Uranium biomineralization as a result of bacterial phosphatase activity: insights from bacterial isolates from a contaminated subsurface

Uranium contamination is an environmental concern at the Department of Energy's Field Research Center in Oak Ridge, Tennessee. In this study, we investigated whether phosphate biomineralization, or the aerobic precipitation of U(VI)-phosphate phases facilitated by the enzymatic activities of microorganisms, offers an alternative to the more extensively studied anaerobic U(VI) bioreduction. Three heterotrophic bacteria isolated from FRC soils were studied for their ability to grow and liberate phosphate in the presence of U(VI) and an organophosphate between pH 4.5 and 7.0. The objectives were to determine whether the strains hydrolyzed sufficient phosphate to precipitate uranium, to determine whether low pH might have an effect on U(VI) precipitation, and to identify the uranium solid phase formed during biomineralization. Two bacterial strains hydrolyzed sufficient organophosphate to precipitate 7395% total uranium after 120 h of incubation in simulated groundwater. The highest rates of uranium precipitation and phosphatase activity were observed between pH 5.0 and 7.0. EXAFS spectra identified the uranyl phosphate precipitate as an autunite/meta-autunite group mineral. The results of this study indicate that aerobic heterotrophic bacteria within a uranium-contaminated environment that can hydrolyze organophosphate, especially in low pH conditions, may play an important role in the bioremediation of uranium.     

Mass-transfer limitations for nitrate removal in a uranium-contaminated aquifer

A field test on in situ subsurface bioremediation of uranium(VI) is underway at the Y-12 National Security Complex in the Oak Ridge Reservation, Oak Ridge, TN. Nitrate has a high concentration at the site, which prevents U(VI) reduction, and thus must be removed. An acidic-flush strategy for nitrate removal was proposed to create a treatment zone with low levels of accessible nitrate. The subsurface at the site contains highly interconnected fractures surrounded by matrix blocks of low permeability and high porosity and is therefore subject to preferential flow and matrix diffusion. To identify the heterogeneous mass transfer properties, we performed a novel forced-gradient tracer test, which involved the addition of bromide, the displacement of nitrate, and the rebound of nitrate after completion of pumping. The simplest conceptualization consistent with the data is that the pore-space consists of a single mobile domain, as well as a fast and a slowly reacting immobile domain. The slowly reacting immobile domain (shale matrix) constitutes over 80% of the pore volume and acts as a long-term reservoir of nitrate. According to simulations, the nitrate stored in the slowly interacting immobile domain in the fast flow layer, at depths of about 12.2-13.7 m, will be reduced by an order of magnitude over a period of about a year. By contrast, the mobile domain rapidly responds to flushing, and a low average nitrate concentration can be maintained if the nitrate is removed as soon as it enters the mobile domain. A field-scale experiment in which the aquifer was flushed with acidic solution confirmed our understanding of the system. For the ongoing experiments on microbial U(VI) reduction, nitrate concentrations must be low in the mobile domain to ensure U(VI) reducing conditions. We therefore conclude that the nitrate leaching out of the immobile pore space must continuously be removed by in situ denitrification to maintain favorable conditions.     

Real-time X-ray absorption spectroscopy of uranium, iron, and manganese in contaminated sediments during bioreduction

The oxidation status of uranium in sediments is important because the solubility of this toxic and radioactive element is much greater for U(VI) than for U(IV) species. Thus, redox manipulation to promote precipitation of UO2 is receiving interest as a method to remediate U-contaminated sediments. Presence of Fe and Mn oxides in sediments at much higher concentrations than U requires an understanding of their redox status as well. This study was conducted to determine changes in oxidation states of U, Fe, and Mn in U-contaminated sediments from Oak Ridge National Laboratory. Oxidation states of these elements were measured in real-time and nondestructively using X-ray absorption spectroscopy on sediment columns supplied with synthetic groundwater containing organic carbon (OC, 0, 3, 10, 30, and 100 mM OC as lactate) for over 400 days. In sediments supplied with OC > or = 30 mM, 80% of the U was reduced to U(IV), with transient reoxidation at about 150 days. Mn(III,IV) oxides were completely reduced to Mn(II) in sediments infused with OC > or = 3 mM. However, Fe remained largely unreduced in all sediment columns, showing that Fe(III) can persist as an electron acceptor in reducing sediments over long times. This result in combination with the complete reduction of all other potential electron acceptors supports the hypothesis that the reactive Fe(III) fraction was responsible for reoxidizing U(IV).     

