Low Concentrations Of Radionuclides Research Articles

Actinide Ion (Americium-241 and Uranium-232) Interaction with Hybrid Silica-Hyperbranched Poly(ethylene imine) Nanoparticles and Xerogels.

The binding of actinide ions (Am(III) and U(VI)) in aqueous solutions by hybrid silica-hyperbranched poly(ethylene imine) nanoparticles (NPs) and xerogels (XGs) has been studied by means of batch experiments at different pH values (4, 7, and 9) under ambient atmospheric conditions. Both materials present relatively high removal efficiency at pH 4 and pH 7 (>70%) for Am(III) and U(VI). The lower removal efficiency for the nanoparticles is basically associated with the compact structure of the nanoparticles and the lower permeability and access to active amine groups compared to xerogels, and the negative charge of the radionuclide species is formed under alkaline conditions (e.g., UO2(CO3)34- and Am(CO3)2-). Generally, the adsorption process is relatively slow due to the very low radionuclide concentrations used in the study and is basically governed by the actinide diffusion from the aqueous phase to the solid surface. On the other hand, adsorption is favored with increasing temperature, assuming that the reaction is endothermic and entropy-driven, which is associated with increasing randomness at the solid-liquid interphase upon actinide adsorption. To the best of our knowledge, this is the first study on hybrid silica-hyperbranched poly(ethylene imine) nanoparticle and xerogel materials used as adsorbents for americium and uranium at ultra-trace levels. Compared to other adsorbent materials used for binding americium and uranium ions, both materials show far higher binding efficiency. Xerogels could remove both actinides even from seawater by almost 90%, whereas nanoparticles could remove uranium by 80% and americium by 70%. The above, along with their simple derivatization to increase the selectivity towards a specific radionuclide and their easy processing to be included in separation technologies, could make these materials attractive candidates for the treatment of radionuclide/actinide-contaminated water.

Role of alkaline barriers in radionuclide distribution in river valley environments on the Russian Black Sea coast

This paper reports on the radioecological properties of environmental components in the Mzymta and Sochi River valleys on the Russian Black Sea coast. The environmental components covered are river sediments, alluvial soils, mosses, and fluvial water. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was used to determine the distribution patterns of Th and U stemming from two geochemical alkaline barriers present in the river valleys. One is a calcium barrier resulting from the metamorphic transition from neutral mudstones to alkaline carbonate rocks. The other is a sodium barrier formed in estuaries under the influence of Na-rich tidal seawater. The sodium barrier was responsible for an increase in Th and U concentrations in river water, a slight decrease in soil and sediments, and strong sorption on mosses. The calcium barrier reduced Th and U concentrations in river water, but increased them in soil and mosses. In the Sochi River valley, the content of calcium in the components of the natural environment is higher compared to the Mzymta River valley and, on average, 4 times higher in the river water. This factor determines the relatively high Th and U content in the natural environment of the Sochi River valley, as these radionuclides are easily extracted from the mineral component of river water by carbonate solutions. On the whole, the radioecological status of the river valleys was recognized as favourable. Gamma radiation exposure dose rate near the surface (20–27 μR/h or less in mountainous areas and 9–17 μR/h in the lowlands) was below the natural level typical for open mountainous areas of central Russia. River sediments in both valleys had low radionuclide concentrations based on the specific activities of naturally occurring radionuclides 226Ra, 228Ra, 224Ra, 232Th, and 40K. In similar river basins that may be targeted for future development, accumulation of Th and U in soil and mosses on calcium barriers and elevated concentrations in river water on sodium barriers should be expected.

Extending the range of optically stimulated luminescence dating using vein-quartz and quartzite sedimentary pebbles

