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

Research output: Contribution to journalArticlepeer-review


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

Colleges, School and Institutes

External organisations

  • Chinese Academy of Sciences


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