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Investigation of Bacterial Transport in the Large-Block test, A Thermally Perturbed Block of Topopah Spring Tuff

Published online by Cambridge University Press:  10 February 2011

C.-I Chen ,
A. Meike ,
Y.-J. Chuu ,
A. Sawvel  and
W. Lin
C.-I Chen
Affiliation:
Earth and Environmental Sciences Department, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94551–9989
A. Meike
Affiliation:
Earth and Environmental Sciences Department, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94551–9989
Y.-J. Chuu
Affiliation:
Earth and Environmental Sciences Department, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94551–9989
A. Sawvel
Affiliation:
Earth and Environmental Sciences Department, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94551–9989
W. Lin
Affiliation:
Earth and Environmental Sciences Department, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94551–9989
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Abstract

Transport of bacteria is investigated as part of the Large-Block Test (LBT), a thermally perturbed block of Topopah Spring tuff. Two bacterial species, Bacillus subtilis and Arthrobacter oxydans, were isolated from the Yucca Mountain tuff. Natural mutants that can grow under the simultaneous presence of the two antibiotics, streptomycin and rifampicin, were selected from these species by laboratory procedures, cultured, and injected into the five heater boreholes of the large block hours before heating was initiated. The temperature, as measured 5 cm above one of the heater boreholes, rose slowly over a matter of months to a maximum of 142°C and to 60°C at the top and the bottom of the block. Samples were collected from boreholes located approximately 5 ft below the injection points. Double-drug-resistant bacteria were found in the collection boreholes nine months after injection. Biochemical tests support the identification of B. subtilis in the collection boreholes. Double-drug-resistant microbes also appeared in the heater boreholes where the temperature had been sustainably high throughout the test. The number of double-drugresistant bacteria that were identified in the collection boreholes increased with time until the heater was deactivated. Negative indications in the collection holes after the heater was deactivated support the supposition that these bacteria were the species that were injected. An apparent homogeneous distribution among the collection boreholes suggests no pattern to the migration of bacteria through the block. The relationship between bacterial migration and the movement of water is not yet understood. These observations indicate the possibility of rapid bacterial transport in a thermally perturbed geologic setting. The implications for colloid transport need to be reviewed.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 556: Symposium QQ – Scientific Basis for Nuclear Waste Management XXII , 1999 , 1151
Copyright
Copyright © Materials Research Society 1999

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References

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