June 13, 2021

The microplastics have also reached the mountains | Science

The microplastics have also reached the mountains | Science

Even the great mountains do not get rid of plastic. A study has found in the remotest of the Pyrenees a concentration of microplastics similar to what can be found in a capital such as Paris or the industrious Chinese cities. Taken up there by the wind, the plastic particles can travel many kilometers to fall dragged by rain or snow. In the mountain ranges, valleys and other natural environments there could be the plastic that is missing in the statistics.

Of the 335 million tons of plastics created in 2016, some 60 million tons were made in Europe, according to data from plastic sector. That same year, 27.1 tons arrived at the recycling plants and garbage dumps. Although many plastic materials are designed to last for years or decades (such as those of a car dashboard or the insulators of many buildings), several studies have estimated that a good percentage ends up in the sea, the most optimistic speak of 10% of the annual production. Where is the rest?

In the Bernadouze weather station, in the French part of the Pyrenees, they measure the temperature of the air, the speed of the wind and its direction, the rain or the height of the snow if there is one. But for five months between 2017 and 2018 it also recorded the amount of plastic that fell from the ground. The results, published now in Nature Geoscience, show that up to this station, located 1,425 meters high and twenty-five kilometers away from the first town worthy of the name, there is an average of 365 particles per square meter per day.

"The amount of microplastic particles found when studying the remote Pyrenees is within the range of the amount found in a megacity like Paris," says the researcher of the Laboratory of Functional Ecology and Environment (EcoLab, based in Toulouse, France) and co-author of the Deonie Allen study. Indeed, two recent studies carried out in the French capital (here Y here) collected a comparatively similar number of plastic fibers. Also, the figure exceeds the top of the fork obtained in Dongguan, a populous Chinese city of more than 8 million inhabitants, where a extensive study on the presence of microplastics in the air which has estimated a range of between 175 and 313 particles per square meter per day.

This new work found plastics of almost every type, fragments, fibers and film, the one used in plastic bags. They identified some spheres, but their wear prevented them from confirming that they were microspheres, which still use some cosmetics. In terms of size, most of the fragments had a diameter of less than 50 microns (thousandth of a millimeter) and almost all fibers and films did not exceed 100 microns in length. The most abundant plastics are polystyrene and polyethylene. Both are used to make bags and containers and, in theory, are recyclable. Another great category, with 18%, are polypropylene fibers, common in the textile industry.

Most of the plastics collected in the Pyrenees are invisible to the human eye.
Most of the plastics collected in the Pyrenees are invisible to the human eye.

Professor of the Guangdong University of Technology, Jinping Peng, has spent years studying air pollution by microplastics. Although he has not intervened in the study of the Pyrenees, he remembers that, in his works monitoring depositions in Dongguan and surrounding districts, the amount of microplastics was related to population density. "But there may be other reasons that affect the abundance of microplastics, such as the speed and direction of the wind that may explain that there is a similar concentration of microplastics in the Pyrenees," he says.

Given that there are no large urban centers nearby that explain such concentration, only air transport can explain that they have arrived there. Previous studies had already shown that the bacteria can travel thousands of kilometers up to mountains such as those of the Sierra Nevada and the incursions of Saharan dust to the center of Europe are well known. The plastic fragments can be even smaller than a grain of sand and the fibers and film still have a greater capacity to float. So the answer would be in the wind.

"What we can demonstrate unequivocally is that they are being transported there by the wind," says in a note the researcher from the Strathclyde University (United Kingdom) and co-author of the study, Steve Allen. Using a model fed with the velocities and trajectory of the winds and the deposition data, they were able to estimate that the microparticles reached the mountains from at least 95 kilometers away. But Toulouse, Zaragoza or Barcelona are even further away from that distance and with the second two the plastic would still have to overcome much more mountain. It is the next thing that they want to investigate, how much the microplastic can travel through the air.

In Dongguan, a Chinese industrial city of 8 million inhabitants, the concentration of microplastics was lower than that found in the Pyrenees

For the researcher of the Paris-Est Rachid Dris University, specialized in the study of microplastics in urban environments, "these can reach anywhere, as has been proven in all habitats, including the most distant, as the remote lakes or the Arctic, therefore, air was already considered as an important transport route for microplastics. "· Not related to this study, Dris is not surprised that they have now been found in the Pyrenees." It is evident that weather conditions play an important role. paper: the microplastics are probably transported in the moments of greatest wind and fall when it slows down. In addition, snow and rain can cause a drag that increases the deposition of these microplastics, "he adds.

It remains to know how microplastics affect human health. Found already in the human intestine, all the researchers mentioned in this article believe forced and urgent to determine the impact of a breath of air full of plastics.


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