Distribution Of Radionuclides Research Articles

Optimizing gamma-ray spectrometers for UAV-borne surveys with geophysical applications

Heavy duty unmanned aerial vehicles (UAVs) have made it possible to fly with large gamma-ray spectrometers that weigh several kilograms. Moreover, they can be purchased at an affordable price. These large UAV-borne gamma-ray detection systems are used to map the naturally occurring radionuclides 40K, 238U, 232Th. Such platforms have the advantage that they can be deployed over terrain that is difficult to access, while still maintaining a high spatial resolution. In contrast to UAV-borne radioactive pollution studies, the naturally occurring radionuclides have a much lower activity and therefore require longer integration time, slower flying speed or a larger detector, in order to effectively determine the spatial radionuclide distribution. Therefore, the question arises: what is the minimum practical detector size required to successfully map 40K, 238U and 232Th concentrations from UAV platforms.In this study an agricultural field has been mapped with three different scintillator-based gamma-ray spectrometers: a 2000 ml, 1000 ml, and 350 ml detector. They were mounted together on the same UAV. At a flying height of 20 m and a speed of 5.6 m s−1 the field was mapped. The various aerial measurements were compared to each other and to the ground-based measurements. The field had a low spatial variation in the 40K concentration (relative standard deviation (RSD) = 9%) and a larger variation for 238U and 232Th concentrations (RSD = 24% and 31% respectively).Radionuclide concentrations have been extracted from the survey data by Full Spectrum Analysis (FSA). Uncertainties and variances of the radionuclides have been determined by using two methods. Firstly, they are calculated directly from the FSA output and secondly they are extracted from a variogram. The latter incorporates spatial variation and was shown to provide a lower uncertainty. When using small detectors, the former approach could lead to the conclusion that the uncertainty is larger than the variance, while the variogram approach does capture the spatial variation.All three detectors were able to characterize the spatial distribution of the 232Th concentration. It is shown that the 232Th concentration is a good predictor of the sand and clay fraction of the topsoil in the field. By comparing the UAV-borne measurements to the ground-based measurements it is found that UAV-borne measurements at 20 m height are less sensitive to extreme values than ground-based measurements and they have the tendency to shift to the mean concentration of the area.The results of this study can be used to optimize the detector volume, survey height, and survey speed to maintain an acceptable accuracy for gamma-ray studies with small UAV-borne detectors.

Distribution of natural and anthropogenic radionuclides in sediments from the Vefsnfjord, Norway

Areas in central Norway were heavily contaminated with fallout from the Chernobyl accident in 1986. In this study, we assess 137Cs in surface sediments and sediment cores collected in the Vefsnfjord in Nordland county. Concentrations of 137Cs in surface sediments ranged from 159 to 191 Bq kg−1 dry weight (d.w.). Sub-surface peaks of 137Cs were observed in all cores, with a maximum concentration of 432 Bq kg−1 d.w. Given that little is known about the distribution of naturally occurring radionuclides in Norwegian fjords and coastal areas, a better understanding of the total burden of radioactivity is important for the Norwegian fishing and aquaculture industries. Therefore, analyses of the natural radionuclides 40K, 226Ra, 228Ra and 210Pb were included in the study. Analyses of total sulphur (TS), total carbon (TC), total organic carbon (TOC) and grain size distribution have been performed to provide a sedimentologic context for interpreting the radionuclide results.

A review of transfer distribution and content of radionuclides in mushrooms

Since the Chernobyl nuclear accident, the radioactive contamination in food caused by the nuclear accident has been widely concerned by people. There have been a lot of studies on concentrated radionuclides in mushrooms in foreign countries, but the research on radionuclides content and transfer distribution mechanism of radionuclides in mushrooms is almost blank in China. Studies have shown that mushrooms have a strong adsorption capacity on radionuclides. As a common food in daily life, therefore, it is of great significance to study the content of radionuclides in mushrooms for evaluating the internal dose in the human body. In this paper, the types of radionuclides in mushrooms and the methods of their transfer and distribution in mushrooms were reviewed, and the research status and development trends at domestic and abroad in recent years were emphasized, in order to provide theoretical support for the future basic research. 摘要： 切尔诺贝利核事故后, 由核事故导致的食品中放射性污染受到广泛关注。国外对蘑菇浓集放射性核素已有大 量研宄, 而我国目前关于蘑菇中放射性核素含量及转移分布机理的研宄几乎处于空白。蘑菇作为人们日常消费的食 品, 研宄表明其对放射性核素具有较强的吸附作用, 因此开展蘑菇中的放射性核素含量研宄对评估人体内照射剂量具 有重要意义。本文综述了蘑菇中放射性核素的种类、蘑菇中放射性核素的转移分布研宄方法, 并重点阐述了近年来国 内外研宄现状, 旨在为今后的基础研宄提供理论支撑。

