Plutonium and americium in sediment samples along the Romanian sector of the Danube river and the Black Sea coast

The concentrations of²³⁸Pu,^239,240Pu and²⁴¹Am were determined in eight sediment samples, collected from the bed of the Romanian sector of the Danube river and the Black Sea coast during 1994 and 1995. Fusion with potassium carbonate was used to achieve complete dissolution of the samples. Tracers,²⁴²Pu and²⁴³Am, were added and the separation of plutonium from americium, uranium and thorium was performed by anion exchange. Americium was separated from uranium in two steps, using a conventional anion exchange resin and an extraction chromatographic resin for transuranics. After electrodeposition on stainless steel discs the nuclides were counted with -spectrometry with -PIPS detectors. The total plutonium concentrations obtained by this method were compared with the acid leachable plutonium concentrations reported for the same samples in a previous paper.     

Plutonium Isotopes in Sediments from the Sudanese Coast of the Red Sea

This paper presents the activity concentrations of Pu isotopes in surface marine sediments collected from the Sudanese coast of the Red Sea. The following concentration ranges were determined: ²³⁸Pu, 4.7–28.6 mBq/kg; ^239+240Pu, 53–343 mBq/kg dry weight. The average activity ratios of ²³⁸Pu/^239+240Pu (0.075±0.045 mBqk/kg) and ^239+240Pu/¹³⁷Cs (0.026±0.025 mBq/kg) are appropriately comparable to the literature values that are characteristic of the global fallout from the atmospheric nuclear weapon tests. However, ^239+240Pu/¹³⁷Cs ratio in sediments collected from the biologically rich fringing reef is an order of magnitude higher compared to other sampling locations.     

Simultaneous determination of plutonium and americium in soils by extraction chromatography

A radiochemical method is described for the determination of²³⁸Pu,^239(240)Pu and²⁴¹Am in a single soil sample. Plutonium is separated from a HNO₃ leaching solution by a Microthene-TNOA column; amcricium is coprecipitated by oxalic acid, decontaminated from polonium by a TNOA-column in HCl medium, separated from the rare earth elements by a Microthene-HDEHP column, eluted with a 0.07M DTPA+1M lactic acid solution and finally purified by a PMBP-TOPO extraction. The method supplies a good decontamination of Am and Pu from natural alpha emitters; starting from 50 g soil, the average yields were 75.1±13.4% for plutonium and 57.7±10.8% for Am.^239(240)Pu,²³⁸Pu and²⁴¹Am concentrations (mBq/kg) in three different kinds of soil were the following: 255, 10.4, 81.3 (uncultivated soils); 236, 11.6, 76.7 (cultivated soils); 46, 1.9, 19.8 (river sediment). The average ratios²³⁸Pu to^239(240)Pu and²⁴¹Am to^239(240)Pu were 0.044 and 0.350, respectively.     

Artificial radioactive contamination of sediment samples along the Romanian sector of the Danube river and the Black Sea coast

The concentrations of¹³⁷Cs were determined by in 11 sediment samples, collected along the Romanian sector of the Danube river and the Black Sea coast during 1994 γ-ray spectrometry. The concentrations of⁹⁰Sr in the same sediment samples were determined by β-counting of the⁹⁰Y oxalate, precipitated after strontium separation using a strontium extraction chromatography column. The concentration distributions of¹³⁷Cs and⁹⁰Sr are compared with the²³⁸Pu and^239,240Pu concentration distributions in the same samples, reported in a previous paper. The accumulation potential of¹³⁷Cs,⁹⁰Sr and plutonium isotopes in the river and sea sediments analysed is discussed.     

