Sector field inductively coupled plasma mass spectrometry, another tool for plutonium isotopes and plutonium isotope ratios determination in environmental matrices

The transfer of radio nuclides into the different compartments of the environment are widely studied and leads to the elaboration of transfer models in order to evaluate potential impact onto the environment and humans. Accurate experimental data are needed to validate these models for all types of matrices (air, water, sediments, soils, biota and food...). Among these radionuclides, 238Pu, 239Pu, 240Pu and 241Pu, are often mentioned. They have been released into the environment by nuclear weapon tests, nuclear facilities, reactors or satellite accidents. These different sources have different 240Pu/239Pu ratios and therefore this ratio is used to provide information on the source of contamination into the environment. The most conventional analytical tools used for plutonium isotope determination are liquid scintillation and alpha spectrometry, and thermal ionisation mass spectrometry (TIMS) is still considered as the primary method for determination of plutonium isotope ratios. During the last decade, mass spectrometers equipped with plasma ion sources and sector field analysers were developed and can offer now another alternative method for the accurate determination of isotope content and ratios of long-lived radionuclides in environmental samples. This paper presents and discusses the results obtained for 239Pu, 240Pu and 241Pu content and isotope ratios by sector field ICP-MS in different environmental matrices.     

An overview of BORIS: Bioavailability of Radionuclides in Soils

The ability to predict the consequences of an accidental release of radionuclides relies mainly on the level of understanding of the mechanisms involved in radionuclide interactions with different components of agricultural and natural ecosystems and their formalisation into predictive models. Numerous studies and databases on contaminated agricultural and natural areas have been obtained, but their use to enhance our prediction ability has been largely limited by their unresolved variability. Such variability seems to stem from incomplete knowledge about radionuclide interactions with the soil matrix, soil moisture, and biological elements in the soil and additional pollutants, which may be found in such soils. In the 5th European Framework Programme entitled Bioavailability of Radionuclides in Soils (BORIS), we investigated the role of the abiotic (soil components and soil structure) and biological elements (organic compounds, plants, mycorrhiza, and microbes) in radionuclide sorption/desorption in soils and radionuclide uptake/release by plants. Because of the importance of their radioisotopes, the bioavailability of three elements, caesium, strontium, and technetium has been followed. The role of one additional non-radioactive pollutant (copper) has been scrutinised in some cases. Role of microorganisms (e.g., K(d) for caesium and strontium in organic soils is much greater in the presence of microorganisms than in their absence), plant physiology (e.g., changes in plant physiology affect radionuclide uptake by plants), and the presence of mycorrhizal fungi (e.g., interferes with the uptake of radionuclides by plants) have been demonstrated. Knowledge acquired from these experiments has been incorporated into two mechanistic models CHEMFAST and BIORUR, specifically modelling radionuclide sorption/desorption from soil matrices and radionuclide uptake by/release from plants. These mechanistic models have been incorporated into an assessment model to enhance its prediction ability by introducing the concept of bioavailability factor for radionuclides.     

Fractionation of natural radionuclides in soils from a uranium mineralized area in the south-west of Spain

A new version of a classical method was applied to study the distribution of natural radionuclides (238U, 230Th, and 226Ra) in the soil fractions obtained by a sequential extraction procedure. The potential significance of the fractions obtained with this method was tested on two very similar soils but with very different contents of the three radionuclides, collected in the proximity of a disused uranium mine located in the Extremadura region in the south-west of Spain. The results confirmed that, if only non-residual fractions are considered, the sequential method applied shows a characteristic speciation pattern of these natural radionuclides in this soil matrix, i.e., the distribution of each of the three radionuclides was very similar for the two soil samples.     

