Urban roof gardens can help with removal of atmospheric pollutants at measurable, controllable rates, according to a study in the International Journal of Environment and Pollution. The research suggests that rather than simply being decorative, recreational features, such gardens can become part of an active and living environmental infrastructure.
The team report that a dynamically managed rooftop system can be established to absorb hazardous fine particulate matter from the cityscape including (PM2.5, airborne particles that are smaller than 2.5 micrometres) at a rate of about 42.5 micrograms per square metre per hour. It can also absorb nitrogen oxides (NOx, toxic combustion gases) at a rate of 15.6 micrograms per square metre per hour.
The work begins to address growing concern that conventional urban greening, typically static plantings designed for visual appeal, has limited capacity to respond to pollution or climate change. More adaptive and responsive planting, on the other hand, to construct layered plant communities in roof gardens could be functional as well as aesthetic. The team suggests that by grouping species together according to their known capacity to absorb different pollutants, it should be possible to address the problem of different contaminants in the same growing patch. They have carried out tests in an environmental chamber and found that such coordinated but mixed planting can be more effective than single-species approaches given the common mix of urban pollution.
The work also demonstrated that by using a lightweight, bioactive growing substrate containing activated carbon (pollutant absorbing) and vermiculite (for aeration and moisture retention), such planting could improve the rate of pollutant mineralisation.
Guo, R. and Xiao, Z. (2025) ‘Roof garden plant selection and ecological application: comprehensive strategies to deal with environmental pollution’, Int. J. Environment and Pollution, Vol. 75, No. 4, pp.338–360.
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