AAAR 37th Annual Conference October 14 - October 18, 2019 Oregon Convention Center Portland, Oregon, USA
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Oxidative Potential of PM2.5 Semi-volatile Species in an Urban Atmosphere
MILAD PIRHADI, Amirhosein Mousavi, Sina Taghvaee, Mohammad Sowlat, Constantinos Sioutas, University of Southern California
Abstract Number: 21 Working Group: From Aerosol Dosimetry and Toxicology to Health
Abstract In this study, we investigated the physicochemical characteristics and oxidative potential of the semi-volatile components of the ambient particulate matter (PM). The versatile aerosol concentration enrichment system (VACES) was used to collect concentrated ambient and thermodenuded fine particulate matter (PM2.5) concurrently, at an urban site located in the central Los Angeles during summer 2018 and winter 2019. We used a thermodenuder to selectively remove the semi-volatile components of the concentrated PM2.5 at the 45-50 and 95-100 ºC. The oxidative potential of the collected samples was quantified by means of an in-vitro cell-based alveolar macrophage (AM) assay. The volatility profile of the various PM2.5 components and corresponding effect on oxidative potential was quantified by conducting chemical analysis on the collected samples including elemental and organic carbon, inorganic ions, water soluble organic carbon (WSOC), metals, and polycyclic aromatic hydrocarbons (PAHs). While the refractory PM constituents including elemental carbon and metals were slightly affected by the heating, the labile components of PM2.5 such as PAHs and organic carbon illustrated progressive concentration losses with increase in the thermodenuder temperature. Significant reductions in the PM2.5 oxidative potential were observed as the semi-volatile components of the PM2.5 were removed. While the losses were 45% and 74% at the 50 and 100 ºC, respectively, in the summer period, the corresponding losses at the winter campaign were 56% and 85%, respectively. Therefore, the semi-volatile components are responsible for a significant fraction of the PM2.5 oxidative potential. Furthermore, the results of the regression analysis illustrated a strong association between the PM2.5 oxidative potential and organic carbon (OC), water soluble organic carbon (WSOC) and PAHs in both summer and winter periods.