Petrophysical properties of saprolites from the Oak Ridge Integrated Field Research Challenge site, Tennessee

Geophysics ◽  
2013 ◽  
Vol 78 (1) ◽  
pp. D21-D40 ◽  
Author(s):  
André Revil ◽  
Magnus Skold ◽  
Susan S. Hubbard ◽  
Yuxin Wu ◽  
David B. Watson ◽  
...  
Keyword(s):  
Field Research ◽  
Surface Conductivity ◽  
Complex Conductivity ◽  
Fluid Composition ◽  
Excess Charge ◽  
Petrophysical Properties ◽  
Conductivity Measurements ◽  
Oak Ridge ◽  
Core Samples ◽  
Research Challenge

At the Oak Ridge Integrated Field Research Challenge site, near Oak Ridge, Tennessee, the shallow saprolitic aquifer is contaminated by nitric acid, uranium, and metals originating from the former S3 settling ponds. To interpret low-frequency geophysical methods used to image contaminant plumes, we have characterized the petrophysical properties of three representative saprolite core samples. Their hydraulic conductivity ranges from [Formula: see text] to [Formula: see text] in agreement with field data. Complex conductivity measurements, in the frequency range of 1 mHz to 45 kHz, were performed with NaCl solutions with electrical conductivities in the range [Formula: see text] to [Formula: see text], a range representative of field conditions. The electrical conductivity data were well reproduced with a simple linear conductivity model between the saprolite conductivity and the pore water conductivity. The conductivity plots were used to estimate the formation factor (the cementation exponent was about [Formula: see text]) and the surface conductivity ([Formula: see text]). The magnitude of the surface conductivity depended on the degree of weathering and therefore on the amount of smectite and mixed layer (illite-smectite) clays present in the saprolite. The chargeability of the core samples was in the range of [Formula: see text] and is strongly dependent on the salinity. We also performed streaming potential measurements with the same pore fluid composition as that used for the complex conductivity measurements. We found an excess of movable electrical charges on the order of 100 to [Formula: see text] in agreement with previous investigations connecting the movable excess charge density to permeability. The zeta potential was in the range of [Formula: see text] to [Formula: see text] independent on the salinity. The electrical measurements were consistent with an average cation exchange capacity in the range of 1.4 to [Formula: see text] and a specific surface area on the order of 4000 to about 30,000 [Formula: see text].

Hydrogeophysical investigations of the former S-3 ponds contaminant plumes, Oak Ridge Integrated Field Research Challenge site, Tennessee

Geophysics ◽  
2013 ◽  
Vol 78 (4) ◽  
pp. EN29-EN41 ◽  
Author(s):  
A. Revil ◽  
M. Skold ◽  
M. Karaoulis ◽  
M. Schmutz ◽  
S. S. Hubbard ◽  
...  
Keyword(s):  
Field Research ◽  
Clay Content ◽  
Surface Conductivity ◽  
Dc Resistivity ◽  
High Concentration ◽  
Resistivity Tomography ◽  
Contaminant Plumes ◽  
Oak Ridge ◽  
Nitrate Concentrations ◽  
Research Challenge

At the Oak Ridge Integrated Field Research Challenge site, near Oak Ridge, Tennessee, contaminants from the former S-3 ponds have infiltrated the shallow saprolite for over 60 years. Two- and three-dimensional DC-resistivity tomography is used to characterize the number and location of the main contaminant plumes, which include high concentration of nitrate. These contaminant plumes have typically an electrical resistivity in the range 2–20 ohm-m while the background saprolite resistivity is in the range 60–120 ohm-m, so the difference of resistivity can be easily mapped using DC-resistivity tomography to locate the contaminant pathways. We develop a relationship to derive the in situ nitrate concentrations from the 3D resistivity tomograms accounting for the effect of surface conductivity. The footprint of the contamination upon the resistivity is found to be much stronger than the local variations associated with changes in the porosity and the clay content. With this method, we identified a total of five main plumes (termed CP1 to CP5). Plume CP2 corresponds to the main plume in terms of nitrate concentration (∼50,000 [Formula: see text]). We also used an active time constrained approach to perform time-lapse resistivity tomography over a section crossing the plumes CP1 and CP2. The sequence of tomograms is used to determine the changes in the nitrate concentrations associated with infiltration of fresh (meteoritic) water from a perched aquifer. This study highlights the importance of accounting for surface conductivity when characterizing plume distributions in clay-rich subsurface systems.

