Wear and tear on tires, brakes and other parts of vehicles or the road release thousands of tons of microplastics into the atmosphere each year, according to a new analysis. Much of these pollutants, especially the smallest, end up in the world's oceans and even in the Arctic.
Pollution by microplastics of different sizes reaches terrestrial, marine and freshwater ecosystems through various routes. One of them is road traffic due to mechanical abrasion and corrosion of vehicle tires, brakes, clutch and engine, which, depending on environmental conditions, friction, speed and other factors, release pollutant particles.
Currently, microplastic road emissions - which include resuspension or the so-called “grasshopper effect” of particles through traffic-induced turbulence - constitute 30% of microplastic pollution in ocean and freshwater ecosystems .
Although they mainly come from the most densely populated regions of the world such as the eastern United States, northern Europe and Southeast Asia, some of these compounds are dispersed through the atmosphere for days and can end up in places as unsuspected as oceans or the Arctic.
This is the conclusion of a study, published in the journalNature Communications, which has made it possible to simulate atmospheric transport routes to determine its trajectory and quantify its propagation for the first time globally.
“Our main finding is that atmospheric road transport of microplastics, a source that is underestimated or not even considered, has the same impact on the oceans as river transport.”, Says Nikolaos Evangeliou, from the Norwegian Institute for Air Research and first author of the work.
Smaller microplastics go further
According to the scientists, although the larger particles are deposited close to the source of production, microplastics of 2.5 micrometers and smaller are transported through the air much further, although in this sense their concentrations are much smaller. "They are lost through dry and wet deposition, such as raindrops, during long-distance transportation”Says the expert.
The team calculated that PM10-sized particles have an atmospheric lifespan of 5.5-11 days and end up in their countries of production such as China, the US and Europe. However, the smallest particles travel 18 to 37 days. "They fly for longer periods, which means that they are subject to long-range transport and therefore show concentrations and deposits in the ocean or in the Arctic.”Emphasizes Evangeliou.
According to estimates and simulations carried out, an annual total of 29,000 tons of PM2.5 pollutants from tire wear were dispersed around the world: about 12,000 tons on land and about 16,000 in the oceans. According to the study, more than 8,000 tons of these particles spread on ice and snow surfaces in polar regions and mountains.
Similarly, the total of PM2.5 compounds from brake wear was 97,000 tons, of which 45,000 (46%) were deposited on land and 52,000 (54%) in the oceans. A considerable amount, some 30,000 tons, ended up on snow and ice surfaces.
In the case of the larger particles (PM10) from brake wear, 72% of the 102,000 tonnes was deposited on land, mainly in Asia, Europe and North America, and the rest in the oceans. In this case, about 20,000 tons reached remote areas, although the transport to Antarctica was less than in the rest of the continents.
Some 284,000 tons of PM10 particles from tire wear settled in total on the planet; 65% of them on land, especially in Europe, America, Russia and Asia. Some 28,000 tons reached the polar regions and mountains.
Pollution in these remote areas, particularly in the Arctic, comes from North America, on the one hand, and northern Europe, on the other. The transport of microplastics occurs mainly during the winter and spring months.
For the authors, these results could be worrisome in the most sensitive regions, where the dark particles decrease the albedo of the surface - the amount of sunlight reflected from the Earth's surface - and could accelerate the thaw.
Nikolaos Evangeliou et al. "Atmospheric transport is a major pathway of microplastics to remote regions"Nature Communications July 14, 2020