Bioresource and Agricultural Engineering Commons^™

Complete Genome Sequence Of Lactobacillus Buchneri Nrrl B-30929, A Novel Strain From A Commercial Ethanol Plant, Siqing Liu, Timothy D. Leathers, Alex Copeland, Olga Chertkov, Lynne Goodwin, David A. Mills

United States Department of Energy: Publications

Lactobacillus buchneri strain NRRL B-30929 was a contaminant obtained from a commercial ethanol fermentation. This facultative anaerobe is unique because of its rapid growth on xylose and simultaneous fermentation of xylose and glucose. The strain utilizes a broad range of carbohydrate substrates and possesses a high tolerance to ethanol and other stresses, making it an attractive candidate for bioconversion of biomass substrates to various bioproducts. The genome sequence of NRRL B-30929 will provide insight into the unique properties of this lactic acid bacterium.

Vista Region Viewer (Rviewer)—A Computational System For Prioritizing Genomic Intervals For Biomedical Studies, Igor Lukashin, Pavel Novichkov, Dario Boffelli, Alex R. Paciorkowski, Simon Minovitsky, Song Yang, Inna Dubchak

United States Department of Energy: Publications

Summary:
Current genome browsers are designed for linear browsing of individual genomic regions, but the high-throughput nature of experiments aiming to elucidate the genetic component of human disease makes it very important to develop user-friendly tools for comparing several genomic regions in parallel and prioritizing them based on their functional content. We introduce VISTA Region Viewer (RViewer), an interactive online tool that allows for efficient screening and prioritization of regions of the human genome for follow-up studies. The tool takes as input genetic variation data from different biomedical studies, determines a number of various functional parameters for both coding …

Complete Genome Sequence Of The Plant Growth-Promoting Endophyte Burkholderia Phytofirmans Strain Psjn, Alexandra Weilharter, Birgit Mitter, Maria V. Shin, Patrick S. G. Chain, Jerzy Nowak, Angela Sessitsch

United States Department of Energy: Publications

Burkholderia phytofirmans PsJN^T is able to efficiently colonize the rhizosphere, root, and above-ground plant tissues of a wide variety of genetically unrelated plants, such as potatoes, canola, maize, and grapevines. Strain PsJN shows strong plant growth-promoting effects and was reported to enhance plant vigor and resistance to biotic and abiotic stresses. Here, we report the genome sequence of this strain, which indicates the presence of multiple traits relevant for endophytic colonization and plant growth promotion.

Characterization Of The Intragranular Water Regime Within Subsurface Sediments: Pore Volume, Surface Area, And Mass Transfer Limitations, Michael B. Hay, Deborah L. Stoliker, James A. Davis, John M. Zachara

United States Department of Energy: Publications

Although ‘‘intragranular’’ pore space within grain aggregates, grain fractures, and mineral surface coatings may contain a relatively small fraction of the total porosity within a porous medium, it often contains a significant fraction of the reactive surface area, and can thus strongly affect the transport of sorbing solutes. In this work, we demonstrate a batch experiment procedure using tritiated water as a high-resolution diffusive tracer to characterize the intragranular pore space. The method was tested using uranium contaminated sediments from the vadose and capillary fringe zones beneath the former 300A process ponds at the Hanford site (Washington). Sediments were contacted …

Multispecies Diffusion Models: A Study Of Uranyl Species Diffusion, Chongxuan Liu, Jianying Shang, John M. Zachara

United States Department of Energy: Publications

Rigorous numerical description of multispecies diffusion requires coupling of species, charge, and aqueous and surface complexation reactions that collectively affect diffusive fluxes. The applicability of a fully coupled diffusion model is, however, often constrained by the availability of species self-diffusion coefficients, as well as by computational complication in imposing charge conservation. In this study, several diffusion models with variable complexity in charge and species coupling were formulated and compared to describe reactive multispecies diffusion in groundwater. Diffusion of uranyl [U(VI)] species was used as an example in demonstrating the effectiveness of the models in describing multispecies diffusion. Numerical simulations found …

Transient Groundwater Chemistry Near A River: Effects On U(Vi) Transport In Laboratory Column Experiments, Jun Yin, Roy Haggerty, Deborah L. Stoliker, Douglas B. Kent, Jonathan D. Istok, Janek Greskowiak, John M. Zachara

