AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
The Effect of Sound Wall - Vegetation Combination Barriers on Pollution Dispersion from the Freeways
DILHARA RANASINGHE, Isis Frausto-Vicencio, Eon Lee, Yifang Zhu, Seyedmorteza Amini, Faraz Enayati Ahangar, Akula Venkatram, Steve Mara, Suzanne Paulson, University of California, Los Angeles
Abstract Number: 682 Working Group: Urban Aerosols
Abstract The differential exposure to high levels of air pollution near heavily trafficked roadways, compared to other locations, raises serious health concerns in land usage in such locations. A widely considered mitigation strategies for exposure reduction is the optimization of sound walls and roadside vegetation barriers. Physical barriers affect pollutant concentrations around it by blocking initial dispersion, and increasing turbulence and initial mixing of the emitted pollutants. Vegetation can also remove some gaseous pollutants by absorption and particulate matter by deposition. Though it is well established that sound walls, vegetation barriers and combination barriers; that is sound walls together with vegetation barriers, affect the pollution dispersion downwind of roadways, there are many inconsistent results about the dispersion patterns found from different field, tracer, wind tunnel and numerical modeling studies done so far. The complexity of pollutant movement under varying conditions makes accurate prediction of exposure reduction difficult.
An extensive field measurement campaign was conducted to look at the effectiveness of sound wall-vegetation combination barriers as a near-roadway pollutant mitigation strategy. Mobile measurements of several air pollutants were done at two sites near heavily-trafficked freeways in Santa Monica, CA and Sacramento, CA. Measurements were done in two different seasons in Santa Monica; fall, 2015 and winter, 2016. In Sacramento, the measurements were done in summer, 2016. Pollution variation behind the barriers were analyzed together with local meteorology measurements to find general patterns of the pollution dispersion behind combination and vegetation barriers. This study will provide insights into the value and best practices for siting and design of vegetation and combination barriers, to reduce downwind pollution from roadways. The results could provide planners and decision makers with additional tools to evaluate and consider potential near-roadway air pollution mitigation options for existing and future development.