137Cs Activity Research Articles

Analysis of causal effects of 137Cs deposition on 137Cs concentrations in trees after the Fukushima accident using machine learning

Radioactive contamination of forests by long-lived radionuclides from nuclear accidents such as Chernobyl and Fukushima continues to be studied and quantitatively modeled. Whereas traditional statistical and machine learning (ML) techniques generate predictions by focusing on correlations between variables, quantification of causal effects of radioactivity deposition levels on contamination of plant tissues represents a more fundamental and relevant research goal. Modeling of cause-and-effect relationships is advantageous over standard predictive modeling, particularly by improving the generalizability of results to other situations, where the distributions of variables, including potential confounders, differ from those in the training data. Here we used the state-of-the-art causal forest (CF) algorithm to quantify the causal effect of 137Cs land contamination after the Fukushima accident on 137Cs activity concentrations in the wood of four common Japanese forest tree species: Hinoki cypress (Chamaecyparis obtusa), konara oak (Quercus serrata), red pine (Pinus densiflora), and Sugi cedar (Cryptomeria japonica). We estimated the average causal effect for the population, quantified how it was influenced by other environmental variables, and produced effect estimates at the individual level. The estimated causal effect was quite robust to various refutation methods, and was negatively influenced by high mean annual precipitation, elevation, and time after the accident. Wood subtype (e.g. sapwood, heartwood) and tree species made smaller contributions to the causal effect. We believe that causal ML techniques have promising potential in radiation ecology and can usefully expand the toolkit of modeling approaches available to researchers in this field.

Evaluating the transport of surface seawater from 1956 to 2021 using 137Cs deposited in the global ocean as a chemical tracer

Abstract. We analyzed the spatiotemporal variations in the 137Cs activity concentrations in global ocean surface seawater from 1956 to 2021 using the HAMGlobal2021 (Historical Artificial radioactivity database in Marine environment, Global integrated version 2021) and other published data. The global ocean was divided into 37 boxes. When observing the 0.5-year median value of 137Cs in each box in the Pacific Ocean, we noticed that the values gradually increased or had almost constant levels in the 1950s and 1960s, and then decreased exponentially in 1970–2010, immediately before the Fukushima Daiichi Nuclear Power Plant Station (F1NPS) accident. In the northern North Atlantic Ocean and its marginal sea, the 0.5-year median values of 137Cs showed large variations in the directly discharged 137Cs from the reprocessing plants. The 137Cs inventory in the surface mixed layer in 1970, when 137Cs was released into the surface seawater, was estimated to be 184±26 PBq. In 1975 and 1980, the 137Cs inventory increased to 201±27 and 214±11 PBq, respectively, due to direct discharge from the Sellafield and La Hague nuclear fuel reprocessing plants. In 2011, the 137Cs inventory in the global ocean mixed layer increased to 50.7±7.3 PBq compared to that before the F1NPS accident, in which the contribution from the accident was estimated to be approximately 15.5±3.9 PBq. Mass balance analysis indicates that 137Cs deposited by the global fallout in the western North Pacific Ocean moved to the eastern North Pacific Ocean. Subsequently, 137Cs was transported southwards, followed by westward transport in the subtropical and equatorial Pacific Ocean, and then inflowed into the Indian Ocean via the Indonesian Archipelago. The longer apparent half-residence times in the Indonesian Archipelago (36.7 years from 1973 to 1997) and central Atlantic Ocean (38.0 years from 1992 to 2016) also support the interpretation of the global-scale transport of 137Cs from the western North Pacific Ocean to the Indian (20–30 years) and Atlantic oceans (30–40 years). In the northern North Atlantic Ocean and its marginal sea, 137Cs discharged from nuclear reprocessing plants is transported to the North Sea, Barents Sea and coast of Norway, and Arctic Ocean on a decadal scale. The dataset is available at https://doi.org/10.34355/CRiED.U.Tsukuba.00085 (Aoyama, 2021), https://doi.org/10.34355/Ki-net.KANAZAWA-U.00149 (Inomata and Aoyama, 2022a), https://doi.org/10.34355/Ki-net.KANAZAWA-U.00150 (Inomata and Aoyama, 2022b), and https://doi.org/10.34355/Ki-net.KANAZAWA-U.00151 (Inomata and Aoyama, 2022c).

