The Gulf of Mexico (GoM), the world’s largest gulf, faces significant exposure to microplastic pollution due to the close link between river flux and the transport of microplastics from land to sea. As the primary receiving body of the Mississippi-Atchafalaya River System, the North America's largest river network, the northern GoM is a critical hotspot for microplastic accumulation. This pollution poses a serious threat to marine ecosystems, affecting aquatic life and water quality. Despite the gravity of this issue, comprehensive studies investigating the transport and fate of microplastics in the GoM remain scarce. In this study, we applied a Lagrangian particle-tracking model coupled with a high-resolution (1 km) 3D ocean model to examine the transport of microplastic particles released from major rivers in the northern GoM. The model results identified the area west of the Mississippi River Delta as a potential hotspot and accumulation zone for microplastics, with the size and location of these regions varying seasonally, influenced by currents, winds, and river discharges. Additionally, our model framework incorporates the influence of microplastic density and size on the transport of microplastics, as well as the effects of Stokes drift on the transport of buoyant microplastics. The results show that accounting for the density and size characteristics of microplastics alters the distribution of settled microplastics, while having minimal impact on non-settled microplastics. Furthermore, Stokes drift was found to have a minor effect on the spatial distribution of microplastics in the GoM.
 

microplastic