AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Methods for Quantifying the Total Oxidative Potential of Ambient Particles
DONG GAO, Ting Fang, Vishal Verma, Rodney J. Weber, Georgia Institute of Technology
Abstract Number: 461 Working Group: Health Related Aerosols
Abstract Both water-soluble and water-insoluble components of ambient particulate matter (PM) have been shown to contribute to the oxidative potential (OP) of PM. In this study, we develop and compare methods for quantifying the total oxidative potential (OP_Total) of ambient particles using the dithiothreitol (DTT) assay. The approach involved analysis of fine PM extracted from high-volume filters (23h integrated samples). Three methods for measuring OP_Total were compared: 1) sonicating filter punches in a vial with water and then performing the DTT assay in this vial containing the filter, 2) extracting punches in methanol, evaporating an aliquot of the methanol extract to near dryness, reconstituting with water and measuring DTT activity and 3) the sum of a standard water extraction with DTT analysis of the filtered liquid extract, followed by methanol extraction (method 2) performed in series on the same filter punches. Based on the results obtained from these three methods, for filters collected at a roadside and at a representative urban site, OP_Total from method 1 (OP_Total_1) was generally the highest, indicating, of these three methods, the first method is the most efficient way to measure OP_Total. It is also the method most easily automated. By subtracting OP of water-soluble components (OP_WS) from OP_Total, the relative contribution of water-soluble and water- insoluble compounds to the OP of ambient fine aerosols can be further determined. At the representative urban site, 60-75 percent of the OP_Total was associated with water-soluble species. Whereas at the roadside site, roughly 50 percent of the OP_Total was water-soluble, indicating a large contribution of water-insoluble compounds, such as DTT-active compounds associated with black carbon or insoluble road dust associated with traffic emissions. The application of this method can help to more comprehensively identify sources of PM toxicity and an automated analytical system applied to large population health studies.