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Taking to the water

Seas, rivers and lakes around the world are increasingly polluted by plastic waste. In two joint projects, researchers now want to find out – for the first time spanning across ecosystems – how much microplastics reach the North Sea and the Baltic Sea via the Weser and Warnow rivers. Jülich scientist are on board.

We should have known in advance, actually: using durable plastics for short-lived packaging and objects cannot turn out well. Plastic bags, food packaging, buckets, plastic bottles, disposable diapers or fishing lines have long since formed huge garbage patches on the ocean surfaces. According to estimates, more than five trillion plastic parts with a weight of more than 268,000 tons are floating in the oceans – with an upward trend. We know the alarming pictures: turtles with straws in their noses, albatrosses starving to death because their stomach is filled with plastic, or – most recently – the discovery of eight kilograms of plastic waste in the stomach of a pilot whale. More than 330 animal species swallow the plastic waste of the seas, more than 132 species die from cigarette butts, plastic lids and can closures: suffocated, starved, strangled.

The ravages of time gnaw – too slowly

The ravages of time also gnaw at the plastics – but too slowly. Smashed by sea waves, decomposed by light or oxygen, macroplastic turns into microplastic: these are plastic crumbs that are smaller than five millimetres and larger than one micrometre. Accordingly, we often do not even recognise them with the naked eye, still we eat, drink and breathe them in. Plastic may change shape and colour, but it remains plastic – and it does so for decades. For example, a plastic bottle lasts an estimated 450 years, a fishing line 600 years, a coffee cup 50 years. The tiny particles eventually sink to the bottom of the ocean – at the Australian Great Barrier Reef as well as in the 11-kilometre deep Mariana Trench in the Pacific Ocean, or in the Arctic Deep Sea. Nobody knows yet how large these quantities are. Researchers assume that only 15 per cent of marine waste ends up on beaches and another 15 per cent drift on the water surface. The lion’s share of 70 per cent is deep down in the sea.

However, most of the microplastics form much earlier – through the abrasion of our car tires or in our washing machines, for example: when we wash fleece jackets, they are not only clean, they are also always a little lighter as tiny particles of the plastic fibres detach with every washing and end up as microplastic in the waste water. The problem is that sewage treatment plants cannot filter microplastic out of the water. They eventually reach the oceans via the various rivers.

weggeworfene Flasche am StrandCopyright: CC 0 Creative Commons:

Closely interlinked: PLAWES and Microcatch_Balt

This is the precise starting point of two, closely interlinked, collaborative projects in which the Jülich research group “Modelling and Management of Catchments” from the Institute of Bio- and Geosciences (IBG-3) is involved: “PLAWES” focuses on the Weser, from its source to the estuary into the North Sea, and “Microcatch_Balt” concentrates on the Mecklenburg river system Warnow, which flows into the Baltic Sea.

“If we want to initiate measures to reduce microplastic pollution, we need to know first of all where the hotspots are in the river basins – that is, the main sources of microplastics – and how microplastics get into the rivers,” states Professor Frank Wendland, head of the group, getting to the heart of the matter. Whether point sources such as sewage treatment plants and sewage systems or diffuse sources such as material inputs in agriculture, soil erosion or the air – with the aid of models, the researchers want to analyse in both pioneering projects which sources in which subspaces of the river catchments are most important and how the microplastics get there. In this context, the Jülich researchers analyse the results of the concerted measurement campaigns of colleagues at individual sites and transfer them to comparable sites in the study area: “This means we are developing so-called export coefficients for our models for various microplastic sources and their input pathways, which we can transfer to the entire river catchment,” explains Wendland.

Proven model for new tasks

His team is actually known for modelling nutrient input into water bodies at the federal state level. “We are now adapting these proven models so that they also work for microplastics,” according to the professor. However, the science is still in its infancy globally and there are virtually no reference values for river catchments or other cross-ecosystem projects that could provide starting points.

In the two microplastics projects, the Jülich research group has so far modelled the water balance for the Weser and Warnow rivers and determined how the individual subspaces are drained. “This hydrological framework is in place,” says the researcher. Now he and his team are waiting for their colleagues’ results regarding the samples. “The analyses are still ongoing,” says Wendland. He assumes that, based on the data, his research group will be able to start developing the basic microplastic transfer functions in autumn. These functions are to provide information on where the microplastics come from. “We are trying to transfer the quantity found at certain measuring stations in the Weser and Warnow rivers to the area behind the catchment area, so to speak,” the scientist explains and adds: “We will then see on which scale, in which subspaces and via which discharge units relevant amounts of microplastics reach the river courses.”
The results could provide first indications for recommended actions. “There is still a long way to go, but at least we succeeded in taking a first step – and this the hardest, as is well known,” Wendland sums up.

About the projects

Contact for the subprojects in Jülich:

Prof. Dr Frank Wendland
Forschungszentrum Jülich
Institute of Bio- and Geosciences (IBG)
IBG-3: Agrosphere
52425 Jülich
Tel.: +49 2461 61 3165

The Federal Ministry of Education and Research (BMBF) has been funding and will continue to fund both projects under the FONA programme (Research for Sustainable Development) from 1 September 2017 until 31 August 2020.

PLAWES – an overview

("Contamination of Microplastics in the Model System Weser – Wadden Sea National Park: a Cross-ecosystem Approach")
In the PLAWES project, the microplastic input into the North Sea is modelled for the river catchment of the Weser, that is, for a large and hydrologically heterogeneous catchment area with several large conurbations inland as well as different landscape structures and forms of land use. This project is coordinated by the University of Bayreuth and the Alfred Wegener Institute (AWI Helgoland). Other project partners besides Forschungszentrum Jülich are the Goethe University Frankfurt, the University of Oldenburg and the Lower Saxon State Department for Waterway, Coastal and Nature Conservation (NLWKN).

Microcatch_Balt – an overview

Investigation of Sinks and Sources of Microplastics from a Typical Catchment Area to the Open Baltic Sea

In the MikroCatch_Balt project, the microplastic inputs into the Baltic Sea are modelled for the catchment of the river Warnow, that is, for a predominantly rural, small and hydrologically homogeneous catchment area with a large settlement in the estuary area (Rostock). This project is coordinated by the Institute for Baltic Sea Research (IOW) in Warnemünde. Other project partners besides Forschungszentrum Jülich are Thünen Institute in Braunschweig (TI), Leibniz Institute of Polymer Research Dresden (IPF) and Fraunhofer Institute for Computer Graphics Research in Rostock (FhIGD).

Katja Lüers