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Full-Text Articles in Engineering
Transformation Of 2-Line Ferrihydrite To 6-Line Ferrihydrite Under Oxic And Anoxic Conditions, Ravi K. Kukkadapu, John M. Zachara, James K. Fredrickson, Steven C. Smith, Alice C. Dohnalkova, Colleen K. Russel
Transformation Of 2-Line Ferrihydrite To 6-Line Ferrihydrite Under Oxic And Anoxic Conditions, Ravi K. Kukkadapu, John M. Zachara, James K. Fredrickson, Steven C. Smith, Alice C. Dohnalkova, Colleen K. Russel
US Department of Energy Publications
Mineralogical transformations of 2-line ferrihydrite were studied under oxic and Fe3+-reducing conditions to establish the role, if any, of 6-line ferrihydrite (“well” organized ferrihydrite) in the reaction pathway and as a final product. In oxic experiments, concentrated suspensions (0.42 mol/L Fe3+ in 0.1 mol/L NaClO4) of freshly synthesized 2-line ferrihydrite, with and without 3% Ni2+, were aged at an initial pH = 7.2 (unbuffered and unadjusted) and 25°C for more than three years. X-ray diffraction, transmission electron microscopy, and Mössbauer spectroscopy measurements were performed on the solids after different aging periods. The primary mineralogical products …
Murdock, Nebraska, Groundwater Flow And Transport Modeling In Support Of Long-Term Monitoring, Applied Geosciences And Environmental Management Section Environmental Research Division, Argonne National Laboratory
Murdock, Nebraska, Groundwater Flow And Transport Modeling In Support Of Long-Term Monitoring, Applied Geosciences And Environmental Management Section Environmental Research Division, Argonne National Laboratory
US Department of Energy Publications
Fall 2002 Assignments:
• Update all models to MODFLOW-2000
• Re-calibrate original Murdock steady-state groundwater flow model to November 25, 1998 observed water levels (Phase 1 hydrology)
• Determine time when climatological/hydrolic regime changed in eastern Nebraska. Groundwater levels observed in 2002 are significantly lower than all values observed previously (1997-1999). Palmer Hydrologic Drought Index.
• Determine appropriate groundwater level data for calibration of new (Phase 2) groundwater flow model representing current hydrologic regime (avg. of 2002 observations)
• Re-evaluate/recalculate initial CCl4 concentrations for MT3D-99 solute transport model calibration – 1996/97 concentration data. Too much CCl4 mass …
Global Optical Lightning Flash Rates Determined With The Forte Satellite, Tracy E. Light, Sean M. Davis, William Boeck, Abram Jacobson, David Suszcynsky
Global Optical Lightning Flash Rates Determined With The Forte Satellite, Tracy E. Light, Sean M. Davis, William Boeck, Abram Jacobson, David Suszcynsky
US Department of Energy Publications
Using FORTE photodiode detector (PDD) observations of lightning, we have determined the geographic distribution of nighttime flash rate density. We estimate the PDD flash detection efficiency to be 62% for total lightning through comparison to lightning observations by the TRMM satellite's Lightning Imaging Sensor (LIS), using cases in which FORTE and TRMM viewed the same storm. We present here both seasonal and total flash rate maps. We examine some characteristics of the optical emissions of lightning in both high and low flash rate environments, and find that while lightning occurs less frequently over ocean, oceanic lightning flashes are somewhat more …
Microbial Reduction Of Structural Fe(Iii) In Illite And Goethite, Hailiang Dong, Ravi K. Kukkadapu, James K. Fredrickson, John M. Zachara, David W. Kennedy, Heather M. Kostandarithes
Microbial Reduction Of Structural Fe(Iii) In Illite And Goethite, Hailiang Dong, Ravi K. Kukkadapu, James K. Fredrickson, John M. Zachara, David W. Kennedy, Heather M. Kostandarithes
US Department of Energy Publications
Microbial reduction of Fe(III) in illite was studied to evaluate the possibility of microbial utilization of Fe(III) in sedimentary clays and to determine the effects of bioreduction on clay composition and structure. A subsurface bacterium (Shewanella putrefaciens CN32) and illite separates (
