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A Low-Cost Device for Bulk Sampling of Airborne Particulate Matter: Evaluation of an Ionic Charging Device
Nima Afshar-Mohajer1, Wesley H. Godfrey1, Ana M. Rule1, Elizabeth C. Matsui2, Julian Gordon3, Kirsten Koehler1
1 Department of Environmental Health and Engineering, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
2 Department of Pediatrics, Johns Hopkins School of Medicine, Baltimore, MD 21205, USA
3 Inspirotec Inc., Chicago, IL 60647, USA
- Ion-charging devices (ICDs) are ideal bulk aerosol samplers.
- ICDs underestimate aerosol concentrations compared to conventional samplers.
- ICDs provide up to 9x greater mass of particles that the conventional aerosol samplers.
- Particle collection performance strongly depends on particles chargeability.
- ICDs roughly estimate PM concentration via linear correlations to other samplers.
Bulk sampling of aerosols is often needed for the determination of physical properties, chemical composition and toxicity assessments of airborne particulate matter. Conventional aerosol samplers have several limitations for use as bulk aerosol collectors including cost, noise levels, power requirements associated with the use of a pump, limited flow rate, and a relatively long sampling time needed to collect sufficient mass to achieve gravimetric or other method limits of detection. In this study, a low-cost ionic charging device (ICD) was evaluated that addresses many of the drawbacks of conventional aerosol samplers. Different types of particles including incense fume, Arizona Road Dust (ARD) powders and Polystyrene Latex (PSL) spheres of different sizes were aerosolized then sampled using three ICDs and compared to conventional inhalable and PM2.5 (particulate matter with aerodynamic diameter less than 100 µm and 2.5 µm, respectively) aerosol samplers in a controlled laboratory chamber at varying concentrations. The device was also evaluated in indoor environments. ICDs operate at almost 18.5 times higher flow rate than conventional personal samplers and provided up to 9 times greater total collected mass compared to the conventional samplers over the same time frame. Using a regression analysis, aerosol-specific linear equations with slopes (CPM2.5/CICD) from 1.21 to 7.10 and R2 from 0.74 to 0.99 for estimating the inhalable and PM2.5 mass concentrations using the ICD were derived. This study suggests that the ICD provides a less accurate estimate of size-selective PM mass concentrations than conventional personal aerosol samplers; however, it collects coarse particles efficiently and increases total sampled mass per time at a lower cost and without noise associated with traditional sampling methods. Therefore, the ICD can be used as a bulk aerosol collector for composition analyses and in-vitro toxicology tests of coarse PM.
Bulk aerosol sampling; Inhalable aerosol sampler; PM2.5 aerosol sampler; Coarse PM; Indoor air.