Levels Of Radioactive Contamination Research Articles

Phytohormonal balance and differential gene expression in chronically irradiated Scots pine populations from the chernobyl affected zone.

The impact of chronic radiation exposure on phytohormone content and expression of phytohormone- and stress-related genes of Scots pine in the zone affected by the Chernobyl accident was studied. Needle samples were collected from three plots with contrasting levels of radioactive contamination in the Polesye State Radiation-Ecological Reserve, Republic of Belarus, and two reference plots in the Kozeluzhsky forest in June 2022. The experimental plots were located within the artificial plantations of Scots pine established in 1982, before the accident in 1986. The activity of radionuclides 137Cs, 90Sr, 241Am, 238Pu, and 239+240Pu in soil and needles ensured dose rates ranging from 3.3 to 87 mGy × year-1, while at the reference plots, the range was 0.7‒0.8 mGy × year-1. Concentrations of plant hormones, including indole-3-acetic acid (IAA), indole-3-butyric acid (IBA), zeatin, and abscisic acid (ABA) in needles were evaluated using high-performance liquid chromatography (HPLC). We demonstrate that chronic radiation exposure is a significant stress factor that affects both phytohormonal balance and the expression of some important phytohormone- and stress-related genes. We found a tendency toward decreased ABA and auxin concentrations in trees from plots contaminated with radionuclides. The ratio (IAA + IBA + zeatin)/ABA was drastically raised at the most contaminated plots Masany and Kulazhin, reflecting the functional rearrangements of cellular metabolism that ensure plant adaptation under chronic radiation exposure. Changes in gene expression indicated modulation of ABA and Ca2+ signalling pathways, decreased potential of zeatin biosynthesis, and activation of heat shock proteins biosynthesis.

Comparison between the Baltic Sea and Irish Sea level of Cs-137 contamination on benthic, demersal and pelagic fish species

The Irish Sea and the Baltic Sea are nowadays still the two most Cs-137 contaminated Seas worldwide. However, the origins of this contaminations are completely different. While the Baltic Sea was unintentionally contaminated due to global fallout after the accident in the Chernobyl nuclear powerplant in 1986, the Irish sea was intentionally used for low level liquid radioactive waste discharges from the Sellafield nuclear reprocessing facility (called Windscale until 1981) between the 1950s and 1990s. Nowadays, more than 30 years later, it is still possible to detect these contaminations in fish, water and sediments of both seas. Since fish are an important part of the human diet, monitoring Cs-137 levels in fish is essential for assessing the potential radiation exposure to humans. In 2019 and 2020 two surveys were dedicated to study the current levels of radioactive contamination in fish species from both Seas. During both surveys, fish samples were collected and analysed by gamma spectrometry later on. The results show that the average Cs-137 activity in benthic, demersal and pelagic fish species from the Baltic Sea are 2.7, 4.6 and 4.2, respectively, times higher than the corresponding values of the Irish Sea. Based on this and two other comparisons, it is concluded that the Baltic Sea is the most contaminated with Cs-137.

Methodological principles of searching for disposal sites of radioactively contaminated materials by geophysical methods

This article is devoted to radiometric studies at one of the sites of the Chornobyl nuclear power plant (the “Sandy Plateau” site), which is located on the south-eastern outskirts of the city of Pripyat. Radioactive substances, both artificial and natural, resulting from incidents and disasters at nuclear facilities pose the greatest danger. The disposal sites for radioactively contaminated materials considered in this work are sources of groundwater pollution. Currently, there is a problem of searching for their location for reburial in specialized stationary burial grounds, to solve which detailed complex geophysical studies are used. Various geophysical methods are considered, including micro-sensing and radiometric studies, to determine the location of burials. Particular attention is paid to the analysis and interpretation of geophysical data, as well as the economic and practical aspects of the application of these methods. As a result of the study, it was established: that when searching and studying burial sites of radioactively contaminated materials, the use of surface gamma photography makes it possible to assess the level of radioactive contamination of the upper layers of the soil (to a depth of 0.8-1 m). However, if the thickness of buried radioactively contaminated materials exceeds a certain level, which leads to weak contamination of rocks at a depth of more than 1-1.5 m, then burial objects may go undetected when using only gamma-ray imaging. In such cases, microgamma probing becomes an effective method. Increased values of exposure dose rate and the nature of microgamma sounding curves serve as indicators of the presence (increase in exposure dose rate with depth) or absence (sharp decrease in exposure dose rate with depth) of radioactively contaminated materials in the studied area.

