Download or read book Reductive Immobilization of U VI in Fe III Oxide reducing Subsurface Sediments written by and published by . This book was released on 2004 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: Although the fundamental microbiological and geochemical processes underlying the potential use of dissimilatory metal-reducing bacteria (DMRB) to create subsurface redox barriers for immobilization of uranium and other redox-sensitive metal/radionuclide contaminants are well-understood (Lovley et al., 1991; Gorby and Lovley, 1992; Lovley and Phillips, 1992; Lovley, 1995; Fredrickson et al., 2000; Wielinga et al., 2000; Wielinga et al., 2001), several fundamental scientific questions need to be addressed in order to understand and predict how such treatment procedures would function under in situ conditions in the subsurface. These questions revolve around the dynamic interactions between hydrologic flux and the coupled microbial-geochemical processes which are likely to occur within a redox barrier treatment zone. A brief summary of such questions includes the following: (1) What are the kinetic limitations to the efficiency of microbial U(VI) scavenging in subsurface sediments? (2) Is U(VI) sorbed to Fe(III) oxide and other solid-phase surfaces subject to enzymatic reduction? If so, what are the relative kinetics of aqueous vs. sorbed U(VI) reduction? (3) What are the relative kinetics of direct, enzymatic U(VI) reduction vs. abiotic reduction of U(VI) by surface-bound biogenic Fe(II)? (4) Can coupled Fe(III) oxide/U(VI) reduction be sustained long-term in subsurface environments? What are the kinetic relationships between Fe(III) oxide reduction, DMRB growth, and U(VI) reduction in advectively open sedimentary systems? The overall objective of our research is to address the questions listed above through laboratory-based batch and reactive transport experiments with natural Fe(III) oxide-bearing subsurface materials and a representative pure culture DMRB. A unique feature of our research is that we are using levels of total uranium (ca. 10−6 to 10−4 mol per dm3 bulk volume) and aqueous/solid-phase ratios ((less-than or equal to) ca. 10−3 mol U per kg sediment) which are much closer to those present in contaminated subsurface environments compared to levels employed in previous experimental studies of microbial U(VI) reduction. The goal is to develop a more realistic picture of the dynamics of U(VI) reduction and its interaction with Fe(III) oxide reduction in subsurface sedimentary environments. In doing so, our studies will provide benchmark information on process dynamics that will be useful for scaling up (e.g. through the use of field-scale reactive transport models) to in situ treatment scenarios. In addition, the experimental methodologies and modeling strategies developed for the project may applicable to the evaluation of in situ remediation technologies for other redox-sensitive metal-radionuclide contaminants such as Cr(VI) and Tc(VII). Numerical simulations are being developed hand-in-hand with the experimental work to aid in the interpretation of the observed dynamics of U(VI) behavior, and to contribute to the development of a predictive framework for assessing in situ metal-radionuclide remediation strategies driven by the activity of DMRB.

Download or read book Influence of Reactive Transport on the Reduction of U VI in the Presence of Fe III and Nitrate written by and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Subsurface contamination by metals and radionuclides represent some of the most challenging remediation problems confronting the Department of Energy (DOE) complex. In situ remediation of these contaminants by dissimilatory metal reducing bacteria (DMRB) has been proposed as a potential cost effective remediation strategy. The primary focus of this research is to determine the mechanisms by which the fluxes of electron acceptors, electron donors, and other species can be controlled to maximize the transfer of reductive equivalents to the aqueous and solid phases. The proposed research is unique in the NABIR portfolio in that it focuses on (i) the role of flow and transport in the initiation of biostimulation and the successful sequestration of metals and radionuclides [specifically U(VI)], (ii) the subsequent reductive capacity and stability of the reduced sediments produced by the biostimulation process, and (iii) the potential for altering the growth of biomass in the subsurface by the addition of specific metabolic uncoupling compounds. A scientifically-based understanding of these phenomena are critical to the ability to design successful bioremediation schemes. The laboratory research will employ Shewanella putrefaciens (CN32), a facultative DMRB that can use Fe(III) oxides as a terminal electron acceptor. Sediment-packed columns will be inoculated with this organism, and the reduction of U(VI) by the DMRB will be stimulated by the addition of a carbon and energy source in the presence of Fe(III). Separate column experiments will be conducted to independently examine: (1) the importance of the abiotic reduction of U(VI) by biogenic Fe(II); (2) the influence of the transport process on Fe(III) reduction and U(VI) immobilization, with emphasis on methods for controlling the fluxes of aqueous species to maximize uranium reduction; (3) the reductive capacity of biologically-reduced sediments (with respect to re-oxidation by convective fluxes of O2 and NO3- ) and the long-term stability of immobilized uranium mineral phases after bioremediation processes are complete, and (4) the ability for metabolic uncoupling compounds to maintain microbial growth while limiting biomass production. The results of the laboratory experiments will be used to develop mathematical descriptive models for the coupled transport and reduction processes.

