Nutrient Composition and Flavor Profile of Crucian Carp Soup Utilizing Fish Residues through Comminution and Pressure-Conduction Treatment.

In conventional fish soup processing, valuable aquatic resources like fish skins, bones, and scales are often squandered. This study was aimed at investigating if comminution combined with pressure-conduction treatment has the potential to enhance the reutilization of cooking residues. The different blending ratios of original soup (OS), made from the initial cooking of fish, and residue soup (RS), produced from processed leftover fish parts, were alternatively investigated to satisfy the new product development. Comminution combined with pressure-conduction treatment significantly increased the nutrient contents of calcium, soluble proteins and total solids in crucian carp soup (p < 0.05). With the increase in RS ratio, the decomposition of inosine monophosphate (IMP) and free amino acids was accelerated, but the accumulation of aromatic compounds was promoted simultaneously. In addition, the Maillard reaction may lead to a reduction in aldehydes, causing a diminution in the characteristic flavor of fish soup, while the formation of 1-octen-3-ol can enhance the earthiness of the fish soup. The electronic tongue test results and the sensory results showed that the blend ratio of OS and RS at 7:3 had a more significant umami and fish aroma (p < 0.05). Under this condition, the mixed soup has better nutritional values and flavor characteristics.

Effect of Adsorbed Carboxylates on the Dissolution of Boehmite Nanoplates in Highly Alkaline Solutions.

Understanding the dissolution of boehmite in highly alkaline solutions is important to processing complex nuclear waste stored at the Hanford (WA) and Savannah River (SC) sites in the United States. Here, we report the adsorption of model carboxylates on boehmite nanoplates in alkaline solutions and their effects on boehmite dissolution in 3 M NaOH at 80 °C. Although expectedly lower than at circumneutral pH, adsorption of oxalate occurred at pH 13, with adsorption decreasing linearly to 3 M NaOH. Classical molecular dynamics simulations suggest that the adsorption of oxalate dianions onto the boehmite surface under high pH can occur through either inner- or outer-sphere complexation mechanisms depending on adsorption sites. However, both adsorption models indicate relatively weak binding, with an energy preference of 1.26 to 2.10 kcal/mol. By preloading boehmite nanoplates with oxalate or acetate, we observed suppression of dissolution rates by 23 or 10%, respectively, compared to pure solids. Scanning electron microscopy and transmission electron microscopy characterizations revealed no detectable difference in the morphologic evolution of the dissolving boehmite materials. We conclude that preadsorbed carboxylates can persist on boehmite surfaces, decreasing the density of dissolution-active sites and thereby adding extrinsic controls on dissolution rates.

Effect of Cr(III) Adsorption on the Dissolution of Boehmite Nanoparticles in Caustic Solution.

The incorporation of relatively minor impurity metals onto metal (oxy)hydroxides can strongly impact solubility. In complex highly alkaline multicomponent radioactive tank wastes such as those at the Hanford Nuclear Reservation, tests indicate that the surface area-normalized dissolution rate of boehmite (γ-AlOOH) nanomaterials is at least an order of magnitude lower than that predicted for the pure phase. Here, we examine the dissolution kinetics of boehmite coated by adsorbed Cr(III), which adheres at saturation coverages as sparse chemisorbed monolayer clusters. Using 40 nm boehmite nanoplates as a model system, temperature-dependent dissolution rates of pure versus Cr(III)-adsorbed boehmite showed that the initial rate for the latter is consistently several times lower, with an apparent activation energy 16 kJ·mol-1 higher. Although the surface coverage is only around 50%, solution analysis coupled to multimethod solids characterization reveal a phyicochemical armoring effect by adsorbed Cr(III) that substantially reduces the number of dissolution-active sites on particle surfaces. Such findings could help improve kinetics models of boehmite and/or metal ion adsorbed boehmite nanomaterials, ultimately providing a stronger foundation for the development of more robust complex radioactive liquid waste processing strategies.

Cr(III) Adsorption by Cluster Formation on Boehmite Nanoplates in Highly Alkaline Solution.

