共查询到20条相似文献,搜索用时 15 毫秒
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M. Carmo Freitas 《Journal of Radioanalytical and Nuclear Chemistry》1995,192(2):171-181
k0-Based instrumental neutron activation analysis (k0 INAA) was used to determine the concentrations of Cr, Fe, Co, Zn, Se, Sb and Hg in the vascular plantsCistus salvifolius andInula viscosa and in the lichenParmelia sulcata. The samples were collected in the neighbourhood of industrial complexes. The elemental accumulation in the vascular plants and the lichen are compared to optimize the choice of the bioaccumulator. It is concluded thatP. sulcata seems to be the best accumulator of the three species for the elements studied;Cistus salvifolius is sensitive to the contents of Zn, Fe, Cr and Sb in the air;Inula viscosa seems to accumulate Fe, Sb, Co, Cr and Zn. Nevertheless, it is concluded that lichen is a good air pollution indicator, while the vascular plants are not due to the large seasonal variations found in the elemental concentrations. 相似文献
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Luminescence phenomena are of value in the analysis of air pollutants. The problems arising in the use of excitation and emission spectra under various conditions are discussed. Phenomena such as solvent, pH, and photochemical effects are shown to play an important role in the fluorimetric analysis of air pollutants. Many of the fluorimetric methods used in the trace analysis of organic airborne particulates involve factors such as direct measurement of the separated pollutant on a chromatogram or pherogram, quenching phenomena, scanning, excimer formation, charge-transfer fluorescence, sensitized fluorescence, and photo-oxidation on adsorbent or in solution. In addition, fluorescence assay methods are discussed in terms of selectivity, sensitivity, speed, simplicity, accuracy, precision, interferences, and the relation between concentration and fluorescence intensity. 相似文献
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E. Cortés 《Journal of Radioanalytical and Nuclear Chemistry》2004,262(1):169-276
A project has been undertaken to carry out a long term study on atmospheric air pollution in Chile using biomonitors. Samples
of different species of lichens were collected in clean areas (native forest), analyzed and transplanted to the Santiago Metropolitan
Area. In addition, samples of Tillandsia recurvata were collected in the Metropolitan Area for comparison purposes. The preparation of the samples was done under controlled,
cryogenic conditions and analyzed by neutron activation analysis and solid sampling atomic absorption spectrometry. As part
of the routine QA/QC procedures, the analytical laboratories, have participated in intercomparison runs organized by the IAEA
for the determination of trace and minor elements in two lichens samples. The present paper describes the activities carried
out within the framework of this project.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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Andrzej Szczurek 《International journal of environmental analytical chemistry》2015,95(10):936-949
This work examined the acquisition of information about gases using a virtual sensor array and classification. We were particularly interested in the approach in which classes are defined in a qualitative–quantitative manner, that is, by identifying the gas and concentration range. This type of information will be of interest for air pollution assessment purposes. In this field of application, it is often not necessary to provide very precise information. The idea of the virtual sensor array exploits the dependence of a gas sensor’s response on operating conditions. Originally it was developed as a means to improve the selectivity of an electronic nose when energy consumption by this device was a serious limitation. If the response of one sensor is measured in n time points, and each time point is characterised by different controlled exposure conditions, the sensor becomes analogous to an n-dimensional virtual sensor array. Compared with conventional approaches, a virtual sensor array based on a single sensor offers low power consumption, low volume, and low cost, which opens up new markets for wide application of portable and handheld devices. In this article, we show that a virtual sensor array and classification may serve as a reliable source of qualitative–quantitative information about gases. Twenty-six classes (five substances, each at five concentration ranges, and pure air) were recognised with a true positive rate higher than 99.14 ± 0.49% and a true negative rate higher than 99.21 ± 0.52%. As demonstrated, the basis for recognition could be a virtual sensor array associated with a low-power consuming sensor (210–280 mW). The complexity of the applied classifier could be adjusted depending on the choice of sensor operating conditions. For a complex classifier like support vector machine, dynamic exposure was sufficient to obtain high classification performance. A simpler classifier like k-nearest neighbours required more information, that is, information associated with static as well as dynamic exposure. 相似文献
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S. M. Frolov V. I. Zvegintsev V. S. Ivanov V. S. Aksenov I. O. Shamshin D. A. Vnuchkov D. G. Nalivaichenko A. A. Berlin V. M. Fomin 《Doklady Physical Chemistry》2017,474(1):75-79
