07 Jun 2022
07 Jun 2022
Status: this preprint is currently under review for the journal ACP.

Composition and Reactivity of Volatile Organic Compounds in the South Coast Air Basin and San Joaquin Valley of California

Shang Liu1, Barbara Barletta2, Rebecca S. Hornbrook3, Alan Fried4, Jeff Peischl5,6, Simone Meinardi2, Matthew Coggon5,6, Aaron Lamplugh5,6, Jessica B. Gilman6, Georgios I. Gkatzelis5,6,a, Carsten Warneke6, Eric C. Apel3, Alan J. Hills3, Ilann Bourgeois5,6, James Walega4, Petter Weibring4, Dirk Richter4, Toshihiro Kuwayama1, Michael FitzGibbon1, and Donald Blake2 Shang Liu et al.
  • 1Research Division, California Air Resources Board, Sacramento, 95814, USA
  • 2Department of Chemistry, University of California, Irvine, 92697, USA
  • 3Atmospheric Chemistry Observations & Modeling Laboratory, National Center for Atmospheric Research, Boulder, 80301, USA
  • 4Institute of Arctic & Alpine Research, University of Colorado, Boulder, 80303 USA
  • 5Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder 80309, USA
  • 6NOAA Chemical Science Laboratory, Boulder, 80305, USA
  • anow at: Institute of Energy and Climate Research, IEK-8: Troposphere, Forschungszentrum Jülich GmbH, Jülich, 52428, Germany

Abstract. Comprehensive aircraft measurements of volatile organic compounds (VOCs) covering the South Coast Air Basin (SoCAB) and San Joaquin Valley (SJV) of California were obtained in the summer of 2019. Combined with the CO, CH4, and NOx data, the total measured gas-phase hydroxyl radical reactivity (OHRTOTAL) was quantified. VOCs accounted for ~60 %−70 % of the OHRTOTAL in both basins. In particular, oxygenated VOCs (OVOCs) contributed > 60 % of the OHR of total VOCs (OHRVOC) as well as the total observed VOC mixing ratio. Primary biogenic VOCs (BVOCs) represented a minor fraction (< 2 %) of the total VOC mixing ratio but accounted for 21 % and 6 % of the OHRVOC in the SoCAB and SJV, respectively. Furthermore, the contribution of BVOCs to the OHRVOC increased with increasing OHRVOC in the SoCAB, suggesting that BVOCs was important ozone precursors during high ozone episodes. Spatially, the trace gases were heterogeneously distributed in the SoCAB with their mixing ratios and OHR significantly greater over the inland regions than the coast, while their levels were more evenly distributed in the SJV. The results highlight that a better grasp of the emission rates and sources of OVOCs and BVOCs is essential for a predictive understanding of the ozone abundance and distribution in California.

Shang Liu et al.

Status: open (until 19 Jul 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-399', Anonymous Referee #1, 23 Jun 2022 reply

Shang Liu et al.


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Short summary
California’s ozone persistently exceeds the air quality standards. We studied the spatial distribution of volatile organic compounds (VOCs) that produce ozone over the most polluted regions in California using aircraft measurements. We find that the oxygenated VOCs have the highest ozone formation potential. Spatially, biogenic VOCs are important during high ozone episodes in the South Coast Air Basin, while dairy emissions may be critical for ozone production in the San Joaquin Valley.