Assessing the vertical synergies between outdoor thermal comfort and air quality in an urban street canyon based on field measurements

Abstract

Outdoor thermal comfort and air quality are two key aspects of urban environmental quality. Understanding the synergies between outdoor thermal comfort and air quality in urban street canyons is of great importance to human health and well-being. Therefore, outdoor thermal factors, PM2.5, SO2, CO, NO2, O3 concentrations were recorded, and the correlation between them was analyzed at pedestrian, middle, and roof levels in an urban street canyon. Physiological equivalent temperature (PET) at middle level was 1.3 °C higher than that at roof level, and higher than that at pedestrian level. O3 concentration showed a stronger synergistic relationship between PET than all other air pollutants. It increased as PET increase in an exponential equation at three height levels. SO2 and CO concentrations increased with thermal perception at pedestrian and roof levels, whereas they decreased and then increased with thermal perception at middle level. Moreover, NO2 increased with PET in a linear equation at pedestrian level, but decreased with PET at roof level. PM2.5 concentrations fit PET at pedestrian level better than that at either middle or roof level. Overall, this study provides an in-depth understanding of the synergistic relationship between air pollutants and thermal comfort, and contributes to strategies for improvement of outdoor air quality and thermal comfort.