137Cs Contamination Research Articles

СТАТИСТИЧЕСКОЕ ПРОГНОЗИРОВАНИЕ НАКОПЛЕНИЯ 137Cs В ПРОДУКЦИИ РАСТЕНИЕВОДСТВА НА РАДИОАКТИВНО ЗАГРЯЗНЕННЫХ ТЕРРИТОРИЯХ

Purpose: the development of statistical models for forecasting the accumulation of 137Cs in crop production, model parameterisation and prognostic estimates for the territories of the Bryansk region contaminated with 137Cs because of the Chernobyl accident. Material and methods: The use of a probabilistic approach for correct predictive assessments of the safety of agricultural products from radioactively contaminated agricultural lands has been substantiated. Analytical models were developed in the framework of a probabilistic approach to predict the risks of radioactive contamination of crop products, to assess the permissible levels of contamination of arable lands and the time of their natural remediation. Results: Based on a statistical analysis of radioecological survey data, it was established that the 137Cs contamination density of the soil follows a lognormal distribution law with a high level of significance. For farms in the south-western districts of the Bryansk region, it was shown that, if the average values of 137Cs content in crop production corresponded to the established standard, the risks of its excess could reach 30 %. This is due to the variability of 137Cs soil contamination densities and migration parameters. The dependences of limiting soil contamination densities of 137Cs on the risk of exceeding the standards (RES) of the content of this radionuclide in products were presented. The time of natural rehabilitation of arable agricultural land with a given risk for products of 10 % can exceed 30 years. Conclusion: The application of probabilistic methods to predict the consequences of 137Cs contamination of agricultural lands makes it possible to correct practical recommendations developed on the basis of a deterministic approach. The results of prognostic calculations are the basis for planning and evaluating the possibility of returning territories contaminated by 137Cs to economic use. The developed methodology and models can be used in the development of decision support systems for the remediation of agricultural lands exposed to radioactive fallout.

Оцінка можливості повернення до господарського обігу виведених, внаслідок аварії на ЧАЕС, пасовищ і cіножатей

A radiological assessment of hayfields and pastures (Narodychy district, Zhytomyr region), which were taken out of economic use due to contamination after the Chornobyl accident, was performed. The possibility and ways of returning the lands to original use were considered. Maps of 137Cs and 90Sr soil contamination densities for the field were made and the corresponding statistical characteristics of the contamination were estimated. Estimates of 137Cs and 90Sr activity concentration in natural grasses, cow milk, and meat as well as the risks of exceeding by the values the permissible levels have been calculated. The possibility of using the land for the production of milk and meat has been shown in the example of the considered radioactively contaminated pastures.

137Cs and 40K activity concentrations in edible wild mushrooms from China regions during the 2014–2016 period

Introduction. Contamination by radiocaesium of edible wild mushrooms after major nuclear accidents is a long-lasting process in some regions of the world. Following greater awareness of radioactive pollution in Asia, particularly after the Fukushima accident, this study investigated the radioactivity of 137Cs and 40K contamination in edible wild mushrooms in China.
 Study objects and methods. The objects of the research were edible wild mushrooms collected during 2014 to 2016, from the Inner Mongolian and Yunnan regions of China. To obtain an insight into any environmental impacts to distant regions of mainland Asia, the mushrooms were analyzed for 137Cs activity. In parallel, the natural activity of 40K was also determined and used to estimate the content of total K. The topsoil underneath the mushrooms was also investigated from a few sites in Bayanhushu in Inner Mongolia in 2015.
 Results and discussion. The results showed that in 4 to 6 mushrooming seasons after the accident, mushrooms from both regions were only slightly contaminated with 137Cs, which implied negligible consequences. The activity concentrations of 137Cs in dried caps and whole mushrooms in 63 of 70 lots from 26 locations were well below 20 Bq kg–1 dry weight. Two species (Lactarius hygrophoroides L. and Lactarius volemus L.), from Jiulongchi in Yuxi prefecture showed higher 137Cs activities, from 130 ± 5 to 210 ± 13 Bq kg–1 dw in the caps. 40K activities of mushrooms were around two- to three-fold higher. A composite sample of topsoil (0–10 cm layer) from the Bayanhushu site (altitude 920 m a.s.l.) in Inner Mongolia showed 137Cs activity concentration at a low level of 6.8 ± 0.7 Bq kg–1 dw, but it was relatively rich in potassium (40K of 595 ± 41 Bq kg–1 and total K of 17000 ± 1000 mg kg–1 dw).
 Conclusion. Wild mushrooms from the Yunnan and Inner Mongolia lands only slightly affected with radioactivity from artificial 137Cs. Lack of 134Cs showed negligible impact from Fukushima fallout. Ionizing radiation dose from 137Cs in potential meals was a fraction of 40K radioactivity. The associated dietary exposure to ionizing irradiation from 137Cs and 40K contained in mushrooms from the regions studied was considered negligible and low, respectively. Mushroom species examined in this study are a potentially good source of dietary potassium.

