ARB Research Seminar

This page updated June 19, 2013

Development of Reactivity Scales via 3-D Grid Modeling of California Ozone Episodes

Robert Harley, Ph.D., Professor of Civil and Environmental Engineering, University of California, Berkeley

July 22, 2002
Cal EPA Headquarters, 1001 "I" Street, Sacramento, CA

Research Project


The reactivity of carbon monoxide and 30 individual organic compounds was assessed using a 3-D photochemical air quality model with online sensitivity analysis based on the direct decoupled method (DDM-3D). Reactivity was assessed using an extended version of the SAPRC-99 chemical mechanism in the South Coast Air Basin and in Central California (including San Francisco Bay Area, Sacramento, and the San Joaquin Valley). Reactivity scales developed using 3-D modeling resulted in similar rankings to those developed by Carter using a box model. Relative measures varied less than absolute measures of reactivity as a function of location. Different measures of reactivity including MIR, MOIR, population exposure, and 1-hour vs. 8-hour average ozone all gave similar results. Isoprene and a-pinene in the South Coast Air Basin were found to be less reactive than previous calculations have suggested because of a different spatial distribution vs. anthropogenic emissions. Alkenes and carbonyls were found to vary in their relative reactivity as a function of location due to special features of their atmospheric chemistry. Uncertainties in relative reactivity of individual VOCs were dominated by uncertainties in the rate parameters of their primary oxidation reactions.

Speaker Biography

Robert Harley has been on the faculty at UC Berkeley for ten years, and is now Professor and Vice Chair of the Department of Civil and Environmental Engineering. Professor Harley's research interests include mathematical modeling of photochemical air pollution, solar ultraviolet radiation transfer, motor vehicle emissions, and the impact of reformulated fuels. Current projects include analysis and modeling of weekday-weekend differences in air pollution, assessment of motor vehicle emissions and VOC speciation for the summer 2000 Central California Ozone Study, assessment of the air quality impacts of using ethanol in California gasoline, and development and application of new online sensitivity analysis techniques for use in photochemical models.

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