A number with 18 zeros - five trillion. This is the number of plastic pieces that The Ocean Cleanup project estimates to be floating around in the oceans¹. People use plastics in many areas of life, and plastic products often travel great distances from their point of origin. Between 1970 and 2013, plastic production increased by 620%². Eight million tonnes of plastic are released into oceans every year, much of it through rivers³. As plastic is non-biodegradable, it disintegrates into tiny fragments and accumulates as microplastics on land, in water and in organisms. The total plastic mass in aquatic environments is difficult to estimate as it is currently only recorded sporadically.

There is not yet a generally accepted definition for microplastics. In the literature, microplastics are usually defined as “synthetically produced plastic fragments less than five millimetres long". A distinction is currently made between primary microplastics, which are industrially produced at this size, and secondary microplastics, which result from the disintegration of larger macroplastic pieces such as bottles or bags. Primary microplastics are found in detergents and cosmetics such as skin scrubs, or in the construction industry in powder coatings and abrasives. Secondary microplastic particles are released simply through abrasion during the daily use of plastic products. If you wash synthetic clothing, up to 2,000 tiny plastic fibres are released, which end up in the wastewater. Of the 27 million tonnes of plastic waste generated each year in Europe, about 31% are recycled, 41% used for energy production and 27% landfilled⁴. The proportion of improper plastic disposal is not known. Nor do we know the paths that plastic takes into rivers and what effects microplastics have on the living environment. "Research is still in its infancy," says Orlowski from the Department of Hydrology at the University of Freiburg. She is supervising three recently started bachelor theses that are analysing the concentration of microplastics in the Dreisam River near Freiburg.

The Great Pacific Garbage Patch is already well known, and a very high concentration of one million plastic particles per cubic metre has been found in Arctic sea ice⁵. But even though the oceans are a sink for plastic waste, microplastics are not purely a marine problem. Orlowski believes that it is high time to investigate running waters not only from the perspective of their role in transporting garbage into the oceans, but also regarding their own pollution. Such an investigation, she believes, should be both transnational and comprehensive.

According to the research group that carried out the investigation, the "Microplastics in inland waters of Southern and Western Germany" study has led to one of the largest and most detailed data sets on plastic pollution in inland waters. During a single year between autumn 2014 and autumn 2015, water samples were taken from the top 15 centimetres of 25 rivers in the Rhine and Danube catchment areas in Baden-Württemberg, Bavaria, Rhineland-Palatinate, Hesse and North Rhine-Westphalia and subsequently analysed. Lake Constance was included in the investigation due to its special status as part of the Rhine. The environmental offices of the five federal states collected a comprehensive data set on microplastic pollution over a wide range of hydrological conditions and anthropogenic influences. Analysis of the 52 samples was carried out centrally at the University of Bayreuth to ensure comparability of methods and data. The number, size, shape and nature of the plastic parts were measured and analysed using light microscopes. The composition of the plastic was investigated using a Fourier-transform-infrared-spectrometer (FTIR spectrometer), which practically reveals the optical fingerprint of each substance.

The study came up with the following result: microplastics were found in all rivers investigated, including the headwaters close to the sources of the rivers. The researchers found and analysed more than 19,000 objects, of which nearly 25% were pieces of plastic. The samples contained a particularly large number of very small pieces. Around 99% of the plastic particles were smaller than 5 millimetres and hence microplastics; only 0.6 percent were larger than five millimetres. Fragments of larger plastic products constituted the dominant plastics fraction; plastic fibres were also found to a lesser degree, and granules and pellets that are normally used for further processing and cosmetics beads (primary microplastics) were the least frequent. More than half of the plastic particles were polyethylene, around a third were polypropylene. This came as no surprise as these two types of plastic are the most common plastics used in Europe.

Interestingly, higher microplastics concentrations were more frequently found in smaller and medium-sized tributaries than in larger bodies of water, where relatively small pieces of plastic were found. Moreover, elevated plastic concentrations were only found in a few urban centres. The rivers sampled in the study had a similar plastic level to other European and North American bodies of water. Moreover, the Rhine, which at the time of sampling was considered highly polluted, in fact had a below-average plastic pollution level.

