Tiny microplastics travel far in the wind

Plastic pollution by Paris does not necessarily stay in Paris.

A study reveals that tiny pieces of plastic from cities have been blown to a distant mountain at least 95 kilometers away. This is the first demonstration that microplastics, tiny particles of a few nanometers to 5 millimeters, can travel very far in the atmosphere.

Researchers say the amount of microplastics dropped from the sky in such a remote place is even more surprising. The results of the study suggest that rain microplastics in some remote locations may rival that of some large cities.

"We found them somewhere they should not be," says Deonie Allen, environmental and environmental scientist at EcoLab in Castanet-Tolosan, France, who co-wrote the study.

The researchers installed two types of atmospheric deposition collectors at the weather station of Bernadouze, in the Pyrenees, between France and Spain. Scientists visited the site approximately once a month from November 2017 to March 2018 to retrieve the samples, and then analyzed the collected particles to separate, identify and count the pieces of plastic.

The team announced that on April 15, microplastic particles per square meter per day would have been deposited on the site. Nature Geoscience. It's a rate that "looks like what's happening in Paris," says Allen.

But the size and relative composition of plastics were different from those measured in previous studies of atmospheric deposition of microplastics in Paris or Dongguan, China. The dominant particles deposited in these cities were thin fibers of a size greater than 100 microns and composed of polypropylene or polyethylene terephthalate, called PET. These fibers often come from clothing or other textiles.

At the Pyrenees site, however, most plastic pieces were smaller than 25 microns and consisted mainly of polystyrene and polyethylene fragments, which are common in many packaging materials.

Polystyrene is particularly susceptible to degradation from the effects of the weather or the sun's ultraviolet rays, making used objects more easily transportable by the wind, the researchers say. On the Pyrenees site, periods of high wind speed and brief gusts of rain or heavy snow seem to be linked to higher deposition rates.

Although the study did not identify the source of plastics, a simulation of wind speeds and direction during the study period suggested that plastics travel at least 95 kilometers to reach the site. But it is likely that plastics come from further afield, says Allen, because no densely populated and industrialized city is part of this region.

"Sadly, [the study] confirms the omnipresent contamination of our environment by microplastics, "says Johnny Gaspéri, environmental scientist at Paris-Est Créteil University.

The team plans to expand its research by collecting more detailed samples more often and in other remote areas. "It's not just local pollution, or something that only happens in cities," says Steve Allen, co-author of the study, also an atmospheric and environmental scientist at EcoLab. "Invisible pollution is making its way around the world."