The use of extraction chromatography resins to concentrate actinides and strontium from soil for radiochromatographic analyses

An analytical technique utilizing selective extractant resins to concentrate strontium and actinides from soil followed by separation with radiochromatography was evaluated. The technique was tested using uncontaminated soil samples spiked with a radionuclide tracer solution that were either microwave-aided acid digested or leached with a strong acid. Extraction of the strontium and actinides from the acidified solution was accomplished using a serial arrangement of Sr-Resin and TRU-Resin columns. The combined eluate solutions from the extraction resins were treated with HNO(3) and H(2)O(2) to oxidize residual extractant and eluates prior to separation and analysis of the radionuclides by radiochromatography. Chromatograms obtained with larger soil mass loadings resulted in either incomplete peak resolution of the tracers or had highly variable peak elution times, indicative of an ionic interfering constituent(s). Better separations (e.g., chromatograms that resolved all radioactive constituents) were obtained when the sample mass loading was decreased, but with a concurrent decreased sensitivity for the radionuclides. Elemental analyses of the soil were conducted to provide data on the ionic constituents in unprocessed soil and post-processed soil samples. These results identified aluminum as an interfering contributor to the poor performance exhibited by the radiochromatographic separations.     

Non-invasive matrices in human biomonitoring: a review

Humans and other living organisms are exposed to a variety of chemical pollutants that are released into the environment as a consequence of anthropogenic activities. Environmental pollutants are incorporated into the organism by different routes and can then be stored and distributed in different tissues, which leads to an internal concentration that can induce different alterations, adverse effects and/or diseases. Control measures should be taken to avoid these effects and human biomonitoring is a very useful tool that can contribute to this aim. Human biomonitoring uses different matrices to measure the target chemicals depending on the chemical, the amount of matrix necessary for the analysis and the detection limit (LOD) of the analytical technique. Blood is the ideal matrix for most chemicals due to its contact with the whole organism and its equilibrium with organs and tissues where chemicals are stored. However, it has an important disadvantage of being an invasive matrix. The development of new methodology and modern analytical techniques has allowed the use of other matrices that are less or non-invasive, such as saliva, urine, meconium, nails, hair, and semen or breast milk. The presence of a chemical in these matrices reflects an exposure, but correlations between levels in non-invasive matrices and blood must be established to ensure that these levels are related to the total body burden. The development of new biomarkers that are measurable in these matrices will improve non-invasive biomonitoring. This paper reviews studies that measure Cd, Pb, Hg, polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), polycyclic aromatic hydrocarbons (PAHs), polybrominated diphenyl ethers (PBDEs), organochlorine pesticides and phthalates in non-invasive matrices, the most used techniques for measurements and what alternative techniques are available.     

Studies on the distribution of 210Po and 210Pb in the ecosystem of Point Calimere Coast (Palk Strait), India

A systematic study on the natural radionuclides such as 210Po and 210Pb in the environmental matrices of Point Calimere ecosystem has been undertaken to establish a baseline data on the radiation profile of Point Calimere environment. The environmental samples such as water, sediment and biota (seaweeds, crustaceans, molluscs and fish) have been subjected to analyses. It has been observed that the concentration of 210Po and 210Pb in the water samples of Point Calimere to be 0.5 mBq/l and 1.3 mBq/l, respectively. The soft tissues of the organisms accumulated higher 210Po content while shells and bones contained more 210Pb. The bivalve molluscs Meretrix casta have been identified to accumulate higher concentration of 210Po suggesting that they could serve as bio-indicator of radionuclides like 210Po in the Point Calimere ecosystem. The concentration factor of 210Po for the biotic components ranged from approximately 10(3) to 10(6) while for 210Pb it ranged from approximately 10(3) to 10(5).     

Radioactive discharges from an alkaline pulp mill located in the south of Spain

Artificial and natural radionuclides present in environmental samples (Eucalyptus wood and bark) can be transferred in an alkaline pulp mill and concentrated in the recycling process. Some part of the radionuclides can be released into the environment associated with the discharges from such a factory. An alkaline pulp mill located in the South of Spain was extensively sampled during 1993 and different radionuclides analysed in the collected samples. Thus the concentrations and fluxes of natural (40K, 226Ra, 228Ra and 228Th) and artificial (137Cs and 90Sr) radionuclides associated with the samples collected along the pulp production process are presented. It is shown that radium and thorium radionuclides behave similarly to strontium and calcium and, consequently, concentrate within the Ca-cycle. Furthermore, 40K and 137Cs are concentrated during the Na-cycle. Finally, the results obtained by the authors are compared with the levels found in similar factories, though situated in the North of Europe, by other researchers.     

