The Effect on Air Pollution Distribution of Wind in Different Street Canyons: The Case of Erzurum

Abstract

The rapid increase in the population of cities leads to the diversification and new dimensions of environmental problems. Air pollution, which increases especially in winter, negatively affects outdoor comfort in terms of liveability in cities. The aim of this study is to analyze the movement of wind, the presence of trees and their effect on the distribution of air pollution in street canyons with different characteristics and to determine more comfortable design criteria for pedestrians at street scale. Air pollution data for 2018 were analyzed using the Interpolation method in ArcGIS 10.3 Spatial Analysis Module. Erzurum air pollution spatial analysis map was produced. According to the spatial analysis map of air pollution, four different street canyons, with and without trees, were randomly selected from the streets where the pollution is intense and less intense. Computational Fluid Dynamics (CFD) ANYSY 16.0 software program was used in the analysis of the determined street canyons. Street analysis was compared according to wind flow velocity, building roof, trees and pedestrian level, and it was found to be lower at pedestrian level. In the streets with less air pollution, it has been calculated that there is 23% decrease in wind speed in treeless streets and 25% in tree-lined streets. In the streets with high air pollution; It was determined that there was a decrease in wind speed by 29% in the treeless street and 57% in the tree-lined street. As a result, it has been determined that street canyons play an important role in the distribution of air pollution by affecting the direction and speed of the wind according to their characteristics. The fact that the street is parallel to the prevailing wind direction and that it receives the wind unimpeded has been seen as a healing factor in the dispersion of air pollution. It has been determined that the use of trees in narrow street canyons reduces wind speed. In addition, it has been determined that the air pollution is more intense in the streets with narrow canyon characteristics with less distance between buildings. It was emphasized that tree species that do not slow down the wind speed, for example species with high branches and a permeable texture should be preferred in the afforestation of wide street canyons. It was emphasized that if the streets are designed considering the natural characteristics of the area, they will be pedestrian friendly and more liveable places.