Vertical Distribution Of 137Cs Research Articles

Echoes of a Cold War

The Kara Sea was an area of radionuclide contamination as a result of nuclear weapons testing, since it is located in close proximity to the nuclear test site on the Novaya Zemlya archipelago. The vertical distribution of 137Cs and 210Pb in 15 sediment cores from the sea made it possible to reconstruct the chronology of 137Cs entry into marine sediments. The reconstruction was based on the age-depth model RUS2023 (Rusakov et al., 2024) for 210Pbex, taking into account the grain-size composition and sorption capacity of sediments. Our study showed that higher 137Cs concentrations in sediments of the Novaya Zemlya Trough correspond to the time of active nuclear weapons testing in 1961–63 (about 9.0±1.6 Bq kg‒1), as well as in estuarine sediments of the Yenisei Bay in 1986 (85.2±3.2 Bq kg‒1). The abnormally high flux in 1980s represents the superposition of 137Cs fluxes as a result of global fallout (Chernobyl trace) and as a result of the release of radionuclide from regional source located in the Yenisei River catchment. Both of these events are associated with increased the sedimentation and mass accumulation rates of marine sediments. In 1961‒63, this was a consequence of the release of sediment into the atmosphere due to nuclear explosions, and in the 1980s, as a result of an increase in sediment supply with river runoff. Currently, against the backdrop of a decrease in sediment fluxes into the sea, Novaya Zemlya and Yenisei River remain the main sources of 137Cs supply to marine sediments. Background values for recent sediments in the Kara Sea are <2.0 Bq kg‒1.

Spatiotemporal variations in vertical profiles of Fukushima-derived 137Cs in the Kuroshio-Oyashio confluence region from 2011 to 2018: Implications for local water mass dynamics and basin-scale circulations

Tracking the processes of the spread of Fukushima-derived 137Cs (137CsF) contributes to a better understanding of North Pacific water dynamics. In this study, the vertical distributions of 137Cs and 90Sr in the Kuroshio-Oyashio confluence region were investigated in May 2018, and 137CsF was separated from the background 137Cs by exploiting the constant global fallout 137Cs/90Sr ratio. To the north of 35°N, 137CsF peaked in the upper 100 m layer, whereas in and just south of the Kuroshio Extension (KE), 137CsF exhibited subsurface peaks at depths of 300–500 m. The T/S diagram indicated that the 137CsF maxima were distributed mainly within the range of lighter central mode water (L-CMW) during May 2018, even in and just south of the KE. We found that anticyclonic (cyclonic) eddies can promote (prevent) the intrusion of 137CsF into the ocean interior. In addition, the high activity of regional anticyclonic eddies in the upstream KE resulted in the modification of 137CsF-rich subtropical mode water (STMW) to L-CMW. Temporal changes in the 137CsF vertical profiles and inventories revealed that 137CsF in transitional and subarctic regions has increased since July 2014, implying the existence of additional sources of 137CsF after July 2014, whereas 137CsF in and just south of the KE has remained constant since July 2014, indicating that the 137CsF entrained by STMW has recirculated in the western subtropical gyre. The comparison between surface 137CsF concentrations in transitional and subarctic regions and those observed in Oyashio waters during 2018 did not support the return of 137CsF to our study area via the western or whole subarctic gyre by May 2018. In contrast, the sea surface height distributions from 2016 to 2017 provide clear evidence that the warm-core rings and quasistationary Isoguchi western jet generated from the Kuroshio Current and KE intruded into the transitional region and even into the subarctic region. Therefore, we concluded that a portion of the 137CsF that subducted into the subtropical western North Pacific during 2011–2012 have entered the transition zone and even the subarctic region since 2016. These results not only enhance our understanding of the protracted spread and fate of 137CsF in the North Pacific but also provide important insights into North Pacific water mass circulation and mixing patterns.

