Passive aerosol sampler. Part I: principle of operation.
Aerosol Sci Tech 2001 Feb; 34(2):186-192
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 ım. 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 flux as a function of aerodynamic diameter. The flux and a deposition velocity model are then used to estimate the average mass concentration and size distribution over the sampling period. The deposition velocity model consists of a theoretical component and an empirical component. The theoretical component incorporates gravitational, inertial, and diffusive mechanisms, but can be approximated by the simple terminal settling velocity in many cases. This article, Part I, describes how measurements are made with the passive sampler. The sampler design, theoretical component of the deposition velocity model, and microscopy methods are presented. Part II describes wind tunnel experiments performed to measure sampler precision and determine the empirical component of the deposition velocity.
Jeff Wagner, University of North Carolina, Department of Environmental Sciences and Engineering, CB#7400, Rosenau Hall, Chapel Hill, NC 27599
Disease and Injury: Asthma and Chronic Obstructive Pulmonary Disease
Aerosol Science and Technology
University of North Carolina