Speaker

Irina Rypina, Ph.D., Assoc. Scientist, Woods Hole Oceanographic Institution

Aggregation of slightly buoyant microplastics in 3D vortex flows

Abstract

Marine microplastic pollution is a rising concern for the ocean environmental and human health. The highest concentrations of microplastics are found at the ocean surface, but significant amounts are also observed at depth. What sets the 3D distribution of these suspended particles, and is it possible that they accumulate in certain regions of the oceanic circulation? Using a combination of theory, numerical simulations, and lab experiments, we explore the aggregation of small rigid spheres obeying the Maxey-Riley equations in an idealized model of a 3D eddy with an azimuthal and overturning circulation. Our results indicate the existence of multiple attractors, as well as regions of retention, and regions that get rapidly devoid of particles. Attractors consist of closed loops located near periodic orbits of fluid parcels. This work is intended to provide some basic insights into the mechanisms behind the subsurface aggregation of marine microplastics and inform future sampling strategies in the ocean.