Beside inputs from wastewater treatment plants, untreated stormwater runoff can also be an important source of pollutants affecting urban surface waters. To evaluate the relevance of micropollutants in urban stormwater runoff for the city of Berlin, an event-based, one-year monitoring program was conducted in five homogeneous catchments of different urban structure types. Volume proportional samples were analysed for a comprehensive set of ~100 micropollutants (e.g. biocides/pesticides, plasticisers, flame retardants, PAH, heavy metals) as well as standard parameters (TSS, total P, phosphate, ammonium, COD, BOD). Micropollutant concentrations found in stormwater runoff were extrapolated to annual loads for the city of Berlin (impervious connected area of ~170 km2) based on the concentration patterns found in each of the five specific city structure types. Results show that micropollutants of several substance types can enter Berlin surface waters at loads in the order of 10-700 kg/yr via stormwater runoff. These loads are in a similar order of magnitude as micropollutants that enter Berlin surface waters via (treated) sewage, such as pharmaceutical residues carbamazepine or ibuprofen.

When it comes to well loss and efficiency, the occurrence of wellbore skin layers is one of the strongest influencing factors. Besides difficulties to remove the skin layer that is necessary during the drilling process, it is also not easily possible to determine if a skin layer is present in a well and whether or not it imposes a certain degree of well loss. With this work, three types of skin layers are presented (surface cake, deep-bed filtration, layered cake in the aquifer), that have been observed at dewatering wells excavated in open-pits of the Rhenish lignite mining district in western Germany. Disturbed and undisturbed samples were analyzed for their geochemical and mineralogical composition in order to better understand the formation of the skin layer types and their fate during well operation. Geochemical analysis revealed the skin layer to be mainly composed of quartz (˜ 40 wt-%), kaolinite/illite (˜ 30 wt-%), organic material (5-15 %) and secondary gypsum precipitates (up to 12.5 wt-%). Despite the high quartz contents, the granulometry yields high fractions of clay and silt (75-85 %). However, preferential flow paths, transecting the skin layer are created by micro-cracks and erosion-pathways which will cause a higher hydraulic conductivity than could be expected from the granulometry.