Depth profile of ²³⁶U/²³⁸U in soil samples in La Palma, Canary Islands

The vertical distribution of the ²³⁶U/²³⁸U isotopic ratio was investigated in soil samples from three different locations on La Palma (one of the seven Canary Islands, Spain). Additionally the ²⁴⁰Pu/²³⁹Pu atomic ratio, as it is a well establish tool for the source identification, was determined. The radiochemical procedure consisted of a U separation step by extraction chromatography using UTEVA^® Resin (Eichrom Technologies, Inc.). Afterwards Pu was separated from Th and Np by anion exchange using Dowex 1x2 (Dow Chemical Co.). Furthermore a new chemical procedure with tandem columns to separate Pu and U from the matrix was tested. For the determination of the uranium and plutonium isotopes by alpha spectrometry thin sources were prepared by microprecipitation techniques. Additionally these fractions separated from the soil samples were measured by Accelerator Mass Spectrometry (AMS) to get information on the isotopic ratios ²³⁶U/²³⁸U, ²⁴⁰Pu/²³⁹Pu and ²³⁶U/²³⁹Pu, respectively. The ²³⁶U concentrations [atoms/g] in each surface layer (∼2 cm) were surprisingly high compared to deeper layers where values around two orders of magnitude smaller were found. Since the isotopic ratio ²⁴⁰Pu/²³⁹Pu indicated a global fallout signature we assume the same origin as the probable source for ²³⁶U. Our measured ²³⁶U/²³⁹Pu value of around 0.2 is within the expected range for this contamination source.     

Determination of U, Pu and Am isotopes in Irish Sea sediment by a combination of AMS and radiometric methods

Samples from a marine sediment core from the Irish Sea (54.416 N, 3.563 W) were analyzed for the isotopic composition of uranium, plutonium and americium by a combination of radiometric methods and AMS. The radiochemical procedure consisted of a Pu separation step by anion exchange, subsequent U separation by extraction chromatography using UTEVA^® and finally Am separation with TRU^® Resin.Additionally to radiometric determination of these isotopes by alpha spectrometry, the separated samples were also used for the determination of ²³⁶U/²³⁸U and plutonium isotope ratios by Accelerator Mass Spectrometry (AMS) at the VERA facility.     

The inflow of (238)Pu and (239+240)Pu from the Vistula River catchment area to the Baltic Sea

The aim of the work was to estimate plutonium inflow from the Vistula River’s catchments area to the Baltic Sea. There were differences in plutonium activities depending on season and sampling site. The highest activities of ²³⁸Pu and ^239+240Pu were transported from the Vistula River watershed to the Baltic Sea in spring and the lowest in summer. Annually, the southern Baltic Sea is enriched via the Vistula River with 10.3 MBq of ²³⁸Pu and 89.0 MBq of ^239+240Pu. The enhanced concentration of plutonium in water from the Vistula River is the result of its runoff from the Vistula drainage area, mostly from snowmelt, enhanced rainfalls and leached materials from river bed.     

Isotopic composition and origin of uranium and plutonium in selected soil samples collected in Kosovo

Soil samples collected from locations in Kosovo where depleted uranium (DU) ammunition was expended during the 1999 Balkan conflict were analysed for uranium and plutonium isotopes content (234U, 235U, 236U, 238U, 238Pu, (239 + 240)Pu). The analyses were conducted using gamma spectrometry (235U, 238U), alpha spectrometry (238Pu, (239 + 240)Pu), inductively coupled plasma-mass spectrometry (ICP-MS) (234U, 235U, 236U, 238U) and accelerator mass spectrometry (AMS) (236U)). The results indicated that whenever the U concentration exceeded the normal environmental values (approximately 2 to 3 mg/kg) the increase was due to DU contamination. 236U was also present in the released DU at a constant ratio of 236U (mg/kg)/238U (mg/kg) = 2.6 x 10(-5), indicating that the DU used in the ammunition was from a batch that had been irradiated and then reprocessed. The plutonium concentration in the soil (undisturbed) was about 1 Bq/kg and, on the basis of the measured 238Pu/(239 + 240)Pu, could be entirely attributed to the fallout of the nuclear weapon tests of the 1960s (no appreciable contribution from DU).     

