Sunlight turns plastic in the ocean into a “soup” of new toxic chemicals

A study by scientists at the Woods Hole Oceanographic Institute has shown that sunlight can not only destroy plastic, but also convert base polymers and additives into a “soup” of new chemicals. The journal Environmental Science & Technology writes about the work of scientists.

The process the researchers talk about is not quite slow, like the decomposition of plastic under sunlight. Scientists have experimented with various plastic bags. For example, leaching of a significant mixture of soluble organic carbon compounds after exposure to sunlight took place in less than 100 hours.

The researchers collected samples of consumer plastic bags from commercial businesses such as Target and Walmart. The researchers also included a used bag from CVS, from a municipality that has banned the use of plastic bags, but they can still be found. A low density film bag without additives from Goodfellow was used as a control.

The bags were defined in terms of organic matter and metal content, as well as spectral characteristics. The researchers placed the samples from the bags in sterile beakers filled with an ionized solution to simulate immersion in seawater. Half of the beakers were immersed in darkness for six days. The rest were left in a temperature-controlled chamber for five days in a constant stream of radiation, simulating exposure to sunlight.

It was found that the samples left in the dark released a small amount of dissolved organic compounds into the saline solution. However, those who remained in the light “bathed” in new chemicals. The used CVS bag showed the largest difference in concentration between a darkened container and a container exposed to sunlight, and this figure increased as it was exposed to light.

Dividing this plastic soup into a list of its constituent molecules revealed tens of thousands of dissolved organic compounds, all produced on a time scale equivalent to only weeks of sailing in the ocean in bright sunlight.

The dissolution process turned out to be at least ten times more difficult than chemists had assumed: those toxic materials were found that were not even considered a problem.

“It’s amazing that sunlight can destroy plastic, which is essentially one compound with some additives, for tens of thousands of compounds that dissolve in water,” notes chemist Colleen Ward.

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Alexandr Ivanov earned his Licentiate Engineer in Systems and Computer Engineering from the Free International University of Moldova. Since 2013, Alexandr has been working as a freelance web programmer.
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Alexandr Ivanov

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