- No. 1(5) 2024
«Meteorology. Hydrology. Environmental monitoring»
“RADIATION STATE OF THE EXCLUSION ZONE OF 2023 IN ACCORDANCE WITH THE RESULTS OF RADIATION ENVIRONMENTAL MONITORING
The article presents results of radiation and environmental monitoring in the Exclusion Zone for the year 2023, after de-occupation of the territory, which was carried out in accordance with the current regulation of work, with the exception of objects on which it is temporarily impossible to carry out work due to the lack of safe access. In 2022, due to the full-scale invasion of russian federation, radiation monitoring of the environment was interrupted, monitoring of radiation-hazardous objects and environmental components of the Exclusion Zone was not carried out. Implementation of priority measures to restore the radiation and environmental monitoring system in the Exclusion Zone, after occupation by russian troops, made it possible to resume the work of the automated radiation monitoring system points, to create an additional network of measurement of gamma radiation indicators in the Exclusion Zone, to restore work of the central analytical laboratory and to restore the work of aspiration units. Thus, the enterprise resumed obtaining the necessary data on the dose rate of gamma radiation, information on the radiation state of the surface layer of the atmosphere, radiation state of surface and underground waters, radiation state of landscapes and places of residence of self-settlers. According to the results of radiation and environmental monitoring in the Exclusion Zone in 2023, important analytical data were obtained: - Maximum power values of the ambient dose equivalent of gamma radiation are characteristic of the territories in the northern and western 'traces' of radioactive fallout; - Radiation state of the Exclusion Zone air environment and its dynamics during 2023 were determined by the nature of surface contamination of the territory, man-made and biological factors, as well as meteorological conditions. Control levels exceeding by 2.5 times of 137Cs volumetric activity in the air was recorded in Chornobyl; - Surface waters remain an important route of radionuclide removal beyond the Exclusion Zone. Removal of 90Sr from Pripyat River in the area of Chornobyl in 2023 was at a level that was 2.4 times higher than the average value for the last 5 years; - As a result of observations of the radiation state of underground waters, it was determined that the average value of radionuclide contamination of eocene and cenomanian-lower cretaceous water-bearing complexes does not exceed 1 Bq/m3 for 137Cs and 5.7 Bq/m3 for 90Sr; - Monitoring results at landscape landfills indicate that the most contaminated component of the environment is the top layer of soil cover; - Radiation survey results of unauthorized residence places of the population in the Exclusion Zone showed that over the years there is an increase in the intake of 90Sr in the food products of 'self-settlers'.
“OVERVIEW OF THE RESULTS OF RESEARCH OF RADIOACTIVE CONTAMINATION OF THE KAKHOVKA RESERVOIR, WHICH WERE CONDUCTED AFTER THE ACCIDENT AT THE CHERNOBYL NPP (1986-1921)
The available data on the state of radioactive contamination of water and bottom sediments of the Kakhovka Reservoir were analyzed in order to assess the possible deterioration of the quality of the environment based on the indicators of radioactive contamination in the zone of influence of the emergency discharge of water due to destruction of the Kakhovka NPP dam by the Russian military. Contamination of the Kakhovka Reservoir with 137Cs occurred mainly through the fallouts of this radionuclide with aerosols on the water surface in May 1986. A much smaller part of this radionuclide transported by water runoff directly from the headwaters of the Dnieper basin. Strontium-90 entered the reservoir exclusively by water pathway starting from October 1986. The steady trends of decreasing activity of both radionuclides in water has been observed since 1987. Approximately to 1996 137Cs activity concentrations had decreased to pre-accident level, 90Sr activity demonstrated a slow decrease and by 2022 remained slightly higher than pre-accidental level. The average levels of contamination of the Kakhovka reservoir bottom with 137Cs and 90Sr turned out to be the lowest compared to the other reservoirs of the Dnieper cascade. It was shown that in 1994 137Cs activity levels were 0.06 Ci/km2(2,2 kBq/m2) on 80% of the bottom surface (submerged former floodplain of the Dnieper) and were lower than on the territory adjacent to the reservoir. In the areas of silt accumulation (former channel of the Dnieper) 137Cs activity was on average three times higher. Balance calculations based on the data of radiation monitoring of water showed that the amount of 137Cs activity in the bottom sediments in the period 1987-2022 halved due to natural radioactive decay, the amount of 90Sr activity decreased by approximately 20%, since activity losses due to natural radioactive decay were partially compensated by the constant supply of this radionuclide with water runoff from the contaminated part of the catchment. After a catastrophic water leak from the reservoir, the Dnieper floodplain had exposed. According to the calculations, the average density of soil contamination of the ехposed areas with 137Cs does not exceed 0.03 Ci/km2 (1,1 kBq/m2), with 90Sr – less than 0.1 Ci/km2 (3,7 kBq/m2). Silt deposits of the former Dnieper channel, which had an increased level of 137Cs contamination, were re-suspended, probably, and carried out into the Dnipro-Bug estuary and further into the Black Sea. However, according to our assumptions, this should not have a negative effect on the radioecological state of the sea, because the 137Cs activity concentrations in the water of north-western part of the Black Sea were always 20-30 times higher than in the Dnieper water.
