Induced-polarization measurements on unconsolidated sediments from a site of active hydrocarbon biodegradation

Abstract

To investigate the potential role that indigenous microorganisms and microbial processes may play in altering lowfrequency electrical properties, induced-polarization (IP) measurements in the frequency range of 0.1 to 1000 Hz were acquired from sediment samples retrieved from a site contaminated by hydrocarbon undergoing intrinsic biodegradation. Increased imaginary conductivity and phase were observed for samples from the smear zone (contaminated with residual-phase hydrocarbon), exceeding values obtained for samples contaminated with dissolved-phase hydrocarbons, and in turn, exceeding values obtained for uncontaminated samples. Real conductivity, although generally elevated for samples from the smear zone, did not show a strong correlation with contamination. Controlled experiments on uncontaminated samples from the field site indicate that variations in surface area, electrolytic conductivity, and water content across the site cannot account for the high imaginary conductivity observed within the smear zone. We suggest that microbial processes may be responsible for the enhanced IP response observed at contaminated locations. Scanning electron microscopy and IP measurements during acid leaching indicate that etched pits on mineral surfaces — caused by the production of organic acids or formed during microbial colonization of these surfaces — are not the cause of the IP enhancement. Rather, we postulate that the accumulation of microbial cells (biofilms) with high surface area at the mineral-electrolyte interface generates the IP response. These findings illustrate the potential use of electrical measurements to noninvasively monitor microbial activity at sites undergoing natural hydrocarbon degradation.

Spectral induced polarization signatures of abiotic FeS precipitation

“…Previous experiments showed that SIP responses resulting from biomineralization processes ͑Ntarlagiannis et al, 2005a; Williams et al, 2005;Slater et al, 2007;Personna et al, 2008͒ are significantly higher than SIP responses resulting from microbial activity in the absence of metallic mineral precipitation ͑Abdel Aal et al, 2004;Abdel Aal et al, 2006;Davis et al, 2006͒. Based on such previous experience, we expected that the precipitation of metallic minerals, regardless of the driving processes, would lead to substantial SIP responses.…”

Geophysical Signatures of Microbial Activity at Hydrocarbon Contaminated Sites: A Review

“…Early geophysical studies that reported higher bulk electrical conductivity and attenuated ground penetrating radar (GPR) signals at LNAPL-contaminated sites were linked to microbial activity associated with biodegradation (e.g., Benson et al 1997;Sauck et al 1998). A large volume of literature now exists supporting the early findings of anomalous geophysical signatures at LNAPL contaminated sites undergoing bioremediation (e.g., Atekwana et al 2000Atekwana et al , 2002Atekwana et al 2004a, b, c, d;Abdel Aal et al 2006;Bradford 2007;Cassidy 2007Cassidy , 2008Allen et al 2007). Attempts to understand the role of microorganisms in altering the physical properties of geologic systems has resulted in the development of a new sub-discipline in geophysics called ''biogeophysics'' ).…”

“…Over the past two decades, geophysical techniques have been employed at several LNAPL contaminated sites to characterize both the spatial (e.g., Benson and Stubben 1995;Bermejo et al 1997;Sauck et al 1998;Atekwana et al 2000;2004a;Osella et al 2002;Werkema et al 2003;Tezkan et al 2005;Abdel Aal et al 2006;Sogade et al 2006;Bradford 2007;Cassidy 2007) and temporal (e.g., Lopes de Castro and Branco 2003;Che-Alota et al 2009) extent to understand the evolution of the contamination in the subsurface. Many of these geophysical studies have provided valuable insights into the behavior of LNAPL contamination; however, the results remain mixed.…”

The Microbial Community Structure in Petroleum-Contaminated Sediments Corresponds to Geophysical Signatures

“…The growth and metabolic activities of microorganisms are known to alter the chemical and physical conditions of the environment. The biodegradation of hydrocarbons results in the production of bacterial metabolites, including organic acids and CO 2 . Carbonic acid and organic acids such as acetate and fumarate drive mineral dissolution by releasing ions from the sediment grains (18,37,45).…”

“…Carbonic acid and organic acids such as acetate and fumarate drive mineral dissolution by releasing ions from the sediment grains (18,37,45). Moreover, microorganisms alter their physical surroundings by colonizing sediment surfaces in the form of microcolonies or biofilms or by driving the precipitation of metal sulfides at cell or sediment grain surfaces (1,2,40,57). In addition, the presence of microbial nanowires, which have recently been identified as highly conductive pili on the surfaces of iron-reducing bacteria such as Geobacter (43) and Shewanella (27) species, may also play a role in increasing subsurface conductivity levels in certain geomicrobiological environments.…”