10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Characterization of Particulate Matter Sources in Summer Using High-Resolution Aerosol Mass Spectrometry in San Antonio
FANGZHOU GUO, Benjamin Schulze, Alexander Bui, Henry Wallace, James Flynn, Matthew H. Erickson, Sergio Alvarez, Alex Kotsakis, Subin Yoon, Sascha Usenko, Rebecca J. Sheesley, Robert Griffin, Rice University
Abstract Number: 797 Working Group: Aerosol Chemistry
Abstract Currently the seventh most populous city in the United States and the second most populous city in Texas, San Antonio has been one of the most rapidly growing large cities in the country over the past decade. As evidenced by an ozone design value in violation of the federal threshold for a recent three-year period (2014-2016), the city suffers from poor air quality. To understand the sources of particulate matter (PM) that contribute to the degradation of San Antonio’s air quality, we assembled and deployed a mobile air quality laboratory and operated it in two locations in the southeast (Traveler’s World RV Park) and northwest (University of Texas at San Antonio campus) of downtown San Antonio from May 2 through May 30, 2017. Chemical characterization of non-refractory submicron PM (NR-PM1) at high time resolution was conducted using an Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). Additional measurements included meteorological parameters, trace gas mixing ratios (of ozone, total nitrogen oxides, total reactive nitrogen, carbon monoxide, and volatile organic compounds), and off-line speciation of PM collected using filters. This is the first time that detailed real-time aerosol measurement results have been reported from San Antonio.
From the preliminary results, organic and sulfate aerosols dominated the total aerosol burden, averaging 5.42 mg/m3 (54% of the total mass) and 3.43 mg/m3 (31% of the total mass), respectively. The average concentrations of ammonium (1.21 mg/m3; 11%), nitrate (0.33 mg/m3; 3.6%), and chloride (0.04 mg/m3; 0.4%) were relatively smaller throughout the campaign period. Total aerosol mass concentrations displayed two high-loading periods (May 9-12 and May 27-29), with the first one propelled by both organics and sulfate and the second one dominated by sulfate aerosols.
Positive matrix factorization, in conjunction with meteorological and trace gas data, will be used to apportion the organic portion of NR-PM1 to various types of organic aerosol, including proxies for primary and secondary organic aerosol. Preliminary results indicate atypically large sulfate aerosol plumes; the relative contribution of biogenic and anthropogenic sources to this sulfate will be quantified. In addition, large spikes of biomass burning organic aerosol appear to originate from agricultural fires in Central America. This combination of data will allow us to estimate the fraction of PM in San Antonio in summer that is local and anthropogenic, potentially providing guidance for development of emission control strategies.