"EPA420-D-02-004."; "October 2002." "EPA contract no. 68-C-01-164"; "Work assignment no. 0-5." Includes bibliographical references.

The purpose of this project was to compare estimated diesel particulate matter (diesel PM or DPM) concentrations based on elemental carbon (EC) and black carbon (BC) data with modeled ambient concentrations of DPM from the 1996 National-Scale Air Toxics Assessment (NSATA). The NSATA used DPM inventory estimates from EPA's final rule promulgating 2007 heavy duty engine standards. Using the ASPEN dispersion model, NSATA developed estimates of 1996 annual average concentrations of DPM at census tracts nationwide. The goal of this project was to evaluate the reasonableness of DPM estimates from dispersion models for this case by comparing the NSATA DPM concentration estimates with estimates based on measured EC and BC concentrations. EC measurements can be obtained from PM2.5 monitoring sites that sample PM2.5 using quartz fiber media. The EC is measured using thermo-optical analysis of the carbonaceous material. Many studies have used thermal optimal transmission (TOT), the NIOSH method developed at Sunset lablaboratories. Some studies have used thermal optical reflectance (TOR), a method developed by Desert Research Institute. In addition, some sites measure ambient BC with an Aethalometer. EPA's Office of Air Quality Planning and Standards is reviewing the measurement of EC through the Speciation Trends Network, and an Agency statement on the issue is forthcoming. For now, however, existing values developed using the TOT method are being used. All these carbon concentration measurements can be used to estimate ambient DPM by using conversion factors based on 1) source apportionment studies, 2) source-receptor model studies, and 3) studies which examine the fraction of EC in DPM.