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

TLDR

The study augments a dilution source sampling system to measure the size‑distributed chemical composition of fine particle emissions from motor vehicles. Measurements were performed with an optical particle counter, a DMA/CNC combination, and MOUDIs on catalyst‑equipped gasoline, noncatalyst gasoline, and medium‑diesel vehicles. Gasoline‑powered vehicles emitted mainly organic particles, while diesel engines released roughly equal organic and elemental carbon; all sources showed a single‑mode mass distribution peaking at 0.1–0.2 µm, and the diesel vehicle with the lowest emission rate produced the most ultrafine particles, with size distributions unchanged between cold and hot starts. Technical Report 76 (Health Effects Institute, Cambridge, MA, 1996).

Abstract

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.