Laser decontamination microscopic process study on radioactive contaminations with Cs+ ion of 304 stainless steel surface

The decommissioning of contaminated metal equipment in nuclear facilities may produce a wide range of radioactive waste. For metallic equipment like the primary loop, the radioactivity is mainly located in the oxide surface. Laser decontamination was performed on 304 stainless steel specimens with a stable isotope Cs contamination layer. Laser melting was used to create oxide layer on the surface of polished specimen for enhancing the penetration of Cs+ ion. The interaction between laser and matter (contamination, oxide and substrate) was studied by the stratification theory considering the difference in the thickness of contamination layer. At higher pulse duration (τp = 5ns), laser decontamination is mainly caused by thermal effects. The metal near oxide layer melts and vaporizes to form a molten pool and crater. For short pulse duration (τp = 1ns), the removal of surface contaminations mainly depends on thermal effect and stress wave, CsCl particles were removed by vaporization; however, oxide layer was stripped from the substrate in the form of solid fragment. For ultra-short pulse duration (τp = 150ps), the oxide layer has been partially ablated. Most of the heat absorbed by γ (austenite) is used for heating and evaporation to form porous structure, while the great mass of heat absorbed by M (martensite) is used for thermal diffusion. Therefore, the M regions only form a dynamic molten pool on its surface without vaporization.

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.

The impact of radioactive contamination on tree regeneration and forest development in the Chernobyl Exclusion Zone

AbstractQuestionsNuclear power is under increasing consideration in many countries because it is a low‐carbon strategy to satisfy growing energy demands. Yet, the long‐term environmental impacts of nuclear accidents remain unclear. Here we asked how ionizing radiation affects tree regeneration and forest development after the Chernobyl nuclear accident. We hypothesized that high levels of 137Cs contamination in the soil: (a) inhibit tree establishment; (b) accelerate structural development (i.e., facilitation of an early differentiation of tree sizes); while (c) prolonging the dominance of early‐seral deciduous communities (because of an elevated susceptibility of conifers to ionizing radiation).LocationChernobyl Exclusion Zone, Ukraine.MethodsWe sampled 103 plots on former agricultural lands in the Chernobyl Exclusion Zone that were abandoned after the accident in 1986.ResultsContamination had no significant effect on the stem density of forests established on former agricultural lands (p = 0.769). Structural development was not accelerated by radioactive contamination (p > 0.191), but we did find weak indications that the presence of tree regeneration was reduced by high radiation levels (p = 0.054). Tree species composition did not vary significantly with contamination (p = 0.250). Individual Scots pine trees did, however, experience a considerably higher proportion of deformed stems when contamination levels were high (p = 0.009).ConclusionsOur analyses confirm negative effects of radioactive contamination on the individual tree health of Scots pine, yet early stand development in the Chernobyl Exclusion Zone was largely insensitive to different levels of radiation. As wildfires threaten to remobilize and redistribute radionuclides stored in the growing forests of the Chernobyl Exclusion Zone, our findings have potential implications for human health. We conclude that forest dynamics is a key element for assessing the long‐term risk at nuclear accident sites and requires intensified research and monitoring.

Агрохимические аспекты реабилитации радиоактивно загрязнённых заливных лугов Брянской области

Natural fodder lands are a fodder base for livestock production in Bryansk region. The lands cover the area of 5500 km2, its greater part was contaminated with long-lived artificial radionuclides due to the Chernobyl accident. Therefore, there was a risk of contamination of the forage for dairy livestock with Cs-137 and its content in the grass would exceed the acceptable limit. Long after the Chernobyl accident the measures to remediate contaminated floodplains in Iput River in Novozybkovsky district of the Bryansk region for further use in feed production were examined. It was found that if Cs-137 contamination density exceeded 555 kBq/m2 the radionuclide content in the mass of air-dry wild grasses would be ≥5.5 times higher than the acceptable limit depending on a harvesting period. Due to the use of agrotechnical and organizational measures to improve the quality of radiation contaminated flood meadows the Cs-137 specific activity in air-dry cultivated grasses reduced by 10% as compared with the radionuclide activity in natural/wild grasses. The use of agrochemical measures for remediation of radiation contaminated flood meadows allowed to obtain air-dry masses of wild and cultivated grasses with the acceptable limit of Cs-137 radioactivity in fodders. The maximum effect was obtained when applying mineral fertilizers with a ratio of nitrogen to potassium as 1:2. Due to the use of correlation analysis it became made evident that the presence of nitrogen fertilizer increased Cs-137 specific activity in the fodder and there was the correlation between calendar years of the study and the amount of nitrogen fertilizers in soil. The correlation between the amount of nitrogen fertilizer in the soil and the specific activity of Cs-137 in the air-dry mass of natural and cultivated grasses during the years of 2003-2008 was strong and ranged from 0.76 to 0.85. In the study periods from 2009 to 2014, the impact of nitrogen fertilizer on the radionuclide specific activity in feed decreased regardless of the harvest period of natural and cultivated grasses. The correlation coefficient ranged from 0.38 to 0.58, the correlation strength was average. With the use of correlation analysis nitrogen fertilizers were found to increase the specific activity of Cs-137 in airdry grass mass, the correlation strength depends on calendar years of the study, it may be strong and average. Adding potassium fertilizer into soil negate the negative effect of nitrogen fertilizers. The use of radioactive floodplains as hay fields without the use of agrochemical measures is unacceptable. According to made calculations, the use of coarse fodder grown on radiation contaminated lands leads to milk contaminated with Cs-137 content that exceeds the limit established by standard.

241Am and 137Сs in the Khoiniki district of Belarus: updated radiological assessment of the local existing exposure situation

The results covered in this paper relate to the “Khoiniki” research sub-unit of a larger-scale sequence of studies focused on the local assessments of the present-day 241Am and 137Cs concentrations in the soils and locally produced foods, with the estimation of the public internal radiation doses in the residential areas of the Gomel region of the Republic of Belarus most closely adjacent to the ChNPP resettlement zone. The objective was to make a conservative estimate of a committed annual dose of internal exposure from 241Am and 137Сs received by the villagers of 96 farmsteads in 30 settlements of the private sector of Khoiniki countryside through both, inhalation and consumption of local foodstuffs. The results obtained in this study include an update of the existing contamination levels of 241Am and 137Сs present in the local soils and foods grown or produced in private backyards and households. 241Am in food samples was determined by alpha-spectroscopy radiochemical analysis with the use of selective extraction-chromatographic resins. Gamma-spectrometry techniques were used to measure 241Am in soil samples and 137Сs in soil and food samples. Based on our findings, the present-day deposition density of 241Am in the soils does not exceed 4 kBq/m2 , while the values of 137Cs contamination are by one to two orders of magnitude higher than that of 241Am and vary between 30 and 500 kBq/m2 . Generally, the values of activity concentration of 241Am detected in local soils are well within 10 Bq/kg in the majority of inspected villages, with the exception of three sites where higher levels of 241Am contamination is soils were detected ranging from 14 to 16 Bq/kg. The ambient dose rates in the countryside range from 0.05 to 0.38 μSv/hour, with the average of 0.15 μSv/hour. No cases of 137Сs contamination above the established reference levels of 80, 100 and 90 Bq/ kg have been found in the local food samples of, respectively, potatoes, vegetables (incl. roots and tubers) and grains. The content of 241Am in the staple foods produced in the area varies from single digits to tenths of mBq/ kg, which is less by three orders of magnitude than 137Сs activities concentrationd found in the same staples. Of the two pathways contributing to the local committed internal exposure from 241Am, the dominant one is through inhalation (0.006–0.038 mSv/year) prevailing over the consumption pathway of this same radioisotope by at least one order of magnitude. At the time of gardening and other household field works, the existing levels of 241Am contamination in soils are estimated to produce from 85 to 98% of the internal radiation dose received by individuals from inhaling the total of 241Am and 137Сs. The maximum committed annual doses of internal exposure from 137Сs are estimated to be above 1 mSv/year in 6 out of 30 villages engaged in our study. At the same time, the estimated internal radiation dose due to 241Am does not surpass 0.04 mSv/year. The 137Сs major contribution to the internal exposure of villages in the Khoiniki countryside is through food consumption.

Transport and Fate of 137Cs Released From Multiple Sources in the North Atlantic and Arctic Oceans

The North Atlantic and Arctic oceans, along with the North Pacific, are the main reservoirs of anthropogenic radionuclides introduced in the past 75 years. The POSEIDON-R compartment model was applied to the North Atlantic and Arctic oceans to reconstruct 137Cs contamination in 1945–2020 due to multiple sources: global fallout, exchange flows with other oceans, point-source inputs in the ocean from reprocessing plants and other nuclear facilities, the impact of the Chernobyl accident and secondary contamination resulting from river runoff and redissolution from bottom sediments. The model simulated the marine environment as a system of 3D compartments comprising the water column, bottom sediment, and biota. The dynamic model described the transfer of 137Cs through the pelagic and benthic food chains. The simulation results were validated using the marine database MARIS. The calculated concentrations of 137Cs in the seaweed and non-piscivorous and piscivorous pelagic fish mostly followed the concentration of 137Cs in water. The concentration in coastal predator fish lagged behind the concentration in water as a result of a diet that includes both pelagic and benthic organisms. The impact of each considered source on the total concentration of 137Cs in non-piscivorous fish in the regions of interest was analyzed. Whereas the contribution from global fallout dominated in 1960–1970, in 1970–1990, the contribution of 137Cs released from reprocessing plants exceeded the contributions from other sources in almost all considered regions. Secondary contamination due to river runoff was less than 4% of ocean influx. The maximum total inventory of 137Cs in the Arctic Ocean (31,122 TBq) was reached in 1988, whereas the corresponding inventory in the bottom sediment was approximately 6% of the total. The general agreement between simulated and observed 137Cs concentrations in water and bottom sediment was confirmed by the estimates of geometric mean and geometric standard deviation, which varied from 0.89 to 1.29 and from 1.22 to 1.87, respectively. The approach used is useful to synthesize measurement and simulation data in areas with observational gaps. For this purpose, 13 representative regions in the North Atlantic and Arctic oceans were selected for monitoring by using the “etalon” method for classification.

Machine learning analysis of 137Cs contamination of terrestrial plants after the Fukushima accident using the random forest algorithm

Radioactive contamination of terrestrial plants was extensively investigated and quantitatively modeled after the Fukushima nuclear power plant accident. This phenomenon, which is important for ecosystem functioning and protection of human health, is influenced by multiple factors, including plant species, time after the accident, and climate. Machine learning algorithms such as random forests (RF) have a record of strong performance on large multi-dimensional data sets, but, to our knowledge, combined data on post-Fukushima plant contamination with radionuclides were not yet subjected to a machine learning analysis. Here we performed such analysis on two large published data sets: (1) 137Cs activity concentrations in four common Japanese forest tree species. (2) Plant/soil 137Cs concentration ratios in multiple perennial plant species. The goal was to show the usefulness of machine learning for identifying and quantifying the main trends of 137Cs contamination in terrestrial plants. Each data set was split randomly into training and testing parts, RF was fitted and tuned on the training parts, and its performance was assessed on the testing parts by three metrics: coefficient of determination (R2), root mean squared error, and mean absolute error. Synthetic noise variables and the Boruta algorithm were used in a customized procedure to identify the most important predictor variables, which consistently outperformed random noise. Good agreement between observations and RF predictions (e.g. R2∼0.9 on testing data) was obtained on both data sets. The effects of the most important predictors (e.g. time after the accident, 137Cs land contamination level, and plant species) and interactions between them were quantified by partial dependence plots. These results of machine learning analyses of large data collections can help to complement previous modeling efforts, and to clarify the patterns of 137Cs contamination of plants after the Fukushima accident.

Spatial risk assessment of radiocesium contamination of edible mushrooms – Lessons from a highly frequented recreational area

The radioactive contamination of edible mushrooms increases human health hazards, especially in high mushroom collection intensity areas. Today only coarse-scale data with low spatial resolution are available, which prevents us from predicting human risk. To reduce the risk for human health, we need spatially explicit recommendations at landscape-scale. We used the Bavarian Forest National Park, a famous mushroom hunting location in Europe, as a model system. We aimed to increase the predictability of the contamination of the two most prominent mushroom species, bay boletus (Imleria badia) and ceps (Boletus edulis), and provide an efficient evidence-based risk assessment at landscape-scale. We revealed a high and a low 137Cs-activity impact area based on soil samples, which is also reflected by the mushroom species. 137Cs-activity of Imleria badia is about five times higher than the contamination of Boletus edulis; with one-third of the Imleria badia samples being over the statutory limit. The difference of contamination between species is more pronounced in the high-impact area. Elevation is a strong predictor in contrast to orientation of slopes. In high-impact areas, mushrooms showed higher 137Cs-activities at lower elevations. Soil analysis revealed that the maximum of the 137Cs-activity is still in the organic layers, indicating further mushroom contamination. We recommend using only Boletus edulis in the low-impact area for diet. We suggest that Boletus edulis bear a lower health risk than Imleria badia due to lower 137Cs-activities. Nevertheless, we need more landscape-scale studies to assess the 137Cs contamination risk for humans. Studies are primarily important in high-impact areas, which can be roughly identified by using soil contamination maps. The focus should be on high accumulating mushroom species like Imleria badia. Our study can serve as a blueprint to rapidly assess human health risks caused by radioactive contamination in landscapes intensively used by mushroom collectors.

Benthic macroinvertebrates as reference indicators for monitoring of anthropogenic isotope 137Cs contamination in the marine environment

Due to the limited studies dealing with isotopes levels in benthic macroinvertebrates other than Mytilus sp. in period 2011–2018, macroinvertebrates and seawater samples from the southern Baltic Sea were collected. Activity of 137Cs was measured in most common benthic macroinvertebrates inhabiting southern Baltic Sea in the context of choosing the best bioindicators. Taking into account the narrow range of CR coefficients, statistically significant correlation between 137Cs activities in seawater and species, a high frequency of occurrence and thus high biomass and the common occurrence, only Limecola balthica could potentially serve as indicators for shallow and deep-sea areas accordingly. Widely spread Mytillus trossulus was characterised by large size variability in samples and shows no significant correlation between activities in species and seawater and appears not so common as L. balthica.

Вплив додаткового «чистого» годування на вміст 90Sr і 137Cs в карасях сріблястих (Carassius Gibelio) у Чорнобильській зоні відчуження

Under natural conditions, in one of the most radioactively contaminated water bodies of the Chornobyl exclusion zone, lake Glyboke in 2020, experimental studies were carried out to assess the effectiveness of the use of additional "clean" feeding to reduce the levels of radioactive contamination of 90Sr and 137Cs in fish. The radiological efficiency of decreasing the 137Cs intake into the muscle tissue of fish with the use of additional "clean" feeding, mainly due to biological dilution, was 2.9 ± 0.4 times. The biological half-life of 137Cs in the muscle tissue of radioactively contaminated fish was 115 ± 25 days with the consumption of natural and additional "clean" food, which is approximately 2 times longer compared to the case when the fish consumes only clean food. In contrast to 137Cs, using additional "clean" feeding led to an increase of 90Sr content in the fish organism as compared to the control (up to 5 times) in proportion to the relative increase in the mass of fishbone tissue, which contains the bulk of strontium.

Прогнозування надходження радіонуклідів 137Cs і 90Sr у сільськогосподарські культури

Maps of the 137Cs contamination of abandoned agricultural land in Narodychi district (Zhytomyr region) were built using data of the radiological survey. Statistical characteristics of the soil contamination with 137Cs, 90Sr, and plutonium isotopes (median, geometric standard deviation, upper limit for Р = 0.9) were estimated. Contamination of the local crops with 137Cs and 90Sr as well as the risk of exceeding permissible levels were estimated. Recommendations for the return of these lands for commercial use are provided.

