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.

A study is conducted to determine the relevance of micropollutants in urban stormwater runoff. To evaluate for the first time city-wide annual loads of stormwater-based micropollutants entering urban surface waters, an event-based, one-year monitoring program was set up in separate storm sewers in Berlin. Monitoring points were selected in 5 catchments of different urban structures (old building areas <1930, newer building areas >1950, single houses with gardens, roads >7500 vehicles/day and commercial areas) to consider catchment-specific differences. Storm events of different characteristics were sampled up to four hours during different seasons by automatic samplers triggered by flow meters. Volume-proportional samples (one composite sample per event) were analysed for a set of 100 parameters including 85 organic micropollutants (e.g. flame retardants, phthalates, pesticides/biocides, PAH), heavy metals and standard parameters. So far (70/88 samples), 60 organic micropollutants were at least once detected in stormwater runoff of the investigated catchment types. Concentrations were highest for phthalates with average concentrations of 13 µg/L for diisodecyl phthalate. For heavy metals, concentrations were highest for zinc (average: 950 µg/L). Results also showed catchment-specific differences for many compounds as well as seasonal differences for selected pollutants which can be used to improve micropollutant strategies and potentially prevent loads at the source.

We investigate water quality of a small urban river during dry and wet weather conditions, including both standard parameters and trace organics. The monitored river stretch receives both effluents from WWTP as well as (separate) stormwater runoff of an impervious area of 11 km2. Results show increases in concentrations in the river during rain events with a factor > 20 for zinc, polycyclic aromatic hydrocarbons, two herbicides and one flame retardant. Also, substances which are expected both in WWTP effluent and in stormwater effluents were detected at important concentrations in the river during wet weather, such as the corrosion inhibitor Benzotriazole (0.8 µg/L on average) and the plasticizer Diisodecyl phthalate (4.0 µg/L on average). The presented results are preliminary and will be complemented by more results and substances as well as an assessment of the relevance of the findings.