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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)



Response of eleven forage species to treatment of acid soil with calcitic and dolomitic lime  

Microsoft Academic Search

The cost and difficulty of applying lime on hilly pastures or small forage fields makes it appropriate to devote attention to efficiency of lime utilization. This study evaluated effects of calcitic and dolomitic lime on yield and mineral composition of 11 forage species grown on soil with a low base status of 0.46 cmolc as Ca and 0.18 cmolc as

A. L. Pires; J. L. Ahirichs; C. L. Rhykerd



Molecular models of a hydrated calcite mineral surface  

NASA Astrophysics Data System (ADS)

Hydrated mineral surfaces play an important role in many processes in biological, geological, and industrial applications. An energy force field was developed for molecular mechanics and molecular dynamics simulations of hydrated carbonate minerals and was applied to investigate the behavior of water on the (101¯4) calcite surface. The force field is a significant development for large-scale molecular simulations of these systems, and provides good agreement with experimental and previous modeling results. Simulations indicate that water molecules are significantly ordered near the calcite surface. The predominant surface configuration (75-80%) results from coordination of a water molecule with a single calcium cation-carbonate anion pair, while the less common situation involves water coordination with two ion pairs. Surface restructuring and variation in coordination in the water layers results in distinct distances for water oxygens above the calcite surface—a two-component first monolayer (2.3 and 3.0 Å) and a secondary monolayer (5.0 Å). The different coordinations also alter lateral displacement, hydrogen bonding, and surface-normal orientation of the water molecules. The ordering of water molecules and the formation of a unique hydrogen bonding network at the calcite surface influence the physical properties of the interfacial water. Surface exchange of water molecules is observed by molecular dynamics simulation to occur at a rate of one exchange per 10 ps. Diffusion coefficients derived from mean square displacement analysis of atomic trajectories indicate a dependence of water transport based on the distance of the water molecules from the calcite surface.

Perry, Thomas D.; Cygan, Randall T.; Mitchell, Ralph



Effects of direct land application of calcitic lime and lime- and cement kiln dust-sanitized biosolids on the chemical and spectroscopic characteristics of soil lipids  

SciTech Connect

To determine the extent to which applications of calcitic lime and sanitized biosolids affect the quality of soil organic matter (SOM), lipids extracted from an unamended soil (CON) and from soils amended with calcitic lime (CAL), and lime (LSB)- and cement kiln dust (CDB)-sanitized biosolids were characterized by chemical analysis and Pyrolysis-Gas chromatography (Py-GC). From diethyl ether (DEE) and CHCl[sub 3] soluble lipids, and from weight ratios of the extracts, the organic matter in the soil amended with CDB-treated biosolids seemed to be more biodegraded and biochemically inert than the organic matter in soils that received LSB-treated biosolids and calcitic lime and that in the control soil.

Dinel, H.; Schnitzer, M.; Pare, T.; Topp, E. (Agriculture and AgriFood Canada, Ottawa, Ontario (Canada)); Lemee, L.; Ambles, A. (Univ. de Poitiers (France). Lab. de Chimie); Pelzer, N. (Univ. du Quebec, Montreal (Canada))



Rutting evaluation of hydrated lime and SBS modified asphalt mixtures for laboratory and field compacted samples  

Microsoft Academic Search

The purpose of this study is to evaluate permanent deformation for hydrated lime and SBS modified asphalt mixtures. Control (C), 2% hydrated lime (2L), 5% SBS polymer mixtures and 2%hydrated lime–5%SBS (2L5SBS) mixtures were prepared. The Laboratoire Central des Ponts et Chaussées (LCPC) wheel tracker, also known as French Rutting Tester were realized with two different stages. Same LCPC slabs

Halit Özen



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: implications for shellfish aquaculture by Carolyn Duckham B.Sc., Simon Fraser University, 2007 Research Project No.: 577 Title of Project: Impacts of ocean acidification and mitigative hydrated lime addition


Additive enhancement of pressure-hydrated lime for control of SOâ\\/NO\\/sub x\\/ emissions  

Microsoft Academic Search

Control of SOâ\\/NO\\/sub x\\/ emissions from low-rank coal combustion is investigated. This paper presents results from bench- and pilot-scal studies using pressure-hydrated lime and doped pressure-hydrated lime for the removal of SOâ\\/NO\\/sub x\\/. These results indicate that greater utilization of sorbent may be achieved through pressure-hydration. Activation energies, reaction orders, and possible rate-limiting mechanisms for the sorbent-SOâ reactions are also

M. H. Bobman; G. F. Weber; T. C. Keener



Additive enhancement of pressure-hydrated lime for control of SOâ\\/NO\\/sub x\\/ emissions  

Microsoft Academic Search

Control of SOâ\\/NO\\/sub x\\/ emissions from low-rank coal combustion is investigated. This paper presents results from bench- and pilot-scale studies using pressure-hydrated lime and doped pressure-hydrated lime for the removal of SOâ\\/NO\\/sub x\\/. These results indicate that greater utilization of sorbent may be achieved through pressure-hydration. Activation energies, reaction orders, and possible rate-limiting mechanisms for the sorbent-SOâ reactions are also

M. H. Bobman; G. F. Weber; T. C. Keener



Hydrated lime for metals immobilization and explosives transformation: Treatability study.  


Fragmentation grenades contain Composition B (RDX and TNT) within a steel shell casing. There is the potential for off-site migration of high explosives and metals from hand grenade training ranges by transport in surface water and subsurface transport in leachate. This treatability study used bench-scale columns and mesocosm-scale laboratory lysimeters to investigate the potential of hydrated lime as a soil amendment for in situ remediation of explosives and metals stabilization in hand grenade range soils. Compared to the unamended soil there was a 26-92% reduction of RDX in the leachate and runoff water from the lime treated soils and a 66-83% reduction of zinc in the leachate and runoff water samples; where the hand grenade range metals of concern were zinc, iron, and manganese. The amended soil was maintained at the target pH of greater than 10.5 for optimum explosives decomposition. The treatability study indicated a high potential of success for scale-up to an in situ field study. PMID:22445717

Martin, W Andy; Larson, S L; Nestler, C C; Fabian, G; O'Connor, G; Felt, D R



Properties of fly ash concrete modified with hydrated lime and silica fume  

Microsoft Academic Search

This paper presents the results of an experimental investigation on the properties of fly ash concrete incorporating either hydrated lime or silica fume to improve the early strength of concrete. Test results indicated that the addition of lime and silica fume improved the early age compressive strength of fly ash concrete. The inclusion of silica fume was also found to

S. A. Barbhuiya; J. K. Gbagbo; M. I. Russell; P. A. M. Basheer



Dry absorption of HCl and SOâ with hydrated lime from humidified flue gas  

Microsoft Academic Search

The simultaneous absorption of HCl and SOâ by hydrated lime in a fixed-bed reactor has been studied at conditions simulating humidified flue gas dry scrubbing. At 120 C, an increase in relative humidity from 0% to 19% increased HCl removal and sorbent utilization. At 19% relative humidity (RH), the final loading of hydrated lime was 1.64 mol of HCl\\/mol of

P. N. Chisholm; G. T. Rochelle



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


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 CO2 gas bubbling. The colour removal rate approximately exceeded 50% with M-CSH-lime addition rates of>0.15 w/v%. The removal rate of [Formula: see text] 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 P2O5 in the recovered matter was>15% when the weight ratio of influent [Formula: see text] 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



Evaluating Pond Shoreline Treatments of Slurried Hydrated Lime for Reducing Marsh Rams-Horn Snail Populations  

Microsoft Academic Search

Trematode parasites can cause massive infections in commercially raised fish. The most promising approach for the control of these infections is the reduction or elimination of snails that serve as vectors for the trematodes. A recent approach, the application of high concentrations of slurried hydrated lime (SHL) or copper sulfate pentahydrate (CSP) along pond margins (shoreline treatment), has shown promise

Andrew J. Mitchell; Scott Snyder; David J. Wise; Charles C. Mischke



Effect of current-season application of calcitic lime and phosphorus fertilization on soil pH, potato growth, yield, dry matter content, and cadmium concentration  

Microsoft Academic Search

Two glasshouse and three field experiments were conducted to investigate the effects of current-season application of calcitic lime and phosphorus (P) fertilizer on (i) soil pHw, (ii) growth of haulms (tops), (iii) tuber number, yield and dry matter content, and (iv) cadmium (Cd) concentrations in tubers of the potato (Solanum tuberosum L.) cultivars Russet Burbank, Crystal, and Pontiac grown in

N. A. Maier; M. J. McLaughlin; M. Heap; M. Butt; M. K. Smart



[Bactericidal effect of hydrated lime in aqueous solution].  


This study determined the bactericidal effect of the supernatants of saturated solutions of common lime and of micronized calcium hydroxide (Ca(OH)2) (1500 mg/L), which was used as a control, compared with disinfectants made of solutions of 0.33% colloidal silver (0.0016 mg/L), toluene sulfachloramine (41 mg/L) with sodium bicarbonate (9 mg/L), and sodium hypochlorite (5 mg/L). The test involved four strains of Vibrio cholerae 01, V. parahaemolyticus, Escherichia coli, Salmonella typhimurium, Shigella flexneri, Sh. sonnei, and Sa. enterititidis. These bacteria were inoculated into the bactericidal substances listed above and, after different incubation times, the number of surviving bacteria was determined in vitro by using a counting plate. The results were expressed in colony-forming units (CFU). An in situ estimate was made of the amount of V. cholerae on 35 strawberries and 35 radishes (having a weight of about 10 g per unit) after they were washed under a flow of potable water, submerged in the supernatant of the saturated lime solution (1.5 g/L), or both. The greatest bactericidal effect was obtained against V. cholerae 01 and was observed in 3 minutes. Other enterobacteria were resistant to the effect for up to 30 minutes. PMID:7779285

Muñoz Ruiz, C; Collazo Ponce, A; Alvarado, F J



Methanogenic calcite, 13C-depleted bivalve shells, and gas hydrate from a mud volcano offshore southern California  

USGS Publications Warehouse

Methane and hydrogen sulfide vent from a cold seep above a shallowly buried methane hydrate in a mud volcano located 24 km offshore southern California in?? 800 m of water. Bivalves, authigenic calcite, and methane hydrate were recovered in a 2.1 m piston core. Aragonite shells of two bivalve species are unusually depleted in 13C (to -91??? ??13C), the most 13C-depleted shells of marine macrofauna yet discovered. Carbon isotopes for both living and dead specimens indicate that they used, in part, carbon derived from anaerobically oxidized methane to construct their shells. The ??13C values are highly variable, but most are within the range -12??? to -91???. This variability may be diagnostic for identifying cold-seep-hydrate systems in the geologic record. Authigenic calcite is abundant in the cores down to ???1.5 m subbottom, the top of the methane hydrate. The calcite is depleted in 13C (??13C = -46??? to -58???), indicating that carbon produced by anaerobically oxidized methane is the main source of the calcite. Methane sources include a geologic hydrocarbon reservoir from Miocene source rocks, and biogenic and thermogenic degradation of organic matter in basin sediments. Oxygen isotopes indicate that most calcite formed out of isotopic equilibrium with ambient bottom water, under the influence of gas hydrate dissociation and strong methane flux. High metal content in the mud volcano sediment indicates leaching of basement rocks by fluid circulating along an underlying fault, which also allows for a high flux of fossil methane. ?? 2006 Geological Society of America.

Hein, J. R.; Normark, W. R.; McIntyre, B. R.; Lorenson, T. D.; Powell, II, C. L.



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


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. PMID:25074402

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



Effects of hydrated lime and quicklime on the decay of buried human remains using pig cadavers as human body analogues.  


Recent casework in Belgium involving the search for human remains buried with lime, demonstrated the need for more detailed understanding of the effect of different types of lime on cadaver decomposition and its micro-environment. Six pigs (Sus scrofa) were used as body analogues in field experiments. They were buried without lime, with hydrated lime (Ca(OH)(2)) and with quicklime (CaO) in shallow graves in sandy loam soil in Belgium and recovered after 6 months of burial. Observations from these field recoveries informed additional laboratory experiments that were undertaken at the University of Bradford, UK. The combined results of these studies demonstrate that despite conflicting evidence in the literature, hydrated lime and quicklime both delay the decay of the carcass during the first 6 months. This study has implications for the investigation of clandestine burials and for a better understanding of archaeological plaster burials. Knowledge of the effects of lime on decomposition processes also has bearing on practices involving burial of animal carcasses and potentially the management of mass graves and mass disasters by humanitarian organisations and DVI teams. PMID:22030481

Schotsmans, Eline M J; Denton, John; Dekeirsschieter, Jessica; Ivaneanu, Tatiana; Leentjes, Sarah; Janaway, Rob C; Wilson, Andrew S



Modeling dry-scrubbing of gaseous HCl with hydrated lime in cyclones with and without recirculation.  


A mathematical model describing the dry-scrubbing of gaseous hydrogen chloride (HCl) with solid hydrated lime particles (Ca(OH)(2)) was developed and experimentally verified. The model applies to cyclone systems with and without recirculation, where reaction and particle collection occurs in the same processing unit. The Modified Grain Model was selected to describe the behavior of the reaction process and it was assumed that the gas and the solid particles flow in the reactor with a plug flow. In this work, this behavior is approximated by a cascade of N CSTRs in series. Some of the model parameters were estimated by optimization taking into account the experimental results obtained. A good agreement was observed between the experimental results and those predicted by the model, where the main control resistance is the diffusion of the gaseous reactant in the layer of solid product formed. PMID:20185231

Chibante, Vania G; Fonseca, Ana M; Salcedo, Romualdo R



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



Material-specific effects of hydrated lime on the properties and performance behavior of asphalt mixtures and asphaltic pavements  

Microsoft Academic Search

This study evaluates hydrated lime-treated hot-mix asphalt (HMA) mixtures through various laboratory tests, including the dynamic modulus test and performance tests to characterize permanent deformation and fatigue damage resistance both in displacement-controlled and force-controlled modes. Two different asphalt mixtures — the asphalt concrete mixture and the fine aggregate asphalt matrix mixture — which differ only in the amount of additional

Francisco Thiago Sacramento Aragão; Junghun Lee; Yong-Rak Kim; Pravat Karki



Utilization of calcite and waste glass for preparing construction materials with a low environmental load.  


In this study, porous calcite materials are hydrothermally treated at 200 °C using powder compacts consisting of calcite and glasses composed of silica-rich soda-lime. After treatment, the glasses are converted into calcium aluminosilicate hydrates, such as zeolite phases, which increase their strength. The porosity and morphology of new deposits of hydrothermally solidified materials depend up on the chemical composition of glass. The use of calcite and glass in the hydrothermal treatment plays an important role in the solidification of calcite without thermal decomposition. PMID:21794973

Maeda, Hirotaka; Imaizumi, Haruki; Ishida, Emile Hideki



Short-term effects of hydrated lime and quicklime on the decay of human remains using pig cadavers as human body analogues: Laboratory experiments.  


Contradictions and misconceptions regarding the effect of lime on the decay of human remains have demonstrated the need for more research into the effect of different types of lime on cadaver decomposition. This study follows previous research by the authors who have investigated the effect of lime on the decomposition of human remains in burial environments. A further three pig carcasses (Sus scrofa), used as human body analogues, were observed and monitored for 78 days without lime, with hydrated lime (Ca(OH)2) and with quicklime (CaO) in the taphonomy laboratory at the University of Bradford. The results showed that in the early stages of decay, the unlimed and hydrated lime cadavers follow a similar pattern of changes. In contrast, the application of quicklime instigated an initial acceleration of decay. Microbial investigation demonstrated that the presence of lime does not eliminate all aerobic bacteria. The experiment also suggested that lime functions as a sink, buffering the carbon dioxide evolution. This study complements the field observations. It has implications for the investigation of time since death of limed remains. Knowledge of the effects of lime on decomposition processes is of interest to forensic pathologists, archaeologists, humanitarian organisations and those concerned with disposal of animal carcasses or human remains in mass disasters. PMID:24513401

Schotsmans, Eline M J; Denton, John; Fletcher, Jonathan N; Janaway, Robert C; Wilson, Andrew S



Long-term effects of hydrated lime and quicklime on the decay of human remains using pig cadavers as human body analogues: Field experiments.  


An increased number of police enquiries involving human remains buried with lime have demonstrated the need for more research into the effect of different types of lime on cadaver decomposition and its micro-environment. This study follows previous studies by the authors who have investigated the effects of lime on the decay of human remains in laboratory conditions and 6 months of field experiments. Six pig carcasses (Sus scrofa), used as human body analogues, were buried without lime with hydrated lime (Ca(OH)2) and quicklime (CaO) in shallow graves in sandy-loam soil in Belgium and recovered after 17 and 42 months of burial. Analysis of the soil, lime and carcasses included entomology, pH, moisture content, microbial activity, histology and lime carbonation. The results of this study demonstrate that despite conflicting evidence in the literature, the extent of decomposition is slowed down by burial with both hydrated lime and quicklime. The more advanced the decay process, the more similar the degree of liquefaction between the limed and unlimed remains. The end result for each mode of burial will ultimately result in skeletonisation. This study has implications for the investigation of clandestine burials, for a better understanding of archaeological plaster burials and potentially for the interpretation of mass graves and management of mass disasters by humanitarian organisation and DVI teams. PMID:24513400

Schotsmans, Eline M J; Fletcher, Jonathan N; Denton, John; Janaway, Robert C; Wilson, Andrew S



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

E-print Network

The presence of Salmonella and/or Campylobacter in poultry litter may contribute to contaminated processed carcasses. Initially in our first study, we evaluated the effect of 5, 10, or 20% added lime on in vitro survival of Salmonella enteritidis...

Stanush, Deborah Denise



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


The removal of dissolvable inorganic phosphate (H(2)PO(4)(-)) 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 adsorption capacity increases, suggesting that the HL plays the important role in the removal process in the gross. However, in the lower HL content, it is interesting that the adsorption capacity of as-prepared sorbents exceed the sum of the capacities of the same ratio of BFS and HL. The further analysis indicate the excess capacities linearly depend on the specific surface area of sorbents, suggesting that the removal of H(2)PO(4)(-) is closely related with the microstructure of sorbents in the lower HL content, according to the characterization with SEM, XRD and pore analysis. Additionally, an adsorption model and kinetic are discussed in this paper. PMID:19124194

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



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... lime, hydratecl lime, linlestone screenings, ground limestone rocks, ground oyster shells and marl deposits. Fifty-six pounds of fresh pulverized quicklin~e are equal to seventy-four ponnds dry water-slacked lime or hydrated lime, and one hundred...

Fraps, G. S. (George Stronach)



Geochemical constraints for coexisting CO"2 gas hydrate and calcite: implications for sheet cracks, stromatactis, zebra and tepee-like structures [rapid communication  

NASA Astrophysics Data System (ADS)

The Ordovician Meiklejohn Peak mud-mound in western Nevada contains sedimentary structures (e.g., stromatactis and "zebra-rock") that resemble features found in modern methane hydrate deposits. However, the ?13C of the mud-mound carbonates (-1 to 1‰ PDB) does not suggest interaction with ?13C-depleted methane. Consequently, Krause (Sedimentary Geology 145 (2001) 189) proposed that the Meiklejohn structures might have been produced by the formation and dissociation of CO 2 gas hydrate rather than methane gas hydrate. Structures in Neoproterozoic cap carbonates, sheet cracks and tepee-like structures have also been suggested to represent gas hydrate interaction with carbonate sediments (Geology 29 (2001) 443), but, similarly, ?13C values do not suggest direct interaction with methane. The objective of this contribution is to see if the presence of CO 2 gas hydrate is plausible for either setting. To test the feasibility of CO 2 gas hydrate involvement in the formation of these structures, necessary concentrations of TCO 2 were calculated based on required phase equilibria using the quadruple points Q1 (-1.73 °C, 10.2 atm) and Q2 (10.2 °C, 44.5 atm) from the phase diagram for CO 2 gas hydrate (Miller, S.L., 1974. The Nature and Occurrence of Clathrate Hydrates. In: Kaplan, I.R. (Ed.), Natural Gases in Marine Sediments. Plenum, New York, NY, pp. 151-178). A limit for Ca +2 was established based on the lack of evidence for gypsum formation in this environment and the assumption that sulfate was up to 100% of its present oceanic value; the calculated TCO 2 concentration, however, is relatively insensitive to the concentration of SO 4-2 used. The lowest permissible value of pCO 2 and TCO 2 were found at Q1, where TCO 2 must be at least 300 times the present value. These conditions are implausible for the formation of the Meiklejohn Peak mud-mound. Although some models for Neoproterozoic "Snowball Earth" require highly elevated atmospheric CO 2, these models predict pCO 2 that is still too low to permit the formation of CO 2 gas hydrates in carbonate sediments. In addition, if the required conditions could be achieved during "Snowball Earth", one would expect to find the associated structures only at the base of the section, while they are commonly observed meters to tens of meters above the base. Therefore, we conclude that it is unlikely these structures were produced by the formation and dissociation of CO 2 gas hydrate.

DiFilippo, Erica L.; Hammond, Douglas E.; Corsetti, Frank A.



Hydrate adhesive and tensile strengths  

NASA Astrophysics Data System (ADS)

The physical properties of hydrate-bearing sediments depend on the interaction between hydrates and minerals. In particular, hydrates prefer to nucleate on mineral surfaces, therefore, the hydrate-mineral adhesive strength and the tensile strength of the hydrate mass itself affect the mechanical response of hydrate-bearing sediments. In this study, ice and hydrates made with various guest molecules (CO2, CH4, and THF) are formed between mica and calcite substrates. Adhesive and tensile strengths are measured by applying an external pull-out force. Results show that tensile failure occurs in CO2 and CH4 hydrates when calcite is the substrate, while ice and all hydrates exhibit adhesive failure on mica. The debonding strength is higher when calcite substrates are involved rather than mica substrates. A nominal pull-out strength of 0.15 ± 0.03 MPa can be adopted for mechanical analyses of hydrate-bearing sediments.

Jung, J. W.; Santamarina, J. Carlos



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

Texas, limestone and caliche soil, were tested extensively to examine the effect of carbonate cementation due to the addition of small percentages of lime. Testing included mineralogical analysis of the two materials, strength analysis in terms of texas...

Bhuiyan, Jasim Uddin



Role of lime in salty spoil genesis  

SciTech Connect

Acid pyritic spoils are often limed to facilitate revegetation efforts. Substantial quantities of soluble sulfate salts are associated with such spoils, before and after liming. Such salts can cause revegetation attempts to fail at seeding and/or during drought stress periods. As magnesium sulfate (MgSO/sub 4/) is more soluble than gypsum (calcium sulfate) under field conditions, MgSO/sub 4/ has more often been associated with soluble salt problems. Since lime reaction chemistry can influence salt genesis in spoils, this was evaluated in a incubation study using calcite and dolomite amendments to an acid, pyritic spoil. Rates of 0, 14.4, and 28.8 meq/100 g (rate equal to total potential acidity) of lime were used. Amended spoils were maintained at 30/sup 0/C and -100 cm moisture tension. Samples were taken periodically and a portion suspended in water at a soil:solution ratio of 1:20 for two hours. Unamended spoil extract pH dropped from 4.8 to 3.2 in nine weeks. Soluble magnesium sulfate doubled (from 2.9 to 6.1 meq/100 g) in the unlimed spoil between weeks one and sixteen. Dolomite amended spoils generated twice as much magnesium salt as calcite amended spoils. Pyrite oxidation, acid generation, i.e., salt genesis, was reduced when calcitic lime was used at the recommended rate based on a measure of total potential acidity. A prompt liming program with calcitic lime can substantially alter the quantity and quality of soluble salts released. The results suggest that dolomite is unacceptable as a liming material for sandy spoils with an appreciable pyrite content.

Grove, J.H.; Evangelou, V.P.



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.



A study of fly ash–lime granule unfired brick  

Microsoft Academic Search

In this paper, the properties of fly ash–lime granule unfired bricks are studied. Granules were prepared from mixtures of fly ash and lime at fly ash to hydrated lime ratios of 100:0 (Ca\\/Si=0.2), 95:5 (Ca\\/Si=0.35) and 90:10 (Ca\\/Si=0.5). After a period of moist curing, the microstructure and mineralogy of the granules were studied. Microstructure examination reveals that new phases in

P. Chindaprasirt; K. Pimraksa



Tetravalent uranium in calcite  


X-ray absorption spectroscopy and x-ray fluorescence microprobe studies of 35-million-year-old calcite from a Mississippi Valley-type zinc ore deposit indicate substitution of tetravalent uranium for divalent calcium. Thus, tetravalent uranium has a stable location in calcite deposited under reducing conditions. This result validates uranium-series dating methods (including uranium/lead dating) for ancient calcite and shows that calcite provides a sink for uranium in deep groundwater aquifers and anoxic lacustrine and marine basins. PMID:9703507

Sturchio; Antonio; Soderholm; Sutton; Brannon



Tetravalent uranium in calcite.  

SciTech Connect

X-ray absorption spectroscopy and x-ray fluorescence microprobe studies of 35-million-year-old calcite from a Mississippi Valley-type zinc ore deposit indicate substitution of tetravalent uranium for divalent calcium. Thus, tetravalent uranium has a stable location in calcite deposited under reducing conditions. This result validates uranium-series dating methods (including uranium/lead dating) for ancient calcite and shows that calcite provides a sink for uranium in deep groundwater aquifers and anoxic lacustrine and marine basins.

Sturchio, N. C.; Antonio, M. R.; Soderholm, L.; Sutton, S. R.; Brannon, J. C.; Univ. of Chicago; Washington Univ.



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.



Liming fish ponds  

Microsoft Academic Search

Fish production in ponds can often be improved by liming with agricultural limestone, calcium hydroxide, calcium oxide, basic slag, or liquid lime. Properly applied, these materials react with acidity to form bicarbonate which is then available as a carbon source to plants. In sediments liming increases the rates of organic matter decomposition and nutrient cycling. Other effects of liming on



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)



Dislocation Creep in Magnesium Calcite  

Microsoft Academic Search

To investigate the effect of dissolved Mg on plastic deformation of calcite, we performed triaxial deformation experiments on synthetic calcite with varying amount of Mg content. Mixtures of powders of calcite and dolomite were isostatically hot pressed (HIP) at 850° C and 300 MPa confining pressure for different intervals (2 to 20hrs) resulting in homogeneous aggregates of high-magnesium calcite; Mg

L. Xu; X. Xiao; B. J. Evans



Gypsum And Liming Effect On Surface Reactivity In Chilean Acid Soils Effet de l'apport de gypse et du chaulage sur la réactivité de surface de sols acides du Chili  

Microsoft Academic Search

Changes in the chemistry of the acidic Chilean Andisols in response to various ameliorant treatments (gypsum, dolomitic and calcitic lime) and their effects on Lolium perenne ryegrass production were studied in laboratory incubation and greenhouse experiments. Dolomitic and calcitic liming alone and in combination with gypsum increased pH significantly and, at the same time, decreased exchangeable Al concentration to low

MORA G. María; DEMANET F. Rolando


The Mechanism of Vapor Phase Hydration of Calcium Oxide: Implications for CO2 capture.  


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



Microbial precipitation of pedogenic calcite  

Microsoft Academic Search

Pedogenic calcite in desert soils has become increasingly important as an indicator of paleoclimate, landscape stability, and landscape age. This study indicates that calcic and petrocalcic horizons in desert soils are not simply the result of inorganic precipitation of calcite. Soil microorganisms were found to be involved in calcite precipitation in a typical desert soil near Las Cruces, New Mexico.

H. Curtis Monger; LeRoy A. Daugherty; William C. Lindemann; Craig M. Liddell



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.



Microbial precipitation of pedogenic calcite  

SciTech Connect

Pedogenic calcite in desert soils has become increasingly important as an indicator of paleoclimate, landscape stability, and landscape age. This study indicates that calcic and petrocalcic horizons in desert soils are not simply the result of inorganic precipitation of calcite. Soil microorganisms were found to be involved in calcite precipitation in a typical desert soil near Las Cruces, New Mexico. Fossilized remains of calcified fungal hyphae and Microcodium structures are abundant in the petrocalcic horizon. Soil bacteria and fungi precipitated calcite when cultured on a Ca-rich medium. In an experiment where soil columns were irrigated on a Ca-rich solutions, calcite formed in soils containing soil microorganisms, but no calcite formed in sterile soils. Thus, biomineralization of calcite by soil microorganisms appears to be an important mechanism of unknown magnitude.

Monger, H.C.; Daugherty, L.A.; Lindemann, W.C.; Liddell, C.M. (New Mexico State Univ., Las Cruces (United States))



A thermodynamic approach to the hydration of sulphate-resisting Portland cement  

Microsoft Academic Search

A thermodynamic approach is used to model changes in the hydrate assemblage and the composition of the pore solution during the hydration of calcite-free and calcite-containing sulphate-resisting Portland cement CEM I 52.5 N HTS. Modelling is based on thermodynamic data for the hydration products and calculated hydration rates for the individual clinker phases, which are used as time-dependent input parameters.Model

Barbara. Lothenbach; Erich Wieland




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...


Calcite in Lesquerella ovalifolia Trichomes.  


By chemical analysis, trichomes of Lesquerella ovalifolia Rydb. have been shown to contain a high percentage of calcium carbonate. X-ray diffraction patterns showed that it was in the form of calcite. The calcite was inside the trichomes, and its depositional pattern conformed to the shape of the trichomes. A small amount of opal was present in the trichomes. PMID:17815828

Lanning, F C



Material-Related Forensic Analysis and Special Testing: Assessment of Original Free Lime Content of Weathered Iron and Steel Slag.  

National Technical Information Service (NTIS)

The purpose of Work Order No. 96-09-21 is to conduct Thermogravimetric Analysis and either ASTMC 114 total lime content and/or the anhydrous ethylene glycol total lime content determinations. The hydration and dissolution of calcium oxide to form calcium ...

M. Boyle, E. Shkolnik



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



Hydration of bagasse ash-blended portland cement  

Microsoft Academic Search

Hydration of bagasse ash (BA)-blended portland cement has been studied by employing a number of experimental techniques. It is found that in presence of BA setting times are increased and free lime is decreased. The compressive strength values increased with hydration time in the presence of BA and the values were found to be higher than that of control. The

N. B Singh; V. D Singh; Sarita Rai



Gas Hydrates  

Microsoft Academic Search

This review states contemporary views about gas hydrates, and also about non-stoichiometric clathrates with the general formula M·nH2O. The known types of the hydrates and their crystal structure are described. The thermodynamics of hydrate formation is considered. Methods of determining the composition of the hydrates are described. Factual information concerning the hydrates of individual gases and organic liquids and mixed

S. Sh Byk; V. I. Fomina



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.



