Nanoplastics at lofty heights

Nanoplastics are created primarily through the degradation of macro- and microplastics in the environment – through abiotic and biotic decomposition processes such as enzymes, oxidation, hydrolysis, and mechanical abrasion. The contribution of macro- and microplastics to environmental pollution has been well researched. However, far less is known about nanoplastic particles, which may pose even greater risks to humans. “Nanoplastics are particularly concerning because, unlike microplastics, they are not filtered out. Humans can easily inhale the particles, which – because their small size – can penetrate membranes and enter the bloodstream”, says Dr Dušan Materić, the scientific lead of the project and chemist at the UFZ.

Because of their low weight, nanoparticles can be transported over long distances through the atmosphere. However, there is still a lack of global studies on how they reach remote regions far from industrial and urban centres. In their research work, Materić and his colleagues investigated the extent to which glaciers in the Alps are contaminated with nanoparticles and the sources from which they originate.

The researchers first had to collect samples from over 3,000 m above sea level. “For researchers, it is hardly possible and often too dangerous to get into these regions. Not only do you need time for long excursions and specialised local knowledge, but above all, you must be physically fit in order to be able to spend several days travelling on glaciers with a heavy rucksack”, says the firstauthor Leonie Jurkschat.

The scientists therefore cooperated with a team of mountaineers. Along the historic Alpine Trail High Level Route from Chamonix (France) to Zermatt (Switzerland), they collected snow and ice from the glaciers at 14 locations in France, Italy, and Switzerland away from the tourist hiking trails and then sent the samples to the UFZ for analysis.

“The climbers removed the ice from the top layer of the glacier because we wanted to analyse the exposure to nanoplastics over the past few weeks”, explains Materić. To prevent contamination, UFZ researchers extensively trained the alpinists in on-line workshops beforehand. For example, climbers were to use new clothing and new ropes, the sampler was always to be the first in the rope team, and sampling was to take place as quickly as possible in order to prevent contamination.

When analysing the samples at the UFZ, the researchers used a high-resolution proton transfer reaction mass spectrometer (PTR-MS), which is coupled to thermal desorption (TD) and measures the concentrations of organic trace gases. The TD-PTR-MS burns the plastic present in the samples. The mass spectrometer quantifies the gases released during heating. Because each polymer produces a kind of fingerprint of gases, the identity and concentration can be determined. The UFZ researchers mainly found tyre abrasion and the plastics polyethylene (PE) and polystyrene (PS) in the glacier samples, whereas polyethylene terephthalate (PET) was found much less frequently. In total, they were only able to detect nanoplastics at five out of 14 locations. “This shows that not all areas of a glacier are polluted. Where the wind is particularly strong, the nanoparticles are blown away and re-accumulate in areas of the glacier that are more sheltered from the wind”, says Materić. The nanoplastic concentrations at the five sites were 2–80 ng/ml of melted snow.

The UFZ researchers also wanted to know where the detected nanoplastic particles came from. To this end, they collaborated with colleagues from NILU in the Norway. They used the particle dispersion model “Flexpart” to model and analyse the atmospheric transport of particles. Taking into account various parameters such as wind, temperature, cloud cover, and air pressure, they were able to model where nanoplastics of different sizes, densities, and weights are most likely to have originated based on where they were found on the glacier. “The nanoparticles are virtually sent to their place of origin in the modelling”, says Materić. The research team discovered that the nanoplastics are most likely transported to the Alpine glaciers from the west and are deposited there. At the locations where nanoplastics have been found, more than 50% of the particles come from the Atlantic. “There is a lot of macro- and microplastic in the sea. This breaks down into nanoplastic and is whirled up by waves and bubble bursting and ultimately enters the atmosphere”, explains Materić. On the land side, most particles originate in France (more than 10%) followed by Spain and Switzerland.

To find out even more about nanoplastic pollution on glaciers, Materić took on the role of scientific director in the Citizen Science project GAPS 2024. The aim is to have teams of mountaineers collect samples from glaciers around the world. These will then be analysed at the UFZ.  Some – for example from Antarctica, New Zealand, and the Himalayas – have already arrived at the UFZ laboratories and are waiting to be analysed.