Results of modern radiation-hygienic surveys of settlements of Bryansk Oblast of the Russian Federation bordering the Republic of Belarus. Part 3: Radionuclide content in agricultural food products

The third article in a series of publications devoted to the results of studying the current radiation situation in the territories of the Bryansk region bordering the Republic of Belarus presents results of studies of the content of radionuclides (137Cs and 90Sr) in samples of agricultural food products produced in the personal subsidiary plots of the population. The regularities of changing 137Cs and 90Sr content in samples of cow’s milk and potatoes depending on the level of radioactive contamination of the territory were studied; the present values of the quantities characterizing the distribution of the ratio of the activity concentration of radionuclides in agricultural food products to the density of radioactive contamination of the soil of the territory were deter -mined. The ratios of average values of 137Cs activity concentration in milk from stalled and grazing periods for cattle were analyzed. The results of the study show that some dairy product samples (less than 1%) do not meet the radiological safety criterion. Exceedances of the hygienic standards were not found in the studied samples of potatoes, vegetables, and meat of farm animals.

Влияние загрязнённой радионуклидами среды на сердечный ритм детей в современных условиях

The main aim was to study the characteristics of heart rate variability in 8- and 10-year boys and girls that permanently reside in areas with an increased level of radioactive contamination. The body functions are formed by close interaction of the body and the environment. The adaptive responses of the developing organism are improved at each ontogenetic stage as its contact with the environment become more complex. We found that features of heart rate regulation depend on the area of residence. The contribution of the autonomous circuit of heart rate regulation is increased for 8- and 10-year-old girls from radio-ecologically safe areas (RESA). Based on the principle of functional antagonism this leads to a weakening of the central circuit of regulation. The shift gradient of indicators is higher for 8-year-old girls from radio-ecologically unfavorable areas (REUA) compared to 10-year-old girls. This reflects the greater sensitivity of their organism to adverse factors. The dominance of the autonomous circuit of regulation was marked for 8- and 10-year-old boys from the RESA. In contrast an imbalance in the operation of regulatory mechanisms with an increase in the central regulatory circuit was found for boys from the REUA. High centralization of cardiac control indicates that adaptation mechanisms are in a state of pronounced tension. The increase in the shift gradient for boys from REUA falls at the age of 10 years. The results of the study revealed gender differences in the regulation of heart rhythm. The obtained data is important diagnostic aspects of morphofunctional maturation of the organism for subsequent ontogenetic stages depending on environmental living conditions.

STUDY OF THE PLANT COVER AND CONTENTS OF RADIONUCLIDES AT THE AKTAN-BERLI SITE

The article presents characteristics of the plant cover at the “Aktan-Berli” site including the content of natural (40K, 232Th, 226Ra) and artificial (137Cs, 90Sr, 241Am, 239+240Pu, 3Н) radionuclides. It has been found that the plant cover of the site is represented by ecosystems of high Kazakh hammocks bordering on ecosystems of lowlands in the west and ecosystems of ancient alluvial and modern alluvial plains. The content of free-water 3Н (FWT) and organic constituent (OBT) is below the detection limit of the methodological instrumentation in use (<8 Bq/kg). The concentration of natural radionuclides is typical, especially for Kazakhstani soil. The range of 90Sr activity concentration in plants range from <0.7 to 6.7 Bq/kq, 137Cs – from <0.6 to 1.1 Bq/kg, the content of 241Am and 239+240Pu are below the detection limit in most cases (<0,2 Bq/kg). Values of the radiation dose rate of plants are below the accepted international criteria. In general, the content of radionuclides in the plant cover of the “Aktan-Berli” site is significantly below the maximum permissible levels of radioactive contamination of forage plants posing no hazard when using the territory of interest for economic activities.

