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Investigating the long-range dispersion of atmospheric microplastics in the free atmosphere with a numerical model
Summary
Using a computer simulation model called MILORD, researchers traced the long-range atmospheric transport of microplastics to two locations in Europe — above Madrid and at a high-altitude mountain site in the French Pyrenees. The simulations revealed that microplastics detected in the free atmosphere above cities mostly originated from distant sources rather than local emissions, and that ocean spray is a significant contributor to airborne microplastics. This work confirms that plastic particles can travel hundreds or thousands of kilometers through the air, depositing in even remote mountain and ocean environments.
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. • Long-range transport has the main role for microplastic pollution in free atmosphere. • Microplastics from urban sites enter the free atmosphere mostly far from the release. • The sea is confirmed to be a potential source of microplastics in the atmosphere.