FY 1989

Estuarine transport of trace metals in a buoyant riverine plume

Paulson, A.J., R.A. Feely, H.C. Curl, Jr., and D.A. Tennant

Estuar. Coast. Shelf Sci., 28(3), doi: 10.1016/0272-7714(89)90015-2, 231–248 (1989)

The distributions of dissolved and particulate trace metals in Elliott Bay, Washington were determined in April, 1985 during the period of maximum discharge of freshwater for the year. The high freshwater discharge generated a thin buoyant plume (<2 m) which carried a high suspended load. Calculations made from high resolution sampling of salinity and total suspended matter in the plume suggest that their residence times in the upper 2 m of the water column ranged between 15 and 24 h. Total suspended matter, dissolved and particulate Fe, Mn and Pb, and particulate Cu and Zn in the plume were found to be conservative during their transit through Elliott Bay. Dissolved Cu and Zn exhibited a linear relationship with salinity downstream of a significant anthropogenic source. The particulate phase dominated the horizontal transport of Fe and Pb originating from freshwater sources. In contrast, the dissolved phase contributed 66%, 75% and 35% of the respective total horizontal fluxes of Mn, Zn and Cu that originated from riverine and anthropogenic sources. The trace metal concentrations of the suspended matter were uniform in Elliott Bay except for Mn concentrations. Mn concentrations of suspended matter increased with salinity due to mixing of lower concentration, riverine particulates with Puget Sound particulates of higher Mn concentrations. The lack of trace metal enrichments of Elliott Bay surface suspended matter during this period of high discharge was the result of the small vertical loss of suspended matter (<2% of the horizontal transport) and the rapid transit of suspended matter through the Bay.