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1

Opacity reduction using hydrated lime injection  

SciTech Connect

The purpose of this investigation is to study the effects of injecting dry hydrated lime into flue gas to reduce sulfur trioxide (SO{sub 3}) concentrations and consequently stack opacity at the University of Missouri, Columbia power plant. Burning of high sulfur coal (approx. 4% by weight) at the power plant resulted in opacity violations. The opacity problem was due to sulfuric acid mist (H{sub 2}SO{sub 4}) forming at the stack from high SO{sub 3} concentrations. As a result of light scattering by the mist, a visible plume leaves the stack. Therefore, reducing high concentrations of SO{sub 3} reduces the sulfuric acid mist and consequently the opacity problem. The current hydrated lime injection system has reduced the opacity to acceptable limits. To reduce SO{sub 3} concentrations, dry hydrated lime is injected into the flue gas upstream of a particulate collection device (baghouse) and downstream of the induced draft fan. The lime is periodically injected into the flue via a pneumatic piping system. The hydrated lime is transported down the flue and deposited on the filter bags in the baghouse. As the hydrated lime is deposited on the bags a filter cake is established. The reaction between the SO{sub 3} and the hydrated lime takes place on the filter bags. The hydrated lime injection system has resulted in at least 95% reduction in the SO{sub 3} concentration. Low capital equipment requirements and operating cost coupled with easy installation and maintenance makes the system very attractive to industries with similar problems. This paper documents the hydrated lime injection system and tests the effectiveness of the system on SO{sub 3} removal and subsequent opacity reduction. Measurements Of SO{sub 3} concentrations, flue gas velocities, and temperatures have been performed at the duct work and baghouse. A complete analysis of the hydrated lime injection system is provided.

Wolf, D.E.; Seaba, J.P. [Univ. of Missouri, Columbia, MO (United States)

1993-12-31

2

Removal of phosphate from greenhouse wastewater using hydrated lime.  

PubMed

Phosphate (P) contamination in nutrient-laden wastewater is currently a major topic of discussion in the North American greenhouse industry. Precipitation of P as calcium phosphate minerals using hydrated lime could provide a simple, inexpensive method for retrieval. A combination of batch experiments and chemical equilibrium modelling was used to confirm the viability of this P removal method and determine lime addition rates and pH requirements for greenhouse wastewater of varying nutrient compositions. Lime: P ratio (molar ratio of CaMg(OH)?: PO??P) provided a consistent parameter for estimating lime addition requirements regardless of initial P concentration, with a ratio of 1.5 providing around 99% removal of dissolved P. Optimal P removal occurred when lime addition increased the pH from 8.6 to 9.0, suggesting that pH monitoring during the P removal process could provide a simple method for ensuring consistent adherence to P removal standards. A Visual MINTEQ model, validated using experimental data, provided a means of predicting lime addition and pH requirements as influenced by changes in other parameters of the lime-wastewater system (e.g. calcium concentration, temperature, and initial wastewater pH). Hydrated lime addition did not contribute to the removal of macronutrient elements such as nitrate and ammonium, but did decrease the concentration of some micronutrients. This study provides basic guidance for greenhouse operators to use hydrated lime for phosphate removal from greenhouse wastewater. PMID:25176490

Dunets, C Siobhan; Zheng, Youbin

2014-01-01

3

Impacts of ocean acidification and mitigative hydrated lime addition on Pacific oyster larvae  

E-print Network

Impacts of ocean acidification and mitigative hydrated lime addition on Pacific oyster larvae No.: 577 Title of Project: Impacts of ocean acidification and mitigative hydrated lime addition observed mass die offs of larvae, potentially from ocean acidification. This study aims to elucidate

4

EFFECT OF ADDITION OF HYDRATED LIME TO LITTER ON RECOVERY OF SELECTED BACTERIA AND POULT PERFORMANCE  

Technology Transfer Automated Retrieval System (TEKTRAN)

Recently, we demonstrated that 10 or 20% (wt/v) hydrated lime in used poultry litter significantly reduced Salmonella enteritidis survival in vitro. However, preliminary studies with day-of-hatch poults suggested that lime in excess of 5% (wt/v) in new litter caused mild but apparent ocular and res...

5

Advanced treatment of swine wastewater using an agent synthesized from amorphous silica and hydrated lime.  

PubMed

Advanced treatment using an agent synthesized from amorphous silica and hydrated lime (M-CSH-lime) was developed and applied to swine wastewater treatment. Biologically treated wastewater and M-CSH-lime (approximately 6 w/v% slurry) were fed continuously into a column-shaped reactor from its bottom. Accumulated M-CSH-lime gradually formed a bed layer. The influent permeated this layer and contacted the M-CSH-lime, and the treatment reaction progressed. Treated liquid overflowing from the top of the reactor was neutralized with CO?gas bubbling. The colour removal rate approximately exceeded 50% with M-CSH-lime addition rates of > 0.15 w/v%. The removal rate of PO(3?)(4) exceeded 80% with the addition of>0.03 w/v% of M-CSH-lime. The removal rates of coliform bacteria and Escherichia coli exceeded 99.9% with > 0.1 w/v%. Accumulated M-CSH-lime in the reactor was periodically withdrawn from the upper part of the bed layer. The content of citric-acid-soluble P?O? in the recovered matter was>15% when the weight ratio of influent PO(3?)(4) -P to added M-CSH-lime was > 0.15. This content was comparable with commercial phosphorus fertilizer. The inhibitory effect of recovered M-CSH-lime on germination and growth of leafy vegetable komatsuna (Brassica rapa var. perviridis) was evaluated by an experiment using the Neubauer's pot. The recovered M-CSH-lime had no negative effect on germination and growth. These results suggest that advanced water treatment with M-CSH-lime was effective for simultaneous removal of colour, [Formula: see text] and coliform bacteria at an addition rate of 0.03-0.15 w/v%, and that the recovered M-CSH-lime would be suitable as phosphorus fertilizer. PMID:25189846

Tanaka, Yasuo; Hasegawa, Teruaki; Sugimoto, Kiyomi; Miura, Keiichi; Aketo, Tsuyoshi; Minowa, Nobutaka; Toda, Masaya; Kinoshita, Katsumi; Yamashita, Takahiro; Ogino, Akifumi

2014-01-01

6

Influence of Artificial Zeolite and Hydrated Lime Amendments on the Erodibility of an Acidic Soil  

Microsoft Academic Search

In this study, the effectiveness of artificial zeolite and hydrated lime, as amendments, to reduce surface runoff and soil loss from acidic soil taken from Yamaguchi prefecture in Japan was assessed. Air?dried soil aggregates (?2 mm) were amended with zeolite at 10% and with lime at 0.5%. The amended aggregates were packed to an average dry?bulk density of 1.30 Mg m in small

Henintsoa Andry; Tahei Yamamoto; Mitsuhiro Inoue

2009-01-01

7

The role of brick pebbles and dust in conglomerates based on hydrated lime and crushed bricks  

Microsoft Academic Search

Phoenicians were probably the first ones to use mortars based on hydrated lime and crushed or dust bricks, followed by all other people who were in contact with them. The Romans employed those mortars any time they needed a rendering exposed to severe environment or a floor at a very humid ground level, in foundations where the water table was

G. Baronio; L. Binda; N. Lombardini

1997-01-01

8

Engineering properties of water\\/wastewater-treatment sludge modified by hydrated lime, fly ash and loess  

Microsoft Academic Search

The purpose of this research was to present engineering properties of modified sludge from water\\/wastewater treatment by modifiers such as hydrated lime, loess, and fly ash. The proper mixing ratio was determined to hold the pH of the modified sludge above 12.0 for 2h. Laboratory tests carried out in this research included particle analysis, compaction and CBR, SEM and X-ray

Sungjin Lim; Wangi Jeon; Jaebok Lee; Kwanho Lee; Namho Kim

2002-01-01

9

CONTROL OF SOX EMISSIONS BY IN-FURNACE SORBENT INJECTION: CARBONATES VS HYDRATES  

EPA Science Inventory

The paper provides high-temperature isothermal data on SO2 capture by calcium-based sorbents, obtained in a dispersed-phase reactor for limestones, dolomites, hydrated calcitic limes, and hydrated dolomitic limes as a function of Ca/S molar ratio, temperature, and SO2 partial pre...

10

Full quantitative phase analysis of hydrated lime using the Rietveld method  

SciTech Connect

Full quantitative phase analysis (FQPA) using X-ray powder diffraction and Rietveld refinements is a well-established method for the characterization of various hydraulic binders such as Portland cement and hydraulic limes. In this paper, the Rietveld method is applied to hydrated lime, a non-hydraulic traditional binder. The potential presence of an amorphous phase in this material is generally ignored. Both synchrotron radiation and a conventional X-ray source were used for data collection. The applicability of the developed control file for the Rietveld refinements was investigated using samples spiked with glass. The results were cross-checked by other independent methods such as thermal and chemical analyses. The sample microstructure was observed by transmission electron microscopy. It was found that the consistency between the different methods was satisfactory, supporting the validity of FQPA for this material. For the samples studied in this work, the amount of amorphous material was in the range 2-15 wt.%.

Lassinantti Gualtieri, Magdalena, E-mail: magdalena.gualtieri@unimore.it [Dipartimento Ingegneria dei Materiali e dell'Ambiente, Universita Degli Studi di Modena e Reggio Emilia, Via Vignolese 905/a, I-41100 Modena (Italy); Romagnoli, Marcello; Miselli, Paola; Cannio, Maria [Dipartimento Ingegneria dei Materiali e dell'Ambiente, Universita Degli Studi di Modena e Reggio Emilia, Via Vignolese 905/a, I-41100 Modena (Italy)] [Dipartimento Ingegneria dei Materiali e dell'Ambiente, Universita Degli Studi di Modena e Reggio Emilia, Via Vignolese 905/a, I-41100 Modena (Italy); Gualtieri, Alessandro F. [Dipartimento di Scienze della Terra, Universita Degli Studi di Modena e Reggio Emilia, I-41100 Modena (Italy)] [Dipartimento di Scienze della Terra, Universita Degli Studi di Modena e Reggio Emilia, I-41100 Modena (Italy)

2012-09-15

11

Three-dimensional hydration layer mapping on the (10.4) surface of calcite using amplitude modulation atomic force microscopy  

NASA Astrophysics Data System (ADS)

Calcite, the most stable modification of calcium carbonate, is a major mineral in nature. It is, therefore, highly relevant in a broad range of fields such as biomineralization, sea water desalination and oil production. Knowledge of the surface structure and reactivity of the most stable cleavage plane, calcite (10.4), is pivotal for understanding the role of calcite in these diverse areas. Given the fact that most biological processes and technical applications take place in an aqueous environment, perhaps the most basic—yet decisive—question addresses the interaction of water molecules with the calcite (10.4) surface. In this work, amplitude modulation atomic force microscopy is used for three-dimensional (3D) mapping of the surface structure and the hydration layers above the surface. An easy-to-use scanning protocol is implemented for collecting reliable 3D data. We carefully discuss a comprehensible criterion for identifying the solid-liquid interface within our data. In our data three hydration layers form a characteristic pattern that is commensurate with the underlying calcite surface.

Marutschke, Christoph; Walters, Deron; Cleveland, Jason; Hermes, Ilka; Bechstein, Ralf; Kühnle, Angelika

2014-08-01

12

Hydration layer structures on calcite facets and their roles in selective adsorptions of biomolecules: A molecular dynamics study  

NASA Astrophysics Data System (ADS)

The selective adsorptions of biomolecules onto crystal faces are the key issues in the studies of biomineralization. Frequently, the adsorption processes are understood by using the direct binding model between organic compounds and inorganic crystals during the molecular dynamic studies. However, water molecules near crystals always exhibit intense ordering and preferential orientation to form structured hydration layer. By using the adsorption of poly acrylic acid oligomer, acrylic acid (AA) dimer, onto calcite as an example, we demonstrate that the induced hydration layers contribute significant effects on the organic-inorganic interactions. In particular, on calcite (104) plane, two carboxyl groups of AA dimer both interact with the crystal but the molecule has to compete with water due to the well-structured hydration layer. On (110) plane, although only one carboxyl group of AA dimer interacts with this surface, the water layer is relatively loose so that the molecule can easily replace water. With a consideration of the hydration layer, our free energy analysis indicates that AA dimer has a stronger interaction with (110) face than with (104) face, which is consistent with the experimental observations. The study follows that the attachment of organic additive onto inorganic crystal facet is greatly mediated by near-surface hydration layers, and therefore, the critical role of structured water layers must be taken into account in the understanding of biomineralization interfaces.

Zhu, Beibei; Xu, Xurong; Tang, Ruikang

2013-12-01

13

Evaluating slurried-hydrated lime pond-shoreline treatments for reducing populations of rams-horn snails  

Technology Transfer Automated Retrieval System (TEKTRAN)

Trematodes can cause massive infections in fish, and the most promising approach for the control of these infections is the reduction or elimination of snails that vector the trematodes. A recent approach, the application of high concentrations of slurried-hydrated lime (SHL) or copper sulfate pent...

14

DISPOSAL, RECYCLE, AND UTILIZATION OF MODIFIED FLY ASH FROM HYDRATED LIME INJECTION INTO COAL-FIRED UTILITY BOILERS  

EPA Science Inventory

The paper gives results of an assessment of the disposal, utilization, and recycle os a modified fly ash from the injection of hydrated lime into a coal-fired utility boiler. The process, developed as a low-cost alternative for achieving moderate degrees of SO2 control at coal-fi...

15

In-place stabilization of pond ash deposits by hydrated lime columns  

SciTech Connect

Abandoned coal ash ponds cover up vast stretches of precious land and cause environmental problems. Application of suitable in situ stabilization methods may bring about improvement in the geotechnical properties of the ash deposit as a whole, converting it to a usable site. In this study, a technique of in-place stabilization by hydrated lime columns was applied to large-scale laboratory models of ash ponds. Samples collected from different radial distances and different depths of the ash deposit were tested to study the improvements in the water content, dry density, particle size distribution, unconfined compressive strength, pH, hydraulic conductivity, and leachate characteristics over a period of one year. The in-place stabilization by lime column technique has been found effective in increasing the unconfined compressive strength and reducing hydraulic conductivity of pond ash deposits in addition to modifying other geotechnical parameters. The method has also proved to be useful in reducing the contamination potential of the ash leachates, thus mitigating the adverse environmental effects of ash deposits.

Chand, S.K.; Subbarao, C. [Indira Gandhi Institute of Technology, Orissa (India). Dept. of Civil Engineering

2007-12-15

16

Investigation of the benefits of carbonate cementation due to addition of low percentage of hydrated lime in the base courses of pavements  

E-print Network

triaxial strength, atterberg limit testing, scanning electron microscopy examinations, resilient moduli determination of the materials in the lab and in the field. Caliche and limestone base materials stabilized with either I or 2 percent hydrated lime were...

Bhuiyan, Jasim Uddin

1994-01-01

17

Preparation of a new sorbent with hydrated lime and blast furnace slag for phosphorus removal from aqueous solution  

Microsoft Academic Search

The removal of dissolvable inorganic phosphate (H2PO4?) by sorbents prepared from hydrated lime (HL) and blast furnace slag (BFS) was fundamentally studied by an orthogonal experiment design. Based on statistic analysis, it is revealed that the weight ratio of BFS\\/HL is the most significant variable, and an optimized preparation condition is figured out. With the increase of HL content, the

Guozhuo Gong; Shufeng Ye; Yajun Tian; Qi Wang; Jiandi Ni; Yunfa Chen

2009-01-01

18

The effect of hydrated lime on Salmonella enteritidis survival in poultry litter and poult performance  

E-print Network

in used poultry litter during incubations of 24, 48, or 96 h. In experiment one, addition of lime at any concentration reduced Salmonella recovery from artificially-contaminated litter by more than 1.79 log 10 cfu to undetectable levels based on direct...

Stanush, Deborah Denise

2000-01-01

19

Trichloroethylene decomposition and in-situ dry sorption of Cl-products by calcium oxides prepared from hydrated limes.  

PubMed

A comparison of CaOs produced by calcining two types of hydrated lime and calcium carbonate was made for decomposition of trichloroethylene and in-situ dry sorption of the decomposed Cl-products using a lab-scale gas flow type tubular packed bed reactor. About 20 mg of CaO sample was mixed with about 2 g of Al2O3 particles and packed in the reactor and allowed to react with a flowing standard gas containing 500 ppm of C2HCl3 (N2 balance) at 673 and 873 K, under the condition that the reaction of CaO with C2HCl3 might be completed within a few hours. It was found that no thermal decomposition of C2HCl3 at or below 673 K was observed in a reactor packed only with Al2O3 particles. However, a considerable amount of decomposition of C2HCl3 was obtained in a reactor packed with CaO and Al2O3, even at 673 K. For 1 mol of CaO prepared by calcining highly reactive Ca(OH)2 at 673 K, decomposition of 0.42 mol of C2HCl3 and in-situ absorption product of 0.53 mol of CaCl2 were obtained. At 873 K, about 46% of C2HCl3 was thermally decomposed. The total amount of C2HCl3 decomposed in CaO-Al2O3 particle bed at 873 K became nearly twice larger than that at 673 K. For 1 mol of CaO prepared by calcining highly reactive Ca(OH)2 at 873 K, decomposition of 0.59 mol of C2HCl3 and in-situ absorption product of 0.67 mol of CaCl2 were obtained. Small amounts of C2Cl2, C2Cl4, CCl4, etc. were detected during decomposition of C2HCl3 at 673 and 873 K. It was recognized that the data on decomposition of C2HCl3 as well as in-situ dry sorption of Cl-products in CaO particle bed were correlated with specific surface area of the CaO employed. PMID:21821273

Gotoh, Yoshimi; Iwata, Goichi; Choh, Kyaw; Kubota, Mitsuhiro; Matsuda, Hitoki

2011-10-01

20

Evaluation of Ohio fly ash/hydrated lime slurries and Type 1 cement sorbent slurries in the U.C. Pilot spray dryer facility. Final report, September 1, 1993--August 31, 1994  

SciTech Connect

The objectives of this year`s work included an evaluation of the performance of fly ash/hydrated lime as well as hydrated cement sorbents for spray drying adsorption (SDA) of SO{sub 2} from a simulated high-sulfur flue gas. These sorbents were evaluated for several different hydration methods, and under different SDA operating conditions. In addition, the physical properties of surface area and porosity of the sorbents was determined. The most reactive fly ash/hydrated lime sorbent studied was prepared at room temperature with milled fly ash. Milling fly ash prior to hydration with lime did have a beneficial effect on calcium utilization. No benefit in utilization was experienced either by hydrating the slurries at a temperature of 90{degrees}C as compared to hydration at room temperature, or by increasing hydration time. While the surface areas varied greatly from sorbent to sorbent, the pore size distributions indicated ``ink bottle`` pores with surface porosity on the order of 0.5 microns. No correlation could be drawn between the surface area of the sorbents and calcium utilization. These results suggest that the composition of the resulting sorbent might be more important than its surface area. The most effective sorbent studied this year was produced by hydrating cement for 3 days at room temperature. This sorbent provided a removal efficiency and a calcium utilization over 25 percent higher than baseline results at an approach to saturation temperature of 30{degrees}F and a stoichiometric ratio of 0.9. A maximum SO{sub 2} removal efficiency of about 90 percent was experienced with this sorbent at an approach to saturation temperature of 20{degrees}F.

Keener, T.C.; Khang, S.J.; Meyers, G.R. [Cincinnati Univ., OH (United States)

1995-02-01

21

Sulfate induced heave in lime stabilized soil  

E-print Network

The addition of hydrated lime to clay soils is one of the most common methods of soil stabilization. However, when sulfates are present in the soil, the calcium in the lime reacts with the sulfates to form ettringite, an expandable mineral...

Bredenkamp, Sanet

1994-01-01

22

The Needs of Texas Soils for Lime.  

E-print Network

.. Chief; Sheep and Goat Investigations. SJ. C BURNS B. S Animal Husbartdman in ~hirge of ~Lef ~a'ifle Investigations (on lean?) P. V. EWING. M. S.. Anrmal Husbandman In -. Charge of Swine Invesfigations. C. M. HUBBARD, B. S., Assrstant Animal... the original alkali. Alkali carbonates are also injurious to the soil, as they cause it to puddle and run together. Hydrated lime or stone lime would be more injurious than the carbonate of lime, since it would probably form caustic socla at first. Lime...

Fraps, G. S. (George Stronach)

1919-01-01

23

Evaluation of liming and magnesium materials for increasing soil pH and available magnesium  

Microsoft Academic Search

Four liming and Mg materials were compared in a greenhouse experiment with soybeans for their ability to raise soil pH, supply Mg, and their effect on the availability of Mn, Cu, Fe, and Zn. Three materials were added at rates of 0, 1, and 2 times the lime requirement, calcitic lime, dolomitic lime, and Hydra?Mag (an industrial by?product containing 20%

L. M. Shuman

1985-01-01

24

Immobilisation of Fe floc: Part 1, pre-treatment of floc with slaked lime  

NASA Astrophysics Data System (ADS)

A series of radioactive iron (Fe 3+) hydroxide flocs are produced during reprocessing of nuclear fuel at Sellafield, UK. Before the flocs can be successfully encapsulated in a pulverised fuel ash/ordinary Portland cement composite cement to form a durable cemented wasteform, they need to be pre-treated with slaked lime. This paper reports results after investigating the reaction between a simulant floc and the slaked lime and shows that the floc reacts readily to form an X-ray amorphous hydrated calcium ferrite. Calcite (CaCO 3), formed from carbonation of Ca(OH) 2, appears to contribute to the formation of a crystalline iron hydroxy carbonate phase (Fe 6(OH) 12(CO 3)). This work concludes that pre-treatment allows a pozzolanic reaction to occur between the pulverised fuel ash and the Ca(OH) 2 produced during cement hydration. This increases the quantity of C sbnd S sbnd H formed and increases the compressive strength of the hardened wasteform enough to withstand forces generated during curing and prevent cracking.

Collier, N. C.; Milestone, N. B.; Hill, J.; Godfrey, I. H.

2009-08-01

25

Effects of watershed liming on the soil chemistry of Woods Lake, New York  

Microsoft Academic Search

The effects of watershed liming on the exchange complex of a forest soil were investigated at Woods Lake, in the west-central Adirondack Park, New York. Attempts to neutralize lake acidity via direct application of calcite during the 1980\\

Veronica L. Blette; Robert M. Newton

1996-01-01

26

Kinetics of the reaction of iron blast furnace slag/hydrated lime sorbents with SO{sub 2} at low temperatures: effects of the presence of CO{sub 2}, O{sub 2}, and NOx  

SciTech Connect

The effects of the presence of CO{sub 2}, O{sub 2}, and NOx in the flue gas on the kinetics of the sulfation of blast furnace slag/hydrated lime sorbents at low temperatures were studied using a differential fixed-bed reactor. When O{sub 2} and NOx were not present simultaneously, the reaction kinetics was about the same as that under the gas mixtures containing SO{sub 2}, H{sub 2}O, and N{sub 2} only, being affected mainly by the relative humidity. The sulfation of sorbents can be described by the surface coverage model and the model equations derived for the latter case. When both O{sub 2} and NOx, were present, the sulfation of sorbents was greatly enhanced, forming a great amount of sulfate in addition to sulfite. The surface coverage model is still valid in this case, but the model equations obtained show a more marked effect of relative humidity and negligible effects of SO{sub 2} concentration and temperature on the reaction. The effect of sorbent composition on the reaction kinetics was entirely represented by the effects of the initial specific surface area (S{sub g0}) and the Ca molar content (M{sup -1}) of sorbent. The initial conversion rate of sorbent increased linearly with increasing S{sub g0}, and the ultimate conversion increased linearly with increasing S{sub g0}M{sup -1}. The model equations obtained in this work are applicable to describe the kinetics of the sulfation of the sorbents in the low-temperature dry and semidry fine gas desulfurization processes either with an upstream NOx, removal unit or without.111

Liu, C.F.; Shih, S.M. [Industrial Technological Research Institute, Hsinchu (Taiwan)

2009-09-15

27

High surface area calcite  

NASA Astrophysics Data System (ADS)

Calcite (CaCO3) is important in many fields—in nature, because it is a component of aquifers, oil reservoirs and prospective CO2 storage sites, and in industry, where it is used in products as diverse as paper, toothpaste, paint, plastic and aspirin. It is difficult to obtain high purity calcite with a high surface area but such material is necessary for industrial applications and for fundamental calcite research. Commercial powder is nearly always contaminated with growth inhibitors such as sugars, citrate or pectin and most laboratory synthesis methods deliver large precipitates, often containing vaterite or aragonite. To address this problem, we (i) adapted the method of carbonating a Ca(OH)2 slurry with CO2 gas to develop the first simple, cheap, safe and reproducible procedure using common laboratory equipment, to obtain calcite that reproducibly had a surface area of 14-17 m2/g and (ii) conducted a thorough characterization of the product. Scanning electron microscopy (SEM) revealed nanometer scale, rhombohedral crystals. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR) confirmed highly crystalline, pure calcite that more closely resembles the dimensions of the biogenic calcite produced by algae in coccoliths than other methods for synthesizing calcite. We suggest that this calcite is useful when purity and high surface area are important.

Schultz, L. N.; Andersson, M. P.; Dalby, K. N.; Müter, D.; Okhrimenko, D. V.; Fordsmand, H.; Stipp, S. L. S.

2013-05-01

28

Molecular Structure of Calcite  

NSDL National Science Digital Library

Calcite is an essential mineral in limestone and marble which are used in the building, steel, chemical, and glass industries. It is found in abundance on the earth. Calcite was first produced in translucent ("Iceland Spar") form in the seventeenth century for optical uses. In 1928, William Nicol used it for Polaroid Sunglasses in an effort to deflect the sunlight. Today, calcite has a large number of uses: optical and crystallography research; as a component of animal feed, antacids, statues, and dough strengthener; in the production of paper and photography; and to make mortar, cement, concrete and asphalt.

2002-08-14

29

PRIMARY CALCITE Cfluid << Csolid ~  

E-print Network

to foraminfer nannofossil ooze nannofossil chalk to foraminfer nannofossil chalk nannofossil chalk to foraminfer nannofossil chalk Determinng the fractionation factor between Ca in calcite and Ca in solu- tion is important

Fantle, Matthew

30

The mechanism of vapor phase hydration of calcium oxide: implications for CO2 capture.  

PubMed

Lime-based sorbents are used for fuel- and flue-gas capture, thereby representing an economic and effective way to reduce CO2 emissions. Their use involves cyclic carbonation/calcination which results in a significant conversion reduction with increasing number of cycles. To reactivate spent CaO, vapor phase hydration is typically performed. However, little is known about the ultimate mechanism of such a hydration process. Here, we show that the vapor phase hydration of CaO formed after calcination of calcite (CaCO3) single crystals is a pseudomorphic, topotactic process, which progresses via an intermediate disordered phase prior to the final formation of oriented Ca(OH)2 nanocrystals. The strong structural control during this solid-state phase transition implies that the microstructural features of the CaO parent phase predetermine the final structural and physicochemical (reactivity and attrition) features of the product hydroxide. The higher molar volume of the product can create an impervious shell around unreacted CaO, thereby limiting the efficiency of the reactivation process. However, in the case of compact, sintered CaO structures, volume expansion cannot be accommodated in the reduced pore volume, and stress generation leads to pervasive cracking. This favors complete hydration but also detrimental attrition. Implications of these results in carbon capture and storage (CCS) are discussed. PMID:25233236

Kud?acz, Krzysztof; Rodriguez-Navarro, Carlos

2014-10-21

31

Elastic constants of calcite  

USGS Publications Warehouse

The recent measurements of the elastic constants of calcite by Reddy and Subrahmanyam (1960) disagree with the values obtained independently by Voigt (1910) and Bhimasenachar (1945). The present authors, using an ultrasonic pulse technique at 3 Mc and 25??C, determined the elastic constants of calcite using the exact equations governing the wave velocities in the single crystal. The results are C11=13.7, C33=8.11, C44=3.50, C12=4.82, C13=5.68, and C14=-2.00, in units of 1011 dyncm2. Independent checks of several of the elastic constants were made employing other directions and polarizations of the wave velocities. With the exception of C13, these values substantially agree with the data of Voigt and Bhimasenachar. ?? 1962 The American Institute of Physics.

Peselnick, L.; Robie, R.A.

1962-01-01

32

LIMESTONE AND LIME NEUTRALIZATION OF FERROUS IRON ACID MINE DRAINAGE  

EPA Science Inventory

The U.S. Environmental Protection Agency conducted a 2-yr study on hydrated lime and rock-dust limestone neutralization of acid mine drainage containing ferrous iron at the EPA Crown Mine Drainage Control Field Site near Rivesville, West Virginia. The study investigated optimizat...

33

LimeWire  

NSDL National Science Digital Library

LimeWire, version 2.1.1, is a software package that enables individuals to search for and share computer files with anyone on the Internet. This software lets you log on to the Gnutella peer-to-peer network and contains a list of MP3's, digital home movies, documents, and other software. Furthermore, it allows you to chat with other LimeWire users. This latest version incorporates several performance improvements, including enhanced tools for handling downloads from slow servers and bad connections. LimeWire is written in Java and will run on Windows, Macintosh, Linux, Sun, and other computing platforms.

34

Hydrate detection  

SciTech Connect

Project objectives were: (1) to create methods of analyzing gas hydrates in natural sea-floor sediments, using available data, (2) to make estimates of the amount of gas hydrates in marine sediments, (3) to map the distribution of hydrates, (4) to relate concentrations of gas hydrates to natural processes and infer the factors that control hydrate concentration or that result in loss of hydrate from the sea floor. (VC)

Dillon, W.P.; Ahlbrandt, T.S.

1992-06-01

35

Hydrate detection  

SciTech Connect

Project objectives were: (1) to create methods of analyzing gas hydrates in natural sea-floor sediments, using available data, (2) to make estimates of the amount of gas hydrates in marine sediments, (3) to map the distribution of hydrates, (4) to relate concentrations of gas hydrates to natural processes and infer the factors that control hydrate concentration or that result in loss of hydrate from the sea floor. (VC)

Dillon, W.P.; Ahlbrandt, T.S.

1992-01-01

36

Calcite: The multiuse mineral  

SciTech Connect

If people were told that a newly discovered mineral polarizes light, provides a raw material for sculptors, diminishes the danger of hip breakage, makes long-lasting foundations for buildings, reduces pollution at power plants, serves as a soil conditioner and water purifier, and saves life on earth from suffocation, they might be inclined to say either {open_quotes}Ain`t science wonderful!{close_quotes} or {open_quotes}Come on, now!{close_quotes} Luckily for humanity, such a mineral has been around for a billion years or so, and things would not be quite the same without it. It is calcite (CaCO{sub 3}) which in its most common natural form is known as limestone. Hubbard and Ericksen (1973) reported, {open_quotes}Limestone and dolomite [which is calcium or magnesium carbonate and bears the name of the Dolomites of northern Italy], commonly referred to as the carbonate rocks, are among the world`s most widely used mineral commodities and are essential to modern industrial society.{close_quotes}

Paschall, R.

1994-11-01

37

Evolution and the Calcite Eye Lens  

E-print Network

Calcite is a uniaxial, birefringent crystal, which in its optically transparent form, has been used for animal eye lenses, the trilobite being one such animal. Because of the calcite birefringence there is a difficulty in using calcite as a lens. When the propagation direction of incoming light is not exactly on the c-axis, the mages blur. In this paper, calcite blurring is evaluated, and the non-blurring by a crystallin eye lens is compared to a calcite one.

Vernon L. Williams

2013-04-03

38

Water transfer properties and shrinkage in lime-based rendering mortars  

NASA Astrophysics Data System (ADS)

Rendering is the practice of covering a wall or a building façade with one or more layers of mortar, with the main aim to protect the masonry structure against weathering. The render applied must show high flexibility, good adhesion and compatibility with the support (i.e. stone, brick) and, overall, it should be characterised by low water absorption and high water vapour permeability. Water (in the solid, liquid and vapour state) is one of the main factors that drive construction materials to deterioration. Therefore, to evaluate the quality and durability of a rendering mortar, thus ensuring its protective function in the masonry structure, it is fundamental to assess the behaviour of this mortar towards water. Mortars were elaborated with a calcitic dry hydrated lime, a calcareous aggregate, a pozzolan, a lightweight aggregate, a water-retaining agent and a plasticiser. Four types of lime mortars were prepared, in which the binder-to-aggregate ratios were 1:3, 1:4, 1:6 and 1:9 by weight, whilst the pozzolan was kept at 10% of the lime (by mass) and the total admixtures proportion was less than 2% of the total mass. The influence of the characteristics of mortars pore system on the amount of water absorbed and the kinetics of absorption was investigated by means of: free water absorption and drying; capillary uptake; water permeability; water vapour permeability. Interesting deductions can be made from the values of water and water vapour permeability found for mortars: the former increases exponentially with the sand volume of the mortar, whilst the latter increases almost exponentially with the initial water content added to the mortar mixes during their elaboration. However, the relationship obtained between porosity of mortars and permeability values is not really clear. This finding suggests that the permeability of a material cannot be estimated on the basis of its porosity as it can be made for the capillary uptake and free water absorption. Another aspect to be considered in the evaluation of the decay caused by water is the high shrinkage suffered by renders when they are applied on an extended surface (i.e. a wall), especially when they are aerial lime-based mortars. The shrinkage causes the formation of fissures that become an easy way for water to entry and diffuse through the mortar pore system. This factor is rarely taken into consideration during the hydric assays performed in the laboratory, since mortar samples of 4x4x16 or 4x4x4 cm in size do not undergo to such degree of shrinkage. For this reason, we have also studied the shrinkage of these mortars and considered it in the final assessment of mortars hydric properties. The shrinkage was evaluated according to a non-standardized method, by means of a shrinkage-measuring device that measures the mortar dimensional variations over time. This measurement has shown that the highest the lime content the biggest the mortar shrinkage and, consequently, the strongest the decay due to water.

Arizzi, A.; Cultrone, G.

2012-04-01

39

Analysis of CaCO3 products from lime solution  

NASA Astrophysics Data System (ADS)

CaCO3 particles derived from limestone are obtained from quarry in Tuwiri Wetan, Tuban, East Java and have been produced by calcination at temperature of 850°C for 6 hours and by dissolving into water for 24 hours to result in a precipitate at the bottom and a layer floating on the top of the lime solution. Characterization of the as received limestone with XRF and ICP showed a very high purity. Further characterization of secondary precipitatin using XRD showed the presence of CaCO3 (calcite) as much as 35% and Ca(OH)2 (calcium hydroxide) 65%, while the secondary layer contained pure CaCO3 (calcite). Analysis using SEM has revealed the presence cubic shape CaCO3 particles.

Arifin, Zaenal; Pratapa, Suminar; Triwikantoro, Darminto

2013-09-01

40

Experimental study of the replacement of calcite by calcium sulphates  

NASA Astrophysics Data System (ADS)

Among the most relevant mineral replacement reactions are those involving sulphates and carbonates, which have important geological and technological implications. Here it is shown experimentally that during the interaction of calcite (CaCO3) cleavage surfaces with sulphate-bearing acidic solutions, calcite is ultimately replaced by gypsum (CaSO4 2H2O) and anhydrite (CaSO4), depending on the reaction temperature. Observations suggest that this occurs most likely via an interface-coupled dissolution-precipitation reaction, in which the substrate is replaced pseudomorphically by the product. At 120 and 200 °C gypsum and/or bassanite (CaSO4·0.5H2O) form as precursor phases for the thermodynamically stable anhydrite. Salinity promotes the formation of less hydrated precursor phases during the replacement of calcite by anhydrite. The reaction stops before equilibrium with respect to calcite is reached and during the course of the reaction most of the bulk solutions are undersaturated with respect to the precipitating phase(s). A mechanism consisting of the dissolution of small amounts of solid in a thin layer of fluid at the mineral-fluid interface and the subsequent precipitation of the product phase from this layer is in agreement with these observations. PHREEQC simulations performed in the framework of this mechanism highlight the relevance of transport and surface reaction kinetics on the volume change associated with the CaCO3-CaSO4 replacement. Under our experimental conditions, this reaction occurs with a positive volume change, which ultimately results in passivation of the unreacted substrate before calcite attains equilibrium with respect to the bulk solution.

Ruiz-Agudo, E.; Putnis, C. V.; Hövelmann, J.; Álvarez-Lloret, P.; Ibáñez-Velasco, A.; Putnis, A.

2015-05-01

41

Lime-induced phytophotodermatitis.  

PubMed

This case describes a scenario of lime-induced phytophotodermatitis. Phytophotodermatitis is a dermatitis caused after the skin is exposed to photosensitizing compounds in plants and then exposed to sunlight. Many common plants including citrus fruits, celery, and wild parsnip contain these photosensitizing compounds which cause phytophotodermatitis. It is important for a physician to be aware of phytophotodermatitis because it may often be misdiagnosed as other skin conditions including fungal infection, cellulitis, allergic contact dermatitis, and even child abuse. PMID:25317269

Hankinson, Andrew; Lloyd, Benjamin; Alweis, Richard

2014-01-01

42

Lime-induced phytophotodermatitis  

PubMed Central

This case describes a scenario of lime-induced phytophotodermatitis. Phytophotodermatitis is a dermatitis caused after the skin is exposed to photosensitizing compounds in plants and then exposed to sunlight. Many common plants including citrus fruits, celery, and wild parsnip contain these photosensitizing compounds which cause phytophotodermatitis. It is important for a physician to be aware of phytophotodermatitis because it may often be misdiagnosed as other skin conditions including fungal infection, cellulitis, allergic contact dermatitis, and even child abuse. PMID:25317269

Hankinson, Andrew; Lloyd, Benjamin; Alweis, Richard

2014-01-01

43

COMBINATION LIMESTONE-LIME NEUTRALIZATION OF FERROUS IRON ACID MINE DRAINAGE  

EPA Science Inventory

Studies were conducted on ferrous-iron acid mine drainage (AMD) treatment by a two-step neutralization process in which rock-dust limestone was mixed with the influent AMD and then hydrated lime was added in a polishing reactor. This combination treatment process resulted in reag...

44

Authigenic carbonates from the Cascadia subduction zone and their relation to gas hydrate stability  

Microsoft Academic Search

Authigenic carbonates are intercalated with massive gas hydrates in sediments of the Cascadia margin. The deposits were recovered from the uppermost 50 cm of sediments on the southern summit of the Hydrate Ridge during the RV Sonne cruise SO110. Two carbonate lithologies that differ in chemistry, mineralogy, and fabric make up these deposits. Microcrystalline high-magnesium calcite (14 to 19 mol%

Gerhard Bohrmann; Jens Greinert; Erwin Suess; Marta Torres

1998-01-01

45

Authigenic carbonates from the Cascadia subduction zone and their relations to gas hydrate stability  

Microsoft Academic Search

Authigenic carbonates are intercalated with massive gas hydrates in sediments of the Cascadia margin. The deposits were recovered from the uppermost 50 cm of sediments on the southern summit of the Hydrate Ridge during the RV Sonne cruise SO110. Two carbonate lithologies that differ in chemistry, mineralogy, and fabric make up these deposits. Microcrystalline high-magnesium calcite (14 to 19 mol%

G. Bohrmann; J. Greinert; E. Suess; M. Torres

1998-01-01

46

A model for trace metal sorption processes at the calcite surface: Adsorption of Cd2+ and subsequent solid solution formation  

USGS Publications Warehouse

The rate of Cd2+ sorption by calcite was determined as a function of pH and Mg2+ in aqueous solutions saturated with respect to calcite but undersaturated with respect to CdCO3. The sorption is characterized by two reaction steps, with the first reaching completion within 24 hours. The second step proceeded at a slow and nearly constant rate for at least 7 days. The rate of calcite recrystallization was also studied, using a Ca2+ isotopic exchange technique. Both the recrystallization rate of calcite and the rate of slow Cd2+ sorption decrease with increasing pH or with increasing Mg2+. The recrystallization rate could be predicted from the number of moles of Ca present in the hydrated surface layer. A model is presented which is consistent with the rates of Cd2+ sorption and Ca2+ isotopic exchange. In the model, the first step in Cd2+ sorption involves a fast adsorption reaction that is followed by diffusion of Cd2+ into a surface layer of hydrated CaCO3 that overlies crystalline calcite. Desorption of Cd2+ from the hydrated layer is slow. The second step is solid solution formation in new crystalline material, which grows from the disordered mixture of Cd and Ca carbonate in the hydrated surface layer. Calculated distribution coefficients for solid solutions formed at the surface are slightly greater than the ratio of equilibrium constants for dissolution of calcite and CdCO3, which is the value that would be expected for an ideal solid solution in equilibrium with the aqueous solution. ?? 1987.

Davis, J.A.; Fuller, C.C.; Cook, A.D.

1987-01-01

47

Comparison of surface properties between kaolin and metakaolin in concentrated lime solutions.  

PubMed

The surface adsorption of calcium hydroxide onto kaolin and metakaolin was investigated by monitoring with atomic emission spectroscopy and pH measurements the amounts of ions left in solution after exposing clays to calcium hydroxide solutions of various concentrations. Both clays adsorb calcium and hydroxyl ions but differently. Kaolin adsorbs calcium hydroxide not only at the edges of the clay particles but also onto the basal faces. The adsorbed hydrated calcium ions form a layer on the clay particle surfaces, preventing further dissolution of the clay mineral platelet. Metakaolin shows high pozzolanic activity, which provides the quick formation of hydrated phases at the interfaces between metakaolin and lime solutions. The nature of the hydration products has been investigated using X-ray diffraction (XRD) and differential thermal analysis (DTA). The most important hydrated phases like CSH (hydrated calcium silicate) and C(2)ASH(8) (gehlenite) have been identified. PMID:19682702

Konan, K L; Peyratout, C; Smith, A; Bonnet, J-P; Rossignol, S; Oyetola, S

2009-11-01

48

The Elimination of Sodium and Potassium Hydroxides from Desiccated Soda Lime Diminishes Degradation of Desflurane to Carbon Monoxide and Sevoflurane to Compound A but Does Not Compromise Carbon Dioxide Absorption  

Microsoft Academic Search

Normal (hydrated) soda lime absorbent (approxi- mately 95% calcium hydroxide (Ca(OH)2), the remain- ing 5% consisting of a mixture of sodium hydroxide (NaOH) and potassium hydroxide (KOH)) degrades sevoflurane to the nephrotoxin Compound A, and des- iccated soda lime degrades desflurane, enflurane, and isoflurane to carbon monoxide (CO). We examined whether the bases in soda lime differed in their capaci-

M. A. Neumann; M. J. Laster; R. B. Weiskopf; D. H. Gong; R. Dudziak; E. I Eger II

1999-01-01

49

Effect of calcite on lead-rich cementitious solid waste forms  

SciTech Connect

The effect of calcite on lead-rich solidified waste forms generated using Portland cement has been investigated. Samples of cementitious wastes in the absence and presence of Pb and in the absence and presence of calcite were examined separately at 2, 7, 14 and 28 days of hydration by X-ray diffraction and SEM/EDS and for compressive strength. The presence of lead was observed to produce lead carbonate sulfate hydroxide (Pb{sub 4}SO{sub 4}(CO{sub 3}){sub 2}(OH){sub 2}), lead carbonate hydroxide hydrate (3PbCO{sub 3}.2Pb(OH){sub 2}.H{sub 2}O) and two other unidentified lead salts in cavity areas, and was observed to significantly retard the hydration of cement. Calcite addition to the Pb wastes was found to induce the rapid crystallization of calcium hydroxide coincident with the onset of C-S-H gel germination. The rapid dissolution of lead precipitates was observed with the subsequent development of very insoluble gel products of the form C-Pb-S-H. These products are formed by chemical incorporation of re-dissolved Pb species into silicate structures.

Lee, Dongjin [School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW 2052 (Australia); Swarbrick, Gareth [School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW 2052 (Australia); Waite, T. David [School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW 2052 (Australia)]. E-mail: D.waite@unsw.edu.au

2005-06-01

50

A study of the effects of repeated loadings and free water on the stability of a lime stabilized clay  

E-print Network

Snowdrift Hydrate . Typical Screen Analysis Snowdrift Hydrate . 4. Atterberg Limit Determinations 5. Nodified AASHO Compaction Determinations 6. Optimum Moisture Content - Density Relationships 7. Normally Loaded Triaxial Results (Non-repetitive) 8... typioal chemical and sieve analysis~ supplied by the manufaoturer, is shown in Tables 2 and 3 respectively Atterberg Limit, tests (24. 2) were performed on the raw soil and on samples oontaining varying percentages of lime sddative (2, 4, 6 and S 17...

Jantos, Carl Thomas

1959-01-01

51

Origin of cone-in-cone calcite veins during calcitization of dolomites and their subsequent diagenesis: A case study from the Gogolin Formation (Middle Triassic), SW Poland  

NASA Astrophysics Data System (ADS)

Although bedding-parallel cone-in-cone structure calcite veins are present in the Middle Triassic Gogolin Formation in Opole Silesia, their occurrence is limited to the Emilówka Cellular Limestone Member. Marly limestones (dedolomites) consisting of calcite pseudospar are the host rocks. The veins, which are up to 3 mm high and 30 cm long, are built of densely packed cone columns, with individual cones up to 0.7 mm high and 0.6 mm wide at their bases, and with vertex angle values ranging from 30° to 50°. The cones are microfractured, and the adjacent cones are vertically shifted in oblique planes. The exceptionally small veins consist of calcite fibres up to 0.15 mm high. The veins are built of low-magnesium and non-ferroan calcite, characterized by low ? 18O values ranging from - 6.8‰ to - 7.4‰, and low ? 13C values ranging from - 2.9‰ to - 4.5‰ vs. PDB. These isotopic values are similar to those obtained from the host rocks (? 18O from - 6.8‰ to - 7.4‰, and ? 13C from - 3.2‰ to - 3.6‰ vs. PDB) and they are strongly depleted in comparison with the isotopic values of other carbonate particles from the Gogolin Formation. The veins only formed in one lithostratigraphic member, suggesting that their origin is related to processes which acted only locally. There are two unique processes that the Emilówka Cellular Limestone Member alone in the Gogolin Formation underwent: early diagenetic evaporitic dolomitization of lime mud in the sabkha environment, and subsequent calcitization of dolomite. Dolomitization led to sediment cohesion loss, porosity increase and initial horizontal laminae separation as a result of the transformation of calcium carbonate to dolomite within anisotropic deposits. Similar values of geochemical parameters obtained from the vein calcite and the host rock calcite are evidence that vein-filling precipitation was contemporary with dedolomitization. Geochemical data combined with sedimentological research and burial history show meteoric-derived waters saturated with respect to calcite as a source of the vein calcite. Dedolomitization and vein precipitation may have taken place from the Norian/Early Jurassic to the Late Jurassic when the study area became eroded land, and the Emilówka Cellular Limestone Member may have acted as a local paleoaquifer conducting the meteoric-derived waters. Solid inclusions in the veins, detached from the host rock and the calcitized nodules, show that the force of calcite crystallization was the main factor responsible for vein widening. Vertical shifts of adjacent cones, remnants of primary fibrous calcite crystals, as well as the burial history justify the application of Tarr's theory in interpreting the origin of the secondary cone-in-cone structure within the fibrous structure veins. The timing and the particular conditions required for the cones to develop are uncertain.

Kowal-Linka, Monika

2010-03-01

52

Crystal lattice tilting in prismatic calcite.  

PubMed

We analyzed the calcitic prismatic layers in Atrina rigida (Ar), Haliotis iris (Hi), Haliotis laevigata (HL), Haliotis rufescens (Hrf), Mytilus californianus (Mc), Pinctada fucata (Pf), Pinctada margaritifera (Pm) shells, and the aragonitic prismatic layer in the Nautilus pompilius (Np) shell. Dramatic structural differences were observed across species, with 100-?m wide single-crystalline prisms in Hi, HL and Hrf, 1-?m wide needle-shaped calcite prisms in Mc, 1-?m wide spherulitic aragonite prisms in Np, 20-?m wide single-crystalline calcite prisms in Ar, and 20-?m wide polycrystalline calcite prisms in Pf and Pm. The calcite prisms in Pf and Pm are subdivided into sub-prismatic domains of orientations, and within each of these domains the calcite crystal lattice tilts gradually over long distances, on the order of 100 ?m, with an angle spread of crystal orientation of 10-20°. Furthermore, prisms in Pf and Pm are harder than in any other calcite prisms analyzed, their nanoparticles are smaller, and the angle spread is strongly correlated with hardness in all shells that form calcitic prismatic layers. One can hypothesize a causal relationship of these correlated parameters: greater angle spread may confer greater hardness and resistance to wear, thus providing Pf and Pm with a structural advantage in their environment. This is the first structure-property relationship thus far hypothesized in mollusk shell prisms. PMID:23806677

Olson, Ian C; Metzler, Rebecca A; Tamura, Nobumichi; Kunz, Martin; Killian, Christopher E; Gilbert, Pupa U P A

2013-08-01

53

HEMATITE AND CALCITE COATINGS ON FOSSIL VERTEBRATES  

Microsoft Academic Search

Hematite coatings are common on vertebrate fossils from Paleocene\\/Eocene paleosol deposits in the Bighorn Basin, Wyoming. In general, hematite coatings are found only on fossils and are limited to soils exhibiting hydromorphic features and moderate maturity. Pet- rographic and isotopic evidence suggests that hematite and micritic calcite formed at nearly the same time in a pedogenic environment, whereas sparry calcite

HUIMING BAO; PAUL L. KOCH; ROBERT P. HEPPLE

54

Lime pretreatment of lignocellulosic biomass  

NASA Astrophysics Data System (ADS)

Lignocellulose is a valuable alternative energy source. The susceptibility of lignocellulosic biomass to enzymatic hydrolysis is constrained due to its structural features, so pretreatment is essential to enhance enzymatic digestibility. Of the chemicals used as pretreatment agents, it has been reported that alkalis improve biomass digestibility significantly. In comparison with other alkalis such as NaOH and ammonia, lime (calcium hydroxide) has many advantages; it is very inexpensive, is safe, and can be recovered by carbonating wash water. The effects of lime pretreatment were explored on switchgrass and poplar wood, representing herbaceous and woody biomass, respectively. The effects of pretreatment conditions (time, temperature, lime loading, water loading, particle size, and oxygen pressure) have been systematically studies. Lime alone enhances the digestibility of switchgrass significantly; under the recommended conditions, the 3-d total sugar (glucose + xylose) yields of lime-treated switchgrass were 7 times that of untreated sample. When treating poplar wood, lime must be combined with oxygen to achieve high digestibility; oxidative lime pretreatment increased the 3-d total sugar yield of poplar wood to 12 times that of untreated sample. In a fundamental study, to determine why lime pretreatment is effective, the effects of three structural features on enzymatic digestibility were studied: lignin content, acetyl content, and crystallinity index (CrI). Poplar wood was treated with peracetic acid, potassium hydroxide, and ball milling to produce model lignocelluloses with a broad spectrum of lignin contents, acetyl contents, and CrI, respectively. Enzymatic hydrolysis was performed on the model lignocelluloses to determine the digestibility. Correlations between lignin/carbohydrate ratio, acetyl/carbohydrate ratio, CrI and digestibility were developed. The 95% prediction intervals show that the correlations predict the 1-h and 3-d total sugar conversions of a biomass sample within a precision of 5% and 20%, respectively. The digestibility of a variety of lime-treated biomass and ball-milled alpha-cellulose was compared to the correlations determined from the model compounds. The agreement between the measured and predicted values shows that the correlations are satisfactory and the three structural features---lignin content, acetyl content, and CrI---are the major factors that determine enzymatic digestibility.

Chang, Shushien

55

Alginic Acid Accelerates Calcite Dissolution  

NASA Astrophysics Data System (ADS)

Accelerated carbonate weathering through biological activity affects both geochemical cycling and the local pH and alkalinity of terrestrial and marine waters. Microbes affect carbonate dissolution through metabolic activity, production of acidic or chelating exudates, and cation binding by cell walls. Dissolution occurs within microbial biofilms - communities of microorganisms attached to stone in an exopolymer matrix. We investigated the effect of alginic acid, a common biological polymer produced by bacteria and algae, on calcite dissolution using a paired atomic force microscopy/flow-through reactor apparatus. The alginic acid caused up to an order of magnitude increase in dissolution rate at 3 < pH < 12. Additionally, the polymer preferentially binds to the obtuse pit steps and increases step velocity. We propose that the polymer is actively chelating surficial cations reducing the activation energy and increasing dissolution rate. The role of biologically produced polymers in mineral weathering is important in the protection of cultural heritage materials and understanding of marine and terrestrial systems.

Perry, T. D.; Duckworth, O. W.; McNamara, C. J.; Martin, S. T.; Mitchell, R.

2003-12-01

56

Development and pilot plant evaluation of silica-enhanced lime sorbents for dry flue gas desulfurization  

SciTech Connect

EPA's efforts to develop low cost, retrofitable flue gas cleaning technology include the development of highly reactive sorbents. Recent work addressing lime enhancement and testing at the bench-scale followed by evaluation of the more promising sorbents in a pilot plant are discussed here. The conversion of Ca(OH)/sub 2/ with SO/sub 2/ increased several-fold compared with Ca(OH)/sub 2/ alone when Ca(OH)/sub 2/ was slurried with fly ash first and later exposed to SO/sub 2/ in a laboratory packed bed reactor. Ca(OH)/sub 2/ enhancement increased with the increased fly ash amount. Diatomaceous earths were very effective reactivity promoters of lime-based sorbents. Differential scanning calorimetry of the promoted sorbents revealed the formation of a new phase (calcium silicate hydrates) after hydration, which may be the basis for the observed improved SO/sub 2/ capture. Fly ash/lime and diatomaceous earth/lime sorbents were tested in a 100 m/sup 3//h pilot facility incorporating a gas humidifier, a sorbent duct injection system, and a baghouse. The inlet SO/sub 2/ concentration range was 1000-2500 ppm. With once-through dry sorbent injection into the humidified flue gas, the total SO/sub 2/ removal ranged from 50 to 90 percent for a stoichiometric ratio of 1 to 2. Recycling the collected solids resulted in a total lime utilization exceeding 80-90 percent. Increased lime utilization was also investigated by the use of additives.

Jozewicz, W.; Jorgensen, C.; Chang, J.C.S.; Sedman, C.B.; Brna, T.G.

1988-06-01

57

LIME FGD SYSTEMS DATA BOOK  

EPA Science Inventory

The Data Book is intended to aid engineers in understanding the process design features that are unique to lime flue gas desulfurization (FGD) systems. It is intended to supplement, not replace, basic information on engineering design. It is addressed to engineers who must design...

58

H 2O speciation in float glass and soda lime silica glass  

Microsoft Academic Search

The speciation of H2O in float glass (FG) and soda lime silica glass (SLS) was investigated using IR and NMR spectroscopy. Molar absorption coefficients for the near-infrared (NIR) combination bands at 4500 and 5200 cm?1, assigned to OH groups and H2O molecules, respectively, were determined using hydrated glasses containing 0.5–7.4 wt.% of dissolved H2O. Water contents of the samples used

A. Stuke; H. Behrens; B. C. Schmidt; R. Dupree

2006-01-01

59

Evaluation of pozzolanic activity and physico-mechanical characteristics in ceramic powder-lime pastes  

Microsoft Academic Search

Ceramic powder has been used as an artificial pozzolanic addition, in preparing pozzolanic mortars for the historic\\/traditional\\u000a structures’ construction. In order to evaluate the pozzolanic activity of ceramic powder, several pastes were prepared, by\\u000a mixing it with hydrated lime, in different ratios. The pastes were stored in standard conditions (RH=99±1%, T=25±1°C) and evaluated using thermal analysis (DTA\\/TG), X-ray diffraction (XRD),

A. Bakolas; E. Aggelakopoulou; A. Moropoulou

2008-01-01

60

LIMESTONE PARTICLE SIZE AND RESIDUAL LIME CONCENTRATION AFFECT PH BUFFERING IN CONTAINER SUBSTRATES  

Microsoft Academic Search

The objective was to quantify how the concentration and particle size of unreacted “residual” limestone affected pH buffering capacity for ten commercial and nine research container substrates that varied in residual calcium carbonate equivalents (CCE) from 0.3 to 4.9 g CCE·L. The nine research substrates contained 70% peat:30% perlite (by volume) with dolomitic hydrated lime at 2.1 g·L, followed by

Jinsheng Huang; Paul R. Fisher; W. E. Horner; William R. Argo

2010-01-01

61

Do organic ligands affect calcite dissolution rates?  