Procedures to define Pu isotopic ratios characterizing a contaminated area in Palomares (Spain)

Plutonium isotopic ratios have been calculated in soils contaminated by the Palomares accident which occurred in 1966 (Almería, Southeastem Spain). Contrasted techniques have been used to determine the radionuclide activities:²³⁸Pu and^238+240Pu were analysed by -spectrometry prior purification on anion-exchange resins, the ratio²³⁹Pu/²⁴⁰Pu was estimated by -spectra deconvolution and²⁴¹Pu was directly measured by liquid scintillation counting and indirectly through quantification of in-grown²⁴¹Am from aged plutonium discs. The mean activity ratios²³⁸Pu/²³⁹Pu,²³⁹Pu/²⁴⁰Pu,²⁴¹Pu/²³⁹Pu, backdated to 1966, were 0.027±0.002 (1), 4.5±0.2 (1) and 8.2±0.8 (1), respectively, characterizing the accident of Palomares as the source term of the measured plutonium.     

241Pu in the biggest Polish rivers

In the paper the results of ²⁴¹Pu activity concentration determination in the biggest Polish rivers are presented. The analysis of more than 100 river water samples showed the Vistula and the Odra as well as three Pomeranian Rivers are important sources of ²⁴¹Pu in the southern Baltic Sea. There were differences in ²⁴¹Pu activities depending on season and sampling site and the plutonium contamination came mainly from the global atmospheric fallout as well as the Chernobyl accident, which is confirmed by plutonium activity ratios of ²⁴¹Pu/^239+240Pu and ²³⁸Pu/^239+240Pu.     

Alpha-emitting radionuclide contents in food samples as related to the Chernobyl accident

As a preliminary survey to establish intake of -emitting nuclides, in particular^239,240Pu, from a daily diet for inhabitants living near the Chernobyl reactor site, some kinds of food samples including total diet samples were collected in the Chernobyl (Ukraine) area and in the Ibaraki prefecture (Japan). Plutonium-239 and 240 were determined together with naturally occurring -emitters²²⁶Ra and U isotopes (²³⁴U,²³⁵U and²³⁸U) by -spectrometry after chemical separation. In most of the samples studied,^239,240Pu was less than the detectable amount, but in some mushrooms from the Ukraine it was found to be 41.6 mBq kg^–1 (wet mass) with a high activity ratio(0.58±0.08) of²³⁸Pu/^239,240Pu, indicating that nearly 100% of the^239,240Pu was attributable to the accident. Concentrations of²²⁶Ra and²³⁸U varied largely, depending on the samples. The measured activity ratios of²³⁵U/²³⁸U for some samples showed the isotopic composition of natural uranium.     

Vertical profiles of 239+240Pu in seawater from the East China Sea

Seawater samples were collected from the East China Sea continental shelf and analyzed for ^239+240Pu activities. The vertical profiles of ^239+240Pu had a similarity for all three stations in the East China Sea. ^239+240Pu concentrations were low in the surface layer (3-4 mBq/m³) and increased gradually with depth to become high in the near-bottom layer (7-10 mBq/m³). ^239+240Pu concentrations in seawater and the concentrations of suspended particles showed almost the same vertical profiles in the East China Sea continental shelf. The maximum value of ^239+240Pu found in the near-bottom layer may be due to the contribution of Pu-rich suspended particles.     

240Pu/239Pu atom ratios in the bottom sediments of the NW Pacific Ocean

^239+240Pu concentrations and ²⁴⁰Pu/²³⁹Pu atom ratios in bottom sediments of the Yellow Sea, Korea Strait, East Sea (Sea of Japan), Sea of Okhotsk, and Northwest Pacific Ocean were determined. In coastal sediments near the Korean Peninsula, ^239+240Pu concentrations varied from 0.02 to 1.72 Bq^.kg^-1, and their ²⁴⁰Pu/²³⁹Pu atom ratios from 0.15 to 0.24, with an average of 0.20±0.03. ²⁴⁰Pu/²³⁹Pu atom ratios of bottom sediments in the deep NW Pacific Ocean and its marginal seas (East, Okhotsk seas) were in the range of 0.15-0.23. A little elevated ²⁴⁰Pu/²³⁹Pu atom ratios in the bottom layer sediment may be due to Pu released into the environment during the pre-moratorium period, having high ²⁴⁰Pu/²³⁹Pu atom ratios and low ²³⁸Pu/^239+240Pu activity ratios.     