140 years-long sedimentary records of PAHs and CN stable isotopes from Ninomiya River, Japan

Anthropogenic activities' impacts over 140 years were studied at West Nanao Bay using a variety of geochemical techniques on sedimentary records. The bay is influenced by the Ninomiya River which is fed by a small watershed at which Tatzuruhama Town is located. Sedimentation rate was calculated using 210Pb-excess and 137Cs activities. C/N decreased after 1975, indicating a decrease in lignin-rich organic matter. From δ13C, δ15N and biogenic silica it was indicated that the population increased sewage-discharges until the construction of waste-water treatment plant in 1986. Several recorded changes in the landuse matched with the variation of the particle size. Total PAHs concentration was 1.17–62.78 μg g−1, being highest during Japan's fastest economic growth period (1946–1975). Using diagnostic ratios and PCA analysis, PAHs' sources were identified as pyrogenic for all depths, varying from coal combustion (90.7 %) before 1946 to a mixture of biomass and vehicle combustion after 1961.

Measurement of the radiation hazards and distribution of natural radioactive elements in the Graduate University of Advanced Technology

The radiation hazards in each region depend on its surface distribution and activity of 232Th, 137Cs, 40K, and 238U radioactive elements. Due to the presence of personnel, professors, and students in the Graduate University of Advanced Technology (KGUT) environment, it is important to investigate the dose received due to 232Th, 137Cs, 40K, and 238U elements in the soil of this area. For this purpose, first, 44 soil samples were collected from different areas of the university, and the specific activity of 232Th, 137Cs, 40K, and 238U elements was obtained with the CsI (Tl) scintillation detector. Then, using radiation hazard equations, the distribution of radiation hazard parameters at the university zone has been calculated. The research results show that the average specific activity of 232Th, 137Cs, 40K, and 238U elements at the university zone is equal to 13.51, 4.53, 47.64, and 13.01 Bq/kg. The activities of 232Th, 40K, and 238U elements are below the permissible limit and 137Cs is higher than the permissible limit. Also, the average of Raeq, DY, Dout, Din, Dtot, Hex, Hin, Iγ, and ELCR radiation hazard quantities are 81.26 (Bq/kg), 72.31 (mGy/y), 0.088 (mGy/y), 0.088 (mGy/y), 0.17 (mGy/y), 0.11, 0.15, 0.18 and 0.62 respectively. According to the results the DY and Dout radiation hazards are more than the permissible limit and the rest of the radiation hazard parameters are less than the permissible limit. Results have shown that the Annual Effective Dose outside (soil) and inside (soil and granite) of the KGUT office building was (22 ± 0.22) μSv/y, (0.13 ± 0.0013) mSv/y. Finally, the distribution of natural radioactive elements and radiation hazards in different parts of the university shows that except for DY and Dout, all radiation hazard parameters in the administrative buildings and dormitories of the university are less than the permissible limit. Therefore, the annual presence of staff, students, and professors in the university are allowed.

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

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

Low-protein diets supplemented with glycine improves pig growth performance and meat quality: An untargeted metabolomic analysis.

For the purpose to improve meat quality, pigs were fed a normal diet (ND), a low protein diet (LPD) and a LPD supplemented with glycine (LPDG). Chemical and metabolomic analyses showed that LPD increased IMF deposition and the activities of GPa and PK, but decreased glycogen content, the activities of CS and CcO, and the abundance of acetyl-CoA, tyrosine and its metabolites in muscle. LPDG promoted muscle fiber transition from type II to type I, increased the synthesis of multiple nonessential amino acids, and pantothenic acid in muscle, which should contributed to the improved meat quality and growth rate. This study provides some new insight into the mechanism of diet induced alteration of animal growth performance and meat quality. In addition, the study shows that dietary supplementation of glycine to LPD could be used to improved meat quality without impairment of animal growth.

Occurrence of radioactive cesium-rich micro-particles (CsMPs) in a school building located 2.8 km south-west of the Fukushima Daiichi Nuclear Power Plant

