Variations in Summertime Aerosol Physicochemical Mixing State Observed during NYC-METS

EMILY COSTA, Yao Xiao, Xu He, Corin Tyler, Kayleigh Reilly, Tiantian Zhu, Jessica Mirrielees, Drew Gentner, Rachel O'Brien, Andrew Ault, University of Michigan

     Abstract Number: 469
     Working Group: Coast to Coast Campaigns on Aerosols, Clouds, Chemistry, and Air Quality

Abstract
Air pollution in densely populated urban and downwind areas poses a significant threat to human health. Airborne particulate matter (PM) in these regions can be produced in a variety of ways, including from both primary and secondary processes. Secondary organic aerosol (SOA) is known to contribute to poor summertime air quality, and its formation is driven by the emission of gas-phase organic compounds, including volatile organic compounds (VOCs). VOC emissions in urban areas are evolving such that non-traditional sources including volatile chemical products (e.g., paints, personal care products) may now be more prominent SOA precursors. In order to understand summertime SOA formation under these changing conditions, single-particle analysis is needed to characterize the chemical composition, sources, and physicochemical mixing state of airborne PM in a variety of locations. Simultaneous size-resolved atmospheric particle sampling was conducted in New York City, NY and in downwind Guilford, CT as part of the New York City metropolitan Measurements of Emissions and TransformationS (NYC-METS) campaign in summer 2023. The chemical composition of individual atmospheric particles collected at each site was examined using a variety of offline microscopic and spectroscopic techniques, including scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), and simultaneous optical-photothermal infrared spectroscopy (O-PTIR) and Raman microspectroscopy. These analyses reveal clear compositional differences between the two sampling sites, suggesting different sources and aging mechanisms of airborne PM.