Polonium concentration distribution in bed load sediment samples along the Romanian sector of the Danube river and the Black Sea coast

The concentrations of²¹⁰Po have been determined in 12 sediment samples collected from the bed of the Romanian Danube river and the Black Sea coast during June–September 1994. After the sample preparation and the addition of the²⁰⁸Po tracer, polonium was coprecipitated with manganese dioxide, the precipitate was dissolved in hydrochloric acid and the polonium isotopes deposited on silver planchettes were counted by -spectrometry. The resolution of the subsequent -spectra was typically 40 to 60 keV full-width-half-maximum with 450 mm² silicon surface-barrier detectors at 30% counting efficiency. The procedure is quite fast, giving chemical yields between 60 and 80%. The²¹⁰Po concentrations range between 5 and 73 Bq kg^–1 dry, showing for the first time the polonium contamination distribution along the Romanian sector of the Danube river and the Black Sea coast.     

239+240Pu and137Cs concentrations in salmon (Oncorhynchus keta) collected on the Pacific coast of Japan

Salmon (Oncorhynchus keta) samples were collected on the Pacific coast of Japan and analyzed for their^239+240Pu and¹³⁷Cs concentrations in six places, i.e., muscle, viscera, gill, gonad, skin and spine. The^239+240Pu concentrations in muscle ranged from 0.07 to 0.14 mBq/kg (wet) and had the lowest value among the six regions. The mean^239+240Pu concentrations in viscera, gonad and spine were more than 1 mBq/kg (wet_ while those in muscle and skin were one order of magnitude lower. The largest amounts of^239+240Pu were accumulated in gonad. The^239+240Pu/¹³⁷Cs activity ratios in all positions were lower than that of the global fallout ratio of 0.022, suggesting that¹³⁷Cs could be accumulated with greater ease than^239+240Pu in all positions and ratios of uptake differed remarkably from position to position. The total accumulations of^239+240Pu and¹³⁷Cs in salmon were 1.32 and 328 mBq/individual, respectively.     

Application of isotope-dilution laser ablation ICP–MS for direct determination of Pu concentrations in soils at pg g<Superscript>−1</Superscript> levels

The methods available for determination of environmental contamination by plutonium at ultra-trace levels require labor-consuming sample preparation including matrix removal and plutonium extraction in both nuclear spectroscopy and mass spectrometry. In this work, laser-ablation inductively coupled plasma mass spectrometry (LA–ICP–MS) was applied for direct analysis of Pu in soil and sediment samples. Application of a LINA-Spark-Atomizer system (a modified laser ablation system providing high ablation rates) coupled with a sector-field ICP–MS resulted in detection limits as low as 3×10^–13 g g^–1 for Pu isotopes in soil samples containing uranium at a concentration of a few g g^–1. The isotope dilution (ID) technique was used for quantification, which compensated for matrix effects in LA–ICP–MS. Interferences by UH⁺ and PbO₂⁺ ions and by the peak tail of ²³⁸U⁺ ions were reduced or separated by use of dry plasma conditions and a mass resolution of 4000, respectively. No other effects affecting measurement accuracy, except sample inhomogeneity, were revealed. Comparison of results obtained for three contaminated soil samples by use of -spectrometry, ICP–MS with sample decomposition, and LA–ICP–IDMS showed, in general, satisfactory agreement of the different methods. The specific activity of ^239+240Pu (9.8±3.0 mBq g^–1) calculated from LA–ICP–IDMS analysis of SRM NIST 4357 coincided well with the certified value of 10.4±0.2 mBq g^–1. However, the precision of LA–ICP–MS for determination of plutonium in inhomogeneous samples, i.e. if "hot" particles are present, is limited. As far as we are aware this paper reports the lowest detection limits and element concentrations yet measured in direct LA–ICP–MS analysis of environmental samples.Sergei F. Boulyga is on leave from The Radiation Physics and Chemistry Problems Institute, 220109 Sosny, Minsk, Belarus.     

