Microscopic particles of plastic are falling out of the sky with snow, even in remote regions such as the Arctic and the Alps, according to a study. Over the past several years, microplastic particles have repeatedly been detected in sea-water, drinking water, and even in animals.
Researchers from the Alfred Wegener Institute (AWI) in Germany have now found that microplastic particles can apparently be transported over tremendous distances by the atmosphere and are later washed out of the air by precipitation, particularly snow.
The study conducted on snow samples from Helgo-land, Bavaria, Bremen, the Swiss Alps and the Arctic confirms that the snow at all sites contained high concentrations of microplastic -- even in remote reaches of the Arctic, on the island Svalbard, and in snow on drifting ice floes.
"It's readily apparent that the majority of the microplastic in the snow comes from the air," said Melanie Bergmann, who led the study published in the journal Science Advances.
Her hypothesis is supported by past research conducted on grains of pollen, in which experts confirmed that pollen from the middle latitudes is transported by the air to the Arctic.
These grains are roughly the same size as the microplastic particles, researchers said.
They found the highest concentration in samples gathered near a rural road in Bavaria -- 154,000 particles per litre.
Even the snow in the Arctic contained up to 14,400 particles per litre, researchers said.
The types of plastic found also varied greatly between sampling sites: in the Arctic, the researchers chiefly found nitrile rubber, acrylates and paint, which are used in a host of applications.
Given its resistance to various types of fuel and broad temperature range, nitrile rubber is often used in gaskets and hoses.
Near the rural road in Bavaria, the samples especially contained various types of rubber, which is used in countless applications, such as automotive tyres, researchers said.
The microplastic concentrations found are considerably higher than those in studies conducted by other researchers, they said.
According to Gunnar Gerdts, who co-led the study, this could be due to one of two reasons.
"First of all, snow is extremely efficient when it comes to washing microplastic out of the atmosphere. Secondly, it could be due to the infrared spectroscopy we used, which allowed us to detect even the smallest particles -- down to a size of only 11 micrometres," Gerdts said.
The researchers melt the snow and pour the meltwater through a filter; the residue trapped in the filter is then examined with an infrared microscope.
Depending on the type of plastic, different wavelengths of the infrared light are absorbed and reflected.
In this way, an optical fingerprint can be used to determine what type of plastic they have found.