Experience of using the portable gamma spectrometer MKS AT6101D for in situ measurements of the density of &lt;sup&gt;137&lt;/sup&gt;Cs soil contamination in the Bryansk region of Russia

We have tested applicability of the commercially available portable spectrometer-dosimeter MKS AT6101D (the manufacturer: ATOMTEX, Belarus) to measure the density of 137Cs soil contamination (inventory of 137Cs in soil) in situ. The study was performed in 2015–2020 at the territories of the Bryansk region of Russia contaminated due to the Chernobyl accident. The in situ measurements were performed in the 17 ground plots (7 grasslands and 10 kitchengargens) for which the 137Cs inventory and the mean migration depth of the radionuclide in soil was available from laboratory (ex situ) measurements of soil samples. It was found that the in situ data obtained with the method that was provided by the manufacturer of the instrument required additional correction on the vertical distribution of 137Cs in the soil. The correction procedure was developed; in 2020–2021, it has been successfully tested in 114 kitchengarden plots located at the settlements in the zones of radioactive contamination in the Bryansk region.

Моделирование нисходящего переноса 210Pb на примере естественного торфяника Иласского болотного массива Европейской Субарктики России: модель IP-CRS

The paper presents the results of the modelling of the transport of 210Pb down the peat core for the Ilassky natural bog massif. The activities of radionuclides 210Pb and 137Cs were investigated in the core layer by layer. Due to the nonexponential decrease of 210Pb activity, significant errors are possible in determining the age and accumulation rates of peat when applying classical dating models. The article presents 210Pb dating data obtained using the IP-CRS model. Data analysis showed that the vertical distribution of 137Cs and 210Pb is related to peat parameters: ash content and bulk density. The 210Pb dating of the core showed an age of 1963 for a depth of 17—19 cm, which is consistent with the 137Cs data. The dating of this horizon is indirectly confirmed by the data of the ash content and bulk density of peat. The above mentioned confirms the correctness and adequacy of the chosen model of dating of the natural peat bog. The peak of anthropogenic radionuclide content in peat deposits corresponds to 1963, the date of signing the Partial Nuclear Test Ban Treaty, being a reference point for geochronological studies. The results of linear accumulation rate, peat deposit mass accumulation rate and the magnitude of the atmospheric flux of 210Pb presented in the study are in good agreement with the data on peatlands of Northern Europe and the European Subarctic of Russia.

Assessment of secondary radioactive contamination of a decontaminated land plot located on the territory of a recreation base in a wooded area

The article presents results of a long-term (1998–2021) radiological monitoring survey of a recreation base located in a wooded area in the zone of radioactive contamination after the accident at the Chernobyl nuclear power plant. Local mechanical decontamination of the soil had been made on the territory of the base in 1997. The evaluation of the secondary radioactive contamination of the decontaminated territory was performed by comparing dynamics of the radiological situation at the treated plot and the control, nondecontaminated, part of the base according to four main criteria: 1) dose rate of gamma radiation in the air from cesium radionuclides; 2) inventory of 137Cs in soil; 3) vertical distribution of 137Cs in soil; 4) activity concentration of 137Cs in plants and fungi. In 1998, the value of the 137Cs inventory in the upper 20 cm of soil in the control part of the territory of the base and in the decontaminated plot was 930 kBq/m2 and 143 kBq/ m2, respectively. By 2015, the value of the 137Cs inventory in the control area and the decontaminated plot had significantly decreased: by 35% and 36%, respectively. A decrease in the dose rate of gamma radiation in the air at the decontaminated plot and control area proceeded at the same rate, which is currently mainly determined by the decay of 137Cs. There was a gradual self-restoration of the forest ecosystem at the plot subjected to decontamination. Activity concentration of 137Cs in biota (pine, edible mushrooms) in the treated plot was many times lower than that in the control part of the recreation base. In general, there was no significant secondary radioactive contamination of the decontaminated plot in the 24 years after the intervention.

Radiological situation in the young pine forest that grew after the Chernobyl accident

