A fuel-based motor vehicle emission inventory for the San Francisco Bay area
- Univ. of California, Berkeley, CA (United States). Dept. of Civil and Environmental Engineering
- Bay Area Air Quality Management District, San Francisco, CA (United States)
Traditionally, regional motor vehicle emission inventories (MVEI) have been estimated by combining travel demand model and emission factor model predictions. The accuracy of traditional MVEIs is frequently challenged, and development of independent methods for estimating vehicle emissions has been identified as a high priority for air quality research. In this study, an alternative fuel-based MVEI was developed for the San Francisco Bay Area using data from 1990--1992. To estimate CO emissions from motor vehicles in the Bay Area, estimates of gasoline sales were combined with infrared remote sensing measurements of CO and CO{sub 2} exhaust concentrations from over 10,000 light-duty vehicles in summer 1991. Once absolute estimates of CO emissions have been computed, it is possible to use ambient NO{sub x}/CO and NMOC/CO ratios from high traffic areas to estimate emissions for NO{sub x} and NMOC (excluding some resting loss and diurnal evaporative emissions). Ambient ratios were generated from special-study measurements of NMOC and CO in 1990 and 1992, and from routine sampling of NO{sub x} and CO in 1991. All pollutant concentrations were measured on summer mornings at Bay Area monitoring sites in areas with high levels of vehicle traffic and no other significant sources nearby. Stabilized CO emissions calculated by the fuel-based method for cars and light-duty trucks were 1720{+-}420 tons/day. This value is close to California`s MVEI 7G model estimates. Total on-road vehicle emissions of CO in the Bay Area were estimated to be 2900{+-}800 tons/day. Emissions of NMOC were estimated to be 570{+-}200 tons/day, which is 1.6{+-}0.6 times the value predicted by MVEI 7G. In the present study, emissions of NO{sub x} from on-road vehicles were estimated to be 250{+-}90 tons/day, which is 0.6{+-}0.2 times the value predicted by MVEI 7G.
- OSTI ID:
- 351692
- Report Number(s):
- CONF-970677--
- Country of Publication:
- United States
- Language:
- English
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