In this project funded by the Environmental Chemical Sciences Program, Professors Krishna Foster and Matthias Selke of California State University, Los Angeles are investigating the impact of urban particulate matter on the lower atmosphere of Earth. The project is performed in collaboration with Professor Donald Dabdub of the University of California at Irvine. Urban particulate matter contains polycyclic aromatic hydrocarbons (PAH) generated from incomplete combustion processes, including motor vehicles fueled by gasoline and diesel. Although some PAHs are known to transfer energy to oxygen forming more reactive molecules, it is hard to know which PAHs are responsible for this energy transfer and how many times this occurs in the environment. The scope and accuracy of these energy transfer measurements is being improved with this project. Success in this research may improve air quality models and that are used to understand the impact of pollution on people, especially those living in urban areas. The students assisting in this research reflect the diverse population of southern California. Consequently, this project has the potential to increase the number of underserved students that select careers in the chemical sciences and pursue graduate education, addressing the nation's need for students preparing for chemical sciences careers.
The investigators work to identify PAH and oxygenated-PAH that are net sources of singlet molecular oxygen in solution by measuring singlet oxygen quantum yields and quenching rates. Alkene oxidation products formed from reactions with singlet molecular oxygen are characterized using multiple analytical techniques. Both laboratory experiments and air quality models are used to determine the potential role of PAH photoexcitation on oxidation in emission plumes and at the air/particle interface.