Concentration and characterization of plutonium in soils of Hubei in central China

To study the Pu concentration and isotope ratio distributions present in China, the ^239+240Pu total activities and ²⁴⁰Pu/²³⁹Pu atom ratios in core soil samples from Hubei Province in central China were investigated using Accelerator Mass Spectrometry (AMS). The activities ranged from 0.019 to 0.502 mBq g⁻¹ and the ^239+240Pu inventories of 45 and ∼55 Bq m⁻² agree well with that expected from global fallout. The ²⁴⁰Pu/²³⁹Pu atom ratios in the soil ranged from 0.172 to 0.220. The ratios are similar to typical global fallout values. Hence, any close-in fallout contribution from the Chinese nuclear weapons tests, mainly conducted in the 1970s, must have either been negligible or had a similar ²⁴⁰Pu/²³⁹Pu ratio to that of global fallout. The top 10 cm layer of the soil contributes ∼90% of the total inventory and the maximum concentrations appeared in the 2-4 cm or 4-6 cm layers. It is suggested that climatic conditions and organic content are the two main factors that affect the vertical migration of plutonium in soil.     

Americium,plutonium and uranium contamination and speciation in well waters,streams and atomic lakes in the Sarzhal region of the Semipalatinsk Nuclear Test Site,Kazakhstan

New data are reported on the concentrations, isotopic composition and speciation of americium, plutonium and uranium in surface and ground waters in the Sarzhal region of the Semipalatinsk Test Site, and an adjacent area including the settlement of Sarzhal. The data relate to filtered water and suspended particulate from (a) streams originating in the Degelen Mountains, (b) the Tel′kem 1 and Tel′kem 2 atomic craters, and (c) wells on farms located within the study area and at Sarzhal. The measurements show that ²⁴¹Am, ^239,240Pu and ²³⁸U concentrations in well waters within the study area are in the range 0.04–87 mBq dm⁻³, 0.7–99 mBq dm⁻³, and 74–213 mBq dm⁻³, respectively, and for ²⁴¹Am and ^239,240Pu are elevated above the levels expected solely on the basis of global fallout. Concentrations in streams sourced in the Degelen Mountains are similar, while concentrations in the two water-filled atomic craters are somewhat higher. Suspended particulate concentrations in well waters vary considerably, though median values are very low, at 0.01 mBq dm⁻³, 0.08 mBq dm⁻³ and 0.32 mBq dm⁻³ for ²⁴¹Am, ^239,240Pu and ²³⁸U, respectively. The ²³⁵U/²³⁸U isotopic ratio in almost all well and stream waters is slightly elevated above the ‘best estimate’ value for natural uranium worldwide, suggesting that some of the uranium in these waters is of test-site provenance. Redox analysis shows that on average most of the plutonium present in the microfiltered fraction of these waters is in a chemically reduced form (mean 69%; 95% confidence interval 53–85%). In the case of the atomic craters, the proportion is even higher. As expected, all of the americium present appears to be in a reduced form. Calculations suggest that annual committed effective doses to individual adults arising from the daily ingestion of these well waters are in the range 11–42 μSv (mean 21 μSv). Presently, the ground water feeding these wells would not appear to be contaminated with radioactivity from past underground testing in the Degelen Mountains or from the Tel′kem explosions.     

Sources and distributions of Cs, Pu, Pu radionuclides in the north-western Barents Sea

