AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Ambient Size Distributions of Particulate Matter Oxidative Potential and Estimated Deposition in the Human Respiratory System
TING FANG, Linghan Zeng, Vishal Verma, Rodney J. Weber, Georgia Institute of Technology
Abstract Number: 523 Working Group: Health Related Aerosols
Abstract Oxidative potential (OP), referred as to the capability of aerosols to generate reactive oxygen species, has been proposed as a better health relevant indicator than particulate matter (PM) mass. Particle size is an important factor in the health effects of OP since it controls deposition efficiency, thus influences where each inhaled particle is likely to deposit in the human respiratory system. Particle size distributions also provide evidence on sources and processes that affect ambient concentrations. Size-segregated ambient PM samples were collected from an urban background site and a road-side site in Atlanta, GA. Samples were measured for OP, elemental and organic carbon, and sulfate. Water extracts of samples were measured using the dithiothreitol (DTT) and ascorbic acid (AA) assays. Total DTT activity, which includes both water-soluble and water-insoluble fractions, was also measured with the DTT method. Results show that OP size distributions do not have the typical minimum at PM2.5. Instead, water-soluble OP shows a mono-modal distribution which peaks at 0.8-2.5 µm. Water-soluble AA activity has a much narrower distribution and peaks at a larger size than that for water-soluble DTT activity at both sites. Water-soluble DTT distribution is quite spatially uniform while total DTT activity at the road-side site has a significant contribution from larger size particles. Our results suggest the contribution from both organic species and metals to the OP in Atlanta from both primary emissions and secondary processes. The estimated deposition of oxidative potential in the human respiratory tract suggests that although ultrafine particles are considerably more oxidatively active per mass, given that the mass of ultrafine particles in ambient air is rather small, fine and coarse fractions are more significant in terms of OP deposition throughout the respiratory system and so potentially more health-relevant.