Radioactive Cs-rich microparticles (CsMPs) released from the Fukushima Daiichi Nuclear Power Plant (FDNPP) are a potential health risk through inhalation. Little has been documented on the occurrence of CsMPs, particularly their occurrence inside buildings. In this study, we quantitatively analyze the distribution and number of CsMPs in indoor dust samples collected from an elementary school located 2.8 km to the southwest of FDNPP. The school had remained deserted until 2016. Then, using a modified version of the autoradiography-based “quantifying CsMPs (mQCP) method,” we collected samples and determined the number of CsMPs and Cs radioactive fraction (RF) values of the microparticles (defined as total Cs activity from CsMPs/bulk Cs activity of the entire sample). The numbers of CsMPs ranged from 653 to 2570 particles/(g dust) and 296–1273 particles/(g dust) on the first and second floors of the school, respectively. The corresponding RFs ranged between 6.85 – 38.9% and 4.48–6.61%, respectively. The number of CsMPs and RF values in additional outdoor samples collected near the school building were 23–63 particles/(g dust or soil) and 1.14–1.61%, respectively. The CsMPs were most abundant on the school's first floor near to the entrance, and the relative abundance was higher near the stairs on the second floor, indicating a likely CsMP dispersion path through the building. Additional wetting of the indoor samples combined with autoradiography revealed that indoor dusts had a distinct absence of intrinsic, soluble Cs species, such as CsOH. These combined observations indicate that a significant amount of poorly soluble CsMPs were likely contained in initial radioactive airmass plumes from the FDNPP and that the microparticles penetrated buildings. CsMPs could still be abundant at the location, with locally high Cs activity in indoor environments near to openings.

Using microcomputed tomography (μCT) to count varves in lake sediment sequences: Application to Lake Sagtjernet, Eastern Norway

Varved lake sediments are one of the most important natural archives that allow annual resolution paleoclimate reconstructions. Conventional varve counting techniques use thin sections to manually identify lamina. However, this technique is destructive, labour intensive and limited to a 2D representation of complex 3D features which may lead to misidentification of varve boundaries. This study presents the use of microcomputed tomography (μCT) scans in constructing varve chronologies, utilizing scanning resolutions of ∼50 μm (binned to ∼200 μm) for core sections up to 150 cm long. To evaluate this method, we cored and analysed Lake Sagtjernet in Eastern Norway — revealing a 593 cm-long sediment record of the past 10274 (+220/-329) years, with continuous laminations from 84 to 533 cm depth (75% of the sediments). Through limnological monitoring and microfacies analyses we demonstrate that the laminations are rare ferrogenic varves, with an annual deposition pattern comprised of seasonal changes in biogenic production superimposed on seasonal precipitates of iron and manganese hydroxides. The floating μCT-counted varve chronology presented here is the first non-glacial varve chronology in Norway and covers 4023 +113/-185 years. We find that μCT scans allow for a very fast and non-destructive way of counting varves with sufficient detail of varve boundaries. In the few sections where varve boundaries are too vague to resolve, we recommend using complimentary techniques such as thin sections in parallel. The varve chronology is in good agreement with the 95% confidence interval of the independent radiocarbon chronology based on 16 14C dates, and 210Pb and 137Cs activity peaks, indicating that the varve chronology can be equated to calendar age.

Hygienic assessment of 90Sr and 137Cs contamination of water and fish in the lakes of the head part of the peripheral zone of the East Ural radioactive trace

Introduction. The article presents the results of studies of the specific activity of 90Sr and 137Cs in the water and fish of the Irtyash and Kazhakul lakes located in the peripheral zone of the head of the East Ural Radioactive trace in 2014-2017.
 Materials and methods. Determination of the levels of specific 90Sr and 137Cs in the water and the body of the resource-forming species of Siberian roach (soroga, chebak) Rutilus rutilus lacustris (Linnaeus, 1758) from the studied lakes was carried out over the period of 2012–2017. The measurements were carried out using standardized methods adopted in in the Federal State Budgetary Institution of Health “Central Medical and Sanitary Unit No. 71 of the Federal Medical and Biological Agency of Russia” (FGBUZ TsMSCH No. 71 of the Federal Medical and Biological Agency of Russia) and the Southern Ural.
 Results. The research was carried out over 2014 to 2017. Since the accident at the Mayak enterprise in the fall of 1957, the specific radioactivity of the water in the studied lakes was found to decrease. The concentration of 90Sr in the water of Irtyash lake was 0.019±0.008, and 137Cs – 0.028±0.009, and in Lake Kazhakul – 0.19±0.06 and 0.14±0.06, respectively. These values are much lower than the level of intervention according to NRB-99/2009. 
 The water of the lakes is used to meet household needs. The water of Lake Irtyash is used for drinking water supply of the city of Ozersk. The specific activity of the raw mass of a roach carcass from the Irtyash and Kazhakul lakes for the accumulation of 90Sr is 2.7± 1.7 and 64.5±19 and 137Cs – 1.68± 0.8 and 38±33.5Bq/kg, respectively. All the samples studied separately according to 90Sr and 137Cs had levels of radioactive contamination at or below the regulatory compliance indicator (SanPiN 2.3.2.1078–01). At the same time, taking into account the absolute extended uncertainty (with a coverage factor of k = 2) roach from Kazhakul lake has a significant excess of the limit level of radioactive contamination.
 Limitations. Hydrochemical parameters of the aquatic environment in various reservoirs can vary significantly over time and affect the accumulation of radionuclides by hydrobionts. Therefore, the research results are relevant only for the research period. To obtain more reliable results, long-term comprehensive monitoring is necessary.
 Conclusion. Over the past 60 years after the accident at the Mayak enterprise in 1957, the levels of radioactive contamination of water and fish in the studied lakes Irtyash and Kozhakul have decreased by more than 10 times. Calculation of doses of ionizing radiation for certain groups of the population of areas contaminated as a result of accidents, living near lakes, is a complex task, for which additional research is needed.

