This study aims to further investigate the role of urban green infrastructures (vegetation barrier and street trees) on urban air quality and/or thermal comfort. The tools of this investigation include the application of a micro-scale, computational fluid dynamics model called ENVI-met, along with wind tunnel experimental data and field measurements. The study is divided into two broad sections based on settings of the idealized or real world study area: open-environment and street canyon.
In the open-environment setting, the benefit of roadside vegetation barrier on near-road air quality was evaluated using an integrated dispersion-deposition approach. A technique based on distance between source (road) and point of peak concentration before dwindling concentration downwind begins, referred to as ‘distance to maximum concentration, DMC’, has been developed and proposed to determine optimum position from source and thickness of vegetation barrier for improved dispersion and deposition-based benefit, respectively.
In the street-canyon configuration, impacts of different tree-configuration (such as aspect ratios of trees, leaf area index tree-planting pattern and trunk height), wind condition and street canyon’s aspect ratio on in-canyon air quality and thermal comfort were studied. Finally, a synthesis on the implementation of street tree-planting for both thermal comfort and air quality benefit was presented.