25 Jan 2021

25 Jan 2021

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

Formation kinetics and mechanism of ozone and secondary organic aerosols from photochemical oxidation of different aromatic hydrocarbons: dependence of NOx and organic substituent

Hao Luo1,2,, Jiangyao Chen1,2,, Guiying Li1,2, and Taicheng An1,2 Hao Luo et al.
  • 1Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control, Guangdong-Hong Kong-Macao Joint Laboratory for Contaminants Exposure and Health, Institute of Environmental Health and Pollution control, Guangdong University of Technology, Guangzhou 510006, China
  • 2Guangzhou Key Laboratory of Environmental Catalysis and Pollution Control, Key Laboratory of City Cluster Environmental Safety and Green Development, School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou 510006, China
  • These authors contributed equally to this work.

Abstract. Aromatic hydrocarbons (AHs) contribute significantly to ozone and secondary organic aerosol (SOA) formation in atmosphere, but formation mechanisms are still unclear. Herein, photochemical oxidation of nine AHs was investigated in chamber. Only small amount of ozone was produced from direct photochemical oxidation of AHs, while fewer AH substituent number resulted in higher concentrated ozone. Addition of NOx increased ozone and SOA production. Synergetic effect of accelerated NO2 conversion and NO reaction with AHs boosted ozone and volatile intermediate formation. Promoting AH concentration in VOC / NOx ratio further increased formation rates and concentrations of both ozone and SOA. Additionally, ozone formation was enhanced with increasing AH's substituent number but negligibly affected by their substituent position. Differently, SOA yield decreased with increased substituent number of AHs, but increased with ortho methyl group substituted AHs. Model fitting and intermediate consistently confirmed that increasing substituent number on phenyl ring inhibited generating dicarbonyl intermediates, which however were preferentially produced from oxidation of ortho methyl group substituted AHs, resulting in different changing trend of SOA yield. The restrained oligomerization by increased substituent number was another main cause for decreased SOA yield. These results are helpful to understand photochemical transformation of AHs to secondary pollutants in real atmosphere.

Hao Luo et al.

Status: open (until 22 Mar 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-29', Anonymous Referee #1, 12 Feb 2021 reply
    • AC1: 'Reply on RC1', Taicheng An, 17 Feb 2021 reply
      • RC3: 'Reply on AC1', Anonymous Referee #1, 18 Feb 2021 reply
        • AC3: 'Reply on RC3', Taicheng An, 18 Feb 2021 reply
  • RC2: 'Comment on acp-2021-29', Anonymous Referee #2, 16 Feb 2021 reply
    • AC2: 'Reply on RC2', Taicheng An, 17 Feb 2021 reply

Hao Luo et al.


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Short summary
Formation kinetics & mechanism of O3 and SOA from different AHs are still unclear. Thus photochemical oxidation mechanism of 9 AHs with NO2 is comparably studied. Increased formation rate and yield of O3 and SOA is observed via promoting AH content. Raising number of AH's substituent enhances O3 formation, but decreases SOA yield, which is promoted by increasing methyl group number of AHs. Results are helpful to clear conversion of AHs to secondary pollutants in real atmospheric environment.