Improving the representation of HONO chemistry in CMAQ and examining its impact on haze over China
oleh: S. Zhang, S. Zhang, S. Zhang, G. Sarwar, J. Xing, B. Chu, B. Chu, B. Chu, C. Xue, C. Xue, A. Sarav, D. Ding, H. Zheng, Y. Mu, Y. Mu, Y. Mu, F. Duan, T. Ma, H. He, H. He, H. He
| Format: | Article |
|---|---|
| Diterbitkan: | Copernicus Publications 2021-10-01 |
Deskripsi
<p>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 underestimates the observed HONO concentrations with a normalized mean bias of <span class="inline-formula">−</span>97 %. We revise the HONO chemistry in the model by implementing six additional heterogeneous reactions in the model: the reaction of nitrogen dioxide (NO<span class="inline-formula"><sub>2</sub></span>) on ground surfaces, the reaction of NO<span class="inline-formula"><sub>2</sub></span> on aerosol surfaces, the reaction of NO<span class="inline-formula"><sub>2</sub></span> on soot surfaces, the photolysis of aerosol nitrate, the nitric acid displacement reaction, and the 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 <span class="inline-formula">−</span>5 %. The photolysis of HONO enhances daytime hydroxyl radical by almost a factor of 2. 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.</p>