Density Of Soil Contamination Research Articles

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.

CURRENT RADIOLOGICAL STATUS OF CONTAMINATED MEADOWS AND PASTURES AND ASSESSMENT OF THE POSSIBILITY OF THEIR RETURN TO USE

Meadows and pastures are the fodder base for milk and meat production. The rehabilitation and return to economic use of the radionuclide-contaminated meadows and pastures is an important and urgent national economic task. The criterion of returning radionuclide-contaminated meadows and pastures to economic use may be individual doses to residents who consume milk and meat produced on these lands. Values that determine the doses are the terrestrial density of soil contamination and permissible levels of radionuclides in food products (PL-2006). Considering abandoned agricultural lands, it is necessary to note the time that passed after the accident. The contamination of the territory by 137Cs and 90Sr decreased in more than 2 times due to radioactive decay only. The decreasing due to radioactive decay and self-remediation processes (fixation of radionuclides by soil, their redistribution in the root layer of the soil, etc.) resulted in declining of radioactive contamination of products. This allows us to consider the issue of returning reclaimed lands to use in accordance with the current radiological criteria and existing legal acts. Agricultural lands are a territorial resource and the main means of agricultural production, therefore the rehabilitation of the lands will contribute to the development of both individual producers and settlements as a whole. After the Chornobyl accident, in accordance with the Law of Ukraine "On the Legal Regime of the Territory Exposed to Radioactive Contamination Due the Chornobyl Catastrophe", the territory exposed to radioactive contamination had been divided into zones. However, the belonging of the lands to a zone does not guarantee that the products produced there will meet the requirements of PL-2006. Therefore, in 1998, taking into account the type of soil, the UIAR assessed the maximum permissible levels of soil contamination which ensure the fulfillment of the requirements of PL-2006 in terms of the content of 137Cs in produced products. However, in the 25 years that have passed since the establishment of these levels and the cesium transfer factors into plants have decreased significantly. Therefore, the values of the maximum permissible levels of soil contamination are conservative and their use leads to conservative conclusions. The current radiological state of meadows and pastures contaminated with radionuclides and the possibility of returning them to use were assessed. It is shown that most of the considered abandoned lands actually belong to the third zone of radioactive contamination. Some of the lands belong to the second zone of radioactive contamination - radiation-hazardous lands. It was found that the restrictions set in the recommendations for conducting agriculture in the conditions of radioactive contamination for the production of milk and meat are very conservative. Assessment of the possibility of using contaminated meadows and pastures for milk and meat production requires more precise and targeted forecasting methods.

Geometry factor for in-situ soil contamination density estimation

A method is proposed for estimating the density of soil contamination with gamma-emitting radionuclides (Bc·m-2) in situ (in the field without sampling). The method allows to take into account the peculiarities of the distribution of radionuclides along the soil profile at a given site by the ratio of scattered and non-scattered photon fluxes. The scope of application has been expanded and the uncertainty of the previously developed method used for radiological examination of agricultural lands contaminated with 137Cs without sampling has been reduced. The proposed method of remote assessment of the pollution density practically does not introduce an additional error in comparison with the traditional method, which includes soil sampling and subsequent analysis in laboratory conditions. The duration of the spectrum set and its automatic processing at a 137Cs contamination density of more than 100 kBq·m-2 does not exceed 1 min.

Influence of daily feeding ration of cattle on the transfer of 137Cs and 90Sr to animal organisms and manure in the agroecosystems of Central Forest-Steppe

