Tracing Plastic Pathways: Laboratory Validation and Sensitivity Insights in Overland Transport Numerical Models

Plastic pollution is a significant environmental problem of high magnitude, with far-reaching impacts on terrestrial and marine ecosystems. Plastic has various pathways to reach the ocean, with the land-to-ocean route being a critical one. Across both terrestrial and marine environments, plastic pollution threatens biodiversity, disrupts food chains, and accumulates in remote regions. Despite its importance, the mechanisms governing this transition remain understudied, particularly in overland systems. In this study, experiments in the laboratory are used in conjunction with numerical modeling tools to study the hydrodynamics of plastic transport overland under ideal conditions. Laboratory experiments utilized a controlled flume setup that simulates overland flow and analyzes the movement of plastic bottles, considering variations in size, shape, orientation, and weight. Then, numerical simulations were conducted to recreate the laboratory experiments as a simplified finite-element flume domain using a loosely coupled hydrodynamic and particle tracking framework. The framework was then validated against experimental results that proved the model's capability to reproduce the observed transport patterns. After validation, simulations were extended to a real-life-scale idealized domain to investigate the sensitivity of plastic transport to various parameters through a sensitivity analysis. The main results show the dependency of plastic mobility on hydrodynamic forces and particle characteristics. This integrated approach gives insight into overland plastic transport and informs mitigation strategies for plastic pollution in terrestrial environments. Future work will extend these findings to real-world scenarios, evaluating the interplay of rainfall and coastal flooding in plastic mobilization, such as during compound flood events. Thus, this research lays the foundation for developing comprehensive models that enhance our understanding of plastic pollution dynamics and support efforts to protect terrestrial and aquatic ecosystems from the escalating impacts of plastic waste.