The regularities of 137Cs accumulation in the aboveand underground parts of aerial-and-aquatic plants originated from various types of reservoirs in the Polissia and the Forest-Steppe of Ukraine

The aim of the study was to establish the regularities of 137Cs accumulation in the above- and underground parts of aerial-and-aquatic plants originated from various types of reservoirs in the Polissia and the Forest-Steppe of Ukraine, located in territories varying in the degrees of radioactive contamination. The studies were carried out in 2014–2018. Higher aquatic plants were sampled in eutrophic, oligotrophic, and dystrophic reservoirs including large and small ones as well as lakes and ponds used for various purposes. The reservoirs were located in the areas that are considered conditionally clean relative to the density of 137Cs contamination, or are classifed as zones of enhanced radiological control, guaranteed voluntary resettlement, unconditional (guaranteed) resettlement and exclusion zones. The objects of research were 8 species of aerial aquatic plants widespread in the fresh water reservoirs of the Polissya and the Forest-Steppe of Ukraine. The specifc content of 137Cs in the aboveground parts, rhizomes, and roots of the plants was determined by common gamma-spectrometric methods. The analysis of the obtained results revealed a common regularity typical of plants from all the studied reservoirs – the levels of 137Cs in the aboveground parts and the rhizomes did not differ signifcantly, but in the ground roots they were signifcantly higher. The specifc activity of 137Cs in ground roots of Phragmites australis exceeded its activity in above ground parts by 6–25 times, in Tupha angustifolia – by 5–20, Glyceria maxima by 7–10, Scirpus lacustris by 4–9, Alisma plantago-aquatica – by 3 times, Sagittaria saggitifolia - by 2, Butomus umbellatus – by 3, Iris pseudacorus - by 4 times. The levels of 137Cs content in aboveground parts and rhizomes in most of the studied plants did not differ signifcantly. The results of the study will further make it possible to assess the role of aerial-and-aquatic plants in the bottom sediments radioactive contamination and to improve the understanding of the role of higher aquatic plants in the processes of radioactive elements migration and redistribution in aquatic ecosystems. The revealed regularities of 137Cs levels formation in the underground parts of plants should be taken into account in determining the radiation dose of plants growing in radionuclides contaminated reservoirs. Key words: aerial-and-aquatic plants, aboveground parts, underground parts, roots, rhizomes, 137Cs, reservoirs, lakes, ponds.