After the Chernobyl accident, a certain proportion of agricultural land was withdrawn from normal use due to significant radioactive contamination. Forestry is one of the options currently under consideration to return the abandoned agricultural land to economic circulation in Russia. When using former agricultural land for forestry in radioactively contaminated areas, it is important to have an assessment of the potential radiation doses for forestry workers and the public. The aim of this study was to assess the radiological situation in a young pine forest planted and grown after the Chernobyl accident in the resettlement zone on a former arable field. A nearby old pine forest, which had grown before the Chernobyl accident, was taken for comparison. The study of the radiological situation was performed in the period 1998–2022. In the young forest, 137Cs was fairly evenly distributed in the upper 20 cm soil layer; further with depth, the activity concentration of 137Cs sharply decreased. In the old forest, the maximum activity concentration of 137Cs in the soil was in the top 0–2 cm layer. The activity concentration of 137Cs decreased with depth. In 1998, the average value of the absorbed dose rate in the air from 137Cs+134Cs was lower by a factor of 3 in the young forest compared to the old forest. The difference was associated with differences in the vertical distributions of 137Cs in the soil. Over time, the absorbed dose rate in air from 137Cs+134Cs decreased at both sites with the same effective halftime period of 21.7 year. The activity concentration of 137Cs in the biota (pine trees, edible mushrooms) in the young forest was lower by a factor of 4–30 compared to the old forest. The “forest” component of the external effective dose to adults from the 137Cs source in the young forest was lower by a factor of 3 compared to the old forest. The “forest” component of the internal effective dose from 137Cs was lower by a factor of 10 when eating edible mushrooms from the young forest compared to the old one. In general, the performed study shows that the use of radioactively contaminated abandoned arable land for forestry can be expedient and justified from a radiological point of view.

Estimation of Physicochemical Parameters and Vertical Migration of Atmospheric Radionuclides in a Raised Peat Bog in the Arctic Zone of Russia

The article presents the results of a study of activity levels and features of the vertical distribution of 210Pb, 137Cs, 234U, 238U and their relationship with the physicochemical parameters of peat deposits. Analysis of the data showed that the vertical distribution of 137Cs and 210Pb was related to the content of water-soluble salts, the water saturation of the deposit, and the values of Eh (oxidation–reduction potential) and rH (relative humidity), which indicates a complex geochemical barrier at a depth of 20 cm in the peat core. The 210Pb dating of the peat core, carried out according to the CF model using the Monte Carlo method (to improve the dating accuracy), showed that the above horizon corresponded to 1963, which is consistent with the data of the 137Cs reference horizon and in terms of several physicochemical parameters (in particular, ash content) also corresponds to the age of 1963, which confirms the correctness and adequacy of the chosen peat core dating model. The peak of anthropogenic radionuclides in peat deposits correlates with a particular major event in the history of radioactive fallout, the Partial Nuclear Test Ban Treaty of 1963, providing a benchmark for geochronological research. The obtained results of the linear accumulation rate, the mass accumulation rate of the peat deposit, and the value of the atmospheric flux of 210Pb are congruent with the data on the peatlands of Northern Europe and the data obtained by earlier analysts of the Subarctic region of European Russia.

Distributions of fallout 137Cs, 239+240Pu and 241Am in a soil core from South Central China

The source and vertical distribution of 137Cs,239+240Pu and 241Am activity concentrations in a soil core from Hunan Province, China were investigated. The maximum 137Cs and 239+240Pu activity concentrations were 15.45 ± 0.76 mBq/g and 0.819 ± 0.066 mBq/g, respectively. While the maximum 241Am activity concentration in samples obtained from the core was 0.341 ± 0.019 mBq/g. The 240Pu/239Pu atom ratio and the 137Cs/239+240Pu activity ratio were 0.183 ± 0.011 and 19.5 ± 1.8, respectively, and both were consistent with the characteristic value of global fallout. The integrated 241Am/239+240Pu activity ratio for global fallout was also re-estimated. The measured 241Am/239+240Pu activity ratio (average 0.43 ± 0.07) in the samples was very close to the estimated value (0.45), which suggested their 241Am also came from the global fallout. Regarding the vertical distribution of 137Cs, 239+240Pu and 241Am in these red soil samples, all these radionuclides had higher concentrations in upper layers of several centimeters of soil while they had slightly lower concentrations in lower soil layers down to 30 cm. Vertical distributions of 137Cs/239+240Pu and 241Am/239+240Pu activity ratios indicated the migration velocity was Am ≈ Pu > Cs. The intrinsic chemical properties of the radionuclides as well as soil type and properties (acidic, nutrient-deficient and low in organic matter and cation exchange capacity) might be reasons for the differences in their migration behaviors.