United States Department of Energy: Publications

In the 300 Area of a U(VI)-contaminated aquifer at Hanford, Washington, USA, inorganic carbon and major cations, which have large impacts on U(VI) transport, change on an hourly and seasonal basis near the Columbia River. Batch and column experiments were conducted to investigate the factors controlling U(VI) adsorption/desorption by changing chemical conditions over time. Low alkalinity and low Ca concentrations (Columbia River water) enhanced adsorption and reduced aqueous concentrations. Conversely, high alkalinity and high Ca concentrations (Hanford groundwater) reduced adsorption and increased aqueous concentrations of U(VI). An equilibrium surface complexation model calibrated using laboratory batch experiments accounted for the decrease …

Simulating Adsorption Of U(Vi) Under Transient Groundwater Flow And Hydrochemistry: Physical Versus Chemical Nonequilibrium Model, Janek Greskowiak, Michael Hay, Henning Prommer, Chongxuan Liu, Vincent Post, Rui Ma, James Davis, Chunmiao Zheng, John M. Zachara

United States Department of Energy: Publications

Coupled intragrain diffusional mass transfer and nonlinear surface complexation processes play an important role in the transport behavior of U(VI) in contaminated aquifers. Two alternative model approaches for simulating these coupled processes were analyzed and compared: (1) the physical nonequilibrium approach that explicitly accounts for aqueous speciation and instantaneous surface complexation reactions in the intragrain regions and approximates the diffusive mass exchange between the immobile intragrain pore water and the advective pore water as multirate first-order mass transfer and (2) the chemical nonequilibrium approach that approximates the diffusion-limited intragrain surface complexation reactions by a set of multiple first-order surface complexation …

Transition Of Cellulose Crystalline Structure And Surface Morphology Of Biomass As A Function Of Ionic Liquid Pretreatment And Its Relation To Enzymatic Hydrolysis, Gang Cheng, Patanjali Varanasi, Chenlin Li, Hanbin Liu, Yuri B. Melnichenko, Blake A. Simmons, Michael S. Kent, Seema Singh

United States Department of Energy: Publications

Cellulose is inherently resistant to breakdown, and the native crystalline structure (cellulose I) of cellulose is considered to be one of themajor factors limiting its potential in terms of cost-competitive lignocellulosic biofuel production. Here we report the impact of ionic liquid pretreatment on the cellulose crystalline structure in different feedstocks, including microcrystalline cellulose (Avicel), switchgrass (Panicum virgatum), pine (Pinus radiata), and eucalyptus (Eucalyptus globulus), and its influence on cellulose hydrolysis kinetics of the resultant biomass. These feedstocks were pretreated using 1-ethyl-3-methyl imidazolium acetate ([C2mim][OAc]) at 120 and 160°C for 1, 3, 6, and 12 …

Absolute High-Resolution Se+ Photoionization Cross-Section Measurements With Rydberg-Series Analysis, D. A. Esteves, R. C. Bilodeau, N. C. Sterling, R. A. Phaneuf, A. L. D. Kilcoyne, E. C. Red, A. Aguilar

United States Department of Energy: Publications

Absolute single photoionization cross-section measurements for Se⁺ ions were performed at the Advanced Light Source (ALS) at Lawrence Berkeley National Laboratory using the photo-ion merged-beams technique. Measurements were made at a photon energy resolution of 5.5 meV from 17.75 to 21.85 eV spanning the 4s²4p³4S^o_3/2 ground-state ionization threshold and the ²P^o_3/2,²P^o_1/2,²D^o_5/2, and²D^o_3/2 metastable state thresholds. Extensive analysis of the complex resonant structure in this region identified numerous Rydberg series of resonances and …

Photoionization Measurements For The Iron Isonuclear Sequence Fe3+, Fe5+, And Fe7+, M. F. Gharaibeh, A. Aguilar, A. M. Covington, E. D. Emmons, S. W. J. Scully, R. A. Phaneuf, A. Muller, J. D. Bozek, A. L. D. Kilcoyne, A. S. Schlachter, I. Alvarez, C. Cisneros, G. Hinojosa

