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Observations of Volatile Organic Compounds in the Los Angeles Basin during COVID-19

Van Rooy, Paul and Tasnia, Afsara and Barletta, Barbara and Buenconsejo, Reina and Crounse, John D. and Kenseth, Christopher M. and Meinardi, Simone and Murphy, Sara and Parker, Harrison and Schulze, Benjamin and Seinfeld, John H. and Wennberg, Paul O. and Blake, Donald R. and Barsanti, Kelley C. (2021) Observations of Volatile Organic Compounds in the Los Angeles Basin during COVID-19. ACS Earth and Space Chemistry, 5 (11). pp. 3045-3055. ISSN 2472-3452. doi:10.1021/acsearthspacechem.1c00248.

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Volatile organic compounds (VOCs) were measured in the Los Angeles (LA) Basin from mid-April to mid-July 2020 during the COVID-19 pandemic, as a part of the Los Angeles Air Quality Campaign (LAAQC). VOCs were quantified in over 450 samples using one- and two-dimensional gas chromatography with different detectors; mixing ratios were determined for 150 compounds associated with on- and off-road mobile, volatile chemical product, and biogenic sources. During the sampling period, traffic counts increased from ∼55% to ∼80% of pre-COVID levels. While the average afternoon combustion-derived VOCs and carbon monoxide (CO) mixing ratios did not change significantly between April–May and June–July, there was a shift in the distribution to higher mixing ratios in June–July, particularly for VOCs associated with gasoline evaporation. Compared to observations made in the last major air quality campaign in the LA Basin (CalNex-2010), emission ratios for 40 compounds relative to acetylene (VOC/acetylene) have remained similar, while emission ratios relative to CO (VOC/CO) have dropped to ∼60% of their 2010 values. This divergence in trends suggests that whereas mobile sources are still the dominant source of the combustion-derived VOCs measured in the LA Basin, there has been a shift in the mobile source sectors, with a growing contribution from sources that have lower CO/acetylene emission ratios, including off-road equipment and vehicles. In addition to the observed shift in source sector contributions, estimated OH exposure was 70–120% higher than in 2010.

Item Type:Article
Related URLs:
URLURL TypeDescription
Van Rooy, Paul0000-0003-1193-0994
Tasnia, Afsara0000-0002-3048-5083
Barletta, Barbara0000-0003-3046-014X
Buenconsejo, Reina0000-0002-0162-905X
Crounse, John D.0000-0001-5443-729X
Kenseth, Christopher M.0000-0003-3188-2336
Meinardi, Simone0000-0003-4828-9889
Parker, Harrison0000-0002-0041-2764
Schulze, Benjamin0000-0002-6405-8872
Seinfeld, John H.0000-0003-1344-4068
Wennberg, Paul O.0000-0002-6126-3854
Blake, Donald R.0000-0002-8283-5014
Barsanti, Kelley C.0000-0002-6065-8643
Additional Information:© 2021 American Chemical Society. Received: July 9, 2021; Revised: September 27, 2021; Accepted: October 9, 2021; Published: October 28, 2021. The authors would like to sincerely thank Joost de Gouw for conversations during the campaign period in which he shared his knowledge of the composition and chemistry in the LA Basin. The authors would also like to thank Joost de Gouw and Carsten Warneke for the quality data collected during the CalNex-2010 campaign and subsequent analysis of that data, which were foundational to this study. PVR, AT, KCB acknowledge funding support from NSF RAPID award #2030049. BB, SM, and DRB acknowledge funding support from NSF RAPID award #2030112. Author Contributions: The study was conceived by KCB, JHS, DRB, and POW. All authors contributed to data collection, analysis, and/or interpretation. The manuscript was written largely by PVR and KCB, with contributions from AT, BB, JDC, HP, PS, and POW. The manuscript was edited through contributions of all authors. All authors have given approval to the final version of the manuscript. The authors declare no competing financial interest.
Funding AgencyGrant Number
Subject Keywords:VOCs, urban air quality, COVID-19, mobile source emissions, off-road emissions, VCPs
Issue or Number:11
Record Number:CaltechAUTHORS:20211118-233559021
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Official Citation:Observations of Volatile Organic Compounds in the Los Angeles Basin during COVID-19. Paul Van Rooy, Afsara Tasnia, Barbara Barletta, Reina Buenconsejo, John D. Crounse, Christopher M. Kenseth, Simone Meinardi, Sara Murphy, Harrison Parker, Benjamin Schulze, John H. Seinfeld, Paul O. Wennberg, Donald R. Blake, and Kelley C. Barsanti. ACS Earth and Space Chemistry 2021 5 (11), 3045-3055; DOI: 10.1021/acsearthspacechem.1c00248
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:111955
Deposited By: Tony Diaz
Deposited On:18 Nov 2021 23:51
Last Modified:18 Nov 2021 23:51

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