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Linking Spectral Induced Polarization (SIP) and Subsurface Microbial Processes: Results from Sand Column Incubation
Adrian Mellage1, Christina M Smeaton1, Alex Furman2
1University of Waterloo , Water Institute and Department of Earth & Environmental Sciences, 200 University Ave. W, Waterloo, Ontario Canada N2L 3G1.
Environmental Science & Technology
|January 17, 2018
Summary
Spectral induced polarization (SIP) effectively monitors subsurface biogeochemistry by tracking microbial activity. SIP signals correlate with microbial growth and decay, revealing cell surface properties and electron accepting processes.
Area of Science:
- Geophysics
- Environmental Science
- Microbiology
Background:
- Geophysical techniques like spectral induced polarization (SIP) show promise for in situ monitoring of subsurface biogeochemistry.
- Successful application requires deconvoluting multiple signal contributions in reactive transport phenomena.
Purpose of the Study:
- To investigate the sensitivity of SIP to microbial dynamics and biogeochemical processes in a controlled column experiment.
- To correlate SIP measurements with microbial abundance, cell surface properties, and electron accepting processes.
Main Methods:
- SIP spectra and biogeochemical data were collected from saturated columns with ferrihydrite-coated and pure quartz sand.
- Columns were inoculated with Shewanella oneidensis and supplied with lactate and nitrate.
- A biomass-explicit diffusion-reaction model was fitted to the biogeochemical data.
Main Results:
- Temporal SIP responses, specifically imaginary conductivity peaks, paralleled microbial growth and decay.
- SIP demonstrated sensitivity to microbial abundance (<10^8 cells mL^-1) and cell surface charging.
- Relaxation times (τ) varied with dominant electron accepting processes (nitrate or ferric iron reduction).
Conclusions:
- SIP is a viable tool for monitoring microbial dynamics in subsurface environments.
- The study suggests bacterial cell polarization, not grain size, governs observed chargeability and relaxation.
- SIP provides insights into microbial cell surface properties and their influence on geophysical signals.
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