Every year approximately 8 million tons of plastic find their way to the ocean with 367 million tons of plastic being produced in 2020 alone. Tens of millions of tonnes of plastics flow down rivers to the oceans each year, with 90% originating from 2 rivers in Africa and 8 in Asia. While some plastic waste floats, tiny particles, known as microplastics, can settle through the water column ending up in sediments in estuaries and in the coastal ocean where they may be taken up by and accumulate in marine life. Besides being deleterious to marine life, microplastics taken up by fish and bivalves can be then be consumed by humans, posing a long-term physical and chemical hazard.

While there has been significant research into the impact of plastic waste on aquatic ecosystems, less is known about the pathways through which microplastics are carried within estuaries to the coastal ocean and beyond. Of the estimated 8 million tonnes of plastic pollution that enters coastal waters each year, less than 0.3 million tonnes is associated with floating debris. The fate of the vast majority of plastic waste is unknown. Due to biofouling or degradation by visible and ultraviolet light, floating waste ultimately settles, though this process can take months, years or even centuries. Even after settling, particles may be re-suspended again by currents, waves and turbulence. This growing environmental problem has recently drawn a broad range of scientist into the field. Clearly, now is the time to take advantage of the growing observational databases to develop a combination of mathematics guided by experiments, observations and simulations to advance the predictive understanding of microplastics transport, deposition and resuspension processes.

The colloquium will bring together mathematicians, engineers, geoscientists, plastic pollution experts and physical oceanographers examining the fluid mechanic problem of predicting the transport, dispersion, deposition and resuspension of microplastics in lakes, rivers and the coastal oceans. This relies on a multidisciplinary approach utilizing mathematical methods in conjunction with laboratory experiments, numerical simulations, in situ observations and statistical analyses to predict how these pollutants disperse and where microplastics might accumulate. An important mission of the colloquium is to foster new collaborations between researchers with these diverse backgrounds.