17 Nov 2022
17 Nov 2022
Status: this preprint is currently under review for the journal ACP.

Unambiguous identification of N-containing oxygenated organic molecules using CI-Orbitrap in an eastern Chinese megacity

Yiqun Lu1,2, Yingge Ma1, Dan Dan Huang1, Shengrong Lou1, Sheng’ao Jing1, Yaqin Gao1, Hongli Wang1, Yanjun Zhang3, Hui Chen4, Naiqiang Yan2, Jianmin Chen4, Christian George3, Matthieu Riva3, and Cheng Huang1 Yiqun Lu et al.
  • 1State Environmental Protection Key Laboratory of Formation and Prevention of Urban Air Pollution Complex, Shanghai Academy of Environmental Sciences, Shanghai 200233, China
  • 2School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
  • 3Univ. Lyon, Université Claude Bernard Lyon1, CNRS, IRCELYON, 69626 Villeurbanne, France
  • 4Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3), Department of Environmental Science & Engineering, Jiangwan Campus, Fudan University, Shanghai 200438, China

Abstract. Oxygenated organic molecules (OOMs) are dominated by the N-containing species in polluted urban environment. As N-containing OOMs, especially those with more than one nitrogen atoms, prevailed in the high m/z range (m/z > 350Th), unambiguous identification of N-containing OOMs is highly desirable for understanding of their formation processes, precursors and influencing factors. To achieve this, we applied an ultra-high-resolution chemical ionization-orbitrap (CI-Orbitrap) in a field campaign and found that OOMs contain one (1N-OOMs), two (2N-OOMs) and three (3N-OOMs) nitrogen atoms respectively comprised 50 %, 26 % and 4 % of total OOMs. More interestingly, the fraction of 2N-OOMs increased with the increase of carbon number (nC) and were dominated by the ones derived from aliphatic precursors (2N-OOMAli, 64.2 %), indicating the importance of multistep oxidation. Plausible precursors of 2N-OOMs were aliphatics (2N-OOMAli, 64.2 %), aromatics (2N-OOMAro, 16 %), and monoterpenes (2N-OOMMT, 15.4 %). The 2N-OOMAli was the most abundant 2N-OOMs and its fraction even increased in the polluted day with enhanced proportion of the ones with nC>10. While 2N-OOMAli and 2N-OOMAro were dominated by daytime photochemical production, nighttime NO3-initiated oxidation dominated the formation of 2N-OOMMT. 2N-OOMAro were of highest oxygenation level, followed by 2N-OOMMT and 2N-OOMAli, which were affected by photochemistry and NOx concentrations. These results highlight the significant formation of 2N-OOMs and the influencing factors, on their formation in polluted urban environment, where various VOC precursors and atmospheric oxidants present.

Yiqun Lu et al.

Status: open (until 29 Dec 2022)

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  • RC1: 'Comment on acp-2022-774', Anonymous Referee #1, 08 Dec 2022 reply

Yiqun Lu et al.


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Short summary
The N-containing oxygenated organic molecules have been expected as the important precursors of aerosol particles. This study used an ultra-high-resolution mass spectrometer coupled with an online sample inlet to accurately measure their molecular composition, concentration level and variation patterns. We demonstrated their formation process and the influencing factors in a Chinese megacity involving various VOC precursors and atmospheric oxidants, and highlight the influence of PM episode.