Rapid dissolution of soluble uranyl phases in arid, mine-impacted catchments near Church Rock, NM

We tested the hypothesis that runoff of uranium-bearing particles from mining waste disposal areas was a significant mechanism for redistribution of uranium in the northeastern part of the Upper Puerco River watershed (New Mexico). However, our results were not consistent with this hypothesis. Analysis of > 100 sediment and suspended sediment samples collected adjacent to and downstream from uranium source areas indicated that uranium levels in the majority of the samples were not elevated above background. Samples collected within 50 m of a known waste disposal site were subjected to detailed geochemical characterization. Uranium in these samples was found to be highly soluble; treatment with synthetic pore water for 24 h caused dissolution of 10--50% of total uranium in the samples. Equilibrium uranium concentrations in pore water were > 4.0 mg/L and were sustained in repeated wetting events, effectively depleting soluble uranium from the solid phase. The dissolution rate of uranium appeared to be controlled by solid-phase diffusion of uranium from within uranium-bearing mineral particles. X-ray adsorption spectroscopy indicated the presence of a soluble uranyl silicate, and possibly a uranyl phosphate. These phases were exhausted in transported sediment suggesting that uranium was readily mobilized from sediments in the Upper Puerco watershed and transported in the dissolved load. These results could have significance for uranium risk assessment as well as mining waste management and cleanup efforts.     

Bioaccessibility of uranium in soil samples from port hope, ontario, Canada

Adequate assessment of human health risk of uranium contamination at hazardous waste sites, which is an important step in determining the cleanup strategy, is based on bioavailability data. Bioavailability of uranium from contaminated soil has not been properly determined yet. Bioaccessibility is an in vitro conservative estimate of bioavailability and is thus frequently used for site-specific risk assessment. Bioaccessibility of uranium was measured in 33 soil samples from the Port Hope area in Ontario, Canada, by the physiologically based extraction test (PBET). Higher bioaccessibility values in the gastric plus intestinal phase, 48.4% ± 16.8%, than in the gastric phase, 20.8% ± 11.7%, are very probably the result of more efficient extraction of uranium from soil by intestinal fluid rich in carbonate ions. The observed variability of measured bioaccessibility values is discussed in light of the results of scanning electron microscope examination of the soil samples. Uranium bioaccessibility values in both gastric (acidic) and gastric plus intestinal (neutral) phases are higher in soil samples with smaller uranium-bearing particles and lower in samples where the uranium-bearing particles are larger. We postulate that the most important reason for variability of measured bioaccessibility values in Port Hope soil samples may be the difference in particle size of uranium-bearing particles.     

Response Surface Methodology Study for Optimization of Effects of Fiber Level, Frying Temperature, and Frying Time on Some Physicochemical, Textural, and Sensory Properties of Wheat Chips Enriched with Apple Fiber

In this study, wheat chips enriched with apple fiber were produced, and response surface methodology was used for the determination of the simultaneous effects of processing variables selected as fiber level (0–15 %), frying temperature (160–180 °C), and frying time (40–60 s) on some physicochemical, textural, and sensorial properties of chips. Ridge analysis was conducted to determine the optimum levels of processing variables. Predictive regression equations with high coefficient of determination (R ²?≥?0.728) were constructed. Addition of apple fiber increased the dry matter; ash content; L, a, and b values of samples, while increase of frying temperature caused decrease of the hardness values. Overall acceptability of chips enriched with apple fiber decreased with the increase of frying temperature, but wheat chips enriched with apple fiber and fried at low temperatures received highest sensory score. Ridge analysis showed that maximum taste score would be attained at fiber level?=?15 %, frying temperature?=?170 °C and frying time?=?40 s.     

