Large particle collection characteristics of ambient aerosol samplers

Abstract

Large particle sampling effectiveness of commercially available and prototype particle collectors was determined by wind tunnel testing. Included in the tests were the standard 1 CFM Andersen and a specially modified version of it which utilizes a weatherproof, directionally insensitive inlet; the standard Hi-Volume sampler; a Prototype Dichotomous sampler; and a prototype sampler which utilizes the 20 CFM Andersen with a rotating cowl inlet. The tests were performed using particles ranging in size from 5 to 50 µ , approach velocities from 5 to 15 ft/s (1.5-4.6 m/s), turbulence levels of <1 and 8%, and orienting the samplers at different directions to the flow. By use of a base condition for comparison purposes of 15 ft/s (4.6 m/s), a 15-µ aerosol, and an 8% level of turbulence intensity approaching the samplers in the wind tunnel, the following sampler effectivenesses (aerosol deposited on collection substrates of the particular sampler to that detected by an isokinetic sampling system) were noted: commerically available 1 CFM Andersen 2%; modified 1 CFM Andersen with the special inlet, 50%; standard Hi-Volume sampler 55% (wind at 45°to the ridge of the roof); Prototype Dichotomous sampler 45%; and the 20 CFM Andersen with a rotating cowl inlet 82% (tested at 5 ft/s, 1.5 m/s).

Feasibility of High Volume Sampling for Determination of Total Suspended Particulate Matter and Trace Metals

“…The indicated TSP mass collected corresponded to an average rural aerosol concentration of some 50 uglnfi; the maximal concentration observed amounted to «160 jug/m 3 . The corresponding HVS standard devia-tion was found as 0.9 /*g/m 3 or «2% with respect to the indicated TSP concentration, clearly below the computed maximum of 15%. During agricultural activities the standard deviation was found to^increase to some 10%.…”

“…The results of an ambient test 8 of the EPA HVS with monodisperse aerosol of 17 ixm aerodynamic diameter, performed under conditions of neutral atmospheric stability are seen to be in fair agreement with the EPA wind tunnel results. 3 It is worthwhile to note that the sampling effectiveness of the so-called all-weather inlet 9 does not show any major deviation from the aforementioned HVS effectiveness (cf. Figure 1).…”

“…Coarse particle size dependent sampling effectiveness was determined experimentally in wind tunnel tests. 3 Among others, the EPA standardized HVS was tested as a function of wind speed and wind direction relative to the sampler's orientation (Figure la) using monodisperse test aerosol up to 50 ;um aerodynamic diameter. The gradually decreasing sampling effectiveness with increasing particle size is in qualitative agreement with the pertinent effectiveness formulae given by Durham and Lundgren 7 for a yaw angle of 90° ("vertical sampling from a horizontal flow field").…”

“…In view of a) the correspondence of the ambient results of Hofschreuder et al 8 and the EPA wind tunnel results 3 and b) considerations on the applicability of wind tunnel results, 4 it is assumed that the coarse particle effectiveness characteristics obtained in the EPA wind tunnel tests can be considered as indicative of the sampling effectiveness under ambient conditions of stable to neutral stability classes.…”

“…For coarse particles, wind tunnel experiments 3 show a sampling effectiveness decreasing from 100% for higher particle sizes. Also, variation in effectiveness with wind direction relative to the sampler has been observed for the EPA standardized HVS.…”