Kinetics of Mg partition and Mg stable isotope fractionation during its incorporation in calcite  

NASA Astrophysics Data System (ADS)

Calcite growth experiments have been performed in the presence of aqueous Mg at 25 °C and 1 bar pCO2 to quantify magnesium partition coefficient D={(Mg/Ca)}/{(Mg/Ca)} and Mg isotope fractionation between calcite and reactive fluid (?26Mgcalcite-fluid) as a function of calcite precipitation rate rp (mol m-2 s-1). Mg partition coefficient, DMg, increases with calcite growth rate according to: LogD=0.2517(±0.0150)×Logrp+0.0944(±0.0182); R2=0.93,(10-8.3?rp?10-6.6molms) ?26Mgcalcite-fluid was found to depend heavily on calcite growth rate with preferential incorporation of 24Mg in calcite and the extent of isotope fractionation decreasing with increasing calcite growth rate in accord with: ?26Mg=0.7918(±0.0452)×Logrp+3.2366(±0.3360); R2=0.97(10-8.3?rp?10-6.6molms) The negative ?26Mgcalcite-fluid values found in this study, with calcite overgrowths enriched in light Mg, are consistent with (i) recent experimental data on Mg isotope fractionation during low-Mg calcite homogeneous precipitation (Immenhauser et al., 2010) and magnesite growth (Pearce et al., 2012) and (ii) with theoretical values calculated for Mg-calcite by density-functional electronic structure models (Rustad et al., 2010). The deviation of the isotopic composition of precipitated Mg-calcite from the equilibrium mass fractionation line in a three isotope diagram is a linear function of calcite growth rate. The equilibrium ?26Mgcalcite-fluid value at 25 °C derived from this linear extrapolation, ?26Mgcalcite-fluid = -3.5 ± 0.2‰ (2?), is in good agreement with the theoretical value calculated by Rustad et al. (2010) for Mg-calcite (?26Mgcalcite-fluid = -3.6‰; BP86 functional). A striking feature of the results of this study is the decrease of the extent of Mg isotope fractionation (from -3.16‰ to -1.88‰) with the increase of calcite precipitation rate (from 10-8.3 to 10-6.6 mol m-2 s-1) which is opposite to the variation of Ca, Ba and Sr isotope fractionation with calcite precipitation rate. This behavior likely stems from the strong free energy of hydration of the Mg2+ ion compared to Ca2+, Ba2+ and Sr2+ which leads, during fast calcite growth, to the entrapment in calcite overgrowths of hydrated Mg ions whose isotopic composition is close to that of aqueous Mg2+. The strong dependence of Mg isotope fractionation on calcite growth rate suggests that, using the three isotopes method, Mg isotopic signatures of calcite in association with those of other divalent metals (Zn2+, Cu2+) have the potential to reveal mineral precipitation rates and thus environmental conditions of the oceans over geological time.

Mavromatis, Vasileios; Gautier, Quentin; Bosc, Olivier; Schott, Jacques



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




Microsoft Academic Search

Previous research demonstrated that phosphorus (P) fertilization of tall fescue (Festuca arundinacea Schreb.) pastures on acidic soils increased leaf P, magnesium (Mg), and calcium (Ca) concentrations and reduced the risk of grass tetany. It has been suggested that liming could have a similar effect by increasing soil pH and remobilizing sorbed P. To investigate this option, calcitic or dolomitic limestone

Elizabeth J. Hamilton; Randall J. Miles; Krystyna Lukaszewska; Melissa Remley; Matt Massie; Dale G. Blevins



Setting process of lime-based conservation mortars with barium hydroxide  

SciTech Connect

This paper presents the effect of barium hydroxide on the setting mechanism of lime-based conservation mortars, when used as an additive material. The study focuses on the monitoring of the setting process and the identification of the mineral phases formed, which are essential for furthering the study of the durability of barium mixtures against chemical degradation. X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and thermal analysis (DTA-TG) were used to monitor the setting processes of these mixtures and identify new phases formed. The results suggest that barium hydroxide is evenly distributed within the lime and produces a homogeneous binding material, consisting of calcite (CaCO{sub 3}), witherite (BaCO{sub 3}) and barium-calcium carbonate [BaCa(CO{sub 3}){sub 2}]. Finally, it was found that barium carbonate can be directly bonded to calcitic aggregates and therefore increases its chemical compatibility with the binding material.

Karatasios, Ioannis [Institute of Materials Science, NCSR Demokritos, Aghia Paraskevi, 153 10 Athens (Greece)]. E-mail:; Kilikoglou, Vassilis [Institute of Materials Science, NCSR Demokritos, Aghia Paraskevi, 153 10 Athens (Greece); Colston, Belinda [Department of Forensic and Biomedical Sciences, University of Lincoln, Lincoln, LN6 7TS (United Kingdom); Theoulakis, Panagiotis [Department of Conservation of Antiquities and Works of Art, TEI of Athens, Athens, 122 10 (Greece); Watt, David [Hutton and Rostron Environmental Investigations Limited/Centre for Sustainable Heritage, University College London (United Kingdom)



Effect of maturation time on the fresh and hardened properties of an air lime mortar  

Microsoft Academic Search

The restoration and maintenance of old renders is one of the key aspects of correct rehabilitation practice. The ideal course of action is to replace the damaged material by a material with compatible characteristics. This work aims to analyze the effect of the maturation process on hardened state characteristics of hydrated powder lime mortars. The rheological characterization shows an air

H. Paiva; A. Velosa; R. Veiga; V. M. Ferreira



A thermodynamic approach to the hydration of sulphate-resisting Portland cement.  


A thermodynamic approach is used to model changes in the hydrate assemblage and the composition of the pore solution during the hydration of calcite-free and calcite-containing sulphate-resisting Portland cement CEM I 52.5 N HTS. Modelling is based on thermodynamic data for the hydration products and calculated hydration rates for the individual clinker phases, which are used as time-dependent input parameters. Model predictions compare well with the composition of the hydrate assemblage as observed by TGA and semi-quantitative XRD and with the experimentally determined compositions of the pore solutions. The calculations show that in the presence of small amounts of calcite typically associated with Portland cement, C-S-H, portlandite, ettringite and calcium monocarbonate are the main hydration products. In the absence of calcite in the cement, however, siliceous hydrogarnet instead of calcium monocarbonate is observed to precipitate. The use of a higher water-to-cement ratio for the preparation of a calcite-containing cement paste has a minor effect on the composition of the hydrate assemblage, while it significantly changes the composition of the pore solution. In particular, lower pH value and higher Ca concentrations appear that could potentially influence the solubility and uptake of heavy metals and anions by cementitious materials. PMID:16529919

Lothenbach, Barbara; Wieland, Erich



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.




Microsoft Academic Search

An experimental lake liming program in the Adirondack Mountains of New York State—the largest and most comprehensive in the United States—will initially entail neutralizing two acidified Adirondack lakes now devoid of fish. One lake will be limed with CaCO3and maintained in a circumneutral condition. Brook trout will be stocked in the lake, and their survival and growth monitored. The second

Douglas L. Britt; James E. Fraser



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:



In What Form is Lime Present in Portland Cement  

E-print Network

lime. Another proposed test depends on the fact that calcium hydroxide loses its water of constitution at 450* to 480° c , while the other constitutents of set Portland cement lose their water of hydration at 160° C. In, this test a sample... for , - Jr. of Ind. and Eng. Chem. Jan. 1909. The Am. Shem.Soc. Easton,Pa Constitution of P. C. D. B. Butler (Book) K.U.Chem Library, P.257-268. Spon and Chamberlain Hew York, 1899. Constitution of P.C. In Micro structure of P.C "by Stern Ahs. J...

Wright, Claude W.



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



Trace concentration - Huge impact: Nitrate in the calcite/Eu(III) system  

NASA Astrophysics Data System (ADS)

The interactions of trivalent lanthanides and actinides with secondary mineral phases such as calcite is of high importance for the safety assessment of deep geological repositories for high level nuclear waste (HLW). Due to similar ionic radii, calcium-bearing mineral phases are suitable host minerals for Ln(III) and An(III) ions. Especially calcite has been proven to retain these metal ions effectively by both surface complexation and bulk incorporation. Since anionic ligands (e.g., nitrate) are omnipresent in the geological environment and due to their coordinating properties, their influence on retentive processes should not be underestimated. Nitrate is a common contaminant in most HLW forms as a result of using nitric acid in fuel reprocessing. It is also formed by microbial activity under aerobic conditions. In this study, atomic force microscopy investigations revealed a major influence of nitrate upon the surface of calcite crystals. NaNO3 causes serious modifications even in trace amounts (<10-7 M) and forms a soft surface layer of low crystallinity on top of the calcite crystal. Time-resolved laser fluorescence spectroscopy of Eu(III) showed that, within this layer, Eu(III) ions are incorporated, while losing most of their hydration shell. The results show that solid solution modelling for actinides in calcite must take into account the presence of nitrate in pore and ground waters.

Hofmann, Sascha; Voïtchovsky, Kislon; Schmidt, Moritz; Stumpf, Thorsten



The Alumina- Lime Soda Water Treatment Process.  

National Technical Information Service (NTIS)

A new pretreatment process for brackish water desalting has been developed and evaluated in the laboratory. The alumina-lime-soda process involves treating raw saline water with sodium aluminate and lime, separating precipitated solids, and neutralizing t...

J. W. Nebgen, E. P. Shea, S. Y. Chiu



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




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...


Control of Kagzi Lime Decline.  

National Technical Information Service (NTIS)

The Common lime, variously known as Key, Mexican, West Indian, Galago, Kagzi etc., has in recent years suffered a serious setback as a result of a serious malady referred to as 'die-back' or 'decline'. The principal component of this malady is a Tristeza ...



Comparison of solidification/stabilization effects of calcite between Australian and South Korean cements  

SciTech Connect

The differences in the effect of calcite on the strength and stability of Pb-rich wastes solidified and stabilized using Australian and South Korean ordinary Portland cements are examined in this study. Pb-rich waste stabilized using Australian OPC has been shown to possess both substantially higher unconfined compressive strength and lead immobilization ability than South Korean OPC as a result of its higher C{sub 3}S content and the associated enhanced degree of precipitation of lead on the surfaces of silicate phases present. Calcite addition is observed to have an accelerating effect on the OPC-induced solidification/stabilization of Pb-rich wastes as gauged by the unconfined compressive strength and leachability of the solids formed. This effect is observed to be far more dramatic for South Korean OPC than for Australian OPC. Using scanning electron microscopy, waste stabilized with cement and calcite was observed to develop significantly greater proportions of hydrated crystals than wastes stabilized with cement alone. The results of X-ray diffraction studies have shown that the presence of calcite in South Korean OPC results in greater acceleration in the formation of portlandite than is the case for Australian OPC.

Lee, Dongjin [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:; Swarbrick, Gareth [School of Civil and Environmental Engineering, University of New South Wales, Sydney, NSW 2052 (Australia); Lee, Sookoo [School of Environmental Engineering, Seoul National University of Technology, Nowon-Gu, Seoul, 139-743 (Korea, Republic of)



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.



Thermodynamic modelling of the hydration of Portland cement  

SciTech Connect

A thermodynamic model is developed and applied to calculate the composition of the pore solution and the hydrate assemblage during the hydration of an OPC. The calculated hydration rates of the individual clinker phases are used as time dependent input. The modelled data compare well with the measured composition of pore solutions gained from OPC as well as with TGA and semi-quantitative XRD data. The thermodynamic calculations indicate that in the presence of small amounts of calcite typically included in OPC cements, C-S-H, portlandite, ettringite and calcium monocarbonates are the main hydration products. The thermodynamic model presented in this paper helps to understand the interactions between the different components and the environment and to predict the influence of changes in cement composition on the hydrate assemblage.

Lothenbach, Barbara [Empa, Laboratory for Concrete and Construction Chemistry, Uberlandstrasse 129, 8600 Duebendorf (Switzerland)]. E-mail:; Winnefeld, Frank [Empa, Laboratory for Concrete and Construction Chemistry, Uberlandstrasse 129, 8600 Duebendorf (Switzerland)




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



Adsorption of sevoflurane by soda-limes  

Microsoft Academic Search

Dry soda-lime adsorbs significant quantities of halothane, thus influencing on the speed of the induction of anaesthesia with\\u000a the agent and also on the recovery from anesthesia. Sevoflurane is a new inhaled anesthetic. Although the chemical degradation\\u000a of sevoflurane with soda-lime has been studied, no information is available about its adsorption by soda-lime. This issue\\u000a can not be neglected clinically.

Mihoko Kudo; Tsuyoshi Kudo; Akitomo Matsuki



Integrated Approach for Understanding Impurity Adsorption on Calcite: Mechanisms for Micro-scale Surface Phenomena  

NASA Astrophysics Data System (ADS)

A longstanding goal within the field of environmental geochemistry has been the development of a fundamental understanding of the kinetics that governs the interactions of solution-borne impurities with the calcite mineral surface. Recent dissolution experiments using Mg2+, Mn2+, and Sr2+ have shown distinct differences in the interaction of these three impurity ions with the calcite crystal surface. Because the dissolution of carbonate minerals in soils and sediments influences the uptake and migration of groundwater contaminants, a rigorous understanding of the basic processes that occur at the mineral-fluid interface is necessary. We have used vertical scanning interferometry (VSI) coupled with scanning probe microscopy (SPM) to examine calcite crystal dissolution in the presence of Mg2+, Mn2+, and Sr2+, all known dissolution inhibitors and possible groundwater contaminants. We have studied the kinetics of impurity-crystal interactions at a pH 8.8, and in the presence or absence of dissolved inorganic carbon. Our data show that, when individually introduced into undersaturated solutions, Mg2+ and Mn2+ are shown to activate the calcite crystal surface, resulting in enhanced etch pit nucleation rates and step density. Conversely, Sr2+ is shown to cause passivation of the calcite surface. The effect is intensified when solutions are saturated with respect to atmospheric CO2. Results indicate that aqueous CO32- (or HCO3-) may influence how aqueous metal ionic complexes interact with the crystal surface. Furthermore, the influence is differently exhibited, and passivation or activation ultimately depends on the properties of the diffusing metal ion or metal-hydroxide complex. These properties include for example, differences in hydration enthalpy, the effective ionic radius, and electron shell configuration.

Vinson, M. D.; Arvidson, R. S.; Luttge, A.



Framboidal Vaterite and its Transformation to Calcite  

Microsoft Academic Search

Vaterite, the most soluble of the three anhydrous calcium carbonate polymorphs, is observed to form in laboratory experiments performed at high degrees of supersaturation. Under standard condition it rapidly transforms into calcite and (or) aragonite. Experimental studies on vaterite are generally based on bubbling carbon dioxide through a calcium carbonate solution. The morphology of the crystals formed is often described

G. Nehrke; P. van Cappellen; C. H. van der Wijden



Calcite Reaction Kinetics in Saline Waters  

E-print Network

The effect of ionic strength (I), pCO2, and temperature on the reaction kinetics of calcite was investigated in magnesium-free, phosphate-free, low calcium (mCa^2 ? 0.01 – 0.02 molal) simple KCl and NaCl solutions from both undersaturated...

Finneran, David



& Microarrays Calcite Microneedle Arrays Produced by Inorganic Ion-Assisted  

E-print Network

& Microarrays Calcite Microneedle Arrays Produced by Inorganic Ion-Assisted Anisotropic Dissolution solution in the presence of ammo- nium salts. The lengths and the aspect ratios of the calcite microneedles of the calcite microneedles could be attributed to the tri-symmetric feature of rhombohedral cal- cite atomic

Qi, Limin


Microstructures and rheology of a calcite-shale thrust fault  

NASA Astrophysics Data System (ADS)

A thin (˜2 cm) layer of extensively sheared fault rock decorates the ˜15 km displacement Copper Creek thrust at an exposure near Knoxville, TN (USA). In these ultrafine-grained (<0.3 ?m) fault rocks, interpenetrating calcite grains form an interconnected network around shale clasts. One cm below the fault rock layer, sedimentary laminations in non-penetratively deformed footwall shale are cut by calcite veins, small faults, and stylolites. A 350 ?m thick calcite vein separates the fault rocks and footwall shale. The vein is composed of layers of (1) coarse calcite grains (>5 ?m) that exhibit a lattice preferred orientation (LPO) with pores at twin-twin and twin-grain boundary intersections, and (2) ultrafine-grained (0.3 ?m) calcite that exhibits interpenetrating grain boundaries, four-grain junctions and lacks a LPO. Coarse calcite layers crosscut ultrafine-grained layers indicating intermittent vein formation during shearing. Calcite in the fault rock layer is derived from vein calcite and grain-size reduction of calcite took place by plasticity-induced fracture. The ultrafine-grained calcite deformed primarily by diffusion-accommodated grain boundary sliding and formed an interconnected network around shale clasts within the shear zone. The interconnected network of ultrafine-grained calcite indicates that calcite, not shale, was the weak phase in this fault zone.

Wells, Rachel K.; Newman, Julie; Wojtal, Steven



in situ Calcite Precipitation for Contaminant Immobilization  

SciTech Connect

in situ Calcite Precipitation for Contaminant Immobilization Yoshiko Fujita ( (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



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:; 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)



Lime for environmental uses. STP 931  

Microsoft Academic Search

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





Microsoft Academic Search

Eight male sheep were used to determine digestibility and voluntary intake of rice strew untreated and treated with slaked lime. The straw was soaked in water (1 kg straw in 10 l water) containing 40 g lime\\/kg straw for 48 hours in a concrete pit and then washed with water (5 1 water \\/ kg straw) before sun drying. The

M Saadullah; M Haque; F Dolberg


Framboidal Vaterite and its Transformation to Calcite  

NASA Astrophysics Data System (ADS)

Vaterite, the most soluble of the three anhydrous calcium carbonate polymorphs, is observed to form in laboratory experiments performed at high degrees of supersaturation. Under standard condition it rapidly transforms into calcite and (or) aragonite. Experimental studies on vaterite are generally based on bubbling carbon dioxide through a calcium carbonate solution. The morphology of the crystals formed is often described to be "of some spherical shape", with a typical diameter of about 5æm. A detailed investigation of the morphology by means of a high resolution scanning electron microscope (SFEG-SEM) revealed that these spheres in turn are build up of smaller spherical particles with diameters typically 100 nm. Here we propose the following mechanism for the formation of these "framboidal" structures. Nucleation of the first particles occurs on the carbon dioxide to solution interface of the bubble. The fast growth of the individual crystals leads to a depletion in solution around the crystal, which stops crystal growth at a size of about 100 nm. The collapsing gas bubble concentrates the particles within its former volume. Additional evidence for such a mechanism comes from the observation that terminating the experiment after formation of the first particles does not result in any "framboidal" aggregates. Using CO2 bubbling sometimes results in a vaterite powder containing additional calcite. A pure vaterite powder and a powder containing calcite were compared to show different transformation pathways. The morphology of the solids is identical, i.e. the calcite present is not visible under the SFEG-SEM. Calcite formation is observed immediately after a pure vaterite is added to water. Synchronous nucleation at many different sites was observed. The observation that crystal growth was not effected by changes in stirring speed confirms that diffusion did not limit crystal growth. On the hand the powder initially already containing calcite transforms by growth of a few bigger sized crystals. The impact of differences in stirring speed on the transformation rate can be explained by diffusion limited growth of a restricted number of bigger crystals, i.e. less nucleation sites available. Due to Oswald Ripening smaller crystals will eventually disappear and the final morphology of both solids will look similar. However, the different kinetics be explained only by following the change in morphology during the complete transformation process. All evidence of different transformation pathways gets lost as the morphology of the solids before and after transformation is nearly identical.

Nehrke, G.; van Cappellen, P.; van der Wijden, C. H.



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.



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.



Third-Order Elastic Constants of Calcite  

Microsoft Academic Search

The third-order elastic constants of calcite at 0°C have been determined by measuring the stress and temperature dependence of sound velocities in it by means of an improved pulse-superposition method (average sensitivity of 2×10-7). Within the small temperature range considered (about 2°C), a nonlinear temperature dependence which varies with pressure has been clearly observed. Out of 14 independent third-order moduli,

H. Kaga



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


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



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.



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.



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.



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.



Calcite precipitation induced by polyurethane-immobilized Bacillus pasteurii.  


Polyurethane (PU) foam was used to immobilize the whole cell of Bacillus pasteurii. The immobilized cells exhibited the rates of calcite precipitation and ammonia production as high as those of the free cells. Scanning electron micrographs identified the cells embedded in calcite crystals throughout PU matrices. Calcite in PU showed little effect on the elastic modulus and tensile strength of the polymer, but increased the compressive strengths of concrete cubes, whose cracks were remediated with PU-immobilized cells. These observations led us to believe that the calcite might remain as a form of precipitation, not as a bonding material within the matrices. PMID:11240198

Bang, S S.; Galinat, J K.; Ramakrishnan, V



The Coordination of Mg in Foraminiferal Calcite  

NASA Astrophysics Data System (ADS)

The Mg/Ca ratio in calcite shells ('tests') of foraminifera is an empirical ocean temperature proxy widely used to interpret palaeoclimates. We explore the distribution and local environment of Mg in foram tests using STXM and NEXAFS spectroscopy to test the fundamental assumptions behind the proxy, and shed light on the mechanisms underpinning this vital oceanographic tool. Throughout the development of the Mg/Ca proxy, it has been assumed that Mg in foraminifera tests substitutes directly into the calcite lattice (1). This assumption is based on XRD analyses of various high-Mg biogenic carbonates, where Mg concentrations are manifest in the shifted position of diffraction peaks (2, 3). The extrapolation of this trend to foraminiferal calcite links the proxy to inorganic precipitation experiments, and provides a theoretical mechanistic framework to understand the link between Mg/Ca and temperature: the substitution of Mg is endothermic, and favoured at higher temperatures. However, the concentration of Mg in most foraminifera (0-10 mmol/mol Mg/Ca) is below the detection limit of XRD methods, and the analogy to inorganic systems has not been explicitly tested. Electron microprobe (4-6), LA-ICP-MS (7) and high-resolution nanoSIMS mapping (Sadekov, unpub.) of foraminifera tests have revealed the presence of high 'trace element' bands running in plane with the test surface, enriched in Mg, Sr, S, organic molecules and other trace elements. This emphasises a key question highlighted by Dodd (1) when the proxy was still in its infancy: how is Mg incorporated into mineral skeletons? By direct substitution into the calcite lattice, interstitially in a separate distinct mineral phase, or associated with organic compounds? We address this fundamental question using scanning transmission X-ray microscopy (STXM) and X-ray absorption spectroscopy at ALS beamline 11.0.2 to examine the distribution and local atomic environment of Mg in two contrasting species of foraminifera. Our data conclusively demonstrate that the Mg in the high- and low-trace element bands in the two different species is incorporated in the same mode. Foraminiferal Mg K-edge spectra are most similar to that of dolomite, where Ca and Mg are interchangeable and both present in octahedral sites. This indicates that Mg directly substitutes for Ca in the calcite test, validating the assumptions underlying the use of the Mg/Ca proxy. The uniformity of Mg environment also sheds light on the drivers of Mg heterogeneity, suggesting that Mg banding is driven by fluctuations in medium chemistry, rather than any change in Mg incorporation mechanism. The ultimate cause of Mg heterogeneity remains an open question, however. 1. J. R. Dodd, J Paleontology, 1313-1329 (1967). 2. K. E. Chave, J Geol 62, 266-283 (1954). 3. J. Titschack, F. Goetz-Neunhoeffer, J. Neubauer, Am Min 96, 1028 (2011). 4. J. Lipps, P. Ribbe, J Paleontology 41, 492-496 (1967). 5. A. Y. Sadekov, S. M. Eggins, P. de Deckker, G3 6, Q12P06 (2005). 6. J. Erez, Rev Min Geochem 54, 115 (2003). 7. A. Y. Sadekov, S. M. Eggins, G. P. Klinkhammer, Y. Rosenthal, Earth Planet Sc Lett 292, 312-324 (2010).

Branson, O.; Redfern, S. A.; Tyliszczak, T.; Sadekov, A.; Langer, G.; Elderfield, H.



IQENS from hydrated lysozyme  

NASA Astrophysics Data System (ADS)

We present quasi-elastic incoherent neutron scattering data on wet lysozyme powders at water contents (grams of water/grams of protein) of h=0.20 and 0.45, corresponding to hydration levels below and above the full monolayer coverage of the protein surface. The data were collected under H2O and D2O hydration condition; using the IRIS spectrometer with a resolution of 11 ?eV (full-width). From spectra for the D2O hydrated sample we obtain information on the protein dynamics. These spectra are used to separate from the H2O hydrated sample the contribution due to the hydration water. We show that at low hydration the dynamics of water is very slow and on the same time scale as that of the protein dynamics, while at higher hydration the water molecules show a faster dynamics. The results support the idea that there are clusters of hydration water.

Wanderlingh, U. N.; Giordano, R.; Kagunya, W. W.



Hydrate-phobic surfaces  

E-print Network

Clathrate hydrate formation and subsequent plugging of deep-sea oil and gas pipelines represent a significant bottleneck for ultra deep-sea production. Current methods for hydrate mitigation focus on injecting thermodynamic ...

Smith, Jonathan David, S.M. Massachusetts Institute of Technology



Nucleation of gas hydrates  

Microsoft Academic Search

The kinetics of nucleation of one-component gas hydrates in aqueous solutions are analyzed. The size of the hydrate nucleus and the work for nucleus formation are determined as functions of the supersaturation ??. Expressions for the stationary rate J of hydrate nucleation are derived. These expressions describe the J(??) dependence for homogeneous nucleation and for heterogeneous nucleation at the solution\\/gas

Dimo Kashchiev; Abbas Firoozabadi



Emission polarization study on quartz and calcite.  

NASA Technical Reports Server (NTRS)

Calculation of the spectral emission polarization of quartz and calcite polished plates for observation angles of 20 and 70 deg by the substitution of complex index of refraction values for each mineral into Fresnel's equations. The emission polarization is shown to be quite wavelength-dependent, demonstrating that selected narrow or medium-width spectral bands exhibit a significantly higher percentage of polarization than a broad spectral band for these two minerals. Field measurements with a broadband infrared radiometer yield polarizations on the order of 2% for a coarse-grained granite rock and beach sand (both quartz-rich). This implies that a more sensitive detector with a selected medium-width filter may be capable of measuring emission polarization accurately enough to make this parameter useful as a remote sensing tool for discrimination among rocks on the basis of texture.

Vincent, R. K.



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 structure. Among these elements, selenium is important because of its high toxicity in natural systems and for human health. In the form of selenite (Se(IV) ), selenium can be incorporated into calcite during growth


Mg isotope fractionation during calcite precipitation: An experimental study  

NASA Astrophysics Data System (ADS)

Experimental precipitations of calcite and other carbonate minerals were performed under various conditions of pH, temperature and solution Mg/Ca to determine the Mg partition coefficient and Mg isotope fractionation. Fifteen experiments were performed at pH ranging from 7.41 ± 0.07 to 8.51 ± 0.39, temperature ranging from 16.2 ± 0.7 to 26.5 ± 0.3 °C and Mg/Casolution ranging from 0.11 to 0.52 mol/mol. The apparent Mg partition coefficient between calcite and solution (DMg) spans a large range of values from 0.018 ± 0.014 to 0.15 ± 0.11 and carbonate Mg isotope fractionation (?26Mg) ranges from -2.53 ± 0.25‰ to -1.33 ± 0.14‰ and does not correlate with either pH or temperature. The range in DMg and ?26Mg suggests non-equilibrium partitioning controlled by the processes of calcite growth, i.e. mixing between calcite grown at equilibrium and fluid inclusions, and entrapment of a surface Mg-rich calcite layer in isotopic equilibrium with the solution. The equilibrium Mg isotope fractionation between inorganic calcite and solution is estimated to be -2.13 ± 0.24‰. Additional Mg elemental and isotopic fractionations are observed to occur during biogenic formation of calcite due to variable removal of Mg by the organisms (high-Mg calcite corals, foraminifera) of seawater Mg from their calcification medium.

Saulnier, Ségolène; Rollion-Bard, Claire; Vigier, Nathalie; Chaussidon, Marc



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.




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



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 ...


Structure and bonding environments at the calcite surface as observed with X-ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED)  

NASA Astrophysics Data System (ADS)

The pure calcite surface was examined using techniques sensitive to the near-surface (XPS and LEED) immediately after fracture in ultra-high vacuum (10 -10 mbar) and then following exposure to various atmospheres and aqueous solutions that were free of trace metals. These spectroscopic techniques allow molecular-level observations that offer the possibility of gaining more insight into geochemical processes elucidated from macroscopic solution studies. Several absolute electron binding energies for the atoms in calcite were redetermined with XPS using the gold dot method. The results are 290.1 ± 0.1 eV for C 1 s, 347.7 and 351.2 ± 0.15 eV for Ca 2 psol3/2 and Ca 2 psol1/2, respectively, and 531.9 ± 0.15 eV for O 1 s. Photoelectron energy shifts from main peak positions suggest that immediately after fracture in ultra-high vacuum, bond reconfiguration leads to the formation of carbide-like bonds between Ca and C at the surface. Calcite that has been exposed to water, even as vapour from the atmosphere, shows binding energy shifts that indicate the presence of S · CO 3H and S · CaOH where S · represents the calcite surface. Surface hydration is also supported, independently, by the XPS peak intensity ratios and is consistent with adsorption theory derived from macroscopic solution studies. The modified oxygen Auger parameter, ?', (using O 1 s and O(KVV)), was found to be 1043.9 eV for all samples of calcite tested, whether powder or cleaved from Iceland Spar, clean or contaminated by adventitious carbon, freshly fractured, or exposed briefly to water, or in the process of dissolution or precipitation. LEED patterns of the {101} cleavage surface of samples that were freshly fractured in air and that were exposed to dissolving or precipitating solutions showed that the top few atomic layers exhibit long range order. Lattice spacings at the surface are statistically identical to those of bulk calcite, though some surface CO 3 groups may be rotated relative to the bulk structure. This work provides direct, molecular-level evidence for the processes of reconfiguration and hydration at the calcite surface. These results provide a basis for future spectroscopic studies of trace metal adsorption on calcite and subsequent solid-solution formation.

Stipp, Susan L.; Hochella, Michael F., Jr.



Use of wastes of the sugar industry as pozzolana in lime-pozzolana binders: Study of the reaction  

SciTech Connect

Mineralogical studies of different wastes of the sugar industry, mainly sugar cane bagasse ash and sugar cane straw ash, have shown that such by-products are likely to be pozzolanic. Their use in lime-pozzolana binders could become an interesting alternative for developing countries. This paper presents a study that was aimed at monitoring the reaction between lime and wastes of the sugar industry having pozzolanic properties by evaluating (1) content of calcium hydroxide, dependent on time; (2) development of the pore structure, dependent on time; (3) study on the reaction products at different stages; and (4) mechanical properties of hardened pastes. The presence of calcium hydroxide was confirmed by x-ray diffraction analysis and thermogravimetric analysis of powder from samples of hydrated lime-pozzolana pastes. The reaction products in hydrated pastes were observed in a scanning electron microscope, and the pore structure was assessed using a mercury intrusion porosimeter. The results of the study show that sugar cane bagasse ash does not act like a reactive pozzolana, mainly due to the presence of unburned material and carbon, whereas sugar cane straw ash shows good pozzolanic activity comparable to that of rice husk ash.