The ration of feeding for large cattle was investigated and analyzed in terms of the transfer of 137Cs and 90Sr to muscle tissue, bones, milk, and manure biomass. The specific activity of radionuclides 137Cs and 90Sr was determined in the daily feeding ration of animals. It was found that the soil contamination density of 137Cs at the «Nadiya» farm ranged from 104.2 to 396.5 Bq/m2, while for 90Sr, it ranged from 9.4 to 36.2 Bq/m2. The fields at the «Ivanivske» farm had soil contamination densities of 137Cs ranging from 37.5 to 283.6 Bq/m2 and 90Sr ranging from 7.4 to 32.1 Bq/m2. The soil contamination density of 137Cs at the NNDC BNAU ranged from 4.18 to 8.66 Bq/m2, while for 90Sr, it ranged from 0.44 to 0.88 Bq/m2. The results of the ration assessment indicate that the average daily intake of 137Cs from feed into the animal’s body at the «Nadiya» farm was 375.3±84.2 Bq/kg, and for 90Sr, it was 345.1±98.2 Bq/kg. Significantly lower amounts of radionuclides from the ration entered the animals’ bodies at the «Ivanivske» farm, with an average daily intake of 137Cs at 174.9 Bq/kg and 90Sr at 236.0 Bq/kg. The lowest transfer coefficients of 137Cs and 90Sr from the daily ration to the body were observed at the NNDC BNAU, with 8.56 Bq for 137Cs and 9.69 Bq for 90Sr. It was determined that, overall, the muscle tissue of animals received 6.37% of 137Cs and 0.06% of 90Sr from the ration at the «Nadiya» farm; 2.0% of 137Cs and 0.02% of 90Sr at the «Ivanivske» farm, and 2.22% of 137Cs at the NNDC BNAU. In the case of bones, it was 6.47% of 90Sr at the «Nadiya» farm; 5.47% of 90Sr at the «Ivanivske» farm, and 0.41% of 90Sr at the NNDC BNAU. The obtained results confirmed that 137Cs is capable of evenly accumulating in all organs of the animal, while 90Sr selectively or predominantly accumulates in specific organs. It was established that under conditions of prolonged intake of radionuclides through the ration into the body of large cattle, 85–90% is excreted with the manure biomass.

Оценка мощности амбиентного эквивалента дозы на лесных участках в юго-западных районах Брянской области

The large areas of forests in the Bryansk region are still contaminated with radionuclides released due to the accident at the Chernobyl NPP in April, 1986. The recovery of the economic and ecosystems potentials in the contaminated areas is the need to create a favorable living conditions for the population. This involves a full range of remediation activities in the contaminated areas aimed at the forests protection and regeneration. The aim of the work is to assess the ambient dose equivalent rate (ADER) in forest sites located in the zone of radioactive contamination. More than 1 thousand forest sites in the south-western part of the Bryansk region were surveyed from 2019 to 2022. The ADER and the density of the soil contaminated by Cs-137 for every surveyed forest site are available. The relationship between the ADER and the density of the soil radioactive contamination in various sites was analyzed. The dose rates were normalized with respect to the density of soil contamination. The ADER rates in the Bryansk forest areas ranged from 0.07 to 3.15 mSv/h. No reliable difference between the ADER in the areas of coniferous and deciduous forests was observed. There was reliable linear relationship between ADER and the density of soil contaminated by Cs-137. During forestry operations in radioactive contaminated areas the maximum permissible external radiation effective dose was the dose accumulated for the whole period of work in the forest sites with the average density of soil contaminated by Cs-137 of 450 kBq/m2.

Оцінка радіоекологічної ситуації для території природного заповідника «Древлянський» станом на 2023 р.

Technological methods for preparing geospatial data for assessing the radioecological situation and visualizing the results using geographic information system (GIS) software packages are presented in the article. The current levels of soil l37Cs contamination density within the grid of forest quarters of the reserve are given. The article emphasizes that the current levels of radiation contamination in the reserve have an irregular distribution. In this work, the procedure for data preparation was developed and technological methods were tested to assess the current state of the radioactively contaminated territory by forest quarters. The interpolation method was used to eliminate unevenness in the mapping layer of the source data. Radioecological zoning of the territory based on the density of soil contamination with l37Cs for 2023 was carried out to determine the suitability of the territory for the implementation of forest protection measures. Critical areas that generate hazardous levels of dose load for the employees of the Reserve were identified on the maps. The spatial distribution of forest fallout density was calculated. The spatial distribution of radiation contamination of timber and flammable fuel material within the forest quarters of the reserve was estimated. The analysis of the current radioecological situation for the territory of the Drevlians Reserve showed the effectiveness of using modern ArcGIS and MapInfo software packages. Such software combines the following capabilities: preparation of information matrices for calculations and interpolation, in case of limited input data, grouping and classification by values, formation of thematic data sets for storage and further display of results on map schemes.

