Current Activities

Our research has covered a wide variety of areas in atmospheric chemistry and physics and, in particular, the impacts of global air pollution on human health, ecosystems, and climate:

(i) Photochemical oxidation of hydrocarbons emitted from anthropogenic and biogenic sources has major implications for local and regional air quality. We conduct laboratory work to investigate the hydrocarbon oxidation reactions initiated by hydroxyl radical OH and other radical species, focussing on the formation of intermediate radicals and their subsequent degradation reactions. In addition, calculations using quantum chemical and kinetic rate theories are performed to study the structures, energetics, and isomeric branching to assess the preferred pathways of the organic radicals. Our objective is to quantitatively understand the kinetics and mechanism of atmospheric volatile organic compounds (VOCs) and their roles in tropospheric ozone and secondary aerosol formation.

(ii) Aerosols in the atmosphere profoundly impact human health, radiative transfer, weather, and climate. We combine experimental and theoretical approaches to investigate nucleation, growth, and transformation of aerosols at the fundamental molecular level. These include elucidation of the formation of thermodynamically stable clusters from molecular complexes and clusters, the growth of stable clusters to nano- and submicrometer-sized particles, and transformation and properties of submicrometer-sized particles. The chemical and physical properties of aerosols are measured to assess their effects on weather, human health, visibility, and climate.

(iii) We develop state-of-the-art instrumentation to measure trace gaseous compounds and aerosols in the atmosphere. Our instruments have been deployed to study multi-phase atmospheric chemical processes in Houston and Mexico City. Most recently, our team participated in air quality studies in Beijing during the 2008 summer Olympic Games (CAREBeijing-08) and in Guangzhou during the field campaign, the Program of Regional Integrated Experiments of Air Quality in the Pearl River Delta (PRIDE-PRD).

(iv) Air pollutants emitted from anthropogenic and natural sources are transported in the atmosphere while undergoing chemical transformation, affecting human health, agricultural activity, and climate. An understanding of the chemistry and transport of air pollutants is critical for devising strategies to improve urban, rural, and regional air quality. We employ chemical transport models (CTMs) to investigate formation of ozone and particulate matter and air quality on the urban and regional scales. We also investigate aerosol-cloud-climate interaction using cloud-resolving models and mesoscale models.