United States Department of Energy: Publications

Cross sections for single photoionization of Fe³⁺, Fe⁵⁺, and Fe⁷⁺ ions were measured at spectral resolutions of 0.04, 0.15, and 0.13 eV, respectively, by merging mass- and charge-selected ion beams with a beam of monochromatized synchrotron undulator radiation. The measurements span photon energy ranges beginning at the ionization thresholds and extending several tens of electron volts to include the most important resonant contributions due to 3p–nd transitions to autoionizing states. The photoion yield spectra are characterized by narrow resonances and also broad features in Fe³⁺ and Fe⁵⁺ that are believed to result …

An Approach To Crystallizing Proteins By Metal-Mediated Synthetic Symmetrization, Arthur Laganowsky, Minglei Zhao, Angela B. Soriaga, Michael R. Sawaya, Duilio Cascio, Todd O. Yeates

United States Department of Energy: Publications

Combining the concepts of synthetic symmetrization with the approach of engineering metal-binding sites, we have developed a new crystallization methodology termed metal-mediated synthetic symmetrization. In this method, pairs of histidine or cysteine mutations are introduced on the surface of target proteins, generating crystal lattice contacts or oligomeric assemblies upon coordination with metal. Metal-mediated synthetic symmetrization greatly expands the packing and oligomeric assembly possibilities of target proteins, thereby increasing the chances of growing diffraction-quality crystals. To demonstrate this method, we designed various T4 lysozyme (T4L) and maltose-binding protein (MBP) mutants and cocrystallized them with one of three metal ions: copper (Cu …

Modification Of Native Grasses For Biofuel Production May Increase Virus Susceptibility, Abbie C. Schrotenboer, Michael S. Allen, Carolyn M. Malmstrom

United States Department of Energy: Publications

Bioenergy production is driving modifications to native plant species for use as novel biofuel crops. Key aims are to increase crop growth rates and to enhance conversion efficiency by reducing biomass recalcitrance to digestion. However, selection for these biofuel-valuable traits has potential to compromise plant defenses and alter interactions with pests and pathogens. Insect-vectored plant viruses are of particular concern because perennial crops have potential to serve as virus reservoirs that influence regional disease dynamics. In this study, we examined relationships between growth rates and biomass recalcitrance in five switchgrass (Panicum virgatum) populations, ranging from near wild type …

2011 Nebraska Water Monitoring Programs Report, Marty Link

Nebraska Department of Environmental Quality: Reports

The Nebraska Department of Environmental Quality (NDEQ) is charged with monitoring, assessing, and to the extent possible, managing the state’s water resources. The purpose of this work is to protect and maintain good quality water and encourage or execute activities to improve poor water quality. Monitoring is done on the over 18,000 miles of flowing rivers and streams, our greater than 280,000 acres of surface water in lakes and reservoirs, and the vast storage of groundwater in Nebraska’s aquifers.

Charge And Fluence Lifetime Measurements Of A Dc High Voltage Gaas Photogun At High Average Current, J. Grames, R. Suleiman, P. A. Adderley, J. Clark, J. Hansknecht, D. Machie, M. Poelker, M. L. Stutzman

United States Department of Energy: Publications

GaAs-based dc high voltage photoguns used at accelerators with extensive user programs must exhibit long photocathode operating lifetime. Achieving this goal represents a significant challenge for proposed high average current facilities that must operate at tens of milliamperes or more. This paper describes techniques to maintain good vacuum while delivering beam, and techniques that minimize the ill effects of ion bombardment, the dominant mechanism that reduces photocathode yield of a GaAs-based dc high voltage photogun. Experimental results presented here demonstrate enhanced lifetime at high beam currents by: (a) operating with the drive laser beam positioned away from the electrostatic center …

Zinc Speciation In Power Plant Burning Mixtures Of Coal And Tires, Luis F.O. Silva, Marcos L.S. Oliveira, Carmen Serra, James C. Hower

Coal Combustion and Gasification Products Journal Archive

Fly ash from the cyclone-boiler co-combustion of high-S, high volatile bituminous coal and tire-derived fuel (tdf) was studied using a variety of chemical, optical, and microbeam techniques. Fly ash, dominated by Al-Si glass with lesser amounts of coalderived carbons, Fe-spinels, and tire-derived carbons, has Zn concentrations ranging from 2200 ppm (1st ESP row) to 6900 ppm Zn (3rd ESP row). Zinc occurs in Zn-rich nanoparticles in the Al-Si glass phases and as ZnO in amorphous and crystalline nanominerals, Fe- and Zn-sulfides, Pb-Al-Fe sulfates, and Zn sulfates. Iron-rich, Al- and Ti-bearing spinels contain accessory Zn2+,Cr3+,Mn2+, and Pb2+. Fe-sulfates and phosphates nanoparticles …

