Roofs filled roofs or green roofs are not only pretty. It was shown that they reduce the urban “heat island effects”, reduce energy costs in buildings, contain rainwater outflows and deliver safe ports for local species.
And now a group of researchers from Tongji University in China has uncovered an unexpected advantage: green roofs are also effective when recording microplastics.
Microplastics are small plastic fragments that are often smaller than 5 millimeters in size. They are increasingly in the environment – in the ground, in water and in the air – and even in our own bodies.
With the confirmation that green roofs can filter contamination and excess nutrients, the researchers also determined whether they can also filter microplastics in urban environments.
“These natural-based solutions can offer unexpected co-genes for the mitigating air pollution in densely built environments,” the researcher Shuiping Cheng told anthropocene.
To carry out their study, Cheng and his colleagues set up an “empty” roof, a green roof module “without plants”, a green roof full Rhodiola Rosea (a multi -year flowering plant) and a green roof Sedum (a sun -loving succulent).
Both Rhodiola Rosea And Sedum Are Plants together on the roof in Shanghai, China, where the study took place.
After the roofs had been prepared, the researchers created their own “artificial” weather simulations with precipitation generators.
“Before the start of the experiments, every green roof module was subjected to a 30-day stabilization period in which they were watered down with tap water every four to five days,” wrote Cheng and his team in their study, which was published in the Journal Communication Earth & Environment.
“Subsequently, the precipitation events simulated were introduced. The study used four types of precipitation events (easy, moderate, severe and radiant) classified by intensity … each event was repeated three times and lasted one to two hours per feeding.”
In the end, the researchers found that the green roofs had grasped 97.5% of the microplastic particles that fell in a “light” precipitation generator. Surprisingly, they found that it was the soil, more than the plants that retained and filtered the microplastics.
“This study shows the promising potential of green roofs in the mitigating microplastic pollution in urban areas on coasts,” concluded the researchers.
“Green roofs showed an impressive average impact efficiency of more than 97.5% for taking microplastics from atmospheric deposit.”
Shanghai currently has 3.56 million square meters.
Although this number is microscopic compared to the number of roofs without Plants in the city that researchers estimated that even the present number of green roofs could record 56.2 tons of microplastic particles annually.
Nevertheless, the researchers of Tongji University approached with caution of their conclusion.
“It is important to note that this estimate is based on controlled experimental conditions and does not generally represent the efficiency of all green roofs in Shanghai,” emphasized Cheng and his team in their study.
“In practice, the performance of the green roof can vary due to differences in the roof pitch, the substrate composition, plant selection and local climate conditions.”
Despite endless combinations of “temporal variations” and “seasonal weather patterns”, the study could have more comprehensive effects – not only for green roofs throughout Shanghai, but on green roofs around the world.
“A key in the next step is to validate these results under real conditions on complete green roofs,” Complete Cheng. “We actively examine the opportunity to carry out long -term field studies in order to better understand microplastic storage and dynamics over time.”
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Header image over the open -air system (CC0 1.0) / Stock cake (PDM 1.0)))