Hernandez, J.F.M. [Univ. Central de las Villas, Santa Clara (Cuba); Middendorf, B.; Gehrke, M.; Budelmann, H. [Univ. of Kassel (Germany). Dept. of Structural Materials



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



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




Nucleation of gas hydrates  

NASA Astrophysics Data System (ADS)

The kinetics of nucleation of one-component gas hydrates in aqueous solutions are analyzed. The size of the hydrate nucleus and the work for nucleus formation are determined as functions of the supersaturation ? ?. Expressions for the stationary rate J of hydrate nucleation are derived. These expressions describe the J(? ?) dependence for homogeneous nucleation and for heterogeneous nucleation at the solution/gas interface or on solid substrates and nucleation-active microparticles in the solution. The results are applied to nucleation of methane hydrate in solutions containing additives that may act as kinetic inhibitors of the process.

Kashchiev, Dimo; Firoozabadi, Abbas



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.



Strontium Incorporation Into Calcite Generated by Bacterial Ureolysis  

NASA Astrophysics Data System (ADS)

Strontium incorporation into calcite generated by bacterial ureolytic activity was investigated as part of a larger effort to evaluate the use of in situ urea hydrolysis for accelerating co-precipitation of trace metals and radionuclides in contaminated aquifers. 90Sr, a uranium fission product with a half-life of 29 years, is a significant subsurface contaminant at several Department of Energy facilities and could be immobilized using this remediation strategy. Experiments were conducted in a medium designed to simulate the groundwater of the Snake River Plain Aquifer in eastern Idaho, amended with strontium. Initially the solution was undersaturated with respect to calcite. As a model ureolytic organism, we used Bacillus pasteurii, a well-characterized bacterium known for high urease activity and previously shown to induce calcite precipitation in urea-amended medium. To gain information on the effect of the bacterial surfaces, we also looked at precipitation in the presence of a bacterial species that did not hydrolyze urea, as well as in the absence of bacteria. In the absence of bacterial ureolysis, carbonate precipitation was induced by addition of ammonium carbonate. All products were identified as calcite by X-ray diffraction. Strontium uptake was observed in all cases, but was greatest in the system including bacterial ureolysis. Sputter depth element profiling by time-of-flight secondary ion mass spectrometry (TOF-SIMS) confirmed this finding, showing highest Sr:Ca ratios in the bacterially generated calcite throughout the depth (~350 nm) investigated. Environmental Scanning Electron Microscopy (ESEM) of the solids revealed regular crystals containing the outlines of embedded or entombed bacterial cells, suggesting that calcite precipitated directly on the cell surfaces when present. Analysis by X-ray Absorption Near Edge Spectroscopy (XANES) indicated that in both the biotically and abiotically generated calcites the Sr was incorporated into the calcite lattice structure, rather than forming strontium carbonate. These findings are encouraging with respect to long term containment and stabilization of strontium by the proposed remediation strategy.

Fujita, Y.; Ingram, J. A.; Cortez, M. M.; Redden, G. D.; Smith, R. W.



Distinguishing between natural and recarbonated calcite in oil shale ashes  

Microsoft Academic Search

Oil shale ashes from the PAMA demonstration power plant in the Negev region of Israel are produced by fluidized bed combustion\\u000a (700–850C) under short residence time. The FED is organic-rich calcareous raw material rich in carbonate rather than clays.\\u000a Thus it is important to ascertain whether the calcite in the ashes is original natural calcite from the raw material or

S. Shoval; O. Yofe; Y. Nathan



Gas hydrate inhibition  

Microsoft Academic Search

This patent describes a process for inhibiting gas hydrate formation in the production fluid of a well, connected facilities and pipelines of the well comprising injecting into the well inhibitor comprising a carrier and a polycyclicpolyetherpolyol. This patent also describes a process for shutting-in a well having a fluid therein which is susceptible to the formation of gas hydrates. It

A. H. Hale; A. K. R. Dewan; G. C. Blytas



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.



Gas hydrate inhibition  

SciTech Connect

This patent describes a process for inhibiting gas hydrate formation in the production fluid of a well, connected facilities and pipelines of the well comprising injecting into the well inhibitor comprising a carrier and a polycyclicpolyetherpolyol. This patent also describes a process for shutting-in a well having a fluid therein which is susceptible to the formation of gas hydrates. It comprises preparing a gas hydrate inhibitor by admixing an alcohol with a carrier, the carrier and the alcohol and the quantities thereof being selected to be compatible with the well and effective to prevent the formation of gas hydrates in the well fluid; selecting an appropriate location, depending upon the type of well being shut-in, and injecting the gas hydrate inhibitor into the well at the location; and shutting-in the well.

Hale, A.H.; Dewan, A.K.R.; Blytas, G.C.



Using the new lime recommendations in  

E-print Network

of reagent grade CaCO3 added to each soil (3x) 2. Soil and CaCO3 were thoroughly mixed 3. Water added 4. SoilUsing the new lime recommendations in Wisconsin John Peters and Carrie Laboski Soil Science SMP & Woodruff buffers SMP vs. LR (r = 0.949) Woodruff vs. LR (r=0.818) pH x OM vs. LR (r=0

Balser, Teri C.


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



Economics of Variable Rate Lime in Indiana  

Microsoft Academic Search

In Indiana, variable rate application (VRA) of lime is often considered a good place to start site-specific management (SSM). This is because soil pH is one of the most variable of manageable soil characteristics in the state, the availability of essential nutrients is closely related to soil pH, and because spreaders can be retrofitted relatively inexpensively to do VRA. The

R. Bongiovanni; J. Lowenberg-Deboer



The relative merits of dolomitic and calcitic limestone in detoxifying and revegetating acidic, nickel- and copper-contaminated soils in the Sudbury mining and smelting region of Canada  

SciTech Connect

Soils in the Sudbury mining and smelting region have been rendered phytotoxic and barren by acidification and Particulate metal contamination, but can be detoxified revegetated by the surface application of an growth is better on soil treated ground limestone. On certain barren sites, plant growth is better on soil treated with dolomitic limestone than with calcitic limestone and greenhouse experiments using mung beans (Vigna radiata) have shown superior root and shoot growth on certain contaminated soils when the limestone is dolomitic rather than calcitic. Results of experiments with species used in revegetation (Agrostis gigantea and Lotus corniculatus) suggest that leguminous species are more sensitive to Ca:Mg ratio than grasses, that the plant response to this ratio is greater at lowering liming levels, and that the response is more marked on more toxic soils. The effects of calcium:magnesium ratio of the limestone used in revegetating acidic, metal-contaminated soils are clearly complex, interactive and difficult to interpret. Further studies are needed, but meanwhile it is recommended that the practice of using dolomitic limestone to detoxify barren Sudbury soils be continued, since there is a risk of induced magnesium deficiency at certain sites when calcitic limestone is used.

McHale, D.; Winterhalder, K. [Laurentian Univ., Sudbury, Ontario (Canada)



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



Here's butane hydrates equilibria  

SciTech Connect

In 1961 McLeod and Campbell studied hydrates formation for binary mixtures of methane with ethane through butane at pressures up to 10,000 psia. Their data showed that butane lowered the pressure of hydrate formation for methane up to pressures ranging from 1,500 to 2,000 psia. At pressures above this range methane-n-butane mixtures generally followed the curve for pure methane or were slightly above it. McLeod and Campbell conclude that the crystal lattice is deformed at higher pressures (above 6,000 psia) and that hydrate composition on a water-free basis is the same as the gas.

Peettman, F.H.



Methane Hydrates: Chapter 8  

USGS Publications Warehouse

Gas hydrate is a solid, naturally occurring substance consisting predominantly of methane gas and water. Recent scientific drilling programs in Japan, Canada, the United States, Korea and India have demonstrated that gas hydrate occurs broadly and in a variety of forms in shallow sediments of the outer continental shelves and in Arctic regions. Field, laboratory and numerical modelling studies conducted to date indicate that gas can be extracted from gas hydrates with existing production technologies, particularly for those deposits in which the gas hydrate exists as pore-filling grains at high saturation in sand-rich reservoirs. A series of regional resource assessments indicate that substantial volumes of gas hydrate likely exist in sand-rich deposits. Recent field programs in Japan, Canada and in the United States have demonstrated the technical viability of methane extraction from gas-hydrate-bearing sand reservoirs and have investigated a range of potential production scenarios. At present, basic reservoir depressurisation shows the greatest promise and can be conducted using primarily standard industry equipment and procedures. Depressurisation is expected to be the foundation of future production systems; additional processes, such as thermal stimulation, mechanical stimulation and chemical injection, will likely also be integrated as dictated by local geological and other conditions. An innovative carbon dioxide and methane swapping technology is also being studied as a method to produce gas from select gas hydrate deposits. In addition, substantial additional volumes of gas hydrate have been found in dense arrays of grain-displacing veins and nodules in fine-grained, clay-dominated sediments; however, to date, no field tests, and very limited numerical modelling, have been conducted with regard to the production potential of such accumulations. Work remains to further refine: (1) the marine resource volumes within potential accumulations that can be produced through exploratory drilling programs; (2) the tools for gas hydrate detection and characterisation from remote sensing data; (3) the details of gas hydrate reservoir production behaviour through additional, well-monitored and longer duration field tests and (4) the understanding of the potential environmental impacts of gas hydrate resource development. The results of future production tests, in the context of varying market and energy supply conditions around the globe, will be the key to determine the ultimate timing and scale of the commercial production of natural gas from gas hydrates.

Boswell, Ray; Yamamoto, Koji;Lee, Sung-Rock; Collett, Timothy S.; Kumar, Pushpendra; Dallimore, Scott



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))



Liming of acidified waters: issues and research - a report of the International Liming Workshop  

USGS Publications Warehouse

Acidic deposition is a problem of significant national and international concern. It is strongly suspected that acidic deposition has adversely affected aquatic resources in Scandinavia and North America. While substantial resources are being devoted to understanding the causative factors associated with surface water acidification, much less research is being conducted on mitigative strategies. Mitigative techniques involving liming may be useful for short-term protection of specific component of aquatic communities or for renovation of seriously impacted aquatic ecosystems. The selection of effective liming strategies is based on an integrated understanding of the following key factors: biological systems, water chemistry, sediment chemistry, hydrology, and watershed characteristics, effectiveness of neutralizing materials, and application techniques. Research in Scandinavia, Canada, and the U.S. has led to a partial understanding of some of the key factors for successful neutralization of surface waters (Bengtsson, 1982; Fraser and Britt, 1982). However, conflicting results of liming operations and experiments have been reported. (Fraser et al., 1982; Fraser and Britt, 1982; Sverdrup and Bjerle, 1982). Additional research is required to improve the ability of scientists and resource managers to select effective liming strategies. An International Liming workshop was convened during 19-25 September 1982 at the University of Washington's Friday Harbor Laboratories. The major objective of this workshop were: - To identify the most critical deficiencies in the scientific understanding of liming techniques and their long-term consequences. - To develop and document a research strategy to address information deficiencies that are pertinent to the protection or renovation of acidic surface waters in the United States. The participants who contributed to this workshop are listed in Table 1.

Schreiber, R. Kent



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.



Uranyl Incorporation in Organic-Bearing Soil Calcite  

NASA Astrophysics Data System (ADS)

Phosphor imaging and fission track maps reveal a close correlation between uranium and organic-rich calcite that lines roots in an ancient caliche soil. Concordant U-Pb ages show that this uranium has not been mobilized since the soil calcite formed 298 ñ 1 Ma ago. Luminescence spectroscopic analysis of the organic-rich calcite demonstrates that uranium is present in the oxidized state. More or less comparable luminescence spectra were collected using a CW lamp at room temperature and at liquid nitrogen (LN2) temperature. Spectra for inorganic U species are generally greatly enhanced at liquid nitrogen temperatures over room temperature and thus the similarity may suggest that the U is bound to organic matter. UV-excitation Raman spectroscopy of the calcite samples reveals a vibrational signature that is, in addition to the calcite peaks, essentially identical to that of sodium humate, acquired under similar conditions and consistent with those reported previously for humate substances. Since these spectra are dominated by the carbon backbone structure, the persistence of a carbon backbone structure is noted, but persistence of the ligating functional groups cannot be proven directly. We suggest that this sample records a snapshot of the process of uranium complexation with organic acids in natural systems. In our model organic acids with active functional groups that complex uranyl are sorbed onto the calcite surface and then incorporated as humate into the mineral with further calcite precipitation. Further, the uranyl complex is preserved through near-surface reducing conditions and temperatures to the conditions associated with 2700 meters burial depths. These combined observations suggest that the encapsulating calcite not only prevents reduction of uranium in the surface environment, but also inhibits the breakdown of the humate with burial. Due to the long time scale of immobilization of uranium, evidenced by the age of the calcite, this study has profound implications for understanding sampling for U-series and U-Pb dating of carbonates as well as for developing strategies for nuclear waste management. This study also has implications for any other deposits where uranium is associated with organic matter.

Rasbury, E.; Tait, C.; Donohoe, R. J.



Calcite veins in northeastern Puente Hills, southern California  

SciTech Connect

Calcite vein fillings are locally exposed in the northeastern Puente Hills, 2 mi southwest of Pomona on the northeast margin of the Los Angeles basin. They occur within northeast- and northwest-trending faults in the middle Miocene Glendora Volcanics and in the Soquel Member of the upper Miocene Puente Formation. The veins range in width from 1 in. to 15 ft, and several can be traced hundreds of feet. The veins exhibit complex banded and brecciated textures and emit a strong hydrocarbon odor when broken. The carbon isotopic composition is light (delta/sup 13/C = -22.1 to -45.6 per thousand PDB). The range of the oxygen isotopic composition (delta/sup 18/O = +21.3 to +31.1 per thousand SMOW) generally compares with those reported for diagenetic carbonates in marine Miocene shales of California and Oregon. Dissolution of unusual local Soquel marine carbonates, now primarily dolomite, and diagenetic cements seems to be the most likely source of the calcite that was deposited incrementally along faults to form the calcite-filled veins. The extremely depleted carbon isotope values represent the addition of carbon derived from the chemical and/or biological oxidation of methane; a petroleum source of the methane is suggested by the presence of solid hydrocarbon inclusions in the vein calcite. The formation temperature of the vein calcite was probably below hydrothermal.

Spira, M.O.; Zenger, D.H.



Aragonite and magnesian calcite fluxes to the deep Sargasso Sea  

NASA Astrophysics Data System (ADS)

Aragonite and magnesium calcite fluxes were estimated from a 14-month series of sediment trap samples from depths of 500, 1500 and 3200 m in the Sargasso Sea. No significant difference with depth was observed in fluxes of either carbonate phase. At 3200 m, the mean aragonite flux was 2.8 mg m -2 day -1, or 13% of the total CaCO 3 flux. At all depths pteropods were the major source of aragonite, contributing more carbonate than heteropods by a factor of 3-24. Most of the pteropod aragonite occurred in the size fraction >0.5 mm. At 3200 m, more than half of the pteropod mass flux in the size fraction >0.5 mm comprised four species: Styliola subula, Clio pyramidata, Limacina inflata and Cuvierina columnella. The mean magnesian calcite flux at 3200 m was 1.7 mg m -2 day -1, or 8% of the total CaCO 3 flux. The majority of the magnesian calcite (9-12 mole % MgCO 3) occurred in the finest size fraction. <37 ?m. Evidence suggests that bryozoans attached to floating Sargassum are the source of this magnesian calcite. The combined fluxes of aragonite and magnesian calcite accounted for 21-25% of the mean annual CaCO 3 flux to 1500 and 3200 m.

Fabry, Victoria J.; Deuser, Werner G.



Effects of liming on aquatic macrophytes, with emphasis on Scandinavia  

Microsoft Academic Search

The effects of liming on soft-water aquatic macrophytes are reviewed, based on data from the many limed lakes and rivers in Sweden and Norway. Liming usually leads to a re-establishment of acidification-sensitive species such as Fontinalis spp., Myriophyllum alterniflorum and Potamogeton spp. Most sensitive species have a critical level at pH ca. 5.5, and are believed to depend on availability

Tor Erik Brandrud



Hydrate morphology: Physical properties of sands with patchy hydrate saturation  

USGS Publications Warehouse

The physical properties of gas hydrate-bearing sediments depend on the volume fraction and spatial distribution of the hydrate phase. The host sediment grain size and the state of effective stress determine the hydrate morphology in sediments; this information can be used to significantly constrain estimates of the physical properties of hydrate-bearing sediments, including the coarse-grained sands subjected to high effective stress that are of interest as potential energy resources. Reported data and physical analyses suggest hydrate-bearing sands contain a heterogeneous, patchy hydrate distribution, whereby zones with 100% pore-space hydrate saturation are embedded in hydrate-free sand. Accounting for patchy rather than homogeneous hydrate distribution yields more tightly constrained estimates of physical properties in hydrate-bearing sands and captures observed physical-property dependencies on hydrate saturation. For example, numerical modeling results of sands with patchy saturation agree with experimental observation, showing a transition in stiffness starting near the series bound at low hydrate saturations but moving toward the parallel bound at high hydrate saturations. The hydrate-patch size itself impacts the physical properties of hydrate-bearing sediments; for example, at constant hydrate saturation, we find that conductivity (electrical, hydraulic and thermal) increases as the number of hydrate-saturated patches increases. This increase reflects the larger number of conductive flow paths that exist in specimens with many small hydrate-saturated patches in comparison to specimens in which a few large hydrate saturated patches can block flow over a significant cross-section of the specimen.

Dai, S.; Santamarina, J. C.; Waite, William F.; Kneafsey, T. J.



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: [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)



Experimental investigation of sediment control on the saturation level of gas hydrate in sediments  

NASA Astrophysics Data System (ADS)

Except for those occurring at the seafloor, most natural gas hydrates form in sediments and are subject to the influence of the sediment. Investigations on natural gas hydrate have found that the saturation level of gas hydrate in sediments is closely related to the sediment type: comparatively enriched in coarse sediments such as sands but poorly saturated in fine sediments such as clay. However, due to the limitation of the current geological and geophysical investigations and the rarity of the recovery of intact hydrate samples, the knowledge about sediment control on hydrate saturation in sediments is still limited, and the mechanism is not yet understood. This research investigated the possible factors involved in sediment control on hydrate saturation using an experimental approach. The experiments were carried out with both natural and artificial sediments. The natural sediments were recovered from gas hydrate reservoirs in the Nankai Trough, offshore Japan, Cascadia, offshore Vancouver Island, K-G basin, offshore India, and offshore Andaman Island. The artificial sediments were prepared with quartz powder, a representative of silicates and aluminosilicates, kaolinite and Na-montmorillonite, representatives of clay minerals, and calcite, representative of carbonate minerals. Methane hydrate was synthesized in the artificial sediments under conditions simulating the reservoir of natural gas hydrate, and its saturation levels were determined from the gas amount released from a known volume of sediment. The results indicate that particle size and mineral composition are the two main factors affecting hydrate saturation in sediments. In the range from 20 to 250 ?m, the degree of conversion of water into hydrate increases dramatically with increase in particle size, from 3% to 82%, corresponding to a pore saturation from 4% to ~ 100%. Studies also found that the sorting effect of sediment particles can also play a certain role in affecting hydrate saturation, although not as significantly as particle size. With increasing clay content, hydrate saturation decreased dramatically. When the clay content is over 40%, the degree of pore water converted to hydrate is only about 2%, corresponding to hydrate saturation lower than 3%. The NMR proton relaxation times of water confined in silica sands, show a logarithmic relationship with particle size, and it was found that the samples with higher hydrate saturation are those with longer proton relaxation times.

Lu, H.; Ukita, T.; Noguchi, S.; Moudrakovski, I.; Shimada, T.; Ripmeester, J.; Ratcliffe, C.



Chemistry and kinetics of calcite dissolution in passive treatment systems  

SciTech Connect

Reaction of calcite with AMD is a key remediation process in anoxic limestone drains, (ALD), SAPS, and many wetlands, but predictions of effluent quality are currently based mainly on rules of thumb and prior experience. The PHREEQC computer program can be used to calculate the progress of this and similar reactions, and aid in understanding, design and evaluation of these systems. At pH values less than 5, calcite dissolution rates are strongly influenced by transport parameters such as flow velocity. Estimated calcite dissolution rates from ALD's and column experiments indicate little change in rate with pH, in contrast to published data for well stirred lab experiments. The dissolution rate is affected by concentration of SO{sub 4}, Fe, Al, Ca, P, and other trace solutes. The optimum contact time and sizing of ALD's will be dependent on these and possibly other parameters. Additional experiments are needed to evaluate these dependencies.

Rose, A.W.



Arsenic removal by gypsum and calcite in lacustrine environments  

NASA Astrophysics Data System (ADS)

After the closure of the coal mining activities in the Massif Central range, France, several lakes were formed as a consequence of mine collapse. The old mines, located at the bottom of lakes, are certified sources of As and heavy metals. During a time period of one year, we have monitored the water column of one of these lakes in order to identify geochemical process controlling water quality dominated by precipitation of gypsum and calcite. We have therefore performed laboratory experiments to study how As is trapped during calcite and gypsurn precipitation in presence of As III and V respectively.

Roman-Ross, G.; Charlet, L.; Cuello, G. J.; Tisserand, D.



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.



Magnesium stable isotope fractionation in marine biogenic calcite and aragonite  

NASA Astrophysics Data System (ADS)

This survey of magnesium stable isotope compositions in marine biogenic aragonite and calcite includes samples from corals, sclerosponges, benthic porcelaneous and planktonic perforate foraminifera, coccolith oozes, red algae, and an echinoid and brachiopod test. The analyses were carried out using MC-ICP-MS with an external repeatability of ±0.22‰ (2SD for ? 26Mg; n = 37), obtained from a coral reference sample (JCp-1). Magnesium isotope fractionation in calcitic corals and sclerosponges agrees with published data for calcitic speleothems with an average ? 26Mg calcite-seawater = -2.6 ± 0.3‰ that appears to be weakly related to temperature. With one exception ( Vaceletia spp.), aragonitic corals and sclerosponges also display uniform Mg isotope fractionations relative to seawater with ? 26Mg biogenic aragonite-seawater = -0.9 ± 0.2. Magnesium isotopes in high-Mg calcites from red algae, echinoids and perhaps some porcelaneous foraminifera as well as in all low-Mg calcites (perforate foraminifera, coccoliths and brachiopods) display significant biological influences. For planktonic foraminifera, the Mg isotope data is consistent with the fixation of Mg by organic material under equilibrium conditions, but appears to be inconsistent with Mg removal from vacuoles. Our preferred model, however, suggests that planktonic foraminifera synthesize biomolecules that increase the energetic barrier for Mg incorporation. In this model, the need to remove large quantities of Mg from vacuole solutions is avoided. For the high-Mg calcites from echinoids, the precipitation of amorphous calcium carbonate may be responsible for their weaker Mg isotope fractionation. Disregarding superimposed biological effects, it appears that cation light isotope enrichments in CaCO 3 principally result from a chemical kinetic isotope effect, related to the incorporation of cations at kink sites. In this model, the systematics of cation isotope fractionations in CaCO 3 relate to the activation energy required for cation incorporation, which probably reflects the dehydration of the cation and the crystal surface and bond formation at the incorporation site. This kinetic incorporation model predicts (i) no intrinsic dependence on growth rate, unless significant back reaction upon slow growth reduces the isotope fractionation towards that characteristic for equilibrium isotope partitioning (this may be observed for Ca isotopes in calcites), (ii) a small decrease of isotope fractionation with increasing temperature that may be amplified if higher temperatures promote back reaction and (iii) a sensitivity to changes in the activation barrier caused by additives such as anions or biomolecules or by the initial formation of amorphous CaCO 3.

Wombacher, F.; Eisenhauer, A.; Böhm, F.; Gussone, N.; Regenberg, M.; Dullo, W.-Chr.; Rüggeberg, A.




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...


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.



Sulfate attack in lime-treated subbases  

SciTech Connect

Sulfate-induced heave or buckling in pavements is the phenomenon that occurs when the calcium in various lime-based stabilizers combines with the alumina and sulfate present in clay to form calcium sulfoaluminate, or ettringite. Ettringite, a crystal, can grow between clay particles, pushing them apart and causing swelling in the soil. When this happens in pavement subbases, the resulting heaving may cause the pavement to rupture and fail, sometimes in a dramatic way. In this paper the authors examine the mechanism of sulfate attack, review some of the work done on this problem, and present some examples of pavement failures.

Day, D.C.; Salami, M.R. [North Carolina A and T State Univ., Greensboro, NC (United States). Dept. of Civil Engineering; Rollings, R.S. [Army Engineering Waterways Experiment Station, Vicksburg, MS (United States). Pavement Div.



Element partitioning in calcite as a function of solution flow rate: a study on vein calcites from the Harz Mountains  

NASA Astrophysics Data System (ADS)

A semi-empirical treatment of isothermal element partitioning caused by flow rate-dependent calcite growth from hydrothermal solutions yields element/Ca ratios that are qualitatively similar to those observed in calcite bands of the Pb-Zn banded ores from the Harz Mountains, Germany. The comparison of the calculations with the analytical results suggests that flow rates varied between episodes of calcite precipitation as well as during formation of individual bands. Based on a flow rate-dependent element partition coefficient, changing element/Ca ratios in precipitates from a hydrotherm are therefore not necessarily indicative of changing compositions of the fluid. The variations in element/Ca ratios to be envisaged could be as much as a factor of three.

Möller, P.; Lüders, V.; Schröder, J.; Luck, J.



Mitigation of acid deposition: Liming of surface waters. Final report  

SciTech Connect

In recent years acid deposition has become a serious concern internationally. Scientific literature has documented the acidification of numerous lakes and streams in North America and Scandinavia resulting in the depletion or total loss of fisheries and other aquatic biota. Liming represents the only common corrective practice aimed specifically at remediating an affected acid receptor. This report reviews a range of liming technologies and liming materials, as well as the effect of surface-water liming on water quality and aquatic biota. As background to the liming discussion, the hydrologic cycle and the factors that make surface waters sensitive to acid deposition are also discussed. Finally, a brief review of some of the liming projects that have been conducted, or are currently in operation is presented, giving special emphasis to mitigation efforts in Maryland. Liming has been effectively used to counteract surface-water acidification in parts of Scandinavia, Canada, and the U.S. To date, liming has generally been shown to improve physical and chemical conditions and enhance the biological recovery of aquatic ecosystems affected by acidification.

Bartoshesky, J.; Price, R.; DeMuro, J.



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)



Microencapsulation of Kaffir Lime Oil and Its Functional Properties  

Microsoft Academic Search

This paper describes the effects of spray drying temperature and wall materials on functional properties of kaffir lime oil microcapsules. The effects of spray drying were studied at inlet air temperatures at 160, 180, and 200°C. Two coating materials (konjac glucomannan and gum arabic) were employed in this study. The results indicate that kaffir lime oil had antibacterial activity against

J. Adamiec; C. Borompichaichartkul; G. Srzednicki; W. Panket; S. Piriyapunsakul; J. Zhao



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



Calcite veins in northeastern Puente Hills, southern California  

Microsoft Academic Search

Calcite vein fillings are locally exposed in the northeastern Puente Hills, 2 mi southwest of Pomona on the northeast margin of the Los Angeles basin. They occur within northeast- and northwest-trending faults in the middle Miocene Glendora Volcanics and in the Soquel Member of the upper Miocene Puente Formation. The veins range in width from 1 in. to 15 ft,

M. O. Spira; D. H. Zenger



Influence of Bacillus subtilis Cell Walls and EDTA on Calcite  

E-print Network

Influence of Bacillus subtilis Cell Walls and EDTA on Calcite Dissolution Rates and Crystal Surface and the Gram-positive cell walls of Bacillus subtilis on the dissolution rates and development of morphological that the presence of metabolically inactive B. subtilis does not affect the dissolution rates significantly

Long, Bernard


Thermoluminescence measurements of a calcite shell for dating  

NASA Astrophysics Data System (ADS)

For thermoluminescence (TL)-dating of fossil calcite shells of Pecten, a new procedure is introduced. A supralinear function fitted to the 'first-glow growth' of the fossil shell makes it possible to evaluate the natural dose. From the natural doses obtained, we can estimate TL ages of fossil shells from about 5 × 10 5 years ago to more recently.

Ninagawa, Kiyotaka; Takahashi, Nobusuke; Wada, Tomonori; Yamamoto, Isao; Yamashita, Nobuhiko; Yamashita, Yoshihiko


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.



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.



Wetland vegetation responses to liming an Adirondack watershed  

SciTech Connect

Watershed liming as a long-term mitigation strategy to neutralize lake acidity, from increasing acid deposition, was initiated in North America at Woods Lake in the west central Adirondack region of New York. In October 1989, a dose of 10 MT lime (83.5% CaCO[sub 3]) ha[sup [minus]1] was aerially applied to 48% of the watershed. The wetlands adjacent to Woods Lake showed two distinct community types: one dominated by Chamaedaphne calyculata, and one dominated by graminoids and other herbaceous species. Within two years, liming did not alter the structure of either community type, and changed the cover or frequency of only 6 of 64 individual taxa. Most of these changes occurred in the herbaceous community type. The only strong positive response to liming was a nearly threefold increase in cover of the rhizomatous sedge Cladium mariscoides. The cover of Carex interior and Sphagnum spp. benefited from lime addition, while cover of Drosera intermedia and Muhlenbergia uniflora, and frequency of Hypericum canadense responded negatively to lime. Liming influenced the competitive release of only three taxa, all forbs with small growth forms. The tissue chemistry of foliage and twigs of Myrica gale, Chamaedaphne calyculata, and Carex stricta in the Chamaedaphne calyculata community type clearly illustrated species-specific patterns of nutrient accumulation and allocation both before and after liming. Concentrations of 17 of 20 elements responded to liming, although the responses varied among species and plant parts. Carex foliage was least responsive to liming, and Chamaedaphne twigs were most responsive. Elemental changes in plant tissues will be reflected in litter and many influence long-term nutrient dynamics in the wetland community.

Mackun, I.R.



Potential of gas hydrates outlined  

SciTech Connect

This paper reports on large volumes of natural gas, composed mainly of methane, which can occur in sediments as gas hydrates. These substances are solids, composed of rigid cages of water molecules that trap molecules of gas. At standard conditions (STP), 1 cu ft of methane hydrate will contain as much as 180 cu ft of methane; because of this large gas storage capacity, gas hydrates may represent an important source of natural gas. Cold surface temperatures at high latitudes are conducive to the development of onshore permafrost and gas hydrate in the subsurface. The combined information from Arctic gas hydrate studies shows that in permafrost regions gas hydrates may exist at subsurface depths ranging from about 130-2,000 m. The amount of gas sequestered in gas hydrates is probably enormous, but estimates are highly speculative. For example, worldwide estimates of the amount of gas within continental gas hydrates range from 500 trillion to 1,200,000 trillion cu ft.

Collett, T.S. (Geological Survey, Lakewood, CO (United States))



Gas Hydrates: It's A Gas!  

