Compilation of PM Characterization Data for Diesel Fueled Heavy-Duty Trucks and Buses: Impact of Tailpipe Controls and Fuel Sulfur on the EC/OC Ratio and the Particles' Chemical Species Content

As part of a multi-year program known as the ‘ECD Technology Validation Study’, which was conducted over the past few years (1999-2003) detailed data were obtained on the chemical characteristics of PM from diesel fueled trucks and buses operated with and without various after-treatment devices. This study has been conducted collaboratively by industry, federal, state and local government agencies, along with academic research institutions. Descriptive presentations of the results of the various phases of this study have been previously reported. The current study offers further insight into the data by investigating finer details of the association between the various chemical species and classes of compounds characterized.

This paper provides an approach to such detailed analyses by using the chemical speciation data from the ECD Technology Validation Study (SAE2002-01-2873) as a case study. It demonstrates how the introduction of diesel particle filters (DPF) into the heavy-duty vehicle fleet might change the Elemental Carbon/Organic Carbon (EC/OC) ratios and the Soluble Organic Fraction (SOF) emissions from heavy-duty vehicles leading to a change in the source-receptor signature in the ambient atmosphere. The paper also highlights the correlation between detailed speciation results of PAHs and bulk organic characteristics of the particulate matter, such as EC and OC. The results of this study demonstrate the correlations observed between the OC and the EC determinations and the quantity high mass (3-rings and higher) PAH compounds that are bound to the particles. These results have implications to the possibility of using such bulk properties as indicators for the impact of DPFs on the emission of air toxics (PAHs vs. OC) and climate change associated aerosols (PAHs vs. EC).