Распределение радиоактивного и стабильного цезия в почвах и растениях лесных экосистем

The paper presents the results of determining the content of radioactive (137Cs) and stable (133Cs) isotopes of cesium in soil and plant samples (lichens, mosses, bark, wood) collected in a medium-aged pine forest on the territory of the Polesye State Radiation-Ecological Reserve, as well as the results of the experiment to assess the vertical precipitation of 137Cs on horizontal plates. The ratios of concentrations of 137Cs to 133Cs have been calculated, which can be used to quantify the level of equilibrium between 137Cs and 133Cs in the forest ecosystems. Based on the assumption that the physicochemical properties of 133Cs and 137Cs are similar, the analysis of 133Cs and comparison of its ratios with 137Cs can be useful for understanding the long-term behavior of the radionuclide and its equilibrium distribution in forest ecosystems. As a result of the conducted research, it was established that the precipitation activity of 137Cs in the composition of tree litter is higher in comparison with the atmospheric precipitation of the radionuclide on horizontal plates. In the autumn season, there is a decrease in the average daily values of 137Cs activity observed in the samples of radioactive fallout from the atmosphere and an increase in the tree litter samples. At the same time, more than half of the total activity of the radionuclide is retained by the tree litter. The vertical distribution of the 137Cs exchange form in the forest soil’s mineral layers was compared to that of 133Cs. The total content of 137Cs in the soil profile decreases with depth. The content of the 137Cs exchange form in the soil profile has an uneven distribution, and the concentration of the stable isotope’s exchange form increases with depth. The 137Cs to 133Cs ratios in the soil profile decrease with a soil depth from the horizon of 0-5 cm to the horizon of 15-20 cm, which indicates a nonequilibrium ratio of these isotopes. It is shown that the content of 137Cs and 133Cs in lichens, mosses, bark and wood varies depending on the type of a sample and the part of a plant. The highest activity values of 137Cs were determined in lichens and mosses. Under conditions of co-growth, mosses are characterized by a higher concentration of 133Cs when compared to lichens. A good correlation was noted between the content of 137Cs and 133Cs for all types of the plant samples. This result suggests the conclusion that these plants absorb 137Cs similarly to 133Cs.

Activity concentrations and radiological hazard assessments of 226Ra, 232Th, 40K, and 137Cs in soil samples obtained from the Dongnam Institute of Radiological & Medical Science, Korea

The radioactivity concentration of environmental radionuclides was analyzed for soil and sand at eight locations within a radius of 255 m centered on the Dongnam Institute of Radiological & Medical Science (DIRAMS), Korea. The average activity concentrations of 40K, 137Cs, 226Ra, and 232Th were 661.1 Bq/kg-dry, 0.9 Bq/kg-dry, 21.9 Bq/kg-dry, and 11.1 Bq/kg-dry, respectively. The activity of 40K and 137Cs was lower than the 3-year (2017–2019) average reported by the Korea Institute of Nuclear Safety, respectively. Due to the nature of granite-rich soil, the radioactivity of 40K was 0.6-fold higher than in other countries, while 137Cs was in the normal fluctuation range (15–30 Bq/kg-dry) of the concentration of radioactive fallout from nuclear tests. The activity of 226Ra and 232Th was lower than in Korean soils reported by the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). The average activity concentrations of 232Th and 40K for the soil and sand samples from DIRAMS were within the range specified by UNSCEAR in 2000. The radium equivalent activity and internal and external hazard index values were below the recommended limits (1 mSv/y). These radionuclide concentration (226Ra, 232Th, 40K, and 137Cs) data can be used for regional environmental monitoring and ecological impact assessments of nuclear power plant accidents.

