Plastic Pollution Dynamics in Albufera Lagoon: Assessing the Impact of an Extreme Flood Event

This study assessed the spatial distribution, temporal dynamics, and morphological characteristics of macroplastic (MAP), mesoplastic (MEP), and microplastic (MP) fractions in Albufera Lagoon, a protected Mediterranean lagoon, following the October 2024 flash flood event. Stratified sediment cores were separated into an operationally defined flood deposit (Layer A) and the underlying sediment matrix (Layer B), while two shoreline campaigns evaluated post-event conditions in February 2025 and conditions after manual cleanups in May 2026. Lagoon sediments showed mean MP concentrations of 1.77 to 4.52 MP/g in Layer A and 2.67 to 7.29 MP/g in Layer B; fibers dominated the matrix, and PET and polyamides were the main identified polymers. The northwest sector showed elevated MP concentrations potentially consistent with proximity to direct inputs, whereas the central sector exhibited the highest mean concentration in Layer B, which may represent a zone of hydrodynamic convergence. Along the shoreline, MAP densities reached 12.38 MAP/m2 and MEP concentrations 0.26 MEP/g in 2025. Although visible debris was lower in 2026 after manual cleanups, the emergent vegetation persistently retained plastics, potentially promoting fragmentation into secondary MP. These results suggest that shoreline cleaning alone may not completely remove the finer fractions retained in sediments. Future research integrating coupled hydrodynamic and particle-tracking models is required to delineate transport pathways from upstream sources.