FY 1984

Behavior of Fe, Mn, Cu and Cd in the Duwamish River estuary downstream of a sewage treatment plant

Paulson, A.J., R.A. Feely, H.C. Curl, Jr., and J.F. Gendron

Water Res., 18(5), doi: 10.1016/0043-1354(84)90214-8, 633–641 (1984)

The behavior of dissolved Fe, Mn, Cu and Cd in the Duwamish River downstream of a sewage treatment plant located near Seattle, Washington, was investigated in three distinct zones: (1) immediately downstream of the effluent outfall, (2) further downstream in the freshwater portion of the river and (3) in the estuarine mixing zone. A three-end-member tracer model utilizing salinity and dissolved inorganic nitrogen was developed to distinguish physical mixing processes from biogeochemical reactions. The results of this investigation indicate that Fe was removed from the dissolved phase onto particulates near the plant. Although no additional reactions controlled the distribution of dissolved Fe, Mn and Cu in the freshwater portion of the river, Cd was removed from the dissolved phase. In the estuarine mixing zone, a significant fraction of the dissolved Fe and Cu was removed from solution, while Mn and Cd desorbed from particulates. The chemical forms of the trace metals rather than their sources appear to determine their participation in these reactions.