AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Evolving Urban Emissions: Increasing Impact of Non-Combustion Secondary Organic Aerosol Precursor Sources on Urban Air Quality
PEEYUSH KHARE, Drew Gentner, Yale University
Abstract Number: 81 Working Group: Urban Aerosols
Abstract Particulate matter less than 2.5 μm in size (PM2.5) is directly emitted but is also formed as secondary organic aerosol (SOA) via the atmospheric oxidation of key, reactive gas-phase precursors (e.g., volatile organic compounds). Decades of successful policy on combustion-related emissions in the developed regions has elevated the relative impact of SOA precursor emissions from other anthropogenic sources. In our case study megacity Los Angeles, we find that emissions from consumer products and commercial/industrial processes now contribute a similar fraction of SOA precursor gases as on-road vehicles. Through chemical analyses and surveys of highly used consumer/industrial products, we demonstrate that these product/process-related sources have chemically diverse emission profiles with a wide range of SOA and ozone formation potentials that rival automobile sources. Key SOA precursors observed include intermediate- to semi-volatile organic compounds (I/SVOCs) and single-ring aromatics with weight fractions reaching up to 95% and 93% of product composition respectively, and emission timescales ranging from minutes to years. I/SVOCs are excluded or underrepresented in current inventories, and are largely exempt from emission targets. As major contributors to outdoor SOA, product/process-related sources warrant inclusion or updating in emission inventories taking into account their regional variability. Moreover, existing bottom-up estimates and top-down assessments of the SOA produced from gasoline and diesel vehicles (on- and off-road) cannot explain all of the observed fossil SOA in Los Angeles in 2010, which indicates the potential for other major sources of fossil-derived SOA precursors. We show that products/process related emissions in Los Angeles could be misattributed to fossil fuel combustion emissions due to the isotopic signature of their petroleum feedstocks. Our study highlights new avenues of research in the characterization of urban sources of VOCs, IVOCs, and SVOCs that will improve emissions inventories and urban air quality management plans.