Structural and radiological characterization of irradiated RBMK-1500 reactor graphite

This study aims to characterize the irradiated RBMK-1500 nuclear graphite in terms of both structural and radiological properties. The experimental results of morphological and structural analysis of the irradiated graphite samples by using SEM, Raman spectroscopy as well as the theoretical evaluation of primary displacement damage are presented. Moreover, the experimental and theoretical evaluation of the neutron flux is provided and the presence of several γ emitters in the analyzed graphite samples is assessed. Furthermore, the improved version of rapid analysis method for 14C activity determination is applied and the experimentally obtained results are compared with calculated ones. Results indicate that structural changes are uniform enough in all the analyzed samples. However, the distribution of radionuclides is non-homogeneous in the irradiated RBMK-1500 reactor graphite matrix. The comprehensive understanding of both structural and radiological characteristics of nuclear graphite is very important when dealing with decision about irradiated graphite waste management strategy or treatment options prior to its final disposal.

Radioactive gas diffusion simulation and inhaled effective dose evaluation during nuclear decommissioning

During the decommissioning of the nuclear facilities, the radioactive gases in pressure vessels may leak due to the demolition operations. The decommissioning site has large space, slow air circulation, and many large nuclear facilities, which increase the difficulty of workers' inhalation exposure assessment. In order to dynamically evaluate the activity distribution of radionuclides and the committed effective dose from inhalation in nuclear decommissioning environment, an inhalation exposure assessment method based on the modified eddy-diffusion model and the inhaled dose conversion factor is proposed in this paper. The method takes into account the influence of building, facilities, exhaust ducts, etc. on the distribution of radioactive gases, and can evaluate the influence of radioactive gases diffusion on workers during the decommissioning of nuclear facilities.

A Conjugation Strategy to Modulate Antigen Binding and FcRn Interaction Leads to Improved Tumor Targeting and Radioimmunotherapy Efficacy with an Antibody Targeting Prostate-Specific Antigen.

Simple SummaryThe present study demonstrates that a radiolabeling strategy can positively modify hu5A10′s capacity to bind PSA and complex with the FcRn receptor, which results in a more homogenous activity distribution in tumors and enhanced therapy efficacy. These new innovative radiochemistry ideas could potentially decrease relapse of tumors in patients treated with internalizing antibodies.Background: The humanized monoclonal antibody (mAb) hu5A10 specifically targets and internalizes prostate cancer cells by binding to prostate specific antigen (PSA). Preclinical evaluations have shown that hu5A10 is an excellent vehicle for prostate cancer (PCa) radiotheranostics. We studied the impact of different chelates and conjugation ratios on hu5A10′s target affinity, neonatal fc-receptor interaction on in vivo targeting efficacy, and possible enhanced therapeutic efficacy. Methods: In our experiment, humanized 5A10 (hu5A10) was conjugated with DOTA or DTPA at a molar ratio of 3:1, 6:1, and 12:1. Surface plasmon resonance (SPR) was used to study antigen and FcRn binding to the antibody conjugates. [111In]hu5A10 radio-immunoconjugates were administered intravenously into BALB/c mice carrying subcutaneous LNCaP xenografts. Serial Single-photon emission computed tomography (SPECT) images were obtained during the first week. Tumors were harvested and radionuclide distribution was analyzed by autoradiography along with microanatomy and immunohistochemistry. Results: As seen by SPR, the binding to PSA was clearly affected by the chelate-to-antibody ratio. Similarly, FcRn (neonatal fc-receptor) interacted less with antibodies conjugated at high ratios of chelator, which was more pronounced for DOTA conjugates. The autoradiography data indicated a higher distribution of radioactivity to the rim of the tumor for lower ratios and a more homogenous distribution at higher ratios. Mice injected with ratio 3:1 111In-DOTA-hu5A10 showed no significant difference in tumor volume when compared to mice given vehicle over a time period of 3 weeks. Mice given a similar injection of ratio 6:1 111In-DOTA-hu5A10 or 6:1 111In-DTPA-hu5A10 or 12:1 111In-DTPA-hu5A10 showed significant tumor growth retardation. Conclusions: The present study demonstrated that the radiolabeling strategy could positively modify the hu5A10′s capacity to bind PSA and complex with the FcRn-receptor, which resulted in more homogenous activity distribution in tumors and enhanced therapy efficacy.