Assessment of annual effective dose from external exposure in forests of the south-western districts of the Bryansk region of Russia: 2015–2021

During a stay in a radioactively contaminated forest, a person is inevitably exposed to ionizing radiation from the man-made radionuclides. The purpose of this study was to evaluate the external component of the annual effective dose due to exposure in the forests contaminated following the Chernobyl accident. The study was conducted in the south-western districts of the Bryansk region of Russia in the period 2015–2021. Field (in situ) gamma spectrometric measurements were carried out on 46 forest plots located in the areas of 27 settlements. As of 01.01.2017, the officially established values of soil contamination density with 137Cs in the territory of the settlements themselves were in the range from 33 to 2050 kBq/m2 . According to the field gamma spectrometry, the density of soil contamination with 137Cs on the forest plots varied from 21 to 1930 kBq/m2 . The density of soil contamination with 137Cs in forest was in good agreement with the officially established level of soil contamination with 137Cs in the nearby settlement: the ratio of one indicator to another ranged from 0.70 to 1.32 (mean = 0.94; median = 0.95). The scatter in the measured values of the ambient dose equivalent rate from 137Cs was quite significant: more than one order of magnitude, from 31 to 2700 nSv/h. The variability of the ambient dose equivalent rate from natural radionuclides was relatively small: from 13 to 29 nSv/h. Based on the obtained experimental data and on published values of the duration of human stay in forest, the annual effective dose to selected groups of population was estimated. The dose from natural radionuclides, even in the case of a prolonged stay in the forest (1400 hours per year for foresters), did not exceed 0.02 mSv/year. The estimated values of the effective dose from 137Cs varied very widely from 0.001 to 1.9 mSv/year, depending on the selected forest plot and population group. On the whole, the data obtained indicate that the officially established values of the density of soil contamination with 137Cs in a settlement can be directly used in dosimetric models to estimate the component of the effective dose to a person due to his/her staying in the forest which is located in the area of this settlement. The currently recommended conversion coefficient from the density of soil contamination with 137Cs in a settlement to the ambient dose equivalent rate from 137Cs in the nearby forest is 1.28 (nSv/h)/(kBq/m2 ). To estimate the effective dose from natural radionuclides, it is recommended to use the value of the ambient dose equivalent rate equal to 21 nSv/h.

Restoration of surface soil contamination density to radionuclides at according to aerial photography

The problems that arise in the surface layer of the soil during periodic emissions at nuclear power plants are considered. The necessity of constant monitoring of this soil layer at different times of the year is substantiated. Various methods of this control are considered. It has been established that it is extremely difficult to implement them in remote areas. A method has been developed for monitoring the surface layer of the soil using aerodynamic survey of the distribution of γ-radiation on the soil surface. This is extremely important during the preparation of agricultural fields for sowing crops in the spring. A new algorithm for restoring images obtained using aerodynamic imaging of γ-radiation is proposed. The results of a new algorithm for image processing and identification are presented.

Экологические особенности накопления радионуклидов компонентами наземных экосистем зоны отчуждения

The studies were carried out 30 years after the Chernobyl accident on the lands of the former land use subject to natural successional changes. The patterns of the lateral distribution of 137Cs, 90Sr, 241Am in the upper 20-cm soil layer of various biogeocenoses, including those depending on the height fluctuations of the relief, have been studied. The values of the coefficient of variation (V) of the content of radionuclides in the upper soil layer decrease with the time that has passed since the accident. The highest value of the coefficient of variation (75.2 %) was obtained for 90Sr in the soil in the pine forest. The influence of various soil conditions on the entry of radionuclides into birch sap, cap mushrooms, and meadow grasses was studied. Despite the significant excess of the density of soil contamination with 137Cs of all the studied communities (up to 9.1 times), its volumetric activity in the juice is significantly lower than 90Sr, which indicates a lower availability of 137Cs compared to 90Sr. Dynamic processes of accumulation of radionuclides during the entire period of the movement of sap are studied. With increase in extent of moistening of the soil, accumulation of radionuclides in mushrooms tends to decrease. At the same time differences between types is established that connected with feeding habits of mushroom and variability of microclimatic conditions. The effect of soil moisture content, the ratio of 137Cs mobility forms in the soil on the biological availability of the radionuclide by meadow grasses was studied. A decrease in the specific activity of radionuclides in the plant components of ecosystems was found as the phytocenoses moved away from the epicenter of the accident at an identical density of soil contamination. A relationship has been established between the accumulation of radionuclides and the agrochemical parameters of the soil: maintenance of humus, absorption capacity, cation exchange capacity, hydrolytic acidity, content of exchange phosphorus, concentration of mobile calcium, magnesium and potassium on post-agrogenic lands. The analysis of the soil-to-plant transfer factors (Cf) and aggregated transfer factors (Tag), the discrimination coefficient (DF) of 137Cs by a chemical analog element (potassium) was carried out. Species features of plants associated with the transport of K+ - Cs+ cations make significant adjustments to the mechanisms of 137Cs accumulation. Attention is drawn to the significant increase in the concentration of 90Sr in all components in recent years.

