Urban vegetation as a filter for airborne particles: brief studies
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abstract
Urban vegetation has been widely recognized for its capability to improve air quality. Vegetation absorbs air pollutants through leaf stomata and intercepts airborne particles on their foliar surfaces. To investigate the overall interaction between vegetation and airborne particles, PM10 measurements were carried out in a small Portuguese city (Bragança), under two distinct experimental designs. In the first one, PM10 concentrations were sequentially monitored in six different points, placed on two linear paths intersecting areas with contrasting plant cover and crossed by a low traffic urban road. Real time measurements were conducted throughout the growing season encompassing a total of twelve trials. In the second experimental configuration, diesel exhaust particles were released into the ambient air using an internal combustion engine while real-time measurements of PM10 were taken in different locations in front and behind a 2-meter-high by 1.5-meter-wide Pyracantha hedge. Results from both experiments showed the ability of vegetation in filtering air particles. Although no significant linear relationship was found between PM10 and foliar density, PM10 levels were predominantly lower in the path with higher foliar coverage. A good filtering performance was also found for the Pyracantha hedge when exposed to diesel exhaust particles, especially when the pollution source was positioned closer to the green barrier. Particle reductions up to 95% were measured, indicating that placing dense vegetation near pollution sources (e.g. roads) will certainly be an excellent choice for improving air quality in any urban system.
