City-scale model to assess rooftops performance on air pollution mitigation; validation for Tehran

Cities have a significant role in the current climate change and air pollution crisis; hence, it is urgent to mitigate the negative effects of pollution in urban settlements. This situation requires developing agile plans to simultaneously investigate the efficiency of green infrastructures and feedback from their targets. A crucial consideration for these plans is the potential rooftops have - broadly abundant and underused in urban areas - to harbour sustainable, effective, and viable alternatives. This study aims to develop a new model to optimize the utilization of feasible pollutant reducers, investigate the ability rooftops present to reduce air pollution and recommend the most suitable city-scale solutions. The proposed model combines mathematical patterns, GIS, and sensitivity analysis. This systematic and adaptable approach was first applied to heavily air-polluted Tehran city, which has vastly unused rooftops. This leading application identified: i) two appropriate pollutant reducing alternatives - photovoltaic and green roofs -; ii) optimized total performance alternative when simultaneous mitigation of PM and CO2 is required - compound alternative -; iii) three significant indicators for target building groups - land use, building height, and surface scale -; and iv) the most suitable group - residential medium height in medium surface scale buildings. Applying a compound alternative with a 3:1 ratio (photovoltaic:green roof) to all potential target buildings enables a 9% decrease in the total city level for PM and CO2 emissions.