Microplastics in marine sediments from Burgas Bay, Black Sea: Abundance, polymer composition, and comparison of sodium chloride and magnesium chloride density separation methods using μFTIR imaging

Microplastics are increasingly detected in marine sediments, where they can accumulate over time.The aim of this study was to determine the abundance and polymer composition of microplastics in sediments from Burgas Bay, western Black Sea.Sediment samples were collected from six stations across three coastal areas with differing anthropogenic influence: Burgas Beach, Chengene Skele, and St. Anastasia Island.Microplastics were extracted using density separation with two flotation solutions (NaCl and MgCl 2 ), followed by filtration and FTIR imaging spectroscopy.Particle abundances ranged from 0.0 to 5497.8 MPs kg dry sediment depending on the station and extraction solution.MgCl 2 generally yielded higher particle counts than NaCl, although higher values were observed with NaCl at some stations, indicating that extraction efficiency may depend on particle density and sediment characteristics.Nine polymer types were identified, with polyamide (48.6%), polypropylene, polyethylene, and ethylene vinyl alcohol being the most frequent.These findings provide detailed quantification and polymer characterization of microplastics in Burgas Bay sediments, extending previous regional observations and offering targeted data for future monitoring and comparative studies in the Black Sea region.