AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Contrasting Oxidative Potential of Ambient Water-Soluble PM2.5 Measured by Dithiothreitol (DTT) and Ascorbic Acid (AA) Assays: Spatiotemporal Distribution, Source Apportionment, and Health Impacts
TING FANG, Vishal Verma, Josephine Bates, James Mulholland, Armistead G. Russell, Rodney J. Weber, Georgia Institute of Technology
Abstract Number: 99551 Working Group: Health Related Aerosols
Abstract The mechanisms of PM health effects are uncertain, however, it has been hypothesized that a possible route is the ability of PM to induce oxidative stress via catalytic generation of reactive oxygen species (ROS). Thus aerosol oxidative potential might be a better predictor of PM toxicity than more generic aerosol properties, such as mass. We developed a semi-automated system to quantify oxidative potential of filter aqueous extracts utilizing the dithiothreitol (DTT) assay and have recently adapted it to the Ascorbic Acid (AA) assay. We analyzed approximately 500 PM$_(2.5) samples collected at contrasting environments in southeastern US using both assays, and found that DTT activity on a per air volume basis was spatially uniform and had higher levels in winter than in summer (winter$_(avg)/summer$_(avg)=1.5). In contrast, AA activity was heterogeneously distributed, with highest levels near traffic, and higher in summer compared to winter (summer$_(avg)/winter$_(avg)=1.9). In contrast to DTT, which is sensitive to organic and metal species, AA activity was only correlated with water-soluble metals (especially Cu, r=0.70-0.91). Source apportionment models suggest a strong contribution from secondary processes and traffic emissions to both DTT and AA activities in urban Atlanta. Biomass burning was a large source for DTT activity, but not AA. DTT activity was generally well correlated with PM$_(2.5) mass (r=0.49-0.88), while AA activity did not co-vary with mass. Time series epidemiological analyses using reconstructed oxidative potential based on the past 10-year source impacts suggest that DTT activity was associated with emergency department visits for both asthma/wheeze and congestive heart failure, while AA activity was not linked to any investigated health outcomes (Bates et al., 2015). The lack of correlation of AA with PM$_(2.5) and greater chemical selectivity of AA assay (specific to Cu) may explain these results. We conclude the DTT assay is a more comprehensive multi-pollutant ROS indicator.