title: Complex resistivity signatures of ethanol biodegradation in porous media.
abstract: Numerous adverse effects are associated with the accidental release of ethanol (EtOH) and its persistence in the subsurface. Geophysical techniques may permit non-invasive, real time monitoring of microbial degradation of hydrocarbon. We performed complex resistivity (CR) measurements in conjunction with geochemical data analysis on three microbial-stimulated and two control columns to investigate changes in electrical properties during EtOH biodegradation processes in porous media. A Debye Decomposition approach was applied to determine the chargeability (m), normalized chargeability (m(n)) and time constant (τ) of the polarization magnitude and relaxation length scale as a function of time. The CR responses showed a clear distinction between the bioaugmented and control columns in terms of real (σ') and imaginary (σ″) conductivity, phase (ϕ) and apparent formation factor (F(app)). Unlike the control columns, a substantial decrease in σ' and increase in F(app) occurred at an early time (within 4 days) of the experiment for all three bioaugmented columns. The observed decrease in σ' is opposite to previous studies on hydrocarbon biodegradation. These columns also exhibited increases in ϕ (up to ~9 mrad) and σ″ (up to two order of magnitude higher) 5 weeks after microbial inoculation. Variations in m and m(n) were consistent with temporal changes in ϕ and σ″ responses, respectively. Temporal geochemical changes and high resolution scanning electron microscopy imaging corroborated the CR findings, thus indicating the sensitivity of CR measurements to EtOH biodegradation processes. Our results offer insight into the potential application of CR measurements for long-term monitoring of biogeochemical and mineralogical changes during intrinsic and induced EtOH biodegradation in the subsurface.
authors: Department of Earth and Environmental Sciences, Rutgers University, 101 Warren Street, Newark, NJ, 07102 USA. Electronic address: personna@andromeda.rutgers.edu.
authors: Yves Robert
authors: YR
authors: Personna
authors: Lee
authors: L
authors: Slater
authors: Dimitrios
authors: D
authors: Ntarlagiannis
authors: Dale
authors: D
authors: Werkema
authors: Zoltan
authors: Z
authors: Szabo
mesh_terms: D000085:Acetates / Q000378:metabolism; D001419:Bacteria / Q000378:metabolism / Q000648:ultrastructure; D018407:Bacterial Physiological Phenomena; D001673:Biodegradation, Environmental; D018441:Biofilms; D004563:Electrochemistry; D004785:Environmental Pollutants / Q000378:metabolism*; D000431:Ethanol / Q000378:metabolism*; D008855:Microscopy, Electron, Scanning; D016062:Porosity; D012822:Silicon Dioxide
chemical_list: D000085:Acetates; D004785:Environmental Pollutants; D000431:Ethanol; D012822:Silicon Dioxide
keywords: Biodegradation; Biofuels; Biogeophysics; Complex resistivity; Ethanol; Redox reactions