Mercury accumulation in the sediment of the Western Mediterranean abyssal plain: A reliable archive of the late Holocene

Temporal reconstruction of Hg deposition from sediment archives is relatively straightforward in organic-rich or high sedimentation rate environments, such as lakes and ocean margins. To retrieve long-term records at regional or global scales, deep-sea sediments are more appropriate, but such records are scarce and their reliability has been questioned because of possible post-depositional Hg diagenetic remobilization. Here, we investigated the accumulation of Hg in the Balearic Abyssal Plain (2850 m deep) of the Western Mediterranean through a comprehensive characterization of the chemical and isotopic composition (organic carbon, nitrogen, sulfur, major and redox-sensitive elements) of sediment trap material and sediment cores. The analysis of material collected in the sediment traps, deployed at 250, 1440, and 2820 m, indicates that Hg is (i) partially re-emitted to the atmosphere and mobilized in the twilight zone and that (ii) the Hg downward flux depends on the primary production in surface waters, suggesting that organic matter (OM) acts as the main Hg-carrier phase. As the Hg concentrations of material collected in the traps vary little with depth but the Hg:Corg ratio of the settling particulate matter decreases with depth, Hg must be re-adsorbed onto the more refractory fraction of the settling OM. Results of selective chemical extractions of the sediment indicate that Hg is very weakly coupled to the iron cycle but strongly associated with sulfur, supporting the assumption that its vertical distribution was only weakly altered by diagenetic remobilization. In addition, the distributions of S and δ34S in the sedimentary column exclude the possibility that local volcanism impacted on Hg enrichment of the sediments. Accordingly, a reconstruction of Hg accumulation rates (Hg-AR) during the Late Holocene is readily achieved. Biological mixing and smoothing of the sediment record, as revealed by the distribution of radionuclides in surface sediments, was considered in the interpretation of the Hg-AR record. The first anthropogenic Hg signal recorded in the studied cores corresponds to the Iron Age and the Roman Empire period, as Hg-ARs rose from the baseline (0.7 ± 0.2 µg m−2 yr−1) to an average value of 2.2 ± 0.5 µg m−2 yr−1. The Hg-ARs return to baseline values at the decline of the Roman Empire, display a small increase during the Medieval Period (1.5 ± 0.5 µg m−2 yr−1), increase abruptly at the onset of the Industrial Era, leading to a ~ 10-fold increase in Hg deposition in the last 120 years (8.9 ± 1.4 µg m−2 yr−1), and retreat progressively over the past 50 years.

Association of 241Am and 137Cs in finer size-fractioned saltmarsh sediments from north-west England, UK and potential health risk to coastal population

ABSTRACT This study provides an in-depth analysis of the relationship between radionuclide and particle size-class abundance through an investigation of radionuclide distribution in finer sediments within surface core samples collected from two contaminated upper saltmarsh areas of the Dee estuary and Biggar marsh in north-west England. The particle size fractionation (PSF) analysis was carried out following gravitational settling and pipette method to separate all samples into six size-fractioned groups ranging from 63 to <2 µm (very coarse silt to clay), and radioactivity analysis was performed using a well-type High Purity Germanium (HPGe) detector. The highest 241Am and 137Cs activities in PSF samples were found to be 291 ± 5 and 2071 ± 16 Bq kg−1, respectively, for the Dee estuary saltmarsh and 3832 ± 14 and 4840 ± 23 Bq kg−1, respectively, for Biggar saltmarsh and found in the clay fractions for both sites. Correlation of radioactivity concentration data of three size groups ranging from 63 to <2 µm (very coarse silt to clay) confirms a strong and increasing association of radioactivity with fine particles from coarse to fine clay-size particles. Also, examination of textural and radionuclide data of all bulk core and size-fractioned samples revealed that upper saltmarshes are made up of both contaminated and uncontaminated sediments. Furthermore, the annual outdoor external effective dose range for all short core data (0.001–0.11 mSv y−1) and for PSF sample data (0.001–0.08 mSv y−1) reveal that some values exceed the world average value of 0.07 mSv y−1as reported in UNSCEAR [43], for outdoor, which are non-negligible. Thus, the total annual external effective dose associated with existing contaminated saltmarsh sediments represents a possible health risk to saltmarsh users and coastal populations living nearby these saltmarshes.

