Nitrous acid in the polluted coastal atmosphere of the South China Sea: Ship emissions, budgets, and impacts

Rongrong Gu, Weihao Wang, Xiang Peng, Men Xia, Min Zhao, Yingnan Zhang, Ya'nan Wang, Yiming Liu, Hengqing Shen, Likun Xue, Tao Wang, Wenxing Wang

Research output: Journal article publicationJournal articleAcademic researchpeer-review


Nitrous acid (HONO) can significantly contribute to hydroxyl radicals ([rad]OH) and thus regulate atmospheric oxidation chemistry; however, ambient HONO sources are not well quantified and vary in different environments. In this study, we conducted comprehensive field observations at a coastal site in the South China Sea and performed chemical box modelling to demonstrate contrasting budgets and impacts of diurnal atmospheric HONO derived from the sea, coastline and continent. The ship emission ratio of HONO/nitrogen oxides (NOx) (1.21 ± 0.99%) was calculated from hundreds of night-time fresh plume measurements. Offshore marine air was frequently influenced by ship exhausts, and the sea acted as an HONO sink. Heterogeneous conversions of nitrogen dioxide (NO2) on underlying surfaces and photolysis of adsorbed nitric acid (HNO3(ads)) were the major HONO sources in coastal air, when heterogeneous NO2 conversions on the ground surface and the homogeneous NO + [rad]OH reaction dominated HONO formation in continental air. HONO photolysis was a significant source of reactive radicals (ROx = [rad]OH + HO2[rad] + RO2[rad]) in these air masses. Atmospheric box model including only homogeneous HONO source of the NO + [rad]OH reactions significantly underpredicted the [rad]OH concentration and atmospheric oxidising capacity in coastal and continental air. This study provides new insights into the complex sources and significant impacts of HONO in the polluted coastal boundary layer.

Original languageEnglish
Article number153692
JournalScience of the Total Environment
Publication statusPublished - 20 Jun 2022


  • Atmospheric oxidising capacity
  • Budget analysis
  • Coastal boundary layer
  • Nitrous acid (HONO)
  • Ship emission

ASJC Scopus subject areas

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

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