NASA Astrophysics Data System (ADS)

Steady state Iceland-spar calcite dissolution rates were measured at 25 °C in aqueous solutions containing 0.1 M NaCl and up to 0.05 M dissolved bicarbonate at pH from 7.9 to 9.1 in the presence of 13 distinct dissolved organic ligands in mixed-flow reactors. The organic ligands considered in this study include those most likely to be present in either (1) aquifers at the conditions pertinent to CO 2 sequestration or (2) soil/early diagenetic environments: acetate, phthalate, citrate, EDTA 4-, succinate, D-glucosaminate, L-glutamate, D-gluconate, 2,4-dihydroxybenzoate, 3,4-dihydroxybenzoate, fumarate, malonate, and gallate. Results show that the presence of <0.05 mol/kg of these organic anions changes calcite dissolution rates by less than a factor of 2.5 with the exception of citrate and EDTA 4-. The presence of 0.05 mol/kg citrate and EDTA 4- increases calcite dissolution rates by as much as a factor of 35 and 500, respectively, compared to rates in organic anion-free solutions. Further calcite dissolution experiments were performed in the presence of organic polymers similar to bacterial exudates, cell exopolysaccharides, and analogs of microbial cell envelopes: alginate, lichen extract, humic acid, pectin, and gum xanthan. In no case did the presence of <100 ppm of these organics change calcite dissolution rates by more than a factor of 2.5. Results obtained in this study suggest that the presence of aqueous organic anions negligibly affects calcite forward dissolution rates in most natural environments. Some effect on calcite reactivity may be observed, however, by the presence of organic anions if they change substantially the chemical affinity of the fluid with respect to calcite.

Oelkers, Eric H.; Golubev, Sergey V.; Pokrovsky, Oleg S.; Bénézeth, Pascale

2011-04-01

62

Nickel adsorption on chalk and calcite  

NASA Astrophysics Data System (ADS)

Nickel uptake from solution by two types of chalk and calcite was investigated in batch sorption studies. The goal was to understand the difference in sorption behavior between synthetic and biogenic calcite. Experiments at atmospheric partial pressure of CO2, in solutions equilibrated with calcite and chalk and pH ranging from 7.7 to 8.8, explored the influence of initial concentration and the amount and type of sorbent on Ni uptake. Adsorption increases with increased surface area and pH. A surface complexation model describes the data well. Stability constants for the Ni surface complex are log KNi = - 1.12 on calcite and log KNi = - 0.43 and - 0.50 on the two chalk samples. The study confirms that synthetic calcite and chalk both take up nickel, but Ni binds more strongly on the biogenic calcite than on inorganically precipitated, synthetic powder, because of the presence of trace amounts of polysaccharides and clay nanoparticles on the chalk surface.

Belova, D. A.; Lakshtanov, L. Z.; Carneiro, J. F.; Stipp, S. L. S.

2014-12-01

63

Calcite dissolution in two deep eutrophic lakes  

SciTech Connect

The calcium cycle, in particular carbonate dissolution, was analyzed in two deep eutrophic lakes, Lago di Lugano (288 m maximum depth) and Sempachersee (87 m) located in Switzerland. A box model approach was used to calculate calcite dissolution in the water column and at the sediment-water interface based on various lake monitoring data such as sediment traps, sediment cores, water and pore-water interface based on various lake monitoring data such as sediment traps, sediment cores, water and pore-water analysis. A model for stationary conditions allowing the calculation of calcite dissolution in the water column for a given particle size distribution was developed. The relative values of the simulated flux were consistent with sediment trap observations. The best fit of the dissolution rate constant of sinking calcite in Lago di Lugano was on the same order of magnitude (3 {center{underscore}dot} 10{sup {minus}10} kg{sup 1/3} s{sup {minus}1}) as published laboratory values for this surface controlled process. Both lakes show a similar specific calcite precipitation rate of 170 g Ca m{sup {minus}2} a{sup {minus}1}. The diffusive flux across the sediment-water interface amounts to about 15 and 10% of total calcite precipitation in Sempachersee and Lago di Lugano, respectively. However, 61% of the precipitated calcite is dissolved in the water column of Lago di Lugano compared to only 13% in Sempachersee. These results point towards the importance of grain size distributions and settling times in stratified deep waters as the two most important factors determining calcite retention in sediments of hard water lakes.

Ramisch, F.; Dittrich, M.; Mattenberger, C.; Wehrli, B.; Wueest, A.

1999-10-01

64

pH-dependence of calcite growth kinetics at constant solution calcium to carbonate activity ratio and supersaturation: an in situ Atomic Force Microscopy study  

NASA Astrophysics Data System (ADS)

Calcite-solution reactions (growth, dissolution and replacement) are critical in a range of both engineering and natural processes. Classical crystal growth theory relates calcite growth rates to the degree of supersaturation. The solution composition may also affect the growth rate of carbonate minerals, via the Ca2+ to CO32- concentration ratio (Nehrke et al., 2007; Perdikouri et al., 2009), ionic strength (Zuddas and Mucci, 1998) or the presence of organic matter (Hoch et al., 2000). Most calcite growth studies so far have been performed at a constant pH of ca. 8 or 10, or changing the pH together with the degree of supersaturation with respect to calcite and/or the aCa2+ to aCO32- ratio in solution, which hinders an evaluation of the pH effect on calcite growth kinetics. In this work, in situ Atomic Force Microscopy (AFM) was employed to study the growth of calcite at a constant supersaturation (? = 6.46) and solution stoichiometry (Ca2+-CO32- = 1) in the pH range 7.5 to 12. How pH may influence calcite growth is relevant to improve our understanding of the effects on carbonate-solution reactions when variations in atmospheric CO2result in changes in the pH of the oceans and surface waters. We observed that the calcite growth rate decreases with increasing pH in the studied range. The results can be successfully explained by the mechanistic model for calcite growth based on surface complexation proposed by Nilsson and Sternbeck (1999) and by solute hydration. At pH below 8.5, growth occurs mainly by CaCO30 incorporation at >CaHCO30 surface sites. CaCO30 should be more easily incorporated than free Ca2+ ions, as water exchange usually is faster if water molecules in the ion hydration shells are substituted for by other ligands, as in CaCO30. However, at pH above 9, Ca2+ incorporation at >CaHCO30 sites also contributes to calcite growth as a result of increased frequency of water exchange in calcium hydration shells due to the presence of strongly hydrated OH-. The decrease in calcite growth rate is a consequence of decreasing surface concentration of growth active sites (i.e. >CaHCO30) with increasing pH in our experimental conditions. Changes in 2D island morphology were observed at high pH (12), possibly due to the stabilization of polar scalenohedral faces by the presence of OH- ions. References Hoch, A.R.; Reddy, M.M.; Aiken, G.R. Calcite crystal growth inhibition by humic substances with emphasis on hydrophobic acids from the Florida Everglades. Geochim. Cosmochim. Acta 2000, 64, 61-72. Nehrke, G.; Reichart, G. J.; Van Cappellen, P.; Meile, C.; Bijma, J. Dependence of calcite growth rate and Sr partitioning on solution stoichiometry: Non-Kossel crystal growth. Geochim. Cosmochim. Acta 2007, 71, 2240-2249 Nilsson O.; Sternbeck J. A mechanistic model for calcite crystal growth using surface speciation. Geochim. Cosmochim.Acta 1999, 63, 217-225. Perdikouri, C.; Putnis, C.V.; Kasioptas, A.; Putnis, A. An Atomic Force Microscopy Study of the Growth of a Calcite Surface as a Function of Calcium/Total Carbonate Concentration Ratio in Solution at Constant Supersaturation. Cryst. Growth Des. 2009, 9, 4344-4350. Zuddas, P.; Mucci, A. Kinetics of Calcite Precipitation from Seawater: II. The Influence of the Ionic Strength. Geochim. Cosmochim. Acta 1998, 62, 757-766.

Ruiz-Agudo, Encarnación; Putnis, Christine V.; Rodriguez-Navarro, Carlos Manuel; Putnis, Andrew

2010-05-01

65

Experimental investigation of calcium silicate hydrate (CSH) nucleation  

Microsoft Academic Search

Due to the importance of calcium silicate hydrate (C-S-H) in cement chemistry, its nucleation mode and parameters influencing it were investigated. It has been observed that the C-S-H nucleation follows the general laws governing the nucleation. The degree of supersaturation has been found to be the main parameter controlling homogeneous nucleation rates. The lime concentration in solution, well known to

S. Garrault-Gauffinet; A Nonat

1999-01-01

66

Lime for environmental uses. STP 931  

SciTech Connect

This book STP 931 discusses the use of lime and industrial limestone for the control of factors that influence the environment - including the treatment of gaseous, liquid, and solid wastes. Current research shows that lime is one of the key chemicals that can help solve the problem of air, water, and land pollution. Topics covered are: the many environmental uses of lime including water treatment, sewage and industrial waste treatment, and the scrubbing of sulfur dioxide from power plant gases; various lime types and the engineering considerations in the design of lime handling systems; a hazardous waste incident where the waste was solidified with quicklime and lime kiln dust for burial; the growing use of lime and fly-ash for stabilizing scrubber sludges produced in wet scrubbing installations at more than 20 power plants in the United States; use of lime for stabilizing sewage sludge for land fill disposal; neutralization of calcium and magnesium calcium hydroxides through the use of carbon dioxide; and lime stabilization of expansive clays and silty clays for use in earth dams, irrigation canals, and levees.

Gutschick, K.A. (Ed.)

1987-01-01

67

46 CFR 148.230 - Calcium oxide (lime, unslaked).  

Code of Federal Regulations, 2012 CFR

...2012-10-01 2012-10-01 false Calcium oxide (lime, unslaked). 148.230...for Certain Materials § 148.230 Calcium oxide (lime, unslaked). (a) When transported by barge, unslaked lime (calcium oxide) must be carried in an...

2012-10-01

68

46 CFR 148.230 - Calcium oxide (lime, unslaked).  

Code of Federal Regulations, 2014 CFR

...2014-10-01 2014-10-01 false Calcium oxide (lime, unslaked). 148.230...for Certain Materials § 148.230 Calcium oxide (lime, unslaked). (a) When transported by barge, unslaked lime (calcium oxide) must be carried in an...

2014-10-01

69

46 CFR 148.230 - Calcium oxide (lime, unslaked).  

Code of Federal Regulations, 2011 CFR

...2011-10-01 2011-10-01 false Calcium oxide (lime, unslaked). 148.230...for Certain Materials § 148.230 Calcium oxide (lime, unslaked). (a) When transported by barge, unslaked lime (calcium oxide) must be carried in an...

2011-10-01

70

46 CFR 148.230 - Calcium oxide (lime, unslaked).  

Code of Federal Regulations, 2013 CFR

...2013-10-01 2013-10-01 false Calcium oxide (lime, unslaked). 148.230...for Certain Materials § 148.230 Calcium oxide (lime, unslaked). (a) When transported by barge, unslaked lime (calcium oxide) must be carried in an...

2013-10-01

71

Examination of the system fly ash lime calcined gypsum water  

NASA Astrophysics Data System (ADS)

The feasibility of the utilization of the system fly ash lime calcined gypsum (?-hemihydrate) water (the mass ratio 2:1:2:2.5) for the production of building ceramics was investigated. The system was cured under different conditions, i.e., tap water and ambient air. It was confirmed by X-ray diffraction analysis that three hydration products (gypsum, portlandite and ettringite) were formed in the water-cured system and two (gypsum and portlandite) in the air-cured system. Due to the formation of these products, a compressive strength of 4.01 MPa in the water-cured and 7.83 MPa in air-cured system developed. When the air-cured system was exposed to three alternate heating cooling or three alternate cooling heating cycles, the compressive strength increased (from 7.83 to 9.47 and 10.55 MPa, respectively). The fly ash lime calcined gypsum water systems prepared in this work can be applied for the manufacture of products for internal walls (bricks and blocks).

Marinkovic, S.; Kostic-Pulek, A.

2007-05-01

72

Marine Diagenesis of Shallow Marine Lime-Mud Sediments: Insights from dgrO18 and dgrC13 Data.  

PubMed

Shallow marine lime-mud sediments of the Ste. Genevieve Formation (Mississippian), in part of the Illinois Basin, underwent at least three diagenetic changes: (i) local dolomitization in seawater or a brine, producing dolostone having average deltaC(13) of +2.5 per mille and deltaO(18) of +1.9 per mille (versus PDB-1); (ii) more usually cementation of unreplaced CaCO(3), in intrasediment seawater, yielding isotopically marine lime mudstone mainly composed of calcite, 4-micron or finer, with deltaO(18) of from -1 to +1 per mille; (iii) later partial alteration of CaCO(3), in permeable dolomitic rocks, by isotopically "lighter" waters, to calcite with an estimated deltaO(18) of -10 per mille or less. Isotope data appraised by petrographic analysis thus suggest "submarine" cementation of these carbonates in shallow marine conditions. PMID:17812283

Choquette, P W

1968-09-13

73

Cyclic Cratonic Carbonates and Phanerozoic Calcite Seas.  

ERIC Educational Resources Information Center

Discusses causes of cyclicity in cratonic carbonate sequences and evidence for and potential significance of postulated primary calcite sediment components in past Paleozoic seas, outlining problems, focusing on models explaining existing data, and identifying background. Future sedimentary geologists will need to address these and related areas…

Wilkinson, Bruce H.

1982-01-01

74

Interaction of alcohols with the calcite surface.  

PubMed

A clearer understanding of calcite interactions with organic molecules would contribute to a range of fields including harnessing the secrets of biomineralisation where organisms produce hard parts, increasing oil production from spent reservoirs, remediating contaminated soils and drinking water aquifers and improving manufacturing methods for industrial products such as pigments, soft abrasives, building materials and optical devices. Biomineralisation by some species of blue green algae produces beautifully elaborate platelets of calcite where the individual crystals are of nanometer scale. Controlling their growth requires complex polysaccharides. Polysaccharide activity depends on the functionality of OH groups, so to simplify the system in order to get closer to a molecular level understanding, we investigated the interaction of OH from a suite of alcohols with clean, freshly cleaved calcite surfaces. X-ray photoelectron spectroscopy (XPS) provided binding energies and revealed the extent of surface coverage. Molecular dynamics (MD) simulations supplemented with information about molecule ordering, orientation and packing density. The results show that all alcohols studied bond with the calcite surface through the OH group, with their carbon chains sticking away in a standing-up orientation. Alcohol molecules are closely packed and form a well-ordered monolayer on the surface. PMID:25533590

Bovet, N; Yang, M; Javadi, M S; Stipp, S L S

2015-02-01

75

Genesis of filamentary pyrite associated with calcite crystals  

E-print Network

Abstract: The calcite of the hydrothermal Surneshko Kladenche copper vein deposit from the Rossen ore field, Bulgaria, sometimes encloses peculiar filamentary pyrite crystals. Three successive calcite generations were observed belonging to a low-temperature (<235°C) carbonate paragenesis formed

Eur J. Mineral; Ivan K. Bonev; Juan Manuel Garcia-ruiz; Radostina Atanassova

2005-01-01

76

Effects of carbonation on the pore structure of non-hydraulic lime mortars  

SciTech Connect

The pore structures of carbonated non-hydraulic lime mortars made with a range of different aggregates and concentrations of lime have been determined using mercury intrusion porosimetry (MIP). MIP data have been correlated with scanning electron microscopy images and other porosity data. During carbonation there is an increase in pore volume in the {approx} 0.1 {mu}m pore diameter range across all mortar types which is attributed to the transformation of portlandite to calcite. Also there is a monotonic increase in the volumes of pores with diameters below 0.03 {mu}m. A model is proposed for the changes in pore structure caused by carbonation. This attributes the increase in the volume of sub 0.03 {mu}m pores to the attachment of calcite crystals to the surface of aggregate particles, and in some cases to the surface of portlandite crystals. This phenomenon may explain the continuing presence of portlandite in mortars that, apparently, have fully carbonated.

Lawrence, Robert M. [Department of Architecture and Civil Engineering, University of Bath, BATH, BA2 7AY (United Kingdom)]. E-mail: mike@cc-w.co.uk; Mays, Timothy J. [Department of Chemical Engineering, University of Bath, BATH, BA2 7AY (United Kingdom); Rigby, Sean P. [Department of Chemical Engineering, University of Bath, BATH, BA2 7AY (United Kingdom); Walker, Peter [Department of Architecture and Civil Engineering, University of Bath, BATH, BA2 7AY (United Kingdom); D'Ayala, Dina [Department of Architecture and Civil Engineering, University of Bath, BATH, BA2 7AY (United Kingdom)

2007-07-15

77

The ionic conductivity in high-pressure polymorphs of calcite  

Microsoft Academic Search

Ionic conductivity of polycrystalline calcite containing varying amounts of PO43-ions was measured in the pressure range of 1–6 GPa and at room temperature. Electrical conductivity increased with pressure corresponding to the phase transition of calcite I to calcite II. The conductivity in calcite III decreased exponentially with pressure. Calculated activation volumes of the conductivity varied with PO43-content in the range

M. Ishikawa; A. Sawaoka; M. Ichikuni

1982-01-01

78

Hypogene calcitization: Evaporite diagenesis in the western Delaware Basin  

Microsoft Academic Search

Evaporite calcitization within the Castile Formation of the Delaware Basin is more widespread and diverse than originally\\u000a recognized. Coupled field and GIS studies have identified more than 1000 individual occurrences of calcitization within the\\u000a Castile Formation outcrop area, which includes both calcitized masses (limestone buttes) and laterally extensive calcitized\\u000a horizons (limestone sheets). Both limestone buttes and sheets commonly contain a

Kevin W. Stafford; Dana Ulmer-Scholle; Laura Rosales-Lagarde

2008-01-01

79

Experimental determination of calcite dissolution rates and equilibrium concentrations in deionized water approaching calcite equilibrium  

Microsoft Academic Search

The calcite dissolution rates at 50–250 °C and 20 MPa in deionized water with flow rate varying from 0.2 to 5 mL\\/min were\\u000a experimentally measured in a continuous flow column pressure vessel reactor. Equilibrium concentration (c\\u000a eq) of calcite dissolution in deionized water at 20 MPa was determined using dissolution data according to the iterative method\\u000a presented by Jeschke and

Qingjie Gong; Jun Deng; Qingfei Wang; Liqiang Yang; Min She

2010-01-01

80

Phosphorus versus Lime in Plant Ash  

Microsoft Academic Search

THAT in the mineral constituents of leaves a strong proportion of lime is an obstacle to the presence of a considerable quantity of potass has been recognised as a feature of calcifugous species of plants. It has been sought, indeed, to explain, apparently on this ground alone, the existence of special plants which shun lime soils, or at least to

P. Q. Keegan

1902-01-01

81

Brittlestar-Inspired Microlens Arrays Made of Calcite Single Crystals.  

PubMed

Unique concave microlens arrays (MLAs) made of calcite single crystals with tunable crystal orientations can be readily fabricated by template-assisted epitaxial growth in solution without additives under ambient conditions. While the non-birefringent calcite (001) MLA showed excellent imaging performance like brittlestar's microlens arrays, the birefringent calcite (104) MLA exhibited remarkable polarization-dependent optical properties. PMID:25366272

Ye, Xiaozhou; Zhang, Fei; Ma, Yurong; Qi, Limin

2014-11-01

82

Experimental pressure solution compaction of synthetic halite/calcite aggregates  

E-print Network

Experimental pressure solution compaction of synthetic halite/calcite aggregates Sergey Zubtsova of weakening of sediment-like aggregates by addition of hard particles. Sieved mixtures of calcite and halite solution. The individual halite grains deform easily by pressure solution creep whereas calcite grains act

83

Sequestration of Selenium on Calcite Surfaces Revealed by Nanoscale Imaging  

E-print Network

Sequestration of Selenium on Calcite Surfaces Revealed by Nanoscale Imaging Christine V. Putnis provides a new mechanism for selenium sequestration and extends the range of thermodynamic conditions under into calcite during calcite precipitation was the main mechanism of sequestration as they could replace either

84

in situ Calcite Precipitation for Contaminant Immobilization  

SciTech Connect

in situ Calcite Precipitation for Contaminant Immobilization Yoshiko Fujita (Yoshiko.fujita@inl.gov) (Idaho National Laboratory, Idaho Falls, Idaho, USA) Robert W. Smith (University of Idaho-Idaho Falls, Idaho Falls, Idaho, USA) Subsurface radionuclide and trace metal contaminants throughout the U.S. Department of Energy (DOE) complex pose one of DOE’s greatest challenges for long-term stewardship. One promising stabilization mechanism for divalent trace ions, such as the short-lived radionuclide strontium-90, is co-precipitation in calcite. Calcite, a common mineral in the arid western U.S., can form solid solutions with trace metals. The rate of trace metal incorporation is susceptible to manipulation using either abiotic or biotic means. We have previously demonstrated that increasing the calcite precipitation rate by stimulating the activity of urea hydrolyzing microorganisms can result in significantly enhanced Sr uptake. Urea hydrolysis causes the acceleration of calcium carbonate precipitation (and trace metal co-precipitation) by increasing pH and alkalinity, and also by liberating the reactive cations from the aquifer matrix via exchange reactions involving the ammonium ion derived from urea: H2NCONH2 + 3H2O ? 2NH4+ + HCO3- + OH- urea hydrolysis >X:2Ca + 2NH4+ ? 2>X:NH4 + Ca2+ ion exchange Ca2+ + HCO3- + OH- ? CaCO3(s) + H2O calcite precipitation where >X: is a cation exchange site on the aquifer matrix. This contaminant immobilization approach has several attractive features. Urea hydrolysis is catalyzed by the urease enzyme, which is produced by many indigenous subsurface microorganisms. Addition of foreign microbes is unnecessary. In turn the involvement of the native microbes and the consequent in situ generation of reactive components in the aqueous phase (e.g., carbonate and Ca or Sr) can allow dissemination of the reaction over a larger volume and/or farther away from an amendment injection point, as compared to direct addition of the reactants at a well (which can lead to clogging). A final particularly attractive characteristic of this approach is its long-term sustainability; the remediation scheme is geared toward environments that are already saturated with respect to calcite, and in such systems the bulk of any newly precipitated calcite will remain stable once engineered manipulations cease. This means that the co-precipitated contaminants will be effectively sequestered over the long term. We are currently conducting integrated field, laboratory, and computational research to evaluate a) the relationships between urea hydrolysis rate, calcite precipitation rate, and trace metal partitioning under environmentally relevant conditions; and b) the coupling between flow/flux manipulations and calcite precipitate distribution and metal uptake. We are also assessing the application of geophysical and molecular biological tools to monitor the relevant chemical and physical processes. The primary emphasis is on field-scale processes, with the laboratory and modeling activities designed specifically to support the field studies. Field experiments are being conducted in perched water (vadose zone) at the Vadose Zone Research Park (VZRP) at the Idaho National Laboratory; the VZRP provides an uncontaminated setting that is an analog of the 90Sr-contaminated vadose zone at the Idaho Nuclear Technology and Engineering Center. A summary of results to date will be presented.

Yoshiko Fujita; Robert W. Smith

2009-08-01

85

LIMEDS  

PubMed Central

Most Decision Support Systems (DSSs) in medicine have been developed in hospital environments, for use in hospitals. Only a few are designed for use by General Practitioners (GPs) in primary care. The work reported in this paper has a twofold aim: [List: see text

Timpka, Toomas

1986-01-01

86

The role of silicate surfaces on calcite precipitation kinetics  

NASA Astrophysics Data System (ADS)

The aim of this study is to illuminate how calcite precipitation depends on the identity and structure of the growth substrate. Calcite was precipitated at 25 °C from supersaturated aqueous solutions in the presence of seeds of either calcite or one of six silicate materials: augite, enstatite, labradorite, olivine, basaltic glass and peridotite rock. Calcite saturation was achieved by mixing a CaCl2-rich aqueous solution with a NaHCO3-Na2CO3 aqueous buffer in mixed-flow reactors containing 0.5-2 g of mineral, rock, or glass seeds. This led to an inlet fluid calcite saturation index of 0.6 and a pH equal to 9.1. Although the inlet fluid composition, flow rate, and temperature were identical for all experiments, the onset of calcite precipitation depended on the identity of the seeds present in the reactor. Calcite precipitated instantaneously and at a constant rate in the presence of calcite grains. Calcite precipitated relatively rapidly on labradorite, olivine, enstatite, and peridotite (mainly composed of Mg-olivine) surfaces, but more slowly on augite and basaltic glass. Calcite precipitation rates, however, became independent of substrate identity and mass over time, and all rates approach 10-9.68 ± 0.08 mol/s for ?10 day long experiments and 10-9.21 ± 0.2 mol/s for ?70 day long experiments. Scanning Electron Microscope images showed olivine, enstatite and peridotite surfaces to be covered extensively with calcite coatings at the end of the experiments. Less calcite was found on labradorite and augite, and the least on basaltic glass. In all cases, calcite precipitation occurs on the mineral, rock or glass surfaces. Calcite precipitation on these surfaces, however, negligibly affects the dissolution rates of the silicate grains. These results support ultramafic and basalt carbonation as a long-term carbon storage strategy, as calcite readily precipitates on the surfaces of minerals contained in these rocks without inhibiting their dissolution.

Stockmann, Gabrielle J.; Wolff-Boenisch, Domenik; Bovet, Nicolas; Gislason, Sigurdur R.; Oelkers, Eric H.

2014-06-01

87

Calcite growth-rate inhibition by fulvic acid and magnesium ion—Possible influence on biogenic calcite formation  

USGS Publications Warehouse

Increases in ocean surface water dissolved carbon dioxide (CO2) concentrations retard biocalcification by reducing calcite supersaturation (?c). Reduced calcification rates may influence growth-rate dependent magnesium ion (Mg) incorporation into biogenic calcite modifying the use of calcifying organisms as paleoclimate proxies. Fulvic acid (FA) at biocalcification sites may further reduce calcification rates. Calcite growth-rate inhibition by FA and Mg, two common constituents of seawater and soil water involved in the formation of biogenic calcite, was measured separately and in combination under identical, highly reproducible experimental conditions. Calcite growth rates (pH=8.5 and ?c=4.5) are reduced by FA (0.5 mg/L) to 47% and by Mg (10?4 M) to 38%, compared to control experiments containing no added growth-rate inhibitor. Humic acid (HA) is twice as effective a calcite growth-rate inhibitor as FA. Calcite growth rate in the presence of both FA (0.5 mg/L) and Mg (10?4 M) is reduced to 5% of the control rate. Mg inhibits calcite growth rates by substitution for calcium ion at the growth site. In contrast, FA inhibits calcite growth rates by binding multiple carboxylate groups on the calcite surface. FA and Mg together have an increased affinity for the calcite growth sites reducing calcite growth rates.

Reddy, Michael M.

2012-01-01

88

Calcite growth-rate inhibition by fulvic acid and magnesium ion—Possible influence on biogenic calcite formation  

NASA Astrophysics Data System (ADS)

Increases in ocean surface water dissolved carbon dioxide (CO2) concentrations retard biocalcification by reducing calcite supersaturation (?c). Reduced calcification rates may influence growth-rate dependent magnesium ion (Mg) incorporation into biogenic calcite modifying the use of calcifying organisms as paleoclimate proxies. Fulvic acid (FA) at biocalcification sites may further reduce calcification rates. Calcite growth-rate inhibition by FA and Mg, two common constituents of seawater and soil water involved in the formation of biogenic calcite, was measured separately and in combination under identical, highly reproducible experimental conditions. Calcite growth rates (pH=8.5 and ?c=4.5) are reduced by FA (0.5 mg/L) to 47% and by Mg (10-4 M) to 38%, compared to control experiments containing no added growth-rate inhibitor. Humic acid (HA) is twice as effective a calcite growth-rate inhibitor as FA. Calcite growth rate in the presence of both FA (0.5 mg/L) and Mg (10-4 M) is reduced to 5% of the control rate. Mg inhibits calcite growth rates by substitution for calcium ion at the growth site. In contrast, FA inhibits calcite growth rates by binding multiple carboxylate groups on the calcite surface. FA and Mg together have an increased affinity for the calcite growth sites reducing calcite growth rates.

Reddy, Michael M.

2012-08-01

89

Calcite surface structure observed at microtopographic and molecular scales with atomic force microscopy (AFM)  

NASA Astrophysics Data System (ADS)

Atomic force microscopy (AFM) was used to study calcite cleavage surfaces in air and under aqueous solution at the microtopographic and molecular scales. Surfaces freshly fractured and imaged in air showed wide, flat terraces with steps only a few monolayers high. Exposure to distilled water promoted development of etch pits with differential dissolution rates on inequivalent sides. The pits became broad and shallow with apparent approach to equilibrium after about fifteen minutes. Exposure of the freshly fractured surfaces to air for more than a couple of hours resulted in the appearance of narrow and deepening, irregular-sided pits. These observations indicate a highly dynamic surface capable of incorporating adsorbed material into the near-surface bulk. Molecular resolution images revealed a regular array of corrugations that were interpreted to represent the covalent carbonate groups. The unit cell dimensions of the lattice were the same as those expected for the cleavage plane of bulk calcite but the two-dimensional surface symmetry was not conserved. Apparent displacement of every second carbonate row probably results from frictional forces as the tip scans over rows of alternating orientation; likewise, it may be an expression of surface hydration species adsorbed to these alternate rows and/or the adsorbed species may enhance the effect of the frictional forces. A 2 × 1 structure is observed on surfaces of pure calcite imaged by AFM in air and under water and supports observations made previously using low energy electron diffraction (LEED) in vacuum. The 2 × 1 pattern may be caused by slight twisting of some surface carbonate groups in order to stabilize "dangling bonds" and surface charge after cleavage and surface hydration. However, exact interpretation of row-pairing and the 2 × 1 structure is difficult because of the convolution of information in the AFM images resulting from topography, elastic surface deformation, and electrostatic forces.

Stipp, S. L. S.; Eggleston, C. M.; Nielsen, B. S.

1994-07-01

90

Effects of Pretreatment and Drying on Composition and Bitterness of High-Dietary-Fiber Powder from Lime Residues  

Microsoft Academic Search

Lime residues after juice extraction were used as a starting raw material to produce high-dietary-fiber powder. The effects of pretreatment—i.e., blanching and ethanol soaking (55–95% v\\/v)—and hot air drying at 60–100°C on the proximate composition and limonin, a substance responsible for bitterness in citrus fruits, were evaluated. Hydration properties—i.e., water retention capacity and swelling capacity—and visual color were also determined.

P. Wuttipalakorn; W. Srichumpuang; N. Chiewchan

2009-01-01

91

Thorough investigation of the oxygen heterocyclic fraction of lime (Citrus aurantifolia (Christm.) Swingle) juice.  

PubMed

Reversed-phase-HPLC analysis by means of superficially porous silica particle columns (fused-core) was applied to the investigation of flavonoids, coumarins, and psoralens in lime juice samples. Hesperidin (367.0 ± 16.0 ppm) and eriocitrin (148.0 ± 7.9 ppm) were the most abundant flavonoids. Fifteen coumarins and furocoumarins were determined, including bergamottin (29.6 ± 1.1 ppm), 5-geranyloxy-7-methoxycoumarin (16.5 ± 0.6 ppm), and oxypeucedanin hydrate (9.9 ± 0.5 ppm) as predominant compounds. These molecules are today well known for their beneficial effects on human health. As a consequence, the present study, beyond investigating for the first time the chemical composition of lime juice, highlights also its health-promoting qualities, due to its content of flavonoids and coumarins. PMID:24478239

Costa, Rosaria; Russo, Marina; De Grazia, Selenia; Grasso, Elisa; Dugo, Paola; Mondello, Luigi

2014-04-01

92

Rare earth elements in natural calcite  

NASA Astrophysics Data System (ADS)

Rare earth elements (REE) have been used for years as a tool for interpreting rock genesis but recently they have come to be used as good analogues for the tri--valent actinides. Although there are abundant data in the literature describing their relative proportions in rocks, data for individual minerals and factors controlling their uptake are lacking. Better understanding of the extent of REE incorporation in all minerals would provide valuable information about the extent of immobilisation one could expect in the event of escape of radioactive elements. When concrete waste repositories break down, calcite forms in the high pH, Ca-rich solutions. Calcium's electronic structure permits significant distortion in its octahedral coordination, so divalent ions substitute extensively when size is compatible. The trivalent REE's, whose radii are similar to calcium, substitute to some extent but the range of possible uptake is unknown. This study was designed to fill that gap. With help from museums and mineral collectors internationally, we have collected a suite of calcite samples from well--characterised genetic environments. These include limestone, dolomite, marble, pegmatite, hydrothermal vein fillings, regionally metamorphosed settings and skarn, as well as several types of calcitic fossils. We used inductively coupled plasma-mass spectroscopy (ICP--MS) with isotope dilution to analyse the REE content. Data show expected trends. The most interesting result so far is that the highest natural REE concentrations are significantly lower than expected from the distribution coefficients we determined experimentally, suggesting calcite takes up essentially all REE's available from solution. This is good news for natural attenuation in the vicinity of decomposing concrete repositories because one could expect immobilisation of the actinides whose behaviour is similar to that of the lanthanides. The negative side is that recrystallisation or dissolution could release them again.

Jensen, J. T.; Harstad, A. O.; Waight, T. E.; Stipp, S. L. S.

2003-04-01

93

Calcite cements in the modern Floridan aquifer  

SciTech Connect

Calcite cements in the Ocala (Eocene) and Suwannee (Oligocene) formations, southwestern Floridan aquifer have been studied to determine updip to downdip variations in cement chemistries and cathodoluminescence within a modern regional confined aquifer. Interparticle, intraparticle, and fracture-fill cements comprise 5-15% of the limestones. Five different calcite cement morphologies are distinguishable and occur throughout the aquifer: (1) circumgranular microspar, (2) fine- to medium-crystalline rhombs, (3) medium-crystalline syntaxial overgrowths on echinoderms, (4) fine-crystalline pore-filling mosaics, and (5) micrite. Type 5 occurs only below former exposure surfaces. Volumetrically, type 3 is the most important and type 4 is the least. Cathodoluminescence observations reveal only nonluminescent cements updip and an increase in luminescent zones and luminescent intensity downdip. Updip nonluminescent cements have very low Fe and Mn concentrations, but high Mg and Sr concentrations. These relations are interpreted to reflect oxidizing conditions and high rock/water interaction. Fe and Mn concentrations increase and Sr and Mg contents decrease downdip. These trends are interpreted to reflect reducing conditions, cross-formational flow, and slower rock/water interaction. Downdip cathodoluminescence zonations consist of a broad nonluminescent zone, followed by a thin bright orange zone, and then a dull luminescence zone. These geochemical and luminescent patterns along a regional flow line in the confined Floridan aquifer have many similarities to those observed in calcite cements described from ancient aquifers.

Hammes, U.; Budd, D.A. (Univ. of Colorado, Boulder (United States))

1991-03-01

94

Authigenic carbonates from the Cascadia subduction zone and their relations to gas hydrate stability  

SciTech Connect

Authigenic carbonates are intercalated with massive gas hydrates in sediments of the Cascadia margin. The deposits were recovered from the uppermost 50 cm of sediments on the southern summit of the Hydrate Ridge during the RV Sonne cruise SO110. Two carbonate lithologies that differ in chemistry, mineralogy, and fabric make up these deposits. Microcrystalline high-magnesium calcite (14 to 19 mol% MgCO{sub 3}) and aragonite are present in both semiconsolidated sediments and carbonate-cemented clasts. Aragonite occurs also as a pure phase without sediment impurities. It is formed by precipitation in cavities as botryoidal and isopachous aggregates within pure white, massive gas hydrate. Variations in oxygen isotope values of the carbonates reflect the mineralogical composition and define two end members: a Mg-calcite with {delta}{sup 18}O = 4.86% PDB and an aragonite with {delta}{sup 18}O = 3.68% PDB. On the basis of the ambient bottom-water temperature and accepted equations for oxygen isotope fractionation, the authors show that the aragonite phase formed in equilibrium with its pore-water environment, and that the Mg-calcite appears to have precipitated from pore fluids enriched in {sup 18}O. Oxygen isotope enrichment probably originates from hydrate water released during gas-hydrate destabilization.

Bohrmann, G.; Greinert, J.; Suess, E. [GEOMAR, Kiel (Germany). Forschungszentrum fuer Marine Geowissenschaften] [GEOMAR, Kiel (Germany). Forschungszentrum fuer Marine Geowissenschaften; Torres, M. [Oregon State Univ., Corvallis, OR (United States). Coll. of Oceanic and Atmospheric Sciences] [Oregon State Univ., Corvallis, OR (United States). Coll. of Oceanic and Atmospheric Sciences

1998-07-01

95

Arsenic removal in conjunction with lime softening  

DOEpatents

A method for removing dissolved arsenic from an aqueous medium comprising adding lime to the aqueous medium, and adding one or more sources of divalent metal ions other than calcium and magnesium to the aqueous medium, whereby dissolved arsenic in the aqueous medium is reduced to a lower level than possible if only the step of adding lime were performed. Also a composition of matter for removing dissolved arsenic from an aqueous medium comprising lime and one or more sources of divalent copper and/or zinc metal ions.

Khandaker, Nadim R.; Brady, Patrick V.; Teter, David M.; Krumhansl, James L.

2004-10-12

96

Phytoplankton responses to biomanipulated grazing pressure and nutrient additions--enclosure studies in unlimed and limed Lake Njupfatet, central Sweden.  

PubMed

Enclosure experiments aimed to assess the role of Chaoborus larvae in regulating lower trophic levels under natural and nutrient-enriched conditions were performed in situ in the dimictic, oligotrophic clearwater Lake Njupfatet, central Sweden. One experiment was performed before, and one after, whole-lake calcite treatment. In the acidic system, total planktonic biomass (TPB; the sum of phyto-, bacterio-, protozoo-, and metazooplankton), dominated by the cyanobacterium Merismopedia, was only weakly stimulated by the nutrients while the predator had no effect. In the limed environment, TPB increased strongly in response to the nutrients in combination with a negative response to the predator. Principally phytoplankton, but also bacterioplankton and protozooplankton (ciliates) were stimulated by the nutrients. It is argued that Merismopedia acted as a dead-end in the energy flow in the acidic system. Liming resulted in the disappearance of Merismopedia and this opened the flow of material to higher trophic levels. Since liming also led to a significant reduction in the concentrations of phosphorus in the lake water, it is proposed that a combination of liming and gentle fertilization might be used to restore the productivity of acidified lakes. PMID:11202737

Blomqvist, P

2001-01-01

97

Effects of calcite and magnesite application to a declining Masson pine forest on strongly acidified soil in Southwestern China.  

PubMed

Liming of strongly acidified soil under a Masson pine (Pinus massoniana Lamb.) forest was studied through a seven-year field manipulation experiment at Tieshanping, Chongqing in Southwestern China. To distinguish between the individual effects of Ca(2+) and Mg(2+) addition, we separately applied calcite (CaCO3) and magnesite (MgCO3), rather than using dolomite [CaMg(CO3)2]. Both calcite and magnesite additions caused a significant increase in pH and a decrease in dissolved inorganic monomeric aluminium (Ali) concentration of soil water. Ecological recovery included increases of herb biomass (both treatments) and Mg content in Masson pine needles (magnesite treatment only). However, the growth rate of Masson pine did not increase under either treatment, possibly because of nutrient imbalance due to phosphorus (P) deficiency or limited observation period. In China, acid deposition in forest ecosystems commonly coincides with large inputs of atmogenic Ca(2+), both enhancing Mg(2+) leaching. Calcite addition may further decrease the Mg(2+) availability in soil water, thereby exacerbating Mg(2+) deficiency in the acidified forest soils of southern and southwestern China. The effect of anthropogenic acidification of naturally acid forest soils on P availability needs further study. PMID:24631610

Huang, Yongmei; Kang, Ronghua; Ma, Xiaoxiao; Qi, Yu; Mulder, Jan; Duan, Lei

2014-05-15

98

Effect of whole catchment liming on the episodic acidification of two adirondack streams  

USGS Publications Warehouse

During the fall of 1989 7.7Mg/ha of calcium carbonate was applied on two tributary catchments (40 ha and 60 ha) to Woods Lake, a small (25 ha) acidic headwater lake in the western Adirondack region of New York. Stream-water chemistry in both catchment tributaries responded immediately. Acid-neutralizing capacity (ANC) increased by more than 200 ??eq/L in one of the streams and more than 1000 ??eq/L in the other, from pre-liming values which ranged from -25 to +40 ??eq/L. The increase in ANC was primarily due to increases in dissolved Ca2+ concentrations. Most of the initial response of the streams was due to the dissolution of calcite that fell directly into the stream channels and adjacent wetlands. A small beaver impoundment and associated wetlands were probably responsible for the greater response observed in one of the streams. After the liming of subcatchmentIV (60 ha), Ca2+ concentrations increased with increasing stream discharge in the stream during fall rain events, suggesting a contribution from calcite dissolved within the soil and transported to the stream by surface runoff or shallow interflow. Concentrations of other ions not associated with the calcite (e.g. Na+) decreased during fall rain events, presumably due to mixing of solute-rich base flow with more dilute shallow interflow. The strong relation between changes in Ca2+ and changes in NO3- concentrations during spring snowmelt, (r2 = 0.93, slope = 0.96, on an equivalent basis) suggests that both solutes had a common source in the organic horizon of the soil. Increases in NO3- concentrations during snowmelt were balanced by increases in Ca2+ that was released either directly from the calcite or from exchange sites, mitigating episodic acidification of the stream. However, high ambient NO3- concentrations and relatively low ambient Ca2+ concentrations in the stream during the spring caused the stream to become acidic despite the CaCO3 treatment. In stream WO2 (40ha), Ca2+ concentrations were much higher than in stream WO4 because of the dissolution of calcite which fell directly into the upstream beaver pond and its associated wetlands. Calcium concentrations decreased as both NO3- concentrations and stream discharge increased, due to the dilution of Ca-enriched beaver pond water by shallow interflow. Despite this dilution, Ca2+ concentrations were high enough to more than balance strong acid anion (SO42-, NO3-, Cl-) concentrations, resulting in a positive ANC in this stream throughout the year. These data indicate that liming of wetlands and beaver ponds is more effective than whole catchment liming in neutralizing acidic surface waters. ?? 1996 Kluwer Academic Publishers.

Newton, R.M.; Burns, D.A.; Blette, V.L.; Driscoll, C.T.

1996-01-01

99

FULL SCALE DEMONSTRATION OF LIME STABILIZATION  

EPA Science Inventory

The project objective was to demonstrate and evaluate the feasibility, economics, and benefits of stabilizing primary, waste activated, septic, and anaerobically digested sludges by lime addition. The project confirmed the findings of previous laboratory and pilot scale tests and...

100

Lime and Phosphoric Acid Requirements for Chicks.  

E-print Network

t 1 BRARY, A & COLLEGE, CAhTPUS. :XAS AGRICULTURAL EXPERIMENT STATION A. B. CONNER, DIRECTOR COLLEGE STATION, BRAZOS COUNTY, TEXAS BULLETIN NO. 462 NOVEMBER, 1932 DIVISION OF POULTRY HUSBANDRY Lime and Phosphoric Acid Requirements... and it is probable that in many cases excessive amounts of minerals are being fed. Experiments were conducted in 1930 and 1931 to determine the lime and phosphoric acid requirements for growing chicks in order that definite recommendations regarding the use...

Sherwood, R. M. (Ross Madison)

1932-01-01

101

Oxidative Lime Pretreatment of Dacotah Switchgrass  

Microsoft Academic Search

Oxidative lime pretreatment increases the enzymatic digestibility of lignocellulosic biomass primarily by removing lignin.\\u000a In this study, recommended pretreatment conditions (reaction temperature, oxygen pressure, lime loading, and time) were determined\\u000a for Dacotah switchgrass. Glucan and xylan overall hydrolysis yields (72 h, 15 FPU\\/g raw glucan) were measured for 105 different\\u000a reaction conditions involving three different reactor configurations (very short term, short term,

Matthew Falls; Rocio Sierra-Ramirez; Mark T. Holtzapple

102

Hydrate characterization research overview  

SciTech Connect

Gas hydrate research has been focused primarily on the development of a basic understanding of hydrate formation and dissociation in the laboratory, as well as in the field. Laboratory research on gas hydrates characterized the physical system, which focused on creating methane hydrates samples, tetrahydrofuran (THF) hydrate samples, consolidated rock samples, frost base mixtures, water/ice-base mixtures, and water-base mixtures. Laboratory work produced measurements of sonic velocity and electrical resistivity of hydrates. As work progressed, areas, such as the Gulf of Mexico and the Guatemala Trench, where gas hydrates are likely to occur were identified, and specific high potential areas were targeted for detailed investigation. The testing of samples and recovered cores from such areas provided information for detection of hydrate formations in the natural environment. Natural gas hydrate samples have been tested for thermal properties, dissociation properties, fracture mechanics, and optical properties. Acoustical properties were investigated both in the laboratory and, as possible, in the field. Sonic velocity and electrical resistivity measurements will continue to be obtained. These activities have been undertaken in hydrate deposits on Alaska`s North Slope, the Gulf of Mexico and the US East coast offshore, as well as other gas hydrate target areas.

Malone, R.D.

1993-06-01

103

Recycled sand in lime-based mortars.  

PubMed

The increasing awareness of the society about safe guarding heritage buildings and at the same time protecting the environment promotes strategies of combining principles of restoration with environmentally friendly materials and techniques. Along these lines, an experimental program was carried out in order to investigate the possibility of producing repair, lime-based mortars used in historic buildings incorporating secondary materials. The alternative material tested was recycled fine aggregates originating from mixed construction and demolition waste. Extensive tests on the raw materials have been performed and mortar mixtures were produced using different binding systems with natural, standard and recycled sand in order to compare their mechanical, physical and microstructure properties. The study reveals the improved behavior of lime mortars, even at early ages, due to the reaction of lime with the Al and Si constituents of the fine recycled sand. The role of the recycled sand was more beneficial in lime mortars rather than the lime-pozzolan or lime-pozzolan-cement mortars as a decrease in their performance was recorded in the latter cases due to the mortars' structure. PMID:25266158

Stefanidou, M; Anastasiou, E; Georgiadis Filikas, K

2014-12-01

104

Zinc isotope fractionation during adsorption on calcite  

NASA Astrophysics Data System (ADS)

Zinc is an important element as a nutrient in the marine biosphere. However, our understanding of its biogeochemical cycling in the oceans is relatively limited. The Zn stable isotope system holds the promise of providing novel insights, since published Zn isotopic values for various natural samples reveal significant fractionations in the marine environment. Surface seawater, basalts, shales, deep-sea clay sediments, sediment trap material, bulk plankton and zooplankton samples, and eolian dust fall within a tight range (?66/64Zn from -0.1 to 0.5‰), but modern ferromanganese crusts (?66/64Zn from 0.5 to 1.2‰), as well as carbonates (?66/64Zn from 0.3 to 1.4‰), are notably enriched in heavy Zn isotopes [1-4]. In this study we seek to constrain the mechanism by which carbonates are enriched in heavier isotopes. In particular, we have conducted experiments to quantify isotope fractionation during adsorption of Zn onto the surfaces of calcite crystals that are in equilibrium with solution. The adsorption experiments were carried out in a series of small-volume batch reactions in a clean laboratory environment, using high-purity reagents and calcite seed crystals. The calcite was equilibrated with the solution prior to addition of Zn at atmospheric CO2 pressure (i.e., in air) for 5 days until a stable pH of 8.3 was reached. Later, a small aliquot of dissolved ZnCl2 was added such that the solution remained undersaturated with respect to hydrozincite. Experimental duration varied among the replicates from 6 to 144 hours, and then all solids and solutions were separated by filtration, purified by ion exchange chromatography, and analyzed by MC-ICP-MS. Zn adsorbed on calcite is isotopically heavier than in the co-existing solutions, with ?68/66Zncalcite-solution of approximately 0.3‰. The variation of ?68/66Zncalcite-solution beyond 24 hours is insignificant, so we infer that isotopic equilibrium is reached by this time. Previous work strongly suggests that a difference in coordination number between dissolved Zn and adsorbed Zn is drives the observed fractionation. Elzinga and Reeder[5] determined using EXAFS (Extended X-ray Absorption Fine Structure) that Zn adsorbed to calcite surfaces is tetrahedrally coordinated, sharing three oxygens with the calcite surface. Meanwhile density functional theory calculations[6] predicted that tetrahedral Zn-O species should be heavier than octahedral Zn-O species. Thus we infer that equilibrium between octahedrally coordinated, dissolved Zn and tetrahedrally coordinated, adsorbed Zn is the mechanism of fractionation in our experiments. Our further studies will determine whether the isotopically heavy pool of adsorbed Zn becomes the Zn incorporated within carbonates; if so, then we are closer to understanding the mechanism by which carbonate rocks in nature are enriched in heavier isotopes of zinc. [1] Bermin et al., 2006, Chem. Geol. 226, 280. [2] Maréchal et al., 2000, Geochem. Geophys. Geosyst. 1, 1999GC-000029. [3] Dong et al., 2013, Talanta 114, 103-109. [4] Pichat et al., 2003, Earth Planet. Sci. Lett. 210, 167-178. [5] Elzinga and Reeder, 2002, Geochim. Cosmochim. Acta 66, 3943-3954. [6] Schauble, 2003, EOS, Trans. AGU, Fall Meet. Suppl. 84(46), B12B-0781.

Dong, S.; Wasylenki, L. E.

2013-12-01

105

Removal of organic magnesium in coccolithophore calcite  

NASA Astrophysics Data System (ADS)

Coccolithophore calcite refers to the plates of calcium carbonate (CaCO3) produced by the calcifying phytoplankton, coccolithophores. The empirical study of the elemental composition has a great potential in the development of paleoproxies. However, the difficulties to separate coccolithophore carbonates from organic phases hamper the investigation of coccoliths magnesium to calcium ratios (Mg/Ca) in biogeochemical studies. Magnesium (Mg) is found in organic molecules in the cells at concentrations up to 400 times higher than in inorganically precipitated calcite in present-day seawater. The aim of this study was to optimize a reliable procedure for organic Mg removal from coccolithophore samples to ensure reproducibility in measurements of inorganic Mg in calcite. Two baseline methods comprising organic matter oxidations with (1) bleach and (2) hydrogen peroxide (H2O2) were tested on synthetic pellets, prepared by mixing reagent grade CaCO3 with organic matter from the non-calcifying marine algae Chlorella autotrophica and measured with an ICP-AES (inductively coupled plasma-atomic emission spectrometer). Our results show that treatments with a reductive solution [using hydroxylamine-hydrochloride (NH2OH·HCl + NH4OH)] followed by three consecutive oxidations (using H2O2) yielded the best cleaning efficiencies, removing >99% of organic Mg in 24 h. P/Ca and Fe/Ca were used as indicators for organic contamination in the treated material. The optimized protocol was tested in dried coccolithophore pellets from batch cultures of Emiliania huxleyi, Calcidiscus leptoporus and Gephyrocapsa oceanica. Mg/Ca of treated coccolithophores were 0.151 ± 0.018, 0.220 ± 0.040, and 0.064 ± 0.023 mmol/mol, respectively. Comparison with Mg/Ca literature coccolith values, suggests a tight dependence on modern seawater Mg/Ca, which changes as a consequence of different seawater origins (<10%). The reliable determination of Mg/Ca and Sr/Ca, and the low levels of organic contamination (Fe/Ca and P/Ca) make this protocol applicable to field and laboratory studies of trace elemental composition in coccolithophore calcite.

Blanco-Ameijeiras, S.; Lebrato, M.; Stoll, H. M.; Iglesias-Rodriguez, M. D.; Méndez-Vicente, A.; Sett, S.; Müller, M. N.; Oschlies, A.; Schulz, K. G.

2012-07-01

106

Fibrous calcite from the Middle Ordovician Holston Formation (east Tennessee)  

SciTech Connect

Fibrous calcite from buildups, which occur near the top of the Middle Ordovician Holston Formation, were examined from two localities near Knoxville, TN (Alcoa Highway and Deanne Quarry). Buildups at these localities were deposited under open-marine conditions, slightly down-slope from the platform edge. Fibrous calcite (mainly radiaxial fibrous) occur most commonly as cements in mainly stromatactis structures present in bioherms and intergranular porosity in beds that flank bioherms. Fibrous calcite is interpreted to have been precipitated in a marine setting. Fibrous calcite is uniformly turbid or banded with interlayered turbid and clearer cement. Fibrous calcite most commonly shows patchy or blotchy dull-non-luminescence under cathodoluminescence. Bands of uniformly non-luminescent and relatively bright luminescent calcite are present. [delta][sup 13]C compositions of fibrous calcite vary little (0.6 to 1.0%) but [delta][sup 18]O values are highly variable ([minus]4.8 to [minus]7.1%). Post-marine cement consists of ferroan and non-ferroan, dull luminescent equant calcite ([delta][sup 13]C = 0.3 to 0.8; [delta][sup 18]O = [minus]8.6 to [minus]11.5) and is interpreted as precipitated in a deep meteoric or burial setting. Depleted [delta][sup 18]O compositions of fibrous calcite reflect addition of post-depositional calcite during stabilization. Most enriched [delta][sup 13]C and [delta][sup 18]O fibrous calcite composition are similar to enriched values from other Middle Ordovician southern Appalachian buildups (other localities of Holston (TN) and Effna (VA) formations) ([delta][sup 13]C = 0.3 to 0.8; [delta][sup 18]O = [minus]3.9 to [minus]4.8) and may reflect fibrous calcite precipitated in isotopic equilibrium with Middle Ordovician sea water.

Tobin, K.J.; Walker, K.R. (Univ. of Tennessee, Knoxville, TN (United States). Dept. of Geological Sciences)

1993-03-01

107

Global calcite cycling constrained by sediment preservation controls  

NASA Astrophysics Data System (ADS)

We assess the global balance of calcite export through the water column and burial in sediments as it varies regionally. We first drive a comprehensive 1-D model for sediment calcite preservation with globally gridded field observations and satellite-based syntheses. We then reformulate this model into a simpler five-parameter box model, and combine it with algorithms for surface calcite export and water column dissolution for a single expression for the vertical calcite balance. The resulting metamodel is optimized to fit the observed distributions of calcite burial flux. We quantify the degree to which calcite export, saturation state, organic carbon respiration, and lithogenic sedimentation modulate the burial of calcite. We find that 46% of burial and 88% of dissolution occurs in sediments overlain by undersaturated bottom water with sediment calcite burial strongly modulated by surface export. Relative to organic carbon export, we find surface calcite export skewed geographically toward relatively warm, oligotrophic areas dominated by small, prokaryotic phytoplankton. We assess century-scale projected impacts of warming and acidification on calcite export, finding high sensitive to inferred saturation state controls. With respect to long-term glacial cycling, our analysis supports the hypothesis that strong glacial abyssal stratification drives the lysocline toward much closer correspondence with the saturation horizon. Our analysis suggests that, over the transition from interglacial to glacial ocean, a resulting ˜0.029 PgC a-1decrease in deep Atlantic, Indian and Southern Ocean calcite burial leads to slow increase in ocean alkalinity until Pacific mid-depth calcite burial increases to compensate.

Dunne, John P.; Hales, Burke; Toggweiler, J. R.

2012-09-01

108

Improved control of sucrose losses and clarified juice turbidity with lime saccharate in hot lime clarification of sugarcane juice and other comparisons with milk of lime  

Technology Transfer Automated Retrieval System (TEKTRAN)

A comparative investigation of adding milk of lime (MOL) versus lime saccharate (SACCH) in hot lime clarification of juice at a U.S. sugarcane factory was undertaken to quantify performance across the 2009 processing season after a preliminary factory study in 2008. SACCH was prepared by adding hyd...

