Researchers Discover Sunlight can Break Down Plastic in Oceans

Plastic floating in the oceans can be slowly broken down by UV light from the sun. How that works, researchers at the Royal Netherlands Institute for Sea Research (NIOZ) have discovered with experiments in their laboratory on Texel.

Under the influence of sunlight, some of the plastic disintegrates into tiny particles that still pollute the sea. But another part of the plastic appears to decompose into substances that bacteria can further break down.

According to doctoral student Annalisa Delre and her colleagues, annually 1.7 percent of all floating plastic can be broken down by sunlight in this way. "That may seem little, but year on year, this breakdown by sunlight does explain a good portion of the plastic soup we have lost in the oceans since the 1950s," Delre explained. The researchers published their findings in the scientific monthly journal Marine Pollution Bulletin.

The amount of plastic found in oceans is large, and the negative effects of this pollution have also received a lot of attention. At the same time, the question has always been why only a fraction of the waste believed to be dumped is found back in the oceans.

"In science, this problem is known as the disappeared-plastic paradox," explains NIOZ. According to the researchers, degradation by sunlight can explain about one-fifth of this phenomenon.

Plastics soup grows due to waste from rivers

NIOZ researcher Helge Niemann, who supervised the study, sees "potentially good news" in the results. As far as she is concerned, the best solution to the plastic problem remains to stop the supply of plastic through rivers into the oceans.

There are at least five large piles of waste floating in the oceans. The largest of these is the "Great Pacific Garbage Patch" in the Pacific Ocean. It is about three times the size of France and consists of an estimated 1.8 trillion pieces of trash, weighing about 80 million kilograms combined. The four other floating garbage piles together contain another 80 million kilograms of debris and plastic.

The plastics soup is getting bigger every year as millions of tons of waste flow into the sea through rivers. This waste comes mostly from slums of Asian metropolises, where no garbage trucks come and all the waste ends up in the rivers.