Ten-year trends in vertical distribution of radiocesium in Fukushima forest soils, Japan

To elucidate interannual changes in the vertical distribution of 137Cs in forest ecosystems contaminated by the Fukushima Dai-ichi Nuclear Power Plant accident, we investigated 137Cs inventories in forest soils (both organic and mineral soil horizons) at 10 sampling plots with different 137Cs deposition levels and dominant species for up to 10 years after the accident. We examined the temporal variation of the 137Cs inventories by depth with exponential regression models (assuming that the transition and partitioning of 137Cs are still active) and exponential offset regression models (assuming a shift to a stable 137Cs distribution, defined as the “quasi-equilibrium steady-state” in the Chernobyl accident). In the organic horizon, the 137Cs inventories were exponentially decreasing, and it might take more time to converge in the quasi-equilibrium steady-state at most plots. In the mineral soil horizon, most of 137Cs was found in the surface layer of the mineral soil horizon (0–5 cm). In this layer, the inventories first increased and then become relatively constant, and the exponential offset model was selected at most plots, suggesting entry into the quasi-equilibrium steady-state over the observation period. Although we also observed exponentially increasing trends in a lower layer (5–10 cm) of the mineral soil horizon, there was no clear increasing or decreasing trend of 137Cs inventory in the deeper mineral soil layers (10–15 and 15–20 cm). Our calculation of the relaxation depth and migration center revealed that downward migration of 137Cs is not significant in terms of the overall 137Cs distribution in the mineral soil horizon over 10 years.

Study of radionuclides and heavy metal migration through soil profiles (0-60cm) at points near the targets of NATO strikes in 1995: environmental monitoring and assessment.

The activity concentrations of natural and artificial radionuclides (40K, 232Th, 226Ra, 238U, 137Cs) and concentrations of six heavy metals of interest (Cd, Cr, Cu, Ni, Pb and Zn) were investigated in 18 soil samples through soil depths (0-10, 10-20, 20-30, 30-40.40-50, 50-60cm) at the three selected sites in the Hadžići. Since at this area ammunition with depleted uranium had been used during the NATO strikes in 1995, this study was conducted with the aim to assess the radiological and environmental health hazards. Radioactivity was determined by gamma spectrometry using HPGe and LEGE detectors and content of heavy metals by using a flame atomic absorption spectrometry. The correlation with distribution of the radionuclides and their activity concentrations through depths was found only at the site 1 for 40K, 232Th and 226Ra, where minimum/maximum activity concentrations for 40K were 814.42Bq/kg/1039.48Bq/kg, for 232Th 53.98Bq/kg/74.12Bq/kg and for 226Ra 50.32Bq/kg/65.73Bq/kg. Vertical distribution of 137Cs along 3 site profiles was used for distinction of cultivated and uncultivated soil. Using the activity ratio of 238U/226Ra and 235U/238U, the presence of depleted uranium (DU) was established at the site 3. Obtained Igeo values for determined heavy metals showed that all of three sites were unpolluted to moderately polluted. Pb content in all three sites showed correlation with concentration decreasing with increasing soil depth.

Effects of temperature and oxygen on 137Cs desorption from bottom sediment of a dam lake

The temperature and oxygen environment play important roles in the desorption of 137Cs from freshwater lake sediment to lake water. In this study, 12 quarterly surveys were performed to measure the dissolved 137Cs concentration in surface and bottom lake water, the vertical distribution of water temperature, and the dissolved oxygen (DO) concentration at the upstream, midstream, and downstream sites of the Yokokawa Dam Lake in Fukushima Prefecture, Japan. Higher concentrations of dissolved 137Cs were detected in the bottom water than in the surface water, especially in the summer and midstream lake regions at depths of 8–21 m owing to higher temperatures, which activated the bacterial decomposition of organic matter, and anaerobization, which enhanced the NH4+ in the pore water and 137Cs desorption from mineral particles. To compare the effects of anaerobization and increasing temperature on 137Cs desorption from sediment particles, intact sediment core samples were collected from the lake midstream and incubated for 1–14 days in a chamber under three controlled temperature and oxygen environment conditions: aerobic +10 °C; anaerobic +10 °C; and anaerobic +20 °C. The vertical distribution of 137Cs in the sediment pore water showed a similar profile as NH4+ and K+, and both the increased temperature and reduced DO concentration enhanced the 137Cs desorption. A comparison of the standard partial regression coefficients of temperature and DO concentration in the multiple regression equation for the 137Cs concentration in pore water shows that the reduction of DO from saturation to zero at the water–sediment interface accelerated the desorption of 137Cs more strongly than did the temperature rise from 10 to 20 °C. The experimental results show a nearly inverse proportional relationship between NH4+ and the distribution coefficients of 137Cs after thermodynamic correction, except in the surface layer. These findings indicate that the 137Cs concentration in pore water can be explained by the temperature-dependent chemical distribution between the solid–aqueous phase and its equilibrium with NH4+.