Distribution of strontium-90 in soils affected by Fukushima dai-ichi nuclear power station accident in the context of cesium-137 contamination

90Sr and 137Cs activity concentrations were determined by radiometric methods in 76 soil samples (soil, litter, rain gutter deposit, and roadside sediment samples) affected by the Fukushima Dai-ichi Nuclear Power Station (FDNPS) accident and collected from the Fukushima exclusion zone. The 90Sr and 137Cs activity concentrations were in the range of 3 to 1050 Bq kg−1 (median 82 Bq·kg−1) and 0.7 to 6770 kBq·kg−1 (median 890 kBq·kg−1), respectively (decay correction date: March 15, 2011). A strong positive correlation was found between 90Sr and 137Cs activity concentration and higher mobility of 90Sr was confirmed in Japanese soil samples. The activity ratio of 90Sr/137Cs in 85% of all samples was in the range of 5.0 × 10−5 to 5.0 × 10−4 with a median of 1.2 × 10−4. From the activity ratio values it was concluded that the 90Sr released to the atmosphere was only around 0.0003–0.02 PBq which is negligible compared to the Chernobyl accident (∼10 PBq) or other nuclear accident contaminations. From the standpoints of radioecology and radiation safety, 137Cs remains the primary pollutant of the FDNPS accident.

On the additional risk for human health in the use of sandblasting of building walls.

In 2021, concentrations of heavy metals (Ba, Cr, Fe, Mn, Pb, Ru, Sr, Zn, Zr) and radiocesium (137Cs) were measured in 13 locations in Vilnius in surface samples of walls and facades of buildings built of yellow bricks in order to evaluate possible aerosol air pollution due to sandblasting. The activity concentrations of 137Cs appeared there as a result of global fallout and precipitation of the products of the accident at the Chernobyl Nuclear Power Plant, and the concentration of Pb, as a component of road transport emissions. Other trace elements turned out to be impurities in the material of yellow bricks. In spring 2018, sandblasting of the walls of the building adjacent to the school led to the long-term significant aerosol contamination of school premises (up to 660µg/m3). Due to sandblasting, the surface of the school sport yard was covered with a thin layer of scraped particles, which were transported by gusts of wind into the school premises. Sandblasting of walls and facades can also be a source of aerosols with 137Cs activity concentrations reaching ~ 40Bq/kg and Pb - up to 98ppm. Estimates show that along with 137Cs, the formation of aerosols with activity concentrations of 239, 240Pu reaching 1.6Bq/kg is possible. Isotopes of 239, 240Pu are analogues of calcium and, when ingested, are deposited in the bones. The ingress of radioactive aerosols into the respiratory tract, especially of children of primary school age, creates additional risks of malignant diseases.

Evaluation of current natural and anthropogenic radionuclide activity in coastal area bottom sediments of the Barents Sea (North of the Kola Peninsula)

This article is devoted to the study of the activity of technogenic 137Cs and 90Sr, as well as natural radionuclides 40K, 232Th and 226Ra in bottom sediments of the Kola coast of the Barents Sea, where a significant number of radiation objects are concentrated. In order to characterize and assess the accumulation of radioactivity in the bottom sediments, we studied the particle size distribution and some physicochemical parameters, such as the content of organic matter, carbonates and ash components. The average activities of natural radionuclides 226Ra, 232Th and 40K were 325.0, 25.1 and 466.7 Bq·kg−1, respectively. Levels of natural radionuclides in the coastal zone of the Kola Peninsula are within the range of marine sediments worldwide. Still, they are slightly higher than those observed in the central areas of the Barents Sea, most likely due to the formation of coastal bottom sediments as a result of the destruction of the natural radionuclide-enriched crystalline basement rocks that make up the Kola coast. The average activities of technogenic 90Sr and 137Cs in the bottom sediments of the Kola coast of the Barents Sea are 3.5 and 5.5 Bq·kg−1, respectively. The highest activities of 90Sr and 137Cs were found in the bays of the Kola coast, while they remain below detection limits in the open parts of the Barents Sea. Despite the presence of potential sources of radiation pollution in the coastal zone of the Barents Sea, we did not find any short-lived radionuclides in the bottom sediments, which indicates the absence of a significant influence of local sources on the transformation of the technogenic radiation background. The study of particle size distribution and physicochemical parameters showed that the accumulation of natural radionuclides is largely related to the content of organic matter and carbonates, while the accumulation of technogenic isotopes occurs in the composition of organic matter and the smallest fractions of bottom sediments.