First experimental investigations were carried out into the detonation combustion of hydrogen in a demonstrator of an original-design air-breathing ramjet while blowing with an air flow at Mach 4 to 8 in an impulse wind tunnel, and for the first time under these conditions, continuous spin and longitudinal pulsed modes of detonation combustion of hydrogen in an annular combustor were detected. 相似文献
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M. C. Freitas M. A. Reis L. C. Alves H. Th. Wolterbeek T. Verburg M. A. Gouveia 《Journal of Radioanalytical and Nuclear Chemistry》1997,217(1):21-30
During the months of July and August 1993 a lichen collection campaign was held in Portugal where about 250 samples were collected and analysed by thick target TIPIXE and INAA. Results for 44 different elements were obtained and a data base was built and subjected to Monte Carlo Aided Target Transform Factor Analysis (MCATTFA), a method developed at IRI (Delft). 10×10 km2 coast and 50×50 km2 far from coast sampling grids were used for collection. In this work we will present the results which were obtained based on a reduced data set of 36 elements measured by INAA. The results for 22 elements obtained by TTPIXE were published elsewhere. In this work we will also present the conclusions considering all the 44 elements determined by both techniques. 相似文献
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M. Boazi J. Gabay S. Devir C. Shenberg 《Journal of Radioanalytical and Nuclear Chemistry》1978,45(2):395-406
Aerosol samples from urban, industrial and traffic areas were collected and analyzed for various elements. The correlation
between the multielement content of the samples and their sources was studied. It was found necessary to anlayze samples before
and after ashing because, while ashing improves the peak-to-background ratio, volatile elements may be lost. Samples collected
at heights of 1.5 and 15 m were found to have the same elemental composition. Samples collected on consecutive filters showed
sharp elemental fractionation An example of source identification is given for a high traffic area as compared with an area
in which a large bromine plant is located. In both cases different Pb∶Br ratios were observed, with high bromine concentration
in the latter. The analytical method used was based on the detection of characteristic K and L X-rays induced by a241Am-I source-target assembly. 相似文献
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Summary This paper discusses the application of X-ray photoelectron spectroscopy to the determination of the chemical composition of sulfur and nitrogen species in air pollution particulates. Core electron chemical shift measurements are augmented by the determination of relative concentrations and volatility of particulate species.
Untersuchung von Verunreinigungsteilchen in der Luft durch Röntgenphotoelektronen-Spektroskopie
Zusammenfassung Die Anwendung der Röntgenphotoelektronen-Spektroskopie auf die Bestimmung der chemischen Zusammensetzung von Schwefel und Stickstoff enthaltenden Verunreinigungsteilchen in Luft wird diskutiert. Messungen der chemischen Verschiebung werden ergänzt durch die Bestimmung der relativen Konzentrationen und der Flüchtigkeit der Verbindungen.
Presented at the 6th Annual Symposium on Recent Advances in the Analytical Chemistry of Pollutants, April 21–23, 1976; Vienna, Austria. 相似文献
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S. Romano 《Liquid crystals》1988,3(3):323-336
A classical system, consisting of identical cylindrically symmetric particles, with centres fixed on a simple-cubic lattice, may or may not support nematic—like orientational order depending on the interaction potential. For example, a Lebwohl-Lasher potential model produces orientational order, as does an anisotropic London—de Boer dispersion potential restricted to nearest neighbours, although increasing its range destroys the orientational order and brings about a staggered configuration of the system. In consequence, a Maier-Saupe molecular field treatment is appropriate in the first two cases, but not in the last. On the other hand, according to computer simulation results, a purely dipolar interaction produces a low temperature antiferroelectric phase which can be regarded as an extreme case of a nematogen. We carried out Monte Carlo simulations on a potential model defined by a linear combination of dipolar and full ranged London-de Boer dispersion terms, in order to study their competition. To save computer time and yet monitor the physically relevant changes, we have varied their relative weights, while keeping fixed both the temperature and the anisotropy parameter in the dispersion potential. Simulation results show that in energetic terms the two interactions are cooperative, whereas in structural terms their interplay brings about first a weak but recognizable increase of nematic ordering, and then its collapse with the onset of the staggered configuration. 相似文献
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I. I. L. Cunha R. C. L. Figueira R. T. Saito 《Journal of Radioanalytical and Nuclear Chemistry》1999,239(3):477-482
Methodologies for analysis of anthropogenic and natural radionuclides in marine samples were developed and applied in environmental
samples. Results of systematic measurements of these radionuclides have showed that artificial radioactivity levels are in
