Microplastics and mesoplastics in surface water, beach sediment, and crude salt from the northern Bay of Bengal, Bangladesh coast

Marine plastic debris is extensively documented as a worldwide ecological issue. This study elucidated the quantity and distribution of plastic items in surface water at Moheshkhali Channel, sandy beaches (Laboni beach and Crab beach), and salt beds at Moheshkhali Island from the Cox’s Bazar coast of the northern Bay of Bengal, Bangladesh in Asia. The mean concentrations of microplastics (< 5 mm) in surface water, beach sediments, and crude salt were recorded to be 0.021–0.023 items/m2, 41.00–140.60 items/m2, and 490–630 items/kg, respectively. However, the mean concentrations of mesoplastics (5–25 mm) in surface water, beach sediments, and crude salt were recorded to be 0.004–0.006 items/m2, 14.00–43.20 items/m2, and 5–9 items/kg, respectively. The abundance of plastics in surface water was higher in early summer than in winter. In the case of beach sediments and crude salt, plastics abundance was higher in late monsoon and early summer, respectively. Furthermore, numerous microplastics have been found in the crude salt of Cox’s Bazar coast, suggesting the possibility of ingesting such particles through food. Besides, six different types of plastics (fragment, film, fiber, foam, pellet, and microbead) were recorded, and positive correlations were found between mesoplastic and microplastic debris size classes. Fourier Transform Infrared spectroscopy was used to identify the plastic polymer types (> 300 μm items). Polyethylene (28–31%), polypropylene (25–28%), polystyrene (13–18%), and polyethylene terephthalate (12–15%) were the most common polymers in Cox’s Bazar Coast of the northern Bay of Bengal that may arise from coastal tourism activities and riverine inputs. Detailed and long-term investigations are necessary to comprehend, monitor, and avoid further plastic contamination in this coastal region.