Mobile trace elements in sediments from lakes Hawassa, Koka, and Ziway in the Ethiopian Rift Valley.

The present work focuses on total concentrations of trace elements such as chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), selenium (Se), cadmium (Cd), and lead (Pb) and their operationally defined speciation in surface sediments from three Ethiopian Rift Valley Lakes (Hawassa, Koka, and Ziway). Total concentrations were determined using inductively coupled plasma-mass spectrometer (ICP-MS). A six-step sequential extraction was also applied to evaluate the mobilization potential of these elements. Compared with the consensus-based sediment quality guidelines (SQGs) developed for freshwater ecosystems, the total Zn concentration in sediments from Lakes Hawassa and Ziway, as well as Cr, Ni, and Zn in sediments from Lake Koka, was higher than the probable effect concentration (PEC), suggesting that these elements could have a negative effect on benthic organisms. The sequential extraction results showed that Cd, Mn, and Se were to a certain extent associated with the reversible fractions (F1-F3) in sediments, and thereby more mobile than the other investigated trace elements. Predictions of mobility of trace elements using the distribution coefficients (Kd) values were also in agreement with the sequential extraction results. Furthermore, multivariate statistical analyses showed that redox-sensitive fractions (F4 and F6) and the residual fraction (F7) were the dominant factors controlling most trace element mobility. Finally, applying the Risk Assessment Code (RAC) classification system, results showed that Mn in Lake Koka could pose a high risk, while Cd and Mn in Lake Hawassa as well as Cd, Mn, and Se in Lake Ziway sediments could pose medium risk to benthic organisms.

Bioaccumulation of trace elements in liver and kidney of fish species from three freshwater lakes in the Ethiopian Rift Valley.

The objective of the present work was to obtain scientific information on the ecological health of three freshwater lakes (Awassa, Koka, and Ziway) situated in the Ethiopian Rift Valley by investigating possible trace element contamination accumulated in fish. Accordingly, fish liver and kidney samples were collected from three commercially important fish species (Barbus intermedius, Clarias gariepinus, and Oreochromis niloticus) in the lakes to determine the concentrations of chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), selenium (Se), cadmium (Cd), and lead (Pb), using ICP-MS. Trace element concentrations were generally higher in O. niloticus compared with concentrations in B. intermedius and C. gariepinus. Compared to background values of most freshwater fish species, higher liver concentrations of Cu in C. gariepinus and O. niloticus, Mn in O. niloticus, Co in all except B. intermedius, and Zn in C. gariepinus from Lakes Ziway and Awassa were found. Cr, Co, Ni, Cd, and Pb were enriched in kidney, while Mn, Cu, Zn, As, and Se seems retained in the liver tissues. Assessment of transfer factors indicated that bioaccumulation from water and diet occurred, while uptake from sediments was low. Furthermore, the transfer factor values were generally higher for essential elements compared to the non-essential elements. Multivariate statistical analyses showed that the differences between the trace element levels were generally not significant among the lakes (p = 0.672), while significant differences were found between the fish species (p = 0.042), and between accumulation in kidney and liver (p = 0.002).

Evaluation of uncertainties in environmental impact assessment of naturally occurring radiation exposure situations on example of undisturbed and legacy NORM sites in the Fen Complex, Norway.

The risk from naturally occurring radioactive materials (NORM) has been extensively assessed, and this has led to the integration of specific NORM radiation protection requirements within the latest EU Directive 2013/59. Nevertheless, it has been internationally recognised that remaining NORM knowledge gaps and uncertainties now present similarly significant issues in addressing recent regulatory requirements. The multi-tiered nature of environmental impact assessment (EIA) implies per se possibility for uncertainties, but when EIA at radiation exposure sites includes consideration of sites with multiple radiation and contamination sources, different ecosystem transport pathways, effects and risks by applying different parameters and models, level of overall uncertainty increases. The results of EIA study in the Fen area in Norway, comprised of undisturbed and legacy NORM sites, have been evaluated in this analysis, in order to identify all existing input uncertainties and how they may impact the final conclusions, and thus, influence any subsequent decision-making. The main uncertainties have been identified in the measurement and exposure analysis tier, and were related to the heterogeneous distribution of radionuclides, radionuclide speciation, as well as to generic variability issues in the concepts used for mobility and biota uptake analysis (such as distribution coefficient, transfer factors and concentration ratios) as well as radioecological modelling. The uncertainties in the input values to the calculation of the dose arising from radon exposure in the Fen area led to an overall elevated uncertainty of the magnitude of the radiation exposure dose of humans. It has been concluded that an integrated, ecosystem-based approach with consideration of complexity of prevailing environmental conditions and interconnections must be applied to fully understand possible radiation effects and risks.

