AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Fog Enhances Toxicity of Ambient Particulate Matter
Stefano Decesari, MOHAMMAD SOWLAT, Sina Hasheminassab, Silvia Sandrini, Stefania Gilardoni, M. Cristina Facchini, Sandro Fuzzi, Constantinos Sioutas, University of Southern California
Abstract Number: 53 Working Group: Aerosol Chemistry
Abstract Numerous studies have demonstrated that outdoor exposure to atmospheric particulate matter (PM) is associated with adverse health effects. However, it should be pointed out that the actual chemical species responsible for PM toxicological properties remain a subject of investigation. Carbonaceous species and transition metals have been clearly identified as triggers of PM toxicity in urban environments, however little is known for background continental sites. We provide here reactive oxygen species (ROS) activity data for PM samples collected at a rural site in the Po Valley, Italy, during the fog season (i.e., November-March). We show that the intrinsic ROS activity of Po Valley PM, which is mainly composed of biomass burning and secondary aerosols, is comparable to that of traffic-related particles in urban areas. The airborne concentration of PM components responsible for the ROS activity decreases in fog conditions, when water-soluble species are scavenged within the droplets, and the intrinsic ROS activity of fog droplets is even greater than that of the PM on which droplets are formed, indicating that redox-active compounds are not only scavenged from the particulate phase, but are also produced within the droplets. Therefore, even if fog formation exerts a scavenging effect on PM mass and redox-active compounds, the aqueous-phase formation of reactive secondary organic compounds can eventually enhance ROS activity of PM when fog evaporates. These findings demonstrate that a significant portion of airborne toxicity in the Po Valley is largely produced by environmental conditions (fog formation and fog processing) and not simply by the emission and transport of pollutants.