Characterization of Fuel and Aftertreatment Device Effects on Diesel Emissions(Includes the Commentary of the Institute's Health Review Committee)

摘要

The effect of emission control devices on the composition and mutagenicity ofexhaust was examined with heavy-duty diesel engines operated with a low-sulfur fuel under steady-state conditions. A ceramic particle trap substantially decreased the mass and numbers of particles in emissions from a 1988-model heavy-duty engine. As a result, particle-associated organic chemicals and the mutagenicity of the diesel exhaust also diminished. Use of the trap caused no appreciable change in the amount or type of chemicals in the emission vapors. Regenerating the particle-loaded trap by heating it to combust the particles produced negligible increases in emission constituents and mutagenicity. Compared with an earlier study with conventional, high-sulfur fuel, the low-sulfur fuel considerably decreased sulfate emissions and the number of small sulfate particles, but had little effect on the mass of total particulate matter. An oxidation catalytic converter had no effect on the number of particles, but substantially lowered the amount of organic chemicals both in the vapors and adsorbed to the particles in emissions from a 1991-model heavy-duty engine. Because most of the particle-adsorbed chemicals were removed, the mass of the total particulate matter decreased. Despite a substantial reduction in the mass of total particulate matter, the number of nuclei-mode particles in emissions from the more advanced 1991-model engine was 30 to 60 times greater than from the 1988 engine when the engines were operated without emission control devices.