10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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A Multi-Site Chemical Characterization of Organic Aerosol Demonstrates Extensive Variability in Molecular-Level Composition
DREW GENTNER, Jenna Ditto, Emily Barnes, Peeyush Khare, Taekyu Joo, Masayuki Takeuchi, Gamze Eris, Nga Lee Ng, Alexander Bui, Robert Griffin, Yale University
Abstract Number: 1630 Working Group: Aerosol Chemistry
Abstract The lifecycles of organic compounds in the atmosphere occur amongst the evolution of a remarkably diverse complex mixture of 10,000’s of compounds spread across volatility and polarity scales. Yet, its molecular-level chemical composition is key to its transformations, fates, and impacts; and is essential to understanding and modeling the dynamics of complex organic aerosol mixtures in the atmosphere. Using liquid chromatography and very-high resolution mass spectrometry with “soft” ionization, we perform a detailed molecular-level characterization and intercomparison of oxidized organic aerosol from 3 very different field sites and an oxidation chamber. Despite similar aerosol bulk properties measured by multiple instruments, we report very large day-to-day molecular-level variability between ambient organic aerosol samples at each of the 3 sites, with 57-94% of compounds being unique sample-to-sample. Chamber experiments with small variations confirm this variability could be due to emitted precursor mixtures and/or chemical oxidation pathways, which is further supported by 0-D chemical modeling. In contrast to less speciated measurements, these results demonstrate much greater variability in the atmosphere under roughly similar conditions, which has implications for fundamental studies and air quality-climate models.