The Content and Speciation of Radionuclides in Water and Bottom Sediments of the Laptev Sea

In the presented work, the features of the distribution of Cs-137 and plutonium isotopes in modern sediments of various parts of the Laptev Sea, selected during the expedition studies on the RV “Academician Mstislav Keldysh” in 2017 and 2019, were studied. It was found that the activity of Cs-137 in water and sediments is within the global level, which is typical for the seas of the Arctic region. In all the collected samples the specific content of Pu-239,240 isotopes is below the level of the minimum detectable activity. According to the results of isotope analysis of Pb-210, the sedimentation rates in two columns collected in the Laptev Sea are 0.18 and 0.23 cm/year. The study by several methods of the speciation forms of Pu-239, introduced into the samples of bottom sediments under laboratory conditions, showed that the main content of Pu-239 is associated with difficult-to-dissolve organo-mineral components. 30-39% Pu-239 was found in the composition of organic easily soluble acids and humic substances, which include fulvic and humic acids of bottom sediments.

Monitoring of <sup>137</sup>Cs, <sup>90</sup>Sr and <sup>40</sup>K in Gray Forest Soils and Plants of Reference Sites of the Vladimir Region

The paper presents the results of radiation monitoring of gray forest soils of reference agricultural plots of the Vladimir region, conducted in 2011 and 2016. The study established background values of specific activities of the studied radionuclides in the soils of reference sites. According to the density of contamination of the arable horizon of soils 137Cs and 90Sr, the level of the ecological situation was determined, which made it possible to attribute the soils of all reference areas of the region to uncontaminated territories suitable without restrictions for agricultural use. The power of the exposure dose of gamma radiation of soils and the contribution of 40K and 137Cs to the formation of the gamma background of soils are established. Correlation ana-lysis determined the influence of individual physical and chemical properties of soils on the behavior and distribution of radionuclides in the soil and the relationship between the radionuclides themselves. Based on the values of the specific activity of 137Cs and 90Sr in plant products grown on the soils of reference sites in 2011 and 2016, rows of cultivated plants were constructed, with a decreasing ability to accumulate these radionuclides from the soil. All grown plant products for all types of crops fully met the sanitary and hygienic standards required to limit the content of 137Cs and 90Sr in plant feeds (green mass, straw and grain) and food products (apples). According to the transition coefficients, it was found that the process of transition of 90Sr from soil to plants of all kinds proceeded more intensively than the transition of 137Cs. The calculated coefficients of linear correlation between the values of the specific activity of 137Cs and 90Sr in soils and plants revealed the strength and nature of their dependencies.

<sup>137</sup>Cs Pollution in Soils and Plants of Urban Ecosystems Near the Elektrostal Heavy Machinery Plant

In urban ecosystems to the west of the Elektrostal Heavy Machinery Plant, 6 years after the radiation incident, local areas with a total area of 0.2 km2 with an increased equivalent dose rate of γ radiation of 0.15–0.40 μSv/hour and a high specific activity of 137Cs reaching 8328–8740 Bq/kg in the upper soil horizons were identified. Statistically significant direct correlations were noted between the specific activity of 137Cs in a layer of 0–10 cm of soil and the equivalent dose rate of γ radiation at the surface and height of 1 meter. The types of vertical distribution of 137Cs in soils of polluted urban ecosystems, including those on which earth decontamination works were carried out, have been determined. The calculated 137Cs transfer coefficients increase in row of tree: Salix alba Sórbus aucupária Ácer platanoídes Malus domestica Alnus incana Ácer negúndo; and grassy vegetation: Týpha angustifólia Artemísia vulgáris Tussilágo fárfara Cirsium arvense Urtíca dióica.

