Condensed chemical mechanisms and their impact on radical sources and sinks in Houston

dc.contributor.advisorAllen, David T.en
dc.contributor.advisorMcDonald-Buller, Elenaen
dc.creatorHeo, Gookyoungen
dc.date.accessioned2011-01-25T15:54:01Zen
dc.date.available2011-01-25T15:54:01Zen
dc.date.issued2009-08en
dc.descriptiontexten
dc.description.abstractFree radicals play a critical role in the formation of tropospheric air pollution, but current condensed chemical mechanisms used in gridded photochemical models under-predict total radical concentrations. This dissertation evaluates three hypotheses regarding radical sources and sinks using environmental chamber data and ambient data from southeast Texas. The first hypothesis, that aromatics chemistry is under-represented as a radical source in condensed chemical mechanisms, was evaluated mainly by using environmental chamber simulations and in part by using ambient simulations. Results indicate that improved characterization of aromatics chemistry in condensed chemical mechanisms will lead to more rapid and extensive free radical formation. The second hypothesis, that alkene reactions are under-represented as a radical source in condensed chemical mechanisms, was also evaluated using chamber data and TexAQS-2000 data. Results indicate that the methods used in mechanism condensation lead to lower estimates of free radical production than detailed, compound specific models. The third hypothesis, chlorine emissions and chemistry as a radical source, was also evaluated in a series of sensitivity analyses with various levels of molecular chlorine emissions. Results imply that incorporating chlorine chemistry in condensed chemical mechanisms is expected to lead to more accurate modeling of OH, HO₂ and O₃, particularly for the southeast Texas region where relatively large chlorine emissions occur from various anthropogenic sources of molecular chlorine. The relative magnitudes of these radical sources (aromatics, alkenes, and molecular chlorine) in southeast Texas were also compared using box modeling with TexAQS-2000 data. Results indicate that the relative importance of these three types of radical sources depends on the strengths of their corresponding emissions.en
dc.description.departmentCivil, Architectural, and Environmental Engineeringen
dc.format.mediumelectronicen
dc.identifier.urihttp://hdl.handle.net/2152/9702en
dc.language.isoengen
dc.rightsCopyright is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works.en
dc.subjectFree radicalsen
dc.subjectRadical sourcesen
dc.subjectSinksen
dc.subjectAromatics chemistryen
dc.subjectAlkene reactionsen
dc.subjectCondensed chemical mechanismsen
dc.subjectMolecular chlorine emissionsen
dc.subjectHouston, Texasen
dc.subjectSoutheast Texasen
dc.titleCondensed chemical mechanisms and their impact on radical sources and sinks in Houstonen
thesis.degree.departmentCivil, Architectural, and Environmental Engineeringen
thesis.degree.disciplineCivil Engineeringen
thesis.degree.grantorThe University of Texas at Austinen
thesis.degree.levelDoctoralen
thesis.degree.nameDoctor of Philosophyen

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