Date: January 1, 2018
Author(s): Suzanne Paulson, Dilhara Ranasinghe; Liye Zhu
Abstract
Exposure to roadway pollutants is associated with negative health outcomes, raising concerns for sensitive areas like homes, schools, and parks located next to highways. Roadside barriers are a mitigation strategy commonly used to reduce the exposure of nearby communities to air pollution. The effectiveness of a barrier in reducing pollutant concentrations depends on a number of factors, including physical characteristics of the barrier. While studies have shown that traditional solid barriers reduce pollutant concentrations downwind of the barrier by upwards of 50 percent compared to open road values, the impacts of unconventional barriers are less clear. In 2013, the City of Long Beach installed a novel type of barrier, called the “Great Wall of Mulch,” constructed using mulch contained within a chain link fence enclosure. The barrier separates a park from a highway with large volumes of truck traffic, and it was touted by city officials as mitigation for nearby freight and industrial activity. This research found that the air quality at Hudson Park is consistent with a moderate amount of pollution reduction behind the Great Wall of Mulch. Part of the observed reduction, however, may be due to tall trees planted in the park near the barrier. A very effective barrier would usually result in even less air pollution than that observed at Hudson Park.
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