The transport, effective half-lives and age distributions of radioactive releases in the northern Indian Ocean

A Lagrangian model which describes radionuclide transport in the northern Indian Ocean is described. Water circulation is obtained from HYCOM ocean model for year 2017. The model includes advection by currents, turbulent mixing and radionuclide interactions between water and sediments, described in a dynamic way using kinetic transfer coefficients. Hypothetical releases from five coastal nuclear power plants operating in the northern Indian Ocean were simulated. Releases were supposed to start both during the winter and summer monsoons, to study reversing circulation effects. Age distributions of releases were calculated, which adds information about circulation and radionuclide pathways. It was found that, for some of the NPPs, radionuclide distributions resulting from releases starting in both seasons were not as different as could be expected from the opposed circulation schemes during each monsoon. Effective 137Cs half-lives in the ocean surface were calculated and results were two orders of magnitude below previous estimations.

Application of energy dispersive X-ray fluorescence, γ-ray spectrometry and multivariate statistical approach for the classification of soil/sand from Douala – Cameroon

The distribution of natural radionuclides in sediments from Douala, Cameroon has been carried out based on X- and γ-ray spectrometry. Radiological health parameters were evaluated and found to be lower than the internationally approved values for actions. Soil elemental characterization and differentiation displayed the concentration of major elements. In addition, the principal component analysis (PCA) established correlations between different parameters of the study by calculating linear Pearson, Kendall's tau, Spearman's rho correlation coefficients, and cumulative probabilities. The total average concentrations of radionuclides 235U, 232Th, 226Ra, and 40K were 3.2, 53.1, 33.4, and 301.2 Bq/kg, respectively. The principal component analysis based on linear Pearson, Kendall's tau, Spearman's rho correlation coefficients, and cumulative probabilities calculations displays a strong correlation coefficient only between Ra-226 and U-235. The combination of spectrometry, PCA results, and comparison with previous studies highlighted the main characteristics of the investigated area to be illustrative dregs from the Continental margin. As a pioneering study using both spectrometric and PCA methods in Douala, the method was proved to be useful, and the results would be set as a database for future investigations.

Assessment of herb field mouse (Sylvaemus uralensis) migration in the area of the East Urals Radioactive Trace using measurements of bone-seeking 90Sr

The dynamics of rodent population in the area of East Urals Radioactive Trace (EURT) is one of the controversial issues, which are of key importance for the radiobiological and radioecological interpretation of the observed radiation effects. The objective of the paper is to evaluate the probability of migration in population of the herb field mouse (Sylvaemus uralensis Pall., 1811) based on 90Sr activity concentrations in the mouse bones. Radiometric data for bones of 768 mice captured at 9 sites in the EURT territory (with different environmental contamination levels) in 2001–2012 were used. The distribution of bone-seeking 90Sr in the juvenile age group of mice is used as a model of the width of radionuclide distribution in the bones of permanent inhabitants. Comparison of the model predictions and observations in different age and functional groups within the population structure allows simulating the probability of migration and evaluating the fraction of migrants. It is shown that the accumulation of 90Sr in bones correlates with soil contamination at the capture sites. Individual variability in the specific activity of 90Sr in the skeleton tends to increase with the age of animals. The rate of herb field mouse migration is estimated as 7 and 15% per year (for underyearlings and wintered individuals, respectively). The animals captured in the EURT area (all animals, including juvenile individuals) are “diluted” with animals from non-contaminated territories by 5–12%. The average half-time of substitution of the exposed population by migrants from non-contaminated territories is 8 years. Today, the fraction of descendants of the animals, that for generations have permanently inhabited the EURT territory since 1957, is negligible (on average-1.2% and not exceeding 17%). The proposed method of probabilistic analysis of 90Sr in the bones could be used to study migration activity of other species of rodents.

