River plastic emissions to the world’s oceans

TLDR

Plastics in the marine environment have become a major concern because of their persistence at sea and adverse consequences to marine life and potentially human health. Implementing mitigation strategies requires an understanding and quantification of marine plastic sources, taking spatial and temporal variability into account. The authors developed a global river‑to‑ocean plastic input model calibrated against literature measurements, using waste management, population density, and hydrological data. The model estimates 1.15–2.41 million tonnes of plastic enter oceans annually from rivers, with 74 % released between May and October, 67 % of the total from the top 20 rivers—mostly in Asia—providing baseline data for mass‑balance exercises and guiding monitoring and mitigation priorities.

Abstract

Abstract Plastics in the marine environment have become a major concern because of their persistence at sea, and adverse consequences to marine life and potentially human health. Implementing mitigation strategies requires an understanding and quantification of marine plastic sources, taking spatial and temporal variability into account. Here we present a global model of plastic inputs from rivers into oceans based on waste management, population density and hydrological information. Our model is calibrated against measurements available in the literature. We estimate that between 1.15 and 2.41 million tonnes of plastic waste currently enters the ocean every year from rivers, with over 74% of emissions occurring between May and October. The top 20 polluting rivers, mostly located in Asia, account for 67% of the global total. The findings of this study provide baseline data for ocean plastic mass balance exercises, and assist in prioritizing future plastic debris monitoring and mitigation strategies.