Relative Ozone Forming Potential of Methanol-Fueled Vehicle Emissions and Gasoline-Fueled Vehicle Emissions in Outdoor Smog Chambers

摘要

The experimental program compares the relative NO oxidation and O3 forming capabilities of surrogate VOC mixtures that are representative of urban air, emissions from vehicles using methanol fuels, and emissions from vehicles using industry-average gasoline. The experiments used a dual side-by-side outdoor chamber with initial NOx of 330 ppb and hydrocarbon-to-NOx ratios 4.5, 6, and 9:1. The urban VOC mixture was based upon ambient air analyses conducted by EPA for 6-9 AM in 41 cities over the period 1984-1988. The automotive VOC mixtures were based upon exhaust, evaporative, and running loss measurements made in the Auto/Oil Air Quality Improvement Research Program and upon the application of EPA's MOBILE4 emissions model applied in a model scenario in Dallas/Fort Worth in the year 2005. Each of the VOC mixtures had about 55 individual species in which about 45 species were surrogates for the remaining measured carbon. In addition to testing the relative reactivity of each VOC mixture against the other mixtures, the majority of the experiments used mixtures in which 50% of the carbon was from the urban mix and 50% of the carbon was from industry-average gasoline vehicle emissions or 50% of the carbon was from the methanol-fueled vehicle emissions. Some experiments were also conducted with higher fractions of formaldehyde (HCHO) in either the urban mix or in the methanol mix.