As part of this program, a chemical characterization study was performed in the spring of 2001 to compare the exhaust emissions using the test fuels with and without aftertreatment. A detailed speciation of volatile organic hydrocarbons (VOC), polycyclic aromatic hydrocarbons (PAH), nitro-PAH, carbonyls, polychloro-dibenzo- p-dioxins (PCDD) and polychlorodibenzo-p-furans (PCDF), inorganic ions, elements, PM10, and PM2.5 in diesel exhaust was performed for a select set of vehicles. The testing was carried out on four diesel vehicles and two compressed natural gas (CNG) vehicles, using a representative California diesel fuel, ECD-1, and ECD, all with and without DPFs. One diesel vehicle was also tested with Fischer-Tropsch (F-T) diesel fuel. The CNG vehicles were tested using motor-vehicle- grade compressed natural gas.
Results presented in this paper provide vehicle emissions profiles for total particulate matter (TPM), PM₁₀ and PM₂.₅, inorganic ions, elements, and VOCs. Ethene, C₂-C₅ olefins, BTEX, and benzene have been highlighted due to their high reactivity or toxicity for the diesel and CNG vehicles. Additional speciated exhaust emissions will be published in a future paper.
The TPM and particle-bound element emissions are greatly reduced on vehicles equipped with aftertreatment devices and the CNG vehicles. The DPFs effectively reduce the light olefins and EC/OC. Emissions of particle-bound inorganic ions are very low for all vehicles, regardless of fuel/aftertreatment.