“DEFINITION OF THE NATURALIZED FLOW OF THE DNIPRO USING THE RESTORATION METHOD
The issue of determining the quantitative characteristics of the Dnipro River's streamflow and bringing them to natural indicators is quite relevant today. However, the history of studying this issue is quite long. A short review at the beginning of the article is devoted to this. For large regulated rivers, natural, anthropogenic, and naturalized flow are distinguished. In the study, based on the available data of regular instrumental observations, the naturalization of the Dnipro River's average annual flow was conducted using the restoration method. Additionally, a comparison with the actual flow was provided using the example of 2023. The average long-term naturalized flow of the Dnieper along the Locsmanska Kamianka (1818-2020) was obtained, which is 1648 m3/s (±31 m3/s) with a maximum of 3040 m3/s in 1877 and a minimum of 687 m3/s in 2015. The reduction in the natural runoff of the Dnipro River in 2023 due to the influence of reservoirs ranged from 4.8% for the Kyiv Reservoir to 14.8% for the Dnipro Reservoir. Analyzing the series of naturalized runoff of the Dnipro River over 203 years, it is worth noting that in the modern period, a historical minimum of average annual flow was observed. This is quite a concerning sign, as if the likelihood of low-water years similar to 2015 persists, and with the absence of the Kakhovka Reservoir, it will have severe consequences for the entire south of Ukraine. This situation could become especially critical if low water levels persist for several consecutive years, similar to 2019-2020 (with 98% reliability in the naturalized series). In the future, it is advisable to compare the given results with the average annual water consumption determined by other methods of naturalization, for example, through the use of the water balance.
“ASSESSMENT OF THE RADIOACTIVE CONTAMINATION AT THE “PCHP” URANIUM PRODUCTION LEGACY SITE
The article summarizes the results of long-term (2005-2021) site characterization and radioecological monitoring at the former U-production “Prydniprovsk Chemical Plant” (PChP site) and adjacent territories during period of preparedness and justification of the large scale of remediation project activities, which have been recently started at the site. Data analysis have been determined the activity levels of the wide spectra of naturally occurring radionuclides (in particular 238U, 226Ra, 230Th, 210Pb, 210Po, 222R) identified in soils, groundwaters and surface waters, air, atmospheric fallout and some biota at the contaminated site. The results present the dynamics and time-series in contamination of the varies environment elements, which play significant role in exposure of workers at the site and public living at the surrounding areas. The radiological surveys carried out at the site show the areas with elevated dose rate (≥0.5 μSv·h-1) at the more than 30% of the entire legacy site territory. The activity 238U in the local soils identified with high range of variability and level of contamination exceeding its local background (30-50 Bq·kg-1) from 10 to 1000 times. The ambient activity concentrations of 238U and 226Ra in aerosols in some weather condition may exceed the background level at the surrounding areas (0.1 μBq·m-2·s-1, 11.5 μBq·m3) in 100-200 times (in particular locally at the areas were earthworks had place. In case of no actions the typical air contaminations were observed at the legacy site in 1.5-2.0 times higher of the levels outside of the U-legacy site. The monthly averaged activity 222Rn in the air of open space are 4-5 times higher of the local background contamination level for the dwellings (median 200±68 Bq∙m-3), however in some locations at the site (former U-production facilities) the ambient activity concentration of 222Rn can exceed its background levels by up to 50 and even 100 times. The data analysis proves that main ways of exposure of workers are external gamma radiation, the inhalation exposure routes from aerosol pollution and the spread of OA 222Rn in the air can be significant only for workers work at the legacy site and do not pose a threat to the city‘s population. The time-series of radionuclides in the groundwaters waters and some surface rivers at the site are given as well. Radiological assessment showed that aquatic pathways cannot form any significant contributions to the radiation exposure dose of the public (at least in nearest future). The analysis of site characterization studies and obtained monitoring were used for justification of the remediation strategy legacy site. It was shown the main sources of radiological hazard at the site are facilities where concentrated residues of uranium-containing materials are concentrated (in the former ore processing buildings, ore storage facilities and tailings of the U-processing residues). These objects are requiring the application of the priority remediation measures bringing this site in a safe state.