NSDL National Science Digital Library

In this activity, students will investigate the occurrence of gas hydrates on the ocean floor. They will discover the importance of carbon, where carbon is stored on Earth, and that the largest reservoir of carbon is gas hydrates. Students will discover that Earth's climate changes, and how the greenhouse effect works. They will also learn about the potential of hydrates as a major new energy resource and explore the conditions under which hydrates form.


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 formation of calcium carbonate minerals (e.g. calcite) occurs in a wide range of natural envi- ronments (e

Benning, Liane G.


Calcite crystal growth orientation: implications for trace metal uptake into coccoliths  

E-print Network

Calcite crystal growth orientation: implications for trace metal uptake into coccoliths V. E. PAYNE inducing specific orientations of calcite crystal growth can cause the enrichment of cations larger than Ca growth on obtuse kink sites, causing calcite crystals elongated along their c-axes to form in a mechanism

Benning, Liane G.


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


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



Fluid mediated transformation of aragonitic cuttlebone to calcite  

NASA Astrophysics Data System (ADS)

The aragonite to calcite transition has been studied extensively over the years because of its wide spectra of applications and of its significant geochemical interest. While studies of kinetics (e.g. Topor et al., 1981), thermodynamics (e.g. Wolf et al., 1996) and behavior of ions such as Sr and Mg (e.g. Yoshioka et al., 1986) have been made there are still unanswered questions regarding this reaction especially in the cases where the effects of fluid composition are considered. It is well known that when heated in air, aragonite transforms by a solid state reaction to calcite. The aragonite cuttlebone of the sepia officinalis that was used for our experiments undergoes a phase transition at ~370-390Ë? C, measured by in situ heating experiments in a Philips X'pert X-ray powder diffractometer equipped with a HTK 1200 High temperature oven. Successive X-ray scans were taken at isothermal temperatures at 200C intervals. A similar temperature range was found by Vongsavat et al. 2006, who studied this transition in Acropora corals. It is possible however to promote this transition at considerably lower temperatures by means of a fluid mediated reaction where the replacement takes place by a dissolution-precipitation mechanism (Putnis & Putnis, 2007). We have successfully carried out hydrothermal experiments where cuttlebone has been converted to calcite at 200Ë? C. Using the PhreeqC program we calculated the required composition of a solution that would be undersaturated with respect to aragonite and saturated with respect to calcite leading to dissolution of the aragonite and to a consequent precipitation of the new calcite phase, similar to the experiments described in an earlier study (Perdikouri et al, 2008). This reaction is not pseudomorphic and results in the destruction of the morphology, presumably due to the molar volume increase. A total transformation of the cuttlebone produced a fine calcite powder. The cuttlebone exhibits a unique microstructure, made up of interconnected chambers. The aragonite grown during biomineralization of the cuttlebone is interlaced with a β-chitin organic phase that provides the framework for the morphology that is observed. Experiments carried out with the same constant conditions but for different periods of time have revealed the evolution of the transformation to calcite. At shorter reaction times the product was made up of calcite powder and of well preserved aragonite septa, as was confirmed by powder X-ray diffraction. In other words, the vertical pillars appear to react at faster rates than the horizontal septa. It has been reported by Florek et al. 2008 that the septa contain higher quantities of β-chitin. The aim of this study is the investigation of these observations and the determination of the effect of the organic component on the kinetics of the aragonite to calcite transformation. Florek M., Fornal E., Gómez-Romero P., Zieba E., Paszkowicz W., Lekki J.,Nowak J., Kuczumow A. Materials Science and Engineering C, In Press (2008) Perdikouri C., Kasioptas A., Putnis C.V., Putnis A. Mineralogical Magazine 72, 111-114 (2008) Putnis A., Putnis C.V. Solid State Chemistry 180, 1783-1786 (2007) Topor N. D., Tolokonnikova L. I., Kadenatsi B. M. Journal of Thermal Analysis 20, 169-174 (1981) Vongsavat V., Winotai P., Meejoo S. Nuclear Instruments and Methods in Physics Research B 243, 167-173 (2006) Wolf G., Lerchner J., Schmidt H., Gamsjäger H., Königsberger E., Schmidt P. Journal of Thermal Analysis 46, 353-359 (1996) Yoshioka S., Ohde S., Kitano Y., Kanamori N. Marine Chemistry 18, 35-48 (1986)

Perdikouri, C.; Kasioptas, A.; Putnis, A.



Stabilit de l'association fayalite + calcite dans les formations ferrifres mtamorphoses ; l'exemple des minralisations en  

E-print Network

minerals of the ore bodies are magnetite, hematite, siderite, quartz, calcite, fayalite, hedenbergite and garnet, resulting from the metamorphism of siderite + calcite + quartz rocks with variable proportions

Boyer, Edmond


Enhancement of gas desulfurization with hydrated lime at low temperature by the presence of NOâ  

Microsoft Academic Search

The effect of NOâ on the desulfurization reaction of simulated flue gas by Ca(OH)â was investigated in a fixed-bed reactor at 333-353 K and at relative humidities (RHs) in the range of 30%-70%. NOâ was determined to be a promoter for SOâ uptake, because its retention can be increased up to 200%. The effect of NOâ and Oâ concentration on

M. Bausach; M. Pera-Titus; F. Cunill; J. F. Izquierdo; J. Tejero; M. Iborra



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.



[Retention of selenium volatility using lime in coal combustion].  


For understanding the volatility of selenium, the effect of the contents of exchangeable cations of coal on it, and the retention of selenium using CaO in coal combustion, the sequential chemistry extraction, the fixed bed and circulating fluidized bed (CFB) combustion, X-ray diffraction (XRD) and atomic fluorescence spectrometry (AFS) were undertaken. The results showed that the volatility of selenium was more than 97% in coal combustion at 815 degrees C, and the volatility of selenium was affected by the content of exchangeable cations of coal in low-middle temperature. It was identified that lime can restrain the volatility of selenium. In fixed bed combustion of coal, the retention rates of selenium volatility were between 11.6% and 50.7% using lime. In circulating fluidized bed combustion of coal, partitioning of selenium changed very much in ash of different size fraction between without lime and with lime. Comparing with combustion without lime, the content of selenium in ash from chimney was less than fourth times and that in leaching water from chimney decreased by two orders of magnitude using lime. Retention of selenium volatility using lime is so effective in coal combustion, especially in CFB combustion of coal. PMID:11507891

Zhang, J; Ren, D; Zhong, Q; Xu, F; Zhang, Y; Yin, J



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.



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.



Microbial activity affected by lime in a long-term no-till soil  

Microsoft Academic Search

Under conventional farming practices, lime is usually applied on the soil surface and then incorporated into the soil to correct soil acidity. In no-till (NT) systems, where lime is surface applied or only incorporated into the soil to very shallow depth, lime will likely not move to where it is required within reasonable time. Consequently, lime may have to be

Juan P. Fuentes; David F. Bezdicek; Markus Flury; Stephan Albrecht; Jeffrey L. Smith



Regeneration of lime from sulfates for fluidized-bed combustion  


In a fluidized-bed combustor the evolving sulfur oxides are reacted with CaO to form calcium sulfate which is then decomposed in the presence of carbonaceous material, such as the fly ash recovered from the combustion, at temperatures of about to C., to regenerate lime. The regenerated lime is then recycled to the fluidized bed combustor to further react with the evolving sulfur oxides. The lime regenerated in this manner is quite effective in removing the sulfur oxides.

Yang, Ralph T. (Middle Island, NY); Steinberg, Meyer (Huntington Station, NY)



Arsenic-bearing calcite in natural travertines: evidence from sequential extraction, ?XAS, and ?XRF.  


Recent studies demonstrated that synthetic calcite may host considerable amounts of arsenic (As). In this paper, the concentration of As in natural calcite was determined using two novel, specifically designed, sequential extraction procedures. In addition, the oxidation state of As and its distribution between calcite and coexisting Fe-oxyhydroxides was unravelled by ?XRF elemental mapping and As K-edge ?XAS spectroscopy. Our results conclusively demonstrate that arsenic can be found in natural calcite up to 2 orders of magnitude over the normal crustal As abundances. Because of the large diffusion of calcite in the environment, this phase may exert an important control on As geochemistry, mobility, and bioavailability. PMID:23738848

Costagliola, Pilario; Bardelli, Fabrizio; Benvenuti, Marco; Di Benedetto, Francesco; Lattanzi, Pierfranco; Romanelli, Maurizio; Paolieri, Mario; Rimondi, Valentina; Vaggelli, Gloria



Fluoride removal in a fixed bed packed with granular calcite  

Microsoft Academic Search

A fixed bed reactor filled with calcite particles (mean strokes diameter, 0.20mm) was constructed and the reactor was used to treat synthetic wastewater containing HF, NaF, NH4F or Na2SiF6 under various conditions. Calcium ions (Ca2+) were found to exist in the treated effluent and the molar Ca2+ concentration ([Ca2+]) was related to the molar ratio of H+ to F? ([H+]0\\/[F?]0)

Min Yang; Takayuki Hashimoto; Nobuyuki Hoshi; Haruki Myoga



Does Calcite Encrustation in Provide a Phosphorus Nutrient Sink?  

Microsoft Academic Search

We studied the effect of calcite encrustation in stoneworts (Chara spp.) on P cycling in an aquatic ecosystem. Sequential fractiona- tion was performed to quantify P fractions of the internodes of cal- cified (Ca-CF) and uncalcified (UCa-CF) Chara fibrosa Agardh ex Bruzelius. Our results showed that Ca-CF was able to store more P and about 14 to 23% of total

Kian Siong; Takashi Asaeda



Molecular Expressions: Optical Microscopy Primer - Birefringence in Calcite Crystals  

NSDL National Science Digital Library

This item is an interactive Java simulation for students of introductory physics or optics relating to birefringence. It features a virtual calcite crystal superimposed over the word "Birefringence". Due to the refractive properties of this type of crystal, the letters appear as a ghosted double image. The user can rotate the crystal and the polarizer to alter the transmission axis. This item is part of a larger collection of materials on introductory optics developed by the National High Magnetic Field Laboratory.

Davidson, Michael; Parry-Hill, Matthew J.; Murphy, Douglas B.; Spring, Kenneth R.; Long, John



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



Long-Term Effects of a Watershed Liming Experiment on Soils and Surface Waters at Woods Lake, New York  

NASA Astrophysics Data System (ADS)

In October 1989, approximately 1000 Mg of pelletized limestone was applied to two subcatchments of the Woods Lake Watershed located in the western Adirondacks of New York State. This experiment was designed to evaluate the effectiveness of calcite addition to watershed soils as a strategy to mitigate the effects of surface water acidification from acidic deposition. Woods Lake is 23 ha in size and lies within a 207 ha thin-till dominated watershed. In 1979 the lake was highly acidic (pH 4.8, ANC -8 ?eq/L). The watershed treatment followed two earlier lake liming experiments. These experiments successfully raised the pH and ANC of the lake but only for a short time as the residence time of water in the lake is only 174 days. Because calcite applied to the soil would be continuously exposed to precipitation falling on the land surface, it was hypothesized that watershed liming would have a much longer impact. The limed subcatchments (102 ha) were treated with limestone that had been crushed to the consistency of fine sand and pelletized with a lignosulfonate binder to form pellets 1.41 to 4.00 mm in diameter. The chemical composition of the pellets was approximately 82% CaCO3, 8% MgCO3, 4% organic binder, and 6% inorganic salts and insoluble silicate minerals. Application rates were targeted at 10 Mg CaCO3/ha but limefall collectors measured lower rates with a mean of 7.85 Mg/ha falling in subcatchment II and 3.42 Mg/ha in subcatchment IV. During the first two years after watershed liming lake pH averaged 6.62, ANC 138 ?eq/L and Ca2+ 119 ?eq/L. Samples collected during the summer of 2005 show that, even after 16 years, the lake has maintained its positive ANC (37.7 ?eq/L) and still has high concentrations of Ca2+ (151.7 ?eq/L). A viable fish population has also survived in this previously fishless lake. Even more surprising, soil samples collected in 2005 still have significant quantities of undissolved CaCO3. In the time since treatment, the CaCO3 has been displaced downward through the organic horizon of the soil through seasonal deposition of organic debris from above. It now lies within an Oa horizon having a pH of approximately 4.5. Organic coatings on the CaCO3 are likely inhibiting reactions with soil water. Some reaction must still be occurring as the pH is higher and exchangeable acidity lower in treated catchments as compared to untreated control catchments. The pH of the organic horizons in the control catchments is as low as 3.6 while the exchangeable acidity is as high as 11.2 meq/100 gm. Exchangeable acidity of organic horizons in the treated catchments is generally less than 2 meq/100 gm. Calcite weathering rates are likely lower in this field experiment than expected due to the presence of organic coatings on the mineral grain surfaces that are formed during organic decomposition reactions in the soil. Despite this, the rate of Ca2+ release from the treated catchments is high enough to maintain a positive ANC in the lake.

Newton, R. M.



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



Carbon isotopic thermometry calibrated by dolomite-calcite solvus temperatures  

NASA Astrophysics Data System (ADS)

The temperature dependence of carbon isotopic fractionations between calcite and graphite, and between dolomite and graphite are calibrated by the calcite-dolomite solvus geothermometry using marbles collected from the contact metamorphic aureole in the Kasuga area, central Japan. The carbon isotopic fractionations ( ?13CCc- Gr and ?13CDo? Gr) systematically decrease with increasing metamorphic temperature. The concordant relationships between the fractionations and solvus temperatures are approximately linear with T-2 over the temperature range. 400° to 680°C: ?13CCc? Gr (%.) = 5.6 × 10 6 × T-2 (K) - 2.4 ?13CDo? Gr (%.) = 5.9 × 10 6 × T-2 ( K) - 1.9 These systematic relationships between fractionation and temperature suggest that carbon isotopic equilibria between carbonates and graphite were attained in many cases. The equation for the calcite-graphite system has a slope steeper than BOTTINGA'S (1969) results. It is, however, in good agreement with that of VALLEY and O'NEIL (1981) in the temperature range from 600° to 800°C. Because of the relatively high sensitivity to temperature, these isotopic geothermometers are useful for determining the temperatures in moderate- to high-grade metamorphosed carbonate rocks.

Wada, Hideki; Suzuki, Kazuhiro



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))



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.



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


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




EPA Science Inventory

The report gives results of an evaluation of lime precipitation for treating boiler tube cleaning wastes. In this project, wastewater samples were collected from six boiler tubeside chemical cleanings, using complexing and chelating agents. The samples represented: (1) ammoniacal...


27 CFR 9.27 - Lime Kiln Valley.  

Code of Federal Regulations, 2010 CFR

...California,” 1968, 7.5 minute series. (c) Boundaries. The Lime Kiln Valley viticultural area is located in San Benito County, California. From the beginning point at the intersection of Thompson Creek and Cienega Road, the...




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


106. (Credit JTL) Interior of lime storage room (above storeroom ...  

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

106. (Credit JTL) Interior of lime storage room (above storeroom in machine shop wing) at station, looking west. - McNeil Street Pumping Station, McNeil Street & Cross Bayou, Shreveport, Caddo Parish, LA


Strontium isotope fractionation of planktic foraminifera and inorganic calcite  

NASA Astrophysics Data System (ADS)

We have investigated the strontium isotope fractionation (?88/86Srcarb-aq) between inorganic calcite and aqueous Sr2+ ions by precipitation experiments at a constant temperature of 25 °C and precipitation rates (R) ranging from 102.3 to 104.2 ?mol/m2/h. Strontium isotope ratios were measured using the 87Sr-84Sr double spike technique. It was found that strontium isotope fractionation in these calcites is strongly dependent on the precipitation rate: ?Sr carb-aq =-0.08?log(R[?mol/m/h])+0.08 The measured ?88/86Sr values are significantly correlated with previously measured ?44/40Ca and Sr/Ca values of the same calcite samples: ?Sr=+0.18??Ca-0.01 ?Sr=-1.5?KdSr-0.03 The slope of 88Sr/86Sr versus 44Ca/40Ca fractionation is 0.18 ± 0.04 and compatible with a kinetic fractionation during dehydration of the strontium and calcium ions, but not with isotope fractionation in a diffusive boundary layer. Using published equilibrium ?44/40Cacarb-aq and KdSr values we estimate the equilibrium isotope fractionation of strontium to be very close to zero (?88/86Sreq(carb-aq) = -0.01 ± 0.06‰). This estimate is confirmed by strontium isotope values of natural inorganic calcites that precipitated very slowly in basalts of the ocean crust. The results from the inorganic calcites are used to explain strontium isotope fractionation of planktic foraminifera. Specimens of two warm water species (Globigerinoides ruber and Globigerinoides sacculifer) were picked from the Holocene section of a Caribbean sediment core. We found no significant difference in ?88/86Sr between the two species. In addition, G. ruber specimens from Marine Isotope Stage 2 in the same core show ?88/86Sr values identical to the Holocene specimens. The strontium isotopes of both foraminifera species are strongly fractionated (?88/86Srcarb-aq = -0.248 ± 0.005‰) when compared to published data of other major marine calcifiers. Applying the results from the inorganic precipitation experiments we find that the strong foraminiferal strontium isotope fractionation can be explained by calcification in a largely open system at high precipitation rates, comparable in magnitude to rates known from scleractinian reef corals. This interpretation is in good agreement with the kinetic calcification model for planktic foraminifera by Kisakürek et al. (2011), which was based on calcium isotopes and elemental Sr/Ca ratios.

Böhm, Florian; Eisenhauer, Anton; Tang, Jianwu; Dietzel, Martin; Krabbenhöft, Andre; Kisakürek, Basak; Horn, Christian



Shock, release, and tension response of soda lime glass  

SciTech Connect

This work describes the result of shock wave experiments on soda lime glass in which the shock wave profiles were recorded simultaneously at or near the impact surface and the free surface of the glass specimen by means of multi-beam VISAR. Since earlier work indicated that the glass under shock compression does not follow the Gladstone-Dale model, these profiles provide accurate and self consistent values of transit times for shock, release, and tensile waves propagating in soda lime glass.

Dandekar, Dattatraya P. [Army Research Laboratory, Weapons and Materials Research Directorate, Aberdeen Proving Ground, Maryland 21005 (United States)



Effects of lime-sludge discharge on an Arctic river  

Microsoft Academic Search

The Fairbanks Water Treatment Plant in Fairbanks, Alaska, processes approximately 3 MGD of drinking water using lime softening. Approximately 0.3 MGD of lime-sludge from the treatment process is combined with effluent from a nearby power plant and discharged to the Chena River. There is little information available on the impact of water-treatment sludge discharges, and virtually no information on the




Cation--anion balance in lime-induced chlorosis. [Soybeans  

Microsoft Academic Search

Lime-induced chlorosis in plants is characterized by some phenomena which fit into a simple hypothesis that internal pH balance is upset due to shifts in cation-anion balances. These pH changes result in precipitation of Fe in plants and fit our previous hypothesis of competitive chelation as an explanation of the multiple causes of lime-induced chlorosis. The oft-times higher concentrations of

A. Wallace; R. A. Wood; S. M. Soufi



Cation?anion balance in lime?induced chlorosis  

Microsoft Academic Search

Lime?induced chlorosis in plants is characterized by some phenomena which fit into a simple hypothesis that internal pH balance is upset due to shifts in cation?anion balances. These pH changes result in precipitation of Fe in plants and fit our previous hypothesis of competitive dictation as an explanation of the multiple causes of lime?induced chlorosis. The oft?times higher concentrations of

A. Wallace; R. A. Wood; S. M. Soufi



Wetland vegetation responses to liming an Adirondack watershed  

Microsoft Academic Search

Watershed liming as a long-term mitigation strategy to neutralize lake acidity, from increasing acid deposition, was initiated in North America at Woods Lake in the west central Adirondack region of New York. In October 1989, a dose of 10 MT lime (83.5% CaCO[sub 3]) ha[sup [minus]1] was aerially applied to 48% of the watershed. The wetlands adjacent to Woods Lake




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.



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.



Hydration-dependent dynamic crossover phenomenon in protein hydration water  

NASA Astrophysics Data System (ADS)

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.

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



Surfactant effects on gas hydrate formation  

Microsoft Academic Search

Micellar solutions were found to increase gas hydrate formation rate and alter formation mechanism for ethane and natural gas hydrates. A critical micellar concentration (CMC) of sodium dodecyl sulfate water solution was found to be 242 ppm at hydrate-forming conditions, where CMC was best determined by hydrate induction time. At surfactant concentrations above the CMC, hydrate formation rates in a

Y. Zhong; R. E. Rogers



Rapid gas hydrate formation process  


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.



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


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



Oxygen isotopes in calcite grown under cave-analogue conditions  

NASA Astrophysics Data System (ADS)

Speleothem oxygen isotopes and growth rates are valuable proxies for reconstructing climate history. There is debate, however, about the conditions that allow speleothems to grow in oxygen isotope equilibrium, and about the correct equilibrium fractionation factors. We report results from a series of carbonate growth experiments in karst-analogue conditions in the laboratory. The setup closely mimics natural processes (e.g. precipitation driven by CO 2-degassing, low ionic strength solution, thin solution film) but with a tight control on growth conditions (temperature, pCO 2, drip rate, calcite saturation index and the composition of the initial solution). Calcite is dissolved in water in a 20,000 ppmV pCO 2 environment. This solution is dripped onto glass plates (coated with seed-carbonate) in a lower pCO 2 environment (<2500 ppmV), where degassing leads to calcite growth. Experiments were performed at 7, 15, 25 and 35 °C. At each temperature, calcite was grown at three drip rates (2, 6 and 10 drips per minute) on separate plates. The mass of calcite grown in these experiments varies with temperature ( T in K) and drip rate ( d_ r in drips min -1) according to the relationship daily growth mass = 1.254 + 1.478 ? 10 -9 ? e0.0679 T + ( e0.00248 T - 2) ? (-0.779 d_ r2 + 10.05 d_ r + 11.69). This relationship indicates a substantial increase of growth mass with temperature, a smaller influence of drip rate on growth mass at low temperature and a non-linear relationship between drip rate and growth mass at higher temperatures. Low temperature, fast dripping conditions are found to be the most favourable for reducing effects associated with evaporation and rapid depletion of the dissolved inorganic carbon reservoir (rapid DIC-depletion). The impact of evaporation can be large so caves with high relative humidity are also preferable for palaeoclimate reconstruction. Even allowing for the maximum offsets that may have been induced by evaporation and rapid DIC-depletion, ? 18O measured in some of our experiments remain higher than those predicted by Kim and O'Neil (1997). Our new results are well explained by equilibrium at a significantly higher ?calcite-water, with a kinetic-isotope effect that favours 16O incorporation as growth rate increases. This scenario agrees with recent studies by Coplen (2007) and Dietzel et al. (2009). Overall, our results suggest that three separate processes cause ? 18O to deviate from true isotope equilibrium in the cave environment. Two of these drive ? 18O to higher values (evaporation and rapid DIC-depletion) while one drives ? 18O to lower values (preferential incorporation of 16O in the solid carbonate at faster growth rates). While evaporation and DIC-depletion can be avoided in some settings, the third may be inescapable in the cave environment and means that any temperature to ? 18O relationship is an approximation. The controlled conditions of the present experiments also display limitations in the use of the Hendy test to identifying equilibrium growth.

Day, C. C.; Henderson, G. M.



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.



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



Geochemistry of post-uplift calcite in the Permian Basin of Texas and New Mexico  

Microsoft Academic Search

Integration whole-oil gas chromatography of produced oil and oil inclusions, formation-water chemistry, and stable isotopes has identified environment-diagnostic differences in calcite cements between oil field and outcrop environments in the Permian Basin of Texas and New Mexico. Calcite-[delta][sup 13]C and fluid-inclusion composition are the most diagnostic of pore-fluid evolution and can help interpret rock-fluid reactions. Late-stage calcite cement in the

W. D. Wiggins; P. M. Harris; R. C. Burruss



Influence of Calcite and Dissolved Calcium on Uranium(VI) Sorption to a Hanford Subsurface Sediment  

Microsoft Academic Search

The influence of calcite and dissolved calcium on U(VI) adsorption was investigated using a calcite-containing sandy silt\\/clay sediment from the U. S. Department of Energy Hanford site. U(VI) adsorption to sediment, treated sediment, and sediment size fractions was studied in solutions that both had and had not been preequilibrated with calcite, at initial [U(VI)] - 10-7-10-5 mol\\/L and final pH

Wenming Dong; William P. Ball; Chongxuan Liu; Zheming Wang; Alan T. Stone; Jing Bai; John M. Zachara



Liming Induced Changes in Arsenic Dissolution from Mine Wastes  

NASA Astrophysics Data System (ADS)

Incorporation of lime amendments into mine wastes is an effective treatment to neutralize active and potential acidity, reduce soluble metals, and facilitate plant growth. Many mine wastes contain arsenic. In general, the solubility of As (a metalloid) increases with increasing pH. However, a number of laboratory and field studies with mine waste have shown decreased solubility of arsenic with increasing pH. These studies have not identified what factors are influencing the fate of arsenic in these mine wastes, nor determined the mechanisms involved in reducing the soluble arsenic. This research project evaluated the physical, chemical, and morphological factors affecting a decrease in soluble arsenic concentrations upon liming and whether characteristics of an unamended waste can be used to determine the mobility of arsenic in the amended waste. Testing a mine waste for the parameters soluble Fe plus Al plus Mn; percent clay; total lime requirement; arsenic oxyanions; sequential extraction of metals; mineralogy; soluble Ca and Ni; and potentially EC and CEC/AEC will enable prediction of the potential fate of arsenic following liming of an arsenic-laden, acidic-metalliferrous mine waste. Inverse geochemical modeling was used to identify potential reaction pathways explaining the difference in As solubility induced by liming.

Dudley, L. M.



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)



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.



Porosity and hydric behavior of typical calcite microfabrics in stalagmites  

NASA Astrophysics Data System (ADS)

Petrophysical techniques commonly used for material characterization are applied for the first time to speleothem samples to investigate the porosity and hydric behavior of calcite stalagmites used in paleoclimatology. These techniques allow the determination of the stalagmites' potential to undergo diagenetic transformations when substantial changes in drip waters occur in the cave environment. The petrophysical techniques include water absorption under vacuum and by capillarity, nuclear magnetic resonance, environmental scanning electron microscopy, and mercury intrusion porosimetry. The studied samples comprise five common calcite microfabrics, which have markedly different porosities and hydric behaviors and, as a consequence, different sensibilities to diagenetic processes related to the influx of water. The experiments show that stalagmites can behave as complex, small-scale hydrological systems and that the circulation of water through them by complex nets of interconnected pores might be common. As the circulation of water favors diagenetic transformations that involve geochemical and isotopic changes, the characterization of flow patterns is key for outlining areas that are susceptible to such modifications, which is critical to paleoclimatic studies that are based on speleothems because geochemical and stable isotopic data are used as paleoenvironmental proxies and absolute ages are obtained by using radioactive isotope ratios. These potential modifications also have obvious implications for studies based on fluid inclusions in speleothems. The integrated methodology, which uses primarily non-destructive techniques, shows a high potential for characterization of any type of speleothem and other continental carbonates such as tufas or sinters.

Muñoz-García, M. B.; López-Arce, P.; Fernández-Valle, M. E.; Martín-Chivelet, J.; Fort, R.



Lattice Boltzmann Simulation of Calcite Precipitation and Isotope Fractionation  

NASA Astrophysics Data System (ADS)

The Lattice-Boltzmann (LB) method can be used to simulate aspects of chemical reactions such as vapor condensation or mineral precipitation from a fluid phase. It has the advantage of allowing the solute phase to evolve depending on local conditions rather than being specified, so that the controls on precipitated phase grain shape can be studied simultaneously with the controls on chemical compositions and growth rate. We have used the LB approach to simulate the precipitation of calcite from oversaturated water as an effort in developing methods for treating complex chemical reaction problems, including isotopic effects. The formation of calcite is a classic problem in diffusion and reaction-limited mineral growth. There are many complexities, but the process is attractive for modeling purposes because there is abundant information on reaction kinetics and the relationships between crystal morphology and growth conditions. In this paper we describe the LB approach used, address strategies for properly conserving mass at a surface of a growing 73"0?crystal?73"0?"08, the scaling of the calculations to the actual physical problem, and the conditions for growth of dendritic versus compact crystals.

Lu, G.; Depaolo, D.; Kang, Q.; Zhang, D.



Formation of submarine gas hydrates  

Microsoft Academic Search

and bottom sampling in many offshore regions. This paper reports on expeditions carried out in the Black, Caspian and Okhotsk Seas. Gas hydrate accumulations were discovered and investigated in all these areas. The data and an analysis of the results of the deep-sea drilling programme suggest that the infiltration of gas-bearing fluids is a necessary condition for gas hydrate accumulation.



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.



Brine induced low-Magnesium calcite formation at cold seeps  

NASA Astrophysics Data System (ADS)

Low-Mg calcite (LMC; < 5 mol% Mg), commonly observed during time intervals of "calcite seas," since the beginning of the Paleozoic Era, is a good indicator of low Mg/Ca ratio (< 2) in seawater. Calcite seas were coincident with times of active seawater-basalt interactions along mid-ocean ridges at high temperatures, which extract Mg from seawater and release Ca to it. In the modern aragonite sea, most carbonate minerals precipitate at the seafloor, including deposits from cold seep environments are primarily either aragonite or high-Mg calcite (HMC). Here, we report the finding of non-skeletal LMC from cold seeps in Alaminos Canyon block 601 (AC 601), 2200 m below the sea surface on northern Gulf of Mexico (GOM) continental slope. Low-Mg calcite usually represents the only carbonate mineral in the studied samples. Dominant allochems in these seep carbonates are peloids, grain aggregates, pelagic forams, and fragments of mollusks and echinoids. The limestone is heavily cemented. The observed cements include micrite, microspar, mosaic, bladed, fan, and needle cements. The dissolution of grains and cements was observed. Not only originally aragonitic mollusks shells, but also carbonate cement have been dissolved. The aerobic oxidation of reduced chemical species such as methane and H2S is responsible for an increase in pCO2 and a decrease of pH, leading to local carbonate dissolution. The occurrence of oxic conditions is confirmed by the presence of negative Ce anomalies of the carbonates. Further, we report on analyses showing that the ambient porewater Mg/Ca ratio actually governs the carbonate mineralogy. The occurrence of LMC may be attributed to the brine fluids, which is relatively Mg-depleted (Mg/Ca mole ratio is below 0.7) compared to pore fluid of the subsurface sediments from the reference site (Mg/Ca mole ratio is above 4.1) that usually produce HMC. The 87Sr/86Sr values of LMC (mean = 0.708001, sd = 0.000034, n=2) are significantly lower than that of the seawater (0.709175). Strong deviation of the Sr isotope ratios of LMC from seawater is interpreted as the modification of the strontium from less radiogenic sources like older marine sediments and/or the locally abundant Jurassic salt. Therefore, we speculate that the seep fluids at the studied site most likely have a deep origin and may also have been influenced by dissolved halite during their ascent through conduits along the margins of salt bodies. The understanding of the processes that control the LMC precipitation in the GOM will also contribute to an improved understanding of the presence or absence of LMC in other oceans margin settings today, and in geological deposits as well.

