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PM2.5 Sampler Errors Due to the Interaction of Particle Size and Sampler Performance Characteristics
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ABSTRACT Agricultural operations across the United States are encountering difficulties in complying with the current air pollution regu-lations for particulate matter (PM). The National Ambient Air Quality Standards (NAAQS) for PM in terms of PM2.5, are ambient air concentration limits set by EPA that should not be exceeded. Further, State Air Pollution Regulatory Agencies (SAPRA's) utilize the NAAQS to regulate criteria pollutants emitted by industries by applying the NAAQS as property line concentration limit. The primary NAAQS are health-based standards and therefore, an exceedance implies that it is likely that there will be adverse health effects for the public. Since the proposal of the PM2.5 regulation, numerous journal articles and technical references have been written to discuss the epidemiological effects, trends, regulation, methods of determining PM2.5, etc. A common trend among many of these publications is the use of samplers to collect information on PM2.5. All too often, the sampler data are assumed to be an accurate measure of PM2.5. The fact is that issues such as sampler uncertainties, environmental conditions, and material characteristics for which the sampler is measuring must be incorporated for accurate sampler measurements. The focus of this manuscript is on the errors associated with the particle size distribution (PSD) characteristics of the material in the air that is being sampled, sampler performance characteristics, the interaction between these two characteristics, and the effect of this interaction on the regulatory process. Theoretical simulations were conducted to determine the range of errors associated with this interaction for the PM2.5 sampler. Results from these simulations indicated that a source emitting PM characterized by a mass median diameter (MMD) of 20 μm and a geometric standard deviation (GSD) of 1.5 could be forced to comply with a 14 times more stringent regulation than a source emitting PM characterized by a MMD of 10 μm and a GSD of 1.5. Therefore, in order to achieve equal regulation among differing industries, PM2.5 measurements MUST be based on true concentration measurements. |
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Document last modified April 16, 2003
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