Radiocaesium retention in bog meadows: an analysis based on soil properties.

The vertical distribution of 137Cs in peat bog soils in the remote period after the Chernobyl Nuclear Power Plant accident (ChNPP, 1986) was investigated. The study was conducted on bog meadows in the Bryansk region of Russia. Soil samples were taken at 4 locations: 2 sites on lowland bogs and 2 sites on transitional bogs. Fifteen years after the accident, analysis of soils showed that the peak of 137Cs activity was still in the upper 10-cm layer. The highest percentage of the initial 137Cs deposition (92%) has been observed in the top 10-cm layer in the drained transitional bog. The lowest part of the initial 137Cs deposition (40%) has been found in 0-10-cm horizon in lowland bog with the deep peat layer. The findings revealed that elevated soil moisture promotes 137Cs downward migration. It was shown that ammonium has a major impact on mobility of 137Cs in bog soils. On average, the soil solution NH4+ concentrations exceeded the K+ concentrations by about a factor 5. A significant linear relationship was found between the rates of 137Cs removal from the top layers with the soil solution NH4+ concentrations.

Evaluation of contribution rate of the infiltrated water collected using zero-tension lysimeter to the downward migration of 137Cs derived from the FDNPP accident in a cedar forest soil

The vertical distribution of 137Cs in forest soil is important for predicting air dose rates and future cycling in forest ecosystems. However, there are many unexplained questions about the mechanisms of its downward migration. In this study, the 137Cs flux by rainfall infiltration was observed for three years from August 2017 using zero-tension lysimeters in a mature cedar forest where monitoring of the vertical distribution of 137Cs has been conducted since 2011. As a result, the 137Cs concentration in infiltrated water through the litter layer, 5 cm and 10 cm showed a tendency to be high in summer, but no such seasonal variation was found at 20 cm. Although the 137Cs inventory in the litter layer has been exponentially decreasing, the annual 137Cs fluxes in infiltrated water through the litter layer were almost the same in three years, and about 0.14–0.17% of the deposition density of 137Cs. Comparing these 137Cs fluxes with the apparent amounts of downward migration of 137Cs estimated from the change in the vertical distribution of 137Cs, the contribution rate of the infiltrated water to downward migration of 137Cs from litter to soil was calculated to be 8.5–17.7%. Similarly, the contribution rate in mineral soil layers was calculated to be 0.6–0.8% on a measured basis and estimated to be 3.0 ± 0.2% after correcting the amount of collected water, which is a problem with zero-tension lysimeter. It indicates that rainfall infiltration can explain a small part of the downward migration of 137Cs, thus further studies are required to clarify the contribution rate of remaining mechanisms such as advection-diffusion, colloidal transport, physical mixing, bioturbation, and growth and death of plant roots.

Vertical distribution of 137Cs and plutonium in Lake Taihu and Dianchi sediment cores: loss of radionuclides in shallow, eutrophic lakes

Plutonium and 137Cs deposited in lacustrine sediments have been used for dating and radionuclide source identification. In order to determine if the radionuclides can be applied to chronogram in shallow lakes with disturbances, we investigated the vertical distribution profiles and loss ratio of plutonium isotopes and 137Cs in sediment cores from Lakes Taihu and Dianchi. We obtained that the inventory of 239+240Pu and 137Cs were lower than those for global fallout for the corresponding latitude and the loss ratios of 137Cs in Lake Taihu was 96%, evident that the loss of 137Cs inventory led to invalid chronological time scales.

137 Cs contaminations in wild-growing medicinal plants of Zhytomyr polissya forests: A 34 years after Chernobyl accident

The contamination of 137Cs in wild-growing medicinal plants was studied with regards to the species, type of forest vegetation conditions and soil specific activity of 137Cs in Zhytomyr polissya forest phytocenoses (Ukraine). The research was carried out in two plots planted in the most region typical edatopes - fresh and wet subor (Querceto-Pinetum). Species composition of phytocenoses was analyzed and the plants that can be harvested for pharmaceutical industry were identified on these test plots,. The herbal substance samples were tested to determine the specific activity of 137Cs. The studies have shown significant variability in the content of radionuclides due to differences in the level of radioactive contamination in the soil and accumulative capacity of plant species. For European blueberry, the peculiarities of 137Cs accumulation in vegetative and generative organs were studied. Comparison of the content of 137Cs in pants of different edatopes showed more higher intensity of radionuclide accumulation in wet suborbs compared to fresh suborbs. The average values of concentration factors were calculated and their rankings were built according to the intensity of 137Cs accumulation for the plants in each edatope. All studied medicinal plants were divided into four groups according to the contration factor: with weak accumulation, moderate accumulation, strong accumulation, and very strong accumulation. Based on the permissible content of 137Cs in wild-growing medicinal plants (600 Bq/kg), the maximum permissible level of soil contamination with radionuclides was determined for each medicinal plant species.

