AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Oxidative Potential of Coarse Particulate Matter (PM10–2.5) and Its Relation to Water Solubility and Sources of Trace Elements and Metals in the Los Angeles Basin
FARIMAH SHIRMOHAMMADI, Sina Hasheminassab, Dongbin Wang, Arian Saffari, James Schauer, Martin Shafer, Ralph J. Delfino, Constantinos Sioutas, University of Southern California
Abstract Number: 237 Working Group: Health Related Aerosols
Abstract Results from this study emphasize the role of non-exhaust traffic emissions, which are currently understudied and largely unregulated, in the potential toxicity of ambient coarse particles (CPM) (2.5 < dp < 10 micro-meter). The relative importance of non-exhaust traffic-related emissions has increased as the contribution of vehicle tailpipe emissions to total ambient PM concentrations has decreased due to the stringent regulations in the Los Angeles (LA) Basin. In this study, potential sources of water-soluble (WS) and water-insoluble (WI) fractions of metals and trace elements in CPM were identified and their association with the redox properties of CPM, measured by means of reactive oxygen species (ROS), was explored. CPM was collected during 2012–2013 in Central LA and 2013–2014 in Anaheim, CA. Generally, WI components contributed to a larger fraction of CPM ROS activity (as much as 64% and 54% at Central LA and Anaheim, respectively). Two major source factors were identified by principal component analysis for both the WS and WI fractions: vehicular abrasion and re-suspended road dust. In WS fraction, metals such as Mn, Fe, Cd and Zn were associated with WS ROS, while in WI fraction Ti, Fe, Ni, Pb and Cr had the highest correlations with WI ROS activity. Multiple linear regression analysis revealed that both vehicular abrasion and re-suspension of road dust were associated with WS ROS activity, while only vehicular abrasion contributed significantly to the WI ROS activity. Moreover, comparison with previous studies indicated that the ROS activity of CPM has increased in the past 5 years in Central LA. We attribute this increase mainly to the elevated levels of re-suspension of road dust caused by the increase in vehicle speed and number of trucks in recent years in this area, reaffirming the growing importance of non-tailpipe traffic emissions on CPM toxicity.