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Applied and Environmental Microbiology, April 1999, p. 1548-1555, Vol. 65, No. 4
Division of Biological
Sciences1 and Department of
Geology,2 University of Montana, Missoula,
Montana 59812
Received 24 August 1998/Accepted 15 January 1999
The fluvial deposition of mine tailings generated from historic
mining operations near Butte, Montana, has resulted in substantial surface and shallow groundwater contamination along Silver Bow Creek.
Biogeochemical processes in the sediment and underlying hyporheic zone
were studied in an attempt to characterize interactions consequential
to heavy-metal contamination of shallow groundwater. Sediment cores
were extracted and fractionated based on sediment stratification.
Subsamples of each fraction were assayed for culturable heterotrophic
microbiota, specific microbial guilds involved in metal redox
transformations, and both aqueous- and solid-phase geochemistry.
Populations of cultivable Fe(III)-reducing bacteria were most prominent
in the anoxic, circumneutral pH regions associated with a ferricrete
layer or in an oxic zone high in organic carbon and soluble iron.
Sulfur- and iron-oxidizing bacteria were distributed in discrete zones
throughout the tailings and were often recovered from sections at and
below the anoxic groundwater interface. Sulfate-reducing bacteria were
also widely distributed in the cores and often occurred in zones
overlapping iron and sulfur oxidizers. Sulfate-reducing bacteria were
consistently recovered from oxic zones that contained high
concentrations of metals in the oxidizable fraction. Altogether, these
results suggest a highly varied and complex microbial ecology within a
very heterogeneous geochemical environment. Such physical and
biological heterogeneity has often been overlooked when remediation strategies for metal contaminated environments are formulated.
0099-2240/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Microbiological and Geochemical Characterization of
Fluvially Deposited Sulfidic Mine Tailings
*
Corresponding author. Present address: Department of
Geology and Environmental Science, 118 Braun Hall, Stanford University, Palo Alto, CA 94305-2115. Phone: (650) 723-0847. Fax: (650)
725-0979. E-mail: wielinga{at}pangea.stanford.edu.
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