Organics are major contributors to particulate pollution in the atmosphere at many locations around the world. Organic aerosols are either directly emitted from a multitude of sources or are formed in the atmosphere through chemical reactions of gas phase organics forming secondary organic aerosol. Recent research has shown that formation of organic aerosol is much more dynamic than previously understood with organic aerosols evaporating in the atmosphere with dilution, reacting in the gas phase to produce lower volatility products and recondensing back to particle phase. Organic aerosol changes both physically and chemically in the atmosphere due to physical processes such as dilution, condensation of other organic species on existing particles, and chemical reactions. These physical and chemical changes cause the particles to have different health and climate consequences as compared to fresh emissions. Recent smog chamber studies have found primary emissions such as diesel emissions generate secondary organic aerosol, greatly exceeding the contribution from known secondary organic-aerosol precursors.
This project will investigate the fate and transformation of diesel exhaust emissions in terms of air quality. Diesel engines are in widespread use throughout the world, and the United States is leading the way in requiring new diesel fuel formulations and emission control technologies. While there new requirements clearly reduce tailpipe emissions, their full impacts on air quality such as secondary organic aerosol forming potential of diesel emissions are not well understood. This project will establish a method to generate, characterize, and quantify secondary organic aerosol formation by diesel emissions to evaluate the effectiveness of vehicle exhaust after-treatment systems. A significant change in chemical composition of diesel fuels is underway in many sectors especially in terms of fuel sulfur level. This project will investigate the influence of fuel change on water uptake of diesel particles. The water uptake impairs visibility and radiative forcing of diesel particles therefore impacting both environment and climate change. The project will use a smog chamber and state-of-art aerosol instrumentation to investigate chemical and physical transformation of diesel emissions under well-controlled conditions.
The project will provide important insights into the fate and transformation of diesel exhaust emissions in the atmosphere in terms of air quality. Diesel engines contribute significantly to air pollution. It is necessary to understand how incorporation of new technologies, such as wider use of alternative fuels and after-treatment systems, affect air pollution. The results of this study will inform government technology policy-making. The investigator will also disseminate his air pollution research to the public through exhibitions at museums to increase scientific literacy and serve as the basis for education modules in math and science aimed at diverse group of middle and high school students.
