Investigation of Microplastic Pollution in Sediments of the Sefidrud River, Gilan Province

This study aimed to investigate the microplastic pollution in the sediments of the Sefidrud River. To achieve this goal, sediment samples were collected from five locations, including the river mouth, residential area, agricultural area, tourist area, and the wastewater inlet into the river. Three surface sediment samples and three deep sediment samples were collected from each station. The sediment samples were then analyzed to identify microplastics after separation using the Sediment-Microplastic Isolation (SMI) method and passed through a sieve. Stereomicroscopy was used to count microplastics' number, color, and size, while Raman spectroscopy and FESEM-EDS analysis were employed for polymer identification and elemental composition analysis. Among the 30 surface and deep sediment samples examined, 86 microplastic particles per 100 grams of dry sediment were identified. The wastewater station (27.90%) and the tourist area (24.41%) exhibited the highest microplastic pollution. Black color (37.20%), fiber shape (63.95%), and a size range of 0.5–1 millimeter (46.51%) were the most prevalent characteristics. Raman spectroscopy analysis of three random samples revealed that the polymer types were nylon, polyethylene, and polystyrene, while FESEM-EDS analysis showed that the microplastic particles had rough surfaces and contained elements such as iron, aluminum, and titanium in addition to the main plastic components like carbon and oxygen. These additional elements pose a significant threat to marine ecosystems. Given the concerning levels of pollution observed in the Sefidrud River, periodic monitoring of microplastics in water, sediments, and river organisms is essential. Furthermore, effective waste and wastewater management strategies are crucial, especially near river inlets. Above all, public awareness and education regarding microplastic pollution can play a significant role in its control.