scholarly journals Unique Ecophysiology among U(VI)-Reducing Bacteria as Revealed by Evaluation of Oxygen Metabolism in Anaeromyxobacter dehalogenans Strain 2CP-C

2009 ◽  
Vol 76 (1) ◽  
pp. 176-183 ◽  
Author(s):  
Sara H. Thomas ◽  
Robert A. Sanford ◽  
Benjamin K. Amos ◽  
Mary Beth Leigh ◽  
Erick Cardenas ◽  
...  
Keyword(s):  
Field Research ◽  
Oxygen Metabolism ◽  
Pilot Scale ◽  
Aerobic Growth ◽  
Soil Particles ◽  
Oak Ridge ◽  
Oxygen Intrusion ◽  
Research Challenge ◽  
Reducing Bacteria

ABSTRACT Anaeromyxobacter spp. respire soluble hexavalent uranium, U(VI), leading to the formation of insoluble U(IV), and are present at the uranium-contaminated Oak Ridge Integrated Field Research Challenge (IFC) site. Pilot-scale in situ bioreduction of U(VI) has been accomplished in area 3 of the Oak Ridge IFC site following biostimulation, but the susceptibility of the reduced material to oxidants (i.e., oxygen) compromises long-term U immobilization. Following oxygen intrusion, attached Anaeromyxobacter dehalogenans cells increased approximately 5-fold from 2.2 × 107 ± 8.6 × 106 to 1.0 × 108 ± 2.2 × 107 cells per g of sediment collected from well FW101-2. In the same samples, the numbers of cells of Geobacter lovleyi, a population native to area 3 and also capable of U(VI) reduction, decreased or did not change. A. dehalogenans cells captured via groundwater sampling (i.e., not attached to sediment) were present in much lower numbers (<1.3 × 104 ± 1.1 × 104 cells per liter) than sediment-associated cells, suggesting that A. dehalogenans cells occur predominantly in association with soil particles. Laboratory studies confirmed aerobic growth of A. dehalogenans strain 2CP-C at initial oxygen partial pressures (pO2) at and below 0.18 atm. A negative linear correlation [μ = (−0.09 × pO2) + 0.051; R 2 = 0.923] was observed between the instantaneous specific growth rate μ and pO2, indicating that this organism should be classified as a microaerophile. Quantification of cells during aerobic growth revealed that the fraction of electrons released in electron donor oxidation and used for biomass production (fs ) decreased from 0.52 at a pO2 of 0.02 atm to 0.19 at a pO2 of 0.18 atm. Hence, the apparent fraction of electrons utilized for energy generation (i.e., oxygen reduction) (fe ) increased from 0.48 to 0.81 with increasing pO2, suggesting that oxygen is consumed in a nonrespiratory process at a high pO2. The ability to tolerate high oxygen concentrations, perform microaerophilic oxygen respiration, and preferentially associate with soil particles represents an ecophysiology that distinguishes A. dehalogenans from other known U(VI)-reducing bacteria in area 3, and these features may play roles for stabilizing immobilized radionuclides in situ.

scholarly journals Denitrifying Bacteria from the Genus Rhodanobacter Dominate Bacterial Communities in the Highly Contaminated Subsurface of a Nuclear Legacy Waste Site

2011 ◽  
Vol 78 (4) ◽  
pp. 1039-1047 ◽  
Author(s):  
Stefan J. Green ◽  
Om Prakash ◽  
Puja Jasrotia ◽  
Will A. Overholt ◽  
Erick Cardenas ◽  
...  
Keyword(s):  
Community Structure ◽  
Microbial Community ◽  
Community Composition ◽  
Field Research ◽  
Denitrifying Bacteria ◽  
Rrna Genes ◽  
Content Type ◽  
Oak Ridge ◽  
Dna And Rna ◽  
Research Challenge

ABSTRACTThe effect of long-term mixed-waste contamination, particularly uranium and nitrate, on the microbial community in the terrestrial subsurface was investigated at the field scale at the Oak Ridge Integrated Field Research Challenge (ORIFRC) site in Oak Ridge, TN. The abundance, community composition, and distribution of groundwater microorganisms were examined across the site during two seasonal sampling events. At representative locations, subsurface sediment was also examined from two boreholes, one sampled from the most heavily contaminated area of the site and another from an area with low contamination. A suite of DNA- and RNA-based molecular tools were employed for community characterization, including quantitative PCR of rRNA and nitrite reductase genes, community composition fingerprinting analysis, and high-throughput pyrotag sequencing of rRNA genes. The results demonstrate that pH is a major driver of the subsurface microbial community structure and that denitrifying bacteria from the genusRhodanobacter(classGammaproteobacteria) dominate at low pH. The relative abundance of bacteria from this genus was positively correlated with lower-pH conditions, and these bacteria were abundant and active in the most highly contaminated areas. Other factors, such as the concentration of nitrogen species, oxygen level, and sampling season, did not appear to strongly influence the distribution ofRhodanobacterbacteria. The results indicate that these organisms are acid-tolerant denitrifiers, well suited to the acidic, nitrate-rich subsurface conditions, and pH is confirmed as a dominant driver of bacterial community structure in this contaminated subsurface environment.

