Effects of sampling artifacts on occupational samples of diesel particulate matter.
Environ Sci Technol 2008 Jul; 42(14):5223-5228
Total carbon (TC) is sometimes used to measure or characterize diesel particulate matter (DPM) in occupational settings such as underground mines. DPM samples are collected on quartz fiber filters. When using quartz fiber filters, adsorption of gas phase organic carbon (OC) has been reported, causing a positive bias in the particulate TIC results (adsorption artifact). Most of the data on the sampling artifacts and corrections apply to environmental air sampling, where samples are collected at a much higher filter face velocity and the OC concentrations are generally much lower relative to occupational sampling. In this study, we investigated the effects of adsorption artifact on samples from occupational settings. Samples were collected with and without denuders to determine the amount of gas phase OC collected and the accuracy of certain corrections. In underground stone mines, the adsorption artifact was found to positively bias the particulate TC by greater than 20% for filter loadings below 25 mu g/cm(2) TC (8-h time weighted average = 262 mu g/m(3)). The tandem filter correction reduced the effect of the artifact, as high as 60% of the TC value, to less than 11% for laboratory data. It also significantly reduced the effect of the artifact obtained for field samples.
Diesel-emissions; Particulate-sampling-methods; Particulate-dust; Particle-aerodynamics; Gas-sampling; Mine-gases; Work-areas; Work-environment; Statistical-analysis
James Noll, Pittsburgh Research Laboratory, U.S. Department of Health and Human Services, Public Health Service, CDC, NIOSH, 626 Cochrans Mill Road, Pittsburgh, PA 15236
Environmental Science and Technology