Isotopic and nuclear analytical techniques for health and environment.
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Biomedical subjects
Publications and source records attributed to M Rossbach.
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The IAEA established in 1994 a co-ordinated research programme (CRP) on "Reference Materials for Microanalytical Nuclear Techniques" as part of its efforts to promote and strengthen the use of nuclear analytical technologies in member states with the specific aim of improving the quality of analysis of nuclear, environmental, and biological materials. The objectives of this initiative were: to identify suitable biological reference materials which could serve the needs for quality control in microanalytical techniques; to evaluate existing CRMs for use in microanalytical investigations; to evaluate appropriate sample pretreatment procedures for materials being used for analysis with microanalytical techniques; to identify analytical techniques which can be used for characterisation of homogeneity determination, and to apply such techniques to the characterization of candidate reference materials for use with microanalytical techniques. The CRP lasted for 4 years and seven laboratories and the Agency's Laboratories in Seibersdorf participated. A number of materials including the candidate reference materials IAEA 338 (lichen) and IAEA 413 (single cell algae, elevated level) were evaluated for the distribution of elements such as Cl, K, Ca, Cr, Mn, Fe, Zn, As, Br, Rb, Cd, Hg, and Pb. The results obtained during this CRP suggest that: each element exhibits its characteristic distribution in a matrix described by the "Ingamels' sampling constant" or the "relative homogeneity factor" of Kurfuerst; both concepts are valid over a large range of sample mass used for analysis (from 0.1 microg to around 100 mg); and materials being characterised quantitatively for element homogeneity could be used for the experimental determination of total uncertainty of other analytical techniques. As far as we are aware this is the first time the concept of quantitative characterisation of homogeneity has been applied to potential reference materials and the first demonstration of the feasibility and usefulness of the concept with particular emphasis on enhancing quality control opportunities for microanalytical techniques.
The design of sampling and sample processing has a tremendous effect on the analytical results from which conclusions are drawn with respect to the quality of the environment and any possible impact on human health. Large scale environmental surveys need rigorous planning and extensive screening experiments to evaluate their boundary conditions. Representativeness and sample homogeneity are highlighted here in the context of a long-term biological monitoring survey for trace elements using spruce shoots. Several aspects concerning the selection of samples, amount of material, material processing and sample preparation prior to chemical characterisation are illustrated by selected examples.
Biological indicator organisms have been widely used for monitoring and banking purposes for many years. Although the complexity of the interactions between organisms and their environment is generally not easily comprehensible, environmental quality assessment using the bioindicator approach offers some convincing advantages compared to direct analysis of soil, water, or air. Measurement of air particulates is restricted to experienced laboratories with access to expensive sampling equipment. Additionally, the amount of material collected generally is just enough for one determination per sampling and no multidimensional characterization might be possible. Further, fluctuations in air masses have a pronounced effect on the results from air filter sampling. Combining the integrating property of bioindicators with the world wide availability and particular matrix characteristics of air particulate matter as a prerequisite for global monitoring of air pollution is discussed. A new approach for sampling urban dust using large volume filtering devices installed in air conditioners of large hotel buildings is assessed. A first experiment was initiated to collect air particulates (300-500 g each) from a number of hotels during a period of 3-4 months by successive vacuum cleaning of used inlet filters from high volume air conditioning installations reflecting average concentrations per 3 months in different large cities. This approach is expected to be upgraded and applied for global monitoring. Highly positive correlated elements were found in lichens such as K/S, Zn/P, the rare earth elements (REE) and a significant negative correlation between Hg and Cu was observed in these samples. The ratio of concentrations of elements in dust and Usnea spp. is highest for Cz, Zn and Fe (400-200) and lowest for elements such as Ca, Rb, and Sr (20-10).
For more than a decade environmental specimen banking (ESB) has been an established approach for monitoring and retrospective environmental survey purposes in a number of developed countries. Specimen banking is carried out on regional or national scales for various environmental materials. The ecological or problem-oriented approach, as pursued e.g. in Germany or USA has the advantages of a restricted survey and a clear political mandate. Environmental problems, however, are by no means national or regional issues, since the diversity and dispersion of hazardous substances make environmental monitoring clearly a global affair. The structuring of our environment suggests that banking should not be limited by national boundaries, but rather be based on eco-systematic principles. Such distinct banking efforts should be devoted to the monitoring of physico-chemical aspects of climatic change and air pollution, soil quality, and aquatic monitoring on a world-wide scale. As some experience already exists with specialized banking programs for marine samples, such as the National Marine Mammal Tissue Bank or the Mussel Watch Program in the United States, an international marine specimen bank, based on principles of national ESB's, is advocated to be established in due time. Following the recommendations of the 1992 Rio 'Earth Summit' to pursue sustainable development strategies, such an establishment could strongly facilitate efforts concerning pollution control and mitigation, overexploitation and mining of ocean resources on a regional or global scale.
An investigation has been carried out to study the pattern of heavy metal abundance in buds, needles, twigs and cones from single trees and to compare the results with the integrated (composite, homogenized) ESB material of the same origin. It has been evident that (i) pine and spruce shoots are comparable in terms of the pattern of trace element abundance with the exception of Ni, Ba, Sr and Pb, (ii) twigs contribute substantially to the overall concentration of the homogeneous material, and (iii) heavy metal concentrations are remarkably different in samples from remote and industrialized sampling sites. To distinguish the influence of soil at different sampling sites on the overall concentration levels, an extensive investigation using chemometrical data evaluation has still to be carried out.
Arsenic compounds have been determined in some environmental samples from the German Environmental Specimen Bank (ESB) (marine mussels, freshwater mussel and fish, sea-gull eggs) and certified reference materials (DORM-1, DOLT-1, NBS Oyster Tissue) after separation by open column cation and anion exchange chromatography by two different methods of total arsenic determination in separated fractions (instrumental neutron activation analysis or hydride generation atomic absorption spectrometry). Arsenobetaine has been identified as the major species in all the different materials.
The necessity to establish a small scale Environmental Specimen Bank projects in tropical countries is stressed. An example from Sri Lanka demonstrates the needs, the benefits and the prospects of such an integrated research project.
The combined application of instrumental-, radiochemical- and prompt gamma neutron activation analysis to two spruce shoot materials from the German Environmental Specimen Bank (ESB) resulted in information on 50 elements, covering more than 50% of the total mass. Comparison of the element concentrations in the 'fingerprint' mode clearly indicated a different status of heavy metal pollution at the two distinct collecting sites.
A straightforward method for demonstrating the powerful background reduction of Compton suppression spectrometers for neutron activation purposes is presented. The shorter acquisition time needed in Anti-Compton mode (A/C on) for peaks of appropriate counting statistics, compared to normal gamma counting (A/C off), allows a much higher sample throughput, thus compensating for the higher cost of the instrument. Two examples of artificial mixtures of radionuclides demonstrate the drastic time saving for measurement of monoenergetic decaying isotopes. The comparison of results from three different instruments proves the general usefulness of Compton suppression spectrometers for Neutron Activation Analysis of biological samples.