Sediment deposits are the ultimate sink for anthropogenic radionuclides entering the marine environment. The major sources of anthropogenic radionuclides to the Barents Sea are fallout from nuclear weapons tests, long range transport from other seas, and river and non-point freshwater supplies. In this study we investigated activity concentrations, ratios, and inventories of the anthropogenic radionuclides, ¹³⁷Cs, ²³⁸Pu, ^239,240Pu in dated sediment cores collected along a north-south transect in the northwestern Barents Sea. The data were used to evaluate the influence of different sources on the derived spatial and temporal patterns of anthropogenic radionuclides in seafloor sediment deposits. Activity concentrations of ¹³⁷Cs ranged from <0.1 Bq/kg to 10.5 Bq/kg while ^239,240Pu ranged from <0.01 Bq/kg to 2.74 Bq/kg and ²³⁸Pu activity concentrations ranged from <0.01 Bq/kg to 0.22 Bq/kg. Total inventories of ¹³⁷Cs ranged from 29.5 ± 1.5 Bq/m² to 152.7 ± 5.6 Bq/m² and for ^239,240Pu inventories (6 sediment layers only) ranged from 9.5 ± 0.3 Bq/m² to 29.7 ± 0.4 Bq/m². Source contributions varied among stations and between the investigated radionuclides. The ²³⁸Pu/^239,240Pu ratios up to 0.18 indicate discharges from nuclear fuel reprocessing plants as a main contributor of plutonium. Based on ²³⁸Pu/^239,240Pu ratio, it was calculated that up to 19-27% of plutonium is supplied from sources other than atmospheric global fallout. Taking into account Atlantic current flow trajectories and that both activity concentrations and inventories of plutonium negatively correlate with latitude, Sellafield is a major source for the Barents Sea. Concentrations and inventories of ¹³⁷Cs correlate positively with latitude and negatively with distance from the Svalbard archipelago. The ¹³⁷Cs concentrations are highest in an area of intensive melting of sea ice formed along the Siberian coast. Thus, sea ice and supplies from Svalbard may be important source of ¹³⁷Cs to the Barents Sea seafloor.     

Characterization of Pu concentration and its isotopic composition in soils of Gansu in northwestern China

The total ^239+240Pu activities and ²⁴⁰Pu/²³⁹Pu atom ratios in surface soil samples (0–5 cm) in the Kumtag Desert in western Gansu Province, and in a soil core sample in Lanzhou were investigated using a sector-field ICP-MS. In the surface soil samples, ^239+240Pu activities in fine particles (<150 μm) were 1.3–2.1 times of those in coarse particles (150 μm–1 mm) which ranged from 0.005 to 0.157 mBq/g. Atom ratios of ²⁴⁰Pu/²³⁹Pu in the surface soils ranged from 0.168 to 0.192 with a mean of 0.182 ± 0.008. The mean ratio was similar to the typical global fallout value although the Kumtag Desert was believed to have received close-in fallout derived from Chinese nuclear weapons tests mainly conducted in the 1970s. Furthermore, the mean ²⁴⁰Pu/²³⁹Pu atom ratio observed in the soil core sample in Lanzhou was similar to the typical global fallout value. In the soil core sample, ^239+240Pu activities in the various layers ranged from 0.012 to 0.23 mBq/g, and the inventory of ^239+240Pu (32.4 Bq/m², 0–23 cm) was slightly lower than that expected from global fallout (42 Bq/m²) at the same latitude. Rapid downward migration of Pu isotopes was observed in Lanzhou soil core sample layers. The contribution of the 10-cm deep top layers of surface soils to total inventory was only 17%, while the contribution of deeper layers (10–23 cm) was as high as 83%. The ^239+240Pu activity levels and ²⁴⁰Pu/²³⁹Pu atom ratios in soils in Gansu Province, China are similar to those in atmospheric deposition samples collected in the spring in recent years in Japan.     

Plutonium contamination from accidental release or simply fallout: study of soils at Palomares (Spain)

The activity concentration of plutonium in an environmental sample does not usually constitute sufficient information to determine if it is due only to fallout. Alpha and gamma spectrometry are used here conjointly in the study of environmental soil samples to distinguish between samples showing plutonium contamination due to fallout exclusively, and samples contaminated with plutonium from another source. The method was applied to soil samples collected in Palomares (Spain), where an accidental release of aerosols contaminated with plutonium occurred. The two contributions (fallout and accidentally released plutonium) were separated by means of the activity ratios between various radionuclides present in the samples analyzed. The fallout level was estimated from the 239 + 240Pu/137Cs activity ratio. For samples showing contamination due to the accident, the 238Pu/239 + 240Pu and 239Pu/240Pu activity ratios were also calculated to determine the grade of plutonium of this contamination.     