The development of advanced functional nanomaterials for selective adsorption in complex chemical environments requires partner studies of binding mechanisms. Motivated by observations of selective Cr(III) adsorption on boehmite nanoplates (γ-AlOOH) in highly caustic multicomponent solutions of nuclear tank waste, here we unravel the adsorption mechanism in molecular detail. We examined Cr(III) adsorption to synthetic boehmite nanoplates in sodium hydroxide solutions up to 3 M, using a combination of X-ray diffraction (XRD), Raman, X-ray photoelectron spectroscopy (XPS), scanning/transmission electron microscopy (S/TEM), electron energy loss spectroscopy (EELS), high-resolution atomic force microscopy (HR-AFM), time-of-fight secondary ion mass spectrometry (ToF-SIMS), Cr K-edge X-ray absorption near edge structure (XANES)/extended X-ray absorption fine structure (EXAFS), and electron paramagnetic resonance (EPR). Adsorption isotherms and kinetics were successfully fit to Langmuir and pseudo-second-order kinetic models, respectively, consistent with monotonic uptake of Cr(OH)4- monomers until saturation coverage of approximately half the aluminum surface site density. High resolution AFM revealed monolayer cluster self-assembly on the (010) basal surfaces with increasing Cr(III) loading, possessing a structural motif similar to guyanaite (ß-CrOOH), stabilized by corner-sharing Cr-O-Cr bonds and attached to the surface with edge-sharing Cr-O-Al bonds. The selective uptake appears related to short-range surface templating effects, with bridging metal connections likely enabled by hydroxyl anion ligand exchange reactions at the surface. Such a cluster formation mechanism, which stops short of more laterally extensive heteroepitaxy, could be a metal uptake discrimination mechanism more prevalent than currently recognized.

Uranium Release from Acidic Weathered Hanford Sediments: Single-Pass Flow-Through and Column Experiments.

The reaction of acidic radioactive waste with sediments can induce mineral transformation reactions that, in turn, control contaminant fate. Here, sediment weathering by synthetic uranium-containing acid solutions was investigated using bench-scale experiments to simulate waste disposal conditions at Hanford's cribs (Hanford, WA). During acid weathering, the presence of phosphate exerted a strong influence over uranium mineralogy and a rapidly precipitated, crystalline uranium phosphate phase (meta-ankoleite [K(UO2)(PO4)·3H2O]) was identified using spectroscopic and diffraction-based techniques. In phosphate-free system, uranium oxyhydroxide minerals such as K-compreignacite [K2(UO2)6O4(OH)6·7H2O] were formed. Single-pass flow-through (SPFT) and column leaching experiments using synthetic Hanford pore water showed that uranium precipitated as meta-ankoleite during acid weathering was strongly retained in the sediments, with an average release rate of 2.67 × 10-12 mol g-1 s-1. In the absence of phosphate, uranium release was controlled by dissolution of uranium oxyhydroxide (compreignacite-type) mineral with a release rate of 1.05-2.42 × 10-10 mol g-1 s-1. The uranium mineralogy and release rates determined for both systems in this study support the development of accurate U-release models for the prediction of contaminant transport. These results suggest that phosphate minerals may be a good candidate for uranium remediation approaches at contaminated sites.

Phosphate-Induced Immobilization of Uranium in Hanford Sediments.

Phosphate can be added to subsurface environments to immobilize U(VI) contamination. The efficacy of immobilization depends on the site-specific groundwater chemistry and aquifer sediment properties. Batch and column experiments were performed with sediments from the Hanford 300 Area in Washington State and artificial groundwater prepared to emulate the conditions at the site. Batch experiments revealed enhanced U(VI) sorption with increasing phosphate addition. X-ray absorption spectroscopy measurements of samples from the batch experiments found that U(VI) was predominantly adsorbed at conditions relevant to the column experiments and most field sites (low U(VI) loadings, <25 µM), and U(VI) phosphate precipitation occurred only at high initial U(VI) (>25 µM) and phosphate loadings. While batch experiments showed the transition of U(VI) uptake from adsorption to precipitation, the column study was more directly relevant to the subsurface environment because of the high solid:water ratio in the column and the advective flow of water. In column experiments, nearly six times more U(VI) was retained in sediments when phosphate-containing groundwater was introduced to U(VI)-loaded sediments than when the groundwater did not contain phosphate. This enhanced retention persisted for at least one month after cessation of phosphate addition to the influent fluid. Sequential extractions and laser-induced fluorescence spectroscopy of sediments from the columns suggested that the retained U(VI) was primarily in adsorbed forms. These results indicate that in situ remediation of groundwater by phosphate addition provides lasting benefit beyond the treatment period via enhanced U(VI) adsorption to sediments.

