10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Measuring the Real-Time Oxidative Potential of Ambient Particulate Matter Using an Online Mist Chamber System
JOSEPH PUTHUSSERY, Chen Zhang, Vishal Verma, University of Illinois Urbana-Champaign
Abstract Number: 1008 Working Group: Aerosols and Health - Connecting the Dots
Abstract The oxidative potential (OP) of ambient particulate matter (PM) has been shown to be associated with various adverse health effects. Although there exist automated instruments which can measure the OP of ambient particles collected onto filters, there are both positive and negative artifacts associated with conventional filter sampling and their storage. Therefore, reactive oxygen species (ROS) activity measured on the archived filters is not representative of the real potential of ambient particles to generate ROS in the biological system on inhalation. To address this issue, we developed an automated online mist chamber (OMC) system to measure the hourly averaged OP of ambient PM using dithiothreitol (DTT) assay and tested it in the actual field conditions for over 50 days. The ambient particles were collected inside the mist chamber, and OP of the PM suspension was quantified using an automated instrument based on the DTT assay. The results from the online system correlated well (R2 > 0.80) with conventional filter extraction method using both deionized water and methanol. The diurnal trend in the ambient particle OP during weekdays, measured by the online system showed a bi-modal trend with a peak during the morning period, followed by a broad peak (extending from 1 PM to 7 PM, but with a slight dip at 4 PM) during afternoon and early evening periods. We also conducted chemical speciation of the collected PM to link the diurnal variations in the concentrations of the redox active components (i.e., water soluble transition metals, organic carbon, water-soluble organic carbon, and elemental carbon) with the DTT activity. Based on our results, water-soluble Cu from non-exhaust emissions appear to be the major driver of the PM-induced OP during the daytime. Additionally, the secondary particles generated by the photochemical transformation of primary emissions were found to enhance the OP during the afternoon and evening periods. Future work in this direction aims to couple the OMC system to a comprehensive OP measuring instrument, which can measure both DTT consumption rate and hydroxyl radical (•OH) generation capability of aerosol particles using multiple assays (such as DTT assay and surrogate lung fluid assay).