Secondary Mineralization Pathways Induced By Dissimilatory Iron Reduction Of Ferrihydrite Under Advective Flow, Colleen M. Hansel, Shawn G. Benner, Jim Neiss, Alice Dohnalkova, Ravi K. Kukkadapu, Scott Fendorf
Secondary Mineralization Pathways Induced By Dissimilatory Iron Reduction Of Ferrihydrite Under Advective Flow, Colleen M. Hansel, Shawn G. Benner, Jim Neiss, Alice Dohnalkova, Ravi K. Kukkadapu, Scott Fendorf
US Department of Energy Publications
Iron (hydr)oxides not only serve as potent sorbents and repositories for nutrients and contaminants but also provide a terminal electron acceptor for microbial respiration. The microbial reduction of Fe (hydr)oxides and the subsequent secondary solid-phase transformations will, therefore, have a profound influence on the biogeochemical cycling of Fe as well as associated metals. Here we elucidate the pathways and mechanisms of secondary mineralization during dissimilatory iron reduction by a common iron-reducing bacterium, Shewanella putrefaciens (strain CN32), of 2-line ferrihydrite under advective flow conditions. Secondary mineralization of ferrihydrite occurs via a coupled, biotic-abiotic pathway primarily resulting in the production of magnetite …
Heterogeneous Electron-Transfer Kinetics With Synchrotron 57fe Mossbauer Spectroscopy, J. E. Amonette, Ravi K. Kukkadapu, E. E. Alp, W. Sturhahn, T. S. Toellner
Heterogeneous Electron-Transfer Kinetics With Synchrotron 57fe Mossbauer Spectroscopy, J. E. Amonette, Ravi K. Kukkadapu, E. E. Alp, W. Sturhahn, T. S. Toellner
US Department of Energy Publications
In the first known kinetic application of the technique, synchrotron 57Fe-Mössbauer spectroscopy was used to follow the rate of heterogeneous electron transfer between aqueous reagents and a solid phase containing Fe. The solid, a synthetic 57Fe-enriched Fe (III)-bearing pyroaurite-like phase having terephthalate (TA) in the interlayer [Mg3Fe (OH)8(TA)0.5 • 2H2O], was reduced by Na2S2O4 and then reoxidized by K2Cr2O7 by means of a novel flow-through cell. Synchrotron Mössbauer spectra were collected in the time domain at 30-s intervals. Integration of the …
Mossbauer And Optical Spectroscopic Study Of Temperature And Redox Effects On Iron Local Environments In A Fe-Doped (0.5 Mol% Fe2o3)18na2o–72sio2 Glass, Ravi K. Kukkadapu, Hong Li, Gary L. Smith, J.D. Crum, Jun-Sik Jeoung, W. Howard Poisl, Michael C. Weinberg
Mossbauer And Optical Spectroscopic Study Of Temperature And Redox Effects On Iron Local Environments In A Fe-Doped (0.5 Mol% Fe2o3)18na2o–72sio2 Glass, Ravi K. Kukkadapu, Hong Li, Gary L. Smith, J.D. Crum, Jun-Sik Jeoung, W. Howard Poisl, Michael C. Weinberg
US Department of Energy Publications
Local environments of ferric and ferrous irons were systematically studied with Mössbauer (at liquid helium temperature)and ultraviolet–visible–near infrared spectroscopic methods for various 18Na2O–72SiO2 glasses doped with 0.5 mol% Fe2O3. These were prepared at temperatures of 1300–1600 °C in ambient air or at 1500 °C under reducing conditions with oxygen partial pressures from 12.3 to 0.27 x 10-7 atmospheres. The Mössbauer spectroscopic method identified three types of local environments, which were represented by the Fe3+ sextet, the Fe3+ doublet, and the Fe2+ doublet. The Fe3+ sextet ions were assigned …
Influence Of Electron Donor/Acceptor Concentrations On Hydrous Ferric Oxide (Hfo) Bioreduction, James K. Fredrickson, Sreenivas Kota, Ravi K. Kukkadapu, Chongxuan Liu, John M. Zachara
Influence Of Electron Donor/Acceptor Concentrations On Hydrous Ferric Oxide (Hfo) Bioreduction, James K. Fredrickson, Sreenivas Kota, Ravi K. Kukkadapu, Chongxuan Liu, John M. Zachara
US Department of Energy Publications
Dissimilatory metal-reducing bacteria (DMRB) facilitate the reduction of Fe and Mn oxides in anoxic soils and sediments and play an important role in the cycling of these metals and other elements such as carbon in aqueous environments. Previous studies investigating the reduction of Fe(III) oxides by DMRB focused on reactions under constant initial electron donor (lactate) and electron acceptor (Fe oxide) concentrations. Because the concentrations of these reactants can vary greatly in the environment and would be expected to influence the rate and extent of oxide reduction, the influence of variable electron acceptor and donor concentrations on hydrous ferric oxide …
