Effects of Reformulated Gasoline and Motor Vehicle Fleet Turnover on Emissions and Ambient Concentrations of Benzene
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- 作者：Robert A. Harley ; Daniel S. Hooper ; Andrew J. Kean ; Thomas W. Kirchstetter ; James M. Hesson ; Nancy T. Balberan ; Eric D. Stevenson ; Gary R. Kendall
- 刊名：Environmental Science & Technology
- 出版年：2006
- 出版时间：August 15, 2006
- 年：2006
- 卷：40
- 期：16
- 页码：5084 - 5088
- 全文大小：144K
- 年卷期：v.40,no.16(August 15, 2006)
- ISSN：1520-5851
文摘
Gasoline-powered motor vehicles are a major source oftoxic air contaminants such as benzene. Emissions from light-duty vehicles were measured in a San Francisco areahighway tunnel during summers 1991, 1994-1997, 1999, 2001,and 2004. Benzene emission rates decreased over thistime period, with a large (54 ± 5%) decrease observedbetween 1995 and 1996 when California phase 2 reformulatedgasoline (RFG) was introduced. We attribute this one-year change in benzene mainly to RFG effects: 36% fromlower aromatics in gasoline that led to a lower benzenemass fraction in vehicle emissions, 14% due to RFG effectson total nonmethane organic compound mass emissions,and the remaining 4% due to fleet turnover. Fleet turnovereffects accumulate over longer time periods: between1995 and 2004, fleet turnover led to a 32% reduction in thebenzene emission rate. A ~4 
g m-3 decrease in benzeneconcentrations was observed at a network of ambientair sampling sites in the San Francisco Bay area betweenthe late 1980s and 2004. The largest decrease in annualaverage ambient benzene concentrations (1.5 ± 0.7 g m-3or 42 ± 19%) was observed between 1995 and 1996. Thereduction in ambient benzene between spring/summer monthsof 1995 and 1996 due to phase 2 RFG was larger (60 ±20%). Effects of fuel changes on benzene during fall/wintermonths are difficult to quantify because some wintertimefuel changes had already occurred prior to 1995.
g m-3 decrease in benzeneconcentrations was observed at a network of ambientair sampling sites in the San Francisco Bay area betweenthe late 1980s and 2004. The largest decrease in annualaverage ambient benzene concentrations (1.5 ± 0.7 g m-3or 42 ± 19%) was observed between 1995 and 1996. Thereduction in ambient benzene between spring/summer monthsof 1995 and 1996 due to phase 2 RFG was larger (60 ±20%). Effects of fuel changes on benzene during fall/wintermonths are difficult to quantify because some wintertimefuel changes had already occurred prior to 1995.