Sound Walls and Air Quality Mitigation

Vehicular emissions are one of the major sources of air pollution in urban areas and several epidemiological studies have shown that long term exposure to vehicle related pollutants increases the risk of respiratory diseases, birth defects, premature mortality, cardiovascular disease, and cancer. Since mid-20th century major highways are commonly accompanied with roadside structures known as sound walls. These structures are mainly designed to protect residential areas close to the highway by damping the roadway noise. The incorporation of these roadside structures brought up the question: how do these structures impact the air quality in residential areas located in the vicinity of highways? A thorough understanding on the direct impact of sound walls on flow and dispersion can significantly help air quality modelers in development of dispersion models that can accurately predict the human exposure in the areas close to highways. These models can be further incorporated into regulatory approved dispersion models such as USEPA AERMOD which are used in project-level conformity and hot spot analysis.

The presented research addresses the effects of sound walls through systematic water channel simulations accompanied with numerical modeling, Quick Urban and Industrial Complex (QUIC) model, and traditional simple Gaussian-type dispersion models. In our laboratory setup we visualized the dye spread to observe the average behavior of traffic related pollutants released into the atmosphere. Such visualizations can provide us with great details on the processes involved with the dispersion of such pollutants.