Deep coastal sediments of the Persian Gulf: a potential sink for microplastic pollution

Microplastic (MP) pollution represents a serious hazard to marine ecosystems. The present study investigated the distribution, abundance, and properties of MPs in coastal sediments along Bandar-Abbas city (∼ 25 km) in the northern Persian Gulf. Samples were obtained from 24 sites at two depths (0 to ∼ 20 cm and ∼ 20 to ∼ 40 cm) to gather information about historical pollutions. MP concentrations were significantly higher in deep sediments (58.40 ± 27.87 particles/kg) than in surface sediments (41.58 ± 20.25 particles/kg) (p < 0.05) and were also higher at locations near wastewater outlets (128.66 ± 27.97 particles/kg) compared to more distant locations (90.44 ± 39.43 particles/kg) (p < 0.05). No significant differences (p < 0.05) were observed in MP concentrations between intertidal and supratidal zone samples, nor between industrial and urban areas. Fibers were the dominant MP type (> 88 % of the total), followed by fragments and films. The dominance of colored and large MPs (1000 ≤ L< 5000 µm) in deep sediments is indicative limited physical weathering at depth. Polyamide (PA) and polyethylene terephthalate (PET) were the most abundant polymer types identified. The results highlight the evolution of MP contamination in coastal area and accentuate the necessity of an effective plan to reduce its impact on marine ecosystems.