Ambient dose equivalent rate from <sup>137</sup>Cs and natural radionuclides in one-story residential buildings in settlements of the Bryansk region in 2020–2021

Method of in situ gamma-ray spectrometry was used to discriminate contributions of 137Cs and natural radionuclides to ambient dose equivalent rate indoors in settlements located in the zones of radioactive contamination after the Chernobyl accident. The measurements using a portable scintillation gamma spectrometer-dosimeter were carried out in 115 individual one-story residential buildings in 46 settlements of the Bryansk region of Russia in the summer period of 2020–2021. According to official data, the average density of soil contamination with 137Cs in the settlements ranged from 27 to 533 kBq/m2. Based on the type of building materials that had been used to construct the walls, the surveyed houses were divided into three large groups: wooden (walls made of logs) – 51 buildings, stone (walls built of bricks and/or concrete panels) – 34 buildings, and frame-panel – 30 buildings. The latter had walls constructed of wooden panels with the inclusion of heat-insulating material. Outside, the walls of the frame-panel houses were lined with a layer of silicate (white) bricks. 70 houses were built before the accident and 37 – after the accident. In eight cases it was not possible to reliably estimate the period of construction. The total ambient dose equivalent rate ranged from 42 to 228 nSv/h (average = 77 nSv/h). The values of the ambient dose equivalent rate from natural radionuclides were in the range 27–122 nSv/h. The average values of the ambient dose equivalent rate from natural radionuclides in the groups of wooden, frame-panel, and stone houses were 42, 42 and 58 nSv/h, respectively. The difference between stone houses and panel houses was statistically significant (P < 0.01). The same difference was found between stone houses and wooden houses (P < 0.01). The average values of the ambient dose equivalent rate from 137Cs, normalized to the density of soil contamination with 137Cs, were 0.13, 0.16, and 0.05 (nSv/h)/(kBq/m2) in wooden, frame-panel, and stone houses, respectively. The normalized ambient dose equivalent rates from 137Cs in the group of stone houses were statistically significantly (P < 0.01) lower compared to the corresponding values for the groups of wooden houses and frame-panel houses. The small differences between frame-panel and wooden houses turned out to be statistically significant (P < 0.05). The median and mean values of the normalized ambient dose equivalent rate from 137Cs for houses built before the accident were lower compared to those for houses built after the accident. These differences were statistically significant (P < 0.01) for all groups of houses. The mean values of the normalized ambient dose equivalent rate from 137Cs and the ambient dose equivalent rate from natural radionuclides obtained in this study can be used to estimate the external effective dose to a person staying inside a one-story residential building. In this case, one should take into account not only the type of building materials used to construct the house, but also the time period of the construction: before or after the Chernobyl accident.

Accumulation of 90SR by Betula pendula within the East Ural Radioactive Trace zone

This study was conducted in 2010–2020 at the head of the East Ural Radioactive Trace (EURT), which was formed in 1957 as a result of the Kyshtym accident at the Mayak Production Association. The main contaminant in this zone is the long-lived radionuclide Strontium-90 (90Sr). Secondary forests dominated by silver birch (Betula pendula) occupy 45% of the EURT area. Concentration of 90Sr in birch leaves and small branches was higher than that in the trunks. The 90Sr content in birch sapwood varied slightly in the radial direction and did not depend on tree age. This was due to the dynamic equilibrium of the migration processes responsible for the accumulation and horizontal transfer of 90Sr. The 90Sr concentration increases in false heartwood, which is formed as a result of the secondary metabolism of dying parenchyma in the inner part of sapwood and is characterised by a high content of ash elements. The concentration of radionuclides in the aboveground organs of birch increased and the aggregated transfer factors (Tag) decreased with an increase in the soil contamination density, in accordance with the power function. The reasons for these patterns are also discussed.

