New Insights into the Formation and Evolution of Air Pollutants Via Atmospheric Multiphase Chemistry

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Atmospheric aerosol refers to suspended particles with diameters 1/10 to 1/1000 that of an average human hair. Although small in size, aerosol exerts a huge impact on two of the arguably most emergent environmental issues of the 21st century: air pollution and climate change. Carrying harmful chemicals with it, aerosol can penetrate deep into the respiratory tract, affecting human health. In 2012, 7 million deaths worldwide were associated with ambient and indoor aerosol. Additionally, suspended aerosol can offset the warming effect of greenhouse gases by reflecting sunlight, which gives rise to a cooling effect on the planet. ******Understanding the chemistry of aerosol is currently a major scientific challenge. The toxicity and the magnitude of the aerosol cooling effect remain highly uncertain. One of the least understood aspects of aerosol is also a major fraction of it, referred to as Secondary Organic Aerosol (SOA), that contains hundreds of unidentified organic compounds produced through complex atmospheric chemistry. The research program proposed here aims to unravel the complex chemistry that leads to the formation and continuous evolution of SOA in the atmosphere. The outcome of the proposed research will guide the efforts of atmospheric chemists, environmental toxicologists and epidemiologists, as well as climatologists to better evaluate the environmental impact of aerosol. Such evaluations provide essential guidelines for policies, and ultimately, for a sustainable future. ******The proposed research program has two research directions. In the first direction, we will analyze the complex, unresolved fraction of SOA that is currently a major obstacle in understanding the SOA chemistry. We will develop innovative analytical methods for a direct measurement that avoids excess sample preparation and treatment, since delicate and reactive compounds can be lost during such processes. Employing both newly-developed and well-established analytical techniques, we will investigate the unidentified chemical species and undiscovered chemical reactions taking place in SOA. ******In the second direction, we will target an urgent environmental problem: air pollution from solid fuel burning. Solid fuel, including coal, firewood, agriculture residue and animal dung cake, is used by 3 billion people worldwide for cooking. Air pollution from solid fuel burning is the third most important health risk factor on the global scale. We will analyze the poorly understood chemical composition of aerosol arising from solid fuel burning. We will further study the atmospheric chemistry of emissions from solid fuel burning, which can give rise to toxic chemical pollutants and affect the air quality at a local to regional scale.