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

Abstract

In mid-1996, California implemented Phase 2 Reformulated Gasoline (RFG). The new fuel was designed to further decrease emissions of hydrocarbons (HC), oxides of nitrogen (NO), carbon monoxide (CO), sulfur dioxide (SO), and other toxic species. In addition, it was formulated 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 introduction of California Phase 2 RFG, the Desert Research Institute (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 RFG on emissions from real-world vehicles. Compared with the 1995 experiment, CO and NO emissions exhibited statistically significant decreases, while the decrease in non-methane hydrocarbon emissions was not statistically significant. Changes in the speciated HC emissions were evaluated. 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 ether (MTBE) exhibited a larger increase. Overall changes in the ozone-forming potential of the emissions were not significantly different, with the increased contributions to reactivity from paraffins, ole-fins, and MTBE being offset by a large decrease in reactivity due to aromatics.

Peroxyacetyl Nitrate and Peroxypropionyl Nitrate during SCOS 97-NARSTO

“…Higher daytime temperatures were recorded in 1997, i.e., thermal decomposition of PAN and PPN may have been more important in 1997 than in 1993 (see discussion below). Other differences between summer 1993 and summer 1997 include significant changes in vehicle fuel composition that resulted from the mandated use of California Phase 2 reformulated gasolines in 1996 ( − ). These changes were likely to impact the nature and magnitude of vehicle emissions of oxides of nitrogen (NO x ) and of volatile organic compounds (VOC) that are precursors to PAN and PPN.…”

“…In Azusa, the slope in eq 1 is essentially the same as that of 0.166 ± 0.018 ( n = 331) measured in summer 1993 (). Thus, changes in vehicle fuel composition and vehicle emissions between 1997 and 1993, including those that resulted from the introduction of California Phase 2 reformulated gasoline in 1996 ( − ), have had no measurable effect on the abundance of the VOC that are precursors to PPN relative to that of the VOC that are precursors to PAN.…”

Trends in ozone, its precursors, and related secondary oxidation products in Los Angeles, California: A synthesis of measurements from 1960 to 2010

“…Since 1960, several short‐term ground‐based field studies have been conducted at selected locations within the SoCAB. Basin‐wide measurements from instrumented research aircraft began in the 1970s [ Husar et al ., ], and near‐tailpipe measurements from mobile roadside monitors began in the early 1990s [ Beaton et al ., ; Bishop and Stedman , ; Gertler et al ., ; Lawson et al ., ]. Long‐term trends in ozone and emissions of its precursors in the SoCAB have been extensively studied using the data collected in these experiments [ Ban‐Weiss et al ., ; Bishop and Stedman , ; Dallmann and Harley , ; Fortin et al ., ; Fujita et al ., ; Fujita et al ., ; Grosjean , ; Harley et al ., ; McDonald et al ., ; Parrish et al ., ; Parrish et al ., ; Warneke et al ., ].…”

Effects of Reformulated Gasoline and Motor Vehicle Fleet Turnover on Emissions and Ambient Concentrations of Benzene

“…Kirchstetter et al ( 14) report a 30-40% reduction in benzene emissions associated with the introduction of California phase 2 RFG in the San Francisco Bay area. Gertler et al (15) report a 13% reduction in the mass fraction of benzene relative to total nonmethane organic compound (NMOC) emissions in a Los Angeles traffic tunnel between 1995 and 1996. Fuel-related benzene reductions had already occurred prior to the baseline year in that study: unlike the San Francisco Bay area, Los Angeles was subject to Federal RFG requirements in 1995.…”