Аккумуляция радионуклида в гибридном материале желтого люпина

In the 90s of the last century, in the breeding nurseries of the Novozybkov Agricultural Experimental Station, samples with a relatively low concentration of cesium-137 in the seeds and green mass of yellow lupine were selected: 4-83, SN-1408, 52-87-2113, variety Kastrychnik, etc. They were involved in hybrid combinations and received numbers 1-00-2-9, 1-02 and 10-04, 7-09, 8-12, which have been repeatedly used as parental forms in crosses in recent years. Studies have shown the possibility of obtaining positive results in blocking the accumulation of cesium-137 at the early stages of the breeding process, which contributes to the preservation of valuable material for further study during hybridization and the creation of yellow lupine varieties with the lowest possible content of 137Cs in the final product. For 2018–2019 varieties of hybrid origin of yellow lupine with a consistently low accumulation of cesium-137 in the grain were identified, regardless of the density of soil pollution: 5-14-11 (112 and 243 Bq/kg), 5-12-92 (206 and 221 Bq/kg), 13-10-96 (270 and 243 Bq/kg), 15-10-7212 (235 and 271 Bq/kg). Despite the higher density of soil contamination by 13–33% in 2019, in the hybrid material 2-08-57, 4-08-116, 11-10-65 and 12-10-66, the concentration of 137Cs in grain decreased by 63% with indirect participation in crosses of variety samples selected in 1994–1996. In 2020, the analysis of 13 samples showed a significant decrease in the accumulation of cesium-137 in grain to 61–136 Bq/kg, regardless of the decrease (8–34%) or increase (5–46%) in the density of soil contamination relative to 2018–2019, as well as grain yield. Stability in terms of the content of cesium-137 in the green mass was not obtained: in 2018, out of 60 samples, 12 variety samples fit into the standard for dry matter (400 Bq/kg), in 2019 they were absent due to the low yield of green mass. Accessions 5-12-92, 5-14-11, 13-10-96, 4-08-116, etc. were included in crosses as parental forms, and the resulting offspring are being tested in hybrid and breeding nurseries for the purpose of research on blocking the accumulation of 137Cs in yellow lupine grain. It has been established that within three years the lowest radionuclide content in yellow lupine grain was obtained from samples 5-12-92 and 5-14-11, with which seed nurseries for testing offspring will be established.

Оценка радиационной обстановки в районе расположения АО «ГНЦ НИИАР» до начала эксплуатации ИЯУ МБИР. Часть 1. Наземные экосистемы

The paper presents results of radiation survey of terrestrial (natural and agrarian) ecosystems in the 30-km zone around the State Scientific Centre "Research Institute of Atomic Reactors" (SSC RIAR, Institute) before the commissioning of the fast neutron reactor MBIR. Due to long-term emissions during the RIAR operation, 137Cs was mainly emitted into the environment. The most part of the radionuclide activity never extends beyond the border of the Institute sanitary protec-tion zone. In 2011 the average density contamination of the soil with 137Cs was 11.16.5 in the sanitary protection zone (0-5 km), 3.12.3 in the observation zone (5-12.5 km), 1.30.4 kBq/m2 in the influence zone (12.5-30 km). The 137Cs/90Sr ratio is maximum in the soil cover in the sanitary protection zone – 24.519.4; it is 8.26.8 in the observation zone and it is close to the level of global fallout – 2.00.5 in the influence zone. More than 90% of 137Cs is deposited in the 0-5 cm soil layer in forest and meadow cenoses and the radionuclide is deposited at a depth of up to 20 cm in a swamp. The highest 137Cs concentration was found in ecosystems components: in vege-tation in the RIAR sanitary protection zone and, to a greater extent, in forest litter. At the initial pe-riod of RIAR operation discharges of process water happened, a piece of land of 0.12 km2 was contaminated with 137Cs, 90Sr and 239,240Pu. Over the past 15 years (2005-2020), the density of soil contamination with 137Cs and 90Sr in RIAR zones of observation and influence has been decaying in accordance with the radioactive decay law. It means that no significant emissions from the In-stitute have been registered. The content of artificial radionuclides in agricultural products and foodstuffs of local production fully meets the established radiological standards and does not have a significant effect on the additional exposure of the population living near RIAR. To assess the impact of the SSC “RIAR" activities on the environment and to assess the radiation safety of the MBIR after putting it in operation, a forecast of 137Cs and 90Sr contamination levels in soils of terrestrial ecosystems within 30-km around the Institute until 2080 was made.

