11 Mar 2021

11 Mar 2021

Review status: this preprint is currently under review for the journal ACP.

Highly Oxygenated Organic Molecules Produced by the Oxidation of Benzene and Toluene in a Wide Range of OH Exposure and NOx Conditions

Xi Cheng1, Qi Chen1, Yong Jie Li2, Yan Zheng1, Keren Liao1, and Guancong Huang1 Xi Cheng et al.
  • 1State Key Joint Laboratory of Environmental Simulation and Pollution Control, BIC-ESAT and IJRC, College of Environmental Sciences and Engineering, Peking University, Beijing, China
  • 2Department of Civil and Environmental Engineering, Faculty of Science and Technology, University of Macau, Taipa, Macau, China

Abstract. Oxidation of aromatic volatile organic compounds (VOCs) leads to the formation of tropospheric ozone and secondary organic aerosol, for which gaseous oxygenated products are important intermediates. We show herein experimental results of highly oxygenated organic molecules (HOMs) produced by the oxidation of benzene and toluene in a wide range of OH exposure and NOx conditions. The results suggest multi-generation OH oxidation plays an important role in the product distribution, which likely proceeds more preferably via H subtraction than OH addition for early-generation products from light aromatics. Our experimental conditions promote the formation of more oxygenated products than previous flow-tube studies. The formation of dimeric products however was suppressed and might be unfavorable under conditions of high OH exposure and low NOx in toluene oxidation. Under high-NOx conditions, nitrogen-containing multifunctional products are formed, while the formation of other HOMs is suppressed. Products containing two nitrogen atoms become more important as the NOx level increases, and the concentrations of these compounds depend significantly on NO2. The highly oxygenated nitrogen-containing products might be peroxyacylnitrates, implying a prolonged effective lifetime of RO2 that facilitates regional pollution. Our results call for further investigation on the roles of high-NO2 conditions in the oxidation of aromatic VOCs.

Xi Cheng et al.

Status: open (until 06 May 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-201', Anonymous Referee #1, 30 Mar 2021 reply
  • RC2: 'Comments on acp-2021-201', Anonymous Referee #2, 13 Apr 2021 reply

Xi Cheng et al.


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Short summary
In this study we conducted laboratory studies to investigate the formation of gas-phase highly oxygenated organic molecules (HOMs). We provide a thorough analysis on the importance of multi-step auto-oxidation and multi-generation OH reaction. It also gives intensive investigation on the roles of high-NO2 conditions that represent a wide range of anthropogenically influenced environments.