DESIGN AND EVALUATION OF A LOW-VOLUME TOTAL SUSPENDED PARTICULATE SAMPLER

摘要

The regulation of paniculate matter (PM) emitted by agricultural sources, e.g., cotton gins, feed mills, and concentrated animal feeding operations (CAFOs), is based on downwind concentrations of paniculate matter less than 10 and 2.5 μm (PM{sub}10 and PM{sub}(2.5)) aerodynamic equivalent diameter (AED). Both PM{sub}10 and PM{sub}(2.5) samplers operate by pre-separating PM larger than the size of interest (10 and 2.5μm) prior to capturing the PM on the filter. It has been shown that Federal Reference Method (FRM) PM{sub}10 and PM{sub}(2.5) samplers have concentration measurement errors when sampling PM with mass median diameters (MMD) larger than the size of interest in ambient air. It has also been demonstrated that most PM from agricultural sources typically have particle size distributions with MMDs larger than 10 μm AED. The PM{sub}10 concentration measurement error can be as much as 343% for ambient PM with MMD = 20 μm. These errors are a consequence of the PM{sub}10 pre-separator allowing a larger mass of PM greater than 10 μm to penetrate to the filter than the mass of PM less than 10 am captured by the pre-separator. The mass of the particles greater than 10 μm that are allowed to penetrate to the filter introduces a substantial error in the calculated concentration of PM{sub}10. Researchers have reported that sampling PM larger than 2.5 μm AED resulted in a shift in the cutpoint of the pre-separator. If this is true for all PM{sub}10 and PM{sub}(2.5) samplers, then the resulting errors in measurement of ambient concentrations could be even larger. One solution to this problem is to measure the concentration of total suspended paniculate (TSP) matter and calculate the concentration of PM{sub}10 by determining the mass fraction of PM less than size of interest from the panicle size distribution (PSD). The "standard" high-volume TSP sampler operates at a volume rate-of-flow in excess of 1.13 m{sup}3min{sup}(-1) (40 ft{sup}3 min{sup}(-1)). Most of the current PM{sub}10 and PM{sub}(2.5) samplers operate at 1 m{sup}3 h{sup}(-1) (0.589 ft{sup}3 min{sup}(-1)). Other researchers reported that TSP samplers have a cutpoint of a nominal 45 [tm AED. The U.S. EPA specifies the engineering design parameters for TSP samplers. This article reports the engineering design and evaluation of a low-volume (1 m{sup}3 h{sup}(-1)) TSP sampler (TSP{sub}(LV)). The results suggest that the new TSP{sub}(LV) may be more robust and more accurate than the "standard" high-volume TSP sampler.