Green leaf volatiles (GLVs) are potentially significant but of unknown importance as a source of aqueous-phase secondary organic aerosol (SOA). GLVs are reactive, oxygenated, organic compounds that are emitted from plants in significant quantities and that can react both at the surface of fog drops and within the bulk of the drops. These aqueous reactions can occur via photochemically generated oxidants such as hydroxyl radical, singlet molecular oxygen, and excited triplet states of organic compounds. GLVs are also oxidized in the gas phase to make more water soluble products that could also participate in fog-drop reactions to form SOA. The hypothesis driving this research is that the uptake and photooxidation of GLVs and their first generation oxidation products can be a significant source of secondary organic carbon in fogwater. This hypothesis will be tested through four objectives: (1) Collect and chemically characterize fogwaters from Louisiana and California. (2) Measure GLV photooxidation, changes in organic composition, and the formation of SOA in illuminated fogwaters. (3) Quantify photooxidants in the illuminated fog waters and their reactivity with GLVs. (4) Integrate results from each objective in order to determine the mechanisms for GLV reactions in fogwaters and assess the significance of GLVs as an aqueous source of SOA.
A post-doctoral scholar, a graduate student, and undergraduate students will be mentored during the project, including through an LSU-UCD undergraduate exchange research program. The results from the research will be integrated into undergraduate and graduate teaching at both institutions. And, because fog events can affect the concentrations of regulated pollutants, especially PM2.5, in both Louisiana and California, results from this work will inform state air quality policy agencies.