Thesis (Ph. D.)--University of Washington, 1997. / Vita. Includes bibliographical references (p. [109]-119).

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 456-471). Available also in a digital version from Dissertation Abstracts.

Thesis (M.S.)--University of Wisconsin, 1972. / Bound typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 134-141).

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 199-212).

Thesis (Ph. D.)--University of Texas at Austin, 2005. / Vita. Includes bibliographical references. Also available from UMI.

No description available.

Thesis (Ph. D.)--Earth and Atmospheric Sciences, Georgia Institute of Technology, 2007. / Robert Dickinson, Committee Member ; Athanasios Nenes, Committee Member ; David Tan, Committee Member ; Armistead Russell, Committee Member ; Yuhang Wang, Committee Chair.

<p> Photoactive roadways have been suggested as a mitigation method to improve air quality in urban areas. However, difficulties translating laboratory results to real world conditions has complicated a wider adoption of this technology. This work presents a methodology to determine first-order loss coefficients of ozone precursors on photoactive asphalt and concrete using a continuously-stirred tank reactor under different conditions of humidity and UV illumination. The experimental loss coefficients were used to determine uptake coefficients that can be incorporated in air quality models to represent photoactive surfaces. </p><p> The laboratory findings indicate that paving materials respond differently to variations in humidity, with concrete efficiency more influenced by the increase in water vapor. The uptake of NO on asphalt was found to have a power dependence with UV irradiance. The uptake of NO₂ was smaller than that of NO, suggesting that any impact on air quality would occur mainly through removal of NO. The uptake of VOC was found to decrease exponentially with the increase in the vapor pressure of the organic compound indicating a competitive adsorption mechanism driving the photocatalytic removal of mixtures. Molar yields of HONO, NO₂ and aldehydes were detected during the removal of pollutants in asphalt, while only NO₂ was detected from concrete, indicating potential disadvantages of TiO₂ treated surfaces. </p><p> The use of the CO/NOx molar ratio was explored to monitor changes in NOx levels in experiments performed in an outdoor chamber. CO removal was not observed during the time scale at which NOx removal occurs, suggesting that CO could be used as tracer in field studies to follow changes in vehicle emissions caused by photoactive roads. </p><p> The uptake coefficients for NO determined in this work were incorporated in a one-dimensional model to understand the overall impact of photoactive surfaces on atmospheric chemistry. Preliminary results indicate that a moderate reduction of up to 20% in NO could be achieved for a scenario simulating Houston conditions. No significant effect on ozone was observed as result of adding HONO yields. However, further investigation needs to address aldehyde and NO₂ yields to determine if these byproducts offset the benefits of this strategy.</p>

During 1988-89, the 1.5 m telescope on Mt. Bigelow, Arizona, combined with the Lunar and Planetary Laboratory echelle spectrograph, recorded 20 spectral CCD images of Mars during early spring, mid- and late summer, and autumnal equinox in its southern hemisphere. These images contained absorption features which permitted latitudinally resolved measurements of water vapor column abundance in the martian atmosphere on these four occasions, corresponding to the areocentric longitudes (L(s)) 208, 320, 340, and 360°. This dissertation describes the acquisition, analysis, and modeling of this data set. Photochemical models at different latitudes predicted ozone column abundance at L(s) = 208° when initialized by the observed water vapor abundances. Matching simultaneous ozone abundances, also measured from the ground, required eddy diffusivities at altitudes between 5 and 15 km that were at least two orders of magnitude lower than the values greater than 10⁸ cm² sec⁻¹ assumed above 30 km altitude, especially at south polar latitudes. Legendre polynomials and interpolating parabolas described the observed spatial and temporal behavior of the martian water vapor for L(s) = 320, 340, and 360°. Integrating the fits with latitude derived visible disk and globally averaged abundances as a function of time. A budget based on these abundances suggested the southern hemisphere subsurface to be a source, and therefore a reservoir, of water vapor during this season. The large magnitudes and signs of effective meridional diffusivities for the data implied the water vapor's disappearance to be more likely due to condensation and adsorption into local sinks than to atmospheric transport. When compared with Viking water vapor data, the Catalina abundances hinted that dust was a mechanism for shielding water vapor from ground-based observation and that northward transport was more efficient during a dusty southern spring and summer than during a dustless one. Finally, a one-dimensional analytical meridional diffusive model and a two-dimensional diabatic circulation water transport model confirmed the idea of a southern hemisphere surface source and sink for the Catalina water vapor, and more efficient northward water transport during dusty southern spring and summer. Moreover, both transport models suggested that the large amount of water seen from the ground during 1969 was not sublimed from a south polar residual cap of water ice.

The chemical aging of organic aerosols by OH-initiated heterogeneous oxidation was investigated using both model organic and ambient aerosol particles. Organic aerosol particles were exposed to OH radicals in an aerosol flow tube and the modification of their chemical composition and particle properties was studied. Overall, this work has shown that OH-initiated heterogeneous oxidation enhanced the degree of oxidation and the Cloud Condensation Nucleus (CCN) activity of organic aerosol particles for equivalent OH exposure timescales of a few days to a week. Aerosol Mass Spectrometer (AMS) measurements showed that the heterogeneous uptake kinetics of OH radicals onto model primary organic aerosols was efficient. The heterogeneous reaction of organic aerosols with OH led to the production of high molecular weight particle-phase species with the addition of multiple oxygenated functional groups. These results were consistent with the observed increase in particle density with OH exposure. With the exception of solid organic aerosols, the particle volume and mass of organic particles were reduced by less than 20% from OH oxidation at high OH exposures due to volatilization of particle-phase reaction products. The degree of oxidation of the organic fraction of urban ambient aerosols was significantly enhanced for an equivalent atmospheric OH exposure time of 4 days for a daily average atmospheric OH concentration of 2×106 cm-3. Ambient aerosol particles sampled from a sparsely populated, forested region were initially more oxygenated than the urban aerosol particles and did not become more oxidized from reaction with OH radicals. The modification of the hygroscopicity of model primary and secondary organic aerosols from chemical aging was investigated by measuring the CCN activity of organic aerosols exposed to OH radicals. Primary organic aerosols, initially CCN inactive, became as CCN active as secondary organic aerosols due to heterogeneous reaction, where surface tension reduction played a major role. The CCN activity for model secondary organic aerosols was also enhanced due to OH oxidation, but changes were less dramatic than for the model primary organic aerosols.