Variations and sources of nitrous acid (HONO) during a severe pollution episode in Beijing in winter 2016

Wenqian Zhang, Shengrui Tong, Maofa Ge, Junling An, Zongbo Shi, Siqi Hou, Kaihui Xia, Yu Qu, Hongxing Zhang, Biwu Chu, Yele Sun, Hong He

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34 Citations (Scopus)
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HONO is an important precursor of OH radical and plays a key role in atmospheric chemistry, but its source and formation mechanism remain uncertain, especially during complex atmospheric pollution processes. In this study, HONO mixing ratios were measured by a custom-made instrument during a severe pollution event from 16 to 23 December 2016, at an urban area of Beijing. The measurement was divided into three periods: I (haze), II (severe haze) and III (clean), according to the levels of PM2.5. This pollution episode was characterized by high levels of NO (75 ± 39 and 94 ± 40 ppbV during periods I and II, respectively) and HONO (up to 10.7 ppbV). During the nighttime, the average heterogeneous conversion frequency during the two haze periods were estimated to be 0.0058 and 0.0146 h-1, and it was not the important way to form HONO. Vehicle emissions contributed 52% (± 16)% and 40% (± 18)% to ambient HONO at nighttime during periods I and II. The contribution of homogeneous reaction of NO with OH should be reconsidered under high-NOx conditions and could be noticeable to HONO sources during this pollution event. Furthermore, HONO was positively correlated with PM2.5 during periods I and II, suggesting a potential chemical link between HONO and haze particles.
Original languageEnglish
Pages (from-to)253-262
Number of pages10
JournalScience of the Total Environment
Early online date11 Aug 2018
Publication statusPublished - 15 Jan 2019


  • Daytime HONO budget
  • Haze
  • Homogeneous reaction
  • Nitrous acid measurement
  • Vehicle emissions

ASJC Scopus subject areas

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


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