In situ bioreduction of uranium (VI) to submicromolar levels and reoxidation by dissolved oxygen

Groundwater within Area 3 of the U.S. Department of Energy (DOE) Environmental Remediation Sciences Program (ERSP) Field Research Center at Oak Ridge, TN (ORFRC) contains up to 135 microM uranium as U(VI). Through a series of experiments at a pilot scale test facility, we explored the lower limits of groundwater U(VI) that can be achieved by in-situ biostimulation and the effects of dissolved oxygen on immobilized uranium. Weekly 2 day additions of ethanol over a 2-year period stimulated growth of denitrifying, Fe(III)-reducing, and sulfate-reducing bacteria, and immobilization of uranium as U(IV), with dissolved uranium concentrations decreasing to low levels. Following sulfite addition to remove dissolved oxygen, aqueous U(VI) concentrations fell below the U.S. Environmental Protection Agengy maximum contaminant limit (MCL) for drinking water (< 30/microg L(-1) or 0.126 microM). Under anaerobic conditions, these low concentrations were stable, even in the absence of added ethanol. However, when sulfite additions stopped, and dissolved oxygen (4.0-5.5 mg L(-1)) entered the injection well, spatially variable changes in aqueous U(VI) occurred over a 60 day period, with concentrations increasing rapidly from < 0.13 to 2.0 microM at a multilevel sampling (MLS) well located close to the injection well, but changing little at an MLS well located further away. Resumption of ethanol addition restored reduction of Fe(III), sulfate, and U(VI) within 36 h. After 2 years of ethanol addition, X-ray absorption near-edge structure spectroscopy (XANES) analyses indicated that U(IV) comprised 60-80% of the total uranium in sediment samples. Atthe completion of the project (day 1260), U concentrations in MLS wells were less than 0.1 microM. The microbial community at MLS wells with low U(VI) contained bacteria that are known to reduce uranium, including Desulfovibrio spp. and Geobacter spp., in both sediment and groundwater. The dominant Fe(III)-reducing species were Geothrix spp.     

Hexavalent uranium diffusion into soils from concentrated acidic and alkaline solutions

Uranium contamination of soils and sediments often originates from acidic or alkaline waste sources, with diffusion being a major transport mechanism. Measurements of U(VI) diffusion from initially pH 2 and pH 11 solutions into a slightly alkaline Altamont soil and a neutral Oak Ridge soil were obtained through monitoring uptake from boundary reservoirs and from U concentration profiles within soil columns. The soils provided pH buffering, resulting in diffusion at nearly constant pH. Micro X-ray absorption near edge structure spectra confirmed that U remained in U(VI) forms in all soils. Time trends of U(VI) depletion from reservoirs and U(VI) concentration profiles within soil columns yielded Kdvalues consistent with those determined in batch tests at similar concentrations (approximately 1 mM) and much lower than values for sorption at much lower concentrations (nM to microM). These results show that U(VI) transport at high concentrations can be relatively fast at non-neutral pH, with negligible surface diffusion, because of weak sorption.     

Permeable environmental leaching capsules (PELCAPs) for in situ evaluation of contaminant immobilization in soil

We encapsulated radioisotope-spiked soil within a water-permeable polyacrylamide matrix cast in a small cylindrical geometry (approximately to 5 cm3) to measure the persistence of immobilized soil contaminants. As a proof-of-principle, soils contained within these permeable environmental leaching capsules (PELCAPs) were labeled with either 85Sr or 134Cs and were leached in both laboratory tests and continuously in situ with ground and streamwaters at two field sites on the Oak Ridge reservation. Groups of PELCAPs were retrieved, assayed nondestructively for radioisotopes via gamma spectroscopy, and then replaced in ground and surface water repeatedly over a 6-month period. PELCAPs that contained no soil readily and quantitatively leached either 85Sr or 134Cs into laboratory extractants or ground or surface water with effective diffusion coefficients (D(eff)) of (1.14 +/- 0.06) and (4.8 +/- 0.2) x 10(-6) cm2/s, respectively. PELCAPs containing untreated soil readily leached > 90% of 85Sr but < 1% of 134Cs during field leaching at both sites, whereas thermally treated soils quantitatively retained both isotopes under all conditions. Permeable polymer encapsulation methods, such as PELCAPs, offer the potential capability to conveniently test large numbers of soils and soil treatments for contaminant release and uptake under actual field environmental conditions.     

