The Best of Both Worlds – Combining a Revised Global River Model to In-Situ River Plastic Transport Data

To tackle the accumulation of plastic in the open oceans and along the shorelines, it is necessary to identify and understand its input paths. With more than 4smaller coastal systems draining into the global oceans, this is a complex task. A global model representing a plethora of different systems is one way to approach this problem. For this purpose we improved the global river model presented in Meijer et al., 2021 which is using multiple datasets such as topography, land cover, runoff, precipitation, wind, population density, landfills, dams and mismanaged plastic waste per country to estimate the magnitude of the input of plastic into the oceans. This is achieved by a mouth-2-source algorithm that originates from each river mouth. How far the influence of a given network reaches inland is dependent on the discharge within it and is parametrized with an abstract, global parameter, γ. The value of the latter can be calibrated using an analysis of both Eulerian and Lagrangian in-situ river plastic transport data from different river systems worldwide. Our analysis highlights the importance of plastic transport experiments with high data-density. The model results put the global plastic input into the ocean close to 500 kt/yr and indicate that the influence of the numerous smaller coastal catchments needs to be taken into account  With this model we are further able to identify river systems that interesting for targeted action.