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dc.contributor.advisorBrooks, Sarah D.
dc.creatorSuter, Katie Ann
dc.date.accessioned2012-10-19T15:28:31Z
dc.date.accessioned2012-10-22T17:59:46Z
dc.date.available2012-10-19T15:28:31Z
dc.date.available2012-10-22T17:59:46Z
dc.date.created2011-08
dc.date.issued2012-10-19
dc.date.submittedAugust 2011
dc.identifier.urihttp://hdl.handle.net/1969.1/ETD-TAMU-2011-08-9734
dc.description.abstractHeterogeneous freezing processes in which atmospheric aerosols act as ice nuclei (IN) cause nucleation of ice crystals in the atmosphere. Heterogeneous nucleation can occur through several freezing mechanisms, including contact and immersion freezing. The mechanism by which this freezing occurs depends on the ambient conditions and composition of the IN. Aerosol properties change through chemical aging and reactions with atmospheric oxidants such as ozone. We have conducted a series of laboratory experiments using an optical microscope apparatus equipped with a cooling stage to determine how chemical oxidation changes the ability of atmospheric aerosols to act as IN. Freezing temperatures are reported for aerosols composed of fresh and oxidized soot and polyaromatic hydrocarbons (PAHs) including anthracene, phenanthrene, and pyrene. Our results show that oxidized soot particles initiate ice freezing events at significantly warmer temperatures than fresh soot, 3 °C on average. All oxidized PAHs studied had significantly warmer freezing temperatures than fresh samples. The chemical changes presumably causing the improved ice nucleation efficiency were observed using Fourier Transform Infrared Spectroscopy with Horizontal Attenuated Total Reflectance (FTIR-HATR). The addition of C=O bonds at the surface of the soot and PAHs led to changes in freezing temperatures. Finally, we have used classical nucleation theory to derive heterogeneous nucleation rates for the IN compositions in this research. The overall efficiency of the IN can be compared in order of least efficient to most efficient: fresh phenanthrene, fresh anthracene, fresh soot, oxidized phenanthrene, fresh pyrene, oxidized anthracene, oxidized soot, and oxidized pyrene. Overall oxidation of aerosols increases their ability to act as IN. Our results suggest that oxidation processes facilitate freezing at warmer temperatures at a broader range of conditions on the atmosphere.en
dc.format.mimetypeapplication/pdf
dc.language.isoen_US
dc.subjectheterogeneous ice nucleationen
dc.subjectsooten
dc.subjectPAHsen
dc.subjectoxidationen
dc.titleHow Physical and Chemical Properties Change Ice Nucleation Efficiency of Soot and Polyaromatic Hydrocarbon Particlesen
dc.typeThesisen
thesis.degree.departmentAtmospheric Sciencesen
thesis.degree.disciplineAtmospheric Sciencesen
thesis.degree.grantorTexas A&M Universityen
thesis.degree.nameMaster of Scienceen
thesis.degree.levelMastersen
dc.contributor.committeeMemberPanetta, Richard L.
dc.contributor.committeeMemberMarlow, William H.
dc.contributor.committeeMemberZhang, Renyi
dc.type.genrethesisen
dc.type.materialtexten


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