Effect of stormwater runoff on metal distribution in the sediment and interstitial waters of an urban river.

Metals were analysed in the interstitial waters and sediments of an urban river, receiving stormwater and combined sewer overflow, over a two month period and interpreted in terms of rain events. Depth profiles for metal concentrations showed the highest interstitial water concentrations in samples with low sedimentary organic material. Storm events can both resuspend sediments and associated metal-rich interstitial waters and alter the metal distribution between interstitial water and sediment. Metal profiles downstream of a combined sewer overflow showed elevated interstitial water concentrations compared to an upstream site. Downstream sites also reveal evidence of metal burial and resuspension processes during and between wet periods.