Download or read book Iron Reduction and Radionuclide Immobilization written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Our research focused on (1) microbial reduction of Fe(III) and U(VI) individually, and concomitantly in natural sediments, (2) Fe(III) oxide surface chemistry, specifically with respect to reactions with Fe(II)and U(VI), (3) the influence of humic substances on Fe(III) and U(VI) bioreduction, and on U(VI) complexation, and (4) the development of reaction-based reactive transport biogeochemical models to numerically simulate our experimental results. We have continued our investigations on microbial reduction of Fe(III) oxides. Modeling our earlier experimental results required assumption of a hydrated surface for hematite, more reactive than predicted based on theoretical solubility (Burgos et al. 2002). Subsequent studies with Shewanella putrefaciens and Geobacter sulfurreducens confirmed the rates of Fe(III) bioreduction depend on oxide surface area rather than oxide thermodynamic properties (Roden,2003a, b;2004; Burgos et al,2003). We examined the potential for bioreduction of U(VI) by Geobacter sulfurreducens in the presence of synthetic Fe(III) oxides and natural Fe(III) oxide-containing solids (Jeon et al,2004a, b) in which more than 95% of added U(VI) was sorbed to mineral surfaces. The results showed a significant portion of solid-associated U(VI) was resistant to both enzymatic and abiotic (Fe(II)-driven) reduction, but the rate and extent of bioreduction of U(VI) was increased due to the addition of anthraquinone-2,6-disulfonate (AQDS). We conducted long-term semicontinuous culture and column experiments on coupled Fe(III) oxide/U(VI) reduction. These experiments were conducted with natural subsurface sediment from the Oyster site in Virginia, whose Fe content and microbial reducibility are comparable to ORNL FRC sediments (Jeon et al, 2004b). The results conclusively demonstrated the potential for sustained removal of U(VI) from solution via DMRB activity in excess of the U(VI) sorption capacity of the natural mineral assemblages. Jang (2004) demonstrated that the hydrated surface of nano-particles of hematite (prepared according to well-cited recipes and confirmed to be 100% hematite by Mossbauer spectroscopy and XRD) exhibited the solubility of hydrous ferric oxide (HFO). Jang (2004) also demonstrated that the sorptive reactivity of hematite and HFO were identical except for different specific surface area and pHzpc, and that the reduction of U(VI) by sorbed Fe(II) in the presence of the two phases was also similar in spite of theoretical predictions of large differences in Nernst potential. These results are consistent with the modeling of hematite bioreduction experiments where the thermodynamic potential of hematite had to be adjusted to represent a more disordered surface phase in order to accurately model bioreduction kinetics (Burgos et al, 2002, 2003). We have demonstrated that humic substances enhance solid-phase Fe(III) bioreduction via both electron shuttling and Fe(II) complexation(Royer et al, 2002a, b). We have found that humic substances were shown to inhibit the bioreduction of dissolved U(VI) and that soluble humic-U(IV) complexes were likely formed (Burgos et al, 2004). Kirkham (2004) measured and modeled complexation of U(VI) by humic substances as a function of pH, pCO2, U(VI) concentration, and humic concentration, and demonstrated that humic substances can complex U(VI) even at neutral pH values and in the presence of high (ca. 30 mM) carbonate concentrations. Jang(2004) measured the abiotic reduction of U(VI) by Fe(II) sorbed to Fe(III) oxides in the presence/absence of humic substances and demonstrated that humic substances inhibited the heterogeneous reduction of U(VI). We have recently developed, validated, and documented a series of diagonalized reaction-based reactive transport computer models (HYDROGEOCHEM; Yeh et al,2004a, b). We demonstrated that parallel kinetic reactions could be modeled if separate experiments are used to independently measure each contributing kinetic reaction (Burgos et al, 2003). We have demonstrated the use of a reaction-based reactive transport model (HYDROGEOCHEM) for the simulation of biological iron reduction in natural sediment columns (Burgos and Yeh, unpublished results). Finally, we have developed a preliminary reaction-based model of coupled Fe(III) oxide/U(VI) reduction that has been employed in numerical simulations of U(VI) bioreduction in bench-scale (Roden, 2003d) and field-scale (Roden and Scheibe, 2003;Roden, 2003c) systems.