Identification of the contamination source of plutonium in environmental samples with isotopic ratios determined by inductively coupled plasma mass spectrometry and alpha-spectrometry

Concentrations of^239+249Pu in environmental samples were detemined by ICP-MS and spectrometry, showing consistent results, which suggests an applicability of ICP-MS to²³⁹Pu and²⁴⁰Pu measurement. The activity ratios of²³⁸Pu/^239+240Pu and²⁴⁰Pu/²³⁹Pu were significantly different in samples from the general environment and near Sellafield reprocessing plants, indicating the usefulness of these ratios for identification of the Pu contamination source.     

Activity concentrations of selected artificial and natural radionuclides in water and sediment samples from the North Western Black Sea, 1999

Radioactive concentrations of several artificial and natural radionuclides were determined in water and sediment samples collected from various locations in the NW Black Sea in December 1999. For water samples, ⁹⁰Sr and ¹³⁷Cs activity concentrations were of approximately 11 mBq/l and 26.3-41.2 mBq/l, respectively. The concentration of tritium ranged from 7 to 24 T.U. In sediment samples, maximum concentrations of ¹³⁷Cs, ^239+240Pu and ²⁴¹Am were found of 128±6 Bq·kg^-1, 1.8±0.1 Bq·kg^-1 and 0.05±0.04 Bq·kg^-1, respectively. For U and Th radionuclides, the concentrations ranged from 20-80 Bq·kg^-1 and 30-50 Bq·kg^-1, respectively. The results were consistent with those reported in earlier research for the Black Sea. This revised version was published online in July 2006 with corrections to the Cover Date.     

Simultaneous determination of238Pu,239+240Pu,241Pu,241Am,242Cm,244Cm,89Sr,and90Sr in vegetation samples,and application to Chernobyl-fallout contaminated grass

A radiochemical procedure is described for the simultaneous determination of²³⁸Pu,^239+240Pu,²⁴¹Pu,²⁴¹Am,²⁴²Cm,²⁴⁴Cm,⁸⁹Sr, and⁹⁰Sr in vegetation samples. The method was applied for the determination of these, radionuclides in grass, collected near Munich after the fallout from the reactor accident at Chernobyl, USSR. The specific activities observed were (in Bq kg^–1 dry weight):²³⁸Pu, 0.077;^239+240Pu, 0.15;²⁴¹Pu, 3.9;²⁴¹Am, 0.031;²⁴²Cm, 3.0;²⁴⁴Cm, 0.008;⁸⁹Sr, 2000;⁹⁰Sr, 99.     

ICP-MS analysis of plutonium activities and <Superscript>240</Superscript>Pu/<Superscript>239</Superscript>Pu ratio in alpha spectrometry planchet deposits

Plutonium isotopes were measured by alpha-spectrometry and ICP-MS in sediment samples from two European lakes: Blelham Tarn in U.K. and Stechlin lake in Germany. The ICP-MS measurements were made after alpha-spectrometry counting of the planchets. The planchets were prepared by traditional electrodeposition method after radiochemical extraction, separation and purification of the Pu fraction. A short radiochemical separation using plutonium selective resin, between the two spectrometry measures, is presented. The results show that these two complementary methods are in good agreement, the plutonium activity concentrations are the same. Alpha-spectrometry allows the ²³⁸Pu determination and ICP-MS individual measurement of ²³⁹Pu and ²⁴⁰Pu. ²³⁸Pu/^239+240Pu and ²⁴⁰Pu/²³⁹Pu ratios are calculated to determine the plutonium contamination source. With the results of these two techniques, it could be demonstrate that the plutonium is of global fallout origin.     