A dosimetric comparison between ICRP and ORNL phantoms from exposure to 137Cs contaminated soil

The 137Cs soil contamination has detrimental effects on human health. The penetration and distribution of 137Cs radionuclides at different soil depths were investigated. Two sampling campaigns in 2001 and 2018 were performed to determine the 137Cs activity in soil at 11 locations around the city of Kragujevac in central Serbia. The ICRP and ORNL humanoid phantom models were used to determine equivalent and effective doses from the experimentally measured data, and conversion coefficients were obtained from Monte Carlo computations. The results show a general decrease in 137Cs concentration in samples that were taken in 2018. However, variation of 137Cs concentration was observed at different locations that did not match the expected reduction of 137Cs concentration based on its half-life.Considering the computational results, no significant difference between the estimated equivalent dose rate per unit activity of 137Cs (conversion coefficients) between ICRP and ORNL phantoms was observed. In addition, two open-source computer programs for PC and Android devices were developed for users to determine the equivalent and effective doses for their specific cases; this gives the users an easy-to-use interface and portable tools to determine dosimetric quantities. The obtained results and the developed tools would be useful for future investigations related to soil contamination by 137Cs radionuclides that require extensive future studies.

Distribution characteristics of radionuclides (137Cs, 239+240Pu, 237Np, and 241Am) in vertical vegetation zone in Changbai Mountain, China

Changbai Mountain has vegetation distribution characteristics, which is an important location in northeast China to study the variation characteristics of radionuclides with vegetation distribution. Soils from three vegetation zones of mixed broadleaf and coniferous forest (MBCF), coniferous forest (CF), and alpine birch forest (ABF) in Changbai Mountain were collected to measure the artificial radionuclides of 239+240Pu, 237Np, and 241Am by SF-ICP-MS, as well as 137Cs by anti-Compton HPGe. The mean values of 240Pu/239Pu and 237Np/239Pu atomic ratios, 241Am/239+240Pu and 137Cs/239+240Pu activity ratios were 0.19 ± 0.02, 0.37 ± 0.23, 0.56 ± 0.31, 22 ± 17, respectively, indicating that the global fallout was the main source of 239+240Pu, 237Np, 137Cs and 241Am in these regions. 137Cs, 239+240Pu, 237Np, and 241Am activities in the samples are 1.1–218, 0.065–9.1, (0.018–2.9) × 10-3, and 0.039–2.0 Bq/kg, respectively. The activities of 137Cs, 239+240Pu, and 237Np in the surface soil have a similar distribution characteristic, i.e. CF > MBCF > ABF, and 241Am is CF > ABF > MBCF. The simulation results of the CDE model suggest that the migration of these radionuclides is dominant in Changbai Mountain forest soil. The inventories of 137Cs, 239+240Pu, 237Np, and 241Am in the soil cores are 1263–20843, 110–1425, 0.017–0.38, and 91–493 Bq/m2, respectively. The inventories distribution of these nuclides in the vegetation zone were as follows: 137Cs and 239+240Pu had similar distribution characteristics as ABF > CF > MBCF; 237Np as CF > MBCF > ABF; 241Am as ABF > MBCF > CF. These results showed that the content, accumulated inventory, and vertical distribution characteristics of these radionuclides were influenced by the vegetation zone distribution in the Changbai Mountain.

Distribution of 90Sr and 137Cs in biotic and abiotic elements of the coastal zone of the King George Island (South Shetland Archipelago, Antarctic Peninsula)

For many years Antarctic ecosystems have been considered pristine, however recent studies, including our results, contradict this assumption. Our comprehensive study on the activity of anthropogenic radioisotopes (137Cs and 90Sr) in the most common species of green algae, bryophytes, lichens, and vascular plants, as well as soil and guano samples collected over a large area on King George Island (South Shetland Archipelago) in the austral summer 2018/2019 clearly indicate the importance of large-scale transport in shaping the level of pollution in areas very distant from potential sources of contamination. Additionally, radioisotope pollution can be measured even after a very long period (>60 years) since their occurrence. The mean activity of 137Cs measured in lichens, bryophytes, vascular plants, green algae, soil, and guano was, respectively: 3.72 Bq kg−1dw, 3.70 Bq kg−1dw, 2.62 Bq kg−1dw, 2.26 Bq kg−1dw, 4.07 Bq kg−1dw and 2.08 Bq kg−1dw. For 90Sr mean activity in lichens, bryophytes, vascular plants, green algae, and soil was, respectively: 1.99 Bq kg−1dw, 3.05 Bq kg−1dw, 2.42 Bq kg−1dw, 1.08 Bq kg−1dw, and 6.43 Bq kg−1dw. Increased activities of 90Sr and 137Cs were observed in species collected in the area influenced by glacier melt and penguin guano.