scholarly journals Draft Genome Sequences of Two Janthinobacterium lividum Strains, Isolated from Pristine Groundwater Collected from the Oak Ridge Field Research Center

2017 ◽  
Vol 5 (26) ◽  
Author(s):  
Xiaoqin Wu ◽  
Adam M. Deutschbauer ◽  
Alexey E. Kazakov ◽  
Kelly M. Wetmore ◽  
Bryson A. Cwick ◽  
...  
Keyword(s):  
Draft Genome ◽  
Field Research ◽  
Research Center ◽  
Purple Pigment ◽  
Genome Sequences ◽  
Content Type ◽  
Oak Ridge ◽  
Background Site ◽  
Janthinobacterium Lividum ◽  
Groundwater Samples

ABSTRACT We present here the draft genome sequences of two Janthinobacterium lividum strains, GW456P and GW458P, isolated from groundwater samples collected from a background site at the Oak Ridge Field Research Center. Production of a purple pigment by these two strains was observed when grown on diluted (1/10) LB agar plates.

Surface conductivity measurements in nanometric to micrometric foam films

2015 ◽  
Vol 27 (19) ◽  
pp. 194118 ◽  
Author(s):  
Oriane Bonhomme ◽  
Anne Mounier ◽  
Gilles Simon ◽  
Anne-Laure Biance
Keyword(s):  
Surface Conductivity ◽  
Conductivity Measurements ◽  
Foam Films

Electrokinetic properties of Cassiterite

1953 ◽  
Vol 6 (3) ◽  
pp. 278 ◽  
Author(s):  
DJ O'Connor ◽  
AS Buchanan
Keyword(s):  
Negative Charge ◽  
Positive Charge ◽  
Weak Acid ◽  
Surface Conductivity ◽  
Surface Ionization ◽  
Conductivity Measurements ◽  
The Third ◽  
Three Samples ◽  
Negative Surface ◽  
Flotation Collector

Simultaneous ζ-potential and surface conductivity measurements have been made on three samples of cassiterite (SnO2) in water, in solutions of HCl, alkalis, inorganic salts, and the flotation collector reagent sodium cetyl sulphate. It is probable that the intrinsic surface charge of cassiterite in water is negative and that it is due to surface ionization as a very weak acid. Two of the solids possessed a negative surface whilst the positive charge of the third seemed to be due to ionization of a strongly basic impurity. Those samples having a negative charge showed little reaction with sodium cetyl sulphate alone, but appreciable adsorption of cetyl sulphate ion took place in acid solution. On the other hand, the sample with the positive surface reacted with cetyl sulphate ion even in the absence of acid. In all cases adsorption of cetyl sulphate was completely reversible.

MICRO-FOUR-POINT PROBES IN A UHV SCANNING ELECTRON MICROSCOPE FOR IN-SITU SURFACE-CONDUCTIVITY MEASUREMENTS

2000 ◽  
Vol 07 (05n06) ◽  
pp. 533-537 ◽  
Author(s):  
ICHIRO SHIRAKI ◽  
TADAAKI NAGAO ◽  
SHUJI HASEGAWA ◽  
CHRISTIAN L. PETERSEN ◽  
PETER BØGGILD ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Surface Defects ◽  
High Energy ◽  
Surface Conductivity ◽  
Conductivity Measurements ◽  
Surface Domains ◽  
Unambiguous Detection ◽  
Scanning Electron

For in-situ measurements of surface conductivity in ultrahigh vacuum (UHV), we have installed micro-four-point probes (probe spacings down to 4 μm) in a UHV scanning electron microscope (SEM) combined with scanning reflection–high-energy electron diffraction (RHEED). With the aid of piezoactuators for precise positioning of the probes, local conductivity of selected surface domains of well-defined superstructures could be measured during SEM and RHEED observations. It was found that the surface sensitivity of the conductivity measurements was enhanced by reducing the probe spacing, enabling the unambiguous detection of surface-state conductivity and the influence of surface defects on the electrical conduction.

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