The work was conducted from 2004 to 2019 at Polys’kiy Branch of Ukrainian Research Institute of Forestry and Agro-Forest Melioration named after G.M. Vysotskiy.
The thesis is devoted to the analysis of regularities of migration and distribution of 137Cs among components in bog ecosystems of the Western Polissia of Ukraine (Volynska and Rivnenska oblast). The studies were conducted on 23 experimental plots representing bog ecosystems of oligotrophic, mesotrophic and eutrophic types.
Studies of the regularities of vertical distribution of 137Cs in peat of different bog types showed that in all cases upper peat layer was characterized by the highest content of radionuclide (20-cm layer for eutrophic, 40 cm – for oligotrophic and mesotrophic bogs), where the main part of root system of species of grass–dwarf-shrub layer, undergrowth and a significant part of tree roots is located. This makes the investigated ecosystems critical in the radioecological sense.
Analysis of the values of the transfer factor of radionuclide from peat-bog soil to organs and tissues of tree species showed little difference in accumulation of 137Cs by Scots pine Pinus sylvestris in several types of habitat conditions: humid bors (A5), humid subors (B5), wet subors (B4). For the birch the transfer factor of 137Cs in all organs and tissues decreased in a such row: wet sugruds (C4) – wet subors (B4) – humid bors (A5) – humid subors (B5). It was found that in eutrophic bogs 137Cs was accumulated more intensively by the white birch Betula pendula than the black alder Alnus glutinosa. It also was found that all investigated tree species had the maximum values of the transfer factor of 137Cs in the most physiologically active organs and tissues.
For oligotrophic and mesotrophic bogs an elevated content of 137Cs was observed in the grass–dwarf-shrub layer species that grow in hollows as compared to species inherent in hummocks and peat mounds. In general within each of the experimental plots significantly higher content of 137Cs compared to other systematic groups was found in ferns, horsetails, and representatives of the sedge family (Cyperaceae), and the lowest specific activity of radionuclide was in ericoid shrubs and dwarf bush willow. For ecosystems of eutrophic bog the high variability in the accumulation of radionuclide by species of grass layer was demonstrated, which is caused by the wide amplitude of agrochemical parameters of peats in the mentioned bogs, degree of their watering, character of their water regime (stagnant or flowing), as well as by topographical microrelief shapes.
The calculations were shown that in all studied bog ecosystems, the main part of the total 137Cs activity was contained in peat-bog soils, much higher in forestless bogs (95,8-99,8 %) than in forest-bog biogeocenosis (63,9-94,9 %). In bog soils, the main role in retrieving the radionuclide belongs to semi-decomposed plant residuals (or litter); role of peat itself in the accumulation of 137Cs was 2-3 times lower. It was observed that there is a similarity of the distribution of phytomass per unit of area and the distribution of total 137Cs activity by the components of phytocenoses of bog ecosystems. The leading role in the retention of radionuclide among the components of phytocenosis in the oligotrophic and mesotrophic bogs played moss layer, and in the eutrophic forestless bogs – grass layer.
The results obtained while conducting the dissertation research allow a differentially use of resources of wild berries and medicinal raw materials, and partly wood products (especially alder and birch wood) in the conditions of radioactive contamination of Western Polissia, to determine the hydrogeochemical role of bogs in the formation of water quality in the objects hydrologically connected with them.
