The Relationship of Air Pollution Sources and the Oxidative Potential of Particulate Matter (PM) in Different Cities Around the World

VAHID JALALI FARAHANI, Constantinos Sioutas, Ramin Tohidi, Abdulmalik Altuwayjiri, University of Southern California

     Abstract Number: 656
     Working Group: Aerosol Chemistry

Abstract
In this study, six sets of PM samples were collected in five urban location sites around the world which were selected for their PM to be dominated by unique emission sources: 1) PM2.5 emitted mainly by traffic emissions in central Los Angeles, United States (US); 2) PM2.5 produced by biomass burning activities in Milan, Italy; 3) PM2.5 formed by secondary photochemical reactions thus dominated by secondary aerosols in Athens, Greece; 4) PM10 emitted by refinery and dust resuspension in Riyadh, Saudi Arabia (SA); 5) PM10 generated by dust storms in Riyadh, SA, and 6) PM2.5 produced mainly by industrial and traffic emissions in Beirut, Lebanon. Chemical composition and associated oxidative potential of these PM samples were quantitatively analyzed to characterize the sources and their resulting health impacts. The dithiothreitol (DTT) assay was employed to quantify the corresponding oxidative potential of each PM sample. The results revealed that the Milan's ambient PM were rich in water soluble organic carbon (WSOC) and PAHs, tracers of biomass burning during the cold period, while PM in Athens exhibited high levels of inorganic ions, further corroborating the impact of photochemical reactions in this city. The ambient PM in LA was impacted by the traffic-emitted primary organic and elemental carbon. Additionally, the contribution of metals and elements per mass of PM in Riyadh and Beirut samples were more pronounced relative to other location sites. The highest intrinsic PM redox activity was observed for PM with the highest WSOC fraction, including Milan (biomass burning) and Athens (secondary organic aerosols, SOA). PM in areas characterized by high metal emissions such as Riyadh and Beirut, constituted the lowest oxidative potential as shown by the DTT assay.