109

Calcite dissolution: Effects of trace cations naturally present in Iceland spar calcites  

NASA Astrophysics Data System (ADS)

In situ dissolution experiments on a set of pure, optical quality Iceland spar calcite samples from four different localities showed etch pit step retreat rates to be inversely proportional to total inherent trace cation composition. Atomic absorption spectroscopy (AAS) revealed Fe 2+, Mg 2+, Mn 2+ and Sr 2+ in amounts varying from a few to hundreds of ppm. We used a very simple experimental set-up, with an Atomic Force Microscope (AFM) fluid cell and a droplet of MilliQ water. As the calcite dissolved and approached equilibrium with the solution, trace cations were released, which were then present for interaction with the dissolving surface. We monitored continuous free-drift dissolution, in situ, on fresh {101¯4} cleavage surfaces for up to 40 min. Dissolution produced one-layer-deep, rhombic etch pits that continually expanded as we collected images. The rhombohedral symmetry of calcite defines two obtuse and two acute edges on the cleavage surface of etch pits and these, as expected from previous work, had different dissolution rates. Despite identical experimental conditions for all samples, we observed lower step retreat rates for both obtuse and acute edges on calcite characterised by relatively high trace cation composition. Increased cation concentration, particularly Mn, was also correlated with rounding of obtuse-obtuse corners, resulting in obtuse step retreat rates similar to those for acute sides. Physcial limitations of the AFM technique were taken into account when measuring step rate retreat and results were collected only from single-layer etch pits, which represent crystalline calcite with minimal defects. Dissolution rates presented here are thus lower than previous reports for studies of deep etch pits and where the physical limitations of imaging may not have been considered. In addition to molecular-level proof that divalent cations inherent at ppm levels in the calcite affect the dissolution process, these results show that pure, optical quality Iceland spar calcite should not be considered pure in the chemical sense. The results imply that dissolution rates determined for ideal systems with pure, synthetic or natural, materials may be considered as the boundary condition for dissolution in real systems in nature, where cations are always present both in the solution and in the initial solid.

Harstad, A. O.; Stipp, S. L. S.

2007-01-01

110

A mild alkali treated jute fibre controlling the hydration behaviour of greener cement paste  

NASA Astrophysics Data System (ADS)

To reduce the antagonistic effect of jute fibre on the setting and hydration of jute reinforced cement, modified jute fibre reinforcement would be a unique approach. The present investigation deals with the effectiveness of mild alkali treated (0.5%) jute fibre on the setting and hydration behaviour of cement. Setting time measurement, hydration test and analytical characterizations of the hardened samples (viz., FTIR, XRD, DSC, TGA, and free lime estimation) were used to evaluate the effect of alkali treated jute fibre. From the hydration test, the time (t) required to reach maximum temperature for the hydration of control cement sample is estimated to be 860 min, whilst the time (t) is measured to be 1040 min for the hydration of a raw jute reinforced cement sample. However, the time (t) is estimated to be 1020 min for the hydration of an alkali treated jute reinforced cement sample. Additionally, from the analytical characterizations, it is determined that fibre-cement compatibility is increased and hydration delaying effect is minimized by using alkali treated jute fibre as fibre reinforcement. Based on the analyses, a model has been proposed to explain the setting and hydration behaviour of alkali treated jute fibre reinforced cement composite.

Jo, Byung-Wan; Chakraborty, Sumit

2015-01-01

111

A mild alkali treated jute fibre controlling the hydration behaviour of greener cement paste  

PubMed Central

To reduce the antagonistic effect of jute fibre on the setting and hydration of jute reinforced cement, modified jute fibre reinforcement would be a unique approach. The present investigation deals with the effectiveness of mild alkali treated (0.5%) jute fibre on the setting and hydration behaviour of cement. Setting time measurement, hydration test and analytical characterizations of the hardened samples (viz., FTIR, XRD, DSC, TGA, and free lime estimation) were used to evaluate the effect of alkali treated jute fibre. From the hydration test, the time (t) required to reach maximum temperature for the hydration of control cement sample is estimated to be 860?min, whilst the time (t) is measured to be 1040?min for the hydration of a raw jute reinforced cement sample. However, the time (t) is estimated to be 1020?min for the hydration of an alkali treated jute reinforced cement sample. Additionally, from the analytical characterizations, it is determined that fibre-cement compatibility is increased and hydration delaying effect is minimized by using alkali treated jute fibre as fibre reinforcement. Based on the analyses, a model has been proposed to explain the setting and hydration behaviour of alkali treated jute fibre reinforced cement composite. PMID:25592665

Jo, Byung-Wan; Chakraborty, Sumit

2015-01-01

112

Friction characteristics of Cd-rich carbonate films on calcite surfaces: implications for compositional differentiation at the nanometer scale  

PubMed Central

Lateral Force Microscopy (LFM) studies were carried out on cleaved calcite sections in contact with solutions supersaturated with respect to otavite (CdCO3) or calcite-otavite solid solutions (SS) as a means to examine the potential for future application of LFM as a nanometer-scale mineral surface composition mapping technique. Layer-by-layer growth of surface films took place either by step advancement or by a surface nucleation and step advancement mechanisms. Friction vs. applied load data acquired on the films and the calcite substrate were successfully fitted to the Johnson Kendall Roberts (JKR) model for single asperity contacts. Following this model, friction differences between film and substrate at low loads were dictated by differences in adhesion, whereas at higher load they reflect differences in contact shear strength. In most experiments at fixed load, the film showed higher friction than the calcite surface, but the friction-load dependence for the different surfaces revealed that at low loads (0–40 nN), a calcian otavite film has lower friction than calcite; a result that is contrary to earlier LFM reports of the same system. Multilayer films of calcian-otavite displayed increasing friction with film thickness, consistent with the expectation that the film surface composition will become increasingly Cd-rich with increasing thickness. Both load- and thickness-dependence trends support the hypothesis that the contact shear strength correlates with the hydration enthalpy of the surface ions, thereby imparting friction sensitivity in the LFM to mineral-water interface composition. PMID:19549312

2009-01-01

113

Methane Hydrate Field Program  

SciTech Connect

This final report document summarizes the activities undertaken and the output from three primary deliverables generated during this project. This fifteen month effort comprised numerous key steps including the creation of an international methane hydrate science team, determining and reporting the current state of marine methane hydrate research, convening an international workshop to collect the ideas needed to write a comprehensive Marine Methane Hydrate Field Research Plan and the development and publication of that plan. The following documents represent the primary deliverables of this project and are discussed in summary level detail in this final report. • Historical Methane Hydrate Project Review Report • Methane Hydrate Workshop Report • Topical Report: Marine Methane Hydrate Field Research Plan • Final Scientific/Technical Report

None

2013-12-31

114

Origins of hydration lubrication  

NASA Astrophysics Data System (ADS)

Why is friction in healthy hips and knees so low? Hydration lubrication, according to which hydration shells surrounding charges act as lubricating elements in boundary layers (including those coating cartilage in joints), has been invoked to account for the extremely low sliding friction between surfaces in aqueous media, but not well understood. Here we report the direct determination of energy dissipation within such sheared hydration shells. By trapping hydrated ions in a 0.4–1 nm gap between atomically smooth charged surfaces as they slide past each other, we are able to separate the dissipation modes of the friction and, in particular, identify the viscous losses in the subnanometre hydration shells. Our results shed light on the origins of hydration lubrication, with potential implications both for aqueous boundary lubricants and for biolubrication.

Ma, Liran; Gaisinskaya-Kipnis, Anastasia; Kampf, Nir; Klein, Jacob

2015-01-01

115

Sorption and desorption of arsenate and arsenite on calcite  

NASA Astrophysics Data System (ADS)

The adsorption and desorption of arsenate (As(V)) and arsenite (As(III)) on calcite was investigated in a series of batch experiments in calcite-equilibrated solutions. The solutions covered a broad range of pH, alkalinity, calcium concentration and ionic strength. The initial arsenic concentrations were kept low (<33 ?M) to avoid surface precipitation. The results show that little or no arsenite sorbs on calcite within 24 h at an initial As concentration of 0.67 ?M. In contrast, arsenate sorbs readily and quickly on calcite. Likewise, desorption of arsenate from calcite is fast and complete within hours, indicating that arsenate is not readily incorporated into the calcite crystal lattice. The degree of arsenate sorption depends on the solution chemistry. Sorption increases with decreasing alkalinity, indicating a competition for sorption sites between arsenate and (bi)carbonate. pH also affects the sorption behavior, likely in response to changes in arsenate speciation or protonation/deprotonation of the adsorbing arsenate ion. Finally, sorption is influenced by the ionic strength, possibly due to electrostatic effects. The sorption of arsenate on calcite was modeled successfully using a surface complexation model comprising strong and weak sites. In the model, the adsorbing arsenate species were HAsO4- and CaHAsO40. The model was able to correctly predict the adsorption of arsenate in the wide range of calcite-equilibrated solutions used in the batch experiments and to describe the non-linear shape of the sorption isotherms. Extrapolation of the experimental results to calcite bearing aquifers suggests a large variability in the mobility of arsenic. Under reduced conditions, arsenite, which does not sorb on calcite, will dominate and, hence, As will be highly mobile. In contrast, when conditions are oxidizing, arsenate is the predominant species and, because arsenate adsorbs strongly on calcite, As mobility will be significantly retarded. The estimated retardation factors for arsenate in carbonate aquifers range from 25 to 200.

Sø, Helle U.; Postma, Dieke; Jakobsen, Rasmus; Larsen, Flemming

2008-12-01

116

Hydration-dependent dynamic crossover phenomenon in protein hydration water  

E-print Network

The characteristic relaxation time ? of protein hydration water exhibits a strong hydration level h dependence. The dynamic crossover is observed when h is higher than the monolayer hydration level h[subscript c] =0.2–0.25 ...

Wang, Zhe

117

A field application for lime stabilization  

NASA Astrophysics Data System (ADS)

This study presents the improvements achieved as a result of the lime stabilization application conducted by the joint effort of the Turkish Association of Lime Industrialists and the General Directorate of Rural Services on the 200 m long section of the Ankara Province Yukar? Yurtçu Village road where green and brown clays are dominant. The study also numerically demonstrates the impacts of these improvements on the road section based on the results of various laboratory and field tests. The lime stabilization in field conditions was performed with 5% lime for both clays and was applied as a 30 cm thick single layer. In the soaked California bearing-ratio (CBR) tests conducted in the laboratory, increases that reach up from 16 and 21 times compared to initial soaked CBR values were observed in green and brown clays, respectively, at the end of 28 days. The high increases observed in soaked CBR values would reduce the upper layer thickness of the roads. The similar improvements are also achieved in unconfined compression and plate loading tests. The comparisons performed with the plate loading tests clearly demonstrated the behavior of the surface to lime and its cure impact.

Kavak, Ayd?n; Akyarl?, Adnan

2007-01-01

118

Experimental pressure solution compaction of synthetic halite\\/calcite aggregates  

Microsoft Academic Search

Experimental observations are reported of weakening of sediment-like aggregates by addition of hard particles. Sieved mixtures of calcite and halite grains are experimentally compacted in drained pressure cells in the presence of a saturated aqueous solution. The individual halite grains deform easily by pressure solution creep whereas calcite grains act as hard objects and resist compaction. The fastest rate of

Sergey Zubtsova; François Renard; Jean-Pierre Gratier; Robert Guiguet; Dag K. Dysthe; Vladimir Traskine

2004-01-01

119

62. INTERIOR VIEW OF THE LIME KILN BUILDING, LOOKING AT ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

62. INTERIOR VIEW OF THE LIME KILN BUILDING, LOOKING AT THE LIME KILNS AND MOTOR DRIVES FOR THE KILNS. (DATE UNKNOWN). - United States Nitrate Plant No. 2, Reservation Road, Muscle Shoals, Muscle Shoals, Colbert County, AL

120

LIME KILN BUILDING, KILN BOTTOM SHOWING ROTATOR GEAR. (GEAR IS ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

LIME KILN BUILDING, KILN BOTTOM SHOWING ROTATOR GEAR. (GEAR IS POINTED DOWN FOR PROPER ORIENTATION). - Solvay Process Company, Lime Kiln Building, Between Willis & Milton Avenues, Solvay, Onondaga County, NY

121

VIEW OF TUNNEL TO MLT BUILDING UNDER LIME KILNS. CONVEYOR ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

VIEW OF TUNNEL TO MLT BUILDING UNDER LIME KILNS. CONVEYOR MOVES HOT STONE TO MLT'S. THIS IS THE DRIVE END OF CONVEYOR BELT. - Solvay Process Company, Milk of Lime Towers Building, Between Willis & Milton Avenues, Solvay, Onondaga County, NY

122

VIEW OF TUNNEL TO MLT BUILDING UNDER LIME KILNS, CONVEYOR ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

VIEW OF TUNNEL TO MLT BUILDING UNDER LIME KILNS, CONVEYOR MOVES HOT STONE TO MLT'S (CONVEYOR ON RIGHT). - Solvay Process Company, Milk of Lime Towers Building, Between Willis & Milton Avenues, Solvay, Onondaga County, NY

123

Determination of the pozzolanic activity of fluid catalytic cracking residue. Thermogravimetric analysis studies on FC3R-lime pastes  

SciTech Connect

Spent fluid catalytic cracking catalyst (FC3R) from a petrol refinery played a pozzolanic role in portland cement system as revealed by previous experimental data. In the present study, the pozzolanic activity of FC3R was investigated by means thermogravimetry (TG) of cured lime-FC3R pastes. The influence of pozzolan/lime ratio on the pozzolanic activity was investigated. Due to the chemical composition of FC3R is similar to metakaolin (MK), and knowing that MK has a high pozzolanic activity, the latter was used as a material of comparison in this study. The scope of the study is the determination of the pozzolanic activity of FC3R and the evaluation of amount and nature of pozzolanic products. The products obtained from the reaction between FC3R components (SiO{sub 2}/Al{sub 2}O{sub 3}) and calcium hydroxide (CH) have been characterized, finding that the main pozzolanic reaction product was similar to hydrated gehlenite (calcium aluminosilicate hydrate) CSH and CAH were also formed in the reaction. FC3R showed higher pozzolanic reactivity than metakaolin, for low-lime content pastes and early curing age. Thermogravimetry, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) became very useful techniques for evaluation of reactivity.

Paya, J.; Monzo, J.; Borrachero, M.V.; Velazquez, S.; Bonilla, M

2003-07-01

124

An improved clearing and mounting solution to replace chloral hydrate in microscopic applications1  

PubMed Central

• Premise of the study: This study presents Visikol™, a new proprietary formulation that can be used as an efficient replacement for chloral hydrate as a clearing agent for microscopic examination. In the United States, chloral hydrate is regulated and therefore difficult to acquire. • Methods and Results: Fresh and dry samples of the following plants: ginger (Zingiber officinale), maté (Ilex paraguariensis), lime basil (Ocimum americanum), oregano (Origanum vulgare), and mouse-ear cress (Arabidopsis thaliana), were cleared using Visikol or chloral hydrate solution and compared using a light microscope. • Conclusions: This new method can be used successfully to clear specimens, allowing identification of diagnostic characteristics for the identification of plant materials. Visikol is as effective as chloral hydrate in providing clarity and resolution of all tissues examined. Tissues become transparent, allowing observation of deeper layers of cells and making it effective in research, botanical and quality control, and for educational applications. PMID:25202549

Villani, Thomas S.; Koroch, Adolfina R.; Simon, James E.

2013-01-01

125

LIME STABILIZATION AND ULTIMATE DISPOSAL OF MUNICIPAL WASTEWATER SLUDGES  

EPA Science Inventory

Twenty-eight lime stabilization facilities were visited. None of these plants were originally designed for sludge lime stabilization. Lime stabilization was instituted either as a permanent sludge handling mechanism to replace a more costly process, as an interim sludge handling ...

126

Gas Hydrates Burning  

USGS Multimedia Gallery

An image of gas hydrates burning. Gas hydrates are naturally-occurring “ice-like” combinations of natural gas and water that have the potential to provide an immense resource of natural gas from the world’s oceans and polar regions....

127

Mallik Gas Hydrate Sample  

USGS Multimedia Gallery

A sample of gas hydrates collected from Mallik, Canada. Gas hydrates are naturally-occurring “ice-like” combinations of natural gas and water that have the potential to provide an immense resource of natural gas from the world’s oceans and polar regions....

128

Effects of lime rate, lime ECCE, and B rate on rose clover and coastal bermudagrass dry matter yields  

E-print Network

~), followed by Lz and Lo, respectively. Lime particle size did not affect rose clover dry matter yields. Boron rate 1 (B~) resulted in higher dry matter yields than Bz and Bo. Lime rate and B rate did not affect Coastal bermudagrass dry matter yields... Soil Infertility . Aluminum Toxicity Manganese Toxicity Liming Acid Soils Boron in Soils Boron Adsorpion in Soils Forage Response to Liming and B Applications . . . Page Vl . . . . . Vll . . x XIV . . 3 . . 3 . . 5 . . 7...

Villavicencio Batres, Rodolfo

1990-01-01

129

Oriented Calcite Micropillars and Prisms Formed through Aggregation and Recrystallization of Poly(Acrylic Acid) Stabilized  

E-print Network

Oriented Calcite Micropillars and Prisms Formed through Aggregation and Recrystallization of Poly+ into oriented calcite micropillars with {104} faceted coaligned platelike subunits. Moreover, in situ AFM

Qi, Limin

130

MICROWAVE ASSISTED EXTRACTION OF LIME PECTIN  

Technology Transfer Automated Retrieval System (TEKTRAN)

Pectin was extracted from lime flavedo, albedo and pulp by employing microwave assisted extraction (MAE) under pressure. Advantages of MAE over conventional heating methods in the extraction of pectin from citrus residues include 10 fold or better reduction in heating time, better control of extrac...

131

Fertilizer and Lime: Why They Are Used.  

ERIC Educational Resources Information Center

This unit teaching guide is designed to help teachers explain the principles of fertilizer and lime use. The first of four major sections is a teaching outline keyed to transparency masters and student handouts. Thirteen major areas are covered in the teaching outline: (1) plant needs; (2) uses of fertilizer; (3) nutrients for plant growth; (4)…

McCaslin, Judith Strand

132

Microstructure evolution of lime putty upon aging  

NASA Astrophysics Data System (ADS)

The microstructure evolution of lime putty upon aging was investigated by slaking quicklime (CaO) with an excess of water for 3, 12, 24, 36, 48 and 66 months. The as-obtained lime putties were characterized in the water retention and in the particle size distribution using the static laser scattering (SLS). The same lime putties, dehydrated by lyophilization, were also investigated in the pore size distribution by mercury intrusion porosimetry, in the surface area by the BET method and, finally, in particle morphology by scanning electron microscopy (SEM). The effect of the extended exposure of quicklime to water confirms a shape change from prismatic crystals of portlandite, Ca(OH) 2, into platelike ones. Simultaneously a growth of larger hexagonal crystals at the expense of the smallest ones (Ostwald ripening) favours a secondary precipitation of submicrometer platelike crystals of portlandite. The shape change and the broader particles size distribution of portlandite crystals upon aging seem to contribute to a better plasticity of lime putty.

Mascolo, Giuseppe; Mascolo, Maria Cristina; Vitale, Alessandro; Marino, Ottavio

2010-08-01

133

Chromium behavior during cement-production processes: A clinkerization, hydration, and leaching study  

Microsoft Academic Search

The behavior of chromium during the production of cement clinker, during the hydration of cement and during the leaching of cement mortars was investigated. The microstructures of clinker and mortar properties were investigated using free lime, XRD, SEM\\/EDS, and TG\\/DTA techniques. Chromium was found to be incorporated in the clinker phase. The formation of new chromium compounds such as Ca6Al4Cr2O15,

Suthatip Sinyoung; Prayoon Songsiriritthigul; Suwimol Asavapisit; Puangrat Kajitvichyanukul

2011-01-01

134

Calcite surface structure and reactivity: molecular dynamics simulations and macroscopic surface modelling of the calcite-water interface.  

PubMed

Calcite-water interactions are important not only in carbon sequestration and the global carbon cycle, but also in contaminant behaviour in calcite-bearing host rock and in many industrial applications. Here we quantify the effect of variations in surface structure on calcite surface reactivity. Firstly, we employ classical Molecular Dynamics simulations of calcite surfaces containing an etch pit and a growth terrace, to show that the local environment in water around structurally different surface sites is distinct. In addition to observing the expected formation of more calcium-water interactions and hydrogen-bonds at lower-coordinated sites, we also observed subtle differences in hydrogen bonding around acute versus obtuse edges and corners. We subsequently used this information to refine the protonation constants for the calcite surface sites, according to the Charge Distribution MUltiSite Ion Complexation (CD-MUSIC) approach. The subtle differences in hydrogen bonding translate into markedly different charging behaviour versus pH, in particular for acute versus obtuse corner sites. The results show quantitatively that calcite surface reactivity is directly related to surface topography. The information obtained in this study is not only crucial for the improvement of existing macroscopic surface models of the reactivity of calcite towards contaminants, but also improves our atomic-level understanding of mineral-water interactions. PMID:23042085

Wolthers, M; Di Tommaso, D; Du, Z; de Leeuw, N H

2012-11-21

135

Subaerial meteoric calcitization and lithification of high-magnesian calcite muds, Belize  

SciTech Connect

Holocene ({lt}1000-1500 yrs old) high-magnesian calcite-dominated muddy sediments (1 m thick) on subaerially exposed cays in northern Belize are in the process of being converted to low-magnesian calcite micrite. Mineralogic stabilization and attendant lithification result from interaction of the sediments with meteoric fluids believed to be derived from seasonal upward discharge through subjacent Pleistocene limestones. The initial marine-derived sediments, composed of {gt}85% HMC (and minor skeletal aragonite), consist of mud and associated soritid and miliolid foraminifera both with MgCO{sub 3} content of 11-15 mol%, and isotopic compositions of -1.0 to -2.5{per thousand} PDB (O), 0 to +1.5{per thousand} PDB (C). With depth, lithified LMC crusts appear in the section, and the Mg concentration of the sediments and associated crusts decreases rapidly to 3 mol% or less, with a corresponding isotopic depletion to values approaching -7.0{per thousand} (O) and -5.8{per thousand} (C). Concomitantly there is progressive dissolution of skeletal aragonite in the sediments, reduction of porosity due to cementation by LMC, and in the muds, a decrease in Sr and increase in Mn contents. The resultant petrofabric of these lithified LMC deposits, derived from the alteration of HMC-dominated muds, is characterized by micrite with patches of pore-filling micritic and microsparitic LMC cements. Such a fabric is similar to and can be confused easily with calcitized aragonite-dominated precursor muds, except for the relative rarity in the samples examined of aragonite relicts in component microspar and/or pseudospar.

Mazzullo, S.J.; Bischoff, W.D. (Wichita State Univ., KS (United States))

1991-03-01

136

Calcite crystal growth rate inhibition by polycarboxylic acids  

USGS Publications Warehouse

Calcite crystal growth rates measured in the presence of several polycarboxyclic acids show that tetrahydrofurantetracarboxylic acid (THFTCA) and cyclopentanetetracarboxylic acid (CPTCA) are effective growth rate inhibitors at low solution concentrations (0.01 to 1 mg/L). In contrast, linear polycarbocylic acids (citric acid and tricarballylic acid) had no inhibiting effect on calcite growth rates at concentrations up to 10 mg/L. Calcite crystal growth rate inhibition by cyclic polycarboxyclic acids appears to involve blockage of crystal growth sites on the mineral surface by several carboxylate groups. Growth morphology varied for growth in the absence and in the presence of both THFTCA and CPTCA. More effective growth rate reduction by CPTCA relative to THFTCA suggests that inhibitor carboxylate stereochemical orientation controls calcite surface interaction with carboxylate inhibitors. ?? 20O1 Academic Press.

Reddy, M.M.; Hoch, A.R.

2001-01-01

137

Defluoridation of Drinking Water by Boiling with Brushite and Calcite  

Microsoft Academic Search

Existing methods for defluoridating drinking water involve expensive high technology or are slow, inefficient and\\/or unhygienic. A new method is now suggested, encompassing brushite and calcite suspension followed by boiling. Our aim was to examine the efficiency of the method and the chemical reactions involved. Brushite, 0.3–0.5 g, and an equal weight of calcite were suspended in 1 litre water

M. J. Larsen; E. I. F. Pearce

2002-01-01

138

Comparative effectiveness of different organic and industrial wastes on peanut: Plant growth, yield, oil content, protein content, mineral composition and hydration coefficient of kernels  

Microsoft Academic Search

The present study aimed to evaluate the relative efficacy of different organic and industrial wastes, namely, farmyard manure (FYM), water hyacinth (WH) and paper factory sludge (PFS) in combination with chemical fertilizer (CF) along with or without soil amendments like lime or rice husk ash (RHA) on plant growth, yield, mineral composition, oil content, protein content and hydration coefficient of

Manisha Basu; Pratap Bhanu Singh Bhadoria; Subhas Chandra Mahapatra

2007-01-01

139

The calcium silicate hydrates  

Microsoft Academic Search

This article is concerned with the calcium silicate hydrates, including crystalline minerals and the extremely variable and poorly ordered phase (C-S-H) that is the main binding phase in most concrete. Up-to-date composition and crystal-structure information is tabulated for the most important crystalline calcium (alumino) silicate hydrates and related phases. A number of models for the nanostructure of C-S-H are summarized

I. G. Richardson

2008-01-01

140

Uptake of chloride and carbonate ions by calcium monosulfoaluminate hydrate  

SciTech Connect

Decommissioning of old nuclear reactors may produce waste streams containing chlorides and carbonates, including radioactive {sup 36}Cl{sup -} and {sup 14}CO{sub 3}{sup 2-}. Their insolubilization by calcium monosulfoaluminate hydrate was investigated. Carbonates were readily depleted from the solution, giving at thermodynamic equilibrium monocarboaluminate, monocarboaluminate + calcite, or calcite only, depending on the initial ratio between the anion and calcium monosulfoaluminate hydrate. Chloride ions reacted more slowly and were precipitated as Kuzel's salt, Kuzel's and Friedel's salts, or Friedel's salt only. Rietveld refinement of X-Ray powder diffraction patterns was successfully used to quantify the phase distributions, which were compared to thermodynamic calculations. Moreover, analysing the lattice parameters of Kuzel's salt as a function of its chloride content showed the occurrence of a restricted solid solution towards the sulfate side with general formula 3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}xCaCl{sub 2}{center_dot}(1 - x)CaSO{sub 4}{center_dot}(12 - 2x){center_dot}H{sub 2}O (0.36 {<=} x {<=} 0.50).

Mesbah, Adel [Commissariat a l'Energie Atomique et aux Energies Alternatives, CEA DEN/DTCD/SPDE, F-30207 Bagnols sur Ceze (France); Clermont Universite, ENSCCF, Laboratoire des Materiaux Inorganiques, BP 10448, F-63000 Clermont-Ferrand (France); Cau-dit-Coumes, Celine, E-mail: celine.cau-dit-coumes@cea.fr [Commissariat a l'Energie Atomique et aux Energies Alternatives, CEA DEN/DTCD/SPDE, F-30207 Bagnols sur Ceze (France); Renaudin, Guillaume [Clermont Universite, ENSCCF, Laboratoire des Materiaux Inorganiques, BP 10448, F-63000 Clermont-Ferrand (France); CNRS, UMR 6002, F-63177 Aubiere (France); Frizon, Fabien [Commissariat a l'Energie Atomique et aux Energies Alternatives, CEA DEN/DTCD/SPDE, F-30207 Bagnols sur Ceze (France); Leroux, Fabrice [Clermont Universite, Universite Blaise Pascal, Laboratoire des Materiaux Inorganiques, BP 10448, F-63000 Clermont-Ferrand (France); CNRS, UMR 6002, F-63177 Aubiere (France)

2012-08-15

141

Calcite Farming at Hollow Ridge Cave: Calibrating Net Rainfall and Cave Microclimate to Dripwater and Calcite Chemical Variability  

NASA Astrophysics Data System (ADS)

Stable isotope (?18O and ?13C) and trace element records in cave speleothems are often interpreted as climate changes in rainfall amount or source, cave air temperature, overlying vegetation and atmospheric pCO2. However, these records are difficult to verify without in situ calibration of changes in cave microclimate (e.g., net rainfall, interior ventilation changes) to contemporaneous variations in dripwater and speleothem chemistry. In this study at Hollow Ridge Cave (HRC) in Marianna, Florida (USA), cave dripwater, bedrock, and modern calcite (farmed in situ) were collected in conjunction with continuous cave air pCO2, temperature, barometric pressure, relative humidity, radon-222 activity, airflow velocity and direction, rainfall amount, and drip rate data [1]. We analyzed rain and dripwater ?D and ?18O, dripwater Ca2+, pH, ?13C and TCO2, cave air pCO2 and ?13C, and farmed calcite ?18O and ?13C to examine the relationships among rainwater isotopic composition, cave air ventilation, cave air temperature, calcite growth rate and seasonal timing, and calcite isotopic composition. Farmed calcite ?13C decreases linearly with distance from the front entrance to the interior of the cave during all seasons, with a maximum entrance-to-interior gradient of ??13C = -7‰ . A whole-cave "Hendy test" at distributed contemporaneous farming sites reveals that ventilation induces a +1.9 ± 0.96‰ ?13C offset between calcite precipitated in a ventilation flow path and out of flow paths. Farmed calcite ?18O exhibits a +0.82 ± 0.24‰ offset from values predicted by both theoretical calcite-water calculations and by laboratory-grown calcite [2]. Unlike calcite ?13C, oxygen isotopes show no ventilation effects and are a function only of temperature. Combining our data with other speleothem studies, we find a new empirical relationship for cave-specific water-calcite oxygen isotope fractionation across a range of temperatures and cave environments: 1000 ln ? = 16.1(1000/T) - 24.6 We analyzed anions, cations, and trace elements in dripwater, bedrock, and farmed calcite to examine the relationships between net rainfall, drip rates, drip water chemistry, and calcite chemistry. Dripwater Mg/Ca and Sr/Ca ratios fall on coherent mixing lines between three geochemical endmembers: rainwater, dissolved dolomite, and dissolved limestone. Dripwater Sr/Ca vs. Mg/Ca ratios are also influenced by evaporative enrichment within the epikarst as a function of net rainfall amount [3]. Farmed calcite trace Cation/Ca ratios faithfully track short-term seasonal variations in dripwater chemistry for Na, Mg, Sr, Ba and U. However, speleothem calibrations are unique to each drip site regardless of proximity to one another, suggesting that individual speleothems are unlikely to be useful as a whole-cave hydrologic proxy. [1] Kowalczk, A. J., Froelich, P. N., 2010. Cave air ventilation and CO2 outgassing by radon-222 modeling: How fast do caves breathe? Earth & Planet. Sci. Lett. 289, 209-219. [2] Tremaine, D. M., Froelich, P. N., Wang, Y., 2011. Speleothem calcite farmed in situ: Modern calibration of ?18O and ?13C paleoclimate proxies in a continuously-monitored natural cave system. Geochim. Cosmochim. Acta 75, 4929-4950. [3] Tremaine, D. M., Froelich, P. N., 2012. Speleothem trace element signatures: A modern hydrologic geochemical study of cave drip waters and farmed calcite. Geochim. Cosmochim. Acta (submitted)

Tremaine, D. M.; Kilgore, B. P.; Froelich, P. N.

2012-04-01

142

Depression of legume growth by liming  

Microsoft Academic Search

Summary  Early growth or nodulation of certain species was depressed when a Hawaiian Oxisol was limed at rates above 6 tons\\/ha (pH\\u000a 6). In 8 legumes, the depression later gave way to positive response. This was evident in plant weights of Desmodium intortum and Glycine wightii var. Cooper, and in pod weights of Phaseolus vulgaris. A transient depression was observed visually

D. N. Munns; R. L. Fox

1976-01-01

143

Hypothetical assessment of regional liming costs for the Adirondacks  

SciTech Connect

Previous studies of lake liming costs in the Adirondacks have developed methods for predicting liming costs for individual lakes and reported these costs both for representative and specific lakes in the region. This study develops a method for estimating lake liming costs for a large number of lakes. The specific objectives of this study consisted of developing a methodology for predicting regional lake liming costs that can be extended to other regions in the United States; developing total and marginal cost (i.e., supply) curves for liming and restocking lakes in the Adirondacks Lake region; and assessing the sensitivity of the total cost and supply curves in the Adirondack Lakes region to alternative selection criteria. Lake liming and restocking costs were estimated using a version of the DeAcid model, modified specifically for this study. 2 figs.

Tawil, J.J.; Bold, F.C. (Research Enterprises, Inc., Richland, WA (USA)); Britt, D.L.; Steiner, A.J. (International Science and Technology, Inc., Reston, VA (USA)); Callaway, J.M. (Pacific Northwest Lab., Richland, WA (USA))

1990-02-01

144

Rate limitations of lime dissolution into coal ash slag  

SciTech Connect

The rate-limiting mechanisms of lime dissolution from a solid pellet into coal ash slag and synthetic slag was investigated using an experiment involving a rotating cylinder of lime in a liquid slag bath at temperatures of 1450-1650{degree}C. Scanning electron microscopy (SEM) analysis of the slag composition around the lime cylinder was used to determine the nature of the boundary layer surrounding the pellet and the calcium concentration profile. Predictions using shrinking core models of a cylindrical pellet were compared to experimental results, suggesting that diffusion through the slag boundary layer and the change of the phase of lime from solid to liquid in the boundary layer combine to limit the process. These results indicate that a combination of controlling steps: diffusion through the boundary layer and the phase change of lime from solid to liquid, must be considered when predicting lime dissolution rates. 24 refs., 5 figs., 3 tabs.

L.K. Elliott; John A. Lucas; Jim Happ; John Patterson; Harry Hurst; Terry F. Wall [University of Newcastle, Callaghan, NSW (Australia). School of Chemical Engineering

2008-11-15

145

Calcite-specific coupling protein in barnacle underwater cement.  

PubMed

The barnacle relies for its attachment to underwater foreign substrata on the formation of a multiprotein complex called cement. The 20 kDa cement protein is a component of Megabalanus rosa cement, although its specific function in underwater attachment has not, until now, been known. The recombinant form of the protein expressed in bacteria was purified in soluble form under physiological conditions, and confirmed to retain almost the same structure as that of the native protein. Both the protein from the adhesive layer of the barnacle and the recombinant protein were characterized. This revealed that abundant Cys residues, which accounted for 17% of the total residues, were in the intramolecular disulfide form, and were essential for the proper folding of the monomeric protein structure. The recombinant protein was adsorbed to calcite and metal oxides in seawater, but not to glass and synthetic polymers. The adsorption isotherm for adsorption to calcite fitted the Langmuir model well, indicating that the protein is a calcite-specific adsorbent. An evaluation of the distribution of the molecular size in solution by analytical ultracentrifugation indicated that the recombinant protein exists as a monomer in 100 mm to 1 m NaCl solution; thus, the protein acts as a monomer when interacting with the calcite surface. cDNA encoding a homologous protein was isolated from Balanus albicostatus, and its derived amino acid sequence was compared with that from M. rosa. Calcite is the major constituent in both the shell of barnacle base and the periphery, which is also a possible target for the cement, due to the gregarious nature of the organisms. The specificity of the protein for calcite may be related to the fact that calcite is the most frequent material attached by the cement. PMID:18021251

Mori, Youichi; Urushida, Youhei; Nakano, Masahiro; Uchiyama, Susumu; Kamino, Kei

2007-12-01

146

On the complex conductivity signatures of calcite precipitation  

NASA Astrophysics Data System (ADS)

Calcite is a mineral phase that frequently precipitates during subsurface remediation or geotechnical engineering processes. This precipitation can lead to changes in the overall behavior of the system, such as flow alternation and soil strengthening. Because induced calcite precipitation is typically quite variable in space and time, monitoring its distribution in the subsurface is a challenge. In this research, we conducted a laboratory column experiment to investigate the potential of complex conductivity as a mean to remotely monitor calcite precipitation. Calcite precipitation was induced in a glass bead (3 mm) packed column through abiotic mixing of CaCl2 and Na2CO3 solutions. The experiment continued for 12 days with a constant precipitation rate of ˜0.6 milimole/d. Visual observations and scanning electron microscopy imaging revealed two distinct phases of precipitation: an earlier phase dominated by well distributed, discrete precipitates and a later phase characterized by localized precipitate aggregation and associated pore clogging. Complex conductivity measurements exhibited polarization signals that were characteristic of both phases of calcite precipitation, with the precipitation volume and crystal size controlling the overall polarization magnitude and relaxation time constant. We attribute the observed responses to polarization at the electrical double layer surrounding calcite crystals. Our experiment illustrates the potential of electrical methods for characterizing the distribution and aggregation state of nonconductive minerals like calcite. Advancing our ability to quantify geochemical transformations using such noninvasive methods is expected to facilitate our understanding of complex processes associated with natural subsurface systems as well as processes induced through engineered treatments (such as environmental remediation and carbon sequestration).

Wu, Yuxin; Hubbard, Susan; Williams, Kenneth Hurst; Ajo-Franklin, Jonathan

2010-06-01

147

Primary magmatic calcite reveals origin from crustal carbonate  

NASA Astrophysics Data System (ADS)

We have investigated lava flows representative of the whole eruptive history of the Colli Albani ultrapotassic volcanic district (Central Italy). One of the most intriguing features concerning some of these lava flows is the occurrence of primary, magmatic calcite in the groundmass. The primary, magmatic nature of calcite has been inferred by microtextural investigations showing that it typically occurs i) interstitially, associated with clinopyroxene, nepheline and phlogopite, ii) in spherical ocelli, associated with nepheline, fluorite and tangentially arranged clinopyroxene, and iii) in corona-like reaction zones around K-feldspar xenocrysts. These microtextural features distinctly indicate that calcite crystallized from a carbonate melt in a partially molten groundmass, implying that the temperature of the system was above the solidus of the hosted lava flow (> 850 °C). Geochemical features of calcite crystals (i.e., stable isotope values and trace element patterns) corroborate their primary nature and give insights into the origin of the parental carbonate melt. The trace element patterns testify to a high-temperature crystallization process (not hydrothermal) involving a carbonate melt coexisting with a silicate melt. The high ?18O (around 27‰ SMOW) and wide ?13C (- 18 to + 5‰ PDB) values measured in the calcites preclude a mantle origin, but are consistent with an origin in the crust. In this framework, the crystallization of calcite can be linked to the interaction between magmas and carbonate-bearing wall rocks and, in particular, to the entrapment of solid and/or molten carbonate in the silicate magma. The stability of carbonate melt at low pressure and the consequent crystallization of calcite in the lava flow groundmass are ensured by the documented, high activity of fluorine in the studied system and by the limited ability of silicate and carbonate melts to mix at syn-eruptive time scales.

Gozzi, Fernando; Gaeta, Mario; Freda, Carmela; Mollo, Silvio; Di Rocco, Tommaso; Marra, Fabrizio; Dallai, Luigi; Pack, Andreas

2014-03-01

148

Defluoridation of drinking water by boiling with brushite and calcite.  

PubMed

Existing methods for defluoridating drinking water involve expensive high technology or are slow, inefficient and/or unhygienic. A new method is now suggested, encompassing brushite and calcite suspension followed by boiling. Our aim was to examine the efficiency of the method and the chemical reactions involved. Brushite, 0.3-0.5 g, and an equal weight of calcite were suspended in 1 litre water containing 5-20 ppm fluoride. The suspensions were boiled in an electric kettle, left to cool and the calcium salts to sediment. Solution ion concentrations were determined and sediments were examined by X-ray diffraction. In distilled water initially containing 5, 10 and 20 ppm fluoride the concentration was reduced to 0.06, 0.4 and 5.9 ppm, respectively. Using Aarhus tap water which contained 2.6 mmol/l calcium the final concentrations were 1.2, 2.5 and 7.7 ppm, respectively, and runs without calcite gave results similar to those with calcite. Without boiling the fluoride concentration remained unaltered, as did the brushite and calcite salts, despite occasional agitation by hand. All solutions were supersaturated with respect to fluorapatite and hydroxyapatite and close to saturation with respect to brushite. Boiling produced well-crystallised apatite and traces of calcite, while boiling of brushite alone left a poorly crystallised apatite. We conclude that boiling a brushite/calcite suspension rapidly converts the two salts to apatite which incorporates fluoride if present in solution, and that this process may be exploited to defluoridate drinking water. PMID:12399694

Larsen, M J; Pearce, E I F

2002-01-01

149

Compressibility of gas hydrates.  

PubMed

Experimental data on the pressure dependence of unit cell parameters for the gas hydrates of ethane (cubic structure I, pressure range 0-2 GPa), xenon (cubic structure I, pressure range 0-1.5 GPa) and the double hydrate of tetrahydrofuran+xenon (cubic structure II, pressure range 0-3 GPa) are presented. Approximation of the data using the cubic Birch-Murnaghan equation, P=1.5B(0)[(V(0)/V)(7/3)-(V(0)/V)(5/3)], gave the following results: for ethane hydrate V(0)=1781 Å(3) , B(0)=11.2 GPa; for xenon hydrate V(0)=1726 Å(3) , B(0)=9.3 GPa; for the double hydrate of tetrahydrofuran+xenon V(0)=5323 Å(3) , B(0)=8.8 GPa. In the last case, the approximation was performed within the pressure range 0-1.5 GPa; it is impossible to describe the results within a broader pressure range using the cubic Birch-Murnaghan equation. At the maximum pressure of the existence of the double hydrate of tetrahydrofuran+xenon (3.1 GPa), the unit cell volume was 86% of the unit cell volume at zero pressure. Analysis of the experimental data obtained by us and data available from the literature showed that 1) the bulk modulus of gas hydrates with classical polyhedral structures, in most cases, are close to each other and 2) the bulk modulus is mainly determined by the elasticity of the hydrogen-bonded water framework. Variable filling of the cavities with guest molecules also has a substantial effect on the bulk modulus. On the basis of the obtained results, we concluded that the bulk modulus of gas hydrates with classical polyhedral structures and existing at pressures up to 1.5 GPa was equal to (9±2) GPa. In cases when data on the equations of state for the hydrates were unavailable, the indicated values may be recommended as the most probable ones. PMID:21717564

Manakov, Andrey Yu; Likhacheva, Anna Yu; Potemkin, Vladimir A; Ogienko, Andrey G; Kurnosov, Alexander V; Ancharov, Aleksei I

2011-09-12

150

Post-Laramide Epiorogeny through Crustal Hydration?  

NASA Astrophysics Data System (ADS)

The most perplexing part of the Cordilleran orogen in the western U.S. has been the Cenozoic uplift of broad regions with insufficient crustal shortening to produce the change in elevation following retreat of the Western Interior Seaway. These regions (most notably the High Plains, Wyoming craton, and Colorado Plateau) generally also have heat flow values comparable to much of the tectonically inactive (and low) parts of the U.S. Explanations have included dynamic effects, erosion of mantle lithosphere, cryptic crustal thickening, and hydration of the mantle lithosphere. We suggest that an alternative worthy of investigation is the hypothesis that a garnet-rich lower crust throughout the region was hydrated, producing increased buoyancy capable of driving uplift. A profile from Canada to southernmost Wyoming contains coincident increases in lower crustal hydration, decreases in lower crustal wavespeed, and increases in elevation. Xenoliths from near the Canadian border in Montana are pristine and lack hydrous alteration. Similar xenoliths from the lower crust at the 50 Ma Homestead kimberlite in central Montana have been altered such that garnet+feldspar is partially replaced by a chlorite-calcite-albite assemblage that may have occurred under high-pressure conditions, reducing the rock density from 3.19 Mg/m3 to 3.05 Mg/m3. Farther south, lower crustal hornblende granulite xenoliths from Quaternary volcanic rocks in the Leucite Hills lack garnet and exhibit evidence for hydration reactions, some of which are late Archean. Along the same general trend, the DeepProbe seismic profile yielded a ~20 km thick lower crustal layer with wavespeeds decreasing from 7.7 km/s in Canada to ~7.2 km/s in central Wyoming to <7.0 km/s in southern Wyoming (Gorman et al., 2002). If this variation coincides with a 5-10% decrease in density of this layer, 1-2 km of topography should be produced, comparable to the ~1.5 km difference observed. Evidence for late-stage deep crustal hydration has also been described from xenoliths in the Four Corners region of the Colorado Plateau (Broadhurst, 1986; Selverstone et al., 1999). The presence of a partially hydrated high-wavespeed layer at the base of the crust could complicate attempts to define the Moho using receiver functions, a problem encountered in several areas in Wyoming and the Colorado Plateau.The timing of the observed lower crustal hydration is unknown, but if related to Cenozoic uplift this implies that fluids were added in Late Cretaceous to Early Tertiary, potentially via dehydration of shallowly subducting oceanic lithosphere. If correct, this idea requires some means of passing significant amounts of fluid to the lower crust through the lithospheric mantle.

Jones, C. H.; Mahan, K. H.; Farmer, G.

2011-12-01

151

Calcite and Picocyanobacteria in Lakes: Factors Affecting Their Interaction  

NASA Astrophysics Data System (ADS)

Calcites build large deposits which have been observed in the rock record throughout geological time at various localities around the globe. Carbonate deposits have affected atmospheric carbon dioxide concentration. As it has been generally accepted, inorganic precipitation represents a source of carbon dioxide on short geological time scales and a sink of inorganic carbon at long time scales from millions to thousands of millions years. However, recent research indicates that calcite deposits may result from microbial calcification instead of inorganic precipitation. In this case the process may reduce atmospheric carbon dioxide on geologically short time scales. Thus the effect of carbonate sediment deposition on global carbon cycling depends on the origin of carbonate. Thus it is essential to understand the cause and the key parameters affecting calcite precipitation. The role of algae and bacteria in calcite formation in lakes has not been evaluated in detail. Some evidence, however, exists supporting precipitation of calcium carbonate by microbes as the origin of whiting. Several field studies on lakes have also produced puzzling results: The peaks of algal blooms were often not found at the same time as precipitation events of calcite. We suspect that parts of the discrepancies in the interpretation of field observations are due to the activity of autotrophic picoplankton. The unicellular autotrophic picoplankton (APP) is a ubiquitous component of pelagic ecosystems. But it has often been overlooked due to its small cell size of 0.2 - 2 ? m in diameter. Coccoid picocyanobacteria of the Synechococcus-type dominate the picoplankton community in most oligotrophic systems. Recently, laboratory experiments and field observations suggested that APP may play an important role in calcite precipitation. The aim of this study was to examine the influence of environmental factors such as saturation state, concentration of different dissolved ions and characteristics of the surface of cells on interaction between calcite and picocyanobacteria under both laboratory and field conditions. Laboratory experiments were performed with a picocyanobacteria strain Synechococcus-type. Using ion selective electrodes we monitored calcite precipitation induced by bacteria in the solutions of a different composition (calcium 0.7 - 48 mM, inorganic carbonate 6 - 35 ? M). Electron and atomic force microscopy measurements provided insight into the cell-mineral interface. Furthermore, quantitative investigations of the types and densities of proton binding sites on a bacterial surface will be reported from the acid-base titrations on bacteria. Results of these initial experiments are encouraging and demonstrate by direct measurements the potential of picocyanobacteria to precipitate calcite. The amount of the precipitated calcite varied in experiments with a different ratio of dissolved inorganic carbon and calcium. The microscopic observations provide some evidence that the cell walls of cyanobacteria act as a substrate of nucleation of calcite. Temporal and spatial correlations of cyanobacteria and calcite, as well as images of bacterial shape particles indicated that picoplankton plays an important role in calcite precipitation in Lake Lucerne. This class of phytoplankton has to be considered in studying the biogeochemical cycling of oligotrophic hardwater lakes.

Dittrich, M.; Obst, M.; Mavrocordatos, D.

2003-12-01

152

Nuclear anomalies in the buccal cells of calcite factory workers  

PubMed Central

The micronucleus (MN) assay on exfoliated buccal cells is a useful and minimally invasive method for monitoring genetic damage in humans. To determine the genotoxic effects of calcite dust that forms during processing, MN assay was carried out in exfoliated buccal cells of 50 (25 smokers and 25 non-smokers) calcite factory workers and 50 (25 smokers and 25 non-smokers) age- and sex-matched control subjects. Frequencies of nuclear abnormalities (NA) other than micronuclei, such as binucleates, karyorrhexis, karyolysis and ‘broken eggs', were also evaluated. Micronuclei and the other aforementioned anomalies were analysed by two way analysis of covariance. The linear correlations between the types of micronucleus and nuclear abnormalities were determined by Spearman's Rho. There was a positive correlation between micronuclei and other types of nuclear abnormalities in accordance with the Spearman's Rho test. Results showed statistically significant difference between calcite fabric workers and control groups. MN and NA frequencies in calcite fabric workers were significantly higher than those in control groups (p < 0.05). The results of this study indicate that calcite fabric workers are under risk of significant cytogenetic damage. PMID:21637497

2010-01-01

153

Sequestration of selenium on calcite surfaces revealed by nanoscale imaging  

NASA Astrophysics Data System (ADS)

Selenium is an important element because of its high toxicity in natural systems. In-situ atomic force microscopy observations of calcite surfaces during contact with selenium-bearing solutions demonstrate that selenium trapping can occur under conditions in which calcite both dissolves and precipitates. The contact of solutions containing selenium in two states of oxidation (either Se(IV ) or Se(V I)) onto a growing or dissolving calcite surface either changes the growth pattern or results in precipitates formed during dissolution. In the form of selenite (Se(IV )), but not as selenate (Se(IV )), selenium can be incorporated into calcite during growth. During dissolution, in the presence of selenate (Se(V I)), the precipitates formed remained small during the observation period. When injecting selenite (Se(IV )), the precipitates grew significantly, and were identified as CaSeO3·H2O, based on SEM observations, Raman spectroscopy and thermodynamic calculations. An interpretation is proposed where dissolution of calcite increases the calcium concentration in a thin boundary layer in contact with the surface, allowing the precipitation of a selenium phase. This process of dissolution-precipitation provides a new mechanism for selenium sequestration and extends the range of thermodynamic conditions under which such a process is efficient.

Putnis, Christine V.; Renard, François; King, Helen E.; Montes-Hernandez, German; Ruiz-Agudo, Encarnacion

2014-05-01

154

Electrical conduction and polarization of calcite single crystals  

NASA Astrophysics Data System (ADS)

The electrical conductivity and polarization properties of calcite single crystals with three orientations, namely, a (00.1) plane perpendicular to the crystallographic c axis (10.0) plane parallel to the crystallographic c axis, and a (10.4) cleavage plane, were studied by both complex impedance and thermally stimulated depolarization current (TSDC) measurements. Conductivities for (00.1)-, (10.0)-, and (10.4)-oriented single calcite crystals at 400-600 °C were 1.16 × 10-7 - 1.05 × 10-5, 7.40 × 10-8 - 4.27 × 10-6, and 4.27 × 10-7 - 2.86 × 10-5 ?-1 m-1, respectively, and the activation energies for conduction were 112, 103, and 101 kJ mol-1, respectively. The TSDC spectra verified the electrical polarizability of calcite crystals. The activation energy for depolarization, estimated from TSDC spectra, of the (00.1)-, (10.0)-, and (10.4)-oriented calcite substrates were 112, 119, and 114 kJ mol-1, respectively. Considering the correlation between the processes of conduction and electric polarization, we proposed the mechanisms of conduction and polarization in calcite on the assumption of oxide ion transport.

Wada, Norio; Horiuchi, Naohiro; Wang, Wei; Hiyama, Tetsuo; Nakamura, Miho; Nagai, Akiko; Yamashita, Kimihiro

2012-10-01

155

HYDRATE CORE DRILLING TESTS  

SciTech Connect

The ''Methane Hydrate Production from Alaskan Permafrost'' project is a three-year endeavor being conducted by Maurer Technology Inc. (MTI), Noble, and Anadarko Petroleum, in partnership with the U.S. DOE National Energy Technology Laboratory (NETL). The project's goal is to build on previous and ongoing R&D in the area of onshore hydrate deposition. The project team plans to design and implement a program to safely and economically drill, core and produce gas from arctic hydrates. The current work scope includes drilling and coring one well on Anadarko leases in FY 2003 during the winter drilling season. A specially built on-site core analysis laboratory will be used to determine some of the physical characteristics of the hydrates and surrounding rock. Prior to going to the field, the project team designed and conducted a controlled series of coring tests for simulating coring of hydrate formations. A variety of equipment and procedures were tested and modified to develop a practical solution for this special application. This Topical Report summarizes these coring tests. A special facility was designed and installed at MTI's Drilling Research Center (DRC) in Houston and used to conduct coring tests. Equipment and procedures were tested by cutting cores from frozen mixtures of sand and water supported by casing and designed to simulate hydrate formations. Tests were conducted with chilled drilling fluids. Tests showed that frozen core can be washed out and reduced in size by the action of the drilling fluid. Washing of the core by the drilling fluid caused a reduction in core diameter, making core recovery very difficult (if not impossible). One successful solution was to drill the last 6 inches of core dry (without fluid circulation). These tests demonstrated that it will be difficult to capture core when drilling in permafrost or hydrates without implementing certain safeguards. Among the coring tests was a simulated hydrate formation comprised of coarse, large-grain sand in ice. Results with this core showed that the viscosity of the drilling fluid must also be carefully controlled. When coarse sand was being cored, the core barrel became stuck because the drilling fluid was not viscous enough to completely remove the large grains of sand. These tests were very valuable to the project by showing the difficulties in coring permafrost or hydrates in a laboratory environment (as opposed to a field environment where drilling costs are much higher and the potential loss of equipment greater). Among the conclusions reached from these simulated hydrate coring tests are the following: Frozen hydrate core samples can be recovered successfully; A spring-finger core catcher works best for catching hydrate cores; Drilling fluid can erode the core and reduces its diameter, making it more difficult to capture the core; Mud must be designed with proper viscosity to lift larger cuttings; and The bottom 6 inches of core may need to be drilled dry to capture the core successfully.

John H. Cohen; Thomas E. Williams; Ali G. Kadaster; Bill V. Liddell

2002-11-01

156

COLOR REMOVAL FROM KRAFT PULPING EFFLUENT BY LIME ADDITION. CAPSULE REPORT  

EPA Science Inventory

A full scale process for lime decolorization of kraft pulping total mill effluent was operated. Slaked lime addition was followed by primary sedimentation for removal of mixed fibrous and lime decolorization sludges. The clarified effluent subsequently underwent biochemical stabi...

157

Kinetics of lime/bentonite pozzolanic reactions at 20 and 50 °C: Batch tests and modeling  

SciTech Connect

The effects of duration (1–100 days) and temperature (20 and 50 °C) were assessed from batch tests for Ca-bentonite mixed with 10 wt.% lime. The pozzolanic processes were monitored over time by {sup 29}Si NMR (Cement Concr. Res. 42, 2012), TGA-DTA, XRD and chemical analysis. Modeling considered kinetics and thermodynamics of mineralogical transformations and cation exchange. Kinetic laws were dependent on pH and temperature (Arrhenius energy). Lime hydration occurs within hours, modifying the bentonite exchangeable population and increasing the pH. These alkaline conditions initiate the pozzolanic reactions in a second stage. The rate-limiting step is the dissolution kinetics of the bentonite minerals, i.e. a relatively fast and total consumption of cristobalite in parallel to a long-term slower dissolution of montmorillonite. First C–S–H and then C–A–S–H are formed consequently. Temperature speeds up the pozzolanic reaction kinetics by a factor 5 from 20 to 50 °C, corresponding to an apparent activation energy of 40–50 kJ/mol.

