Traffic, transport, and vegetation drive VOC concentrations in a major urban area in Texas

Sujan Shrestha; Subin Yoon; Matthew H Erickson; Fangzhou Guo; Manisha Mehra; Alexander A T Bui; Benjamin C Schulze; Alexander Kotsakis; Conner Daube; Scott C Herndon; Tara I Yacovitch; Sergio Alvarez; James H Flynn; Robert J Griffin; George P Cobb; Sascha Usenko; Rebecca J Sheesley

doi:10.1016/j.scitotenv.2022.155861

Traffic, transport, and vegetation drive VOC concentrations in a major urban area in Texas

Sci Total Environ. 2022 Sep 10;838(Pt 2):155861. doi: 10.1016/j.scitotenv.2022.155861. Epub 2022 May 12.

Authors

Sujan Shrestha¹, Subin Yoon², Matthew H Erickson³, Fangzhou Guo⁴, Manisha Mehra¹, Alexander A T Bui⁴, Benjamin C Schulze⁵, Alexander Kotsakis⁶, Conner Daube⁷, Scott C Herndon⁷, Tara I Yacovitch⁷, Sergio Alvarez⁸, James H Flynn⁸, Robert J Griffin⁴, George P Cobb¹, Sascha Usenko¹, Rebecca J Sheesley⁹

Affiliations

¹ Department of Environmental Science, Baylor University, Waco, TX, USA.
² Department of Environmental Science, Baylor University, Waco, TX, USA; Department of Earth and Atmospheric Sciences, University of Houston, Houston, TX, USA.
³ Department of Earth and Atmospheric Sciences, University of Houston, Houston, TX, USA; TerraGraphics Environmental Engineering, Pasco, WA, USA.
⁴ Department of Civil and Environmental Engineering, Rice University, TX, USA.
⁵ Department of Civil and Environmental Engineering, Rice University, TX, USA; Department of Environmental Science and Engineering, California Institute of Technology, Pasadena, CA, USA.
⁶ Department of Earth and Atmospheric Sciences, University of Houston, Houston, TX, USA; Universities Space Research Association, NASA/GSFC, Columbia, MD, USA.
⁷ Aerodyne Research, Inc., Billerica, MA, USA.
⁸ Department of Earth and Atmospheric Sciences, University of Houston, Houston, TX, USA.
⁹ Department of Environmental Science, Baylor University, Waco, TX, USA. Electronic address: Rebecca_Sheesley@baylor.edu.

PMID: 35568171
DOI: 10.1016/j.scitotenv.2022.155861

Abstract

The population of Texas has increased rapidly in the past decade. The San Antonio Field Study (SAFS) was designed to investigate ozone (O₃) production and precursors in this rapidly changing, sprawling metropolitan area. There are still many questions regarding the sources and chemistry of volatile organic compounds (VOCs) in urban areas like San Antonio which are affected by a complex mixture of industry, traffic, biogenic sources and transported pollutants. The goal of the SAFS campaign in May 2017 was to measure inorganic trace gases, VOCs, methane (CH₄), and ethane (C₂H₆). The SAFS field design included two sites to better assess air quality across the metro area: an urban site (Traveler's World; TW) and a downwind/suburban site (University of Texas at San Antonio; UTSA). The results indicated that acetone (2.52 ± 1.17 and 2.39 ± 1.27 ppbv), acetaldehyde (1.45 ± 1.02 and 0.93 ± 0.45 ppbv) and isoprene (0.64 ± 0.49 and 1.21 ± 0.85 ppbv; TW and UTSA, respectively) were the VOCs with the highest concentrations. Additionally, positive matrix factorization showed three dominant factors of VOC emissions: biogenic, aged urban mixed source, and acetone. Methyl vinyl ketone and methacrolein (MVK + MACR) exhibited contributions from both secondary photooxidation of isoprene and direct emissions from traffic. The C₂H₆:CH₄ demonstrated potential influence of oil and gas activities in San Antonio. Moreover, the high O₃ days during the campaign were in the NO_x-limited O₃ formation regime and were preceded by evening peaks in select VOCs, NO_x and CO. Overall, quantification of the concentration and trends of VOCs and trace gases in a major city in Texas offers vital information for general air quality management and supports strategies for reducing O₃ pollution. The SAFS campaign VOC results will also add to the growing body of literature on urban sources and concentrations of VOCs in major urban areas.

Keywords: Ethane; Methane; Ozone; PTR-MS; San Antonio; VOC.

MeSH terms

Acetone
Air Pollutants* / analysis
China
Environmental Monitoring / methods
Ozone* / analysis
Texas
Volatile Organic Compounds* / analysis

Substances

Air Pollutants
Volatile Organic Compounds
Acetone
Ozone