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Urban swales collect stormwater runoff containing micropollutants such as biocides washed off from facades during wind driven rain. Although swales retain contaminants, they might eventually reach groundwater through soil. However, there is little data available of biocide occurrence in urban swale sediment. In this study, we measured the biocide entry to an urban swale and its distribution in sediment. The selected swale in south-west Germany collects runoff from a 3 ha residential area with 46 houses. Two pipes lead into the swale, one collecting runoff from a 1 ha area (“East”) and one from a 2 ha area (“West”). We took sediment samples after dry and wet periods close to both pipes and additional water grab samples during wet periods. In total, we collected 19 stormwater samples during 7 events and 116 sediment samples during 8 days over a period of two years. Water samples were analyzed for three biocides (diuron, terbutryn, octylisothiazoline= OIT) and four transformation products (= TPs, diuron-desmethyl, terbuthylazine-2-hydroxy, terbutryn-desethyl, terbumeton) using LC-MS/MS. Sediment samples were analyzed for terbutryn, OIT and 3 TPs of terbutryn. Finally, we linked a water balance model to a leaching model and simulated longterm biocide input into the swale. This we compared with biocide concentration in the swale sediments using a mass balance approach. We found all biocides and all TPs in water samples at both pipes confirming biocide input to the swale. In the sediment, terbutryn concentrations were generally below 1 ng/g. Of three measured TPs of terbutryn we detected only one, terbutryn-desethyl ( |