Feng, Dong; Roberts, Harry; Joye, Samantha; Heydari, Ezat



Hydration and physical performance.  


There is a rich scientific literature regarding hydration status and physical function that began in the late 1800s, although the relationship was likely apparent centuries before that. A decrease in body water from normal levels (often referred to as dehydration or hypohydration) provokes changes in cardiovascular, thermoregulatory, metabolic, and central nervous function that become increasingly greater as dehydration worsens. Similarly, performance impairment often reported with modest dehydration (e.g., -2% body mass) is also exacerbated by greater fluid loss. Dehydration during physical activity in the heat provokes greater performance decrements than similar activity in cooler conditions, a difference thought to be due, at least in part, to greater cardiovascular and thermoregulatory strain associated with heat exposure. There is little doubt that performance during prolonged, continuous exercise in the heat is impaired by levels of dehydration >or= -2% body mass, and there is some evidence that lower levels of dehydration can also impair performance even during relatively short-duration, intermittent exercise. Although additional research is needed to more fully understand low-level dehydration's effects on physical performance, one can generalize that when performance is at stake, it is better to be well-hydrated than dehydrated. This generalization holds true in the occupational, military, and sports settings. PMID:17921463

Murray, Bob




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 ...


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.



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  

Microsoft Academic Search

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 3mm high and 30cm long, are built of densely packed cone columns, with individual cones up

Monika Kowal-Linka



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.



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,...



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,...



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,...



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,...



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))



Paired gill slits in a fossil with a calcite skeleton.  


The chordates, hemichordates (such as acorn worms) and echinoderms (such as starfish) comprise the group Deuterostomia, well established as monophyletic. Among extant deuterostomes, a skeleton in which each plate has the crystallographic structure of a single crystal of calcite is characteristic of echinoderms and is always associated with radial symmetry and never with gill slits. Among fossils, however, such a skeleton sometimes occurs without radial symmetry. This is true of Jaekelocarpus oklahomensis, from the Upper Carboniferous of Oklahoma, USA, which, being externally almost bilaterally symmetrical, is traditionally placed in the group Mitrata (Ordovician to Carboniferous periods, 530-280 million years ago), by contrast with the bizarrely asymmetrical Cornuta (Cambrian to Ordovician periods, 540 to 440 million years ago). Using computer X-ray microtomography, we describe the anatomy of Jaekelocarpus in greater detail than formerly possible, reveal evidence of paired gill slits internally and interpret its functional anatomy. On this basis we suggest its phylogenetic position within the deuterostomes. PMID:12075349

Dominguez, Patrício; Jacobson, Antone G; Jefferies, Richard P S



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.



Calcite orientations and composition ranges within teeth across Echinoidea.  


Sea urchin's teeth from four families of order Echinoida and from orders Temnopleuroida, Arbacioida and Cidaroida were studied with synchrotron X-ray diffraction. The high and very high Mg calcite phases of the teeth, i.e. the first and second stage mineral constituents, respectively, have the same crystallographic orientations. The co-orientation of first and second stage mineral, which the authors attribute to epitaxy, extends across the phylogenic width of the extant regular sea urchins and demonstrates that this is a primitive character of this group. The range of compositions ?x for the two phases of Ca1-xMgxCO3 is about 0.20 or greater and is consistent with a common biomineralization process. PMID:25158180

Stock, Stuart R; Ignatiev, Konstantin; Lee, Peter L; Almer, Jonathan D



Understanding control of calcitic biomineralization-proteomics to the rescue.  


The avian eggshell is one of the fastest calcifying processes known and represents a unique model for studying biomineralization. Eggshell strength is a crucial economic trait for table egg production, and ensures that a safe egg reaches the consumer kitchen. However, a common toolkit for eggshell mineralization has not yet been defined. In this issue, label-free MS-based protein quantification technology has been used by Sun et al. (Proteomics 2013, 13, 3523-3536) to detect differences in protein abundance between eggshell matrix from strong and weak eggs and between the corresponding uterine fluids bathing strong and weak eggs. Proteins associated with the formation of strong eggshells are identified, which are now candidates for further investigations to define the regulatory relationship between specific eggshell matrix proteins and calcite crystal texture. PMID:24307661

Hincke, Maxwell T



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.



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



Selenium incorporation into calcite and its effect on crystal growth: An atomic force microscopy study  

E-print Network

Selenium incorporation into calcite and its effect on crystal growth: An atomic force microscopy Crystal growth Selenium The atomic processes leading to calcite growth are still debated. The presence of foreign impurities in solution is known to change the rate of step propagation during growth as well

Montes-Hernandez, German


Author's personal copy Selenium incorporation into calcite and its effect on crystal growth: An atomic force  

E-print Network

Author's personal copy Selenium incorporation into calcite and its effect on crystal growth Atomic force microscopy Crystal growth Selenium The atomic processes leading to calcite growth are still during growth as well as the growth mechanism. Among trace elements, selenium, in the form of oxyanions


Improved strength and durability of fly ash-amended concrete by microbial calcite precipitation  

Microsoft Academic Search

Fly ash acts as a partial replacement material for both Portland cement and fine aggregate. An innovative approach of microbial calcite precipitation in fly ash-amended concrete has been investigated. This is the first report to discuss the role of microbial calcite precipitation in enhancing the durability of fly ash-amended concrete. The present study investigated the effects of Bacillus megaterium ATCC

Varenyam Achal; Xiangliang Pan; Nilüfer Özyurt



In-situ synchrotron X-ray reflectivity measurements at the calcite-water interface  

NASA Astrophysics Data System (ADS)

In-situ synchrotron X-ray reflectivity (SXR) measurements of the calcite-water interface were made. These data were used to model the angstrom-scale interfacial width and electron density profile of the interface. Measurements were made on the (10T4) cleavage surface of Iceland spar calcite in contact with pure N 2, humid N 2, deionized water, and dilute nitric acid solutions at 25°C. The measurements were performed in an X-ray transparent reaction cell in which fluid pH was monitored during SXR data acquisition. Analysis of the data indicated that the pristine calcite surface in contact with pure N 2 has an interfacial width (statistical roughness) of 2.60 ± 0.15 Å. Exposure to water vapor (humid N 2) resulted in the deposition of a water film 19.9 ± 0.4 Å thick. There was no evidence from the SXR data that the adsorbed water film caused roughening of the calcite surface. However, when reacted with deionized water the calcite was roughened, yielding an interfacial width of 23.1 Å. During successive reactions with fluids having decreasing initial pH the calcite/fluid interfacial width increased from 23.1 to 45.3 Å. The SXR results indicate that intraterrace areas participate in the dissolution of calcite. A linear correlation was observed between interfacial width of the intraterrace areas and the quantity of calcite dissolved.

Chiarello, Ronald P.; Wogelius, Roy A.; Sturchio, Neil C.



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

Microsoft Academic Search

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,




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



Assessing the potential for using biogenic calcites as dosemeters for luminescence dating  

Microsoft Academic Search

Calcium carbonate emits an intense thermoluminescence (TL) signal and previous work has explored the potential of using this signal to date both inorganic carbonates such as limestones and stalagmites and biogenic calcite produced by marine organisms. Luminescence analysis of biogenic calcites directly dates the secretion of the mineral by the organism and is therefore not reliant upon exposure of the

G. A. T. Duller; K. E. H. Penkman; A. G. Wintle



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


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



Gas hydrate on the continental margin  

Microsoft Academic Search

Because the stability of gas hydrate is constrained mainly by the temperature and pressure condition, gas hydrate on the continental margins had dissociated in response to the global climate changes during the earth's history. Marine gas hydrate hosts isotopically light carbon as gas (mostly methane) and heavy oxygen as water, dissociation of gas hydrate liberates these isotopes into the environment,

Hitoshi Tomaru


Effective kinetic inhibitors for natural gas hydrates  

Microsoft Academic Search

Kinetic inhibition is a new means of preventing flow channel blockage by natural gas hydrates. In kinetic inhibition the system is allowed to exist within the hydrate thermodynamic stability zone, so that small crystals are stabilized without agglomerating to larger hydrate masses which plug pipelines. A hydrate formation mechanism is reviewed to suggest the new inhibition method. Macroscopic experiments on

J. P. Lederhos; J. P. Long; A. Sum; R. L. Christiansen; E. D. Sloan



Induction time in crystallization of gas hydrates  

Microsoft Academic Search

The kinetics of the initial stage of crystallization of one-component gas hydrates in aqueous solutions are analyzed. The temporal evolution of the volume of hydrate crystallized and the moles of gas consumed are determined. Expressions are derived for the supersaturation dependence of the hydrate crystallite growth rate and the induction time in hydrate crystallization. These expressions are used for revealing

Dimo Kashchiev; Abbas Firoozabadi



Natural gas hydrates: problem or opportunity  

Microsoft Academic Search

Natural gas hydrates, once viewed solely as a nuisance by the gas processing industry, are rapidly gaining favorable status as an unconventional natural gas resource. Hydrates are solids which form when gas is contacted with water, both above and below 273 Kelvin. Conditions are favorable for hydrate formation in permafrost regions and in many oceans. Natural gas hydrates are solid



Gas Hydrates: It's a Gas  

NSDL National Science Digital Library

In this activity, students will discover the importance of carbon, where carbon is stored on Earth, and that the largest reservoir of carbon is in the form of gas hydrates where methane and other hydrocarbon gases are trapped in a lattice of water molecules in deep sea sediments. Students will learn how climate change is related to the greenhouse effect. They will also learn about the potential of hydrates as a major new energy resource, and explore the conditions under which hydrates form. In addition, students will understand the use of acoustics for mapping the sea floor and sub-sea floor.


Precipitation of calcite induced by Synechocystis sp. PCC6803.  


Calcite with laminate structure was successfully prepared by culturing Synechocystis sp. PCC6803 with different concentrations of calcium chloride (CaCl?) in BG11 media. S. PCC6803 was examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), laser confocal scanning microscope (LCSM) and energy dispersive spectroscopy (EDS). The effects of Ca²? concentrations and pH values on calcification were investigated and the micro morphs of the CaCO? crystals were observed by means of SEM. These results showed that CaCO? crystals could be more easily formed with increasing the concentration of CaCl? in S. PCC6803 culture solution. S. PCC6803 could largely bind calcium ions, most of which were present in extracellular polymeric substances and on the cell wall. Inside the cells there were a lot of circular areas rich in calcium ions without the crystallization of calcium. Some cells produced a thicker gelatinous sheath outside of the translucent organic thin layer. And the cells inside also produced major changes that the original chloroplasts were almost transformed into starch grains whose sizes were from 0.5 to 1 ?m with relatively uniform in sizes. At the same time the cell sizes significantly reduced to only about 8-9 ?m almost changing to half of its original diameters. The calcite crystals with a highly preferred orientation induced by S. PCC6803 were observed with X-ray diffraction (XRD). A critical implication was that S. PCC6803 could induce bio-calcification and then mediate the further growth of CaCO? crystals in the biological system. PMID:23543209

Han, Zuozhen; Yan, Huaxiao; Zhou, Shixue; Zhao, Hui; Zhang, Yan; Zhang, Ningning; Yao, Chuankai; Zhao, Lin; Han, Chunyan



Partitioning of Sr2+ into Calcite Precipitates Induced by Bacterial Ureolysis in Artificial Groundwater.  

NASA Astrophysics Data System (ADS)

A suite of experiments were performed to investigate the partitioning of Sr2+ (to mimic the radionuclide 90Sr) between calcite and groundwater, in response to the hydrolysis of urea by B. pasteurii under simulated in-situ aquifer conditions. Three duplicate experiments were performed at 25° C over 8 days in microcosms inoculated with B. pasteurii ATCC 11859 and containing an artificial groundwater (AGW). The AGW composition was based upon the aqueous chemistry of the metal and radionuclide contaminated Snake River Plain Aquifer, Idaho,USA. Microcosms also contained 25 mM urea, and 1 mM of Sr as a contaminant treatment. Control experiments were run with non urea hydrolyzing bacteria, B. subtillus. Control experiments exhibited little change in pH, and dissolved ammonium and Ca2+ concentrations. Conversely during experiments inoculated with B. pasteurii, ammonium production increased asymptotically, peaking two days into the experiment when approximately all urea had been hydrolyzed. The production of ammonium and bicarbonate from urea hydrolysis caused an asymptotic increase in pH from 6.5 to 9.1 one day into the experiment. Dissolved Ca2+ and Sr2+ decreased asymptotically from the beginning of the experiment, and was accompanied by the development of solid precipitates identified as calcite by X-Ray diffraction. This caused an asymptotic decrease in the saturation state of calcite (S) after one day of the experiment. Specific rate constants were derived for calcite precipitation and critical saturation state from the time course data following a second-order chemical affinity based law. Calcite precipitation rate is fundamentally controlled by, and exhibits a positive association with S. Mass balance indicates the percentage of total Sr (dissolved and in calcite) incorporated into the calcite precipitate increases rapidly to 59 % after two days of the experiment, and increases less rapidly thereafter to a maximum of 67 %. Corresponding measured distribution coefficients (DMe) exhibit a positive association with S and calcite precipitation rates. Therefore DMe is greatest after one day of the experiment (DMe maximum = 0.39), which corresponds to the highest S and calcite precipitation rate, and decreases thereafter (DMe minimum = 0.16) as S and calcite precipitation rate decreases. Therefore the extent of Sr incorporation into calcite precipitates resulting from the hydrolysis of urea by B. pasteurii appears to be a primary function of precipitation rate, which is controlled by S. The median DMe determined by this study (0.22) is greater than previously published coefficients for Sr in calcite by up to an order of magnitude. This demonstrates the potential of calcite precipitation by bacterial ureolysis as a remediation strategy for 90Sr in calcite saturated aquifers.

Mitchell, A. C.; Ferris, F. G.; Mancini, A.; Litwin, Y.



Aragonite shells are more ancient than calcite ones in bivalves: new evidence based on omics.  


Two calcium carbonate crystal polymorphs, aragonite and calcite, are the main inorganic components of mollusk shells. Some fossil evidences suggest that aragonite shell is more ancient than calcite shell for the Bivalvia. But, the molecular biology evidence for the above deduction is absent. In this study, we searched for homologs of bivalve aragonite-related and calcite-related shell proteins in the oyster genome, and found that no homologs of calcite-related shell protein but some homologs of aragonite-related shell proteins in the oyster genome. We explained the results as the new evidence to support that aragonite shells are more ancient than calcite shells in bivalves combined the published biogeological and seawater chemistry data. PMID:25063580

Wang, Xiaotong; Li, Li; Zhu, Yabing; Song, Xiaorui; Fang, Xiaodong; Huang, Ronglian; Que, Huayong; Zhang, Guofan



The quantitative determination of calcite associated with the carbonate-bearing apatites  

USGS Publications Warehouse

The CO2 combined as calcite in carbonate-bearing apatites as been distinguished from that combined as carbonate-apatite, or present in some form other than calcite, by use of X-ray powder patterns, differential thermal analyses, and differential solubility tests. These methods were applied to several pure apatite minerals, to one fossil bone, and to a group of phosphorites from the Phosphoria formation of Permian age from Trail Canyon and the Conda mine, Idaho, and the Laketown district, Utah. With the exceptions of pure fluorapatite, pure carbonate-flueorapatite, and one phosphorite from Trail Canyon, these substances contain varying amounts of calcite, but in all the samples an appreciable part of the carbonite content is not present as calcite. The results of solubility tests, in which the particle size of sample and the length of solution time were varied, imply that the carbonate content is not due to shielded calcite entrapped along an internal network of surfaces.

Silverman, Sol R.; Fuyat, Ruth K.; Weiser, Jeanne D.



Microstructure and hydration characteristics of artificial pozzolana-cement pastes containing burnt kaolinite clay  

SciTech Connect

The reaction of pozzolana with the lime liberated during the hydration process of Portland cement modifies some properties of cement and resulting concrete. This study aimed to investigate experimentally the change occurring in the phase composition and microstructure of pozzolanic cement pastes containing activated kaolinite clay. The artificial pozzolana (burnt kaolinite clay) were thermally activated by firing at 850 C for two hours. The ordinary Portland cement (OPC) was partially replaced by different amounts of activated kaolinite clay by weight. The changes in the electrical conductivity were reported during setting and hardening processes after gauging with water. The change occurring in the phase composition and microstructure of cement pastes were investigated by differential thermal analysis and scanning electron microscopy. The results of this investigation show that, the thermal activated kaolinite clay prolonged the initial and final setting times and reduced the porosity, it also improved the microstructure of the formed hydrates by recrystallization of hydrated calcium silicates (mainly as CSH-(I)) together with the formation of hexagonal calcium aluminate hydrate (mainly as C{sub 4}AH{sub 13}).

Morsy, M.S.; Hanna, G.B. [Building Research Center, Cairo (Egypt)] [Building Research Center, Cairo (Egypt); El-Enein, S.A.A. [Ain Shams Univ., Cairo (Egypt). Faculty of Science] [Ain Shams Univ., Cairo (Egypt). Faculty of Science



Evaluation of a lime-mediated sewage sludge stabilisation process. Product characterisation and technological validation for its use in the cement industry.  


This paper describes an industrial process for stabilising sewage sludge (SS) with lime and evaluates the viability of the stabilised product, denominated Neutral, as a raw material for the cement industry. Lime not only stabilised the sludge, raised the temperature of the mix to 80-100°C, furthering water evaporation, portlandite formation and the partial oxidation of the organic matter present in the sludge. Process mass and energy balances were determined. Neutral, a white powder consisting of portlandite (49.8%), calcite (16.6%), inorganic oxides (13.4%) and organic matter and moisture (20.2%), proved to be technologically apt for inclusion as a component in cement raw mixes. In this study, it was used instead of limestone in raw mixes clinkerised at 1400, 1450 and 1500°C. These raw meals exhibited greater reactivity at high temperatures than the limestone product and their calcination at 1500°C yielded clinker containing over 75% calcium silicates, the key phases in Portland clinker. Finally, the two types of raw meal (Neutral and limestone) were observed to exhibit similar mineralogy and crystal size and distribution. PMID:22119052

Rodríguez, N Husillos; Granados, R J; Blanco-Varela, M T; Cortina, J L; Martínez-Ramírez, S; Marsal, M; Guillem, M; Puig, J; Fos, C; Larrotcha, E; Flores, J



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.



Shock, Release, and Tensile Response of Soda Lime Glass  

Microsoft Academic Search

This work describes the results of shock wave experiments on soda lime glass in which the shock wave profiles were recorded simultaneously at the impact surface and the free surface of the glass specimen by means of multiple VISAR beams. Maximum stress attained in these experiments was 6. 6 GPa. These two wave profiles provide accurate and self consistent values

Dattatraya P. Dandekar




E-print Network

A number of utilities are implementing alkaline stabilization systems for biosolids to achieve a Class A Product. Application of biosolids to agricultural land is the predominant I method of disposal. Due to low nitrogen concentrations and high calcium carbonate equivalence (CCE), application rates need to be based on the neutralizing capacities of the materials. This research compared alkaline stabilized biosolid (ASB) with a standard agricultural dolomitic lime to determine the chemical properties of the ASB, reaction rates of the material, how long these reactions would continue, and how plant nutrition may be affected. Three types of experiments were initiated: incubation, greenhouse, and field. Soils selected for studies contained a range in clay and organic matter content. The ASB neutralized soil acidity as well as the agricultural lime at the same CCE application rates. ASB reacted more quickly than agricultural lime in the greenhouse and field studies. This was due to the finer particle size of the ASB. The ASB was able to supply more calcium, but considerably less magnesium, than agricultural lime. The deficiency of magnesium will be of concern when ASB is applied on soils that are naturally deficient in magnesium.

William Rogers; Scott Carr; Dr. Fred Cox; Dr. Robert Holman; Trille Mendenhall


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)




EPA Science Inventory

The report describes a lime spray dryer/baghouse (FORTRAN) computer model that simulates SO2 removal and permits study of related impacts on design and economics as functions of design parameters and operating conditions for coal-fired electric generating units. The model allows ...


Lime pretreatment and fermentation of enzymatically hydrolyzed sugarcane bagasse.  


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



Manganese-aided lime clarification of municipal wastewater  

Microsoft Academic Search

A preliminary study was carried out to assess the usefulness of manganese as an aid in the lime clarification of municipal wastewater. The approach was intended to take advantage of the potential sorption ability of manganese oxides for organic matter in the presence of divalent cations. In a batch clarification test, 94–95% and 75–77% reduction in turbidity and chemical oxygen

Praveen Kumar Goel; Malay Chaudhuri



Wood Residues as Fuel Source for Lime Kilns  

E-print Network

One of the main obstacles to total energy self sufficiency of kraft mills appears to be the fossil fuel requirements of the lime kilns. If an economical technology can be developed which allows fossil fuel to be replaced in whole or in part by wood...

Azarniouch, M. K.; Philp, R. J.



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


Kinetic hydrate inhibitor provides treatment alternative  

SciTech Connect

An inherent problem with natural gas production or transmission is the formation of gas hydrates. Historically, methanol has been injected into the gas stream to combat hydrate formation. Unichem, a division of B.J. Services Co., has developed a hydrate inhibitor that is a safe, effective, competitively priced alternative method of preventing hydrate formation. The paper briefly describes hydrate formation, the alternative inhibitor, and a successful trial.




Evaluation of methods of mixing lime in bituminous paving mixtures in batch and drum plants  

E-print Network

Two methods were util1zed to introduce lime into the mixtures produced with the drum plant. One method employed the fines feeder from the baghouse. Dry lime was metered into the f1nes feeder using a vane feeder equipped with a strateg1cally located... of lime into the baghouse. The second method involved adding the dry lime directly to the total aggregates on the cold feed belt utilizing the above vane feeder system. Lime slurry was added to the individual aggregates (pea gravel, washed sand...

Button, Joseph Wade



Cd 2+ uptake by calcite, solid-state diffusion, and the formation of solid-solution: Interface processes observed with near-surface sensitive techniques (XPS, LEED, and AES)  

NASA Astrophysics Data System (ADS)

Cadmium uptake by calcite from aqueous solution was studied using techniques sensitive to the near-surface: X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), and Auger electron spectroscopy (AES). These techniques allowed direct observations of structure and bonding environments at the calcite surface. The results indicate that the main processes involved in cadmium uptake by calcite are adsorption and solid-state diffusion into the crystal, which leads eventually to the formation of solid-solution. Pure calcite crystals were cleaved from precleaned Iceland spar and were briefly exposed to aqueous solutions containing various concentrations of Cd 2+, CO 32-, ClO 4-, and/or Cl -. Some Cd 2+ was radiolabelled. LEED results demonstrate that the calcite surface is atomically ordered, even after hydration and cadmium uptake. ?-scintillation data from crystals exposed briefly to solutions of 109Cd 2+ indicate that surface uptake ranged from the equivalent of about 1 to 4 monolayers. XPS analyses in the first 2 hours after exposure detected Cd within the top 30 Å, but crystals stored in air or in ultra-high vacuum showed a decrease in Cd surface concentration with time such that after two days, Cd was barely detectable in the near-surface region. In other experiments, LEED verified the crystallinity of otavite (CdCO 3) grown epitaxially over the {101} cleavage faces of calcite, and XPS showed almost no Ca in the near-surface on scans taken immediately after precipitation; but after storage for a month in ultrahigh vacuum, binding energy shifts and the presence of a Ca peak strongly suggested the development of solid-solution by diffusion through the solid. No Cd enrichment was observed at sites of surface defects using AES, indicating that solid-state diffusion into the mineral surface was not accomplished simply by migration along microfractures alone. This work suggests that solid-state diffusion may play a role in the rate and extent of uptake of certain trace metals from solution and probably leads to the formation of solid-solution in calcite and other carbonate minerals. It also suggests that the process of diffusion into the solid mineral host should be considered in hydrogeochemical models that intend to simulate and predict trace-metal mobility in carbonate terrains.

Stipp, Susan L.; Hochella, Michael F., Jr.; Parks, George A.; Leckie, James O.



Hydrate control in deepwater drilling  

SciTech Connect

Gas-hydrate formation during deepwater offshore drilling and production is a well-recognized operational hazard. In water depths greater than 1,000 ft, seabed conditions of pressure and temperature become conducive to gas-hydrate formation. In a well-control situation, although the kick fluid leaves the formation at a high temperature, it can cool to seabed temperature with an extended shut-in period. With high enough hydrostatic pressure at the mudline, hydrates could form in the blowout-preventer (BOP) stack and choke and kill lines, as has been observed in field operations. The current practice in deepwater drilling is to suppress the hydrate-formation temperature by use of highly saline drilling fluids formulated from NaCl or other salts. This solution is applicable for the Gulf of Mexico but insufficient for the conditions encountered in Norwegian deep waters. At extreme water depths or extremely low mudline temperatures, this thermodynamic inhibition alone may not be sufficient to prevent hydrate formation. Instead, the use of kinetic inhibitors or crystal modifiers, in conjunction with thermodynamic inhibitors, may allow successful operations in such an environment. The definition of kinetic inhibitors (to distinguish them from the classic thermodynamic inhibitors, such as polar compounds and electrolytes) comes from the effect of the chemicals on the nucleation and growth of natural gas hydrates, both of which are time-dependent, stochastic processes. The paper describes deepwater drilling fluids, polar and surface-active additives, kinetic inhibition and crystal modifiers, laboratory measurements, and test results.




Comparison of brook trout reproductive success and recruitment in an acidic adirondack lake following whole lake liming and watershed liming  

Microsoft Academic Search

Limestone applications to the catchment of one tributary to Woods Lake were highly effective in reducing stream acidity and stabilizing seasonal fluctuations in pH. The resulting improvement in stream water quality also led to a dramatic shift in reproductive strategy of the Woods Lake brook trout population. Prior to catchment liming, brook trout in Woods Lake were restricted to spawning

Carl L. Schofield; Chris Keleher



Stability of the association fayalite + calcite within metamorphosed banded iron formations: the case of the magnetite ores of Edough massif (N-E  

E-print Network

. The main minerals of the ore bodies are magnetite, hematite, siderite, quartz, calcite, fayalite, hedenbergite and garnet, resulting from the metamorphism of siderite + calcite + quartz rocks containing

Paris-Sud XI, Université de


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.



Calcite formation in soft coral sclerites is determined by a single reactive extracellular protein.  


Calcium carbonate exists in two main forms, calcite and aragonite, in the skeletons of marine organisms. The primary mineralogy of marine carbonates has changed over the history of the earth depending on the magnesium/calcium ratio in seawater during the periods of the so-called "calcite and aragonite seas." Organisms that prefer certain mineralogy appear to flourish when their preferred mineralogy is favored by seawater chemistry. However, this rule is not without exceptions. For example, some octocorals produce calcite despite living in an aragonite sea. Here, we address the unresolved question of how organisms such as soft corals are able to form calcitic skeletal elements in an aragonite sea. We show that an extracellular protein called ECMP-67 isolated from soft coral sclerites induces calcite formation in vitro even when the composition of the calcifying solution favors aragonite precipitation. Structural details of both the surface and the interior of single crystals generated upon interaction with ECMP-67 were analyzed with an apertureless-type near-field IR microscope with high spatial resolution. The results show that this protein is the main determining factor for driving the production of calcite instead of aragonite in the biocalcification process and that -OH, secondary structures (e.g. ?-helices and amides), and other necessary chemical groups are distributed over the center of the calcite crystals. Using an atomic force microscope, we also explored how this extracellular protein significantly affects the molecular-scale kinetics of crystal formation. We anticipate that a more thorough investigation of the proteinaceous skeleton content of different calcite-producing marine organisms will reveal similar components that determine the mineralogy of the organisms. These findings have significant implications for future models of the crystal structure of calcite in nature. PMID:21768106

Rahman, M Azizur; Oomori, Tamotsu; Wörheide, Gert



Induction time in crystallization of gas hydrates  

NASA Astrophysics Data System (ADS)

The kinetics of the initial stage of crystallization of one-component gas hydrates in aqueous solutions are analyzed. The temporal evolution of the volume of hydrate crystallized and the moles of gas consumed are determined. Expressions are derived for the supersaturation dependence of the hydrate crystallite growth rate and the induction time in hydrate crystallization. These expressions are used for revealing how additives in the solution that act as kinetic inhibitors of hydrate crystallization can affect the induction time of the process. The results obtained are applied to crystallization of methane, ethane and cyclopropane hydrates.

Kashchiev, Dimo; Firoozabadi, Abbas



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



Lime pretreatment of crop residues bagasse and wheat straw  

Microsoft Academic Search

Lime (calcium hydroxide) was used as a pretreatment agent to enhance the enzymatic digestibility of two common crop residues:\\u000a bagasse and wheat straw. A systematic study of pretreatment conditions suggested that for short pretreatment times (1–3 h),\\u000a high temperatures (85-135°C) were required to achieve high sugar yields, whereas for long pretreatment times (e.g., 24 h),\\u000a low temperatures (50–65°C) were effective.

Vincent S. Chang; Murlidhar Nagwani; Mark T. Holtzapple



Experimental Research on Failure Waves in Soda-Lime Glass  

Microsoft Academic Search

A series of plate impact experiment with soda-lime glass specimens in different thicknesses are conducted on a 57 mm diameter\\u000a one-stage gas gun in order to further investigate the so-called failure wave phenomena under dynamic compressive loads. With\\u000a the aid of the VISAR technique, the failure wave trajectory is explored, which shows that, apart from a constant failure wave\\u000a velocity, an

Y.-G. Zhang; Z.-P. Duan; L.-S. Zhang; Z.-C. Ou; F.-L. Huang



Precipitation kinetics in ultra-high lime softening  

E-print Network

available for industrial processes has Fueled the development of new treatment technologies to increase water recycle capacity. As a major consumer of water supplies, cooling water systems are prime targets of these new technologies. Because of this need..., the ultra-high lime process has been proposed as a method to eliminate the constituents of chemical scale which reduce the recycle capacity of water in cooling systems. Reported herein are the results of a bench scale reactor study designed to evaluate...

Peacock, Edward Dale



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


Simulation of calcite dissolution and porosity changes in saltwater mixing zones in coastal aquifers  

USGS Publications Warehouse

Thermodynamic models of aqueous solutions have indicated that the mixing of seawater and calcite-saturated fresh groundwater can produce a water that is undersaturated with respect to calcite. Mixing of such waters in coastal carbonate aquifers could lead to significant amounts of limestone dissolution. The potential for such dissolution in coastal saltwater mixing zones is analyzed by coupling the results from a reaction simulation model (PHREEQE) with a variable density groundwater flow and solute transport model. Idealized cross sections of coastal carbonate aquifers are simulated to estimate the potential for calcite dissolution under a variety of hydrologic and geochemical conditions. Results show that limestone dissolution in mixing zones is strongly dependent on groundwater flux and nearly independent of the dissolution kinetics of calcite. -from Authors

Sanford, W. E.; Konikow, L. F.



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.



