16 Aug 2023
 | 16 Aug 2023

Secondary reactions of aromatics-derived oxygenated organic molecules lead to plentiful highly oxygenated organic molecules within an intraday OH exposure

Yuwei Wang, Yueyang Li, Gan Yang, Xueyan Yang, Yizhen Wu, Chuang Li, Lei Yao, Hefeng Zhang, and Lin Wang

Abstract. Highly oxygenated organic molecules (HOMs) can participate in new particle formation (NPF) and enhance growth of newly formed particles partially because of their low volatility. Previous studies have shown formation of HOMs via autoxidation reactions of RO2 intermediates generated by OH-initiated oxidation of anthropogenic volatile organic compounds (VOCs). It was also suggested that multi-generation OH oxidation could be an important source for aromatics-derived HOMs. However, our understanding on the generation of aromatics-derived HOMs are still insufficient, especially for their formation mechanisms, which determine molar yields of HOMs and are essential to the establishment of global chemical box models related to HOMs. In this study, with a potential aerosol formation oxidation flow reactor (PAM OFR), a series of OH-initiated oxidation experiments of 1,3,5-trimethylbenzene (1,3,5-TMB) were conducted to investigate the influences of the extent of OH exposure on the formation of aromatics-derived HOMs. The evolution of oxidation products of 1,3,5-TMB in an OH exposure range of (0.5 – 5.0)×1010 molecules cm-3 s, equivalent to an OH exposure of 0.7 – 6.9 hours at an OH concentration of 2×106 molecules cm-3, was investigated by a nitrate-based chemical ionization mass spectrometer and a Vocus proton-transfer-reaction mass spectrometer, indicating significant secondary OH chemistry during the ageing of stabilized first generation oxygenated products within an intraday OH exposure and formation of various HOMs with more oxygen content and thus lower volatility. In addition, organonitrates, formed after the introduction of NOx into the reaction systems, further confirmed the existence of such secondary reactions. Our study suggests an important role of secondary OH chemistry in the oxidation of aromatics and elucidates detailed formation mechanisms of certain HOM products.

Yuwei Wang et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-1702', Matti Rissanen, 24 Sep 2023
  • RC2: 'Comment on egusphere-2023-1702', Anonymous Referee #2, 03 Oct 2023

Yuwei Wang et al.


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Short summary
The formation and evolution mechanisms of aromatics-derived highly oxygenated organic molecules (HOMs) is essential to understanding the formation of secondary organic aerosol pollution. Our conclusion highlights an underappreciated formation pathway of aromatics-derived HOMs and elucidates detailed formation mechanisms of certain HOMs, which advances our understanding on HOMs and potentially explains the existing gap between model prediction and ambient measurement on the HOMs concentrations.