Forest trees absorb nanoplastics, research finds

A laboratory study shows that forest trees absorb plastic particles through their roots and transport them to the aerial tissues of the plant.

A research study by the Swiss Federal Institute for Snow and Landscape Research WSL published in iForest found evidence that forests can absorb plastic items

The impact of this situation on the food chain is not yet clear.

It has been estimated that humans ingest about five grams of plastic each week, which is equivalent to about half a bowl of rice, according to Reuters. However, this new data could change these calculations.

Plastic waste now pollutes all ecosystems on the planet, even those located far from civilization. Increasing the use of single-use plastics to reduce Covid-19 infection rates alone has generated around 8.4 million tonnes of plastic waste generated by 193 countries since the start of the pandemic.

Plastic is extremely slow to break down. According to the German Union for Nature and Biodiversity Conservation, a plastic bag takes 10 to 20 years, a plastic straw 200 years and a plastic bottle 450 years to decompose. During decomposition, these objects are ground into smaller and smaller particles over time. They are called microplastics (particles smaller than 5 mm) or nanoplastics (particles smaller than 1000 nm).

Nanoplastic particles in particular pose a potential hazard to living organisms, as they can absorb the particles. The particles accumulate in the tissues and there are indications that they can cause chronic inflammation.

Only a handful of studies have so far been conducted to determine whether plants take up nanoplastics via their roots, with no studies looking at forest trees. Previous studies on onions indicate that nanoplastics can damage root cells and thus inhibit root growth.

The research team led by Arthur Gessler from the WSL Ecosystem Ecology Group investigated the uptake of nanoplastics in three common species of forest trees, namely birch, spruce and sessile oak. The researchers labeled polystyrene nanoparticles measuring 28 nm with the heavy carbon variant 13C and added them to water, which was then administered to the lower roots of tree seedlings.

Using this method, the team was able to detect 13C in plant tissues after one to four days, mainly in the parts of the roots in direct contact with water mixed with nanoplastics. However, small amounts of nanoplastics also accumulated in the upper parts of the roots and in the leaves. In birch, which consumes large volumes of water, significant amounts of nanoplastics are also deposited in the trunk.

The researchers’ theory is that the nanoparticles are transported via the xylem, the vessels that move water around the plant.

Although the amount of plastic absorbed by the analyzed trees is small, it could still have serious repercussions on the global food chain.

“If trees are exposed to these concentrations for years, we can certainly expect significant volumes to be transported and consequently accumulate in the leaves, trunk and branches,” says Gessler.

The team is currently conducting further experiments to determine whether nanoplastics interfere with photosynthesis, specifically the photochemical reaction of seedlings, and therefore affect plant nutrition. Gessler believes that only by banning single-use plastic packaging wherever possible and recycling it whenever possible can we solve the plastic problem.

Sign up for the E&T News email to get great stories like this delivered to your inbox every day.