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Urban water bodies are strongly modified ecosystems. They typically receive large loads of nutrients, organic carbon, suspended solids and a wide variety of other macro- and micropollutants such as heavy metals, pharmaceuticals and personal care products. Furthermore, the morphology of urban water bodies has usually been changed and habitat heterogeneity has been reduced, which limits the ability to support aquatic biodiversity. In this common topic we aim to enhance the understanding of interface processes in natural and technical urban water systems. Several doctoral students work on different biogeochemical processes associated with urban water interfaces within this common topic.
The first project addresses the degradation of organic trace pollutants in biofilms at solid-water interfaces (Project N1 ). It specifically tackles the potential of both defined and natural biofilm communities to degrade pollutants such as diclofenac, carbamazepine and iodinated contrast media in urban water systems. The second project aims to understand the patterns and controls of greenhouse gas (GHG) fluxes in urban waters (Project N3 ), with special emphasis on methane emissions. Closely collaborating with this is the third project also dealing with GHG fluxes, focusing specifically on ecosystem metabolism in urban aquatic environments (Project N4 ). The objectives are to: (i) estimate whole-ecosystem metabolism based on diel O2-dynamics in a variety of urban water bodies, (ii) estimate CO2 concentrations, their dynamics and resulting fluxes across the water-atmosphere interface, (iii) scale up aquatic ecosystem metabolism and CO2 fluxes to the metropolitan area of Berlin, and (iv) identify the key drivers and gradients of metabolism and CO2 fluxes. A further project is dealing with sulphur cycles in sewers (Project T2 ), specifically at the interface defined by wastewater – atmosphere – biofilm – construction material. Finally, one project aims to improve our understanding of deiodination of iodinated contrast media during bank filtration of urban waters (Project T6 ). Mass balances of iodine will be established that consider both abiotic and biologically mediated transformations.
Clara Romero (corresponding doctoral student)
Fatima El-Athman 
Daneish Despot 
- solid – water interface (N1- Marcella Nega )
- surface water – atmosphere (N3 - Sonia Herrero , N4 - Clara Romero )
- wastewater – sewer atmosphere (T2 - Daneish Despot)
- sediment – surface water (T6 – Fatima El-Athman )
- Berliner Wasserbetriebe (BWB) 
- Senatsverwaltung für Stadtentwicklung und Umwelt, Berlin 
- Helmholtz Centre for Environmental Research (UFZ), Leipzig 
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