Contaminants in Urban Stormwater: Barcelona case study

Abstract. Today's cities face simultaneous challenges due to rapidly growing populations, urban sprawl, climate change, and environmental pollution which pose a pressure on our traditional urban drinking water supplies. In this context, stormwater could augment our over-drafted urban groundwater resources. However, urban stormwater runoff carries a myriad of dissolved contaminants (e.g., organics, metals, nutrients), which pose a serious risk to the environmental and public health. Moreover, dissolved contaminants of urban origin – such as trace metals and organic compounds of emerging concern – may not be adequately removed by conventional stormwater treatments. Therefore, it is of the utmost importance to fully understand stormwater contaminant presence, transport, and fate in the built environment to design novel or improve conventional treatment systems. To address this knowledge gap, we have conducted 7 field sampling campaigns during storm events at different Barcelona locations (within 3 districts) to investigate contaminant presence in different urban compartments (e.g., roofs, conventional streets with automobile traffic, pedestrian streets, and green infrastructure outlets). Preliminary results have confirmed presence of toxic metals in Barcelona urban rain and stormwater runoff along with significant differences depending on the catchment areas. After a storm event, trace metal concentrations followed the order: roof rain < pedestrian street runoff < conventional street runoff. Additionally, blue-green infrastructures (bioretention systems) had lower mean metal concentrations at the effluent (outlet) than the influents (inlet). Our initial results on metal occurrence in stormwater collected in the city of Barcelona will provide stormwater quality foundation for water agencies, municipalities, and companies in other water-stressed regions with Mediterranean climate.