NOVOSIBIRSK, November 17. /TASS/. Scientists in Novosibirsk used mathematical modeling to see mechanisms and trajectory of microplastics' spread in the Arctic seas, the official publication of the Russian Academy of Sciences' Siberian Branch, Science in Siberia, wrote.

"Modern physical and mathematical models, using scenario calculations allow restoring spatial and temporal variability of oceanic waters characteristics, simulating the system of ocean currents and sea ice drift, as well as identifying possible areas of pollutants accumulation," senior researcher at the Institute of Computational Mathematics and Mathematical Geophysics, Elena Golubeva, said.

Numerical modeling used the SibCIOM three-dimensional model of the ocean and sea, developed at the institute. The model calculates currents fields, ocean temperature and salinity, ice thickness and drift. The model had been proved as efficient in the study of climate change in the Arctic Ocean.

Rivers are considered to be the main sources of microplastics entering the ocean - as they are running, they take in sewage and litter. As for Siberian Arctic rivers, the Ob and the Yenisei are considered the most polluted. Scientists have found that the spread of plastics in the ocean is determined by the system of ocean currents, but when they freeze into the ice, they are transported by drift. The scientists analyzed spherical particles of different plastics - both floating and heavy. The results of modeling the continuous flow of microplastics with river waters for five years have shown that light plastic particles spread both in the shelf area and beyond it. The process of plastic particles entering the ice significantly affects the trajectories of the particles, since the ice circulation may differ from the upper ocean layer circulation.

"Ice moves fast, especially in straits connecting the Arctic with the North Atlantic. Therefore, the lightest particles, having got beyond the Kara Sea, can spread quite far. Heavy plastic particles quickly settle in the immediate vicinity of the river mouth, before they may freeze into the ice cover, and they are transported by a system of bottom currents over short distances along the Kara Sea," the scientist explained.

Under favorable conditions, plastic particles can accumulate on the surface of living organisms, which is called the biofouling process, and sink, said Marina Gradova, the institute's junior researcher. Biofouling affects significantly the particle trajectory and the depth of its immersion to the bottom. The simulation has shown that light particles that overgrow algae gradually sink deeper, but at a certain depth, due to temperature differences and a decrease in light, the algae lose their ability to reproduce and die off. As a result, the microplastics float to the surface, where they again can overgrow with biomass. Noteworthy, in winter, particles can freeze into the ice. The smallest particles - 0.01 mm - rise to the surface after purification for about a year. Scientists stress it is important to pay attention to the biological migration of microplastics through the absorption by living organisms.

Microplastics in the Arctic seas

Between 8 and 13 million tons of plastic litter enter the ocean every year, scientists say. Under the influence of sunlight, waves, temperatures and friction, the debris crumbles and turns into microplastics fragments less than five millimeters in size. Plastic particles are hazardous to the environment - for example, living organisms can perceive such particles as food, which leads to their death. In addition, pollutants get adsorbed on the surface of microplastics, and further on they may enter the human body.