Kinetics of polyphenol extraction from wood chips in wine model solutions: effect of chip amount and botanical species

The extraction of polyphenols from wood chips into a wine model system was described using kinetics, over a period of 20 days. The wood chips tested were made from oak (Quercus alba), false acacia (Robinia pseudoacacia) and cherry (Prunus avium) wood. Kinetics were established using nonlinear regression and the leaching of polyphenols into the liquid model systems was found to obey a second‐order model. The determination of basic kinetic parameters enabled the identification of leaching trends and comparison among the difference wood species used, as well as determination of the effect of the amount of chips added. Oak chips were found to enrich the model wine in polyphenolic substances significantly more compared with either acacia or cherry. Furthermore, the wine model treated with oak chips displayed a much higher reducing power on day 20 of the treatment. The correlation of the total polyphenol concentration at saturation with the amount of chips added, using nonlinear regression, revealed that in every case the maximum concentration of total polyphenols attained was linked with the amount of chips by a three‐parameter exponential growth function. Possible differences pertaining to wood botanical species and polyphenolic load are discussed on the grounds of theoretical considerations for diffusion. Copyright © 2015 The Institute of Brewing & Distilling     

Pilot-scale in situ bioremedation of uranium in a highly contaminated aquifer. 2. Reduction of u(VI) and geochemical control of u(VI) bioavailability

In situ microbial reduction of soluble U(VI) to sparingly soluble U(IV) was evaluated at the site of the former S-3 Ponds in Area 3 of the U.S. Department of Energy Natural and Accelerated Bioremediation Research Field Research Center, Oak Ridge, TN. After establishing conditions favorable for bioremediation (Wu, et al. Environ. Sci. Technol. 2006, 40, 3988-3995), intermittent additions of ethanol were initiated within the conditioned inner loop of a nested well recirculation system. These additions initially stimulated denitrification of matrix-entrapped nitrate, but after 2 months, aqueous U levels fell from 5 to approximately 1 microM and sulfate reduction ensued. Continued additions sustained U(VI) reduction over 13 months. X-ray near-edge absorption spectroscopy (XANES) confirmed U(VI) reduction to U(IV) within the inner loop wells, with up to 51%, 35%, and 28% solid-phase U(IV) in sediment samples from the injection well, a monitoring well, and the extraction well, respectively. Microbial analyses confirmed the presence of denitrifying, sulfate-reducing, and iron-reducing bacteria in groundwater and sediments. System pH was generally maintained at less than 6.2 with low bicarbonate level (0.75-1.5 mM) and residual sulfate to suppress methanogenesis and minimize uranium mobilization. The bioavailability of sorbed U(VI) was manipulated by addition of low-level carbonate (< 5 mM) followed by ethanol (1-1.5 mM). Addition of low levels of carbonate increased the concentration of aqueous U, indicating an increased rate of U desorption due to formation of uranyl carbonate complexes. Upon ethanol addition, aqueous U(VI) levels fell, indicating that the rate of microbial reduction exceeded the rate of desorption. Sulfate levels simultaneously decreased, with a corresponding increase in sulfide. When ethanol addition ended but carbonate addition continued, soluble U levels increased, indicating faster desorption than reduction. When bicarbonate addition stopped, aqueous U levels decreased, indicating adsorption to sediments. Changes in the sequence of carbonate and ethanol addition confirmed that carbonate-controlled desorption increased bioavailability of U(VI) for reduction.     

不同来源橡木片在干红葡萄酒中的应用比较

用干红葡萄酒对不同来源的四种橡木片进行了浸泡，并对浸泡后的葡萄酒的色度、总酚、单宁、固形物、感官品评结果进行了分析，结果表明：2^#和3^#橡木片中多酚物质在酒中的溶出率高于1^#和4^#；经过浸泡2^#橡木片的酒质最好，其次为浸泡过1^#和3^#橡木片的酒，浸泡过4^#橡木片的酒质最差。     

Simple and Fast Determination of Acrylamide and Metabolites in Potato Chips and Grilled Asparagus by Liquid Chromatography Coupled to Mass Spectrometry

