Experimental Study and Characterization of Diesel PM Pollution of Urban Bus

Urban air pollution caused by vehicle exhaust has already become a great public concern. Among the vehicle pollutants, diesel combustion PM (particulate matter) was deeply explored by some health and scientific institutes and proved toxic even carcinogenic. An urban bus was tested on road with a real-time aerosol instrument to measure its PM emission. The result shows that PM emitted by the bus mainly ranges from 0 to 1.5 μm. Particles smaller than 300 nm take up nearly 90 percent of the total number emission, while ones of 300 nm-1.5 μm take up more than four fifths of the total mass emission. Particulate emission rate during acceleration stages is 5-6 times more in number and 10 times more in mass than that generated during steady cruise. Aggressive acceleration processes at velocity of about 30 km/h will cause the most serious particulate emission, with number concentration as high as 1.0×10⁸/cm³. It was also found that the PM number and mass emission coefficients of the tested bus are respectively 2.72 × 10¹⁴#/km and 0.468 g/km, more than 2 times of the limit specified by the emission regulation.