Preprints
https://doi.org/10.5194/egusphere-2024-1638
https://doi.org/10.5194/egusphere-2024-1638
24 Jul 2024
 | 24 Jul 2024
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

Formation drivers and photochemical effects of ClNO2 in a coastal city of Southeast China

Gaojie Chen, Xiaolong Fan, Haichao Wang, Yee Jun Tham, Ziyi Lin, Xiaoting Ji, Lingling Xu, Baoye Hu, and Jinsheng Chen

Abstract. Nitryl chloride (ClNO2) is an important precursor of chlorine (Cl) radical, significantly affecting ozone (O3) formation and photochemical oxidation. However, the key drivers of ClNO2 production are not fully understood. In this study, the field observations of ClNO2 and related parameters were conducted in a coastal city of Southeast China during the autumn of 2022, combining with machine learning and model simulations to elucidate its key influencing factors and atmospheric impacts. Elevated concentrations of ClNO2 (> 500 ppt) were notably observed during nighttime in late autumn, accompanied by increased levels of dinitrogen pentoxide (N2O5) and nitrate (NO3). Nighttime concentrations of ClNO2 peaked at 3.4 ppb, while its daytime levels remained significant, reaching up to 100 ppt and sustaining at approximately 40 ppt at noon. Machine learning and field observations identified nighttime N2O5 heterogeneous uptake as the predominant pathway for ClNO2 production, whereas NO3 photolysis contributed to its daytime generation. Additionally, ambient temperature (T) and relative humidity (RH) emerged as primary meteorological factors affecting ClNO2 formation, mainly through their effects on thermal equilibrium and N2O5 hydrolysis processes, respectively. Ultraviolet (UV) radiation was found to play a dual role in ClNO2 concentrations around noon. Box model simulations showed that under high ClNO2 conditions, the rates of alkane oxidation by Cl radical in the early morning exceeded those by OH radical. Consequently, VOC oxidation by Cl radical contributed ~ 19 % to ROx production rates, thereby significantly impacting O3 formation and atmospheric oxidation capacity. This research enriched the understanding of ClNO2 generation and loss pathways, providing valuable insights for the regulation of photochemical pollution in coastal regions.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Gaojie Chen, Xiaolong Fan, Haichao Wang, Yee Jun Tham, Ziyi Lin, Xiaoting Ji, Lingling Xu, Baoye Hu, and Jinsheng Chen

Status: open (extended)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-1638', Anonymous Referee #1, 31 Jul 2024 reply
    • AC1: 'Reply on RC1', Jinsheng Chen, 07 Oct 2024 reply
Gaojie Chen, Xiaolong Fan, Haichao Wang, Yee Jun Tham, Ziyi Lin, Xiaoting Ji, Lingling Xu, Baoye Hu, and Jinsheng Chen
Gaojie Chen, Xiaolong Fan, Haichao Wang, Yee Jun Tham, Ziyi Lin, Xiaoting Ji, Lingling Xu, Baoye Hu, and Jinsheng Chen

Viewed

Total article views: 499 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
319 109 71 499 52 9 9
  • HTML: 319
  • PDF: 109
  • XML: 71
  • Total: 499
  • Supplement: 52
  • BibTeX: 9
  • EndNote: 9
Views and downloads (calculated since 24 Jul 2024)
Cumulative views and downloads (calculated since 24 Jul 2024)

Viewed (geographical distribution)

Total article views: 500 (including HTML, PDF, and XML) Thereof 500 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 08 Dec 2024
Download
Short summary
Our study revealed that the nighttime heterogeneous N2O5 uptake process was the major contributor of ClNO2 sources, while nitrate photolysis promoted the elevation of daytime ClNO2 concentrations. The rates of alkane oxidation by Cl radical in the early morning exceeded those by OH radical, significantly promoted the formation of ROx and O3, further enhanced the atmospheric oxidation capacity levels.