Microplastics in Swiss Nature Reserves

It is one of the first studies on the occurrence of microplastics in soils: Scientists from the University of Bern have examined floodplain soils in Swiss nature reserves for microplastics — and found them.

They estimate that approximately 53 tonnes of microplastics are present in the top five centimetres of floodplain soils. Even many soils in remote mountain areas are contaminated with microplastics.

Images of microplastic-polluted oceans and inland lakes are nothing new. Far less known, however, is that soils are also contaminated with microplastics. The problem: until now, methods for measuring and quantifying the tiniest plastic particles in soil were lacking. Researchers at the Geographical Institute of the University of Bern therefore developed a new method and, for the first time, examined 29 floodplain soils across the whole of Switzerland, from Geneva to Graubünden.

Almost all nature reserves affected

«Although the sites are located in nature reserves, microplastics were found in 90 percent of the soils,» says Moritz Bigalke, one of the co-authors of the study from the Geographical Institute of the University of Bern. Even in many remote mountain areas, microplastic particles were detected — an indication that microplastics are transported through the air. The researchers estimate the quantity of microplastics in the top 5 cm of Swiss floodplain soils at 53 tonnes. These findings were recently published in the journal «Environmental Science and Technology».

The highest concentrations of microplastics occur where larger plastic waste has been found in the soil. In these cases, microplastics likely form through the breakdown of larger plastic pieces. However, microplastics are also found in many soils that contain no larger plastic pieces. This microplastic is extremely fine (under 0.5 mm in diameter), differs in its composition from the larger plastic waste, and is even present in some remote mountain areas. In addition, the researchers were able to demonstrate a link between the population in a river's catchment area and the concentration of microplastics in the soil: the more people living in the area, the more heavily contaminated the soils.

«These findings are alarming,» explains co-author Michael Scheurer. Because: «New studies suggest that microplastics in the soil can, for example, kill earthworms.» Since earthworms perform important functions in the soil, this could also impair soil fertility.

Effects on the food chain unknown

The precise effects on plants and soil fertility, and how microplastics are transported via crops into the human food chain, remain largely unresearched. Projections suggest that the amount of microplastic entering the soil each year through sewage sludge alone is greater than the amount ending up in the world's oceans. There is therefore a great need for research in this still emerging field. Moritz Bigalke says: «There is, for instance, a need for research into how microplastics affect food production and whether they can enter the food chain.» More on Environment and Nature Conservation.