Industrialization and urbanization lead to large emissions of trace gases and particulates into the atmosphere. Understanding their impacts on air quality, the oxidizing capacity and the radiative budget of the atmosphere is the focus of international atmospheric chemistry and climate research. Asia is a particularly important and unique region in view of its phenomenal economic growth in the past 30 years resulting in a sharp increase in energy consumption and serious atmospheric pollution problems such as photochemical ozone, regional haze, and acid deposition.

The overall objective of our research is to understand the levels, sources, and atmospheric processes, and impact of air pollution and to support the development of control policies. We measure trace gases and aerosols using surface, mountain-top, and aircraft platforms in diverse geographical settings and use satellite remote sensed data and meteorological and chemical models to help interpret the data. 

Since 1995, we have studied air pollution in Hong Kong, the Pearl River delta, the Yangtze River delta, the North China plain (including Beijing), and atmospheric chemistry in maritime regions of the South China Sea and the western Pacific, and the inland Qinghai-Tibet Plateau (see figure below). The atmospheric composition data are invaluable for understanding the impact of the phenomenal economic development in the past 20 years on the atmospheric environment in China. Through analysis of the data, we gain understanding of unique sources, chemical and dynamical processes in China’s atmosphere. 

In the recent decade, our research focus has been on the sources and processes of reactive nitrogen compounds (HONO and N2O5) and of reactive halogens (ClNO2, Cl2, BrCl, and Br2) and their roles in photochemical pollution and haze, using lab, field and modeling techniques. We improved the mainstream air quality models for presenting reactive nitrogen and halogens. We also assessed the responses of secondary pollutants to emission reductions after the implementation of China’s Clean Air Action Plan and during Covid related city lockdown, recommended air-pollution control measures.