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



Kinetic and thermodynamic factors controlling the distribution of SO32- and Na+ in calcites and selected aragonites  

USGS Publications Warehouse

Significant amounts of SO42-, Na+, and OH- are incorporated in marine biogenic calcites. Biogenic high Mg-calcites average about 1 mole percent SO42-. Aragonites and most biogenic low Mg-calcites contain significant amounts of Na+, but very low concentrations of SO42-. The SO42- content of non-biogenic calcites and aragonites investigated was below 100 ppm. The presence of Na+ and SO42- increases the unit cell size of calcites. The solid-solutions show a solubility minimum at about 0.5 mole percent SO42- beyond which the solubility rapidly increases. The solubility product of calcites containing 3 mole percent SO42- is the same as that of aragonite. Na+ appears to have very little effect on the solubility product of calcites. The amounts of Na+ and SO42- incorporated in calcites vary as a function of the rate of crystal growth. The variation of the distribution coefficient (D) of SO42- in calcite at 25.0??C and 0.50 molal NaCl is described by the equation D = k0 + k1R where k0 and k1 are constants equal to 6.16 ?? 10-6 and 3.941 ?? 10-6, respectively, and R is the rate of crystal growth of calcite in mg??min-1??g-1 of seed. The data on Na+ are consistent with the hypothesis that a significant amount of Na+ occupies interstitial positions in the calcite structure. The distribution of Na+ follows a Freundlich isotherm and not the Berthelot-Nernst distribution law. The numerical value of the Na+ distribution coefficient in calcite is probably dependent on the number of defects in the calcite structure. The Na+ contents of calcites are not very accurate indicators of environmental salinities. ?? 1985.

Busenberg, E.; Niel, Plummer L.



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



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)



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



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



Calcite-graphite isotope thermometry in amphibolite facies marble, Bancroft, Ontario  

Microsoft Academic Search

This study presents calcite-graphite carbon isotope fractionations for 32 samples from marble in the northern Elzevir terrane of the Central Metasedimentary Belt, Grenville Province, southern Ontario, Canada. These results are compared with temperatures calculated by calcite-dolomite thermometry (15 samples), garnet-biotite thermometry (four samples) and garnet-hornblende thermometry (three samples). Dcal-gr values vary regularly across the area from >6.5& in the south




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.



Precipitation of aragonite by calcitic bivalves in Mg-enriched marine waters  

Microsoft Academic Search

To understand the relative importance of biological versus physicochemical control over biomineralization, we have tested\\u000a if the chemical composition of the medium (i.e., the Mg\\/Ca ratio) can change the mineralogy of mollusk shells. The shells\\u000a of mollusks are made of calcite and\\/or aragonite, which are by far the most common CaCO3 polymorphs. Several species of bivalves with predominantly calcitic shells

Antonio G. Checa; Concepción Jiménez-López; Alejandro Rodríguez-Navarro; Jorge P. Machado



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



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

E-print Network

. 20 1 0. 08 1. 86 4 0. 11 116. 02' 2 0. 04 8. 61 2 0. 07 1 3. 62 28. 15' 27. 78' 0. 36 17. 47 3. 05 0. 07 0. 07 0. 001 19. 03 16. 17' 7. 93 377. 49' 375. 20"' 2. 28 1 68. 77* 5. 12 1. 05 0. 59 0. 44 81. 35 121. 95 20. 91 4 0.... 17 6. 3 205 1 5 lg g' 0. 24 0. 30 0. 31 0. 35 0. 26 0. 28 0. 31 Table 9. Effects of lime x lime ECCE and B interactions on the surface (10-15 cm) soil pH, extractable soil P, Ca, Mg, and HWSB Lp Li L2 Lp Li L2 Lp Li L2 Lp L) L2...

Villavicencio Batres, Rodolfo



Microstructural control of calcite via incorporation of intracrystalline organic molecules in shells  

NASA Astrophysics Data System (ADS)

It is widely accepted that organic substances regulate or influence the structure of biominerals, but its direct evidences are not plenty. Here we show that the crystallographic microstructures in biotic calcites arise from incorporated intracrystalline organic molecules (IOMs), through a comparison between biotic calcites in shells and synthetic ones with the IOMs extracted from the shells. Although the prismatic layers of a pearl oyster (Pinctada fucata) and a pen shell (Atrina pectinata) morphologically resemble each other, the crystallographic features of constituent calcites are considerably different; in Pinctada, the IOMs are distributed inhomogeneously to form small-angle grain boundaries and associated crystal defects, whereas in Atrina, the IOMs are distributed almost homogeneously and defects are rare in the calcite crystals. We conducted in vitro calcite syntheses in the presence of the IOMs in EDTA-soluble extracts from the prisms. The IOMs in the extracts from Pinctada and Atrina were incorporated into synthetic calcites in a different manner, exhibiting defect-rich/free features as observed in the natural shells. With regard to amino acid compositions of the IOMs, the extract from Atrina has a higher proportion of acidic amino acids than that from Pinctada, implying that acidic proteins do not correlate directly to their affinity for calcium carbonate crystals.

Okumura, Taiga; Suzuki, Michio; Nagasawa, Hiromichi; Kogure, Toshihiro



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.



Shock temperature in calcite (CaCO 3) at 95-160 GPa  

NASA Astrophysics Data System (ADS)

The temperatures induced in crystalline calcite (CaCO 3) upon planar shock compression (95-160 GPa) are reported from two-stage light gas gun experiments. Temperatures of 3300-5400 K are obtained by fitting six-channel optical pyrometer radiances in the 450-900 nm range to the Planck gray-body radiation law. Thermodynamic calculations demonstrate that these temperatures are some 400-1350 K lower than expected for vibronic excitations of the lattice with a 3 R/mole-atom specific heat ( R is gas constant). The temperature deficit along the Hugoniot is larger than that expected from only melting. In addition to melting, it appears likely that shock-induced decomposition of calcite occurs behind the shock front. We modeled disproportionation of calcite into CaO (solid) plus CO 2 (gas). For temperature calculations, specific heat at constant volume for 1 mole of CO 2 is taken to be 6.7 R as compared to 9 R in the solid state; whereas a mole of calcite and a mole of CaO have their solid state values 15 R and 6 R, respectively. Calculations suggest that the calcite decomposes to CaO and CO 2 at ˜110±10 GPa along the Hugoniot. Recent reanalysis of earlier VISAR measurements of particle velocity profiles [1] indicates that calcite shocked to 18 GPa undergoes disproportionation at much lower pressures upon isentropic expansion.

Gupta, Satish C.; Love, Stanley G.; Ahrens, Thomas J.



The promotion effect of coexisting hygroscopic composition on the reaction between oxalic acid and calcite during humidifying process  

NASA Astrophysics Data System (ADS)

Internally mixed oxalic acid with mineral dust has been frequently detected in field measurements (Sullivan and Prather, 2007; Wang et al., 2012; Yang et al., 2009). Meanwhile, Furukawa and Takahashi (Furukawa and Takahashi, 2011) found that most of the oxalic acid in mineral mixture is present as metal oxalate complexes in the aerosols, however, the formation mechanism of these complexes is not well known. It was reported that cloud process of H2C2O4/CaCO3 mixture could lead to the formation of calcium oxalate (Gierlus et al., 2012). Recently, we used Raman spectroscopy to investigate the hygroscopic behavior of H2C2O4/CaCO3 mixture below saturation condition as well as the effect of coexisting hygroscopic compositions, e.g. Ca(NO3)2, NaCl, NH4NO3, and (NH4)2SO4. It was found that there was no interaction between H2C2O4 and calcite without third component during humidifying process under ambient condition. In contrast, the presence of coexisting Ca(NO)3, NaCl, or NH4NO3 could promote the reaction between H2C2O4 and calcite by providing an aqueous circumstance after deliquescence, resulting in the formation of calcium oxalate hydrates. Moreover, substitution of strong acid (HNO3) by medium acid (H2C2O4) occurred when water vapor was absorbed in Ca(NO3)2/H2C2O4 mixture (Ma and He, 2012). As for (NH4)2SO4, there existed a competition effect between (NH4)2SO4 and H2C2O4 for the reaction with CaCO3. CaCO3 was preferentially reacted with (NH4)2SO4 to form gypsum in the solution, while the residual NH4+ and C2O42- ions were bonded to (NH4)2C2O4 after efflorescence. These results implies a potential formation pathway of metal oxalate complexes in the atmosphere and also suggests that synergistic effect between different constituents in humidifying process of mixed particles should be considered in future hygroscopic behavior studies.

Ma, Q.; He, H.



Electron microscopy of frozen hydrated biological specimens  

Microsoft Academic Search

The use of frozen hydrated specimens for molecular structure determination is limited primarily by radiation damage. The radiation damage effect in frozen hydrated catalase crystals has been measured in terms of the loss of electron diffraction. The results show an improvement for this type of specimen relative to wet hydrated or glucose embedded catalase crystals at room temperature. Bright field

K. A. Taylor; R. M. Glaeser



Multipole Electrostatics in Hydration Free Energy Calculations  

E-print Network

Multipole Electrostatics in Hydration Free Energy Calculations YUE SHI,1 CHUANJIE WU,2 JAY W and biochemical processes. The ability to accu- rately calculate the hydration free energy (HFE) is critical: Hydration free energy (HFE) is generally used for evaluating molecular solubility, which is an important

Ponder, Jay


Mechanisms of gas hydrate formation and inhibition  

Microsoft Academic Search

The formation of gas hydrates in gas and oil subsea pipelines often results in blockage and shutdown of these pipelines. Modern control methods depend on understanding the mechanisms through which gas hydrates form. This paper reviews our recent studies of clathrate hydrate formation and inhibition mechanisms using neutron diffraction, differential scanning calorimetry (DSC) and a multiple cell photo-sensing instrument. The

C. A. Koh; R. E. Westacott; W. Zhang; K. Hirachand; J. L. Creek; A. K. Soper



Inhibition of Gas Hydrates in Deepwater Drilling  

Microsoft Academic Search

With the movement of offshore rigs into deep water, the problem of gas hydrates has become an important issue in drilling. If a kick is taken, gas hydrates can form in the blowout preventer (BOP) or chokelines while the kick is circulated out. The water-based pill presented here significantly improves gas-hydrate inhibition. This pill, which can be spotted in the

Arthur Hale; Ashok Dewan



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



(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.



Effect of Lime Stabilized Soil Cushion on Strength Behaviour of Expansive Soil  

Microsoft Academic Search

An experimental investigation was undertaken to study the effects of lime-stabilized soil-cushion on the strength behavior\\u000a of expansive soil. In the present investigation, a series of laboratory tests (Unconfined compression tests and CBR tests)\\u000a were conducted on both expansive soil alone and expansive soil cushioned with lime-stabilized non-expansive cohesive soil.\\u000a Lime contents of 2, 4, 6, 8 and 10% by

Jagadish Prasad Sahoo; Pradip Kumar Pradhan



Short-term responses of wetland vegetation after liming of an Adirondack watershed  

SciTech Connect

Watershed liming has been suggested as a long-term mitigation strategy for lake acidity, particularly in areas subject to high levels of acidic deposition. However, virtually no information has been available on the impacts of liming on wetland vegetation. In 1989, 1100 Mg of limestone (83.5% CaCO[sub 3]) were aerially applied to 48% (100 ha) of the Woods Lake watershed in the west-central Adirondack region of New York as part of the first comprehensive watershed liming study in North America. We inventoried wetland vegetation in 1.0-m[sup 2] plots before liming and during the subsequent 2 yr. Within this period liming influenced the cover, frequency, or importance values of only 6 of 64 wetland taxa. The cover of Sphagnum spp. and of the cespitose sedge Carex interior decreased in control relative to limed plots, and cover of the rhizomatous sedge Cladium mariscoides increased nearly threefold in limed areas. These two sedges, which are relatively tall, are characteristic of more calcareous habitats. Cover of the grass Muhlenbergia uniflora, cover and importance were adversely affected or inhibited by lime. It is unclear whether liming directly inhibited the growth of these three small-statured species, or whether the adverse effects of lime were mediated through shifts in competitive interactions with other species. The limited responses that we observed to liming, along with changes that occurred in control plots over the study period, may indicate that in the short term watershed liming was no more of a perturbation than the environmental factors responsible for natural annual variation in wetland communities.

Mackun, I.R.; Leopold, D.J.; Raynal, D.J. (State Univ. of New York, Syracuse, NY (United States))



Gas hydrate reservoir characteristics and economics  

SciTech Connect

The primary objective of the DOE-funded USGS Gas Hydrate Program is to assess the production characteristics and economic potential of gas hydrates in northern Alaska. The objectives of this project for FY-1992 will include the following: (1) Utilize industry seismic data to assess the distribution of gas hydrates within the nearshore Alaskan continental shelf between Harrison Bay and Prudhoe Bay; (2) Further characterize and quantify the well-log characteristics of gas hydrates; and (3) Establish gas monitoring stations over the Eileen fault zone in northern Alaska, which will be used to measure gas flux from destabilized hydrates.

Collett, T.S.; Bird, K.J.; Burruss, R.C.; Lee, Myung W.



Tropical Silurian Paleotemperatures from Clumped Isotope Analysis of Coexisting Dolomite and Calcite  

NASA Astrophysics Data System (ADS)

In many instances, pervasive diagenetic alteration of original material prevents the use of quantitative climate proxies on Paleozoic or older rocks. As an inherently diagenetic phase, dolomite may provide a more resilient paleotemperature resource. The ?47 carbonate clumped isotope thermometer has been shown to be an accurate paleothermometer and, in a limited way, has been shown to be applicable to dolomites. The shallow water carbonates of the Pipe Creek Jr. Reef in central Indiana offer an opportunity to test the viability of the technique in ancient dolomite. After formation in the late Silurian, a sea level drop resulted in a diagenetic sequence of meteoric phreatic alteration of marine cement and biotic components, which included precipitation of dolomite cements inter-grown within the meteoric phreatic calcite cement. This was post-dated by a coarse void filling calcite spar formed at burial temperatures of ~100°C (based on fluid inclusion analysis). Preliminary analyses of coexisting dolomite and calcite suggest that near-surface temperatures are preserved in dolomites despite having experienced elevated thermal diagenetic effects.. In contrast, co-existing early-formed calcites exhibit resetting of earth surface temperatures to elevated values. ?47 measurements in dolomites yield temperatures around 30°C using the Guo et al., (2009) theoretical calibration. This contrasts with analyses of early (original) and late (hydrothermal) calcites, which record temperatures greater than ~80°C using the ?47-calcite calibration of Dennis and Schrag (2010). These data support the hypothesis that dolomite can be a more resilient paleotemperature proxy relative to calcite in deep-time studies. Temperatures from dolomites compare reasonably with other late Silurian paleoclimate studies, and offer insight into regional-scale paleoclimate.

Winkelstern, I. Z.; Lohmann, K. C.



Coprecipitation of Uranium(VI) with Calcite: XAFS, micro-XAS, and luminescence characterization  

NASA Astrophysics Data System (ADS)

X-ray absorption and luminescence spectroscopies have been used to characterize the local structure and coordination of uranium(VI) species coprecipitated with calcite (CaCO 3) from room-temperature aqueous solutions. Different solution chemistries and pHs are found to result in differences in the equatorial coordination of the uranyl species (UO 22+) incorporated in the calcite, with multiple coordination environments of uranyl evident in one sample. Differences in the equatorial coordination between the aqueous uranyl species and those found in the calcite indicate that coordination changes occur during incorporation of at least some species. This contrasts with previous findings showing no change in equatorial coordination during uranyl incorporation into aragonite, and may explain the greater incorporation in this latter phase. The absence of calcium backscatterers and well defined structure beyond the equatorial shell is consistent with disorder associated with disruption of the local calcite structure. This may indicate an inability of the uranyl unit to assume a stable structural environment in the host calcite, which could decrease the stability of uranyl-containing calcite. Calcite single crystals grown in uranyl-containing solutions exhibit polygonized spiral growth hillocks on (101¯4) surfaces composed of four vicinal surfaces, consistent with face symmetry. Micro-X-ray fluorescence reveals that uranium is differentially incorporated between nonequivalent vicinal surfaces, reflecting step-selective incorporation of uranyl species during growth. Micro-X-ray absorption near-edge structure spectra from the nonequivalent vicinal faces fail to reveal any differences in speciation between the vicinals or that might account for the presence of the multiple coordination environments identified by luminescence and X-ray absorption spectroscopies.

Reeder, Richard J.; Nugent, Melissa; Tait, C. Drew; Morris, David E.; Heald, Steve M.; Beck, Kenneth M.; Hess, Wayne P.; Lanzirotti, Anthony



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.



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

NASA Astrophysics Data System (ADS)

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.



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



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



Effect of fatty acids, water composition and pH on the wettability alteration of calcite surface  

Microsoft Academic Search

Fatty acids in presence of water film alter calcite surface to oil-wet. The wettability alteration is dependent on the structure of the fatty acids, water composition and pH. Long chain fatty acid (stearic acid), strongly adsorbs onto the calcite surface from “oil phase” (n-C10) in oil\\/water\\/calcite system as indicated by contact angle measurements. On the other hand, short chain fatty

K. A. Rezaei Gomari; A. A. Hamouda



Lead adsorption at the calcite-water interface: Synchrotron X-ray standing wave and X-ray reflectivity studies  

Microsoft Academic Search

By combining synchrotron X-ray standing wave (XSW) measurements with synchrotron X-ray reflectivity measurements, we have determined: (1) the precise three-dimensional location within the calcite unit cell of submonolayer Pb ions adsorbed at the calcite (104) surface from dilute aqueous solutions, and (2) the precise one-dimensional location of these unit cells relative to the calcite surface. Our XSW measurements, using three

Neil C. Sturchio; Ronald P. Chiarello; Likwan Cheng; Paul F. Lyman; Michael J. Bedzyk; Yonglin Qian; Hoydoo You; Dennis Yee; Phillip Geissbuhler; Larry B. Sorensen; Yong Liang; Donald R. Baer



Dolomite-magnesian calcite relations at elevated temperatures and CO2 pressures  

USGS Publications Warehouse

The equilibrium thermal decomposition curve of dolomite has been determined up to a CO2 pressure of 20,000 lb/in.2, at which pressure dolomite decomposes at 857??C. Equilibrium was approached from both directions, by the breakdown and by the solid-state synthesis of dolomite. At elevated temperatures and pressures, calcites in equilibrium with periclase as well as those in equilibrium with dolomite contain Mg in solid solution. In the former, the Mg content increases with increasing CO2 pressure, and decreases with increasing temperature. In the latter, it is a function of temperature only. The exsolution curve of dolomite and magnesian calcite has been determined between 500?? and 800??C; at 500?? dolomite is in equilibrium with a magnesian calcite containing ~6 mol per cent MgCO2; at 800??, ~22 mol per cent. There appears to be a small but real deviation from the ideal 1 : 1 Ca : Mg ratio of dolomite, in the direction of excess Ca, for material in equilibrium with magnesian calcite at high temperature. The experimental findings indicate that very little Mg is stable in the calcites of sedimentary environments, but that an appreciable amount is stable under higher-temperature metamorphic conditions, if sufficient CO2 pressure is maintained. ?? 1955.

Graf, D. L.; Goldsmith, J. R.



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


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



Monitoring bacterially induced calcite precipitation in porous media using magnetic resonance imaging and flow measurements  

NASA Astrophysics Data System (ADS)

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 quantitative one-dimensional profiles and three-dimensional images, applied before and after the formation of calcite in order to characterise the spatial distribution of the precipitate. It was shown through modification and variations of the calcite precipitation treatment that differences in the calcite fill would occur but all methods were successful in partially blocking the different porous media. Precipitation was seen to occur predominantly at the inlet of the bead pack, whereas precipitation occurred almost uniformly along the sandstone core. Transport properties are quantified using pulse field gradient (PFG) NMR measurements which provide probability distributions of molecular displacement over a set observation time (propagators), supplementing conventional permeability measurements. Propagators quantify the local effect of calcite formation on system hydrodynamics and the extent of stagnant region formation. Collectively, the combination of NMR measurements utilised here provides a toolkit for determining the efficacy of a biological-precipitation reaction for partially blocking porous materials.

Sham, E.; Mantle, M. D.; Mitchell, J.; Tobler, D. J.; Phoenix, V. R.; Johns, M. L.



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



Predicting stripping and moisture induced damage of asphalt concrete prepared with polymer modified bitumen and hydrated lime  

Microsoft Academic Search

Many highway agencies have been experiencing premature failures that decrease the performance and service life of pavements. One of the major causes of premature pavement failure is the moisture damage of the asphalt concrete layer. Many variables affect the amount of water damage in the asphalt concrete layer such as the type of aggregate, bitumen, mixture design and construction, level

Cagri Gorkem; Burak Sengoz



Infrared spectroscopy and density functional theory investigation of calcite, chalk, and coccoliths-do we observe the mineral surface?  


We have measured infrared spectra from several types of calcite: chalk, freshly cultured coccoliths produced by three species of algae, natural calcite (Iceland Spar), and two types of synthetic calcite. The most intense infrared band, the asymmetric carbonate stretch vibration, is clearly asymmetric for the coccoliths and the synthetic calcite prepared using the carbonation method. It can be very well fitted by two peaks: a narrow Lorenzian at lower frequency and a broader Gaussian at higher frequency. These two samples both have a high specific surface area. Density functional theory for bulk calcite and several calcite surface systems allows for assignment of the infrared bands. The two peaks that make up the asymmetric carbonate stretch band come from the bulk (narrow Lorenzian) and from a combination of two effects (broad Gaussian): the surface or near surface of calcite and line broadening from macroscopic dielectric effects. We detect water adsorbed on the high surface area synthetic calcite, which permits observation of the chemistry of thin liquid films on calcite using transmission infrared spectroscopy. The combination of infrared spectroscopy and density functional theory also allowed us to quantify the amount of polysaccharides associated with the coccoliths. The amount of polysaccharides left in chalk, demonstrated to be present in other work, is below the IR detection limit, which is 0.5% by mass. PMID:25318063

Andersson, M P; Hem, C P; Schultz, L N; Nielsen, J W; Pedersen, C S; Sand, K K; Okhrimenko, D V; Johnsson, A; Stipp, S L S



National workshop on gas hydrates  

NASA Astrophysics Data System (ADS)

The range of present knowledge on the subject of gas hydrates and related federal research programs was the topic of discussion at the National Workshop on Gas Hydrates, April 23-24. The intention of the meeting was to provide the impetus for an expanded and broader-based national research program in both academia and government. Held at the U.S. Geological Survey National Center, Reston, Va., the workshop was organized by Michael D. Max, Naval Research Laboratory, Washington, D.C.; William P. Dillon, USGS, Woods Hole, Mass.; and Rodney D. Malone, U.S. Department of Energy, Morgantown Energy Technology Center, Morgantown, W.Va. The 33 attendees represented academia (33%), federal agencies (58%), and industry (9%).

Max, Michael D.; Dillon, William P.; Malone, Rodney D.; Kvenvolden, Keith A.


Keeping nursing home residents hydrated.  


The purpose of this research is to ascertain nursing home (NH) staffs' perspectives of the problem of dehydration in NHs (skilled nursing facilities) and have them identify clinically practical interventions to ensure that NH residents consistently take adequate fluids. Four focus groups with 28 NH staff members in attendance are held in three NHs in metropolitan Los Angeles. The majority of participants are certified nursing assistants; however, licensed vocational nurses, registered nurses, and other NH staff also attend the groups. Content analytic techniques are used to analyze the data. Three themes emerge focusing on residents' reasons for not drinking, signs and symptoms of dehydration, and strategies for improving hydration in NH residents. NH staff members identify the complexity of providing adequate hydration that was influenced by the resident's relationship with family and NH staff and communication between staff members. PMID:16672630

Mentes, Janet C; Chang, Betty L; Morris, Joseph



40 CFR Table S-1 to Subpart S of... - Basic Parameters for the Calculation of Emission Factors for Lime Production  

Code of Federal Regulations, 2011 CFR

...Basic Parameters for the Calculation of Emission Factors for Lime Production S Table S-1 to Subpart S of Part 98 ...Basic Parameters for the Calculation of Emission Factors for Lime Production Variable Stoichiometric ratio SRCaO...



40 CFR Table S-1 to Subpart S of... - Basic Parameters for the Calculation of Emission Factors for Lime Production  

Code of Federal Regulations, 2013 CFR

...Basic Parameters for the Calculation of Emission Factors for Lime Production S Table S-1 to Subpart S of Part 98 ...Basic Parameters for the Calculation of Emission Factors for Lime Production Variable Stoichiometric ratio SRCaO...



40 CFR Table S-1 to Subpart S of... - Basic Parameters for the Calculation of Emission Factors for Lime Production  

Code of Federal Regulations, 2012 CFR

...Basic Parameters for the Calculation of Emission Factors for Lime Production S Table S-1 to Subpart S of Part 98 ...Basic Parameters for the Calculation of Emission Factors for Lime Production Variable Stoichiometric ratio SRCaO...



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


Effects of liming on forage availability and nutrient content in a forest impacted by acid rain.  


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



Mechanical and thermal properties of lime and hemp concrete (“hempcrete”) manufactured by a projection process  

Microsoft Academic Search

Concrete blocks, made of a mixture of lime and hemp shives (also called “hemp hurds”), have been manufactured by a recently developed projection process. Lime carbonatation kinetics is determined by X-ray diffraction. Density measurements are made within blocks, and thermal and mechanical properties are measured (flexural strength, compression strength and hardness). The main observations are moderate density variations within a

S. Elfordy; F. Lucas; F. Tancret; Y. Scudeller; L. Goudet



Liming to mitigate acidification in freshwater ecosystems: A review of the biological consequences  

Microsoft Academic Search

The use of lime to mitigate the biological effects of surface water acidification, has recently become a widespread practice. Following a background section on liming strategies and physico-chemical effects, the observed effects of this treatment on the decomposition process and major biological components of freshwater ecosystems are reviewed. Available studies, which cover up to about 6 to 8 yr post-treatment,

N. S. Weatherley




EPA Science Inventory

This summary report describes the use of lime or limestone as an option for the treatment of sulfur oxides at fossil fuel steam and electric generating facilities. n this treatment, an aqueous slurry of slaked lime or wet ground limestone absorbs sulfur oxide from flue gas. bsorb...


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



Lime stabilized sludge treatment of acid soils relative to soil acidity minimums for sludge application  

Microsoft Academic Search

Lime stabilized sludge (LSS) from wastewater treatment plants contains lime, which may neutralize soil acidity, and P, an essential plant nutrient. Guidelines for use of land application of secondary sludges call for the soil pH to be at 6.5 or above prior to application. This greenhouse study was initiated to determine the effects of placement of LSS from two sources

J. R. Brown; Lyndon Brush




E-print Network

CONTROLLED LOW-STRENGTH MATERIAL (CLSM) PRODUCED WITH HIGH-LIME FLY ASH By Tarun R. Naik Director, Milwaukee, WI 53201 For presentation at the International Conference on the Utilization of Fly Ash and Other (CLSM) PRODUCED WITH HIGH-LIME FLY ASH Tarun R. Naik,* Bruce W. Ramme** and Henry J. Kolbeck** Abstract

Wisconsin-Milwaukee, University of


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



Design of green concrete made of plant-derived aggregates and a pumice–lime binder  

Microsoft Academic Search

The use of particles from agricultural lignocellulosic resources in concrete gives it desirable environmental and multiphysics qualities. In this study, parallels are drawn between particles derived from hemp and sunflower stems, in terms of their morphological and physical properties. A pumice–lime binder is proposed as an alternative to the traditional cement or lime based solutions for both environmentally friendly and

V. Nozahic; S. Amziane; G. Torrent; K. Saïdi; H. De Baynast


Behaviour of a starch as a viscosity modifier for aerial lime-based mortars  

Microsoft Academic Search

Different dosages of a commercialized potato starch were added to aerial lime-based mortars in order to check its efficiency as a rheological modifier. Several fresh state properties of the mortars were studied: consistency, density, air content, water retention capacity, setting time and evolution when applied on support. The effect of the starch on ?-potential of the lime particle surface as

A. Izaguirre; J. Lanas; J. I. Álvarez




Microsoft Academic Search

Crude ethanolic extracts of kaffir lime leaf, bitter cucumber fruit and tobacco leaf were examined for their ability to control the growth of A. flavus on PDA. The results showed that the ethanolic extracts of all herbs had an inhibitory effect on fungal growth. Kaffir lime at 10 % and tobacco at 8-10 % showed significantly higher inhibition than at

Dusanee Thanaboripat; Sittichai Chareonsettasilp; Kanokwan Pandee


Fruit spot of sweet lime ( Citrus limetta ) caused by Septoria sp. in Peru  

Microsoft Academic Search

In 2002, a severe fruit spot of sweet lime (Citrus limetta) was observed in Piura and Lambayeque provinces in northern Peru. Affected fruits showed large oval and sunken lesions, often\\u000a surrounded by chlorotic haloes. Septoria sp. was isolated from affected fruits. Sweet lime isolates showed larger pycnidia and pycnidiospores than those of Septoria spp. previously described on citrus. In addition,

Luis A. Álvarez-Bernaola; Javier Javier-Alva; Antonio Vicent; Maela León; José García-Jiménez




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 ...


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)



Quantification of ammonia-oxidising bacteria in limed and non-limed acidic coniferous forest soil using real-time PCR  

Microsoft Academic Search

Ammonia-oxidising bacteria (AOB) in limed and non-limed acidic coniferous forest soil were investigated using real-time PCR. Two sites in southern Sweden were studied, 244 Åled and Oxafällan. The primers and probe used earlier appeared to be specific to the 16S rRNA gene of AOB belonging to the ?-subgroup of the Proteobacteria [Appl. Environ. Microbiol. 67 (2001) 972]. Plots treated with

Anna Hermansson; Jenny S. K. Bäckman; Bo H. Svensson; Per-Eric Lindgren



Dielectric response of hydrated proteins  

NASA Astrophysics Data System (ADS)

We study dipolar susceptibility of hydrated proteins, representing the average dipole moment induced at the hydrated protein by a uniform external field. This parameter shows remarkable variation among proteins. We find a negative value of the dipolar susceptibility for some proteins, which implies a dia-electric dipolar response and negative dielectrophoresis. Such proteins, even though carrying significant permanent dipole moments, repel from the electric field. This outcome is the result of a negative cross-correlation between the protein and water dipoles, compensating for the positive variance of the intrinsic protein dipole in the overall dipolar susceptibility. We therefore suggest that the dipolar response of proteins in solution is strongly affected by the coupling of the protein surface charge to the hydration water. The protein-water dipolar cross-correlations are long-ranged, extending approximately 2 nm from the protein surface into the bulk. A similar correlation length of about 1 nm is found for the electrostatic potential. The model is applied to the analysis of light absorption by protein solutions in the THz window of radiation. Here we also find significant deviations of the absorption coefficient from the predictions of traditional theories.

Matyushov, Dmitry



Approach towards zero discharge tanning: role of concentration on the development of eco-friendly liming–reliming processes  

Microsoft Academic Search

Beam house processes1Beam house processes generally mean liming–reliming processes, which employ beam.1 in leather processing are known for their uncleanness. More than 60% of the total pollution is emerging from the liming–reliming processes. The use of lime and sodium sulphide is purely empirical without quantification. Lime has a potential to drive swelling in a gradual manner due to its low

P. Thanikaivelan; J. Raghava Rao; B. U. Nair; T. Ramasami



Characterization of limes (Citrus aurantifolia) grown in Bhutan and Indonesia using high-throughput sequencing.  