De Windt, Laurent, E-mail: laurent.dewindt@mines-paristech.fr [Mines-ParisTech (Ecole des Mines de Paris), Centre de Géosciences, 35 Rue St-Honoré, 77305 Fontainebleau Cedex (France); Deneele, Dimitri [LUNAM, IFSTTAR, Institut Français des Sciences et des Technologies des Transports, de l'Aménagement et des Réseaux, BP 4129, route de Bouaye, 44332 Bouguenais (France); Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, CNRS, 2 rue de la Houssinière, BP 32229, 44322 Nantes Cedex 3 (France); Maubec, Nicolas [LUNAM, IFSTTAR, Institut Français des Sciences et des Technologies des Transports, de l'Aménagement et des Réseaux, BP 4129, route de Bouaye, 44332 Bouguenais (France)

2014-05-01

158

Rheological behaviour of hydraulic lime-based grouts. Shear-time and temperature dependence  

NASA Astrophysics Data System (ADS)

This paper deals with the coupled effect of temperature and fly ash (FA) addition on rheological behaviour of natural hydraulic lime (NHL5) based grouts, currently used in masonry consolidation. The use of a grout injection technique for masonry consolidation may lead to an increase of hydrostatic pressure and lead to structural damage. This means that the thixotropic effects become self-evident in grout design. It was shown that there is a relation between the structuration rate of each grout and the pressure that occurs inside masonry during its consolidation. According to the results, it seems also that there is a grout threshold temperature ( T limit) that separates a domain where the grout build-up structure area is almost constant, from another where flocculation area starts to increase significantly. We believe that in the first region the thixotropic effects are almost isolated from the irreversible effects (due to hydration). For the NHL5 based grout T limit=20 °C and for the grout with NHL5+15 % of FA T limit=15 °C. Grouts' characterization based on maximum resisting time, structuration rate and on the analysis of the hydraulic lime grout behaviour tested at different shear rates was performed using a shear thinning model and assuming that the structure is shear- and time-dependent. The goal is to use this methodology during mix proportioning and design for masonry injection purpose. The tested grout compositions were optimized compositions obtained in previous research using the design of experiments method.

Bras, Ana; Henriques, Fernando M. A.; Cidade, M. T.

2013-05-01

159

Lime and cement industry particulate emissions: source category report. Volume 1. Lime industry. Final report, June 1984-July 1986  

SciTech Connect

The report gives results of a study to develop particulate emission factors based on cutoff size for inhalable particles for the lime industry. After reviewing available information characterizing particulate emissions from lime plants, the data were summarized and rated in terms of reliability. Size-specific emission factors were developed from these data for the major processes used in the manufacture of lime. A detailed process description was presented with emphasis on factors affecting the generation of emissions. A replacement for Section 8.15 (Lime Manufacturing) of EPA report AP-42, Compilation of Air Pollutant Emissions Factors, was prepared, containing the size-specific emission factors developed during this program.

Kinsey, J.S.

1986-09-01

160

Time and metamorphic petrology: Calcite to aragonite experiments  

USGS Publications Warehouse

Although the equilibrium phase relations of many mineral systems are generally well established, the rates of transformations, particularly in polycrystalline rocks, are not. The results of experiments on the calcite to aragonite transformation in polycrystalline marble are different from those for earlier experiments on powdered and single-crystal calcite. The transformation in the polycrystalline samples occurs by different mechanisms, with a different temperature dependence, and at a markedly slower rate. This work demonstrates the importance of kinetic studies on fully dense polycrystalline aggregates for understanding mineralogic phase changes in nature. Extrapolation of these results to geological time scales suggests that transformation of calcite to aragonite does not occur in the absence of volatiles at temperatures below 200??C. Kinetic hindrance is likely to extend to higher temperatures in more complex transformations.

Hacker, B.R.; Kirby, S.H.; Bohlen, S.R.

1992-01-01

161

EVALUATION OF HAZARDOUS WASTE INCINERATION IN A LIME KILN: ROCKWELL LIME COMPANY  

EPA Science Inventory

During a one-week test burn, hazardous waste was used as supplemental fuel and co-fired with petroleum coke in a lime kiln in eastern Wisconsin. Detailed sampling and analysis was conducted on the stack gas for principal organic hazardous constituents (POHCs), particulates, parti...

162

Radiaxial-fibrous calcites of shallow subsurface diagenetic origin  

SciTech Connect

Radiaxial-fibrous calcites (RFC) in marine carbonates are generally considered syndepositional cements. In Upper Triassic and basal Liassic reef and platform limestones in Austria (Steinplatte complex), however, isopachous RFC is demonstrably a postdepositional diagenetic component that precipitated in shallow-burial phreatic environments during a time of periodic meteoric exposure. Isopachous RFC occurs solely within solution cavities and is interlayered with internal red sediment; discontinuities due to leaching separate sequential generations of RFC in the rocks. Accordingly, one possibility is that the RFC was originally low-magnesium calcite that precipitated in the meteoric phreatic zone during lowstands. Such calcites contain relatively low magnesium concentrations (average 0.87 mole % MgCO/sub 3/) and are /sup 18/O depleted (average - 5.81 /per thousand/ PDB). However, most other RFC cements in the sequence average slightly higher magnesium comparable to crinoidal calcites (1.13 mole % MgCO/sub 3/), are less depleted in /sup 18/O (average - 1.88 /per thousand/ PDB), and are partly dolomitized. Additionally, all the RFC cements are enriched in /sup 13/C to values similar to that of Triassic and Jurassic seawater (+ 2.86 /per thousand/ PDB) and are nonluminescent. Trace element studies indicate alteration of the rocks in partly closed, rock-dominated diagenetic systems. By these facts, the authors favor a precursor high-magnesium calcite mineralogy for the RFC cements, which possibly precipitated during highstands when meteoric pore waters were replaced by marine fluids. Thus, the geochemical trends observed are likely due to variations in the degree of meteoric alteration of high-magnesium calcite RFC rather than to differences in original mineralogy.

Mazzullo, S.J.; Bischoff, W.D.; Lobitzer, H.

1989-03-01

163

Microbially Induced Calcite Precipitation for Subsurface Immobilization of Contaminants  

NASA Astrophysics Data System (ADS)

Subsurface radionuclide and metal contaminants throughout the U.S. Department of Energy (DOE) complex pose one of the greatest challenges for long-term stewardship. One promising stabilization mechanism for divalent trace ions, such as the short-lived radionuclide 90Sr, is co-precipitation in calcite. We have found that calcite precipitation and co-precipitation of Sr can be accelerated by the activity of urea hydrolyzing microorganisms, that higher calcite precipitation rates can result in increased Sr partitioning, and that nutrient additions can stimulate ureolytic activity. To extend our understanding of microbially induced calcite precipitation (MICP) in an aquifer setting a continuous recirculation field experiment evaluating MICP was conducted at the Integrated Field Research Challenge (IFRC) site located at Rifle, CO. In this experiment, groundwater extracted from an onsite well was amended with urea (total mass of 42.5 kg) and molasses (a carbon and electron donor) and re-injected into a well approximately 4 meters up-gradient for a period of 12 days followed by 10 months of groundwater sampling and monitoring. Crosshole radar and electrical tomographic data were collected prior, during, and after the MICP treatment. The urea and molasses treatment resulted in an enhanced population of sediment associated urea hydrolyzing organisms as evidenced by increases in the number of ureC gene copies, increases in 14C urea hydrolysis rates, and long-term observations of ammonium (a urea hydrolysis product) in the injection, extraction and down gradient monitoring wells. Permeability changes and increases in the calcite saturation indexes in the well field suggest that mineral precipitation has occurred; ongoing analysis of field samples seeks to confirm this. Changes in dielectric constant and electrical conductivity were used to interpret the spatiotemporal distribution of the injectate and subsequent calcite precipitation. Modeling activities are underway to define field-scale urea hydrolysis rates.

Smith, R. W.; Fujita, Y.; Ginn, T. R.; Hubbard, S. S.; Dafflon, B.; Delwiche, M.; Gebrehiwet, T.; Henriksen, J. R.; Peterson, J.; Taylor, J. L.

2011-12-01

164

A Cretaceous scleractinian coral with a calcitic skeleton.  

PubMed

It has been generally thought that scleractinian corals form purely aragonitic skeletons. We show that a well-preserved fossil coral, Coelosmilia sp. from the Upper Cretaceous (about 70 million years ago), has preserved skeletal structural features identical to those observed in present-day scleractinians. However, the skeleton of Coelosmilia sp. is entirely calcitic. Its fine-scale structure and chemistry indicate that the calcite is primary and did not form from the diagenetic alteration of aragonite. This result implies that corals, like other groups of marine, calcium carbonate-producing organisms, can form skeletons of different carbonate polymorphs. PMID:17916731

Stolarski, Jaroslaw; Meibom, Anders; Przenioslo, Radoslaw; Mazur, Maciej

2007-10-01

165

Sulfated Macromolecules as Templates for Calcite Nucleation and Growth  

NASA Astrophysics Data System (ADS)

Mineralization of egg and seashells is controlled by an intimate association of inorganic materials with organic macromolecules. Among them, particular polyanionic sulfated macromolecules referred to as proteoglycans have been described to be involved in the calcification of these biominerals. The sulfated moieties of the proteoglycans are part of polymer chains constituted of building-blocks of disaccharide units, referred to as sulfated glycosaminoglycans (GAGs), which are covalently attached to a protein core. By using a sitting drop crystallization assay under controlled conditions of time, pH and reactants concentration, we have tested several sulfated and non-sulfated GAGs (i.e.: dermatan and keratan sulfate, hyaluronic acid and heparin), differing in their sulfonate and carboxylate degree and pattern, in their ability to modify calcium carbonate crystal morphology as observed under scanning electron microscopy. Without the addition of GAGs, regular \\{104\\} rhombohedral calcite crystals were obtained. When hyaluronic acid (HA), a non-sulfated but carboxylated GAG, was added, 20 mm long piles of unmodified calcite crystals were observed. When desulfated dermatan, which is an epimeric form of HA but shorter polymer, having their carboxylate groups in an inverted configuration, was added, isolated rhombohedral \\{104\\} calcite crystals showing rounded corners with planes oriented parallel to the c axis were observed. When dermatan sulfated was added, isolated calcite crystals exhibit a columnar morphology as a \\{hk0\\} cylinder with three \\{104\\} faces forming a cap at both ends. Heparin activity depends on the fraction added. Fast-moving heparin fraction (FM), is an undersulfated, low-molecular-weight heterogeneous polymer, while slow-moving heparin fraction (SM) is an high-molecular-weight homogeneous polymer rich in trisulfated-disaccharide units. When FM was added, isolated calcite crystals displayed rhombohedrical \\{104\\} faces but flat corners of \\{111\\} faces. The addition of the hypersulfated heparin SM induce the formation of large rosette-like aggregated calcite crystals, where the majority of the \\{104\\} faces appeared not to be lost, although aggregation is done by different kind of faces. It is concluded that, the variation of the sulfate and carboxylate content and configuration drastically changed the morphology of the calcite crystals. The production of calcite particles with defined morphologies could be interesting for the design of novel materials with desirable shape- and texture-depending properties. Granted by FONDAP 11980002.

David, M.; Passalacqua, K.; Neira, A. C.; Fernandez, M. S.

2003-12-01

166

Aluminum Sulfate 18 Hydrate  

ERIC Educational Resources Information Center

A chemical laboratory information profile (CLIP) of the chemical, aluminum sulfate 18 hydrate, is presented. The profile lists physical and harmful properties, exposure limits, reactivity risks, and symptoms of major exposure for the benefit of teachers and students using the chemical in the laboratory.

Young, Jay A.

2004-01-01

167

Lime slurry use at the Industrial Wastewater Pretreatment Facility  

SciTech Connect

The use of lime slurry at the IWPF demonstrated many benefits. Hazardous chemical use was reduced, solids handling was improved, water quality was enhanced and there has been a cost savings. The lime slurry also enabled the plant to begin treating the soluble oil waste, which we were not able to do in the past.

Rice, L.E. [Allied-Signal Aerospace Co., Kansas City, MO (United States). Kansas City Div.; Hughes, R.W. [Professional Services Group, Inc., Kansas City, MO (United States); Baggett, G. [Genex/Praxair, Inc., Kansas City, MO (United States)

1996-04-01

168

Investigation of Copper Sorption by Sugar Beet Processing Lime Waste  

EPA Science Inventory

In the western United States, sugar beet processing for sugar recovery generates a lime-based waste product (~250,000 Mg yr-1) that has little liming value in the region?s calcareous soils. This area has recently experienced an increase in dairy production, with dairi...

169

Engineering Properties of Bentonite Stabilized with Lime and Phosphogypsum  

NASA Astrophysics Data System (ADS)

Engineering properties such as compaction, unconfined compressive strength, consistency limits, percentage swell, free swell index, the California bearing ratio and the consolidation of bentonite stabilized with lime and phosphogypsum are presented in this paper. The content of the lime and phosphogypsum varied from 0 to 10 %. The results reveal that the dry unit weight and optimum moisture content of bentonite + 8 % lime increased with the addition of 8 % phosphogypsum. The percentage of swell increased and the free swell index decreased with the addition of 8 % phosphogypsum to the bentonite + 8 % lime mix. The unconfined compressive strength of the bentonite + 8 % lime increased with the addition of 8 % phosphogypsum as well as an increase in the curing period up to 14 days. The liquid limit and plastic limit of the bentonite + 8 % lime increased, whereas the plasticity index remained constant with the addition of 8 % phosphogypsum. The California bearing ratio, modulus of subgrade reaction, and secant modulus increased for the bentonite stabilized with lime and phosphogypsum. The coefficient of the consolidation of the bentonite increased with the addition of 8 % lime and no change with the addition of 8 % phosphogypsum.

Kumar, Sujeet; Dutta, Rakesh Kumar; Mohanty, Bijayananda

2014-12-01

170

Control of Particulate Emissions from Lime Plants-a Survey  

Microsoft Academic Search

Lime has become the world’s leading reagent for use in the treatment of both water and air pollution and, after sulfuric acid, is the No. 2 basic chemical in commercial use. As a result, the production capacities of the manufacturing plants are being rapidly expanded to meet the increasing demand for liming materials. This paper describes the achievements of the

L. John Minnick

1971-01-01

171

Bioconversion of lime pretreated wheat straw to fuel ethanol  

Technology Transfer Automated Retrieval System (TEKTRAN)

Lime pretreatment and enzymatic saccharification methods were evaluated for conversion of wheat straw cellulose and hemicellulose to fermentable sugars. The maximum yield of monomeric sugars from wheat straw (8.6%, w/v) by lime pretreatment (100 mg/g straw, 121 deg C, 1 h) and enzymatic hydrolysis ...

172

Fly Ash as a Liming Material for Corn Production  

Technology Transfer Automated Retrieval System (TEKTRAN)

Fly ash produced as a by-product of sub-bituminous coal combustion can potentially serve as an alternative liming material without negatively affecting corn (Zea mays L.) production in areas where use of conventional liming materials can be uneconomical due to transportation costs. A study was cond...

173

Petrology of UHP calcite marble from the Kokchetav Massif  

NASA Astrophysics Data System (ADS)

In the Kumdy-kol area, Kokchetav Massif, northern Kazakhstan, three types of UHP marbles have been described: diamond-bearing dolomite marble, Ti-clinohumite-bearing dolomitic marble (Ogasawara et al., 2000) and titanite-bearing calcite marble (Ogasawara et al., 2002). UHP calcite marble is distinguished from other types of UHP marbles by pure calcite (after aragonite) as a dominant carbonate phase. This calcite marble has unique evidence of UHP metamorphism; titanite with coesite exsolution and its precursor compositions indicated that the peak P-T conditions was > 6 GPa and 980-1250 C (Ogasawara et al., 2000; 2002). This rock shows typical granoblastic texture consisting of calcite, diopside, K-feldspar, titanite and symplectite (diopside + zoisite) after garnet. The peak assemblage was aragonite + diopside + K-feldspar + garnet + titanite. Based on the phase relations in the system CaO-MgO-TiO2-SiO2-CO2-H2O, aragonite + diopside + rutile tie-triangle is stable under UHP conditions and divides the compositional space into dolomite-bearing or dolomite-free tetrahedrons (Kikuchi et al., 2003). The presence of titanite in calcite marble means that P-T condition was located at the right-hand side of the reaction rutile + aragonite + coesite = titanite + CO2. Previously described titanite-bearing calcite marble is diamond-free (A-type) and is characterized by titanite with coesite exsolution (Ogasawara et al., 2002). Recently, we found a small amount of diamond in calcite marble (B-type) that is characterized by microdiamond in diopside, and by the lack of K-feldspar and low amount of titanite. No diamond occurs in titanite. Rutile, aragonite and calcite inclusions in titanite were found in titanite of B-type calcite marble. These three inclusion phases in titanite that were confirmed by laser Raman spectroscopy are the evidence for titanite formation reaction described above. This titanite forming reaction occurs at extremely low XCO2 conditions as 0.02. In B-type calcite marble, microdiamond occurs locally and its amount is low; only 61 grains were found in two thin sections. Distributions of titanite, K-feldspar and diamond are heterogeneous and seem to form layers. Diamond occurs in the domain where amounts of titanite and K-feldspar are relatively low. Low amount of microdiamond may be related with extremely low-XCO2 condition under UHP metamorphism. References Ishida et al. (2003: Journal of Metamorphic Geology, Vol. 21, p. 515-522. Kikuchi et al. (2003): EOS Transactions AGU, Vol. 84, F1532. Ogasawara et al. (2000): The Island Arc, Vol. 9, p 400-416. Ogasawara et al. (2002): American Mineralogist, Vol. 87, p. 454-461.

Aoki, K.; Adachi, T.; Kikuchi, M.; Ogasawara, Y.

2004-12-01

174

Effect of microstructure and microchemistry on improvement of hydration and slag attack resistance of ilmenite-doped refractory limestone  

NASA Astrophysics Data System (ADS)

This work studies densification, resistance to hydration and slag attack of 0.0-2.0 wt% ilmenite-doped lime refractories in relation to their thermal equilibrium and microfabric after firing at 1,400-1,700 °C. XRF, XRD, SEM-EDAX, transmitted light microscopy and mercury intrusion methods were used to characterize the fired samples. The ternary diagram CaO-C2S-C4AF was applied to the thermal equilibrium data. The rates of hydration and attack by steel-slag were also assessed using cathode-luminescence microscope. Doping limestone with 0.5 wt% ilmenite leads maximizes the rate of densification after firing for 2 h at 1,600 °C. A direct-bonded CaO-CaO network is found in the doped sample with separated islands of Ca-silicate, alumino-ferrite and TiO2-rich Ca, Mg- solid solutions all filling the pores and triple points of the lime grains. Due to the dense microstructure of the doped sample with the direct-bonded lime grains, hydration and slag-attack resistance are enhanced compared with the un-doped sample.

Soltan, Abdel Monem; Serry, Mohamed

2015-02-01

175

Lime and cement industry particulate emissions: source category report. Volume 1. Lime industry. Final report, June 1984July 1986  

Microsoft Academic Search

The report gives results of a study to develop particulate emission factors based on cutoff size for inhalable particles for the lime industry. After reviewing available information characterizing particulate emissions from lime plants, the data were summarized and rated in terms of reliability. Size-specific emission factors were developed from these data for the major processes used in the manufacture of

1986-01-01

176

Performance of lime-BHA solidified plating sludge in the presence of Na2SiO3 and Na2CO3.  

PubMed

This research investigated the performance of lime-BHA (black rice husk ash) solidified plating sludge with 2 wt% NaO from Na(2)SiO(3) and Na(2)CO(3) at the level of 0, 30 and 50 wt%. The sludge was evaluated for strength development, leachability, solution chemistry and microstructure. The lime-BHA solidified plating sludge with Na(2)SiO(3) and Na(2)CO(3) had higher early strength when compared to the control. The addition of Na(2)SiO(3) and Na(2)CO(3) increased the OH(-) concentration and decreased the Ca(2+) and heavy metal ions in solution after the first minute. The XRD patterns showed that the addition of Na(2)SiO(3) resulted in the formation of calcium silicate hydrates, while the addition of Na(2)CO(3) resulted in CaCO(3). The heavy metals from the plating sludge, especially Zn, were immobilized in calcium zincate and calcium zinc silicate forms for the lime-BHA with and without Na(2)SiO(3) solidified wastes, while samples with Na(2)CO(3) contained Zn that was fixed in the form of CaZnCO(3). The cumulative leaching of Fe, Cr and Zn from the lime-BHA solidified plating sludge decreased significantly when activators were added, especially Na(2)CO(3). PMID:21549500

Piyapanuwat, Rungroj; Asavapisit, Suwimol

2011-09-01

177

Mechanical and leaching behaviour of slag-cement and lime-activated slag stabilised/solidified contaminated soil.  

PubMed

Stabilisation/solidification (S/S) is an effective technique for reducing the leachability of contaminants in soils. Very few studies have investigated the use of ground granulated blast furnace slag (GGBS) for S/S treatment of contaminated soils, although it has been shown to be effective in ground improvement. This study sought to investigate the potential of GGBS activated by cement and lime for S/S treatment of a mixed contaminated soil. A sandy soil spiked with 3000mg/kg each of a cocktail of heavy metals (Cd, Ni, Zn, Cu and Pb) and 10,000mg/kg of diesel was treated with binder blends of one part hydrated lime to four parts GGBS (lime-slag), and one part cement to nine parts GGBS (slag-cement). Three binder dosages, 5, 10 and 20% (m/m) were used and contaminated soil-cement samples were compacted to their optimum water contents. The effectiveness of the treatment was assessed using unconfined compressive strength (UCS), permeability and acid neutralisation capacity (ANC) tests with determination of contaminant leachability at the different acid additions. UCS values of up to 800kPa were recorded at 28days. The lowest coefficient of permeability recorded was 5×10(-9)m/s. With up to 20% binder dosage, the leachability of the contaminants was reduced to meet relevant environmental quality standards and landfill waste acceptance criteria. The pH-dependent leachability of the metals decreased over time. The results show that GGBS activated by cement and lime would be effective in reducing the leachability of contaminants in contaminated soils. PMID:21420148

Kogbara, Reginald B; Al-Tabbaa, Abir

2011-05-01

178

Utricular otoconia of some amphibians have calcitic morphology  

NASA Technical Reports Server (NTRS)

This report concerns the morphological features of otoconia removed from the inner ear of four amphibian species. Results from scanning electron microscopic examination are compared based on the site of origin. These results show that utricular otoconia have a mineral structure that mimics calcite, rather than the widely accepted idea that they are mineralized by calcium carbonate of the aragonite polymorph.

Pote, K. G.; Ross, M. D.

1993-01-01

179

A data-driven model of the global calcite lysocline  

Microsoft Academic Search

Gridded maps of sediment calcium carbonate (calcite) concentration and overlying water saturation state [Archer, 1996] are combined with maps of benthic oxygen fluxes and sediment accumulation rates from Jahnke [1996] and Cweink [1986] to drive a diagenetic model of calcium carbonate preservation in deep-sea sediments. The only model input for which we cannot draw a detailed map is the rain

David Archer

1996-01-01

180

The behavior of Ni 2+ on calcite surfaces  

Microsoft Academic Search

Transport of Ni2+ in the geosphere plays a role in the formation of ore deposits as well as in the dispersion of contaminants in the environment. Some elements (Cd2+, Zn2+, Na+, K+, and Cl?) are known to diffuse in calcite at the rate of nanometers in months, so questions arose about the ability of Ni2+ to move away from adsorption

U. Hoffmann; S. L. S. Stipp

2001-01-01

181

Synthesis of a Se0 /Calcite Composite Using Hydrothermal  

E-print Network

Synthesis of a Se0 /Calcite Composite Using Hydrothermal Carbonation of Ca(OH)2 Coupled in a batch system by hydrothermal carbonation of calcium hydroxide under high CO2-Ar pressure (90 bar of Geological Processes, UniVersity of Oslo, Norway, LCABIE, IPREM, UMR CNRS 5254, UniVersite´ de Pau et des

Montes-Hernandez, German

182

Temperature limits for preservation of primary calcite clumped isotope paleotemperatures  

NASA Astrophysics Data System (ADS)

Solid-state reordering of C-O bonds in the calcite lattice can alter the clumped isotope composition of paleotemperature archives such as fossil brachiopod shells without inducing significant changes in shell microstructure and trace element concentrations, metrics commonly used to gauge preservation quality. To correctly interpret the paleoenvironmental significance of clumped isotope-derived paleotemperatures, it is necessary to understand the temperature-time domain in which solid-state C-O bond reordering is important. We address this question using a combination of laboratory and natural geological experiments on Paleozoic brachiopod shells. The laboratory experiments involve heating fossil brachiopod calcite at different temperatures and times to directly observe rates of 13C-18O bond reordering. The resulting Arrhenius parameters are indistinguishable from values previously determined for an optical calcite with similar trace element compositions. We develop an alternative kinetic model for reordering that accounts for non-first-order reaction progress observed during the initial several hundred minutes of laboratory heating experiments, and show that the simplified first-order approximation model (Passey and Henkes, 2012) predicts reaction progress equally well for temperatures and timescales relevant to sedimentary basins. We evaluate our laboratory-based rate predictions by studying brachiopod calcite from several sedimentary basins with independently constrained burial temperature histories. Specifically, we use the laboratory-derived Arrhenius parameters to predict the evolution of brachiopod calcite clumped isotope compositions during successive one million-year time steps reflecting the burial and exhumation temperature paths of each basin. While this exercise is limited by the relatively large uncertainties in the temperature histories of these basins, we find general correspondence, within error, between predicted and observed clumped isotope values. We present simplified temperature-time diagrams for calcite showing domains where primary clumped isotope compositions will be preserved, partially reordered, and fully reordered. In conclusion, calcite samples dwelling at ?100 °C or lower for 106-108 year timescales should not be affected by solid-state C-O bond reordering.

Henkes, Gregory A.; Passey, Benjamin H.; Grossman, Ethan L.; Shenton, Brock J.; Pérez-Huerta, Alberto; Yancey, Thomas E.

2014-08-01

183

The behavior of Ni 2+ on calcite surfaces  

NASA Astrophysics Data System (ADS)

Transport of Ni 2+ in the geosphere plays a role in the formation of ore deposits as well as in the dispersion of contaminants in the environment. Some elements (Cd 2+, Zn 2+, Na +, K +, and Cl -) are known to diffuse in calcite at the rate of nanometers in months, so questions arose about the ability of Ni 2+ to move away from adsorption sites at the surface into the bulk. Nickel incorporation into calcite is limited by its high dehydration enthalpy and by its ligand field hindrance to entering the distorted octahedra of calcite, but evidence exists that calcite can tolerate several percent Ni 2+ in the structure. Cleaved samples of Iceland spar were exposed for 1 minute to solutions of 10 -3 M and 10 -2 M Ni(ClO 4) 2, the solution was physically removed and the samples were examined using the surface sensitive techniques: X-ray Photoelectron Spectroscopy (XPS), Time-of-Flight Secondary Ion Mass Spectroscopy (TOF-SIMS) and Atomic Force Microscopy (AFM). XPS and TOF-SIMS showed that Ni 2+ was adsorbed while AFM confirmed that dissolution was taking place. The sample was stored in air and relative surface concentration and physical morphology were monitored for 2 years. Trends in the chemical data suggested statistically significant loss of surface Ni 2+ with time, but the decrease was very close to the limits for significance. AFM images demonstrated that surface topography of the Ni-exposed samples is modified by spontaneous recrystalization in the water layer adsorbed from air in exactly the same way that clean calcite surfaces typically rearrange. This process could bury a small amount of Ni 2+ in the bulk, explaining the very weak loss. Limited burial of Ni 2+ within the near-surface could renew calcite adsorption sites, thus increasing uptake capacity. Evidence indicates that surface recrystalization occurs even in very dry environments (<5% humidity). This means that burial could play a role in Ni 2+ mobility in unsaturated groundwater regimes or in fractures (such as in concrete) where water flow is intermittent. An important point is, however, in comparison to incorporation rates for divalent Cd and Zn, the extent of movement of Ni 2+ is extremely low. Thus, incorporation might have an effect on Ni 2+ retardation in flow paths extending over very long time scales (>10,000 years) such as would be relevant for geological processes and for long-term radioactive waste disposal. However, incorporation by burial would have negligible effect on the amount of Ni 2+ removed from groundwater by adsorption, in systems where the transport times are short (<100 years) such as for drinking water supplies from calcite-bearing porous media.

Hoffmann, U.; Stipp, S. L. S.

2001-11-01

184

Carbon and O Isotopic Ratios, Trace Element Abundances and Cathodoluminescence Observation of Calcite in Murchison  

NASA Astrophysics Data System (ADS)

We found two types of calcite in Murchison with respect to C isotopic ratios, trace element concentrations and CL intensities. In contrast, they have similar O isotopic ratios, suggesting the presence of at least two C sources for calcite.

Fujiya, W.; Sugiura, N.; Marrocchi, Y.; Takahata, N.; Hoppe, P.; Shirai, K.; Sano, Y.; Hiyagon, H.

2014-09-01

185

Molecular ordering of ethanol at the calcite surface.  

PubMed

To produce biominerals, such as shells, bones, and teeth, living beings create organic compounds that control the growth of the solid phase. Investigating the atomic scale behavior of individual functional groups at the mineral-fluid interface provides fundamental information that is useful for constructing accurate predictive models for natural systems. Previous investigations of the activity of coccolith-associated polysaccharides (CAP) on calcite, using atomic force microscopy (AFM) [Henriksen, K., Young, J. R., Bown, P. R., and Stipp, S. L. S. Palentology 2004, 43 (Part 3), 725-743] and molecular dynamics (MD) modeling [Yang, M., Stipp, S. L. S., and Harding, J. H. Cryst. Growth Des. 2008, 8 (11), 4066-4074], have suggested that OH functional groups control polysaccharide attachment. The purpose of this work was to characterize, using X-ray reflectivity (XR) combined with molecular dynamics (MD) simulations, the structuring on calcite of a layer of the simplest carbon chain molecule that contains an OH group, ethanol (CH(3)-CH(2)-OH). We found evidence that EtOH forms a highly ordered structure at the calcite surface, where the first layer molecules bond with calcite. The ethanol molecules stand up perpendicularly at the interface or nearly so. As a consequence, the fatty, CH(3) ends form a new surface, about 6 Å from the termination of the bulk calcite, and beyond that, there is a thin gap where ethanol density is low. Following is a more disordered layer that is two to three ethanol molecules thick, about 14 Å, where density more resembles that of bulk liquid ethanol. The good agreement between theory and experiment gives confidence that a theoretical approach can offer information about behavior in more complex systems. PMID:22060260

Pasarín, I S; Yang, M; Bovet, N; Glyvradal, M; Nielsen, M M; Bohr, J; Feidenhans'l, R; Stipp, S L S

2012-02-01

186

Dissolution enthalpies of synthetic magnesian calcites: Comparison with biogenic phases  

SciTech Connect

A series of synthetic magnesian calcites (0--15 mol% MgCO[sub 3]) were dissolved in weak acetic acid solutions to measure enthalpies of the reaction at 25 C. Heat released was 33.5 KJ/mol for calcite, decreasing to 33 KJ/mol for a Mg-Calcite of 2 mol% MgCO[sub 3], and increasing to 35 KJ/mol for a phase of 15 mol%. Excess enthalpies of formation Hf for these phases were calculated using calcite and magnesite as end-members. Values of Hf average about [minus]1 KJ/mol for the synthetic phases with a trend of increasingly negative values of Hf with Mg content. Excess entropies of formation Sf, corrected for excess entropies associated with ideal solid solutions, were calculated form available data on Gibbs free energies of formation and the values of Hf from this study. These values of Sf range from about [minus]2 J/mol-K for the phase with 2 mol% MgCO[sub 3] to [minus]5 J/mol-K at 15 mol%. The values of Sf suggest that some form of ordering (probably cation ordering) is obtained from these phases. In contrast, biogenic phases have positive values of Hf, increasing from about 1 KJ/mol for phases containing 5 mol% MgCO[sub 3] to 3 KJ/mol for those with 20 mol%. Values of Sf for the biogenic phases are positive, approximately 5 J/mol-K for a phase containing 15 mol% MgCO[sub 3]. For the biogenic phases, some form of disordering is suggested from the entropy calculations and may be the result of positional disordering is suggested from the entropy calculations and may be the result of positional disordering of the carbonate ion. The disorder in biogenic phases compared to the ordering in synthetic phases indicates significant structural differences that account for the higher solubilities of biogenic Mg-Calcites.

Bischoff, W.D. (Wichita State Univ., KS (United States). Geology Dept.); Wollast, R. (Univ. Libre de Bruxelles (Belgium))

1992-01-01

187

Atomistic molecular dynamics simulations of carbohydrate-calcite interactions in concentrated brine.  

PubMed

We report atomistic molecular dynamics simulations to study the interactions of a model carbohydrate monomer (Glucopyranose) and calcite slabs in brine. We show that the interactions between the sugar molecules and the mineral decrease with increasing salinity. The decrease is due to the formation of salt layers on the calcite surfaces, which screen the carbohydrate-calcite hydrogen bonding. This screening effect depends on the affinities of calcite surface to specific ions as well as to the carbohydrate molecules. PMID:25665050

Chen, Hsieh; Panagiotopoulos, Athanassios Z; Giannelis, Emmanuel P

2015-03-01

188

Aragonite, breunnerite, calcite and dolomite in the CM carbonaceous chondrites: High fidelity recorders of progressive parent body aqueous alteration  

NASA Astrophysics Data System (ADS)

Carbonate minerals in CM carbonaceous chondrite meteorites, along with the silicates and sulphides with which they are intergrown, provide a detailed record of the nature and evolution of parent body porosity and permeability, and the chemical composition, temperature and longevity of aqueous solutions. Fourteen meteorites were studied that range in petrologic subtype from mildly aqueously altered CM2.5 to completely hydrated CM2.0. All of them contain calcite, whereas aragonite occurs only in the CM2.5-CM2.2 meteorites and dolomite in the CM2.2-CM2.0. All of the aragonite crystals, and most of the calcite and dolomite grains, formed during early stages of parent body aqueous alteration by cementation of pores produced by the melting of tens of micrometre size particles of H2O-rich ice. Aragonite was the first carbonate to precipitate in the CM2.5 to CM2.2 meteorites, and grew from magnesium-rich solutions. In the least altered of these meteorites the aragonite crystals formed in clusters owing to physical restriction of aqueous fluids within the low permeability matrix. The strong correlation between the petrologic subtype of a meteorite, the abundance of its aragonite crystals and the proportion of them that have preserved crystal faces, is because aragonite was dissolved in the more altered meteorites on account of their higher permeability, and/or greater longevity of the aqueous solutions. Dolomite and breunnerite formed instead of aragonite in some of the CM2.1 and CM2.2 meteorites owing to higher parent body temperatures. The pore spaces that remained after precipitation of aragonite, dolomite and breunnerite cements were occluded by calcite. Following completion of cementation, the carbonates were partially replaced by phyllosilicates and sulphides. Calcite in the CM2.5-CM2.2 meteorites was replaced by Fe-rich serpentine and tochilinite, followed by Mg-rich serpentine. In the CM2.1 and CM2.0 meteorites dolomite, breunnerite and calcite were replaced by Fe-rich serpentine and Fe-Ni sulphide, again followed by Mg-rich serpentine. The difference between meteorites in the mineralogy of their replacive sulphides may again reflect greater temperatures in the parent body regions from where the more highly altered CMs were derived. This transition from Fe-rich to Mg-rich carbonate replacement products mirrors the chemical evolution of parent body solutions in response to consumption of Fe-rich primary minerals followed by the more resistant Mg-rich anhydrous silicates. Almost all of the CMs examined contain a second generation of calcite that formed after the sulphides and phyllosilicates and by replacement of remaining anhydrous silicates and dolomite (dedolomitization). The Ca and CO2 required for this replacive calcite is likely to have been sourced by dissolution of earlier formed carbonates, and ions may have been transported over metre-plus distances through high permeability conduits that were created by impact fracturing.

Lee, Martin R.; Lindgren, Paula; Sofe, Mahmood R.

2014-11-01

189

Nutrition, Hydration & Health  

NSDL National Science Digital Library

The following resource is a NFL sponsored, National Science Foundation funded program intended to teach students about scientific concepts by using the popular sport of Football. Each lesson is accompanied by an informative and fast paced video. In this lesson, athletic trainers from the Pittsburgh Steelers explain what NFL players must do to stay hydrated and replenish the essential nutrients needed to maintain good health during rigorous practices.

2010-01-01

190

The kinetics and mechanisms of amorphous calcium carbonate (ACC) crystallization to calcite, via vaterite.  

E-print Network

The kinetics and mechanisms of amorphous calcium carbonate (ACC) crystallization to calcite, via calcium carbonate (ACC) crystallization to calcite, via vaterite, were studied at a range controlled by the surface area of calcite. The second stage of the reaction is approximately 10 times slower

Benning, Liane G.

191

Paleotransport of lanthanides and strontium recorded in calcite compositions from tuffs at Yucca Mountain, Nevada, USA  

Microsoft Academic Search

Secondary calcite occurs in both saturated and unsaturated hydrologic zones (SZ and UZ, respectively) in the tuffs at Yucca Mountain, Nevada, USA. In the upper UZ, the major constituents of the calcite crystal structure (C, O) have surface origins. At greater depth there is a “barren zone,” straddling the water table, where calcite is rare and mixing of surface and

David T. Vaniman; Steve J. Chipera

1996-01-01

192

Cite this: CrystEngComm, 2013, 15, Calcite formation by hydrothermal carbonation of  

E-print Network

Cite this: CrystEngComm, 2013, 15, 3392 Calcite formation by hydrothermal carbonation by hydrothermal carbonation of calcium hydroxide by a simulation strategy, in which both the chemical evolution calcite formation by hydrothermal carbonation of portlandite. Calcite is an important ubiquitous mineral

Montes-Hernandez, German

193

Lime kiln source characterization: Lime manufacturing industry Fourier transform infrared spectroscopy. Final report  

SciTech Connect

The purpose of this testing program is to obtain uncontrolled and controlled hydrogen chloride (HCl) and speciated hydrocarbon Hazardous Air Pollutants (HAPs) emissions data from lime production plants to support a national emission standard for hazardous air pollutants (NESHAP). This report presents data from the Fourier Transform Infrared Spectroscopy (FTIR) measurements. FTIR source testing was conducted for the following purposes: Quantify HCl emission levels; and Gather screening (i.e., qualitative) data on other HAP emissions.

Toney, M.L.

1999-07-01

194

Effect of lime concentration on gelatinized maize starch dispersions properties.  

PubMed

Maize starch was lime-cooked at 92 °C with 0.0-0.40% w/w Ca(OH)2. Optical micrographs showed that lime disrupted the integrity of insoluble remnants (ghosts) and increased the degree of syneresis of the gelatinized starch dispersions (GSD). The particle size distribution was monomodal, shifting to smaller sizes and narrower distributions with increasing lime concentration. X-ray patterns and FTIR spectra showed that crystallinity decreased to a minimum at lime concentration of 0.20% w/w. Lime-treated GSD exhibited thixotropic and viscoelastic behaviour. In the linear viscoelastic region the storage modulus was higher than the loss modulus, but a crossover between these moduli occurred in the non-linear viscoelastic region. The viscoelastic properties decreased with increased lime concentration. The electrochemical properties suggested that the amylopectin-rich remnants and the released amylose contained in the continuous matrix was firstly attacked by calcium ions at low lime levels (<0.20% w/w), disrupting the starch gel microstructure. PMID:25442564

Lobato-Calleros, C; Hernandez-Jaimes, C; Chavez-Esquivel, G; Meraz, M; Sosa, E; Lara, V H; Alvarez-Ramirez, J; Vernon-Carter, E J

2015-04-01

195

Hydration-dependent dynamic crossover phenomenon in protein hydration water.  

PubMed

The characteristic relaxation time ? of protein hydration water exhibits a strong hydration level h dependence. The dynamic crossover is observed when h is higher than the monolayer hydration level hc=0.2-0.25 and becomes more visible as h increases. When h is lower than hc, ? only exhibits Arrhenius behavior in the measured temperature range. The activation energy of the Arrhenius behavior is insensitive to h, indicating a local-like motion. Moreover, the h dependence of the crossover temperature shows that the protein dynamic transition is not directly or solely induced by the dynamic crossover in the hydration water. PMID:25375521

Wang, Zhe; Fratini, Emiliano; Li, Mingda; Le, Peisi; Mamontov, Eugene; Baglioni, Piero; Chen, Sow-Hsin

2014-10-01

196

DEFINITIVE SOX CONTROL PROCESS EVALUATIONS: LIMESTONE, LIME, AND MAGNESIA FGD PROCESSES  

EPA Science Inventory

The report gives economic and ground-to-ground energy evaluations of limestone slurry, lime slurry, and magnesia (producing sulfuric acid) flue gas desulfurization (FGD) processes. The lime slurry process, using purchased lime and lime calcined onsite, remains lower in capital in...

197

Capital costs of lime treatment at the Augusta wastewater treatment plant  

Microsoft Academic Search

The capital costs were estimated for the addition of lime treatment facilities to the Augusta sewage treatment plant as a means of reducing the phosphorus loading of L Lake and consequently reducing the algae populations in the lake. Primary lime treatments and tertiary lime treatments were considered. The capital cost of a primary lime treatment addition would be lower than

1988-01-01

198

The effect of additives on lime dissolution rates. Final report  

SciTech Connect

Based on the previous years` studies concerning the efficiency of SO{sub 2} removal by spray dryers with high sulfur coal flue gas, the work for year five included investigations of lime dissolution rates at different slaking conditions and with the effect of additives. The prominent additives that have significant effects on lime dissolution rates were tested with the mini pilot spray drying absorber to see their effects on spray drying desulfurization applications. The mechanisms of these additive effects along with the properties of hygroscopic additives have been discussed and incorporated into the spray drying desulfurization model ``SPRAYMOD-M.`` Slaking conditions are very important factors in producing high quality lime slurry in spray drying desulfurization processes. At optimal slaking conditions, the slaked lime particles are very fine (3-5{mu}m) and the slaked lime has high BET surface areas which are beneficial to the desulfurization. The slaked lime dissolution rate experiments in our study are designed to determine how much lime can dissolve in a unit time if the initial lime surface area is kept constant. The purpose of the dissolution rate study for different additives is to find those effective additives that can enhance lime dissolution rates and to investigate the mechanisms of the dissolution rate enhancement properties for these additives. The applications of these additives on spray drying desulfurization are to further verify the theory that dissolution rate is a rate limiting step in the whole spray drying desulfurization process as well as to test the feasibility of these additives on enhancing SO{sub 2} removal in spray dryers.

Khang, S.J.

1996-07-31

199

Leaching behavior of lime-fly ash mixtures  

SciTech Connect

As part of a larger investigation that included numerical and field-based components, the use of lime to reduce the leachability of a coal combustion fly ash was evaluated in the laboratory. The focus of this paper is on the experimental assessment of lime-fly ash leachability through sequential leach (SL), freeze-thaw (FT), and wet-dry (WD) leaching as well as multileachant sequential extraction (SE) tests. The results suggest that lime addition reduces the leachability for Cd, Se, and to some extent As. They also suggest that Cr is rendered more leachable with increasing lime content, for the conditions and low levels tested. It appears that there is a threshold lime content ({gt} 1.0%) that must be exceeded prior to reducing the leachability of As and Se. In particular, this threshold likely corresponds to the level at which appreciable cementitious reactions have developed. For example, in the case of As after the first cycle of leaching, the concentration was below the reporting limit (10 {mu} g/L) for 0% lime. However, at 0.5% lime amendment, the leached concentration increased to nearly 50 {mu} g/L. Subsequent lime additions reduced this concentration. No such threshold was observed for Cd leachability as was expected as a direct consequence of hydroxide precipitation, which is well established under the measured pH conditions. As such, Cd mobility is insensitive to the extent to which cementitious reactions are initiated. Overall, the results suggest that while lime stabilization may be effective for reducing leachability, sufficient amounts must be added; otherwise, the leachability of some constituents can actually be exacerbated.

Daniels, J.L.; Das, G.P. [University of North Carolina, Charlotte, NC (United States). Dept. of Civil Engineering

2006-01-15

200

Using the new lime recommendations in  

E-print Network

equation T/a of 60-69 lime to apply 5.2 36.1 ­ (3.29 x BpH) ­ (2.67 x pH) 5.4 48.2 ­ (4.84 x BpH) ­ (3.03 x pH) 5.6 51.0 ­ (5.40 x BpH) ­ (2.67 x pH) 5.8 57.2 ­ (5.55 x BpH) ­ (3.50 x pH) 6.0 72. 7 ­ (7.59 x BpH) ­ (3.78 x pH) 6.3 103 ­ (12. 6 x BpH) ­ (3.18 x pH) 6.5 134 ­ (17.2 x BpH) ­ (2.73 x pH) 6.6 152

Balser, Teri C.

201

Rapid gas hydrate formation process  

DOEpatents

The disclosure provides a method and apparatus for forming gas hydrates from a two-phase mixture of water and a hydrate forming gas. The two-phase mixture is created in a mixing zone which may be wholly included within the body of a spray nozzle. The two-phase mixture is subsequently sprayed into a reaction zone, where the reaction zone is under pressure and temperature conditions suitable for formation of the gas hydrate. The reaction zone pressure is less than the mixing zone pressure so that expansion of the hydrate-forming gas in the mixture provides a degree of cooling by the Joule-Thompson effect and provides more intimate mixing between the water and the hydrate-forming gas. The result of the process is the formation of gas hydrates continuously and with a greatly reduced induction time. An apparatus for conduct of the method is further provided.

Brown, Thomas D.; Taylor, Charles E.; Unione, Alfred J.

2013-01-15

202

Crystal growth of calcite from calcium bicarbonate solutions at constant PCO2 and 25??C: a test of a calcite dissolution model  

USGS Publications Warehouse

A highly reproducible seeded growth technique was used to study calcite crystallization from calcium bicarbonate solutions at 25??C and fixed carbon dioxide partial pressures between 0.03 and 0.3 atm. The results are not consistent with empirical crystallization models that have successfully described calcite growth at low PCO2 (< 10-3 atm). Good agreement was found between observed crystallization rates and those calculated from the calcite dissolution rate law and mechanism proposed by Plummer et al. (1978). ?? 1981.

Reddy, M.M.; Plummer, L.N.; Busenberg, E.

1981-01-01

203

Gas hydrate cool storage system  

DOEpatents

The invention presented relates to the development of a process utilizing a gas hydrate as a cool storage medium for alleviating electric load demands during peak usage periods. Several objectives of the invention are mentioned concerning the formation of the gas hydrate as storage material in a thermal energy storage system within a heat pump cycle system. The gas hydrate was formed using a refrigerant in water and an example with R-12 refrigerant is included. (BCS)

Ternes, M.P.; Kedl, R.J.

1984-09-12

204

Fracture-aperture alteration induced by calcite precipitation  

NASA Astrophysics Data System (ADS)

Mineral precipitation significantly alters the transport properties of fractured rock. Chemical solubility gradients that favor precipitation induce mineral growth, which decreases the local aperture and alters preferential flow paths. Understanding the resulting development of spatial heterogeneities is necessary to predict the evolution of transport properties in the subsurface. We present experimental results that quantify the relationship between mineral precipitation and aperture alteration in a transparent analog fracture, 7.62cm x 7.62cm, with a uniform aperture of ~200 ?m. Prior to flow experiments, a pump circulated a super-saturated calcite solution over the bottom glass, coating the glass surface with calcite. This method of seeding resulted in clusters of calcite crystals with large reactive surface area and provided micro-scale variability in the aperture field. A continuous flow syringe pump injected a reactive fluid into the fracture at 0.5 ml/min. The fluid was a mixture of sodium bicarbonate (NaHCO3, 0.02M) and calcium chloride (CaCl2 0.0004M) with a saturation index, ?, of 8.51 with respect to calcite. A strobed LED panel backlit the fracture and a high-resolution CCD camera monitored changes in transmitted light intensity. Light transmission techniques provided a quantitative measurement of fracture aperture over the flow field. Results from these preliminary experiments showed growth near the inlet of the fracture, with decreasing precipitation rates in the flow direction. Over a period of two weeks, the fracture aperture decreased by 17% within the first 4mm of the inlet. Newly precipitated calcite bridged individual crystal clusters and smoothed the reacting surface. This observation is an interesting contradiction to the expectation of surface roughening induced by mineral growth. Additionally, the aperture decreased uniformly across the width of the fracture due to the initial aperture distribution. Future experiments of precipitation within variable-aperture fields will investigate the dependency of growth patterns on heterogeneous aperture distributions. (a) Aperture strain (?b/bi) after 14 days. Precipitation is concentrated near the inlet and decreases in the flow direction. (b) Width-averaged profiles of the initial and final aperture field show changes in aperture and smoothing that results from calcite precipitation between the initial discrete crystals.

Jones, T.; Detwiler, R. L.

2013-12-01

205

Hydration of a low-alkali CEM III/B-SiO{sub 2} cement (LAC)  

SciTech Connect

The hydration of a low-alkali cement based on CEM III/B blended with 10 wt.% of nanosilica has been studied. The nanosilica reacted within the first days and 90% of the slag reacted within 3.5 years. C-S-H (Ca/Si {approx} 1.2, Al/Si {approx} 0.12), calcite, hydrotalcite, ettringite and possibly straetlingite were the main hydrates. The pore water composition revealed ten times lower alkali concentrations than in Portland cements. Reducing conditions (HS{sup -}) and a pH value of 12.2 were observed. Between 1 month and 3.5 years of hydration more hydrates were formed due to the ongoing slag reaction but no significant differences in the composition of the pore solution or solid phase assemblage were observed. On the basis of thermodynamic calculations it is predicted that siliceous hydrogarnet could form in the long-term and, in the presence of siliceous hydrogarnet, also thaumasite. Nevertheless, even after 3.5 year hydration, neither siliceous hydrogarnet nor thaumasite have been observed.

Lothenbach, Barbara, E-mail: barbara.lothenbach@empa.ch [Empa, Laboratory for Concrete and Construction Chemistry, CH-8600 Duebendorf (Switzerland); Le Saout, Gwenn; Ben Haha, Mohsen; Figi, Renato [Empa, Laboratory for Concrete and Construction Chemistry, CH-8600 Duebendorf (Switzerland); Wieland, Erich [PSI, Laboratory for Waste Management, CH-5232 Villigen PSI (Switzerland)

2012-02-15

206

SEM observations on the replacement of Bahaman aragonitic mud by calcite  

NASA Astrophysics Data System (ADS)

Conversion of Holocene aragonitic mud to calcite microspar occurs in fresh pore waters beneath hammocks on the tidal flats of west Andros Island, Bahamas, to a subsurface depth of 2.7 m. The conversion process involves both dissolution of aragonite and precipitation of calcite as a cement in pre-existing pores and displacive calcite crystallization. Neomorphism of aragonite to calcite with preservation of grain shape has not been observed. Resulting diagenetic products are lithified nodules, composed of well-sorted interlocking rhombs of microspar and of stiff, unlithified calcitic aragonite mud.

Steinen, Randolph P.

1982-09-01

207

U(VI) behaviour in hyperalkaline calcite systems  

NASA Astrophysics Data System (ADS)

The behaviour of U(VI) in hyperalkaline fluid/calcite systems was studied over a range of U(VI) concentrations (5.27 × 10-5 ?M to 42.0 ?M) and in two high pH systems, young and old synthetic cement leachate in batch sorption experiments. These systems were selected to be representative of young- (pH 13.3) and old-stage (pH 10.5) leachate evolution within a cementitious geological disposal facility. Batch sorption experiments, modelling, extended X-ray absorption fine structure spectroscopy, electron microscopy, small angle X-ray scattering and luminescence spectroscopy were used to define the speciation of U(VI) across the systems of study. At the lowest concentrations (5.27 × 10-5 ?M 232U(VI)) significant U removal was observed for both old and young cement leachates, and this was successfully modelled using a first order kinetic adsorption modelling approach. At higher concentrations (>4.20 ?M) in the young cement leachate, U(VI) showed no interaction with the calcite surface over an 18 month period. Small angle X-ray scattering techniques indicated that at high U concentrations (42.0 ?M) and after 18 months, the U(VI) was present in a colloidal form which had little interaction with the calcite surface and consisted of both primary and aggregated particles with a radius of 7.6 ± 1.1 and 217 ± 24 Å, respectively. In the old cement leachate, luminescence spectroscopy identified two surface binding sites for U(VI) on calcite: in the system with 0.21 ?M U(VI), a liebigite-like Ca2UO2(CO3)3 surface complex was identified; at higher U(VI) concentrations (0.42 ?M), a second binding site of undetermined coordination was identified. At elevated U(VI) concentrations (>2.10 ?M) in old cement leachate, both geochemical data and luminescence spectroscopy suggested that surface mediated precipitation was controlling U(VI) behaviour. A focused ion beam mill was used to create a section across the U(VI) precipitate-calcite interface. Transmission electron microscope images of the section revealed that the calcite surface was coated with a nano crystalline, U containing phase. Selected area electron diffraction images of the U precipitate which was formed at a U(VI) concentration of 4.20 ?M were consistent with the formation of calcium uranate. XAS spectroscopy at higher concentrations (?21.0 ?M) suggested the formation of a second U(VI) phase, possibly a uranyl oxyhydroxide phase. These results indicated that in the young cement leachate, U(VI) did not react with the calcite surface unless U(VI) concentrations were very low (5.27 × 10-5 ?M). At higher concentrations, speciation calculations suggested that U(VI) was significantly oversaturated and experimental observations confirmed it existed in a colloidal form that interacted with the mineral surface only weakly. In the old cement leachate systems at low concentrations batch sorption and luminescence data suggested that U(VI) removal was being driven by a surface complexation mechanism. However, at higher concentrations, spectroscopic methods suggest a combination of both surface complexation and surface mediated precipitation was responsible for the observed removal. Overall, U(VI) behaviour in hyperalkaline calcite systems is distinct from that at circumneutral pH conditions: at high pH and anything but low U(VI) concentrations, a surface mediated precipitation mechanism occurs; this is in contrast to circumneutral pH conditions where U(VI) surface complexation reactions tend to dominate.

Smith, Kurt F.; Bryan, Nicholas D.; Swinburne, Adam N.; Bots, Pieter; Shaw, Samuel; Natrajan, Louise S.; Mosselmans, J. Frederick W.; Livens, Francis R.; Morris, Katherine

2015-01-01

208

The solubility of Fish Produced High Magnesium Calcite in Seawater  

NASA Astrophysics Data System (ADS)

Fish have been shown to produce high 10 to 30% magnesium calcite as part of the physiological mechanisms responsible for maintaining salt and water balance. The importance of this source to the marine carbon cycle is only now being considered. In this paper we report the first measurements of the solubility of this CaCO3 in seawater. The resulting solubility (pKsp = 5.85 ± 0.07) is more than two times higher than aragonite and similar to the high magnesium calcite generated on the Bahamas Banks (pKsp = 5.90). This high solubility of fish produced CaCO3 renders it soluble in near surface (<2000 m) waters contributing to the input of carbonate to surface ocean waters, and at least partially explaining the increase in total alkalinity above the aragonite saturation horizon.

Woosley, R. J.; Millero, F. J.; Grosell, M.

2011-12-01

209

Geobacillus thermoglucosidasius endospores function as nuclei for the formation of single calcite crystals.  

