HR: 1340h
AN: B53A-0982    [Abstracts]
TI: Spectral-IP Characteristics of Bacterial Activity on Sulfide Mineral Surfaces: Implications for Detection and Environmental Impact Assessment of Acid Mine Drainage.
AU: * Blackmore, S R
EM: arcticnewfie@yahoo.ca
AF: University of Western Ontario, Department of Earth Sciences, Biological and Geological Sciences Building, London, ON N6A 5B7 Canada
AU: Southam, G
EM: gsoutham@uwo.ca
AF: University of Western Ontario, Department of Earth Sciences, Biological and Geological Sciences Building, London, ON N6A 5B7 Canada
AU: Katsube, J
EM: jkatsube@nrcan.gc.ca
AF: Natural Resources Canada, Geological Survey of Canada, Mineral Resources Division, 601 Booth Street, Ottawa, ON K1A 0E8 Canada
AB: Spectral induced polarization (IP) measurements were carried out, over a frequency range of 1.0-106 Hz, on pyrite crystal surfaces colonized by thiobacilli at different growth stages and in `sedimentary systems' with different pyrite-quartz ratios. The purpose was to determine if these varied pyrite-bacteria conditions are reflected in the spectral-IP responses and whether IP, as a geophysical tool, is able to detect and assess the potential for acid mine drainage due to bacterial activity. The study used an Acidithiobacillus ferrooxidans subspecies, isolated from the Kam Kotia mine tailings, Timmins, Ontario, using limiting dilutions in 9K buffer medium (pH 3; (NH4)2SO4, 0.4 g; K2HPO4, 0.1 g; MgSO47H2O, 0.1 g) supplemented with 3.3 g/L of filter sterilized FeSO47H2O as their energy source. Duplicate syringe columns experiments were prepared using varying concentrations of acid-washed silica and/or pyrite (simulating either disseminated or stratified pyritic ore) and colonized with thiobacilli. All columns were maintained under saturating conditions with circumneutral 9K buffer. Each column began with an acidic pH and became more alkaline over the 2-month experiment, typically ending close to the circumneutral pH of the media. The spectral-IP measurements responded directly to bacterial activity, i.e., changes in impedance were observed in all samples. Samples that contained bacteria were higher in impedance (with significant differences observed between frequencies of 10-100000Hz). Over time, scanning electron microscopy revealed increases in the bacterial corrosion surface area, bacterial ferric-sulfate encasement, the number of bacteria colonies and abundance of ferric precipitates. Bacterially induced mineralization was observed as patches in all systems. In the disseminated and stratified environments, the patches covered 8-10% of the grains, predominantly along the fractured mineral edges. In the `massive' 100% pyrite systems, bacteria-mineral patches covered up to 15% of grain surfaces and were not constrained to specific mineralogical features. Spectral-IP responses differed for each of these bacterial systems and can be modeled by equivalent circuits, implying that the application of these principles to field geophysics is possibile.
DE: 4803 Bacteria
DE: 1594 Instruments and techniques
DE: 1615 Biogeochemical processes (4805)
DE: 0400 Biogeosciences
DE: 0614 Biological effects
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting