The challenge of demonstrating amounts of micro- and nano-plastics
After initial difficulties, the two began their work. First, they had to find methods with which they could detect particles of micro- and nano-plastics in plants, raising. the question which stems or shoots of the native flora to use for analyses. Taking any green plant from any field was out of the question. “It might sound simple to laymen, who might think that all one has to do is pick a random plant and look at it under the microscope to see which micro- and nano-plastic particles are to be found there. But not all plastic is the same. Car tires, for example, consist of different particles than a plastic bag. And the particles have to be detected in different ways. In addition, there are environmental influences that change the surface properties and, therefore, make detection more difficult,” says biochemist Dr. Harald Seitz. That is why they decided to use cultivated organisms that were as unaffected by the environment as possible for their experiments. They found them directly on site, at Fraunhofer IZI-BB: the algae strains from Dr. Thomas Leya. Their basic idea was to mix the algae with plastic particles of a single plastic, such as polystyrene or polyethylene, and then watch how they absorb the foreign matter.
How fluorescent markings make plastic particles visible
With the right plants and the right plastic as a basis, what remained was the question of a suitable method for detecting micro- and nano-plastics. “This is a big analytical challenge, as particles from micro- and nano-plastics have certain properties that other particles can also have,” explains Professor Susanne Baldermann. So, they started testing different methods. In order to recognize the microscopic plastic particles, it has proven useful, for example, to work with markings. In practice, this process works something like this: researchers receive plastics from a company that contain fluorescent markings. They mix these with nutrient solutions in which the algae and plants are cultivated. “We can then use special light to make the fluorescent markings visible. If we look at the algae or plants under the microscope, we see, to put it simply, small plastic pieces that shine brightly,” says Dr. Seitz.
Proving the concentration of micro-plastics? “Unfortunately, this does not work without destructive processes.”
However, the detection of micro- and nano-plastic particles is only a small part of this complex field of research. Microscopy may allow researchers to detect particles, but it does not allow them to estimate its concentration. As of the project’s current status (November 2021), fully established method to do so still remains to be found. Until then, researchers combine different approaches and models in order to “understand the means of absorption and the quantity”, as is the technical term. To estimate concentration, they use a detector, for example. “This is a specialized device that can record the concentration of the plastics. We can concretely specify that the device records, for example, polystyrene or polyethylene. But this only works with substances in a gaseous state. So, we have to heat the alga or plant with the plastic particles, which causes the plastics to decompose. But this method also has its disadvantages: “Unfortunately, it cannot be done without destructive processes. It’s a shame because then, we won’t get all the information we’d like. This includes, for example, the question of what effects the plastic particles have on the DNA and RNA of the plant. Are metabolic processes changing, for example? Are the division processes of cells slowing down?” These are questions that Seitz asks.
Plastic-free drinking water?
All in all, there is still a lot of research ahead for Dr. Seitz from Fraunhofer IZI-BB and Professor Baldermann from the IGZ. If you will, their research is still in its infancy. But at least the two are working to ensure that things start to get up and running. When the dream of plastic-free vegetables or drinking water will come true is a question of time – and of determination as well as industry’s and municipalities’ willingness to invest. “If politics and business make more efforts to support companies and our research accordingly, a period of five years is realistic, for example, for detecting and solving the issue of micro-plastics in water treatment plants,” says Dr. Seitz. With Professor Baldermann’s main focus, it becomes much more difficult to remove plastic products from food. “Unfortunately, the circumstances are a bit more complex here,” explains Professor Baldermann. “Plants for the food industry are grown in greenhouses, for example. They are covered with foil to promote quick growth. This means that you have a higher possibility of plastic absorption,” says the chemist. That is why it will probably take ten years or more before a “plastic-free” label would be realistic.
EMINA – a prime example of co-operation in the Berlin-Brandenburg metropolitan region
The collaboration between the two organizations is astonishing. This is because Dr. Seitz works at the Fraunhofer IZI-BB in the Potsdam Science Park and Professor Baldermann conducts research at the Leibniz Institute for Vegetable and Ornamental Plant Production (IGZ) in Großbeeren, south of Berlin. Although the two locations are about 30 km apart, they make an effort to exchange information regularly. Both have three employees each, who work a lot in the laboratory; there, especially, short communication channels are essential. Both benefit from very good research conditions at their locations. According to Dr. Seitz, “working in the Potsdam Science Park has many advantages. With the university, the two Max Planck institutes and the two Fraunhofer institutes, we have an excellent position in the field of natural sciences. But working together with the many research institutions in the Berlin-Brandenburg metropolitan region is also possible.” He has been working at the site since 2014 and also draws a positive conclusion when it comes to development and change: “The campus has developed very well,” says Dr. Seitz. “The station has been expanded, and there are shops and a day-care center for children. This growth also brings people into contact with other institutes, and individuals can work together quickly and positively.”