Macroplastic items in the ocean can move differently than the water surrounding them, because their size and density are different than that of water. We investigate how to implement this effect for macroplastic items in simulations in the North West European Shelf region. For this region we find that the large drag force makes the macroplastics trajectories very closely follow the water itself, meaning that simulating macroplastic is simpler than previously expected. 

This paper investigates the aggregation of small, spherical, slightly buoyant, rigid particles in a simple 3D vortex flow. Our goal was to gain insights into the behaviour of slightly buoyant marine microplastics in a flow that qualitatively resembles ocean eddies. Attractors are mapped out for the steady, axisymmetric; steady, asymmetric; and nonsteady, asymmetric vortices over a range of flow and particle parameters. Simple theoretical arguments are used to interpret the results.