The purpose of this study was to evaluate an analytical procedure for the determination of acrylamide in different starchy foods such as potato chips and grilled asparagus. The method is based on high-performance liquid chromatography coupled to triple quadrupole tandem mass spectrometry (HPLC-QqQ-MS/MS). A solid–liquid extraction procedure, using water as extraction solvent, has been developed followed by a cleanup procedure based on solid-phase extraction (SPE) or dispersive solid-phase extraction (d-SPE). Polymeric cartridges (Oasis HLB) and aluminum oxide (Al₂O₃) were used for potato and asparagus matrices, respectively. The optimized procedures were validated, and limits of detection and quantitation were 4 and 12 μg/kg for potato chips and 2 and 5 μg/kg for grilled asparagus, respectively. Recoveries were evaluated, and good values were obtained, ranging from 90 to 117 % for potato chips and from 90 to 116 % for grilled asparagus. The method was applied to real samples, and concentrations ranged from 105 to 860 μg/kg in potato chips, whereas higher values were detected in grilled asparagus (from 292 to 1469 μg/kg). Furthermore, single-stage Orbitrap high-resolution mass spectrometry has been used for the putative identification of acrylamide-N-acetyl-S-(2-carbamoylethyl)-l-cysteine (AAMA) in urine.     

U(VI) adsorption to heterogeneous subsurface media: application of a surface complexation model

The pH-dependent adsorption of U(VI) onto three heterogeneous, subsurface media from the Department of Energy (DOE) Oak Ridge Reservation, Savannah River Site, and Hanford Reservation was investigated. The three materials contained significant quantities of iron and manganese oxides with nearly identical extractable iron oxide contents (25.3-25.8 g/kg). A model independently developed for the adsorption of U(VI) to synthetic ferrihydrite (Waite, T. D.; Davis, J. A.; Payne, T. E.; Waychunas, G. A.; Xu, N. Geochim. Cosmochim. Acta 1994, 58, 5465-5478) was able to predict the major features of the pH-dependent U(VI) adsorption to the materials under the assumption that all the dithionite-citrate-bicarbonate extractable iron oxide was present as ferrihydrite. Further experiments with the Oak Ridge soil as a function of carbonate and U(VI) concentration indicated that the model could predict pH-dependent U(VI) adsorption to within a root mean square error of 0.163-0.408, even under conditions outside of those for which the model was developed. These results indicate that this model could be used as a first approximation in predicting U(VI) adsorption and transport in the subsurface. U(VI) adsorption also decreased at pH >10, even in the absence of carbonate, which is of potential importance to U(VI) mobility in extreme environments present in the subsurface at some DOE facilities. The pH-dependent adsorption of U(VI) was fundamentally different in systems with a constant CO2 partial pressure as compared to a constant total carbonate concentration. Experiments at constant CO2 partial pressure may not be representative of the conditions present in the subsurface, and a constant carbonate concentration does not always result in decreased U(VI) adsorption at higher pH values.     

Changes in uranium speciation through a depth sequence of contaminated Hanford sediments

The disposal of basic sodium aluminate and acidic U(VI)-Cu(ll) wastes in the now-dry North and South 300 A Process Ponds atthe Hanford site resulted in a groundwater plume of U(VI). To gain insight into the geochemical processes that occurred during waste disposal and those affecting the current and future fate and transport of this uranium plume, the solid-phase speciation of uranium in a depth sequence of sediments from the base of the North Process Pond through the vadose zone to groundwater was investigated using standard chemical and mineralogical analyses, electron and X-ray microprobe measurements, and X-ray absorption fine structure spectroscopy. Near-surface sediments contained uranium coprecipitated with calcite, which formed due to overneutralization of the waste ponds with base (NaOH). At intermediate depths in the vadose zone, metatorbernite [Cu(UO2PO4)2 x 8H2O] precipitated, likely during pond operations. Uranium occurred predominantly sorbed onto phyllosilicates in the deeper vadose zone and groundwater; sorbed uranium was also an important component at intermediate depths. Since the calcite-bearing pond sediments have been removed in remediation efforts, uranium fate and transport will be controlled primarily by desorption of the sorbed uranium and dissolution of metatorbernite.     

