Effective Tree Species for Local Air- Quality Management

Particulate pollution is a term that covers a broad spectrum of specific pollutant types, including smoke and aerosols, which permeate the atmosphere. The effects of such pollutants on human health have prompted a great deal of research effort in recent years, with the establishment of PM10 (particulate matter having an aerodynamic diameter of <10 μm) as the definition for the health-damaging fraction of the total suspended mass of particles in the atmosphere (DoE 1995). There have been a number of important medical studies that have linked high concentrations of PM10 with adverse human health effects (the first being by Dockery et al. 1993), and more recently concern has moved to the finer PM2.5 (<2.5 μm) and ultrafine particle fractions (<1 μm). The sources of these particles are many and varied in the urban atmosphere, including both naturally and anthropogenically produced matter. However, the most significant source in many urban areas comes from the exhaust fumes of road traffic (Watkins 1991). There have been a number of important medical studies linking high concentrations of PM 10 with adverse human health effects, the first being Dockery et al. (1993). More recently, concern has moved to the finer PM 2.5 (<2.5 μm) and ultrafine particle fractions (<1 μm) (Donaldson et al. 1998) As discussed by Beckett et al. (1998), trees provide many beneficial characteristics that enable them to capture pollutant particles and hence reduce their concentration in the air. The aim of this paper, therefore, is to provide the first step in a comprehensive study of the most effective use that can be made of trees for improving local air quality. The initial focus is to examine the differences in particulate capturing ability between species of tree appropriate for urban planting schemes.