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Author: Matthew Robert Baker
Publisher:
ISBN:
Category :
Languages : en
Pages : 154
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Book Description
Uranium (U) contamination is a major environmental problem associated with the mining and processing of nuclear materials for both weapons and power production. When possible in situ soil remediation techniques are preferable for reducing the risk associated with diffuse low-level U contamination. Uranium is known to form sparingly soluble phosphate compounds that persist in the environment. Therefore, batch experiments were performed to evaluate the efficacy of three phosphate amendments, hydroxyapatite (HA), sodium phytate (IP6) and sodium tripolyphosphate (TPP), to immobilize U in contaminated sediments. The amendments were added at equivalent phosphorus (P) concentrations and then equilibrated under a range of test conditions, with changes in soluble U and P-total monitored at pre-set time intervals. Only HA was effective at reducing soluble U when compared to the control, with IP6 and TPP increasing soluble U. After equilibration, changes in contaminant partitioning in the amended sediments was evaluated using operational extraction methods.
Author: Matthew Robert Baker
Publisher:
ISBN:
Category :
Languages : en
Pages : 154
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Book Description
Uranium (U) contamination is a major environmental problem associated with the mining and processing of nuclear materials for both weapons and power production. When possible in situ soil remediation techniques are preferable for reducing the risk associated with diffuse low-level U contamination. Uranium is known to form sparingly soluble phosphate compounds that persist in the environment. Therefore, batch experiments were performed to evaluate the efficacy of three phosphate amendments, hydroxyapatite (HA), sodium phytate (IP6) and sodium tripolyphosphate (TPP), to immobilize U in contaminated sediments. The amendments were added at equivalent phosphorus (P) concentrations and then equilibrated under a range of test conditions, with changes in soluble U and P-total monitored at pre-set time intervals. Only HA was effective at reducing soluble U when compared to the control, with IP6 and TPP increasing soluble U. After equilibration, changes in contaminant partitioning in the amended sediments was evaluated using operational extraction methods.
Author: Vrajesh Sanat Mehta
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 191
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Book Description
Anthropogenic activities associated with the production of nuclear materials have resulted in uranium contaminated soil and groundwater. The carcinogenic and toxic effects of uranium contamination pose a significant risk to the environment and human health. Phosphate addition to uranium-contaminated subsurface environments has been proposed as a strategy for in situ remediation. Addition of phosphate amendments can result in uranium sequestration in its oxidized +VI state without sustaining reducing conditions as is needed for in situ immobilization via chemical or biological reduction of U(VI) to less soluble U(IV) species. Phosphate addition can be used as a stand-alone process or as a complementary process to bioremediation-based methods, especially for sites with naturally oxic conditions. Although recent studies have reported phosphate-induced precipitation of U(VI)-phosphates in laboratory and field-scale tests, the fundamental mechanisms controlling U(VI) immobilization are not well known. Hence understanding the mechanisms at the microscopic and molecular levels is imperative to successfully designing and implementing phosphate-based in situ uranium immobilization. Interactions with phosphate can result in uranium immobilization through various processes. This study investigated the dominant mechanisms of U(VI)-phosphate reactions using an integrated approach of aqueous phase and solid phase characterization techniques. Batch experiments were performed to study the effect of pH and co-solutes (dissolved inorganic carbon (DIC), Na+ and Ca2+) on the products and solubility