Distribution of uranium isotopes in surface water of the Llobregat river basin (Northeast Spain)

A study is presented on the distribution of ²³⁴U, ²³⁸U, ²³⁵U isotopes in surface water of the Llobregat river basin (Northeast Spain), from 2001 to 2006. Sixty-six superficial water samples were collected at 16 points distributed throughout the Llobregat river basin. Uranium isotopes were measured by alpha spectrometry (PIPS detectors). The test procedure was validated according to the quality requirements of the ISO17025 standard. The activity concentration for the total dissolved uranium ranges from 20 to 261 mBq L⁻¹. The highest concentrations of uranium were detected in an area with formations of sedimentary rock, limestone and lignite. A high degree of radioactive disequilibrium was noted among the uranium isotopes. The ²³⁴U/²³⁸U activity ratio varied between 1.1 and 1.9 and the waters with the lowest uranium activity registered the highest level of ²³⁴U/²³⁸U activity ratio. Correlations between uranium activity in the tested water and chemical and physical characteristics of the aquifer were found.     

Cs,Pu and Am in bottom sediments and surface water of Lake Päijänne,Finland

The concentrations and vertical distribution of ^239,240Pu, ²⁴¹Am and ¹³⁷Cs in the bottom sediments and water samples of Lake Päijänne were investigated. This lake is important, since the Päijänne area received a significant deposition from the Chernobyl fallout. Furthermore Lake Päijänne is the raw water source for the Helsinki metropolitan area. In addition no previous data on the distribution of plutonium and americium in the sediment profiles of Lake Päijänne exist. Only data covering the surface layer (0–1 cm) of the sediments are previously available. In the sediments the average total activities were 45 ± 15 Bq/m² and 20 ± 7 Bq/m² for ^239,240Pu and ²⁴¹Am, respectively. The average ²⁴¹Am/^239,240Pu ratio was 0.45 ± 0.14. The ²⁴¹Am/^239,240Pu ratio is lowest in the surface layer of the sediments and increases as a function of depth. The ²³⁸Pu/^239,240Pu ratio of the sediment samples varied between 0.012 ± 0.025 and 0.162 ± 0.079, decreasing as a function of depth. The average activity in water was 4.9 ± 0.9 mBq/m³ and 4.1 ± 0.2 mBq/m³ for ^239,240Pu and ²⁴¹Am, respectively. The ²⁴¹Am/^239,240Pu ratio of water samples was 0.82 ± 0.17. ^239,240Pu originating from the Chernobyl fallout calculated from the average total activities covers approximately 1.95 ± 0.01% of the total ^239,240Pu activity in the bottom sediments. The average total ¹³⁷Cs activity of sediment profiles was 100 ± 15 kBq/m² and 19.3 ± 1.4 Bq/m³ in water samples.     

Application of ICP-QMS for the determination of plutonium in environmental samples for safeguards purposes

Aiming to determine the plutonium amount as well as its isotopic composition, in particular, in swipe samples for safeguards purposes, an analytical method was developed with a plutonium separation step based on extraction chromatography using 2 cm TEVA columns and detection with quadrupole ICP-MS applying an ultra-sonic nebulizer coupled with membrane desolvation system. The method was successfully applied to New Brunswick plutonium certified reference materials as well as to Lawrence Livermore National Laboratory round robin samples, based on the round robin samples provided by the Institute for Reference Materials and Measurements (Belgium), as part of the Regular European Interlaboratory Measurement Evaluation Programme (REIMEP), campaign 16 (isotopic abundances of plutonium in plutonium nitrate samples), with a total plutonium amount between 1 and 0.25 ng per sample. After the introduction of an additional separation step, it was also possible to carry out precise and accurate total plutonium, (240)Pu/(239)Pu, (241)Pu/(239)Pu and (242)Pu/(239)Pu atom ratios determination in sediment sample showing its applicability to environmental samples in general, reaching a detection limit equivalent to 5 mBq(239)Pu kg(-1).     

