ABSTRACT
Diesel particulate matter (DPM) is the solid portion of diesel exhaust. In underground mines prone to high DPM concentrations for prolonged time periods, exposures can be hazardous. For monitoring, filter samples are often collected and subject to thermal-optical analysis to measure the two primary components of DPM: elemental (EC) and particulate organic carbon (POC). However, the presence of volatile organic carbon (VOC) can interfere. The standard approach to correcting for VOC is use of a “dynamic blank” filter, but errors have been reported. Alternative approaches have also been proposed, including pre-baking samples to drive off VOC before typical thermal-optical analysis, or addition of low temperature isotherm(s) to the beginning of the analysis routine for the same purpose. As a preliminary study, these simple thermal correction methods were compared to the standard correction using field samples collected in three locations (two in an underground mine, one at a highway truck stop). The pre-baking method (at 175°C) was found to overcorrect for VOC, resulting in underestimation of POC. Efficacy of the modified thermal-optical analysis (with addition of an initial isotherm at 175°C) appeared to be dependent on sample mass and/or composition.