PubMed

Geobacillus thermoglucosidasius colonies were placed on an agar hydrogel containing acetate, calcium ions, and magnesium ions, resulting in the formation of single calcite crystals (calcites) within and peripheral to the plating area or parent colony. Microscopic observation of purified calcites placed on the surface of soybean casein digest (SCD) nutrient medium revealed interior crevices from which bacterial colonies originated. Calcites formed on the gel contained [1-(13)C]- and [2-(13)C]acetate, demonstrating that G. thermoglucosidasius utilizes carbon derived from acetate for calcite formation. During calcite formation, vegetative cells swam away from the parent colony in the hydrogel. Hard-agar hydrogel inhibited the formation of calcites peripheral to the parent colony. The calcite dissolved completely in 1 M HCl, with production of bubbles, and the remaining endospore-like particles were easily stained with Brilliant green dye. The presence of DNA and protein in calcites was demonstrated by electrophoresis. We propose that endospores initiate the nucleation of calcites. Endospores of G. thermoglucosidasius remain alive and encapsulated in calcites. PMID:23455343

Murai, Rie; Yoshida, Naoto

2013-05-01

210

Geobacillus thermoglucosidasius Endospores Function as Nuclei for the Formation of Single Calcite Crystals  

PubMed Central

Geobacillus thermoglucosidasius colonies were placed on an agar hydrogel containing acetate, calcium ions, and magnesium ions, resulting in the formation of single calcite crystals (calcites) within and peripheral to the plating area or parent colony. Microscopic observation of purified calcites placed on the surface of soybean casein digest (SCD) nutrient medium revealed interior crevices from which bacterial colonies originated. Calcites formed on the gel contained [1-13C]- and [2-13C]acetate, demonstrating that G. thermoglucosidasius utilizes carbon derived from acetate for calcite formation. During calcite formation, vegetative cells swam away from the parent colony in the hydrogel. Hard-agar hydrogel inhibited the formation of calcites peripheral to the parent colony. The calcite dissolved completely in 1 M HCl, with production of bubbles, and the remaining endospore-like particles were easily stained with Brilliant green dye. The presence of DNA and protein in calcites was demonstrated by electrophoresis. We propose that endospores initiate the nucleation of calcites. Endospores of G. thermoglucosidasius remain alive and encapsulated in calcites. PMID:23455343

Murai, Rie

2013-01-01

211

Chemistry and petrography of calcite in the KTB pilot borehole, Bavarian Oberpfalz, Germany  

USGS Publications Warehouse

The KTB pilot borehole in northeast Bavaria, Germany, penetrates 4000 m of gneiss, amphibolite, and subordinate calc-silicate, lamprophyre and metagabbro. There are three types of calcite in the drilled section: 1) metamorphic calcite in calc-silicate and marble; 2) crack-filling calcite in all lithologies; and 3) replacement calcite in altered minerals. Crack-filling and replacement calcite postdate metamorphic calcite. Multiple calcite generations in individual cracks suggest that different generations of water repeatedly flowed through the same cracks. Crack-filling mineral assemblages that include calcite originally formed at temperatures of 150-350??C. Presently, crack-filling calcite is in chemical and isotopic equilibrium with saline to brackish water in the borehole at temperatures of ???120??C. The saline to brackish water contains a significant proportion of meteoric water. Re-equilibration of crack-filling calcite to lower temperatures means that calcite chemistry tells us little about water-rock interactions in the crystal section of temperatures higher than ~120??C. -from Author

Komor, S.C.

1995-01-01

212

63. INTERIOR VIEW OF THE LIME KILN BUILDING, LOOKING AT ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

63. INTERIOR VIEW OF THE LIME KILN BUILDING, LOOKING AT THE FIRE BOX AND KILN FOR DILLUTANT. APRIL 22, 1919. - United States Nitrate Plant No. 2, Reservation Road, Muscle Shoals, Muscle Shoals, Colbert County, AL

213

Blue Mojito 7 Bacardi rum, mint & lime, blue curacao,  

E-print Network

Signature Cocktails Blue Mojito 7 Bacardi rum, mint & lime, blue curacao, simple syrup and seltzer juice, cucumber, mint and seltzer Eric's Royale 7 Crown Royal, cranberry juice, peach schnapps, sprite

Azevedo, Ricardo

214

Gehlenite and anorthite crystallisation from kaolinite and calcite mix  

Microsoft Academic Search

Clay products can be reinforced by using clay and calcite mixes, even if sintering is at low temperature (1100 °C). The formation of a micro-composite microstructure favours a significant strength increase as fired materials contain anorthite grains embedded in a silico-aluminate matrix. The clay used, rich in kaolinite mineral, is originated from Burkina-Faso. It is contaminated by a moderate iron level,

Karfa Traoré; Tibo Siméon Kabré; Philippe Blanchart

2003-01-01

215

Cosmogenic Chlorine36 Production in Calcite by Muons  

Microsoft Academic Search

At depths below a few metres, 36Cl production in calcite is initiated almost entirely by cosmic ray muons. The principal reactions are (1) direct negative muon capture by Ca; 40Ca(??,?)36Cl, and (2) capture by 35Cl of secondary neutrons produced in muon capture and muon-induced photodisintegration reactions. We have determined rates for 36Cl and neutron production due to muon capture in

J. O. H. Stone; J. M. Evans; L. K. Fifield; G. L. Allan; R. G. Cresswell

1998-01-01

216

A re-evaluation of aragonite versus calcite seas  

Microsoft Academic Search

Some workers have argued that the mineralogy of ancient carbonates may have been different from that of modern sediments,\\u000a with calcite being considered the dominant mineral during the Ordovician, Devonian-mid Carboniferous, and Jurassic-Cretaceous\\u000a to Early\\/Middle Cenozoic (e.g. Sandberg 1983; Wilkinson and Algeo 1989). Variation in carbonate mineralogy has been related\\u000a to the position of global sea level (emergent or submergent

Mohammad H. Adabi

2004-01-01

217

Interaction of copper with the surface of calcite  

SciTech Connect

The interaction of Cu ions in solution with the surface of calcite has been studied in a range of solutions from pure water to seawater. Observations of the uptake of Cu from solution onto calcite indicates that the process is rapid and strong in both distilled water and seawater. In distilled water, Cu uptake is directly proportional to the concentration of Cu in solution; Cu/sub s/ = K/sub s/Cu/sub 1/. This Cu/sub s/ dependence on Cu/sub 1/ is linear over the entire Cu concentration range studied (0.1 to 200 ..mu..M). Results do not indicate the formation of a precipitate of either malachite or copper carbonate. In seawater, the uptake of Cu is also directly proportional to the concentration of Cu/sub 1/ up to a limiting value of approximately 13 ..mu..M. The average value for K/sub s/ in seawater, 0.24 +- 0.06 (Cu/sub 1/ less than or equal to 13 ..mu..M), is approximately an order of magnitude less than in distilled water. This is probably the result of smaller Cu/sub 1/ activity coefficients and increased site competition by other ions in seawater. Attempts to increase the Cu/sub 1/ concentration above 13 ..mu..M resulted in the additional Cu being deposited on the surface of the calcite. A possible explanation for this behavior is the formation of a precipitate of malachite on the calcite surface. The value of K/sub s/ decreased slightly with increasing solid to solution ratios in seawater.

Franklin, M.L.; Morse, J.W.

1981-05-01

218

Siderite and calcite in lignite overburden of East Texas  

E-print Network

Siderite and Calcite in Lignite Overburden of Ease Texas. (December W982) David Hugh Durham, B. S. , Texas A&M University Chairman of Advisory Committee: Dr. Joe B. Dixon Cores from four locations were examined to characterize carbon- ates present.... , 1974; Curtis et al. , 1 972; Curtis et al. , 1 975) . Also, siderite forms in buried plant material (Ho and Coleman, 1969). Genesis of Siderite Siderites of all these different types have something in common. They have formed in a reduced...

Durham, David Hugh

1982-01-01

219

Nucleation, growth and evolution of calcium phosphate films on calcite.  

PubMed

Marble, a stone composed of the mineral calcite, is subject to chemically induced weathering in nature due to its relatively high dissolution rate in acid rain. To protect monuments and sculpture from corrosion, we are investigating the application of thin layers of hydroxyapatite (HAP) onto marble. The motivation for using HAP is its low dissolution rate and crystal and lattice compatibility with calcite. A mild, wet chemical synthesis route, in which diammonium hydrogen phosphate salt was reacted with marble, alone and with cationic and anionic precursors under different reaction conditions, was used to produce inorganic HAP layers on marble. Nucleation and growth on the calcite substrate was studied, as well as metastable phase evolution, using scanning electron microscopy, grazing incidence X-ray diffraction, and atomic force microscopy. Film nucleation was enhanced by surface roughness. The rate of nucleation and the growth rate of the film increased with cationic (calcium) and anionic (carbonate) precursor additions. Calcium additions also influenced phase formation, introducing a metastable phase (octacalcium phosphate) and a different phase evolution sequence. PMID:25233226

Naidu, Sonia; Scherer, George W

2014-12-01

220

Growth modification of seeded calcite using carboxylic acids: atomistic simulations.  

PubMed

Molecular dynamics simulations were used to investigate possible explanations for experimentally observed differences in the growth modification of calcite particles by two organic additives, polyacrylic acid (PAA) and polyaspartic acid (p-ASP). The more rigid backbone of p-ASP was found to inhibit the formation of stable complexes with counter-ions in solution, resulting in a higher availability of p-ASP compared to PAA for surface adsorption. Furthermore the presence of nitrogen on the p-ASP backbone yields favorable electrostatic interactions with the surface, resulting in negative adsorption energies, in an upright (brush conformation). This leads to a more rapid binding and longer residence times at calcite surfaces compared to PAA, which adsorbed in a flat (pancake) configuration with positive adsorption energies. The PAA adsorption occurring despite this positive energy difference can be attributed to the disruption of the ordered water layer seen in the simulations and hence a significant entropic contribution to the adsorption free energy. These findings help explain the stronger inhibiting effect on calcite growth observed by p-ASP compared to PAA and can be used as guidelines in the design of additives leading to even more marked growth modifying effects. PMID:20304410

Aschauer, Ulrich; Spagnoli, Dino; Bowen, Paul; Parker, Stephen C

2010-06-01

221

Calcite deposition at Miravalles geothermal field, Costa Rica  

SciTech Connect

The calcite deposition problem at Miravalles has been studied since it was observed in the first three wells drilled on the slopes of the Miravalles Volcano. Long-term tests have been carried out to study reservoir characteristics. The change in the production behavior of the wells with the restriction imposed by the deposited calcite has been studied trying to evaluate and quantify the scaling problem. Work is being done on predictions of the deposition rate, location and distribution of the deposited mineral inside the wells. This work was compared with real data obtained from caliper logs of the wells before and after production. The feasibility of the first 55 MW power plant has been demonstrated. It was considered that the solution for the calcite problem is the reaming during discharge of the wells trying at the same time to minimize the cleaning interventions with a new well design. It is believed, due to the thermodynamics and chemical characteristics of the extracted fluids, that it is possible to find a non-deposition zone which will permit the drilling of wells without a scaling problem.

Vaca, L.; Alvarado, A.; Corrales, R. (Instituto Costarricense de Electricidad, San Jose (Costa Rica))

1989-01-01

222

Earthworm-produced calcite granules: A new terrestrial palaeothermometer?  

NASA Astrophysics Data System (ADS)

In this paper we show for the first time that calcite granules, produced by the earthworm Lumbricus terrestris, and commonly recorded at sites of archaeological interest, accurately reflect temperature and soil water ?18O values. Earthworms were cultivated in an orthogonal combination of two different (granule-free) soils moistened by three types of mineral water and kept at three temperatures (10, 16 and 20 °C) for an acclimatisation period of three weeks followed by transfer to identical treatments and cultivation for a further four weeks. Earthworm-secreted calcite granules were collected from the second set of soils. ?18O values were determined on individual calcite granules (?18Oc) and the soil solution (?18Ow). The ?18Oc values reflect soil solution ?18Ow values and temperature, but are consistently enriched by 1.51 (± 0.12)‰ in comparison to equilibrium in synthetic carbonates. The data fit the equation 1000 ln ? = [20.21 ± 0.92] (103 T-1) - [38.58 ± 3.18] (R2 = 0.95; n = 96; p < 0.0005). As the granules are abundant in modern soils, buried soils and archaeological contexts, and can be dated using U-Th disequilibria, the developed palaeotemperature relationship has enormous potential for application to Holocene and Pleistocene time intervals.

Versteegh, Emma A. A.; Black, Stuart; Canti, Matthew G.; Hodson, Mark E.

2013-12-01

223

In What Form is Lime Present in Portland Cement  

E-print Network

KU ScholarWorks | The University of Kansas Pre-1923 Dissertations and Theses Collection In What Form is Lime Present in Portland Cement 1910 by Claude W. Wright This work was digitized by the Scholarly Communications program staff in the KU... Libraries’ Center for Digital Scholarship. http://kuscholarworks.ku.edu Submitted to the School of Engineering of the University of Kansas for completion of Masters of Cheimcal Engineering. IN WHAT FORM IS LIME PRESENT IN PORTLAND CEMENT. A Dissertation...

Wright, Claude W.

1910-01-01

224

Using Earthworms to Incorporate Lime into Subsoil to Ameliorate Acidity  

Microsoft Academic Search

Acid soils threaten agriculture in Australia as well as in many parts of the world by reducing plant productivity. Surface-applied lime (CaCO3) moves into the root zone only slowly but the process can be considerably hastened in the presence of earthworms. In a laboratory experiment, the abilities of three earthworm species in incorporating lime into the subsoil and the mechanisms

K. Y. Chan

2003-01-01

225

Investigation of copper sorption by sugar beet processing lime waste.  

PubMed

In the western United States, sugar beet processing for sugar recovery generates a lime-based waste product (?250,000 Mg yr) that has little liming value in the region's calcareous soils. This area has recently experienced an increase in dairy production, with dairies using copper (Cu)-based hoof baths to prevent hoof diseases. A concern exists regarding soil Cu accumulation because spent hoof baths may be disposed of in waste ponds, with pond waters being used for irrigation. The objective of this preliminary study was to evaluate the ability of lime waste to sorb Cu. Lime waste was mixed with increasing Cu-containing solutions (up to 100,000 mg Cu kg lime waste) at various buffered pH values (pH 6, 7, 8, and 9) and shaken over various time periods (up to 30 d). Copper sorption phenomenon was quantified using sorption maximum fitting, and the sorption mechanism was investigated using X-ray absorption spectroscopy. Results showed that sorption onto lime waste increased with decreasing pH and that the maximum Cu sorption of ?45,000 mg kg occurred at pH 6. X-ray absorption spectroscopy indicated that Cu(OH) was the probable species present, although the precipitate existed as small multinuclear precipitates on the surface of the lime waste. Such structures may be precursors for larger surface precipitates that develop over longer incubation times. Findings suggest that sugar beet processing lime waste can viably sorb Cu from liquid waste streams, and thus it may have the ability to remove Cu from spent hoof baths. PMID:23673960

Ippolito, J A; Strawn, D G; Scheckel, K G

2013-01-01

226

Odor Control for Land Application of Lime Stabilized Biosolids  

Microsoft Academic Search

Over three million dry metric tons of biosolids produced in the United States are land applied as Class B. Lime stabilization\\u000a is employed for biosolids treatment at approximately 20% of the wastewater treatment plants because it is a simple and inexpensive\\u000a process. During lime stabilization, the pH of sewage sludge is raised above 12 for pathogen inactivation and odor reduction.

Kenneth R. Krach; Benjamin R. Burns; Baikun Li; Alison Shuler; Charles Cole; Yuefeng Xie

2008-01-01

227

Hydration of pectic polysaccharides.  

PubMed

The hydration and swelling of pectic polysaccharides was examined at different pHs and ionic strengths as a function of osmotic stress. For weakly charged pectic polysaccharides at low concentrations of a monovalent salt (20 mM), the main driving force for swelling originates from a polyelectrolyte effect due to the translational entropy of ions within the film. Swelling is reduced at higher salt concentrations and lower pHs. Polyelectrolyte collapse and minimal swelling is observed for more highly charged pectic polysaccharides. Replacement of the Na(+) counterion with Ca(2+) results in minimal swelling and the formation of network structures even for the weakly charged pectic polysaccharides. PMID:10951326

Ryden, P; MacDougall, A J; Tibbits, C W; Ring, S G

2000-11-01

228

Imaging surface contacts: Power law contact distributions and contact stresses in quartz, calcite, glass and acrylic plastic  

USGS Publications Warehouse

A procedure has been developed to obtain microscope images of regions of contact between roughened surfaces of transparent materials, while the surfaces are subjected to static loads or undergoing frictional slip. Static loading experiments with quartz, calcite, soda-lime glass and acrylic plastic at normal stresses to 30 MPa yield power law distributions of contact areas from the smallest contacts that can be resolved (3.5 ??m2) up to a limiting size that correlates with the grain size of the abrasive grit used to roughen the surfaces. In each material, increasing normal stress results in a roughly linear increase of the real area of contact. Mechanisms of contact area increase are by growth of existing contacts, coalescence of contacts and appearance of new contacts. Mean contacts stresses are consistent with the indentation strength of each material. Contact size distributions are insensitive to normal stress indicating that the increase of contact area is approximately self-similar. The contact images and contact distributions are modeled using simulations of surfaces with random fractal topographies. The contact process for model fractal surfaces is represented by the simple expedient of removing material at regions where surface irregularities overlap. Synthetic contact images created by this approach reproduce observed characteristics of the contacts and demonstrate that the exponent in the power law distributions depends on the scaling exponent used to generate the surface topography.

Dieterich, J.H.; Kilgore, B.D.

1996-01-01

229

Mallik Gas Hydrates Test Well  

USGS Multimedia Gallery

A test-well for collecting gas hydrates in Mallik, Canada. Gas hydrates are naturally-occurring “ice-like” combinations of natural gas and water that have the potential to provide an immense resource of natural gas from the world’s oceans and polar regions....

230

Ductile flow of methane hydrate  

USGS Publications Warehouse

Compressional creep tests (i.e., constant applied stress) conducted on pure, polycrystalline methane hydrate over the temperature range 260-287 K and confining pressures of 50-100 MPa show this material to be extraordinarily strong compared to other icy compounds. The contrast with hexagonal water ice, sometimes used as a proxy for gas hydrate properties, is impressive: over the thermal range where both are solid, methane hydrate is as much as 40 times stronger than ice at a given strain rate. The specific mechanical response of naturally occurring methane hydrate in sediments to environmental changes is expected to be dependent on the distribution of the hydrate phase within the formation - whether arranged structurally between and (or) cementing sediments grains versus passively in pore space within a sediment framework. If hydrate is in the former mode, the very high strength of methane hydrate implies a significantly greater strain-energy release upon decomposition and subsequent failure of hydrate-cemented formations than previously expected.

Durham, W.B.; Stern, L.A.; Kirby, S.H.

2003-01-01

231

Interaction of copper with the surface of calcite  

SciTech Connect

The interaction of Cu ions in solution with the surface of calcite has been studied in a range of solutions from pure water to seawater. Observations of the uptake of Cu from solution onto calcite indicates that the process is rapid and strong in both distilled water and seawater. In distilled water, Cu uptake is directly proportional to the concentration of Cu in solution; Cu/sub s/ = K/sub s/Cu/sub 1/. The average value for K/sub s/ is 3.5 +- 1.7. The Cu/sub s/ dependence on Cu/sub 1/ is linear over the entire Cu concentration range studied (0.1 to 200 ..mu..M). Results do not indicate the formation of a precipitate of either malachite or copper carbonate. A precipitate of the form Cu/sub x/Ca/sub 1-x/CO/sub 3/ may be deposited onto the calcite surface in distilled water. The value of K/sub s/ in distilled water decreased sharply over the solid to solution ratio range of 0.1 to 2 g CaCO/sub 3/ 1/sup -1/. This was followed by a small change in K/sub s/ for solid to solution ratios in the range of 2 to 10 g CaCO/sub 3/ 1/sup -1/. In seawater, the uptake of Cu is also directly proportional to the concentration of Cu/sub 1/ up to a limiting value of approximately 13 ..mu..M. The average value for K/sub s/ in seawater, 0.24 +- 0.06 (Cu/sub 1/ less than or equal to 13 ..mu..M), is approximately an order of magnitude less than in distilled water. This is probably the result of smaller Cu/sub 1/ activity coefficients and increased site competition by other ions in seawater. Attempts to increase the Cu/sub 1/ concentration above 13 ..mu..M resulted in the additional Cu being deposited on the surface of the calcite. A possible explanation for this behavior is the formation of a precipitate of malachite on the calcite surface. The value of K/sub s/ decreased slightly with increasing solid to solution ratios in seawater.

Franklin, M.L.; Morse, J.W.

1981-12-01

232

Hydrothermal replacement of calcite by Mg-carbonates  

NASA Astrophysics Data System (ADS)

The transport of heat and mass through the Earth's crust is coupled to mineral reactions and the exchange of isotopes and elements between different phases. Carbonate minerals are a major constituent of the Earth's crust and play an important role in different physical, chemical and even biological processes. In this experimental study, the element exchange reaction between calcite (CaCO3) and a Mg-rich fluid phase is investigated under hydrothermal conditions. Single crystals of calcite (2x2x2 mm) react with 1 ml of a 1 M MgCl2 solution at 200° C in a Teflon-lined steel autoclave for different times between one day and four weeks. The reaction leads to the formation of a porous reaction front and the pseudomorphic replacement of calcite by dolomite [CaMg(CO3)2] and magnesite (MgCO3). Scanning electron microscopy revealed that the reaction rim consists of small Mg-carbonate rhombs closely attached to each other, suggesting that the replacement reaction takes place by a dissolution-precipitation mechanism. Typically, the observed reaction front can be divided into two different domains. The outer part of the reaction rim, i.e. from the mineral surface in contact to the fluid inwards, consists of magnesite, whereas the inner part of the rim surrounding the unreacted calcite core consists of Ca-rich dolomite. The formation of a porous microstructure that varies in different parts of the reaction rim is a direct result of the large molar volume change induced by the replacement of calcite by magnesite and dolomite. The developing porosity therefore creates fluid pathways that promote the progress of the reaction front towards the unreacted core of the single crystal. Compositional profiles measured perpendicular to the mineral surface across the reactions rims using electron microprobe (EMPA) further revealed a compositional gradient within the reaction rim with regard to the structure-forming elements Mg and Ca. Here, the amount of Mg incorporated in both product phases increases with increasing distance from the unreacted calcite core, countered by a decrease of Ca incorporated. Both the coexistence of two different product phases and the distinct compositional gradient within the forming reaction rim are unequivocal signs of a chemical zonation of Ca and Mg in the fluid phase which mediates the element exchange between the reaction interface and the bulk solution. Atomic adsorption spectroscopy revealed that the Ca/Mg ratio in the reacted fluid increases as a function of time, reflecting the progressive exchange of Mg and Ca between the fluid and the solid phase. The time-dependence of the evolving Ca/Mg ratio can be fitted with a square root of time relation that indicates a transport controlled reaction. We interpret the hydrothermal replacement of calcite to operate via a dissolution/re-precipitation mechanism, whereas the reaction progress is controlled by the transport of the structure forming elements through the developing reaction rim.

Jonas, Laura; Mueller, Thomas; Dohmen, Ralf

2014-05-01

233

Speciation of As in calcite by micro-XAFS: Implications for remediation of As contamination in groundwater  

NASA Astrophysics Data System (ADS)

To evaluate the role of calcite as a host phase of arsenic (As) in As-contaminated groundwater, distribution behavior of Asbetween natural calcite and groundwater in deep underground was investigated based on As oxidation state. Speciation analyses of As in natural calcite by ?-XRF-XAFS analyses showed (i) preferentialarsenate uptake by calcite, and (ii) promptness of arsenate uptake by minor iron (Fe) carbonate minerals coprecipitated with calcite. These findings suggest that the effect of calcite on As remediation of the As-contamination systems stronglydepends on arsenite to arsenate ratio (i.e., redox condition) in groundwater, and maybe governed bythe amount of Fe coprecipitated with calcite.

Yokoyama, Y.; Iwatsuki, T.; Terada, Y.; Takahashi, Y.

2013-04-01

234

Anthropogenic oligotrophication via liming: Long-term phosphorus trends in acidified, limed, and neutral reference lakes in Sweden.  

PubMed

Restoration of acidified lakes by liming does not, in many cases, improve productivity to a pre-acidified state. We hypothesize that the poor recovery detected in many of these lakes is due to constrained in-lake phosphorous (P) cycling caused by enhanced precipitation of metals in higher pH, limed waters. Long-term (1990-2012) data for 65 limed, circum-neutral (pH 6-8), and acidified lakes in Sweden were analyzed to determine trends for P and potential drivers of these trends. Limed lakes not only had lower mean values and stronger decreasing trends for total P than non-limed lakes, but they also had the highest percentage of decreasing trends (85 %). A P release factor (Hypolimnetic P/Epilimnetic P) was developed to elucidate differences in internal P cycling between lake groups. Consistently, lower P release factors in limed lakes show limitation of internal P cycling during summer months that may be a factor limiting P bioavailability and thus productivity of these systems. PMID:25403973

Hu, Qian; Huser, Brian J

2014-01-01

235

Biochemical clues to origin of lime mud  

SciTech Connect

A detailed biochemical analysis of proteins in major sediment producing algae, bottom sediment, and whiting sediment suggests whiting sediment is not wholly derived from the algae. Non-skeletal grains differ from skeletal components in that they lack an organic (proteinaceous) component, allowing use of proteins as a tracer to determine extent of algal contribution to the bottom sediment and to determine whether or not this component can be observed in whitings. Samples were decalcified, supernatent dialyzed, lyophilized, and analyzed using a reverse phase column on a High-Performance Liquid Chromatograph (HPLC). The algae Penicillus revealed a number of hydrophilic proteins that may be associated with the formation of aragonite needles. At least one of these proteins may be found in the bottom sediment HPLC profile. This suggests that Penicillus contributes at least partially to lime mud bottom sediments. The bottom sediment, however, demonstrated a complex HPLC protein profile, composed of many large molecular weight components. Whiting sediment, on the other hand, showed markedly fewer protein components than bottom sediment, although they contained two or three common non-algal proteins. The protein data suggest that whiting sediment may not be stirred-up bottom sediment, as previously suggested, but may be produced within the water column.

Robbins, L.L.

1988-02-01

236

Recovery of aluminum oxide by the Ames lime-soda sinter process: scale-up using a rotary kiln  

SciTech Connect

The Ames Lime-Soda Sinter Process provides a means for recovering aluminum oxide from power plant fly ash while producing a residue that can be used in the manufacture of sulfate resistant (Type V) portland cement. The process has been fully researched and its feasibility is now being demonstrated through pilot plant scale investigation. This paper reports results of the pelletized feed preparation by agglomeration in a rotary pan granulator, continuous feed sintering in an electrically heated rotary kiln, and product recovery from the clinker by aqueous extraction, desilication of the filtrate, and precipitation of a hydrated aluminum oxide. Results from earlier bench-scale research have been found to apply consistently to the pilot plant scale work.

Murtha, M.J.; Burnet, G.; Harnby, N.

1985-01-01

237

Water, Hydration and Health  

PubMed Central

This review attempts to provide some sense of our current knowledge of water including overall patterns of intake and some factors linked with intake, the complex mechanisms behind water homeostasis, the effects of variation in water intake on health and energy intake, weight, and human performance and functioning. Water represents a critical nutrient whose absence will be lethal within days. Water’s importance for prevention of nutrition-related noncommunicable diseases has emerged more recently because of the shift toward large proportions of fluids coming from caloric beverages. Nevertheless, there are major gaps in knowledge related to measurement of total fluid intake, hydration status at the population level, and few longer-term systematic interventions and no published random-controlled longer-term trials. We suggest some ways to examine water requirements as a means to encouraging more dialogue on this important topic. PMID:20646222

Popkin, Barry M.; D’Anci, Kristen E.; Rosenberg, Irwin H.

2010-01-01

238

Principles of calcite dissolution in human and artificial otoconia.  

PubMed

Human otoconia provide mechanical stimuli to deflect hair cells of the vestibular sensory epithelium for purposes of detecting linear acceleration and head tilts. During lifetime, the volume and number of otoconia are gradually reduced. In a process of degeneration morphological changes occur. Structural changes in human otoconia are assumed to cause vertigo and balance disorders such as benign paroxysmal positional vertigo (BPPV). The aim of this study was to investigate the main principles of morphological changes in human otoconia in dissolution experiments by exposure to hydrochloric acid, EDTA, demineralized water and completely purified water respectively. For comparison reasons artificial (biomimetic) otoconia (calcite gelatin nanocomposits) and natural calcite were used. Morphological changes were detected in time steps by the use of environmental scanning electron microscopy (ESEM). Under in vitro conditions three main dissolution mechanisms were identified as causing characteristic morphological changes of the specimen under consideration: pH drops in the acidic range, complex formation with calcium ions and changes of ion concentrations in the vicinity of otoconia. Shifts in pH cause a more uniform reduction of otoconia size (isotropic dissolution) whereas complexation reactions and changes of the ionic concentrations within the surrounding medium bring about preferred attacks at specific areas (anisotropic dissolution) of human and artificial otoconia. Owing to successive reduction of material, all the dissolution mechanisms finally produce fragments and remnants of otoconia. It can be assumed that the organic component of otoconia is not significantly attacked under the given conditions. Artificial otoconia serve as a suitable model system mimicking chemical attacks on biogenic specimens. The underlying principles of calcite dissolution under in vitro conditions may play a role in otoconia degeneration processes such as BPPV. PMID:25048115

Walther, Leif Erik; Blödow, Alexander; Buder, Jana; Kniep, Rüdiger

2014-01-01

239

Principles of Calcite Dissolution in Human and Artificial Otoconia  

PubMed Central

Human otoconia provide mechanical stimuli to deflect hair cells of the vestibular sensory epithelium for purposes of detecting linear acceleration and head tilts. During lifetime, the volume and number of otoconia are gradually reduced. In a process of degeneration morphological changes occur. Structural changes in human otoconia are assumed to cause vertigo and balance disorders such as benign paroxysmal positional vertigo (BPPV). The aim of this study was to investigate the main principles of morphological changes in human otoconia in dissolution experiments by exposure to hydrochloric acid, EDTA, demineralized water and completely purified water respectively. For comparison reasons artificial (biomimetic) otoconia (calcite gelatin nanocomposits) and natural calcite were used. Morphological changes were detected in time steps by the use of environmental scanning electron microscopy (ESEM). Under in vitro conditions three main dissolution mechanisms were identified as causing characteristic morphological changes of the specimen under consideration: pH drops in the acidic range, complex formation with calcium ions and changes of ion concentrations in the vicinity of otoconia. Shifts in pH cause a more uniform reduction of otoconia size (isotropic dissolution) whereas complexation reactions and changes of the ionic concentrations within the surrounding medium bring about preferred attacks at specific areas (anisotropic dissolution) of human and artificial otoconia. Owing to successive reduction of material, all the dissolution mechanisms finally produce fragments and remnants of otoconia. It can be assumed that the organic component of otoconia is not significantly attacked under the given conditions. Artificial otoconia serve as a suitable model system mimicking chemical attacks on biogenic specimens. The underlying principles of calcite dissolution under in vitro conditions may play a role in otoconia degeneration processes such as BPPV. PMID:25048115

Walther, Leif Erik; Blödow, Alexander; Buder, Jana; Kniep, Rüdiger

2014-01-01

240

The sensitized luminescence of manganese-activated calcite  

USGS Publications Warehouse

Synthetic manganese-activated calcites are shown to be practically inert to ultraviolet excitation in the range 2000-3500A, while they are luminescent under cathode-ray excitation. The incorporation of small amounts of an auxiliary impurity along with the manganese produces the strong response to ultraviolet radiation hitherto ascribed to CaCO3:Mn itself. Three such impurities have been studied: lead, thallium, and cerium. The first two induce excitation in the neighborhood of the mercury resonance line, while the cerium introduces a response principally to longer wave ultraviolet. The strong response to 2537A excitation shown by some natural calcites is likewise found to be due to the presence of lead along with the manganese, rather than to the manganese alone. The data do not warrant ascribing the longer wave-length ultraviolet-excited luminescence of all natural calcites to the action of an auxiliary impurity. The essential identity of the cathode-ray excited luminescence spectra of CaCO 3:Mn, CaCO3: (Pb+Mn), CaCO3:(Tl+Mn), and CaCO3:(Ce+Mn) with the 2537A-excited spectra of the latter three is evidence that the luminescent center in all cases is the manganese ion or the MnO6 group. It is shown that a "cascade" mechanism for the action of the auxiliary impurities, lead, thallium, and cerium, is incorrect; and that the phenomenon must be considered as a case of sensitized luminescence. Owing to the nature of cathode-ray excitation, the manganese activator can be excited by this agent even in the absence of a second impurity. For optical excitation, however, an absorption band for the ultraviolet must be established by building into the CaCO3:Mn a second impurity or "sensitizer.".

Schulman, J.H.; Evans, L.W.; Ginther, R.J.; Murata, K.J.

1947-01-01

241

Dynamics of Protein Hydration Water  

E-print Network

We present the frequency- and temperature-dependent dielectric properties of lysozyme solutions in a broad concentration regime, measured at subzero temperatures and compare the results with measurements above the freezing point of water and on hydrated lysozyme powder. Our experiments allow examining the dynamics of unfreezable hydration water in a broad temperature range including the so-called No Man's Land (160 - 235 K). The obtained results prove the bimodality of the hydration shell dynamics and are discussed in the context of the highly-debated fragile-to-strong transition of water.

Wolf, M; Gulich, R; Lunkenheimer, P; Loidl, A

2014-01-01

242

Dynamics of Protein Hydration Water  

E-print Network

We present the frequency- and temperature-dependent dielectric properties of lysozyme solutions in a broad concentration regime, measured at subzero temperatures and compare the results with measurements above the freezing point of water and on hydrated lysozyme powder. Our experiments allow examining the dynamics of unfreezable hydration water in a broad temperature range including the so-called No Man's Land (160 - 235 K). The obtained results prove the bimodality of the hydration shell dynamics and are discussed in the context of the highly-debated fragile-to-strong transition of water.

M. Wolf; S. Emmert; R. Gulich; P. Lunkenheimer; A. Loidl

2014-12-08

243

Hydrates represent gas source, drilling hazard  

SciTech Connect

Gas hydrates look like ordinary ice. However, if a piece of such ice is put into warm water its behavior will be different from the ordinary melting of normal ice. In contrast, gas hydrates cause bubbles in the warm water, which indicates the high content of gas in the hydrate crystals. The presence of four components is required: gas itself, water, high pressure, and low temperature. The paper discusses how hydrates form, hydrates stability, South Caspian hydrates, and hydrates hazards for people, ships, pipelines, and drilling platforms.

Bagirov, E. [Azerbaijan Academy of Sciences, Baku (Azerbaijan); Lerche, I. [Univ. of South Carolina, Columbia, SC (United States)

1997-12-01

244

Strain rate dependent calcite microfabric evolution at natural conditions  

NASA Astrophysics Data System (ADS)

Crystal plastic deformational behaviour of calcite has been the focus of many experimental studies. Different strain rates, pressure and temperature conditions have been addressed to investigate a wide range of deformation regimes. However, a direct comparison with natural fault rocks remains difficult because of extreme differences between experimental and natural strain rates. A flanking structure developed in almost pure calcite marble on Syros (Cyclades, Greece). Due to rotation of a planar feature (crack) a heterogeneous strain field in the surrounding area occurred resulting in different strain domains and the formation of the flanking structure. Assuming that deformation was active continuously during the development of the flanking structure, the different strain domains correspond to different strain-rate domains. The outcrop thus represents the final state of a natural experiment and gives us a great opportunity to get natural constraints on strain rate dependent deformation behaviour of calcite. Comparing the microfabrics in the 1 to 2.5 cm thick shear zone and the surrounding host rocks, which formed under the same metamorphic conditions but with different strain rates, is the central focus of this study. Due to the extreme variation in strain and strain rate, different microstructures and textures can be observed corresponding to different deformation mechanisms. With increasing strain rate we observe a change in dominant deformation mechanism from dislocation glide to dislocation creep and finally diffusion creep. Additionally, a change from subgrain rotation to bulging recrystallization can be observed in the dislocation creep regime. Crystallographic preferred orientations (CPO) and the grade of intracrystalline deformation were measured on a FEI Quanta 3D FEG instrument equipped with an EDAX Digiview IV EBSD camera. At all strain rates clear CPOs developed leading to the assumption that calcite preferentially deforms within the dislocation creep field. However, we can also find clear evidence for grain size sensitive deformation mechanisms at smaller grain sizes (3.6 ?m) consistent with experimental observations and determined flaw laws. The results of this study are compared with experimental data, closing the gap between experimental and natural geological strain rates.

Rogowitz, Anna; Grasemann, Bernhard; Huet, Benjamin; Habler, Gerlinde

2014-05-01

245

Lime enhances moving bed filters for mercury and dioxin control  

SciTech Connect

Moving bed carbon filters were developed and used in Europe to control mercury and dioxin emissions from municipal waste combustors (MWCs), crematories, hazardous waste incinerators and power plants. Although some operating problems such as a potential for fires to form in the carbon beds have caused operators some concern, more stable bed materials are presently being produced which can maintain the moving bed filter`s capability in reducing mercury and dioxin emissions to very low levels while providing safe operations. Maerker Umwelttechnik GmbH (Maerker) and Dravo Lime Company (Dravo) have developed a pelletized form of Sorbalit{reg_sign} that replaces the carbon in moving bed filters and is effective in removing mercury, dioxins, and acid gases without the inherent problems of using a carbon only adsorbent system. Sorbalit pellets are a formulation of portland cement, lime, carbon, and sulfur compounds. These pellets are currently being successfully applied in a hazardous waste incinerator, a foundry, a crematory, and a contaminated soil treatment plant. This paper discusses the development of pellet technology and its application in moving bed filters. Safety aspects for the use of composite carbon/lime pellets will be discussed and a review of removal efficiencies among carbon alone, a composite carbon/lime material in a powder form, and composite carbon/lime adsorbents in a pellet form will be provided.

Licata, A. [Dravo Lime Co., Yonkers, NY (United States); Goetz, E. [Dravo Lime Co., Pittsburgh, PA (United States); Nethe, L.P. [Maerker Umwelttechnik GmbH, Harburg (Germany)

1997-12-01

246

Water release patterns of heated speleothem calcite and hydrogen isotope composition of fluid inclusions  

Microsoft Academic Search

Speleothem fluid inclusions are a potential paleo-precipitation proxy to reconstruct past rainwater isotopic composition (?18O, ?D). To get a better insight in the extraction of inclusion water from heated speleothem calcite, we monitored the water released from crushed and uncrushed speleothem calcite, heated to 900 °C at a rate of 300 °C\\/h, with a quadrupole mass spectrometer. Crushed calcite released water in

Sophie Verheyden; Dominique Genty; Olivier Cattani; Martin R. van Breukelen

2008-01-01

247

Compaction creep of wet granular calcite by pressure solution at 28°C to 150°C  

Microsoft Academic Search

Uniaxial compaction experiments have been carried out on wet calcite powders prepared from milled limestone, analytical grade calcite, and superpure calcite. The tests were performed at 28°C–150°C, effective stresses of 20–47 MPa, and a pore pressure of 20 MPa, using presaturated CaCO3 solution as the pore fluid. Sample grain sizes ranged from 12 to 86 ?m. The aim was to

Xiangmin Zhang; Christopher J. Spiers; Colin J. Peach

2010-01-01

248

The ubiquitous nature of accessory calcite in granitoid rocks: Implications for weathering, solute evolution, and petrogenesis  

USGS Publications Warehouse

Calcite is frequently cited as a source of excess Ca, Sr and alkalinity in solutes discharging from silicate terrains yet, no previous effort has been made to assess systematically the overall abundance, composition and petrogenesis of accessory calcite in granitoid rocks. This study addresses this issue by analyzing a worldwide distribution of more than 100 granitoid rocks. Calcite is found to be universally present in a concentration range between 0.028 to 18.8 g kg-1 (mean = 2.52 g kg-1). Calcite occurrences include small to large isolated anhedral grains, fracture and cavity infillings, and sericitized cores of plagioclase. No correlation exists between the amount of calcite present and major rock oxide compositions, including CaO. Ion microprobe analyses of in situ calcite grains indicate relatively low Sr (120 to 660 ppm), negligible Rb and 87Sr/86Sr ratios equal to or higher than those of coexisting plagioclase. Solutes, including Ca and alkalinity produced by batch leaching of the granitoid rocks (5% CO2 in DI water for 75 d at 25??C), are dominated by the dissolution of calcite relative to silicate minerals. The correlation of these parameters with higher calcite concentrations decreases as leachates approach thermodynamic saturation. In longer term column experiments (1.5 yr), reactive calcite becomes exhausted, solute Ca and Sr become controlled by feldspar dissolution and 87Sr/ 86Sr by biotite oxidation. Some accessory calcite in granitoid rocks is related to intrusion into carbonate wall rock or produced by later hydrothermal alteration. However, the ubiquitous occurrence of calcite also suggests formation during late stage (subsolidus) magmatic processes. This conclusion is supported by petrographic observations and 87Sr/86Sr analyses. A review of thermodynamic data indicates that at moderate pressures and reasonable CO2 fugacities, calcite is a stable phase at temperatures of 400 to 700??C. Copyright ?? 2005 Elsevier Ltd.

White, A.F.; Schulz, M.S.; Lowenstern, J. B.; Vivit, D.V.; Bullen, T.D.

2005-01-01

249

Addition of calcite reduces iron's bioavailability in the Pennsylvania coals--potential use of calcite for the prevention of coal workers' lung diseases.  

PubMed

In the present study, a hypothesis was tested that the addition of calcite into the Pennsylvania coals may reduce levels of bioavailable iron (BAI), an important component in the mixed coal dust that may contribute to coal workers' lung diseases. Predetermined proportions of calcite (0, 1, 2, 5, 10% w/w) were added into three PA coals. After suspending the mixtures in an aqueous phosphate solution (10 mM, pH 4.5), which mimics the phagolysosomal conditions of the cells, levels of pH as well as calcium ions (Ca2+) in the coals were increased in a calcite concentration-dependent manner. In contrast, levels of BAI (both Fe2+ and Fe3+) were decreased. The inhibitory effects of calcite on the bioavailability of iron in human lung epithelial A549 cells and primary rat alveolar macrophages (AMs) were also examined. It was found that levels of low-molecular-weight (LMW) iron were significantly decreased in both A549 cells and AMs treated with the 10% calcite-PA coal mixture compared to those treated with the PA coal alone, while calcite itself had no effect on intracellular LMW iron. Calcite also showed a significant inhibitory effect on PA coal-induced ferritin synthesis in A549 cells. Reverse-transcription polymerase chain reaction (RT-PCR) studies revealed that the iron-containing PA coal downregulated levels of transferrin receptor (TfR) mRNA in A549 cells, which was partially restored by the addition of calcite. Our results indicate that calcite can inhibit the bioavailability of iron in the iron-containing PA coals. PMID:16195220

Zhang, Qi; Huang, Xi

2005-10-01

250

Module 11 – Withdrawing Nutrition, Hydration  

Cancer.gov

Module eleven of the EPEC-O Self-Study Original Version discusses the general aspects of withholding or withdrawing of life-sustaining therapies, and presents a specific application to artificial nutrition and hydration.

251

Deep water cycle: Mantle hydration  

NASA Astrophysics Data System (ADS)

The fate of water that enters the mantle within subducting slabs is unclear. Laboratory experiments indicate that subducted crust can transport large amounts of water into the deep Earth, and the lower mantle may become more hydrated over time.

Nishi, Masayuki

2015-01-01

252

High-pressure gas hydrates   

E-print Network

pressures. Clathrate hydrates have been extensively studied because they occur widely in nature, have important industrial applications, and provide insight into water-guest hydrophobic interactions. Until recently, the expectation-based on calculations...

Loveday, J. S.; Nelmes, R. J.

253

Crystallization of a polymorphic hydrate system.  

PubMed

Nitrofurantoin can form two monohydrates, which have the same chemical composition and molar ratio of water, but differ in the crystal arrangements. The two monohydrates (hydrates I and II) could be produced independently via evaporative crystallization, where supersaturation and solvent composition were both found to have an effect. Hydrate I showed much slower crystallization than hydrate II. During cooling crystallization, the nucleation and growth of hydrate II was again dominant, consuming all supersaturation and leading to no hydrate I formation. Seeding of hydrate I during cooling crystallization was also applied, but the hydrate I seeds were not able to initiate its nucleation rather than dissolving into crystallizing solution. Although solubility tests revealed that hydrate II is more stable than hydrate I due to its lower solubility (110 +/- 4 and 131 +/- 12 microg/mL for hydrates II and I, respectively), this difference is rather small. Therefore, the small free energy difference between the two hydrates, together with the slow crystallization of hydrate I, both lead to a hindrance of hydrate I formation. Furthermore, the crystal structure of hydrate II demonstrated a higher H-bonding extent than hydrate I, suggesting its more favorable crystallization. This is in good agreement with experimental results. PMID:19569226

Tian, F; Qu, H; Louhi-Kultanen, M; Rantanen, J

2010-02-01

254

Methane hydrate stability in seawater  

Microsoft Academic Search

Experiment data are presented for methane hydrate stability conditions in seawater (S ⼠33.5 {per_thousand}). For the pressure range of 2.75-10.0 MPa, at any given pressure, the dissociation temperature of methane hydrate is depressed by approximately -1.1 °C relative to the pure methane-pure water system. These experimental results are consistent with previously reported thermodynamic predictions and experimental results obtained with

Gerald R. Dickens; M. S. Quinby-Hunt

1994-01-01

255

Liming, reacidification, and the mobilization of cadmium from sediments  

SciTech Connect

Over several decades severe acidification of streams and lakes has taken place in Scandinavia and North America, with catastrophic consequences for aquatic life. In certain water systems in southern Norway fish populations have been completely eliminated by severe acidification. This fish mortality has been attributed largely to increased concentrations of toxic aluminum and, since liming counteracts acidification and reduces the aluminum levels in the water, it has become the most widespread remedy to restore fish habitats. Cadmium concentrations in the water are also pH-dependent and, therefore, affected by liming. This laboratory experiment was conducted to clarify the significance of liming as a factor in reducing cadmium concentrations from lake water and the behavior of cdamium following reacidification. In addition the behavior of organic materials under varying pH conditions was studied. 16 refs., 4 figs., 2 tabs.

Fimreite, N.; Nenseter, B.; Steen, B. [Telemark College, Bo (Norway)] [Telemark College, Bo (Norway)

1996-12-01

256

Calcitic microlenses as part of the photoreceptor system in brittlestars  

NASA Astrophysics Data System (ADS)

Photosensitivity in most echinoderms has been attributed to `diffuse' dermal receptors. Here we report that certain single calcite crystals used by brittlestars for skeletal construction are also a component of specialized photosensory organs, conceivably with the function of a compound eye. The analysis of arm ossicles in Ophiocoma showed that in light-sensitive species, the periphery of the labyrinthic calcitic skeleton extends into a regular array of spherical microstructures that have a characteristic double-lens design. These structures are absent in light-indifferent species. Photolithographic experiments in which a photoresist film was illuminated through the lens array showed selective exposure of the photoresist under the lens centres. These results provide experimental evidence that the microlenses are optical elements that guide and focus the light inside the tissue. The estimated focal distance (4-7µm below the lenses) coincides with the location of nerve bundles-the presumed primary photoreceptors. The lens array is designed to minimize spherical aberration and birefringence and to detect light from a particular direction. The optical performance is further optimized by phototropic chromatophores that regulate the dose of illumination reaching the receptors. These structures represent an example of a multifunctional biomaterial that fulfills both mechanical and optical functions.

Aizenberg, Joanna; Tkachenko, Alexei; Weiner, Steve; Addadi, Lia; Hendler, Gordon

2001-08-01

257

Calcitic microlenses as part of the photoreceptor system in brittlestars.  

PubMed

Photosensitivity in most echinoderms has been attributed to 'diffuse' dermal receptors. Here we report that certain single calcite crystals used by brittlestars for skeletal construction are also a component of specialized photosensory organs, conceivably with the function of a compound eye. The analysis of arm ossicles in Ophiocoma showed that in light-sensitive species, the periphery of the labyrinthic calcitic skeleton extends into a regular array of spherical microstructures that have a characteristic double-lens design. These structures are absent in light-indifferent species. Photolithographic experiments in which a photoresist film was illuminated through the lens array showed selective exposure of the photoresist under the lens centres. These results provide experimental evidence that the microlenses are optical elements that guide and focus the light inside the tissue. The estimated focal distance (4-7 micrometer below the lenses) coincides with the location of nerve bundles-the presumed primary photoreceptors. The lens array is designed to minimize spherical aberration and birefringence and to detect light from a particular direction. The optical performance is further optimized by phototropic chromatophores that regulate the dose of illumination reaching the receptors. These structures represent an example of a multifunctional biomaterial that fulfills both mechanical and optical functions. PMID:11518966

Aizenberg, J; Tkachenko, A; Weiner, S; Addadi, L; Hendler, G

2001-08-23

258

Texture effects on megahertz dielectric properties of calcite rock samples  

NASA Astrophysics Data System (ADS)

Dielectric measurements have been made from 0.5 to 1300 MHz on Whitestone, a quarried calcite rock, saturated with salty water. Whitestone shows a large increase in dielectric permittivity (dispersion) at the low end of this frequency range. When the conductivity of the water is varied, the dielectric permittivity of Whitestone is found to scale as water conductivity/frequency, i.e., as the complex dielectric constant of water. This is believed to be unique in measurements on insulator-conductor mixtures, and establishes that the dispersion is primarily caused by the geometry of the sample. Two other calcite samples show much lower dielectric dispersion. Micrographs indicate that the variation in dispersion among the three samples is in rough proportion to grain platiness. This is consistent with the platey grain mechanism, one of three mechanisms proposed by Sen to explain dielectric dispersion in water-saturated rocks. A model consisting of water containing insulating spheroids of identical aspect ratio, isotropically distributed in orientation, predicts that increased grain platiness reduces both low-frequency conductivity and high-frequency dielectric permittivity in a closely related way; this is observed experimentally. However, this model does not fit simultaneously all electrical properties of Whitestone; evidently a more complex geometrical model is needed. Dielectric dispersion caused by texture is of practical importance in estimating water content of subsurface rocks from borehole measurements of dielectric permittivity, particularly at high water salinities.

Kenyon, W. E.

1984-04-01

259

Upscaling Calcite Growth Rates From the Mesoscale to the Macroscale  

SciTech Connect

Quantitative prediction of mineral reaction rates in the subsurface remains a daunting task partly because a key parameter for macroscopic models, the reactive site density, is poorly constrained. Here we report atomic force microscopy (AFM) measurements on the calcite surface of monomolecular step densities, treated as equivalent to the reactive site density, as a function of aqueous calcium-to-carbonate ratio and saturation index. Data for the obtuse step orientation are combined with existing step velocity measurements to generate a model that predicts overall macroscopic calcite growth rates. The model is quantitatively consistent with several published macroscopic rates under a range of alkaline solution conditions, particularly for two of the most comprehensive data sets without the need for additional fit parameters. The model reproduces peak growth rates and its functional form is simple enough to be incorporated into reactive transport or other macroscopic models designed for predictions in porous media. However, it currently cannot model equilibrium, pH effects, and may overestimate rates at high aqueous calcium-to-carbonate ratios. The discrepancies in rates at high calcium-to-carbonate ratios may be due to differences in pre-treatment, such as exposing the seed material to SI 1.0 to generate/develop growth hillocks, or other factors.

Bracco, Jacquelyn N [ORNL; Stack, Andrew G [ORNL; Steefel, Carl I [Lawrence Berkeley National Laboratory (LBNL)

2013-01-01

260

Crystallographic orientation inhomogeneity and crystal splitting in biogenic calcite  

PubMed Central

The calcitic prismatic units forming the outer shell of the bivalve Pinctada margaritifera have been analysed using scanning electron microscopy–electron back-scatter diffraction, transmission electron microscopy and atomic force microscopy. In the initial stages of growth, the individual prismatic units are single crystals. Their crystalline orientation is not consistent but rather changes gradually during growth. The gradients in crystallographic orientation occur mainly in a direction parallel to the long axis of the prism, i.e. perpendicular to the shell surface and do not show preferential tilting along any of the calcite lattice axes. At a certain growth stage, gradients begin to spread and diverge, implying that the prismatic units split into several crystalline domains. In this way, a branched crystal, in which the ends of the branches are independent crystalline domains, is formed. At the nanometre scale, the material is composed of slightly misoriented domains, which are separated by planes approximately perpendicular to the c-axis. Orientational gradients and splitting processes are described in biocrystals for the first time and are undoubtedly related to the high content of intracrystalline organic molecules, although the way in which these act to induce the observed crystalline patterns is a matter of future research. PMID:23804442

Checa, Antonio G.; Bonarski, Jan T.; Willinger, Marc G.; Faryna, Marek; Berent, Katarzyna; Kania, Bogusz; González-Segura, Alicia; Pina, Carlos M.; Pospiech, Jan; Morawiec, Adam

2013-01-01

261

Environmental controls on the Emiliania huxleyi calcite mass  

NASA Astrophysics Data System (ADS)

Although ocean acidification is expected to impact (bio) calcification by decreasing the seawater carbonate ion concentration, [CO32-], there is evidence of nonuniform response of marine calcifying plankton to low seawater [CO32-]. This raises questions about the role of environmental factors other than acidification and about the complex physiological responses behind calcification. Here we investigate the synergistic effect of multiple environmental parameters, including seawater temperature, nutrient (nitrate and phosphate) availability, and carbonate chemistry on the coccolith calcite mass of the cosmopolitan coccolithophore Emiliania huxleyi, the most abundant species in the world ocean. We use a suite of surface (late Holocene) sediment samples from the South Atlantic and southwestern Indian Ocean taken from depths lying above the modern lysocline (with the exception of eight samples that are located at or below the lysocline). The coccolith calcite mass in our results presents a latitudinal distribution pattern that mimics the main oceanographic features, thereby pointing to the potential importance of seawater nutrient availability (phosphate and nitrate) and carbonate chemistry (pH and pCO2) in determining coccolith mass by affecting primary calcification and/or the geographic distribution of E. huxleyi morphotypes. Our study highlights the importance of evaluating the combined effect of several environmental stressors on calcifying organisms to project their physiological response(s) in a high-CO2 world and improve interpretation of paleorecords.

Horigome, M. T.; Ziveri, P.; Grelaud, M.; Baumann, K.-H.; Marino, G.; Mortyn, P. G.

2014-04-01

262

The coordination and distribution of B in foraminiferal calcite  

NASA Astrophysics Data System (ADS)

The isotopic ratio and concentration of B in foraminiferal calcite appear to reflect the pH and bicarbonate concentration of seawater. The use of B as a chemical proxy tracer has the potential to transform our understanding of the global carbon cycle, and ocean acidification processes. However, discrepancies between the theory underpinning the B proxies, and mineralogical observations of B coordination in biomineral carbonates call the basis of these proxies into question. Here, we use synchrotron X-ray spectromicroscopy to show that B is hosted solely as trigonal BO3 in the calcite test of Amphistegina lessonii, and that B concentration exhibits banding at the micron length scale. In contrast to previous results, our observation of trigonal B agrees with the predictions of the theoretical mechanism behind B palaeoproxies. These data strengthen the use of B for producing palaeo-pH records. The observation of systematic B heterogeneity, however, highlights the complexity of foraminiferal biomineralisation, implying that B incorporation is modulated by biological or crystal growth processes.

Branson, Oscar; Kaczmarek, Karina; Redfern, Simon A. T.; Misra, Sambuddha; Langer, Gerald; Tyliszczak, Tolek; Bijma, Jelle; Elderfield, Henry

2015-04-01

263

Conformal mapping-based 3D face recognition Przemyslaw Szeptycki, Mohsen Ardabilian, Liming Chen  

E-print Network

.ardabilian, liming.chen}@ec-lyon.fr Wei Zeng, Davig Gu, Dimitris Samaras Computer Science Department, Stony BrookConformal mapping-based 3D face recognition Przemyslaw Szeptycki, Mohsen Ardabilian, Liming Chen MI

264

REMOVAL OF BERYLLIUM FROM DRINKING WATER BY CHEMICAL COAGULATION AND LIME SOFTENING  

EPA Science Inventory

The effectiveness of conventional drinking water treatment and lime softening was evaluated for beryllium removal from two drinking water sources. ar test studies were conducted to determine how common coagulants (aluminum sulfate and ferric chloride and lime softening performed ...

