Research Program Area: Atmospheric Processes
The objective of this program is to address the research needs of California Air Resources Board (ARB) concerning the development and implementation of a state-of-the-art photochemical mechanism used in airshed models and the application of these models for developing effective control strategies to reduce ozone. In response to the ARB's requests, the major focus of this program was the development of the Maximum Incremental Reactivity (MIR) scale which was implemented in the ARB's "Clean Fuels/Low-Emissions Vehicle" regulations as a means to calculate ozone reactivity adjustment factors (RAFs) so that volatile organic compound (VOC) emissions from different fuel/vehicle combinations can be regulated on an equal ozone impact basis. The main body of this report documents the development of the MIR and other reactivity scales, and discusses how best to develop an optimum scale for ozone reactivity assessment for VOCs. It is concluded that the MIR scale gives similar RAFs as a scale based on effects of VOCs on integrated ozone, and that either type of scale is appropriate for applications requiring use of a single reactivity scale.
Appendices to this report give the details of the chemical mechanism, airshed model scenarios, and calculation methodology employed, and give tabulations of results of selected sensitivity calculations on reactivity scales which were carried out. The latter include comparing reactivity scales developed in this work with those calculated using the two chemical mechanisms most commonly used in airshed models, and using a preliminary alternative aromatics mechanism which was developed for this program.
For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753
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