Radon revealed: The hidden connection between construction and contamination in Jazan region

Indoor radon levels, when high, can silently set the stage for lung cancer. Many are actively searching for the reason behind these spikes in radon in our living spaces. The investigation includes buildings in the picturesque Jazan region, where we use the advanced CR-39 solid-state detector. We explored houses built using two interesting methods: traditional soil compaction, innovative pore filling, and simple columns only. Surprisingly, houses built using soil pressure have always remained safe. However, as summer arrived in the Jazan region, 16% of homes with columns revealed radon levels above international safety lines. Even more surprising is that the summer radiation doses in 32% of these homes exceeded international standards. In contrast, pore-filling homes showed unwavering integrity throughout the year. The results showed that the average concentration of radon gas in the first type decreased from 358.97 Bq/cm3 in summer to 209.36 Bq/cm3 in winter. As for the second type, the concentration of radon gas decreased from 153.67 Bq/cm3 in the summer to 88.67 Bq/cm3 in the winter. This study highlights the profound impact of building and home ventilation strategies on radon levels. By combining soil compaction and the tuff layer, we ensure that Jazan homes have a healthy, radon-free environment. Furthermore, constant, up-to-date ventilation is key to staying healthy and radon-free during the hot summer months. It is advised that research into various building types worldwide be continued to determine the most secure method of construction that can lessen gas leakage from the ground and preserve public health. Future research should also look into how different building designs and ventilation systems affect radioactive contamination levels.

Biological activity of sod-podzolic soils at different levels of radioactive contamination

The biological (enzymatic) activity of sod-podzolic soils has been investigated in the zone of mandatory resettlement and in the alienation zone of the Chornobyl Nuclear Power Plant (CNPP) under the influence of ionizing radiation. Gas chromatographic methods were used to determine potential nitrogenfixing (nitrogenase) activity, biochemical methods were applied to study the activity of hydrolytic enzymes (cellulase and protease) responsible for the decomposition of plant residues in the soil, as well as enzymes involved in oxidative-reductive reactions of organic matter transformation (catalase and polyphenoloxidases). Statistical analysis was also employed. The results of the conducted research indicate that a relatively low increase in the total dose rate in the radioactive contamination area (from 0.2 to 1.6 µGy/h) at Polygon No. 1 (the zone of mandatory resettlement near the village of Khrystynivka, Narodychi district, Zhytomyr region) stimulated potential nitrogenase activity of soil diazotrophs and the activity of both hydrolytic enzymes and oxidoreductases. High dose rates (up to 22.2, 61.6, and especially up to 84.0 mGy/h) at Polygon No. 2, located in the alienation zone of the CNPP directly in the area of the former Red Forest, led to a decrease in soil enzymatic activity. Thus, the obtained results unequivocally demonstrate the different nature of the impact of ionizing radiation levels on the biological activity of sod-podzolic soils. The more radioactive soil in the zone of mandatory resettlement stimulates the enzymatic activity of soil microbiota. This could be attributed to adaptive changes in the development and activity of microorganisms or changes in the composition of their communities, with a prevalence of radio-tolerant microbiota representatives. It is also possible that the manifestation of a radiobiological effect, such as radiation stimulation (radiation hormesis), accelerating the growth and development of microorganisms, may occur. In the alienation zone of the CNPP, with high radioactive contamination, the negative influence of ionizing radiation on the metabolism of soil microorganisms is preserved. The obtained results are highly correlated with the indicators of the abundance of nitrogen-fixing microorganisms in the investigated soils, as well as microorganisms representing the saccharolytic (fungi and cellulolytic bacteria) and peptolytic (ammonifiers) pathways of plant residue degradation, as previously demonstrated by us.

