10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Seasonal Variations in Source Apportionment of the Redox Activity of Urban Fine Particulate Matter in Athens, Greece
SINA TAGHVAEE, Mohammad Sowlat, Christopher Lovett, Konstantinos Eleftheriadis, Evangelia Diapouli, Manos Manousakas, Constantinos Sioutas, University of Southern California
Abstract Number: 896 Working Group: Source Apportionment
Abstract In this study, we examined possible changes in the compositions and oxidative potential of airborne particulate matter<2.5 µm in diameter (PM2.5) at two urban sites in Athens, Greece: an urban traffic (UT) site located in the city center of Aristotelous, and a residential, urban background (UB) site in the outlying neighborhood of Demokritos. We were not only interested in differences between these two sites, but also in changes of PM composition and oxidative potential as the seasons change from summer (July-September) to fall (October-November) to winter (January-March). Chemical and biological analyses were done to determine PM composition and oxidative potential, then source apportionment of the PM redox activity was done using Principal Component Analysis of the chemical components of PM followed by Multiple Linear Regression of the measured oxidative potential on factor tracers (PCA-MLR). PM samples were analyzed for chemical composition, and the dithiothreitol (DTT) and in vitro alveolar macrophage assays were performed to determine PM oxidative potential. Chemical analysis was done for metals, water-soluble organic carbon (WSOC), elemental and organic carbon (EC/OC), organic compounds, inorganic ions, and markers of biomass burning (e.g. levoglucosan). To examine changes in the source apportionment of PM oxidative potential during different seasons, we first conducted a bivariate correlational analysis of the compositional and oxidative potential data to calculate Spearman’s rho coefficients. The correlational data indicating associations between PM components and oxidative potential were then used to perform PCA-MLR in apportioning the measured oxidative potential to distinct source groups and compositional source factor scores. Our findings revealed that the oxidative potential of urban traffic PM was much lower than urban background PM, and the major source contributors to this redox activity were vehicular traffic at the UT site, which was increased during the longer daylight hours of summer that enhanced photo-oxidation of PM, and biomass burning at the UB site, which was enhanced during the winter period.