Contamination of the Caspian Sea Southern coast sediments with microplastics: A marine environmental problem.

Marine ecosystem pollution with microplastics (MPs) is a global problem. The current study aimed to assess the occurrence of MPs in the sediments of the Caspian Sea southern coasts. For sampling, two distinct areas were selected including recreational-tourism areas (No = 24), and non-tourist areas (No = 24). MPs were studied in 5 and 5-15 cm from the top sediment surface. All 96 samples were taken and analyzed according to the methodology provided by the US national oceanic and atmospheric administration (NOAA). The combination of observational techniques, FTIR, and SEM analysis was applied to identify MPs. MPs were classified into two categories in terms of size: small MPs and large MPs. The average, maximum, and minimum abundance of MPs (based on dry weight) in sediments of the southern coast of the Caspian Sea was 183.5 ± 154.4 MP/kg, 542 MP/kg, and 13 MP/kg, respectively. On the basis of morphology, fragment-shaped (30.3%) MPs showed the highest prevalence, while film-shaped (18.7%) MPs were the least contributory. Polyethylene (PE) and polyethylene terephthalate (PET), each of them with a 20% share, were the most common MPs found in the studied samples. The distribution of MPs on the southern coasts of the Caspian Sea revealed a sporadic and irregular spatial pattern. Correspondingly, it can be concluded that probably environmental factors (the current of the sea surface water from west to east), enclosed environment of the Caspian Sea, anthropogenic activities (e.g., industrialization and urbanization, improper waste management, fishing, and tourism activity, residential wastewater), and also discharging of rivers (which can carry plastics) into the sea, have all influenced the abundance and polymer diversity of MPs in the sediments of the southern coast of the sea. More attention should be paid to the health and environmental effects of MPs and to the protection of this sensitive marine ecosystem through implementing proper waste management system by all surrounding littoral countries.

Ghayebzadeh M ，Aslani H ，Taghipour H ，Mousavi S ... -  《-》

Abundance and distribution of microplastics in the sediments of the estuary of seventeen rivers: Caspian southern coasts.

Given the increase in plastic production, persistence, and toxicity in the environment, understanding the probability of microplastics (MPs) accumulation in the sediments of the rivers' estuary is urgently needed. In this study, sediments of the estuary of 17 rivers, ending to the Caspian Sea, were evaluated at two depths (0-5 cm and 5-15 cm). Plastic particles were categorized into two groups in terms of size: small MPs and large MPs. The combination of observational techniques, FTIR, and SEM analysis was applied to identify MPs. The mean of MPs in 17 rivers was obtained at a depth of 0 to 15 cm of sediments 350.6 ± 232.6 MP/kg. The fiber was identified as the predominant particles in sediments, and foam-shaped particles were the least amount in the sediment. In terms of polymer structure, polyethylene (PE) (20%) and polyvinyl chloride (PVC) (2%) showed the highest and lowest prevalence, respectively. In the current study, the number of MPs was higher than the average of MPs in sediments of recreational-tourist areas and non-tourist areas of the southern Caspian coast. Results from this study indicate that sediments of the rivers' estuary are a hotspot of plastic particle pollution. Therefore, plastic management in the path of the Caspian catchment area of Iran, and cleaning rivers coast and rivers mouth from plastic is recommended.

Ghayebzadeh M ，Taghipour H ，Aslani H 《-》

Spatial distribution of microplastics in sandy beach and inshore-offshore sediments of the southern Caspian Sea.

The occurrence of microplastics (MPs) in nearshore zones of the southern Caspian coasts is well documented; however, no data are available on MP occurrence in offshore sediments. In this study, six sandy beach stations and 18 inshore-offshore stations (six transects) were surveyed. MPs were detected in all sediment samples. The mean abundances of MPs in the beach and inshore-offshore stations were 196.67 ± 11.58 and 103.15 ± 7.21 MPs/kg, respectively. Fibers constituted the most common shape of MPs. Polystyrene (PS) and polyethylene terephthalate (PET) were the major polymer types found in the beach and inshore-offshore sediments, respectively. In most transects, negative MP gradients were observed from nearshore to offshore, which showed that coastal fishing, tourism, and rivers were the main sources of MPs in this area. These results will improve our understanding on MPs pollution in the marine ecosystem. We recommend further MP studies in different parts of the Caspian Sea to develop appropriate management programs.

Manbohi A ，Mehdinia A ，Rahnama R ，Dehbandi R ，Hamzehpour A ... -  《-》

Identification of microplastics in the sediments of southern coasts of the Caspian Sea, north of Iran.

Microplastic (MPs) pollution in the aquatic and terrestrial environments has caught many attentions in the scientific literatures. Currently, no information is available about MPs pollution in Caspian Sea, the largest lake in the world. This study indicates the first report on the MPs pollution in the sediments of the southern Caspian coastal zones, northern Iran. Density separation method was conducted on 17 surficial sediments. The combination of observation techniques including SEM-EDS analysis, polarized light microscopy and Raman micro-spectroscopy were used to identify MPs. The abundance and size of microplastics in the samples ranged between 25 and 330 items/kg and 250-500 μm, respectively. Fibers constituted the most common MPs shape and polystyrene (PS) and polyethylene (PE) were major polymer types in the samples. The distribution of MPs in the study area reflected a patchy and irregular spatial pattern implying that the higher MPs concentration are near mouth of permanent rivers and in the regions with higher level of the fishing and tourism activities. The results showed the wide occurrence of MPs in the sediments of the world's largest lake which extend the knowledge on MPs pollution in the marine system. We also recommend further research on microplastics in different compartments of Caspian Sea to inform policy discussions and the development of appropriate management responses.

Mehdinia A ，Dehbandi R ，Hamzehpour A ，Rahnama R ... -  《-》

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 ... -  《-》