Effect of Reaction Pathway on the Extent and Mechanism of Uranium(VI) Immobilization with Calcium and Phosphate.

Phosphate addition to subsurface environments contaminated with uranium can be used as an in situ remediation approach. Batch experiments were conducted to evaluate the dependence of the extent and mechanism of uranium uptake on the pathway for reaction with calcium phosphates. At pH 4.0 and 6.0 uranium uptake from solution occurred via autunite (Ca(UO2)2(PO4)2) precipitation irrespective of the starting forms of calcium and phosphate. At pH 7.5, a condition at which calcium phosphate solids could form, the uptake mechanism depended on the nature of the calcium and phosphate as determined by X-ray absorption spectroscopy and laser-induced fluorescence spectroscopy. When dissolved uranium, calcium, and phosphate were added simultaneously, uranium was structurally incorporated into a newly formed amorphous calcium phosphate solid. Adsorption was the dominant removal mechanism for uranium contacted with preformed amorphous calcium phosphate solids. When U(VI) was added to a suspension containing amorphous calcium phosphate solids as well as dissolved calcium and phosphate, then removal occurred through precipitation (57 ± 4%) of autunite and adsorption (43 ± 4%) onto calcium phosphate. Dissolved uranium, calcium, and phosphate concentrations with saturation index calculations helped identify removal mechanisms and determine thermodynamically favorable solid phases.

Transport of U(VI) through sediments amended with phosphate to induce in situ uranium immobilization.

Phosphate amendments can be added to U(VI)-contaminated subsurface environments to promote in situ remediation. The primary objective of this study was to evaluate the impacts of phosphate addition on the transport of U(VI) through contaminated sediments. In batch experiments using sediments (<2 mm size fraction) from a site in Rifle, Colorado, U(VI) only weakly adsorbed due to the dominance of the aqueous speciation by Ca-U(VI)-carbonate complexes. Column experiments with these sediments were performed with flow rates that correspond to a groundwater velocity of 1.1 m/day. In the absence of phosphate, the sediments took up 1.68-1.98 µg U/g of sediments when the synthetic groundwater influent contained 4 µM U(VI). When U(VI)-free influents were then introduced with and without phosphate, substantially more uranium was retained within the column when phosphate was present in the influent. Sequential extractions of sediments from the columns revealed that uranium was uniformly distributed along the length of the columns and was primarily in forms that could be extracted by ion exchange and contact with a weak acid. Laser induced fluorescence spectroscopy (LIFS) analysis along with sequential extraction results suggest adsorption as the dominant uranium uptake mechanism. The response of dissolved uranium concentrations to stopped-flow events and the comparison of experimental data with simulations from a simple reactive transport model indicated that uranium adsorption to and desorption from the sediments was not always at local equilibrium.

Investigation of U(VI) adsorption in quartz-chlorite mineral mixtures.

A batch and cryogenic laser-induced time-resolved luminescence spectroscopy investigation of U(VI) adsorbed on quartz-chlorite mixtures with variable mass ratios have been performed under field-relevant uranium concentrations (5×10(-7) M and 5×10(-6) M) in pH 8.1 synthetic groundwater. The U(VI) adsorption Kd values steadily increased as the mass fraction of chlorite increased, indicating preferential sorption to chlorite. For all mineral mixtures, U(VI) adsorption Kd values were lower than that calculated from the assumption of component additivity possibly caused by surface modifications stemming from chlorite dissolution; The largest deviation occurred when the mass fractions of the two minerals were equal. U(VI) adsorbed on quartz and chlorite displayed characteristic individual luminescence spectra that were not affected by mineral mixing. The spectra of U(VI) adsorbed within the mixtures could be simulated by one surface U(VI) species on quartz and two on chlorite. The luminescence intensity decreased in a nonlinear manner as the adsorbed U(VI) concentration increased with increasing chlorite mass fraction-likely due to ill-defined luminescence quenching by both structural Fe/Cr in chlorite, and trace amounts of solubilized and reprecipitated Fe/Cr in the aqueous phase. However, the fractional spectral intensities of U(VI) adsorbed on quartz and chlorite followed the same trend of fractional adsorbed U(VI) concentration in each mineral phase with approximate linear correlations, offering a method to estimate of U(VI) concentration distribution between the mineral components with luminescence spectroscopy.

