CHARACTERIZATION OF HEAVY-DUTY DIESEL VEHICLE EMISSIONS

Emissions of heavy duty diesel-powered vehicles were measured at the Phoenix Transit Yard in South Phoenix between 31 March 1992 and 25 April 1992 using the West Virginia University Transportable Heavy-Duty Vehicle Emissions Testing Laboratory (Mobile Lab). Thirteen heavy-duty trucks and buses were tested over this period. The vehicles were operated with diesel No. 2 and Jet A fuels, with and without a fuel additive, and with and without particulate control traps. The chassis dynamometer Mobile Lab tested vehicles over the Central Business District (CBD) driving cycle. Particulate matter in the diluted exhaust was sampled proportionally from a total-exhaust dilution tunnel. Emission rates and compositions of PM2.5 particulate mass, elements, ions, bulk organic and elemental carbon, and gaseous and particulate polycyclic aromatic hydrocarbons were averaged for various classes of fuels and particulate matter control. Emission rates for PM2.5 mass averaged 0.2 and 1 g mile-1 for trucks and buses with and without particulate traps, respectively. Emission rates for elemental carbon averaged 0.02 and 0.5 g mile-1 for trucks and buses with and without particulate traps, respectively. Diesel particulate exhaust was comprised mainly of organic and elemental carbon (80-90%) and sulfate (up to 14%). The new diesel source composition profiles are similar to one determined earlier in Phoenix. Polycyclic aromatic hydrocarbons comprised no more than a few percent of the particulate organic carbon but their relative abundances may be useful for distinguishing diesel emissions from those of other combustion sources.