ARB Research Seminar

This page updated June 19, 2013

Toxicity of Ambient Particulate Matter: The Role of Peroxides as Generated by Aerosol Particles in Southern California

Photo of Suzanne Paulson, Ph.D.

Suzanne Paulson, Ph.D., Department of Atmospheric Sciences, University of California, Los Angeles

March 03, 2010
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA



Hydrogen peroxide (H₂O₂) is an important member of the family of reactive oxygen species (ROS), which have been associated with a range of adverse health outcomes. Previous results indicated that freshly collected ambient aerosols generate large amounts of H₂O₂ in aqueous solutions. This study probed the source of that H₂O₂ activity by examining the chemical composition of ambient aerosols and the activity of source materials. Fine and coarse mode aerosols were collected at three sites: two in Riverside (one upwind and one downwind of a major freeway), and one on the UCLA campus.

H₂O₂ generation by coarse mode aerosols at these sites was strongly correlated with soluble iron, zinc, and copper. H₂O₂ generation increased as the acidity of the particle extraction solutions increased.

In contrast, H₂O₂ generation activity for the fine mode aerosols was correlated with a combination of metals and organics, including quinones. Significant correlation was found with soluble iron, zinc, and copper when their concentrations were relatively high. H₂O₂ generation was highest when the particle extraction solutions were moderately acidic.

Lab experiments showed that ammonium sulfate particles do not generate H₂O₂, while secondary organic aerosol and diesel/biodiesel exhaust particles generate substantial quantities of H₂O₂.

Speaker Biography

Susan Paulson, Ph.D., has been a professor in the Department of Atmospheric & Oceanic Sciences at University of California, Los Angeles since 1994. She earned a B.A. in Chemistry from the University of Colorado, an M.S. in Plant Biology at the University of Illinois, and a Ph.D. in Environmental Engineering Science from the Caltech. Dr. Paulson's current research is focused on impacts of tiny particles that are produced by both natural and human activities on the Earth's climate and on human health. Professor Paulson has received a Faculty Early Career Development (CAREER) award from the National Science Foundation for her research.

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