An existing method for the measurement of atmospheric gaseous species was modified to collect data on aerosol concentrations. Data from biomass burning events in different regions (Canada, the Arctic and California) were collected during April to July, 2008 and the concentrations and evolution of secondary organic aerosols were discussed. And finally, data on the light absorbing properties of water soluble organic aerosols were collected in Atlanta, GA and compared with filter data for the same properties. The results presented in this thesis showed that a negative ion chemical ionization mass spectrometer (CIMS), can be modified by the addition of a thermally denuded inlet to measure aerosol phase sulfuric acid. This system can also be used to measure other aerosol phase organic acids. In the biomass burning plumes studied in the second part, no clear indication of formation of secondary aerosol or gaseous species was observed, except for peroxyacetyl nitrate (PAN). Filter data collected from FRM sites in the Southeastern U.S. showed that biomass burning is the most dominant source of water soluble light absorbing carbonaceous aerosol in this region. The data from a study in Atlanta, GA showed that the online PILS-LWCC-WSOC system might be used for measurements of light absorbing properties of aerosols and WSOC.

This thesis focuses on the characterization of soluble iron in ambient/urban and source emission aerosols, primarily focusing on the sources and atmospheric processes contributing to iron solubility. Multiple techniques, including bulk and single particle measurements, were used to investigate the complex chemistry of iron solubility. A technique was developed and validated (PILS-LWCC), allowing for 12-minute measurements of water-soluble ferrous iron (WS_Fe(II)) in aerosols with a limit of detection of 4.6 ng m-3 and 12% relative uncertainty. The PILS-LWCC was deployed at several urban field sites (Atlanta, GA and Dearborn, MI) and a biomass burning event to determine major sources and atmospheric processes of WS_Fe(II) in aerosols. PILS-LWCC measurements suggest that industrial and biomass burning are sources of WS_Fe(II). In addition, acid-processing mechanisms also appeared to influence WS_Fe(II) concentrations, based on a strong correlation between WS_Fe(II) and SO42- (r2 = 0.76) as well as apparent aerosol acidity (r2 =0.78) during a field campaign in Atlanta, GA. Synchrotron-based techniques, such as X-ray Absorption Near-Edge Structure (XANES) spectroscopy and micro X-ray fluorescence measurements, were also used to identify the chemical composition (redox state and phase) and mixing state (two properties that may influence iron solubility) of source emission and ambient single iron-containing particles. These single particle measurements were used in conjunction with bulk iron solubility to assess the influence of chemical composition and mixing state on iron solubility. Single particle (synchrotron-based) and bulk iron solubility measurements suggested that iron solubility is not primarily driven by chemical composition in source emission and ambient particles. Differences in iron solubility, however, were related to single particle sulfur content in ambient and source emission aerosols, suggesting that similar sources/atmospheric processes control iron solubility in these samples. The relationship between iron solubility and sulfur content corresponded well with bulk ground-based measurements of ambient aerosol using the PILS-LWCC. Combined single particle and bulk online measurements provide compelling evidence that atmospheric acid processing, involving sulfur-containing acids (H2SO4), is an important formation route of soluble iron in ambient urban aerosols. The results of this thesis provide valuable information to further understanding the controls of iron solubility in atmospheric aerosols.

900 archived FRM filters from 15 sites over the southeast during 2007 were analyzed for PM2.5 chemical composition and physical properties. Secondary components (i.e. sulfate aerosol and SOA) were the major contributors to the PM2.5 mass over the southeast, whereas the contribution from biomass burning varied with season and was negligible (2%) during summer. Excluding biomass burning influence, FRM WSOC was spatially homogeneous throughout the region, similar to sulfate, yet WSOC was moderately enhanced in locations of greater predicted isoprene emissions in summer. On smaller spatial scale, a substantial urban/rural gradient of WSOC was found through comparisons of online WSOC measurements at one urban/rural pair (Atlanta/Yorkville) in August 2008, indicating important contribution from anthropogenic emissions. A comparative study between Atlanta and LA reveals a number of contrasting features between two cities. WSOC gas-particle partitioning, investigated through the fraction of total WSOC in the particle phase, Fp, exhibited differing relationships with ambient RH and organic aerosols. In Atlanta, both particle water and organic aerosol (OA) can serve as an absorbing phase. In contrast, in LA the aerosol water was not an important absorbing phase, instead, Fp was correlated with OA mass. Fresh LA WSOC had a consistent brown color and a bulk absorption per soluble carbon mass at 365 nm that was 4 to 6 times higher than freshly-formed Atlanta soluble organic carbon. Interpreting soluble brown carbon as a property of freshly-formed anthropogenic SOA, the difference in absorption per carbon mass between the two cities suggests most WSOC formed within Atlanta is not from an anthropogenic process similar to LA.

