HR: 10:20h
AN: H42B-01 INVITED    [Abstracts]
TI: Pore-scale Spectral Induced Polarization (SIP) signatures associated with FeS biomineral transformations
AU: * Slater, L
EM: lslater@andromeda.rutgers.edu
AF: Rutgers-Newark, 101 Warren St, Newark, NJ 07102, United States
AU: Ntarlagiannis, D
EM: d.ntarlagiannis@qub.ac.uk
AF: Queen's University - Belfast, Stranmillis Road, Belfast, BT9 5AG, United Kingdom
AU: Personna, Y
EM: personna@pegasus.rutgers.edu
AF: Rutgers-Newark, 101 Warren St, Newark, NJ 07102, United States
AU: Hubbard, S
EM: sshubbard@lbl.gov
AF: Lawrence Berkeley Laboratory, Cyclotron Rd, Berkeley, CA 94720, United States
AB: We measured Spectral Induced Polarization (SIP) signatures in sand columns during (1) FeS biomineralization produced by sulfate reducing bacteria (D. vulgaris) under anaerobic conditions, and (2) subsequent biomineral dissolution upon return to an aerobic state. The low-frequency (0.1-10 Hz peak) relaxations produced during biomineralization can be modeled with a Cole-Cole formulation, from which the evolution of the polarization magnitude and relaxation length scale can be estimated. We convert the polarization magnitude to an equivalent FeS surface area per unit pore volume using a previously published empirical relation. The modeled time constant is converted to an equivalent polarizable sphere diameter using a theoretical relation and an assumed value of the surface diffusion coefficient. We find that the modeled time constant is consistent with the polarizable elements being biomineral encrusted pores rather than the biominerals themselves. The temporal SIP signatures suggest FeS surface area increases and pore-size reduction during biomineral growth, with subsequent FeS surface area decreases and pore expansion upon FeS dissolution that occurs during the return of the system to an aerobic state. The geoelectrical interpretation is consistent with changes in aqueous chemistry during the experiment, and solid phase analysis conducted at the termination of the experiment. We conclude that SIP signatures are diagnostic of pore-scale geometrical changes associated with FeS biomineralization by sulfate reducing bacteria. The study highlights the potential for using geoelectrical methods to monitor microbial driven changes in hydraulic conductivity resulting from biomineralization.
DE: 0416 Biogeophysics
DE: 1835 Hydrogeophysics
SC: Hydrology [H]
MN: 2007 Fall Meeting