137Cs Activity Research Articles

Emission Pattern of NORMs and 137Cs in the Sediments of the Gaz River and the Gorgan Bay, North Iran

Information on the distribution and emission patterns of natural and artificial radionuclides and their radiation level in the environment is very important for assessing the health effects of people living in a given region. In this study, the specific activity of radionuclides was measured using high purity germanium detector and a map of their distribution was drawn. The samples were collected from the Gaz River sediment in northern Iran, in the mountains of Golestan Province, and sediments on the middle and southern side of Gorgan Bay. The average of specific activities of 226Ra, 232Th, 40K, and 137Cs was 17.61, 35.91, 398.65, and 4.01 Bq/kg, respectively, which for natural radioactive nuclei are lower than the global average. The highest concentration of 40K was obtained in the sediments of the Gaz River estuary due to the use of potassium fertilizers for agriculture in this region. The highest concentration of 137Cs was obtained in the sediments of Gorgan Bay because 137Cs is injected both directly through the atmosphere and transfer by river water from upstream points to the Gorgan Bay. The diffusion pattern of 137Cs in the Gorgan Bay was exactly the opposite of 232Th and showed the tendency of 137Cs to precipitate in calm areas in the middle of the Bay.

Estimation of 137Cs Distribution and Recovery Using Various Types of Sorbents in the Black Sea Surface Layer

Monitoring 137Cs in seawater is necessary for the timely detection of radioactive contamination. The possibility of sorption and the sorption efficiency of 137Cs from seawater were studied for the first time during several cruises of the R/V (research vessel) Professor Vodyanitsky using various types of sorbents based on transition metal ferrocyanides (Anfezh, Niket, Uniket, FSS, FD-M, FIC, Termoxid 35, NKF-C) and zirconium phosphate (Termoxid 3A). The influence of the seawater flow rate and volume of the sorbent used for the recovery of 137Cs was estimated. The ferrocyanide sorbents Niket, Uniket, Termoxid 35, and FIC showed the best sorption efficiency (60–100%) at a seawater flow rate of 2–4 column volumes per minute. The data obtained during three cruises on the R/V Professor Vodyanitsky were analyzed. A detailed (28 sampling points) spatial distribution of 137Cs in the Black Sea along the southern coast of Crimea was studied using the sorbents that showed the best characteristics. An increase in 137Cs activity in the study area was not found, and the average activity was 9.01 ± 0.87 Bq/m3.

Vertical distributions of radionuclides along the tourist-attractive Marayon Tong Hill in the Bandarban district of Bangladesh.

This is the first attempt in the world to depict the vertical distribution of radionuclides in the soil samples along several heights (900 feet, 1550 feet, and 1650 feet) of Marayon Tong hill in the Chittagong Hill Tracts, Bandarban by HPGe gamma-ray spectrometry. The average activity concentrations of 232Th, 226Ra, and 40K were found to be 37.15 ± 3.76 Bqkg-1, 19.69 ± 2.15 Bqkg-1, and 347.82 ± 24.50 Bqkg-1, respectively, where in most cases, 232Th exceeded the world average value of 30 Bqkg-1. According to soil characterization, soils ranged from slightly acidic to moderately acidic, with low soluble salts. The radium equivalent activity, outdoor and indoor absorbed dose rate, external and internal hazard indices, external and internal effective dose rates, gamma level index, and excess lifetime cancer risk were evaluated and found to be below the recommended or world average values; but a measurable activity of 137Cs was found at soils collected from ground level and at an altitude of 1550 feet, which possibly arises from the nuclear fallout. The evaluation of cumulative radiation doses to the inhabitants via periodic measurement is recommended due to the elevated levels of 232Th.This pioneering work in mapping the vertical distribution of naturally occurring radioactive materials (NORMs) can be an essential factual baseline data for the scientific community that may be used to evaluate the variation in NORMs in the future, especially after the commissioning of the Rooppur Nuclear Power Plant in Bangladesh in 2024.

Influence of Precipitation on the Spatial Distribution of 210Pb, 7Be, 40K and 137Cs in Moss

Mosses have been widely used as biomonitors of a variety of atmospheric pollutants, including radionuclides. Here we determine the radionuclide activity concentration of 210Pb, 137Cs, 7Be, and 40K in moss tissue (Hylocomium splendens) collected from 24 sites across Ireland and assess the influence of precipitation on radionuclide spatial distribution. Lead-210 was the most abundant radionuclide (range: 226–968 Bq kg–1), followed by 7Be (range: <DL—604 Bq kg–1), 40K (range: <DL—155 Bq kg–1), and 137Cs (range: <DL—41 Bq kg–1). Albeit nearly thirty years since the Chernobyl disaster, 137Cs activity concentration was detected at 67% of the study sites; however, the spatial distribution was not fully consistent with the 1986 Chernobyl deposition pattern. Rather, 137Cs was weakly correlated with rainfall, with higher concentrations along the west coast, suggesting that the 2011 Fukushima Dai-ichi nuclear accident was also a potential source. Average annual rainfall was a significant predictor of 210Pb activity (linear regression, R2 = 0.63, p < 0.001). As such, the highest radionuclide activity was observed for 210Pb (average: 541 Bq kg–1), owing to the high levels of precipitation across the study sites (average: 1585 mm). In contrast, 7Be or 40K were not correlated with precipitation; rather, 40K and 7Be were significantly correlated to each other (rs = 0.7), suggesting that both radionuclides were transferred from the substrate or through soil re-suspension. Precipitation is widely reported as an important factor in the spatial distribution of radionuclides; however, only 210Pb activity concentrations in moss were strongly influenced by precipitation in the current study.

Relating 137Cs and sediment yield from uncultivated catchments: the role of particle size composition of soil and sediment in calculating soil erosion rates at the catchment scale

PurposeSoil loss is considered one of the most important consequences of land degradation as it affects the production of agricultural and forested areas, and the natural equilibrium of aquatic ecosystems downstream. For these reasons, the availability of tools and techniques able to identify areas at risk of land degradation is essential. Over the last 3–4 decades, theoretical models, based on the use of 137Cs, an anthropogenic radiotracer, proved to be very effective for this purpose. However, these models require specific information on soil and sediment particle size to provide estimates of soil erosion or deposition and this information is summarised by a particle size correction factor ‘P’. Empirical methods of calculation of this factor assume the basic hypothesis that a particle size selectivity takes place in erosion processes and this results in a general enrichment of the fine component in sediments and a corresponding higher radionuclide activity. In this contribution, we demonstrate that this hypothesis is not valid everywhere, and consequently, the P factor cannot be estimated using traditional approaches.Materials and methodsA long-term experiment, conducted in Southern Italy and based on two small experimental catchments (approximately 1.5 ha in size), for which measurements of sediment yield are available for the period 1978–2020, is used in this work. More specifically, 137Cs measurements carried out within the catchments and on a reference area provided the basis to obtain long-term estimates of soil erosion rate in these sites. Combined measurements of 137Cs activity and particle size on both soils and sediments, obtained for 46 events, were also carried out to explore possible particle size effects on the final estimates of soil loss.Results and discussionParticle size analyses of soil and sediments showed that there is evidence of a general enrichment of the eroded soil in the finer size fractions. Conversely, radiometric analyses revealed that 137Cs activity in sediments is generally lower than that in surface soil. These results reflect both the decreasing 137Cs activity associated with depth in undisturbed soils and the higher specific surface area of the deeper horizon in these soils. These findings preclude the application of the available empirical models to calculate P, and suggest the opportunity to use, for long-term estimates of soil erosion, a particle size correction factor P = 1. This assumption and an uncertainty analysis associated with the spatial variability of the 137Cs reference value were incorporated into the Diffusion and Migration Model (DMM) to obtain estimates of soil erosion rates for the study catchments.ConclusionsThe final estimates of soil erosion provided by the DMM showed values very close to the measurements of sediment yield obtained for the two catchments during the study period. The overall results demonstrated that the DMM, if properly calibrated using specific information of particle size and of 137Cs reference value, can be considered a useful tool to individuate areas more prone to risks of land degradation and to identify appropriate strategies able to reduce soil loss in forested sites.

Spectrum processing method for measuring low levels of specific activity of 137Cs with a NaI(Tl) detector in the presence of natural radionuclides

When measuring low levels of 137 Cs in soil samples using spectrometers with a NaI ( Tl ) detector , identification of the 137 mBa peak ( the 662 keV gamma line of the daughter radionuclide ) is difficult due to the influence of natural radionuclides , the peaks of which fall within the 137 mBa detection region . To i dentify a nd estimate t he a rea u nder t he p eak o f 137 mBa, i t i s n ecessary t o k now t he c ontribution o f t he b ackground c omponent t o t his a rea a nd t he c ontribution o f e ach n atural r adionuclide . W hen u sing s uch a pproach , t he a ccuracy o f e stimating t he 137 mBa p hotopeak a rea d epends o n t he a ccuracy w ith w hich t he l evels o f n atural r adionuclides a re d etermined . The a rticle p roposes a m ethod o f s pectrum d ecomposition b ased o n t he t aking i nto a ccount i ndividual p arameters o f t he s pectrometer a nd a m ore a ccurate d etermination o f s pecific a ctivities o f n atural r adionuclides . The m ethod i nvolves t he m odeling t he s pectral r egions f or e ach n atural r adionuclide i n t he a rea o f 137 mBa p eak a nd s ubtracting t he s imulated r egions a nd t he b ackground s pectrum f rom t he t otal s pectrum u nder t he p eak o f 137 mBa. The u se o f t his a pproach a llows t o m easure w ith a 63×63 N aI ( T l ) d etector t he s pecific a ctivity o f 137 Cs a t a l evel o f 0.7–1 B q / k g w ith a n u ncertainty o f 3 0-50 % i n t he M arinelly g eometry w ith a v olume o f 1 l iter a nd w ith t he m easurement t ime o f 6 h ours .

Factors affecting 137Cs radioactivity and water-to-body concentration ratios of fish in river and pond environments near the Fukushima Dai-ichi Nuclear Power Plant

To elucidate 137Cs contamination levels and mechanisms of fish inhabiting river and pond environments near the Fukushima Dai-ichi Nuclear Power Plant, 137Cs activity concentrations in fish (15 species, n = 164) and water collected from Maeda River (3.3–8.9 km from the plant) and Shimofukazawa Pond (2.9 km) in 2017 were analyzed. Also, an 8-week rearing experiment using Japanese dace Pseudaspius hakonensis fed on non-contaminated pellets and the pond water (mean 137Cs concentration of 2.0 Bq/L) was conducted to evaluate 137Cs accumulation from water to fish. The 137Cs concentrations in Japanese dace, the only species collected throughout five sampling sites from estuarine to upstream areas in Maeda River, were found to be correlated with ambient air dose rates and fish size, exhibiting large variations (16.5–2.6×103 Bq/kg-wet). By contrast, dissolved 137Cs in river waters increased from the upper to lower course (0.025–0.28 Bq/L), which caused large variations of the water-to-body concentration ratio (CR) in Japanese dace (60.0–35700 L/kg-wet). These CRs (geometric mean of 3670 L/kg-wet) were much higher than the steady-state CR of reared fish (9.7 L/kg-wet), indicating that river fish uptake 137Cs mainly from prey items from aquatic and riparian zones, rather than from water. Statistically significant negative correlations between K+ concentrations in water and river fish CRs were detected, resulting in the decreasing trend of CRs from upstream to estuarine areas. These results suggest that the large heterogeneity of air dose rates, K+ concentration, and estuarine processes in brackish water habitats, in association with the feeding habit and size effect in fish, can engender wide variation of 137Cs concentrations and CRs of river fish along a river course. In contrast, 137Cs concentrations in pond fish (4.3–14.6 kBq/kg-wet) were higher than in river fish. The CRs of pond fish were constantly high but the range was smaller (1010–3440 L/kg-wet) with larger values in fish of higher trophic levels. These findings suggest that biomagnification within a pond was inferred as the main cause of 137Cs contamination of pond fish.

A Systematic Approach to the Development of a Methodology for Comparative Analysis of Scenarios for the Shelter Object Transformation into an Ecologically Safe System

A comprehensive assessment of the impact of wildfires in the Chornobyl Exclusion Zone on the adjacent territory within a radius of 100 km in the spring of 2020 and 2022 was carried out, considering the potential and realized radioecological criticality of the territory. The realized radioecological criticality was expressed in the estimated specific activity of 137Cs in plants, which was formed as a result of aerial and root pollution of agricultural vegetation in farm fields and gardens during the transfer and deposition of radionuclides during fires. The specific activity of 137Cs in plants was calculated based on the data on the integrated volumetric activity of 137Cs, obtained by the WRF-LEDI model of atmospheric transport, using the set of models “AeralPlant — SoilPlant” depending on the biological stage of plant development. According to the results of the calculations, thematic mapping was carried out with the selection of zones of maximum and minimum contamination of the territory, taking into account potential radioecological criticality. Regardless of the volume activity of 137Cs in the air and the direction of air transfer, the spatial nature of the distribution of the most critical areas is preserved. As a result, the most critical areas were identified, where dangerous levels of radiation exposure on the population are possible due to atmospheric transport of radionuclides caused by wildfires and extreme weather phenomena (dust storms) in the Chornobyl Exclusion Zone. Different scenarios of the regional land use structure were considered and thematic assessment maps were built, which are the basis of preventive planning of rehabilitation measures in case of critical situations in accordance with radiation safety norms.

ON THE METHODOLOGY OF PASSPORT DOSES CALCULATION FOR UKRAINIAN SETTLEMENTS RADIOACTIVELY CONTAMINATED DUE TO THE CHORNOBYL NPP ACCIDENT.

scientific substantiation of the new methodology for estimation of passport doses of the settlementswhich belong to Zone of Unconditional (obligatory) Resettlement, or 2nd zone and Zone of Granted VoluntaryResettlement, or 3rd zone in the framework of dosimetric passportization in accordance with the legislation ofUkraine. 37 years after the accident, radioactive contamination of the environment has significantly decreased. However, it is still necessary to carry out ecological and dosimetric monitoring and apply countermeasures in certain territories of Ukraine affected by the accident at the Chornobyl Nuclear Power Plant: restriction of the consumption of locally produced milk, forest products, etc. The methodology, which was since 1996 used to estimate the passport doses of Ukrainian settlements, no longer corresponds to the current level of scientific knowledge about radioactive contamination of environment. The new methods of passport doses calculating presented in the work involves the use of a model whose parameters are determined by the types, quality and completeness of radio-ecological and dosimetric monitoring carried out on the radioactively contaminated territories in 1986-2013. The methodology takes into account the specific of radioactive contamination of each settlement. The passport dose of external exposure is reconstructed only from 137Cs radionuclide, because the contributions of other Chornobyl radionuclides influence the radiation dose only in the first years after the accident. The passport dose of internal exposure is formed as a result of the consumption of 137Cs contaminated food products. It is calculated depending on the availability in the settlement in the current year of the results of measurements of the 137Cs radionuclide activity incorporated in the human body using a whole body counter (WBC) and the activity of 137Cs in the private milk. At the same time, priority is given precisely to the results of WBC measurements of 137Cs. A new methodology (Methodology-2023) for passport doses calculation of Ukrainian settlements was substantiated. A comparison of passport doses based on the results of radioecological and dosimetric monitoring in 2011 calculated by Methodology-2023 and passport doses calculated by Methodology-96 was made.Passport doses calculated by Methodology-2023 increased by 40 % on average compared to doses calculated by Methodology-96. At the same time, passport doses of internal radiation calculated by the new methodologyincreased by 1.5 times, and passport doses of external radiation increased by 1.7 times. The passport dose of 2011, calculated by Methodology-2023, exceeds the legally established limit of 1 mSv in 71 settlements, most of which are located in Korostenkyi raion of Zhytomyr Oblast.

Миграция 137Cs в экосистеме поймы р. Унеча

Purpose: to study the ¹³⁷Cs migration and concentration in the alluvial soils profile and the radionuclide transfer to plants in the river Unecha floodplain ecosystem. Materials and methods. Field studies were carried out in 2019–2021 in Bryansk region (Klintsovsky district, the village of Lopatni, the right bank of the river Unecha, the current reclamation system). The density of ¹³⁷Cs contamination of the territory after the Chernobyl accident was 185–555 kBq/m². Conjugated soil and plant samples were taken in various sub-systems of the floodplain (near-channel, central, near-terrace). Agrochemical indicators of fer-tility and ¹³⁷Cs specific activity in soil and plants were determined using generally accepted laboratory methods. Results. A strong variability of the agrochemical parameters of alluvial soils in layers every 5 cm within 0–20 cm was determined. A high content of mobile phos-phorus and a low content of potassium, a strongly acid reaction of the environment, and a ten-dency to the growth in the organic carbon content from the near-channel to near-terraсе floodplain subsystem was found. The ¹³⁷Cs horizontal distribution in the river Unecha flood-plain soils was determined by soil genesis of the floodplain subsystems; the maximum specific activity of ¹³⁷Cs 3953 Bq/kg was found in the near-terrace part of the floodplain. The ¹³⁷Cs maximum concentration was found in the near-channel and central subsystem in the soil layer of 0–5 cm, and in the near-terrace subsystem in the layer of 5–10 cm. In the floodplain of the river Unecha, the ¹³⁷Cs coefficient transfer from soil to plants decreases from the central to the near-channel and near-terrace. Conclusions. The formation of agrochemical indicators of al-luvial soil fertility and the ¹³⁷Cs vertical distribution is determined by soil genesis in floodplain subsystems; it can be uniformly decreasing or concentrated in separate layers at biochemical barriers. In the floodplain ecosystem, the ¹³⁷Cs concentration in the 0–20 cm layer increases from the near-channel to near-terrace subsystem. Forage production under the conditions of radioactive contamination of the near-river and central parts of the floodplain is possible without the use of protective measures.

Spatial distribution of 137Cs, 40K, 226Ra, 232Th in soils of Olenegorsk city (Murmansk region)

The goal of the study is obtain original data and identify the main patterns of spatial distribution of radionuclides in the soils of Olenegorsk, depending on zoning and urban development, focusing one specific activity of 137Cs and natural radionuclides, namely 232Th, 226Ra, 40K, in soils. Such studies of urban soils in Olenegorsk have not been carried out earlier. Location and time of the study. Soil samples in the city of Olenegorsk, Murmansk region, were collected in the summer of 2018. Methods. Soil samples were collected at 24 study sites on the territory of the Olenegorsk city from the upper 0-5 cm layer. Under laboratory conditions, the samples were dried at 105° C to constant mass. Then soil aliquots were placed in a Marinelli vessel to measure isotope specific activity using gamma spectrometry. Registration of gamma radiation from a countable soil sample, as well as processing of spectra, was carried out using the Progress-gamma software and hardware complex FVKM.412131.002-03. Calibration of the gamma spectrometer by energy to monitor the safety of the installation parameters was carried out after each measurement using a combined control source OISN-137-1 in a 1-liter Marinelli vessel. The minimum exposure time for the counting sample was 3600 seconds. However, depending on the activity of a sample, the exposure time in individual samples with weak activity was increased. Main results: The maximal specific activity of 137Cs in urban soils of Olenegorsk was 47.5 Bq/kg in the northwestern part of the city in the undisturbed soils of the natural landscape. Maximal values of 40K specific activity reached 293.8 Bq/kg in the central and south-eastern parts of the city within the boundaries of multi-storey residential district. The maximal specific activity of 226Ra in soils reached 14.6, and that of 232Th reached 12.2 Bq/kg, being confined to soils in the area of high-rise and mid-rise buildings, most likely, due to the differential vegetation density since the latter easily involves 40K into the biotic turnover. Maximal values of soil 226Ra and 232Th specific activity (14.6 and 12.2, respectively) were determined in areas with multi-storey and mid-rise buildings. The correlation analysis between the radionuclides and soil skeleton particles (≥2 mm) and finer (≤ 1 mm) fractions showed rather close association of radionuclides with soil skeleton and <45 µm particles, as well as a moderately strong correlation with the 45 µm fraction. Moderately strong correlation was found between 232Th and 226Ra, and between 40K and soil skeleton particles. Conclusion. The obtained data about the accumulation of 137Cs and natural radionuclides (232Th, 226Ra, 40K) in the soils of Olenegorsk do not exceed the maximum permissible concentrations, characteristic of the urbanized areas of the Murmansk region.

ACCUMULATION OF 137Cs, Pb, Cd, Сu IN THE MUSCLE TISSUE AND LIVER OF PIGS GETTING DIFFERENT RATIONS

Experimental studies on young pigs of the large white breed were conducted on the territory of the physiological yard of the Polissia Institute of Agriculture of the National Academy of Sciences (III zone of radioactive contamination due to the accident at the Chernobyl Nuclear Power Plant). To conduct the experiment, 2 groups of experimental animals were formed: Group I (control) was fed with grain mixture № 1 with narrow-leaved lupine (alkaloid-free) and sunflower cake; II group (experimental) received grain mixture № 2 with genetically modified soy. Experimental pigs were kept in one room according to the accepted technology in group cages equipped with a wooden floor. The mode of feeding and drinking, parameters of the microclimate in both groups were the same. According to the results of tests conducted at the Ukrainian Laboratory of Quality and Safety of Agricultural Products, it was established that soybeans contain genetically modified deoxyribonucleic acid (DNA), have the target sequence of the 35S+FMV promoter of the cauliflower mosaic virus and the NOS terminator (nopaline synthase) of Agrobacterium tumefaciens. The specific activity of 137Cs in the longest back muscle of pigs varied by group within 3.7-10.3 Bq/kg and did not exceed permissible levels (DR-2006 = 200 Bq/kg). When used as part of the GM soybean grain mixture, the concentration of radiocesium in the muscle tissue of animals of the II (experimental) group relative to the control decreased by 6.6 Bq/kg, or by 64.1% with a statistically significant difference (Р> 0.95). Moreover, the accumulation rate of 137Cs in the longest back muscle of piglets was 0.46-0.95 and was 2.1 times higher in young pigs that received grain mixture No. 1 without GM soybeans, compared to the use of grain mixture No. 2. The concentration of Pb in the slaughter products of experimental animals was significantly lower than the MPC, while the level of contamination of the longest back muscle of pigs Cd exceeded the regulatory requirements by 1.40-1.44 times. The introduction of 60% (by mass) of corn gain and 10% of GM soybeans into the grain mixture instead of the same amount of wheat grain, lupine and sunflower cake for fattening young pigs in the III zone of radioactive pollution contributes to a smaller accumulation of heavy metals in meat: Pb – by 17.5%, Cd – by 2.8%, Cu – by 4.2%. Therefore, the transition coefficients of Pb and Cd into the muscle tissue of animals of the II (experimental) group relative to the analogues of the I (control) group increased by 1.24% and 3.02% respectively, and Cu decreased by 0.23%.

Spatiotemporal patterns in differences between the 137Cs concentrations of forest and stream litters: effect of leaching.

Forest-stream ecotones possess prominent detritus-based food webs, and 137Cs-contaminated litter can influence the contamination levels of animals inhabiting such ecosystems. The effects of leaching on contaminated litter induce greater absolute differences between the 137Cs concentrations of forest and stream litter in more contaminated sites. Because 137Cs concentrations in litter can be attenuated temporally, spatiotemporal patterns in the differences in 137Cs concentrations between forest and stream litter may vary depending on both the amount of 137Cs deposition and the passage of time. To test this hypothesis, we sampled coniferous needle and broad-leaved deciduous litter in forests and streams at seven forested headwater sites affected by the Fukushima nuclear accident 3.24 and 11.24 years after the accident. We found that 137Cs concentrations in the two litter types were one order of magnitude lower 11.24 years after the accident than 3.24 years afterwards. The absolute difference in 137Cs activity concentrations of litter between forest and stream ecosystems was higher at more contaminated sites both 3.24 and 11.24 years after the accident. The spatiotemporal changes in litter contamination provide insight into 137Cs dynamics and complex transfer in the detritus-based food webs of forest-stream ecotones.

<sup>137</sup>Cs IN THE ORGANISMS OF MOUSE-LIKE RODENTS INHABITED THE AREA OF NUCLEAR WEAPON TESTING

The paper presents the results of researching 137Cs radionuclide concentration in the organisms of mouse-like rodents (organisms of jerboa (Allactaga major Kerr and Allactaga saltator Eversmann) and marmots (Citellus erythrogenus Brandt)) living in the field of nuclear-weapon testing at the Semipalatinsk test site and the parameters of 137Cs radionuclide transition to organisms of studied animals. It is revealed that relatively elevated magnitudes of 137Cs activity concentration in organisms of jerboa and marmots are observed on the assumption of their residence in local contamination sites. With venturing from contamination sites at the distance exceeding the radius of animal activity, high values of radionuclides’ activity concentration are not reported. Despite the fact that animals live in the environment which components display high activity concentration of radionuclides, the extremely high concentration of radionuclide in these animals’ organisms has not identified.The midpoint measures (AM±SD) of CRmuscl of 137Cs radionuclide for the muscle tissue of Allactaga saltator Eversmann amounted (2.1±1.3)×10−3 (n-11), for muscle tissue of Allactaga major Kerr – (4.7±2.7)×10−3 (n-9), for the muscle tissue of Citellus Erythrogenus Brandt – (7.0±5.6)×10−3 (n-6).

Temporal evolution of plutonium concentrations and isotopic ratios in the Ukedo - Takase Rivers draining the Difficult-To-Return zone in Fukushima, Japan (2013–2020)

In 2011, the Fukushima Dai-Ichi Nuclear Power Plant (FDNPP) accident released significant quantities of radionuclides into the environment. Japanese authorities decided to progressively reopen the Difficult-To-Return Zone after the decontamination of priority reconstruction zones. These areas include parts of the initially highly contaminated municipalities located to the north of the FDNPP, including Namie Town, an area drained by the Ukedo and Takase Rivers. Eleven years after the accident, research focused on the spatial distribution of plutonium (Pu) and radiocesium (Cs) isotopes at contrasted individual locations. To complement previous results, the current research was conducted on flood sediment deposits collected at the same locations after major flooding events during eleven fieldwork campaigns organised between 2013 and 2020 at the outlet of the Ukedo and Takase Rivers (n = 22).The results highlighted a global decrease of the Pu and 137Cs contents in sediment with time during the abandonment phase in the region, from 2013 (238.20 fg g−1) to 2020 (4.28 fg g−1). Furthermore, based on the analysis of the 240Pu/239Pu isotopic ratios, the plutonium transiting these rivers (range: 0.166 – 0.220) essentially originated from the global fallout (0.180 ± 0.014 (Kelley et al., 1999)). Sediment showed contrasted properties in the two investigated rivers, which is likely mainly the result of the occurrence of Ogaki Dam on upper sections of the Ukedo River as it strongly impacts the material supply from this river to the Pacific Ocean. A statistical analysis highlighted the strong correlation between Pu activity concentrations and 137Cs activities in both rivers, confirming that both radionuclides are transported with a similar pathway. Despite it was detected early after the accident (2011–2013), the current research demonstrates that plutonium originating from FDNPP is no longer detected in these rivers draining the Difficult-To-Return Zone at the onset of the reopening of the area to its former inhabitants.

