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Published April 1, 2000 | public
Journal Article

Size and Composition Distribution of Fine Particulate Matter Emitted from Motor Vehicles


A dilution source sampling system is augmented to measure the size-distributed chemical composition of fine particle emissions from motor vehicles. Measurements are made using an optical particle counter (OPC), a differential mobility analyzer (DMA)/condensation nucleus counter (CNC) combination, and a pair of microorifice uniform deposit impactors (MOUDIs). The sources tested with this system include catalyst-equipped gasoline-powered light-duty vehicles, noncatalyst gasoline-powered light-duty vehicles, and medium-duty diesel trucks. Chemical composition analysis demonstrates that particles emitted from the gasoline-powered vehicles tested are largely composed of organic compounds while particles emitted from diesel engines contain roughly equal amounts of organic compounds and elemental carbon. The particle mass distributions from all mobile sources tested have a single mode that peaks at approximately 0.1−0.2 μm particle diameter. Of the two diesel vehicles tested, the vehicle with the lowest fine particle emissions rate released the largest number of ultrafine particles, a finding similar to that of Bagley et al. (Characterization of fuel and aftertreatment device effects on diesel emissions; Technical Report 76; Health Effects Institute:  Cambridge, MA, 1996). Particle size distribution measurements taken throughout the FTP urban driving cycle used to test all of the vehicles described in this paper reveal that particulate mass emission rates and particulate size distributions from the vehicles tested here are similar during the cold start and hot start segments of the driving cycle.

Additional Information

© 2000 American Chemical Society. Received for review December 8, 1998. Revised manuscript received November 11, 1999. Accepted December 6, 1999. This research was supported by the Caltech Center for Air Quality Analysis. Thanks are due to Dr. Kent Hoekman and Dr. Steve Ziman of Chevron for assistance with this research. Rapheal Susnowitz, Thu Vo, Pons Lazo, and the staff at the California Air Resources Board's Haagen-Smit Laboratory in El Monte, CA, are thanked for their assistance and cooperation in conducting all of the motor vehicle source tests. Thanks also are due to Bob Cary (Sunset Labs) for aerosol carbon analyses; Ilhan Olmez, Michael Ames, and Jec Gone (MIT) for neutron activation analysis of trace metals; and Lynn Salmon (Caltech) for ion chromatography/colorimetric analyses.

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