Education and training in radioecology during the EU-COMET project-successes and suggestions for the future.

The 2014 Strategic Research Agenda (SRA) for Radioecology identified the key challenge in education and training (E&T) as being 'to maintain and develop a skilled workforce in Europe and world-wide, through university candidates and professionals trained within radioecology' since 'scientific research in radioecology and application of that knowledge … requires scientists and workers with adequate competence and appropriate skills.' Radioecology is a multidisciplinary science and E&T is needed by both students and professionals within research, industry and radiation protection. In order to address these needs, the EU COMET project has developed an E&T web platform and arranged a number of field courses, training courses, PhD and MSc courses, refresher courses and workshops, drawing on the COMET consortium to assemble relevant experts. In addition, COMET has been engaged in discussions with stakeholders for more long-term solutions to maintain the sustainability of radioecology E&T after the end of the project. Despite much progress in some areas, many of the challenges outlined in the 2014 SRA remain, mainly due to the lack of sustainable dedicated funding. Future plans within the ALLIANCE radioecology platform and the CONCERT-European Joint Programme for the Integration of Radiation Protection Research must urgently address this lack of sustainability if radioecological competence is to be maintained in Europe.

Organochlorine pesticides and polychlorinated biphenyls in fish from Lake Awassa in the Ethiopian Rift Valley: human health risks.

Dietary intake of fish containing organic contaminants poses a potential threat to human health. In the present work, an assessment has been carried out to look at the human health risk associated with consumption of fish contaminated with organochlorine pesticides (OCPs) and polychlorinated biphenyles (PCBs) in certain fish species collected from Lake Hawassa, Ethiopia. The health risk assessment was made by comparing the concentrations of OCPs and PCBs in fish muscle tissues with reference doses given in the USEPA guidelines. Dichlorodiphenyltrichloroethanes (DDTs), endosulfans, PCBs and chloridanes were identified in fish species collected from Lake Hawassa. The most predominant pesticides were DDTs, with mean concentrations of ΣDDT ranging from 19 to 56 ng g(-1) wet weights. The highest concentrations of DDTs were found in Barbus intermedius, representing the highest trophic level. PCBs, DDT and endosulfan concentrations found in B. intermedius exceeded the reference dose for children between the ages of 0-1 year (with hazard index of above 1.0). Therefore, consumption of fish from a high trophic level (e.g. B. intermedius) from Lake Hawassa may pose a special health risk to children.

Transfer of radionuclides through ecological systems: Lessons learned from 10 years of research within CERAD CoE.

Norway's Centre of Excellence for Environmental Radioactivity (CERAD) research programme included studies on transfer of radionuclides in various ecosystems within the context of environmental risk assessment. This article provides highlights from 10 years of research within this topic and summarises lessons learnt from the process. The scope has been extensive, involving laboratory-based experiments, field studies and the implementation of transfer models quantifying radionuclide uptake directly from the surrounding environment and via food chains. Field studies have had a global span and have, inter alia, covered sites contaminated with radionuclides associated with particles, ranging from nanoparticles to fragments, due to nuclear accidents (e.g., Chornobyl and Fukushima accidents) along with sites having enhanced levels of naturally occurring radioactive materials (e.g., Fen Complex in Norway and Taboshar in Tajikistan). Focus has been put on speciation and kinetics in determining radionuclide behavior and fate as well as on the influence of environmental factors that are potentially critical for the transfer of radionuclides. In particular, seasonal factors have been shown to greatly affect the dynamics of 137Cs and 90Sr bioaccumulation and loss in freshwater fish. The work has led to the collation of organism-specific (i) parameters important for kinetic models, i.e., uptake and depuration rates, and (ii) steady-state concentration ratios, CRs, where the use of stable analogue CRs as proxies for radionuclides has been brought into question. Dynamic models have been developed and applied for radiocaesium transfer to reindeer, radionuclide transfer in Arctic marine systems, transfer to fish via water and feed and commonly used agricultural food-chain transfer models applied in the context of nuclear emergency preparedness. The CERAD programme should contribute substantially to the scientific community's understanding of radionuclide transfer in environmental systems.

