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Significant contribution of heterogeneous reactions to the nitrous acid formation during winter in Beijing, China
Citation:
Zhang, S., G. Sarwar, J. Xing, B. Chu, C. Xue, A. Sarav, T. Ma, D. Ding, H. Zheng, Y. Mu, F. Duan, AND H. He. Significant contribution of heterogeneous reactions to the nitrous acid formation during winter in Beijing, China. 19th Annual CMAS Conference, Chapel Hill, NC, October 26 - 30, 2020.
Impact/Purpose:
Nitrous acid (HONO) plays important roles in atmospheric chemistry since it undergoes photolysis during the day and produces hydroxyl radical (OH) which reacts with organic and inorganic compounds and alters atmospheric composition. In this study, we apply the Community Multiscale Air Quality (CMAQv5.3) model to simulate air quality in China for December 2015 and compare model predictions with observed data in Beijing. The CMAQv5.3 model severely underestimates observed HONO concentration (Normal Mean Bias = -95%). We revise the original HONO formation reactions and also implement several additional HONO formation reactions. The revised chemistry substantially enhances HONO prediction and improves the model performance (Normal Mean Bias = -5%). Model results suggest that the heterogeneous reaction on the ground surface is the most significant reaction contributing ~80% of the predicted night-time and ~60% of the day-time surface HONO concentration. Enhanced HONO production increases OH concentrations. Predicted OH concentration without the updated HONO chemistry is substantially lower than the observed data. However, the model with the updated HONO chemistry successfully reproduces the observed OH concentration. The updated model also enhances ozone, inorganic aerosols, and secondary organic aerosols in Beijing winter. The presentation will include additional analysis and a comparison of model predictions with available observed data in China.
Description:
Nitrous acid (HONO) plays important roles in atmospheric chemistry since it undergoes photolysis during the day and produces hydroxyl radical (OH) which reacts with organic and inorganic compounds and alters atmospheric composition. In this study, we apply the Community Multiscale Air Quality (CMAQv5.3) model to simulate air quality in China for December 2015 and compare model predictions with observed data in Beijing. The CMAQv5.3 model severely underestimates observed HONO concentration (Normal Mean Bias = -95%). We revise the original HONO formation reactions and also implement several additional HONO formation reactions. The revised chemistry substantially enhances HONO prediction and improves the model performance (Normal Mean Bias = -5%). Model results suggest that the heterogeneous reaction on the ground surface is the most significant reaction contributing ~80% of the predicted night-time and ~60% of the day-time surface HONO concentration. Enhanced HONO production increases OH concentrations. Predicted OH concentration without the updated HONO chemistry is substantially lower than the observed data. However, the model with the updated HONO chemistry successfully reproduces the observed OH concentration. The updated model also enhances ozone, inorganic aerosols, and secondary organic aerosols in Beijing winter. The presentation will include additional analysis and a comparison of model predictions with available observed data in China.
