Heterogeneous and multiphase chemistry of reactive nitrogen oxides in the marine boundary layer

Dinitrogen pentoxide (N₂O₅), a primary nocturnal reservoir for NOx (NOx [equivalence] NO + NO₂), readily undergoes heterogeneous reaction on aqueous interfaces. These reactions potentially alter the chemical, physical, and hygroscopic properties of ambient particles, and ultimately their climate impact. Upon reacting with aqueous chloride-containing surfaces, such as sea spray, nitryl chloride (ClNO₂) is produced. ClNO₂ is capable of extending the lifetime of NOx and inducing ozone production in high NOx environments via chlorine radical creation. The extent to which N₂O₅ reactivity impacts atmospheric oxidant loadings depends on the heterogeneous reaction rate of N₂O₅ with a given surface. This, in turn, is directly influenced by interfacial chemical composition, morphology, and phase state. In this dissertation, I describe advances in the understanding of how organic and inorganic constituents at atmospheric interfaces regulate N₂O₅ reactivity. First, I developed an observation-based framework for assessing the aerosol particle mixing state role on N₂O₅ heterogeneous reaction kinetics using simultaneous measurements of the N₂O₅ reactive uptake coefficient to ambient aerosol with direct measurements of aerosol mixing state before and after reaction. Second, as part of the NSF Center for Aerosol Impacts on Climate and the Environment, I extended the use of a novel Marine Aerosol Reference Tank (MART) capable of generating nascent sea-spray aerosol, to determine heterogeneous reaction kinetics. Here, the MART was doped with ocean organic mimics to assess how organics present in the sea surface microlayer (SSML), and subsequently ejected into sea-spray, impact N₂O₅ reaction kinetics. Third, I conducted laboratory studies to investigate suppressed ClNO₂ production rates at the ocean surface, using ambient seawater from various locations and under varied biological conditions, along with model sea salt solutions with proxy organics. This study was designed to determine the role of unsaturated organics and surface-enhanced inorganic ions in the SSML in altering ClNO₂ production rate