The CODASC database for analyzing the impact of morpho-climatic characteristics of canyon streets on the concentration of air pollutants

Canyon-type urban street is one of the urban forms in which critical and harmful situations for health and the urban environment are appearing today, such as urban heat island, areas of poor ventilation, and retention areas for pollutants emitted by road traffic, heating, and concentration of industrial activities. The higher pollution levels are due to inappropriate relationships between morphological and microclimatic parameters specific to urban street canyons. Previous studies have mentioned the most common ones, namely the aspect ratio (H/W), the orientation of the street to the prevailing winds, and the vegetation. In the city of Algiers, the urban street canyon is very noticeable in two dominant urban fabrics, the medieval organic fabric and the colonial fabric dating back to the French occupation. This paper aims to explain the effect of different factors specific to urban canyons in Algiers on the concentration trend of air pollutants. By adopting the CODASC database containing data on normalized average pollutant concentrations (C+) related to different canyon street models according to aspect ratios H/W values, wind flow direction (α), tree stand density (ρs), and tree crown porosity (PVol). The results showed that LARBI BEN M'HIDI Street is more polluted than MOHAMED AZOUZI Street due to the effect of the maximum values of the aspect ratio and the density of trees on the wind behavior. The study results could provide a strategic guide for pollution mitigation to be used by urban planners in the design and implementation phases of sustainable urban development projects in Algiers.