265

Liming Poultry Manures to Kill Pathogens and Decrease Soluble Phosphorus  

SciTech Connect

Received for publication September 9, 2005. Stabilizing phosphorus (P) in poultry waste to reduce P losses from manured soils is important to protect surface waters, while pathogens in manures are an emerging issue. This study was conducted to evaluate CaO and Ca(OH){sub 2} for killing manure bacterial populations (pathogens) and stabilizing P in poultry wastes and to investigate the influence on soils following amendment with the treated wastes. Layer manure and broiler litter varying in moisture content were treated with CaO and Ca(OH){sub 2} at rates of 2.5, 5, 10, and 15% by weight. All treated wastes were analyzed for microbial plate counts, pH, and water-soluble phosphorus (WSP), while a few selected layer manures were analyzed by phosphorus X-ray absorption near edge structure (XANES). A loamy sand and a silt loam were amended with broiler litter and layer manure treated with CaO at rates of 0, 2.5, 5, 10, and 15% and soil WSP and pH were measured at times 1, 8, and 29 d. Liming reduced bacterial populations, with greater rates of lime leading to greater reductions; for example 10% CaO applied to 20% solids broiler litter reduced the plate counts from 793 000 to 6500 mL{sup -1}. Liming also reduced the WSP in the manures by over 90% in all cases where at least 10% CaO was added. Liming the manures also reduced WSP in soils immediately following application and raised soil pH. The liming process used successfully reduced plate counts and concerns about P losses in runoff following land application of these limed products due to decreased WSP.

Maguire,R.; Hesterberg, D.; Gernat, A.; Anderson, K.; Wineland, M.; Grimes, J.

2006-01-01

266

Speciation of aluminium, arsenic and molybdenum in excessively limed lakes  

Microsoft Academic Search

The possible existence of the potentially toxic oxyanions of Al (Al(OH)4?), As (HAsO42?), and Mo (MoO42?) was examined in excessively limed lakes. In-situ dialysis (MWCO 1 kDa) was performed in the surface and bottom waters of two excessively limed lakes (pH 7.1–7.7) and one acidic lake (pH?5.4). The dialysable metal concentrations were compared to the equilibrium distribution of species as calculated

Carin Sjöstedt; Teresia Wällstedt; Jon Petter Gustafsson; Hans Borg

2009-01-01

267

Catalytic iron oxide for lime regeneration in carbonaceous fuel combustion  

DOEpatents

Lime utilization for sulfurous oxides absorption in fluidized combustion of carbonaceous fuels is improved by impregnation of porous lime particulates with iron oxide. The impregnation is achieved by spraying an aqueous solution of mixed iron sulfate and sulfite on the limestone before transfer to the fluidized bed combustor, whereby the iron compounds react with the limestone substrate to form iron oxide at the limestone surface. It is found that iron oxide present in the spent limestone acts as a catalyst to regenerate the spent limestone in a reducing environment. With only small quantities of iron oxide the calcium can be recycled at a significantly increased rate.

Shen, Ming-Shing (Rocky Point, NY); Yang, Ralph T. (Middle Island, NY)

1980-01-01

268

Paleotransport of lanthanides and strontium recorded in calcite compositions from tuffs at Yucca Mountain, Nevada, USA  

NASA Astrophysics Data System (ADS)

Secondary calcite occurs in both saturated and unsaturated hydrologic zones (SZ and UZ, respectively) in the tuffs at Yucca Mountain, Nevada, USA. In the upper UZ, the major constituents of the calcite crystal structure (C, O) have surface origins. At greater depth there is a "barren zone," straddling the water table, where calcite is rare and mixing of surface and subsurface sources may occur. Deep in the SZ, distinctive Mn calcites reflect deep sources, including Ca released as analcime or albite formed and carbonates derived from underlying Paleozoic rocks. In the UZ and in the barren zone, above the deep Mn calcites, variations in calcite lanthanide chemistry can be used to distinguish rhyolitic from quartz-latitic sources. Lanthanide ratios and Sr contents of calcites record the chemical evolution of waters flowing through the UZ and upper SZ. Variations in calcite chemistry in the UZ and in the barren zone show that (1) Sr, which is readily exchanged with clays or zeolites, is essentially removed from some flowpaths that are in contact with these minerals and (2) traces of Mn oxides found in the tuffs have a significant effect on groundwater chemistry in the UZ and in the barren zone by removing almost all Ce from solution (evidenced by characteristic Ce depletions in calcite throughout this zone). Extreme Ce removal may be a result of Ce oxidation (Ce 3+? Ce 4+) at the surfaces of some Mn oxides, particularly rancieite. Higher Sr contents and lack of Ce depletions in the deeper Mn calcites reflect different ages, origins, and transport systems. The calcite record of lanthanide and Sr transport in the UZ shows that minor minerals (clays and zeolites) and even trace minerals (Mn oxides) will affect the compositions of groundwaters that flow over distances greater than a few tens of meters.

Vaniman, David T.; Chipera, Steve J.

1996-11-01

269

Raman Mapping of the Indentation-Induced Densification of a Soda-Lime-Silicate Glass  

E-print Network

to the soda-lime silicate glasses, window or float glasses, is not straight- forward.11,12 The maximumRaman Mapping of the Indentation-Induced Densification of a Soda-Lime-Silicate Glass Assia Kassir to map the Vickers indentation-induced densification on a window glass (soda-lime silicate glass), from

Paris-Sud XI, Université de

270

Presentation and analysis of a model simulating the pH response of lake liming  

Microsoft Academic Search

Lake liming is a very common remedy for acidification in Sweden. This study presents a practically useful management model to plan and predict the outcome and duration of the liming. It is a mixed model including both statistical regressions, based on catchment and lake morphometric data, and dynamic, mass-balance interactions. It is driven by data on the amount of lime

Fredrik Ottosson; Lars Håkanson

1997-01-01

271

Effect of liming and phosphorus application on performance of Leucaena leucocephala in acid soils  

Microsoft Academic Search

Pot experiments were conducted to assess the lime and phosphorus requirements ofLeucaena leucocephala (LAM.) De Wit grown on three acid soils (Ultisols) from southeastern Nigeria. Liming and phosphorus application significantly enhanced growth ofL. leucocephala. Ammakama soil showed best effect to phosphorus application, while acidity problems were more pronounced on Onne and Isienu soils. High lime rate (2000 ppm) reduced plant

B. Duguma; B. T. Kang; D. U. U. Okali

1988-01-01

272

40 CFR 180.1232 - Lime-sulfur; exemption from the requirement of a tolerance.  

Code of Federal Regulations, 2010 CFR

...2010-07-01 2010-07-01 false Lime-sulfur; exemption from the requirement of a...From Tolerances § 180.1232 Lime-sulfur; exemption from the requirement of a...tolerance is established for residues of lime-sulfur. [70 FR 33363, June 8,...

2010-07-01

273

40 CFR 180.1232 - Lime-sulfur; exemption from the requirement of a tolerance.  

Code of Federal Regulations, 2012 CFR

...2012-07-01 2012-07-01 false Lime-sulfur; exemption from the requirement of a...From Tolerances § 180.1232 Lime-sulfur; exemption from the requirement of a...tolerance is established for residues of lime-sulfur. [70 FR 33363, June 8,...

2012-07-01

274

40 CFR 180.1232 - Lime-sulfur; exemption from the requirement of a tolerance.  

Code of Federal Regulations, 2011 CFR

...2011-07-01 2011-07-01 false Lime-sulfur; exemption from the requirement of a...From Tolerances § 180.1232 Lime-sulfur; exemption from the requirement of a...tolerance is established for residues of lime-sulfur. [70 FR 33363, June 8,...

2011-07-01

275

40 CFR 180.1232 - Lime-sulfur; exemption from the requirement of a tolerance.  

Code of Federal Regulations, 2013 CFR

...2013-07-01 2013-07-01 false Lime-sulfur; exemption from the requirement of a...From Tolerances § 180.1232 Lime-sulfur; exemption from the requirement of a...tolerance is established for residues of lime-sulfur. [70 FR 33363, June 8,...

2013-07-01

276

Remediation of Pb-contaminated soils by washing with hydrochloric acid and subsequent immobilization with calcite and allophanic soil.  

PubMed

Removal of heavy metals from contaminated soil is not popular because of its high cost. Reducing the bioaccessible heavy metals content to an allowable level by washing with inorganic acids and subsequent immobilization of remained metals may be a low cost option for soil remediation. The applicability of this combined treatment was investigated using three different types of soil, a kaolinitic, a smectitic and an allophanic soil, which were artificially contaminated with Pb. The effectiveness of the treatment was evaluated using two main criteria: (i) reduction of the HCl extractable Pb (bioaccessible Pb) below 150 mg kg(-1), reduction of water extractable Pb below the concentration of 0.01 mg L(-1). These values correspond to allowable levels suggested by the Japanese Ministry of Environment. The soils were washed batch-wise at a solution to soil ratio of 5 L kg(-1) successively with 1 mol L(-1) HCl and 0.1 mol L(-1) CaCl(2) solutions. The two solutions were separated by filtration from one batch and reused for washing the next batch of soil without processing. The Pb concentration in the solutions increased after repeated use and removal efficiency gradually declined. The efficiency of the treatment was highly dependent on the type of soil. In the kaolinitic soil, HCl extractable Pb content of the soil from the first batch was about 50 mg kg(-1) and it exceeded 150 mg kg(-1) in that from sixth batch. But the combined soils from 1st to 10th batches gave bioaccessible Pb content barely below 150 mg kg(-1). For the smectitic soil having higher cation exchange capacity, the acceptable number of times of reuse was estimated to be 4. For the allophanic soil, treatment with the HCl solution was efficient only for the first batch of the soil, and the reuse of the acid solution was found to be ineffective. The application of 50 g kg(-1) of calcite or slacked lime was effective for reducing the water extractable Pb content. To keep soil pH near neutral and secure long term stability, the application of 50 g kg(-1) of calcite and 100 g kg(-1) of allophanic soil was chosen as the best method. This combination of amendments could reduce the water extractable Pb to almost undetectable levels after 3 days of aging. PMID:17267106

Isoyama, Masahiro; Wada, Shin-Ichiro

2007-05-17

277

Isotopic, chemical and textural relations during the experimental alteration of biogenic high-magnesian calcite  

Microsoft Academic Search

Dissolution runs with four biogenic high magnesian calcites (HMC) of different magnesium content were conducted in distilled water saturated with 100% CO 2 and 3% CO 2 at 70°C and 35°C in order to study the mechanism of alteration of HMC to low magnesian calcite (LMC). The isotopic composition ( 13 C and 18 O ) of the solutions (-30%.

J. V. Turner; T. F. Anderson; P. A. Sandberg; S. J. Goldstein

1986-01-01

278

Biotic Control of Skeletal Growth by Scleractinian Corals in Aragonite–Calcite Seas  

PubMed Central

Modern scleractinian coral skeletons are commonly composed of aragonite, the orthorhombic form of CaCO3. Under certain conditions, modern corals produce calcite as a secondary precipitate to fill pore space. However, coral construction of primary skeletons from calcite has yet to be demonstrated. We report a calcitic primary skeleton produced by the modern scleractinian coral Acropora tenuis. When uncalcified juveniles were incubated from the larval stage in seawater with low mMg/Ca levels, the juveniles constructed calcitic crystals in parts of the primary skeleton such as the septa; the deposits were observable under Raman microscopy. Using scanning electron microscopy, we observed different crystal morphologies of aragonite and calcite in a single juvenile skeleton. Quantitative analysis using X-ray diffraction showed that the majority of the skeleton was composed of aragonite even though we had exposed the juveniles to manipulated seawater before their initial crystal nucleation and growth processes. Our results indicate that the modern scleractinian coral Acropora mainly produces aragonite skeletons in both aragonite and calcite seas, but also has the ability to use calcite for part of its skeletal growth when incubated in calcite seas. PMID:24609012

Higuchi, Tomihiko; Fujimura, Hiroyuki; Yuyama, Ikuko; Harii, Saki; Agostini, Sylvain; Oomori, Tamotsu

2014-01-01

279

Uranium in foraminiferal calcite as a recorder of seawater uranium concentrations  

Microsoft Academic Search

The authors present results of an investigation of uranium\\/calcium ratios in cleaned foraminiferal calcite as a recorder of seawater uranium concentrations. For accurate reconstruction of past seawater uranium content, shell calcite must incorporate uranium in proportion to seawater concentration and must preserve its original uranium composition over time. Laboratory culture experiments with live benthic (Amphistegina lobifera) and live planktonic (Globigerinell

A. D. Russell; S. Emerson; B. K. Nelson; J. Erez; D. W. Lea

1994-01-01

280

Struvite and calcite crystallization induced by cellular membranes of Myxococcus xanthus  

NASA Astrophysics Data System (ADS)

In this work we have proved that struvite and calcite crystals can be obtained in the presence of the cellular membrane fraction of Myxococcus xanthus, when appropriate supersaturated solutions are used. Probably, the negative charged points of the external side of the cellular structures could reduce the metastability field of struvite and calcite, acting as heterogeneous nuclei of crystallization.

González-Muñoz, Ma Teresa; Omar, Nabil Ben; Martínez-Cañamero, Magdalena; Rodríguez-Gallego, Manuel; Galindo, Alberto López; Arias, JoséMa

1996-06-01

281

Amorphous Calcium Carbonate Transforms into Calcite during Sea Urchin Larval Spicule Growth  

Microsoft Academic Search

Sea urchin larvae form an endoskeleton composed of a pair of spicules. For more than a century it has been stated that each spicule comprises a single crystal of the CaCO3 mineral, calcite. We show that an additional mineral phase, amorphous calcium carbonate, is present in the sea urchin larval spicule, and that this inherently unstable mineral transforms into calcite

Elia Beniash; Joanna Aizenberg; Lia Addadi; Stephen Weiner

1997-01-01

282

Cathodoluminescence of synthetic and natural calcite: the effects of manganese and iron on orange emission  

Microsoft Academic Search

Summary The orange cathodoluminescence (CL) of calcite is known to be due to the presence of Mn 2+ cations. It has been demonstrated here using CL and electron paramagnetic resonance (EPR) crossed analysis from synthetic calcite that neither Fe 2+ nor Fe 3+ ions influence this luminescence emission. More complex natural calcium carbonates have been investigated to check whether or

S. Cazenave; R. Chapoulie; G. Villeneuve

2003-01-01

283

Biotic control of skeletal growth by scleractinian corals in aragonite-calcite seas.  

PubMed

Modern scleractinian coral skeletons are commonly composed of aragonite, the orthorhombic form of CaCO3. Under certain conditions, modern corals produce calcite as a secondary precipitate to fill pore space. However, coral construction of primary skeletons from calcite has yet to be demonstrated. We report a calcitic primary skeleton produced by the modern scleractinian coral Acropora tenuis. When uncalcified juveniles were incubated from the larval stage in seawater with low mMg/Ca levels, the juveniles constructed calcitic crystals in parts of the primary skeleton such as the septa; the deposits were observable under Raman microscopy. Using scanning electron microscopy, we observed different crystal morphologies of aragonite and calcite in a single juvenile skeleton. Quantitative analysis using X-ray diffraction showed that the majority of the skeleton was composed of aragonite even though we had exposed the juveniles to manipulated seawater before their initial crystal nucleation and growth processes. Our results indicate that the modern scleractinian coral Acropora mainly produces aragonite skeletons in both aragonite and calcite seas, but also has the ability to use calcite for part of its skeletal growth when incubated in calcite seas. PMID:24609012

Higuchi, Tomihiko; Fujimura, Hiroyuki; Yuyama, Ikuko; Harii, Saki; Agostini, Sylvain; Oomori, Tamotsu

2014-01-01

284

The solubility of fish-produced high magnesium calcite in seawater Ryan J. Woosley,1  

E-print Network

The solubility of fish-produced high magnesium calcite in seawater Ryan J. Woosley,1 Frank J 2012; published 11 April 2012. [1] Fish have been shown to produce high (10 to 48 mol %) magnesium 0.09) is approximately two times higher than aragonite and similar to the high magnesium calcite

Grosell, Martin

285

Catalytic Biomineralization of Fluorescent Calcite by the Thermophilic Bacterium Geobacillus thermoglucosidasius?  

PubMed Central

The thermophilic Geobacillus bacterium catalyzed the formation of 100-?m hexagonal crystals at 60°C in a hydrogel containing sodium acetate, calcium chloride, and magnesium sulfate. Under fluorescence microscopy, crystals fluoresced upon excitation at 365 ± 5, 480 ± 20, or 545 ± 15 nm. X-ray diffraction indicated that the crystals were magnesium-calcite in calcite-type calcium carbonate. PMID:20851984

Yoshida, Naoto; Higashimura, Eiji; Saeki, Yuichi

2010-01-01

286

Catalytic biomineralization of fluorescent calcite by the thermophilic bacterium Geobacillus thermoglucosidasius.  

PubMed

The thermophilic Geobacillus bacterium catalyzed the formation of 100-?m hexagonal crystals at 60°C in a hydrogel containing sodium acetate, calcium chloride, and magnesium sulfate. Under fluorescence microscopy, crystals fluoresced upon excitation at 365 ± 5, 480 ± 20, or 545 ± 15 nm. X-ray diffraction indicated that the crystals were magnesium-calcite in calcite-type calcium carbonate. PMID:20851984

Yoshida, Naoto; Higashimura, Eiji; Saeki, Yuichi

2010-11-01

287

SEMI-BATCH PRECIPITATION OF CALCIUM SULFATE DIHYDRATE FROM CALCITE AND SULFURIC ACID  

E-print Network

SEMI-BATCH PRECIPITATION OF CALCIUM SULFATE DIHYDRATE FROM CALCITE AND SULFURIC ACID Frédéric BARD1 a calcite suspension to a sulfuric acid solution from industrial waste. The morphology of the precipitated, sulfuric acid, industrial waste. 1. INTRODUCTION Gypsum is a mineral compound of first importance

Paris-Sud XI, Université de

288

The calcite ??? aragonite transformation in low-Mg marble: Equilibrium relations, transformations mechanisms, and rates  

USGS Publications Warehouse

Experimental transformation of a rather pure natural calcite marble to aragonite marble did not proceed via the expected straightforward polymorphic replacement. Instead, the small amount of Mg in the starting material (0.36 wt %) was excluded from the growing aragonite and diffused preferentially into the remaining calcite grains, producing Mg-rich calcite rods that persisted as relicts. Nucleation of aragonite occurred exclusively on grain boundaries, with aragonite [001] oriented subparallel to calcite [0001]. The aragonite crystals preferentially consumed the calcite crystal on which they nucleated, and the reaction fronts developed preferentially along the {010} and {110} planes of aragonite. Each aragonite neoblast that grew was nearly free of Mg (typically <0.1 wt %). The excess Mg was taken up by the calcite grains in between, stabilizing them and causing a few volume percent rodlike relicts of Mg-enriched calcite (up to 10 wt % MgO) to be left behind by the advancing reaction front. The aragonite growth rates are approximately linear and range from ???3 ?? 10-11 m s-1 at 600??C to ???9 ?? 10-9 m s-1 at 850??C, with an apparent activation enthalpy of 166 ?? 91 kJ mol-1. This reaction mechanism and the resultant texture are akin to cellular precipitation reactions in metals. Similar transformation textures have been reported from high-Mg marbles in Japan and China that disproportionated to low-Mg calcite and dolomite. Copyright 2005 by the American Geophysical Union.

Hacker, B.R.; Rubie, D.C.; Kirby, S.H.; Bohlen, S.R.

2005-01-01

289

Research paper Uranium loss and aragoniteecalcite age discordance in a calcitized aragonite  

E-print Network

Research paper Uranium loss and aragoniteecalcite age discordance in a calcitized aragonite Aragonite Recrystallization Uranium series dating Laser ablation MC-ICPMS a b s t r a c t We analyzed uranium-series concentrations and isotopic ratios in a mixed aragonite and calcite stalagmite from

Asmerom, Yemane

290

A calcite permeable reactive barrier for the remediation of Fluoride from spent potliner (SPL) contaminated groundwater  

Microsoft Academic Search

The use of calcite (CaCO3) as a substrate for a permeable reactive barrier (PRB) for removing fluoride from contaminated groundwater is proposed and is illustrated by application to groundwater contaminated by spent potliner leachate (SPL), a waste derived from the aluminium smelting process. The paper focuses on two issues in the implementation of calcite permeable reactive barriers for remediating fluoride

Brett D. Turner; Philip J. Binning; Scott W. Sloan

2008-01-01

291

Isotopic composition of a calcite-cemented layer in the Lower Jurassic Bridport Sands, southern England: Implications for formation of laterally extensive calcite-cemented layers  

SciTech Connect

[delta][sup 18]O[sub PDB] and [delta][sup 13]C[sub PDB] values have been measured on 107 calcite cement samples from a laterally extensive (> 3 km) and continuous calcite-cemented layer 0.5 m thick in the coastal exposures of the Lower Jurassic shallow-marine Bridport Sands in Dorset, southern England. The samples were taken from a two-dimensional grid with 10-cm horizontal and vertical spacing between samples and along individual vertical lines across the calcite-cemented layer, [delta][sup 18]O[sub PDB] values vary between [minus]4.8% and [minus]9.2% and decrease radially outwards from points with lateral spacings on the order of 0.5-1 m in the middle of the calcite-cemented layer. The [delta][sup 18]O[sub PDB] values therefore indicate that the calcite-cemented layer was formed by merging of concretions. All [delta][sup 13]C[sub PDB] values measured are in the narrow range [minus]2.2% to [minus]0.5%, which suggests that the dominant source of calcite cement in the layer was biogenic carbonate.

Bjoerkum, P.A. (Statoil, Stavanger (Norway)); Walderhaug, O. (Rogaland Research, Stavanger (Norway))

1993-07-01

292

Critical occlusion via biofilm induced calcite precipitation in porous media  

NASA Astrophysics Data System (ADS)

A model for biofilm induced calcite precipitation with pressure driven flow is presented at the scale of a single pore within a porous medium. The system, an extension of previous work (Zhang and Klapper 2010 Water Sci. Technol. 61 2957-64, Zhang and Klapper 2011 Int. J. Non-Linear Mech. 46 657-66), is based on a mixture model including biomaterial, mineral, and water with dissolved components. Computational results suggest the possibility of critical occlusion in the sense that there is a distinguished trans-pore pressure head such that for pressure drops below this level, pore clogging occurs relatively quickly while for pressure drops above, clogging occurs after much longer times if at all. Beyond its relevance to engineered biofilm applications, this phenomenon is suggestive of the subtleties of embedding simple biofilm models in larger media.

Zhang, Tianyu; Klapper, Isaac

2014-05-01

293

Structural evolution of calcite at high temperatures: Phase V unveiled  

PubMed Central

The calcite form of calcium carbonate CaCO3 undergoes a reversible phase transition between Rc and Rm at ~1240?K under a CO2 atmosphere of ~0.4?MPa. The joint probability density function obtained from the single-crystal X-ray diffraction data revealed that the oxygen triangles of the CO3 group in the high temperature form (Phase V) do not sit still at specified positions in the space group Rm, but migrate along the undulated circular orbital about carbon. The present study also shows how the room temperature form (Phase I) develops into Phase V through an intermediate form (Phase IV) in the temperature range between ~985?K and ~1240?K. PMID:24084871

Ishizawa, Nobuo; Setoguchi, Hayato; Yanagisawa, Kazumichi

2013-01-01

294

Shock-induced effects in calcite from Cactus Crater  

NASA Technical Reports Server (NTRS)

The paper discusses shock metamorphism of calcite from coralline limestone samples retrieved from a borehole drilled into rocks beneath Cactus Crater, a nuclear explosion crater at Eniwetok Atoll. The metamorphism was detected and quantified using electron spin resonance (ESR); the ESR spectra of Mn(+) present as a trace constituent in the coral samples, show a consistent decrease in hyperfine peak splitting with decreasing depth of sample. It is suggested that the decrease in hyperfine peak splitting reflects a decrease in crystal field splitting, and therefore, small increases on cation-anion distances produced by mechanical energy input during the shock process. Two alternative crater models suggested by the ESR results are a depiction of a steady decay of the shock wave, and a delineation of a breccia lens with a breccia-bedrock interface at 20 plus or minus 5 m.

Vizgirda, J.; Ahrens, T. J.; Tsay, F.-D.

1980-01-01

295

Age constraints on fluid inclusions in calcite at Yucca Mountain  

SciTech Connect

The {sup 207}Pb/{sup 235}U ages for 14 subsamples of opal or chalcedony layers younger than calcite formed at elevated temperature range between 1.88 {+-} 0.05 and 9.7 {+-} 1.5 Ma with most values older than 6-8 Ma. These data indicate that fluids with elevated temperatures have not been present in the unsaturated zone at Yucca Mountain since about 1.9 Ma and most likely since 6-8 Ma. Discordant U-Pb isotope data for chalcedony subsamples representing the massive silica stage in the formation of the coatings are interpreted using a model of the diffusive loss of U decay products. The model gives an age estimate for the time of chalcedony formation around 10-11 Ma, which overlaps ages of clay minerals formed in tuffs below the water table at Yucca Mountain during the Timber Mountain thermal event.

Neymark, Leonid A.; Amelin, Yuri V.; Paces, James B.; Peterman, Zell E.; Whelan, Joseph F.

2001-04-29

296

COMPUTERIZED SHAWNEE LIME/LIMESTONE SCRUBBING MODEL USERS MANUAL  

EPA Science Inventory

The manual gives a general description of a computerized model for estimating design and cost of lime or limestone scrubber systems for flue gas desulfurization (FGD). It supplements PB80-123037 by extending the number of scrubber options which can be evaluated. It includes spray...

297

SWEDEN'S ISLE OF LIME / COWBOY UP! REJUVENATINGRANGE/TARGETINGSAWFLIES  

E-print Network

SWEDEN'S ISLE OF LIME / COWBOY UP! WEED WARS MARCH 2013 REJUVENATINGRANGE/TARGETINGSAWFLIES #12 lifespan, existing outside the plant for a mere two weeks before laying their eggs in wheat stems. Geneticists, plant breeders, and en- tomologists are working to manip- ulate sawfly behavior and improve solid

Maxwell, Bruce D.

298

Low Velocity Sphere Impact of a Soda Lime Silicate Glass  

Microsoft Academic Search

This report summarizes TARDEC-sponsored work at Oak Ridge National Laboratory (ORNL) during the FY11 involving low velocity (< 30 m\\/s or < 65 mph) ball impact testing of Starphire soda lime silicate glass. The intent was to better understand low velocity impact response in the Starphire for sphere densities that bracketed that of rock. Five sphere materials were used: borosilicate

Andrew A Wereszczak; Ethan E Fox; Timothy G Morrissey; Daniel J Vuono

2011-01-01

299

K'qizaghetnu Ht'ana (Stories from Lime Village).  

ERIC Educational Resources Information Center

A cross section of Athabascan life as related by eight inhabitants of Lime Village, Alaska, is given in this document. The short narratives are printed in English and in Dena'ina. Illustrations accompany the text. The stories tell of making eagle feather robes, birchbark or mooseskin boats, a raincoat from black bear intestines, and boots from…

Bobby, Pete; And Others

300

Lime-Induced Changes in Indices of Soil Phosphate Availability  

Microsoft Academic Search

promotes adsorption, but, at the same time, surface elec- trostatic potential becomes more negative as pH in- Increases in soil P availability due to liming have been reported creases and thus less attractive to phosphate ions. The in a number of glasshouse and field trials, but the mechanism responsi- ble for this effect has not been identified definitely. In a

D. Curtin; J. K. Syers

2001-01-01

301

HAZARDOUS WASTE COMBUSTION IN INDUSTRIAL PROCESSES: CEMENT AND LIME KILNS  

EPA Science Inventory

The report summarizes the results of several studies relating to hazardous waste combustion in cement and lime kilns. The tests included in the study are four kilns tested by the U.S. Environmental Protection Agency, four kilns tested by State agencies or the kiln operator, two C...

302

CHARACTERIZATION OF CARBIDE LIME TO IDENTIFY SULFITE OXIDATION INHIBITORS  

EPA Science Inventory

The report gives results of a study of carbide lime--a by-product of acetylene manufacture, primarily calcium hydroxide--used in a flue gas desulfurization (FGD) system at Louisville Gas and Electric (LGE). The study was undertaken to: identify sulfite ion oxidation inhibitors in...

303

Distribution of polycyclic aromatic hydrocarbons in lime spray dryer ash  

SciTech Connect

Four lime spray dryer (LSD) ash samples were collected from a spreader stoker boiler and measured for their concentrations of 16 U.S. EPA specified polycyclic aromatic hydrocarbons (PAHs). Results showed that the total measured PAH concentration correlated with the organic carbon content of the LSD ash. Each LSD ash sample was then separated using a 140 mesh sieve into two fractions: a carbon-enriched fraction ({gt}140 mesh) and a lime-enriched fraction ({lt}140 mesh). Unburned carbon was further separated from the carbon-enriched fraction with a lithiumheteropolytungstate (LST) solution. PAH measurements on these different fractions showed that unburned carbon had the highest PAH concentrations followed by the carbon-enriched fraction, indicating that PAHs were primarily associated with the carbonaceous material in LSD ash. However, detectable levels of PAHs were also found in the lime-enriched fraction, suggesting that the fine spray of slaked lime may sorb PAH compounds from the flue gas in the LSD process. 37 refs., 5 figs., 4 tabs.

Ping Sun; Panuwat Taerakul; Linda K. Weavers; Harold W. Walker [Ohio State University, Columbus, OH (United States). Department of Civil and Environmental Engineering and Geodetic Science

2005-10-01

304

Method for lime stabilization of wastewater treatment plant sludges  

Microsoft Academic Search

A method for the lime stabilization of wastewater sludge, includes the steps of dewatering sludge so as to produce a sludge cake containing from about 10 to 60% by weight of dry solids and rapidly and intimately mixing and reacting the sludge cake with calcium oxide so as to produce stabilized sludge pellets. An apparatus for performing the process is

Wurtz

1981-01-01

305

Coal conversion of a multiple burner lime kiln  

Microsoft Academic Search

During 1982 Ash Grove Cement Company contracted with Wagester, Walker, Thornton and Company to convert a Calcimatic rotating hearth kiln at its Portland, Oregon lime plant from gas\\/oil to coal firing. Increasing costs of natural gas and No. 6 fuel oil made this conversion mandatory if the plant was to remain competitive. Unique features of this project are the distributors

G. Jones; L. W. Thornton

1984-01-01

306

Lime pretreatment and fermentation of enzymatically hydrolyzed sugarcane bagasse.  

PubMed

Sugarcane bagasse was subjected to lime (calcium hydroxide) pretreatment and enzymatic hydrolysis for second-generation ethanol production. A central composite factorial design was performed to determine the best combination of pretreatment time, temperature, and lime loading, as well as to evaluate the influence of enzymatic loadings on hydrolysis conversion. The influence of increasing solids loading in the pretreatment and enzymatic hydrolysis stages was also determined. The hydrolysate was fermented using Saccharomyces cerevisiae in batch and continuous mode. In the continuous fermentation, the hydrolysates were concentrated with molasses. Lime pretreatment significantly increased the enzymatic digestibility of sugarcane bagasse without the need for prior particle size reduction. In the optimal pretreatment conditions (90 h, 90 °C, 0.47 glime/g bagasse) and industrially realistic conditions of hydrolysis (12.7 FPU/g of cellulase and 7.3 CBU/g of ?-glucosidase), 139.6 kglignin/ton raw bagasse and 126.0 kg hemicellulose in the pretreatment liquor per ton raw bagasse were obtained. The hydrolysate from lime pretreated sugarcane bagasse presented low amounts of inhibitors, leading to ethanol yield of 164.1 kgethanol/ton raw bagasse. PMID:23334836

Rabelo, Sarita C; Maciel Filho, Rubens; Costa, Aline C

2013-03-01

307

Saturn's emitted power Liming Li,1,2  

E-print Network

Saturn's emitted power Liming Li,1,2 Barney J. Conrath,2 Peter J. Gierasch,2 Richard K. Achterberg Composite Infrared Spectrometer are analyzed to precisely measure Saturn's emitted power and its meridional the interannual variability of emitted power and effective temperature between the epoch of Voyager (1 Saturn year

308

EFFECTS OF LIME (CAO) ON THE ENDOTOXIN LEVELS OF BIOSOLIDS  

EPA Science Inventory

Lime addition is a common practice for treating biosolids in order to meet EPA 503 requirements for land application. Since this treatment kills the majority of microorganisms, will it increase the level of endotoxins present in biosolids? And, if endotoxin levels are increased, ...

309

Economics of Stabilizing Bentonite Soil with Lime-Gypsum  

Microsoft Academic Search

For solving problems of expansive soil it is necessary to stabilize it with any of additive substance such as lime, gypsum etc. After stabilization soil properties are altered such as bearing capacity, shear strength and stability of soil which are increased and the shrinkage, swelling are decreased. While planning for treatment of expansive soils with chemical additives, it must be

N. K. Ameta; D. G. M. Purohit; Dangda Sandeep

310

Shock-wave properties of soda-lime glass  

SciTech Connect

Planar impact experiments and wave profile measurements provided single and double shock equation of state data to 30 GPa. Both compression wave wave profile structure and release wave data were used to infer time-dependent strength and equation of state properties for soda-lime glass.

Grady, D.E. [Applied Research Associates, Inc., Albuquerque, NM (United States); Chhabildas, L.C. [Sandia National Labs., Albuquerque, NM (United States)

1996-11-01

311

Coal conversion of a multiple burner lime kiln  

SciTech Connect

During 1982 Ash Grove Cement Company contracted with Wagester, Walker, Thornton and Company to convert a Calcimatic rotating hearth kiln at its Portland, Oregon lime plant from gas/oil to coal firing. Increasing costs of natural gas and No. 6 fuel oil made this conversion mandatory if the plant was to remain competitive. Unique features of this project are the distributors of pulverized coal to eighteen small burners around the inner and outer perimeters of the doughnut-shaped kiln, and the attrition-dryer-pulverizer mill. Ash Grove, a century-old lime and cement producer headquartered in Overland Park, Kansas (Kansas City area), looked at various schemes for multiple burner firing before employing Wagester, Walker, Thornton and Company. W.W.T. of Pittsburgh, Pennsylvania was formed in 1980 by acquiring the Solid Fuels Division of the Pullman Swindell Corporation. This division had been active in developing solid fuel firing for brick tunnel kilns, principally in the Southeast. They continue to supply such systems firing wood waste as well as coal to the brick industry and have also converted two Calcimatic lime kilns for Dixie Lime, Sumterville, Florida, a fluid bed calciner for Texas Gulf in Aurora, North Carolina, and a chrome concentrate kiln for Diamond Chemicals at Castle Hayne, North Carolina. Testing and a proposal have been made for INMETCO, Elwood City, Pennsylvania, on an annular hearth furnace for direct reduction of iron ore to metallic iron.

Jones, G.; Thornton, L.W.

1984-02-01

312

Influence of calcite on uranium(VI) reactive transport in the groundwater–river mixing zone  

SciTech Connect

Calcite is an important mineral that can affect uranyl reactive transport in subsurface sediments. This study investigated the distribution of calcite and its influence on uranyl adsorption and reactive transport in the groundwater-river mixing zone at US Hanford 300A, Washington State. Simulations using a 2D reactive transport model under field-relevant hydrogeochemical conditions revealed a complex distribution of calcite concentration as a result of dynamic groundwater-river interactions. The calcite concentration distribution in turn affected the spatial and temporal changes in aqueous carbonate, calcium, and pH, which subsequently influenced U(VI) mobility and discharge rates into the river. The results implied that calcite distribution and its concentration dynamics is an important consideration for field characterization, monitoring, and reactive transport prediction.

Ma, Rui; Liu, Chongxuan; Greskowiak, Janek; Prommer, Henning; Zachara, John M.; Zheng, Chunmiao

2014-01-23

313

Unusual micrometric calcite-aragonite interface in the abalone shell Haliotis (Mollusca, Gastropoda).  

PubMed

Species of Haliotis (abalone) show high variety in structure and mineralogy of the shell. One of the European species (Haliotis tuberculata) in particular has an unusual shell structure in which calcite and aragonite coexist at a microscale with small patches of aragonite embedded in larger calcitic zones. A detailed examination of the boundary between calcite and aragonite using analytical microscopies shows that the organic contents of calcite and aragonite differ. Moreover, changes in the chemical composition of the two minerals seem to be gradual and define a micrometric zone of transition between the two main layers. A similar transition zone has been observed between the layers in more classical and regularly structured mollusk shells. The imbrication of microscopic patches of aragonite within a calcitic zone suggests the occurrence of very fast physiological changes in these taxa. PMID:24188740

Dauphin, Yannicke; Cuif, Jean-Pierre; Castillo-Michel, Hiram; Chevallard, Corinne; Farre, Bastien; Meibom, Anders

2014-02-01

314

Methane hydrates and global climate  

NASA Astrophysics Data System (ADS)

Methane hydrates are globally widespread in permafrost regions and beneath the sea in sediment of outer continental margins. The amount of methane sequestered in gas hydrates is probably enormous, but estimates of the amounts are speculative and range over three orders of magnitude (about 103 to 106 GT (gigatons = 1015 g)). A question of current interest concerns the possible consequences of an addition of methane to the atmosphere from destabilized methane hydrates due to global warming. Models of greenhouse warming predict that climatic change will be greatest in the Arctic. Thus, if methane from destabilized gas hydrates contributes to greenhouse warming, this destabilization will most likely take place first in the Arctic, particularly in the shallow nearshore regions of the Arctic Ocean where offshore permafrost is found. The process of permafrost warming and release of methane from gas hydrates may already be in progress, but the amount being released now and to be released in the 21st century is probably small. The positive feedback of this atmospheric methane on global climates will likely be minimal.

Kvenvolden, Keith A.

1988-09-01

315

Well log evaluation of natural gas hydrates  

SciTech Connect

Gas hydrates are crystalline substances composed of water and gas, in which a solid-water-lattice accommodates gas molecules in a cage-like structure. Gas hydrates are globally widespread in permafrost regions and beneath the sea in sediment of outer continental margins. While methane, propane, and other gases can be included in the clathrate structure, methane hydrates appear to be the most common in nature. The amount of methane sequestered in gas hydrates is probably enormous, but estimates are speculative and range over three orders of magnitude from about 100,000 to 270,000,000 trillion cubic feet. The amount of gas in the hydrate reservoirs of the world greedy exceeds the volume of known conventional gas reserves. Gas hydrates also represent a significant drilling and production hazard. A fundamental question linking gas hydrate resource and hazard issues is: What is the volume of gas hydrates and included gas within a given gas hydrate occurrence Most published gas hydrate resource estimates have, of necessity, been made by broad extrapolation of only general knowledge of local geologic conditions. Gas volumes that may be attributed to gas hydrates are dependent on a number of reservoir parameters, including the areal extent ofthe gas-hydrate occurrence, reservoir thickness, hydrate number, reservoir porosity, and the degree of gas-hydrate saturation. Two of the most difficult reservoir parameters to determine are porosity and degreeof gas hydrate saturation. Well logs often serve as a source of porosity and hydrocarbon saturation data; however, well-log calculations within gas-hydrate-bearing intervals are subject to error. The primary reason for this difficulty is the lack of quantitative laboratory and field studies. The primary purpose of this paper is to review the response of well logs to the presence of gas hydrates.

Collett, T.S.

1992-10-01

316

Well log evaluation of natural gas hydrates  

SciTech Connect

Gas hydrates are crystalline substances composed of water and gas, in which a solid-water-lattice accommodates gas molecules in a cage-like structure. Gas hydrates are globally widespread in permafrost regions and beneath the sea in sediment of outer continental margins. While methane, propane, and other gases can be included in the clathrate structure, methane hydrates appear to be the most common in nature. The amount of methane sequestered in gas hydrates is probably enormous, but estimates are speculative and range over three orders of magnitude from about 100,000 to 270,000,000 trillion cubic feet. The amount of gas in the hydrate reservoirs of the world greedy exceeds the volume of known conventional gas reserves. Gas hydrates also represent a significant drilling and production hazard. A fundamental question linking gas hydrate resource and hazard issues is: What is the volume of gas hydrates and included gas within a given gas hydrate occurrence? Most published gas hydrate resource estimates have, of necessity, been made by broad extrapolation of only general knowledge of local geologic conditions. Gas volumes that may be attributed to gas hydrates are dependent on a number of reservoir parameters, including the areal extent ofthe gas-hydrate occurrence, reservoir thickness, hydrate number, reservoir porosity, and the degree of gas-hydrate saturation. Two of the most difficult reservoir parameters to determine are porosity and degreeof gas hydrate saturation. Well logs often serve as a source of porosity and hydrocarbon saturation data; however, well-log calculations within gas-hydrate-bearing intervals are subject to error. The primary reason for this difficulty is the lack of quantitative laboratory and field studies. The primary purpose of this paper is to review the response of well logs to the presence of gas hydrates.

Collett, T.S.

1992-10-01

317

Diel cycles in calcite production and dissolution in a eutrophic basin  

SciTech Connect

Calcite production is understood largely as a longer-term phenomenon (e.g., seasonal whitings) that can occur in hardwater lakes, and is significant ecologically because it can slow the rate of eutrophication by reducing, through adsorption, the availability of nutrients to primary producers. In this study the authors show that rapid changes in concentration of dissolved CO{sub 2} by photosynthesis and respiration within a eutrophic basin generated strong day-to-night cycles in calcite production and dissolution. Diel cycles in calcite production and dissolution were large enough that they could drive secondary diel cycles in the availability of metals that strongly sorb to the surfaces of calcite particles. They explored the possibility of the secondary diel cycling of metals by intensive 7-d in situ monitoring of water-quality conditions in a shallow, eutrophic spill-control basin near an industrial facility in eastern Tennessee; inspecting data from a 7-year record of water-quality parameters for this basin; analyzing physicochemical characteristics and mineralogic composition of sediments in the basin; and conducting laboratory experiments to characterize the interaction of calcite with Cd, under solid-liquid nonequilibrium conditions. The authors found that the basin accumulated and stored calcite. In situ monitoring showed that calcite was produced during daylight, and tended to dissolve again at night; the calcite production and dissolution processes seemed to be modulated by dissolved-phase CO{sub 2} dynamics, in concert with large diel fluctuations in pCa, pH, and Po{sub 2}. Laboratory experiments showed a rapid interaction ({lt}6 h) of Cd with calcite, in response to dissolved CO{sub 2} changes. Thus, concentrations of dissolved Cd can vary over daily cycles, mediated by diel changes in calcite production and dissolution. Thermodynamic considerations suggest that other metals, such as Zn, Sr, Ni, and Ba, may demonstrate this behavior as well.

Cicerone, D.S.; Stewart, A.J.; Roh, Y.

1999-10-01

318

New waste based clinkers: Belite and lime formulations  

SciTech Connect

This work describes the formulation of new belite-based (CR2) and lime-based (CR3) cementitious materials derived from industrial wastes, such as sludges (generated in the Al-anodising and surface coating industrial processes, potable water filtration/cleaning operations and in marble sawing processes) and foundry sand. Powder mixtures were prepared and fired at different temperatures. For comparison, similar formulations were prepared with pre-treated and commercially available natural raw materials and processed in similar conditions. The thermal process was followed by differential scanning calorimetry (DSC) and high-temperature powder X-ray diffraction (HT-XRD) studies. The CR2 clinker was found to contain belite as the main cementitious phase, the main polymorph being identified by NMR. The CR3 clinker contained common cementitious phases, such as C{sub 3}A and C{sub 3}S, but free lime and calcium aluminium oxide sulphates were also identified by high temperature XRD and NMR. Then the corresponding cement was prepared and the evolution of the mechanical strength with time was evaluated. The lime-based cement obtained from wastes shows a stronger hardening character than the standard material, which tends to show dusting phenomena due to the presence of a reasonable amount of free lime (as the result of its expansive reaction with ambient moisture). Some fluxing impurities (e.g. alkalis) present in the waste materials improve the overall reactivity of the mixture and induces the combination of the lime in CR3. Raman, XPS and FIB techniques were used to fully characterise the aged cements.

Raupp-Pereira, Fabiano [Ceramics and Glass Engineering Department, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Ball, Richard James [University of Bristol, Interface Analysis Centre, Oldbury House, 121 St Michael's Hill, Bristol, BS2 8BS (United Kingdom)], E-mail: richard.ball@bristol.ac.uk; Rocha, Joao [Department of Chemistry, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Labrincha, Joao A. [Ceramics and Glass Engineering Department, CICECO, University of Aveiro, 3810-193 Aveiro (Portugal); Allen, Geoffrey C. [University of Bristol, Interface Analysis Centre, Oldbury House, 121 St Michael's Hill, Bristol, BS2 8BS (United Kingdom)

2008-04-15

319

Predicting Calcite (CaCO3) Requirements of Sphagnum Peat Moss from pH Titration Curves  

Technology Transfer Automated Retrieval System (TEKTRAN)

Liming materials are required to neutralize acidity in peat moss to make it a suitable substrate for growing container crops. A series of time-consuming incubations of peat:lime mixtures are typically used to determine the liming rate to achieve a desired pH. Our objective was to evaluate the util...

320

Three-way ANOVA interaction analysis and ultrasonic testing to evaluate air lime mortars used in cultural heritage conservation projects  

Microsoft Academic Search

Lime mortar has been used throughout history despite current substitution by hydraulic mortars (cements). The chemical composition of the lime used in its manufacture, however, is determined by local geology. In addition, the type of slaking, which depends on the amount of water used, gives rise to different types of lime. The result is that the behavior of lime mortar

O. Cazalla; E. Sebastián; G. Cultrone; M. Nechar; M. G. Bagur

1999-01-01

321

Hydrophobic hydration of amphipathic peptides.  

PubMed Central

Biomolecular surfaces and interfaces are commonly found with apolar character. The hydrophobic effect thus plays a crucial role in processes involving association with biomolecular surfaces in the cellular environment. By computer simulation, we compared the hydrogen bonding structures and energetics of the proximal hydration shells of the monomer and dimer from a recent study of an extrinsic membrane peptide, melittin. The two peptides were studied in their amphipathic alpha-helical forms, which possess extended hydrophobic surfaces characterized by different topography. The topography of the peptide-water interface was found to be critical in determining the enthalpic nature of hydrophobic hydration. This topographical dependence has far-reaching implications in the regulation of bioactivities in the presence of amphipathicity. This result also engenders reconsideration of the validity of using free energy parameters that depend solely on the chemical nature of constituent moieties in characterizing hydrophobic hydration of proteins and biomolecules in general. PMID:10096874

Cheng, Y K; Sheu, W S; Rossky, P J

1999-01-01

322

Polymorphs and Hydrates of Acyclovir  

PubMed Central

Acyclovir (ACV) has been commonly used as an antiviral for decades. Although the crystal structure of the commercial form, a 3:2 ACV/water solvate, has been known since 1980s, investigation into the structure of anhydrous ACV has been limited. Here, we report the characterization of four anhydrous forms of ACV and a new hydrate in addition to the known hydrate. Two of the anhydrous forms appear as small needles and are stable to air exposure, whereas the third form is morphologically similar but quickly absorbs water from the atmosphere and converts back to the commercial form. The high-temperature modification is achieved by heating anhydrous form I above 180°C. The crystal structures of anhydrous form I and a novel hydrate are reported for the first time. PMID:21280051

LUTKER, KATIE M.; QUIÑONES, ROSALYNN; XU, JIADI; RAMAMOORTHY, AYYALUSAMY; MATZGER, ADAM J.

2011-01-01

323

A marine electromagnetic survey to detect gas hydrate at Hydrate Ridge, Oregon  

Microsoft Academic Search

Gas hydrates are a potential energy resource and hazard for drilling and infrastructure, yet estimates of global volume vary by over three orders of magnitude. Hydrates are electrically resistive compared to water saturated sediment and so electromagnetic methods provide an additional tool to seismic surveys and drilling for determining hydrate saturations. A marine electromagnetic survey was carried out at Hydrate

K. A. Weitemeyer; S. Constable; A. M. Tréhu

2011-01-01

324

Thermodynamics of magnesian calcite solid-solutions at 25??C and 1 atm total pressure  

USGS Publications Warehouse

The stability of magnesian calcites was reexamined, and new results are presented for 28 natural inorganic, 12 biogenic, and 32 synthetic magnesian calcites. The magnesian calcite solid-solutions were separated into two groups on the basis of differences in stoichiometric solubility and other physical and chemical properties. Group I consists of solids of mainly metamorphic and hydrothermal origin, synthetic calcites prepared at high temperatures and pressures, and synthetic solids prepared at low temperature and very low calcite supersaturations (??calcite ??? 1.5) from artificial sea water or NaClMgCl2CaCl2 solutions. Group I solids are essentially binary s of CaCO2 and MgCO2, and are thought to be relatively free of structural defects. Group II solid-solutions are of either biogenic origin or are synthetic magnesian calcites and protodolomites (0-20 and ??? 45 mole percent MgCO3) prepared at high calcite supersaturations (??calcite??? 3) from NaClNa2SO4MgCl2CaCl2 or NaClMgCl2CaCl2 solutions. Group II solid-solutions are treated as massively defective solids. The defects include substitution foreign ions (Na+ and SO42-) in the magnesian calcite lattice (point defects) and dislocations (~2 ?? 109 cm-2). Within each group, the excess free energy of mixing, GE, is described by the mixing model ge = X(1- x)[A0 + A1(2x - 1)], where x is the mole fraction of the end-member Ca0.5Mg0.5CO3 in the solid-solution. The values of A0 and A1 for Group I and II solids were evaluated at 25??C. The equilibrium constants of all the solids are closely described by the equation ln Kx = x(1-x) RT[A0 + A1(2x- 1)]+ (1 - x) ln [KC(1- x)]+ x ln (KDx), where KC and KD are the equilibrium constants of calcite and Ca0.5Mg0.5CO3. Group I magnesian calcites were modeled as sub-regular solid-solutions between calcite and dolomite, and between calcite and "disordered dolomite". Both models yield almost identical equilibrium constants for these magnesian calcites. The Group II magnesian calcites were modeled as sub-regular solid-solutions between defective calcite and protodolomite. Group I and II solid-solutions differ significantly in stability. The rate of crystal growth and the chemical composition of the aqueous solutions from which the solids were formed are the main factors controlling stoichiometric solubility of the magnesian calcites and the density of crystal defects. The literature on the occurrence and behavior of magnesian calcites in sea water and other aqueous solutions is also examined. ?? 1989.

Busenberg, E.; Niel, Plummer L.

1989-01-01

325

Characteristics and reactivity of rapidly hydrated sorbent for semidry flue gas desulfurization  

SciTech Connect

The semidry flue gas desulfurization (FGD) process has many advantages over the wet FGD process for moving sulfur dioxide emissions from pulverized coal-fired power plants. Semidry FGD with a rapidly hydrated sorbent was studied in a pilot-scale circulating fluidized bed (CFB) experimental facility. The sorbent was made from lumps of lime and coal fly ash. The desulfurization efficiency was measured for various operating parameters, including the sorbent recirculation rate and the water spray method. The experimental results show that the desulfurization efficiencies of the rapidly hydrated sorbent were 1.5-3.0 times higher than a commonly used industrial sorbent for calcium to sulfur molar ratios from 1.2 to 3.0, mainly due to the higher specific surface area and pore volume. The Ca(OH){sub 2} content in the cyclone separator ash was about 2.9% for the rapidly hydrated sorbent and was about 0.1% for the commonly used industrial sorbent, due to the different adhesion between the fine Ca(OH){sub 2} particles and the fly ash particles, and the low cyclone separation efficiency for the fine Ca(OH){sub 2} particles that fell off the sorbent particles. Therefore the actual recirculation rates of the active sorbent with Ca(OH){sub 2} particles were higher for the rapidly hydrated sorbent, which also contributed to the higher desulfurization efficiency. The high fly ash content in the rapidly hydrated sorbent resulted in good operating stability. The desulfurization efficiency with upstream water spray was 10-15% higher than that with downstream water spray. 20 refs., 7 figs., 1 tab.

Jie Zhang; Changfu You; Suwei Zhao; Changhe Chen; Haiying Qi [Tsinghua University, Beijing (China). Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering

2008-03-01

326

Gas hydrates in the Gulf of Mexico  

E-print Network

pipelines (Katz et al, 1959). The combination of water, gas and pressure in the pipeline formed hydrates. The hydrates were eliminated by drying the gas before introduction into the pipeline (Hammerschmidt, 1940). The structural types, shapes... of Mexico gas hydrate had porewater chlorinities that increased with depth reaching 41. 8 ppt Cl two meters into the sediment. The increase was attributed to diffusion from underlying salt diapirs and exclusion of salts from the hydrate lattice (Brooks...

Cox, Henry Benjamin

1986-01-01

327

STRONTIUM ISOTOPE EVOLUTION OF PORE WATER AND CALCITE IN THE TOPOPAH SPRING TUFF, YUCCA MOUNTAIN , NEVADA  

SciTech Connect

Yucca Mountain, a ridge of Miocene volcanic rocks in southwest Nevada, is being characterized as a site for a potential high-level radioactive waste repository. One issue of concern for the future performance of the potential repository is the movement of water in and around the potential repository horizon. Past water movement in this unsaturated zone is indicated by fluid inclusions trapped in calcite coatings on fracture footwall surfaces and in some lithophysal cavities. Some of the fluid inclusions have homogenization temperatures above the present-day geotherm (J.F. Whelan, written communication), so determining the ages of the calcite associated with those fluid inclusions is important in understanding the thermal history of the potential repository site. Calcite ages have been constrained by uranium-lead dating of silica polymorphs (opal and chalcedony) that are present in most coatings. The opal and chalcedony ages indicate that deposition of the calcite and opal coatings in the welded part of the Topopah Spring Tuff (TSw hydrogeologic unit) spanned nearly the entire history of the 12.8-million-year-old rock mass at fairly uniform overall long-term rates of deposition (within a factor of five). Constraining the age of a layer of calcite associated with specific fluid inclusions is complicated. Calcite is commonly bladed with complex textural relations, and datable opal or chalcedony may be millions of years older or younger than the calcite layer or may be absent from the coating entirely. Therefore, a more direct method of dating the calcite is presented in this paper by developing a model for strontium evolution in pore water in the TSw as recorded by the strontium coprecipitated with calcium in the calcite. Although the water that precipitated the calcite in fractures and cavities may not have been in local isotopic equilibrium with the pore water, the strontium isotope composition of all water in the TSw is primarily controlled by water-rock interaction in the overlying nonwelded and essentially unfractured Paintbrush Group tuffs (PTn). The method of dating secondary minerals from known strontium evolution rates in rocks cannot be used in this study because it assumes the water that deposited the minerals was in isotopic equilibrium with the rock, which is not the case for the pore water in the TSw. Therefore, the evolution of the strontium isotope composition of the water that deposited the calcite, as recorded by the strontium coprecipitated with calcium in the calcite, was used to develop a model for determining the age of the calcite.

B.D. Marshall; K. Futa

2001-02-07

328

Hydration of highly charged ions  

PubMed Central

Based on a series of ab initio quantum mechanical charge field molecular dynamics (QMCF MD) simulations, the broad spectrum of structural and dynamical properties of hydrates of trivalent and tetravalent ions is presented, ranging from extreme inertness to immediate hydrolysis. Main group and transition metal ions representative for different parts of the periodic system are treated, as are 2 threefold negatively charged anions. The results show that simple predictions of the properties of the hydrates appear impossible and that an accurate quantum mechanical simulation in cooperation with sophisticated experimental investigations seems the only way to obtain conclusive results. PMID:22298911

Hofer, Thomas S.; Weiss, Alexander K.H.; Randolf, Bernhard R.; Rode, Bernd M.