Kirenol exerts a potent anti-arthritic effect in collagen-induced arthritis by modifying the T cells balance.

Rheumatoid arthritis is characterized by the imbalance of T cells, which leads to increased pro-inflammatory and reduced anti-inflammatory cytokines. Modulating the balance among T cells is crucial for the treatment of RA. Kirenol is a major diterpenoid components of Herba Siegesbeckiae, which has been applied for arthritic therapy for centuries. Since prior research showed Kirenol exhibited anti-inflammatory effect in rats, in this study we have evaluated the effect and mechanism of bioactive Kirenol in a rat model of collagen-induced arthritis (CIA) on modulation of T cells. After immunization with bovine type II collagen (CII), Wistar rats were orally administered saline (CIA group), 2 mg/kg Kirenol or 2 mg/kg prednisolone daily for 30 days. The severity of arthritis was clinically and histologically assessed. The numbers of CD4⁺CD25⁺Foxp3⁺ T regulatory cells (Tregs) and IFNγ⁺CD4⁺ and IL4⁺CD4⁺ T cells were determined by flow cytometry, the mRNA expression level of Foxp3 was quantified by RT-PCR, cytokine levels were measured by ELISA and CII-induced cell proliferation was quantified in vitro. Kirenol significantly delayed the occurrence and reduced the disease severity of CIA. Histological analysis confirmed Kirenol suppressed joint inflammation and inhibited cartilage and bone destruction, compared to the CIA group. Kirenol also upregulated the mRNA expression of Foxp3, increased the numbers of CD4⁺CD25⁺Foxp3⁺ and IL4⁺CD4⁺ T cells, and reduced the number of IFNγ⁺CD4⁺ T cells. Kirenol reduced the levels of TNF-α, IL-17A and IL-6 in synovial fluid and TNF-α, IL-17A and IFN-γ in serum, and increased the serum levels of IL-4, IL-10 and TGF-ß1. In addition, Kirenol inhibited the ability of CII to induce splenocyte, PBMC and lymph node cell proliferation in vitro, compared to cells from CIA rats. In conclusion, these results suggest that Kirenol may be a potential immunosuppressant for the treatment for rheumatoid arthritis.

The effect of pH and time on the extractability and speciation of uranium(VI) sorbed to SiO2.

The effect of pH and contact time on uranium extractability from quartz surfaces was investigated using either acidic or carbonate (CARB) extraction solutions, time-delayed spikes of different U isotopes ((238)U and (233)U), and liquid helium temperature time-resolved laser-induced fluorescence spectroscopy (TRLFS). Quartz powders were reacted with (238)U(VI) bearing solutions equilibrated with atmospheric CO(2) at pH 6, 7, and 8. After 42 days, the suspensions were spiked with (233)U(VI) and reacted for an additional 7 days. Sorbed U was then extracted with either dilute nitric acid or CARB. For the CARB, but not the acid, extraction there was a systematic decrease in extraction efficiency for both isotopes from pH 6 to 8, which was mimicked by less desorption of (238)U, after the (233)U spike, from pH 6 to 8. The efficiency of (233)U extraction was consistently greater than that of (238)U, indicating a strong temporal component to the strength of U association with the surface that was accentuated with increasing pH. TRLFS revealed a strong correlation between CARB extraction efficiency and sorbed U speciation as a function of pH and time. Collectively, the observations show that aging and pH are critical factors in determining the form and strength of uranium-silica interactions.

[Comparative study on anti-inflammatory and antipyretic effects between Dao-di herb and non Dao-di herb of Huangqin].