“JUSTIFICATION OF THE EXTENDED COMPOSITION OF OBSERVATIONS AT WATER BALANCE STATIONS AND RESEARCH HYDROGEOPHYSICAL RANGES
The current level of understanding of the subordination and multifactorial dependence of the determining processes in the atmosphere, lithosphere and hydrosphere of the Earth requires a corresponding reorganization of the basic system of environmental monitoring, improvement and expansion of research on water these stations, which can become the supporting 'nodes' of the balance of this system. The appearance of fundamentally new theoretical developments, modern devices and equipment, a large number of software tools, etc., prompts a significant reorganization and strengthening of the environmental monitoring system. The article substantiates an additional set of studies, which should be included in the regulation of observations at already existing water balance stations, with their mandatory modernization. Spheres are subject to control - the atmosphere, surface and underground (subsurface) hydrospheres, which change over time at different rates and pedosphere. A certain inertia of hydrogeological processes implies the possibility of using meteorological indicators, which can be used to predict changes in the moisture regime in the aeration zone and shallow groundwater in the near future; based on the reliably predictable changes of the latter - to forecast changes in interlayer groundwater resources, etc. It is proposed to include in the monitoring regulations the following indicators of the state of the environment, which will allow to identify and analyze the causes of changes in the water situation, balance and resources, to determine the mechanisms of moisture transfer and accumulation, as well as to build models and perform predictive assessments. The results of comprehensive research at the «Lutiz» landfill demonstrate significant variability of hydrogeophysical indicators and changes in the intensity of natural signals depending on the landscape timing, the latest tectonics, the geological basis and the composition of the overlying sediments. Original devices are presented, which are used to determine indicators of electric and thermal fields, the ratio of positive and negative air ions, etc.
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DYNAMICAL CONDITIONS OF THE SPATIAL EXTREMES FORMATION IN OZONE LAYER OVER THE TERRITORY OF UKRAINE
“DYNAMICAL CONDITIONS OF THE SPATIAL EXTREMES FORMATION IN OZONE LAYER OVER THE TERRITORY OF UKRAINE
The paper examines the conditions for the formation of spatial extremes in total ozone content (TOC) over the territory of Ukraine caused by dynamic factors. The study used satellite observations of TOC and meteorological parameters (u,v components of wind and geopotential height) from the ERA5 reanalysis in the Northern Hemisphere. We describe the processes of air advection with significant TOC deviations and implement its classification into the main types. Seventy cases of spatial extremes were identified, 86% of which were observed under air advection with a western component. The intense westerly flow in the lower stratosphere is responsible for both the advection of air with high TOC (total ozone content) and its local formation. Under a well-developed polar vortex, most ozone extremes are transported by the main flow and reach the territory of Ukraine from the west and northwest, forming significant positive deviations. In this case, the polar vortex itself must be displaced into the Eastern Hemisphere for Ukraine to be closer to its outer boundary. When the integrity of the polar vortex is disrupted, it takes on a wavelike structure, leading to greater variability in the processes forming ozone extremes over Ukraine, including TOC advection from the north and local formation. With the breakdown of the polar vortex and the onset of a rapid TOC decrease in late March to April, the likelihood of positive ozone deviations from the north increases, though their recurrence does not exceed 7% of the total number of extremes. Significant negative TOC deviations spread over Ukraine during the period of seasonal minima under two conditions: advection from the northwest when the stratospheric polar vortex is absent (until November), and advection from the west in the early stages of vortex formation (in December). The established and described dynamic conditions for the formation of ozone layer extremes are important for extending the lead time in forecasting ozone anomalies over Ukraine.