Сравнение моделей 210Pb-датирования применительно к торфяным отложениям Европейской Субарктики России (на примере Архангельской области)

The dating of young peatlands with 210Pb method is a difficult task. Standard 210Pb dating models require an exponential decrease in activity down the peat profile. In Arctic peatlands, we note a significant migratory capacity of lead, therefore, for accurate dating of peat, it is necessary to improve the existing dating models to eliminate the effect of migration and their verification using independent isotope chronometers, for example, 137Cs. We applied several models CA, CFCS, PF, CF together with the Monte Carlo method for peat core samples taken within the European Subarctic of Russia (Arkhangelsk region). Comparison with the specific activities of 137Cs, determined at a depth of 19—21 cm, associated with the global fallout in 1963, showed that the closest age to the specified reference point is given by the CFCS and CF models (1965 and 1962, respectively). Among these two options, CF using the Monte Carlo method turned out to be preferable, since it provided, taking into account the error, a slightly better agreement with the specific activities of 137Cs in the reference horizon. Despite the difficulties associated with the complex distribution of 210Pb over the peat section due to migration, the dating methods used were successful and, in the future, can be applied to dating other peat deposits.

Активность основных дозообразуюших радио' нуклидов в водоемах белорусского сектора зоны Чернобыль' ской атомной электростанции и создаваемые ими дозовые нагрузки на биоту

In 2014-2015 we determined the activity of the most abundant radionuclides 90Sr, 137Cs and 241Am in the water column, bottom sediments and dominant species of macrophytes and mollusks in two water bodies of the Belarusian sector of the near zone of the Chernobyl nuclear power plant (ChNPP). Of these, the low-flowing Perstok Lake is the most contaminated with radionuclides water body in Belarus sector of ChNPP, and the flowing Borshchevska waterlogging, which has formed in the past two decades, is characterized by an average level of radiation contamination for the near zone of ChNPP. These data were used to calculate the values of the absorbed dose rate (ADR) during internal exposure for the dominant biota of water bodies from the indicated complex of radionuclides. In the bottom sediments of the Perstok Lake, the activity of 90Sr and 137Cs reached 185 and 468 kBq^m-2, respectively, and in the Borshchevska waterlogging, respectively 61 and 212 kBq^m-2, which significantly exceeds the pre-accident level. Among the biota organisms, macrophytes were characterized by the highest levels of the activity of 90Sr and 137Cs. In the Perstok Lake the values of 90Sr and 137Cs activities for them reached 24700 and 40100 Bq^kg-1 dry weight, respectively, and in the Borshchevska waterlogging -8747 and 3780 Bq^kg-1 dry weight. Among the mollusks of the Perstok Lake Anodonta spp. shells were characterized by the highest activities of 90Sr and 137Cs - up to 50216 and 1049 Bq^kg-1 of wet weight. The activity of 137Cs in the soft tissues of mollusks is much lower - no more than 780 Bq^kg-1 of live weight. The activity of 241Am in bottom sediments and macrophytes of the Perstok Lake during the study period was significantly lower - no more than 4.4 kBq^m-2 and 202 Bq^kg-1 of dry weight, and in the Borshchevska waterlogging - 2.6 kBq^m-2 and 48.1 Bq^kg-1 dry weight. 241Am activity in soft tissues and shells of mollusks from both reservoirs was not recorded in most cases. The total values of ADR from all the studied radionuclides in macrophytes and mollusks varied within 10-28 mkGyday-1, and in the mollusk of Lymnaea stagnalis - 64 mkGyday-1. The greatest contribution to the formation of the total ADR in macrophytes (within 42-99 %) and mollusks (up to 99 %) is made by the 90Sr + 90Y isobar. In most cases, the contributions of the 137Cs+137Ba and 241Am isobar to the total ADR values are extremely insignificant. Only for the roots of Typha angustifolia their contribution reached 37.7 and 20.3 %, respectively. Currently, in the near zone of ChNPP, against the background of a decrease in the activity of 90Sr and 137Cs, an increase in the activity of 241Am is observed. It is predicted that by the middle of the XXI century 241Am will become the main dose-forming radionuclide for the biota of water bodies in the near zone of the ChNPP.

