Simulating the atmospheric dispersion of microplastics with a Lagrangian particles numerical model

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. Several simulations were carried out in the backward mode in order to study the possible origin of the pollutant under consideration, in the two mentioned zones. In the case of the Tibetan Plateau, it was possible to verify the atmospheric provenience of air masses both in the pre-monsoon period and monsoon period and to define in which case the long-range transport of pollutants was more likely to be the responsible of MPs presence, compared to the short-range transport. In the case of the Pacific Ocean, instead, it was noticed that, investigating the Oceanic area close to China and Japan, only the coastal zone was influenced by masses of air coming from the continent, while the areas of the ocean farther from the coast were found to be influenced by air masses coming from eastward and so travelling over the Ocean. Considering another reference article that assumed the Ocean as a possible source of MPs emission to the atmosphere, backward and forward simulations were performed to investigate the circulation of air masses above the Pacific Ocean and the possible transport of MPs inside them. Beside addressing the specific case studies, this study provides also the assessment, with related examples, of the potential of a Lagrangian particles numerical model in application to the investigation of MPs transport in the atmosphere and as regards different topographical areas of the planet. This, even if the obtained results can be at present mostly qualitative because of the emerging nature of the topic of the MPs atmospheric transport, given that still little is known and few data are available up to now.