Secondary organic aerosol formation from alpha-pinene and toluene: Laboratory studies examining the role of pre-existing particles, relative humidity and oxidant type

Secondary organic aerosol (SOA) is a major fraction of fine particulate matter (PM2.5), thus impacting air quality and climate. In the first section of this thesis, experiments were performed to investigate SOA formation from both ozonolysis and hydroxyl radical (OH)-initiated oxidation (so-called photooxidation) of alpha-pinene under conditions with varying relative humidity (RH) and seed aerosol acidity at the UNC dual outdoor smog chamber facility. Formation of dimer esters was observed only in SOA derived from alpha-pinene ozonolysis with increased concentrations at high RH, indicating these compounds could serve as tracers for SOA enhanced by anthropogenic pollution. In the second section of this thesis, toluene photooxidation experiments in presence of nitric oxide were conducted to examine the effect of the pre-existing titanium dioxide (TiO2) seed aerosol, as an instance of engineered metal oxide nanomaterials, considering their unique photocatalytic properties. Results indicate that TiO2 aerosol enhanced and accelerated SOA formation from toluene.