Dynamics of radioactive contamination of lingonberry (Vaccinium vitis-idaea L.) in the forests of Zhytomyr Polissia (Ukraine) since the Chernobyl Nuclear Accident

The article presents results of study of levels of radioactive soil contamination and 137Cs activity concentration in the aboveground part of lingonberry (Vaccinium vitis-idaea L.) phytomass and berries on permanent experimental plots in different years since the Chernobyl Nuclear Power Plant accident (forest site type conditions — moist fairly infertile pine site type (B3), soils — soddy-podzolic sandy-loam on fluvioglacial sands). The research was conducted at the Poliskyi Branch of the Ukrainian Research Institute of Forestry and Forest Melioration named after G.M. Vysotsky over the years 1998–2021, utilized methods generally accepted in forest science and radioecology were used. Results were processed using statistical analysis. To substantiate the research, an official reporting data from forestry enterprises of the Volyn, Rivne and Zhytomyr regions were used. An analytical review of the state of research on this problem revealed that at the last 10–15 years there were no scientific publications on the study of 137Cs contamination of lingonberry. It was demonstrated that there was significant reduction in the density of radioactive soil contamination and 137Cs activity concentration in the aboveground part of lingonberry phytomass and berries in the forests of the research region over the observation period. It was found that the main part of the total 137Cs activity is currently located in the upper (10 cm) layer of the mineral part of the soil — 74.7% where root systems of herbaceous and dwarf-shrub species are concentrated in forest ecosystems. It was established that a considerable content of the radionuclide is retained in the aboveground part of lingonberry phytomass even with low density of radioactive soil contamination. It was found that in 1998, at relatively low value of soil 137Cs contamination density (49±5.6 kBq∙m–2), specific activity of 137Cs in aboveground phytomass of lingonberry was 8043±511 Bq∙kg–1, while in 2021 (value of soil 137Cs contamination density 22±0.3 kBq∙m–2) — 1046±182 Bq∙kg–1. The values of radionuclide transfer coefficients in 1998 were quite significant and varied within wide range: in the air-dry aboveground phytomass from 33.4 to 164.1 m2∙kg–1∙10–3 and in the fresh berries, from 9.5 to 26.0 m2∙kg–1∙10–3. Dependencies between density of radioactive soil contamination and the content of 137Cs in the aboveground part of lingonberry phytomass and berries were calculated, which can be applied in the practice of their harvesting. It was found that lingonberry belongs to the group of plants characterized by the high content of 137Cs in the aboveground vegetative phytomass. Harvesting of lingonberry leaves for the production of medicinal products should be restricted in all areas contaminated with 137Cs. Lingonberry fresh berries can be harvested in areas with a radioactive soil contamination density up to 74 kBq∙m–2.

Potato mycocenoses in the fields of the Novozybkovsky district of the Bryansk region with different levels of radioactive contamination and economic use

The peculiarities of the formation of mycocenoses in potato plantings growing in fields with different levels of radioactive contamination and economic use were studied. The experiments were carried out in 1991–1998 in the fields of the Novozybkov agricultural experimental station in the Bryansk region (pollution density l37Cs = 1.2 ± 0.2 MBq/m2) and the lands of the Komsomolets Agricultural Complex withdrawn from economic use (l37Cs 1.8 MBq/m2). Differences were noted in the incidence of potato plants with diseases in the field small–scale experiment (1992), depending on the fertilizers applied (background – peat manure compost (PMC) or additionally NPK + Mg), their balance (different doses of nutrients), as well as agricultural cultivation techniques. In the variants with the introduction of NPK + Mg and the use of the herbicide Promethrin SC or sodium humate, a significant decrease in the incidence of tubers with scab by 25–60% was revealed. Weather conditions influenced the development of pathogens. In 1994 rhizoctoniosis developed most actively in potato plantings and common scab on tubers (hydrothermal coefficient (GTС)may–august = 2.35, which is significantly higher than the average long–term norm for 1991–1998–1.35). In the experiment on potatoes of the Temp variety of Belarusian selection (1994), the possibility of restraining the development of pathogens due to pre-planting treatment of tubers with fungicides was shown: when using contact the decrease in the total level of development of phytopathogens and saprophytes was 1.4 times less than in the control, and when using the systemic fungicide Tect 450 CS – 2.3 times. The use of biologically active substances for the pre-planting treatment of potato tubers (Agate-25K, TPS, Crezacin, KRP and Epin-Extra R) led to a decrease in plant infestation with late blight by 2.2–4.5 times, infestation of tubers with scab by 17–32%, rhizoctoniosis by 10– 36% and later than in the control, the development of diseases, which determined the tactics of fungicidal protection of potatoes during the growing season. There was an increase in potato yield by 11–29% and a significant decrease in the accumulation of137Cs in tubers by 7–15%.

