Investigating the long-range dispersion of atmospheric microplastics in the free atmosphere with a numerical model

In recent studies available in literature, long-range transport was suggested to play a main role in the motion of microplastics in the free atmosphere, whereas emission sources are located in the planetary boundary layer. In this framework, the Lagrangian particle dispersion model MILORD was used both in forward and in backward modes to investigate the potential effectiveness of the transport and exchange of microplastics between the boundary layer and the free atmosphere. Two pioneering case studies from the literature were considered. The first where microplastics were detected in the free atmosphere above Madrid region, the second where microplastics were collected in the air at the top-mountain site of Pic Du Midi in the French Pyrenees. The simulations showed that the long-range transport plays the main role in determining the presence of microplastics in the free atmosphere above Madrid, while the emissions from the city affect mostly the air in the boundary layer, at regional scale in the surrounding area. The long-range transport towards Pic Du Midi site pointed out also potential contributions connected to the exchange between the marine environments and the atmosphere and to possible dust events from North Africa.