OBJECTIVE: To do some comparative study on anti-inflammatory and antipyretic effects between the Dao-di herb and non Dao-di herb of Huangqin (the roots of Scutellaria baicalensis) and provide thinking and evidence for study on geoherbalism and clinical usage of Huangqin. METHOD: The anti-inflammatory action was assessed by auricular swelling induced by dimethylbenzene in mice and the antipyretic action was monitored by dried yeast-induced mice fever. RESULT: All samples of both Dao-di and non Dao-di herbs of Huangqin showed antipyretic effect. The Dao-di Huangqin samples showed antipyretic effect between 61% to 53% , whereas the non Dao-di Huangqin samples between 53% to 43%. Six Dao-di Huangqin samples showed better antipyretic effect than four non Dao-di Huangqin samples. All samples of both Dao-di and non Dao-di Huangqin showed anti-inflammatory effect. Dao-di Huangqin showed anti-inflammatory effect between 73% to 54%, whereas non dao-di Huangqin between 53% to 34%. Six Dao-di Huangqin showed better anti-inflammatory effect than four non Dao-di Huangqin. In totality, results from analysis of geoherbalism showed that geoherbal production areas of Huangqin had better effect than that of the non geoherbal production areas in anti-inflammatory and antipyretic effects. CONCLUSION: Both the Dao-di and non Dao-di Huangqin have effects of anti-inflammatory and antipyretic to a certain extent, but the efficacy of the Dao-di Huangqin surpass the non Dao-di Huangqin.

Kirenol upregulates nuclear annexin-1 which interacts with NF-κB to attenuate synovial inflammation of collagen-induced arthritis in rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Kirenol is a diterpenoid compound purified from the Chinese Herba Siegesbeckiae. Siegesbeckiae has been employed for the treatment of arthritis for centuries, its safety and efficacy are documented through a long history of human use. AIM OF THE STUDY: To investigate the effects on collagen-induced arthritis (CIA) and anti-inflammatory mechanism of kirenol. MATERIALS AND METHODS: Kirenol was administrated intragastrically in rats after the onset of CIA. Pathological changes were evaluated by paw swelling and histopathology. Concentration of IL-1ß in synovial fluid and adrenal corticotropin (ACTH) in plasma were determined by Elisa. Western blot was performed to detect the expression of annexin-1 and glucocorticoid receptor alpha (GRα) in synovium. NF-κB DNA binding activity was assessed by electrophoretic mobility shift assays (EMSA). RESULTS: Kirenol (1, 2, and 4 mg/kg) and prednisolone depressed paw swelling and reduced IL-1ß of synovial fluid in the CIA rats (p<0.05 or p<0.01). Kirenol and prednisolone upregulated nuclear annexin-1 and inhibited NF-κB activity in synovium of CIA. The inhibitory effect of kirenol and prednisolone on NF-κB activity was enhanced by anti-annexin-1 Ab. Prednisolone, but not kirenol, downregulated plasma ACTH and GRα expression significantly (p<0.01). CONCLUSION: Kirenol and prednisolone can upregulate nuclear annexin-1 which interacts with NF-κB to inhibit NF-κB activity, reduce cytokines expression and thereby attenuate inflammation of CIA joints. Kirenol does not lead to ACTH or GR downregulation, which is in contrast to classic glucocorticoid prednisolone. Kirenol shares with GCs similar anti-inflammatory mechanism but bypass the considerable limitation of GCs treatment.

Effect of grain size on uranium(VI) surface complexation kinetics and adsorption additivity.

The contribution of variable grain sizes to uranium adsorption/desorption was studied using a sediment from the US DOE Hanford site. The sediment was wet sieved into four size fractions: coarse sand (1-2 mm), medium sand (0.2-1 mm), fine sand (0.053-0.2 mm), and clay/silt fraction (<0.053 mm). For each size fraction and their composite (sediment), batch and flow-cell experiments were performed to determine uranium adsorption isotherms and kinetic uranium adsorption and subsequent desorption. The results showed that uranium adsorption isotherms and adsorption/desorption kinetics were size specific, reflecting the effects of size-specific adsorption site concentration and kinetic rate constants. The larger-size fraction had a larger mass percentage in the sediment but with a smaller adsorption site concentration and generally a slower uranium adsorption/desorption rate. The same equilibrium surface complexation reaction and reaction constant could describe uranium adsorption isotherms for all size fractions and the composite after accounting for the effect of adsorption site concentration. Mass-weighted, linear additivity was observed for both uranium adsorption isotherms and adsorption/desorption kinetics in the composite. One important implication of this study is that grain-size distribution may be used to estimate uranium adsorption site and adsorption/desorption kinetic rates in heterogeneous sediments from a common location.