Оценка загрязнения древесины и коры дуба 137Cs в зоне отчуждения Чернобыльской атомной электростанции

The results of studying the 137Cs contamination of English oak (Quercus robur L.) trunks in high-aged oak forests in the most radioactive polluted part of the Polesye State Radiation-Ecological Reserve territory located in the evacuation (exclusion) zone of the Chernobyl nuclear power plant are presented. The features of modern surface contamination soil by 137Cs in oak forest stands have been established, the factors that caused them have been identified: removal of research objects from the release site and conditions for deposition of radioactive fallout, as well as vertical redistribution of radionuclide in the soil over the time since the accident. The density of 137Cs soil contamination varies by types of oak forest. The current indicators of 137Cs accumulation in wood, bark and oak trunks, their changes by forest types, the relationship with the density of soil pollution and the distance to the disaster site are determined. A 2-3-fold excess of 137Cs oak bark contamination was found in comparison with wood, which is due to their morpho-physiological characteristics. Over the past 25 years, the wood and bark proportions of the relative contributions to the specific activity of 137Cs of the oak trunks have changed significantly. The decrease in the contribution of the bark to the specific activity of 137Cs in the trunk is due to a slowdown in the entry of radionuclide into it. The 137Cs distribution in oak wood by classes of growth and development of trees by Craft is shown. It was found that the average values of the radionuclide specific activity in standing and lying deadwood are 25-28 % lower than in the wood of living trees. The tendency of decreasing of 137Cs concentration in oak wood from the periphery to the center of the trunk has been confirmed. As of 2021, according to the sanitary standard of the Republic of Belarus for the content of 137Cs 1480 Bq kg-1, harvesting of oak wood could be allowed in 84 % of the surveyed stands, oak trunks with bark - in 72 %. The standard of 740 Bq kg-1 corresponded to oak wood in bark and without bark in 32 % of forest stands.

A comparison study on the burnup of HTR-10 fuels using radiometric and mass spectrometric methods

Online burnup measurement of a single irradiated spherical fuel element using gamma spectrometry has been applied for years on HTR-10. This reactor has a complex operation history for varies experiments, which raises the uncertainty over the non-destructive measured burnup. In this research, three irradiated spherical fuel elements with different burnup were deconsolidated, and their coated particles were analysed by both radiometric methods based on Cs-137 activity and mass spectrometric methods based on neodymium and actinide mass. The burnup distribution in each spherical fuel element was indicated by fractional U-235 burnup of particles from various radii and relatively uniform. The inventory of Cs-137 in one spherical fuel element was measured by on- and off-line gamma spectrometry and results showed tiny differences. Destructively measured Cs-137 activities from particles indicate negligible portion of Cs-137 in the graphite matrix. Burnup calculated from Cs-137 by radiometric method and Nd-148 by mass spectrometric method were compared. Results showed that the two values were not significantly different for fuels with a clear radiation history, but differences were observed in the fuel with a complex radiation history.

Elevated atmospheric CO2 concentration changes the eco-physiological response of barley to polystyrene nanoplastics

The impacts of plastic particles are being extensively studied, especially in agro-ecosystem. In the simulating experiment, elevated atmospheric CO2 concentration (e[CO2], 800 μmol mol−1) increased nanoplastics (NPs, red fluorescently labeled polystyrene, 95 nm) concentration in NPs-treated roots from 0.0082 mg g−1 to 0.0275 mg g−1. The H2O2 concentrations in NPs-treated leaves and roots were decreased by 28.41 % and 43.29 % responding to e[CO2], due to the intervention of antioxidant enzymes. In NPs-treated plants, e[CO2] increased Pn, Ci and carotenoid concentration by 10.97 %, 118.07 % and 40.83 %, while decreased gs and Tr by 36.36 % and 32.55 %. e[CO2] weakened NPs-induced modulation of photosynthetic light reaction via causing less electron production, but induced higher Ci promoting the Calvin-Benson cycle in NPs-treated plants. In the presence of NPs exposure, e[CO2] aggravated the reduction in glycolysis by decreasing the activities of cytInv, vacInv, cwInv, AGPase, UGPase, PGM, PGI, G6PDH, PFK and Ald, while suppressed the efficiency of tricarboxylic acid and biological oxidation due to the decreased activities of CS, ICDH, α-KGDH, NADH dehydrogenase, succinate dehydrogenase, cytochrome c oxidase and ATP synthase. The results showed the landscapes by which e[CO2] sculpt the eco-physiological response of barley plant to NPs, and provided key insights into the agricultural sustainability in the future under emerging pollution and environmental changes.