Preprints
https://doi.org/10.5194/acp-2021-723
https://doi.org/10.5194/acp-2021-723

  23 Sep 2021

23 Sep 2021

Review status: this preprint is currently under review for the journal ACP.

Exploration of the atmospheric chemistry of nitrous acid in a coastal city of southeastern China: Results from measurements across four seasons

Baoye Hu1,2,3,4, Jun Duan6, Youwei Hong1,2, Lingling Xu1,2, Mengren Li1,2, Yahui Bian1,2, Min Qin6, Wu Fang6, Pinhua Xie1,5,6,7, and Jinsheng Chen1,2 Baoye Hu et al.
  • 1Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China
  • 2Key Lab of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China
  • 3Fujian Provincial Key Laboratory of Pollution Monitoring and Control, Minnan Normal University, Zhangzhou, 363000, China
  • 4Fujian Provincial Key Laboratory of Modern Analytical Science and Separation Technology, Minnan Normal University, Zhangzhou, 363000, China
  • 5University of Chinese Academy of Sciences, Beijing 100086, China
  • 6Key Laboratory of Environment Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei, 230031, China
  • 7School of Environmental Science and Optoelectronic Technology, University of Science and Technology of China, Hefei, 230026, China

Abstract. Because nitrous acid (HONO) photolysis is a key source of hydroxyl (OH) radicals, identifying the atmospheric sources of HONO is essential to enhance the understanding of atmospheric chemistry processes and improve the accuracy of simulation models. We performed seasonal field observations of HONO in a coastal city of southeastern China, along with measurements of trace gases, aerosol compositions, photolysis rate constants (J), and meteorological parameters. The results showed that the average observed concentration of HONO was 0.54 ± 0.47 ppb. Vehicle exhaust emissions contributed an average of 1.64 % to HONO, higher than the values found in most other studies, suggesting an influence from diesel vehicle emissions. The mean conversion frequency of NO2 to HONO in the nighttime was the highest in summer due to water droplets was evaporated under the condition of high temperatures. Based on a budget analysis, the rate of emission from unknown sources (Runknown) was highest around midday, with values of 4.35 ppb · h−1 in summer, 3.53 ppb · h−1 in spring, 3.13 ppb · h−1 in autumn, and 2.05 in winter. Unknown sources made up the largest proportion of all sources in summer (78.55 %), autumn (71.51 %), spring (69.67 %), and winter (55.63 %). The photolysis of particulate nitrate was probably a source in spring and summer while the conversion from NO2 to HONO on BC enhanced by light was perhaps a source in autumn and winter. The variation of HONO at night can be exactly simulated based on the HONO/NOx ratio, while the J(NO3−_R) × pNO3 should be considered for daytime simulations in summer and autumn, or 1/4 × (J(NO3_R) × pNO3) in spring and winter. Compared with O3 photolysis, HONO photolysis has long been an important source of OH except for summer afternoon. Observation on HONO across four seasons with various auxiliary parameters improves the comprehension of HONO chemistry in southeastern coastal China.

Baoye Hu et al.

Status: open (until 04 Nov 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-723', Anonymous Referee #2, 14 Oct 2021 reply
    • AC1: 'Reply on RC1', Jinsheng Chen, 22 Oct 2021 reply
  • RC2: 'Comment on acp-2021-723', Anonymous Referee #1, 14 Oct 2021 reply
    • AC2: 'Reply on RC2', Jinsheng Chen, 22 Oct 2021 reply

Baoye Hu et al.

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Short summary
There has been a lack of research into HONO in coastal cities with low concentrations of PM2.5, but strong sunlight and high humidity. Insufficient research on coastal cities with good air quality has resulted in certain obstacles to assessing the photochemical processes in these areas. Furthermore, HONO contributes to the atmospheric photochemistry depending on the season. Therefore, observations of HONO across four seasons in the southeastern coastal area of China are urgently needed.
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