The feasibility of applying optically stimulated luminescence (OSL) techniques to obtain estimates of the burial age of lithic clasts in the form of pebbles of quartzose lithology is investigated in this study. We applied OSL measurement procedures to vein-quartz and quartzite pebbles from contexts at five sites with fluvial and coastal beach contexts of depositional age ranging from 500 ka to the mid Holocene. As in previous OSL studies with lithics, measured depth-dose profiles were interpreted to identify regions associated with key stages in the burial history of the pebbles, including the extent of pre-burial optical resetting, primary burial and any subsequent secondary stages of exposure to sunlight. While some of the pebbles had not been fully optically reset before burial, none were in field saturation, as commonly encountered with larger lithic clasts such as cobbles. The relatively low concentrations of radionuclides within vein-quartz and quartzite pebbles simplified the assessment of the radiation dose rate. OSL age estimates consistent with independent dating evidence were obtained for the three sites sampled in the UK (Langford Quarry, Leet Hill Quarry, Swanscombe Skull Site and Barnfield Pit) and one of two sites tested in Portugal (Forte Cão), whereas evidence of secondary optical bleaching detected in pebbles from a second site (Vale de Atela) underestimated the independent age for primary burial. The oldest depositional age of the contexts tested was ~500 ka (Leet Hill Quarry), and for some of the pebbles tested there was the capacity to extend the potential dating range further as the age equivalence of the limiting value of D e was in excess of 1 Ma. The advantages of working with smaller, portable, clasts in the form of pebbles and with a lithology of higher transparency opens up a wide range of potential applications, whether the depositional processes are environmental or anthropogenic in origin or modification. • New approach to the dating of Quaternary sediments containing vein-quartz and quartzite pebbles. • OSL techniques applied to sliced pebble cores produce depth-dose profiles that are related to optical exposure history. • Successful comparison of OSL ages with independently dated MIS 12, MIS 11, MIS 5 and Holocene depositional contexts. • Low dose rates for vein-quartz and quartzite pebbles potentially enable further extension of the dating range.

Вміст радіонуклідів у фітопланктоні на різних ділянках Запорізького водосховища

The radionuclides, which have occurred in the aquatic ecosystem are quickly redistributed there. Most of them come through the water phase to the benthal deposit, while the other part of them accumulates in suspensions and hydrobionts. Even low concentrations of radionuclides in water contributes to its radioactive contamination that poses risks to the environment. The radionuclide contamination of freshwater ecosystems is particularly pressing issue, since water with low mineralization enhances the radionuclides activity in the sediments compared to the water by a factor of 10 or even more, and in the animals by hundreds and thousands of times. Phytoplankton is the fundamental autotrophic link of aquatic ecosystems. Due to a large total sorption surface, it is able to absorb, retain and transmit radionuclides along the food chains, leading to a deterioration of the environmental position of the reservoir. Phytoplankton was sampled in the summer of 2019 at 5 sites along the course of the Zaporizke reservoir, which differ in hydrological and hydrochemical conditions: Samara Bay, Festivalnyi pier, Monastyrsky island, creek of the Mokra Sura river and the lower section of the reservoir (near Viyskove village). The specific radioactivity of phytoplankton samples was determined using generally accepted radiochemical methods and gamma spectrometry. The specific radioactivity of radionuclides is given in bequerels per kilogram (Bq/kg) of fresh, natural weight. Statistical processing of research results was carried out using generally accepted methods of variation statistics for a small sample using the Excel 2010 software package. Purpose of the work. To determine the content of natural ( 232 Th, 226 Ra and 40 K) and artificial ( 137 Cs and 90 Sr) radionuclides in phytoplankton at different sites of the Zaporizke reservoir. The content of artificial radionuclides in the phytoplankton of the Zaporizke reservoir averaged as follows: 137 Cs – 7.61±0.501 Bq/kg; 90 Sr – 1.13±0.242 Bq/kg. The maximum values of the content of artificial radionuclides in phytoplankton were recorded in the area of the Festivalnyi pier and the minimum values were recorded near Viyskove village ( 137 Cs) and Samara bay ( 90 Sr). In total, phytoplankton has a relatively low content of artificial radionuclides, which is explained by its low content in water. Hydrobionts receive the main portion of radiation exposure from natural sources of radiation. About 300 natural radionuclides have been identified in the environment; among them 226 Ra, 232 Th and 40 K make a significant contribution to the total natural radioactivity. The specific activity of natural radionuclides in the water area of the Zaporizke reservoir on average was following: 226 Ra – 95.45±7,010 Bq/kg; 232 Th – 85.66±4,013 Bq/kg; 40 K – 185.26±23.74 Bq/kg. The lowest content of natural radionuclides was observed in the phytoplankton of the Samara bay. The maximum recorded specific activity of 226 Ra and 40 K was observed in the creek of the Mokra Sura river, which may indicate an increased content of radionuclides in the water of this river, because the river is polluted throughout its length by industrial, agricultural and municipal wastewater. It has been found that the specific activity of natural radionuclides 226 Ra, 232 Th and 40 K was 80-320 times higher than that of the artificial ones ( 90 Sr and 137 Cs). The distribution of radionuclides in the elements of the freshwater ecosystem is characterized by accumulation coefficients. According to the accumulation coefficients with respect to water, the sequence of accumulation of radionuclides in the phytoplankton of the Zaporizke reservoir has been arranged in descending order: 137 Cs> 232 Th> 226 Ra> 40 K> 90 Sr. The accumulation coefficients of 40 K and 90 Sr are 11-22 times less than those of 137 Cs and 232 Th, which is quite appropriately, because freshwater algae are more able to accumulate 137 Cs. For most of the radionuclides studied, the maximum values of accumulation coefficients have been recorded in phytoplankton in the area of the Festivalnyi pier ( 137 Cs, 90 Sr, 232 Th) and the creek of the Mokra Sura river ( 226 Ra, 40 K). The latter is associated with both the hydrochemical and hydrological conditions of these sites, and with increased anthropogenic impact, especially in the area of the river creek. The data obtained indicate that there is a potential threat of accumulation of radionuclides in phytoplankton and their transfer further along food chains. With reference to the above mentioned, it is important to monitor the content of radionuclides in phytoplankton in order to minimize their transmission through the food chain and preserve the biodiversity of aquatic ecosystems.