Download or read book Geomicrobiology written by Henry Lutz Ehrlich and published by CRC Press. This book was released on 2008-12-22 with total page 630 pages. Available in PDF, EPUB and Kindle. Book excerpt: Uncovers the Key Role Microbes Play in the Transformation of Oxidizable and Reducible MineralsMany areas of geomicrobial processes are receiving serious attention from microbiologists, specifically the role microbes play in the formation and degradation of minerals and fossil fuels and elemental cycling. Most notably, the latest research finds that

Download or read book Influence of Reactive Transport on the Reduction of U VI in the Presence of Fe III and Nitrate written by Brian D. Wood and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The research in FY04 was focused in five specific topics: (1) U(VI) sorption on microbially and abiotically reduced sediments, (2) oxidation of biogenic U(IV) in presence of Fe(II), (3) U(VI) reduction by reduced sediments, (4) kinetics of U(VI) sorption on natural sediments under conditions of flow, and (5) NMR imaging of S. onidensis biofilms in porous media. Two manuscripts are currently in review, and another five (or four?) manuscripts are currently in preparation for submission.

Download or read book Biostimulation of Iron Reduction and Uranium Immobilization written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This project represented a joint effort between Florida State University (FSU), Rutgers University (RU), and the University of Illinois (U of I). FSU served as the lead institution and Dr. J.E. Kostka was responsible for project coordination, integration, and deliverables. This project was designed to elucidate the microbial ecology and geochemistry of metal reduction in subsurface environments at the U.S. DOE-NABIR Field Research Center at Oak Ridge, Tennessee (ORFRC). Our objectives were to: 1) characterize the dominant iron minerals and related geochemical parameters likely to limit U(VI) speciation, 2) directly quantify reaction rates and pathways of microbial respiration (terminal-electron-accepting) processes which control subsurface sediment chemistry, and 3) identify and enumerate the organisms mediating U(VI) transformation. A total of 31 publications and 47 seminars or meeting presentations were completed under this project. One M.S. thesis (by Nadia North) and a Ph. D. dissertation (by Lainie Petrie-Edwards) were completed at FSU during fall of 2003 and spring of 2005, respectively. Ph. D. students, Denise Akob and Thomas Gihring have continued the student involvement in this research since fall of 2004. All of the above FSU graduate students were heavily involved in the research, as evidenced by their regular attendance at PI meetings and ORFRC workshops.

Download or read book Ehrlich s Geomicrobiology written by Henry Lutz Ehrlich and published by CRC Press. This book was released on 2015-10-15 with total page 643 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advances in geomicrobiology have progressed at an accelerated pace in recent years. Ehrlich's Geomicrobiology, Sixth Edition surveys various aspects of the field, including the microbial role in elemental cycling and in the formation and degradation of minerals and fossil fuels. Unlike the fifth edition, the sixth includes many expert contributors

