title: Rapid identification of high particle number emitting on-road vehicles and its application to a large fleet of diesel buses.
abstract: Pollutant concentrations measured in the exhaust plume of a vehicle may be related to the pollutant emission factor using the CO2 concentration as a measure of the dilution factor. We have used this method for the rapid identification of high particle number (PN) emitting on-road vehicles. The method was validated for PN using a medium-duty vehicle and successfully applied to measurements of PN emissions from a large fleet of on-road diesel buses. The ratio of PN concentration to CO2 concentration, Z, in the exhaust plume was estimated for individual buses. On the average, a bus emitted about 1.5 x 10(9) particles per mg of CO2 emitted. A histogram of the number of buses as a function of Z showed, for the first time, that the PN emissions from diesel buses followed a gamma distribution, with most of the values within a narrow range and a few buses exhibiting relatively large values. It was estimated that roughly 10% and 50% of the PN emissions came from just 2% and 25% of the buses, respectively. A regression analysis showed that there was a positive correlation between Z and age of buses, with the slope of the best line being significantly different from zero. The mean Z value for the pre-Euro buses was significantly greater than each of the values for the Euro I and II buses.
authors: International Laboratory for Air Quality and Health, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia.
authors: E R
authors: ER
authors: Jayaratne
authors: L
authors: L
authors: Morawska
authors: Z D
authors: ZD
authors: Ristovski
authors: C
authors: C
authors: He
mesh_terms: D018986:Motor Vehicles; D015203:Reproducibility of Results; D001335:Vehicle Emissions
chemical_list: D001335:Vehicle Emissions