When we look at the river that flows through our city, we often think about the enjoyment it brings and the water it provides. However, a river is much more than that: it is the home to thousands of species of plants and animals, all coexisting in balance, and it is also a provider of ecosystem services (e.g., hydrological cycle regulation, floods mitigation, or self-purification). But when this ecosystem faces constant pollution, that balance is disrupted, and we lose these services.
One of these pollution sources occurs after a heavy rainfall, when the water running through the city streets carries away more than what we see at first glance. This flow, traveling from the sidewalks in industrial, urban, and garden areas, to the rivers, collects a mixture of chemicals that affects aquatic ecosystems.
Within this mixture, there are some pollutants whose concentrations have legal limits set to protect ecosystems. However, in the European Union, only 70 substances are regulated according to the latest update in 2022. This number is small when considering the vast number of compounds that can be present in water, including those known as “emerging pollutants.”
Emerging pollutants are substances found in everyday products such as medications, vehicles, cleaning products, and industrial chemicals, whose environmental impact is not fully understood. Since they are not regulated, their presence in rivers continues to increase without knowledge of the effects they may have on aquatic life and human health.
In recent years, negative effects of certain compounds present in urban runoff have been observed. A recent example is the discovery that 6-PPD quinone, a compound used in tire manufacturing, is released onto roads due to wear and tear, and is carried by rainwater into rivers, where it has been linked to the death of Coho salmon in the United States.
So, the next time it rains, let’s remember our rivers, which not only receive water but also pollutants that disrupt their balance. Let’s take care of rivers not only for their beauty but also because they are ecosystems that host rich biodiversity and provide us with valuable ecosystem services. Preserving rivers is preserving life and the well-being of all.
(Image by gankogroup from Vecteezy)
Biologist and Predoctoral researcher at the Department of Evolutionary Biology, Ecology and Environmental Sciences in University of Barcelona.
Collaborator in CITYPOLL project.