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.

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 Dynamics of Microbial Community Composition and Function during In Situ Bioremediation of a Uranium-Contaminated Aquifer

2011 ◽  
Vol 77 (11) ◽  
pp. 3860-3869 ◽  
Author(s):  
Joy D. Van Nostrand ◽  
Liyou Wu ◽  
Wei-Min Wu ◽  
Zhijian Huang ◽  
Terry J. Gentry ◽  
...  
Keyword(s):  
Microbial Community ◽  
Environmental Protection Agency ◽  
Microbial Community Composition ◽  
Gene Array ◽  
Field Research ◽  
Contaminated Aquifer ◽  
Content Type ◽  
Oak Ridge ◽  
Drinking Water Standard

ABSTRACTA pilot-scale system was established to examine the feasibility ofin situU(VI) immobilization at a highly contaminated aquifer (U.S. DOE Integrated Field Research Challenge site, Oak Ridge, TN). Ethanol was injected intermittently as an electron donor to stimulate microbial U(VI) reduction, and U(VI) concentrations fell to below the Environmental Protection Agency drinking water standard (0.03 mg liter−1). Microbial communities from three monitoring wells were examined during active U(VI) reduction and maintenance phases with GeoChip, a high-density, comprehensive functional gene array. The overall microbial community structure exhibited a considerable shift over the remediation phases examined. GeoChip-based analysis revealed that Fe(III)-reducing bacterial (FeRB), nitrate-reducing bacterial (NRB), and sulfate-reducing bacterial (SRB) functional populations reached their highest levels during the active U(VI) reduction phase (days 137 to 370), in which denitrification and Fe(III) and sulfate reduction occurred sequentially. A gradual decrease in these functional populations occurred when reduction reactions stabilized, suggesting that these functional populations could play an important role in both active U(VI) reduction and maintenance of the stability of reduced U(IV). These results suggest that addition of electron donors stimulated the microbial community to create biogeochemical conditions favorable to U(VI) reduction and prevent the reduced U(IV) from reoxidation and that functional FeRB, SRB, and NRB populations within this system played key roles in this process.

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].

Pilot and Field-Scale Uranium Lysimeter Studies at the Oak Ridge Y-12 Plant

1992 ◽  
Vol 294 ◽  
Author(s):  
Dianne D. Gates ◽  
Chet W. Francis ◽  
Lisa M. Laster ◽  
Rod Kimmiti
Keyword(s):  
Radioactive Waste ◽  
Pilot Scale ◽  
Field Scale ◽  
Oak Ridge ◽  
Decomposition Processes ◽  
Field Lysimeters ◽  
Time Periods ◽  
Biological Decomposition ◽  
Low Level Radioactive Waste

ABSTRACTField- and pilot-scale uranium leaching facilities (lysimeters) have been constructed at the Oak Ridge Y-12 Plant to investigate the rate of uranium (U) leaching and the residual U concentration that can be expected when low level radioactive waste (LLW) is buried in landfills. Current plans are to load three large standard column lysimeters with compacted production trash (blotter, waste wipes, paper etc.) and apply groundwater to the surface of the lysimeters.Several issues had to be addressed before the field lysimeters could be loaded with the LLW. Predominate among these concerns was how to adequately characterize the waste placed in the lysimeters (∼ 10 yd3 waste per lysimeter) and how to effectively collect in situ leachate samples from compacted wasteforms in the absence of soil. Pilot scale studies revealed that monitoring individual bags (30 gal) of LLW with a waste curie monitor would be sufficient to determine the initial U loading and that conventional suction candles would perform adequately within the compacted waste for extended time periods if they are installed properly. In the pilot leaching studies, the highest U concentration (∼ 0.2 mg/l) in the leachate was observed during the first month of leaching, before active biological decomposition processes became dominant making the lysimeter anoxic. After the initial oxic flushing, U concentrations in the leachate became very low (mean = 0.021 mg/l).

Cross‐borehole resistivity tomography of a pilot‐scale, in‐situ vitrification test

Geophysics ◽  
1995 ◽  
Vol 60 (3) ◽  
pp. 886-898 ◽  
Author(s):  
B. R. Spies ◽  
Robert G. Ellis
Keyword(s):  
Weighting Function ◽  
National Laboratory ◽  
A Priori ◽  
Pilot Scale ◽  
Oak Ridge ◽  
Resistivity Data ◽  
Solidification Processes ◽  
Model Weighting ◽  
Melt Phase

Direct current (dc) cross‐borehole resistivity measurements were used to monitor the melting and solidification processes of an in‐situ vitrification (ISV) experiment at Oak Ridge National Laboratory (ORNL) in Tennessee. Six boreholes, 6-m deep, were augured around the ISV site, and five electrodes implanted in each hole. Three sets of crosswell, pole‐pole resistivity data were collected: prior to the melt phase, immediately after power shut‐off, and after the melt zone had solidified and returned to ambient temperature. These three sets of data were inverted using a conjugate‐gradient scheme to produce conductivity images of the melt phase and the vitrified end products. The images obtained depend quite strongly on the model weighting function applied to the inversion. With an optimum weighting function based on a priori spatial constraints, the resistivity images delineate the melt zone and provide a reasonable indication of its geometry. The resistivity data support, but do not require, the existence of the melt zone.

Influence of electron donors and acceptors on the bioremediation of soil contaminated with trichloroethene and nickel: laboratory- and pilot-scale study

2002 ◽  
Vol 45 (10) ◽  
pp. 49-54 ◽  
Author(s):  
R. El Mamouni ◽  
R. Jacquet ◽  
P. Gerin ◽  
S.N. Agathos
Keyword(s):  
Electron Donor ◽  
Electron Acceptor ◽  
Pilot Scale ◽  
Nickel Sulphide ◽  
Indigenous Microorganisms ◽  
Term Operation ◽  
In Situ Conditions ◽  
Reducing Bacteria

Laboratory- and pilot-scale studies were conducted in order to adjust and optimize the in-situ conditions for bioremediation of a soil contaminated with trichlororethene (TCE) and nickel. Results from laboratory studies showed that the indigenous microorganisms of the soil were limited by the type of electron donor. A better TCE dechlorination was obtained when the electron donor was composed of a mixture of methanol and lactate, as compared to that with methanol alone. Addition of up to 10 mM of sulphate as external electron acceptor (in combination with TCE) and with a mixture of methanol and lactate as electron donor had no significant effect on the TCE reducing activity of indigenous microorganisms of the soil, while higher concentrations (15 and 20 mM) yielded a lower dechlorination. Long term operation of a large pilot-scale soil reactor demonstrated the feasibility of a single-process in situ soil remediation. Results showed that, on one hand, TCE was progressively and stepwise reduced to cis-dichloroethene (DCE), vinyl chloride (VC) and finally to ethene, using only the indigenous microorganisms of the soil. On the other hand, stimulating the activity of sulphate-reducing bacteria of the soil with the addition of sulphate as electron acceptor was efficient in precipitating nickel as nickel sulphide.

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.

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