| 1. |
- Akselsson, Roland, et al.
(författare)
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Application of Proton Induced X-Ray Emission Analysis to the St. Louis Regional Air Pollution Study
- 1975
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Ingår i: Advances in X-Ray Analysis. ; 18, s. 588-597
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Tidskriftsartikel (refereegranskat)abstract
- The St Louis aerosol was sampled during the period 16-22 August 1973 simultaneously at two locations using cascade impactors for sequential 12-hour samples. The six particle size fractions of each sampling were individually analyzed using PIXE for elements from S to Br and beyond and for heavy elements including Pb which permitted time variations of concentrations and particle size distributions to be followed and related to meteorological changes during the sampling period. In addition, the data were compared with average levels of the elements in coastal north Florida and maritime Bermuda as well as at a third St. Louis site. From this it appeared that some of the concentrations in St. Louis were at natural levels whereas others appeared to be higher and linked to air pollution sources. These relationships and others in this study may lead to criteria for distinguishing between pollutants and natural background in urban aerosols.
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| 2. |
- Akselsson, Roland, et al.
(författare)
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Proton Scattering for Analysis of Atmospheric Particulate Matter
- 1975
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Ingår i: Bulletin of the American Physical Society Ser II. ; 20
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Tidskriftsartikel (refereegranskat)abstract
- Proton scattering has been applied to the problem of elemental quantitative analysis of air particulate matter. Elements up through chlorine may be resolved using 16 MeV protons incident upon targets up to about 1 mg/cm2 in thickness. Using the FSU Super FM Tandem Accelerator and a large area solid state proton detector, an analysis can be performed in several minutes. Combination of this technique with proton induced X-ray emission analysis provides a means of quantitative analysis for all elements. These accelerator based methods are being applied to studies of the composition of air particulate matter in diverse locations such as St. Louis, Mo.; Los Angeles, Ca.; several cities in Florida; and Bermuda.
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| 3. |
- Akselsson, Roland, et al.
(författare)
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X-Ray Techniques for Aerosol Sulfur Baseline Assessment Along an Urban Freeway
- 1976
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Ingår i: Advances in X-Ray Analysis. ; 19, s. 415-425
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Tidskriftsartikel (refereegranskat)abstract
- Atmospheric aerosol particles have been sampled near a Los Angeles freeway and analyzed by proton-induced X-ray emission, PIXE, as a sulfur baseline study in September 1974 before 1975-model automobiles, equipped with catalytic emission control devices, appeared in large numbers. The sampling plan was optimized according to the requirements of X-ray analysis techniques, fluctuations in air flow across the freeway, and the time and particle size resolution of the aerosol sampling equipment. During five selected two-hour intervals with cross wind conditions, particles were collected as a function of size by six cascade impactors operating simultaneously on three towers at 2 and 7 meters above road level 35 meters upwind and 35 meters downwind of the traffic lanes. Particles as a function of time were sampled continuously, for the 100-hour duration of the experiment, from the tree 7-meter heights using time series streaker filter samplers with two-hour time resolution. Precise analysis of S, Cl, K, Ca, Fe, Br, and Pb established relationships which permit estimates to be made of future increases in particulate sulfur as a consequence of increased sulfate emissions from catalytic automobiles
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| 4. |
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| 5. |
- Nelson, J William, et al.
(författare)
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Aerosol Composition Studies Using Accelerator Proton Bombardment
- 1974
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Ingår i: Proceedings of "Third Conference on Application of Small Accelerators". ; 1, s. 139-147
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Konferensbidrag (refereegranskat)abstract
- The proton beam of the Florida State University Tandem Van de Graaff Accelerator is being used to make quantitative determinations of the composition of particulate matter found in the atmosphere. Proton scattering using 16 MeV incident particle energy is employed to resolve the light elements (up to Cl), while elements Al and heavier are observed via proton induced X-ray emission analysis. In order to realize advantages of these proton excited analyses, specialized techniques are used, such as the use of uniform beams which entirely cover the area of targets of non-uniform areal density. Also, specialized air sampling equipment has been built to take advantage of the small size of samples required for proton induced analyses. The multielement character, ease of automation, and short time (several minutes) needed for analysis make these techniques attractive from the standpoint of analysis cost per sample.
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| 6. |
- Nelson, J William, et al.
(författare)
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Automatic Time Sequence Filter Sampling of Aerosols for Rapid Multi-Element Analysis by Proton-Induced X-Ray Emission
- 1976
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Ingår i: Advances in X-Ray Analysis. ; 19, s. 403-413
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Tidskriftsartikel (refereegranskat)abstract
- An automatic time sequence filter sampler has been developed for atmospheric aerosol particle sampling of ambient air and subsequent analysis for elemental composition using the proton beam of a Van de Graaff accelerator. Some features of the operation of the sampler are given, the retention of particles by the filter material are discussed, examples of the type of data obtained are presented, and some approaches to the numerical analysis of data for environmental interpretation are considered. Lines for further development and improvement in this type of sampler are indicated.
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| 7. |
- Orsini, Celso Q, et al.