Migration of 238U and 226Ra Radionuclides in Technogenic Permafrost Taiga Landscapes of Southern Yakutia, Russia

This article describes the features and migration patterns of natural long-lived heavy radionuclides 238U and 226Ra in the major components of the environment including rocks, river waters, soils, and vegetation of permafrost taiga landscapes of Southern Yakutia, which helped us to understand the scale and levels of their radioactive contamination. Different methods have been used in this study to determine the content of 238U and 226Ra in various samples, including gamma-ray spectrometry, X-ray spectroscopy, laser excited luminescence, and emanation method. It was determined that the main source of radioactive pollution of soil and vegetation cover, as well as surface waters in these technogenic landscapes, are the dumps of radioactive rock that were formed here as the result of geological exploration carried out in this area during the last third of the 20th century. The rocks studied were initially characterized by a coarse, mainly stony gravelly composition and contrasting radiation parameters, where the gamma radiation exposure rate varied between 1.71 and 16.7 µSv/h, and the contents of 238U and 226Ra were within the range 126–1620 mg/kg and 428–5508 × 10−7 mg/kg, respectively, and the 226Ra: 238U ratio was 1.0. This ratio shifted later on from the equilibrium state towards the excess of either 238U or 226Ra, due to the processes of air, water, and biogenic migration. Two types of 238U and 226Ra radionuclides migration were observed in studied soils, namely aerotechnogenic and hydrotechnogenic, each of which results in a different intraprofile radionuclide distribution and different levels of radioactive contamination. In this study, we also identified plants capable of selective accumulation of certain radionuclides, including Siberian mountain ash (Sorbus sibiricus), which selectively absorbs 226Ra, and terrestrial green and aquatic mosses, which accumulate significant amounts of 238U.

Distribution of heavy metals and radionuclides in the sediments and their environmental impacts in Nansha Sea area, South China Sea

Activity concentrations of radionuclides (238U, 226Ra, 232Th, and 40K) in the sediments of eight sampling stations and heavy metal concentrations (Cr, Co, Ni, Cu, Zn, As, Cd, and Pb) in the sediments of two long cores from Nansha Sea area were obtained by high-purity germanium spectroscopy and inductively coupled plasma atomic emission spectrometry. In a correlation analysis between the radionuclides and heavy metals, 232Th was positively correlated with As and Pb. 238U demonstrated a significant positive correlation with Co, Ni, Cu, Zn, and Cd. 40K was positively correlated with Co, Ni, and Cu. The geo-accumulation index, pollution load index, potential ecological risk index, and multivariate statistical techniques were used to evaluate the pollution degree and possible sources of heavy metals in the sediments. An ecological risk assessment suggested that Cr, Co, Ni, Cu, Zn, Cd, and Pb were primarily derived from natural processes, while the source of As may be related to natural processes and human activities.

Reduced soil fauna decomposition in a high background radiation area.

Decomposition of litter and organic matter is a very important soil ecosystem function where soil fauna play an important role. Knowledge of the responses in decomposition and soil fauna to different stressors is therefore crucial. However, the extent to which radioactivity may affect soil fauna is not so well known. There are some results showing effects on soil fauna at uranium mines and near Chernobyl from relatively high levels of anthropogenic radionuclides. We hypothesize that naturally occurring radionuclides affect soil fauna and thus litter decomposition, which will covary with radionuclide levels when accounting for important soil parameters. We have therefore used standardised litterbags with two different mesh sizes filled with birch leaves (Betula pubescens) to assess litter decomposition in an area with enhanced levels of naturally occurring radionuclides in the thorium (232Th) and uranium (238U) decay chains while controlling for variation in important soil parameters like pH, organic matter content, moisture and large grain size. We show that decomposition rate is higher in litterbags with large mesh size compared to litterbags with a fine mesh size that excludes soil fauna. We also find that litter dried at room temperature is decomposed at a faster rate than litter dried in oven (60⁰C). This was surprising given the associated denaturation of proteins and anticipated increased nutritional level but may be explained by the increased stiffness of oven-dried litter. This result is important since different studies often use either oven-dried or room temperature-dried litter. Taking the above into account, we explore statistical models to show large and expected effects of soil parameters but also significant effects on litter decomposition of the naturally occurring radionuclide levels. We use the ERICA tool to estimate total dose rate per coarse litterbag for four different model organisms, and in subsequent different statistical models we identify that the model including the dose rates of a small tube-shape is the best statistical model. In another statistical model including soil parameters and radionuclide distributions, 226Ra (or uranium precursory radionuclides) explain variation in litter decomposition while 228Ra (and precursors) do not. This may hint to chemical toxicity effects of uranium. However, when combining this model with the best model, the resulting simplified model is equal to the tube-shape dose-rate model. There is thus a need for more research on how naturally occurring radionuclides affect soil fauna, but the study at hand show the importance of an ecosystem approach and the ecosystem parameter soil decomposition.