The purpose of this study was to characterize and evaluate the performance of a whole-body human exposure chamber for controlled test atmospheres of gases and particulates. The chamber was constructed from Plexiglass, has a volume of 75 ft 3, operated at a flowrate of 33.8 CFM, and both the makeup and exhaust air are HEPA filtered. Fly ash dust was generated using a Wright Dust Feeder. An elutriator was used to eliminate particles larger 8 μm aerodynamic diameter from the airstream. A direct reading instrument, the Rupprecht and Patashnick PM-10 TEOM, was used for determination of particle concentration. Particle size distributions were determined by a QCM cascade impactor. Data from gravimetric analysis were used to test for the evenness of dust concentrations in the chamber. CO2 is used as a representative gas and its concentration was measured using the Metrosonics aq-5000. Total dust concentrations as measured by the TEOM, in μg/m 3, at 0.2, 0.4, 0.6 and 1.6 RPMs of the Wright Dust Feeder, were 110 + 2.8, 173 + 8.5, 398 + 20 and 550 + 17, respectively. For these RPMs, particle size distributions were associated with a MMD of 1.27 μm and a GSD of 2.35, a MMD of 1.39 and a GSD of 2.22, a MMD of 1.46 and a GSD of 2.08, a MMD of 1.15 and a GSD of 2.2, respectively. Total dust concentrations as measured by gravimetric analysis, in μg/m3 for the respirable fraction. Dust concentrations measured at different points within the chamber showed uniform distribution with a variability less than 10%. Similarly, the particle size distributions were found to be consistent across the different RPMs settings. Regarding carbon dioxide, its concentration was straightforward and the measured and theoretical maximum concentration levels were in agreement. The performance of this whole-body human exposure chamber has been characterized and evaluated for low levels of particles and gases and now it is a valuable research tool for inhalation challenge studies.

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The main objective of this study was to investigate the vertical distribution of aerosols over Durban in relation to the vertical stability structure and horizontal transport of air masses. The importance of aerosols in the region is well recognised and recently there have been many international experiments which have focused on aerosol distribution over the subcontinent. Durban is situated at the approximate centre of a giant plume that is known to transport aerosols and trace gases off the east coast of southern Africa and is therefore strategically located for an investigation of the vertical distribution of aerosols. The vertical distribution of aerosols over Durban was measured using a LIDAR (Light Detection And Ranging) system on selected cloud free days in 1997. Backward trajectory modelling was used at selected pressure (standard) levels to determine the origin and transport pathways of aerosols. Six case studies are presented in an attempt to gain insight into the relationship between the vertical distribution of aerosols and absolutely stable layers. The results of the study revealed that the occurrence of absolutely stable layers governs the vertical distribution of aerosols in the troposphere. An absolutely stable layer at ~5km (~500hPa) appears to be the most effective in capping and trapping aerosols in the atmosphere. Below 5km, the atmosphere was charcterised by marked stratification and relatively higher concentration of aerosols. Above 5km, the concentrations were much lower, but generally increased slightly with height. Low aerosol concentrations are observed during post-frontal situations and relatively higher concentrations during anticyclonic conditions. The background to the problem and the objectives of this investigation are elaborated in Chapter 1. A description of the data sets and derived meteorological variables, along with the methodologies applied in this thesis, are given in Chapter 2. A theoretical review of aerosols, including their sources, effects and distribution over the globe and southern Africa, is discussed in Chapter 3. Atmospheric circulation and weather patterns and their relationship to the transport and dispersion of aerosols are described in Chapter 4. The results of the study and an analysis of the major findings are presented in Chapter 5. Finally, Chapter 6 summarises the major findings of this dissertation. / Thesis (M.Sc.)-University of Natal, Durban, 2000.

Thesis (Ph. D.)--University of Washington, 1989. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Canterbury, 2007. / Typescript (photocopy). "May 2007." Includes bibliographical references (p. 239-253). Also available via the World Wide Web.

Thesis (Ph.D.)--George Mason University, 2008. / Vita: p. 167. Thesis director: Menas Kafatos. Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Earth Systems an GeoInformation Sciences. Title from PDF t.p. (viewed Jan. 11, 2009). Includes bibliographical references (p. 156-166). Also issued in print.

Thesis (Ph. D.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 151-167).