Speciation of radionuclides - analytical challenges within environmental impact and risk assessments

The mobility, biological uptake and accumulation of radionuclides are essentially dependent on the physico-chemical form of the nuclides. As a major fraction of refractory radionuclides released during historical nuclear events is associated with particles, a key analytical challenge within environmental impact and risk assessments is to characterise radioactive particles with respect to properties influencing particle weathering, remobilisation and the subsequent ecosystem transfer of associated radionuclides. Preanalysis techniques are needed to fractionate, identify and localize individual particles in contaminated samples. To obtain information on particle characteristics such as particle size distributions, structures, elemental and radionuclide particle composition as well as oxidation state of matrix elements, solid-state speciation techniques are needed. Electron microscopy as well as X-ray microscopic techniques utilising synchrotron X-ray radiation have proved most useful in providing such information. The present paper summarises the present status on advanced techniques and presents historical sources that have contributed to radioactive particle contamination.     

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.     

Radioactive and radiogenic isotopes in sediments from Cooper Creek, Western Arnhem Land

Protection of the environment post-mining is a key objective of rehabilitation, especially where runoff and erosion from rehabilitated mine sites could potentially lead to contamination of the surrounding land and watercourses. As part of an overall assessment of the success of rehabilitation at the former Nabarlek uranium (U) mine, an appraisal of stable lead (Pb) isotopes, radionuclides and trace metals within sediments and soils was conducted to determine the off site impacts from a spatial and temporal perspective. The study found localised areas on and adjacent to the site where soils had elevated levels of trace metals and radionuclides. Lead isotope ratios are highly radiogenic in some samples, indicating the presence of U-rich material. There is some indication that erosion products with more radiogenic Pb isotope ratios have deposited in sediments downstream of the former ore body. However, there is no indication that the radiogenic erosion products found on the mine site at present have significantly contaminated sediments further downstream of Cooper Creek.     

Invariance of isotope ratios of lithogenic radionuclides: more evidence for their use as sediment source tracers

Activities of radionuclides in the 238U (230Th, 226Ra, 210Pb) and 232Th (232Th, 228Th, 228Ra) decay series were determined in sediments from an east Texas watershed and examined with isotope ratios and compared to particulate organic carbon (POC), % fines (<63 microm) and total concentrations of Al, Fe and Mn. The objective was to elucidate the presence or absence of relationships affecting the effectiveness of these radionuclides in modeling sediment transport. Strong positive correlations were observed between radionuclides and Mn (Th) and % fines (Ra and Th). Isotope ratios effectively reduce these influences, supporting the contention that isotope ratios offset extrinsic variability in terrestrial sediments. Strong associations of 210Pbxs (excess 210Pb) and 226Ra/230Th with POC agree with data from marine and terrestrial settings, indicating that the role of POC in isotope fractionation, transport and sequestration merits further investigation.     

A rapid isotope ratio analysis protocol for nuclear solid materials using nano-second laser-ablation time-of-flight ICP-MS

The analysis of the isotopic composition of nuclear or non-nuclear solid materials is performed in a variety of fields, e.g., for quality assurance in the production of nuclear fuels, as signatures in forensics, nuclear safeguards, and non-proliferation control, in material characterization, geology, and archeology. We have investigated the capability of laser ablation (New Wave Research, 213 nm) coupled to time-of-flight (TOF) ICP-MS (GBC OptiMass 8000) as a rapid analytical protocol for multi-isotope screening of nuclear and non-nuclear solid samples. This includes natural and non-natural isotopic compositions for elements including Cu, Zr, Mo, Cd, In, Ba, Ta, W, Re, Pt, Pb, and U, in pure metals, alloys, and glasses. Without correcting for mass bias (mass fractionation), an overall precision and accuracy of about 4% (1σ) can be achieved by minimizing the deposited laser power and thus fractionation (mass removal based on thermal properties). The precision and accuracy in combination with literally no or minimized sample preparation enables a rapid isotope screening of solid samples that is of particular interest to support nuclear forensic and safeguard analysis.     

