Preprints
https://doi.org/10.5194/acp-2022-426
https://doi.org/10.5194/acp-2022-426
 
28 Jun 2022
28 Jun 2022
Status: this preprint is currently under review for the journal ACP.

Seasonal modeling analysis of nitrate formation pathways in Yangtze River Delta region, China

Jinjin Sun1,2, Momei Qin1, Xiaodong Xie1, Wenxing Fu1, Yang Qin1,2, Li Sheng1, Lin Li1, Jingyi Li1, Ishaq Dimeji Sulaymon1, Lei Jiang1, Lin Huang1, Xingna Yu2, and Jianlin Hu1 Jinjin Sun et al.
  • 1Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, Nanjing University of Information Science & Technology, Nanjing 210044, China
  • 2Key Laboratory of Meteorological Disaster, Ministry of Education, Joint International Research Laboratory of Climate and Environment Change, Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration, Nanjing University of Information Science and Technology, Nanjing 210044, China

Abstract. Nitrate (NO3-) has been the dominant and the least reduced chemical component of fine particulate matter (PM2.5) since the stringent emission control implemented in China in 2013. The formation pathways of NO3- vary seasonally and differ substantially in daytime vs. nighttime. They are affected by precursor emissions, atmospheric oxidation capacity, and meteorological conditions. Understanding NO3- formation pathways provides insights for the design of effective emission control strategies to mitigate NO3- pollution. In this study, the Community Multiscale Air Quality (CMAQ) model was applied to investigate the impact of regional transport, predominant physical processes, and different formation pathways to NO3- and total nitrate (TNO3, i.e., HNO3+NO3-) production in the Yangtze River Delta (YRD) region during the four seasons of 2017. NO3-/PM2.5 and NO3-/TNO3 are the highest in the winter, reaching 21 % and 94 %, respectively. Adjusted gas ratio (adjGR = ([NH3] + [NO3-])/([HNO3] + [NO3-])) in YRD is generally greater than two in different seasons across most areas in YRD, indicating that YRD is mostly in the NH3-rich regime and NO3- is limited by HNO3 formation. Local emissions and regional transportation contribute to YRD NO3- concentrations by 50–62 % and 38–50 %, respectively. Majority of the regional transport of NO3- concentrations is contributed by indirect transport (i.e., NO3- formed by transported precursors reacting with local precursors). Aerosol (AERO, including condensation, coagulation, new particle formation and aerosol growth) processes are the dominant source of NO3- formation. In summer, NO3- formation is dominated by AERO and total transport (TRAN, sum of horizontal and vertical transport) processes. The OH+NO2 pathway contributes to 60–83 % of the TNO3 production, and the N2O5 heterogeneous (HET N2O5) pathway contributes to 10–36 % in YRD. HET N2O5 contribution becomes more important in cold seasons than warm seasons. Within the planetary boundary layer in Shanghai, the TNO3 production is dominated by the OH+NO2 pathway during the day (98 %) in the summer and spring, and by the HET N2O5 pathway during the night (61 %) in the winter. Local contribution dominates the OH+NO2 pathway for TNO3 production during the day, while indirect transport dominates the HET N2O5 pathway at night.

Jinjin Sun et al.

Status: open (until 27 Aug 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-426', Anonymous Referee #1, 29 Jul 2022 reply

Jinjin Sun et al.

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Short summary
NO3- has become the dominant and the least reduced chemical component of fine particulate matter in China. NO3- formation is mostly in the NH3-rich regime in YRD. OH+NO2 pathway contributes to 60–83 % of the TNO3 production rates, and the N2O5 heterogeneous pathway contributes to 10–36 %. N2O5 heterogeneous pathway becomes more important in cold seasons. Local emissions and regional transportation contribute to YRD NO3- concentrations by 50–62 % and 38–50 %, respectively.
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