Fingerprinting and modelling of the Toconao pellet spill in the Iberian Atlantic

On December 8th, 2023, the cargo ship Toconao lost 6 containers, one of them carrying 1050 sacks, each containing 1.25 million plastic pellets, in Portuguese waters approximately 80 km off the coast of Viana do Castelo, in the Northwest Iberian Peninsula. Shortly after, pellets, broken and intact sacks were found on the Galician coast, triggering an environmental crisis that mobilized scientific advisory mechanisms to support crisis managers. This study combines chemical and morphological characterization with Lagrangian modelling to investigate the chemical fingerprint, physical transport and beaching of the spilled pellets. Spectral features of the attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) analysis agrees with previous studies indicating that the pellets are polyethylene-based masterbatch with a high additive content. The Toconao pellets exhibit irregular "top-hat" shapes and smaller sizes (2-3 mm). Particle transport was simulated with the TrackMPD and OpenDrift frameworks, considering the effect of ocean currents and windage. Results indicate that ∼40% of the considered virtual particles reached the Galician coast within three weeks after the incident, while ∼90% beached within five months, extending to the Bay of Biscay reaching the coasts of Western France. The integration of chemical and morphological fingerprints, and modelling, highlights the transport pathways and their potential long-term environmental effects.