QUANTIFICATION OF THE EFFECTS OF CARBON ON FILTER MEDIA IN SKC DPM CASSETTES ON MEASUREMENTS OF DIESEL PARTICULATE MATTER IN UNDERGROUND MINES

摘要

Measuring diesel participate matter (DPM) for underground metalonmetal mine compliance samples is done by collecting DPM onto quartz fiber filters and analyzing the samples via NIOSH method 5040 for elemental carbon (EC) and total carbon (TC). As part of the sampling train, two quartz fiber filters in tandem are housed inside an SKC DPM cassette that includes an impactor. The impactor segregates DPM and mine dust, and the second filter is used to correct for adsorption of vapor phase organic carbon (OC). Since the value of the second filter is subtracted from the first, the pre-existing carbon on the filter media for both filters needs to be comparable. In addition, the pre-existing carbon on the media should be low for accurate and sensitive results. However, there have been some reports of elevated OC on the filter media of the SKC DPM cassettes, which would cause the limit of detection (LOD) to be higher than reported at times. In this study, blank SKC DPM cassettes from different batches and with different expiration dates were analyzed to quantify the amount of carbon on the filter media and to determine the LOD and limit of quantification (LOQ) associated with these samplers. It was found that the organic carbon and total carbon on the media was about five times higher than quartz media used in samplers from other studies. The average TC on the blanks was 2.57 μg/cm~2 with a standard deviation of 0.70, resulting in a LOD of 21 μg/m~3 TC, 8-hr Time Weighted Average (TWA), and LOQ of 69 μg/m~3 TC, 8-hr TWA, when using these samplers for collecting DPM. The LOD and LOQ may be improved through some sample preparation techniques.