Development of local-scale high-resolution atmospheric dispersion model using large-eddy simulation part 6: introduction of detailed dose calculation method

ABSTRACT We developed a LOcal-scale High-resolution atmospheric DIspersion Model using Large-Eddy Simulation (LOHDIM-LES) for the safety assessment of nuclear facilities and emergency responses to accidental or deliberate releases of radioactive materials. In parts 1–5 of this series, the basic performance was examined by comparing with wind tunnel or field experimental results on plume dispersion over various complex surface geometries under ideal and realistic atmospheric conditions. In this study, we introduced a dose calculation method that can simulate air dose rate distributions by considering shielding effects and inhomogeneous distribution of radioactive materials in the air and on the ground and building surfaces. First, we conducted LESs of radioactive plume dispersion and dry deposition in building array and investigated the basic performance of the dose calculation method by comparison with that of Monte-Carlo based three-dimensional radiation transport simulations by Particle and Heavy-Ion Transport code System (PHITS). Then, we compared the LOHDIM-LES results with actual air dose rate obtained from the monitoring posts in a nuclear facility. The observed data were reasonably simulated. Thus, we completed LOHDIM-LES, which can simulate plume dispersion, dry deposition, and air dose rates from complex distributions of radionuclides considering the influence of individual buildings under realistic meteorological conditions.

Indoor and outdoor radionuclide distribution in houses after the Fukushima Dai-ichi Nuclear Power Plant accident

An enormous amount of radionuclides was released into the atmosphere following the Fukushima Dai-ichi Nuclear Power Plant accident, with part of it penetrating houses. Information on radionuclide distribution inside and outside houses is useful for indoor external dose assessments. To investigate the radionuclide distribution, we collected both soil samples around the target houses and house material samples (i.e., floor, inner wall, ceiling, outer wall, and roof) in Fukushima Prefecture in 2019. The activity of the samples was measured using a high-purity germanium detector. The surface contamination densities of the floor, inner wall, ceiling, outer wall, and roof relative to the ground were 3 × 10−3–7 × 10−2, 6 × 10−5–4 × 10−4, 7 × 10−5–3 × 10−4, 2 × 10−3–1 × 10−2, and 4 × 10−3–2 × 10−1, respectively. The relative surface contamination densities varied depending on the surface material, its location, and surface orientation, indicating that these uncertainty factors should be considered in the dose assessment for residents.

RADIATION CONTROL OF SECONDARY TECHNOGENIC RAW MATERIALS

Radiation safety is one of the most important hygienic criteria for environmental safety of a material. Great influence on man and his ecological safety are building materials, which contain substances with a certain content of natural radionuclides. Knowledge of the regularity of the distribution of natural radionuclides in the structure of man-made raw materials, as well as their behavior in the process of technological processing into building materials are very valuable. After all, even at the design stage, you can assess their content in the finished products and make timely adjustments to prevent recycling of building materials and protect human health. The authors assessed the radiation hazard of secondary man-made raw materials according to international standards and showed that slag samples are radiation-safe and can be used as a building material without any significant radiological threat to the population.