Biomagnification of DDT and its metabolites in four fish species of a tropical lake.

The concentrations and biomagnifications of dichlorodiphenyltrichloroethane (DDT) and its metabolites were examined in four fish species (Clarias gariepinus, Oreochromis niloticus, Tilapia zillii, and Carassius auratus) from Lake Ziway, Rift Valley, Ethiopia. Paired stomach content analysis, and stable isotope ratio of nitrogen (δ(15)N, ‰) and carbon (δ(13)C, ‰) were used to study the trophic position of the fish species in the lake. 4,4'-DDE, 4,4'-DDT and 4,4'-DDD were the main DDTs identified in the fish samples, with 4,4'-DDE as the most predominant metabolite, with mean concentration ranging from 1.4 to 17.8 ng g(-1) wet weight (ww). The concentrations of DDTs found in fish from Lake Ziway were, in general lower than those found in most studies carried out in other African Lakes. However, the presence of DDT in all tissue samples collected from all fish species in the lake indicates the magnitude of the incidence. Moreover, the observed mean 4,4'-DDE to 4,4'-DDT ratio below 1 in C. auratus from Lake Ziway may suggest a recent exposure of these species to DDT, indicating that a contamination source is still present. 4,4'-DDE was found to biomagnify in the fish species of the lake, and increases with trophic level, however, the biomagnification rate was generally lower than what has been reported from other areas. Significantly higher concentrations of 4,4'-DDE were found in the top consumer fish in Lake Ziway, C. gariepinus than in O. niloticus (t=2.6, P<0.01), T. zillii (t=2.5, P<0.02) and C. auratus (t=2.2, P<0.03).

Limited access to oxygen reduces the release of harmful trace elements from submerged alum shale debris.

Construction and mining activities in acid-producing alum shale regions often produce large volumes of crushed rock. Disposal under groundwater level (e.g., a bog) may minimize oxygen access. In this study, the effect of varying oxygen access on the leaching potential of alum shale was investigated by submerging tunnel construction rock debris in synthetic rainwater under atmospheric (AOC) and low oxygen conditions (LOC) for 52 weeks. The sulphate increase and nitrate decrease in the leachates suggested that pyrite (FeS2) in the alum shale was oxidized, but carbonates originating from calcite dissolution provided sufficient buffering capacity (leachate pH ~7.7 over 52 weeks), resulting in neutral rock drainage. Less available oxygen led to significantly lower production of sulphate and acid from pyrite oxidation, reducing the release of harmful elements. Under LOC, the leaching of Mo, Co, Ni, Zn and Cd was 2-4 times lower than under AOC and the lower buffering requirement diminished the release of Ca as well as divalent cations (Mg, Sr, Mn) likely present as impurities in calcite. Contrastingly, limited pyrite oxidation led to less oversaturation with respect to BaSO4 and lower release of Fe in the LOC leachates. Thus, co-precipitation of 226Ra was inhibited and scavenging of leached V, As and Sb by newly formed Fe(OH)3 was not as dominant as in the AOC systems. Leaching of U was ~20 % higher under LOC likely due to enhanced complexation by dissolved carbonate. In general, element leaching rates were slower under low O2 levels. Characterization of water collected at the disposal site after ~1.2 years of discarding tunnel materials showed that the weathering of debris submerged in the open, water-filled pond occurred similarly to leaching under low oxygen conditions. Overall, these results highlight the importance of minimal oxygen access or anaerobic conditions when acid-producing rock waste is stored under water.

Tools for harmonized data collection at exposure situations with naturally occurring radioactive materials (NORM).

