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Real-Time Measurement and Source Apportionment of Five Different Endpoints of the Oxidative Potential of Ambient Particulate Matter at an Urban Site
JOSEPH V PUTHUSSERY, Haoran Yu, Yixiang Wang, Ian Cornejo, Vishal Verma, University of Illinois Urbana-Champaign
Abstract Number: 266
Working Group: Health-Related Aerosols
Abstract
The oxidative potential (OP) of ambient particulate matter (PM) has recently gained wide acceptance as an alternate metric for estimating the toxicity of ambient PM. Various studies have reported the OP based on different cellular and acellular assays. However, these studies have been limited to the OP measured on the integrated filter samples collected offline, which usually have poor time resolution. Moreover, different assays capture different combinations of the redox-active PM components, and there is currently no consensus on a standardized OP measurement protocol, which can provide a comprehensive picture of the total PM OP.
In this study, we developed a real-time multi-endpoint online system for measuring the OP of ambient PM based on five different acellular endpoints: oxidation of dithiothreitol (DTT) and ·OH generation in DTT assay; glutathione (GSH) consumption, ascorbic acid (AA) consumption, and ·OH generation in surrogate lung fluid (SLF, mixture of GSH, AA, uric acid and citric acid). We coupled an analytical automated instrument with a mist chamber particle collector and deployed it at a roadside site in Champaign, Illinois for ~2 months. We determined the diurnal trends in the ambient PM OP with a 3-hour time resolution and investigated their association with various chemical species in PM. We found a strong correlation (r >0.8) between ·OH generation rate and the concentration of water-soluble Fe. Additionally, the water-soluble organic carbon was strongly correlated with the DTT consumption rate. We are currently combining the OP data with the PM chemical composition to perform source apportionment analysis. The highly time-resolved OP data obtained from this study would provide a better mechanistic understanding of the redox activity of PM and provide new insights into the best combination of OP endpoints that most comprehensively represent the different aspects of the oxidative properties of ambient PM