Researchers from the "7th Continent Expedition" team have just demonstrated for the first time in the world that microplastics break down to become nano particles. No ocean is preserved by the massive presence of plastics that carry endocrine disruptors, heavy metals, pollutants and are traps for biodiversity, with a likely impact on human health. It is high time to understand, explain and act against this continent. of 3.5 million km2, six times the size of France.
En 1997, Captain Charles Moore, accompanied by Patrick Deixonne, founder and head of the 7th continent mission, was the first to discover a huge area of floating plastic in the Pacific : at least 750,000 debris per km2 , composed of plastics with 90 % of which 80 % is waste from the earth via rivers, and 267 marine species affected.
Since this discovery, several expeditions have been launched to the various waste areas, including that of the explorer Patrick Deixonne set off towards the North Atlantic in May 2015, accompanied by scientists from the Centre National d'Etudes Spatiales (CNES), the European Space Agency (ESA) to map the zones and the CNRS (Centre National de la Recherche Scientifique, Université Paul Sabatier) to analyse the waste. Plastic waste that would represent 30 to 40,000 tons in all the world's oceans. On the North Atlantic, 1,000 tonnes of plastic are spread over an area the size of Europe. 80% of this waste comes from the continents and 6 million tonnes of debris are discarded each year by ships, including 10,000 containers.
According to the NGO Surfrider Foundation (1)Every year, plastic waste causes the death of 1 million marine animals through ingestion or entanglement.
Patrick Deixonne and Alexandra Ter Halle, scientific manager of the association, present a first scientific study " Marine Plastic Litters: the unanalyzed nano fraction." published in the journal Environmental Science, Nano of the Royal Society of chemistry. Study carried out by Julien Gigault, researcher at the CNRS Bordeaux, in collaboration with Boris Pedrono, Benoit Maxit (Cordouan Technologies) and Alexandra Ter Halle, researcher at the CNRS IMRCP in Toulouse, which shows the urgency to preserve our oceans.
A 7th continent in constant formation
The seventh continent is currently forming between the coasts of Japan and North America from millions of tons of plastic rubbish carried by ocean currents. In this part of the world, the currents turn clockwise and create an endless spiral, a powerful vortex that swirls the plastic trash around just as the wind would do with paper in the corner of a square. For years, the subtropical North Pacific vortex has been accumulating plastic waste from coasts and rivers, dragging it along in its rotation and, by centripetal force, gradually bringing it back towards its centre, a zone of low kinetic energy covering 3.43 million square kilometres, or a third of Europe and more than six times the size of France. Because the sea of waste is translucent and lies just below the water surface, it is not detectable in photographs taken by satellites. It is only visible from the deck of ships.
Over most of its surface, the plastic layer of this garbage whirlpool is up to 30 metres thick.
Although it represents a large area of the ocean, it is an area little frequented by shipping. By definition, in international waters, no one is forced to engage in any form of clean-up: this is one possible explanation for the almost total absence of public initiatives dedicated to the issue of macro-waste in the open sea.
The 7th continent: micro and nano particles of plastic waste
What the study of the 7th continent expedition shows is that after two years of research in the North Atlantic, we know that this 7th continent is a plastic soup made up of several million micro plastic debris. This debris is no more than half a centimetre.
READ ALSO IN UP' : Microplastics in the ocean: real trash continents
A recent study (M. Eriksen, PlosOne 2014) estimates that a total of five trillion particles are floating in our oceans. Researchers have also estimated (Jambeck, Science 2015) that of the 300 million tonnes of plastic produced in the world each year, 8 million tonnes end up trapped in sub-tropical gyres (eddies where currents help to concentrate the debris discharged into the water).. As a result of these oceanic gyres, waste from around the world accumulates in five major locations around the globe, including the spectacular Great Pacific Garbage Patch. " Like a powerful marine siphon, the vortex would draw all the residues of our society towards it", popularizes the site notre-planete.info. With disastrous consequences for the present ecosystems: "In this area most of the plastic pieces are very small. ...] In fact they are the same size as the plankton that the fish feed on. Worse still, by 2025 this figure will be multiplied by 10; that is 80 million tonnes of plastic dumped into the oceans every year. »
Plastic waste debris of almost half a centimetre in size, known as microplastics, has attracted the most attention from researchers in recent years. Micro-plastics result from the fragmentation of larger waste.
