Development and Evaluation of a Multi-stage Cascade Impactor for the Collection of Ambient Particulate Matter on Gelatin Filter

Mohammad Aldekheel, Vahid Jalali Farahani, RAMIN TOHIDI, Constantinos Sioutas, University of Southern California

     Abstract Number: 657
     Working Group: Urban Aerosols

Abstract
In this study, we developed and evaluated the performance of a high-volume and multi-stage cascade impactor for the collection of fine and ultrafine particles. This cascade impactor operates at a flow rate of 100 lpm and has two impaction stages with 50% cut-point diameters of 2.5 μm and 0.2 μm, respectively, to separate particles into three size groups: <0.20 μm, 0.20-2.5 μm, and >2.5 μm. The performance of the impactor was evaluated in the laboratory using monodisperse polystyrene latex (PSL) particles as well as polydisperse ammonium sulfate, sodium chloride, and ammonium nitrate aerosols to experimentally obtain the 50% cut-point of each impaction stage. Additionally, lab tests were conducted using our impactor and the Personal Cascade Impactor Sampler (PCIS) to compare the mass concentration of collected particles. The findings of this study showed that the experimentally determined parameters of the impactor, including the 50% cut-point diameters, agreed with the theoretical predictions. Furthermore, the average mass concentration of particles using our designed impactor was in a very good agreement with the PCIS. This impactor has been developed primarily to collect particles on water-soluble gelatin filters which require gentle handling, and efficiently maintain viable biological material. These filters can easily dissolve in water allowing for the extraction of water-insoluble particles into the slurries, for the use in in-invitro and in-vivo exposure studies.