Plastic floating in the oceans can be slowly broken down by UV light from the sun. Scientists from the Royal Netherlands Institute for Sea Research (NIOZ) have discovered how this works through experiments in their laboratory on Texel, an island in the Wadden Sea.
Under the influence of sunlight, the plastic partly disintegrates into tiny particles that still pollute the sea. But another part of the plastic appears to decay into substances that bacteria can break down further.
Image Credit: chaiyapruek youprasert via Shutterstock / HDR tune by Universal-Sci
What is plastic soup?
When talking about plastic soup, the researchers refer to marine plastic pollution; the significant accumulation of plastic debris, notably microplastics, in our oceans.
This debris stems from a wide variety of sources, like the disposal of plastic waste in landfills and the inappropriate disposal of plastic items such as bottles, bags, and packaging materials. The plastic debris is carried out to sea by wind and water and eventually accumulates in ocean gyres (areas where large rotating ocean currents come together, trapping floating debris).
Plastic soup can also form around coastlines and bays. It causes environmental damage and forms a significant threat to marine life, as plastic sometimes gets mistaken for food.
Further reading: The oceans are full of plastic, but why do seabirds eat it?
A garbage patch the size of France
There are currently five large masses of waste floating in the ocean. The biggest of these is known as the Great Pacific Garbage Patch, which is about three times the size of France. It is estimated to contain 1.8 trillion pieces of waste, weighing around 80 million kilograms. The other four floating garbage patches contain another 80 million kilograms of waste and plastic.
The problem of plastic pollution in the ocean is getting worse every year as millions of tons of waste are discharged into the sea via rivers, primarily from urban areas in Asia where there is limited waste management infrastructure.
Large garbage patches and up caught in oceanic gyres - (Image Credit: VectorMine via Shutterstock)
The mystery of the missing plastic soup
Scientists have long been puzzled by the fact that despite large amounts of plastic waste being dumped directly into the ocean or flowing towards it via rivers, only a small part of it is actually found there.
This is known as the 'missing plastic paradox.' In an attempt to understand why this is the case, the Dutch research team conducted experiments in the lab to see if UV light can break down plastic and cause it to disappear. They found that much of the plastic that enters the ocean is lost rather than accumulating there.
The study
The science team conducted an experiment where they placed small plastic pieces in a container filled with water that mimicked seawater.
They then used a lamp to simulate UV light from the sun while stirring the plastic soup. They then captured and analyzed the gases and dissolved compounds, including nano plastics released from the plastic as it degraded.
According to the measurements, about 1.7 percent of all floating plastic can be broken by sunlight every year. 1.7 percent sounds like a small number, but year-on-year, it explains for a large part the portion of plastic soup that we have lost since the 1950s.
Even though there are huge garbage patches floating around, there is still a lot missing compare to what goes into the ocean - (Image Credit: Roman Mikhailiuk via Shutterstock / HDR tune by Universal-Sci)
When taking into account factors such as the release of plastic into the ocean, the washing up of plastic on shores, and the continued breakdown of plastic by sunlight at the ocean's surface, it appears that sunlight may have caused the breakdown of 22% of all the plastic that has ever entered the ocean. This breakdown mainly results in the transformation of plastic into smaller, dissolved particles and compounds.
The team published their findings in the open-access scientific journal Marine Pollution Bulletin. Be sure to check it out if you are interested more details.
Sources and further reading:
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