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produced nearly 300 million tons of plastic in 2012, but where does it
end up? A new study has found plastic debris in a surprising location:
trapped in Arctic sea ice. As the ice melts, it could release a flood of
floating plastic onto the world.
Scientists already knew that microplastics—polymer beads, fibers, or
fragments less than 5 millimeters long—can wind up in the ocean, near
coastlines, or in swirling eddies such as the Great Pacific Garbage Patch.
But Rachel Obbard, a materials scientist at Dartmouth College, was
shocked to find that currents had carried the stuff to the Arctic.
In a study published online this month in Earth’s Future, Obbard and her colleagues argue that, as Arctic ice freezes, it traps floating microplastics—resulting
in abundances of hundreds of particles per cubic meter. That’s three
orders of magnitude larger than some counts of plastic particles in the
Great Pacific Garbage Patch. “It was such a surprise to me to find them
in such a remote region,” she says. “These particles have come a long
The potential ecological hazards of microplastics are still unknown.
But the ice trap could help solve a mystery: Industrial plastic
production has increased markedly in the last half-century, reaching 288
million tonnes in 2012, according to Plastics Europe, an industry
association. But ecologists have not been able to account for the final
disposition of much of it.
The paper shows that sea ice could be an
important sink—albeit one that is melting, says Kara Lavender Law, an
oceanographer at the Sea Education Association in Woods Hole,
Massachusetts, who was not part of the study. “There could be freely
floating plastics, in short order.” The authors estimate that, under
current melting trends, more than 1 trillion pieces of plastic could be
released in the next decade.
Obbard and her colleagues based their counts on four ice cores
gathered during Arctic expeditions in 2005 and 2010. The researchers
melted parts of the cores, filtered the water, and put the sediments
under a microscope, selecting particles that stood out because of their
shape or bright color.
The particles’ chemistry was then determined by
an infrared spectrometer. Most prevalent among the particles was rayon
(54%), technically not a synthetic polymer because it is derived from
natural cellulose. The researchers also found polyester (21%), nylon
(16%), polypropylene (3%), and 2% each of polystyrene, acrylic, and
Co-author Richard Thompson, a marine biologist at the
University of Plymouth in the United Kingdom, says it’s difficult to
pinpoint the source of these materials. Rayon, for instance, can be
found in clothing, cigarette filters, and diapers.
Abundances are likely to grow as scientists learn to sift more
finely. Law points out that microplastic estimates for the Great Pacific
Garbage Patch are based on phytoplankton nets that catch only particles
bigger than 333 microns.
Obbard, who used a much smaller 0.22 micron
filter, says she still probably missed many particles herself; searching
by eye, she easily could have missed brownish or clear plastic
particles that were masquerading as sand grains.
What is the consequence of all this plastic floating around? At this
point, it is hard to say. Plastic is chemically inert. But the plastic
can absorb organic pollutants in high concentrations, says Mark Browne,
an ecologist at the University of California, Santa Barbara.
performed laboratory experiments with marine organisms showing not only
how the microplastics can be retained in tissues, but also how
pollutants might be released upon ingestion.
“We’re starting to worry a
bit more,” he says