of uranium(VI) precipitated with phosphate. The results suggested that in the absence of co-solute cations, chernikovite [H3O(UO2)(PO4)·3H2O] precipitated despite uranyl orthophosphate [(UO2)3(PO4)2·4H2O] being thermodynamically more favorable under certain conditions. The presence of Na+ as a co-solute led to the precipitation of sodium autunite [Na2(UO2)2(PO4)2], and the dissolved U(VI) concentrations were generally in agreement with equilibrium predictions of sodium autunite solubility. In the calcium-containing systems, the observed concentrations were below the predicted solubility of autunite [Ca(UO2)2(PO4)2]. Consequently, specific batch studies were conducted to investigate the dependence of U(VI) uptake mechanisms on the starting forms of calcium and phosphate at concentrations relevant to field sites. Depending on the experimental conditions, uranium uptake occurred through adsorption on calcium-phosphate solids, precipitation of autunite, or incorporation into a calcium-phosphate solid. Extended X-ray absorption fine structure (EXAFS) spectroscopy analysis using structural model fittings and linear combination fitting allowed quantification of the contribution of each uranium uptake mechanism mentioned above. Following the batch experiments with simple systems, the effect of phosphate amendment on uranium immobilization was evaluated for sediments obtained from a field site in Rifle, Colorado using batch sorption studies and column experiments. Batch sorption studies showed that phosphate addition increased the U(VI) adsorption, however the net uranium uptake was limited due to the dominance of the aqueous speciation by Ca-U(VI)-carbonate complexes. Column experiments were performed under conditions that simulated the subsurface environment at the Rifle site. Remobilization experiments showed increased retention of uranium when phosphate was present in uranium-free influent. The response of dissolved uranium concentrations to stopped-flow events and the comparison of experimental data with a simple reactive transport model indicated that uranium transport was controlled by non-equilibrium processes. Intraparticle diffusion is thought to be acting as the rate-limiting process. Sequential extractions and laser induced fluorescence spectroscopy (LIFS) analysis indicated that adsorption was the dominant mode of uranium immobilization. When uranium and phosphate were added concurrently to columns packed with sediments, significant uptake of uranium continued as long as phosphate was present in the influent. Even when phosphate was removed from the influent, the columns retained significant amounts (~ 67 %) of the accumulated uranium. Sequential extractions showed that the uranium accumulated transformed into less easily extractable (i.e., more immobile) species with the relative amounts of accumulated uranium extracted in the acetic acid and hot acid digestion step being highest for the column that was treated with phosphate for the longest duration. The uranium retained in the sediments after the phosphate was removed from the influent was primarily in a form that could be extracted with acetic acid and ammonium acetate. The extraction results, aqueous phase analysis and LIFS analysis showed that uranium uptake occurred through multiple processes. For select conditions, EXAFS analysis was used to quantify the contribution of uranium uptake which confirmed that uranium uptake occurred through a combination of precipitation and adsorption. The information gained from this research project improved our understanding of U(VI)-phosphate reactions that can be used to identify and manipulate the conditions that lead to the greatest decreases in U(VI) mobility. The results illustrate that precipitation of uranyl-phosphates is not the only means of in situ uranium remediation and that a wide range of uranium immobilization mechanisms can control uranium mobility following phosphate addition. Although phosphate addition led to significant retardation of uranium release and also resulted in increased net uptake of uranium for conditions of the Rifle site, phosphate amendments could be more beneficial at sites with lower pH and dissolved inorganic carbon concentrations.
