My tabulation of the current status of ozone reactivity estimates for all the VOCs for which such estimates are or have been made can be downloaded here. It is given as a Portable Document Format (PDF) file, which requires at least the free Acrobat PDF reader to be viewed and printed.

This tabulation gives the preliminary Maximum Incremental Reactivity (MIR) values for all VOCs for which this has been calculated, along with, for comparison purposes, the MIR's which were adopted in the California Air Resources Board (CARB) Clean Fuels/Low Emissions Vehicle (CF/LEV) regulations. To place the MIR's from the different mechanism on the same basis, they are given relative to the base ROG mixture, which is the mixture of reactive organic gases used to represent emissions of non-methane organic compounds from all sources, whose composition is based on air quality data. Note that MIR's relative to the base ROG are more meaningful from a regulatory perspective since they reflect the predicted relative benefit of reducing emissions of the individual VOC alone compared to reducing VOC emissions from all sources equally.

Please be aware that the "1997" MIR's given on the table are preliminary and that a newer set of MIRs calculated using an updated mechanism should be available early next year. The values were calculated using the base mechanism given in the draft report entitled "Environmental Chamber Studies for Development of an Updated Mechanism for VOC Reactivity Assessment", which was submitted to the CARB last march. That version incorporates important updates to the aromatic and alkene mechanism compared to the SAPRC-90 version used to calculate the CF/LEV MIR's, as well as significant changes to the mechanisms for a number of individual VOCs which have been studied subsequent to the development of SAPRC-90. However, this version does not incorporate the compre- hensive update of the base mechanism (the mechanism for the reactions of the inorganics and the common products) which I have nearly completed, which will be used for calculating the next version of the scale. This update to the base mechanism is not expected to significantly change relative reactivities for most VOCs, though absolute reactivities (i.e., O3 formed per gram emitted) may change. In addition, this version also does not incorporate improvements to our ability to estimate mechanisms for oxygenated VOCs which I expect to result from our ongoing studies for the CARB consumer products program and for other projects. These updates may result in significant changes in reactivity estimates for some individual VOCs.

The tabulation also contains footnotes indicating (1) the level of uncertainty in the current reactivity estimates and the likelihood they may change, (2) the availability of experimental data for evaluating the mechanisms for the compound and the extent to which they have been evaluated, (3) documentation notes indicating how the mechanism was derived and giving other relevant comments, and (4) references for reports and papers describing the derivation and evaluation of the mechanisms or the chamber data used for that purpose. The documentation notes also indicate which of current reactivity estimates are most likely to change when the mechanism is updated, and which compound have only highly approximate or "placeholder" mechanisms which may change significantly if they are given priority for improvement. Although it is not feasible (or particularly meaningful in many cases) to give numerical uncertain- ty estimates for the tabulated MIR values, it is hoped that the footnotes will be sufficient to give a sense of the uncertainties involved, and the likelihood that the numbers will change.

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Note: An expanded tabulation, which also includes MOIR, EBIR, and integrated ozone reactivities for the preliminary updated mechanism, is also available (added 3/6/98).

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Other Available VOC Reactivity Data

Send comments or questions to carter@cert.ucr.edu

Last Modified March 6, 1998