Lime [Citrus aurantifolia (Cristm.) Swingle] is a Citrus species that is a popular ingredient in many cuisines. Some citrus plants are known to originate in the area ranging from northeastern India to southwestern China. In the current study, we characterized and compared limes grown in Bhutan (n = 5 accessions) and Indonesia (n = 3 accessions). The limes were separated into two groups based on their morphology. Restriction site-associated DNA sequencing (RAD-seq) separated the eight accessions into two clusters. One cluster contained four accessions from Bhutan, whereas the other cluster contained one accession from Bhutan and the three accessions from Indonesia. This genetic classification supported the morphological classification of limes. The analysis suggests that the properties associated with asexual reproduction, and somatic homologous recombination, have contributed to the genetic diversification of limes. PMID:24781859

Penjor, Tshering; Mimura, Takashi; Matsumoto, Ryoji; Yamamoto, Masashi; Nagano, Yukio



Interpretation of speleothem calcite ?13C variations: Evidence from monitoring soil CO2, drip water, and modern speleothem calcite in central Texas  

NASA Astrophysics Data System (ADS)

We studied the sources and transport of carbon in two active karst systems in central Texas, Inner Space Cavern (IS) and Natural Bridge North and South Caverns (NB), to provide new insights into the interpretation of speleothem (cave calcite deposit) carbon isotope compositions. We have determined the ?13C values of soil CO2 (?13Cs) in grassland and savanna above these caves with ?13C values of cave drip water (?13CHCO3-) and modern speleothem calcite grown on artificial substrates (?13Ccc). We compare ?13CHCO3- values from direct drip sites, where water was sampled immediately upon discharging from the cave ceiling, to values from indirect sites, where water was sampled after flowing along a prolonged path within the cave that allowed for longer CO2 degassing and have found that direct drip sites yield consistently lower ?13CHCO3- values. The ?13CHCO3- values of direct drip water below savanna (-10.6 ± 0.5‰ and -12.6 ± 0.2‰, in NB and IS, respectively) are indistinguishable from (IS) or similar to (NB) calculated ?13CHCO3- values in equilibrium with measured soil CO2 beneath trees (-13.5‰ to -11.3‰ for juniper trees above NB, and -13.6‰ to -12.6‰ for mixed oak and elm trees above IS, respectively). At IS, the ?13CHCO3- values of direct drip water are higher below grassland (-9.7 ± 0.3‰) than below savanna (12.6 ± 0.2‰). These results suggest that the ?13CHCO3- values of drip waters that initially enter the caves are controlled by deep-rooted plants, where present, and are minimally influenced by host-rock dissolution and/or prior calcite precipitation (PCP). The ?13CHCO3- values of indirect drip water vary seasonally with relatively low values during the summer (-10.8 ± 0.8‰ and -9.2 ± 0.4‰ under juniper savanna at NB and under grassland at IS, respectively) that are similar to the direct drip ?13CHCO3- values (-10.6 ± 0.5‰ and -9.7 ± 0.3‰ under savanna at NB and under grassland at IS, respectively). The relatively high ?13CHCO3- values of indirect drip sites during the winter (?13CHCO3- = -8.6 ± 0.8‰ at NB and 8.0 ± 0.1‰ at IS) result from CO2 degassing of water along in-cave flow paths. We also present decade-long records of modern calcite ?13C values from direct and indirect drip sites at IS. The ?13Ccc values vary seasonally with lower values during the summer and higher values during the winter, and with smaller amplitude variations at the direct drip site. Such seasonal variations can be used as a geochronological tool in some speleothems that do not contain visible lamina. The summer ?13Ccc values of direct drip calcite are similar to ?13Ccc values predicted from soil CO2 collected beneath trees above that drip site. The occurrence of highest ?13Ccc values during the winter, when cave CO2 concentrations are low, highlights the significance of ventilation-driven changes in cave-air pCO2. Modern calcite ?13C values are also negatively correlated with drip rate, which suggests that ?13Ccc variations are controlled by kinetic effects during degassing and calcite precipitation associated with the drip water exposure time to a low-pCO2 environment. In all, at the caves we investigated, variability in speleothem ?13Ccc values primarily reflect presence/absence of deep-rooted vegetation and kinetic isotope effects. We therefore infer that increased aridity may result in higher ?13C values of vegetation, lower drip rates and more drip water degassing, and thus higher ?13Ccc values of speleothem calcite.

Meyer, Kyle W.; Feng, Weimin; Breecker, Daniel O.; Banner, Jay L.; Guilfoyle, Amber



In situ study of boron partitioning between calcite and fluid at different crystal growth rates  

NASA Astrophysics Data System (ADS)

The boron isotopic and chemical content of carbonates (expressed as ?11B and B/Ca ratios) have been proposed as proxies for seawater carbonate system parameters. Thermodynamic and kinetic effects on ?11B and B partitioning are not yet fully constrained, underscoring the importance of exploring possible effects of growth rate on boron incorporation in synthetic calcium carbonate minerals, which is the focus of this study. Secondary Ion Mass Spectrometry (SIMS) measurements of B/Ca and ?11B were performed on single crystal of calcite synthesized by diffusion of CO2 under controlled conditions from a solution of NH4Cl-CaCl2 doped with boron. Growth rates of calcite (V, nm/s) within crystals grown isothermally at 24.6 °C were monitored by sequentially spiking calcite-precipitating fluids with rare earth element (REE) dopants. The REE were analyzed with SIMS at spots that match those locations where B/Ca and ?11B ratios were measured. Values for the boron Nernst partition coefficient, defined as DB = B(calcite)/B(fluid), increase from 0.5 (pHNBS = 8.15) to 0.9 (pH = 8.00) with values of V increasing from 0.04 to 0.13 nm/s. For ?11B behavior, it was not possible to draw conclusive results due to the analytical error (2.2‰; 2?). pH effects on DB during calcite precipitation, associated with an increase in pH from 8.00 to 8.15, appear to be masked by the competing effects of changing V. We conclude that over the range of growth rates and other conditions investigated in this study, growth rate effects on B partitioning need to be accounted for when using B/Ca ratios in biogenic calcite as a proxy for seawater carbonate system parameters.

Gabitov, Rinat I.; Rollion-Bard, Claire; Tripati, Aradhna; Sadekov, Aleksey



Fatty acids in sparry calcite fracture fills and microsparite cement of septarian diagenetic concretions  

NASA Astrophysics Data System (ADS)

Sparry calcite fracture fills and concretion body cements in concretions from the Flodigarry Shale Member of the Staffin Shale Formation, Isle of Skye, Scotland, entrap and preserve mineral and organic materials of sedimentary and diagenetic origin. Fatty acids are a major component of the lipids recovered by decarbonation and comprise mainly n-alkanoic and ?-? dicarboxylic acids. Two generations of fracture-fill calcite (early brown and later yellow) and the concretion body microspar yield significantly different fatty acid profiles. Early brown calcites yield mainly medium-chain n-alkanoic acids with strong even predominance; later yellow calcites are dominated by ?-? dicarboxylic acids with no even predominance. Both fracture fills lack the long-chain n-alkanoic and ?-? dicarboxylic acids additionally recovered from the concretion bodies. The absence of longer chain acids in the calcite spar fracture fills is inferred to result from the transport of fatty acids by septarian mineralising fluids whereby low-aqueous solubility of longer chain acids or their salts accounts for their relative immobility. Comparative experiments have been carried out using conventional solvent extraction on the concretion body and associated shales, both decarbonated and untreated. Extracted lipid yields are higher, but the fatty acids probably derive from mixed locations in the rock including both kerogen- and carbonate-associated lipid pools. Only experiments involving decarbonation yielded ?-? dicarboxylic acids in molecular distributions probably controlled mainly by fluid transport. Alkane biomarker ratios indicate very low thermal maturity has been experienced by the concretions and their host sediments. Septarian cracks lined by brown calcite formed during early burial. Microbial CO 2 from sulphate-reducing bacteria was probably the main source of mineralising carbonate. Emplacement of the later septarian fills probably involved at least one episode of fluid invasion.

Pearson, M. J.; Hendry, J. P.; Taylor, C. W.; Russell, M. A.



Uranium in foraminiferal calcite as a recorder of seawater uranium concentrations  

SciTech Connect

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 calida) foraminifera show that the U/Ca ratio of cleaned calcite tests is proportional to the concentration of uranium in solution. After correcting results for the presence of initial calcite, the apparent distribution coefficient D = (U/Ca[sub calcite])/(U/Ca)[sub solution] = 10.6 [+-] 0.3 (x10[sup [minus]3]) for A. lobifera and D = 7.9 [+-] 0.1 (x10[sup [minus]3]) for G. calida. U/Ca ratios in planktonic foraminifera from core tops collected above 3900 m in the equatorial Atlantic and above 2100 m in the Pacific Ocean show no significant difference among the species analyzed. D estimated form core top samples ranges from 7.6 [+-] 0.4 (x10[sup [minus]3]) for O. universa to 8.4 [+-] 0.5 (x10[sup [minus]3]) for G. ruber. In benthic species C. wuellerstorfi, D = 7.0 [+-] 0.8 (x10[sup [minus]3]). U/Ca and Mg/Ca in G. tumida and G. sacculifer from core tops taken near and below the regional lysocline decrease with water depth. Smaller decreases in U/Ca and Mg/Ca with depth were observed in C. wuellerstorfi. In the planktonic species, the authors believe that U/CA and Mg/Ca are lower in the more dissolution-resistant fraction of calcite, leading to lower U/Ca in more highly dissolved samples.

Russell, A.D.; Emerson, S.; Nelson, B.K. (Univ. of Washington, Seattle, WA (United States)); Erez, J. (Univ. of Jerusalem, (Israel)); Lea, D.W. (Univ. of California, Santa Barbara, CA (United States))



Uranium in foraminiferal calcite as a recorder of seawater uranium concentrations  

NASA Astrophysics Data System (ADS)

We 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 ( Globigerinella calida) foraminifera show that the U/Ca ratio of cleaned calcite tests is proportional to the concentration of uranium in solution. After correcting results for the presence of initial calcite, the apparent distribution coefficient D = ( U/Ca) calciteU/Ca) solution = 10.6 ± 0.3 (×10 -3) for A. lobifera and D = 7.9 ± 0.1 (×10 -3) for G. calida. U/Ca ratios in planktonic foraminifera from core tops collected above 3900 m in the equatorial Atlantic and above 2100 m in the Pacific Ocean show no significant difference among the species analyzed. D estimated from core top samples ranges from 7.6 ± 0.4 (× 10 -3) for O. universa to 8.4 ± 0.5 (×10 -3) for G. ruber. In benthic species C. wuellerstorfi, D = 7.0 ± 0.8 (×10 -3). U/Ca and Mg/Ca in G. tumida and G. sacculifer from core tops taken near and below the regional lysocline decrease with water depth. Smaller decreases in U/Ca and Mg/Ca with depth were observed in C. wuellerstorfi. In the planktonic species, we believe that U/Ca and Mg/Ca are lower in the more dissolution-resistant fraction of calcite, leading to lower U/Ca in more highly dissolved samples.

Russell, Ann D.; Emerson, Steven; Nelson, Bruce K.; Erez, Jonathan; Lea, David W.



Origin of platy calcite crystals in hot-spring deposits in the Kenya Rift Valley  

SciTech Connect

Platy calcite crystals, which have their c axis parallel to their shortest length axis, are common components of travertine deposits found around some hot springs in the Kenya Rift Valley. They are composite crystals formed of numerous paper-thin subcrystals. Individual plates allowed to grow without obstruction develop a hexagonal motif. The Kenyan crystals typically form in hot (>75 C) waters that have a low Ca content (<10 mg/l), a high CO{sub 2} content, and a high rate of CO{sub 2} degassing. At Chemurkeu, aggregates of numerous small platy crystals collectively form lattice crystals that superficially resemble ray crystals. The walls of the lattice crystals are formed of large platy crystals that have their long and intermediate length axes aligned parallel to the plane of the long axis of the lattice crystal. Internally, the lattice crystals are formed of small platy calcite crystals arranged in a boxlike pattern that creates the appearance of a lattice when viewed in thin section. Lattice crystals are highly porous, with each pore being enclosed by platy crystals. At Lorusio, travertines are mainly formed of pseudodentrites that are constructed by numerous small platy crystals attached to a main stem which is a large platy crystal that commonly curves along its long axis. The pseudodentrites are the main construction blocks in ledges and lilypads that form in the vent pool and spring outflow channels, where the water is too hot for microbes other than hyperthermophiles. The platy calcite crystals in the Kenyan travertines are morphologically similar to platy calcite crystals that form as scale in pipes in the geothermal fields of New Zealand and hydrothermal angel wing calcite from the La Fe mine in Mexico. Comparison of the Kenyan and New Zealand crystals indicates that platy calcite crystals form from waters with a low Ca{sup 2+} content and a high CO{sub 3}/Ca ratio due to rapid rates of CO{sub 2} degassing.

Jones, B. [Univ. of Alberta, Edmonton, Alberta (Canada). Dept. of Earth and Atmospheric Sciences; Renault, R.W. [Univ. of Saskatchewan, Saskatoon, Saskatchewan (Canada). Dept. of Geological Sciences



Calcium-43 NMR studies of polymorphic transition of calcite to aragonite.  


Phase transformation between calcite and aragonite is an important issue in biomineralization. To shed more light on the mechanism of this process at the molecular level, we employ solid-state (43)Ca NMR to study the phase transformation from calcite to aragonite as regulated by magnesium ions, with (43)Ca enrichment at a level of 6%. Using the gas diffusion approach, the phase of Mg-calcite is formed initially and the system subsequently transforms to aragonite as the reaction time proceeds. Our (43)Ca solid-state NMR data support the dissolution-recrystallization mechanism for the calcite to aragonite transition. We find that the (43)Ca NMR parameters of Mg-calcite are very similar to those of pure calcite. Under the high-resolution condition provided by magic-angle spinning at 4 kHz, we can monitor the variation of the (43)Ca NMR parameters of the aragonite signals for the samples obtained at different reaction times. Our data suggest that in the presence of a significant amount of Mg(2+) ions, aragonite is the most stable polymorph of calcium carbonate. The initial precipitated crystallites of aragonite have spine-like morphology, for which the (43)Ca spin-lattice relaxation data indicate that the ions in the lattice have considerable motional dynamics. As the crystallinity of aragonite improves further, the (43)Ca T(1) parameter of the aragonite phase changes considerably and becomes very similar to that obtained for pure aragonite. For the first time, the difference in crystal morphologies and crystallinity of the aragonite phase has been traced down to the subtle difference in the motional dynamics at the molecular level. PMID:23163540

Huang, Yu-Chieh; Mou, Yun; Tsai, Tim Wen-Tin; Wu, Yu-Ju; Lee, Hsin-Kuan; Huang, Shing-Jong; Chan, Jerry C C



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.



Formulation of production blasting criteria for the construction of a lime plant at a major crushed stone operation  

Microsoft Academic Search

A blast-monitoring program conducted at Chemical Lime Company's new lime calcining facility near St Genevieve, Missouri, USA is discussed. The purpose was to develop blasting criteria for the construction and operation of the lime plant within the quarry operated by Tower Rock Stone. Further, it was imperative to accommodate production requirements into the blasting criteria. The major concern was the

Paul Worsey; Scott G. Giltner; Terry Drechsler; Ron Ecklecamp; Ronnie Inman



The effects of using lime and styrene–butadiene–styrene on moisture sensitivity resistance of hot mix asphalt  

Microsoft Academic Search

This study focuses on determining the effects of styrene–butadiene–styrene (SBS) and using mineral filler with lime on various properties of hot mix asphalt especially moisture damage resistance. The asphalt cement was modified with 2%, 4% and 6% SBS. The lime treated mixtures containing 2% lime by weight of the total aggregate as filler. The physical and mechanical properties of polymer

Baha Vural Kok; Mehmet Yilmaz



Measuring changes in stress and vitality indicators in limed sugar maple on the Allegheny Plateau in north-central Pennsylvania  

Microsoft Academic Search

A study established in 1985 in north-central Pennsylvania to determine effects of lime fertilization on declin - ing sugar maple (Acer saccharum Marsh.) was evaluated in 1993 and showed that liming positively affected growth and crown vitality in sugar maple. This effect of lime on sugar maple offered an opportunity to assess other indicators of tree vitality and their response

Philip M. Wargo; Rakesh Minocha; Betty L. Wong; Robert P. Long; Stephen B. Horsley; Thomas J. Hall



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


Morphological and mechanical characterization of composite calcite/SWCNT-COOH single crystals  

NASA Astrophysics Data System (ADS)

A growing number of classes of organic (macro)molecular materials have been trapped into inorganic crystalline hosts, such as calcite single crystals, without significantly disrupting their crystalline lattices. Inclusion of an organic phase plays a key role in enhancing the mechanical properties of the crystals, which are believed to share structural features with biogenic minerals. Here we report the synthesis and mechanical characterization of composite calcite/SWCNT-COOH single crystals. Once entrapped into the crystals SWCNT-COOH appeared both as aggregates of entangled bundles and nanoropes. Their observation was possible only after crystal etching, fracture or FIB (focused ion beam) cross-sectioning. SWCNT-COOHs occupied a small volume fraction and were randomly distributed into the host crystal. They did not strongly affect the crystal morphology. However, although the Young's modulus of composite calcite/SWCNT-COOH single crystals was similar to that of pure calcite their hardness increased by about 20%. Thus, SWCNT-COOHs provide an obstacle against the dislocation-mediated propagation of plastic deformation in the crystalline slip systems, in analogy with the well-known hardness increase in fiber-reinforced composites.A growing number of classes of organic (macro)molecular materials have been trapped into inorganic crystalline hosts, such as calcite single crystals, without significantly disrupting their crystalline lattices. Inclusion of an organic phase plays a key role in enhancing the mechanical properties of the crystals, which are believed to share structural features with biogenic minerals. Here we report the synthesis and mechanical characterization of composite calcite/SWCNT-COOH single crystals. Once entrapped into the crystals SWCNT-COOH appeared both as aggregates of entangled bundles and nanoropes. Their observation was possible only after crystal etching, fracture or FIB (focused ion beam) cross-sectioning. SWCNT-COOHs occupied a small volume fraction and were randomly distributed into the host crystal. They did not strongly affect the crystal morphology. However, although the Young's modulus of composite calcite/SWCNT-COOH single crystals was similar to that of pure calcite their hardness increased by about 20%. Thus, SWCNT-COOHs provide an obstacle against the dislocation-mediated propagation of plastic deformation in the crystalline slip systems, in analogy with the well-known hardness increase in fiber-reinforced composites. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr01568h

Calvaresi, Matteo; Falini, Giuseppe; Pasquini, Luca; Reggi, Michela; Fermani, Simona; Gazzadi, Gian Carlo; Frabboni, Stefano; Zerbetto, Francesco



The analysis of thermoluminescent glow peaks of natural calcite after beta irradiation.  


In this study, the thermoluminescence properties of natural calcite samples were examined in detail. The glow curve of the sample irradiated with beta radiation shows two main peaks, P1 (at 115 °C) and P4 (at 254 °C). The additive dose, variable heating rate, computer glow curve deconvolution, peak shape and three point methods have been used to evaluate the trapping parameters, namely the order of kinetics (b), activation energy (E) and the frequency factor (s) associated with the dosimetric thermoluminescent glow peaks (P1 and P4) of natural calcite after different dose levels with beta irradiation. PMID:22355170

Yildirim, R Güler; Kafadar, V Emir; Yazici, A Necmeddin; Gün, Esen



Controls on trace-element partitioning in cave-analogue calcite  

NASA Astrophysics Data System (ADS)

We report trace-element data from a series of carbonate growth experiments in cave-analogue conditions in the laboratory with the goal of better understanding environmental controls on trace-element incorporation in stalagmites. The experimental setup closely mimics natural processes (e.g. precipitation driven by CO2-degassing, low ionic strength solution, thin solution-film) but with a tight control on growth conditions (temperature, pCO2, drip rate, calcite saturation index and the composition of the initial solution). Calcite is dissolved in deionized water in a 20,000 ppmV pCO2 environment, with trace-elements (Li, Na, Mg, Co, Sr, Cd, Ba, U) at appropriate concentrations to mimic natural cave drip-waters. This solution is dripped onto glass plates (coated with seed-calcite) in a lower pCO2 environment at 7, 15, 25 and 35 °C and drip rates of 2, 6 and 10 drips per minute. D(Sr) was shown to be statistically invariant over the full range of temperature and growth rate studied. No relationship between Sr/Ca and growth rate is therefore expected in stalagmite samples over comparable growth rates. D(Mg) has a relationship with temperature defined by D(Mg) = 0.01e0.02[±0.006]T, but temperature is not expected to be the dominant control on Mg/Ca in cave calcite due to the larger impact of calcite precipitation on Mg/Ca. Over short timescales, in conditions where temperature is well buffered, the fraction of calcium remaining in solution (f) is likely to be the dominant control on Mg/Ca and other trace-element ratios. But differences in the response of trace-elements to f and T may allow their combined use to assess past cave conditions. High Cd/Castalagmite is particularly indicative of low amounts of prior calcite precipitation and Cd/Ca would be a useful addition to trace-element studies of natural stalagmites. Significant scatter is observed in trace-element ratios during the laboratory experiments, which cannot be explained by simple Rayleigh distillation. This scatter is well explained by solution mixing and by the mixing of calcite with different fractions of calcite growth. Accounting for the effects of mixing on trace-element concentrations or ratios may help to achieve more robust interpretations of stalagmite chemistry as part of a multi-proxy approach to assessment of past environments.

Day, Christopher C.; Henderson, Gideon M.



Simulation of silica fume blended cement hydration  

Microsoft Academic Search

A model is proposed in this paper to simulate silica fume (SF) blended cement hydration based on the kinetics, stoichiometry\\u000a and physical chemistry of cement hydration and pozzolanic reaction. The pozzolanic reaction degree, volume fraction of hydration\\u000a products, capillary porosity and gel porosity can be obtained from model simulation. By using proper amount of silica fume\\u000a replacement, the microstructure of

J. Yajun; J. H. Cahyadi



Inhibition of gas hydrates by methanol  

Microsoft Academic Search

A molecular-thermodynamic correlation has been developed for calculating the inhibition effect of methanol on the formation of hydrates in moist gas mixtures. Six phases are potentially present in these mixtures: gas, aqueous liquid, hydrocarbon liquid, ice, and hydrate structures I and II. For a given temperature and system composition, the molecular-thermodynamic method described allows computation of the hydrate-point pressure as

F. E. Anderson; J. M. Prausnitz



Potential geologic hazards of Arctic gas hydrates  

SciTech Connect

Sediments of the Arctic region may contain enormous quantities of natural gas in the form of gas hydrates, which are crystalline substances composed of water and mostly methane gas. These ice-like substances are generally found in two distinct environments: (1) offshore in sediments of outer continental margins and (2) nearshore and onshore in areas associated with the occurrence of permafrost. Recently, US, Canadian, and Soviet researchers have described numerous drilling and production problems attributed to the presence of gas hydrates, including uncontrolled gas releases during drilling, collapsed casings, and gas leakage to the surface. When the drill bit penetrates a gas hydrate, the drilling mud, unless cooled significantly by the operator, will become highly gasified as the hydrate decomposes. The hydrate adjacent to the well bore will continue to decompose and gasify the drilling mud as long as drilling and/or production introduces heat into the hydrate-bearing interval. The production of hot fluids from depth through the permafrost and gas hydrate-bearing intervals adversely raises formation temperatures, thus decomposing the gas hydrates. If the disassociated, free gas is trapped behind the casing, reservoir pressures may substantially increase and cause the casing to collapse. In several wells in northern Alaska, the disassociated free gas has leaked to the surface outside the conductor casing. An additional drilling hazard associated with gas hydrates results from the sealing attributes of hydrates, which may trap large volumes of over pressured free gas at shallow depths. Even though documented problems attributed to the presence of gas hydrates have been relatively few, it is likely that as exploration and development activity moves farther offshore into deeper water (>300 m) and to higher latitudes in the Arctic, the frequency of gas hydrate-related problems will increase.

Collett, T.S. (Geological Survey, Menlo Park, CA (USA))



Why not use methanol for hydrate control  

SciTech Connect

Methanol, instead of solid bed dehydration, is suggested to avoid hydrate formation in turboexpander plants. Hydrates (crystals resembling wet snow) plug pipeworks and valves. Methanol used as an antifreeze to depress the freezing point of the water is studied. Alcohol to depress the formation temperature of hydrate in a gas is also studied. Confusion between the two methods is clarified. Comparison between methanol injection and solid bed dehydration is made; methanol has lower costs.

Nielsen, R.B.; Bucklin, R.W.



Natural gas hydrates: problem or opportunity  

SciTech Connect

Natural gas hydrates, once viewed solely as a nuisance by the gas processing industry, are rapidly gaining favorable status as an unconventional natural gas resource. Hydrates are solids which form when gas is contacted with water, both above and below 273 Kelvin. Conditions are favorable for hydrate formation in permafrost regions and in many oceans. Natural gas hydrates are solid crystalline compounds composed of cavities, formed by water molecules, which contain a natural gas guest. Hydrates are more properly called clathrates, after a general class of inclusion compounds, because they do not contain the fixed chemical formula characteristics of normal hydrates. These compounds represent a condensed form of natural gas, and each volume of the solid may contain as much as 170 volumes of gas at standard conditions. During the last decade, significant amounts of in situ hydrates have been found in permafrost regions of the earth and in deep oceans in warmer climates. Of the mechanisms proposed for recovery of gas from hydrates, all involve at least one of four principles: (1) pressure reduction; (2) thermal injection; (3) reservoir fracture; or (4) inhibitor injection, to break the hydrogen bonds of the water in the hydrate. Calculations by researchers in the United States indicate that thermal stimulation with a hot fluid, perhaps combined with reservoir fracture is energy efficient when the reservoir contains excess free gas. The question of definite reserve identification and commercialization of gas recovery is still a major challenge for this unconventional natural gas resource.

Sloan, E.D.



Distribution of hydrate on Europa: Further evidence for sulfuric acid hydrate  

Microsoft Academic Search

Sulfuric acid hydrate has been proposed as an important species on Europa's surface, the acid being produced by radiolysis of surficial sulfur compounds. We investigated the spectral properties of disordered and crystalline forms of sulfuric acid and suggest that the hydration properties of Europa's hypothesized sulfuric acid lie between two end members: liquid sulfuric acid and its higher crystalline hydrates.

R. W. Carlson; M. S. Anderson; R. Mehlman; R. E. Johnson



Observations related to tetrahydrofuran and methane hydrates for laboratory studies of hydrate-bearing sediments  

USGS Publications Warehouse

The interaction among water molecules, guest gas molecules, salts, and mineral particles determines the nucleation and growth behavior of gas hydrates in natural sediments. Hydrate of tetrahydrofuran (THF) has long been used for laboratory studies of gas hydrate-bearing sediments to provide close control on hydrate concentrations and to overcome the long formation history of methane hydrate from aqueous phase methane in sediments. Yet differences in the polarizability of THF (polar molecule) compared to methane (nonpolar molecule) raise questions about the suitability of THF as a proxy for methane in the study of hydrate-bearing sediments. From existing data and simple macroscale experiments, we show that despite its polar nature, THF's large molecular size results in low permittivity, prevents it from dissolving precipitated salts, and hinders the solvation of ions on dry mineral surfaces. In addition, the interfacial tension between water and THF hydrate is similar to that between water and methane hydrate. The processes that researchers choose for forming hydrate in sediments in laboratory settings (e.g., from gas, liquid, or ice) and the pore-scale distribution of the hydrate that is produced by each of these processes likely have a more pronounced effect on the measured macroscale properties of hydrate-bearing sediments than do differences between THF and methane hydrates themselves.

Lee, J.Y.; Yun, T.S.; Santamarina, J.C.; Ruppel, C.



Microbial Community Structure and Diversity in Hydrate Ridge Gas Hydrates (Cascadia Margin)  

Microsoft Academic Search

Here, we present the first quantitative study investigating microorganisms physically associated with Hydrate Ridge gas hydrates. Previous studies have shown that the anaerobic oxidation of methane (AOM) in methane enriched surface sediments of Hydrate Ridge is apparently mediated by highly structured microbial consortia (Boetius et al., 2000). These AOM consortia consist of an inner core of methane-oxidizing archaea (ANME2-group) and

T. Lösekann; K. Knittel; A. Boetius; R. Amann



Methane hydrates as potential energy resource: Part 2 – Methane production processes from gas hydrates  

Microsoft Academic Search

Three processes have been proposed for dissociation of methane hydrates: thermal stimulation, depressurization, and inhibitor injection. The obvious production approaches involve depressurization, heating and their combinations. The depressurization method is lowering the pressure inside the well and encouraging the methane hydrate to dissociate. Its objective is to lower the pressure in the free-gas zone immediately beneath the hydrate stability zone,

Ayhan Demirbas



The interaction of magnesium with calcite during crystal growth at 25-90°C and one atmosphere  

Microsoft Academic Search

Calcite crystals were grown in a closed system by recrystallization of synthetic and natural aragonite crystals, in the presence of various CaCl 2 -MgCl 2 solutions with and without NaCl. The distribution of Mg 2+ between calcite and solution at the entire temperature range is heterogeneous, closely following the ( and , 1925) distribution law. Mg 2+ C is strongly

Amitai Katz



Microstructural and textural development of calcite marbles during polyphase deformation of Penninic units within the Tauern Window (Eastern Alps)  

Microsoft Academic Search

The evolution of calcite microstructures and crystallographic preferred orientations (CPOs) is well understood due to well constrained experimental studies. However, the interpretation of naturally deformed calcite marbles is more difficult because of less constrained strain paths, a multiphase deformation history, and variable P–T conditions. The Penninic units within the Tauern Window (Eastern Alps) have been affected by several deformation events

W. Kurz; F. Neubauer; W. Unzog; J. Genser; X. Wang



Experiment Study on the Removal of Phosphorus in Eutrophic Water Bodies by the Utilization of Mineral Calcite  

Microsoft Academic Search

For seeking a new method to solve the problem of eutrophication, we have made the experiments of removing phosphorus in eutropic water by use of mineral calcite. The results indicate that the mineral calcite can remove phosphorus from the solution, and that the initial phosphorus concentration may influence the efficiency of phosphorus removal. The dephosphorization rate is high when the

Hong XU; Jing ZHANG; Yiming GAO



Stabilization of Oklahoma expensive soils using lime and class C fly ash  

SciTech Connect

This study uses lime and class C fly ash, an industrial byproduct of electric power production produced from burning lignite and subbituminous coal, to study the plasticity reduction in highly expensive natural clays from Idabel, Oklahoma. This study is important, especially in Oklahoma, because most of the native soils are expansive and cause seasonal damage to roadways and structures. The addition of lime or fly ash helps to arrest the shrinkage and swelling behavior of soil. Four soil samples with the same AASHTO classification were used in this study to show shrinkage variability within a soil group with the addition of lime and class C fly ash. The plasticity reduction in this study was quantified using the linear shrinkage test. It was found that soils classified within the same AASHTO group had varying shrinkage characteristics. It was also found that both lime and fly ash reduced the lienar shrinkage, however, the addition of lime reduced the linear shrinkage to a greater degree than the same percentage of class C fly ash. Even though it takes much less lime than fly ash to reduce the plasticity of a highly expansive soil, it may be less expensive to utilize fly ash, which is a waste product of electric power production. Lime also has a lower unit weight than fly ash so weight percentage results may be misleading.

