Comparison of particle sampling and collection methods for measurement of their physicochemical and toxicological properties

ZHI NING(1), Kalam Cheung(1), James J. Schauer(2) Arthur K. Cho(3), Ning Li(4), Constantinos Sioutas(1)

(1)Department of Civil and Environmental Engineering, University of Southern California (2)Department of Civil and Environmental Engineering, University of Wisconsin, Madison (3)Department of Molecular and Medical Pharmacology, University of California Los Angeles (4)Department of Medicine, University of California, Los Angeles

     Abstract Number: 168
     Last modified: April 27, 2010

Abstract
This study describes a comprehensive field sampling campaign designed to investigate the differences in the physicochemical and toxicological properties of fine particles (PM2.5) collected using three commonly used methodologies: filtration, impaction and a combination of particle concentration and collection into a liquid impinger (Biosampler). Two versatile aerosol concentration enrichment systems (VACES) were used side by side to provide concentrated ambient particles (CAP) for the samplers. The concentration enrichment of fine particles was accomplished by first drawing air samples through a saturation- condensation system that grows particles to 2-3 micron droplets, which are subsequently concentrated by virtual impaction. The output flow (30 LPM) of the two VACES was split into three branches: a). One leading to a Nano-MOUDI (Micro Orifice Uniform Deposition Impactor, MSP Corporation, Shoreview, MN) running at 10 LPM with selected stages to collect particles in the range of 18nm to 2.5microns by impaction; b) one leading to two 37mm filter holders equipped with Teflon and Quartz filter, respectively, each running at 5 LPM to collect particles by filtration; c) one leading to two identical Biosamplers (BioSampler, SKC Inc. Eighty Four, PA), each running at 5 LPM, directly after the virtual impactors to collect concentrated liquid suspensions of particles. Particles in configurations a and b were diffusion dried prior to collection by the impactors and filter samplers. The gravimetric measurement of the substrates from Nano-MOUDI samples showed excellent agreement with the samples collected on Teflon filters by filtration. The Biosamplers demonstrated very high particle collection efficiency, with an average collection rate of higher than 95%. The collected particle samples by the three different methods were further analyzed for water soluble organic carbon (WSOC), ions, water soluble metals, and organic compounds to compare their chemical properties. Particle toxicity was also characterized by the bioassays including Reactive Oxygen Species (ROS) and Dithiothreitol (DTT) to investigate the consistency of the particle toxicological properties among different samplers.