Sunday, April 26, 2015

Tiny Plastic, Big Ocean, Huge Problem

Tiny Plastic, Big Ocean, Huge Problem

Tiny Plastic, Big Ocean, Huge Problem
Photo: The Beautiful Nation Project
Plastic bottles lying in the gutter. Grocery bags tangled in branches. Food wrappers scuttling across the ground on a windy day. Although such examples of litter easily come to mind, they only hint at the serious and growing problem of plastic pollution — a problem mostly hidden from view.
The problem with plastics is they do not easily degrade. They may break down, but only into smaller pieces. The smaller those pieces get, the more places they can go.
Many pieces wind up at sea. Tiny bits of plastic float throughout the world’s oceans. They wash up on remote islands. They collect in sea ice thousands of kilometers (miles) from the nearest city. They even meld with rock, creating a whole new material. Some scientists have proposed calling it plastiglomerate (pla-stih-GLOM-er-ut).
Exactly how much plastic is out there remains a mystery. Scientists are hard at work trying to find out. So far, though, experts haven’t found as much plastic floating in the oceans as they expected. All that missing plastic is worrisome, because the smaller a plastic bit becomes, the more likely it will make its way into a living thing, whether a tiny plankton or an enormous whale. And that may spell some real trouble.

Into the soup

Plastics are used to make countless everyday products — from bottles to auto bumpers, from homework folders to flowerpots. In 2012, 288 million metric tons (317.5 million short tons) of plastic were produced worldwide. Since then, that amount has only grown.
Just how much of that plastic winds up in the oceans remains unknown: Scientists estimate about 10 percent does. And one recent study suggests as much as 8 million metric tons (8.8 million short tons) of plastic wound up in the ocean in 2010 alone. How much plastic is that? “Five plastic bags filled with plastic for every foot of coastline in the world,” says Jenna Jambeck. She’s the researcher from the University of Georgia, in Athens, who led the new study. It was published February 13 in Science.
Of those millions of tons, as much as 80 percent had been used on land. So how did it get into the water? Storms washed some plastic litter into streams and rivers. These waterways then carried much of the trash downstream to the sea.
The other 20 percent of plastic ocean trash enters the water directly. This debris includes fishing lines, nets and other items lost at sea, dumped overboard or abandoned when they become damaged or are no longer needed.
Once in the water, not all plastics behave the same way. The most common plastic — polyethylene terephthalate (PAHL-ee-ETH-ill-een TEHR-eh-THAAL-ate), or PET — is used to make water and soft-drink bottles. Unless filled with air, these bottles sink. This makes PET pollution tough to track. That’s especially true if the bottles have drifted to the ocean depths. Most other types of plastic, however, bob along the surface. It’s these types — used in milk jugs, detergent bottles and Styrofoam — that make up the abundance of floating plastic trash.
Abundant, indeed: Evidence of plastic pollution abounds across the world’s oceans. Carried by circular currents called gyres (JI-erz), discarded pieces of plastic can travel thousands of kilometers. In some areas, they amass in huge quantities. Reports on the largest of these — the “Pacific Garbage Patch” — are easy to find online. Some sites report it to be twice the size of Texas. But defining the actual area is a difficult task. That’s because the garbage patch is actually quite patchy. It shifts around. And most of the plastic in that area is so tiny that it’s hard to see.

Millions of tons… gone missing

Recently, a group of scientists from Spain set out to tally just how much plastic floats in the oceans. To do so, the experts traveled the world’s oceans for six months. At 141 locations, they dropped a net into the water, dragging it alongside their boat. The net was made of very fine mesh. The openings were only 200 micrometers (0.0079 inch) across. This allowed the team to collect very small bits of debris. The trash included particles called microplastic.
The team picked out the plastic pieces and weighed the total found at each site. Then they sorted the pieces into groups based on size. They also estimated how much plastic might have moved deeper into the water — too deep for the net to reach — due to wind churning up the surface.
What the scientists found came as a complete surprise. “Most of the plastic is lost,” says Andrés Cózar. This oceanographer at the Universidad de Cádiz in Puerto Real, Spain, led the study. The amount of plastic in the oceans should be on the order of millions of tons, he explains. However, the collected samples lead to estimates of just 7,000 to 35,000 tons of plastic floating at sea. That’s just one-hundredth of what they had expected.
Most plastic that Cózar’s team fished out of the seas was either polyethylene or polypropylene. These two types are used in grocery bags, toys and food packaging. Polyethylene is also used to make microbeads. These tiny plastic beads can be found in some toothpastes and facial scrubs. When used, they wash down the drain. Too small to be trapped in filters at wastewater treatment plants, microbeads continue to travel into rivers, lakes — and eventually down to the sea. Some of this plastic would have been too small to have been caught in Cózar’s net.

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