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Metals Release From Mining-Impacted Streambed Sediments: North Fork Clear Creek, Colorado
Citation:
BUTLER, B. Metals Release From Mining-Impacted Streambed Sediments: North Fork Clear Creek, Colorado. Presented at U.S. EPA NRMRL Seminar Series, Cincinnati, OH, May 01, 2008.
Impact/Purpose:
To determine the effect streambed sediments has on metals that were released resulting from changes in pH, DOC, ionic strength, particle size, and time. Metals released from these sediments when held under anaerobic conditions, as a function of size and time, were also examined.
Description:
Many miles of streams in the US (and worldwide) are contaminated by metals originating from both active and abandoned mine sites. Streams affected by mine drainage are often toxic to aquatic life. Thus, it is desirable to remediate these sites through removal or treatment of the source(s). In the absence of mine-drainage input, the stream water will likely increase in pH, decrease in ionic strength (typical mine-drainage contains high concentrations of salts and sulfate), and increase in dissolved organic carbon (DOC) concentration (increased biological activity once metal toxicity is removed). In the western U.S., many of these streams are high gradient and shallow - resulting in the bed sediments being aerobic (oxic) and containing high concentrations of precipitated metal oxyhydroxides and sorbed metals. The sorbed metals are susceptible to release under changing water chemistry. Additionally, disposal of these oxic sediments in a repository that may be anoxic is expected to result in changes in the mineralogy with concurrent release of metals (e.g., through reductive dissolution). North Fork Clear Creek, CO was chosen for study due to its currently being a Superfund site listed on the NPL and recent decisions for its remediation. Streambed sediments were examined to determine the effect on metals release resulting from changes in pH, DOC, ionic strength, particle size, and time. Additionally, a second experiment examined metals release from these sediments when held under anaerobic conditions, as a function of size and time.