Naturally occurring radioactive materials (NORM) contribute to the dose arising from radiation exposure for workers, public and non-human biota in different working and environmental conditions. Within the EURATOM Horizon 2020 RadoNorm project, work is ongoing to identify NORM exposure situations and scenarios in European countries and to collect qualitative and quantitative data of relevance for radiation protection. The data obtained will contribute to improved understanding of the extent of activities involving NORM, radionuclide behaviours and the associated radiation exposure, and will provide an insight into related scientific, practical and regulatory challenges. The development of a tiered methodology for identification of NORM exposure situations and complementary tools to support uniform data collection were the first activities in the mentioned project NORM work. While NORM identification methodology is given in Michalik et al., 2023, in this paper, the main details of tools for NORM data collection are presented and they are made publicly available. The tools are a series of NORM registers in Microsoft Excel form, that have been comprehensively designed to help (a) identify the main NORM issues of radiation protection concern at given exposure situations, (b) gain an overview of materials involved (i.e., raw materials, products, by-products, residues, effluents), c) collect qualitative and quantitative data on NORM, and (d) characterise multiple hazards exposure scenarios and make further steps towards development of an integrated risk and exposure dose assessment for workers, public and non-human biota. Furthermore, the NORM registers ensure standardised and unified characterisation of NORM situations in a manner that supports and complements the effective management and regulatory control of NORM processes, products and wastes, and related exposures to natural radiation worldwide.

A methodology for the systematic identification of naturally occurring radioactive materials (NORM).

Naturally occurring radioactive materials (NORM) are present worldwide and under certain circumstances (e.g., human activities) may give radiation exposure to workers, local public or occasional visitors and non-human biota (NHB) of the surrounding ecosystems. This may occur during planned or existing exposure situations which, under current radiation protection standards, require identification, management, and regulatory control as for other practices associated with man-made radionuclides that may result in the exposure of people and NHB. However, knowledge gaps exist with respect to the extent of global and European NORM exposure situations and their exposure scenario characteristics, including information on the presence of other physical hazards, such as chemical and biological ones. One of the main reasons for this is the wide variety of industries, practices and situations that may utilise NORM. Additionally, the lack of a comprehensive methodology for identification of NORM exposure situations and the absence of tools to support a systematic characterisation and data collection at identified sites may also lead to a gap in knowledge. Within the EURATOM Horizon 2020 RadoNorm project, a methodology for systematic NORM exposure identification has been developed. The methodology, containing consecutive tiers, comprehensively covers situations where NORM may occur (i.e., minerals and raw materials deposits, industrial activities, industrial products and residues and their applications, waste, legacies), and thus, allows detailed investigation and complete identification of situations where NORM may present a radiation protection concern in a country. Details of the tiered methodology, with practical examples on harmonised data collection using a variety of existing sources of information to establish NORM inventories, are presented in this paper. This methodology is flexible and thus applicable to a diversity of situations. It is intended to be used to make NORM inventory starting from the scratch, however it can be used also to systematise and complete existing data.

Outdoor 220Rn, 222Rn and terrestrial gamma radiation levels: investigation study in the thorium rich Fen Complex, Norway.

The present study was done in the Fen Complex, a Norwegian area rich in naturally occurring radionuclides, especially in thorium ((232)Th). Measurement of radioactivity levels was conducted at the decommissioned iron (Fe) and niobium (Nb) mining sites (TENORM) as well as at the undisturbed wooded sites (NORM), all open for free public access. The soil activity concentrations of (232)Th (3280-8395 Bq kg(-1)) were significantly higher than the world and the Norwegian average values and exceeded the Norwegian screening level (1000 Bq kg(-1)) for radioactive waste, while radium ((226)Ra) was present at slightly elevated levels (89-171 Bq kg(-1)). Terrestrial gamma dose rates were also elevated, ranging 2.6-4.4 µGy h(-1). Based on long-term surveys, the air concentrations of thoron ((220)Rn) and radon ((222)Rn) reached 1786 and 82 Bq m(-3), respectively. Seasonal variation in the outdoor gamma dose rates and Rn concentrations was confirmed. Correlation analyses showed a linear relationship between air radiation levels and the abundance of (232)Th in soil. The annual outdoor effective radiation doses for humans (occupancy 5 h day(-1)) were estimated to be in the range of 3.0-7.7 mSv, comparable or higher than the total average (summarized indoor and outdoor) exposure dose for the Norwegian population (2.9 mSv year(-1)). On the basis of all obtained results, this Norwegian area should be considered as enhanced natural radiation area (ENRA).

Trace element mobility and transfer to vegetation within the Ethiopian Rift Valley lake areas.

