Investigating the effect of trees on urban quality in Dublin by combining air monitoring with i-Tree Eco model

Abstract

Fine particulate matter (PM2.5) is a common air pollutant that represents a significant threat to public health. In Dublin, a major source of PM2.5 is diesel exhaust, brake dust, and rubber tire particles from vehicles. Particulate matter can be deposited onto the surface of vegetation thereby removing it from the atmosphere. The presence of trees can increase the amount of surface area on which deposition can occur, but they can also alter wind flow in a way that increases local pollutant concentrations. This study assesses the effect of urban trees on removing PM2.5 using a novel combination of air quality monitoring and the i-Tree Eco (UFORE) deposition model during rush and non-rush hours with different traffic volumes. Monitoring was conducted in a tree alley and an area of no vegetation along the Drumcondra Road Lower in Dublin. Results indicated that there was no difference in PM2.5 concentrations outside of rush hours, but concentrations were significantly lower in the tree alley during rush hours compared to the street section with no trees. The i-Tree Eco model calculated that the tree alley could remove approximately 3 kg of PM2.5 on a yearly basis. Air monitoring found that the presence of trees resulted in a maximum air quality improvement of 126 %, more than double what was predicted by i-Tree Eco. While this study provides an initial exploration of trees and air quality in Dublin, further research combining these techniques with the measurement of local wind speed and direction would allow for a better understanding of how Dublin’s trees can affect its air quality. The results from this study suggest that they do cause a degree of air quality improvement and can be used to inform national clean air strategies aimed at reducing pollutant emissions.