Characterizing Emerging Sources of Organic Aerosol

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Urban activities emit many organic compounds into the atmosphere. Their chemical reactions form particulate matter which contributes to poor air quality and harms human health. Since motor vehicles have usually been identified as the main source of pollutants, regulations in the past decades have focused on controlling vehicular emissions, leading to reductions in air pollution. Future air quality, however, will depend increasingly on other important sources of particulate matter, such as food cooking, wildfires, and vehicular engines with new technologies. In this research program, we identify organic compounds emitted from emerging sources of air pollution and study their chemical reactions in the atmosphere. It is essential to understand these sources in order to predict their impacts on air quality and develop cost-effective control strategies to safeguard public health. Wildfires are becoming more common as a result of a warming climate. Particulate matter from wood burning is known to be harmful for human health, because it contains free radical species that cause damage to the body. With advanced instrumentation we will measure the level of these free radical species in wood smoke, and identify their chemical structures in order to understand the molecular processes that lead to their formation, and their effects on human health. Food cooking emits a large amount of particles in cities, but researchers have typically assumed that these particles readily evaporate in the atmosphere and therefore do not expect them to be important. However, there is little knowledge about evaporation of organic particles, particularly those that have been exposed to the atmosphere for a long time. We will study these atmospheric reactions that prevent particles from evaporating. From our experiments, we will build a mathematical model to describe the evaporation processes and provide computer models with a more accurate way to predict air quality. Engine technologies are rapidly evolving to make them more fuel-efficient, but one such technology, gasoline direct injection, emits more particles that can damage air quality. We will measure organic compounds emitted from these engines and study the chemical reactions that can produce particulate matter. Our measurements will provide a more comprehensive evaluation of how these emerging vehicle technologies will affect air quality and human health. In all research directions, we use detailed chemical measurements to gain fundamental molecular insights, and apply them to understand atmospheric behavior. Through these studies, students gain important scientific and professional skills required for their technical careers. They also work across multiple disciplines (chemistry, engineering, policy, health sciences) and create much needed knowledge to address critical environmental challenges.