Determination of dose rates from natural radionuclides in dental materials

Different types of materials used for dental prosthetics restoration, including feldspathic ceramics, glass ceramics, zirconia-based ceramics, alumina-based ceramics, and resin-based materials, were investigated with regard to content of natural radionuclides by means of thermoluminescence beta dosimetry and gamma spectrometry. The gross beta dose rate from feldspathic and glass ceramics was about ten times higher than the background measurement, whereas resin-based materials generated negligible beta dose rate, similarly to natural tooth samples. The specific activity of uranium and thorium was significantly below the levels found in the period when addition of uranium to dental porcelain materials was still permitted. The high-beta dose levels observed in feldspathic porcelains and glass ceramics are thus mainly ascribable to (40)K, naturally present in these specimens. Although the measured values are below the recommended limits, results indicate that patients with prostheses are subject to higher dose levels than other members of the population. Alumina- and zirconia-based ceramics might be a promising alternative, as they have generally lower beta dose rates than the conventional porcelain materials. However, the dosimetry results, which imply the presence of inhomogeneously distributed clusters of radionuclides in the sample matrix, and the still unsuitable structural properties call for further optimization of these materials.     

Concentrations of natural radionuclides in imported mineral substances

Levels of natural radionuclides, such as thorium-232 (232Th), radium-226 (226Ra) and potassium-40 (40K), were determined in about 2,000 samples of imported mineral substances using gamma spectrometry. The maximum concentration levels of 232Th, 226Ra and 40K were 1,260 +/- 54, 13,400 +/- 94 and 1,256 +/- 260 Bq kg(-1), respectively, in zirconium compounds. Due to relatively high concentrations of the above-mentioned radionuclides in some imported mineral substances, the National Radiation Protection Department (NRPD), as the competent authority, has established national limits (900 Bq kg(-1) for 232Th, 1800 Bq kg(-1) for 226Ra and 11,000 Bq kg(-1) for 40K), based on the external exposures, for general importation permits of these materials.     

Distribution and mobilization of U, Th and 226Ra in the plant-soil compartments of a mineralized uranium area in south-west Spain

The activity concentrations of natural uranium isotopes (238U and 234U), thorium isotopes (232Th, 230Th and 225Th) and 226Ra were studied in soil and vegetation samples from a disused uranium mine located in the Extremadura region in the south-west of Spain. The results allowed us to characterize radiologically the area close to the installation and one affected zone was clearly manifest as being dependent on the direction of the surface water flow from the mine. The activity concentration mean values (Bq/kg) in this zone were: 10,924, 10,900, 10,075 and 5,289 for 238U, 234U, 230Th and 226Ra, respectively, in soil samples and 1,050, 1,060, 768 and 1,141 for the same radionuclides in plant samples. In an unaffected zone, the activity concentration mean values (Bq/kg) were: 184, 190, 234 and 7251 for 235U, 234U, 230Th and 226Ra, respectively, in soil samples and 28. 29, 31 and 80 in plant samples. The activity concentrations obtained for 232Th and 228Th showed that the influence of the mine was only important for the uranium series radionuclides. The relative radionuclide mobilities were determined from the activity ratios. Correlations between radionuclide activity concentrations and stable element concentrations in the soil samples helped to understand the possible distribution paths for the natural radionuclides.     

Natural radioactivity in phosphates, phosphogypsum and natural waters in Morocco

The contents of natural radionuclides (uranium, actinium and thorium series) were measured in sedimentary phosphate rock samples using high-resolution gamma spectrometry. Data obtained for uranium content (ppm) were compared with the results obtained by a method based on the measurements using solid-state nuclear track detectors (SSNTD) in the same samples. The potential leaching of radionuclides from sedimentary phosphate rock during the industrial production of the phosphoric acid was studied. The process of leaching of the radioisotopes from phosphogypsum was discussed. A method for the direct alpha counting of 226Ra thin source, elaborated by the deposition of Ra from aqueous solutions on manganese oxides film deposited on polyvinyl support, have been developed and applied for the determination of 226Ra in natural water samples. The results show that only the water sample from the mine area reveals the presence of 226Ra at a level of about 0.2 Bq l-1.     

