ARB Research Seminar
This page updated June 19, 2013
An Investigation of the Relationship Between Total Non-Methane Organic Carbon and the Sum of Speciated Hydrocarbons and Carbonyls Measured by Standard GC / FID: Measurements in the South Coast Air Basin
Suzanne Paulson, Ph.D., Department of Atmospheric Sciences, University of California, Los Angeles
June 17, 2002
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA
Also presented in El Monte on July 24, 2002
We describe development of a new instrument to measure the total airborne non-methane organic carbon concentration (TNMOC), and the ratio of this value to the sum of speciated volatile organic compounds (VOCs) measured by standard gas chromatography. The TNMOC and sum of speciated VOCs analyses are made simultaneously. Samples are collected in situ, with an inlet designed to minimize sample contact. Whole air samples are cryo-trapped with minimal collection of CO₂, CO and CH4. Organics are desorbed and converted to CO₂ using an oxidation catalyst. CO₂ is analyzed with a flame ionization detector after reduction to methane. The instrument is tested on gas mixtures, ambient air, and on smog chamber samples.
Simultaneous measurements of TNMOC and speciated VOCs were collected by a newly developed instrument. The ratio of the TNMOC to the speciated VOCs measurement indicates the "excess" VOCs; those not detected by routine monitoring techniques. Measurements of ambient air were made in West Los Angeles, Burbank, and Azusa. Primary pollution sources including gasoline vapor and diesel exhaust were tested as well. These primary sources are, not surprisingly, measured well by the standard speciated analysis, with averages of 5-15 percent "excess" VOCs. The Burbank site, which is surrounded by freeways and light industrial sources, had only 10 percent excess VOCs, as did UCLA during winter when there is minimal photochemistry. In contrast, conservatively, averages of between 20 and 40 percent of the TNMOC was unmeasured by standard chromatography at the UCLA and Azusa sites during summer. The dominant source of the unmeasured VOCs may be air that has been aged for more than 12 hours, possibly for a day or more.
Suzanne Paulson is an Associate Professor of Atmospheric Chemistry at the Department of Atmospheric Sciences at the University of California, Los Angeles. She also holds a joint appointment at the UCLA Institute of the Environment, UCLA Molecular Toxicology Interdepartmental Program, Southern California Particulate Matter Center and Supersite. Her research concerns the ozone chemistry of volatile organic compounds and ambient measurements of hydrocarbons. She has published more than 35 peer-reviewed articles and book chapters and received several awards including UC Regents Faculty award and Who's Who in American Women in Science.
Professor Paulson received her B.S. in Chemistry at the University of Colorado, Boulder, M.S. in Plant Biology at the University of Illinois, Urbana-Champaign, and M.S. and Ph.D. in Environmental Engineering Science at the California Institute of Technology. She was a postdoctoral fellow with the Advanced Study Program at the National Center for Atmospheric Research.