When rainwater flows over urban surfaces - roads, roofs, recreational areas - it carries multiple pollutants. Among the most prominent are heavy metals and tyre wear compounds, detected in high concentrations. If this water is not treated, pollutants are eventually discharged into aquatic ecosystems and may impair the growth, reproduction or vital functions of organisms, as well as affect the functioning of freshwater ecosystems connected to urban drainage networks.
These are some of the main conclusions of the CityPoll (2023-2025) project, promoted by the University of Barcelona, the Catalan Institute for Water Research (ICRA) and the University of the Basque Country (EHU) with the aim of analysing the impact of urban runoff on biodiversity and the functions of natural ecosystems.
The project, conducted in the cities of Girona, Viladecans and Donostia-San Sebastián, has found large differences between areas of the same city and also between rainfall events, which makes it difficult to detect and analyse urban runoff. The efficiency of green filters as mitigation structures for these impacts has also been evaluated. Based on the results obtained, the project proposes to use diphenylguanidine, a chemical marker associated with tyre wear, as an indicator of urban runoff pollution.
The study also indicates that the complete separation of stormwater and urban wastewater collection networks is essential to minimise the impact of pollutants. It also emphasizes the need to promote nature-based mitigation structures as urban runoff water treatment measures.
As experts point out, in a context of climate change - with less frequent but more intense rainfall - the effect of urban runoff pollution may be aggravated and receiving aquatic ecosystems can be further affected. It is therefore necessary to minimize its impact by adapting urban systems.
CityPoll is supported by the Ministry of Science, Innovation and Universities and Next Generation EU funds through the Recovery, Transformation and Resilience Plan.
You can watch the video of the CityPoll project.