Transfer of radium-228, thorium-228 and radium-226 from forage to cattle and reindeer

Concentrations of radium-228, thorium-228 and radium-226 were measured in different natural forage materials and in feed supplements. The activity concentrations of these nuclides were then determined in the bones of domestic farm animals, with emphasis on their distributions within the skeleton and humerus. Feeds added in recent years to the forage of domestic animals alter the concentrations of the naturally occurring radionuclides. The modified daily radium uptakes associated with the various feeds are reflected in the radium concentrations observed in the different layers of the humerus. Radium uptake and retention are highly dependent on calcium metabolism.We propose a method for calculation of nuclide retention coefficients via an approach which simplifies theis assesssment and provides important information on radium metabolism. The data obtained here are of value in dosimetric assessments related to these natural radionuclides.     

甘南州生态补偿区域空间选择方案的比较

在预算约束和无预算约束条件下，分别模拟了6种不同的生态补偿区域选择方案，并采用比较研究方法，从补偿资金效率、补偿对象特征、吸纳的贫困人口、补偿额的分配情况、生态重要性、生态脆弱性和项目成本等7个方面对6种方案进行了对比分析。结果表明：风险效益成本比标准方案的补偿资金效率最高，在生态重要性和生态脆弱性方面占优势，但方案的参与率最低，补偿的乡镇数量和贫困人口最少，在项目成本方面占劣势；效益成本比标准方案的补偿资金效率和参与率较高，补偿乡镇数量较多，贫困人口的参与率最高，在生态重要性和项目成本方面占优势，但在生态脆弱性方面占劣势；效益标准方案的补偿资金效率较高，补偿的乡镇数量较多，参与率最高，补偿的贫困人口最多，在生态重要性和生态脆弱性方面占优势，但补偿面积最少，在项目成本方面占劣势；成本标准方案的补偿面积最大，补偿的乡镇数量最多，参与率较高，补偿的贫困人口也较多，在生态重要性和项目成本方面占优势，但补偿资金效率最低，在生态脆弱性方面占劣势；如果不存在预算约束，只考虑生态脆弱性，风险标准方案最合适，可避免处于退化风险的草地没有得到补偿；统一标准方案可补偿整个区域，亩均补偿额相同，补偿额在补偿区上分配公平，方案实施便利，简单易行，但需要庞大的资金预算，且实施困难较大,补偿资金效率很低     

Status report on standard-setting work in the area of environmental radioactivity measurement

Environmental assessment studies are regularly commissioned to study the impact of radioactive substances on the environment and the public, in response to concern about the presence of such substances. The credibility of such studies relies on the quality and reliability of radionuclide analysis as well as the sample representativity of the radiological situation. The recent expansion from national stakeholders to those involving other states requires that activity measured in effluents or environmental samples in a country are reliable and reproducible so as to be accepted by all states potentially concerned by regional contamination. The standard-setting approach, based on consensus, seemed to lend itself to a settlement of technical aspects of potential dispute. This document describes standardization organizations, French and international, the standards published, as well as standardization work under way on the measurement of radionuclides found in environmental matrices.     

Soil-to-plant transfer factors for natural radionuclides and stable elements in a Mediterranean area

The transfer factors (TF) for natural uranium isotopes (238U and 234U), thorium isotopes (232Th, 230Th and 228Th), and 226Ra were obtained in plant samples (grass-pasture) growing in granitic and alluvial soils around a disused uranium mine located in the Extremadura region in the south-west of Spain. Affected and non-affected areas of the mine presented large differences in the activity concentrations of radionuclides of the uranium series. We also determined transfer factors for several stable elements (essential and non-essential). A set of statistical tests were applied to validate the data. The results showed that the transfer factors for both the natural radionuclides and the stable elements are independent of the two substrate types involved and also of the two areas considered in the study.