AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Generation of Reactive Oxygen Species Catalyzed by Mixtures of Atmospheric Humic Substances and Copper/Manganese: Evidence for the Importance of Metal-organic Interactions
MANFEI LIN, Jian Zhen Yu, Hong Kong University of Science & Technology
Abstract Number: 100 Working Group: Health Related Aerosols
Abstract Excessive generation of reactive oxygen species (ROS) and the corresponding oxidative stress has been recognized as one important cause for the adverse health effects associated with exposure to ambient particulate matter (PM). Transition metals (TMs) and humic-like substances (HULIS) in PM have been separately demonstrated to produce ROS, however, the impact of their interactions on their oxidative potentials has not been investigated and little understood. HULIS is an abundant fraction of water-soluble organic material in PM, sharing similarity in functional group composition with terrestrial and aquatic humic substances. In this study, we used a cell-free dithiothreitol (DTT) assay to assess the effects of interactions between TMs and HULIS and between two representative TMs, copper (Cu) and manganese (Mn). HULIS were found to suppress the DTT consumption from Cu by up to 10~20%, possibly due to the organic ligands in HULIS binding Cu and thereby reducing the redox reactivity of Cu. On the contrary, significant enhancement effects on DTT loss rate were observed both in the mixtures of HULIS and Mn and in the mixtures of Cu and Mn. Our work demonstrates the importance of quantifying interactions between components when we evaluate the contribution of individual species to the total oxidative strength. Difficulties encountered in attributing mixture effects to underlying interactions suggest that further work in metal-PM organics interactions should be done using techniques capable of more specific oxidant measurements in order to acquire a deeper mechanistic insight into the interactions.