Sequential separation and determination of plutonium, americium-241 and strontium-90 in soils and sediments

A sensitive and reliable metbod for the sequential separation and determination of plutonium,²⁴¹Am and⁹⁰Sr in soil samples was developed. Plutonium was separated by a Microthene-TNOA column. Then⁹⁰Y (for⁹⁰Sr determination) was separated from americium by a HDEHP column after elimination of large amounts of interfering stable or radioactive nuclides (iron,²¹⁰Bi and²¹⁰Po etc.) by an oxalate precipitation and a Microthene-TNOA column. Finally americium was purified by another HDEHP column and a PMBP-TOPO extraction. A special attention was paid to the decontamination of Pu and Am from²¹⁰Po and of⁹⁰Y from²¹⁰Bi; the relevant decontamination factors resulted greater than 10⁵, 10⁶ and 10⁴ respectively. The detection limits were 1.2 mBq/kg for Pu and 1.7 mBq/kg for²⁴¹Am and 0.32 Bq/kg for⁹⁰Sr. The procedure was checked by analyzing three certified samples supplied by IAEA. Some Italian soil samples were also analyzed giving average yields of 84.9±7.2% for Pu, 57.8±3.2%for Am and 96.7±1.6% for Y; the^239+240Pu,²³⁸Pu,²⁴¹Am and⁹⁰Sr contents (Bq/kg) ranged from 0.347 to 1.53, from 0.013 to 0.048, from 0.126 to 0.556 and from 2.89 to 11.6 respectively and the average ratios were 0.037±0.017 for²³⁸Pu/^239+240Pu, 0.357±0.040 for²⁴¹Am/^239+240Pu and 7.0±1.2 for⁹⁰Sr/^239+240Pu.     

Behavior of plutonium isotopes in the marine environment of Enewetak atoll

There continue to be reports in the literature that suggest a difference in the behavior of^239+240Pu and²³⁸Pu in some aquatic environments. Plutonium isotopes have been measured in marine samples collected over 3 decades from Enewetak atoll, one of the sites in the Marshall Islands used by the United States between 1946 and 1958 to test nuclear devices. The plutonium isotopes originated from a variety of complex sources and could possibly coexist in this environment as different physical-chemical species. However results indicate little difference in the mobility and biological availability of^239+240Pu and²³⁸Pu.     

Development of new centrifuges for fast solvent extraction of transactinide elements

Inductively coupled plasma-mass spectrometry (ICP-MS) was used to concurrently determine multiple long-lived (t_1/2>10⁴ y) actinide isotopes in soil leachates. Ultrasonic nebulization was found to maximize instrument sensitivity. Instrument detection limits for actinides in solution ranged from 50 mBq L^–1 (²³⁹Pu) to 2Bq L^–1 (²³⁵U). Hydride adducts of²³²Th and²³⁸U interfered with the determinations of²³³U and²³⁹Pu; thus, extraction chromatography was used to concentrate the analytes and separate uranium from the other actinides in advance of mass spectrometric determination. Alpha spectrometric determinations of²³⁰Th,²³⁹Pu, and the²³⁴U/²³⁸U activity ratio in soil leachates compared well with ICP-MS determinations; however, there were some small systematic differences (ca. 10%) between ICP-MS and -spectrometric determinations of²³⁴U and²³⁸U activities. These differences were attributed to the use of different isotope dilution spikes for ICP-MS and -spectrometry.     

A gamma-spectrometric method for the determination of plutonium isotope ratios

A gamma-spectrometric method using an intrinsic high resolution germanium detector has been developed for the determination of isotope ratios of plutonium from samples in solution form. The method is based on the assay of low energy gamma-rays of²³⁸Pu,²³⁹Pu,²⁴⁰Pu and²⁴¹Pu and does not require the use of branching intensities or the knowledge of detection efficiencies for different gamma rays. Since low energy gamma-rays are used, the effect of²⁴¹Am has also been studied. It is found that results are not affected up to 0.5 wt% of²⁴¹Am in plutonium samples. An accuracy of 3% is achievable in the determination of²⁴⁰Pu/²³⁹Pu and²⁴¹Pu/²³⁹Pu atom ratios as demonstrated by carrying out measurements on isotopic standards of plutonium.