Nighttime NOxloss and ClNO2formation in the residual layer of a polluted region: Insights from field measurements and an iterative box model

Hui Yun, Tao Wang, Weihao Wang, Yee Jun Tham, Qinyi Li, Zhe Wang, Steven C.N. Poon

Research output: Journal article publicationJournal articleAcademic researchpeer-review

15 Citations (Scopus)


The heterogeneous reaction of dinitrogen pentoxide (N 2O 5) on aerosols is an important sink of nitrogen oxides (NO x) in the polluted boundary layer, and the production of nitryl chloride (ClNO 2) can have significant effects on the atmospheric oxidative capacity. However, the heterogeneous loss of N 2O 5 and the formation of ClNO 2 are still not well quantified, especially in China. In a previous study, we measured ClNO 2 and N 2O 5 concentrations in several air masses at a high-elevation site in Hong Kong, and found the highest levels ever reported at one night. The present study employed an iterative box model to investigate five N 2O 5/ClNO 2-laden nights. We first estimated the N 2O 5 uptake coefficient and ClNO 2 yield and then calculated the relative importance of N 2O 5 heterogeneous reactions to NO x loss and the accumulated ClNO 2 production over the entire night. The average uptake coefficient was 0.004 ± 0.003, and the average yield was 0.42 ± 0.26. As the air masses aged, the accumulated ClNO 2 reached up to 6.0 ppbv, indicating significant production of ClNO 2 in the polluted air from the Pearl River Delta. ClNO 2 formation (N 2O 5 + Cl ), N 2O 5 hydrolysis (N 2O 5 + H 2O), and NO 3 reactions with volatile organic compounds (NO 3 + VOCs) consumed 23%, 27%, and 47% of the produced NO 3, respectively, as the average for five nights. A significant portion of the NO x in the air masses (70% ± 10%) was removed during the night via NO 3 reactions with VOCs (~ 40%) and N 2O 5 heterogeneous loss (~ 60%).

Original languageEnglish
Pages (from-to)727-734
Number of pages8
JournalScience of the Total Environment
Publication statusPublished - 1 May 2018


  • ClNO
  • N O
  • NO loss
  • Uptake coefficient
  • Yield

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution

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