Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published March 1986 | public
Journal Article

Comparative analysis of chemical reaction mechanisms for photochemical smog—II. Sensitivity of EKMA to chemical mechanism and input parameters


The six chemical reaction mechanisms for photochemical smog described in Pan I (Leone and Seinfeld, 1985, Atmospheric Environment 19,437–464) were used to study the effect of input parameters on volatile organic compound (VOC) control requirements needed to meet the National Ambient Air Quality Standard for ozone. The parameters studied were initial VOC composition, dilution rate, post 8-a.m. emissions, base case (present day) O₃ levels, entrainment from aloft of VOC and ozone and initial VOC/NOₓ ratio. The Empirical Kinetic Modeling Approach (EKMA) was used to generate ozone isopleths for each chemical mechanism. The VOC control needed to reduce the maximum ozone concentration from some present day value to 0.12 ppm, assuming no NOₓ control and a specified initial VOC/NOₓ ratio, was calculated using the six chemical reaction mechanisms. The initial VOC/NOₓ ratio was found to have the largest effect of all the parameters studied on VOC control requirements. Choice of chemical mechanism, ozone and VOC entrainment from aloft, base-case ozone and the composition of the initial VOC mixture also had a large effect on predicted control requirements. To reduce the degree of uncertainty in control predictions using EKMA it is necessary to establish as accurately as possible the composition of urban air in early morning. Also, because of the substantial effect the choice of chemical mechanism has on the predicted control requirements using EKMA, it is important that future work continues to be directed toward evaluating candidate chemical mechanisms with respect to their ability to simulate atmospheric smog chemistry.

Additional Information

© 1986 Published by Elsevier. Although the research described in this article has been funded wholly by the United States Environmental Protection Agency through Cooperative Agreement No. 8101845 to the California Institute of Technology, it has not been subjected to the Agency's required peer and policy review and therefore does not necessarily reflect the views of the Agency and no official endorsement should be inferred. We wish to acknowledge the helpful comments of Dr M. C. Dodge.

Additional details

August 22, 2023
October 18, 2023