RADIOACTIVELY CONTAMINATED TERRITORIES OF CHERNIHIVSKA OBLAST OF UKRAINE: THE RADIATION-ECOLOGICAL AND MEDICAL-DEMOGRAPHIC PAST AND PRESENT.

to determine the current radiationecological and medicaldemographic parameters of the territories of Chernihivska oblast of Ukraine, which were recognized as radioactively contaminated as a result of the Chornobyl Nuclear Power Plant accident, and to assess their changes in the postaccident period. The parameters of contamination of natural environments (soil, food products), both with number, structure, natural and migratory movement of population of radioactively contaminated territories of Chernihivska oblast of Ukraine (Kozeletskyi, Koriukivskyi, NovhorodSiverskyi, Ripkynskyi, Semenivskyi, Sosnytskyi, and Chernihivskyi districts) were the study objects. Data from the Chernihiv Regional Office of the State Statistics Service of Ukraine,Department of Ecology and Natural Resources of the Chernihiv Regional State Administration, and CentralEnvironmental Dosimetry Register of the State Institution «National Research Center for Radiation Medicine of the National Academy of Medical Sciences of Ukraine» were used. General scientific, mathematicalstatistical, graphic, cartographic, and softwaretechnological research methods are applied. After the accident at the Chornobyl Nuclear Power Plant the largescale radioecological monitoring was conducted on the territory of Chernihivska oblast, where a significant improvement in the state of radioactively contaminated areas had been observed. The number of settlements where the soil contamination density with cesium isotopes exceeded the lower limit for the zone of guaranteed voluntary resettlement (185 kBq*m2) has decreased from 8 to 1. The average regional concentration of 137Cs in milk mostly did not exceed 50 Bq*l1. The average concentration of 137Cs in potatoes from private households over the entire observation period was 5-10 times lower than in milk. Analysis of medical and demographic data allowed concluding that the districts of Chernihivska oblast, which were most intensively contaminated after the Chornobyl accident, feature now some regional problems. There are trends towards population decline and birth rate decrease along with increase in mortality. The most intensive changes had occurred in Kozeletskyi and Ripkynskyi districts, where destructive processes in the age structure of population and a stable trend of increase of mortality rates were revealed. Research should be continued.

EXPRESS ESTIMATION OF SOIL POLLUTION DENSITY BY PLANTING ISOTOPES OF CHERNOBYL ORIGIN

The article considers an approach of finding a rapid estimate of soil contamination density of plutonium isotopes in a radiological survey of agricultural lands on the south-western trace of Chernobyl radioactive fallout outside the Chernobyl Exclusion Zone. An algorithm based on a linear correlation between values of 90Sr and 238,239,240Pu activity in soil samples was developed. The algorithm was tested during a radiological field survey of abandoned lands in Narodychi district. The results of the approbation showed a satisfactory convergence of obtained estimates of soil contamination with plutonium isotopes of Chernobyl origin with experimental results. The proposed algorithm may be a part of the decision-making system at reviewing the boundaries of radioactive contamination zones and returning in the use agricultural lands that were abandoned after the Chernobyl accident.

Ambient dose equivalent rate and soil contamination density with 137Cs in kitchen gardens in settlements of the Bryansk region, Russia in 2020–2021

The article provides results of application of the field (in situ) gamma spectrometry method for carrying out mass monitoring measurements of ambient dose equivalent rate and soil contamination density with 137Cs in kitchen garden plots located in the zone of radioactive contamination after the Chernobyl accident. In 2020 and 2021, 115 private farmsteads in 46 settlements of the Bryansk region were surveyed. At the time of the survey, the officially established average density of soil contamination with 137Cs in the settlements ranged from 27 to 533 kBq/m2 . The field spectra were measured using a portable scintillation gamma-spectrometer-dosimeter. Results of the field measurements and subsequent calculations of soil contamination density with 137Cs in the kitchen gardens were in good agreement with official data on the average soil contamination density with 137Cs in the surveyed settlements. The mean value of the ratio of the experimental data to the official data was 1.04. Individual values of experimental data deviated from corresponding official values by no more than two times. The use of the gamma spectrometry method in situ made it possible: 1) to determine separately values of the ambient dose equivalent rate from 137Cs and from natural radionuclides in the soil, and 2) to estimate the effective external doses to a person who worked in the kitchen gardens. The measured values of ambient dose equivalent rate varied from 17 to 53 nSv/h (mean ± standard deviation = 35 ± 9 nSv/h) for natural radionuclides and from 8 to 432 nSv/h (mean ± standard deviation = 125 ± 91 nSv/h) for 137Cs. The ambient dose equivalent rate from 137Cs normalized to the soil contamination density with 137Cs in the same kitchen garden was in the range of 0.41–0.84 (nSv/h)/(kBq/m2 ) with a mean value of 0.55 (nSv/h)/(kBq/m2 ). If a person stayed in kitchen garden for 840 hours per year, the estimated effective external doses from natural radionuclides and 137Cs were respectively in the range of 0.008–0.025 mSv/year and 0.004–0.20 mSv/year.