Micro plastics - Photo credit : Expedition 7èmeContinent VinciSato
At sea, plastic waste breaks under the effect of solar radiation and wave abrasion. It was not known to what extent this fragmentation process continued because the fragmentation of micro plastics leads to microscopic particles that are extremely difficult to collect, identify and account for.
After the recent information on the micro particles of plastic constituting the 7th continent, a new study proves the high fragmentation capacity of plastic waste into nano-metric particles.
Researchers subjected the microplastic samples collected in the North Atlantic by Expedition 7e Continent to artificial solar radiation and quickly observed a fragmentation of the micrometric particles into nano-metric particles.
The micro particles of plastic found on the 7th Continent would degrade into nanoparticles... 30,000 times smaller than the thickness of a hair.
Researchers are thus proving that the plastic soup of the 7th Continent does not disappear, but that it fragments. These nanoparticles are more mobile than larger fragments and would be more accessible to organisms.
Moreover, the results of this study confirm the complexity of the sea collection projects and the importance of mobilizing on land to change behaviours in order to prevent this plastic waste from being found in nature.
The challenge of these nano plastics is related to their specific surface. Based on the assumption that a plastic particle of a few millimetres fragments into nanoparticles, a single millimetre particle can form 1,000 billion nanoparticles. Thus the total surface area of this particle is multiplied by several tens of thousands.
Given that the distribution of plastic waste in the ocean is estimated at several million km2, and considering the nanometric scale, this specific surface area amounts to several billion km2, covering in equivalence more than the entire ocean surface.
A stage in the fate of plastics at sea has been reached, opening the door to the study of the impacts that these particles can have on the entire marine world. It is important to continue work to assess the impact of these particles on living organisms.
But for Alexandra Ter Halle, NRC-CNRS IMRCP researcher, scientific leader of the 7th continent expedition, "These particles can affect animals at the top of the food chain. PAHs are toxic to aquatic organisms and carcinogenic to mammals. This raises a host of questions. Where do they come from? What impacts can they have on the marine environment? What is their accumulation in the food chain? We are only at the beginning of this research. In parallel with the studies of chemical compounds, a biologist is studying in the laboratory the bacteria that live on the chaff. This is in line with the findings of our American colleagues last year on what they call "the plastic sphere". Each piece of plastic is colonized by living things, even particles smaller than plankton, and we know nothing about their impact on the environment and on the human species".
According to Julien Gigault, CNRS researcher at the EPOV laboratory, author of the study, "Nanoparticles, the spearhead of nanotechnology, are often studied and praised for their extraordinary properties and the technological revolution they represent. They advance our knowledge of how matter and our environment work. Nevertheless, nanoparticles can also be produced in a non-intentional way by man and his activities, of which plastic waste is unfortunately one. As with any object that degrades, our intuition has led us to wonder whether this debris can also produce nanodebris. We then faced the challenge of detecting and characterizing nanoparticles directly in the study environment. We therefore decided to take up the challenge by developing, in partnership with the SME Cordouan Technologies, a reactor to highlight the appearance of nano-plastics under solar radiation. »
For Alexandra Ter Halle, "The presence of nanoparticles on the 7th Continent had never been detected before. But this laboratory work, based on samples collected in the North Atlantic gyre, shows that microplastics that are already highly degraded after a prolonged stay at sea can produce nanometric particles.
Much work remains to be done to detect these particles in the natural environment or to assess the potential toxicity of these nanoparticles. »
For Patrick Deixonne "This study reinforces our knowledge on the 7th Continent: it enables scientists to identify a link in the plastic degradation chain with certainty and helps to raise public awareness about the fate of our waste. It reinforces our idea that once in the oceans, waste collection solutions are technologically unsuitable. It reinforces our desire to act upstream by raising awareness, education and the implementation of solutions to prevent our plastic waste from inevitably reaching the ocean. »
(1) Surfrider Foundation Europe is an environmental NGO created in 1990 and working for the protection of the coastline and the oceans. It carries out research on various issues (water quality, aquatic waste, climate...), education and political lobbying to advance its cause. After obtaining the ban on single-use plastic bags, which is due to come into force in France on 1 July 2016, Surfrider is starting work this year on plastic bottles. The headquarters of the association, which has various offices in France, including one in Bordeaux, is in Biarritz.
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