Preprints
https://doi.org/10.5194/acp-2021-560
https://doi.org/10.5194/acp-2021-560

  22 Jul 2021

22 Jul 2021

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

Synergetic effect of NH3 and NOx on the production and optical absorption of secondary organic aerosol formation from toluene photooxidation

Shijie Liu1, Dandan Huang2, Yiqian Wang1, Si Zhang1, Can Wu1, Wei Du1, and Gehui Wang1,3 Shijie Liu et al.
  • 1Key Lab of Geographic Information Science of the Ministry of Education, School of Geographic Sciences, East China Normal University, Shanghai 210062, China
  • 2State Environmental Protection Key Laboratory of Formation and Prevention of the Urban Air Pollution Complex, Shanghai Academy of Environmental Sciences, Shanghai 200233, China
  • 3Institute of Eco-Chongming, 3663 North Zhongshan Road, Shanghai 200062, China

Abstract. NH3 is the most important alkaline gas in the atmosphere and one of the key species affecting the behaviors of atmospheric aerosols. However, the impact of NH3 on secondary organic aerosol (SOA) formation remains poorly understood, especially the dynamic evolution of chemical compositions in the SOA formation process. A series of chamber experiments was performed to probe the individual and common effects of NH3 and NOx on toluene SOA formation through OH-photooxidation. The chemical compositions of toluene SOA were characterized using the Aerodyne high-resolution time-of-flight aerosol mass spectrometer (AMS). From 637 ± 14.6 μg m−3 (control), the SOA mass concentration increased to 867 ± 12.7 μg m−3 in the presence of NH3 and decreased to 452 ± 18.9 μg m−3 in the presence of NOx. However, the highest SOA concentration (1020 ± 10.6 μg m−3) and the lowest carbon oxidation state (OSC) occurred in the presence of both NH3 and NOx, indicating that the higher volatility products that formed in the presence of NOx could precipitate into the particle-phase when NH3 was added. This resulted in a synergetic effect on SOA formation when NH3 and NOx co-existed. The heterogeneous reaction was the main pathway by which NH3 participated in SOA formation in the photooxidation process. The synergetic effect of NH3 and NOx was also observed in SOA optical absorption. A peak at 280 nm, which is characteristic of organonitrogen imidazole compounds, was observed in the presence of NH3 and its intensity increased when NOx was added into the chamber. This work improves our understanding of how the synergistic interactions between NH3 and NOx influence SOA formation and offers new insights into mitigating aerosol pollution that factor in mixed atmospheric conditions.

Shijie Liu et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on acp-2021-560', Yujing Mu, 31 Jul 2021
  • RC1: 'Comment on acp-2021-560', Anonymous Referee #1, 20 Aug 2021
  • RC2: 'Reviewer comment on acp-2021-560', Anonymous Referee #2, 21 Aug 2021
  • RC3: 'Comment on acp-2021-560', Anonymous Referee #3, 02 Sep 2021
  • RC4: 'Comment on acp-2021-560', Anonymous Referee #4, 03 Sep 2021

Shijie Liu et al.

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Short summary
A series of chamber experiments was performed to probe the individual and common effects of NH3 and NOx on toluene SOA formation through OH-photooxidation. the Synergetic effects of NH3 and NOx on the toluene SOA concentration and optical absorption was observed. The higher volatility products which were formed in the presence of NOx could precipitate into the particle-phase when NH3 was added. The formation pathways of NOCs through NOx or NH3 are also discussed.
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