Co-Disposal Of Dry Fgd By-Product With Coal Gasification Ash And Inorganic Brines, Jabulani S. Mahlaba, P.C. Pretorius, Subal Maharajh, M.P. Augustyn

Coal Combustion and Gasification Products Journal Archive

There is a growing pressure from the environmental authorities and public bodies to reduce anthropogenic pollution. Stringent environmental legislation is being implemented for industries around the world, even more so for coal consuming industries. Control of gaseous emissions is one of the areas that are receiving considerable attention towards sustainable development. Coal combustion in coal-fired power utilities emits SO~x~ to the atmosphere. Dry flue gas desulphurisation (FGD) is a well known technology often used to mitigate sulphur emissions in coal-fired power utilities. It traditionally uses lime to neutralise SO~x~, and forms a mixture of anhydrite (CaSO~4~), and calcium sulphite (CaSO~3~). …

Magnetite Nanoparticles For Medical Mr Imaging, Zachary R. Stephen, Forrest M. Kievit, Miqin Zhang

Department of Agricultural and Biological Systems Engineering: Faculty Publications

Magnetic resonance imaging (MRI) has become one of the most widely used and powerful tools for non-invasive clinical diagnosis due to its high soft tissue contrast, spatial resolution, and penetration depth1. In addition, images are acquired without the use of ionizing radiation or radiotracers that would cause unwanted harmful side-effects. A considerable amount of research in medical MR imaging is focused on the development of contrast agents that can provide better delineation between healthy and diseased tissue. Magnetic nanoparticles (MNPs) are a major class of nanoscale material currently under extensive development for improved diagnosis of a wide range of diseases, …

A Multi-Analytical Approach To Understand The Chemistry Of Fe-Minerals In Feed Coals And Ashes, Marcos L.S. Oliveira, Frans Waanders, Luis F.O. Silva, Andre Jasper, Carlos H. Sampaio, Dursman Mchabe, Rachel S. Hatch, James C. Hower

Coal Combustion and Gasification Products Journal Archive

Seven feed coals used in the Brazilian power generation industry were obtained and subsequently analysed together with fly ash and bottom ash from a major Brazilian power plant. The samples were investigated by means of room temperature FeMo¨ssbauer analyses, X-ray diffraction, Raman spectroscopy, scanning electron microscope and petrographic analysis. In addition, nanometer-sized crystalline phases in coals and ashes were characterised using an energy-dispersive X-ray spectrometer and a high-resolution transmission electron microscope. The major identified Fe-bearing minerals in the coals were found to be actinolite, ankerite, chalcopyrite, chlorite, goethite, illite, ilmenite, magnesioferrite, natrojarosite, pyrite, pyrrhotite, and siderite; whilst in the fly …

Compositional Variations In Pilot Gasifier And Laboratory-Produced Slags And Their Impacts On Slag Viscosity And Coal Assessment, Alexander Ilyushechkin, Daniel Roberts, David Harris

Coal Combustion and Gasification Products Journal Archive

The flow behaviour of coal mineral matter at high temperatures is an important parameter for coal use in entrained-flow gasification technologies. Recently, gasification performance data was obtained from a series of pilot-scale gasification tests on a suite of well-characterised Australian black coals. Evaluation of the results of the pilot tests and the detailed laboratory investigations provided the opportunity for evaluation of the practical applicability of different laboratory and modelling techniques for coal assessment in terms of mineral matter behaviour in entrained flow gasification. A series of viscosity measurements was made over the range 1200–1600uC using slags produced in a pilot …

Compaction Of High-Ca Fly Ash-Al- And Al-Alloy-Composites: Evaluation Of Their Microstructure And Tribological Performance, Grigorios Itskos, Angeliki Moutsatsou, Pradeep K. Rohatgi, Nikolaos Koukouzas, Charalampos Vasilatos, Eleni Katsika

