Evaluation of the mesoscale effect of photocatalytic pavements and vegetation on air quality

In the last decade, new strategies have been developed to reduce air pollution levels without changing emissions. In this work we analyze and compare the impact of two of them: the use of photocatalytic materials on the streets of cities, and the introduction of trees in the urban canyons. Differently than previous studies that focused mainly on the microscale, here we focus on the mesoscale. So, the scientific question that motivates the work is: what could be the effect on urban air quality of these strategies if they are applied not only in few streets, but over the entire city? The methodology adopted is based on numerical simulations carried on with the mesoscale model WRF, with the multilayer urban parameterization BEP-BEM. Since we do not want to study a specific city, but search for a general tendency, idealized simulations are performed over cities with different population density (e. g. different urban structure), with an approach similar to Martilli (2014). A short description of the model and the urban parameterization is presented in section 2. An essential information for this study is the deposition velocity over the photocatalytic materials, and over vegetation. The first is estimated in the framework of the European project LIFE MINOx-STREET, from a series of laboratory and real scale experiments (section 3). The second (section 4) is deduced from literature information. The set-up of the simulations is presented in section 5, and the results are presented and discussed in section 6. Section 7 is dedicated to conclusions.