Download or read book Idet written by and published by . This book was released on 1950 with total page 319 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Microbiology of Nuclear Waste Disposal written by Jonathan R. Lloyd and published by Elsevier. This book was released on 2020-10-22 with total page 378 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Microbiology of Nuclear Waste Disposal is a state-of-the-art reference featuring contributions focusing on the impact of microbes on the safe long-term disposal of nuclear waste. This book is the first to cover this important emerging topic, and is written for a wide audience encompassing regulators, implementers, academics, and other stakeholders. The book is also of interest to those working on the wider exploitation of the subsurface, such as bioremediation, carbon capture and storage, geothermal energy, and water quality. Planning for suitable facilities in the U.S., Europe, and Asia has been based mainly on knowledge from the geological and physical sciences. However, recent studies have shown that microbial life can proliferate in the inhospitable environments associated with radioactive waste disposal, and can control the long-term fate of nuclear materials. This can have beneficial and damaging impacts, which need to be quantified. - Encompasses expertise from both the bio and geo disciplines, aiming to foster important collaborations across this disciplinary divide - Includes reviews and research papers from leading groups in the field - Provides helpful guidance in light of plans progressing worldwide for geological disposal facilities - Includes timely research for planning and safety case development

Download or read book Subsurface Uranium Fate and Transport written by and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Subsurface bacteria including sulfate reducing bacteria (SRB) reduce soluble U(VI) to insoluble U(IV) with subsequent precipitation of UO2. We have shown that SRB reduce U(VI) to nanometer-sized UO2 particles (1-5 nm) which are both intra- and extracellular, with UO2 inside the cell likely physically shielded from subsequent oxidation processes. We evaluated the UO2 nanoparticles produced by Desulfovibrio desulfuricans G20 under growth and non-growth conditions in the presence of lactate or pyruvate and sulfate, thiosulfate, or fumarate, using ultrafiltration and HR-TEM. Results showed that a significant mass fraction of bioreduced U (35-60%) existed as a mobile phase when the initial concentration of U(VI) was 160 μM. Further experiments with different initial U(VI) concentrations (25 - 900 M) in MTM with PIPES or bicarbonate buffers indicated that aggregation of uraninite depended on the initial concentrations of U(VI) and type of buffer. It is known that under some conditions SRB-mediated UO2 nanocrystals can be reoxidized (and thus remobilized) by Fe(III)-(hydr)oxides, common constituents of soils and sediments. To elucidate the mechanism of UO2 reoxidation by Fe(III) (hydr)oxides, we studied the impact of Fe and U chelating compounds (citrate, NTA, and EDTA) on reoxidation rates. Experiments were conducted in anaerobic batch systems in PIPES buffer. Results showed EDTA significantly accelerated UO2 reoxidation with an initial rate of 9.5 M day-1 for ferrihydrite. In all cases, bicarbonate increased the rate and extent of UO2 reoxidation with ferrihydrite. The highest rate of UO2 reoxidation occurred when the chelator promoted UO2 and Fe(III) (hydr)oxide dissolution as demonstrated with EDTA. When UO2 dissolution did not occur, UO2 reoxidation likely proceeded through an aqueous Fe(III) intermediate as observed for both NTA and citrate. To complement to these laboratory studies, we collected U-bearing samples from a surface seep at the Rifle field site and have measured elevated U concentrations in oxic iron-rich sediments. To translate experimental results into numerical analysis of U fate and transport, a reaction network was developed based on Sani et al. (2004) to simulate U(VI) bioreduction with concomitant UO2 reoxidation in the presence of hematite or ferrihydrite. The reduction phase considers SRB reduction (using lactate) with the reductive dissolution of Fe(III) solids, which is set to be microbially mediated as well as abiotically driven by sulfide. Model results show the oxidation of HS- by Fe(III) directly competes with UO2 reoxidation as Fe(III) oxidizes HS- preferentially over UO2. The majority of Fe reduction is predicted to be abiotic, with ferrihydrite becoming fully consumed by reaction with sulfide. Predicted total dissolved carbonate concentrations from the degradation of lactate are elevated (log(pCO2) ~ -1) and, in the hematite system, yield close to two orders-of-magnitude higher U(VI) concentrations than under initial carbonate concentrations of 3 mM. Modeling of U(VI) bioreduction with concomitant reoxidation of UO2 in the presence of ferrihydrite was also extended to a two-dimensional field-scale groundwater flow and biogeochemically reactive transport model for the South Oyster site in eastern Virginia. This model was developed to simulate the field-scale immobilization and subsequent reoxidation of U by a biologically mediated reaction network.

