Modelling effects of type of trees on urban air pollution with a computational fluid dynamics model

Abstract

Urban trees can change (increase and/or decrease) pollutant concentrations and this study assesses the effect of urban trees on main pollutant concentrations in a 1 km by 1 km area, in a high traffic density zone, in Madrid City (Spain) using numerical computational fluid dynamics (CFD) simulations. A real-life experiment was designed for 1 week of June 2017 with a spatial resolution of 5 m. A zone of vegetation in which the dominant species are broadleaf trees was included in the business as usual (BAU) simulation. The second scenario focused on changing the type of tree from broadleaf in the BAU scenario to needleleaf in the so-called ND scenario. The differences between ND simulation and BAU simulation provide information about the effects of the type of tree on the air quality (NO2 and O3) of the area. The results of the simulations show a high sensitivity to changes in the type of tree in urban parks with strong impacts (hot spots) in several areas located several hundreds of meters away of the green park area. The results of these simulations will provide more knowledge on the effects of trees that will have to be taken into account when developing mitigation strategies for atmospheric pollution.