Large-scale distribution of metal contamination in the fine-grained sediments of the Clark Fork River, Montana, U.S.A.

Applied Geochemistry
By:  and 


  • The Publications Warehouse does not have links to digital versions of this publication at this time
  • Download citation as: RIS | Dublin Core


Historic discharges from the mining and smelting complex at the head-waters of the Clark Fork River have resulted in elevated Ag, Cd, Cu, Pb and Zn concentrations in the <60 ??m fraction of both bed and flood-plain sediments of the river. Processes affecting the trends in longitudinal distributions of these metals were investigated by repeated sampling over a 380 km river reach between August 1986 and July 1989. At the most upstream site, bed-sediment metal concentrations were enriched 18-115 times above least enriched tributaries, depending on the metal. All metals decreased exponentially with distance downstream away from mining. The exponential model predicts that elevated metal concentrations should occur over 550 km downstream, in Lake Pend Oreille. Longitudinal trends, obvious on a scale of hundreds of kilometers, were obscured by small-scale spatial variability when shorter stretches of the river were considered. Longitudinal dispersion appeared to be controlled largely by physical dilution with less-contaminated sediments. Evidence suggests that erosion of contaminated flood-plains contributes to metal contamination in the bed sediments. Tributary input appeared to have little influence on the large-scale, downstream distribution of metals; however, it did contribute to local variability in bed-sediment metal concentrations. Association of metals with specific mineral grains, as well as variability in total organic C and Fe concentration, appeared also to contribute to variability. Some year-to-year variability in bed-sediment metal concentrations was observed, however, trends in longitudinal dispersion were not significantly different between at least two of the years sampled.

Study Area

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Large-scale distribution of metal contamination in the fine-grained sediments of the Clark Fork River, Montana, U.S.A.
Series title Applied Geochemistry
Volume 6
Issue 1
Year Published 1991
Language English
Publisher Elsevier
Contributing office(s) Toxic Substances Hydrology Program
Description 14 p.
First page 75
Last page 88
Country United States
State Montana
Google Analytic Metrics Metrics page