Micropollutant concentrations found in stormwater runoff were extrapolated to annual loads at the scale of the city of Berlin (impervious connected area of ~170 km2). Extrapolation was done by city structure, i.e., it was assumed that concentration patterns found in one of five specific city structure types is representative for every area of this structure type. Preliminary results show that micropollutants of several substance types can enter Berlin surface waters at loads in the order of kg/yr via stormwater runoff: plasticizers (e.g., sum of Di-iso-decylphthalate and Di-iso-nonylphthalate at 770 kg/yr), flame retardants (e.g., tris(2-butoxyethyl) phosphate (TBEP) at 89 kg/yr), biocides from different sources (e.g., Glyphosate at 17 kg/yr and Mecoprop at 30 kg/yr), vulcanizing accelerator benzothiazole (as sum of benzothiazole and metabolites methylthiobenzothiazole and hydroxybenzothiazole at 65 kg/yr) and combustion byproduct polycyclic aromatic hydrocarbons PAH 16 (sum of 16 EPA PAH at 107 kg/yr). These loads are in a similar order of magnitude as micropollutants that enter Berlin surface waters via (treated) sewage, such as pharmaceutical residues carbamazepine and ibuprofen with estimated annual loads of 436 kg/yr and 35 kg/yr, respectively.

According to the European Water Framework Directive, ‘good ecological and chemical status’ must be achieved for all surface waters by 2015 (European Parliament, 2000). Therefore, it is important to extend knowledge on pollutants that run off with urban rainwater. This study has the objective to determine which micropollutants occur in Berlin’s urban rain water run-off and how the most detrimental pollutants can be managed in a sustainable manner to reduce their impact on receiving waters. To reach these objectives, five catchments with different land use characteristics that together represent Berlin were selected for the collection of rainwater samples. These catchments consisted of New buildings (New), Old buildings (Old), One family homes (Ofh), Commercial buildings (Com) and Streets (Str). Actual sampling was done by installing an automated water sampler at each location, together with a flow measuring device to start the sampler during rain events. The following number of rain events were sampled and analysed; New (n=8), Old (n=7), Ofh (n=6), Com (n=11) and Str (n=4). Samples collected during rain events were processed to one volume proportional composite sample that represents the entire event. This sample was then analysed on the presence and concentration of micropollutants. With that information, measures where determined that can be applied for the reduction of pollutant loads. Micropollutants from the following groups were found during this study; pesticides / biocides, industrial chemicals, PAH’s, heavy metals, tracers, flame retardants and phthalates. From these groups, the most detrimental are; Nickel, Diuron, Isoproturon, Cadmium, Lead, PFOA, PFOS , polycyclic aromatic hydrocarbons (PAH), Nonylphenol, DEHP, Zinc, Copper, TCPP, Mecoprop, Glyphosphat, OHBT and Di-iso-decylphthalat. To assess measures for micropollutant reduction, the concept of source-path-threatened object was used to identify where pollutants come from and what pathway they follow to which vulnerable objects. Possible measures to reduce the load of these substances are banning or substituting the pollutant by legislation. Furthermore, vegetation infrastructure, decentralized pre-treatment, infiltration and sedimentation can be applied for reduction of pollutant loads. These measures should be applied in an integrated manner to enhance one another. Pollutant characteristics -and thus behaviour in the environment- is one of the most relevant criteria for the selection of measures to reduce these substances. The most effective approaches for particle and non-particle bound pollutants are end-of-pipe solutions. These consist of sedimentation systems for particle bound, and infiltration structures for non-particle bound micropollutants. Emitting sources (e.g. traffic) and paths (e.g. air) that contribute to pollutants in urban rainwater run-off are further relevant criteria. These can only be directly reduced by legislation, vegetation infrastructure can however be applied to reduce the mobility of these pollutants.

In recent years, organic micropollutants have been detected in urban storm runoff in several European studies. As rain water runoff in Berlin and other German and European cities is often discharged untreated in separated sewer systems, urban stormwater is a large potential source of micropollutants affecting receiving surface waters. As a consequence, it is important to know the local extent of the issue to be able to evaluate potential measures. In this study, a one year monitoring programme is conducted in the city of Berlin to estimate yearly loads of micropollutants from urban stormwater entering Berlin surface waters. Five different catchment types typical for Berlin were determined after analysis of GIS data (old building areas <1930, newer building areas >1950, single houses with gardens, roads and commercial areas) and monitoring points were selected fulfilling a number of criteria (including representativeness of catchment type, accessibility, sufficient flow, manhole size). Samples are taken using automatic samplers and a sampling strategy was developed to obtain best possible representative composite samples representing the average concentration of the sampled storm event. Results will then be used with measured flow data to calculate micropollutant loads of individual catchment types. A runoff model for Berlin applied to the individual catchment types and coupled with pollutant concentration relationships will be used to extrapolate results to city scale.

Regenwasserabfluss ist die größte unbehandelte Quelle von potentiell hohen Spuren-stofffrachten in urbane Oberflächengewässer. In Berlin werden ca. 74% oder jährlich 44 Millionen m³ des Regenwasserabflusses weitgehend unbehandelt eingeleitet. Dies ent-spricht etwa 5% des jährlichen Abflusses der Stadtspree an der Mündung in die Havel. Erste Studien aus der Schweiz und Frankreich zu ausgewählten organischen Spurenstoffen (z.B. Biozide, Kunststoffinhaltsstoffe, Verbrennungsprodukte) im Regenwasserabfluss und Oberflächengewässern zeigen zum Teil hohe Konzentrationen von Substanzen mit möglicher Relevanz für aquatische Organismen oder die mensch-liche Nutzung.