Monodisperse and polydisperse aerosol deposition in a packed bed

Abstract

Although polydisperse aerosols in ambient and occupational settings have been associated with adverse health effects, researchers have mostly used monodisperse aerosols to investigate particle deposition in the human lung. The objective of this work was to determine whether the deposition of a series of monodisperse aerosols is reasonable to simulate the deposition of a polydisperse aerosol. A packed bed was used as an approximate surrogate to the human lung. Polydisperse and monodisperse sebacate aerosols were generated by nebulizers and a Monodisperse Aerosol Generator (MAGE), respectively. A Harvard respirator pump "inhaled" and "exhaled" aerosol through the packed bed. Complete size distributions of inhaled and exhaled aerosol were measured by an Aerodynamic Particle Sizer (APS) and a Scanning Mobility Particle Sizer (SMPS). The deposition for discrete sections of polydisperse aerosols was compared with the deposition of monodisperse aerosols. Also, the total deposition of a polydisperse aerosol was compared with the deposition of a series of monodisperse aerosols that formed the same size distribution as the polydisperse aerosol. Experiments were run with and without a charge neutralizer. With the neutralizer, no difference in deposition occurred between the discrete sections of polydisperse and monodisperse aerosols. Thus, total deposition was the same for both a polydisperse and a series of monodisperse aerosols, indicating that a series of monodisperse aerosols is reasonable to represent a polydisperse aerosol. Without a charge neutralizer, discrete sections of polydisperse aerosols with particle diameters of 3 μm or greater deposited no differently than they did with a neutralizer. However, for particle diameters of 1 μm or less, deposition of discrete sections of polydisperse aerosols was greater than that of monodisperse aerosols. Thus, total deposition was greater for polydisperse aerosols than for a series of monodisperse aerosols, indicating the need to condition aerosol with a neutralizer after the nebulization of a sebacate/alcohol solution.