Microplastics: air pollution from the French mountains would have crossed the Atlantic Ocean

Microplastics traveled thousands of miles across oceans and continents in a fast-moving layer of the atmosphere before being captured on a mountain in the French Pyrenees


December 21, 2021

Capturing microplastics at the Pic du Midi Observatory

Jeroen Sonke

Microplastics found on a mountaintop in the French Pyrenees may have crossed continents and oceans, traveling around 4,500 kilometers through a fast-moving region of the troposphere, which is the lowest layer of the atmosphere. The discovery suggests that the particles can circulate around the world and reach even the most remote regions.

Microplastics are tiny pieces of plastic, each less than 5 millimeters in diameter. They have already been discovered in a lower region of the troposphere called the boundary layer, where friction between the air and the Earth’s surface occurs and where wind speeds are relatively low.

Now, for the first time, we have evidence that microplastics can travel higher in the troposphere in a layer that doesn’t feel the effects of friction with Earth’s surface. In this layer – called the free troposphere – higher wind speeds give microplastics greater potential to travel long distances than previously known.

“Once the microplastics hit the free troposphere, it’s the super highway for pollution movement. There’s high wind speed and very little rain up there, so the pollution doesn’t wash away. and she moves much faster. [than in the planetary boundary layer below]says Steve Allen from the University of Strathclyde in the UK, a member of the research team.

“We are not surprised that it is up there, but we are sad that it is. These tiny particles are excellent carriers of pollution, they act like little balls of Velcro, collecting viruses and other pollutants on the outside of the particle as it moves,” explains Deonie Allen, member of the team, also at the University of Strathclyde.

Researchers captured 15 samples of microplastic particles over several months at the Pic du Midi Observatory in the Pyrenees in southwestern France, which sits nearly 3,000 meters above sea level and provides access to the free troposphere. .

The team used computer models to map the likely routes taken by the microplastics in the week before they were captured. The models were fed with data on the movement of airflows around the globe and took into account the sizes and densities of microplastics to find that the particles traveled about 4500 kilometers on average in the free troposphere. Potential sources included the United States, Canada, North Africa, United Kingdom, the Mediterranean Sea and the Atlantic Ocean.

“Some of the samples we got showed a marine source, coming out of the ocean and managing to go up into the free troposphere,” says Steve Allen. “It basically completes the cycle of what we think plastics do – it doesn’t stop anywhere, there’s never a sink, but a way station to somewhere else.”

Most of the particles were between 5 and 20 micrometers in diameter. These are particles that can be inhaled and potentially cause respiratory problems.

“It’s the size of the particles you breathe in that cause respiratory disease – what makes you cough and gives you asthma,” says Deonie Allen.

Using a laser, the team determined that the most abundant type of plastic was polyethylene, which is commonly used in plastic packaging.

“Rich countries think they are getting rid of plastic waste when they ship it off to be burned or landfilled in other parts of the world – they don’t, they just come back in a few weeks. has no boundaries in nature,” says Steve Allen.

Journal reference: Nature CommunicationDOI: 10.1038/s41467-021-27454-7

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