Apportioned primary and secondary organic aerosol during pollution events of DISCOVER-AQ Houston

Subin Yoon; Stephanie M Ortiz; Adelaide E Clark; Tate E Barrett; Sascha Usenko; Rachelle M Duvall; Lea Hildebrandt Ruiz; Jeffrey K Bean; Cameron B Faxon; James H Flynn 3rd; Barry L Lefer; Yu Jun Leong; Robert J Griffin; Rebecca J Sheesley

doi:10.1016/j.atmosenv.2020.117954

Apportioned primary and secondary organic aerosol during pollution events of DISCOVER-AQ Houston

Atmos Environ (1994). 2021 Jan 1:244:10.1016/j.atmosenv.2020.117954. doi: 10.1016/j.atmosenv.2020.117954.

Authors

Subin Yoon^{1

2}, Stephanie M Ortiz¹, Adelaide E Clark^{3

4}, Tate E Barrett^{5

6}, Sascha Usenko^{1

3}, Rachelle M Duvall⁷, Lea Hildebrandt Ruiz⁸, Jeffrey K Bean⁸, Cameron B Faxon⁸, James H Flynn 3rd², Barry L Lefer⁹, Yu Jun Leong¹⁰, Robert J Griffin^{10

11}, Rebecca J Sheesley^{1

5}

Affiliations

¹ Department of Environmental Science, Baylor University, Waco, TX, USA.
² Department of Earth and Atmospheric Sciences, University of Houston, Houston, TX, USA.
³ Department of Chemistry and Biochemistry, Baylor University, Waco, TX, USA.
⁴ Department of Natural Sciences, Oregon Institute of Technology, Klamath Falls, OR, USA.
⁵ Institute of Ecological, Earth, and Environmental Sciences, Baylor University, Waco, TX, USA.
⁶ Department of Geography and the Environment, University of North Texas, Denton, TX, USA.
⁷ Office of Research and Development, United States Environmental Protection Agency, Research Triangle Park, NC, USA.
⁸ McKetta Department of Chemical Engineering, University of Texas at Austin, Austin, TX, USA.
⁹ Earth Sciences Division, The National Aeronautics and Space Administration, Washington, D.C, USA.
¹⁰ Department of Civil and Environmental Engineering, Rice University, Houston, TX, USA.
¹¹ Department of Chemical and Biomolecular Engineering, Rice University, Houston, TX, USA.

Abstract

Understanding the drivers for high ozone (O₃) and atmospheric particulate matter (PM) concentrations is a pressing issue in urban air quality, as this understanding informs decisions for control and mitigation of these key pollutants. The Houston, TX metropolitan area is an ideal location for studying the intersection between O₃ and atmospheric secondary organic carbon (SOC) production due to the diversity of source types (urban, industrial, and biogenic) and the on- and off-shore cycling of air masses over Galveston Bay, TX. Detailed characterization of filter-based samples collected during Deriving Information on Surface Conditions from Column and VERtically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) Houston field experiment in September 2013 were used to investigate sources and composition of organic carbon (OC) and potential relationships between daily maximum 8 h average O₃ and PM. The current study employed a novel combination of chemical mass balance modeling defining primary (i.e. POC) versus secondary (i.e. SOC) organic carbon and radiocarbon (¹⁴C) for apportionment of contemporary and fossil carbon. The apportioned sources include contemporary POC (biomass burning [BB], vegetative detritus), fossil POC (motor vehicle exhaust), biogenic SOC and fossil SOC. The filter-based results were then compared with real-time measurements by aerosol mass spectrometry. With these methods, a consistent urban background of contemporary carbon and motor vehicle exhaust was observed in the Houston metropolitan area. Real-time and filter-based characterization both showed that carbonaceous aerosols in Houston was highly impacted by SOC or oxidized OC, with much higher contributions from biogenic than fossil sources. However, fossil SOC concentration and fractional contribution had a stronger correlation with daily maximum 8 h average O₃, peaking during high PM and O₃ events. The results indicate that point source emissions processed by on- and off-shore wind cycles likely contribute to peak events for both PM and O₃ in the greater Houston metropolitan area.

Keywords: High resolution time of flight aerosol mass; Organic aerosols; Ozone; Radiocarbon; Source apportionment; Urban air quality; spectrometer.

Grants and funding

EPA999999/ImEPA/Intramural EPA/United States