Development of emissions inventories for the Auto/Oil Air Quality Improvement Research Program

The air quality effects of different reformulated gasolines, various other alternative fuels, and developments in automotive technologies are being studied as part of a joint research project conducted by a consortium of three domestic auto companies and fourteen petroleum companies. As part of the air quality modeling effort, emission inventories are being developed in a near-term year (1995), and 21 fuels in a long-term year (2005 or 2010). A distinctive feature of this effort is that these inventories are the first used in an air quality study that treat light duty vehicle emissions by operating mode as well as by class, and base the speciation characteristics of each operating mode on actual vehicle test results. This incorporates an unusual amount of detail on the relative importance of each of the three vehicle exhaust, two evaporative, and running loss operating modes, both in terms of overall mass emission amounts and in terms of the hydrocarbon speciation and ozone reactivity. This study also allows a better estimate of the relative importance of each vehicle class and technology type to an overall emission inventory, and of the differences in the effects of alternative fuels between vehicle technologies and classes. In addition, the role of mobile source emissions relative to other sources of emissions for both short-term and long-term emission projections, and across a wide geographic range is being assessed. This paper first describes the techniques used in developing these emission inventories, and then examines regional, temporal, and fuel/vehicle effects on emissions