To evaluate critical trace element loads in native vegetation and calculate soil-to-plant transfer factors (TFs), 11 trace elements (Cr, Co, Ni, Cu, Zn, As, Se, Mo, Cd, Pb and Mn) have been determined in leaves of 9 taxonomically verified naturally growing terrestrial plant species as well as in soil samples collected around 3 Ethiopian Rift Valley lakes (Koka, Ziway and Awassa). The Cr concentration in leaves of all the plant species was higher than the "normal" range, with the highest level (8.4 mg per kg dw) being observed in Acacia tortilis from the Lake Koka area. Caper species (Capparis fascicularis) and Ethiopian dogstooth grass (Cynodon aethiopicus) from Koka also contained exceptionally high levels of Cd (1 mg per kg dw) and Mo (32.8 mg per kg dw), respectively. Pb, As and Cu concentrations were low in the plant leaves from all sites. The low Cu level in important fodder plant species (Cynodon aethiopicus, Acacia tortilis and Opuntia ficus-indicus) implies potential deficiency in grazing and browsing animals. Compared to the Canadian environmental quality guideline and maximum allowable concentration in agricultural soils, the total soil trace element concentrations at the studied sites are safe for agricultural crop production. Enrichment factor was high for Zn in soils around Lakes Ziway and Awassa, resulting in moderate to high transfer of Zn to the studied plants. A six step sequential extraction procedure on the soils revealed a relatively high mobility of Cd, Se and Mn. Strong association of most trace elements with the redox sensitive fraction and mineral lattice was also confirmed by partial redundancy analysis. TF (mg per kg dw plants/mg per kg dw soil) values based on the total (TF(total)) and mobile fractions (TF(mobile)) of soil trace element concentrations varied widely among elements and plant species, with the averaged TF(total) and TF(mobile) values ranging from 0.01-2 and 1-60, respectively. Considering the mobile fraction in soils should be available to plants, TF(mobile) values could reflect trace elements transfer to plants in the most realistic way. However, the present study indicates that TF(total) values also reflect the transfer of elements such as Mn, Cd and Se to plants more realistically than TF(mobile) values did.

In-depth understanding of local soil chemistry reveals that addition of Ca may counteract the mobilisation of 226Ra and other pollutants before wetland creation on the Grote Nete river banks.

The "Sigma plan" https://www.sigmaplan.be/en/ aims to create in Belgium inundation zones along the Grote Nete river to prevent Antwerp from flooding in extreme weather conditions. The riverbanks of the Grote Nete are at some hotspots historically contaminated by the phosphate industry resulting in Naturally Occurring Radionuclides (NOR) legacy. 226Ra is from a radiation protection point of view one of the most important radionuclides present at the hot spot under study, with a local soil activity concentration higher than 3000 Bq/kg 226Ra. In this paper, we identify the most relevant mechanisms governing the mobility of 226Ra. We selected for this study the role of CaSO4.2H2O, clay minerals and humic acids as the main contributors determining the speciation of Ra, due to their presence at the hot spot, their cation exchange capacity and their functional group density, respectively. Various novel analytical chemistry approaches were developed to study the prevailing reaction mechanisms that impact the solid-liquid distribution of 226Ra. We show that 226Ra coprecipitates in a (Ca,Ra)SO4 solid solution due to the high Ca2+ and SO42- concentrations in the local hot spot. If CaSO4.2H2O is not saturated in the soil solution, 226Ra adsorption to clay minerals counteracts the tendency of 226Ra partitioning to the liquid phase by interactions with humic and fulvic acids. Interactions between different soil compounds may further alter the partitioning of Ra. As, Cd, Pb and Zn in the hot spot are significantly above background values in Flemish sediments. Pb may be coprecipitated as sulphate salts, whereas Cd and Zn are most probably partially present as arsenate salts. The excess of Zn may interact with humic acids. The observed reaction mechanisms suggest that Ca2+ might play a key role in the immobilisation of Ra. The role of Ca2+ as immobilisation agent of the other contaminants is discussed.

Assessment of radionuclide and metal contamination in a thorium rich area in Norway.