橡木对黄酒陈化效果的影响

研究橡木片对黄酒陈化效果的影响。选用2012年产的黄酒原酒,分别按0、3、6、9 g/L的添加量向其中加入橡木片。4 个月后对黄酒样品中的风味物质和游离氨基酸进行检测,并进行感官分析。结果表明：添加橡木片处理后,黄酒中高级醇类风味物质的种类和含量均显著减少,醛类风味物质的含量显著增加而种类呈现减少的趋势,酯类风味物质的种类和含量均显著增加（P＜0.05）,说明橡木可促进黄酒的陈化,加快了醇成醛、醇醛成缩醛、醇酸成酯、醛成酸等反应;苦味氨基酸中的苯丙氨酸、苏氨酸、精氨酸、组氨酸和涩味氨基酸中的酪氨酸、缬氨酸的含量均减少;综合黄酒中的风味物质、游离氨基酸变化以及感官评定的结果,表明当橡木片添加量为6 g/L时,贮存4 个月后的黄酒样品已具有较好的陈化效果。     

Extraction of Nickel from Soil,Water, Fish,and Plants on Novel Pyridine-Functionalized MCM-41 and MCM-48 Nanoporous Silicas and Its Subsequent Determination by FAAS

Nickel is considered as an important toxic pollutant and is continuously released into the biosphere by some anthropogenic activities such as industrial and urban sewage. The main objective of this study was to determine the concentration of nickel in different samples of soil, water, and muscle tissue of fish species which were collected from the Persian Gulf. For this propose, a simple and sensitive solid-phase extraction using pyridine-functionalized Mobil Composition of Matter (MCM)-41 and MCM-48 nanoporous silica was developed and their application in preconcentration and determination of nickel by flame atomic absorption spectrometry was studied. Limit of detection was found to be lower than 3.5 μg L⁻¹. Recovery and precision of the method were above 98.5% and below 1.5%, respectively. To gauge their ability in terms of application to natural samples, the proposed method was applied to a number of natural samples including plants, water, soil and fish species, and the amount of nickel was determined by spiking known concentrations of nickel into the solution. The results show that pollution of soil and water has some effects on bioaccumulation of Ni on marine organisms and plants that could magnify along the food chain.     

Passive sampling and analyses of common dissolved fixed gases in groundwater

An in situ passive sampling and gas chromatographic protocol was developed for analysis of the major and several minor fixed gases (He, Ne, H2, N2, O2, CO, CH4, CO2, and N2O) in groundwater. Using argon carrier gas, a HayeSep DB porous polymer phase, and sequential thermal conductivity and reductive gas detectors, the protocol achieved sufficient separation and sensitivity to measure the mixing ratio of all these gases in a single 0.5 mL gas sample collected in situ, stored, transported, and injected using a gastight syringe. Within 4 days of immersion in groundwater, the simple passive in situ sampler, whether initially filled with He or air, attained an equivalent and constant mixing ratio for five of the seven detected gases. The abundant mixing ratio of N2O, averaging 2.6%, indicated that significant denitrification is likely ongoing within groundwater contaminated with uranium, acidity, nitrate, and organic carbon from a group of four closed radioactive wastewater seepage ponds at the Oak Ridge Field Research Center. Over 1000 passive gas samples from 12 monitoring wells averaged 56% CO2, 32.4% N2, 2.6% O2, 2.6% N2O, 0.21% CH4, 0.093% H2, and 0.025% CO with an average recovery of 95 +/- 14% of the injected gas volume.     

Speciation of uranium in sediments before and after in situ biostimulation

The success of sequestration-based remediation strategies will depend on detailed information, including the predominant U species present as sources before biostimulation and the products produced during and after in situ biostimulation. We used X-ray absorption spectroscopy to determine the valence state and chemical speciation of U in sediment samples collected at a variety of depths through the contaminant plume at the Field Research Center at Oak Ridge, TN, before and after approximately 400 days of in situ biostimulation, as well as in duplicate bioreduced sediments after 363 days of resting conditions. The results indicate that U(VI) in subsurface sediments was partially reduced to 10-40% U(IV) during biostimulation. After biostimulation, U was no longer bound to carbon ligands and was adsorbed to Fe/Mn minerals. Reduction of U(VI) to U(IV) continued in sediment samples stored under anaerobic condition at < 4 degrees C for 12 months, with the fraction of U(IV) in sediments more than doubling and U concentrations in the aqueous phase decreasing from 0.5-0.74 to < 0.1 microM. A shift of uranyl species from uranyl bound to phosphorus ligands to uranyl bound to carbon ligands and the formation of nanoparticulate uraninite occurred in the sediment samples during storage.