18 Oct 2023
 | 18 Oct 2023

Production of oxygenated volatile organic compounds from the ozonolysis of coastal seawater

Delaney B. Kilgour, Gordon A. Novak, Megan S. Claflin, Brian M. Lerner, and Timothy H. Bertram

Abstract. Dry deposition of ozone (O3) to the ocean surface and the ozonolysis of organics in the sea surface microlayer (SSML) is a potential source of volatile organic compounds (VOC) to the marine atmosphere. We use a gas chromatography system coupled to a Vocus proton transfer reaction time-of-flight mass spectrometer to determine the chemical composition and product yield of select VOC formed from ozonolysis of coastal seawater collected from Scripps Pier in La Jolla, California. Laboratory-derived results are interpreted in the context of direct VOC vertical flux measurements made at Scripps Pier. The dominant products of laboratory ozonolysis experiments and the largest non-sulfur emission fluxes measured in the field correspond to Vocus CxHy+ and CxHyOz+ ions. GC analysis suggests that C5–C11 oxygenated VOC, primarily aldehydes, are the largest contributors to these ion signals. In the laboratory, using a flow reactor experiment, we determine a VOC yield of 0.43–0.62. In the field at Scripps Pier, we determine a maximum VOC yield of 0.04–0.06. Scaling the field and lab VOC yields for an average O3 deposition flux and an average VOC structure results in an emission source of 12.6 to 136 Tg C yr-1, competitive with the DMS source of 21.1 Tg C yr-1. This study reveals that O3 reactivity to dissolved organic carbon can be a significant carbon source to the marine atmosphere and warrants further investigation into the speciated VOC composition from different seawater samples, and the reactivities and secondary organic aerosol yields of these molecules in marine-relevant, low NOx conditions.

Delaney B. Kilgour et al.

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  • RC1: 'Comment on egusphere-2023-2210', Anonymous Referee #2, 31 Oct 2023
  • RC2: 'Comment on egusphere-2023-2210', Anonymous Referee #1, 06 Nov 2023

Delaney B. Kilgour et al.

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Production of oxygenated volatile organic compounds from the ozonolysis of coastal seawater Delaney B. Kilgour, Gordon A. Novak, Timothy H. Bertram

Delaney B. Kilgour et al.


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Short summary
Laboratory experiments with seawater mimics suggest ozone deposition to the surface ocean can be a source of reactive carbon to the marine atmosphere. We conduct both field and laboratory measurements to assess abiotic VOC composition and yields from ozonolysis of real surface seawater. We show that C5–C11 aldehydes contribute to the observed VOC emission flux. We estimate that VOC generated by the ozonolysis of surface seawater is competitive with biological VOC production and emission.