Characterization of the Particulate Phase in the Exhaust from a Diesel Car

Abstract

Diesel vehicles are a major source of fine, atmospheric particulate matter in urban environments. The influences diesel particles exert on solar radiation, on atmospheric chemistry, and on humans depend crucially on the size and chemical character of these particles. In this work, size-resolved diesel particle chemistry has been examined by collecting particles directly from a diesel car exhaust with a low-pressure impactor. The impactor samples have been weighed and analyzed chemically to construct continuous size distributions for selected compounds present in the particulate phase. Submicron diesel-particle mass size distributions displayed three log-normal modes that were centered at 0.09, 0.2, and 0.7−1 μm of particle aerodynamic diameter (EAD) and that had average geometric standard deviations of 1.34, 1.61, and 1.34, respectively. The lowest two modes had approximately the same particulate mass, whereas over 80% of the number of particles were estimated to be found in the mode around 0.1 μm. The third mode contained about 10% of the total particulate mass but less than 0.1% of the particles. The size distributions of elemental (EC) and organic carbon (OC) were quite different: EC peaked at 0.1 μm, and OC peaked somewhere between 0.1 and 0.3 μm of EAD. The mass ratios of OC to EC were between 0.3 and 0.5 in the bulk of the samples but were considerably lower for most of the particles. The presence of a catalytic converter reduced particulate mass by 10−30%, with the removal being more efficient for OC than EC. The principal mechanism producing the mode around 0.1 μm was shown to be Brownian coagulation between small primary particles formed during the combustion. The two larger size modes in the submicron particle range were hypothesized to be formed by activation and subsequent uptake of condensable organic compounds by some of the mode 1 particles.

Development of Molecular Marker Source Profiles for Emissions from On-Road Gasoline and Diesel Vehicle Fleets

“…1 Several studies have been performed to characterize tailpipe emissions of gasoline-powered and diesel-powered vehicles, [2][3][4][5][6][7][8] many with the goal of developing representative profiles for on-road vehicle tailpipe emissions. Most of these studies have investigated a small number of vehicles but have seen variation in emission rate and composition related to vehicle age, fuel type, driving cycle, engine temperature, and engine repair.…”

Effect of Peak Inert-Mode Temperature on Elemental Carbon Measured Using Thermal-Optical Analysis

“…A variety of thermal or thermal-optical measurement techniques have been developed to measure particulate OC and EC (Malissa, Puxbaum, and Pell 1976;Huntzicker et al 1982;Chow et al 1993;Kerminen et al 1997). While these methods generally measure the same amount of total carbon, the OC/EC split is operationally defined with significant differences in the amount of OC and EC measured by different methods Schmid et al 2001;Fung, Chow, and Watson 2002).…”

Characterization of Roadside Fine Particulate Carbon and its Eight Fractions in Hong Kong

“…Motor vehicular emissions are a major source of fine particles in ambient air, especially in urban areas (Harrison et al, 1997;Kerminen et al, 1997;Ruellan et al, 2001;Harley et al, 2005).…”

“…A number of articles and reports have been published regarding the contribution of traffic to OC and EC in Europe and the USA (Kerminen et al, 1997;Miguel et al, 1998;Fraser et al, 1999;Moosmüller et al, 2000;Shi et al, 2000;Kohler et al, 2001;Ruellan et al, 2001). …”