The Fen Central Complex in southern Norway, a geologically well investigated area of magmatic carbonatite rocks, is assumed to be among the world largest natural reservoirs of thorium ((232)Th). These rocks, also rich in iron (Fe), niobium (Nb), uranium ((238)U) and rare earth elements (REE), were mined in several past centuries. Waste locations, giving rise to enhanced levels of both radionuclides and metals, are now situated in the area. Estimation of radionuclide and metal contamination of the environment and radiological risk assessment were done in this study. The average outdoor gamma dose rate measured in Fen, 2.71 µGy h(-1), was significantly higher than the world average dose rate of 0.059 µGy h(-1). The annual exposure dose from terrestrial gamma radiation, related to outdoor occupancy, was in the range 0.18-9.82 mSv. The total activity concentrations of (232)Th and (238)U in soil ranged from 69 to 6581 and from 49 to 130 Bq kg(-1), respectively. Enhanced concentrations were also identified for metals, arsenic (As), lead (Pb), chromium (Cr) and zinc (Zn), in the vicinity of former mining sites. Both radionuclide and heavy metal concentrations suggested leaching, mobilization and distribution from rocks into the soil. Correlation analysis indicated different origins for (232)Th and (238)U, but same or similar for (232)Th and metals As, Cr, Zn, nickel (Ni) and cadmium (Cd). The results from in situ size fractionation of water demonstrated radionuclides predominately present as colloids and low molecular mass (LMM) species, being potentially mobile and available for uptake in aquatic organisms of Norsjø Lake. Transfer factors, calculated for different plant species, showed the highest radionuclide accumulation in mosses and lichens. Uptake in trees was, as expected, lower. Relationship analysis of (232)Th and (238)U concentrations in moss and soil samples showed a significant positive linear correlation.

Transfer of naturally occurring radionuclides from soil to wild forest flora in an area with enhanced legacy and natural radioactivity in Norway.

A study of transfer of naturally occurring radioactive materials (NORM), thorium, uranium and their progeny, from soil to wild plant species was performed to evaluate the environmental impact in an area of enhanced natural and legacy radioactivity in Norway. Three sites were chosen for the study: NORM legacy mining, undisturbed 232Th-rich site and reference site. Tissue concentrations, transfer factors and radiation exposure doses were determined in nine wild plant species. High soil activity concentrations of NORM, statistically indistinguishable, were measured at legacy NORM and undisturbed 232Th-rich sites, respectively, while soil from the reference site exhibited a statistically lower activity concentration. Heterogeneous soil radionuclide distributions were observed. The mobile soil fraction of investigated radionuclides was significantly lower, but properly reflected in measured plant uptake. Plant tissue activity concentrations of NORM were significantly higher at both investigated 232Th-rich sites in comparison to the reference site and varied per plant species and analyzed radionuclide, for instance, from non-detectable 232Th in tree needles and leaves to significantly elevated values of measured 210Po in lichens. As expected, plant roots served as a natural translocation barrier, as the concentration of radionuclides in the analyzed samples was up to 88-fold higher than that in the corresponding aboveground plants. Transfer factors for 232Th, 238U, 226,228Ra and 210Po in the aboveground plants ranged broadly from 4 × 10-5 to 1 × 10-2; 1 × 10-4 to 4 × 10-2, 1.07 × 10-3 to 1.08; 2.18 × 10-2 to 9.53 × 10-2 and 9.18 × 10-2 to 9.69, respectively. Radiological exposure dose rates, calculated using the ERICA tool and site-specific data, were from 1 to 23 µGy h-1. Due to elevated NORM levels in analyzed plants, measured radiation exposure dose rates were higher than those of worldwide background biota. Still, the uptake of NORM, demonstrated in the current study, is not expected to cause significant changes at population levels in wild plant species.

Elevated natural radioactivity in undisturbed forest and mountain areas of arctic Norway - local geology, soil characteristics, and transfer to biota.

This study deals with the geology in areas close to a large unexploited uranium deposit and the impact of bedrock characteristics on levels of radionuclides and other elements in soil and biota. Factors influencing soil inventory and ecosystem transfer are discussed, focussing on 238U, 226Ra, and 210Pb. Field work was carried out in Salangen Valley in Northern Norway. Sampling stations for soil and biota covered different habitats - grassland, birch forest and low alpine heathland. The geological survey confirmed uranium-bearing minerals in granitic gneiss and pegmatites. There was large variation in the local occurrence of uranium, reflecting the irregular nature of the pegmatite. Activity concentrations of 238U, 226Ra, and 210Pb in surface soil were elevated at sites close to U-enhanced bedrock, compared to sites with other types of bedrock. Particularly high soil levels were found for 226Ra and 210Pb, whereas activity concentrations of 238U were more variable, depending of local soil characteristics. Levels of other natural radionuclides (40K, 232Th) merely increased with soil mineral content, and concentrations of heavy metals were generally low at all sites. External dose rate (1 m above ground surface) was closely correlated with 226Ra levels in soil. Plant levels of 238U and 226Ra varied by several orders of magnitude depending on soil level and plant species, whereas plant levels of 210Pb and 210Po were largely affected by aerial fallout. Berries generally contained lower levels of 238U and 226Ra than green plant parts. As was the case for plants, the levels of 238U in earthworms were strongly correlated with the respective concentrations in the soil. Soil-to-plant transfer was markedly higher for 226Ra than for 238U. For both radionuclides, a positive correlation was found between concentration ratios of V. myrtillus (heath) and soil organic matter content. The 238U concentration ratios for earthworms were generally two orders of magnitude higher than for plants.