Author: Peter C. Burns
Publisher:
ISBN:
Category :
Languages : en
Pages : 5
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Book Description
Uranium contamination of the subsurface has remained a persistent problem plaguing remedial design at sites across the U.S. that were involved with production, handling, storage, milling, and reprocessing of fissile uranium for both civilian and defense related purposes. Remediation efforts to date have relied upon excavation, pump-and-treat, or passive remediation barriers (PRB's) to remove or attenuate uranium mobility. Documented cases convincingly demonstrate that excavation and pump-and-treat methods are ineffective for a number of highly contaminated sites. There is growing concern that use of conventional PRB's, such as zero-valent iron, are a temporary solution to a problem that will persist for thousands of years. Alternatives to the standard treatment methods are therefore warranted. The core objective of our research is to demonstrate that a phosphorus amendment strategy will result in a reduction of dissolved uranium to below the proposed drinking water standard. Our hypothesis is that long-chain polyphosphate compounds forestall precipitation of sparingly soluble uranyl phosphate compounds, which is key to preventing fouling of wells at the point of injection. Our other fundamental objective is to synthesize and correctly characterize the uranyl phosphate phases that form in the geochemical conditions under consideration. This report summarizes work conducted at the University of Notre Dame through November of 2003 under DOE grant DE-FG07-02ER63489, which has been funded since September, 2002. The objectives at Notre Dame are development of synthesis techniques for uranyl phosphate phases, together with detailed structural and chemical characterization of the myriad of uranyl phosphate phases that may form under geochemical conditions under consideration. We have developed novel synthesis techniques for many of the uranyl phosphates of interest. Superb single crystals have been obtained by diffusion of crystal nutrients into silica-based gels, as this approach retards crystal nucleation and enhances growth of a small number of crystals. We have also developed mild hydrothermal techniques that provide high-purity uranyl phosphate compounds. Using a CCD-based single-crystal diffractometer, full structure and chemical characterizations have been completed for 21 uranyl phosphates. We emphasize that many of these materials were poorly understood at the outset of our research, with unknown or partially known structures, and uncertainties concerning the water content of the phases. This component of the overall research program is providing a much improved understanding of the synthesis and structures of the uranyl phosphate group, which is an essential step prior to measuring solubilities of these phases. Our development of new synthesis techniques for uranyl phosphates is a necessary step towards measuring the solubilities of well-characterized and pure materials.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Uranium contamination of the subsurface has remained a persistent problem plaguing remedial design at sites across the U.S. that were involved with production, handling, storage, milling, and reprocessing of fissile uranium for both civilian and defense related purposes. Remediation efforts to date have relied upon excavation, pump-and-treat, or passive remediation barriers (PRB's) to remove or attenuate uranium mobility. Documented cases convincingly demonstrate that excavation and pump-and-treat methods are ineffective for a number of highly contaminated sites. There is growing concern that use of conventional PRB?s, such as zero-valent iron, are a temporary solution to a problem that will persist for thousands of years. Alternatives to the standard treatment methods are therefore warranted. The core objective of our research is to demonstrate that a phosphorus amendment strategy will result in a reduction of dissolved uranium to below the proposed drinking water standard. Our hypothesis is that long-chain polyphosphate compounds forestall precipitation of sparingly soluble uranyl phosphate compounds, which is key to preventing fouling of wells at the point of injection. Our other fundamental objective is to synthesize and correctly characterize the uranyl phosphate phases that form in the geochemical conditions under consideration. This report summarizes work conducted at the University of Notre Dame through November of 2003 under DOE grant DE-FG07-02ER63489, which has been funded since September, 2002. The objectives at Notre Dame are development of synthesis techniques for uranyl phosphate phases, together with detailed structural and chemical characterization of the myriad of uranyl phosphate phases that may form under geochemical conditions under consideration.
Author: Ajay Kumar
Publisher: Woodhead Publishing
ISBN: 0323853633
Category : Science
Languages : en
Pages : 442
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Book Description
