Green Roofs Proven to Capture Nearly All Microplastics from Rainwater

Scientists at Tongji University and the Shanghai Academy of Landscape Architecture Science and Planning demonstrated how green roofs can capture nearly all microplastics from rainwater. The researchers described their findings in Communications Earth & Environment, pointing out how roof-mounted plant systems could be a very effective barrier to airborne microplastic pollution.

To conduct the research, the researchers created a controlled laboratory model of a green roof. The model roof was comprised of a thin layer of soil that is supported by two plant species known to inhabit rooftops in Shanghai. Microplastic particles were released into air above the setup at urban environment-representative concentrations. Simulated rain was used to investigate the accumulation and filtration of microplastics through both the plant canopy and soil.

Results showed that the green roof system filtered out around 97.5% of rainwater-transported microplastics. Most of the filtered microplastics ended up in the soil layer, but leaf cover also played a role in filtration. Fragment-shaped microplastics were trapped more efficiently than fibre-shaped microplastics, and microplastic trapping improved slightly with increased rainfall intensity.

These observations indicate that green roofs can prove to be a useful component in mitigating microplastic pollution in urban areas. When rainwater rains down on the surface from air that is laden with microplastics, particles are usually deposited on surfaces and drained into sewerage channels and find their way into water bodies. With green roofs, however, plants and topsoil cover filter most particles from running onto the urban surface.

Although green roofs are already proven to be beneficial in aspects like better insulation of buildings and air pollution alleviation, this latest study adds prevention of microplastics to the list of benefits. While these are up for grabs, Shanghai currently only has 3.56 million square metres of greenspace on rooftops. The city can potentially reap an estimated 56.2 metric tonnes of microplastics each year if all rooftops were turned into a green roof, according to the study.

It also explored the filtering mechanism. When the soil was dry, larger flow channels formed, facilitating rapid transport of rainwater with microplastics into the soil. When soil was wet and swelled, smaller channels formed, reducing infiltration and enhancing particle trapping capacity of the soil. This finding provides an insight into how varying weather and wetness can influence the efficiency of microplastic trapping.

Microplastics have increasingly become accepted as a major environmental problem, and now are present in the air, soil, water, and even human tissues. While no long-term health effects of exposure to microplastics have been determined, studies are still discovering their prevalence and means of dispersal.

Green roof infrastructure is proposed by the authors as it might be integrated into the urban green environment management system. In addition to energy saving and biodiversity, the additional advantage of microplastic trapping might be sufficient grounds for increased investment in and advocacy for policy intervention for green roof development in urban areas worldwide.

This study provides real-world proof that green roofs not only stay green but are capable of being real answers for future pollution issues. Because cities are under increasing pressure to address air and water quality issues, the installation of infrastructure such as green roofs may allow cities to offset present and future environmental strain.

Source
© 2025 Science X Network | Study: Jianshi Huang et al., Communications Earth & Environment (2025), DOI: 10.1038/s43247-025-02407-w
Written by Bob Yirka | Edited by Lisa Lock | Reviewed by Robert Egana