Demonstration of MicroPlastics Distribution Map in the Sediment and Water of Gorgan Bay, Caspian Sea

Gorgan Bay is located along the southeast Caspian Sea and surrounded with significant agricultural and urban areas. Plastic pollution is a significant issue that affects aquatic ecosystems globally. The accumulation and degradation of plastics into microplastics in aquatic ecosystems highlight the importance of studying them to assess pollution risks. So, an investigation was conducted for the assessment of MicroPlastics pollution (MPs) in water and sediment of this ecosystem. The study involved collecting water and sediment samples from 40 stations within the Bay. Microplastics (MPs) extracted from these samples were identified using microscopic detection methods, specifically visual observation under polarized light to SEM–EDX, and µ-Raman. A total of 16,360 MP particles per kilogram of sediment, and 211 particles per liter of water were detected. The research demonstrated that the river inlets situated within agriculturally intensive regions of the watershed exhibited the highest levels of microplastics (MPs) in both water and sediment samples. Fiber MPs were the most frequent (> 50%) shape in sediment and water. The size of mostly MPs (> 90%) was smaller than 1,000 µm. The dominant polymer within MPs in Gorgan Bay sediment identified as polypropylene (PP), polyethylene (PE), and polystyrene (PS), while polypropylene (PP) and polyethylene (PE) were the frequent polymer in water, respectively. The most amount of MPs was found in the areas close to the rivers and agricultural fields (including stations S4, S12, S13, S14, S22).