Stress Tolerance in Horticultural Crops: Challenges and Mitigation Strategies explores concepts, strategies and recent advancements in the area of abiotic stress tolerance in horticultural crops, highlighting the latest advances in molecular breeding, genome sequencing and functional genomics approaches. Further sections present specific insights on different aspects of abiotic stress tolerance from classical breeding, hybrid breeding, speed breeding, epigenetics, gene/quantitative trait loci (QTL) mapping, transgenics, physiological and biochemical approaches to OMICS approaches, including functional genomics, proteomics and genomics assisted breeding. Due to constantly changing environmental conditions, abiotic stress such as high temperature, salinity and drought are being understood as an imminent threat to horticultural crops, including their detrimental effects on plant growth, development, reproduction, and ultimately, on yield. This book offers a comprehensive resource on new developments that is ideal for anyone working in the field of abiotic stress management in horticultural crops, including researchers, students and educators. - Describes advances in whole genome and next generation sequencing approaches for breeding climate smart horticultural crops - Details advanced germplasm tolerance to abiotic stresses screened in the recent past and their performance - Includes advancements in OMICS approaches in horticultural crops
Author: H. Magdi Selim
Publisher: CRC Press
ISBN: 148223680X
Category : Nature
Languages : en
Pages : 381
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Book Description
Edited by One of the Best Specialists in Soil Science Recent studies reveal that Phosphorus (P) in the form of phosphate, a macronutrient essential for plant growth, and crop yields can influence the bioavailability, retention, and mobility of trace elements, metal(loid)s, and radio nuclides in soils. When this occurs, phosphates can affect the dynamics of heavy metals and influence soil characteristics, impacting soil mobility and toxicity. Phosphate in Soils: Interaction with Micronutrients, Radionuclides and Heavy Metals utilizes the latest research to emphasize the role that phosphate plays in enhancing or reducing the mobility of heavy metals in soil, and the soil-water-plant environment. It provides an in-depth understanding of each heavy metal species, and expands on phosphate interactions in geological material. Composed of 12 chapters, this text: Provides an overview of the reactions of metal(loid)s and common P compounds that are used as fertilizer in soils Emphasizes the effect of phosphorus on copper and zinc adsorption in acid soils Discusses findings on the influence of phosphate compounds on speciation, mobility, and bioavailability of heavy metals in soils as well as the role of phosphates on in situ and phytoremediation of heavy metals for contaminated soils Places emphasis on the influence of phosphate on various heavy metals species in soils, and their solubility/mobility and availability Provides extensive information on testing various high phosphate materials for remediation of heavy metal, micronutrients, and radionuclides contaminated sites Explores the reactivity of heavy metals, micronutrients and radionuclides elements in several soils Presents a case study illustrating various remediation efforts of acidic soils and remediation of Cu, Zn, and lead (Pb) contaminated soils around nonferrous industrial plants Emphasizes the significance of common ions (cations and anions) on phosphate mobility and sorption in soils, and more The author includes analytical and numerical solutions along with hands-on applications, and addresses other topics that include the transport and sorption modeling of heavy metals in the presence of phosphate at different scales in the vadose zone.
Author: Xinde Cao
Publisher:
ISBN:
Category : Lead
Languages : en
Pages : 112
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Book Description
Lab tests and a field demonstration were conducted to evaluate the feasibility and effectiveness of immobilizing metals in contaminated soils using phosphate. Phosphate was more effective for Pb immobilization than for Zn, Cu, and Cd. The formation of insoluble pyromorphite-like minerals was responsible for Pb immobilization, whereas Zn, Cu, and Cd immobilization may be attributed to the coprecipitation and surface complexation mechanisms. The most efficient formation of pyromorphite-like minerals was found at pH 3 and at an application rate of 4 P/Pb. Soil acidification was necessary to dissolve soil Pb carbonates and to make them readily available for the formation of pyromorphite-like minerals. Therefore, a two-step phosphate amendment was applied at a contaminated site in which the soil was first acidified with H3PO4, and Ca(H2PO4)2 or phosphate rock was then added. Phosphate effectively induced transformation of soil Pb from the non-residual to the residual fraction, with residual Pb increase by up to 55%. Modeling indicated that lead phosphate minerals controlled Pb2+ activities in the P-treated soils. Phosphate treatments significantly reduced Pb uptake by Stenotaphrum secundatum. A mixture of H3PO4 and phosphate rock yielded the best overall results for in situ Pb immobilization, with less soil pH change and less phosphorus leaching.
