Sustainable urban drainage solutions increasingly use structures, such as wetlands and ponds, to improve water quality. Previous studies have demonstrated the effectiveness of these structures in removing metals from runoff, but the fate of the captured contaminants has been neglected. Whilst organic contaminants and nutrients may biodegrade and be taken up by plants, metals are expected to accumulate in sediments. EDTA-extractable cadmium, chromium, copper, lead, nickel and zinc were measured in sediment sampled from three urban drainage structures (a wetland and two ponds receiving industrial and residential storm drainage) in Scotland, UK. Metal concentrations showed considerable variability within each structure, probably reflecting short-circuiting of flow. Zinc, chromium and cadmium concentrations were at very low levels at all sites, but copper, nickel and lead exceeded background concentrations for aquatic sediments. An index of metal contamination showed that the metal content of sediments increased with the age of the structure.
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