Quantitative Determination of Composition of Particle Type by Morphology of Nanoparticles in Diesel Exhaust and Roadside Atmosphere

Abstract

Particles were collected in diluted diesel exhaust under high-idle and high-torque operating conditions and from the air above roadsides. We analyzed particle morphology of particles that were 30, 50, 70, and 100 nm in electrical mobility diameter (D m) by transmission electron microscope. We classified ten types of particles based on particle morphology and found that diesel exhaust particles (DEPs) of D m =70 and 100 nm composed at least 14% and 58%, respectively, of atmospheric particles at each particle size. From the two-dimensional transmission electron microscope images, we derived three-dimensional morphological properties of the agglomerates and found that the numbers and diameters of the primary particles in the agglomerates were similar to those of DEPs at a given D m. However, the active surface areas of the roadside atmospheric particles were systematically smaller than those of DEPs.