Spatial variations in radiocesium deposition and litter–soil distribution in a mountainous forest catchment affected by the Fukushima nuclear accident

The Fukushima Dai-ichi Nuclear Power Plant accident caused serious 137Cs contamination in mountainous forest areas. To understand the spatial variation in soil 137Cs inventory in complex mountainous topography and the influencing factors, a whole-area investigation of 137Cs deposition in a broad-leaved forest catchment of a mountain stream was conducted using grid sampling. Across the catchment, organic and surface mineral soil layers were collected at 42 locations in 2013 and 6 locations in 2015. Cesium-137 deposition on the forest floor exhibited high spatial heterogeneity and altitude-dependent distribution over the catchment. The 137Cs retention ratio in the organic layer, determined as the inventory in the organic layer divided by the soil (organic and mineral soil layers) inventory, ranged from 6% to 82% in 2013, and the coefficient of variation was 0.6. The 137Cs retention ratios had positive correlations with the material inventory in the organic layer and the elevation. The 137Cs retention ratios in the organic layer were less than 20% in 2015, even at the locations where the retention ratio was higher than 55% in 2013. Although there was spatial variation in the migration speed, 137Cs migration from the organic layer to mineral soil was almost completed within 4 y of the deposition, suggesting a decrease in 137Cs circulation within the forest ecosystem. This study also examined a relationship between the 137Cs inventory and the air dose rate to assess the potential of using the air dose rate to estimate soil 137Cs inventory. Soil 137Cs inventories and air dose rates were highly positively correlated, indicating that measurement of air dose rate can provide an easier and quicker alternative to measurement of soil 137Cs inventory in forest ecosystems.

Assessing the natural and anthropogenic radionuclide activities of the Pechora River estuary: Bottom sediments and water (Arctic Ocean Basin)

This paper studies the activity of natural and technogenic radionuclides in bottom sediments and surface water of the Pechora River estuary, which is the largest Arctic river within the European part of Russia. The relevance of conducting radioecological studies of this region is associated with active oil and gas activities in the Pechora basin and the presence of potential sources of radiation hazard. The average activities of 137Cs, 226Ra, 232Th, and 40K in bottom sediments were 0.16, 18.72, 13.36, and 373.59 Bq·kg-1, respectively. The average activity of 226Ra in the bottom sediments of the Pechora delta was two times higher than in other rivers of the Arctic basin of the European part of Russia, which is associated with oil and gas activities that are carried out in the Pechora basin. This is due to the fact that the decay products of uranium are the main by-products of oil and gas production. The specific activity of technogenic 137Cs in bottom sediments of the Pechora River delta was low and did not exceed 2.2 Bq·kg-1. We did not detect any radioactive 90Sr in bottom sediments. The low 137Cs activity in the bottom sediments of the Pechora delta was associated with both the larger granulometric composition of the sediments in comparison with the estuaries of the Siberian rivers, and with low concentrations of 137Cs in the terrigenous material (soil) entering the river from the catchment area. This was due to the low levels of 137Cs contamination in the soil of the Pechora river basin. We did not find any negative radiation effects of the underground nuclear explosion “Pyrite” carried out in the northern part of the delta, since there were no other technogenic radionuclides. The values of the radionuclides 3H, 137Cs, 226Ra, 232Th and 40K, as well as the total alpha activity in the surface waters of the Pechora River delta, turned out to be below the detection limit. In surface waters, we were able to determine only the total beta activity, which varied over a range from 19.6 to 59.6 Bq·m-3 with an average value of 33.9 Bq·m-3, which was significantly lower than the radiation safety standards. The values of the radiation hazard parameters were below the world average levels and were not significantly hazardous to the health of people living in the area of the Pechora River delta. We concluded that at present, in the Pechora River delta, there are pastures for reindeer with low levels of natural and man-made radioactivity. These conducted studies are the source material in a series of comprehensive studies of the current radioecological state of the tundra territories of the European part of Russia.