Coal Combustion and Gasification Products Journal Archive

In this study, highly calcareous and siliceous fly ash particles were utilized for the fabrication of Al- and Al-alloy-based MetalMatrix Composites (MMCs) by means of powder metallurgy. After compacting and sintering Al and Al/Si powders containing 10, 15, and 20wt. % ash particles, the homogenous (and with minimal amount of voids) microstructure of the produced composites was verified by means of Scanning Electron Microscopy (SEM). The composites were tested for their dry sliding wear behavior using a pin-on-disc machine against spheres of alumina. The worn surfaces of composites were then examined by using SEM and Energy Dispersive X-Ray Spectroscopy (EDS). …

Influence Of Chemical Reagents On Rheological Properties Of Fly Ash-Water Slurry At Varying Temperature Environment, H.K. Nail, M.K. Mishra, Karanam U.M. Rao

Coal Combustion and Gasification Products Journal Archive

About 70% of total electrical energy is generated from thermal power plants in India which in turn release about 160 Mt of fly ash as solid waste annually. Transportation and disposal of such a huge amount of fly ash is a major problem faced by the power plants. Presently fly ash is transported as lean slurry in pipe lines requiring about 80 to 85% of water with high energy input. A major impediment in high volume transportation of fly ash is its high specific gravity as compared to that of water. The objective of the present study was to evaluate …

Impact Of Manufactured Coal Ash Aggregates On Water Quality During Open Pit Restoration: 1. A Statistical Screening Test, Sangchul Hwang, Isomar Latorre

Coal Combustion and Gasification Products Journal Archive

Utilization of manufactured coal ash aggregates (MAs) as a subsoil substitute during restoration of an open pit was assessed in a three-factor, two-level factorial analysis. The factors of interest were the MA application rate (2:1 or 1:2 topsoil/MA volume ratio), rainfall intensity (high or low), and aggregate size (2.36–4.75 mm or 4.75–9.53 mm). Among the water quality parameters examined (pH, turbidity, heavy metal content (lead and cadmium), conductivity, and hardness), the last two parameters were significantly higher (p,0.05) in soil amended with MAs than in a control reactor using sand. A low rainfall intensity and larger aggregate size resulted in …

The Leachability Of Major Elements At Different Stages Of Weathering In Dry Disposed Coal Fly Ash, S.A. Akinyemi, A. Akinlua, W.M. Gitari, R.O. Akinyeye, L.F. Petrik

Coal Combustion and Gasification Products Journal Archive

Large quantities of solid residue are generated by coal-fired power stations in many parts of the World. The disposal and management of the unused fly ash remains a major problem to the environment. The weathered dry disposed ash cores comprise of major element constituents such as Al, Si, Ca, Mg, Fe, Mn, Na+ and K+. The mobility patterns and mineralogical associations of major elements in weathered dry disposed ash dumps aged 1-year-old, 8-year-old and 20-year-old from a coalfired power station in South Africa were investigated using a modified sequential extraction scheme. The extraction sequence was as follows: (1) water soluble, …

Long Term, Continuous Temperature Monitoring Of A Simple Anaerobic Digester And Open Manure Storage Pond In Eastern South Dakota, J. Darrington, E. Cortus

The Journal of Undergraduate Research

A two-cell manure storage system with a cover on the first cell was constructed in the late summer of 2009 in Eastern South Dakota. The covered cell acts as a simple anaerobic digester. Continuous temperature monitoring for 8 months shows the winter effluent temperature equilibrated to around 6°C, and that the effluent temperature trend lagged the ambient temperature trend by a month. Manure composition was also analyzed and was found to be relatively steady throughout the system. Volatile solids were the only component that dropped appreciably across the treatment cell, with an observed maximum of 50% reduction.

Focused Ion Beam Patterned Fe Thin Films: A Study By Selective Area Stokes Polarimetry And Soft X-Ray Microscopy, P. J. Cook, T. H. Shen, P. J. Grundy, M.-Y. Im, P. Fischer, S. A. Morton, A. L. D. Kilcoyne

United States Department of Energy: Publications

A combination of analytical techniques, with special emphasis on selective area Stokes polarimetry, has been used to explore the structural properties and magnetic behavior of focused ion beam patterned Fe thin films under controlled Ga⁺ ion irradiation. Ion irradiation at doses ranging from 7.7×10¹⁵ to 5.2×10¹⁶ Ga ions cm^-2 did not noticeably alter the chemical properties of the Fe, but changes to the film structure and increased coercivity were observed even after the lowest doses. Magnetic transmission x-ray microscopy provided detailed information about the magnetization reversal process occurring within a patterned area of film comprising both …

