A novel approach to include vegetation in air dispersion modeling

Air pollution is a significant problem for the environment and human health, especially in densely populated urban areas where air pollutant levels are often high. Nowadays, finding effective solutions to mitigate pollution is a priority. Urban vegetation is proposed among the solutions to improve air quality by capturing and absorbing air pollutants. However, urban vegetation can also contribute to increase air pollution levels. Trees can alter airflow, reduce ventilation, and increase pollutant concentrations in specific areas. Additionally, trees emit biogenic volatile organic compounds (BVOC), which, when combined with nitrogen oxides, contribute to tropospheric ozone (O3) formation. Therefore, careful planning and assessment of air pollutant sources are essential before introducing trees into urban areas. However, commonly used air dispersion models at urban and neighborhood scales do not directly account for the effects of vegetation. This thesis aims to address this limitation by integrating vegetation effects into an operational air dispersion model. Specifically, the aerodynamic effect of vegetation is incorporated with the surface roughness according to the morphometric method. Additionally, a novel approach is adopted to include BVOC emissions. This approach is implemented in the ADMS-Urban model to simulate air pollutant concentrations in a neighborhood of Bologna, subject of an intensive experimental campaign conducted during the summer of 2023 as part of the H2020 project "I-CHANGE". The obtained results indicate that the inclusion of vegetation emissions has a notable impact on air pollution concentrations, specifically on O3 level, particularly in areas with high vegetation density. In these areas, the model's improvement resulting from vegetation emissions is significant, as it is comparable to integrating the aerodynamic effects of buildings within the urban area.