Time-dependent leakage model for the identification of defective fuel assemblies of VVER-type nuclear reactors, part 1: Theory

Level of radioactive contamination in primary coolant of nuclear reactors must be kept as low as possible, therefore essential conditions is the leakage-free state of the fuel rods. To monitor the leakage defects in VVER reactors, the radioactivity of fission products must be measured in the primary loops. From radioactivity data it is possible to infer the fuel assemblies' hermetic or time-dependent leakage state. A new, time-dependent leakage model was developed for operating conditions of VVER nuclear reactors. This leakage model is able to calculate isotopes’ radioactivity inside the fuel and in the primary coolant originating from nuclear fission and neutron-activated reactions. The core of the leakage model consists of several systems of differential equations describing dominant nuclear processes on time-dependent number of radioactive isotope nuclei within fuel assemblies and primary coolant. The model considers the effect of technological parameters on the activity of radioisotopes in the primary coolant.

Radionuclide content in vegetation and soils in the impact zone of the railway track

Purpose. To identify the harmful radiation impact of railway transport on the environment. Methodology. In order to determine the level of radioactive contamination in the impact zone of the railway, soil and plant samples were collected, and relevant radiometric studies were carried out in accordance with the established and approved methods. The peculiarities of the accumulation capacity of plants and soil were investigated and graphical models of radionuclide migration on the Lviv-Sambir railway section were created. Findings. Measurements of the specific activity of 90Sr and 137Cs in plant samples along the railway track showed that grass plants have a lower content of radionuclides and trees have a higher one. It was found that among the herbaceous plants, the species Galium odoratum (L.) Scop. accumulates radionuclides 90Sr most intensively, Geum urbanum L. accumulates 137Cs. These plants can be used as indicators of the territory contaminated with radionuclides. The highest content of radionuclides in tree species is observed in the leaves of grey alder and oak bark. The highest content of K 40 was observed at a distance of 200 m from the railway track, and the lowest content of Th 232 was observed at a distance of 100 m from the railway track. Originality. The results of the research showed a significant variation in the content of radioactive substances in the soils of protective forest plantations. This variation in soil contamination can be explained by the heterogeneity of the above-ground cover and the local impact of plantations on the contaminants’ airborne transport rate. Practical value. Taking into account the fact that the concentration of radionuclides in plants and soil decreases away from the railway tracks, we can state that protective forest plantations delay the spread of the existing radionuclide content to the territories adjacent to the tracks.

Modeling and optimization of scintillating crystal layers for designing a three-layer phoswich Alpha-Beta-Gamma detector

Monitoring the level of radioactive contamination and the type of radiation in the environment is very important for the protection of facilities, employees, and people. Phoswich detector is one of the useful tools to identify different radiations and separate them from each other using different scintillating crystals. However, their design can be very diverse based on the type of particles analyzed and various parameters of scintillating crystals and needs optimization to have maximum efficiency. This work aims to optimize the scintillating crystal layers for the design of the three-layer alpha-beta-gamma phoswich detector based on Monte Carlo radiation transport calculations. The selection of the appropriate model for the type and thickness of each layer is based on the optimization of parameters such as energy accumulation, produced scintillation optical photons, attenuation of optical photons, and scintillation decay time. The results showed that the three scintillating layers of ZnS(Ag), CaF2(Eu), and LYSO(Ce) with optimal thicknesses of 25.01 μm, 3.50 mm, and 2.54 cm, respectively, have more suitable optical outputs for detecting common alpha-beta-gamma radionuclide emitters.