Suitable gamma energy for gamma-spectrometric determination of U in surface soil samples of a high rainfall area in India

The paper presents a systematic study on suitability of various gamma lines for monitoring of ²³⁸U activity in soil samples around a uranium mineralized zone of Kylleng Pyndengsohiong Mawthabah (Domiasiat), Meghalaya in India. The area lies in a plateau region which recieves the highest average annual rainfall (12,000 mm) in the world. The geochemical behaviour of the uranium and its daughter products at such wet climatic conditions imposes restrictions to assess ²³⁸U through gamma lines of radon decay products. Soil samples were collected from nine locations around the uranium mineralization zone for analysis. The ratio of the concentration of uranium obtained from gamma energies of radium daughter products to the 63.29 keV of ²³⁴Th was found to vary from 1.01 to 2.07, which indicates a pronounced disequilibrium between uranium and radium daughters. The results obtained from various gamma energies were validated from the data generated by Instrumental Neutron Activation Analysis (INAA) technique. The ²³⁸U activities from the two analytical methods show a well fitted regression line with correlation coefficient 0.99 which validates the reliability of 63.29 keV energy for estimation of uranium in such conditions.     

Assessment of the global fallout of plutonium isotopes and americium-241 in the soil of the central region of Saudi Arabia

A radiochemical technique for determination of plutonium isotopes and 241Am in soil samples is tested against IAEA-standard reference materials to determine its accuracy and precision for reliable results. The technique is then used in the investigation of topsoil samples, collected from the natural environment of the central region of Saudi Arabia, to assess the effect of fallout accumulation of these radionuclides in the region. Plutonium and americium were sequentially separated from all other components of the sample by anion-exchange chromatography and co-precipitated with Nd3+ as fluorides. The precipitates were mounted on membrane filters and measured using a high-resolution alpha-spectrometer. The results of the analysis of the reference materials showed satisfactory sensitivity and precision of the technique. The results of the analyzed soil samples show activity levels ranging from < LLD to 0.089 and from 相似文献   

Human bones obtained from routine joint replacement surgery as a tool for studies of plutonium, americium and ⁹⁰Sr body-burden in general public

The paper presents a new sampling method for studying in-body radioactive contamination by bone-seeking radionuclides such as ⁹⁰Sr, ^239+240Pu, ²³⁸Pu, ²⁴¹Am and selected gamma-emitters, in human bones. The presented results were obtained for samples retrieved from routine surgeries, namely knee or hip joints replacements with implants, performed on individuals from Southern Poland. This allowed to collect representative sets of general public samples. The applied analytical radiochemical procedure for bone matrix is described in details. Due to low concentrations of ²³⁸Pu the ratio of Pu isotopes which might be used for Pu source identification is obtained only as upper limits other then global fallout (for example Chernobyl) origin of Pu. Calculated concentrations of radioisotopes are comparable to the existing data from post-mortem studies on human bones retrieved from autopsy or exhumations. Human bones removed during knee or hip joint surgery provide a simple and ethical way for obtaining samples for plutonium, americium and ⁹⁰Sr in-body contamination studies in general public.     

Characterization of plutonium in deep-sea sediments of the Sulu and South China Seas

Anthropogenic Pu isotopes are important geochemical tracers for sediment studies. Their distributions and sources in the water columns as well as the sediments of the North Pacific have been intensively studied; however, information about Pu in the Southeast Asian seas is limited. To study the isotopic composition of Pu, and thus to identify its sources, we collected sediment core samples in the South China Sea and the Sulu Sea during the KH-96-5 Cruise of the R/V Hakuho Maru. We analysed the activities of ^239+240Pu and the atom ratios of ²⁴⁰Pu/²³⁹Pu using isotope dilution sector-field inductively coupled plasma mass spectrometry (SF-ICP-MS). The ²⁴⁰Pu/²³⁹Pu atom ratios in the sediments of both areas (inventory weighted mean: 0.251 for the South China Sea and 0.280 for the Sulu Sea) were higher than the global fallout value (0.178 ± 0.019), suggesting the existence of Pu from the Pacific Proving Grounds in the North Pacific. Low inventories of ^239+240Pu in sediments were observed in the South China Sea (3.75 Bq/m²) and the Sulu Sea (1.38 Bq/m²). Most of the Pu input is still present in the water column. Scavenging and benthic mixing processes were considered to be the main processes controlling the distribution of Pu in the deep-sea sediments of both study areas.     

