Modeling the Trajectory of Microplastics in the Estuary of Hau River Using the Open-Source OpenDrift Model†

The Mekong River estuaries in Vietnam are significant contributors to global plastic waste emissions entering the ocean, yet research on plastic debris impacts in the East Sea is limited. Specifically, studies on microplastics (MPs) transport affected by the complex hydrodynamic conditions in the Mekong estuary are scarce. The study aims to understand the movement of MPs from the Hau estuaries (a branch of the Mekong River) to the East Sea during the Northeast and Southwest Monsoons (January 2024 and July 2023, respectively). Using the OpenDrift trajectory model with the DNORA dynamic downscaling tool, findings reveal that the monsoon climate significantly influences MP transport. Wave action primarily affects MPs dispersion near estuaries and coastal zones, while current dynamics are key to MP movement to the East Sea. A one-month simulation indicates that MPs accumulate in various locations, including the Ca Mau coast, Hon Khoai Island, Phu Quy Island, Do Lon Island, and the Truong Sa Archipelago, with notable concentrations along the Malaysian coast. Additionally, neighboring countries like Thailand and the Philippines face a substantial risk of MPs pollution from the Hau estuaries. © 2025 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.