2011-01-01

329

Gas Hydrate and Pore Pressure  

NASA Astrophysics Data System (ADS)

Many efforts have been devoted to quantify excess pore pressures related to gas hydrate dissociation in marine sediments below the BSR using several approaches. Dissociation of gas hydrates in proximity of the BSR, in response to a change in the physical environment (i.e., temperature and/or pressure regime), can liberate excess gas incrising the local pore fluid pressure in the sediment, so decreasing the effective normal stress. So, gas hydrate dissociation may lead to excess pore pressure resulting in sediment deformation or failure, such as submarine landslides, sediment slumping, pockmarks and mud volcanoes, soft-sediment deformation and giant hummocks. Moreover, excess pore pressure may be the result of gas hydrate dissociation due to continuous sedimentation, tectonic uplift, sea level fall, heating or inhibitor injection. In order to detect the presence of the overpressure below the BSR, we propose two approachs. The fist approach models the BSR depth versus pore pressure; in fact, if the free gas below the BSR is in overpressure condition, the base of the gas hydrate stability is deeper with respect to the hydrostatic case. This effect causes a discrepancy between seismic and theoretical BSR depths. The second approach models the velocities versus gas hydrate and free gas concentrations and pore pressure, considering the approximation of the Biot theory in case of low frequency, i.e. seismic frequency. Knowing the P and S seismic velocity from seismic data analysis, it is possibile to jointly estimate the gas hydrate and free gas concentrations and the pore pressure regime. Alternatively, if the S-wave velocity is not availbale (due to lack of OBS/OBC data), an AVO analysis can be performed in order to extract information about Poisson ratio. Our modeling suggests that the areas characterized by shallow waters (i.e., areas in which human infrastructures, such as pipelines, are present) are significantly affected by the presence of overpressure condition. Moreover, the knoweledge of seismic velocities can be considered an powerful tool to detect the overpressure in case that the pore pressure is equal to the hydrostatic pressure plus the 50% of the difference between the lithostatic and the hydrostatic pressure. In conclusions, an accurate analysis of the BSR nature and the pore pressure are required to improve the reliability of the gas-phase estimation for different target, such as gas hydrate and free gas exploitations and environmental studies.

Tinivella, Umberta; Giustiniani, Michela

2014-05-01

330

Complex gas hydrate from the Cascadia margin  

Microsoft Academic Search

Natural gas hydrates are a potential source of energy and may play a role in climate change and geological hazards. Most natural gas hydrate appears to be in the form of `structure I', with methane as the trapped guest molecule, although `structure II' hydrate has also been identified, with guest molecules such as isobutane and propane, as well as lighter

Hailong Lu; Yu-Taek Seo; Jong-Won Lee; Igor Moudrakovski; John A. Ripmeester; N. Ross Chapman; Richard B. Coffin; Graeme Gardner; John Pohlman

2007-01-01

331

A new high performance gas hydrate inhibitor  

Microsoft Academic Search

In petroleum exploration and production operations, gas hydrates pose serious flow assurance, economic and safety concerns. Thermodynamic inhibitors are widely used to reduce the risks associated with gas hydrate formation. In the present study, systematic laboratory work was undertaken to determine synergistic effects between methanol and a Poly Vinyl Methyl Ether as Low Dosage Hydrate Inhibitors (LDHIs). A valuable effect

Ehsan Heidaryan; Amir Salarabadi; Jamshid Moghadasi; Alireza Dourbash

2010-01-01

332

Hydration mechanisms of mineral trioxide aggregate  

Microsoft Academic Search

Camilleri J. Hydration mechanisms of mineral trioxide aggre- gate. International Endodontic Journal, 40, 462-470, 2007. Aim To report the hydration mechanism of white mineral trioxide aggregate (White MTA, Dentsply, Tulsa Dental Products, Tulsa, OK, USA). Methodology The chemical constitution of white MTA was studied by viewing the powder in polished sections under the scanning electron microscope (SEM). The hydration of

J. Camilleri

2007-01-01

333

In-situ characterization of gas hydrates  

Microsoft Academic Search

Gas hydrates are a dynamic reservoir in the marine carbon cycle and a periodically large and focussed source of methane probably constituting the largest carbon reservoir on earth. Therefore an important issue in gas hydrate research is the need for better tools to remotely estimate the volume and stability conditions of marine gas hydrate in the near sub-surface. It is

T. Moerz; W. Brueckmann; P. Linke; M. Tuerkay

2003-01-01

334

Direct nanoscale observations of the coupled dissolution of calcite and dolomite and the precipitation of gypsum  

PubMed Central

Summary In-situ atomic force microscopy (AFM) experiments were performed to study the overall process of dissolution of common carbonate minerals (calcite and dolomite) and precipitation of gypsum in Na2SO4 and CaSO4 solutions with pH values ranging from 2 to 6 at room temperature (23 ± 1 °C). The dissolution of the carbonate minerals took place at the (104) cleavage surfaces in sulfate-rich solutions undersaturated with respect to gypsum, by the formation of characteristic rhombohedral-shaped etch pits. Rounding of the etch pit corners was observed as solutions approached close-to-equilibrium conditions with respect to calcite. The calculated dissolution rates of calcite at pH 4.8 and 5.6 agreed with the values reported in the literature. When using solutions previously equilibrated with respect to gypsum, gypsum precipitation coupled with calcite dissolution showed short gypsum nucleation induction times. The gypsum precipitate quickly coated the calcite surface, forming arrow-like forms parallel to the crystallographic orientations of the calcite etch pits. Gypsum precipitation coupled with dolomite dissolution was slower than that of calcite, indicating the dissolution rate to be the rate-controlling step. The resulting gypsum coating partially covered the surface during the experimental duration of a few hours. PMID:25161860

Cama, Jordi; Soler, Josep Maria; Putnis, Christine V

2014-01-01

335

U-Th dating of calcitic corals from the Red Sea  

NASA Astrophysics Data System (ADS)

Pristine aragonite skeletons of reef building corals can be rapidly recrystallized to calcite by the interaction of the corals with freshwater in coastal aquifers. The aragonite/calcite transformation is accompanied by opening the coral's U-Th isotope system in which uranium is partly lost while Th remains adsorbed and reincorporates into the newly formed calcite. Depending on the geological setting of the reef, the corals may incorporate secondary aragonite with higher U and 234U/238U isotope ratio, while still submerged, before the recrystallization process. Recrystallization to calcite occurs during sea level drop or coast tectonic uplift and later may follow a subaerial closed system decay scheme. In this study we examine the behavior of the U and Th in calcitic corals from the last interglacial reefs at the northern Gulf of Aqaba. We analyzed several subsamples from selected reef coral skeletons in an attempt to follow the recrystallization scheme of the corals and find a reliable method to estimate the age of these heavily altered corals. The main assumptions were that all subsamples from the same coral have identical deposition age and the sub-samples Th (and hence 230Th) was fully preserved during recrystallization to calcite (increasing the 230Th/238U isotope ratio). Diagenesis to calcite occurred several thousand years after the initial precipitation of the aragonitic skeleton. This calls for wetter (than present) conditions during the last interglacial in the currently hyperarid northern Red Sea.

Stein, M.; Yehudai, M.; Kohn, N.; Shaked, Y.; Agnon, A.; Lazar, B.

2013-12-01

336

Fabrication of porous calcite using chopped nylon fiber and its evaluation using rats.  

PubMed

Although porous calcite has attracted attention as bone substitutes, limited studies have been made so far. In the present study, porous calcite block was fabricated by introducing chopped nylon fiber as porogen. Ca(OH)2 powder containing 10 wt% chopped nylon fiber was compacted at 150 MPa, and sintered to burn out the fiber and to carbonate the Ca(OH)2 under stream of 1:2 O2-CO2. Sintering of Ca(OH)2 at 750 °C or lower temperature resulted in incomplete burning out of the fiber whereas sintering at 800 °C or higher temperature resulted in the formation of CaO due to the thermal decomposition of Ca(OH)2. However, sintering at 770 °C resulted in complete burning out of the fiber and complete carbonation of Ca(OH)2 to calcite without forming CaO. Macro- and micro-porosities of the porous calcite were approximately 23 and 16 %, respectively. Diameter of the macropores was approximately 100 ?m which is suitable for bone tissue penetration. Porous calcite block fabricated by this method exhibited good tissue response when implanted in the bone defect in femur of 12-weeks-old rat. Four weeks after implantation, bone bonded on the surface of calcite. Furthermore, bone tissue penetrated interior to the macropore at 8 weeks. These results demonstrated the good potential value of porous calcite as artificial bone substitutes. PMID:25649514

Ishikawa, Kunio; Tram, Nguyen Xuan Thanh; Tsuru, Kanji; Toita, Riki

2015-02-01

337

Controls of carbonate mineralogy and solid-solution of Mg in calcite: evidence from spelean systems  

SciTech Connect

Precipitation of carbonate minerals in spelean systems occurs under a wide range of fluid chemistry, Mg-Ca ratios, alkalinities, pH and temperatures; thus, spelean systems provide ideal settings to determine factors controlling the mineralogy of precipitated carbonates and solid-solution of Mg in calcite. Cave waters and actively-precipitating carbonate speleothems were collected from Carlsbad Caverns National Park, New Mexico and the Mammoth-Flint Cave System, Kentucky. Carbonate mineralogy of precipitated phases was determined by x-ray diffraction, and major and minor element composition of waters and accompanying minerals were determined by Atomic Absorption Spectrophotometry. Results demonstrate that at a constant CO3 concentration the precipitation threshold for calcite to aragonite is controlled dominantly by the Mg/Ca ratio of the ambient fluid. Aragonite precipitation is favored by high Mg/Ca ratios. Conversely, with increasing CO3 concentration at constant fluid Mg/Ca ratios, calcite is preferentially precipitated. Solid-solution of Mg in calcite is positively correlated with both increased Mg/Ca ratios and CO3 concentrations. These data suggest that Mg contents of calcite can not be defined solely in terms of a homogeneous distribution coefficient. Rather, Mg concentrations can be also be affected by the CO3 concentration and degree of calcite saturation, suggesting that the rate of crystal growth also plays and important role in Mg solid-solution in calcites.

Gonzalez, L.A.; Lohmann, K.C.

1985-01-01

338

Attraction between hydrated hydrophilic surfaces  

NASA Astrophysics Data System (ADS)

According to common knowledge, hydrophilic surfaces repel via hydration forces while hydrophobic surfaces attract, but mounting experimental evidence suggests that also hydrophilic surfaces can attract. Using all-atom molecular dynamics simulations at prescribed water chemical potential we study the crossover from hydration repulsion to hydrophobic attraction for planar polar surfaces of varying stiffness and hydrogen-bonding capability. Rescaling the partial charges of the polar surface groups, we cover the complete spectrum from very hydrophobic surfaces (characterized by contact angles ? ? 135°) to hydrophilic surfaces exhibiting complete wetting (? = 0°). Indeed, for a finite range ?adh < ? < 90°, we find a regime where hydrophilic surfaces attract at sub-nanometer separation and stably adhere without intervening water. The adhesive contact angle ?adh depends on surface type and lies in the range 65° < ?adh < 80°, in good agreement with experiments. Analysis of the total number of hydrogen bonds (HBs) formed by water and surface groups rationalizes this crossover between hydration repulsion and hydrophilic attraction in terms of a subtle balance: Highly polar surfaces repel because of strongly bound hydration water, less polar hydrophilic surfaces attract because water-water HBs are preferred over surface-water HBs. Such solvent reorganization forces presumably underlie also other important phenomena, such as selective ion adsorption to interfaces as well as ion pair formation.

Kandu?, Matej; Schneck, Emanuel; Netz, Roland R.

2014-08-01

339

Hydration rind dates rhyolite flows  

USGS Publications Warehouse

Hydration of obsidian has been used to date rhyolite flows, containing obsidian or porphyritic glass, at Glass Mountain (Medicine Lake Highlands) and Mono Lake, California. The method is simple and rapid and can be used to date flows that erupted between 200 and approximately 200,000 years ago.

Friedman, I.

1968-01-01

340

Hydration rind dates rhyolite flows.  

PubMed

Hydration of obsidian has been used to date rhyolite flows, containing obsidian or porphyritic glass, at Glass Mountain (Medicine Lake Highlands) and Mono Lake, California. The method is simple and rapid and can be used to date flows that erupted between 200 and approximately 200,000 years ago. PMID:17768978

Friedman, I

1968-02-23

341

Activators of photoluminescence in calcite: evidence from high-resolution, laser-excited luminescence spectroscopy  

USGS Publications Warehouse

Laser-excited luminescence spectroscopy of a red-algal, biogenic calcite and a synthetic Mn-calcite can make the distinction between organic and trace-element activators of photoluminescence. Organic-activated photoluminescence in biogenic calcite is characterized by significant peak shifts and increasing intensity with shorter-wavelength excitation and by significant decreases in intensity after heating to ??? 400??C. In contrast, Mn-activated photoluminescence shows no peak shift, greatest intensity under green excitation and limited changes after heating. Examination of samples with a high-sensitivity spectrometer using several wavelengths of exciting light is necessary for identification of photoluminescence activators. ?? 1990.

Pedone, V.A.; Cercone, K.R.; Burruss, R.C.

1990-01-01

342

Nutrient limitations and their implications on the effects of atmospheric deposition in coastal dunes; lime-poor and lime-rich sites in the Netherlands  

Microsoft Academic Search

1 A survey of plant and soil parameters was carried out in dry dune grasslands along the Dutch coast in the lime- and iron-poor Wadden district and initially lime- and iron-rich Renodunaal district, in order to detect differences in nutrient availability related to soil characteristics and potential sensitivity to atmospheric deposition of nitrogen. 2 Plant biomass and phosphorus pools in

A. M. Kooijman; J. C. R. Dopheide; J. Sevink; I. Takken; J. M. Verstraten

1998-01-01

343

Regulation of airway mucosal hydration.  

PubMed

Ion channels control the hydration status of the airway epithelium through apical anion secretion and cation absorption, which is accompanied by osmotically obligated water. The key channels in this process are the cystic fibrosis (CF) transmembrane conductance regulator (CFTR), which is principally responsible for Cl(-) secretion by airway epithelial cells, and the epithelial Na(+) channel (ENaC), which is responsible for the absorption of Na ions. In CF, defective CFTR-mediated Cl(-) secretion and an accompanying upregulation in ENaC-mediated Na absorption results in a reduction in airway surface liquid volume, leading to poorly hydrated mucus and impaired mucociliary clearance. Restoration of normal airway hydration by modulation of ion channel activity represents an important therapeutic strategy for CF. CFTR corrector and potentiator compounds are being developed with the aim of recovering normal Cl(-) secretion. Ca(2+)-activated Cl(-) channels (CaCCs) are expressed by the respiratory epithelia and are reported to be functionally upregulated in CF and offer a 'surrogate' pathway for Cl(-) secretion. TMEM16A has recently been described as a CaCC in the airway epithelium and, as such, represents an alternative target for restoring Cl(-) secretion in CF. An alternative therapeutic strategy for CF is to inhibit ENaC, thereby blocking excessive Na absorption. This can be achieved by direct blockade of ENaC or inhibition of the channel-activating proteases (CAPs), whose activity regulates ENaC function. This review will describe the regulation of airway mucosal hydration by ion channels and the efforts currently underway to restore normal mucosal hydration in disease patients by modulating the function of these channels. PMID:22111616

Paisley, Derek; Gosling, Martin; Danahay, Henry

2010-05-01

344

Physical activity, hydration and health.  

PubMed

Since the beginning of mankind, man has sought ways to promote and preserve health as well as to prevent disease. Hydration, physical activity and exercise are key factors for enhancing human health. However, either a little dose of them or an excess can be harmful for health maintenance at any age. Water is an essential nutrient for human body and a major key to survival has been to prevent dehydration. However, there is still a general controversy regarding the necessary amount to drink water or other beverages to properly get an adequate level of hydration. In addition, up to now the tools used to measure hydration are controversial. To this end, there are several important groups of variables to take into account such as water balance, hydration biomarkers and total body water. A combination of methods will be the most preferred tool to find out any risk or situation of dehydration at any age range. On the other hand, physical activity and exercise are being demonstrated to promote health, avoiding or reducing health problems, vascular and inflammatory disea ses and helping weight management. Therefore, physical activity is also being used as a pill within a therapy to promote health and reduce risk diseases, but as in the case of drugs, dose, intensity, frequency, duration and precautions have to be evaluated and taken into account in order to get the maximum effectiveness and success of a treatment. On the other hand, sedentariness is the opposite concept to physical activity that has been recently recognized as an important factor of lifestyle involved in the obesogenic environment and consequently in the risk of the non-communicable diseases. In view of the literature consulted and taking into account the expertise of the authors, in this review a Decalogue of global recommendations is included to achieve an adequate hydration and physical activity status to avoid overweight/obesity consequences. PMID:24972459

Marcos, Ascensión; Manonelles, Pedro; Palacios, Nieves; Wärnberg, Julia; Casajús, José A; Pérez, Margarita; Aznar, Susana; Benito, Pedro J; Martínez-Gomez, David; Ortega, Francisco B; Ortega, Eduardo; Urrialde, Rafael

2014-01-01

345

Handbook of gas hydrate properties and occurrence  

SciTech Connect

This handbook provides data on the resource potential of naturally occurring hydrates, the properties that are needed to evaluate their recovery, and their production potential. The first two chapters give data on the naturally occurring hydrate potential by reviewing published resource estimates and the known and inferred occurrences. The third and fourth chapters review the physical and thermodynamic properties of hydrates, respectively. The thermodynamic properties of hydrates that are discussed include dissociation energies and a simplified method to calculate them; phase diagrams for simple and multi-component gases; the thermal conductivity; and the kinetics of hydrate dissociation. The final chapter evaluates the net energy balance of recovering hydrates and shows that a substantial positive energy balance can theoretically be achieved. The Appendices of the Handbook summarize physical and thermodynamic properties of gases, liquids and solids that can be used in designing and evaluating recovery processes of hydrates. 158 references, 67 figures, 47 tables.

Kuustraa, V.A.; Hammershaimb, E.C.

1983-12-01

346

Ultrasonic reactivation of phosphonate poisoned calcite during crystal growth.  

PubMed

The effect of ultrasonic irradiation (42,150 Hz, 17 W dm(-3)/7.1 W cm(-2)) on the growth of calcite in the presence of the inhibitor nitrilotris(methylene phosphonic acid) (NTMP) was investigated at constant composition conditions. In seeded growth experiments, it was found that the inhibiting effect of NTMP on crystal growth could be seriously mitigated under influence of ultrasonic irradiation. An approximately twofold increase in volumetric growth rate was achieved during ultrasonic irradiation, and recovery of the growth rate following inhibition was strongly enhanced compared to growth experiments without ultrasonic irradiation. The results could be explained in part by the physical effect of ultrasound that causes breakage and attrition of poisoned crystals, which resulted in an increase in fresh surface area. Mass spectroscopy analysis of sonicated NTMP solutions revealed that there is also a chemical effect of ultrasound that plays an important role. Several breakdown products were identified, which showed that ultrasound caused the progressive loss of phosphonate groups from NTMP, probably by means of physicochemically generated free radicals and/or pyrolysis in the hot bubble-bulk interface. PMID:21463963

Boels, L; Wagterveld, R M; Witkamp, G J

2011-09-01

347

The influence of impurities on the growth rate of calcite  

NASA Astrophysics Data System (ADS)

The effects of 34 different additives on the growth rate of calcite were investigated. An initial growth rate of about one crystal monolayer (3 × 10 -8 cm) per minute was adjusted at a constant supersaturation which was maintained by a control circuit. Then the impurity was added step by step and the reduction of the growth rate was measured. The impurity concentration necessary to reduce the initial growth rate by a certain percentage increased in the order Fe 2+, ATP, P 3O 5-10, P 2O 4-7, (PO 3) 6-6, Zn 2+, ADP, Ce 3+, Pb 2+, carbamyl phosphate, Fe 3+, PO 3-4, Co 2+, Mn 2+, Be 2+, ?-glycerophosphate, Ni 2+, Cd 2+, "Tris", phenylphosphate, chondroitine sulphate, Ba 2+, citrate, AMP, Sr 2+, tricarballylate, taurine, SO 2-4, Mg 2+ by 4 orders of magnitude. The most effective additives halved the initial growth rate in concentrations of 2 × 10 -8 mol/1. For Fe 2+ the halving concentration was nearly proportional to the initial rate. The mechanism of inhibition by adsorption of the impurities at growth sites (kinks) is discussed.

Meyer, H. J.

1984-05-01

348

Kinetic Modeling and Assessment of Lime Pretreatment of Poplar Wood  

E-print Network

is the cheapest alkali, safest to handle, easy to recover, and compatible with oxidants. The main effect of lime pretreatment is to degrade lignin, which occurs with good carbohydrate preservation and is enhanced with oxidants. Among several choices of oxidant... of glucan (after combined pretreatment and enzymatic hydrolysis) for each pretreatment mode. For each pretreatment mode, kinetic models for delignification and carbohydrates degradation were obtained and used to determine the conditions (temperature...

Sierra Ramirez, Rocio

2012-02-14

349

Bonding of soda-lime glass microchips at low temperature  

Microsoft Academic Search

A simple, low-temperature bonding process is described for the fabrication of soda-lime glass microfluidic chips. Due to its\\u000a chemical inertness and temperature stability, glass remains a popular material for microfluidic chips despite the advances\\u000a that have been made with polymer materials. Conventional thermal bonding is performed over the course of 24 h at 600C and\\u000a requires a precise temperature-controlled furnace. Here

Alexander Iles; Akio Oki; Nicole Pamme

2007-01-01

350

Effect of lime on lead uptake by five plant species  

Microsoft Academic Search

Liming at 0, 2.2, and 4.4 tons\\/hectare (0, 1, and 2 English tons\\/acre) was tested as a means of reducing Pb uptake by five species from two Pb contaminated soils. The soils represent the 0- to 10- and 10- to 30-cm horizons of Los Osos clay loam (a Typic Argixeroll) and contained 94 +\\/- 18 and 32 +\\/- 7 ppm

W. J. Cox; D. W. Rains

1972-01-01

351

Economic evaluation of the industrial solar production of lime  

Microsoft Academic Search

The use of concentrated solar energy in place of fossil fuels for driving the endothermic calcination reaction CaCO3?CaO+CO2 at above 1300 K has the potential of reducing CO2 emissions by 20% in a state-of-the-art lime plant and up to 40% in a conventional cement plant. An economic assessment for an industrial solar calcination plant with 25 MWth solar input indicates

Anton Meier; Nicolas Gremaud; Aldo Steinfeld

2005-01-01

352

Enhancement of phosphogypsum with high lime fly ash  

E-print Network

for Pile No. 3. . . . . . . . . . . . . . . , 42 10 Ranges in chemical composition of bituminous ashes and lignite (weight percentages). 47 Summary of evaluated fly ash properties. . 12 Summary of preliminary compressive strength data (Tex-127-E). 53...ENHANCEMENT OF PHOSPHOGYPSUM WITH HIGH LIME FLY ASH A Thesis by CHUCK ALAN GREGORY Submitted to the Graduate College of Texas ASM University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE May 1983 Major...

Gregory, Chuck Alan

1983-01-01

353

Pockmark formation and evolution in deep water Nigeria: Rapid hydrate growth versus slow hydrate dissolution  

NASA Astrophysics Data System (ADS)

In previous works, it has been suggested that dissolution of gas hydrate can be responsible for pockmark formation and evolution in deep water Nigeria. It was shown that those pockmarks which are at different stages of maturation are characterized by a common internal architecture associated to gas hydrate dynamics. New results obtained by drilling into gas hydrate-bearing sediments with the MeBo seafloor drill rig in concert with geotechnical in situ measurements and pore water analyses indicate that pockmark formation and evolution in the study area are mainly controlled by rapid hydrate growth opposed to slow hydrate dissolution. On one hand, positive temperature anomalies, free gas trapped in shallow microfractures near the seafloor and coexistence of free gas and gas hydrate indicate rapid hydrate growth. On the other hand, slow hydrate dissolution is evident by low methane concentrations and almost constant sulfate values 2 m above the Gas Hydrate Occurrence Zone.

Sultan, N.; Bohrmann, G.; Ruffine, L.; Pape, T.; Riboulot, V.; Colliat, J.-L.; De Prunelé, A.; Dennielou, B.; Garziglia, S.; Himmler, T.; Marsset, T.; Peters, C. A.; Rabiu, A.; Wei, J.

2014-04-01

354

Thermal conductivity of hydrate-bearing sediments  

USGS Publications Warehouse

A thorough understanding of the thermal conductivity of hydrate-bearing sediments is necessary for evaluating phase transformation processes that would accompany energy production from gas hydrate deposits and for estimating regional heat flow based on the observed depth to the base of the gas hydrate stability zone. The coexistence of multiple phases (gas hydrate, liquid and gas pore fill, and solid sediment grains) and their complex spatial arrangement hinder the a priori prediction of the thermal conductivity of hydrate-bearing sediments. Previous studies have been unable to capture the full parameter space covered by variations in grain size, specific surface, degree of saturation, nature of pore filling material, and effective stress for hydrate-bearing samples. Here we report on systematic measurements of the thermal conductivity of air dry, water- and tetrohydrofuran (THF)-saturated, and THF hydrate-saturated sand and clay samples at vertical effective stress of 0.05 to 1 MPa (corresponding to depths as great as 100 m below seafloor). Results reveal that the bulk thermal conductivity of the samples in every case reflects a complex interplay among particle size, effective stress, porosity, and fluid-versus-hydrate filled pore spaces. The thermal conductivity of THF hydrate-bearing soils increases upon hydrate formation although the thermal conductivities of THF solution and THF hydrate are almost the same. Several mechanisms can contribute to this effect including cryogenic suction during hydrate crystal growth and the ensuing porosity reduction in the surrounding sediment, increased mean effective stress due to hydrate formation under zero lateral strain conditions, and decreased interface thermal impedance as grain-liquid interfaces are transformed into grain-hydrate interfaces. Copyright 2009 by the American Geophysical Union.

Cortes, D.D.; Martin, A.I.; Yun, T.S.; Francisca, F.M.; Santamarina, J.C.; Ruppel, C.

2009-01-01

355

Speciation of aluminium, arsenic and molybdenum in excessively limed lakes.  

PubMed

The possible existence of the potentially toxic oxyanions of Al (Al(OH)(4)(-)), As (HAsO(4)(2-)), and Mo (MoO(4)(2-)) was examined in excessively limed lakes. In-situ dialysis (MWCO 1 kDa) was performed in the surface and bottom waters of two excessively limed lakes (pH 7.1-7.7) and one acidic lake (pH approximately 5.4). The dialysable metal concentrations were compared to the equilibrium distribution of species as calculated with the geochemical code Visual MINTEQ incorporating the CD-MUSIC and Stockholm Humic models for complexation onto colloidal ferrihydrite and dissolved organic matter. Arsenic and molybdenum in the excessively limed lakes were to a large extent present in the dialysable fraction (>79% and >92% respectively). They were calculated to exist as free or adsorbed oxyanions. Most of the Al was observed to reside in the colloidal fraction (51-82%). In agreement with this, model predictions indicated aluminium to be present mostly as colloids or bound to dissolved organic matter. Only a small fraction was modelled as Al(OH)(4)(-) ions. In most cases, modelled values were in agreement with the dialysis results. The free concentrations of the three oxyanions were mostly low compared to toxic levels. PMID:19540566

Sjöstedt, Carin; Wällstedt, Teresia; Gustafsson, Jon Petter; Borg, Hans

2009-09-01

356

Santaclaraite, a new calcium-manganese silicate hydrate from California.  

USGS Publications Warehouse

Santaclaraite, ideally CaMn4(Si5O14(OH))(OH).H2O, occurs as pink and tan veins and masses in Franciscan chert in the Diablo Range, Santa Clara and Stanislaus counties, California. It is associated with four unidentified Mn silicates, Mn-howieite, quartz, braunite, calcite, rhodochrosite, kutnahorite, baryte, harmotome, chalcopyrite and native copper. Santaclaraite is triclinic, space group B1, a 15.633(1), b 7.603(1) , c 12.003(1) A, alpha 109.71(1)o, beta 88.61(1)o, gamma 99.95(1) o, V 1322.0(3) A3; Z = 4. The strongest lines of the X-ray pattern are 7.04(100), 3.003(84), 3.152(80), 7.69(63), 3.847(57) A. Crystals are lamellar to prismatic (flattened on (100)), with good cleavage on (100) and (010); H. 61/2 Dcalc. 3.398 g/cm3, Dmeas. 3.31 (+ or -0.01); optically biaxial negative, alpha 1.681, beta 1.696, gamma 1.708 (all + or - 0.002), 2Valpha 83 (+ or -1)o. Although chemically a hydrated rhodonite, santaclaraite dehydrates to Mn-bustamite at approx 550oC (in air) . Santaclaraite is a five-tetrahedral-repeat single-chain silicate and has structural affinities with rhodonite, nambulite, marsturite, babingtonite and inesite.-J.A.Z.

Erd, R.C.; Ohashi, Y.

1984-01-01

357

Estimation of uncertain parameters to improve modeling of Mirobially Induced Calcite Precipitation  

E-print Network

in the subsurface or fracking could be reduced with sealing technologies like microbially induced calcite Injectionwellvicinity Fracking CO2 Reservoir Figure 1: Potential application sites of MICP as a sealing technology

Cirpka, Olaf Arie

358

Kinetic and Thermodynamic Study of Calcite Marble Samples from Lesser Himalayas  

NASA Astrophysics Data System (ADS)

A kinetic and thermodynamic study of selected calcite marble samples from Lesser Himalayas has been performed using thermogravimetric and differential thermal analyses at heating rates of and . The minero-petrography of calcite grains, phase analysis, chemical analysis, and minor impurities determination were carried out using thin-section polarized light microscopy, X-ray diffraction, X-ray fluorescence, and electron microprobe analysis, respectively. The calcite content of the investigated marble samples varied from 97.50 mass% to 98.70 mass%. The activation energy, , for the decomposition process increased from to and from to for heating rates of and , respectively, with decreasing calcite content. The activation energy values obtained in the present study were in good agreement with previous studies.

Fahad, M.; Iqbal, Y.

2014-02-01

359

Enhancing mechanical properties of calcite by Mg substitutions: An ab initio study  

NASA Astrophysics Data System (ADS)

Arthropoda representing a majority of all known animal species are protected by an exoskeleton formed by their cuticle. The cuticle represents a hierarchically structured multifunctional bio-composite based on chitin and proteins. Some groups like Crustacea reinforce the load-bearing parts of their cuticle with calcite. As the calcite sometimes contains Mg it was speculated that Mg may have a stiffening impact on the mechanical properties of the cuticle. We present a theoretical parameter-free quantum-mechanical study of thermodynamic, structural and elastic properties of Mg-substituted calcite. Our results show that substituting Ca by Mg causes an almost linear decrease in the crystal volume with Mg concentration and of substituted crystals. As a consequence the calcite crystals become stiffer giving rise e.g. to substantially increased bulk moduli.

Elstnerova, Pavlina; Friak, Martin; Hickel, Tilmann; Fabritius, Helge Otto; Lymperakis, Liverios; Petrov, Michal; Raabe, Dierk; Neugebauer, Joerg; Nikolov, Svetoslav; Zigler, Andreas; Hild, Sabine

2011-03-01

360

High School Forum: "Invitations to Enquiry": The Calcite/Acid Reaction.  

ERIC Educational Resources Information Center

Describes a high school chemistry experiment which involves the reaction between calcite and hydrochloric and sulfuric acids. This reaction can be carried out as a projected demonstration and on an individual basis. (HM)

Herron, J. Dudley, Ed.; Driscoll, D. R.

1979-01-01

361

Retrofit costs for lime/limestone FGD and lime spray drying at coal-fired utility boilers  

SciTech Connect

The paper gives results of a research program the objective of which was to significantly improve engineering cost estimates currently being used to evaluate the economic effects of applying SO2 controls to existing coal-fired utility boilers. The costs of retrofitting conventional lime/limestone wet flue gas desulfurization (L/LS FGD) and lime spray drying (LSD) FGD at 100-200 coal-fired power plants are being estimated under this program. The retrofit capital cost estimating procedures used for L/LS FGD and LSD FGD make two cost adjustments to current procedures used to estimate FGD costs: cost adders (for items not normally included in FGD system costs; e.g., demolition and relocation of existing facilities) and cost multipliers (to adjust capital costs for site access, congestion, and underground obstructions).

Emmel, T.E.; Jones, J.W.

1990-01-01

362

Origin of sulfate in barite and calcite cements in the Jebel Madar salt dome (Oman)  

NASA Astrophysics Data System (ADS)

Jebel Madar is a 500-m high mountain rising in the desert at the Oman Foothills. The Jebel consists of Triassic to Cretaceous carbonate host rocks forming the carapace of a salt dome. Halokinesis caused major fracturing and faulting at Jebel Madar, and the resulting structures acted as the main pathways for fluids that generated diagenetic cements composed of both barite and calcite. The spatial distribution of calcite and barite occurrences shows that calcite is formed in large abundance along the three main faults, whereas barite is more concentrated along faults further away from the three main ones. The stable carbon and oxygen isotope composition of calcite and fluid inclusion data from both calcite and barite show a distinct evolution of the fluid with a highly saline component towards more mixing with meteoric water. This is in agreement with clumped isotopes data on calcite cements indicating an evolution towards lower temperatures, consistent with doming of the Jebel and greater input of lower-temperature descending meteoric fluids. Here, we present sulphur and oxygen isotopic data on barite that suggest a link between the barite formation and the Precambrian salt underlying Jebel Madar. The average ?34S measured in barite is 33‰ CDT (1? = 5‰; n = 33), which falls at the lower end of the ?34S range reported for the Ara Group anhydrite. The average ?18O in the same barite samples is 23‰ VSMOW (1? = 2‰; n = 33). Data from the barite will be compared with sulphur isotopes from the carbonate-associate sulfate in the calcite cements. The overall goal of our research is to gain a better insight in the formation process of barite and calcite in Jebel Madar and its link with salt tectonics. We would like to acknowledge the financial support of QCCSRC (funded jointly by Qatar Petroleum, Shell and the Qatar Science & Technology Park) and the GSA Laubach fund for this study.

Vandeginste, V.; John, C. M.; Gilhooly, W. P.

2012-12-01

363

Effects of chitosan on the alignment, morphology and shape of calcite crystals nucleating under Langmuir monolayers  

SciTech Connect

The growth of calcium carbonate crystals under Langmuir monolayers was investigated in the presence of chitosan, a soluble derivative of chitin added to the subphase to better simulate the polyelectrolyte-containing in vivo environment. Chitosan causes distinct concentration-dependent changes in the orientation, shape and morphology of the calcite crystals nucleating under acid and sulfate monolayers. Our results suggest that polyelectrolytes may play essential roles in controlling the growth of biogenic calcite crystals.

Kim, Kyungil; Uysal, Ahmet; Kewalramani, Sumit; Stripe, Benjamin; Dutta, Pulak; (NWU); (BNL)

2009-04-22

364

Effects of Chitosan on the Morphology and Alignment of Calcite Crystals Nucleating Under Langmuir Monolayers  

SciTech Connect

The growth of calcium carbonate crystals under Langmuir monolayers was investigated in the presence of chitosan, a soluble derivative of chitin added to the subphase to better simulate the polyelectrolyte-containing in vivo environment. Chitosan causes distinct concentration-dependent changes in the orientation, shape and morphology of the calcite crystals nucleating under acid and sulfate monolayers. Our results suggest that polyelectrolytes may play essential roles in controlling the growth of biogenic calcite crystals.

Kim, K.; Uysal, A; Kewalramani, S; Stripe, B; Dutta, P

2009-01-01

365

Stress and Temperature Dependence of Calcite Twinning: New Experimental and Field Constraints  

Microsoft Academic Search

In low-grade metamorphic terrains at temperatures < 300Ë? C e-twinning of calcite is common. The amount and width of e-twins have been suggested to indicate stress and temperature representing robust paleopiezometers and geothermometers. To evaluate the stress- and temperature dependence of e-twins in calcite we have performed a series of deformation experiments on specimens of Carrara marble in the semibrittle

E. Rybacki; C. Janssen; G. Dresen; B. Evans

2009-01-01

366

Fractionation of carbon and oxygen isotopes and magnesium between coexisting metamorphic calcite and dolomite  

Microsoft Academic Search

Fractionations of carbon and oxygen isotopes and magnesium between coexisting dolomite and calcite have been determined for\\u000a marbles and calcareous schists of a wide variety of metamorphic environments from Vermont and the Grenville Province of Ontario.\\u000a Concordant equilibrium fractionations are given by 83% of the samples. Calibration of the isotopic thermometers using the\\u000a Mg-calcite solvus thermometer gave in the temperature

Simon M. F. Sheppard; Henry P. Schwarcz

1970-01-01

367

Rheology and microstructure of synthetic halite\\/calcite porphyritic aggregates in torsion  

Microsoft Academic Search

Polymer jacketed porphyritic samples of 70% halite+30% coarse calcite were subjected to torsion deformation to investigate the effects of a mixture of coarse calcite on the microstructure and mechanical properties of a two-phase aggregate. The experiments were run at 100 and 200°C, a confining pressure of 250MPa, and a constant shear strain rate of 3E-4s?1. Ultimate strengths of single-phase halite

F. O. Marques; L. Burlini; J.-P. Burg

2010-01-01

368

Unravelling the enigmatic origin of calcitic nanofibres in soils and caves: purely physicochemical or biogenic processes?  

NASA Astrophysics Data System (ADS)

Calcitic nanofibres are ubiquitous habits of secondary calcium carbonate (CaCO3) accumulations observed in calcareous vadose environments. Despite their widespread occurrence, the origin of these nanofeatures remains enigmatic. Three possible mechanisms fuel the debate: (i) purely physicochemical processes, (ii) mineralization of rod-shaped bacteria, and (iii) crystal precipitation on organic templates. Nanofibres can be either mineral (calcitic) or organic in nature. They are very often observed in association with Needle Fibre Calcite (NFC), another typical secondary CaCO3 habit in terrestrial environments. This association has contributed to some confusion between both habits, however they are truly two distinct calcitic features and their recurrent association is likely to be an important fact to help understanding the origin of nanofibres. In this manuscript the different hypotheses that currently exist to explain the origin of calcitic nanofibres are critically reviewed. In addition to this, a new hypothesis for the origin of nanofibres is proposed based on the fact that current knowledge attributes a fungal origin to NFC. As this feature and nanofibres are recurrently observed together, a possible fungal origin for nanofibres which are associated with NFC is investigated. Sequential enzymatic digestion of the fungal cell wall of selected fungal species demonstrates that the fungal cell wall can be a source of organic nanofibres. The obtained organic nanofibres show a striking morphological resemblance when compared to their natural counterparts, emphasizing a fungal origin for part of the organic nanofibres observed in association with NFC. It is further hypothesized that these organic nanofibres may act as templates for calcite nucleation in a biologically-influenced mineralization process, generating calcitic nanofibres. This highlights the possible involvement of Fungi in CaCO3 biomineralization processes, a role still poorly documented at present-day. Moreover, on a global scale, the organomineralization of organic nanofibres into calcitic nanofibres might have a great, however overlooked, impact on the biogeochemical cycles of both Ca and C.

Bindschedler, S.; Cailleau, G.; Braissant, O.; Millière, L.; Job, D.; Verrecchia, E. P.

2014-01-01

369

Unravelling the enigmatic origin of calcitic nanofibres in soils and caves: purely physicochemical or biogenic processes?  

NASA Astrophysics Data System (ADS)

Calcitic nanofibres are ubiquitous habits of secondary calcium carbonate (CaCO3) accumulations observed in calcareous vadose environments. Despite their widespread occurrence, the origin of these nanofeatures remains enigmatic. Three possible mechanisms fuel the debate: (i) purely physicochemical processes, (ii) mineralization of rod-shaped bacteria, and (iii) crystal precipitation on organic templates. Nanofibres can be either mineral (calcitic) or organic in nature. They are very often observed in association with needle fibre calcite (NFC), another typical secondary CaCO3 habit in terrestrial environments. This association has contributed to some confusion between both habits, however they are truly two distinct calcitic features and their recurrent association is likely to be an important fact to help understanding the origin of nanofibres. In this paper the different hypotheses that currently exist to explain the origin of calcitic nanofibres are critically reviewed. In addition to this, a new hypothesis for the origin of nanofibres is proposed based on the fact that current knowledge attributes a fungal origin to NFC. As this feature and nanofibres are recurrently observed together, a possible fungal origin for nanofibres which are associated with NFC is investigated. Sequential enzymatic digestion of the fungal cell wall of selected fungal species demonstrates that the fungal cell wall can be a source of organic nanofibres. The obtained organic nanofibres show a striking morphological resemblance when compared to their natural counterparts, emphasizing a fungal origin for part of the organic nanofibres observed in association with NFC. It is further hypothesized that these organic nanofibres may act as templates for calcite nucleation in a biologically influenced mineralization process, generating calcitic nanofibres. This highlights the possible involvement of fungi in CaCO3 biomineralization processes, a role still poorly documented. Moreover, on a global scale, the organomineralization of organic nanofibres into calcitic nanofibres might be an overlooked process deserving more attention to specify its impact on the biogeochemical cycles of both Ca and C.

Bindschedler, S.; Cailleau, G.; Braissant, O.; Millière, L.; Job, D.; Verrecchia, E. P.

2014-05-01

370

Distribution of vesicular-arbuscular mycorrhizal fungi in coal, lignite, and calcite mine spoils of India  

Microsoft Academic Search

We assessed vesicular-arbuscular mycorrhizal (VAM) fungi in coal, lignite, and calcite mine spoils. The level of VAM fungal infection and the population of VAM species in plants on the coal-waste sites were similar to those in plants on the calcite mine spoil. The plants on the coal-waste sites and their associated VAM fungi included Tephrosia purpurea (L.) Pers. with Glomus

V. Ganesan; S. Ragupathy; B. Parthipan; D. B. Rajini Rani; A. Mahadevan

1991-01-01

371

Impact of cyclic wetting–drying on swelling behavior of lime-stabilized soil  

Microsoft Academic Search

In this study, the impact of cyclic wetting and drying on swelling behavior of lime-stabilized clayey soils has been investigated. Swelling potential and swelling pressure tests have been carried out on soil mixtures with various amounts of kaolinite–bentonite clays, and on a high plasticity clayey soil sample. The tests have been repeated after the addition of lime to the lime-treated

Yucel Guney; Dursun Sari; Murat Cetin; Mustafa Tuncan

2007-01-01

372

Influencing factors of compressive strength of solidified inshore saline soil using SH lime-ash  

Microsoft Academic Search

Through unconfined compressive strength test, influencing factors on compressive strength of solidified inshore saline soil\\u000a with SH lime-ash, ratio of lime-ash(1:K), quantity of lime-ash, age, degree of compression and salt content were studied. The results show that because inshore saline\\u000a soil has special engineering characteristic, more influencing factors must be considered compared with ordinary soil for the\\u000a perfect effect of

Yin-hui Qin; Fu-hua Liu; Qi Zhou

2008-01-01

373

Effects of lime treatment on fractionation and extractabilities of heavy metals in sewage sludge  

Microsoft Academic Search

Many studies have focused on heavy metal characteristics in sewage sludges and sludge?amended soils other than lime?stabilized sewage sludge (LS). Thus, the aerobically digested sewage sludge cake (13.61% solids) sampled from the Min?Sheng Wastewater Treatment Plant in Taipei City, Taiwan was lime?stabilized for studying the effects of the lime treatment on fractionation and extractabilities of heavy metals (Cu, Pb, Cr,

1997-01-01

374

NMR characterization of hydrocarbon adsorption on calcite surfaces: a first principles study.  

PubMed

The electronic and coordination environment of minerals surfaces, as calcite, are very difficult to characterize experimentally. This is mainly due to the fact that there are relatively few spectroscopic techniques able to detect Ca(2+). Since calcite is a major constituent of sedimentary rocks in oil reservoir, a more detailed characterization of the interaction between hydrocarbon molecules and mineral surfaces is highly desirable. Here we perform a first principles study on the adsorption of hydrocarbon molecules on calcite surface (CaCO3 (101¯4)). The simulations were based on Density Functional Theory with Solid State Nuclear Magnetic Resonance (SS-NMR) calculations. The Gauge-Including Projector Augmented Wave method was used to compute mainly SS-NMR parameters for (43)Ca, (13)C, and (17)O in calcite surface. It was possible to assign the peaks in the theoretical NMR spectra for all structures studied. Besides showing different chemical shifts for atoms located on different environments (bulk and surface) for calcite, the results also display changes on the chemical shift, mainly for Ca sites, when the hydrocarbon molecules are present. Even though the interaction of the benzene molecule with the calcite surface is weak, there is a clearly distinguishable displacement of the signal of the Ca sites over which the hydrocarbon molecule is located. A similar effect is also observed for hexane adsorption. Through NMR spectroscopy, we show that aromatic and alkane hydrocarbon molecules adsorbed on carbonate surfaces can be differentiated. PMID:25429955

Bevilaqua, Rochele C A; Rigo, Vagner A; Veríssimo-Alves, Marcos; Miranda, Caetano R

2014-11-28

375

Multiple origins for zoned cathodoluminescent and noncathodoluminescent calcite cements in Pennsylvanian limestones  

SciTech Connect

Noncathodoluminescent calcite containing brightly to moderately luminescent zones is a common early cement in limestones. Three such cements in Upper Pennsylvanian limestones from different areas were studied. All three units are overlain up-section by Permian evaporites and consist of carbonate-siliciclastic 'cyclothems' in which individual cycles were subject to subaerial exposure. With such similar settings, one might predict that petrographically similar calcite cements would have similar origins. In the Holder Formation (New Mexico), the zoned calcite predates compaction, and cross-cutting relationships with cycle-capping paleosols show that zoned cements precipitated during 15 events of subaerial exposure. Therefore, cements precipitated from freshwater during early and repeated subaerial exposure. For the Lansing-Kansas City groups in northwestern Kansas, the zoned calcite cements commonly are among the first precipitated but may postdate some compaction. All-liquid fluid inclusions indicated precipitation below about 50C, from brines of approximately 23 weight %. NaCl equivalent. The brines may have refluxed downward during deposition of Permian evaporites. A limestone of the Lansing-Kansas City groups of west-central Kansas contains early zoned calcite cement that predates compaction. The cement contains all-liquid fluid inclusions indicating precipitation below about 50C. The presence of nonluminescent calcite containing bright subzones is not indicative of a single diagenetic environment. Petrographically similar cements from similar settings may originate in markedly different diagenetic environments.

Goldstein, R.H.; Anderson, J.E.; Phares, R.A. (Univ. of Kansas, Lawrence (United States))

1991-03-01

376

NMR characterization of hydrocarbon adsorption on calcite surfaces: A first principles study  

NASA Astrophysics Data System (ADS)

The electronic and coordination environment of minerals surfaces, as calcite, are very difficult to characterize experimentally. This is mainly due to the fact that there are relatively few spectroscopic techniques able to detect Ca2+. Since calcite is a major constituent of sedimentary rocks in oil reservoir, a more detailed characterization of the interaction between hydrocarbon molecules and mineral surfaces is highly desirable. Here we perform a first principles study on the adsorption of hydrocarbon molecules on calcite surface (CaCO3 ( {10bar 14} )). The simulations were based on Density Functional Theory with Solid State Nuclear Magnetic Resonance (SS-NMR) calculations. The Gauge-Including Projector Augmented Wave method was used to compute mainly SS-NMR parameters for 43Ca, 13C, and 17O in calcite surface. It was possible to assign the peaks in the theoretical NMR spectra for all structures studied. Besides showing different chemical shifts for atoms located on different environments (bulk and surface) for calcite, the results also display changes on the chemical shift, mainly for Ca sites, when the hydrocarbon molecules are present. Even though the interaction of the benzene molecule with the calcite surface is weak, there is a clearly distinguishable displacement of the signal of the Ca sites over which the hydrocarbon molecule is located. A similar effect is also observed for hexane adsorption. Through NMR spectroscopy, we show that aromatic and alkane hydrocarbon molecules adsorbed on carbonate surfaces can be differentiated.

Bevilaqua, Rochele C. A.; Rigo, Vagner A.; Veríssimo-Alves, Marcos; Miranda, Caetano R.

2014-11-01

377

Estimation of past seepage volumes from calcite distribution in the Topopah Spring Tuff, Yucca Mountain, Nevada  

USGS Publications Warehouse

Low-temperature calcite and opal record the past seepage of water into open fractures and lithophysal cavities in the unsaturated zone at Yucca Mountain, Nevada, site of a proposed high-level radioactive waste repository. Systematic measurements of calcite and opal coatings in the Exploratory Studies Facility (ESF) tunnel at the proposed repository horizon are used to estimate the volume of calcite at each site of calcite and/or opal deposition. By estimating the volume of water required to precipitate the measured volumes of calcite in the unsaturated zone, seepage rates of 0.005 to 5 liters/year (l/year) are calculated at the median and 95th percentile of the measured volumes, respectively. These seepage rates are at the low end of the range of seepage rates from recent performance assessment (PA) calculations, confirming the conservative nature of the performance assessment. However, the distribution of the calcite and opal coatings indicate that a much larger fraction of the potential waste packages would be contacted by this seepage than is calculated in the performance assessment.

Marshall, B.D.; Neymark, L.A.; Peterman, Z.E.

2003-01-01

378

Estimation of past seepage volumes from calcite distribution in the Topopah Spring Tuff, Yucca Mountain, Nevada.  

PubMed

Low-temperature calcite and opal record the past seepage of water into open fractures and lithophysal cavities in the unsaturated zone at Yucca Mountain, Nevada, site of a proposed high-level radioactive waste repository. Systematic measurements of calcite and opal coatings in the Exploratory Studies Facility (ESF) tunnel at the proposed repository horizon are used to estimate the volume of calcite at each site of calcite and/or opal deposition. By estimating the volume of water required to precipitate the measured volumes of calcite in the unsaturated zone, seepage rates of 0.005 to 5 liters/year (l/year) are calculated at the median and 95th percentile of the measured volumes, respectively. These seepage rates are at the low end of the range of seepage rates from recent performance assessment (PA) calculations, confirming the conservative nature of the performance assessment. However, the distribution of the calcite and opal coatings indicate that a much larger fraction of the potential waste packages would be contacted by this seepage than is calculated in the performance assessment. PMID:12714293

Marshall, Brian D; Neymark, Leonid A; Peterman, Zell E

2003-01-01

379

Sea urchin tooth mineralization: Calcite present early in the aboral plumula  

PubMed Central

In both vertebrate bone, containing carbonated hydroxyapatite as the mineral phase, and in invertebrate hard tissue comprised of calcium carbonate, a popular view is that the mineral phase develops from a long-lived amorphous precursor which later transforms into crystal form. Important questions linked to this popular view are: When and where is the crystallized material formed, and is amorphous solid added subsequently to the crystalline substrate? Sea urchin teeth, in which the earliest mineral forms within isolated compartments, in a time and position dependent manner, allow direct investigation of the timing of crystallization of the calcite primary plates. Living teeth of the sea urchin Lytechinus variegatus, in their native coelomic fluid, were examined by high-energy synchrotron x-ray diffraction. The diffraction data show that calcite is present in the most aboral portions of the plumula, representing the very earliest stages of mineralization, and that this calcite has the same crystal orientation as in the more mature adoral portions of the same tooth. Raman spectroscopy of the aboral plumula confirms the initial primary plate mineral material is calcite and does not detect amorphous calcium carbonate; in the more mature adoral incisal flange, it does detect a broader calcite peak, consistent with two or more magnesium compositions. We hypothesize that some portion of each syncytial membrane in the plumula provides the information for nucleation of identically oriented calcite crystals that subsequently develop to form the complex geometry of the single crystal sea urchin tooth. PMID:22940703

Stock, Stuart R.; Veis, Arthur; Xiao, Xianghui; Almer, Jonathan D.; Dorvee, Jason R.

2012-01-01

380

Mixing-induced calcite precipitation and dissolution kinetics in micromodel experiments.  

SciTech Connect

Dissolved CO2 from geological CO2 sequestration may react with dissolved minerals in fractured rocks or confined aquifers and cause mineral precipitation. The overall rate of reaction can be limited by diffusive or dispersive mixing, and mineral precipitation can block pores and further hinder these processes. Mixing-induced calcite precipitation experiments were performed by injecting solutions containing CaCl2 and Na2CO3 through two separate inlets of a micromodel (1-cm x 2-cm x 40-microns); transverse dispersion caused the two solutions to mix along the center of the micromodel, resulting in calcite precipitation. The amount of calcite precipitation initially increased to a maximum and then decreased to a steady state value. Fluorescent microscopy and imaging techniques were used to visualize calcite precipitation, and the corresponding effects on the flow field. Experimental micromodel results were evaluated with pore-scale simulations using a 2-D Lattice-Boltzmann code for water flow and a finite volume code for reactive transport. The reactive transport model included the impact of pH upon carbonate speciation and calcite dissolution. We found that proper estimation of the effective diffusion coefficient and the reaction surface area is necessary to adequately simulate precipitation and dissolution rates. The effective diffusion coefficient was decreased in grid cells where calcite precipitated, and keeping track of reactive surface over time played a significant role in predicting reaction patterns. Our results may improve understanding of the fundamental physicochemical processes during CO2 sequestration in geologic formations.

Valocchi, Albert J.; Dewers, Thomas A.; Dehoff, Karl; Yoon, Hongkyu; Werth, Charles J.

2010-12-01

381

Multiple stage multiple filter hydrate store  

DOEpatents

An improved hydrate store for a metal halogen battery system is disclosed which employs a multiple stage, multiple filter means or separating the halogen hydrate from the liquid used in forming the hydrate. The filter means is constructed in the form of three separate sections which combine to substantially cover the interior surface of the store container. Exit conduit means is provided in association with the filter means for transmitting liquid passing through the filter means to a hydrate former subsystem. The hydrate former subsystem combines the halogen gas generated during the charging of the battery system with the liquid to form the hydrate in association with the store. Relief valve means is interposed in the exit conduit means for controlling the operation of the separate sections of the filter means, such that the liquid flow through the exit conduit means from each of the separate sections is controlled in a predetermined sequence. The three separate sections of the filter means operate in three discrete stages to provide a substantially uniform liquid flow to the hydrate former subsystem during the charging of the battery system. The separation of the liquid from the hydrate causes an increase in the density of the hydrate by concentrating the hydrate along the filter means.

Bjorkman, Jr., Harry K. (Birmingham, MI)

1983-05-31

382

Multiple stage multiple filter hydrate store  

DOEpatents

An improved hydrate store for a metal halogen battery system is disclosed which employs a multiple stage, multiple filter means for separating the halogen hydrate from the liquid used in forming the hydrate. The filter means is constructed in the form of three separate sections which combine to substantially cover the interior surface of the store container. Exit conduit means is provided in association with the filter means for transmitting liquid passing through the filter means to a hydrate former subsystem. The hydrate former subsystem combines the halogen gas generated during the charging of the battery system with the liquid to form the hydrate in association with the store. Relief valve means is interposed in the exit conduit means for controlling the operation of the separate sections of the filter means, such that the liquid flow through the exit conduit means from each of the separate sections is controlled in a predetermined sequence. The three separate sections of the filter means operate in three discrete stages to provide a substantially uniform liquid flow to the hydrate former subsystem during the charging of the battery system. The separation of the liquid from the hydrate causes an increase in the density of the hydrate by concentrating the hydrate along the filter means. 7 figs.

Bjorkman, H.K. Jr.

1983-05-31

383

Dynamics of hydrated starch saccharides  

NASA Astrophysics Data System (ADS)

We report here elastic neutron scattering data on glucose and on two of its polymeric forms: amylose and amylopectin. We have covered the hydration range from the dry state to about 0.6 g water/g dry saccharide. The data indicate, in all the analysed systems, the presence of a dynamic glass-like transition similar to that observed in hydrated proteins. The fact that this feature is observed also in a relatively small molecule like glucose confirms the hypothesis already put forward by other authors, that this transition in biomolecular species is essentially triggered and driven by the interaction of the macromolecule with the network of fluctuating H-bond of the solvent.

Di Bari, M.; Deriu, A.; Albanese, G.; Cavatorta, F.

2003-08-01

384

Molecular Structure of Acyclovir hydrate  

NSDL National Science Digital Library

Acyclovir hydrate is used in the treatment of shingles and herpes simplex virus and as well as other types of herpes viral infections. This may help people co-infected with HIV and herpes simplex live longer. High dose acyclovir is used to treat hairy leukoplakia, a viral infection which usually shows up on both sides of the tongue. Possible side effects of this therapeutic substance are stomach pain, headache, nausea and/or hair-loss.

