Dissolved Trace Elements In the Mississippi River: Seasonal, Interannual, and Decadal Variability

Document Type

Article

Publication Date

10-1-1997

Department

Marine Science

School

Ocean Science and Engineering

Abstract

A monthly trace element sampling of the lower Mississippi River, utilizing ultra-clean methods, was conducted from October 1991 to December 1993. Dissolved concentrations were determined for Fe, Mn, Zn, Ph, V, Mo, U, Cu, Ni, Cd, Rb, and Ba. The results show significant seasonal dissolved concentration changes for a number of elements. Specifically, dissolved Mn and Fe are found to increase rapidly in the fall and then decrease in the spring. Zn and Pb follow a similar seasonal trend, though with lower percentage concentration changes. V, Mo, and U follow an opposite seasonal trend to Mn and Fe. The data do not allow a complete determination of the causes of this variability. However, changes in the adsorption process do not appear to play an important role. Hydrologic factors are also of minimal importance for most elements, with the probable exception of Ba and U. I suggest here that redox processes, occurring both in-stream and in source regions, play an important role in determining seasonal variations in dissolved trace elements.

No evidence was found of significant dissolved trace element concentration changes over the past decade and interannual variability in mean concentrations was generally small. The time series also encompassed a period of extreme flooding in the U.S. Midwest. However, the flooding did not significantly influence dissolved trace element concentrations in the lower Mississippi River.

Publication Title

Geochimica et Cosmochimica Acta

Volume

61

Issue

20

First Page

4321

Last Page

4330

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