Seminar

Abstract

Heterogeneous reaction involves gaseous reactants and solid/liquid surface. Many field measurements and lab experiments have been conducted in the past decade which suggest a critical role of heterogeneous chemistry in the troposphere. Modeling studies on heterogeneous chemistry are also desired for investigating the impacts on a regional to global scale. Whereas, such research has attracted less attention.

In the present work, the widely-used Weather Research and Forecasting coupled with Chemistry model (WRF-Chem) was developed to include the heterogeneous reactions of several nitrogen and halogen species. The revised WRF-Chem was employed in China to explore the impact of the heterogeneous chemistry on oxidative capacity and air quality. Three separate yet connected work will be demonstrated, including the impact of N2O5 and ClNO2 chemistry on O3 and nitrogen partitioning, the impact of HONO and ClNO2 chemistry on radical and O3, and the impact of HONO and ClNO2 chemistry on O3 sensitivity determination. These studies show that a significant amount of OH and Cl precursors (HONO and ClNO2) was produced from the heterogeneous uptake of N2O5 and NO2. The increased OH and Cl radicals throughout the lower troposphere across China considerably enhanced the production of O3 and altered the partitioning of reactive nitrogen. The impact of HONO and ClNO2 on the budget of radical and nitrogen also influenced the determination of the O3 sensitivity regime which induced the implication for O3 control policy.

Apart from WRF-Chem, another regional model, CMAQ, and a global model, CAM-Chem, have also been utilized for several studies. CMAQ was adopted to look into the role of HONO, produced in part by the heterogeneous reaction, in a severe pollution episode in China. CMAQ was also used to study the impact of halogen chemistry on oxidative capacity in Europe. CAM-Chem was employed for a global flight campaign, Atmospheric Tomography Mission (ATom), to evaluate the impact of very short-lived halogen chemistry on halogen partitioning and on tropospheric ozone in remote area.

These regional and global studies highlight the role of heterogeneous chemistry in various environments around the globe. However, these works were done separately which calls for an overview study to examine the role of heterogeneous chemistry in the troposphere.

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Qinyi Li received a PhD from Hong Kong Polytechnic University, working with Tao Wang. He has collaborated with NOAA scientists to model heterogeneous chemistry in WRF-Chem. His visit is hosted by Ravan Ahmadov (GSD) and Stu McKeen (CSD).