Micro-analytical characterization of thorium-rich aggregates from Norwegian NORM sites (Fen Complex, Telemark).

In this study we performed microscopic characterization of mineral particles that were collected in the thorium-rich Fen Complex in Norway and identified and isolated based on autoradiography in function of their radioactivity. For this we combined information obtained with X-ray absorption µ-CT, µ-XRF and µ-XRD, both in bi- and in three-dimensional (tomographic) mode. We demonstrate that radionuclides and metals are heterogeneously distributed both within soil samples and within individual Th-enriched aggregates, which are characterised as low-density mineral bulk particles with high density material inclusions, where Th as well as several metals are highly concentrated. For these sites, it is important to take into account how these inhomogeneous distributions could affect the overall environmental behaviour of Th and progeny upon weathering due to human or environmental factors. Moreover, the estimated size of the Th-containing inclusions as determined in this work represents information of importance for the characterization of radionuclides and toxic metals exposure, as well as for assessing the viability of mining for Th and rare-earth metals in the Fen Complex and the associated environmental impact.

Determination of technetium-99 using electrothermal vaporization inductively coupled plasma-mass spectrometry (ETV-ICP-MS) and NH4OH as chemical modifier.

In recent years, developments in ICP-MS have led to improved methods for determination of long-lived radionuclides. This paper reports the use of NH(4)OH as a matrix modifier and ETV sample introduction for the determination of technetium-99 ((99)Tc) in a variety of environmental and biological samples, using Re as carrier and (99m)Tc as yield monitor in the chemical separation method. Addition of an excess of NH(4)OH led to a stable (99)Tc signal, reduced memory effect, better reproducibility and reduced detection limits. Following radiochemical separation of (99)Tc from the sample matrix, detection limits in the order of a few microBq have been achieved. ETV has also proved applicable for rapid, direct analysis of a number of environmental samples having relatively high concentrations of (99)Tc (sediment extracts and river water close to nuclear installations). However, in this case, control of matrix effects (signal reduction and enhancement) using standard additions is necessary.

Plutonium contamination in soils and sediments at Mayak PA, Russia.

The Mayak Production Association (Mayak PA) was established in the late 1940's to produce plutonium for the Soviet Nuclear Weapons Programme. In total, seven reactors and two reprocessing plants have been in operation. Today, the area comprises both military and civilian reactors as well as reprocessing and metallurgical plants. Authorized and accidental releases of radioactive waste have caused severe contamination to the surrounding areas. In the present study, [alpha]-spectrometry and inductively coupled plasma-mass spectrometry (ICP-MS) have been used to determine plutonium activities and isotope ratios in soil and sediment samples collected from reservoirs of the Techa River at the Mayak area and downstream Techa River. The objective of the study was to determine the total inventory of plutonium in the reservoirs and to identify the different sources contributing to the plutonium contamination. Results based on [alpha]-spectrometry and ICP-MS measurements show the presence of different sources and confirmed recent reports of civilian reprocessing at Mayak. Determination of activity levels and isotope ratios in soil and sediment samples from the Techa River support the hypothesis that most of the plutonium, like other radionuclides in the Techa River, originated from the very early waste discharges to the Techa River between 1949 and 1951. Analysis of reservoir sediment samples suggest that about 75% of the plutonium isotopes could have been released to Reservoir 10 during the early weapons production operation of the plant, and that the majority of plutonium in Reservoir 10 originates from discharges from power production or reprocessing. Enhanced 240Pu/239Pu atom ratios in river sediment upper layers (0-2 cm) between 50 and 250 km downstream from the plant indicate a contribution from other, non-fallout sources.