The Role of Environmentally Persistent Free Radicals in the Chemistry of Airborne PM2.5

Louisiana State University, Baton Rouge LA

Investigators

Abstract

The Environmental Chemical Sciences (ECS) program of the Division of Chemistry will support the research program of Prof. Barry Dellinger of Louisiana State University. Prof. Dellinger and his students will study the environmental impact of Environmentally Persistent Free Radicals (EPFRs) in airborne fine particles. Prof. Dellinger's group has detected organic free radicals associated with freshly sampled airborne particles that are less than 2.5 micrometers in diameter (PM2.5), which can persist in air for several days after collection. The chemical and toxicological characteristics of these radicals are similar to radicals associated with the tar in cigarette smoke, and detected in samples of combustion-generated PM. Since the radicals are both stable toward decomposition and resistant to reaction with air, they are referred to as environmentally persistent and may serve as effective reducing agents in aqueous solution. Using EPR spectroscopy, EPFRs formed from dosing samples of PM2.5 with suspected EPFR precursors, will be compared to EPFRs formed on controlled surrogate particles containing different transition metals. The decay and lifetimes of the observed EPFRs will be determined as a function of temperature, humidity, and solar irradiation. EPFR-induced formation of reactive oxygen species (ROS) under biological conditions will be determined. The potential for EPFRs to participate in selected atmospheric chemistry will be evaluated. Reactions with NO and O3 will be studied to determine if EPFRs result in depletion or formation of these pollutants as well as formation of nitro-/oxy-PAH, other oxygenated species, and secondary radicals. As part of this project, Dr. Dellinger and his students will present project and research summaries to science-affiliated clubs and undergraduate programs. Collaborative research and interdisciplinary training of graduate students in chemistry, combustion, and environmental health sciences research will be conducted through the LSU Superfund Research Center. The PI is committed to student presentations at national/international meetings and their participation in several high impact education and outreach groups and programs already established at LSU, including the Superfund Research Program seminars and exchange program with biomedical research collaborators.