Uranium isotopes in Tunisian bottled mineral waters

²³⁴U and ²³⁸U activity concentrations and their relative effective doses have been determined in 10 bottled mineral waters in Tunisia. Alpha spectrometry was used as technique to measure uranium isotopes. The obtained isotopic ratio ²³⁴U/²³⁸U varies between 1.1 and 3 which means that the two isotopes are not in radioactive equilibrium. Measured activity concentration varies between 3.2 and 40 mBq/l for ²³⁴U and between 1.5 and 26.3 mBq/l for ²³⁸U. Effective doses (assuming 2 litres per day of water consumption) coming from this two isotopes are found to vary between 0.16 and 2.02 μSv/a which is lower than the maximum recommended dose level by the WHO.     

Bioaccumulation and distribution of plutonium in fish from Gdansk Bay

In this paper, the results of 238Pu and 239 + 240Pu determinations in four representative species of Baltic fish collected in Gdansk Bay; flounder, herring, cod and sprat, are presented and discussed. The plutonium isotopes are amongst the more radiotoxic nuclides. In the marine environment, the highest concentrations of plutonium are found in the sediments, but the complex biogeochemical cycle of the element means that it is also found in all other compartments. The activities of the fish samples were measured using alpha spectrometry and the concentrations of plutonium 238Pu and 239 + 240Pu were estimated for particular organs and tissues and the whole body. The 239 + 240Pu concentrations for fish species were: flounder 0.94 mBq kg-1 w.w., herring 2.22 mBq kg-1 w.w., cod 2.35 mBq kg-1 w.w. and sprat 0.33 mBq kg-1 w.w. On the basis of the 238Pu/239 + 240Pu activity ratio in the organs and tissues, the proportion of Chernobyl-derived plutonium in the Baltic Sea was calculated. The lowest values of Chernobyl plutonium were accumulated in flounder stomach, herring skin, cod intestine, the highest in cod gills and skin.     

Seasonal and spatial variability of Po,U and Pu levels in the river catchment area assessed by application of neural-network based classification

The present study deals with the application of self-organizing maps (SOM) in order to model, classify and interpret seasonal and spatial variability of ²¹⁰Po, ²³⁸U and ^239+240Pu levels in the Vistula river basin. The data set represents concentration values for 3 alpha emitters (²¹⁰Po, ²³⁸U and ^239+240Pu) measured in surface water samples collected at 19 different sampling locations (8 in major Vistula stream while 11 in right or left Vistula tributaries) during four seasons (winter, spring, summer and autumn) in the framework of a one-year quality monitoring study. The advantages of an SOM algorithm, its classification and visualization ability for environmental data sets, are stressed. The neural-network based classification made it possible to reveal specific patterns related to both seasonal and spatial variability. In the middle and upper part of Vistula catchment as well as in the right-shore tributaries, concentrations of ²¹⁰Po and ²³⁸U during summer and winter are the lowest. Concentrations of ²¹⁰Po and ²³⁸U increase significantly during spring and autumn in the Vistula river catchment, especially in the delta of Vistula river. High concentration of anthropogenic originated ^239+240Pu indicates “site-specific” character of pollution in two large left-shore tributaries located in the middle part of the Vistula drainage area. Efficient classification of sampling locations could lead to an optimization of river radiochemical sampling networks and to a better tracing of natural and anthropogenic changes along Vistula river stream.     

Depositional behaviors of plutonium and thorium isotopes at Tsukuba and Mt. Haruna in Japan indicate the sources of atmospheric dust

Monthly plutonium and thorium depositions at Tsukuba (28 m asl) and Mt. Haruna (1370 m asl) were measured during 2006 and 2007 (Jan 2006-Dec 2007 at Tsukuba, Nov 2006-Dec 2007 at Mt. Haruna). The monthly ^239,240Pu depositions ranged from 0.044 to 2.67 mBq m⁻² at Tsukuba and from 0.05 to 0.9 mBq m⁻² at Mt. Haruna during the measurement periods. Monthly ^239,240Pu deposition did not differ markedly between the two sites except in April 2007. Seasonal pattern of monthly ^239,240Pu depositions at both sites showed high in spring and low in summer, and typical of seasonal variations in northeastern Asia. Thorium deposition at Tsukuba was higher than that at Mt. Haruna except in May and June 2007. ²³⁰Th/²³²Th activity ratios were used to partition deposition samples into locally and remotely derived fractions. The results revealed that a major proportion of total ^239,240Pu and Th deposits are derived from remote sources, especially in spring.