Design and Characterization of an Extremely-Sensitive, Large-Volume Gamma-Ray Spectrometer for Environmental Samples.

A large volume gamma spectrometer was designed and constructed to analyze foodstuffs and environmental samples having low radionuclide concentrations. This system uses eight 11-cm × 42.5-cm × 5.5-cm NaI(Tl) detectors, chosen due to their relatively high sensitivity and availability and arranged in an octagonal configuration. The sensitive volume of the system is ~28 cm in diameter and ~42 cm deep. Shielding consists of an 86-cm × 86-cm square, 64-cm-tall lead brick enclosure with 18-cm-thick lead walls lined by 0.3-cm-thick copper plates. An aluminum top was machined to suspend the detectors within this shield. The shielding reduces background counts by 72% at 100 keV and 42% at 1,000 keV. The positional variability in sensitivity of the well was determined by both simulation and experiment. A 2.1-L volume of nearly uniform sensitivity, varying less than 10%, exists in the well's center. Energy resolutions of 14.6% and 7.8% were measured for Am and Cs, respectively. Energy resolution shows a 0.2% variation for both Am and Cs as a function of position within all regions of the well's central sensitive volume. Dead time was also determined to be less than 35% for all sources measured in the system, the largest of which had an activity of 1,760 kBq. Simulated results for various source geometries show higher counts for smaller samples, especially at lower energies due to less attenuation of low energy photons. Minimum detectable activities were determined for all source energies used, less than 5.1 Bq kg for reasonable background and sample counting times.

Radionuclide distributions in Olympic Dam copper concentrates: The significance of minor hosts, incorporation mechanisms, and the role of mineral surfaces

Some iron oxide-copper-gold (IOCG) deposits contain variable amounts of uranium. Developing mineral deportment models for the radiogenic isotopes resulting from decay of 238U presents a singular technical challenge, as concentrations of 226Ra, 210Pb, and 210Po fall far below the detection limits achievable for most in situ analytical methodologies. The nanoscale secondary ion mass spectrometry (nanoSIMS) platform combines low detection limits with sub-micron resolution, revealing previously unseen spatial distribution patterns of radionuclides (RNs) in (and on) particles of copper sulphide concentrates. Many potential host minerals for these radionuclides can be readily predicted based on chemical behaviour, periodic table trends, and published studies documenting likely host minerals. Using nanoSIMS data for ores and metallurgical products from the Olympic Dam IOCG deposit and associated processing facilities, we present compelling evidence for the ability of certain minerals within the copper concentrates to host daughter radionuclides derived from uranium decay. Many of these minerals had not traditionally been considered or previously documented as such. These include high-abundance minerals hosting low concentrations of radionuclides, and several relatively low abundance minerals exhibiting remarkable radionuclide enrichment. Rutile, fluorapatite, fluorite, hematite, zircon, covellite, and molybdenite are all proven to be minor hosts of at least some members of the 238U decay chain, and are, collectively, important for establishing the overall RN budget. Surface effects are found to play a significant role, with elevated levels of 226Ra and 210Pb found on most available surfaces, irrespective of mineral, in acid-leached concentrate. Some rRNs, particularly 226Ra and 210Pb liberated from uranium minerals during sulphuric acid leaching, can become extensively redistributed throughout the concentrate, creating newly-formed RN hosts. This new mineralogical deportment information can be used in developing new flowsheets to enhance radionuclide removal without a corresponding loss of Cu. NanoSIMS has proven invaluable for elucidating the mineral-scale deportment of ultra-trace radionuclides throughout the processing circuit at Olympic Dam.

