Under the clouds of large metropolises, invisible pollution falls on the roofs every day. Among these particles, microplastics accumulate noise without noise, transported by air or rains. Faced with this diffuse threat, an unexpected solution is essential in the urban heights. Where mosses and sedums grow, each green roof becomes a natural trap capable of retaining these plastic fragments before they slip into water networks or do not return to float in the atmosphere.
This performance exceeds expectations. According to the study published in Communications Earth & Environment, the majority of microplastics are trapped in cultivation soil, while a significant part remains attached to the stems and leaves of the plants. In a city like Shanghai, this would represent up to 56 tonnes of filtered microplastics each year, is more than those rejected by domestic wastewater.
How a green roof intercepts microplastics
The mechanism is double. When it rains, the water runs slowly through the plants, then infiltrates the substrate. This deceleration of the flow allows plastic particles to deposit. The soil, rich in organic matter, then acts as a natural sieve. The leaves, on the other hand, capture on the surface certain volatile particles, particularly compact fragments.
In the tests conducted in Shanghai, two local plants – Rhodiola Rosea And Sedum Lineare – were chosen for their resistance and their ability to retain humidity. The analysis revealed that even the intensity of the rain plays a role. The stronger it is, the more effective the retention is. This phenomenon is explained by the progressive saturation of the soil, which slows down rapid infiltration and maximizes retention.
But everything is not ideal. Plastic fibers, more flexible and elongated, escape more easily than rigid fragments. Part of these fibers can be presented by the wind or turbulence, which slightly limits the efficiency of the device.
Towards cities capable of absorbing their own pollution
Beyond its aesthetic or climatic role, the green roof could become an urban depollution tool. If this solution was extended to the scale of large cities, it could considerably reduce the exposure of the inhabitants to microplastics. Provided, however, to avoid certain traps. Researchers alert to the use of plastics in the technical layers of the roofs themselves, such as filters or membranes. Over time, these materials can in turn fragment, relaxing new particles.
The scientific team therefore recommends opting for non -plastic materials, more durable and less likely to deteriorate. Alternatives such as coconut fiber or mineral substrates are envisaged. Other tracks emerge, such as the integration of earthworms or insects capable of degrading part of the microplastics present in the soil.
For Iflscience, this advance is part of a broader logic of sustainable development. Vegetated roofs are not content to capture pollutants, but also participate in thermal regulation, rainwater management and preservation of biodiversity in town.
With an unwavering passion for local news, Christopher leads our editorial team with integrity and dedication. With over 20 years’ experience, he is the backbone of Wouldsayso, ensuring that we stay true to our mission to inform.
