A New Generation of Portable Coarse, Fine, and Ultrafine Particle Concentrators for use in Inhalation Toxicology

Abstract

This study presents the development of prototype portable coarse, fine and ultrafine particle concentrators. A single-round nozzle virtual impactor operating at an intake flow of 120 L/min is used to concentrate coarse particles (e.g., 2.5–10 µm) by a factor up to 40 depending on the minor flow rate. Fine and ultrafine particles are concentrated by first growing to supermicrometer sizes via supersaturation. This is accomplished by first drawing these particles over a pool of warm, deionized, distilled water to achieve saturation and then through a condenser that allows the particles to grow to supermicrometer size, followed by concentration in a virtual impactor. After concentration, particles are returned back to their original size distribution and relative humidity by removing excess moisture in a diffusion drier. The performance of these concentrators was evaluated using generated monodisperse particles as well as ambient air particles. Average concentration enrichment factors were 9.5, 20, and 37 for a minor flow of 12, 6, and 3 L/min, respectively. The average concentration enrichment based on particulate sulfate and nitrate was by a factor of 20 and 22.6, respectively. The HEADS sampler was used as the reference sampler. The enrichment values based on particulate nitrate indicate that no nitrate loss occurs during particle concentration enrichment. The concentration of particular elemental (EC) and organic carbon (OC) was also evaluated, using the MOU DI as a reference sampler. The average concentration enrichment factors obtained for EC and OC were 20.4 and 21.6, respectively. Our experimental results indicated that the enrichment in concentration is not dependent on particle size and chemical composition. Because of their compact size and high concentration efficiency, the concentrators described in this study are inexpensive and portable so can be moved easily to several locations over seasons that differ in PM chemical composition and source profiles.