Predicting wildfire particulate matter and hypothetical re-emission of radiological Cs-137 contamination incidents

Radiological release incidents can potentially contaminate widespread areas with radioactive materials and decontamination efforts are typically focused on populated areas, which means radionuclides may be left in forested areas for long periods of time. Large wildfires in contaminated forested areas have the potential to reintroduce these radionuclides into the atmosphere and cause exposure to first responders and downwind communities. One important radionuclide contaminant released from radiological incidents is radiocesium (137Cs) due to high yields and its long half-life of 30.2 years. An Eulerian 3D photochemical transport model was used to estimate potential ambient impacts of 137Cs re-emission due to wildfire following hypothetical radiological release scenarios. The Community Multiscale Air Quality (CMAQ) model did well at predicting levels and periods of increased PM2.5 carbon due to wildfire smoke at routine surface monitors in California during the summer of 2016. The model also did well at capturing the extent of the surface mixing layer compared to aerosol lidar measurements. Emissions from a large hypothetical wildfire were introduced into the wildland-urban interface (WUI) impacted by a hypothetical radiological release event. While ambient concentrations tended to be highest near the fire, the highest population committed effective dose equivalent by inhalation to an adult from 137Cs over an hour was downwind where wind flows moved smoke to high population areas. Seasonal variations in meteorology (wind flows) can result in differential population impacts even in the same metropolitan area. Modeled post-incident ambient levels of 137Cs both near these wildfires and further downwind in nearby urban areas were well below levels that would necessitate population evacuation or warrant other protective action recommendations such as shelter-in-place. These results suggest that 1) the modeling system captures local to regional scale transport and levels of PM2.5 from wildfire and 2) first responders and downwind population would not be expected to be at elevated risk from the initial inhalathion exposure of 137Cs re-emission.

СВЯЗЬ ЗАБОЛЕВАЕМОСТИ ГЕМОБЛАСТОЗАМИ С ПЛОТНОСТЬЮ РАДИОАКТИВНОГО ЗАГРЯЗНЕНИЯ РАЙОНОВ БЕЛАРУСИ

Introduction. Sustainable development of territories affected by the Chernobyl disaster, require a number of managerial decisions, to reduce the level of radiophobia and psycho-emotional stress in society. Aim. To study the relationship between the indicators of the incidence of hemoblastosis with the density of contamination of territories with radioactive elements. Material and methods. An ecological population epidemiological study based on the calculation of the correlation coefficients of the incidence rates of hemoblastosis with the density of radioactive contamination. Results. There is no connection between the incidence of hemoblastosis and the density of radioactive contamination of territories. A statistically significant risk of multiple myeloma is observed in areas with a 137Cs contamination density of 1.0-4.99 Ci/km2. There was a statistically significant strong (r> 0.95) correlation between the crude incidence rate and standardized by age, sex and place of residence incidence ratio. The presence of strong correlations between these indicators give the possibility to use crude incidence rate instead of SIR in the analysis of morbidity by rayons. Conclusions. No correlation was found between the incidence of hemoblastosis and the density of radioactive contamination.

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.

Effects of nitrogen on caesium allocation in rice plants (Oryza sativa).

After the nuclear accident in Fukushima Prefecture, Japan, in 2011, 137 Caesium (Cs) contaminated nearby agricultural regions. Studies in these rice fields found that low K and high N fertilizer application enhanced Cs uptake in rice shoots. However, the influence of root and soil physics on these findings, as well as precise nutrient levels, remain to be clarified. We sought to analyse these relationships utilizing hydroponically grown rice plants. The rice plants were subjected to various concentrations of K and N nutrient solutions. We measured Cs allocation within the plants and performed transcript analyses using root tissues. Under low-K conditions, low-N plants accumulated less Cs in shoots and more in roots when compared to control-N conditions, even though overall Cs uptake remained unchanged. Expression analyses of root mRNAs showed that low-N plants accumulated reduced levels of OsAKT1 mRNA, encoding a K transporter. We also found a negative relationship between shoot Cs and K status in control-N but not in low-N conditions. Our results suggest that the application of N shifts Cs from roots into the shoots and that OsAKT1 in root vascular tissues influences Cs allocation. In practice, fine tuning N/K application and targeted breeding of K transporters might mitigate Cs contamination in rice plants.