HONO Budget and Its Role in Nitrate Formation in the Rural North China Plain

Chaoyang Xue (1, 2) , Chenglong Zhang (1) , Can Ye (1) , Pengfei Liu (1) , Valéry Catoire (2) , Gisèle Krysztofiak (2) , Hui Chen (3) , Yangang Ren (4, 5) , Xiaoxi Zhao (1) , Jinhe Wang , Fei Zhang (3) , Chongxu Zhang , Jingwei Zhang (6) , Junling An (6) , Tao Wang (7) , Jianmin Chen (3) , Jörg Kleffmann (8) , Abdelwahid S Mellouki (4, 5) , Yujing Mu

1 Department of Soil Environmental Science, Research Centre for Eco-environmental Sciences
2 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace
3 LAP3 - Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention
4 ICARE - Institut de Combustion, Aérothermique, Réactivité et Environnement
5 OSUC - Observatoire des Sciences de l'Univers en région Centre
6 UCAS - University of Chinese Academy of Sciences [Beijing]
7 POLYU - The Hong Kong Polytechnic University [Hong Kong]
8 University of Wuppertal

Nitrous acid (HONO) is a major precursor of tropospheric hydroxyl radical (OH) that accelerates the formation of secondary pollutants. The HONO sources, however, are not well understood, especially in polluted areas. Based on a comprehensive winter field campaign conducted at a rural site of the North China Plain, a box model (MCM v3.3.1) was used to simulate the daytime HONO budget and nitrate formation. We found that HONO photolysis acted as the dominant source for primary OH with a contribution of more than 92%. The observed daytime HONO could be well explained by the known sources in the model. The heterogeneous conversion of NO2 on ground surfaces and the homogeneous reaction of NO with OH were the dominant HONO sources with contributions of more than 36 and 34% to daytime HONO, respectively. The contribution from the photolysis of particle nitrate and the reactions of NO2 on aerosol surfaces was found to be negligible in clean periods (2%) and slightly higher during polluted periods (8%). The relatively high OH levels due to fast HONO photolysis at the rural site remarkably accelerated gas-phase reactions, resulting in the fast formation of nitrate as well as other secondary pollutants in the daytime.

Domains: Sciences of the Universe [physics]

Chaoyang Xue, Chenglong Zhang, Can Ye, Pengfei Liu, Valéry Catoire, et al.. HONO Budget and Its Role in Nitrate Formation in the Rural North China Plain. Environmental Science and Technology, 2020, 54 (18), pp.11048-11057. ⟨10.1021/acs.est.0c01832⟩. ⟨insu-02950517⟩