<p>The investigation of pollutants dispersion and deposition in urban environments necessitates the careful consideration of turbulence and the arrangement of buildings, as these factors play pivotal roles. In this research paper, a Large-Eddy Simulation (LES) model coupled with a Discrete Phase Model (DPM) was employed to examine the transport and deposition of pollutant/particles that are released from various source types and locations, considering different boundary conditions. The first part focused on the dispersion of carbon dioxide pollutant (CO₂), which was treated as continuous phase emitted from rooftop located in a high velocity field. In the second part the hazardous gas was considered as dispersed phase. In this case focus was put on the source types moving/stationary. The computer-Aided Design (CAD) of 1:1 scaled model of Frankfurt city, Germany, is meticulously cleaned, followed by the generation of finely meshed grids. To incorporate realistic weather conditions, power low velocity profiles are introduced at the inlets, assuming neutral atmospheric conditions. The research findings unequivocally indicate that tall buildings exert a significant influence on both vertical and horizontal dispersion, resulting in a substantial increase of CO₂ concentration at ground level, up to 300%. For the dispersed phase the result show that the location of the source has a notable impact on vertical particle dispersion. Furthermore, the nature of the source, whether it is stationary or in motion, plays a crucial role in the deposition mechanism. Specifically, for moving sources, the deposition mechanism is significantly accelerated, showing an increase of approximately 50% compared to stationary sources.</p>