| The focus of this thesis is the experimental investigation of laboratory models of organic atmospheric aerosols. Aerosols are ubiquitous throughout the atmosphere. They are produced from both biogenic and anthropogenic sources and can also be formed in situ. Recent field measurements have observed organic molecules in the composition of many aerosols. The compounds observed include both short- and long-chain carboxylic acids, alcohols, amines and hydrocarbons in addition to polycyclic aromatic hydrocarbons, isoprene, and many others. A few of these organic compounds are water soluble. I used malonic acid as a model for this classification and investigated the photoreactivity of a solution of malonic acid. Many of the organic compounds detected on atmospheric aerosols will preferentially reside at the air-water interface of aerosol. Organic monolayers can be used as model systems for atmospheric surfaces such as dust particles, soot, ice and aqueous aerosols. The focus of my graduate research has been studying the properties of monolayers of organic surfactants residing at the air-water interface.; Monolayer films at the air-water interface have not been extensively studied in the context of atmospheric chemistry. I have done experiments to observe the fundamental morphological properties of these films with a Langmuir trough to build an understanding of organic aerosols in the atmosphere. The structure of a monolayer is dependent on the length of the hydrocarbon tail, the functionality of the head group, and the composition of the subphase. The interfacial regime is shown to preferentially select and concentrate compounds that are more stable at the interface.; Organic compounds that preferentially partition to the surface of aerosols are extremely susceptible to oxidation by OH, O3, halogens and NO3. Thin organic films have been studied in my work as proxies for surface alkane and alkene organic compounds. The chemical mechanisms for processing by O3 and OH of organic films have been determined by GC/MS analysis of the products. In addition, the competition between O 3 and OH for the carbon-carbon double bond is also investigated. Atmospheric consequences of the oxidation of hydrocarbon films are discussed in the context of the chemistry, climate, transport and health. |
