AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Effectiveness of Road-side Vegetation and Noise Barriers on Reducing Ultrafine and Fine Particulate Matters under Variable Wind Speeds
Eon Lee, Dilhara Ranasinghe, Faraz Enayati Ahangar, Seyedmorteza Amini, Steve Mara, Wonsik Choi, Suzanne Paulson, YIFANG ZHU, University of California Los Angeles
Abstract Number: 82 Working Group: Passive Mitigation Strategies to Reduce Exposure to Near-Road Air Pollution
Abstract Recent studies have focused on the effectiveness of road-side barriers, such as soundwall and vegetation barrier as a potential mitigation strategy to reduce near-road air pollution. However, our understanding is limited because of insufficient scientific evidence in this area of study and there are variable findings reported in the literature. This study executed a series of field sampling campaigns at three near-freeway (10-15 m away) sites in California. At each study site, two to three weeks of real-time measurements of ultrafine particles (UFPs, diameter ≤ 100 nm) and PM2.5 (diameter ≤ 2.5 µm) were conducted concurrently at four fixed locations that have different configurations of soundwall and/or vegetation barriers upwind and downwind of the freeways. This study specifically aimed to determine to what extend the soundwall and/or vegetation barrier reduce the near-freeway air pollution under variable wind conditions. Overall finding of this study is that a combination barrier of soundwall and vegetation can be more effective on reducing both UFP and PM2.5 concentrations than either soundwall or vegetation alone. While this is consistent with majority of previous findings, this study also found the effectiveness of road-side barriers could be different for PM2.5 and UFP and specific to wind speeds. The soundwall barrier was more effective for reducing PM2.5 than UFP, and it was most effective when the wind speed ranged between 1 and 2 m/s. In contrast, the vegetation barrier had little effect on reducing PM2.5 but exhibited more effective reduction for UFP than the soundwall barrier. For both types of roadside barrier, decreasing wind speed resulted in greater reduction of UFP concentrations (i.e., inversely proportional). However, this trend was observed only within specific particle size ranges (i.e., diameter < 20 nm for the soundwall barrier and 12-60 nm for the vegetation barrier). Out of these size ranges, additional reduction of UFP concentration was proportionally more effective at increasing wind speed.