Characterization of particulate matter and hydrocarbon emissions from in-use heavy-duty diesel engines

A continued increase in the use of diesel engines in heavy-duty vehicles, and the uncertainties about the effects of the emissions on human health have focused attention on risk assessments of exposure to the diesel exhaust. The characterization of diesel particulate matter (PM) and hydrocarbon (HC) emissions is the primary objective toward assessing potential health hazard. The dependence of DPM nature on engine/vehicle operating conditions, fuel type, different after treatment processes, and measurement process on the size resolved PM emissions was examined by operating the test engines and vehicles under steady-state and transient conditions. The regional deposition of DPM in the human respiratory tract was assessed, by applying a semi-empirical model developed by Kobritch et al. (1994) to the PM size distribution and concentration profiles that were generated in this study. The results of this analysis showed that low PM mass emissions do not necessarily correspond to low number count emissions and a reduced health hazard. The number of DPM deposited in the alveolar region was found to be higher for the exhaust generated using cleaner fuels than Federal diesel no. 2 in spite of significant reductions in PM mass emissions achieved with those fuels. Exhaust treated in the devices coated with oxidation catalyst was characterized with significantly lower PM mass concentration and higher number of particles deposition in the alveolar region than untreated exhaust The study on size-resolved chemical analysis of DPM was performed with the goal of obtaining distribution profiles of the major constituents of PM in the untreated diesel exhaust. The sulfate, chloride, ammonium, potassium, sulfur, and silicon profiles were determined for range of engine operating conditions. Carbon analysis showed that organic carbon was the major constituent of the particulate matter with cut-of diameter less than 56 nm regardless of the engine operating conditions. Elemental carbon was dominant constituent of the DPM with aerodynamic diameters between 56 and 560 nm accounting for up to 86.5% of total carbon. The analyses indicated that sulfate and organic carbon were the major constituents of nanoparticles. In addition, diesel exhaust was speciated with the purpose of establishing qualitative and quantitative hydrocarbon profiles and estimating ozone forming potential of diesel exhaust for selected steady-state and transient engine operating conditions