Effect Of Temperature On Cs+ Sorption And Desorption In Subsurface Sediments At The Hanford Site, U.S.A., Chongxuan Liu, John M. Zachara, Odeta Qafoku, Steve Smith
Effect Of Temperature On Cs+ Sorption And Desorption In Subsurface Sediments At The Hanford Site, U.S.A., Chongxuan Liu, John M. Zachara, Odeta Qafoku, Steve Smith
US Department of Energy Publications
The effects of temperature on Cs+ sorption and desorption were investigated in subsurface sediments from the U.S. Department of Energy Hanford Site. The site has been contaminated at several locations by the accidental leakage of high-level nuclear waste (HLW) containing 137Cs+. The high temperature of the self-boiling, leaked HLW fluid and the continuous decay of various radionuclides carried by the waste supernatant have resulted in elevated vadose temperatures (currently up to 72 °C) below the Hanford S-SX tank farm that have dissipated slowly from the time of leakage (1970). The effect of temperature on Cs+ …
Inhibition Of Bacterial U(Vi) Reduction By Calcium, Scott Brooks, James K. Fredrickson, Sue Carroll, David Kennedy, John M. Zachara, Andrew Plymale, Shelly Kelley, Kenneth Kemner, Scott Fendorf
Inhibition Of Bacterial U(Vi) Reduction By Calcium, Scott Brooks, James K. Fredrickson, Sue Carroll, David Kennedy, John M. Zachara, Andrew Plymale, Shelly Kelley, Kenneth Kemner, Scott Fendorf
US Department of Energy Publications
The rapid kinetics of bacterial U(VI) reduction and low solubility of uraninite (UO2,cr) make this process an attractive option for removing uranium from groundwater. Nevertheless, conditions that may promote or inhibit U(VI) reduction are not well-defined. Recent descriptions of Ca-UO2- CO3 complexes indicate that these species may dominate the aqueous speciation of U(VI) in many environments. We monitored the bacterial reduction of U(VI) in bicarbonate buffered solution in the presence and absence of Ca. XAFS measurements confirmed the presence of a Ca- U(VI)-CO3 complex in the initial solutions containing calcium. Calcium, at millimolar concentrations …
Desorption Kinetics Of Radiocesium From Subsurface Sediments At Hanford Site, Usa, Chongxuan Liu, John M. Zachara, Steven Smith, James Mckinley, Calvin Ainsworth
Desorption Kinetics Of Radiocesium From Subsurface Sediments At Hanford Site, Usa, Chongxuan Liu, John M. Zachara, Steven Smith, James Mckinley, Calvin Ainsworth
US Department of Energy Publications
The desorption of 137Cs+ was investigated on sediments from the United States Hanford site. Pristine sediments and ones that were contaminated by the accidental release of alkaline 137Cs+ -containing high level nuclear wastes (HLW, 2 X 106 to 6 X 107 pCi 137Cs+/g) were studied. The desorption of 137Cs+ was measured in Na+, K+, Rb+, and NH4+ electrolytes of variable concentration and pH, and in presence of a strong Cs+-specific sorbent (self-assembled monolayer on a mesoporous support, SAMMS). 137 …
Nonlocal Bacterial Electron Transfer To Hematite Surfaces, Kevin Rosso, John M. Zachara, James K. Fredrickson, Yuri Gorby, Steven Smith
Nonlocal Bacterial Electron Transfer To Hematite Surfaces, Kevin Rosso, John M. Zachara, James K. Fredrickson, Yuri Gorby, Steven Smith
US Department of Energy Publications
Mechanisms by which dissimilatory iron-reducing bacteria utilize iron and manganese oxide minerals as terminal electron acceptors for respiration are poorly understood. In the absence of exogenous electron shuttle compounds, extracellular electron transfer is generally thought to occur through the interfacial contact area between mineral surfaces and attached cells. Possible alternative reduction pathways have been proposed based on the discovery of a link between an excreted quinone and dissimilatory reduction. In this study, we utilize a novel experimental approach to demonstrate that Shewanella putrefaciens reduces the surface of crystalline iron oxides at spatial locations that are distinct from points of attachment.
