AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Secondary Organic Aerosol and Ozone Formation from Photo-Oxidation of Unburned Whole Gasoline and Diesel in a Surrogate Atmospheric Environment
WEIHUA LI, Chia-Li Chen, Lijie Li, Mary Kacarab, David R. Cocker III, University of California, Riverside
Abstract Number: 393 Working Group: Aerosol Chemistry
Abstract Direct evaporation from unburned gasoline and diesel is an established source of ozone and secondary organic aerosol (SOA) forming precursors. A recent report from California Air Resource Board (CARB) presents that exhaust from tailpipe and evaporative loss contribute to total organic emissions equivalently. As new vehicle control technologies continue to decrease primary organic aerosol and gas-phase emissions, whole fuel evaporation becomes a more significant source of ambient organic aerosol. Therefore, determining the SOA forming potential of whole gasoline and diesel vapor is of significant interest. While SOA formation from some gasoline and diesel components such as aromatics and alkanes have been individually studied under controlled conditions, there are only a few studies on how these complex mixtures behave in the atmosphere.
Given changes in fuel formulations over time, it is important to revisit whole gasoline and diesel as important SOA precursors, especially in light of increased knowledge on the impact of reactivity on aerosol formation and improved atmospheric chambers and instrumentation. Multiple photo-oxidation experiments with the presence of NOx were conducted in the University of California College of Engineering-Center for Environmental Research and Technology dual 90m3 smog chambers to investigate SOA and ozone formation from the select commercial gasoline, #2 diesel and reference diesel samples. Additionally, the fuel samples were also added to a surrogate reactive organic gas (ROG) mixture to best mimic the reactivity of an urban atmosphere. SOA formation from photo-oxidation of gasoline samples was consistent regardless of fuel manufacturer or octane rating and was driven by aromatics content in the gasoline. The greater the estimated hydroxyl radical concentrations, the more SOA formed. Photochemical aging of diesel samples rapidly produce significant SOA in the presence of the surrogate ROG mixture. SOA mass cannot be solely explained by aromatics content.