investigation of Yenisei River sediment samples revealed the presence of artificial radionuclides typical of the MCC radioactive discharge: namely, isotopes of europium, caesium, 60Co and transuranium elements. The concentrations of artificial radionuclides in the sediment layers remain relatively high as far as 200 km downstream of the MCC. In sediment cores collected upstream of the MCC, γ-spectrometric measurements registered only one artificial radionuclide, 137Cs, with a maximal activity of 8 Bq·kg−1. Sequential extraction performed on samples of the upper layers of the sediment core showed different degrees of potential environmental availability for artificial radionuclides: the highest was recorded for 241Am and 152Eu (up to 85% of initial activity), followed by 60Co (up to 32%), and finally, 137Cs (up to 15%). In a few samples, 241Am was present in the unextractable form, which may be accounted for by the presence of reactor fuel microparticles.