It is difficult to make statements about the effects of microplastics on the environment and organisms, as appropriate test and evaluation procedures are not available. Although laboratory studies demonstrate that microplastics have negative effects on mussels and other aquatic organisms, microplastics concentrations in the laboratory exceed the current environmental concentration many times over⁴. In addition to the direct harmful mechanical effects of swallowing small plastic pieces, plasticisers or UV protectants contained in the plastic pieces can also cause indirect negative effects in organisms. "Such persistent organics accumulate above all in the fat tissue of animals and thus enter the food chain," explains Orlowski, "This increases ecotoxicity, as many of the substances are carcinogenic." The researchers also found that the transport of pathogens that colonise the smallest plastic fragments plays a role. Orlowski, who has only been working as an academic counsellor in Freiburg since November 2017, is also investigating the microplastics pollution caused by car tyre wear particles originating from the nearby B31 road. “This problem still requires research,” Orlowski says, “especially as far as the determination of tyre wear particles is concerned, for which no standard procedure is yet available.” In cooperation with the German Weather Service in Freiburg, Orlowski and her team are analysing whether the microplastics mass changes in the Dreisam River, especially after heavy rainfall. Measurement points are located in front of, in the centre and behind the city of Freiburg. Orlowski’s project has only just begun, but “we have already taken samples and unfortunately already found microplastics.” The project framework and budget are small, which is why the samples are analysed and evaluated under the light microscope. The research group does not have an FTIR spectrometer, and Orloswki hopes to be able to work with institutes that own such systems.

Further research is urgently needed. All the results of the transnational pilot study can only provide initial information on the microplastics load in rivers. These results help clarify new questions and pave the way for further microplastics monitoring. Standardisation procedures for sampling, characterisation and ecotoxicological risk assessment of impacts must be developed and optimised so that reproducible results can be obtained across national borders. "We humans got into the microplastics problem very thoughtlessly and we have not spent enough time dealing with the issue," says Orlowski. However, as far as avoiding plastic waste is concerned, every single one of us can do something about it^6,7.

References

1 The Ocean Cleanup, URL: https://www.theoceancleanup.com/ (as of 31st July 2018)

2 Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research: Woher stammt der Plastikabfall, URL: https://www.awi.de/im-fokus/muell-im-meer/10-fragen-10-antworten/frage-2.html (as of 31st July 2018)

3 FOX NETWORKS GROUP GERMANY GmbH (Representation of National Geographic Partners LLC in Germany): 8 Millionen Tonnen landen jährlich im Meer, URL: https://www.nationalgeographic.de/umwelt/2018/04/8-millionen-tonnen-plastik-landen-jaehrlich-im-meer (as of 31st July 2018)

4 Mikroplastik in Binnengewässern Süd- und Westdeutschlands, investigations in the German states of Baden-Württemberg, Bavaria, Hessee, North Rhine-Westphalia and Rhineland Palatinate, URL: http://www4.lubw.baden-wuerttemberg.de/servlet/is/274206/mikroplastik_in_binnengewaessern_sued-_und_westdeutschlands.pdf?command=downloadContent&filename=mikroplastik_in_binnengewaessern_sued-_und_westdeutschlands.pdf (as of 31st July 2018)

5 Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research: Die Suche nach dem Mikroplastik, URL: https://www.awi.de/im-fokus/muell-im-meer/mikroplastik.html (as of 31st July 2018)

6 ZWEITES DEUTSCHES FERNSEHEN: Plastik im Peeling - Der Zusatz von Kunststoff lässt sich erkennen (17th January 2017), URL: https://www.3sat.de/page/?source=/nano/umwelt/190763/index.html (as of 31st July 2018)

7 German Federal Ministry of the Environment, Nature Protection and Nuclear Safety (BMU): Wie lässt sich Mikroplastik in Gewässern vermeiden? (20.04.2017), URL: https://www.umwelt-im-unterricht.de/unterrichtsvorschlaege/wie-laesst-sich-mikroplastik-in-gewaessern-vermeiden/ (as of 31st July 2018)