Experts at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research (AWI) have recently found higher amounts of microplastic in arctic sea ice than ever before. However, the majority of particles were microscopically small.
Bremerhaven/Germany — The term microplastic refers to plastic particles, fibres, pellets and other fragments with a length, width or diameter ranging from only a few micrometres — thousandths of a millimetre — to under five millimetres. A considerable amount of microplastic is released directly into the ocean by the gradual deterioration of larger pieces of plastic. But microplastic can also be created on land — e.g. by laundering synthetic textiles or abrasion of car tyres, which initially floats through the air as dust, and is then blown to the ocean by the wind, or finds its way there through sewer networks.
In order to determine the exact amount and distribution of microplastic in the sea ice, the AWI researchers were the first to analyse the ice cores layer by layer using a Fourier Transform Infrared Spectrometer (FTIR), a device that bombards microparticles with infrared light and uses a special mathematical method to analyse the radiation they reflect back. Depending on their makeup, the particles absorb and reflect different wavelengths, allowing every substance to be identified by its optic fingerprint.
During their work, the scientists found that the ice samples from five regions throughout the Arctic Ocean contained up to 12,000 microplastic particles per litre of sea ice. Further, the different types of plastic showed a unique footprint in the ice allowing the researchers to trace them back to possible sources. This involves the massive garbage patch in the Pacific Ocean, while in turn, the high percentage of paint and nylon particles pointed to the intensified shipping and fishing activities in some parts of the Arctic Ocean. The new study has just been released in the journal Nature Communications.
The scientists realised that more than half of the microplastic particles trapped in the ice were less than a twentieth of a millimetre wide, which means they could easily be ingested by arctic microorganisms like ciliates, but also by copepods. According to AWI biologist and first author Dr Ilka Peeken, this observation is very troubling because, as she explains, no one can say for certain how harmful these tiny plastic particles are for marine life, or ultimately also for human beings.
The AWI researcher team had gathered the ice samples in the course of three expeditions to the Arctic Ocean on board the research icebreaker Polarstern in the spring of 2014 and summer of 2015. They hail from five regions along the Transpolar Drift and the Fram Strait, which transports sea ice from the Central Arctic to the North Atlantic.
Infrared Spectrometer Reveals Heavy Contamination with Microparticles
Using this approach, the scientists also discovered plastic particles that were only eleven micrometres across. That’s roughly one-sixth the diameter of a human hair, and also explains why they found concentrations of over 12,000 particles per litre of sea ice — which is two to three time higher than what they had found in past measurements, says Gunnar Gerdts, in whose laboratory the measurements were carried out. Surprisingly, the researchers found that 67 % of the particles detected in the ice belonged to the smallest-scale category “50 micrometres and smaller”.
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