Date of Award
Doctor of Philosophy (PhD)
Organic aerosols (OA; organic compounds present on the surface or within aerosols) in the atmosphere may play a significant role in various atmospheric processes as well as have an impact on human health. While many primary (direct) sources of OA (POA) are known, a significant portion of OA is formed through the oxidation of primary precursors, creating secondary organic aerosols (SOA) through processes that are still unclear. This dissertation, therefore, focuses on the development of analytical methods for characterizing SOA as well as investigating the mechanism behind their formation and aerosol chemistry.
In the first phase of this work, methods were developed to identify and quantify the large number of products formed during the oxidation of PAHs, utilizing analysis techniques such as chromatography (gas and liquid) and mass spectrometry (low and high resolution). In addition, extraction and sample preparation methods were evaluated with the focus on increasing the sensitivity in detecting PAH oxidation products.
The mechanisms behind the heterogeneous oxidation of 3-4 ring PAHs were investigated by simulating reactions of PAHs in the presence of various gas-phase oxidants under atmospheric conditions. Both a small and large-scale aerosol simulation chamber were designed and constructed to study the oxidation of PAHs adsorbed to the surfaces of diesel exhaust aerosols.
To aid in modeling, the interactions of SOA with aerosol surfaces experiments were performed using thermogravimetry-differential scanning calorimetry (TGA-DSC) to
define the changes in vaporization enthalpies (ΔHvap) of common OA species when adsorbed to different aerosol surface types.
Cochran, Richard, "Investigating The Heterogeneous Chemistry Of Polycyclic Aromatic Hydrocarbons And Other Organic Species In Atmospheric Aerosols" (2014). Theses and Dissertations. 1634.