“Eternal” polystyrene disintegrated under the action of sunlight

Chemists
found that the polystyrene used to make including foam, fully
or partially decomposed under the action of the sun
light, reported
in Environmental
Science and Technology Letters.
They conducted experiments and found
all the polymer degrades over
for several centuries, and partly from a few
decades.

Polystyrene
started doing in the 1960-ies and now
the world produce tens of millions of tons
of this polymer. On it have
about six percent of the world’s
the production of plastic. Polystyrene
do Styrofoam food packaging,
children’s toys, used in construction,
medicine and the military industry.
It was first discovered
in the ocean in the early 1970-ies and regularly
find now.

Scientists
see the problem with waste polystyrene
that it very slowly decomposes.
This polymer is 75 percent
aromatic compounds and it
high molecular weight, so
microorganisms from the environment
bad break down. The authors of one
studies generally concluded that the microbial community
it does not apply — they are not
found signs of decomposition
polystyrene within a few months. But, as it turned out,
this polymer is partially oxidized under
the action of sunlight. However
the speed and completeness of this process
poorly known. For example, it is unknown whether
polystyrene dissolves completely in
photochemical oxidation.

So
Colleen Ward (Collin
P. Ward)
from Oceangraphical Institute woods
Hall and his colleagues decided to see
how this polymer behaves under the action of sunlight. The scientists took
five samples of polystyrene produced by
American companies. They had
different thickness, density, molecular
mass and in the production they added different substances to achieve desired physical or chemical properties. The polymers were placed in a solar simulator
light, the intensity of radiation which
were 3-10 times higher than the intensity
natural sunlight at latitude
from zero to 50 degrees North latitude.
The authors chose these coordinates because
they are 10 large rivers, which
the time bring
in the ocean, 90 percent of polystyrene waste.
Scientists believed the amount of oxygen
which is absorbed during the reaction, and
the amount of carbon dioxide and soluble
carbon compounds that are formed
as a result of photochemical oxidation.
They also looked at what lengths
waves and what temperature degradation of the polymer is faster.

All samples
polystyrene is entirely or almost
fully decomposed under the influence
sunlight (wave-length more
280 nanometers) at different intervals
time. The completeness of the degradation of the polymer and the wavelength at which it has decomposed,
dependent on the substances that it
added during production. They
absorb different amounts of solar
light and thus shortened or
inhibited oxidation process. Speed
decomposition of the polymer
increased by about 25 percent (P
= < 0,05)
when the temperature increases by ten
degrees Celsius.

The authors
calculated how much time will it take
below are two samples of polystyrene, which
they conducted experiments, fully
or partially decomposed in the natural
conditions. According to them a complete decomposition
samples should not take the Millennium
and hundreds of years and partial — tens. At
the authors ‘ calculations, a half-time of
samples with complete degradation of 100 and
300 years, and partial about 10 and 50 years.

“Right now
people, developing recommendations for
the use of plastic, I guess
the polystyrene remains in the surrounding
environment forever,” says
Colleen Ward. “This argument they
justify the creation of rules that
it completely banned. Our goal
to understand whether or polystyrene
remains in the environment forever.
We’re not saying that plastic pollution
there is nothing wrong, but the stability
polystyrene to the environment can
to be less… than we originally thought.
And the likelihood that the polymer will
to harm for decades
still is.”

A few
years ago, scientists have shown,
that polystyrene is able to eat the larvae
a large flour castaneum. Bacteria in
intestinal worms recycle polymer
into carbon dioxide and biodegradable mass.

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