Identification and characterization of UndAHRCR-6, an outer membrane endecaheme c-type cytochrome of Shewanella sp. strain HRCR-6.

UndA(HRCR-6) was identified from the metal-reducing bacterium Shewanella sp. strain HRCR-6. Both in vivo and in vitro characterization results indicate that UndA(HRCR-6) is an outer membrane endecaheme c-type cytochrome and probably has a key functional role in the extracellular reduction of iron [Fe(III)] oxides and uranium [U(VI)] by Shewanella sp. HRCR-6.

A rapid and simple RP-HPLC method for quantification of kirenol in rat plasma after oral administration and its application to pharmacokinetic study.

A rapid and simple reverse-phase high-performance liquid chromatography (RP-HPLC) was developed and validated for the quantification of kirenol in rat plasma after oral administration. Kirenol and darutoside (internal standard, IS) were extracted from rat plasma using Cleanert™ C(18) solid-phase extraction (SPE) cartridge. Analysis of the extraction was performed on a Thermo ODS-2 Hypersil C(18) reversed-phase column with a gradient eluent composed of acetonitrile and 0.1% phosphoric acid. The flow rate was 1.0 mL/min and the detection wavelength was set at 215 nm. The calibration curve was linear over the range of 9.756-133.333 µg/mL (r(2) = 0.9991) in rat plasma. The lower limits of detection and quantification were 2.857 and 9.756 µg/mL, respectively. The intra- and inter-day precisions (relative standard deviation, RSD) were between 2.24 and 4.46%, with accuracies ranging from 91.80 to 102.74%. The extraction recovery ranged from 98.16 to 107.62% with RSD less than 4.81%. Stability studies showed that kirenol was stable in preparation and analytical process. The present method was successfully applied to the pharmacokinetic study of kirenol in male Sprague-Dawley rats after oral administration at a dose of 50 mg/kg.

Inhibition effect of secondary phosphate mineral precipitation on uranium release from contaminated sediments.

The inhibitory effect of phosphate mineral precipitation on diffusion-limited uranium release was evaluated using a U(VI)-contaminated sediment collected from the U.S. Department of Energy Hanford site. The sediment contained U(VI) that was associated with diffusion-limited intragrain regions within its millimeter-sized granitic lithic fragments. The sediment was first treated to promote phosphate mineral precipitation in batch suspensions spiked with 1 and 50 mM aqueous phosphate and calcium in the stoichiometric ratio of the mineral hydroxyapatite. The phosphate-treated sediment was then leached to solubilize contaminant U(VI) in a column system using a synthetic groundwater solution with chemical components representative of Hanford groundwater. Phosphate treatment significantly decreased the extent of U(VI) release from the sediment. Within the experimental duration of about 200 pore volumes, the effluent U(VI) concentrations were consistently lower by over 1 and 2 orders of magnitude after the sediment was treated with 1 and 50 mM of phosphate, respectively. Measurements of solid-phase U(VI) using laser-induced fluorescence spectroscopy, scanning electron microscopy, and chemical extraction of the sediment collectively indicated that the inhibition of U(VI) release from the sediment was caused by (1) U(VI) adsorption to the secondary phosphate precipitates and (2) the transformation of original U(VI) mineral phases to less soluble forms.

Microbial reduction of intragrain U(VI) in contaminated sediment.