Effect of plant growth regulators on accumulation of radiocaesium in potato tubers

An important place among the problems of modern agriculture is occupied by the problems of rational use and protection of land and the ecologically dangerous state of the environment. The Zhytomyr region is one of the most affected by the accident at the Chernobyl nuclear power plant. A significant part of agricultural land has a density of contamination with cesium-137 up to 5 Ki/km2, which is 75 % of all contaminated land in the districts, about 20 % of agricultural land has a density of contamination from 5 to 15 Ki/km2, 5 % – above 15 Ki/km2. On lands with a higher density of pollution, it is necessary to apply a complex of agrochemical, agrotechnical and organizational measures to reduce the transfer of radionuclides from the soil to plants. Solving problems related to farming in radioactively contaminated territories occupies one of the leading places in the complex of measures to mitigate the consequences of the Chernobyl accident. The purpose of the research was to establish the effect of different doses and types of plant growth regulators on the productivity of potatoes, the level of radioactive contamination in the agro-ecological conditions of Polissia. Our research was carried out in the agro-ecological conditions of Polіssia LLC. Councilors of Ovrutsky district of Zhytomyr region. The transition of the radioactive isotope cesium-137 from the soil to the plants depends on the content of exchangeable potassium in the soil, the saturation of the soil-absorbing complex with bases, the reaction of the soil solution, the bonification of the soil, and the content of humus. When the agrochemical parameters of the soil improved, in particular when the content of exchangeable potassium in the soil increased from 2.3 mg/100 g of soil to 14.8 mg/100 g of soil, the specific activity of radiocesium in plants de-creased by 3.4 times. The results of our research show that the foliar treatment of potato plants with Biosil and Poteitin contributed to a decrease in the specific activity of tubers from 29.2 to 6.4–2.1 Bq/kg. It was established that foliar spraying of potato plants with Biosil and Poteitin contributed to the reduction of the coefficient of 137Cs transition to 0.03 and 0.01.

Twelve-crystal prototype of Li2MoO4 scintillating bolometers for CUPID and CROSS experiments

An array of twelve 0.28 kg lithium molybdate (LMO) low-temperature bolometers equipped with 16 bolometric Ge light detectors, aiming at optimization of detector structure for CROSS and CUPID double-beta decay experiments, was constructed and tested in a low-background pulse-tube-based cryostat at the Canfranc underground laboratory in Spain. Performance of the scintillating bolometers was studied depending on the size of phonon NTD-Ge sensors glued to both LMO and Ge absorbers, shape of the Ge light detectors (circular vs. square, from two suppliers), in different light collection conditions (with and without reflector, with aluminum coated LMO crystal surface). The scintillating bolometer array was operated over 8 months in the low-background conditions that allowed to probe a very low, μBq/kg, level of the LMO crystals radioactive contamination by 228Th and 226Ra.

Social component as a factor and indicator of sustainable development of Ukrainian Polissia region

Official international organizations claim that existing notions about the relationship between a decrease in life expectancy and a reduction in population in affected regions are controversial and are a result of the impact of radioactive emissions from the Chornobyl explosion. However, despite the weak link between the level of radioactive contamination and population dynamics in the studied areas, the level of natural decline in rural population on radioactively contaminated land is significantly higher than in other territories. This indicates the need for further research in this direction. The aim of the study was to clarify the social basis for the implementation of balanced development in radioactively contaminated areas of Ukrainian Polissia. The article presents the results of a study on the role of the social component in the implementation of sustainable development in radioactively contaminated areas of Ukrainian Polissia, taking into account both long-term complex ecological, economic, and social challenges and the potential consequences of Russian military aggression. The methodology of the research is based on a systemic approach, which involves using both modern and classical scientific methods of research, including general scientific methods such as data analysis and synthesis; retrospective and comparative analysis for identifying causal relationships; analytical and synthetic methods for studying scientific and statistical data, archival materials, legislative and regulatory documents, among others; and mathematical methods for the mathematical processing of the obtained results. The research is based on the official statistical data provided by the main statistical departments in Volyn, Zhytomyr, Kyiv, Rivne, and Chernihiv regions. Existing trends and results of studies on the interrelation between radioecological and social components have been analyzed. The study examines social indicators of the quality of life of the inhabitants of Ukrainian Polissia region (total income, level of wages, structure of population expenditures, etc.), demographic indicators (population, gender-age structure and population growth/decline), employment rate, morbidity, and consumer basket for rural and urban settlements in the studied regions. It has been established that indicators of the social sphere in the region of Ukrainian Polissіa can serve as additional criteria for assessing the current socio-economic situation and its dynamics. It has been determined that the social factor is an integral component and at the same time a criterion for sustainable development of radioactively contaminated territories. The need for a series of measures aimed at increasing the effectiveness of the state policy on employment of the population and the vocational education system has been proven, taking into account the forecasts of the regional enterprises’ demand for certain skilled personnel by professions and specialties, as well as the list of the most in-demand and promising professions and specialties. The list of such professions is individual for each region