Download or read book The Effects of Bicarbonate and Mineral Surfaces on Uranium Immobilization Under Anaerobic Conditions written by Luis A. Jurado and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: For four decades, from 1940 through 1980, the U.S. Department of Energy (DoE) extensively mined and processed uranium at various sites. As a result, widespread uranium contamination exists in subsurface sediments and aquifers. In subsurface environments, uranium primarily exists as U(VI) or U(IV), oxidized and reduced species, respectively. U(VI) is highly soluble and toxic, U(IV), while relatively toxic, is insoluble which greatly reduces its exposure pathways. We seek to examine the role of ferric iron on U(VI) reduction by adsorbing U(VI) onto ferric and non-ferric mineral surfaces in the presence of a reductant. Further, we seek to understand the role that NaHCO3, a natural groundwater buffer, has in the reductive geochemical transformations of U(VI) adsorbed on ferric and non-ferric mineral surfaces. Bench top studies were performed using 100 uM U(VI) and the reductant AHQDS, in the presence and absence of Fe-Gel (amorphous ferric oxyhydroxide) and gamma-Al2O3. In the presence of a HEPES buffer at pH 8, results demonstrate direct homogeneous reduction in several hours in the absence of Fe-Gel or gamma-Al2O3, and reduction within a 48-hour period in the presence Fe-Gel or gamma-Al2O3. While adsorbed to both ferric and non-ferric mineral surfaces, U(VI) reduction is inhibited. U(VI) reduction in the presence of NaHCO3 buffer also inhibits U(VI) reduction.

Download or read book Manual of Environmental Microbiology written by Christon J. Hurst and published by American Society for Microbiology Press. This book was released on 2007-05-14 with total page 3023 pages. Available in PDF, EPUB and Kindle. Book excerpt: The most definitive manual of microbes in air, water, and soil and their impact on human health and welfare. • Incorporates a summary of the latest methodology used to study the activity and fate of microorganisms in various environments. • Synthesizes the latest information on the assessment of microbial presence and microbial activity in natural and artificial environments. • Features a section on biotransformation and biodegradation. • Serves as an indispensable reference for environmental microbiologists, microbial ecologists, and environmental engineers, as well as those interested in human diseases, water and wastewater treatment, and biotechnology.

Download or read book Trace Elements in Waterlogged Soils and Sediments written by Jörg Rinklebe and published by CRC Press. This book was released on 2016-08-19 with total page 419 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many wetlands around the world act as sinks for pollutants, in particular for trace elements. In comparison to terrestrial environments, wetlands are still far less studied. A collaborative effort among world experts, this book brings the current knowledge concerning trace elements in temporary waterlogged soils and sediments together. It discusses factors controlling the dynamics and release kinetics of trace elements and their underlying biogeochemical processes. It also discusses current technologies for remediating sites contaminated with trace metals, and the role of bioavailability in risk assessment and regulatory decision making. This book is intended for professionals around the world in disciplines related to contaminant bioavailability in aquatic organisms, contaminant fate and transport, remediation technologies, and risk assessment of aquatic and wetland ecosystems.

Download or read book Influence of Reactive Transport on the Reduction of U VI in the Presence of Fe III and Nitrate written by John Zachara and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The purposes of this report are to: (1) to determine how flow and transport influence the distribution of U(VI) under field-relevant conditions and the transfer of reductive equivalents to the aqueous and solid phases by DMRB; and (2) to examine the solid-phase stability of bioreduced uranium phases--effects of mass transfer on reoxidation of U(IV) by O{sub 2} and other oxidants (e.g., NO{sub 3}{sup -}, denitrification products).