The accessibility of precipitated, intragrain U(VI) in a contaminated sediment to microbial reduction was investigated to ascertain geochemical and microscopic transport phenomena controlling U(VI) bioavailability. The sediment was collected from the U.S. Department of Energy Hanford site, and contained uranyl precipitates within the mm-sized granitic lithic fragments in the sediment. Bioreduction was investigated in a culture of a dissimilatory metal-reducing bacterium, Shewanellea oneidensis strain MR-1. Measurements of uranium concentration, speciation, and valence in aqueous and solid phases indicated that microbial reduction of intragrain U(VI) proceeded by two mechanisms: (1) sequentially coupled dissolution of intragrain uranyl precipitates, diffusion of dissolved U(VI) from intragrain regions, and microbial reduction of dissolved U(VI); and (2) U(VI) reduction in the intragrain regions by soluble, diffusible biogenic reductants. The bioreduction rate in the first pathway was over 3 orders of magnitude slowerthan that in comparable aqueous solutions containing aqueous U(VI) only. The slower bioreduction rate was attributed to (1) the release of calcium from the desorption/dissolution of calcium-containing minerals in the sediment, which subsequently altered U(VI) aqueous speciation and slowed U(VI) bioreducton and (2) alternative electron transfer pathways that reduced U(VI) in the intragrain regions and changed its dissolution and solubility behavior. The results implied that the overall rate of bioreduction of intragrain U(VI) will be influenced by the reactive mass transfer of U(VI) and biogenic reductants within intragrain regions, and geochemical reactions controlling major ion concentrations.

Uranium phases in contaminated sediments below Hanford's U tank farm.

Macroscopic and spectroscopic investigations (XAFS, XRF, and TRLIF) on Hanford contaminated vadose zone sediments from the U-tank farm showed that U(VI) exists as different surface phases as a function of depth below ground surface (bgs). Secondary precipitates of U(VI) silicate precipitates (boltwoodite and uranophane) were present dominantly in shallow-depth sediments (15-16 m bgs), while adsorbed U(VI) phases and polynuclear U(VI) surface precipitates were considered to dominate in intermediate-depth sediments (20-25 m bgs). Only natural uranium was observed in the deeper sediments (> 28 m bgs) with no signs of contact with tank wastes containing Hanford-derived U(VI). Across all depths, most of the U(VI) was preferentially associated with the silt and clay size fractions of sediments. Strong correlation between U(VI) and Ca was found in the shallow-depth sediments, especially for the precipitated U(VI) silicates. Because U(VI) silicate precipitates dominate in the shallow-depth sediments, the released U(VI) concentration by macroscopic (bi)carbonate leaching resulted from both desorption and dissolution processes. Having different U(VI) surface phases in the Hanford contaminated sediments indicates that the U(VI) release mechanism could be complicated and that detailed characterization of the sediments using several different methods would be needed to estimate U(VI) fate and transport correctly in the vadose zone.

Spatially resolved U(VI) partitioning and speciation: implications for plume scale behavior of contaminant U in the Hanford vadose zone.

A saline-alkaline brine containing high concentration of U(VI) was accidentally spilled at the Hanford Site in 1951, introducing 10 tons of U into sediments under storage tank BX-102. U concentrations in the deep vadose zone and groundwater plumes increase with time, yet how the U has been migrating is not fully understood. We simulated the spill event in laboratory soil columns, followed by aging, and obtained spatially resolved U partitioning and speciation along simulated plumes. We found after aging, at apparent steady state, that the pore aqueous phase U concentrations remained surprisingly high (up to 0.022 M), in close agreement with the recently reported high U concentrations (up to 0.027 M) in the vadose zone plume (1). The pH values of aged pore liquids varying from 10 to 7, consistent with the measured pH of the field borehole sediments varying from 9.5 to 7.4 (2), from near the plume source to the plume front. The direct measurements of aged pore liquids together with thermodynamic calculations using a Pitzer approach revealed that UO2(CO3)3(4-) is the dominant aqueous U species within the plume body (pH 8-10), whereas Ca2UO2(CO3)3 and CaUO2(CO3)32- are also significant in the plume frontvicinity (pH 7-8), consistent with that measured from field borehole pore-waters (3). U solid phase speciation varies at different locations along the plume flow path and even within single sediment grains, because of location dependent pore and micropore solution chemistry. Our results suggest that continuous gravity-driven migration of the highly stable U02(CO3)34 in the residual carbonate and sodium rich tank waste solution is likely responsible for the detected growing U concentrations in the vadose zone and groundwater.