The lmpact of California Phase 2 Reformulated Gasoline on Real-World Vehicle Emissions

摘要

In mid-1996, California implemented Phase 2 Reformu- lated Gasoline (RFG). The new fuel was designed to tur- ther decrease emissions of hydrocarbons (HCs), oxides of nitrogen (NOx), carbon monoxide (CO), sulfur dioxide (SO2), and other toxic species. In addition, it was formu- lated to reduce the ozone-forming potential of the HCs emitted by vehicles. Previous studies have observed that emissions from on-road vehicles can differ significantly from those predicted by mobile source emissions models, and so it is important to quantify the change in emissions in a real-world setting. In October 1995, prior to the intro- duction of California Phase 2 RFG, the Desert Research In- stitute (DRI) performed a study of vehicle emissions in Los Angeles' Sepulveda Tunnel. This study provided a baseline against which the results of a second experiment, conducted in July 1996, could be compared to evaluate the impact of California Phase 2 AfG on emissions from real-world ve- hicles. Compared with the 1995 experiment, CO and NOx emissions exhibited statistically significant decreases, while the decrease in non-methane hydrocarbon emissions was not statistically significant. Changes in the speciated HC emissions were evalu- ated. The benzene emission rate decreased by 27 and the overall emission rate of aromatic compounds decreased by 22 comparing the runs with similar speeds. Emissions of alkenes were virtually unchanged; however, emissions of combustion related unsaturates (e.g., acetylene, ethene) increased, while heavier alkenes decreased. The emission rate of methyl tertiary butyl et