Diesel particle and organic emissions: engine simulation, sampling, and artifacts.
Several working hypotheses can be drawn relative to measuring diesel exhaust particles and organics. They are: 1. Passenger car dynamometer simulation and driving cycles are adequate for determining mass emission rates. The choice of a simulation condition appears to make little difference. Evidence for trucks is fragmentary, but high load freeway driving produces especially high particle emissions. 2. Sampling of particles and organics can be done in a variety of ways. Since most sampling systems yield similar results, the choice is not critical. If measuring mutagenic agents is the issue, then the distribution between gas and particle phase is also not critical. 3. Artifactual generation of mutating agents in sampling seems to be relatively unimportant. Filter media studies are negative, with respect to artifacts. Although there is evidence of artifact formation from NO2 concentrations above 5 ppm, this condition is not generally present under normal sampling conditions. Consequently, in the context of laboratory studies of diesel emissions, it appears difficult to choose conditions that will produce totally invalid samples. Differences in particle emission factors from various vehicle types are substantial, however, and these influences on air quality are important.