Abstract View
The Impact of Vegetated and Non-vegetated Roadway Barriers on Particle Concentrations and Toxicity
ROBY GREENWALD, Christina Fuller, Christa Wright, Haris Bejdic, Georgia State University
Abstract Number: 536
Working Group: Aerosol Exposure
Abstract
The Trees Reducing Environmental Exposures (TREE) simultaneously sampled particle concentrations in front of and behind roadway barriers along major interstate highways in the Atlanta metropolitan area. We measured PM2.5 and PM1 mass concentration, black carbon (BC) mass concentration, the particle number concentration (PNC), and the size distribution of ultrafine aerosols. In addition, we collected filtered samples of PM1 for use in in vitro toxicology experiments using human airway epithelial cells. Our sample sites include I-75/85 in Midtown Atlanta (with comparatively few tractor-trailer trucks) and numerous locations along the I-285 perimeter highway (with a higher fraction of tractor-trailer trucks). These sites encompass the range of roadway barrier options in the Atlanta area: simple chain-link fences, solid sound barriers, vegetated barriers, or both vegetated and solid sound barriers. Vegetated barriers exhibited the greatest reduction in particle concentrations in terms of PM or BC mass concentration as well as PNC. This effect was more pronounced for barriers comprised of species with larger canopy diameters and denser vegetation as assessed by leaf area index. The ultrafine size distribution was comprised of modestly smaller particles on the highway side of the barrier. In numerous cases, traffic sources from the non-highway side of the barriers reduced the difference in concentration from one side of the barrier to the other. In addition, when wind direction was from the barrier toward the highway, the difference in concentration was similarly reduced. Toxicological evaluation showed higher levels of cellular oxidative stress as assessed by the ratio of oxidized-to-reduced glutathione in exposed cells for particles collected on the highway side of the barriers. In addition, the production of reactive oxygen species (ROS) was higher in cells exposed to highway particles.