Alpha particle autoradiography for high spatial resolution mapping of radionuclides

An autoradiographic technique capable of determining the spatial location of radioactive isotopes within materials on the scale of micrometers is demonstrated in low-activity mineral samples, where the concentrations of radionuclides with short half lives is small and below the detection limits of current measurement techniques. The location of certain radionuclide species within samples with complex structures on the micron scale can yield valuable information, however current methods do not have the spatial resolution required for this purpose.We demonstrate the use of an autoradiographic emulsion to directly image alpha particle events in samples with low radionuclide concentrations, allowing spatial resolution of radionuclide locations on the order of several microns. Exposure over a long time period allows sufficient integration of decay events enabling analysis of samples with low activity but large area, (less than 1×10−4 Bq/mm2). The use of polarising filters to increase contrast between the alpha particle tracks and the substrate during imaging demonstrates the viability of the technique on samples with a complex structure.

RADIOACTIVITY OF GRANITIC ROCKS FROM NORTHERN GREECE

Forty-nine samples from several plutons in northern Greece have been studied for their activity concentrations of 40K, 226Ra and 232Th by using gamma-ray spectroscopy. The activities of 40K, 226Ra and 232Th of the majority of the samples exceed the average level of these radionuclides in soil and building materials. Samples of basic composition have very low concentrations of radionuclides while intermediate and acid rocks are more enriched in 40K, 226Ra and 232Th and their decay products. In order to assess the radiological impact from the investigated rocks, absorbed gamma dose rate (Da), annual effective dose (HE), activity index (AI) and gamma-ray index (Iγ) were estimated. The activity concentrations and hazard indices were compared to those of plutonic rock samples from all over the world, as well as other building materials. The average of hazard indices of Greek granites is below ‘world’ average in all cases. Moreover, it is still bellow the criteria of UNSCEAR (2000). Therefore, at least from radiological point of view and for the investigated rocks, the use of granites from northern Greece as building materials is recommended.

Identifying large chondrites using cosmogenic radionuclides

We measured the concentrations of the cosmogenic radionuclides 10Be, 26Al, 36Cl and 41Ca in the metal and stone fractions of three large chondrite showers to determine their pre-atmospheric size. Large chondrites are characterized by substantial contributions of neutron-capture 41Ca in the stone fraction (up to ∼2 dpm/gCa), low radionuclide concentrations in the metal fraction and high 10Be(stone)/10Be(metal) ratios. Based on the measured concentrations in comparison with calculated cosmogenic nuclide depth profiles, using a semi-empirical and a purely physical model, we conclude that these objects had pre-atmospheric radii ranging from ∼80 cm to >3 m. We conclude that the semi-empirical model is more reliable for spallogenic production rates in large objects, while the purely physical model is more reliable for neutron-capture products.

Spatial distribution investigation of radioactivity of potable waters in Luxembourg

A survey of naturally occurring radio-nuclides was performed on the territory of Luxembourg in order to identify the main physical and chemical parameters in drinking waters. During last summer water samples from 316 different outflows were collected twice and analyzed. A routine laboratory sequentional extraction radiochemistry procedure was applied for monitoring low concentrations of radio-nuclides in natural waters. New investigations were done to optimize some analysis conditions for the different determination procedures. A quality assurance procedure was applied. The obtained results are analyzed in term of spatial distribution, supported geology and chemistry.

