Impact of California Phase 2 reformulated gasoline on atmospheric reactivity of exhaust and evaporative emissions
- Univ. of California, Berkeley, CA (United States). Dept. of Civil and Environmental Engineering
- Bay Area Air Quality Management District, San Francisco, CA (United States). Technical Services Div.
Phase 2 of California`s reformulated gasoline (RFG) program took effect statewide in the first half of 1996. Changes to gasoline composition required by Phase 2 specifications included: lower vapor pressure; lower olefin, aromatic, benzene, and sulfur content; lower T50 and T90; and a minimum oxygen content. In this paper, impacts of Phase 2 RFG on the atmospheric reactivity of motor vehicle exhaust and evaporative emissions are described. Volatile organic compounds in motor vehicle exhaust were measured at the Caldecott tunnel in summer 1995 and 1996. Aggregate emissions of greater than 8000 vehicles were measured each day. Regular and premium grade gasoline samples were collected from service stations in Berkeley concurrently with tunnel measurements both summers. Liquid gasoline samples and their headspace vapors were analyzed to determine detailed chemical composition. Normalized reactivity was calculated for exhaust and evaporative emissions by applying maximum incremental reactivity values to the detailed speciation profiles. Results indicate that the composition of gasoline in 1996 differed markedly from that of 1995. Changes in liquid gasoline composition led to corresponding changes in the speciation of vehicle exhaust and of gasoline headspace vapors. Benzene concentration in liquid gasoline decreased from 2.0 to 0.6 wt%, which contributed to a 70 and 37% reduction in benzene weight fraction in headspace vapors and vehicle exhaust, respectively. Addition of MTBE and reduction of olefins and aromatics in gasoline led to significant reductions in the atmospheric reactivity of unburned gasoline and gasoline headspace vapors. The normalized reactivity of liquid gasoline and headspace vapors decreased by 23 and 19%, respectively, between 1995 and 1996. The normalized reactivity of non-methane organic compounds in vehicle exhaust decreased by about 8%, but the uncertainty in this change was large.
- OSTI ID:
- 351023
- Report Number(s):
- CONF-970677--
- Country of Publication:
- United States
- Language:
- English
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