Vertical Distribution of Cs-137 in the Catena Soils of Agricultural Landscapes in the Bryansk Region

The paper presents data on the vertical distribution of 137Cs of Chernobyl origin in arable and meadow soils to a depth of 40 cm in typical catenary junctions of predpolessie, predopolje, and opolje landscapes with a different density of 137Cs contamination 30 years after the accident at the Chernobyl nuclear power plant. Newly obtained data on the removal of 137Cs beyond the arable horizon presented in the paper indicate that this parameter varies depending on the landscape conditions: it varies in the range of 2.7–17.7% in predpolessie landscapes and in the range of 0.5 to 9% in opolje landscapes. In opolje landscapes, the coefficient of 137Cs removal from the arable horizon was proved to systematically decrease depending on the landscape catenary position: it amounts to 8.5% in the transit zone and is 1.4% in the accumulation zone. The vertical distribution of 137Cs and 210Pbex (excess) in the sod and floodplain soils in the basin of the Kostitsa River was studied to determine the sedimentation rate. Based on the analysis of the distribution of 137Cs in the soil, the sedimentation rate over the past 30 years in various parts of the floodplain was estimated at 0.42 ± 0.08 to 0.58 ± 0.11 cm/year. The average estimated sedimentation rate in the floodplain during approximately 50 past years was, according to the 210Pbex dating was equal to 0.7 ± 0.18 cm/year. The sedimentation rate in the bottom of a ravine was evaluated for sod soils based on the distribution of 210Pbex according to the CRS model for 1961–2016 y. It was revealed that the minimum sedimentation rate of 0.24 cm/year occurred in 1961–1988, and the maximal (0.7 cm/year) in 2000 to 2007.

Radiation-Geochemical Stability of Bottom Sediments in the Ob and Yenisei Estuaries and Adjacent Shoal Area of the Kara Sea

This paper reports the results of investigations on the radioecological state of bottom sediments of the Ob–Yenisei shoal area and Ob and Yenisei estuaries. Materials were obtained in two periods: 1995–2001 and 2014–2019 during seven expeditions on the R/V Akademik Boris Petrov, Professor Shtokman, and Akademik Mstislav Keldysh. Resampling of bottom sediment cores at key-points in areas of increased radiocesium activity and subsequent analysis of the radionuclide distribution made it possible to establish positive trends in the change of the radiation state of the regional ecosystem. The total degradation of the Ob radiocesium overactivity zone and quite significant degradation of the Yenisei zone (primarily the most polluted) were revealed. Comparison of current max-positions of specific activity in the vertical distribution of 137Cs in sediment cores made it possible to determine the sedimentation rate in the distal and proximal facies of the Yenisei estuary: 4.7–5.8 and 3.2–3.7 mm/year, respectively. The established changes that have occurred over ~20 years prove the ability of the Kara Sea ecosystem to self-purify. Pollutant diffusion and assimilation by bottom sediments play a significant role in the self-regeneration of the ecosystem. This is most intense in zone of influence of the river–sea geochemical barrier.

Calculation of the effective external dose rate to a person staying in the resettlement zone of the Vetka district of the Gomel region of Belarus based on in situ and ex situ assessments in 2016–2018