agreement with the values from the regions not affected directly by nuclear accidents or nuclear reprocessing plant discharges
and are due to the global fallout. The average concentration of137Cs is of 1.4 Bq·m−3 in seawater, ranges from 13 to 220 mBq·kg−1 in fish, and from 0.4 to 1.8 Bq·kg−1 for sediments.90Sr levels in seawater are of 1.8 Bq·m−3 and in fish vary from 19 to 75 mBq·kg−1. Sediments present concentrations of90Sr lower than 0.8 Bq·kg−1 and for239+240Pu of 0.03 to 0.18 Bq·kg−1.210Po levels in fish range from 0.5 to 5.3 Bq·kg−1. The data generated represent reference values for our country and are used to estimate the intake levels of these radionuclides
by consuming of marine products. 相似文献
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Shen J Liu J Gao Y Cao D Zhang L 《Langmuir : the ACS journal of surfaces and colloids》2011,27(24):15213-15222
By focusing on the grafted nanoparticles (NPs) embedded in polymer melts, a detailed coarse-grained molecular dynamics simulation is adopted to investigate the effects of the grafting density, the length of the matrix and grafted chains on the dispersion of the NPs. We have employed visualization snapshots, radial distribution functions (RDFs), the interaction energy between NPs, the number of neighbor NPs, and the conformation of the brush chains to clearly analyze the dispersion state of the grafted NPs. Our simulated results generally indicate that the dispersion of the NPs is controlled by both the excluded volume of the grafted NPs and the interface between the brushes and the matrix. It is found that increasing grafting density or grafted chain length leads to better dispersion, owing to larger excluded volume; however, increasing the length of the matrix chains leads to aggregation of NPs, attributed to both a progressive loss of the interface between the brushes and the matrix and the overlap between brushes of different NPs, intrinsically driven by entropy. Meanwhile, it is found that there exists an optimum grafting density (σ(c)) for the dispersion of the NPs, which roughly obeys the following mathematical relation: σ(c) is proportional to N(m)(K)/N(g)(L), where K, L > 0 and N(m) and N(g) represent the length of the matrix and grafted chain length, respectively. Considering the practical situation that the grafted brushes and the matrix polymer are mostly not chemically identical, we also studied the effect of the compatibility between the brushes and the matrix polymer by taking into account the attraction between the grafted chains and the matrix chains. In general, our comprehensive simulation results are believed to guide the design and preparation of high-performance polymer nanocomposites with good or even tailored dispersion of NPs. 相似文献
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Y. Oki K. Kondo Y. Kanda T. Miura 《Journal of Radioanalytical and Nuclear Chemistry》1999,239(3):501-505
Aerosol-size distributions of218Po were determined for the accelerator tunnel air sampled during machine operation and for the basement air of a concrete
building, where the number and the size distribution of non-radioactive aerosols are greatly different from each other. The218Po distributions depended very much on the size distributions of ambient non-radioactive aerosols, and could be well explained
by an attachment model of218Po to ambient non-radioactive aerosols. 相似文献
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R. Zeisler S. F. Heller-Zeisler A. Fajgelj 《Journal of Radioanalytical and Nuclear Chemistry》1998,237(1-2):15-19
In order to study the metabolism of physiological amounts of51Cr (10 μg/100 g of body wt.) intragastrically administered in rats, the activable enriched stable isotope Cr-50 compound Cr2O3 was used as a tracer. The absorption and distribution of51Cr(III) in rats with time were studied. Significant51Cr contents were found in all the organs and tissues of interest. The kidney, liver and bone contain higher amounts of51Cr than others. The fact that specific activities of51Cr are notably high in kidney, bone, spleen and pancreas and decrease gradually with time suggests that there are tighter
binding of chromium in these organs. The excretion of51Cr at various time intervals was also studied. Almost totally intragastrically administered dose was excreted in the feces.
The increased urinary excretion of51Cr with time indicates that the urine-chromium is the metabolic derivative of organism. In view of the tissues distribution
and excretion, it can be concluded that no more that 1% of the dose was absorbed from the gastrointestinal tract. 相似文献
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This study aims to investigate whether known carcinogenic chemical elements in atmospheric deposition might be associated
with child mortality due to leukemia in the Portuguese population. A Bayesian hierarchical model was used to explore the association
between lichen biomonitoring measurements of four elements—As, Hg, Ni, Pb—and childhood leukemia death counts taken at small
administrative units. This geographical epidemiological study found a non-significant positive association between the risk
of childhood leukemia and levels of arsenic, mercury and lead, and a non-significant negative association between the disease
and the level of nickel. Lead seems to show a weaker association with childhood leukemia than arsenic and mercury. 相似文献