AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Reduction in Dithiotreitol Oxidative Potential in Copper/Organic Aerosol Mixtures
SHUNYAO WANG, Jianhuai Ye, Rudraksha Dutta Majumdar, Andre Simpson, Arthur W. H. Chan, University of Toronto
Abstract Number: 621 Working Group: Linking Aerosol Oxidative Potential with Chemical Composition and Biological Endpoints
Abstract The Dithiothreitol (DTT) assay has been widely applied to evaluate the oxidative potential (OP) of particulate matter and its components. However, the relative contribution of each component to overall OP remains unclear. Redox cycling of transition metals and quinone-like substances has been proposed to contribute to DTT consumption, and the OP of these components in a mixed PM are assumed to be additive. In this work, we examine the total OP of a PM mixture containing both quinones and copper, and compare to their individual OPs. Naphthalene secondary organic aerosol (NSOA), phenanthrene secondary organic aerosol (PSOA) and several quinone standards (1,4-naphthoquinone, 1,2-naphthoquinone, 9,10-phenanthrenequinone) were used to represent organic aerosol that is redox active. After mixing these organic compounds with copper (II) at 1:1 molar ratio, significant reduction in DTT activity (50±6%, 43±7%, respectively for NSOA and PSOA) was observed with SOA and copper mixture compared to the sum of the individual DTT activities of copper and SOA. While similar reductions were witnessed for both 1,2-naphthoquinone and 9,10-phenanthrenequinone (41±15%, 68±1%, respectively) no significant DTT activity reduction was detected in a copper / 1,4-naphthoquinone mixture, likely owing to the position of the carbonyl groups. We propose that the mixing between transition metals and organics reduces the OP through metal-organic chelation. The extents of chelation at various metal to organic ratios evaluated by 1H NMR will be discussed. The results of this study indicate OPs of individual components in a metal/organic mixture are not linearly additive, and more studies are needed to characterize metal-organic interactions in ambient particulate matter for a better prediction of adverse health outcomes based on the particle chemical composition.