Mass estimates of plastic pollution based on open water surface samples differ by several orders of magnitude from what is predicted based on production and input rates to the world’s oceans and the Great Lakes. Researchers have proposed that this missing plastic may be located in other reservoirs, including beaches, nearshore water, the water column, or sediment. Studying plastic via sampling efforts is logistically challenging and time consuming. Models, which provide full spatial and temporal distributions, can help fill in the knowledge gaps that sampling efforts leave. Here we present the first three-dimensional modeling effort in the Great Lakes to incorporate vertical diffusion, non-neutrally buoyant particles, a functional biofouling model, and a beaching model. We focus on including mechanisms that could account for removal of plastic from open surface water. Our work suggests that plastic may be accumulating along beaches, with accumulation patterns depending on beach characteristics, current patterns, and near shore population. Additionally, we predict that plastic is accumulating in lake sediment, with the rate of deposition dependent on polymer density, lake depth, and the effects of biofouling. We estimate that there may be 381 tons of plastic in the water of Lake Erie, with the potential for another 2205-2382 tons deposited in the sediment each year in Lake Erie, and 1265-1348 tons per year deposited in Lake Ontario sediments. This work improves existing mass estimates in the water column and sediment deposition rates in Lake Erie and provides a first sediment deposition estimate for Lake Ontario. Together, the results indicate that plastic pollution is likely remaining within the Great Lakes system rather than exporting to the ocean.
Mathematical Modeling (Ph.D)
Department, Program, or Center
School of Mathematical Sciences (COS)
Daily, Juliette, "Mathematically Modeling Plastic Pollution in the Great Lakes" (2021). Thesis. Rochester Institute of Technology. Accessed from
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