On the potential use of highly oxygenated organic molecules (HOMs) as indicators for ozone formation sensitivity

• Published in: Atmospheric chemistry and physics Vol. 24; no. 5; pp. 2885 - 2911
• Main Authors: Zhang, Jiangyi, Zhao, Jian, Luo, Yuanyuan, Mickwitz, Valter, Worsnop, Douglas, Ehn, Mikael
• Format: Journal Article
• Language: English
• Published: Katlenburg-Lindau Copernicus GmbH 05.03.2024; Copernicus Publications
• Subjects: Accretion; Aerosols; Air pollution; Atmosphere; Autoxidation; Chemical reactions; Dimers; Environmental aspects; Environmental conditions; Free radicals; Mitigation; Monomers; Nitrates; Nitrogen compounds; Nitrogen dioxide; Organic chemistry; Organic compounds; Organic nitrates; Outdoor air quality; Oxidants; Oxidation; Oxides; Oxidizing agents; Oxygenation; Ozone; Ozone formation; Peroxy radicals; Photolysis; Secondary aerosols; Sensitivity; Stratosphere; Stratosphere radiation; Trace gases; Troposphere; Ultraviolet radiation; VOCs; Volatile organic compounds; Syria
• ISSN: 1680-7324; 1680-7316; 1680-7324
• DOI: 10.5194/acp-24-2885-2024

Ozone (O.sub.3 ), an important and ubiquitous trace gas, protects lives from harmful solar ultraviolet (UV) radiation in the stratosphere but is toxic to living organisms in the troposphere. Additionally, tropospheric O.sub.3 is a key oxidant and a source of other oxidants (e.g., OH and NO.sub.3 radicals) for various volatile organic compounds (VOCs). Recently, highly oxygenated organic molecules (HOMs) were identified as a new compound group formed from the oxidation of many VOCs, making up a significant source of secondary organic aerosol (SOA). The pathways forming HOMs from VOCs involve autoxidation of peroxy radicals (RO.sub.2 ), formed ubiquitously in many VOC oxidation reactions. The main sink for RO.sub.2 is bimolecular reactions with other radicals, such as HO.sub.2, NO, or other RO.sub.2, and this largely determines the structure of the end products. Organic nitrates form solely from RO.sub.2 + NO reactions, while accretion products ("dimers") form solely from RO.sub.2 + RO.sub.2 reactions. The RO.sub.2 + NO reaction also converts NO into NO.sub.2, making it a net source for O.sub.3 through NO.sub.2 photolysis.