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Spatiotemporal Variability and Source Apportionment of Oxidative Potential Associated with Water-soluble PM2.5 in the Midwest United States
HAORAN YU, Joseph V Puthussery, Yixiang Wang, Yicen Liu, Vishal Verma, University of Illinois Urbana-Champaign
Abstract Number: 60
Working Group: Health-Related Aerosols
Abstract
Oxidative potential (OP) of ambient PM2.5 has been linked with numerous adverse health outcomes in humans. Multiple chemical endpoints have been developed to evaluate the OP of PM2.5, while different endpoints showing different mechanisms of aerosol catalyzed ROS generation. To investigate the comprehensive redox properties of ambient particles, we used five commonly used OP endpoints [ascorbic acid (AA) and glutathione (GSH) consumption in surrogate lung fluid (SLF), dithiothreitol (DTT) consumption and •OH generation in SLF and DTT]. We collected 72 h integrated PM2.5 samples weekly from five sites in the Midwest US (including Illinois, Indiana and Missouri) during May 2018 – May 2019. A semi-automated multi-endpoint ROS activity analyzer (SAMERA), which was recently developed in our lab, was used to analyze all the samples. We also measured the chemical composition of these samples, including carbonaceous species [i.e. elemental carbon (EC), organic carbon (OC) and water-soluble organic carbon (WSOC)], inorganic ions (nitrate, sulfate and ammonium) and thirteen metals. Spatial profiles of the OP were analyzed by calculating coefficient of divergences (CoD) between different site pairs. We also investigated the correlations between various chemical components and OP for different sites and seasons. Preliminary results showed that OP was highest during the summer season at all the sites. Significant correlations were found between multiple OP endpoints and transition metals (i.e. Cu, Fe and Mn) during summer at most of the sites, while the correlation with WSOC was more significant during winter at all the sites. The source apportionment modeling by positive matrix factorization (PMF) is currently underway, which will lead us to identify the emission sources contributing to different OP endpoints. Our study provides the first large-scale development of spatiotemporal profiles of OP, involving almost all possible modes of chemical ROS generation, and investigating their sources in the Midwestern United States.