What’s floating in the Rhine will one day end up in the sea
Kilometer marker “691” along the River Rhine in Cologne marks journey’s end. Here, the association known as K.R.A.K.E. has installed a stationary waste trap. The floating platform complete with catch basket ensures that any trash being carried along the river gets stuck. “We want to gather data on how much macroplastic and other trash is floating in the Rhine,” says Katja Höreth from the Department of Geography, who is involved in the analysis. “That’s why we’re sorting the trash precisely and are classifying it by how much plastic, wood, glass and so on it contains.” The waste trap is emptied every two weeks.
Garbage fished out of the Rhine will not end up in the sea further down the line. The project only began in September, so no data is available yet. “But we’re realizing that we’re finding a wide range of discarded products, such as balloons, shoes, toys, plastic bottles and even the odd message in a bottle,” says Leandra Hamann, a doctoral student at the Institute of Evolutionary Biology and Ecology, who is lending her expertise in her spare time. “For us, the fact that the trap is actually catching waste and we have a lot of volunteers to help us sort it is an excellent start.”
The team from K.R.A.K.E. takes a boat up to the trap, empties the catch baskets and brings the trash ashore, where the helpers sort the individual elements and categorize them according to their material and type so that they can go on to record their size and weight. There are around 200 different product categories, which are analyzed alongside environmental data such as water level, temperature and precipitation. “This tells us a bit about quantities, sizes, product groups and materials,” Höreth explains. The results will go on to inform potential solutions for ensuring that less trash ends up in the Rhine in future. For instance, it could be that we need more trash cans or more extensive recycling and returnable deposit schemes. Alternatively, new biodegradable materials might offer a solution. It would be fantastic if the project were also to serve as a model for other stretches of water.
Making microplastics filters inspired by fish
Each of us is responsible for an estimated 75 grams of microplastic fibers entering the sewage system through our washing machines every year. Some of this plastic then gets into the environment. A team from the Institute of Evolutionary Biology and Ecology has partnered with the Fraunhofer Institute for Environmental, Safety and Energy Technology UMSICHT and the company Hengst to investigate whether a bionic filter can be used to contain these fibers.
“We started by taking a look at how the filters work in five species of fish,” says Prof. Dr. Alexander Blanke. “This enabled us to build models to try out in washing machines on our test benches.” These fish separate out food particles from the surrounding water by building up a concentration of particles on the filter and transporting them away at the same time, meaning that the filter does not clog so quickly. However, different species apply the principle in different ways.
To explore this further, the researchers used microscopes, video recordings and microtomography scans to study the fish. Models of the fish filter were then developed and printed in 3D based on their data. Simulations and experiments in the flow tank revealed how water flows through the fish’s trap apparatus in their gills. The results revealed that the separation principle is new and is not yet state of the art. It is yet another example of how bionics is paving the way for approaches that are beyond the scope of conventional technical solutions. Subsequent experiments on test benches that approximated real-life conditions have shown that a filter modeled on that used by the fish retains over 80 per cent of the test fibers, which are 2 mm long.
Conceivably, this filter principle could also be used in other places where microplastics enter the environment, such as in roadside drains or where wastewater is discharged into rivers. “The fish showed us that their filter system is more complex than we first thought,” Leandra Hamann says. “But it’s fun to keep on working on the puzzle and trying to solve a widespread environmental problem.”
First it gets into the soil, then it gets into your food
“Invisible” plastic known as nanoplastics, no more than several hundred nanometers in diameter, can be found not only in the oceans but also in our soil. “Across the board, we still know very little about this tiny plastic, but initial studies suggest that it’s highly dangerous, perhaps even more so than other kinds,” says Dr. Melanie Braun from the Institute of Crop Science and Resource Conservation (INRES). As a soil scientist, she works to make the invisible visible. “There are signs that plastics get into the soil as a result of agricultural activity, such as applying sewage sludge and compost or using wastewater for irrigation,” she explains. “However, we’ve also been able to show in several studies that littering plays a key role too. This includes food packets that have been thrown away in the countryside, which is particularly frustrating because it’s something that’s easily avoided.”
The question of how much the individual sources of plastic contribute to the contamination of the soil with such tiny nanoplastics needs an urgent answer, she says, because these plastic particles can potentially be absorbed by plants and thus get into the food chain.
But how much plastic is there in the soil? The question has always been a difficult one to answer because there has never yet been a way to measure these kinds of small bits of plastic in the soil. Hoping to change that, Braun and her team are currently developing a new, innovative analytical technique. This uses special marking methods that, in the coming years, will make it possible first of all to identify various types of plastic and then to determine their quantity. Melanie Braun has already been awarded a research prize from the Transdisciplinary Research Area (TRA) Sustainable Futures, which will help her get her project off the ground. It is geared toward supplying the first-ever data on soil contamination by nanoplastics, which can then be fed into forecasts, among other things.
Do nanoplastics affect the brain?
When we eat, we all absorb tiny nanoplastic particles that have found their way into our food via the environment. However, not much is yet known about what damage this can cause. Prof. Dr. Elvira Mass from the LIMES Institute is attempting to find out more about it. The developmental biologist and her team suspect that nanoplastics can damage certain immune cells, known as macrophages, from an early stage—while we are still an embryo, in fact. This can cause pathological changes in our developing organs.
Macrophages are scavenger cells that are present in almost every tissue in our body. As part of our innate immune system, they play an important part in our body’s own defenses, forming the first line of defense against pathogens by ingesting them and breaking them down into their component parts (“antigens”). It is also extremely likely that resident macrophages make a vital contribution to how our organs develop. Among other things, Elvira Mass and her team are investigating how macrophages influence brain development. Specifically, they are trying to find out whether macrophages consume nanoplastics in an embryo and, if so, whether this can cause neurological disorders in the long term.
“We believe that these long-lived macrophages are the ‘messengers,’ if you like, that pass the message down from one generation to the next,” Mass explains. During experimental trials involving microplastics and mice, her and her team have already noticed changes in their brains and livers that enable them to infer the activation of macrophages. In the long term, this could lead to neurogenerative or metabolic diseases.
“With our research, we want to understand the molecular biology processes behind it, i.e. what happens when plastic gets into our bodies,” says Mass, who is also a member of the Transdisciplinary Research Area Life and Health and the ImmunoSensation2 Cluster of Excellence. “We want to use our basic research to show how dangerous plastic can really be and, ideally, prompt a rethink some day,” she emphasizes.
