| Abstract
| - Mining activity along the South Fork of the Coeur d'Alene River in northern Idaho has resulted in fluvial minetailings enriched in Pb, As, Ag, Sb, Hg, Cd, and Zndeposited on the lakebed of Lake Coeur d'Alene, thusserving as a potential benthic source of inorganiccontaminants. Our objective was to characterize thedominant solid phase materials and diagenetic processescontrolling metal(loid) solubilities, and thus their potentialrelease to the overlying water column. Aqueous and solidconcentrations of metal(loid) contaminants were examinedalong with distinct species of Fe and S within sediments andinterstitial water. A gradient from oxic conditions at thesediment−water interface to anoxic conditions below 15 cmexists at all sites, resulting in a dynamic redox environmentthat controls the partitioning of contaminants. Fluvialdeposition from frequent seasonal flood events bury ferricoxides residing at the sediment−water interface leadingto reductive dissolution as they transition to the anoxic zone,consequently releasing associated metal(loids) to theinterstitial water. Insufficient sulfur limits the formation ofsulfidic minerals, but high carbonate content of thismining region buffers pH and promotes formation of siderite.Diagenetic reactions create chemical gradients encouragingthe diffusion of metal(loids) toward the sediment−water interface, thereby, increasing the potential forrelease into the overlying water.
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