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

摘要

The regulation of particulate matter (PM) emitted by agricultural sources (cotton gins, feed mills, concentrated animal feedingoperations (CAFOs) is based upon downwind concentrations of particulate matter less than 10 and 2.5 micrometers (μm)(PM_(10) and PM_(2.5)) aerodynamic equivalent diameter (AED). Both PM_(10) and PM_(2.5) samplers operate by pre-separating PM largerthan the size of interest (10 and 2.5 μm) prior to capturing the PM on the filter. It has been shown that Federal ReferenceMethod (FRM) PM_(10) and PM_(2.5) samplers have concentration measurement errors (Buser et al, 2001, 2002) when sampling PMin ambient air having mass median diameters (MMD) larger than the size of interest. It has also been demonstrated that mostPM from agricultural sources typically have particle size distributions with MMDs larger than 10 μm (AED). The PM_(10) concentrationmeasurement error can be as much as 343% for ambient PM with an MMD=20 μm. These errors are a consequenceof the PM_(10) pre-separator allowing a larger mass of PM greater than 10 μm to penetrate to the filter than the mass ofPM less than 10 μm captured by the pre-separator. The mass of the particles greater than 10μm that are allowed to penetrateto the filter, introduce a substantial error in the calculated concentration of PM_(10). Pargmann et al (2001) reported that samplingPM larger than 2.5 μm (AED) resulted in a shift in the cut-point of the pre-separator. If this is true for all PM_(10) andPM_(2.5), samplers, the resulting errors in measurements of ambient concentrations could be even larger than those reported byBuser.