Assessment of Natural Radioactivity and Radiological Risks in River Sediments from Calabria (Southern Italy)

This study was developed to carry out a comprehensive radiological assessment of natural radioactivity for river sediment samples from Calabria, southern Italy, and to define a baseline background for the area on a radiation map. In the studied area, elevated levels of natural radionuclides are expected, due to the outcropping acidic intrusive and metamorphic rocks from which the radioactive elements derive. To identify and quantify the natural radioisotopes, ninety river sediment samples from nine selected coastal sampling points (ten samples for each point) were collected as representative of the Ionian and the Tyrrhenian coastline of Calabria. The samples were analyzed using a gamma ray spectrometer equipped with a high-purity germanium (HPGe) detector. The values of mean activity concentrations of 226Ra, 232Th and 40K measured for the studied samples are (21.3 ± 6.3) Bq kg−1, (30.3 ± 4.5) Bq kg−1 and (849 ± 79) Bq kg−1, respectively. The calculated radiological hazard indices showed average values of 63 nGy h−1 (absorbed dose rate), 0.078 mSv y−1 (effective dose outdoors), 0.111 mSv y−1 (effective dose indoors), 63 Bq kg−1 (radium equivalent), 0.35 (Hex), 0.41 (Hin), 0.50 (activity concentration index) and 458 µSv y−1 (Annual Gonadal Equivalent Dose, AGED). In order to delineate the spatial distribution of natural radionuclides on the radiological map and to identify the areas with low, medium and high radioactivity values, the Surfer 10 software was employed. Finally, the multivariate statistical analysis was performed to deduce the interdependency and any existing relationships between the radiological indices and the concentrations of the radionuclides. The results of this study, also compared with values of other locations of the Italian Peninsula characterized by similar local geological conditions, can be used as a baseline for future investigations about radioactivity background in the investigated area.

Spatial distribution of fallout and lithogenic radionuclides controlled by soil carbon and water erosion in an agroforestry South-Pyrenean catchment

The mineral composition of soils and weathering processes are known to control the natural radioactivity of soils but research on the influence of water erosion and of main soil properties in the spatial variability of lithogenic and fallout radionuclides remains little investigated in heterogeneous agroecosystems with complex landscape. An extensive study was conducted to determine the mass activities of fallout (137Cs, 210Pbex) and lithogenic radionuclides (238U, 226Ra, 232Th, 40K) an assess the main controls affecting their spatial variations in a representative 2.5 km2 Pre-Pyrenean catchment of north-eastern Spain. The complex agroforestry catchment holds two distinctive parent materials, Muschelkalk limestones and Keuper argillaceous marls, in which the variability of the main soil properties and soil erosion patterns are well characterised. A total of 228 soil samples have been measured by using a high-purity germanium detector. Lithological influence on the variability of radionuclides was investigated and our results indicate that there are strong significant differences between the mass activities of 137Cs, 210Pbex, 226Ra and 40K based on the two different parent materials. Positive correlations were found among the radioactivity contents of 232Th and 40K and the clay content. Total organic carbon (SOC) was also positively correlated with 137Cs, 210Pbex and 226Ra activities, whereas carbonate content and SIC were negatively correlated with the radionuclides with higher significance in soils on limestones.To gain knowledge on the spatial variability of the radionuclides within the landscape, maps of the distribution of radionuclides were generated by GIS interpolation tools of the entire set of measured activities and soil properties within a 100 × 100 m grid. The spatial patterns obtained, besides the variations of radionuclides along four selected transects, confirm the key role of water erosion in the mobilisation of fallout radionuclides, especially 137Cs, while lithogenic radionuclides were sensitive to physical processes in areas where soil loss was intense. This study not only filled the gap of radioactivity data in agroforestry systems with contrasting parent materials, but also shed light on the potential of radionuclides for tracking soil redistribution processes in fingerprints studies.

Natural radionuclides distribution, depth profiles of caesium-137 and risk assessment for soil samples in west regions of China

An analysis of natural radioactivity in soils collected around Chinese Nuclear Test site is presented. The radioactivities of 238U, 226Ra, 232Th, 40K, and 137Cs were determined by HPGe gamma-ray spectrometry, and potential radiological hazards were evaluated. The depth profiles of radionuclides in three selected areas of Gansu were analyzed, and a new method for detection of 137Cs specific activities were measured using ultra-low background gamma spectrometer named GeTHU-II developed by Tsinghua University at China Jinping Underground Laboratory. The radioactivity concentrations of 137Cs were significantly different in these three areas and gradually decreased from surface to underground 15 cm.