Microplastic contamination in the sediments of Qarasu estuary in Gorgan Bay, south-east of Caspian Sea, Iran.

Given the important ecological role of estuaries and implications of microplastics (MPs) in ecosystems, we assessed the occurrence, abundance, size, and polymer types of MPs present in the sediments of the Qarasu estuary in 2019. MPs were extracted from sediments by density separation, after which they were detected under a stereomicroscope and considered according to shape, size and color. Identification was implemented using Fourier-Transform Infrared Spectroscopy (FT-IR). The abundance and size of MPs in the samples ranged between 40 and 460 particles/kg and 200-5000 μm, respectively. The dominant shape of MPs was fiber (72%), followed by fragment (26%) and film (2%). Black and white were the most abundant colors with 48% and 29%, respectively. In total, 4 MPs polymers including polypropylene (33%), polyethylene (24%), polyamide (21%), and polystyrene (14%) were identified. Results from PCA showed that stations with a high abundance of microplastics had a significant correlation with the amount of clay.

Gholizadeh M ，Cera A 《-》

Spatial distribution and risk assessments due to the microplastics pollution in sediments of Karnaphuli River Estuary, Bangladesh.

Microplastics (MPs) have become an emerging global pollutant due to their widespread dispersion and potential threats to marine ecosystems. However, studies on MPs in estuarine and coastal ecosystems of Bangladesh are very limited. Here, we conducted the first study on abundance, distribution, characteristics, and risk assessment of microplastics in the sediment of Karnaphuli River estuary, Bangladesh. Microplastic particles were extracted from sediments of 30 stations along the estuary by density separation and then enumerated and characterized using a stereomicroscope and Fourier Transform Infrared (FT-IR) spectroscopy. In the collected sediment of the Karnaphuli River estuary, the number of MPs varied from 22.29 to 59.5 items kg-1 of dry weight. The mean abundance was higher in the downstream and left banks of the estuary, whereas the predominant shape, colour, and size of MPs were films (35%), and white (19%), and 1-5 mm (30.38%), respectively. Major polymer types were polyethylene terephthalate, polystyrene, polyethylene, cellulose, and nylon. MPs were found to pose risks (low to high) in the sediment of the estuary, with the highest risk occurring at one station near a sewage outlet, according to the results of risk analyses using the pollution risk index, polymer risk index (H), contamination factors, and pollution load index (PLI). The single value index, PLI, clearly demonstrated that all sampling sites were considerably polluted with microplastics (PLI > 1). H values showed toxic polymers, even in lower proportions, possess higher polymeric hazard scores and vice versa. This investigation uncovered new insights on the status of MPs in the sediments of the Karnaphuli River estuary, laying the groundwork for future research and control of microplastic pollution and management.

Rakib MRJ ，Hossain MB ，Kumar R ，Ullah MA ，Al Nahian S ，Rima NN ，Choudhury TR ，Liba SI ，Yu J ，Khandaker MU ，Sulieman A ，Sayed MM ... -  《Scientific Reports》

Identification and distribution of microplastics in the sediments and surface waters of Anzali Wetland in the Southwest Caspian Sea, Northern Iran.

The occurrence, abundance and distribution of microplastics (MPs) were studied in sediments and surface waters of the Anzali coastal wetland, southwest of the Caspian Sea. Sediment and surface water samples were taken at 11 and 6 stations in June 2018 and January 2019 respectively. The abundances of MPs in sediment samples were 140-2820 and 113-3690 items/kg dry weight while in surface waters were 0.40-4.41 and 0.19-2.85 items/m3 in June and January respectively. Fiber was the most common shape, followed by fragment and film. Red, black and blue were the most frequent colors. Particles 1-2 mm were the dominant size. SEM/EDS and ATR-FTIR analyses were used to identify MPs. Polypropylene, polyethylene and polyester were the most frequently found polymers. Our results highlighted the widespread dispersion of MPs in Anzali Wetland which in turn might be a pathway of MPs pollution transporter to the adjacent and connected Caspian Sea.

Rasta M ，Sattari M ，Taleshi MS ，Namin JI ... -  《-》

Microplastic particles in sediments and waters, south of Caspian Sea: Frequency, distribution, characteristics, and chemical composition.

This study assesses the occurrence of microplastics (MPs) in coastal and sea surface sediments, as well as water samples, collected from the coastal region of the southern Caspian Sea, Mazandaran province, Iran. A total of 32 sediment and 10 water samples were studied. The mean concentration of MPs was 15 units kg-1 in the sediments and 710 units m-3 in the coastal water. Fibers constituted by far the dominant MPs in both media, accounting for 97% of the MPs in both sediment and water samples. The MPs were mainly black in color. The dominant size of MP particles in sediment samples was between 250 and 500 μm, while the fraction >1000 μm dominated in the water samples. Polyethylene terephthalate (PET), polystyrene (PS), and nylon (NYL) were the main polymers and/or copolymers composing MPs in both sediment and water samples. The MP particles had a relatively smooth surface morphology, although signs of weathering were observed. The number of MP particles in sediment and water samples showed a general decrease from west to east in the study area. This may be reflecting the spreading of MP loading from the outlets of Sefidrud, Tonekabon, Chalus, the major rivers entering the Caspian Sea just west of the study area, and the overall decrease in the spatial distribution of touristic and fishery activity. The main sources of MP particles could be local emissions from a large number of domestic wastewater effluents and urban surface runoff due to high population density, and industrial and fishing activities in this region. This study indicated that MP particles, based on their characteristics and chemical composition, are circulated between coastal waters, and shore and sea surface sediments of the Caspian Sea, leading to their uneven distribution in the different depths. To the best of our knowledge, this is the first work studying the distribution of MP particles in sea surface sediments and also the most comprehensive on MPs in shoreline sediments and coastal waters in the southern Caspian Sea.

Nematollahi MJ ，Moore F ，Keshavarzi B ，Vogt RD ，Nasrollahzadeh Saravi H ，Busquets R ... -  《-》

Microplastics distribution, abundance and composition in sediment, fishes and benthic organisms of the Gorgan Bay, Caspian sea.

Microplastic is releaseing to the aquatic environment worldwide, so they considered as a global issue and appeare to be widespread in all level of aquatic ecosystems and reveal serious threats to biota. Since they are often ingested by living organisms, the major concern is their transferring from lower trophic level to higher trophic level through the food chain. Due to the importance of Gorgan Bay as one of the ecologically important areas of the Caspian Sea and the need for fundamental information on the pollution status of this region, a study conducted for evaluation of microplastic pollution in sediments, fish and benthose, from 3 areas (north, central, south) through sampling from 21 stations. The range of microplastics (MPs) abundance in sediments was 80 ± 25 to 740 ± 105 n/kg. Fibers, Black MPs, and size of 1-2 mm (42.4%) were prevalence observed in sediment and living organisms. According to the FTIR results, among studied organisms, the most microplastic levels were found in the soft tissues of fish Neogobius melanostomus (39 MP/g) and mussel Cerastoderma lamarcki (19.8 MP/g) dry weight. The results of this study present the comprehensive information on MPs distribution and charecteristics in sediments, fish and mussel of Gorgan Bay which could help to run better management over this sensitive ecosystem and would be a start point for further research on MPs effect on organisms of the Caspian sea.

Bagheri T ，Gholizadeh M ，Abarghouei S ，Zakeri M ，Hedayati A ，Rabaniha M ，Aghaeimoghadam A ，Hafezieh M ... -  《-》