137Cs speciation and distribution in the components of the biogeocenosis of the Yenisei River floodplain such as soils, rhizosphere, and plants were studied. The study was carried out near zones of influence by the Krasnoyarsk Mining and Chemical Combine (MCC). Variation in the specific activity of radionuclides with increasing distance from the pollution source and its ratio in the soil and rhizosphere and distribution in the plant body were studied. A variety of occurrence forms of 137Cs, including mobile ones, was revealed. The amount of 137Cs leached from plants during flooding was calculated from the results of laboratory experiments. © 2011 Pleiades Publishing, Ltd.