Modeling the three-dimensional transport and distribution of multiple microplastic polymer types in Lake Erie.

We model three-dimensional motion of plastic pollution in Lake Erie due to advection, density-driven sinking, and turbulent mixing using a Lagrangian transport model to explore the distribution of plastic in the water column and sediment. Nine polymer types that make up over 75% of predicted worldwide plastic waste were modeled, and the model keeps track of particles that hit the bottom to represent deposition. Modeled spatial distributions are compared with samples from the surface to calibrate the model and derive estimates for the mass of plastic in the lake volume and the flux of plastic into the sediment. The mass estimate of 381 ± 204 metric tons is two orders of magnitude larger than previous surface estimates, though still a fraction of predicted yearly input. The results are a step towards closing the plastic mass balance in Lake Erie as well as understanding the transport of plastic into the sediment.