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This article in JEQ

  1. Vol. 27 No. 2, p. 318-328
     

    * Corresponding author(s): lafo9442@uidaho.edu
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doi:10.2134/jeq1998.00472425002700020011x

A Laboratory Evaluation of Trace Element Mobility from Flooding and Nutrient Loading of Coeur d'Alene River Sediments

  1. M. J. La Force *,
  2. S. E. Fendorf,
  3. G. C. Li,
  4. G. M. Schneider and
  5. R. F. Rosenzweig
  1. Soil Science Division, Univ. of Idaho, Moscow ID 83844;
    Dep. of Biological Sciences, Univ. of Idaho, Moscow ID 83844.

Abstract

Abstract

The main stem (MSCDR) and south fork (SFCDR) of the Coeur d'Alene River, Idaho, are contaminated with heavy metals from many years of mining. To assess the potential impacts of flooding on water quality in the river system, contaminants in undisturbed sediments were subjected to selective extraction, and their rates of release measured in simulated laboratory flooding experiments. To simulate flooding, 18 columns were constructed allowing the sediment-water interface to be monitored for pH, Eh, and dissolved concentrations of As, Fe, Mn, Pb, and Zn. These columns were subjected to four types of treatments. The first two involved overlaying the columns with N2(g)- or air-purged river water, whereas the latter two involved overlaying sediment columns with N2(g)- or air-purged river water amended with C and N. Treatment with unamended river water resulted in the immediate release of Zn at an average concentration of 10.4 mg L−1 from sediment taken along the MSCDR at Cataldo, ID. Treatment with either oxic or anoxic river water amended with glucose and N resulted in an order of magnitude increase in sediment microbial density. These biotic changes correlated with fivefold to 100-fold increases in the release of trace elements into the aqueous phase. Our results suggest that heavy metal loading of waters in the Coeur d'Alene system occurs not only as a result of the resuspension of particulate matter, but also as a result of transformations that are either directly or indirectly mediated by sediment microbiota. Undisturbed sediments currently situated in the riverbanks of the MSCDR and SFCDR have the capacity to release contaminants into the river system during flooding. This release could be dramatically enhanced by increased nutrient levels into the CDA river system.

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