Passive Aerosol Sampler. Part I: Principle of Operation

Abstract

A method has been developed to estimate average concentrations and size distributions with a miniature passive aerosol sampler. To use the passive sampler, one exposes it to an environment for a period of hours to weeks. The passive sampler is intended to monitor ambient, indoor, or occupational aerosols and has potential utility as a personal sampler. The sampler is inexpensive and easy to operate and is capable of taking long-term samples to investigate chronic exposures. After sampling, the passive sampler is covered and brought to the lab. Scanning electron microscopy (SEM) and automated image analysis are used to count and size collected particles with d p > 0.1 ¹m. Alternatively, more advanced microscopy techniques can be used for ambient-pressure analysis or elemental characterization. Image analysis is used in conjunction with particle density and shape factors to obtain the mass ux as a function of aerodynamic diameter.

Emission factors from road dust resuspension in a Mediterranean freeway

“…The operation principle of the samplers is similar to that described by Vawda et al (1990) or Wagner and Leith (2000). The samplers are simply exposed to ambient air for passive collection of PM by deposition.…”

“…The deposition flux can be calculated by the terminal concentration m co divided by the deposition area A, and the sampling time t (h) (Wagner and Leith, 2000):…”

Field tests of a passive aerosol sampler

“…Densities for all compounds and shape factors for sand were found in the literature (Wagner & Leith, 2000a; CRC Handbook of chemistry and Physics, 1997). Shape factors for dolomite, soda ash, and lime were estimated by comparing their SEM-observed shapes to those of particles that appear in the Particle Atlas (McCrone & Delly, 1973a,b) and that have published shape factors (Wagner & Leith, 2000a). Dolomite had a similar shape as sand and was assigned the same shape factors.…”

“…where C is the average mass concentration over the sampling period and F is the mass #ux (particles collected/(area-time)) determined from the microscopy, v is the particle deposition velocity and is comprised of a theoretical component, v , and an empirical mesh factor, , as described previously (Wagner & Leith, 2000a). All terms are calculated as a function of aerodynamic diameter, d .…”

“…The size distribution information can then be used to determine PM2.5, PM10, respirable, inhalable, or any other size-dependent concentration of interest. v represents the ambient particle deposition rate to a #at plate, and has been derived using gravitational, inertial, and di!usive mechanisms (Wagner & Leith, 2000a) v "…”