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Identifying the Transport and Evolution of Oxidized Organic Aerosol across the Urban Core of San Antonio
FANGZHOU GUO, Alexander Bui, Edward Fortner, Sujan Shrestha, Subin Yoon, Rebecca J. Sheesley, Sascha Usenko, Tara Yacovitch, Scott Herndon, James Flynn, Robert Griffin, Rice University
Abstract Number: 372
Working Group: Urban Aerosols
Abstract
San Antonio is the seventh most populous city in the United States and the second-most populous city in Texas. Over the past decade, San Antonio has been one of the most rapidly growing large cities in the country, contributing to the city’s deteriorating air quality. To understand the sources of particulate matter (PM) that contribute to the degradation of San Antonio’s air quality, two mobile air quality laboratories were deployed and operated to the southeast (Traveler’s World (TW) Recreational Vehicle Park, upwind) and northwest (University of Texas at San Antonio (UTSA) campus, downwind) of downtown San Antonio in May 2017. Chemical characterization of non-refractory submicron PM (NR-PM1) at high time resolution was conducted at TW using an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and at UTSA using an Aerodyne soot-particle aerosol mass spectrometer (SP-AMS) in laser-off mode from May 12 to 16. Additional measurements included meteorological parameters and trace gas mixing ratios (of ozone, total nitrogen oxides, total reactive nitrogen, carbon monoxide, and volatile organic compounds). Results from both AMS instruments indicate large sulfate and organic aerosol (OA) plumes. Positive Matrix Factorization (PMF) analysis of the high-resolution spectra identified hydrocarbon-like OA (HOA), a less oxygenated OA (LO-OOA), and a more oxygenated OA (MO-OOA) at both sites. Based on the location and meteorological data of the two sites, a model is constructed to characterize the formation rates of LO-OOA and MO-OOA across the city of San Antonio. Given the uniform 3-factor solutions from the PMF, the modeling analysis allows us to investigate the evolution of secondary organic aerosol species from upwind to downwind on an urban scale.