Urban Trees and Their Relationship with Air Pollution by Particulate Matter and Ozone in Santiago, Chile

Most Latin American cities have air quality problems owing to high levels of particulate matter and ozone. By 2050, it is expected that more than 80% of Latin Americans will live in urban areas, leading to an increment in pollution problems. Santiago, Chile shows a high level of pollution from PM10 and PM2.5, especially during the autumn–winter period and from ozone (O3) during the spring–summer period owing to natural and anthropogenic causes. Information for this chapter was obtained from the official monitoring system of pollutants, but also from scientific papers and experimental work developed in our laboratory. The chapter contains a general description of the particulate matter, some analytical methods of studying it, and their officially reported sources; also, some new findings are included. For tropospheric ozone, a similar procedure was followed. The result is essentially focused on considering the ability of urban trees in capturing PM, while at the same time emitting minimal amounts of biogenic volatile organic compounds (BVOCs) that can potentially generate ozone. Available information shows that native species and a few exotic species were the most frequently appropriated to accomplish both requirements. As the vegetation of Santiago is mainly composed of exotic tree species that lose their leaves during the winter and produce high quantities of BVOCs during spring–summer, it does not contribute to the improvement of air quality; on the contrary. This situation should be remedied as soon as possible through the correct choice of trees and urban planning measures. The chapter also includes some similar variables reported in the literature from other countries of Latin America.