Seasonal changes in mRNA encoding for cell stress markers in the oyster Crassostrea gigas exposed to radioactive discharges in their natural environment

The North Cotentin area (Normandy, France) hosts several nuclear facilities among which the AREVA reprocessing plant of La Hague is responsible for controlled discharges of liquid radioactive wastes into the marine environment. The resulting increase in radioactivity is very small compared to natural radioactivity. However, concerns about environment protection prompted the scientific community to focus on the effects of the chronic exposure to low concentrations of radionuclides in non-human biota. This study contributes to the evaluation of the possible impact of radioactive discharges on the oyster Crassostrea gigas in the field. Real-time polymerase chain reaction was used to quantify the expression levels of genes involved in cell stress in the oyster. They included members of the heat shock protein family (Hsp70, Hsc72, Hsp90), superoxide dismutase (SOD) and metallothionein (MT). Times series measurements were built from periodic samplings in the natural environment in order to characterize the natural variability as well as possible seasonal fluctuations. The genes studied exhibited a general seasonal expression pattern with a peak value in winter. The data inversely correlated with seawater temperature and the nature of the relationship between gene expression and temperature is discussed. In parallel, oysters were collected in four locations on the French shores, exposed or not to radioactive liquid wastes from the nuclear facilities hosted in the North Cotentin. The comparison of data obtained in the reference location on the Atlantic coast (not exposed) and data from oysters of the English Channel (exposed) gave no evidence for any statistical difference. However, because of the complexity of the natural environment, we cannot rule out the possibility that other parameters may have masked the impact of radioactive discharges. This dense set of data is a basis for the use of the expression levels of those genes as biomarkers to address the question of the possible effects of chronic exposure of the oyster to low concentrations of radionuclides in controlled laboratory experimental conditions.

Optical dating of annually laminated lake sediments A test case from Holzmaar/Germany

We present results of an optical dating feasibility study for annually laminated (varved) lake sediments. The fine-silt sized clastic fraction of the sediments was extracted, stimulated with infrared, and the 410 nm emission was detected. A multiple-aliquot additive-dose protocol in combination with a subtraction technique was used for the equivalent dose determinations. Results are promising only for sediments with high amounts of clastic components. For sediments with a high organic component, results are inaccurate, perhaps due to problems in dose-rate calculation. We speculate that besides the low concentrations of radio-nuclides and disequilibria in the U-series, dose-rate determination procedures are inaccurate for sediments with high contents of biogenic silica. Sediment compaction seems to account for minor effects only.

Application of the nuclide identification system SHAMAN in monitoring the Comprehensive Test Ban Treaty

SHAMAN is an expert system for qualitative and quantitative radionuclide identification in gamma spectrometry. SHAMAN requires as input the calibrations, peak search, and fitting results from reliable spectral analysis software, such as SAMPO. SHAMAN uses a comprehensive reference library with 2600 radionuclides and 80 000 gamma-lines, as well as a rule base consisting of sixty inference rules. Identification results are presented both via an interactive graphical interface and in the form of configurable text reports. An organization has been established for monitoring the recent Comprehensive Test Ban Treaty. For radionuclide monitoring, 80 stations will be set up around the world. Air-filter gammaspectra will be collected from these stations on a daily basis and they will need to be reliably analyzed with minimum turnaround time. SHAMAN is currently being evaluated within the prototype monitoring system as an automated radionuclide identifier, in parallel with existing radionuclide identification software. In air-filter monitoring, very low concentrations of radionuclides are measured from bulky sources in close geometry and with long counting time. In this case true coincidence summing and self-absorption become important factors. SHAMAN is able to take into account these complicated phenomena, and the results it produces have been found to be very reliable and accurate.

Chemical Conditions of Synthesis of Th4(PO4)4P2O7. Preparation of Thorium Phosphate−Hydrogenphosphate as Precursor

Thorium phosphate−diphosphate, Th4(PO4)4P2O7, is obtained, at high temperature (800−1250 °C), for a given ratio r = PO4/Th equal to 3/2 from a thorium compound and a phosphating reactant whatever the chemical conditions. This compound, whose solubility is very low, can be loaded in situ and used as a host matrix for radwaste storage. One of the methods for its synthesis involves the precipitation of a precursor, thorium phosphate−hydrogenphosphate. This precursor is used as an adsorber for low concentrations of radionuclides and, after heating in air in the range 800−1200 °C, it is transformed into doped Th4(PO4)4P2O7. The optimum conditions for the precipitation process have been determined. Starting from 0.5−2 M solutions of thorium nitrate or chloride and (NH4)2HPO4 at pH = 9−9.5 at the ratio r = 3/2, a compound of general formula Th2(PO4)2HPO4·nH2O (n = 3−7) is synthesized. Its physicochemical properties have also been studied.

