Citation
Loza, Christine Lauren (2013) Investigations of Secondary Organic Aerosol Formation in Laboratory Chambers. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/WZXD-KX70. https://resolver.caltech.edu/CaltechTHESIS:05312013-115629933
Abstract
Secondary organic aerosol (SOA) is produced in the atmosphere by oxidation of volatile organic compounds. Laboratory chambers are used understand the formation mechanisms and evolution of SOA formed under controlled conditions. This thesis presents studies of SOA formed from anthropogenic and biogenic precursors and discusses the effects of chamber walls on suspended vapors and particles.
During a chamber experiment, suspended vapors and particles can interact with the chamber walls. Particle wall loss is relatively well-understood, but vapor wall losses have received little study. Vapor wall loss of 2,3-epoxy-1,4-butanediol (BEPOX) and glyoxal was identified, quantified, and found to depend on chamber age and relative humidity.
Particles reside in the atmosphere for a week or more and can evolve chemically during that time period, a process termed aging. Simulating aging in laboratory chambers has proven to be challenging. A protocol was developed to extend the duration of a chamber experiment to 36 h of oxidation and was used to evaluate aging of SOA produced from m-xylene. Total SOA mass concentration increased and then decreased with increasing photooxidation suggesting a transition from functionalization to fragmentation chemistry driven by photochemical processes. SOA oxidation, measured as the bulk particle elemental oxygen-to-carbon ratio and fraction of organic mass at m/z 44, increased continuously starting after 5 h of photooxidation.
The physical state and chemical composition of an organic aerosol affect the mixing of aerosol components and its interactions with condensing species. A laboratory chamber protocol was developed to evaluate the mixing of SOA produced sequentially from two different sources by heating the chamber to induce particle evaporation. Using this protocol, SOA produced from toluene was found to be less volatile than that produced from a-pinene. When the two types of SOA were formed sequentially, the evaporation behavior most closely represented that of SOA from the second parent hydrocarbon, suggesting that the structure of the mixed SOA particles resembles a core of SOA from the first precursor coated by a layer of SOA from the second precursor, indicative of limiting mixing.
Item Type: | Thesis (Dissertation (Ph.D.)) |
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Subject Keywords: | secondary organic aerosol, chamber, wall loss, aging |
Degree Grantor: | California Institute of Technology |
Division: | Chemistry and Chemical Engineering |
Major Option: | Chemical Engineering |
Minor Option: | Environmental Science and Engineering |
Thesis Availability: | Public (worldwide access) |
Research Advisor(s): |
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Thesis Committee: |
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Defense Date: | 17 May 2013 |
Record Number: | CaltechTHESIS:05312013-115629933 |
Persistent URL: | https://resolver.caltech.edu/CaltechTHESIS:05312013-115629933 |
DOI: | 10.7907/WZXD-KX70 |
Default Usage Policy: | No commercial reproduction, distribution, display or performance rights in this work are provided. |
ID Code: | 7790 |
Collection: | CaltechTHESIS |
Deposited By: | Christine Loza |
Deposited On: | 14 May 2014 15:42 |
Last Modified: | 04 Oct 2019 00:01 |
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