(författare)
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Variation of Elemental Composition with Particle Size in the St. Louis Aerosol
- 1977
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - 0167-5087. ; 142:1-2, s. 91-96
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Tidskriftsartikel (refereegranskat)abstract
- Detailed particle size distribution of elemental constituents have been determined in the St. Louis aerosol by sampling with cascade impactors for particles >0.25 μm aerodynamic diameter and by analyzing using proton-induced X-ray emission, PIXE, for S, Cl, K, Ca, Ti, Mn, Fe, Zn, Br, and Pb. Two rooftop sites were selected for intensive sampling in industrial and residential locations in St. Louis during February 1974, every 12 h for a 7 d period which included clear, rainy, and snowy weather regimes. The data could be compared with the results of a similar study of the St. Louis aerosol during August 1973 when the weather was generally warm and without rain. Both data sets could also be compared with results of studies of Tallahassee, situated in coastal north Florida, and the north Atlantic marine atmosphere of Bermuda. Although variation in elemental concentrations and their size distributions were observed which could be associated with local weather conditions during the February sampling period, the data set was sufficiently large for meaningful average characteristics to be computed. As examples, two elements of pollution importance, sulfur and iron, show the following comparison between St. Louis and the Florida and Atlantic locations: Sulfur in all data sets was most abundant in the smallest particle size classes. Winter and summer concentration in St. Louis air were the same within a factor of two but generally exceeded north Florida concentrations. Bermuda concentrations were intermediate between St. Louis and north Florida, except for largest particles where sea spray derived material was present. The results reflect the importance of gas phase conversion to particulate forms of sulfur, e.g. sulfate, in all three locations. Iron concentrations in St. Louis generally exceeded those in north Florida for smallest particles and to a lesser extent for larger sizes. Concentrations in Bermuda were about 10-fold lower than in St. Louis for all particle sizes. The results reflect the terrestrial dust origin of iron and also suggest that iron is partially pollution-derived in the St. Louis atmosphere, especially in smaller size ranges.
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| 8. |
- Van Grieken, René E., et al.
(författare)
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Geophysical Applicability of Aerosol Size Distribution Measurements Using Cascade Impactors and Proton Induced X-Ray Emission
- 1976
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310 .- 0004-6981. ; 10:8, s. 571-576
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Tidskriftsartikel (refereegranskat)abstract
- Proton Induced X-ray Emission, (PIXE), is capable of high precision analysis for trace element components of aerosol particle size fractions sampled by cascade impactor. A statistical evaluation of data quality has been carried out in order to distinguish between analytical uncertainties in the PIXE procedure, errors caused by cascade impactor performance and by other factors in the sampling procedure, and geophysical causes of differences in composition and particle size distributions of the elements in aerosols. Replicate analyses and simultaneous samplings taken in north Florida and St. Louis have been used for the data evaluation. In addition to the analytical error the sampling procedure contributes an error of ~ 10% to be added quadratically. The resulting precision is sufficient to evaluate the data in geophysical terms. This is illustrated by means of sample sets taken simultaneously in an urban, forest and coastal environment of the same region.
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| 9. |
- Winchester, John W, et al.
(författare)
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Trace Metals in the St. Louis Aerosol
- 1974
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Ingår i: Proceedings of the Second International Conference on Nuclear Methods in Environmental Research. ; , s. 385-394
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Konferensbidrag (refereegranskat)abstract
- The elemental composition of the St. Louis aerosol has been investigated at rooftop sites in south and central locations in the city as part of the August, 1973 field season of the Regional Air Pollution Study of the U.S. Environmental Protection Agency. Sampling by 5-stage cascade impactor with backup filter permits analysis by proton-induced x-ray emission (PIXE) of size fractions of aerodynamic diameter >4, >2m >1, >0.5, >0.25, <0.25µm for elements 16S to 35Br by K x-ray detection and 82Pb by L x-rays. The aerosol study indicates the following: 1. Particle size distributions of S, Cl, K, Ca, Ti, V, Mn, Fe, Cu, Zn, Br, and Pb can be measured in samples from 0.7 m3 of air collected over 12-hour intervals at 1 liter/min flow rate, with precision of single analyses generally 10-30%, except near the nanogram detection limit. 2. Some elements, e.g. Ca, Fe, Ti, K show a tendency for highest concentrations in air measured in largest particle size fractions, and the pattern of distribution of concentration with size is relatively invariant. Predominantly dispersion source processes may account for their entry into the atmosphere. 3. Other elements, e.g. S, Pb, Zn, have substantial proportions of their atmospheric concentrations on smallest particles and show greater variability in particle size distribution patterns, suggesting aerosol formation processes of vapor condensation at high or low temperatures. 4. During 16-22 August 1973 an atmospheric change occurred from a period of low speed and mostly southerly air flow, with evident haze and air pollution, to higher speed and westerly shifting to easterly air flow, with improved visibility and air quality. The change was associated with drops in concentrations of Ti, Fe, Ca, K, and S but not Zn or Pb at the south site and Ti but not the other elements at the central site. Transport of air pollution from industrial sources south of the city is indicated. 5. The central site showed diurnal variation during the first period where concentrations of Ti, Fe, Ca, K, and S were higher in samples taken from midnight to noon than in those from noon to midnight. Variations were greatest for intermediate sized particles.
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