Download or read book Pollution Control Technologies written by Swatantra P. Singh and published by Springer Nature. This book was released on 2021-06-17 with total page 290 pages. Available in PDF, EPUB and Kindle. Book excerpt: p="" This monograph is based on pollution control technologies available to deal with water and air pollution. It includes removal of variety of pollutants including arsenic, chromium, uranium, pesticides and arsenic from water using adsorption technique. In addition, this book deals with the sampling and removal of microplastics using various techniques. The contents also focus on the role of membrane technology in water and wastewater treatment, and particulate matter air pollution and its control techniques. This volume will be a useful guide for researchers, academics and scientists. ^

Download or read book Elucidating Bioreductive Transformations Within Physically Complex Media written by and published by . This book was released on 2009 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt: In situ stabilization (inclusive of natural attenuation) of toxic metals and radionuclides is an attractive approach for remediating many contaminated DOE sites. By immobilizing toxic metals and radionuclides in place, the removal of contaminated water to the surface for treatment as well as the associated disposal costs are avoided. To enhance in situ remediaton, microbiological reductive stabilization of contaminant metals has been, and continues to be, actively explored. It is likely that surface and subsurface microbial activity can alter the redox state of toxic metals and radionuclides, either directly or indirectly, so they are rendered immobile. Furthermore, anaerobic bacterial metabolic products will help to buffer pulses of oxidation, typically from fluxes of nitrate or molecular oxygen, and thus may stabilize reduced contaminants from oxidative mobilization. Uranium and chromium are two elements of particular concern within the DOE complex that, owing to their abundance and toxicity, appear well suited for biologically mediated reductive stabilization. Subsurface microbial activity can alter the redox state of toxic metals and radionuclides, rending them immobile. Imparting an important criterion on the probability that contaminants will undergo reductive stabilization, however, is the chemical and physical heterogeneity of the media. Our research first examined microbially induced transformation of iron (hydr)oxide minerals and their impact on contaminant attenuation. We revealed that in intricate cascade of geochemical reactions is induced by microbially produced Fe(II), and that during transformation contaminants such as U(VI) can be incorporated into the structure, and a set of Fe(II) bearing solids capable of reducing Cr(VI) and stabilizing resulting Cr(III). We also note, however, that common subsurface constituents such as phosphate can modify iron oxide transformation pathways and thus impact contaminant sequestration--affecting both Cr and U stabilization. We extended our work to explore factors controlling the sequestration of uranium in the subsurface, with a particular emphasis on mineralogic and geochemical complexity. We reveal that one of the primary factors controlling uranium reduction, via both biological and chemical pathways, is the aqueous speciation of U(VI). Specifically, ternary calcium-uranyl-carbonato complexes stabilize U(VI) relative to reduction. However, countering the lack of reduction, we note a novel sequestration pathway in which the U(VI), as the uranate ion, is incorporated into the structure of transformation iron oxides; magnetite and goethite, both products of Fe(II) induced transformation of ferrihydrite, harbor appreciable quantities of uranium. In sum, our results provide important information on predicting and potentially controlling the migration of chromium and uranium within the DOE complex.

Download or read book Mesoscale Biotransformations of Uranium written by Terry C. Hazen and published by . This book was released on 2006 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Bioreduction of U in contaminated sediments is an attractive strategy because of its low cost, and because of short-term studies supporting its feasibility. However, any in-situ immobilization approach for U will require assurance of either permanent fixation, or of very low release rates into the biosphere. Our previous long-term (2 years) laboratory experiments have shown that organic carbon (OC) based U(VI) bioreduction to UO2 can be transient even under sustained reducing (methanogenic) conditions. The biogeochemical processes underlying this finding urgently need to be understood. The current research is designed to identify mechanisms responsible for anaerobic U oxidation, and identify conditions that will support long-term stability of bioreduced U. We are investigating: (1) effects of OC concentration and supply rate on remobilization of bioreduced U, (2) the roles of Fe- and Mn-oxides as potential U oxidants in sediments, and (3) the role of microorganisms in U reoxidation, and (4) influences of pH on U(IV)/U(VI) redox equilibrium.