Where does most of the microplastics come from? Drinking straws, disposable dishes and bags are hotly debated politically, but the abrasion of car tires is far more problematic.
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In total, around 100,000 tons of microplastics are produced in Germany every year. They have Federal Institutes for Hydrology and for Road creatures recently extrapolated. The tiny plastic particles go almost anywhere. Not only in the water, but also in the air and the ground. Science still knows very little about how microplastics, especially from tire wear, affect plants, animals and people.
Natalie Orlowski, Assistant Professor for Hydrology at the University of Freiburg, already did a small research project with students three years ago here at the Dreisam. “We took water samples, which were then purified in the laboratory and examined using a light microscope,” she says.
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Natalie Orlowski has investigated whether the water in the Dreisam is contaminated with microplastics and found what she was looking for.
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Microplastic swims in Freiburg’s Dreisam
The researchers found out that the Dreisam is contaminated with microplastics. The same applies, by the way, according to information from State Institute for the Environment also for the Rhine, the Danube and their tributaries. They would have found plastic beads from cosmetics, for example Plastic fibers from fleece jacketssays Orlowski. But also tire wear. And according to the hydrologist, tire wear is the largest source of microplastics in water in Germany.
More tire wear in the water after rain
Orlowski’s water analysis highlights an otherwise invisible problem. One that is being increasingly researched internationally – with some worrying initial results: For example, it was recently shown that masses of salmon died near Seattle from the conversion product of a chemical that was found in tire abrasion and washed into the river by the rain. In the Dreisam, too, Orlowsi says, more abrasion was measurable after rainfall than usual. What was the reason?
The scientist points to a drain in the concrete of the Ochsenbrücke, a few meters above her head. The tire wear is washed off the road in the rain and then flushed directly and unfiltered into the Dreisam via the drain, according to Orlowski. Similar direct discharges were also built for the wastewater of the entire B31 – customary and permissible in the 1960s.
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The Dreisam is used by the people of Freiburg as a local recreation area. But the rain also flushes tire abrasion into the supposedly clean water.
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picture alliance / dpa | Philipp von Ditfurth (archive image)
Tire wear is harmful to people and nature
Hans-Peter Grossart can explain why tire wear is a problem. At least as well as you can explain that for all open research questions. Grossart is a professor for Water ecology and biodiversity at the University of Potsdam and researches on Leibniz Institute for Aquatic Ecology. Even today, he says, one has to assume that tire wear has similar negative consequences as other types of microplastic. And these are some:
“We know, for example, that microplastics are inhaled as fine dust and can lead to chronic infections in the lungs. These are very serious adverse effects on human health. In addition, microplastics have been shown to reduce the germination capacity of plants and also the reproductive capacity of animals . “
Microplastics have the property of attracting pollutants from the environment – carcinogenic or mutagenic chemicals, for example – and practically taking them piggyback. This is especially true for tire wear. This is because substances that are potentially harmful to the environment and health are often added to the tire rubber during production. “The bad thing is that microplastics can stay in the environment for centuries, making them a permanent hazard,” says Grossart.
Special filters in gullies and cleverly switched traffic lights
Experts like him therefore demand that tire wear must be reduced as a matter of urgency. To do this, a lot of adjusting screws would have to be turned. Possible starting points would be: special filters in gullies for rainwater from the road and cleverly switched traffic lights without constant, abrasion-rich braking and restarting.
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When a car brakes heavily, tire wear occurs. It is often washed into rivers with the rain.
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IMAGO / mhphoto (symbol image)
And what can each and every individual do? Moritz Mottschall from the Berlin branch of the Freiburg Oeko-Institut has put together tips: “It may sound banal, but car-driving consumers can reduce their tire wear by leaving the car parked more often.” If you don’t want to or can’t do that, you should drive with as much foresight as possible, i.e. avoid high-abrasion braking and acceleration. It is also important to check the tire pressure regularly and not to use winter tires for too long, according to Mottschall.
Special probe for microplastic analysis
Back to the Dreisam. Something is happening there: The city of Freiburg has meanwhile converted a large part of the B31 and some bridges and installed rainwater purification systems. And the rest will soon be retrofitted too – including the Ochsenbrücke. And Natalie Orlowski? She is currently developing a portable special probe for microplastic analysis directly in water with industrial partners.
“A camera is attached to the probe. It takes high-resolution images, which are then evaluated by an artificial intelligence and can then be demonstrated using standard samples which microplastic fractions – such as fibers or tire abrasion – are in the water and in what concentrations . “
Orlowski says the probe is intended to replace costly laboratory tests and can be used in sewage treatment plants, for example. In the best case scenario, it would help to understand even faster and more precisely how big the particle problem is in our waters – and above all: which countermeasure works and how well.
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