To date, the largest Russian rivers discharging to the Arctic Ocean remain a “blank spot” on the world map of data on the distribution of microplastics in freshwater systems. This study characterizes the abundance and morphology of microplastics in surface water of the Ob River and its large tributary, the Tom River, in western Siberia. The average number of particles for the two rivers ranged from 44.2 to 51.2 items per m³ or from 79.4 to 87.5 μg per m³ in the Tom River and in the Ob River, respectively. Of the recovered microplastics, 93.5% were less than 1 mm in their largest dimension, the largest group (45.5% of total counts) consisted of particles with sizes range 0.30–1.00 mm. Generally, microfragments of irregular shape were the most abundant among the Ob and Tom samples (47.4%) and exceeded microfibers (22.1%), microfilms (20.8%), and microspheres (9.74%) by average counts. Results from this study provide a baseline for understanding the scale of the transport of microplastics by the Ob River system into the Arctic Ocean and add to currently available data on microplastics abundance and diversity in freshwater systems of differing global geographic locations.

This study is a pioneering attempt to count microplastics (MPs) in the Yenisei River system to clarify the role of Siberian Rivers in the transport of MPs to the Arctic Ocean. The average MPs content in the surface water of the Yenisei large tributary, the Nizhnyaya Tunguska River, varied from 1.20 ± 0.70 to 4.53 ± 2.04 items/m³, tending to increase along the watercourse (p < 0.05). Concentrations of MPs in bottom sediments of the two rivers were 235 ± 83.0 to 543 ± 94.1 with no tendency of downstream increasing. Linear association (r = 0.952) between average organic matter content and average counts of MPs in bottom sediments occurred. Presumably MPs originated from the daily activities of the in-situ population. Further spatial-temporal studies are needed to estimate the riverine MPs fluxes into the Eurasian Arctic seas.

The low production costs and useful properties of synthetic polymers have led to their ubiquitous use, from food packaging and household products to high-tech applications in medicine and electronics. Incomplete recycling of plastic materials results in an accumulation of plastic waste, which slowly degrades to produce tiny plastic particles, commonly known as “microplastics” (MPs). MPs can enter water bodies, but only recently the problem of MP pollution of sea and fresh waters has become clearly evident and received considerable attention. This paper critically reviews the accumulated data about the distribution of MPs in the freshwater ecosystems of Russia. The available data on MP abundance in the lakes and river systems of the Russian Federation are analyzed (including the large Lakes Baikal, Ladoga, Onego, Imandra and Teletskoe, and the Volga, Northern Dvina, Ob, and Yenisei Rivers within their tributaries) and compared with the data on freshwater MP contents in other countries. In Russia, the main sources of MP pollution for rivers and lakes are domestic wastewater, containing microfibers of synthetic textiles, fishing tackle, and plastic waste left on shores. Among the MPs detected in the surface waters and bottom sediments, polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET) particles predominate. The most common types of MPs in the surface freshwaters are fibers and fragments, with fibers prevailing in the bottom sediments. The reported average MP concentrations in the waters range from 0.007 items/m³ at the mouth of the Northern Dvina River to 11,000 items/m³ in the Altai lakes. However, the estimates obtained in different studies must be compared with great precaution because of significant differences in the methods used for MP quantification. The approaches to further improve the relevance of research into MP pollution of fresh waters are suggested.

The objective of the study was a pre-screening of the microplastic (MP) content in surface water and benthic sediments of Kara Darya and Chirchiq rivers, the first-order tributaries of the Syr Darya River (Uzbekistan). For the first time, surface water and benthic sediment samples were taken from this region, and quantitative screening of MPs 0.15–5.00 mm in size was performed. A combined visual and μRaman-based methodology was used to quantify and characterize artificial polymer microparticles from the surface water and bottom sediments of two rivers. The average abundance of MPs in the Kara Darya River and Chirchiq River waters was found to be 4.28 ± 0.09 and 0.95 ± 0.36 items per m³, and that in benthic sediments attained 244 ± 28.9 and 333 ± 11.5 items per kg of dry soil, respectively. MP concentration in surface water and benthic sediments of the Kara Darya River significantly exceeded (p-value < 0.01) that in the Chirchiq River. Microfibers were most abundant; the proportion of MP fibers in the water of the Kara Darya and Chirchiq rivers amounted to 89 and 95%, respectively, and that in benthic sediments of the rivers was 86 and 84%, respectively. The dominance of microfibers may indicate the route of entry to the rivers through domestic wastewater treatment plant discharges. The polymer microparticles in the surface water and benthic sediments of the Kara Darya and Chirchiq rivers were mainly represented by polyethylenterephtalate (PET), which accounted for half of all MPs detected in the Kara Darya River. Microparticles of textile origin were particularly abundant in the Kara Darya River, where viscose and nylon fibers were also found, which suggests the leading role of synthetic textiles in the pollution. The reported data are the first experimental evidence of MP pollution of the Syr Darya tributaries, but the distribution and circulation of MPs in surface water in Central Asia requires further comprehensive studies.

This preliminary study investigated the abundance of microplastic particles in gastrointestinal tracts of the dace (Leuciscus leuciscus L.) from the Tom River, a large tributary of the Ob River in West Siberia. A total of 13 dace specimens of 2+ to 4+ years of age were studied. Microplastic particles extracted from fish guts were counted and classified by shapes and sizes. In average 204 ± 28.7 items of microplastics were detected for one dace specimen. Microplastic particles were categorized as fragments of irregular shape (70%), spheres (16%), films (7%) and fibers (7%), with size ranging from <0.15 to 2.00 mm. The vast majority of detected microplastic particles (almost 80%) were less than 0.15 mm by their largest dimension. These data provide the first evidence of microplastics in fish from the Ob River system.

Microplastic particles in the size range 0.15 to 5.00 mm were quantified and characterised in the gastrointestinal tracts of three wild freshwater fish (n = 141) from the Ob and Yenisei rivers, including common ruffe (Gymnocephalus cernua L.), Siberian dace (Leuciscus baicalensis Dybowski) and European perch (Perca fluviatilis L.). Microplastics were found in the gastrointestinal tract of 62% of the fish examined, ranging from 18.5% in the Yenisei perch sample to 92.6% in the Ob ruffe sample. The vast majority of microplastics in all fish species were fibres (up to 99.7% of all particles detected in perch), followed by irregularly shaped fragments (up to 22.7% in ruffe), with no preference between the three species. Spheres and films were found exclusively in dace and ruffe, with proportions of 3.7% and 1.2% respectively. Particles consisted of polyethylene terephthalate, polypropylene, polyamide and other synthetic polymers with a significant proportion of highly degraded polymers. The mean MP content in fish GITs ranged from 0.44 ± 0.25 items per individual in Yenisei perch to 3.81 ± 0.55 items per individual in Ob ruffe. Particle burdens in fish were significantly higher in the Ob than in the Yenisei (p < 0.05), which may reflect the common level of plastic contamination in these two rivers. MP ingestion varied in species with different feeding habits as ruffe (benthivorous) > dace (omnivorous) > perch (hunter) in both rivers (p < 0.01). This study was the first to quantify MP consumption by freshwater fish of different species in the Ob and Yenisei rivers and to identify patterns associated with different feeding habits.