The aim of this study was to perform a preliminary assessment of the expected effective dose rate from external exposure to an adult individual staying at that part of the radioactively contaminated territory of the Vetka district of the Gomel region of the Republic of Belarus, from where residents had been resettled after the Chernobyl accident. For this assessment, in summer 2016 and 2018 soil samples were taken from 19 sites located in forests (7 plots), virgin meadows (4 plots), cultivated meadows (6 plots) and vegetable gardens (2 plots), with the subsequent estimation of the inventory and vertical distribution of 137Cs in the soil. The values of 137Cs inventory in the soil ranged from 452 to 1620 kBq m−2 (mean = 904 kBq m−2, median = 964 kBq m−2). The results of the measurement of soil samples were used to calculate values of the air kerma rate, normalized to the inventory of radioactive caesium in the soil. On average, the normalized indicator of the air kerma rate from the man-made source was higher in forests (1.13 nGy h−1 per kBq m−2) compared to virgin meadows (0.95 nGy h−1 per kBq m−2). Normalized air kerma rate in cultivated meadows and vegetable gardens was approximately two times lower than the corresponding indicator for virgin meadows. Using a field gamma spectrometer-dosemeter, ambient dose equivalent rate of gamma radiation in the air was measured at the surveyed sites and the contributions of the technogenic and natural components to the dose rate were estimated. Additionally, such measurements were performed on asphalted surfaces (5 sites) and inside two wooden houses. The measured values of the total ambient dose equivalent rate at a height of 1 m above the ground, asphalted surface or house floor varied from 160 to 2260 nSv h−1. The lowest levels were recorded over asphalted surfaces and inside houses, and the highest ones at forest and virgin meadow sites. The contribution of the technogenic component to the total dose rate varied from 61.9% to 98.8% (mean = 88.9%; n = 26). The effective dose of anthropogenic radiation calculated from the results of in situ measurements in a forest, virgin meadow, cultivated meadow, kitchen garden, asphalted area and house was 0.59, 0.80, 0.34, 0.29, 0.06 and 0.06 μSv h−1, respectively. Similar values for land plots were calculated based on ex situ analysis of soil samples. It can be expected that, starting from 2020, the average effective external dose of a person staying in the resettlement zone of the Vetka district will not exceed 1 mSv year−1.

Correlation between calculated and measured values of gamma dose rate in air in forests contaminated with &lt;sup&gt;137&lt;/sup&gt;Cs: the remote period after the Chernobyl accident

In 2015–2016, 13 forest and 7 virgin grassland plots located in the south-western districts of the Bryansk region were surveyed. The aim of the work was to experimentally test the possibility of using a method for calculating the dose rate of gamma radiation in air in radioactively contaminated forests in a remote period after the Chernobyl accident. According to the results of gamma-spectrometric analysis of soil samples obtained at the sites in another study, the values of inventory and vertical distribution of 137Cs in the upper 20 cm layer were established. In this paper, these data were used to calculate the air kerma rate using a method taken from literature. In addition, at the sites of soil sampling, ambient dose equivalent rate in air was measured, and the contribution of 137Cs to the total gamma dose rate was determined with a field gamma spectrometer-dosemeter. The measured values of the ambient dose equivalent rate from 137Cs correlated positively and statistically significantly with the calculated values of the air kerma rate. The Spearman correlation coefficient was 0.989 (P &lt; 0.01) for the location “forest” and 0.893 (P &lt; 0.05) for the location “grassland”. There was no statistically significant difference between the “forest” and “grassland” locations when analyzing the ratio of the measured dose rate values to the calculated dose rate values (the Mann-Whitney U test, P &gt; 0.05). Results of this work show that, when calculating gamma radiation dose rate in air in forests at a remote stage after the Chernobyl accident, it is enough to know the 137Cs inventory in the upper 20 cm soil layer and a detailed picture of vertical distribution of the radionuclide in this layer. The presence of woody biomass can be neglected. This dose rate estimate is conservative. However, a degree of overestimation of the dose rate in air is small, within +10%, which is quite acceptable for determining the external effective dose rate for an individual in the radioactively contaminated forest.

Recent sedimentation rates using 210Pb and 137Cs vertical profiles of core sediments at the Gulf of Corinth, Litochoro Coast and Marmara Sea

In this work, core sediment samples up to 50 cm have been collected from three different marine environments; Gulf of Corinth, Gulf of Thermaikos, specifically from Litochoro Coast and Lake Uluabat from the wider region of Black Sea. Natural (210Pb) and anthropogenic (137Cs) radionuclides in the samples were measured using an HPGe detector, calibrated for sediments geometry. The vertical distribution of 137Cs and 210Pb was used to determine the sedimentation rate. The results were 0.56 cm/year for the Gulf of Corinth and 0.54 cm/year for the coast of Litochoro. In the case of the lake Uluabat the sedimentation rate was 0.41 cm/year.