Allan Hills 88019: An Antarctic H‐chondrite with a very long terrestrial age

Abstract— We have measured the concentrations of the cosmogenic radionuclides 10Be, 26Al and 36Cl (half‐lives 1.51 Ma, 716 ka, and 300 ka, respectively) in two different laboratories by accelerator mass spectrometry (AMS) techniques, as well as concentrations and isotopic compositions of stable He, Ne and Ar in the Antarctic H‐chondrite Allan Hills (ALH) 88019. In addition, nuclear track densities were measured. From these results, it is concluded that the meteoroid ALH 88019 had a preatmospheric radius of (20 ± 5) cm and a shielding depth for the analyzed samples of between 4 and 8 cm. Using calculated and experimentally determined production rates of cosmogenic nuclides, an exposure age of ∼40 Ma is obtained from cosmogenic 21Ne and 38Ar. The extremely low concentrations of radionuclides are explained by a very long terrestrial age for this meteorite of 2 ± 0.4 Ma. A similarly long terrestrial age was found so far only for the Antarctic L‐chondrite Lewis Cliff (LEW) 86360. Such long ages establish one boundary condition for the history of meteorites in Antarctica.

Phytoremediation of soil contaminated with low concentrations of radionuclides

Ecosystems throughout the world have been contaminated with radionuclides by above-ground nuclear testing, nuclear reactor accidents and nuclear power generation. Radioisotopes characteristic of nuclear fission, such as 137Cs and 90Sr, that are released into the environment can become more concentrated as they move up the food chain often becoming human health hazards. Natural environmental processes will redistribute long lived radionuclides that are released into the environment among soil, plants and wildlife. Numerous studies have shown that 137 Cs and 90Sr are not removed from the top 0.4 meters of soil even under high rainfall, and migration rate from the top few centimeters of soil is slow. The top 0.4 meters of the soil is where plant roots actively accumulate elements. Since plants are known to take up and accumulate 137 Cs and 90Sr removal of these radionuclides from contaminated soils by plants could provide a reliable and economical method of remediation. One approach is to use fast growing plants inoculated with mycorrhizal fungi combined with soil organic amendments to maximize the plant accumulation and removal of radionuclides from contaminated soils, followed by harvest of above-ground portion of the plants. High temperature combustion would be used to oxidize plant material concentrating 137 Cs and 90Sr, in ash for disposal. When areas of land have been contaminated with radionuclides are large, using energy intensive engineering solutions to remediate huge volumes of soil is not feasible or economical. Plants are proposed as a viable and cost effective method to remove radionuclides from the soils that have been contaminated by nuclear testing and nuclear reactor accidents.

A Novel PhosphorImager-Based Technique for Monitoring the Microbial Reduction of Technetium

A novel PhosphorImager-based technique which can be used to quantify low concentrations of radionuclides is described. The technique offers several benefits, combining very high sensitivity with containment of the radioisotope in the solid state, thus minimizing disposal procedures. In this study, it was used in conjunction with paper chromatography to quantify different oxidation states of (sup99)Tc in solution. The technique was used to evaluate the potential of anaerobic cultures of Shewanella putrefaciens and Geobacter metallireducens (bacteria with known metal-reducing capabilities) to reduce highly soluble Tc(VII) to insoluble lower-valence species, facilitating its removal from solution. Both organisms reduced Tc(VII), but profiles of Tc species produced in culture supernatants were strain specific. S. putrefaciens produced Tc(V), Tc(IV), and one unidentified species, but no Tc was removed from solution. G. metallireducens removed 70% of the 250 (mu)M Tc added in solution, with trace amounts of Tc(V) and the unidentified species detected in culture supernatants. Possible uses for these organisms in the bioremediation of Tc-contaminated waters are discussed, and other uses of the PhosphorImager technique are highlighted.

