Behavior of Fe, MN, Cu and Cd in the Duwamish River Estuary Downstream of a Sewage Treatment Plant

The fate of dissolved iron, manganese, copper, and cadmium in the Duwamish River downstream of a sewage treatment plant located near Seattle, WA, was examined in three distinct zones: immediately downstream of the effluent outfall, further downstream in the freshwater portion of the river, and in the estuarine mixing zone. Results show that Fe was removed from the dissolved phase onto particulates near the plant. In the estuarine mixing zone, a substantial fraction of the dissolved Fe and Cu was removed from the solution, while MN and Cd desorbed their particulates. The chemical forms of the trace metals rather than their sources appear to determine their participation in these reactions.