Parameters of 137 Cs Migration into the Bottom Sediments of Various Water Bodies as a Result of Phragmites australis and Typha angustifolia Dying Away

The role of helophytes in ¹³⁷Cs migration into various components of aquatic ecosystems of different types was investigated. It has been found that 74-87% of ¹³⁷Cs total storage in the phytomass was registered in the underground organs of Phragmites australis and 61-86% - in the underground organs of . As a result of dying away of the aboveground organs of helophytes, 5-11% of ¹³⁷Cs total content in the phytomass can income into the water due to the release of the exchanged forms of the radionuclide. In this case, 8-31% of ¹³⁷Cs will remain in the detritus. Annually as a result of dying away of the above-ground and underground organs of helophytes, 53-85% of ¹³⁷Cs accumulated in the phytomass incomes into the bottom sediments. In this case, 9-19% of ¹³⁷Cs remains in the wintering rhizomes. The activity of ¹³⁷Cs accumulated in helophytes is not more than 6% of its content in bottom sediments occupied by plant communities. After helophytes dying away, secondary contamination of the water with ¹³⁷Cs can attain 0.4% of its activity in bottom sediments occupied by plant communities, about 1.1% can income into the detritus, and 4.2% - into the bottom sediments.