AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Ambient Size Distributions and Lung Deposition of Aerosol Dithiothreitol-Measured Oxidative Potential: A Contrast between Soluble and Insoluble Particles
TING FANG, Linghan Zeng, Dong Gao, Hongyu Guo, Vishal Verma, Aleksandr Stefaniak, Athanasios Nenes, Rodney J. Weber, Georgia Institute of Technology
Abstract Number: 437 Working Group: Linking Aerosol Oxidative Potential with Chemical Composition and Biological Endpoints
Abstract The association of ambient particulate matter (PM) with adverse health may be through upsetting redox homeostasis by generating reactive oxygen species (ROS) in vivo and leading to oxidative stress. Oxidative potential (OP) measured by the dithiothreitol (DTT) assay has been widely used to represent the capability of aerosols to generate ROS and PM2.5 OPDTT levels have been linked to certain cardiorespiratory health outcomes in recent epidemiological studies. Although bulk measurements of PM2.5 OPDTT are common, size resolved measurements are rare but provide unique insights on the sources and atmospheric processes that contribute to observed OPDTT levels. In this study, ambient size distributions of water-soluble and -insoluble fractions of OPDTT (per air volume) are reported for samples collected at a road-side and urban site in Atlanta, GA. Water-soluble OPDTT size distributions were unimodal with a peak at 1 to 2.5 µm due to contributions from fine-mode organic components plus coarse-mode transition metal ions. In contrast, water-insoluble OPDTT was bimodal with a fine and coarse mode. The fine mode was mainly associated with DTT-active organic species absorbed on soot surfaces and the coarse mode with mainly transition metal ions associated with mineral-tire-brake dust surfaces. These size differences mean that the two main chemical components that drive OP (organic species, such as quinones, and transition metal ions) are largely externally mixed and deposit in different regions in the respiratory system; metals predominately in the upper regions, and quinones deeper in the lung. The data also show the importance of secondary processing for both forms of OPDTT. This talk will present typical urban aerosol OPDTT size distributions and discuss sources and processes that affect overall OPDTT levels and report predicted lung deposition patterns.