The study, published in the journal *Marine Pollution Bulletin*, assessed synthetic particles ranging from 45 micrometers to five millimeters using density separation and infrared spectroscopy.

Specialists detected concentrations ranging from 24 to 9,989 particles per kilogram of dry sediment, the scientific institution reported to Prensa Latina.

This variation is attributed to the proximity of local discharge sources, the hydrodynamic dynamics of the river flow, and the conditions of the depositional environment, according to the study.

Polyethylene (PE) was the most common polymer, accounting for approximately one-fifth of the detected anthropogenic materials, followed by polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC).

The analyses revealed different patterns: lightweight polymers such as PE and PP—linked to urban consumption—predominate in the upper and middle reaches of the Almendares, whereas PVC and petrogenic residues associated with industrial and port activities appear at the river mouth and in the bay’s marine zone.

The results highlight the role of urban rivers as transport pathways and repositories for mismanaged plastic waste, which impacts coastal marine ecosystems.

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