Modeling Microplastic Dispersion in the Salado Estuary Using Computational Fluid Dynamics

Microplastics (MPs) have emerged as a major pollutant in aquatic ecosystems, primarily originating from industrial activities and plastic waste degradation. Understanding their transport dynamics is crucial for assessing environmental risks and developing mitigation strategies. This study employs Computational Fluid Dynamics (CFD) simulations to model the trajectory of MPs in section B of the Salado Estuary in the city of Guayaquil, Ecuador, using ANSYS FLUENT 2024 R2. The transient behavior of Polyethylene Terephthalate (PET) particles was analyzed using the Volume of Fluid (VOF) multiphase model, k-omega SST turbulence model, and Discrete Phase Model (DPM) under a continuous flow regime. Spherical PET particles (5 mm diameter, 1340 kg/m3 density) were used to establish a simplified baseline scenario. Two water velocities, 0.5 m/s and 1.25 m/s, were selected based on typical flow rates reported in similar estuarine systems. Density contour analysis facilitated the modeling of the air-water interface, while particle trajectory analysis revealed that at 0.5 m/s, particles traveled 18–22.5 m before sedimentation, whereas at 1.25 m/s, they traveled 50–60 m before reaching the bottom. These findings demonstrate that higher flow velocities enhance MP transport distances before deposition, emphasizing the role of hydrodynamics in microplastic dispersion. While limited to one particle type and idealized conditions, this study underscores the potential of CFD as a predictive tool for assessing MP behavior in aquatic environments, contributing to improved pollution control and remediation efforts.