Public awareness is growing around the subject of microplastics as harmful pollutants. To date, this problematic source of pollution has primarily been investigated in bodies of water. However, recent studies are beginning to focus more on the presence and various sources of microplastics in soil. Led by biology professor Matthias C. Rillig, a research team from Freie Universität Berlin has now demonstrated that spray paints used for graffiti cause an extensive amount of microplastic pollution in the surrounding soil – the first study of its kind to do so, with previous work on paints having focused on aquatic environments. Analyzing soil samples taken from near the famous graffiti walls in Berlin’s Mauerpark, scientists recorded hundreds of thousands of microplastic particles per kilogram of dry soil. This is the highest concentration of microplastics that has ever been reported in scientific literature. The researchers also suspect that similarly high amounts of microplastics would be found in comparable samples taken from sites exposed to industrial paints.

“Our results provide the first indications that spray painting, a technique with applications ranging from industry to art, leaves behind an unprecedented amount of microplastics in the soil,” says biologist Prof. Dr. Matthias C. Rillig. The aim of his team’s research project was to find out whether microplastics are transferred into the soil through spray paint and, if so, to what extent. To do so, the researchers first had to develop a new method for distinguishing between microplastic particles derived from spray paints and microplastic particles from other sources. They did so by adapting the standard procedure for demonstrating the existence of microplastics. This was necessary because microplastics from spray painting are denser than other microplastics. Had the researchers not adapted the procedure, the particles collected as part of the study would have run the risk of not being detected because part of the traditional extraction process relies on the low density of the microplastics. Soil samples were taken from various locations and soil depths at Berlin’s Mauerpark and analyzed using the new extraction procedure. The results showed that microplastics from graffiti were present in the soil – sometimes in very high concentrations. The numbers of particles that were found are more than one order of magnitude greater than other concentrations found in polluted soils.

“Given the large amount of paint microplastic particles we found in this case study, we strongly suggest that the ecological effects of paint microplastics in soil be a focus of future studies,” says Rillig. The findings also demonstrate that spray painting and similar industrial processes should be regulated in areas where this is not yet the case. The team recommends that spray painting of larger structures that cannot be carried out in enclosed spaces be monitored more closely in order to reduce the risk of environmental contamination. “What is more, we are yet to fully understand the effects that spray paints and other paints have on organisms living in the soil. This is an area that will require more research in the future,” adds Rillig.

Further Information

Contact

• Prof. Dr. Matthias C. Rillig, Ecology of Plants, Institute of Biology, Freie Universität Berlin, Altensteinstraße 6, 14195 Berlin; Email: rillig@zedat.fu-berlin.de

Publication

https://link.springer.com/article/10.1007/s10311-022-01500-2

Rillig Lab Website

https://rilliglab.org/