AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
Abstract View
Chemical Composition and Evaporation Rates of Secondary Organic Aerosol from Cooking Oils
MANPREET TAKHAR, Craig A. Stroud, Arthur W. H. Chan, University of Toronto
Abstract Number: 576 Working Group: Aerosol Chemistry
Abstract Food cooking emissions represent one of the most important sources of primary organic aerosol (POA) in urban areas. However, like many organic emissions, the physical and chemical evolution of food cooking aerosol in the atmosphere is poorly understood. Previous studies have shown significant production of secondary organic aerosol (SOA) formation, but lack the understanding of composition of SOA at molecular level. Therefore, in this work, we investigate the oxidation of cooking oil (canola, olive, beef tallow) vapors using a flow tube reactor coupled to a thermodenuder to study the composition and kinetics of SOA. The chemical analysis using a thermal desorption-gas chromatography-mass spectrometry shows that substantial fraction of SOA from cooking vapors is embedded in the unresolved complex mixture (UCM). Our results highlight that detailed speciation of UCM can be achieved based on the mass fragmentation pattern, and all the GC elutable compounds can be classified by their functional groups. Deconvoluted UCM is thus used to derive a mass-based volatility distribution. Additionally, we can use the information on polarity and volatility of the products into a two-dimensional volatility basis set to better constrain the evolution of cooking emissions. These measurements are then used as inputs into a mass transfer model to predict the evaporation rates of SOA upon heating in a thermodenuder. Moreover, heterogeneous oxidation of these cooking oil particles suggests a slower response to evaporation in a thermodenuder than unoxidized cooking oil particles. Thus, by incorporating measurements of composition and evaporation kinetics into a mass transfer model, we report 1-2 orders of magnitude decrease in mass accommodation coefficients upon heterogeneous oxidation. Similar, measurements of mass accommodation coefficients for SOA from cooking oil vapors will be presented and compared to that of heterogeneous oxidation of POA.