Comparative analysis of epigenetic variability in two pine species exposed to chronic radiation in the Chernobyl and Fukushima affected zones

Comparative analysis of epigenetic variability in two pine species affected as a result of the Chernobyl and Fukushima accidents is presented. The absorbed dose rate within the affected Chernobyl sites varies over a wider range (1.5–24.6 μGy/h) than within the Fukushima sites (3.5–6.5 μGy/h). It was shown that chronic irradiation can change the level of whole genome methylation in pine populations, but in different ways. The genomes of Japanese red pines are hypomethylated, and the degree of methylation and hydroxymethylation decreases with an increase in the level of radiation exposure. In contrast, the percentages of genome methylation and hydroxymethylation in Scots pine populations exceed the reference levels. The observed discrepancy in the patterns of genome-wide DNA methylation can be attributed partly to the design of the study (differences in the climate, radiation dose, age and species of the pines) which could affect the results. In the frame of IRAP analysis, a larger number of different bands was observed in the Chernobyl populations compared to the Japanese populations. Both the Japanese and Chernobyl populations are characterized by significant genetic variability. However, the main part of this variability is observed within populations. The dendrograms, based on presence/absence of IRAP fragments and Nei's genetic distances, revealed subdivisions of the Chernobyl and Japanese populations according to the level of radioactive contamination. Analysis of the results presented will improve our understanding of the mechanisms underlying the responses of pine trees to chronic radiation exposure.

Research into the current radiological state of air and monitoring observations on STS and the adjacent territory

The article presents the assessment of levels and the pattern of STS air radioactive contamination. Levels of air radioactive contamination with artificial radionuclides at different distances from ground zeros of nuclear tests (0.08–10 km) were determined. The maximum concentration of 239+240Pu in the air did not exceed 6.5·10−3 Bq/m3 at the crater ridge of the “Atomic Lake”, the one at the P3 technical site, the “Experimental Field”, reached 1.6·10−2 Bq/m3. Based upon monitoring observation data (2016–2021) on the STS territory, 239+240Pu concentration in the air of the “Balapan” and “Degelen” sites varied between 3.0·10−9 and 1.1·10−6 Bq/m3. In settlements adjacent to the STS territory, 239+240Pu concentrations in the air is: Kurchatov t. – 3.0·10−9 to 6.0·10−7 Bq/m3, the Dolon small village – 4.5·10−9 to 5.8·10−6 Bq/m3, the Sarzhal small village – 4.4·10−7 to 1.3·10−6 Bq/m3. Values derived for concentrations of artificial radionuclides at STS observation posts and the adjacent territory are at the level of background values for this region.

DOSE ESTIMATION TO WILD MEDAKA AROUND FUKUSHIMA DAI-ICHI NUCLEAR POWER PLANT.

More than 10y have passed since the Fukushima Dai-ichi Nuclear Power Plant (F1-NPP) accident, but there are still many areas with high levels of radioactive contamination, especially reservoirs and lakes, where the levels decrease slowly. The exposed dose to non-human biota is of great concern. In this work, the exposure dose to wild medaka (small aquarium fish) around F1-NPP was measured/estimated by two approaches: in situ measurement and with the ERICA assessment tool. S2 is a reservoir located 7.5km from F1-NPP, and the ambient dose rate was 25.0μSv per h in 2012, but decreased to 4.82μSv per h in 2021. The external exposure dose rate to wild medaka living there was 0.8-11.8 μGy per h (2017-21) by in situ measurement, and the estimated dose rate with the ERICA assessment tool was 0.6-54.5 μGy per h (2012-21). The estimated and measured doses to wild medaka are not expected to cause any significant radiation effects.

