10th International Aerosol Conference
September 2 - September 7, 2018
America's Center Convention Complex
St. Louis, Missouri, USA

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Source Apportionment and Associated Oxidative Potential of Ambient PM in Beirut during Saharan and Arabian Dust Events

CHRISTOPHER LOVETT, Mohammad Sowlat, Najat A. Saliba, Alan Shihadeh, Constantinos Sioutas, University of Southern California

     Abstract Number: 226
     Working Group: Remote/Regional Atmospheric Aerosol

Abstract
In this study, we examine possible changes in the oxidative potential of airborne particulate matter (PM) in Beirut, Lebanon, as well as the source apportionment of this PM redox activity, that occur during dust events originating in the Sahara and Arabian deserts. Segregated fine (< 2.5 µm) and coarse (2.5-10 µm) PM samples collected during dust events, as well as during non-dust periods, were analyzed for chemical composition and an in vitro alveolar macrophage assay was performed to determine their oxidative potential. To examine changes in the source apportionment of PM oxidative potential during dust events, we first conducted a bivariate correlational analysis of the compositional and biological data to calculate Spearman’s rho coefficients. The correlational data indicating associations between PM components and oxidative potential were then used to perform principal components analysis (PCA) of the PM components and then multiple linear regression (MLR) to apportion the measured oxidative potential to distinct source groups and compositional source factor scores. Our findings revealed that the oxidative potential of Beirut’s urban PM during non-dust periods was much higher than during dust episodes, and the major contributors to this redox activity were traffic emissions combined with secondary organic aerosols (SOA). During days when aerosols from Saharan and Arabian dust events alter atmospheric PM composition, traffic emissions and SOA continued to dominate as sources of PM oxidative potential, along with the contribution of inorganic secondary ions (SI). The influence of dust aerosols on indigenous Beirut PM did not exacerbate its oxidative potential, thus suggesting that aerosols generated during Saharan and Arabian dust events pose no additional health risks to the population in that area.