How Much Microplastic Does the City of Jena Discharge Into the Saale? A Young Scientist and Three High School Students Set Out to Find Out

Three high school students wanted to know how much microplastic from Jena ends up in the Saale River. Together with researcher Julia Böke, they tackled the question using precise measurement techniques, filtering thousands of liters of river water and analyzing the collected particles in the lab. Their findings are not only relevant for their school project but also for broader scientific research.

It all started with a newspaper article, in which doctoral researcher Julia Böke presented her work on analyzing microplastics. For Sidonie Titjen, Lilli Sonnenkalb, and Tabea Kreher, three students from Grete Unrein Integrated Comprehensive School, it was a real “aha” moment. “We thought it was exciting that there is a researcher in Jena who works specifically on this topic,” they recall. They decided to make the question of whether – and to what extent – the city of Jena contributes to microplastic pollution in the Saale the focus of their senior research project. Julia Böke helped them take a scientific approach to the topic.

Partnering With the Fire Department

Measuring microplastic in a river is no easy task – a small test tube of water wouldn’t be enough. Microplastic particles are tiny and present in low concentrations. The students found between 117 and 200 microplastic particles per liter of Saale water – roughly the equivalent of a tablespoon of fine sand dissolved in a full bathtub. To get enough particles for a reliable analysis, they needed a much larger water sample.

That is where the Jena Volunteer Fire Department stepped in. Using their high-powered hoses, they helped pump 6,000 liters of water at two locations across different seasons –eight times in total. The water was then filtered using fire department pumps, a method that allowed for a high sample volume and provided a solid foundation for meaningful results.

In the Lab: Making ­Microplastics Visible

Back in the lab, the real detective work began. The students separated microplastic particles from mineral components like sand, dried the remaining material, and analyzed it using a specialized laser-based spectroscopy method (LDIR). PD Dr. Christoph Krafft from Leibniz IPHT explained how the technology works: LDIR combines infrared detection with lasers, enabling precise identification of plastic particles.

The students observed seasonal and location-based variations, which could point to sources like tire abrasion or rainfall events. While their results are not yet conclusive, they offer an intriguing starting point. “I didn’t expect to see clear differences between the seasons,” said Tabea Kreher. “And I was surprised that we found so many particles in the first place. The whole process was really exciting!”

Science Meets School – A Win-Win for Both Sides

As a doctoral researcher at Leibniz IPHT, Julia Böke joined the EU project MonPLAS to develop new methods for microplastic analysis. She explores ways to combine spectroscopic techniques to improve plastic particle detection in environmental and food samples.

In the lab, Böke uses Optical Photothermal Infrared Spectroscopy (OPTIR) – a method that merges infrared and Raman spectroscopy in a single measurement step. This technique enables two-dimensional identification of plastics, surpassing the capabilities of traditional methods. She compares different techniques for their reliability and automation potential –an important step toward making microplastic detection more precise and standardized.

The project was primarily one thing: an educational process. For the students, science became tangible – from formulating a research question to conducting structured analysis. The project was also valuable for Julia Böke. “The knowledge I’ve gathered on microplastic sample preparation had to be presented in a way that the students could understand and apply the methods,” says Böke. “In the process, I also learned how to break down complex processes.”

A School Project with Lasting Impact

Over the course of the project, the students took water samples from two locations across four seasons, analyzing them with Julia Böke in the lab. These samples can now serve as reference material for developing or validating new measurement methods at Leibniz IPHT. “This is a great example of how educational projects can generate valuable data for scientific research,” Böke says.

The three students gained firsthand experience in real scientific work – and at the same time, they contributed data that will be useful for ongoing research at Leibniz IPHT.

For Julia Böke, the project highlighted the mutual benefits of collaboration between schools and research institutions. “It was fascinating to see how their questions evolved throughout the project – from ‘How do we collect samples?’ to ‘What do our results mean?’,” she says. “This kind of research shows how complex environmental issues are – and why it’s so important to approach them systematically.”