First evidence for concentrations of transuranium curium in the Yenisei floodplain ecosystem

Abstract

The long-term activity of the Mining‐Chemical Plant (MCP) of the Federal Agency for the Atomic Energy of the Russian Federation (Rosatom) in Zheleznogorsk, Krasnoyarsk region resulted in pollution of the Yenisei River [1‐4]. The radiochemical study of bottom sediments of the Yenisei River revealed in its channel segments concentrations of transuranium elements ( 238 Pu, 239,240 Pu, 241 Am) tens of times higher than the previously published data [1] and 100 times higher than the global background value. The previously performed determinations of concentrations of transuranium elements (particularly, 241 Pu and 237 Np) in bottom sediments have shown that their activity remains high over a distance as long as 200 km downstream from the MCP [3]. Occurrence of bottom sediment layers with anomalously high activity of transuranium elements ( 239,240 Pu up to 280 Bq/kg and 241 Pu up to 1430 Bq/kg) testifies to both a high migration ability of actinoids in the river ecosystem and ongoing discharge of technogenic radionuclides from the MCP [3]. The results of radiochemical analyses for transuranium elements have been obtained previously only for bottom sediments, floodplain soil, and hydrophytes of the Yenisei River [1‐4]. No data are available for land plants in the Yenisei floodplain. By analogy with the published data on concentrations of Cm isotopes ( 243,244 Cm) in the soil polluted as a result of the Chernobyl disaster [5‐7] and taking into account the production of Cm in plutonium reactors [8], it may be expected that this element is contained in samples near the MCP. However, the data on pollution of the Yenisei floodplain with 243,244 Cm isotopes have not been available to date. Curium, a transuranium element with the highest atomic number 96 accessible in gram quantities, is formed by the successive capture of neutrons beginning from 239 Pu or heavier isotopes ( 242 Pu and 243 Am). 243 Cm and 244 Cm are rather longlived isotopes with half-lives equal to 28.5 and 18.1 yr, respectively.