SUBMICROMETER AND SUPERMICROMETER PARTICLES FROM DIESEL VEHICLE EMISSIONS

There is growing evidence that fine airborne particulates could play t he most important role in determining health effects. The a;im bf this work was to investigate the number concentration and size distributio ns of particulates in the exhausts of diesel vehicles (mainly buses) o f different ages and make, operating under different loads. Particle-s izing instruments used were the Scanning Mobility Particle Sizer (SMPS ) and Aerodynamic Particle Sizer (APS). The average particle number co ncentration of the exhausts was in the range (0.7-3.9) x 10(7) cm(-3) in the SMPS range (0.0075-0.304 mu m) and (0.3-32) x 10(3) cm(-3) in t he APS range (0.5-30 mu m). Inmost cases, particle number concentratio ns increased with the increased-power output from the engine and, in b oth SMPS and APS ranges, varied significantly :within each group of ve hicles, but-the differences between the groups were small; For individ ual vehicles, there was no relation between emissions in the smaller a nd larger particle ranges. Emission characteristics did ndt appear to be correlated with engine model or age. The implications of these find ings:to particle emission testing and control as well as to exposure a nd risk analysis are discussed.