Microplastics are pervasive in the environment and often so small they can’t be seen with the naked eye. Removing them has been a big challenge, but recent research finds that water hyacinths can be effective at remediating microplastic from aquatic environments.
Native to South America, water hyacinth (Eichhornia crassipes) has become invasive in waterways across the globe. It’s known for quickly forming dense mats that clog waterways and harm native species, and municipalities have launched campaigns to eradicate the plant also known as “water cancer” in parts of the Middle East.
Despite its reputation as a nuisance, water hyacinth has been shown to clean polluted water, effectively removing agricultural runoff and heavy metals.
Previous studies have shown that water hyacinth can also absorb microplastic, but less well-understood is how they do it and why the plants aren’t harmed in the process. The new study from China sheds light on both questions.
Researchers collected water hyacinths from a river near Shanghai and cultivated them in a greenhouse. They placed seven plants in clean water as a control group, and another seven exposed to a concentration of 50 milligrams per liter of microplastic particles in water, designed to mimic heavily polluted water “hotspots.”
Within 48 hours, plants in the latter group removed 55-69% of the polystyrene microplastic particles present. After five days, they removed as much as 78% of the pollution.
“The plant provides excellent nature-based solutions for enhancing water quality,” Luxon Nhamo, research manager with the Water Research Commission in Johannesburg, South Africa, who wasn’t involved in the study, told Mongabay by email.
The study’s authors also tracked the plants’ health for 14 days and found no significant harm from microplastic exposure. Similar studies on other plants, including cucumber, duckweed and rice, have found that microplastic can significantly inhibit growth, photosynthesis and overall plant health.
In the new study, the vast majority of the microplastics were concentrated on the root caps of the plants, a protective structure on the tip of the plant’s roots. A smaller amount was observed in the roots themselves, and even less was found in the stem. No plastic was detected in the leaves.
The researchers found that the small amount of plastic that did enter the stems was blocked from going to the leaves by the water hyacinth’s vascular ring, a structure that transports water and nutrients through the plants. While the tissue outside the ring, which connects to the roots, had high levels of microplastic, the tissue inside the ring, which connects to the leaves, had no plastic, the researchers found.
That’s significant because it means that the uncontaminated leaves can “be harvested and the biomass can be used in the generation of biogas and can be mixed with other nutrients to become livestock feed,” Nhamo said, adding that this potentially turns a problem plant into a powerful environmental ally.
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Previously Published on news.mongabay with Creative Commons Attribution
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