Error Analysis Of Large-Eddy Simulation Of The Turbulent Non-Premixed Sydney Bluff-Body Flame, A. M. Kempf, B. J. Geurts, J. C, Oefelein

United States Department of Energy: Publications

A computational error analysis is applied to the large-eddy simulation of the turbulent non-premixed Sydney bluff-body flame, where the error is defined with respect to experimental data. The errorlandscape approach is extended to heterogeneous compressible turbulence, which is coupled to combustion as described by a flamelet model. The Smagorinsky model formulation is used to model the unknown turbulent stresses. We introduce several measures to quantify the total simulation error and observe a striking ‘valley-structure’ in the error that arises as function of the spatial resolution and the Smagorinsky length parameter. The optimal refinement strategy that can be extracted from this …

Combining Power Plant Water Needs And Carbon Dioxide Storage Using Saline Formations: Implications For Carbon Dioxide And Water Management Policies, Peter Kobos, Malynda Cappelle, Jim Krumhansl, Thomas Dewers, Andrea Mcnemar, David Borns

United States Department of Energy: Publications

Research involving management of carbon dioxide has increased markedly over the last decade as it relates to concerns over climate change. Capturing and storing carbon dioxide (CO₂) in geological formations is one of many proposed methods to manage, and likely reduce, CO₂ emissions from burning fossil fuels in the electricity sector. Saline formations represent a vast storage resource, and the waters they contain could be managed for beneficial use. To address this issue, a methodology was developed to test the feasibility of linking coal-fired power plants, deep saline formations for CO₂ storage, and extracting and treating …

Solubility Of Fe2(Oh)3cl (Pure-Iron End-Member Of Hibbingite) In Nacl And Na2so4 Brines, Martin Nemer, Yongliang Xiong, Ahmed Ismail, Je-Hun Jang

United States Department of Energy: Publications

Pure-iron end-member hibbingite, Fe₂(OH)₃Cl(s), may be important to geological repositories in salt formations, as it may be a dominant corrosion product of steel waste canisters in an anoxic environment in Na–Cl- and Na–Mg–Cl-dominated brines. In this study, the solubility of Fe₂(OH)₃Cl(s), the pure-iron endmember of hibbingite (Fe^II, Mg)₂(OH)₃Cl(s), and Fe(OH)₂(s) in 0.04 m to 6 m NaCl brines has been determined. For the reaction

Fe₂ (OH)₃Cl(s) + 3H⁺↔ 3H₂O + 2Fe²⁺ + Cl⁻,

the …

Nonlocal Instability Analysis Of Fcc Bulk And (100) Surfaces Under Uniaxial Stretching, Geng Yun, Penghui Cao, Jonathan Zimmerman, Terry Delph, Harold Park

United States Department of Energy: Publications

The objective of this paper is to examine the instability characteristics of both a bulk FCC crystal and a (100) surface of an FCC crystal under uniaxial stretching along a h100i direction using an atomisticbased nonlocal instability criterion. By comparison to benchmark atomistic simulations, we demonstrate that for both the FCC bulk and (100) surface, about 5000–10,000 atoms are required in order to obtain an accurate converged value for the instability strain and a converged instability mode. The instability modes are fundamentally different at the surface as compared to the bulk, but in both cases a strong dependence of the …

Evidence For Multiple Modes Of Uranium Immobilization By An Anaerobic Bacterium, Allison E. Ray, John R. Bargar, Vaideeswaran Sivaswamy, Alice C. Dohnalkova, Yoshiko Fujita, Brent M. Peyton, Timothy S. Magnuson

United States Department of Energy: Publications

Microbial reduction of hexavalent uranium has been studied widely for its potential role in bioremediation and immobilization of soluble U(VI) in contaminated groundwater. More recently, some microorganisms have been examined for their role in immobilization of U(VI) via precipitation of uranyl phosphate minerals mediated by microbial phosphate release, alleviating the requirement for long-term redox control. Here, we investigated the mechanism of U(VI) removal mediated by an environmental isolate, strain UFO1, that is indigenous to the Field Research Center (FRC) in Oak Ridge, TN and has been detected in U(VI)- contaminated sediments. Changes in U(VI) speciation were examined in the presence …