New research from Tongji University in Shanghai reveals that green roofs can act as powerful filters for microplastics washed down by urban rainfall. In lab trials using rooftop models planted with Rhodiola rosea and Sedum lineare, the combination of vegetation and soil trapped up to 97.5% of plastic particles. Soil layers absorbed the majority, while plant surfaces added an extra layer of capture, with fragments being retained more effectively than fibers. The findings highlight how living infrastructure can provide an unexpected defense against plastic pollution in cities.
When scaled up, the results show major environmental potential. Shanghai’s 3.56 million square meters of existing green roofs could prevent around 56.2 metric tons of microplastics from entering waterways each year. Expanding coverage would increase this capacity significantly. Researchers caution that long-term performance may vary depending on soil type, plant selection, rainfall patterns, and wind conditions, but the study strengthens the case for green roofs as not only cooling and biodiversity tools, but also as frontline filters in the fight against microplastic pollution. More