Author: F. Pacheco-Torgal
Publisher: Woodhead Publishing
ISBN: 0128223812
Category : Technology & Engineering
Languages : en
Pages : 429
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Book Description
Bio-based Materials and Biotechnologies for Eco-efficient Construction fills a gap in the published literature, discussing bio-based materials and biotechnologies that are crucial for a more sustainable construction industry. With comprehensive coverage and contributions from leading experts in the field, the book includes sections on Bio-based materials and biotechnologies for infrastructure applications, Bio-based materials and biotechnologies for building energy efficiency, and other applications, such as using biotechnology to reduce indoor air pollution, for water treatment, and in soil decontamination. The book will be an essential reference resource for academic researchers, civil engineers, contractors working in construction works, postgraduate students and other professionals. - Focuses on sustainability and green concepts in construction - Discusses recent trends on bio-based materials and biotechnologies for eco-efficient construction - Covers many important aspects, including infrastructure applications, energy efficiency for building construction, and air, water and soil related problems
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The objective of the treatability test was to evaluate the efficacy of using polyphosphate injections to treat uranium-contaminated groundwater in situ. A test site consisting of an injection well and 15 monitoring wells was installed in the 300 Area near the process trenches that had previously received uranium-bearing effluents. This report summarizes the work on the polyphosphate injection project, including bench-scale laboratory studies, a field injection test, and the subsequent analysis and interpretation of the results. Previous laboratory tests have demonstrated that when a soluble form of polyphosphate is injected into uranium-bearing saturated porous media, immobilization of uranium occurs due to formation of an insoluble uranyl phosphate, autunite [Ca(UO2)2(PO4)2 nH2O]. These tests were conducted at conditions expected for the aquifer and used Hanford soils and groundwater containing very low concentrations of uranium (10-6 M). Because autunite sequesters uranium in the oxidized form U(VI) rather than forcing reduction to U(IV), the possibility of re-oxidation and subsequent re-mobilization is negated. Extensive testing demonstrated the very low solubility and slow dissolution kinetics of autunite. In addition to autunite, excess phosphorous may result in apatite mineral formation, which provides a long-term source of treatment capacity. Phosphate arrival response data indicate that, under site conditions, the polyphosphate amendment could be effectively distributed over a relatively large lateral extent, with wells located at a radial distance of 23 m (75 ft) reaching from between 40% and 60% of the injection concentration. Given these phosphate transport characteristics, direct treatment of uranium through the formation of uranyl-phosphate mineral phases (i.e., autunite) could likely be effectively implemented at full field scale. However, formation of calcium-phosphate mineral phases using the selected three-phase approach was problematic. Although amendment arrival response data indicate some degree of overlap between the reactive species and thus potential for the formation of calcium-phosphate mineral phases (i.e., apatite formation), the efficiency of this treatment approach was relatively poor. In general, uranium performance monitoring results support the hypothesis that limited long-term treatment capacity (i.e., apatite formation) was established during the injection test. Two separate overarching issues affect the efficacy of apatite remediation for uranium sequestration within the 300 Area: 1) the efficacy of apatite for sequestering uranium under the present geochemical and hydrodynamic conditions, and 2) the formation and emplacement of apatite via polyphosphate technology. In addition, the long-term stability of uranium sequestered via apatite is dependent on the chemical speciation of uranium, surface speciation of apatite, and the mechanism of retention, which is highly susceptible to dynamic geochemical conditions. It was expected that uranium sequestration in the presence of hydroxyapatite would occur by sorption and/or surface complexation until all surface sites have been depleted, but that the high carbonate concentrations in the 300 Area would act to inhibit the transformation of sorbed uranium to chernikovite and/or autunite. Adsorption of uranium by apatite was never considered a viable approach for in situ uranium sequestration in and of itself, because by definition, this is a reversible reaction. The efficacy of uranium sequestration by apatite assumes that the adsorbed uranium would subsequently convert to autunite, or other stable uranium phases. Because this appears to not be the case in the 300 Area aquifer, even in locations near the river, apatite may have limited efficacy for the retention and long-term immobilization of uranium at the 300 Area site.
Author: Jean-Louis Morel
Publisher: Springer Science & Business Media
ISBN: 140204688X
Category : Science
Languages : en
Pages : 357
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Book Description
This is the first book aimed at development of a common language among scientists working in the field of Phytoremediation. Authors of the main chapters are leading scientists in this field. Some of them were among the first ones to have suggested the use of hyperaccumulator plants for extraction of metals from soils. Manuscripts based on lectures presented at the ASI have been revised here to take into account ASI participants’ comments and suggestions.
