Modeling and comparison of plastic nurdle drift from the MV X-Press Pearl wreck: Estimating the extent of mangroves and corals affected and peak arrival in Gampaha, Sri Lanka.

A regional trajectory model was developed to simulate and validate the drift patterns of nurdles released on May 25, 2021, following an explosion aboard the Merchant Vessel X-Press Pearl, which caused a significant environmental disaster off the coast of Sri Lanka. This study utilized a Lagrangian oil spill trajectory model driven by Global Forecast System (GFS) winds and INCOIS Hybrid Coordinate Ocean Model (HYCOM) ocean currents to simulate nurdle transport from May 25 to July 7, 2021. Sensitivity analysis was conducted to evaluate the effects of varying windages on drift simulations, with the model achieving optimal accuracy at 0 % windage. The resulting simulations closely matched observed nurdle distributions across multiple observation dates and locations, validated through reduced root mean square error (RMSE). The refined model was further used to estimate the impact on mangroves and coral ecosystems along Sri Lanka's west coast. Kernel Density Estimation (KDE) identified zones of peak nurdle accumulation, offering a robust statistical approach to enhance spatial prediction. Both simulations and field observations indicated that areas north of Sarakkuwa Beach, extending toward Negombo Lagoon, were among the most severely affected by the nurdles spill. This research highlights the significance of trajectory modeling in disaster response, offering a scientific basis for mitigation planning and ecosystem protection.