The transfer of radionuclides from sea to land via the air: A review

Studies of the levels of artificial radionuclides in various environmental media have been carried out over a number of years. In some coastal areas, these have demonstrated that a small fraction of the radionuclides discharged directly into coastal waters from industrial establishments is recycled, via the air-sea interface, back onto land. In the sea, the discharged radionuclides are distributed between dissolved and particulate-associated phases, the fractions being different for different elements. Aerosol is generated above by bubble bursting and wave shearing processes and is enriched in suspended particulates and the associated radionuclides. The aerosol is advected to land by onshore winds and deposited in coastal regions. Sea-to-land transfer has been observed and reported near the British Nuclear Fuels plc Sellafield Works, Cumbria, England, the Dounreay Nuclear Power Development Establishment, Caithness, Scotland and the reprocessing works at Cap de la Hague, Normandy, France. In Cumbria, where the effect has been most fully investigated, plutonium, americium and radiocaesium discharged to the Irish Sea from Sellafield have been observed many kilometres inland. The field studies have included measurements of (a) accumulated deposits in coastal soils, (b) airborne concentrations and depositions near the coast, (c) deposits on muslin screens and mosses, (d) concentrations in lake sediments and sheep faeces. Enrichment factors for actinides in airborne materials, of from one to three orders of magnitude with respect to seawater, have been observed. The average atmospheric deposition appeared to fall with distance from the sea according to a power law relation. A seasonal periodicity was observed in the airborne concentrations and possible explanations have been advanced, including seasonal variations in marine surface currents or effects of surface-active organic materials. In Caithness, the relatively low radionuclide concentrations in the sea meant that a mechanism similar to that used to describe the Cumbria effect would be largely undetectable. The distribution of the marine-derived radionuclides as a function of distance inland was different from that in Cumbria and the effect was detectable in general only within a few hundred metres of the coast. The formation of spume, or stable foam, is a common occurrence along the north Scottish coastline. The spume has a high particulate loading. In high onshore winds, lumps of spume up to about 25 cm in diameter can frequently be observed to be carried inland for up to a few hundred metres. It is proposed that the spume is the transfer medium for the particulate-associated radionuclides. The radiological significance of the sea-to-land transfer in Cumbria has been modelled. The actinide dose estimate for 1987 for a critical population group was about 8% of the dose from the seafood pathway. The relative significance of the sea-to-land pathway will tend to increase and, in the year 2000, the predicted dose is lower but is 20–30% of the dose from the seafood pathway. For Caithness, the radiological significance is smaller than in Cumbria.

Distribution of fission products in dust samples from the region of Thessaloniki, Greece, after the Chernobyl nuclear accident.

The distribution of the fission products (95)Zr, (95)Nb, (103)Ru, (106)Ru (determined through (106)Rh), (125)Sb, (129m)Te, (134)Cs, (137)Cs, (140)Ba, (140)La, (141)Ce and (144)Ce has been determined in dust samples from the region of Thessaloniki, Greece, after the nuclear accident at Chernobyl. The samples studied also included (110m)Ag, not belonging to the products of (235)U fission. Samples showing higher concentrations of radionuclides also show a higher content in clay minerals, whereas samples having low concentrations of radionuclides usually contain large amounts of quartz and feldspars. Desorption and leaching experiments using solutions of chlorides of sodium, potassium, calcium and magnesium (0.5 N), as well as distilled and tap water, were also performed. Sodium and potassium chloride solutions were found to be efficient in desorbing and/or leaching of caesium and ruthenium isotopes to an extent of about 30%.

Radionuclide Export and Elimination by Coyotes at Two Radioactive Waste Disposal Areas in Southeastern Idaho

Coyote fecal samples were collected near a radioactive waste leaching pond and a solid radioactive waste disposal facility and analyzed for radioactivity. Elevated concentrations of 137Cs, 90Sr and 238Pu in the samples from the liquid radioactive waste leaching area were attributed to coyotes ingesting contaminated pond water and/or small mammals. Elevated 241Am concentrations in coyote fecal samples collected around the solid radioactive waste disposal facility were due to ingestion of contaminated small mammals. Assumptions relative to the coyote use of these areas permitted an estimate of the maximum quantity of radioactivity exported and eliminated around the facilities. An annual total of 7.2, 31.4 and 1.8 microCi (90Sr, 137Cs, 238Pu, 239,240Pu, 241Am, 242Cm and 244Cm) was eliminated by coyotes within a 6.3 km radius of the solid radioactive waste disposal facility, liquid waste leaching pond, and control area, respectively. These quantities of radioactivity eliminated by coyotes were similar or less than quantities transported by other mechanisms such as waterfowl and vegetative uptake of radioactivity. Coyotes are a mode of radionuclide transport from the two radioactive waste disposal areas; however, due to the low radionuclide concentrations and low yearly radionuclide inventories in coyote fecal samples, it is doubtful that any significant environmental consequences occur as a result of this transport mechanism.