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PRELIMINARY RESULTS: RELEASE OF METALS FROM ACID-MINE DRAINAGE CONTAMINATED STREAMBED SEDIMENTS UNDER ANOXIC CONDITIONS
Citation:
BUTLER, B. AND D. J. REISMAN. PRELIMINARY RESULTS: RELEASE OF METALS FROM ACID-MINE DRAINAGE CONTAMINATED STREAMBED SEDIMENTS UNDER ANOXIC CONDITIONS. Presented at 2008 National Meeting of the American Society of Mining and Reclamation, Richmond, VA, June 14 - 19, 2008.
Impact/Purpose:
to present information
Description:
Many miles of streams are contaminated with acid-mine drainage (AMD) from abandoned metal mines in the western U.S. Treatment of these streams may include dredging of the existing sediments, with subsequent burial. Burial of previously toxic sediments may result in release of metals through multiple processes, including reductive dissolution of metal oxyhydroxides, with concurrent release of previously sorbed metals. This paper discusses preliminary results from a study examining the release of Cd, Cu, Fe, Mn, and Zn from oxic streambed sediments collected from an acid-mine drainage (AMD) impacted stream (North Fork Clear Creek, CO). The pH, Eh, and metal release were monitored over twenty-eight days in an anaerobic chamber from sediment slurries prepared using 0.45-f.Lm filtered stream water. Additionally, the effect of sediment size was examined by using two size fractions: 2-mm to 63f.Lm and less than 63 f.Lm. All metals showed release from both size fractions, with the exception of Zn, which showed a continual decrease over time. Release varied for each of the size fractions among metals over time. In the case of Cd and Cu, no further release was observed in either size fraction after one week. Release of Fe and Mn declined after the first week in the smaller size fraction and after the second week in the larger size fraction. Because of the presence of sulfate in the stream water, it is believed the metals were re-sequestered as sulfide precipitates. Future studies will include replication and the use of surface chemical techniques to examine the solids for the presence of metal sulfides.