Impact of radioactive contamination of soils on the diversity of micropopulation and the transformation of organic substances

Aim. To study the impact of different levels of radioactive contamination on the organic matter decomposition and the population development of microbial decomposers of organic matter in soil. Methods. Gamma-spectrometry for the determination of the relative activity of 137Cs and beta-spectrometry for the determination of the relative activity of 90Sr in order to choose the contamination range for the studies; Tea Bag Іndex (TBI), the standard glob- ally accepted method to determine the rate of organic matter decomposition; gas chromatography – to determine the impact of the investigated factors on the formation of the biomass of microorganisms by means of the СО2 production potential; classic microbiological methods, using elective media to estimate the population densities of culturable microbial decomposers. Results. The studies (from April to September 2021) comprised two soils with different radioactive contamination ranges: Range No. 1 in Narodychi district of Zhytomyr region (the village Khrystynivka, 3 sampling points) in the unconditional (obligatory) resettlement zone after the catastrophe in the Chornobyl nuclear power plant (ChNPP) (it has an absorbed dose rate gradient, evaluated for soil microorganisms, from 0.2 μGy/h (at sampling point Narodychi-1: 51,24076°N, 29,21497°E) to 1.57 μGy/h (at sampling point Naro- dychi-3: 51,23815°N, 29,22245°E)), located on the agricultural field, abandoned after the catastrophe and Range No. 2, located on the afforested area, directly bordering the territory of the so-called Red Forest in the ChNPP ex- clusion zone (4 sampling points – the first three points – natural ecosystems, and 4th – pyrogenically transformed territory after fires in 2020) with the absorbed dose rate gradient from 3.7 μGy/h (at sampling point ChEZ-1: 51,38595°N, 30,03035°E) to 84.0 μGy/h (at sampling point ChEZ-4: 51,38231°N, 30,03298°E). The dependence of the studied indicators on the gradient of soil contamination with radionuclides was demonstrated and these are the conditions that the difference is more than 400 times in the values of the ionizing radiation absorbed dose rates formed by radionuclides in soil. In Range No. 1 (on the fallow land), with the increase in the dose rate up from 0.2 to 1.57 μGy/h, there was statistically significant increase of mineralization coefficient and percentage of reduced weight of rooibos tea between the least and most contaminated sampling points), stimulation of the development of micromycetes (by 1.2–2.3 times), cellulose-decomposing bacteria (by 7.1–7.9 times), and ammonifying bacteria (by 1.8–6.3 times) due to a significant increasing the number of colony-forming units in points with higher radio- nuclide contamination and an increase of microbial biomass in soil more than twofold between the least and most contaminated sampling point of Range No. 1.In Range No. 2, in the ChNPP exclusion zone, characterized by low parameters of sod-podzolic soil fertility (humus content from 1.2 ± 0.2 to 0.9 ± 0.1 %, exchangeable acidity from 4.0 ± 0.1 to 5.0 ± 0.7), the number of micromycetes and ammonifying bacteria in soil was one-two orders below the indices of Range No. 1. Micromycetes dominated in the groups of cellulose-decomposing microorganisms. There was statistically significant increase of mineralization coefficient and percentage of reduced weight of rooibos tea with increasing of radionuclide contamination level for the first three plots: ChEZ-1, ChEZ-2 and ChEZ-3 of Range No. 2. Conclusions. In the fallow land of the unconditional (obligatory) resettlement zone, the increase of the radia- tion absorbed dose rate in soil by one order from 0.2 to 1.57 μGy/h does not inhibit the development of microorgan- isms in soil, rather it stimulates their activity and increases their numbers. On poor sod-podzolic soils in the exclu- sion zone of the Chernobyl nuclear power plant, the preponderance of development of micromycetes over bacterial cellulolytics is noticeable. The radioactive contamination affected the development of soil microorganisms and the biological processes in soils not only in the first years after the Chornobyl catastrophe, which has been described in the literature, but has had its influence for rather a long time (for over thirty years after the accident). Among the microorganisms of a saccharolytic mode of organic plant residuals decomposition, the micromycetes dominate.