Characterization of polycyclic aromatic hydrocarbons in motor vehicle fuels and exhaust emissions

Motor vehicles are a significant source of polycyclic aromatic hydrocarbon (PAH) emissions. Improved understanding of the relationship between fuel co mposition and PAH emissions is needed to determine whether fuel reformulati on is a viable approach for reducing PAH emissions. PAH concentrations were quantified in gasoline and diesel fuel samples collected in summer 1997 in northern California. Naphthalene was the predominant PAH in both fuels, wi th concentrations of up to 2600 mg L-1 in gasoline and 1600 mg L-1 in diese l fuel. Particle-phase PAH size distributions and exhaust emission factors were measured in two bores of a roadway tunnel. Emission factors were deter mined separately for light-duty vehicles and for heavy-duty diesel trucks, based on measurements of PAHs, CO, and CO2. Particle-phase emission factors , expressed per unit mass of fuel burned, ranged up to 21 mu g kg(-1) for b enzo[ghi]perylene for light-duty vehicles and up to similar to 1000 mu g kg (-1) for pyrene for heavy-duty diesel vehicles. Light-duty vehicles were fo und to be a significant source of heavier (four- and five-ring) PAHs, where as heavy-duty diesel engines were the dominant source of three-ring PAHs, s uch as fluoranthene and pyrene. While no correlation between heavy-duty die sel truck PAH emission factors and PAH concentrations in diesel fuel was fo und, light-duty vehicle PAH emission factors were found to be correlated wi th PAH concentrations in gasoline, suggesting that gasoline reformulation m ay be effective in reducing PAH emissions from motor vehicles.