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The density of plastic accumulation in the northern hemisphere, especially near large cities, is very high: every year from 5 to 13 million tons of plastic garbage enters the marine environment from land, of which almost 2 million tons are garbage, the sources of which are shipping, fish farming and fishing. Russian scientists have examined the arrival of plastic garbage along one of the main ways of its transportation: through the largest rivers of the European North — the Northern Dvina and Onega. These are the only Arctic rivers flowing through settlements in their lower reaches, so they can be significant sources of plastic garbage for the White Sea and further the Arctic Ocean.

The results of the study are published in one of the international scientific journals (Journal of Marine Science and Engineering). The work was carried out with the support of the Ministry of Science and Higher Education of the Russian Federation, the Russian Science Foundation and the Russian Foundation for Basic Research on research Projects.

For the first time, scientists of the Moscow Institute of Physics and Technology (MIPT) and the P.P. Shirshov Institute of Oceanology of the Russian Academy of Sciences and colleagues under the jurisdiction of the Ministry of Education and Science of Russia assessed the arrival of floating debris from the rivers of the Northern Dvina and Onega into the White Sea from May to November 2021.

The results of observations during this period showed that 77% of objects in the rivers were of natural origin: mainly leaves, wood and bird feathers. The average monthly intake of anthropogenic macromusor into the White Sea from the Northern Dvina ranged from 250 to 1700 pieces/hour, with Onega — from 520 to 2350 pieces/ hour.

"Our study was conducted using the MSFD river debris monitoring methodology. From May 5 to November 5, we observed and registered in a special application each floating object according to pre-prescribed parameters. Everything was recorded according to the international list of monitoring objects, which includes 42 items.

Since such studies of rivers have not been conducted before and this is a fairly new type of pollution, we do not have statistics and dynamics of pollution and cannot assess whether the situation was worse or better before. To create a model of the removal of all plastic by rivers into the ocean or a model of the accumulation of this plastic in the ocean, long—term observations are needed," said Maria Mikusheva, a research participant, a graduate student at MIPT.

The objects found were divided into seven types: non-garbage (that is, garbage of natural origin), processed wood, artificial polymers, paper/cardboard, metal, rubber, clothing/textiles. In addition, the garbage was divided into size ranges: 2.5–5 cm; 5-10 cm; 10-20 cm; 20-30 cm; 30-50 cm; >50 cm. The flow itself was calculated in units per hour, and statistical analysis based on the Spearman and Kendall rank correlation was used to assess the correlation between the size of objects and the frequency of occurrence.

Particles of anthropogenic origin were represented by artificial polymers (59.6%), wood (27.7%), paper/cardboard (8.5%), metal (2.7%), rubber (1.1%) and textiles (<1%).

Statistical analysis also showed a strong negative correlation between the size and frequency of occurrence. The most common type of plastic macromusor were small objects 2.5–5 cm in size, of which 74% were cigarette butts. Among plastic bottles (and corks), the size class of 20-30 cm prevailed.

"Most of the anthropogenic garbage is plastic, and it causes significant damage to nature. Large debris (macroplastic) causes direct harm to marine life, mainly through ingestion and entanglement in it. Plastic decomposes extremely slowly in the environment, moreover, macroplastic eventually under the influence of various physico-chemical processes turns into microplastic, which can also be swallowed by fish, birds, mammals and other marine organisms, and in many cases this leads to their illness and death. Microplastic particles trapped in fish can also, in turn, be transmitted to humans through food. They contain substances dangerous to living organisms (plasticizers). In addition, microplastics can adsorb various dangerous pollutants in the environment and poison living organisms that have ingested it, as well as transmit them further along the food chain. Recently, studies have been published showing that microplastic can transmit viruses that live on it longer even in salt water," added Maria Pogozheva, co—author of the study, senior researcher at the N.N. Zubov State Oceanographic Institute (GOIN).

In general, in the Arctic Ocean, the western part of the Barents Sea is more polluted than the Siberian Arctic, and this is quite understandable by the location of residential settlements. Along the Siberian rivers, the areas located upstream are mainly populated, and they are the main sources of pollution. Plastic garbage formed in the upper reaches can be lost along the banks of rivers in the lower reaches with a small population, thereby reducing the amount of plastic they carry out into the sea. The basins of the European Arctic rivers flowing into the White and Barents Seas are inhabited both in the upper and lower reaches, therefore they can be significant sources of anthropogenic garbage.

A comparison of the processes of receipt of organic and plastic garbage shows their difference. The flow of organic waste is mainly influenced by natural processes (storms, landslides, coastal erosion and others). The supply of plastics depends on both natural and anthropogenic factors (garbage collection, population density, urbanization). Indicators of the rate of accumulation of plastic garbage vary unevenly, while there are fairly stable trends in both their increase and decrease. The study of freshwater river systems is necessary to understand the future fate of floating garbage in the ocean. According to recent estimates, global river plastic emissions amount to 0.5–3.2 million tons of waste.

The work was attended by researchers from the Moscow Institute of Physics and Technology (MIPT), the P.P. Shirshov Institute of Oceanology of the Russian Academy of Sciences, the N.N. Zubov State Oceanographic Institute, Tomsk State University, the M.V. Lomonosov Northern (Arctic) Federal University, the Norwegian Institute of Water Research and the Pacific Oceanological Institute. V.I. Ilyicheva FEB RAS.

Information provided by the MIPT press service

Photo source (© RIA Novosti / Ilya Timin): ria.ru

The information is taken from the portal "Scientific Russia" (https://scientificrussia.ru/)