| Abstract | This study explores the sensitivity of microplastic behavior and accumulation zones in riverine environments under varying hydrodynamic conditions through a case study of a 160 km stretch of the Ottawa River, Canada. Using a coupled hydrodynamic model and high-performance particle transport modelling, the work investigates how changes in the river hydrodynamic conditions influence the transport and distribution of microplastics. Twelve simulations were conducted under different flow and water level conditions, testing both neutrally buoyant and sinking particles. Results identified fifty-two possible accumulation zones, but no single location was consistent across all scenarios, highlighting the strong dependence of accumulation patterns on hydrodynamics and particle characteristics. However, seven accumulation zones were found to be consistent in at least 50% of simulations, indicating a greater likelihood of long-term retention. Findings reveal that neutrally buoyant particles predominantly accumulated in bays and low-velocity recirculation zones, while sinking particles settled along shorelines and at the riverbed, particularly in deeper sections where velocities remain low. This study underscores the need for multiple hydrodynamic scenarios when assessing microplastic hotspots, as single-scenario studies may overlook critical accumulation areas. Future work includes field validation of predicted accumulation sites and cloud-based integration of the CaMPSim-3D model for enhanced simulation accessibility and computational efficiency. |
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