Preprints
https://doi.org/10.5194/acp-2021-47
https://doi.org/10.5194/acp-2021-47

  30 Mar 2021

30 Mar 2021

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

Improving the representation of HONO chemistry in CMAQ and examining its impact on haze over China

Shuping Zhang1,2,3, Golam Sarwar4, Jia Xing2, Biwu Chu1,3,5, Chaoyang Xue1,3, Arunachalam Sarav6, Dian Ding2, Haotian Zheng2, Yujing Mu1,3,5, Fengkui Duan2, Tao Ma2, and Hong He1,3,5 Shuping Zhang et al.
  • 1State Key Joint Laboratory of Environment Simulation and Pollution Control, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
  • 2State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China
  • 3University of Chinese Academy of Sciences, Beijing 100049, China
  • 4Center for Environmental Measurement and Modeling, U.S. Environmental Protection Agency, 109 T.W. Alexander Drive, Research Triangle Park, NC, 27711, USA
  • 5Center for Excellence in Regional Atmospheric Environment, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China
  • 6Institute for the Environment, The University of North Carolina at Chapel Hill, 100 Eurpoa Drive, Chapel Hill, NC 27514, USA

Abstract. We compare Community Multiscale Air Quality (CMAQ) model predictions with measured nitrous acid (HONO) concentrations in Beijing, China for December 2015. The model with the existing HONO chemistry in CMAQ severely under-estimates the observed HONO concentrations with a normalized mean bias of −97 %. We revise the HONO chemistry in the model by implementing six additional heterogeneous reactions in the model: reaction of nitrogen dioxide (NO2) on ground surfaces, reaction of NO2 on aerosol surfaces, reaction of NO2 on soot surfaces, photolysis of aerosol nitrate, nitric acid displacement reaction, and hydrochloric acid displacement reaction. The model with the revised chemistry substantially increases HONO predictions and improves the comparison with observed data with a normalized mean bias of −5 %. The photolysis of HONO enhances day-time hydroxyl radical by almost a factor of two. The enhanced hydroxyl radical concentrations compare favorably with observed data and produce additional sulfate via the reaction with sulfur dioxide, aerosol nitrate via the reaction with nitrogen dioxide, and secondary organic aerosols via the reactions with volatile organic compounds. The additional sulfate stemming from revised HONO chemistry improves the comparison with observed concentration; however, it does not close the gap between model prediction and the observation during polluted days.

Shuping Zhang et al.

Status: open (until 25 May 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Shuping Zhang et al.

Shuping Zhang et al.

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Short summary
Six heterogeneous HONO chemistry updates in CMAQ significantly improves HONO concentration. HONO production is primarily controlled by the heterogeneous reactions on ground and aerosol surfaces during haze. Additional HONO chemistry updates increase OH and production of secondary aerosols: sulfate, nitrate, and SOA.
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