Assessment of the radiation exposure dose in air-water plants of various water body types in Polissia

Abstract

The study aimed to determine the exposure patterns in air-water plants of Polissia reservoirs located in the territories with different levels of radionuclide contamination of the catchment area, and to assess the risk of radiation damage to air-water plants based on the radionuclides content in the bottom sediments of the reservoirs. To determine the regularities of the air-aquatic plant irradiation dose formation the results of the 2014– 2020 research were used on the specific activity of 90Sr and 137Cs in water, bottom sediments, and a set of data on the radionuclides content in aerial organs, rhizomes, and roots of Phragmites australis (Cav.) Trin as well as Tуpha angustifolia L. in the ecosystems of reservoirs outside the exclusion zone – Kyivskyi (Strakholissia village) and Povchanskyi (Povch village, Korostensky district, Zhytomyr Region) reservoirs, Bile lake (Bile village, Varasky District, Rivne Oblast), and Lake Lisove (village of Nova Markovka, Vyshgorod district, Kyiv region); in the exclusion zone – Lake Glyboke, Yanivsky Zaton and the averaged samples from the two reservoirs formed in the course of draining of the Chernobyl Nuclear Power Plant cooling reservoir. The specific activity of 90Sr in the samples was determined by the oxalate method, and 137Cs was determined by the gamma spectrometric method in the aquatic radioecology department of the Institute of Hydrobiology of the National Academy of Sciences of Ukraine. The heterogeneity of the plants environment, the attenuation of g-radiation by water masses and biomass, and the level of radionuclide contamination of aboveground and underground organs were taken into account while determining plant radiation dose rates. It was established that during the research period the dose rate of external g-irradiation of underwater organs of air-water plants that is formed by 137Cs concentrated in water masses, is 100 or more times lower than that of 137Cs radiation accumulated in bottom sediments, i.e. it can be neglected when determining the total dose. In the studied reservoirs of the exclusion zone, the external irradiation dose rate in air-water plants was 7.5–271 μGy/day, outside the exclusion zone it was 0.1–33 μGy/day. The dose rate of internal irradiation in the exclusion zone reservoirs air-water plants was 1.2–50 μGy/day, outside the exclusion zone it was 0.01–15 μGy/day. The total radiation dose rate in the exclusion zone reservoirs air-water plants was 9–289 μGy/day, in the reservoirs outside the exclusion zone it was 0.65–48 μGy/day. In the reservoirs outside the exclusion zone, the contribution of the external component to the total dose rate ranged from 69 to 81 %, in reservoirs within the exclusion zone it ranged from 69 to 78 %. The study established the levels of radionuclide content in the bottom sediments corresponding to various degrees of radiobiological effects manifestation in air-water plants. It was established that the plants of most reservoirs, in particular the Kyiv Reservoir, develop in the conditions of radiation well-being zones of and physiological masking, in some reservoirs of the exclusion zone they develop under the conditions of ecological masking zones. Key words: air-water plants, dose rate, bottom sediments, radionuclides.