ЗАКОНОМІРНОСТІ МІГРАЦІЇ 137CS НА ГЕОХІМІЧНИХ БАР’ЄРАХ КРАЙОВОЇ ЗОНИ МЕЗОТРОФНОГО БОЛОТА В УКРАЇНСЬКОМУ ПОЛІССІ

It was shown that in the narrow marginal zone (about 6-8 m wide) of a mezotrophic bog, typical for the northern part of Ukrainian Polissya, a transsuperaquatic landscape is formed between transacumulative and superaquatic landscapes. In the transsuperaquatic landscape a complex biogeochemical barrier has been formed. Here, at a short distance, barriers of different types are spatially connected – physico-chemical (sorption, gley etc.) and phytocenotic (all vegetation layers), lateral and radial. It was found that due to lateral 137Cs redistribution among the geochemically connected landscapes of the catena, there was observed the concentration of the radionuclide on the investigated complex biogeochemical barrier. Three biogeochemical barriers were found in the soil – layers of semi-decomposed residuals of mosses, trees and grasses (H0dt), peat (Т1-Т5) and iluvial humic-ferruginous gley horizon (Ihgl), which slow down 137Cs migration both in lateral and radial directions. Generalization of datа on 137Cs radial distribution in the soil of the geochemical barrier shows that analogs of the forest litter (H0 non-decomposed and layer of H0dt – semi-decomposed plant residuals) contained 8.16% of the total 137Cs activity in the soil; peat (0-25 cm) – 17.14%, and the mineral horizons (Ihgl and Pigl) – 74.7%. This distribution testifies about high speed of radial 137Cs migration in the studied soil, insofar as the main part of the total activity of 137Cs has already migrated beyond the boundaries of the peat layers to the mineral horizons. The calculations showed that the main part of the total stock of 137Cs in biogeocenosis on the biogeochemical barrier in the transsuperaquatic landscape was retained in soil – 86.59%, accordingly phytocenosis contained 13.41% of the total stock of the radionuclide. The geochemical transfer coefficient was 0.16, which was close to the corresponding values for the superaquatic landscapes. Significant interspecific differences in 137Cs accumulation were observed in all layers of vegetation. The migration ability of 137Cs in the chains «soil – plant» and «soil – fungi» in the transsuperaquatic landscape was evaluated based on the mean 137Cs transfer factor (TF) values to be 2-20 times higher than that for the eluvial and transeluvial landscapes. This leads to significant excess of the permissible levels of the 137Cs specific activity in medicinal plants, wild berries and edible mushrooms at soil contamination density with 137Cs which is not officially regarded as radiationally hazardous (about two times less than 37 kBq·m-2).

Накопичення 137Cs у суміші лучних трав на торфово-болотних ґрунтах зони Полісся у Рівненській області

The role and effectiveness of the combined action of various types of mineral fertilizers on the productivity of the agrocenosis and the accumulation of radionuclides by the phytomass of perennial grasses on peat-bog soil (Histic Gleysols) have been investigated. The research was carried out during 2011-2013. In a temporary field experiment with seeded perennial grasses (Dáctylis glomeráta, Bromopsis inermis, Phleum pratense) used for livestock feed. The aim of the research is to identify the features of the effect of radiological load on the quality of agricultural products in fertilized and non-fertilized areas by measuring the specific activity of radioactive 137Cs in the dry phytomass of collected herbs, the density of soil contamination and calculating the coefficients of the transfer of radionuclides from soil to pasture fodder. The activity of 137Cs in plants was determined by gamma spectrometer. The introduction of increased doses of potash (K120) and phosphorus fertilizers together with potash (P60 K120) was effective in reducing the activity of radiocaesium in the dry mass of feed. Over the three years of research on the variant with potash fertilizers, a decrease in 137Cs activity in the feed by an average of 2.9 times was recorded, and at the site of the combined application of potash and phosphate fertilizers – by 2.7 times compared with the control variant of the experiment (without fertilizers).

