AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Macrophage Reactive Oxygen Species Activity of Water-soluble and Water-insoluble Fractions of Ambient Coarse, PM2.5 and Ultrafine PM in Los Angeles
DONGBIN WANG, Payam Pakbin, Martin Shafer, James Schauer, Constantinos Sioutas, University of Southern California
Abstract Number: 29 Working Group: Urban Aerosols
Abstract This study describes an investigation of the relative contributions of water-soluble and water-insoluble portions of ambient PM to the overall PM redox activity. Size-fractionated ambient PM samples (coarse, PM2.5 and ultrafine PM) were collected in August-September of 2012 in an urban site in Los Angeles, using the VACES/BioSampler tandem system. Ambient PM was concentrated and collected directly into an aqueous suspension thereby eliminating solvent extraction required for PM collected on filter substrates, as well as reducing losses of semi-volatile species during sampling. Separation of water-soluble and water-insoluble fractions of PM was achieved by ultra-filtration of the collected suspension slurries. Chemical analysis, including water-soluble and total organic carbon (WSOC/TOC), elements, and inorganic ions, as well as measurement of macrophage reactive oxygen species (ROS) activity were performed on the slurries. Correlation between ROS activity and different chemical components of PM was evaluated to identify the main drivers of PM toxicity. Results from this study illustrate that both water-soluble and water-insoluble portions of PM play important roles in influencing the ability of PM to produce ROS at the cellular level. While the ROS activity per volume of sampled air for soluble species contributes to major portion of total ROS activity, high intrinsic ROS activity (i.e. expressed per PM mass) for insoluble portions is also observed, despite their lower mass fraction. Organic compounds (OC) in both water-soluble and water-insoluble portions of ambient PM, as well as several transition metal species such as Mn, V, Cu and Zn, are highly correlated with ROS activity. Moreover, the observed ROS activity of the PM samples in this study was generally higher than those reported in previous studies using the conventional PM collection by filtration process. Therefore, collecting particles directly into a liquid suspension may be superior to conventional filtration by eliminating extraction and by reducing the losses of semi-volatile organic compounds.