Particle transport under a wind-driven boundary layer

Microplastic pollution accumulates at the surface of the ocean in the surface boundary layer. Ocean surface dynamics, in particular wind-generated turbulence and waves, can influence how these particles disperse below the water surface. Typically, the vertical concentration of particles is modeled using a parameterized turbulent diffusivity profile and a particle rise velocity. These models often assume a constant rise velocity, despite literature showing that the rise velocity is affected by the turbulence and waves present in the flow around the particles. In addition, the turbulent Schmidt number is still uncertain in these flows, especially for buoyant particles. To test these models, we use both Lagrangian data (i.e., particle trajectories from large-scale shadow tracking) and Eulerian data (i.e., velocity fields from particle image velocimetry) to relate the vertical transport of particles to turbulent flow and particle characteristics. This will allow for better estimations of particle fate and transport in wind-driven flows like the ocean surface.