AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Investigating the Health Effects of Fresh and Aged Traffic Aerosols: Linking Particle Oxidative Potential to Chemical Composition
NGA LEE NG, Matthew Kollman, Vasileios Papapostolou, Joy Lawrence, Sriram Suresh, Vishal Verma, Rodney Weber, Armistead Russell, Petros Koutrakis, Georgia Institute of Technology
Abstract Number: 518 Working Group: Linking Aerosols with Public Health in a Changing World
Abstract Emissions from mobile sources are of substantial interest in health effects studies. Most studies have focused on the adverse effects of primary diesel and gasoline emissions. In contrast, studies on the toxicity of secondary mobile emissions, especially that involving gas-particle partitioning upon oxidation and secondary organic aerosol (SOA) formation, is extremely limited and their health effects remain poorly characterized. In this collaborative study between the EPA-funded SCAPE and Harvard Clear Air Centers, we systematically investigate the chemical composition and oxidative properties of primary and secondary particles from vehicular emissions. Measurements are conducted at a moderate-to-heavy traffic density tunnel in the Northeastern US equipped with photochemical chamber and animal exposure facility. The facility produces three test atmospheres: “primary particles” (P), “aged primary plus secondary organic aerosols” (P+SOA), or “secondary organics aerosols” (SOA). For each system, the near real-time chemical composition of the particles is characterized by an Aerosol Chemical Speciation Monitor (ACSM). The ACSM provides mass concentration and mass spectra of organics, sulfate, ammonium, nitrate, and chloride. Filter samples are taken from each system and analyzed for oxidative properties (reactive oxygen species generation properties) using dithiothreitol assay (DTT), as well as complementary chemical composition such as EC/OC, particle mass, and trace elemental concentrations. We apply Positive Matrix Factorization (PMF) to the ACSM organics data to deconvolve the mass spectra into different factors for linking to aerosol oxidative properties. The PMF factors are consistent with offline EC/OC measurements, where we resolve hydrocarbon-like OA and oxygenated OA that are surrogates for primary and secondary organic aerosols. It is found that SOA exhibits the highest intrinsic DTT activity among all test atmospheres. As SOA mass often dominates fine particle matter in the atmosphere, results from this study highlight the importance of understanding the health effects of SOA formed from the photooxidation of primary emissions.