Influence of roadside vegetation barriers on air quality inside urban street canyons
Urban Forestry & Urban Greening
More evidence has shown that exposure to particulate matter (PMs) within urban streets increases adverse health risks, and vegetation barriers have the potential to improve near-road air quality. To gain insight into the influences of vegetation barrier characteristics on the dispersion of PMs (TSP, PM10, PM2.5), field measurements were performed in Wuhan, China. Twenty-four sample belts were selected within oblique wind canyons, on road and roadside TSP, PM10 and PM2.5 concentration were simultaneously monitored in steady periods. Layer shelterbelt porosity was used to represent the vertical configurations of the vegetation barriers. The result indicated that vegetation combination of trees, shrubs, and herbs is effective for reducing the concentration of PMs. Vegetation barriers can reduce TSP and PM10 concentrations to a certain level (5 similar to 23 %) in the areas behind vegetation barriers compared to the control within oblique wind canyons. In contrast, the reduction effect of the vegetation barrier on PM2.5 could be positive or negative was inconsistent. Pearson correlation analysis results indicated that TSP and PM10 reduction efficiencies were negatively correlated with shelterbelt porosity in the 0 similar to 2 m height section, but the vegetation barrier indicators had no obvious effects on the reduction efficiency of PM2.5. To improve roadside air quality, the use of shrubs or hedges with heights lower than 2 m should be encouraged, and large, dense trees should be avoided around roads with heavy traffic. These results provide insight on how to improve roadside air quality by mitigating PM pollution in urban street canyons.
Author(s): Chen, XP; Wang, XS; Wu, XG; Guo, JP; Zhou, ZX
Journal: Urban Forestry & Urban Greening