Remediation of microplastic-polluted soils could be made possible with the help of trees. Researchers from the Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) for the first time have demonstrated that birch trees absorb microplastics via their roots during the growth phase. As soils are many times more polluted with microplastics than oceans, this is good news.
Until now, only little has been known about the interaction of microplastics with greater-order terrestrial plants. New studies have displayed that microplastics are taken up in the roots of agricultural plants like wheat.
Being a part of the cutting-edge interdisciplinary project headed by Berlin-based art studio, Studio Austen, the research group from the IGB and the German Research Centre for Geosciences (GFZ) has demonstrated for the first time that longer-lived woody plants absorb and store microplastics in their tissue.
Birches are Already Being Used for Soil Remediation
Already, birch trees (Betula pendula Roth.) have been utilized to rectify contaminated land since they sequester and store industrial pollutants and heavy metals in their tissues, which later enable the colonization of microbial communities that collapse polyaromatic hydrocarbons.
This tree species’ roots tend to grow close to the soil surface, where microplastic pollution is the greatest, thereby making them a good choice for the study.
5 to 17% of the Root Sections Examined Absorbed Microplastics
The scientists labeled microplastic beads (5 to 50 μm) along with fluorescent dye and added them to the soil of potted trees. After five months, they analyzed root samples with the help of fluorescence and confocal laser scanning microscopy.
They discovered fluorescent microplastic in various sections and layers of the root system. The percentage of root sections along with microplastic particles varied from 5 to 17% in the experimental trees.
The uptake rate of microplastics and the effects on the short- and long-term health of the trees still need to be studied. But this pilot study suggests birch has real potential for long-term soil remediation solutions—including reducing the amount of microplastics in soil and possibly water.
Kat Austen, Study Lead Author and Head, Studio Austen
Kat Austen is the project coordinator for Citizen Science Project ACTION at IGB.
Study with IGB from 2018 Quantified: Pollution of Soils by Microplastics Greater Than in Oceans
On an annual basis, more than 400 million tons of plastic are produced throughout the world. It is evaluated that one-third of all plastic waste ends up in freshwaters or soils. The majority of this plastic falls apart into particles smaller than 5 mm, referred to as microplastics, and breaks down further into nanoparticles, which are below 0.1 mm in size.
Terrestrial microplastic pollution is much higher compared to marine microplastic pollution — an estimate of 4–23 times more, based on the surrounding. Sewage, for instance, is a significant factor in the distribution of microplastics. In fact, 80 to 90% of the particles contained in sewage, like garment fibers, remain in the sludge.
The majority of the sewage sludge has been incinerated in Germany. But throughout the world, it is also partly employed in fields as fertilizer. This implies that several hundreds of thousand tons of microplastics end up in the soils annually.
Also, this is the reason why the microplastic concentrations in field soil are particularly high — just as they are on roadsides because tire abrasion is another considerable source of microplastics.
Austen, K., et al. (2022) Microplastic inclusion in birch tree roots. Science of The Total Environment. doi.org/10.1016/j.scitotenv.2021.152085.