Surveillance and environmental risk of very mobile pollutants in urban stormwater and rainwater in a water-stressed city.

Urban stormwater and rainwater in water-stressed cities serve as critical vectors for the transport and dispersion of pollutants, including very mobile compounds These pollutants, which can be influenced by factors such as land use, rainfall intensity, and urban infrastructure, pose significant risks to both human and environmental health. Although several priority pollutants have traditionally been detected in urban stormwater, little is known about the presence of very mobile compounds that may threaten urban drinking water supplies and pose environmental risks to aquatic species. In this study, 131 urban rain and stormwater samples were collected from three districts of Barcelona (Spain) and analysed for 26 very mobile pollutants that are often overlooked in conventional monitoring efforts. The findings reveal that stormwater and rainwater are major contributors to the spread of pollutants in water-stressed cities, with particular emphasis on substances like lifestyle products, pharmaceuticals, and industrial chemicals. Among the 23 compounds detected, 12 were reported for the first time to occur in urban stormwater with concentrations as high as 271 µg L. Measurements of dissolved organic carbon, electrical conductivity, and the presence of wastewater-borne pollutants within the correlation analysis, suggested the contribution of sanitary sewer overflows (SSO) to urban stormwater. Finally, an environmental risk assessment (worst-case scenario) was performed, showing a moderate risk of target analytes such as acesulfame and 1-naphthalenesulfonic acid (ERQ > 0.1). The results highlight the need for improved surveillance systems, more sustainable stormwater management practices, and strategies for mitigating the environmental risk posed by very mobile pollutants in regions facing water scarcity.