AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Synergistic and Antagonistic Interactions among the Particulate Matter (PM) Components in Generating the Reactive Oxygen Species (ROS)
HAORAN YU, Jinlai Wei, Vishal Verma, University of Illinois, Urbana, IL
Abstract Number: 452 Working Group: Linking Aerosol Oxidative Potential with Chemical Composition and Biological Endpoints
Abstract The capability of individual chemical components in ambient particulate matter (PM) to generate reactive oxygen species (ROS) has been investigated for more than a decade. However, a simple summation of the individual ROS activities of these components to obtain the total ROS activity of ambient PM is not sufficient, as there could be interactions among the PM components to enhance or suppress the ROS activity. Although, it is generally believed that PM components interact in complex ways, the exact nature of these interactions and its impact on the ROS activity of ambient PM is not known. We attempt to understand some of these interactions by investigating the mixtures of the individual ROS active compounds, i.e. four quinones [phenanthraquinone (PQN), 1,4-naphthoquinone (1,4-NQN), 1,2-naphthoquinone (1,2-NQN) and 5-hydroxy-1,4-naphthoquinone (5-H-1,4-NQN)] and three transition metals [Fe(II), Mn(II) and Cu(II)], for their capability in both DTT consumption and OH. generation. Preliminary tests have shown that although the interactions within quinones and within metals were mostly additive in both DTT consumption and OH. generation, there were strong interactions among quinones and metals for both endpoints (i.e. DTT consumption and OH. generation). For example, Cu showed antagonistic effect with most quinones in both DTT consumption and OH. Generation. On the other hand, Mn enhanced the DTT consumption but suppressed OH. generation when interacting with quinones. The nature of these interactions between organic compounds and metals were further confirmed by mixing the fulvic acid/ humic acid with metals mixture (Cu, Mn and Fe). Results showed that the interactions depend on the relative concentrations of Cu, Mn and Fe in the mixture. Higher concentrations of Fe caused a synergistic effect in OH. generation, Cu and Mn lead to antagonistic and synergistic effect in DTT consumption, respectively. To confirm that these interactions as observed from the pure compounds exist in ambient PM as well, we extracted the ambient aerosol samples and separated the humic-like substances (HULIS) and metals by passing the aerosol extracts through a C18 column. The interactions among HULIS and metals mixture were more pronounced in the ROS generation than the DTT consumption. We are currently investigating if these interactions could be explained just by measuring the concentrations of three metals (i.e. Cu, Mn and Fe) in the ambient PM. This research would help in developing a model for predicting the ROS activity of ambient PM based on their measured chemical composition.