This study will take a comprehensive approach to understanding particulate radical formation and its related reactive oxygen species (ROS), by monitoring and modeling hydrogen peroxide and hydroxyl radical generation as well as transition metals, the oxidation state of dissolved iron and organics, including quinones, organic hydroperoxides and potential organic electron donors, in ambient aerosol samples and laboratory generated test aerosols. Field measurements at sites in the San Joaquin Valley and the Los Angeles Basin, California will provide samples for ongoing measurements of hydrogen peroxide and hydroxyl radical production and their relationships to variables of interest, and samples collected at the field sites will enable different particle types to be examined. A series of environmental chamber experiments will generate secondary organic aerosol (SOA) from oxidation of biogenic and anthropogenic hydrocarbons with pure ozone and high and low nitrogen oxide photochemistry, with and without seed aerosols composed of metal salts or diesel soot, and possibly other materials such as crustal dusts. Bulk mixture chemistry will also be explored to probe the interplay between metals, quinones and other organics, and effects of light on ROS chemistry will be examined in simplified systems. A chemical kinetics model will be developed and refined to guide the efforts to accurately assess ROS chemistry.
The project will enhance teaching and training of undergraduate and graduate students and postdoctoral scholars, and will establish a new partnership between the University of California, Los Angeles, and California State University, Fresno. The partnership will benefit the students involved, and will lead to synergistic benefits that will translate into enhanced classroom materials and outreach activities. The project will enhance participation in science by underrepresented groups, and the results will potentially contribute to key scientific questions related to human health and climate.
