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

Abstract

The regulation of particulate matter (PM) emitted by agricultural sources, e.g., cotton gins, feed mills, and concentrated animal feeding operations (CAFOs), is based on downwind concentrations of particulate matter less than 10 and 2.5 .m (PM10 and PM2.5) aerodynamic equivalent diameter (AED). Both PM10 and PM2.5 samplers operate by pre-separating PM larger than the size of interest (10 and 2.5 .m) prior to capturing the PM on the filter. It has been shown that Federal Reference Method (FRM) PM10 and PM2.5 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 .m AED. The PM10 concentration measurement error can be as much as 343% for ambient PM with MMD = 20 .m. These errors are a consequence of the PM10 pre-separator allowing a larger mass of PM greater than 10 .m to penetrate to the filter than the mass of PM less than 10 .m captured by the pre-separator. The mass of the particles greater than 10 .m that are allowed to penetrate to the filter introduces a substantial error in the calculated concentration of PM10. Researchers have reported that sampling PM larger than 2.5 .m AED resulted in a shift in the cutpoint of the pre-separator. If this is true for all PM10 and PM2.5 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 particulate (TSP) matter and calculate the concentration of PM10 by determining the mass fraction of PM less than size of interest from the particle size distribution (PSD). The “standard” high-volume TSP sampler operates at a volume rate-of-flow in excess of 1.13 m3 min-1 (40 ft3 min-1). Most of the current PM10 and PM2.5 samplers operate at 1 m3 h-1 (0.589 ft3 min-1). Other researchers reported that TSP samplers have a cutpoint of a nominal 45 .m 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 m3 h-1) TSP sampler (TSPLV). The results suggest that the new TSPLV may be more robust and more accurate than the “standard” high-volume TSP sampler.