| Diesel PM is known to have adverse effects on human health and environment. As a consequence, the 2007 PM emission standards are significantly reduced and require the newest vehicles to use clean fuels, new engine technology and exhaust control measures, like the Diesel Particulate Filter (DPF). During the transition to the newer standards, both old and modern diesel vehicles coexist and while methods and in-use data exist for the older vehicles, such methods and data are scarce for the cleaner vehicles. For example, measurements of PM at very low emission levels are challenging and still not defined. This dissertation advances PM measurement techniques and establishes new measurement methods for PM characterization from diesel engines, including those equipped with modern after-treatment devices. The role of real-world traffic, fuel changes, new engine technologies, and after-treatment devices on emissions were measured. A total of ten Heavy-Heavy-Duty-Diesel Trucks were selected from different engine model years and manufacturers to determine emission factors. Special focus was given to real-time PM measurements necessary for the inclusion of PM emissions into the US EPA Comprehensive Modal Emissions Model (CMEM) and analysis of impacts of vehicular congestion on emissions. Also, gaseous and PM emissions from eight in-use Yard Trucks (YTs) were quantified for developing port-emissions factors and to examine emissions benefit from potential changes in fuel quality and engine technology.;The influence of dilution conditions and fuel sulfur content on PM mass and size-resolved PM chemical composition was investigated for the development of a PM measurement protocol for engines burning fuels with high sulfur content. The feasibility of "solid" particle number measurements as an alternative to PM mass measurements from diesel engines equipped with DPFs was also investigated as a part of the European Particle Measurement Protocol (PMP). Furthermore, the physical and chemical characteristics of particles emitted from several DPF equipped diesel engines were examined. It was demonstrated that most of the emissions from these devices occur during the process of regenerating the filter. The results show that the PM from these devices is rich in sulfate and organic material, especially in the nucleation mode.;The results of this dissertation could be used to quantify expected improvements in the air quality near freeways and arterial roads, including ports, through the introduction of a new technology fleet, switching to cleaner fuels, and retrofitting existing diesel engines with after-treatment devices for PM control. |
