Impact of California Reformulated Gasoline on Motor Vehicle Emissions. 1. Mass Emission Rates

Abstract

This paper addresses the impact of California phase 2 reformulated gasoline (RFG) on motor vehicle emissions. Phase 2 RFG was introduced in the San Francisco Bay Area in the first half of 1996, resulting in large changes to gasoline composition. Oxygen content increased from 0.2 to 2.0 wt%; and alkene, aromatic, benzene, and sulfur contents decreased. Gasoline density and T 50 and T 90 distillation temperatures also decreased. Light-duty vehicle emission rates were measured in a Bay Area roadway tunnel in summers 1994−1997. Vehicle speeds and driving conditions inside the tunnel were similar each year. The average model year of the vehicle fleet was about one year newer each successive summer. Large reductions in pollutant emissions were measured in the tunnel over the course of this study, due to a combination of RFG and fleet turnover effects. Between summers 1994 and 1997, emissions of carbon monoxide decreased by 31 ± 5%, non-methane volatile organic compounds (VOC) decreased by 43 ± 8%, and nitrogen oxides (NO x ) decreased by 18 ± 4%. It was difficult to separate clearly the fleet turnover and RFG contributions to these changes. Nevertheless, it was clear that the effect of RFG was greater for VOC than for NO x . The RFG effect on vehicle emissions of benzene was estimated to be a 30−40% reduction. Use of RFG increased formaldehyde emissions by about 10%, while acetaldehyde emissions did not change significantly. RFG effects reported here may not be the same for other driving conditions or for other vehicle fleets. RFG effects on evaporative emissions are also important. The combined effect of phases 1 and 2 of California's RFG program was a 20% reduction in gasoline vapor pressure, about one-fifth of which occurred following the introduction of phase 2 RFG.

Megacities and Atmospheric Pollution

“…Tunnel measurements have led to revisions of emission models, 286 determined the effect of reformulated gasoline on HC spp. emitted by vehicles, 287 and quantified carbonyl and PAH emissions.…”

Trends in on-road vehicle emissions of ammonia

“…At the time of these measurements, we estimated based on a license-plate survey that ~99% of vehicles in the center bore are gasoline-powered and >94% of the vehicles were originally outfitted with three-way catalyst systems (Kean et al, 2000). During the rush-hour period of measurement, driving conditions and the mean vehicle age (~6 years old) at the Caldecott Tunnel are consistent from year to year (Kirchstetter et al, 1999;Ban-Weiss et al, 2008).…”

An Assessment of the Impact of California's Phase 2 Reformulated Gasoline on Ozone Air Quality

“…Although the effects of meteorology on the ozone concentrations have been greatly reduced, various factors in addition to CaRFG are responsible for changes in the emissions of ozone precursors. For example, Kirschtetter et al 3 found that both fleet turnover and CaRFG contributed to emission reductions during a multi-year tunnel study in the S.F. Bay Area.…”

“…2 Specifications for CaRFG are given in Table 1. While others have studied changes in vehicle emissions 3 or in ambient levels of ozone precursors 4 before and after the introduction of CaRFG, the goal of this study was to determine whether an ozone-reducing effect could be attributed to CaRFG by comparing ambient ozone concentrations in 1996 to ozone concentrations in earlier years.…”