Emission Sources of Elemental Carbon

Fuel-specific emission rates of elemental carbon are shown in Table 14.1. These rates can vary significantly as they depend strongly on the conditions under which combustion takes place. Woodbuming fireplaces and diesel automobiles are effective sources of EC per unit of fuel burned (Mulhbaier and Williams 1982 Brown et al. 1989 Dod et al. 1989 Mulhbaier and Cadle 1989 Hansen and Rosen 1990 Burtscher 1992). 

Emissions of EC by diesel-burning motor vehicles are easily visible and have been the focus of many studies (Pierson and Brackaczek 1983 Raunemaa et al. 1984 Hildemann et al. 1991b U.S. EPA 1996). Photomicrographs of particles collected from the exhaust of a diesel automobile indicate that the emitted aerosols are similar to the soot particles described above. Volume mean diameters of the aggregates tend to range from 0.05 to 

TABLE 14.1 Estimates of Fuel-Specific Particulate Carbon Emission Rates, g(C) (kg fuel) 1 

The EC percentages of the aerosol mass emitted by automobiles and other sources based on a series of different studies are shown in Table 14.2. All of these values are based on small samples of sources and show significant differences from sample to sample and from study to study. 

A series of tracer techniques have been developed for calculation of the source contribution to EC concentrations, including use of potassium (K) as a woodsmoke tracer (Currie et al., 1994) and use of the carbon isotopic tracers C and C (Klouda et al., 1988 Lewis et al., 1988 Currie et al., 1989). By this procedure 47% of the EC in Detroit, 93% in Los Angeles, and 30 to 60% in a rural area in Pennsylvania have been attributed to motor vehicle sources (Wolff and Korsog, 1985 Pratsinis et al., 1988 Keeler et al., 1990). The corresponding contribution of diesel emissions to EC concentrations in Western Europe is estimated to be 70 to 90% (Hamilton and Mansfield, 1991). EC was also a major constituent of the Kuwait oil fires, with concentrations as high as 178 mg m inside the plume (Cofer et al., 1992 Daum et al., 1993 and references therein). 

TABLE 13.2 Elemental and Organic Carbon Fractions in Emissions by Different Sources 

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