2002-09-12

385

Gas hydrate cool storage system  

DOEpatents

This invention is a process for formation of a gas hydrate to be used as a cool storage medium using a refrigerant in water. Mixing of the immiscible refrigerant and water is effected by addition of a surfactant and agitation. The difficult problem of subcooling during the process is overcome by using the surfactant and agitation and performance of the process significantly improves and approaches ideal.

Ternes, Mark P. (Knoxville, TN); Kedl, Robert J. (Oak Ridge, TN)

1985-01-01

386

The effect of liming on antibacterial and hormone levels in wastewater biosolids.  

PubMed

This study analyzes the effect of liming on levels of triclocarban (TCC), triclosan (TCS), estrone (E1), and progesterone (P), two antimicrobial agents and two natural hormones, respectively. Factors studied include lime particle size, mixing time, and overall lime contact time. The study results suggest that coarse lime may be more active than fine lime due to less interaction with surrounding air. Both TCS and TCC concentrations were lower in coarse limed samples versus unlimed samples and the decrease was a function of time. A similar, but statistically insignificant trend in TCC and TCS levels was observed in fine lime samples with respect to unlimed samples. Liming was also found to decrease apparent E1 levels, with more notable decreases in samples amended with coarse lime. P-levels significantly increased after 1-day of contact time, stabilizing over the next 14 days of the study period. This increase and stabilization of P-levels was attributed to the pH and moisture-driven conversion of more chemically complex steroids into P. PMID:23485235

Olszewski, Jennifer M; Lozano, Nuria; Haines, Christine; Rice, Clifford P; Ramirez, Mark; Torrents, Alba

2013-01-01

387

LIME, a Novel Transmembrane Adaptor Protein, Associates with p56lck and Mediates T Cell Activation  

PubMed Central

In this study, we identify and characterize a novel transmembrane adaptor protein, designated Lck-interacting membrane protein (LIME), as a binding partner of the Lck Src homology (SH)2 domain. LIME possesses a short extracellular domain, a transmembrane domain, and a cytoplasmic tail containing five tyrosine-based motifs. The protein is primarily expressed in hematopoietic cells and lung. Interestingly, LIME expression is up-regulated by TCR stimulation and sustained up to 24 h, suggesting that LIME acts throughout the early to late stages of T cell activation. LIME is localized to membrane rafts and distributed within the T cell–APC contact site. Upon TCR stimulation of Jurkat T cells, LIME associates with Lck as a tyrosine-phosphorylated protein. Experiments using Jurkat T cells expressing CD8–LIME chimera reveal that the protein associates with phosphatidylinositol 3-kinase, Grb2, Gads, and SHP2, and activates ERK1/2 and JNK but not p38. Moreover, overexpression of LIME in Jurkat T cells induces transcriptional activation of the IL-2 promoter. Our data collectively show that LIME is a raft-associated transmembrane adaptor protein linking TCR stimuli to downstream signaling pathways via associations with Lck. PMID:14610044

Hur, Eun Mi; Son, Myoungsun; Lee, Ok-Hee; Choi, Young Bong; Park, Changwon; Lee, Hyunsook; Yun, Yungdae

2003-01-01

388

(U-Th)/He dating and He diffusion in calcite from veins and breccia  

NASA Astrophysics Data System (ADS)

Knowledge of He retention in crystalline calcite is mandatory to estimate the possibility of (U-Th)/He dating of calcite. To this aim, fault-filling calcite crystals from the Eocene/Oligocene Gondrecourt graben, Paris Basin, Eastern France, have been sampled, based on their relatively old, Eocene-Oligocene, precipitation age and cold thermal history (<40°C since precipitation). The samples were sorted into three main tectonic and morphological groups, including successively (1) micro-fracture calcites, (2) breccia and associated geodic calcites, and (3) vein and associated geodic calcites. (U-Th)/He dating of 63 calcite fragments yields ages dispersed from 0.2×0.02 to 35.8×2.7 Ma, as well as two older dates of 117×10 and 205×28 Ma (1s). These He ages correlate to grain chemistry, such as to Sr and ?REE concentrations or (La/Yb)N ratios, and these correlations probably reflect the evolution of parent fluid. Only the oldest He ages are in agreement with the He-retentive character of calcite as determined by Copeland et al. (2007), and these ages were obtained for the most recently precipitated crystals. To better understand the large He-age scatter and why calcites precipitated earlier show younger ages, He diffusion experiments have been conducted on 10 Gondrecourt calcite fragments from 3 samples with He ages of 0.2 to 6 Ma. In addition, a crystallographic investigation by X-Ray Diffraction (XRD) performed on similar samples reveals that the crystal structure evolves with increasing temperature, showing with micro-cracks and cleavage opening. These XRD results indicate that, in fault-filling calcite, He retention is controlled by multiple diffusion domains (MDD, Lovera et al., 1991) with various sizes, and therefore, evolves through time with strong consequences on (U-Th)/He age. We thus interpret the Gondrecourt calcite (U-Th)/He age scatter of older samples as a consequence of cleavage opening due to a succession of calcite crystallization phases related to the deformation history. Finally, we propose that the crystallization age of a calcite crystal with a known thermal history can nevertheless be retrieved by the (U-Th)/He method provided the He diffusion pattern can be measured by careful step-heating degassing analysis. Copeland, P., Watson, E.B., Urizar, S.C., Patterson, D., Lapen, T.J., 2007. Alpha thermochronology of carbonates. Geochim. Cosmochim. Acta, 71: 4488-4511. Cros, A. Gautheron, C., Pagel, M., Berthet, P., Tassan-Got, L., Douville, E., Pinna-Jamme, R., Sarda, P., submitted GCA, He behavior in calcite filling viewed by (U-Th)/He dating, He diffusion and crystallographic studies. Lovera, O.M., Richter, F.M., Harrison, T.M., 1991. Diffusion domains determined by 39Ar released during step heating. Journal of Geophysical Research, 96: 2057-2069.

Gautheron, C.; Cros, A.; Pagel, M.; Berthet, P.; Tassan-Got, L.; Douville, E.; Pinna-Jamme, R.; Sarda, P.

2013-12-01

389

Gas hydrates: Technology status report  

SciTech Connect

In 1983, the US Department of Energy (DOE) assumed the responsibility for expanding the knowledge base and for developing methods to recover gas from hydrates. These are ice-like mixtures of gas and water where gas molecules are trapped within a framework of water molecules. This research is part of the Unconventional Gas Recovery (UGR) program, a multidisciplinary effort that focuses on developing the technology to produce natural gas from resources that have been classified as unconventional because of their unique geologies and production mechanisms. Current work on gas hydrates emphasizes geological studies; characterization of the resource; and generic research, including modeling of reservoir conditions, production concepts, and predictive strategies for stimulated wells. Complementing this work is research on in situ detection of hydrates and field tests to verify extraction methods. Thus, current research will provide a comprehensive technology base from which estimates of reserve potential can be made, and from which industry can develop recovery strategies. 7 refs., 3 figs., 6 tabs.

Not Available

1987-01-01

390

Hydration mechanism of a cementitious material prepared with Si-Mn slag  

NASA Astrophysics Data System (ADS)

A cementitious material was prepared by mixing 80wt% Si-Mn slag powder, 10wt% lime, and 10wt% anhydrite. The compressive strength of mortar samples reaches 51.48 MPa after 28 d curing. The analyses of X-ray diffraction (XRD) and scanning electron microscopy (SEM) show that much ettringite is formed in the sample cured for 3 d, and C-S-H gel increases rapidly during subsequent curing. Nuclear magnetic resonance (NMR) analysis of 29Si and 27Al and infrared spectroscopy (IR) analysis show that aluminum decomposition from tetrahedral network of the slag glass and its subsequent migration and re-combination play an important role in the process of hydration and strength development of the samples.

Zhang, Xu-Fang; Ni, Wen; Wu, Jun-Yu; Zhu, Li-Ping

2011-04-01

391

Hydrate-phobic surfaces: fundamental studies in clathrate hydrate adhesion reduction  

E-print Network

Clathrate hydrate formation and subsequent plugging of deep-sea oil and gas pipelines represent a significant bottleneck for deep-sea oil and gas operations. Current methods for hydrate mitigation are expensive and energy ...

Smith, J. David

392

Development of Alaskan gas hydrate resources  

SciTech Connect

The research undertaken in this project pertains to study of various techniques for production of natural gas from Alaskan gas hydrates such as, depressurization, injection of hot water, steam, brine, methanol and ethylene glycol solutions through experimental investigation of decomposition characteristics of hydrate cores. An experimental study has been conducted to measure the effective gas permeability changes as hydrates form in the sandpack and the results have been used to determine the reduction in the effective gas permeability of the sandpack as a function of hydrate saturation. A user friendly, interactive, menu-driven, numerical difference simulator has been developed to model the dissociation of natural gas hydrates in porous media with variable thermal properties. A numerical, finite element simulator has been developed to model the dissociation of hydrates during hot water injection process.

Kamath, V.A.; Sharma, G.D.; Patil, S.L.

1991-06-01

393

Strain localization and the onset of dynamic weakening in calcite fault gouge  

NASA Astrophysics Data System (ADS)

To determine the role of strain localization during dynamic weakening of calcite gouge at seismic slip rates, single-slide and slide-hold-slide experiments were conducted on 2-3-mm thick layers of calcite gouge at normal stresses up to 26 MPa and slip rates up to 1 m s-1. Microstructures were analyzed from short displacement (< 35 cm) experiments stopped prior to and during the transition to dynamic weakening. In fresh calcite gouge layers, dynamic weakening occurs after a prolonged strengthening phase that becomes shorter with increasing normal stress and decreasing layer thickness. Strain is initially distributed across the full thickness of the gouge layer, but within a few millimeters displacement the strain becomes localized to a boundary-parallel, high-strain shear band c. 20 ?m wide. During the strengthening phase, which lasts between 3 and 30 cm under the investigated conditions, the shear band broadens to become c. 100 ?m wide at peak stress. The transition to dynamic weakening in calcite gouges is associated with the nucleation of micro-slip surfaces dispersed throughout the c. 100 ?m wide shear band. Each slip surface is surrounded by aggregates of extremely fine grained and tightly packed calcite, interpreted to result from grain welding driven by local frictional heating in the shear band. By the end of dynamic weakening strain is localized to a single 2- 3-?m wide principal slip surface, flanked by layers of recrystallized gouge. Calcite gouge layers re-sheared following a hold period weaken nearly instantaneously, much like solid cylinders of calcite marble deformed under the same experimental conditions. This is due to reactivation of the recrystallized and cohesive principal slip surface that formed during the first slide, reducing the effective gouge layer thickness to a few microns. Our results suggest that formation of a high-strain shear band is a critical precursor to dynamic weakening in calcite gouges. Microstructures are most compatible with dynamic weakening resulting from a thermally triggered mechanism such as flash heating that requires both a high degree of strain localization and a minimum slip velocity to activate. The delayed onset of dynamic weakening in fresh calcite gouge layers, particularly at low normal stresses, may inhibit large coseismic slip at shallow crustal levels in calcite-bearing fault zones.

Smith, S. A. F.; Nielsen, S.; Di Toro, G.

2015-03-01

394

The role of disseminated calcite in the chemical weathering of granitoid rocks  

USGS Publications Warehouse

Accessory calcite, present at concentrations between 300 and 3000 mg kg-1, occurs in fresh granitoid rocks sampled from the Merced watershed in Yosemite National Park, CA, USA; Loch Vale in Rocky Mountain National Park CO USA; the Panola watershed, GA USA; and the Rio Icacos, Puerto Rico. Calcite occurs as fillings in microfractures, as disseminated grains within the silicate matrix, and as replacement of calcic cores in plagioclase. Flow-through column experiments, using de-ionized water saturated with 0.05 atm. CO2, produced effluents from the fresh granitoid rocks that were dominated by Ca and bicarbonate and thermodynamically saturated with calcite. During reactions up to 1.7 yr, calcite dissolution progressively decreased and was superceded by steady state dissolution of silicates, principally biotite. Mass balance calculations indicate that most calcite had been removed during this time and accounted for 57-98% of the total Ca released from these rocks. Experimental effluents from surfically weathered granitoids from the same watersheds were consistently dominated by silicate dissolution. The lack of excess Ca and alkalinity indicated that calcite had been previously removed by natural weathering. The extent of Ca enrichment in watershed discharge fluxes corresponds to the amounts of calcite exposed in granitoid rocks. High Ca/Na ratios relative to plagioclase stoichiometries indicate excess Ca in the Yosemite, Loch Vale, and other alpine watersheds in the Sierra Nevada and Rocky Mountains of the western United States. This Ca enrichment correlates with strong preferential weathering of calcite relative to plagioclase in exfoliated granitoids in glaciated terrains. In contrast, Ca/Na flux ratios are comparable to or less than the Ca/Na ratios for plagioclase in the subtropical Panola and tropical Rio Icacos watersheds, in which deeply weathered regoliths exhibit concurrent losses of calcite and much larger masses of plagioclase during transport-limited weathering. These results indicate that the weathering of accessory calcite may strongly influence Ca and alkalinity fluxes from silicate rocks during and following periods of glaciation and tectonism but is much less important for older stable geomorphic surfaces.

White, A.F.; Bullen, T.D.; Vivit, D.V.; Schulz, M.S.; Clow, D.W.

1999-01-01

395

The role of disseminated calcite in the chemical weathering of granitoid rocks  

NASA Astrophysics Data System (ADS)

Accessory calcite, present at concentrations between 300 and 3000 mg kg -1, occurs in fresh granitoid rocks sampled from the Merced watershed in Yosemite National Park, CA, USA; Loch Vale in Rocky Mountain National Park CO USA; the Panola watershed, GA USA; and the Rio Icacos, Puerto Rico. Calcite occurs as fillings in microfractures, as disseminated grains within the silicate matrix, and as replacement of calcic cores in plagioclase. Flow-through column experiments, using de-ionized water saturated with 0.05 atm. CO 2, produced effluents from the fresh granitoid rocks that were dominated by Ca and bicarbonate and thermodynamically saturated with calcite. During reactions up to 1.7 yr, calcite dissolution progressively decreased and was superceded by steady state dissolution of silicates, principally biotite. Mass balance calculations indicate that most calcite had been removed during this time and accounted for 57-98% of the total Ca released from these rocks. Experimental effluents from surfically weathered granitoids from the same watersheds were consistently dominated by silicate dissolution. The lack of excess Ca and alkalinity indicated that calcite had been previously removed by natural weathering. The extent of Ca enrichment in watershed discharge fluxes corresponds to the amounts of calcite exposed in granitoid rocks. High Ca/Na ratios relative to plagioclase stoichiometries indicate excess Ca in the Yosemite, Loch Vale, and other alpine watersheds in the Sierra Nevada and Rocky Mountains of the western United States. This Ca enrichment correlates with strong preferential weathering of calcite relative to plagioclase in exfoliated granitoids in glaciated terrains. In contrast, Ca/Na flux ratios are comparable to or less than the Ca/Na ratios for plagioclase in the subtropical Panola and tropical Rio Icacos watersheds, in which deeply weathered regoliths exhibit concurrent losses of calcite and much larger masses of plagioclase during transport-limited weathering. These results indicate that the weathering of accessory calcite may strongly influence Ca and alkalinity fluxes from silicate rocks during and following periods of glaciation and tectonism but is much less important for older stable geomorphic surfaces.

White, Art F.; Bullen, Thomas D.; Vivit, Davison V.; Schulz, Marjorie S.; Clow, David W.

1999-07-01

396

A coupled THMC model of a heating and hydration laboratory experiment in unsaturated compacted FEBEX bentonite  

SciTech Connect

Unsaturated compacted bentonite is foreseen by several countries as a backfill and sealing material in high-level radioactive waste repositories. The strong interplays between thermal (T), hydrodynamic (H), mechanical (M) and chemical (C) processes during the hydration stage of a repository call for fully coupled THMC models. Validation of such THMC models is prevented by the lack of comprehensive THMC experiments and the difficulties of experimental methods to measure accurately the chemical composition of bentonite porewater. We present here a non-isothermal multiphase flow and multicomponent reactive solute transport model for a deformable medium of a heating and hydration experiment performed on a sample of compacted FEBEX bentonite. Besides standard solute transport and geochemical processes, the model accounts for solute cross diffusion and thermal and chemical osmosis. Bentonite swelling is solved with a state-surface approach. The THM model is calibrated with transient temperature, water content and porosity data measured at the end of the experiment. The reactive transport model is calibrated with porewater chemical data derived from aqueous extract data. Model results confirm that thermal osmosis is relevant for the hydration of FEBEX bentonite while chemical osmosis can be safely neglected. Dilution and evaporation are the main processes controlling the concentration of conservative species. Dissolved cations are mostly affected by calcite dissolution-precipitation and cation exchange reactions. Dissolved sulphate is controlled by gypsum/anhydrite dissolution-precipitation. pH is mostly buffered by protonation/deprotonation via surface complexation. Computed concentrations agree well with inferred aqueous extract data at all sections except near the hydration boundary where cation data are affected by a sampling artifact. The fit of Cl{sup -} data is excellent except for the data near the heater. The largest deviations of the model from inferred aqueous extract data occur for dissolved SO{sub 4}{sup 2-} which is underpredicted by the model. There are uncertainties on the amount of gypsum available for dissolution and its dissolution mechanism (kinetics or local equilibrium).

Zheng, L.; Samper, J.; Montenegro, L.; Fernandez, A.M.

2010-05-01

397

Ages and Origins of Calcite and Opal in the Exploratory Studies Facility Tunnel, Yucca Mountain, Nevada  

USGS Publications Warehouse

Deposits of calcite and opal are present as coatings on open fractures and lithophysal cavities in unsaturated-zone tuffs at Yucca Mountain, Nevada, site of a potential high-level radioactive waste repository. Outermost layers of calcite and opal have radiocarbon ages of 16,000 to 44,000 years before present and thorium-230/uranium ages of 28,000 to more than 500,000 years before present. These ages are young relative to the 13-million-year age of the host rocks. Multiple subsamples from the same outer layer typically show a range of ages with youngest ages from the thinnest subsamples. Initial uranium-234/uranium-238 activity ratios between 1 and 9.5 show a distinct negative correlation with thorium-230/uranium age and are greater than 4 for all but one sample younger than 100,000 years before present. These data, along with micrometer-scale layering and distinctive crystal morphologies, are interpreted to indicate that deposits formed very slowly from water films migrating through open cavities. Exchanges of carbon dioxide and water vapor probably took place between downward-migrating liquids and upward-migrating gases at low rates, resulting in oversaturation of mineral constituents at crystal extremities and more or less continuous deposition of very thin layers. Therefore, subsamples represent mixtures of older and younger layers on a scale finer than sampling techniques can resolve. Slow, long-term rates of deposition (less than about 5 millimeters of mineral per million years) are inferred from subsamples of outermost calcite and opal. These growth rates are similar to those calculated assuming that total coating thicknesses of 10 to 40 millimeters accumulated over 12 million years. Calcite has a wide range of delta carbon-13 values from about -8.2 to 8.5 per mil and delta oxygen-18 values from about 10 to 21 per mil. Systematic microsampling across individual mineral coatings indicates basal (older) calcite tends to have the largest delta carbon-13 values and smallest delta oxygen-18 values compared to calcite from intermediate and outer positions. Basal calcite has relatively small strontium-87/strontium-86 ratios, between 0.7105 and 0.7120, that are similar to the initial isotopic compositions of the strontium-rich tuff units, whereas outer calcite has more radiogenic strontium-87/strontium-86 ratios between 0.7115 and 0.7127. Isotopic compositions of strontium, oxygen, and carbon in the outer (youngest) unsaturated-zone calcite are coincident with those measured in Yucca Mountain calcrete, which formed by pedogenic processes. The physical and isotopic data from calcite and opal indicate that they formed from solutions of meteoric origin percolating through a limited network of connected fracture pathways in the unsaturated zone rather than by inundation from ascending ground water originating in the saturated zone. Mineral assemblages, textures, and distributions within the unsaturated zone are distinctly different from those deposited below the water table at Yucca Mountain. The calcite and opal typically are present only on footwall surfaces of a small fraction of fractures and only on floors of a small fraction of lithophysal cavities. The similarities in the carbon, oxygen, and strontium isotopic compositions between fracture calcite and soil-zone calcite, as well as the gradation of textures from detritus-rich micrite in the soil to detritus-free spar 10 to 30 meters below the surface, also support a genetic link between the two depositional environments. Older deposits contain oxygen isotope compositions that indicate elevated temperatures of mineral formation during the early stages of deposition; however, in the youngest deposits these values are consistent with deposition under geothermal gradients similar to modern conditions. Correlations between mineral ages and varying Pleistocene climate conditions are not apparent from the current data. Cumulative evidence from calcite and opal deposits indicate

Paces, James B.; Neymark, Leonid A.; Marshall, Brian D.; Whelan, Joseph F.; Peterman, Zell E.

2001-01-01

398

Desalination utilizing clathrate hydrates (LDRD final report).  

SciTech Connect

Advances are reported in several aspects of clathrate hydrate desalination fundamentals necessary to develop an economical means to produce municipal quantities of potable water from seawater or brackish feedstock. These aspects include the following, (1) advances in defining the most promising systems design based on new types of hydrate guest molecules, (2) selection of optimal multi-phase reactors and separation arrangements, and, (3) applicability of an inert heat exchange fluid to moderate hydrate growth, control the morphology of the solid hydrate material formed, and facilitate separation of hydrate solids from concentrated brine. The rate of R141b hydrate formation was determined and found to depend only on the degree of supercooling. The rate of R141b hydrate formation in the presence of a heat exchange fluid depended on the degree of supercooling according to the same rate equation as pure R141b with secondary dependence on salinity. Experiments demonstrated that a perfluorocarbon heat exchange fluid assisted separation of R141b hydrates from brine. Preliminary experiments using the guest species, difluoromethane, showed that hydrate formation rates were substantial at temperatures up to at least 12 C and demonstrated partial separation of water from brine. We present a detailed molecular picture of the structure and dynamics of R141b guest molecules within water cages, obtained from ab initio calculations, molecular dynamics simulations, and Raman spectroscopy. Density functional theory calculations were used to provide an energetic and molecular orbital description of R141b stability in both large and small cages in a structure II hydrate. Additionally, the hydrate of an isomer, 1,2-dichloro-1-fluoroethane, does not form at ambient conditions because of extensive overlap of electron density between guest and host. Classical molecular dynamics simulations and laboratory trials support the results for the isomer hydrate. Molecular dynamics simulations show that R141b hydrate is stable at temperatures up to 265K, while the isomer hydrate is only stable up to 150K. Despite hydrogen bonding between guest and host, R141b molecules rotated freely within the water cage. The Raman spectrum of R141b in both the pure and hydrate phases was also compared with vibrational analysis from both computational methods. In particular, the frequency of the C-Cl stretch mode (585 cm{sup -1}) undergoes a shift to higher frequency in the hydrate phase. Raman spectra also indicate that this peak undergoes splitting and intensity variation as the temperature is decreased from 4 C to -4 C.

Simmons, Blake Alexander; Bradshaw, Robert W.; Dedrick, Daniel E.; Cygan, Randall Timothy (Sandia National Laboratories, Albuquerque, NM); Greathouse, Jeffery A. (Sandia National Laboratories, Albuquerque, NM); Majzoub, Eric H. (University of Missouri, Columbia, MO)

2008-01-01

399

Thermodynamics of non-stoichiometric pharmaceutical hydrates.  

PubMed

Different physical and mathematical models of non-stoichiometric hydrates derived form previous work in inorganic hydrates are reviewed. A theoretical link between the order of water molecules in the hydrate and the shape of the isotherm is outlined. The comparison of the models with sorption isotherms and structural data of well-known cases from the literature and one in-house case shows that the model can fit many experimental situations and is in good agreement with qualitative assessments of the order in the hydrates. PMID:16139971

Authelin, Jean-René

2005-10-13

400

Hydration: issues for the 21st century.  

PubMed

Historically, hydration research reflected critical issues of the day. War, illness, surviving a shipwreck or time in the dessert, supplying fall-out shelters, and space exploration drove hydration research in the first half of the 20th century. The fitness revolution of the 1970s spurred research on dehydration in physically active people and athletes. The 1990s introduced the "fluid/disease relationship." What will be the driving force behind hydration research in the 21st century? Where are the gaps in our knowledge? This review provides an overview of issues pertinent to determining future directions in hydration research. PMID:13677588

Grandjean, Ann C; Reimers, Kristin J; Buyckx, Maxime E

2003-08-01

401

Capital costs of lime treatment at the Augusta wastewater treatment plant  

SciTech Connect

The capital costs were estimated for the addition of lime treatment facilities to the Augusta sewage treatment plant as a means of reducing the phosphorus loading of L Lake and consequently reducing the algae populations in the lake. Primary lime treatments and tertiary lime treatments were considered. The capital cost of a primary lime treatment addition would be lower than for a tertiary treatment addition. Depending on whether the existing primary settling tank can be utilized for lime treatment or a new clarifier must be built, a primary lime treatment addition would currently cost between $500,000 and $3 million to construct at the Augusta sewage treatment plant. Primary lime treatment coupled with the existing activated sludge biological treatment system would remove approximately 80% of the phosphorus from the sewage entering the sewage treatment plant, resulting in an effluent concentration of about 2 mg/l. To reduce effluent phosphorus concentration to 1 mg/l or less, additional coagulation and effluent filtration facilities would be necessary. One disadvantage of primary lime treatment, however, would be the two-fold or three-fold increase in sludge to be disposed. Tertiary lime treatment usually results in lower effluent phosphorus levels than primary lime treatment, but the capital cost is significantly higher. Costs for tertiary lime treatment for the Augusta sewage treatment plant would range from $5 million to $14 million. The higher estimate would include an additional settling stage and filtration of the effluent, features which would improve the efficiency of phosphorus removal and reduce the effluent phosphorus concentration. 12 refs.

Halverson, N.V.

1988-08-17

402

Three-dimensional distribution of gas hydrate beneath southern Hydrate Ridge: constraints from ODP Leg 204  

Microsoft Academic Search

Large uncertainties about the energy resource potential and role in global climate change of gas hydrates result from uncertainty about how much hydrate is contained in marine sediments. During Leg 204 of the Ocean Drilling Program (ODP) to the accretionary complex of the Cascadia subduction zone, we sampled the gas hydrate stability zone (GHSZ) from the seafloor to its base

A. M. Tréhu; Philip E. Long; M. E. Torres; G. Bohrmann; F. R. Rack; T. S. Collett; D. S. Goldberg; A. V. Milkov; M. Riedel; P. Schultheiss; N. L. Bangs; S. R. Barr; W. S. Borowski; G. E. Claypool; Mark E. Delwiche; G. R. Dickens; E. Gracia; G. Guerin; M. Holland; Jerry E. Johnson; Y.-J. Lee; C.-S. Liu; X. Su; B. Teichert; H. Tomaru; M. Vanneste; M. Watanabe; Jill L. Weinberger

2004-01-01

403

Dynamical interrogation of the hydration cage of bromine in single crystal clathrate hydrates versus water  

E-print Network

Dynamical interrogation of the hydration cage of bromine in single crystal clathrate hydrates of bromine clathrate hydrates and on bromine dissolved in water. In all cases, excitation into the B of 290 fs, is significantly reduced due to the larger cages and the looser fit around bromine

Apkarian, V. Ara

404

Waters of Hydration of Cupric Hydrates: A Comparison between Heating and Absorbance Methods  

ERIC Educational Resources Information Center

The empirical formulas of four cupric hydrates are determined by measuring the absorbance in aqueous solution. The Beer-Lambert Law is verified by constructing a calibration curve of absorbance versus known Cu[superscript 2+](aq) concentration. A solution of the unknown hydrate is prepared by using 0.2-0.3 g of hydrate, and water is added such…

Barlag, Rebecca; Nyasulu, Frazier

2011-01-01

405

Thermal and Evolved Gas Behavior of Calcite Under Mars Phoenix TEGA Operating Conditions  

NASA Technical Reports Server (NTRS)

The Mars Phoenix Scout Mission with its diverse instrument suite successfully examined several soils on the Northern plains of Mars. The Thermal and Evolved Gas Analyzer (TEGA) was employed to detect organic and inorganic materials by coupling a differential scanning calorimeter (DSC) with a magnetic-sector mass spectrometer (MS). Martian soil was heated up to 1000 C in the DSC ovens and evolved gases from mineral decomposition products were examined with the MS. TEGA s DSC has the capability to detect endothermic and exothermic reactions during heating that are characteristic of minerals present in the Martian soil. Initial TEGA results indicated the presence of endothermic peaks with onset temperatures that ranged from 675 C to 750 C with corresponding CO2 release. This result suggests the presence of calcite (CaCO3. CaO + CO2). Organic combustion to CO2 is not likely since this mostly occurs at temperatures below 550 C. Fe-carbonate and Mg-carbonate are not likely because their decomposition temperatures are less than 600 C. TEGA enthalpy determinations suggest that calcite, may occur in the Martian soil in concentrations of approx.1 to 5 wt. %. The detection of calcite could be questioned based on previous results that suggest Mars soils are mostly acidic. However, the Phoenix landing site soil pH was measured at pH 8.3 0.5, which is typical of terrestrial soils where pH is controlled by calcite solubility. The range of onset temperatures and calcite concentration as calculated by TEGA is poorly con-strained in part because of limited thermal data of cal-cite at reduced pressures. TEGA operates at <30 mbar while most calcite literature thermal data was obtained at 1000 mbar or higher pressures.

Ming, D.W.; Niles, P.B.; Morris, R.V.; Boynton, W.V.; Golden, D.C.; Lauer, H.V.; Sutter, B.

2009-01-01

406

Soap based detergent formulations. V. Amphoteric lime soap dispersing agents  

Microsoft Academic Search

A series of amphoteric surfactants was prepared by the reaction of 1,3-propanesultone with fat derived primary amines, N-methylalkylamines,\\u000a N,N-dimethylalkylamines, and N-acyl-N?,N?-dimethyl-1,3-propanediamines. Both mono- and disulfopropylated derivatives of the\\u000a primary amines were synthesized. All compounds were found to be excellent lime soap dispersing agents. The quaternary sulfobetaines\\u000a were found to possess the best detergency properties both by themselves and when formulated

N. Parris; J. K. Weil; W. M. Linfield

1973-01-01

407

Improvement in hardness of soda-lime-silica glass  

SciTech Connect

Hardness is a key design parameter for structural application of brittle solids like glass. Here we report for the first time the significant improvement of about 10% in Vicker's hardness of a soda-lime-silica glass with loading rate in the range of 0.1-10 N.s{sup -1}. Corroborative dark field optical and scanning electron microscopy provided clue to this improvement through evidence of variations in spatial density of shear deformation band formation as a function of loading rate.

Chakraborty, Riya; De, Moumita; Roy, Sudakshina; Dey, Arjun; Biswas, Sampad K.; Middya, Tapas Ranjan; Mukhopadhyay, Anoop K. [CSIR-Central Glass and Ceramic Research Institute, Kolkata-700032, CSIR (India); Department of Physics, Jadavpur University, Kolkata-700032 (India); CSIR-Central Glass and Ceramic Research Institute, Kolkata-700032, CSIR (India)

2012-06-05

408

Solar chemical reactor technology for industrial production of lime  

Microsoft Academic Search

We developed the solar chemical reactor technology to effect the endothermic calcination reaction CaCO3(s)?CaO(s)+CO2(g) at 1200–1400K. The indirect heating 10kWth multi-tube rotary kiln prototype processed 1–5mm limestone particles, producing high purity lime that is not contaminated with combustion by-products. The quality of the solar produced quicklime meets highest industrial standards in terms of reactivity (low, medium, and high) and degree

Anton Meier; Enrico Bonaldi; Gian Mario Cella; Wojciech Lipinski; Daniel Wuillemin

2006-01-01

409

Oxidation aspects of the lime-concentrate-pellet roasting process  

NASA Astrophysics Data System (ADS)

Thermogravimetry has been employed to follow the progress of the oxidation reaction of cylindrical pellets of chalcopyrite concentrate blended with lime. Metallographic examination of pellet sections established the shrinking core pattern under the various experimental conditions. The rate of oxidation was investigated over the temperature range 753 to 873 K. To enable comparison with earlier work, subsequent leaching of calcines from the 773 K runs was also examined. Factors resulting in low copper recoveries have been examined thermodynamically and confirmed by X-ray diffraction analyses.

Ahmadzai, H.; Blairs, S.; Harris, B.; Staffansson, L.-I.

1983-12-01

410

21 CFR 582.2729 - Hydrated sodium calcium aluminosilicate.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 false Hydrated sodium calcium aluminosilicate. 582.2729 Section...Agents § 582.2729 Hydrated sodium calcium aluminosilicate. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium...

2012-04-01

411

21 CFR 182.2729 - Sodium calcium aluminosilicate, hydrated.  

Code of Federal Regulations, 2014 CFR

...2014-04-01 2014-04-01 false Sodium calcium aluminosilicate, hydrated. 182...Anticaking Agents § 182.2729 Sodium calcium aluminosilicate, hydrated. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium...

2014-04-01

412

21 CFR 182.2729 - Sodium calcium aluminosilicate, hydrated.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Sodium calcium aluminosilicate, hydrated. 182...Anticaking Agents § 182.2729 Sodium calcium aluminosilicate, hydrated. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium...

2013-04-01

413

21 CFR 582.2729 - Hydrated sodium calcium aluminosilicate.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 false Hydrated sodium calcium aluminosilicate. 582.2729 Section...Agents § 582.2729 Hydrated sodium calcium aluminosilicate. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium...

2011-04-01

414

21 CFR 182.2729 - Sodium calcium aluminosilicate, hydrated.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Sodium calcium aluminosilicate, hydrated. 182...Anticaking Agents § 182.2729 Sodium calcium aluminosilicate, hydrated. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium...

2011-04-01

415

21 CFR 582.2729 - Hydrated sodium calcium aluminosilicate.  

Code of Federal Regulations, 2014 CFR

...2014-04-01 false Hydrated sodium calcium aluminosilicate. 582.2729 Section...Agents § 582.2729 Hydrated sodium calcium aluminosilicate. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium...

2014-04-01

416

21 CFR 182.2729 - Sodium calcium aluminosilicate, hydrated.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Sodium calcium aluminosilicate, hydrated. 182...Anticaking Agents § 182.2729 Sodium calcium aluminosilicate, hydrated. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium...

2012-04-01

417

21 CFR 582.2729 - Hydrated sodium calcium aluminosilicate.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 false Hydrated sodium calcium aluminosilicate. 582.2729 Section...Agents § 582.2729 Hydrated sodium calcium aluminosilicate. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium...

2013-04-01

418

21 CFR 582.2729 - Hydrated sodium calcium aluminosilicate.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 false Hydrated sodium calcium aluminosilicate. 582.2729 Section...Agents § 582.2729 Hydrated sodium calcium aluminosilicate. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium...

2010-04-01

419

21 CFR 182.2729 - Sodium calcium aluminosilicate, hydrated.  

Code of Federal Regulations, 2010 CFR

...2010-04-01 2009-04-01 true Sodium calcium aluminosilicate, hydrated. 182...Anticaking Agents § 182.2729 Sodium calcium aluminosilicate, hydrated. (a) Product. Hydrated sodium calcium aluminosilicate (sodium calcium...

2010-04-01

420

Partial face biometry using shape decomposition on 2D conformal maps of Przemyslaw Szeptycki, Mohsen Ardabilian, Liming Chen  

E-print Network

, France {przemyslaw.szeptycki, mohsen.ardabilian, liming.chen}@ec-lyon.fr Wei Zeng, David Gu, Dimitris, Mohsen Ardabilian, Liming Chen MI Department, LIRIS Laboratory, Ecole Centrale de Lyon, 69134 Lyon

421

The puzzling presence of calcite in skeletons of modern solitary corals from the Mediterranean Sea  

NASA Astrophysics Data System (ADS)

The skeleton of scleractinian corals is commonly believed to be composed entirely of aragonite due to the current Mg/Ca molar ratio of seawater, which thermodynamically favours the deposition of this polymorph of calcium carbonate (CaCO3). However, some studies have shown that other forms of CaCO3 such as calcite can be present in significant amount (1-20%) inside tropical coral skeletons, significantly impacting paleo-reconstructions of SST or other environmental parameters based on geochemical proxies. This study aims at investigating for the first time, (1) the skeletal composition of two Mediterranean solitary corals, the azooxanthellate Leptopsammia pruvoti and the zooxanthellate Balanophyllia europaea, across their life cycle, (2) the distribution of the different CaCO3 forms inside skeletons, and (3) their implications in paleoclimatology. The origin of the different forms of CaCO3 observed inside studied coral skeletons and their relationships with the species' habitat and ecological strategies are also discussed. CaCO3 composition of L. pruvoti and B. europaea was investigated at six sites located along the Italian coasts. Skeleton composition was studied by means of X-ray powder diffraction and Fourier transform infrared spectroscopy. A significant amount of calcite (1-23%) was found in more than 90% of the studied coral skeletons, in addition to aragonite. This calcite was preferentially located in the basal and intermediate areas than at the oral pole of coral skeletons. Calcite was also mainly located in the epitheca that covered the exposed parts of the coral in its aboral region. Interestingly in B. europaea, the calcite content was negatively correlated with skeleton size (age). The presence of calcite in scleractinian corals may result from different mechanisms: (1) corals may biologically precipitate calcite crystals at their early stages in order to insure their settlement on the substrate of fixation, especially in surgy environments; (2) calcite presence may result from skeletons of other calcifying organisms such as crustose coralline algae; and/or (3) calcite may result from the infilling of galleries of boring microorganisms which are known to colonize coral skeletons. We suggest that more than one of the above mentioned processes are involved.

Goffredo, Stefano; Caroselli, Erik; Mezzo, Francesco; Laiolo, Leonardo; Vergni, Patrizia; Pasquini, Luca; Levy, Oren; Zaccanti, Francesco; Tribollet, Aline; Dubinsky, Zvy; Falini, Giuseppe

2012-05-01

422

Cotton Profitability with Alternative Lime Application Rates, Cover Crops, Nitrogen Rates, and Tillage Methods  

Microsoft Academic Search

Soil acidity and cotton (Gossypium hirsutum L.) yield may be influenced by cover crop, N, and tillage method. Application of half the recommended lime rate may be possible without reducing lint yield and net revenue. The objective was to determine cotton yields and profitability for full and half recommended rates of lime, cover crops, N rates, and tillage methods. Data

Rebecca L. Cochran; Roland K. Roberts; James A. Larson; Donald D. Tyler

2007-01-01

423

A Comparison between Lime and Alkaline Hydrogen Peroxide Pretreatments of Sugarcane Bagasse for Ethanol Production  

Microsoft Academic Search

Pretreatment procedures of sugarcane bagasse with lime (calcium hydroxide) or alkaline hydrogen peroxide were evaluated and compared. Analyses were performed using 2 × 2 × 2 factorial designs, with pretreatment time, temperature, and lime loading and hydrogen peroxide concentration as factors. The responses evaluated were the yield of total reducing sugars (TRS) and glucose released from pretreated bagasse after enzymatic

Sarita C. Rabelo; Rubens Maciel Filho; Aline C. Costa

2008-01-01

424

Responses of four perennial pasture legumes to soil amendment with lime and superphosphate  

Microsoft Academic Search

Yield response of crownvetch (Coronilla varia) cv. Penngift, lucerne (Medicago sativa) cv. CUF 101, white clover (Trifolium repens) Dusi type and Kenya white clover (T. semipilosum) cv. Safari to differential application of lime and superphosphate were determined in a 5 × 4 factorial experiment on a virgin soil of the Griffin form. Lime rates varied from 0 to 7t\\/ha and

D L Barnes

1986-01-01

425

Mechanism of mechanical strength increase of soda-lime glass by aging  

Microsoft Academic Search

This paper reports on two models proposed to explain the mechanical strength increase of abraded or indented soda-lime glasses upon aging, namely, crack tip blunting and the release of residual tensile stress near the crack tip. To clarify the mechanism, the time dependence of the strengthening of an abraded soda-lime glass was investigated. Effects of aging media, such as moist

Won-Taek Han; Minoru Tomozawa

1989-01-01

426

Extension Bulletin E-1566 Revised September 2011 Facts About Soil Acidity and Lime  

E-print Network

materials to neutralize soil acidity. Pure calcium carbonate has a value of 100, and all other materials carbonate equivalent? Calcium carbonate equivalent (CCE) refers to the equivalent amount (pounds) of pure calcium carbonate in a ton or cubic yard of lime material. If a lime material has a NV of 85, it will have

427

EVALUATION OF SOLIDS DEWATERING FOR A PILOT-SCALE THIOSORBIC LIME SO2 SCRUBBER  

EPA Science Inventory

The paper gives results of an evaluation of solids dewatering for a pilot-scale thiosorbic lime SO2 scrubber. Pilot plant data showed that the dissolved magnesium in thiosorbic lime caused deterioration of solids dewatering properties. The slurry settling rate increased when the ...

428

Long-term manuring effect on weed flora in acid and limed soils  

Microsoft Academic Search

The dominant soils of eastern and western Lithuania are acid. Liming and application of organic fertilizers are therefore the most effective ways to improve properties. Accordingly, two permanent liming and organic manuring trials were initiated in 1949 on an acid soil in the Vezaiciai Branch of the Lithuanian Institute of Agriculture. This study reports the effects of long term manuring

Steponas Ciuberkis; Stasys Bernotas; Steponas Raudonius

2006-01-01

429

Barley seedling growth in soils amended with fly ash or agricultural lime followed by acidification  

SciTech Connect

Calcium-rich coal combustion fly ash can be used as an amendment to neutralize soil acidity because of its oxides and carbonate content, but its aluminum content could inhibit plant growth if soil pH values fall below optimal agronomic levels. This study measured root and shoot growth of an acid-sensitive barley (Hordeum vulgare L. 'Kearney') grown in the greenhouse on three naturally acid soils. The soils were either untreated or amended with various liming materials (dry fly ash, wet fly ash, and agricultural lime) at application rates of 0, .5, 1, and 1.5 times the recommended lime requirement, then treated with dilute acid solutions to simulate management-induced acidification. Plant growth indexes were measured at 30 days after planting. Root mass per plant and root length per plant were greater for the limed treatments than in the acidified check. Root growth in the limed treatments did not differ from root growth in the original nonacidified soils. Top mass per plant in all limed soils was either larger than or not different from that in the original nonacidified soils. Based on top mass per plant, no liming material or application rate was clearly superior. Both fly ash and agricultural lime reduced the impact of subsequent acidification on young barley plants. Detrimental effects of aluminum release on plant growth were not observed. Calcium-rich fly ash at agronomic rates is an acceptable acid-neutralizing material with no apparent negative effects.

Renken, R.R.; McCallister, D.L.; Tarkalson, D.D.; Hergert, G.W.; Marx, D.B. [University of Nebraska, Lincoln, NE (United States)

2006-05-15

430

Effects of liming on forage availability and nutrient content in a forest impacted by acid rain.  

PubMed

Acidic deposition and subsequent forest soil acidification and nutrient depletion can affect negatively the growth, health and nutrient content of vegetation, potentially limiting the availability and nutrient content of forage for white-tailed deer (Odocoileus virginianus) and other forest herbivores. Liming is a mitigation technique that can be used to restore forest health in acidified areas, but little is known about how it affects the growth or nutrient content of deer forage. We examined the effects of dolomitic limestone application on the growth and chemical composition of understory plants in an acidified forest in central Pennsylvania, with a focus on vegetative groups included as white-tailed deer forage. We used a Before-After-Control-Impact study design with observations 1 year before liming and up to 5 years post-liming on 2 treated and 2 untreated 100-ha sites. Before liming, forage availability and several nutrients were below levels considered optimal for white-tailed deer, and many vegetative characteristics were related to soil chemistry. We observed a positive effect of liming on forb biomass, with a 2.7 fold increase on limed sites, but no biomass response in other vegetation groups. We observed positive effects of liming on calcium and magnesium content and negative effects on aluminum and manganese content of several plant groups. Responses to liming by forbs and plant nutrients show promise for improving vegetation health and forage quality and quantity for deer. PMID:22761890

Pabian, Sarah E; Ermer, Nathan M; Tzilkowski, Walter M; Brittingham, Margaret C

2012-01-01

431

Effect of Liming on the Plant Availability and Distribution of Zinc and Copper among Soil Fractions  

Microsoft Academic Search

Information on the redistribution of applied micronutrients into different fractions as a result of lime application is important to predict plant accumulation of nutrients and to select appropriate chemical extraction procedures for evaluation of micronutrient availability. The present work was carried out to study the influence of liming on the availability and redistribution of zinc (Zn) and copper (Cu) among

Clístenes Williams Araújo do Nascimento; Évio Eduardo Chaves de Melo; Robervone Severina de Melo Pereira do Nascimento; Paulo Vinícius Valeriano Leite

2007-01-01

432

Diagnosis of Micronutrient Imbalance in Lime Crop in Semi-arid Region of Rajasthan, India  

Microsoft Academic Search

Low and unstable fruit yield, poor quality of fruits, and excessive fruit dropping are major problems in a lime crop and are due to either micronutrient deficiencies or nutrient imbalance. A study was conducted to assess the micronutrient status in a lime orchard at the Central Soil and Water Conservation Research and Training Institute (CSWCRTI)’s research farm in Kota, Rajasthan,

J. Somasundaram; H. R. Meena; R. K. Singh; S. N. Prasad; A. K. Parandiyal

2011-01-01

433

An Experimental Investigation of Lime Juice Drying in a Pilot Plant Spray Dryer  

Microsoft Academic Search

One of the major problems in spray drying of fruit juices such as lime juice is stickiness and thermoplasticity of their compositions. Lime juice consists of invert sugars and citric acid, which have low glass transition temperatures. Due to this characteristic, the particles stick on the dryer wall upon their collision with it. As a result, drying of these materials

O. R. Roustapour; M. Hosseinalipour; B. Ghobadian

2006-01-01

434

Effects of liming on soil properties and plant performance of temperate mountainous grasslands  

Microsoft Academic Search

The application of lime or liming materials to acid-soil grasslands might help mitigate soil acidity, a major constraint to forage productivity in many temperate mountainous grasslands. Nowadays, in these mountainous grasslands, it is essential to promote agricultural practices to increase forage yield and nutritive value while preserving biodiversity and agroecosystem functioning. Two different field experiments were conducted in the Gorbeia

Iker Mijangos; Isabel Albizu; Lur Epelde; Ibone Amezaga; Sorkunde Mendarte; Carlos Garbisu

2010-01-01

435

Control of Lime Kiln Heat Balance is Key to Reduced Fuel Consumption  

E-print Network

This article discusses the various heat loads in a pulp mill lime sludge kiln, pointing out which heat loads cannot be reduced and which heat loads can, and how a reduction in energy use can be achieved. In almost any existing rotary lime sludge...

Kramm, D. J.

1982-01-01

436

First New World Documentation of an Old World Citrus Pest, the Lime Swallowtail  

E-print Network

First New World Documentation of an Old World Citrus Pest, the Lime Swallowtail Papilio demoleus Boyce, and Brian D. Farrell Abstract. Papilio demoleus L., a well-known citrus pest in the Old World demoleus, invasive species, citrus pest. P apilio demoleus L., commonly known as the lemon, lime, citrus

Farrell, Brian D.

437

Effects of Liming on Forage Availability and Nutrient Content in a Forest Impacted by Acid Rain  

PubMed Central

Acidic deposition and subsequent forest soil acidification and nutrient depletion can affect negatively the growth, health and nutrient content of vegetation, potentially limiting the availability and nutrient content of forage for white-tailed deer (Odocoileus virginianus) and other forest herbivores. Liming is a mitigation technique that can be used to restore forest health in acidified areas, but little is known about how it affects the growth or nutrient content of deer forage. We examined the effects of dolomitic limestone application on the growth and chemical composition of understory plants in an acidified forest in central Pennsylvania, with a focus on vegetative groups included as white-tailed deer forage. We used a Before-After-Control-Impact study design with observations 1 year before liming and up to 5 years post-liming on 2 treated and 2 untreated 100-ha sites. Before liming, forage availability and several nutrients were below levels considered optimal for white-tailed deer, and many vegetative characteristics were related to soil chemistry. We observed a positive effect of liming on forb biomass, with a 2.7 fold increase on limed sites, but no biomass response in other vegetation groups. We observed positive effects of liming on calcium and magnesium content and negative effects on aluminum and manganese content of several plant groups. Responses to liming by forbs and plant nutrients show promise for improving vegetation health and forage quality and quantity for deer. PMID:22761890

Pabian, Sarah E.; Ermer, Nathan M.; Tzilkowski, Walter M.; Brittingham, Margaret C.

2012-01-01

438

Depositional facies and porosity development at Coon Creek Field (Newman [open quotes]Big Lime[close quotes]), Leslie County, Kentucky  

SciTech Connect

Coon Creek field is a significant petroleum reservoir in the [open quotes]Big Lime[close quotes], Middle to Upper Mississippian Newman equivalent, in southeastern Kentucky. Initial production from select wells has exceeded 600 bbl of oil/day at drilling depths averaging 915 m (3300 ft). Facies patterns, dolomitization, porosity, and structure in this carbonate reservoir have been delineated by geophysical logs, subsurface mapping, and examination of cores and cuttings. The reservoir is set within a localized paleotopographic low on the unconformable surface of the underlying siliciclastic Borden Group; the Borden surface can express rapid relief of over a 10% grade within less than 300 m. Transgression across the exposed Borden surface resulted in the deposition of a complex system of carbonates lithofacies. Crinoidal dolostones, representing shallow subtidal skeletal bars and banks, form the basal Big Lime (1.5-6 m thick). They are overlain by a typical facies (30 m thick) of bryozoan grainstones/packstones, crinoid grainstones, and mixed skeletal wakestones/mudstones. The rybryozoanacies are characterized by unfragmented fenestrates cemented by radiaxial-fibrous calcite. Stratigraphic distributions indicate the bryozoan facies were broad buildups with crinoidal flank and cap deposits and muddy skeletal off-mount facies, similar to deeper water Waulsortian mounds in other basins. Pellet and ooid grainstones represent moderate- to high-energy subtidal shoal deposits that covered the mound complex. Hydrocarbon production is restricted in the field to the crinoid-bryozoan facies complex within the basal 30 m. Reservoir porosity and permeability have been enhanced by selective dolomitization of grainstones and fracturing related to postdepositional reactivation of basement faults.

Moshier, S.O. (Wheaton College, IL (United States)); Stamper, M.E. (Equitable Resources Exploration, Kingsport, TN (United States))

1994-08-01

439

Arsenic removal from high-arsenic water by enhanced coagulation with ferric ions and coarse calcite.  

PubMed

Arsenic removal from high-arsenic water in a mine drainage system has been studied through an enhanced coagulation process with ferric ions and coarse calcite (38-74 microm) in this work. The experimental results have shown that arsenic-borne coagulates produced by coagulation with ferric ions alone were very fine, so micro-filtration (membrane as filter medium) was needed to remove the coagulates from water. In the presence of coarse calcite, small arsenic-borne coagulates coated on coarse calcite surfaces, leading the settling rate of the coagulates to considerably increase. The enhanced coagulation followed by conventional filtration (filter paper as filter medium) achieved a very high arsenic removal (over 99%) from high-arsenic water (5mg/l arsenic concentration), producing a cleaned water with the residual arsenic concentration of 13 microg/l. It has been found that the mechanism by which coarse calcite enhanced the coagulation of high-arsenic water might be due to attractive electrical double layer interaction between small arsenic-borne coagulates and calcite particles, which leads to non-existence of a potential energy barrier between the heterogeneous particles. PMID:16352327

Song, S; Lopez-Valdivieso, A; Hernandez-Campos, D J; Peng, C; Monroy-Fernandez, M G; Razo-Soto, I

2006-01-01

440

Model study of initial adsorption of SO 2 on calcite and dolomite  

NASA Astrophysics Data System (ADS)

The rate of calcareous stone degradation is to a significant extent controlled by their surface chemistry with SO 2. Initial surface sulphite is converted to a harmful gypsum upon, e.g. NO 2 catalysed oxidation. However, it has been observed by scanning electron microscopy that the lateral distributions of gypsum crystals differ between calcitic and dolomitic marbles. The first-principles density functional theory is employed to understand the origin of these fundamentally different morphologies. Here, the stability differences of surface sulphite at calcite CaCO 3 (s) and dolomite Ca xMg 1- xCO 3 (s) are determined. A qualitative difference in surface sulphite stability, favouring the former, is reported. This is taken to imply that calcitic micro-crystals embedded in a dolomitic matrix act as sinks in the surface sulphation process, controlled by SO 2 diffusion. The subsequent formation of gypsum under such conditions will not require SO 42- (aq) ion transport. This explains the homogeneous distribution of gypsum observed on the calcitic micro-crystals in dolomite. In contrast, sulphation on purely calcitic marbles never reaches such high SO 2 coverage. Rather, upon oxidation, SO 42- (aq) transport to nucleation centres, such as grain boundaries, is required for the growth of gypsum crystals.

Malaga-Starzec, Katarina; Panas, Itai; Lindqvist, Oliver

2004-01-01

441

Influence of calcite on uranium(VI) reactive transport in the groundwater-river mixing zone.  

PubMed

Calcite is an important, relatively soluble mineral phase that can affect uranium reactive transport in subsurface sediments. This study was conducted to investigate the distribution of calcite and its influence on uranium adsorption and reactive transport in the groundwater-river mixing zone of the Hanford 300A site, Washington State. Simulations using a two-dimensional (2D) reactive transport model under field-relevant hydrological and hydrogeochemical conditions revealed the development of a calcite reaction front through the mixing zone as a result of dynamic groundwater-river interactions. The calcite concentration distribution, in turn, affected the concentrations of aqueous carbonate and calcium, and pH through dissolution, as river waters intruded and receded from the site at different velocities in response to stage changes. The composition variations in groundwater subsequently influenced uranium mobility and discharge rates into the river in a complex fashion. The results implied that calcite distribution and concentration are important variables that need to be quantified for accurate reactive transport predictions of uranium, especially in dynamic groundwater-river mixing zones. PMID:24240103

Ma, Rui; Liu, Chongxuan; Greskowiak, Janek; Prommer, Henning; Zachara, John; Zheng, Chunmiao

2014-01-01

442

Influence of calcite on uranium(VI) reactive transport in the groundwate-river mixing zone  

NASA Astrophysics Data System (ADS)

Calcite is an important, relatively soluble mineral phase that can affect uranium reactive transport in subsurface sediments. This study was conducted to investigate the distribution of calcite and its influence on uranium adsorption and reactive transport in the groundwate-river mixing zone of the Hanford 300A site, Washington State. Simulations using a two-dimensional (2D) reactive transport model under field-relevant hydrological and hydrogeochemical conditions revealed the development of a calcite reaction front through the mixing zone as a result of dynamic groundwate-river interactions. The calcite concentration distribution, in turn, affected the concentrations of aqueous carbonate and calcium, and pH through dissolution, as river waters intruded and receded from the site at different velocities in response to stage changes. The composition variations in groundwater subsequently influenced uranium mobility and discharge rates into the river in a complex fashion. The results implied that calcite distribution and concentration are important variables that need to be quantified for accurate reactive transport predictions of uranium, especially in dynamic groundwate-river mixing zones.

Ma, Rui; Liu, Chongxuan; Greskowiak, Janek; Prommer, Henning; Zachara, John; Zheng, Chunmiao

2014-01-01

443

Monitoring bacterially induced calcite precipitation in porous media using magnetic resonance imaging and flow measurements.  

PubMed

A range of nuclear magnetic resonance (NMR) techniques are employed to provide novel, non-invasive measurements of both the structure and transport properties of porous media following a biologically mediated calcite precipitation reaction. Both a model glass bead pack and a sandstone rock core were considered. Structure was probed using magnetic resonance imaging (MRI) via a combination of