“Plastic is fantastic”… Except for our good old planet. Practical, resistant, with multiple properties, this material has been part of our daily lives for decades. But in recent years, various scientific studies have demonstrated their harmfulness to ecosystems. Whether it is for the oceans across the famous “plastic” continent which, with supporting images, has left its mark. Or microplastics recently found even in the pure air of the Pyrenees.
But no global study had yet scrutinized the life cycle of this material at a global level, whether in the air, on and underground or in the abyss of the ocean. Nor what happened to 9.2 billion tons of plastics produced between 1950 and 2017, i.e. one tonne per person currently living on Earth, and of which we know that less than 10% has been recycled.
A team of Toulouse scientists therefore set to work. And the conclusions that these members of the Functional Ecology and Environment Laboratory and Geosciences and environment laboratory are far from encouraging.
Millennia to “digest” microplastics
“Our study shows that, even if we stop producing them in 2025, they will continue to disperse into the environment, particularly from the ground. And they will take decades to be visibly eliminated from terrestrial systems, and hundreds, even thousands of years for the ocean depths to integrate and digest these plastics,” explains Gaël Le Roux, research director at the CNRS and co-author of the study published in the specialized journal Microplastics and Nonaplastics.
To achieve this, they reviewed all the existing data on the presence of these plastics, in all their forms, from large plastic to nanoplastic, in urban areas, the countryside, remote areas of obvious pollution, deep oceans or oceans. on the surface, but also in the atmosphere. They then estimated the stocks and reservoirs in these different areas, taking into account the progressive and slow phenomena of degradation of this polluting material. And they ran their mathematical models.
Soil issues
We can thus see that in 2015, according to their calculations, there were 3,500 million tonnes of plastic waste “stored” in the ground, significantly more than in the abyss which count 82 million tonnes, the beaches (1, 8 million) or the surface of the oceans (0.3 million).
If the public authorities have decided to act on the visible part of the problem by taking decisions, particularly in terms of plastic bags or household packaging, the difficulty today is on a microscopic scale. “However, in the soil they take a very long time to be eliminated because there has to be erosion, they have to be transported to the rivers, then to the ocean which takes time for the” digest”, and make them sink into the abyss. And in addition, some of the plastics present in the ocean are re-emitted into the atmosphere, so we have a real cycle that takes time to diminish,” continues Gaël Le Roux.
If there are signs of awareness, much more will have to be done than simply banning plastic packaging in France. Especially since the trend in recent years was already going in this direction since over the past twenty years, the planet has produced more plastic than during the previous fifty years.
“Among the simple recommendations that could be taken, there is that of no longer integrating plastics or waste into the soil without being certain that they no longer contain micropollutants. There are a lot of process, such as sewage sludge, which tends to be used in agricultural soils and for which there is no visibility. We also need to be able to estimate where the sources of pollution come from and what types of plastics they are: polypropylene, polyethylene or mixtures of polymers,” concludes the scientist from Toulouse. For him, these questions could be the subject of a new study.