Induction of useful mutations in Triticum aestivum in the conditions of the radionuclide-contaminated alienation zone of the Chornobyl Power Plant

Induced mutagenesis opens great perspectives for radical genetic improvement of cultivated plants. Scientists seeking new sources and methodological approaches to improve the frequency and extend the range of mutations have drawn attention to the Zone of Alienation around the Chornobyl Nuclear Power Plant, where unique conditions of the influence of mutagenic factors have developed, and therefore needs to be studied for possible use of its territory in propagating parent material for selective breeding of wheat. Plants of winter wheat of Albatros Odesky and Zymoiarka varieties were grown within 10 km of the Chernobyl Plant, inside the Alienation Zone, in Chystohalivka, Kopachi and Yaniv villages of Chornobyl district of Kyiv Oblast. The exposure occurred in the dose of 7.2 ∙ 10–12– 50.0 ∙ 10–12 A/kg. As the control, we used the territory of the Research Institute of Physiology of Plants and Genetics of the Academy of Sciences of Ukraine (Hlevaha urbanized settlement of Vasylkivsky District of Kyiv Oblast), where the power of the exposure dose equaled 0.93 ∙ 10–12 A/kg. Frequency and spectrum of mutant forms were determined in M2–M3 generations according to the ratio of the number of families with mutagenic plants to studied M2 families. Among the observed mutations, we determined the share of the ones important for selective breeding. Chronic ionizing radiation throughout the vegetation period of winter wheat increased the level of noticeable mutations, the frequency of which exceeded the control parameters by 8.0–14.9 times. In the conditions of cultivation of winter wheat in the territory of Kopachi village, where the dose was the lowest, we recorded a high level of mutation variability which exceeded the control parameters by 8.0–9.2 times and was notably different from the frequency of mutations induced by radionuclide contamination of soil in the territories of Chystohalivka and Yaniv villages. The mutation range contained 12–20 types and depended on the density of soil contamination with radio nuclides, magnitude of exposure dose and genotype of plants. The predominant mutations were the ones related to the duration of vegetation period, length of the stem, morphology and awns of the ear. Among the detected mutations, the important selective ones accounted for 24.3–49.3%, predominant being low height, intense growth and long cylindrical ear. Because beneficial agronomic traits are highly likely to be inherited in complex with mutations that reduce the productivity of winter wheat, efficiency of direct selection of mutant forms that are valuable for selective breeding is limited. Enlargement of genetic diversity of the initial selection material using the radionuclide-induced mutagenesis resulting from contamination creates the possibility of using it in cross breeding for the purpose of implementing selective breeding genetic programs of improving wheat varieties.

Validation of a method for in situ determination of 137Cs soil contamination density in kitchen gardens using the portable spectrometer-dosimeter MKS AT6101D

The collection of representative soil samples in the territory of settlements and subsequent measurements of the content of radionuclides in these samples under laboratory conditions (the so-called “ex situ method”) is a generally accepted technology for determining the density of soil contamination with 137Cs in the populated areas contaminated due to the Chernobyl accident. Recently, as a supplement or alternative to the ex situ method, researchers are developing field (in situ) gamma-spectrometry methods. These methods allow determining the density of soil contamination with 137Cs directly on site, without soil sampling and laboratory analysis. At the same time, the in situ methodology has several limitations, the most important of which is a lack of generally recognized metrological basis for measurements and interpretation of results. Hence, before using a particular technique and measuring device for carrying out large-scale in situ measurements, it is necessary to validate (to assess the suitability) of the selected in situ method using an established ex situ method. The aim of this study was to validate the method for determining the density of 137Cs soil contamination in kitchen gardens using the MKS AT6101D spectrometer-dosimeter in situ. The method was recently presented by a Russian-Swedish-Belarusian group of researchers in an article published in the Journal of Environmental Radioactivity (https://doi.org/10.1016/j.jenvrad.2021.106562). To validate this method, we selected 10 representative kitchen garden plots. The plots were located in six settlements of the Bryansk region in Russia. The territory of the settlements had been heavily contaminated with 137Cs as a result of the Chernobyl accident: the officially established levels of the density of soil contamination by 137Cs ranged from 111 to 511 kBq/m2 in 2017. Field gamma-ray spectra were recorded at a height of 1 m above the ground in the center of kitchen garden plots using the MKS AT6101D device. The measurement duration was in the range of 1207–1801 s (the mean value = 1383 s). Samples of soil in the kitchen gardens were taken layer by layer (with a step of 5 cm) to a depth of 20 cm using a demountable cylindrical sampler. The 137Cs content in each soil layer was determined in the laboratory using a stationary semiconductor gamma spectrometer. The values of the 137Cs contamination density of the sampled soils ranged from 77 to 548 kBq/m2. It was found that the results of the ex situ analyzes of soil samples were in a good agreement with the contamination density values obtained with the in situ method. On average, the difference between two methodologies was 7% (a maximum of 20%). The results of the study confirm that the method proposed by the international group is suitable for determining the density of soil contamination by 137Cs in kitchen gardens in remote period after the Chernobyl accident.