Baseline assessment of microplastic in sediments of the Almendares River and Havana Harbour, Cuba.

Sediment samples were collected and analysed for microplastic concentrations and identification in the Almendares River, both upstream and at the river mouth, and in Havana Harbour. Microplastic particles (45 μm to 5 mm) isolated by density separation were identified using microFourier-Transform Infrared Spectroscopy (μFT-IR), and found concentrations ranging from 24 to 9989 items kg-1 d.w. This large variation could be due to proximity to local input sources, hydrodynamic conditions, river discharge, tidal transport and/or depositional environment. Principal component analyses indicated that while some samples displayed similar particle composition in terms of organic, mineral, petrogenic/pyrogenic residue and microplastics, the polymer of the composition of the microplastics could differ substantially. Overall, the most identified microplastic particle was the low-density polymer polyethylene (PE), followed by polypropylene (PP), polystyrene (PS) and polyvinyl chloride (PVC). PVC was not detected in sediment from upstream Almendares River. Local input sources may explain the variation in polymer composition in sediment from the river outlet compared to upstream, where sediment from the river mouth is influenced by particle input from both river transport and coastal activities. Concurrently, the high concentration of particles with petrogenic/pyrogenic in the harbour sediment may be explained by the close vicinity to an oil refinery. This baseline study presents a spatial snapshot of microplastic pollution in the Almendares River and Havana Harbour. Future studies should focus on temporal variations and implement comprehensive sample and sediment characteristics to better understand variations in input sources and depositional environment.