Oxidation of Phenolic Aldehydes by Ozone and Hydroxyl Radicals at the Air-Solid Interface

Md Sohel Rana, Marcelo I. Guzman

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Biomass burning emissions contain abundant phenolic aldehydes (e.g., syringaldehyde, vanillin, and 4-hydroxybenaldehyde) that are oxidized during atmospheric transport, altering the physicochemical properties of particulates. Herein, the oxidative processing of thin films made of syringaldehyde, vanillin, and 4-hydroxybenaldehyde is studied at the air-solid interface under a variable O3(g) molar ratio (410 ppbv-800 ppmv) and relative humidity (0-90%). Experiments monitored the absorption changes of C= C, C= O, and -COOH vibration changes during the oxidation of thin films by transmission Fourier transform infrared spectroscopy (FTIR). Selected spectroscopic features of aromatic ring cleavage by O3(g) revealed the production of carboxylic acids. Instead, monitoring O-H stretching provided a comparison of a hydroxylation channel from in situ produced hydroxyl radical. The overall oxidation reactivity trend syringaldehyde > vanillin > 4-hydroxybenzladehyde can be explained based on the additional electron density from methoxide substituents to the ring. The reactive uptake coefficient of O3(g) increases for higher relative humidity, e.g., for syringaldehyde by 18 and 215 times at 74% and 90% relative humidity (RH), respectively, as compared to dry conditions. A Langmuir-Hinshelwood mechanism fits well the kinetics of oxidation under a variable O3(g) molar ratio at 74% RH, providing useful information that should be included in atmospheric chemistry models.

Original languageEnglish
Pages (from-to)2900-2909
Number of pages10
JournalACS Earth and Space Chemistry
Volume6
Issue number12
DOIs
StatePublished - Dec 15 2022

Bibliographical note

Publisher Copyright:
© 2022 American Chemical Society.

Keywords

  • biomass burning
  • hydroxyl radical
  • methoxyphenols
  • ozone
  • secondary organic aerosol

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Atmospheric Science
  • Space and Planetary Science

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