Transport Of Multiple Tracers In Variably Saturated Humid Region Structured Soils And Semi-Arid Region Laminated Sediments, M.A. Mayes, P.M. Jardine, T.L. Mehlhorn, B.N. Bjornstad, J.L. Ladd, John M. Zachara
Transport Of Multiple Tracers In Variably Saturated Humid Region Structured Soils And Semi-Arid Region Laminated Sediments, M.A. Mayes, P.M. Jardine, T.L. Mehlhorn, B.N. Bjornstad, J.L. Ladd, John M. Zachara
US Department of Energy Publications
The processes governing physical nonequilibrium (PNE)—coupled preferential flow and matrix diffusion—are diverse between humid and semi-arid regions, and are directly related to climate and rock/sediment type, and indirectly related to subsequent soil profile development. The fate and transport of contaminants in these variably saturated undisturbed media is largely a function of the influence of PNE processes. Large cores of laminated silts and sands were collected from the US Department of Energy Pacific Northwest National Laboratory (PNNL) in semi-arid south central Washington. Additional cores of weathered, fractured interbedded limestone and shale saprolite were collected from the Oak Ridge National Laboratory (ORNL) …
Quantifying The Effects Of Small-Scale Heterogeneities On Flow And Transport In Undisturbed Cores From The Hanford Formation, M. N. Pace, M. A. Mayes, P. M. Jardine, T. L. Mehlhorn, John M. Zachara, B.N. Bjornstad
Quantifying The Effects Of Small-Scale Heterogeneities On Flow And Transport In Undisturbed Cores From The Hanford Formation, M. N. Pace, M. A. Mayes, P. M. Jardine, T. L. Mehlhorn, John M. Zachara, B.N. Bjornstad
US Department of Energy Publications
Accelerated migration of contaminants in the vadose zone has been observed beneath tank farms at the U.S. Department of Energy’s Hanford Reservation, Richland, WA. This paper focuses on quantifying hydrologic processes that control the fate and transport of contaminants in the unsaturated sediments beneath the Hanford tank farms. The experimental approach involved the use of field relevant, long-term unsaturated nonreactive transport experiments in undisturbed sediments from the Hanford Formation. Undisturbed sediment cores were collected from a laminated fine-grained sand unit within the Hanford Formation in both the vertical direction (flow cross bedding) and the horizontal direction (flow bedding parallel). Laboratory-scale …
Simultaneous Observations Of Mesospheric Gravity Waves And Sprites Generated By A Midwestern Thunderstorm, D.D. Sentman, E.M. Wescott, R.H. Picard, J.R. Winick, H.C. Stenbaek-Nielsen, E.M. Dewan, D.R. Moudry, F.T. São Sabbas, M.J. Heavner, J. Morrill
Simultaneous Observations Of Mesospheric Gravity Waves And Sprites Generated By A Midwestern Thunderstorm, D.D. Sentman, E.M. Wescott, R.H. Picard, J.R. Winick, H.C. Stenbaek-Nielsen, E.M. Dewan, D.R. Moudry, F.T. São Sabbas, M.J. Heavner, J. Morrill
US Department of Energy Publications
The present report investigates using simultaneous observations of coincident gravity waves and sprites to establish an upper limit on sprite-associated thermal energy deposition in the mesosphere. The University of Alaska operated a variety of optical imagers and photometers at two ground sites in support of the NASA Sprites99 balloon campaign. One site was atop a US Forest Service lookout tower on Bear Mt. in the Black Hills, in western South Dakota. On the night of 18 August 1999 we obtained from this site simultaneous images of sprites and OH airglow modulated by gravity waves emanating from a very active sprite …
Deformation Of A Peridynamic Bar, S. A. Silling, M. Zimmermann, R. Abeyaratne
Deformation Of A Peridynamic Bar, S. A. Silling, M. Zimmermann, R. Abeyaratne
US Department of Energy Publications
The deformation of an infinite bar subjected to a self-equilibrated load distribution is investigated using the peridynamic formulation of elasticity theory. The peridynamic theory differs from the classical theory and other nonlocal theories in that it does not involve spatial derivatives of the displacement field. The bar problem is formulated as a linear Fredholm integral equation and solved using Fourier transform methods. The solution is shown to exhibit, in general, features that are not found in the classical result. Among these are decaying oscillations in the displacement field and progressively weakening discontinuities that propagate outside of the loading region. These …