Plastic waste in the Danube consists mainly of packaging and PET bottles
An international team of experts involved in the PlasticFreeDanube project mapped the degree of pollution of the Danube and its banks with plastic waste. It focused on the section between Vienna and the Gabčíkovo hydroelectric power plant. The project researchers were also scientists from the Polymer Institute SAS, who investigated the extent to which plastics pollute the aquatic environment. The results of their experiments showed that polystyrene foam waste decomposes rapidly into microparticles in water.
Experts and volunteers together collected approximately 2,000 kilograms of plastic waste during the lifetime of the project, which consisted mainly of packaging materials from food and sanitary ware, PET bottles or plastic waste from households, as well as construction waste. The researchers subjected the waste samples to several analyses in the laboratories of the Polymer Institute SAS.
"We carried out the so-called washing experiment, in which we placed plastic samples in glass jars with ultrapure water and allowed them to shake for a month at 560 rpm. We subsequently tested the discharged water for the presence of organic substances and metals,” Mária Omastová from the Polymer Institute SAS explained the course of one of the experiments and added: "Concentrations of detected organic substances were below the limit values. However, in the case of a sample from a PET bottle, we detected an increased concentration of antimony, approximately 200 μg/l, while the limit for drinking water is 5 μg/l."
In addition, the scientists found out how the concentrations of various substances in the new PET bottle, which they immersed in water from the Danube, change. "Optical microscopy showed us that after 259 days, the solid particles present in the Danube water clearly adhered to the surface of a piece of PET bottle. The volume of antimony in the water decreased, indicating that it had adsorbed to the plastic surface. However, the value found was still slightly above the limit for water quality,” added the chemist.
The scientists also studied the extent to which various polymeric materials break down into microparticles. "One of the most important findings was the finding that even relatively stable polymers such as polyethylene terephthalates (PET) defragment and form several micron-sized particles. Concurrently, we found that polystyrene foam samples released more microplastic particles at the same time than PET bottle samples. Therefore, if possible, we should try not to leave any plastic waste behind,” emphasised the project researcher Matej Mičušík from the Polymer Institute SAS in conclusion.
The PlasticFreeDanube project lasted from October 2017 to March 2021. It was funded by the European Union within the INTERREG SK-AT program. It was implemented by the University of Natural Resources and Life Sciences (BOKU) in Vienna, Viadonau, RepaNet, n.o., the Polymer Institute SAS and the Donau-Auen National Park.