Numerical Modeling of Microplastics Fate and Transport in a Stretch of the Fraser River

Microplastics and their impact on the environment and human health have increasingly become a global issue. Rivers are the main sources of fresh-water for human activities, and the main route for pollution delivery to seas and oceans. Predicting the behavior of microplastics (i.e. plastic particles smaller than 5 mm) in river systems and identifying their accumulation zone is therefore important to understand their environmental impact, risk exposure assessment and mitigation/remediation planning. The presence of microplastics in the Fraser River has been previously shown in different studies through water sampling at different sites along the river. In an attempt to improve understanding of the fate and transport of microplastics within the Fraser River system, an innovative three-dimensional numerical model was used in this study to predict movement of these particles in a highly urbanized and industrialized 35 km stretch of the Fraser River. The modeling system used herein is based on coupling TELEMAC-3D hydrodynamic model with a three-dimensional Particle Tracking Model (PTM) which incorporates physical characteristic of microplastics in calculating their movement in the water. The hydrodynamic model has been calibrated using available data. The model results provide information on behavior and distribution of different types of microplastics within of the modeled stretch, and support identifying their sources and accumulation hotspots.