Gamma-emitting isotopes speciation in floodplain soils of the Balchugovskaya channel temporary stream (the Yenisei River)

The paper presents the first data on the ratio of gamma-emitting isotopes (137Cs, 152Eu, 154Eu, 60Co) speciation in the floodplain soil and rhizosphere of floodplain plants in the Balchugovskaya channel. This channel is located in the near impact zone of the Krasnoyarsk Mining and Chemical Combine alongside the Yenisei River. The formation of a temporary stream during high floods affects the spatial distribution of isotope specific activities in the soil and rhizosphere of this area. The gross specific activities of isotopes vary in a very wide range. The highest ones are recorded in the lower outlet of the temporary stream (up to 800 Bq kg-1). The procedure of sequential extraction was applied to obtain data on isotope speciation. The hydrological regime characterized by high floods in this section of the Yenisei River, as well as the biological activity of plants, exerts a noticeable influence on the spatial distribution of isotope specific activities and their speciation ratios. Lower percentages or the absence of mobile forms of isotopes in the plant rhizosphere, as compared to the bulk soil, provide evidence for this. In general, isotopes in the soil and rhizosphere tend to accumulate in the organic and residual fractions. There are noticeably different distributions of isotope speciation in central areas and sides of the temporary stream entrance and outlets. The most diverse speciation patterns were observed for 152Eu and 154Eu isotopes, but under different hydrological conditions.