3D Lagrangian model to track fate and transport of plastic particles in the northern Adriatic Sea with a particular focus on physical and biogeochemical processes.

Plastics are a ubiquitous, global scarcely mapped pollutant that poses a particular threat to the marine ecosystem. Once they enter the oceans through sources such as estuaries and wastewater treatment plants, they are subjected to various environmental conditions that transport, fragment and scatter them, while altering their properties and exposing marine biota. These phenomena particularly threaten areas such as semi-enclosed basins where recirculation is limited. This is the case of the Adriatic Sea, a semi-enclosed basin with complex management challenges and strongly affected by marine plastic pollution due to significant anthropogenic pressure from intensive coastal activities, urbanization, and river inflows draining industrial northern Italy. In this study, we perform an analysis in this domain using a 3D Lagrangian-plastic model forced with physical and biogeochemical fields to simulate the direct transport of the plastic particles. We represent their interaction with biotic components, their transformations, alterations and the consequent changes in buoyancy. This approach allows us to investigate the particle’s presence, dynamics and role in the ecosystem, to identify potential accumulation areas, produce hazard maps highlighting the most vulnerable regions and quantify the individual contributions of each source.