The dynamics of buoyant particles at the ocean surface: implications for fate and transport

Buoyant microplastics concentrate near the ocean surface, where their vertical distribution is controlled by particle buoyancy and vertical mixing. This distribution is relevant to multiple processes. For example, near-surface currents are strongly sheared, so horizontal transport couples to vertical position. In addition, solar irradiance decays with depth, thus microplastic vertical position controls photodegradation rates.  In order to predict the vertical distribution of microplastics, we need to better understand the interactions between the particle properties and flows characteristic of the near-surface ocean boundary layer.

In this talk, I will discuss how the physical properties of the microplastics, including size and shape, affect their vertical distribution. I will present results from both laboratory experiments under wind-driven waves and field measurements at the ocean surface, demonstrating how microplastics vertical distribution can vary as a function of particle size and shape.  Finally, I discuss the implications on the fate and transport of microplastics in the ocean.