The aim of this thesis work is to simulate and investigate the dispersion of microplastics (MPs) in the atmosphere with the application of a Lagrangian particles numerical model. In particular, this study aims at examining the long-range transport of this emerging pollutant and for this reason the first chosen area of investigation is a remote region as the Tibetan Plateau. Another goal of this work is to study areas characterised by different topographical features and for this aim the Pacific Ocean is chosen as a second area of investigation. In both cases some reference articles that investigated these areas and found the presence of MPs in such places are studied and taken as starting point for my discussion.