Buhler, R.L.; Cerato, A.B. (eds.) [University of Oklahoma, Norman, OK (USA). Dept. of Civil Engineering and Environmental Science




SciTech Connect

Soda-lime glass (SLG) is a potential low-cost VISAR window for use at moderate shock pressures (up to 2430 GPa) where the material remains transparent. In order for SLG to be practical as a VISAR window, the correction factor, which describes the frequency correction related to the strain dependence of the refractive index, and hence the index of refraction itself, must be characterized as a function of pressure. Characterization data are reported in this paper and compared to previous results. The present data show good agreement with those of Dandekar [J. Appl. Phys. 84, 6614 (1998)] and separate study results by Gibbons and Ahrens [J. Geophys. Res. 76, 5489 (1971)] up to 7 GPa. However, at stresses over 7 GPa, marked discrepancies are evident between the present data and that of Gibbons and Ahrens. Differences in test methods may explain these discrepancies.

Alexander, C. S. [Sandia National Laboratories, Albuquerque NM 87185 (United States)



Shock, Release, and Tensile Response of Soda Lime Glass  

NASA Astrophysics Data System (ADS)

This work describes the results of shock wave experiments on soda lime glass in which the shock wave profiles were recorded simultaneously at the impact surface and the free surface of the glass specimen by means of multiple VISAR beams. Maximum stress attained in these experiments was 6. 6 GPa. These two wave profiles provide accurate and self consistent values of transit times of shock, release, and tensile wave propagations in the glass specimen. The particle wave velocity profile at the impact surface provides reliable information about any dispersion of these waves, if present, without being affected by the impedance mismatch condition at the free surface. In addition, these profiles provide valuable information about the changes in the refractive index of the glass under shock, release and tensile wave propagation. The results highlighting both mechanical and optical response of the glass will be presented.

Dandekar, Dattatraya P.



Effect of shear on failure waves in soda lime glass  

SciTech Connect

By means of in-material stress gauges, failure waves in shock-compressed soda lime glass have been shown to be distinguished by a marked reduction in shear stress. To explore further the relation between failure waves and shearing resistance, a series of pressure-shear impact experiments have been performed involving the impact of a glass plate by a steel flyer plate and vice versa. The latter configuration is designed to allow direct measurements of the shearing resistance of the failed material. In both configurations, the normal and transverse motion of the free surface of the target is monitored using laser interferometry. The transverse velocity-time profiles show a pronounced loss in shearing resistance of the glass at impact velocities above the threshold for failure waves to occur.

Clifton, R. J.; Mello, M. [Division of Engineering, Brown University, Providence, Rhode Island 02912 (United States); Brar, N. S. [University of Dayton Research Institute, Dayton, Ohio 45469-0182 (United States)



Optical properties of Ti and N implanted soda lime glass  

NASA Astrophysics Data System (ADS)

Soda lime glass was implanted sequentially with Ti+ and N+ to doses ranging from 2 to 30×1016 cm-2 in order to study the resulting optical properties. Analysis of the implant distributions was made by using Rutherford backscattering and x-ray photoelectron spectroscopy and revealed profiles which closely followed each other as designed by the selection of implant energies. Analysis of optical properties showed that the highest dose resulted in an increase in the fraction of infrared reflected by more than a factor of 4 versus 1.7 for the visible regime. The percentage of the total solar radiation rejected exceeded 60% at the highest dose, indicating that the buried layer is highly effective in reducing solar load.

Was, G. S.; Rotberg, V.; Platts, D.; Bomback, J.



Index of Refraction of Shock Loaded Soda-Lime Glass  

NASA Astrophysics Data System (ADS)

Soda-lime glass (SLG) is a potential low-cost VISAR window for use at moderate shock pressures (up to approximately 25 GPa) where the material remains transparent. In order for SLG to be practical as a VISAR window, the correction factor, which describes the frequency correction related to the strain dependence of the refractive index, and hence the index of refraction itself, must be characterized as a function of pressure. Characterization data are reported in this paper and compared to previous results. The present data show good agreement with those of Dandekar [J. App. Physics, 84, 6614 (1998)] and separate study results by Gibbons and Ahrens [J. Geophys. Res., 76, 5489 (1971)] up to 7 GPa. However, at stresses over 7 GPa, marked discrepancies are evident between the present data and that of Gibbons and Ahrens. Differences in test methods may explain these discrepancies.

Alexander, Scott



Chemistry of the calcite/water interface: Influence of sulfate ions and consequences in terms of cohesion forces  

SciTech Connect

Calcite suspensions are used to mimic the behavior of more complex cementitious systems. Therefore the characterization of calcite–water interface in strong alkaline conditions, through ionic adsorption, electrokinetic measurements, static rheology and atomic force microscopy is a prerequisite. Calcium, a potential determining ion for calcite, adsorbs specifically onto the weakly positively charged calcite surface in water. This leads to an increase of the repulsive electric double layer force and thus weakens the particle cohesion. Sulfate adsorption, made at constant calcium concentration and ionic strength, significantly increases the attractive interactions between the calcite particles despite its very low adsorption. This is attributed to a lowering of the electrostatic repulsion in connection with the evolution of the zeta potential. The linear relationship found between the yield stress and ?{sup 2} proves that the classical DLVO theory applies for these systems, contrary to what was previously observed with C–S–H particles under the same conditions.

Pourchet, Sylvie, E-mail:; Pochard, Isabelle; Brunel, Fabrice; Perrey, Danièle



Hydration recommendations for sport 2008.  


Fluid replacement remains an important strategy for preserving exercise performance as dehydration in excess of 2% of body weight consistently impairs aerobic exercise performance. Too much of a good thing, however, can have negative health consequences as persistent drinking in excess of sweating rate can induce symptomatic exercise associated hyponatremia. This short review highlights new position stands and/or policy statements regarding fluid replacement for sport, evidence that laboratory findings translate to team sport performance, and current hydration practices of athletes. It is culminated with practical strategies for drinking appropriately during physical activity. PMID:18607219

Montain, Scott J



Atomic-Scale Study of Calcite Nucleation in Calcium Oxide Rmy Besson*  

E-print Network

Atomic-Scale Study of Calcite Nucleation in Calcium Oxide Rémy Besson* Groupe de MétallurgieO-CaCO3 system appears as a good candidate in order to get better insight into these issues. Calcium oxideO. This surprising deficiency may be explained by the complex crystallography of the phase transition, which raises

Paris-Sud XI, Université de


NMR surface relaxivity of calcite with adsorbed Mn{sup 2+}  

SciTech Connect

Calcite particles were exposed to Mn{sup 2+} in aqueous solution to allow adsorption. The calcite particles were then packed, and the NMR longitudinal relaxation time T{sub 1} of water saturating the interparticle pores was measured. NMR surface relaxivity was then computed as 1/(T{sub 1}{times}S{sub p}/V{sub p}), where S{sub p}/V{sub p} is the ratio of surface area to pore volume. Adsorbed manganese increases the NMR surface relaxivity to approximately 2.4 {times} 10{sup {minus}3} cm/s, roughly 50 times the surface relaxivity of very pure calcite. Flowing water with 4 {mu}M Mn{sup 2+} through a porous limestone plug decreased its T{sub 1} by a factor of 6. Iron as adsorbate produced relatively small increases in surface relaxivity. These results suggest that manganese dominates the surface relaxivity, of limestone rocks in situ, which is important in the interpretation of NMR borehole logs. Observations suggest that some adsorbed manganese eventually becomes buried by freshly precipitated calcite. In particular, the surface relaxivity increased with initial adsorption, but gradually decreased at long reaction times, even as the aqueous manganese concentration continued to decrease. NMR evidently senses only the manganese in the outermost atomic layer, and thus might prove useful in more detailed studies of adsorption.

Kenyon, W.E.; Kolleeny, J.A. [Schlumberger-Doll Research, Ridgefield, CT (United States)] [Schlumberger-Doll Research, Ridgefield, CT (United States)



Sea Urchin Spine Calcite Forms via a Transient Amorphous Calcium Carbonate Phase  

Microsoft Academic Search

The skeletons of adult echinoderms comprise large single crystals of calcite with smooth convoluted fenestrated morphologies, raising many questions about how they form. By using water etching, infrared spectroscopy, electron diffraction, and environmental scanning electron microscopy, we show that sea urchin spine regeneration proceeds via the initial deposition of amorphous calcium carbonate. Because most echinoderms produce the same type of

Yael Politi; Talmon Arad; Eugenia Klein; Steve Weiner; Lia Addadi



Calcite precipitation in Lake Constance: Chemical equilibrium, sedimentation,and nucleation by algae  

Microsoft Academic Search

Seasonal shifts in calcium carbonate solution equilibria in the limnetic zone of Lake Constance were documented between 1981 and 1983. Except during mixing times, lake water was supersat- urated with respect to calcite; epilimnetic supersaturation maxima were closely related to changes in pH. Sedimentation of calcium from the lower boundary of the euphotic zone to the lake bottom was also




Inferences of paleoenvironment from petrographic, chemical and stable-isotope studies of calcretes and fracture calcites  

SciTech Connect

Past research has indicated a genetic connection between calcite formed in calcretes at the surface of Yucca Mountain, Nevada, and calcites deposited in underlying fractures of the unsaturated zone. This common genesis suggests that paleoenvironmental information, as well as the timing and pathways of past recharge episodes, might be obtained from studies of the deposits in both the calcretes and the unsaturated fractures. Chemical and isotopic modification of calcite-precipitating fluids appears to begin at the surface, largely under the influence of plant roots and their decay products. Chemical characteristics of the deeper calcites are either initiated or largely defined within the first few meters of fluid migration into the unsaturated tuffs beneath the calcretes. However, petrographic and isotopic data indicate a very unique low-{delta}{sup 13}C microenvironment that is localized at the upper surfaces of the calcretes. These surfaces form an interface in the soil horizon where infiltration may pond above the underlying carbonate ``plug.`` In order to decipher the chemistry and petrology of past recharge events, it is important to first understand microenvironments such as this that contribute to mineral precipitation/dissolution events in the pedogenic environment.

Vaniman, D.T. [Los Alamos National Lab., NM (United States); Whelan, J.F. [Geological Survey, Denver, CO (United States)



Clast-cortex aggregates in experimental and natural calcite-bearing fault zones  

NASA Astrophysics Data System (ADS)

We investigated the formation mechanisms of rounded clast-cortex aggregates, a composite grain found in the slipping zones of faults hosted in calcite- and clay-rich rocks. The natural aggregates contain a central clast commonly made of host-rock fragments or reworked cataclasite from the slipping zone. The central clasts are surrounded by an outer cortex of calcite or clay grains a few ?m or less in size. In laboratory experiments on calcite gouges using two rotary-shear apparatus we investigated the dependence of clast-cortex aggregate formation on the applied slip rate, normal stress, total displacement and ambient humidity. Clast-cortex aggregates formed at all investigated slip rates (100 ?m/s to 1 m/s) but only at relatively low normal stresses (?5 MPa). The aggregates were better developed with increasing displacement (up to 5 m) and did not form in experiments with water-dampened gouges. In the experiments, aggregates formed in low-strain regions within the gouge layers, adjacent to the highest-strain slip zones. We propose that clast-cortex aggregates in calcite-bearing slip zones form in the shallow portions of faults during shearing in relatively dry conditions, but our experiments suggest that they cannot be used as indicators of seismic slip. Formation involves clast rotation due to granular flow accompanied by accretion of fine matrix material possibly facilitated by electrostatic forces.

Rempe, Marieke; Smith, Steven A. F.; Ferri, Fabio; Mitchell, Thomas M.; Di Toro, Giulio



In situ AFM study of the dissolution and recrystallization behaviour of polished and stressed calcite surfaces  

NASA Astrophysics Data System (ADS)

We investigated the dissolution behaviour of polished calcite surfaces in situ using a fluid-cell atomic force microscope. Polished calcite surfaces enabled us to study the effects of applied surface stress and crystallographic orientation on calcite dissolution pattern formation. Thin-sections of Iceland spar single-crystals polished either parallel or with a 5° miscut angle to {101¯4} cleavage planes were studied. Compressive surface stresses of up to 50 MPa were applied to some of the thin-section samples by means of elastic concave bending. Experiments were carried out in semi-stagnant deionized water under mainly transport limited dissolution conditions. Samples polished parallel to {101¯4} cleavage planes dissolved by the formation of etch-pits originating from polishing defects. The dissolution behaviour of 5° miscut surfaces was relatively unaffected by polishing defects, since no etch-pits developed in these samples. Dissolution of the miscut samples led to stepped or rippled surface patterns on the nanometer scale that coarsened during the first 30-40 min of the experiments. Possible reasons for the pattern-coarsening were: (i) progressive bunching of retreating dissolution steps and (ii) surface energy driven recrystallization (Ostwald ripening) under transport limited dissolution conditions. A flat polished miscut surface in calcite may recrystallize into a hill-and-valley structure in a (near-)saturated solution so as to lower its total surface free energy in spite of a larger surface area. No clear effect of applied stress on dissolution pattern formation has been observed.

Bisschop, J.; Dysthe, D. K.; Putnis, C. V.; Jamtveit, B.



Assessing the reliability of magnesium in foraminiferal calcite as a proxy for water mass temperatures  

Microsoft Academic Search

Though many studies on the Mg contents in the calcitic tests of foraminifers exist, the processes controlling its uptake are still a matter of debate. Laboratory cultures offer an excellent opportunity to reveal these mechanisms. The Mg concentrations within single chambers of the planktic foraminifer Globigerinoides sacculifer (BRADY) maintained under controlled laboratory conditions were measured (1) at variable temperatures (19.5–29.5

Dirk Nürnberg; Jelle Bijma; Christoph Hemleben



Thermally-induced grain growth of calcite marbles on Naxos Island, Greece  

Microsoft Academic Search

The island of Naxos is composed of an elliptically shaped structural and thermal dome of Miocene age. Peak metamorphic temperatures within the central migmatite complex exceeded 700° C, decreasing to about 300° C at the most distant exposures on the island. Equigranular calcite marbles which outcrop together with metapelites and metabasites over the whole island show a systematic pattern of

S. J. Covey-Crump; E. H. Rutter




E-print Network

SEMI-BATCH CRYSTALLIZATION OF GYPSUM FROM CALCITE AND SULFURIC ACID F. Bard, D. Garcia , G. Févotte or reusing some compounds they contain in other production processes. The latter is of great interest, both- scale installation modeling the neutralization of a sulphuric acid solution by injection of a diluted

Paris-Sud XI, Université de


On the complex conductivity signatures of calcite precipitation Susan Hubbard,1  

E-print Network

. This precipitation can lead to changes in the overall behavior of the system, such as flow alternation and soilH and alkalinity during subsurface remediation or geotechnical engineering activities. In some cases, calcite; Fujita et al., 2004] and (2) to improve soil strength for engineering purposes [DeJong et al., 2006

Hubbard, Susan


Dissolution of calcite in deep-sea sediments: pH and O 2 microelectrode results  

Microsoft Academic Search

We present microelectrode profiles of oxygen, pH, and porosity measured at in situ depth across the sediment-water interface from stations above and below the calcite saturation horizon in the equatorial Atlantic. Resistivity electrode data indicate that the diffusion coefficient for solutes is attenuated by nearly a factor of two within the top centimeter of the sediment lattice. Oxygen and porosity

David Archer; Steven Emerson; Clare Reimers



Noncrystallographic calcite dendrites from hot-spring deposits at Lake Bogoria, Kenya  

SciTech Connect

Complex calcite crystals are an integral component of precipitates that form around the orifices of the Loburu and Mawe Moto hot springs on the shores of Lake bogoria, Kenya. Two types of large (up to 4 cm long) noncrystallographic dendrites are important components of these deposits. Feather dendrites are characterized by multiple levels of branching with individual branches developed through crystal splitting and spherulitic growth. Scandulitic (from Latin meaning shingle) dendrites are formed of stacked calcite crystals and are generally more compact than feather dendrites. These developed through the incremental stacking of rectangular-shaped calcite crystals that initially grew as skeletal crystals. Feather and scandulitic dendrites precipitated from the same waters in the same springs. The difference in morphology is therefore related to microenvironments in which they grew. Feather dendrites grew in any direction in pools of free-standing water provided that they were in constant contact with the solute. Conversely, scandulitic dendrites grew on rims of dams where water flowed over the surface in concert with the pulses of spring water. Thus, each calcite crystal in these dendrites represents one episode of crystal growth. The orientation of the component crystals in scandulitic dendrites is controlled by the topography of the dam or surface, not crystallographic criteria. The noncrystallographic dendrites formed from spring waters with initial temperatures of 90--99 C. Surficial water cooling, loss of CO{sub 2}, and presence of other elements that can interfere with crystal growth contributed to the formation of these unusual crystals.

Jones, B. [Univ. of Alberta, Edmonton, Alberta (Canada). Dept. of Geology; Renaut, R.W. [Univ. of Saskatchewan, Saskatoon (Canada). Dept. of Geological Sciences



Calcite Deposition during Shell Repair by the Aragonitic Gastropod Murex fulvescens  

Microsoft Academic Search

Shell repair was induced by coating the inner surfaces of gastropod shells with nail polish. In aragonitic gastropods initial deposition on the nail-polish membrane was of aragonite spherulites and, in one species, polygonal calcite crystals; later the normal crossed-lamellar structure of the shell was restored.

E. O. Muzii; H. Catherine W. Skinner; W. Skinner



Particle characteristics and their influence on dewatering of kaolin, calcite and quartz suspensions  

Microsoft Academic Search

The effect of particle properties and dispersion on the filtration and dewatering behaviour of three different minerals namely kaolin, calcite and quartz in aqueous media have been examined. The primary particle properties such as particle size, size distribution, specific surface area, density, surface structure, dry bed porosities and sphericities of particles as well as their dispersion properties like solid concentration,

L. Besra; D. K. Sengupta; S. K. Roy



New insights into the carbon isotope composition of speleothem calcite from vegetation, soil, and subsurface processes  

NASA Astrophysics Data System (ADS)

The purpose of this study was to provide new insights into the interpretation of speleothem (cave calcite deposit) ?13C values. We studied two caves in central Texas, which have been actively monitored for over 12 years. We compared ?13C values of soil CO2 (?13Cs), cave drip water (?13CDIC), and modern cave calcite (?13Ccc). Measured average ?13C values of soil CO2 were -13.9 ± 1.4‰ under mixed, shallowly-rooted C3-C4 grasses and were -18.3 ± 0.7‰ under deeply-rooted ashe juniper trees (C3). The ?13CDIC value of minimally-degassed drip water in Natural Bridge Caverns was -10.7 ± 0.3‰. The carbon isotope composition of CO2 in equilibrium with this measured drip water is -18.1 ± 0.3‰. The agreement between juniper soil CO2 and drip water (within ~0.2‰) suggests that the ?13C value of drip water (?13CDIC) that initially enters the cave is controlled by deeply-rooted plants and may be minimally influenced by host-rock dissolution and/or prior calcite precipitation (PCP). At Inner Space Caverns, ?13CDIC values varied with vegetation above the drip site, distance from the cave entrance, and distance along in-cave flow paths. Whereas CO2 derived from deeply-rooted plants defines the baseline for drip water ?13CDIC entering the caves, kinetic effects associated with the degassing of CO2 and simultaneous precipitation of calcite account for seasonal variability in ?13CDIC and ?13Ccc. We documented increases in ?13CDIC at a rate of up to 0.47‰/hour during the season of peak degassing (winter), suggesting that ?13CDIC variations may be controlled by total elapsed time of CO2 degassing from drip water (exposure time, Texp). We also observed seasonal shifts in the ?13C values of modern calcite grown on glass substrates that are correlated with shifts in drip water ?13CDIC values and drip-rate. We evaluated a 10-year record of modern calcite samples and contrasted the magnitude of variability between calcite precipitated under varying pCO2 conditions and comparative length of the drip water flow paths. We propose that large variability (>2‰) in speleothem ?13Ccc values dominantly reflect major vegetation changes, and/or increasing Texp by slowing drip-rates under low-pCO2 conditions.

Meyer, K.; FENG, W.; Breecker, D. O.; Banner, J. L.; Guilfoyle, A.



A model for microbially induced precipitation of vadose-zone calcites in fractures at LOS Alamos, New Mexico, USA  

NASA Astrophysics Data System (ADS)

Fractures are unique environments that can concentrate the flow of water, nutrients, and contaminants. As such, fractures play an important role in controlling the flux of various substances into and through the vadose zone. Calcite fracture fillings are present in the near surface in the Bandelier Tuff Formation at Los Alamos, New Mexico, and provide a record of the geochemical and hydrologic processes that have occurred in fractures. The objective of this study was to examine calcite fracture fills in order to improve understanding of processes within fractures, and in particular those that lead to precipitation of calcite. Samples of calcite fillings were collected from vertical and horizontal fractures exposed in a shallow waste-burial pit. Scanning electron microscopy show morphologies which suggest that plants, fungi, and bacteria were important in the precipitation process. Quadrupole mass spectrometric analyses of fluid inclusion gases show predominantly methane (17-99%) and little to no oxygen (0-8%), suggesting the development of anaerobic conditions in the fractures. Ester-linked phospholipid biomarkers are evidence for a diverse microbial community in the fractures, and the presence of di-ether lipids indicate that the methane was generated by anaerobic bacteria. The calcite fillings apparently resulted from multiple biological and chemical processes in which plant roots in the fractures were converted to calcite. Roots grew into the fractures, eventually died, and were decomposed by bacteria and fungi. Anaerobic gases were generated from encapsulated organic material within the calcite via microbial decomposition, or were generated by microbes simultaneously with calcite precipitation. It is likely that the biological controls on calcite formation that occurred in the Los Alamos fractures also occurs in soils, and may explain the occurrence of other types of pedogenic calcites.

Newman, Brent D.; Campbell, Andrew R.; Norman, David I.; Ringelberg, David B.



A systematic review of the effectiveness of liming to mitigate impacts of river acidification on fish and macro-invertebrates.  


The addition of calcium carbonate to catchments or watercourses--liming--has been used widely to mitigate freshwater acidification but the abatement of acidifying emissions has led to questions about its effectiveness and necessity. We conducted a systematic review and meta-analysis of the impact of liming streams and rivers on two key groups of river organisms: fish and invertebrates. On average, liming increased the abundance and richness of acid-sensitive invertebrates and increased overall fish abundance, but benefits were variable and not guaranteed in all rivers. Where B-A-C-I designs (before-after-control-impact) were used to reduce bias, there was evidence that liming decreased overall invertebrate abundance. This systematic review indicates that liming has the potential to mitigate the symptoms of acidification in some instances, but effects are mixed. Future studies should use robust designs to isolate recovery due to liming from decreasing acid deposition, and assess factors affecting liming outcomes. PMID:23707951

Mant, Rebecca C; Jones, David L; Reynolds, Brian; Ormerod, Steve J; Pullin, Andrew S



Natural gas hydrates: myths, facts and issues  

Microsoft Academic Search

Gas hydrates are solid-like substances naturally occurring beneath the oceans and in polar regions. They contain vast, and potentially unstable, reserves of methane and other natural gases. Many believe that, if released in the environment, the methane from hydrates would be a considerable hazard to marine ecosystems, coastal populations and infrastructures, or worse, that it would dangerously contribute to global



Well log evaluation of natural gas hydrates.  

National Technical Information Service (NTIS)

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 cont...

T. S. Collett



Hydrate Inhibition Design for Deepwater Completions  

Microsoft Academic Search

This paper will review the design considerations for gas hydrate prevention in deepwater well completions. The influence of seafloor temperature, wellbore pressure, water production rate and composition of gas on hydrate inhibition system design will be discussed. The impact of various inhibitors will be discussed in relationship to the design of the system and potential handling problems. Examples will review

Janardhan Davalath; J. W. Barker



Impact of trace metals on the water structure at the calcite surface  

NASA Astrophysics Data System (ADS)

Carbonate minerals play an important role in regulating the chemistry of aquatic environments, including the oceans, aquifers, hydrothermal systems, soils and sediments. Through mineral surface processes such as dissolution, precipitation and sorption, carbonate minerals affect the biogeochemical cycles of not only the constituent elements of carbonates, such as Ca, Mg, Fe and C, but also H, P and trace elements. Surface charging of the calcite mineral-water interface, and its reactivity towards foreign ions can be quantified using a surface structural model that includes, among others, the water structure at the interface (i.e. hydrogen bridging) [1,2] in accordance with the CD-MUSIC formalism [3]. Here we will show the impact of foreign metals such as Mg and Sr on the water structure around different surface sites present in etch pits and on growth terraces at the calcite (10-14) surface. We have performed Molecular Dynamics simulations of metal-doped calcite surfaces, using different interatomic water potentials. Results show that the local environment around the structurally distinct sites differs depending on metal presence, suggesting that metal substitutions in calcite affect its reactivity. The information obtained in this study will help in improving existing macroscopic surface model for the reactivity of calcite [2] and give more general insight in mineral surface reactivity in relation to crystal composition. [1] Wolthers, Charlet, & Van Cappellen (2008). Am. J. Sci., 308, 905-941. [2] Wolthers, Di Tommaso, Du, & de Leeuw (2012). Phys. Chem. Chem. Phys. 14, 15145-15157. [3] Hiemstra and Van Riemsdijk (1996) J. Colloid Interf. Sci. 179, 488-508.

Wolthers, Mariette; Di Tommaso, Devis; De Leeuw, Nora



Calcite saturation state effects on cultured benthic foraminiferal trace-element distribution coefficients  

NASA Astrophysics Data System (ADS)

Field studies have suggested that calcite saturation states (Ømega) near and below saturation alter trace element distribution coefficients in benthic foraminifera. Recent benthic foraminiferal culture experiments at the University of South Carolina investigated the response of trace element signatures to three different calcite saturation seawater environments by manipulating total alkalinity (TA). Starting with near-surface Gulf Stream water (Ømega = 3, TA=2380 ?eq kg-1), two seawater reservoirs were titrated with HCl to lower their calcite saturation states (Ømega = 2, TA = 1910 ?eq kg-1; Ømega = 1.1, TA = 1320 ?eq kg-1). Mixed-species foraminiferal assemblages, with the calcite-specific fluorescent label calcein, were inoculated into 13 total culture chambers evenly distributed among the control and 2 treatment seawater reservoirs. These cultures were maintained at 7.2 ± 0.1 °C temperature and 36.6 ± 0.4 ‰ salinity for 8 months. Total alkalinity and dissolved inorganic carbon, measured biweekly, characterized the carbonate system and verified that the calcite saturation state remained stable over the culture duration. Trace element concentrations were also measured biweekly. Foraminiferal reproduction ( Bulimina marginata) was observed in each seawater chemistry. These individuals were utilized for trace element and stable isotope (data not presented here) analysis. Additionally, terminal chambers precipitated in alkalinity-adjusted cultures were identified by the absence of the pre-culture calcein label used on all inoculated foraminifera. These cultured chambers were separated by laser microdissection and analyzed for trace element content by isotope dilution inductively-coupled plasma mass spectrometry. We present the initial results of these trace element distribution coefficients measured in cultured benthic foraminifera from three different Ømega. This research was funded by National Science Foundation grants OCE-0351029 and OCE-0437366.

Hintz, C. J.; Shaw, T. J.; Chandler, G. T.; McCorkle, D. C.; Bernhard, J. M.; Blanks, J. K.



Effect of massive gas hydrate formation on the water isotopic fractionation of the gas hydrate system at Hydrate Ridge, Cascadia margin, offshore Oregon  

Microsoft Academic Search

Because gas hydrate is preferentially enriched in the heavy water isotopes, the ?18O and ?D values of pore waters collected from gas hydrate–bearing sediment can provide information on the abundance and mechanisms of gas hydrate formation. Pore waters sampled from deep-seated (40 to 125 mbsf) gas hydrate deposits in Hydrate Ridge during ODP Leg 204 show depletion in dissolved Cl?

Hitoshi Tomaru; Marta E. Torres; Ryo Matsumoto; Walter S. Borowski



Inhibition of gas hydrates in deepwater drilling  

SciTech Connect

With the movement of offshore rigs into deep water, the problem of gas hydrates has become an important issue in drilling. If a kick is taken, gas hydrates can form in the blowout preventer (BOP) or chokelines while the kick is circulated out. The water-based pill presented here significantly improves gas-hydrate inhibition. This pill, which can be spotted in the BOP and weighted up, is environmentally safe and easily adaptable to offshore operations. Compatible with commonly used drilling fluids, the pill can be mixed directly into the mud system without any adverse effects after the danger of hydrate formation diminishes. This technology is an important safety consideration for deepwater drilling well control and hydrate-free operations above the mudline.

Hale, A.H.; Dewan, A.K.R. (Shell Development Co., Houston, TX (USA))



Stable isotopes in pedogenic calcite: Can the positive linear covariant trends be used to quantify paleo-evaporation rates?  

NASA Astrophysics Data System (ADS)

Paleoclimatological models suggest enhanced evaporation rates in subtropical regions during greenhouse- world conditions. Laboratory evaporation experiments show that calcites precipitated from variably saturated solutions yield a positive linear covariant trend (PLCT) in ?18O vs ?13C values. This investigation experimentally quantifies calcite PLCT so that ?13C of subtropical paleosol calcretes may be used as a regional proxy of paleo-evaporation rates. A series of powdered CaCO3 samples with ?18O and ?13C values of -19.6‰ and -37.2‰ VPDB respectively were dissolved in deionized water in a pressure sealed container; it also contained separate vials of calcite reacted with HCl to generate a range of pCO2 environments, thus simulating a soil atmosphere. The variable pCO2 conditions simulate expected soil atmosphere pCO2 conditions in a calcrete horizon during alternative phases of calcite dissolution and precipitation. After 24 hrs, the solutions were placed in an open beaker in an incubator at 36°C and allowed to evaporate. Aliquots of 100 ?L were removed at 24 hr intervals and the time of calcite crystal nucleation was also noted. Water analyses yielded ?18O enrichments ranging from an initial value of -4.8‰ VSMOW to a range of +10.0‰ to +14.8‰ VSMOW after an evaporation period of 75 hrs. The most enriched water values were attained from the solutions formed under lower pCO2 conditions (more enriched calcite ?18O, ?13C). The array of calcite ?18O vs ?13C values fall upon a PLCT that projects from a theoretical meteoric calcite line (MCL) calculated from the incubation temperature and deionized water ?18O and ?13C values. The precipitated calcite ?18O values range from the MCL value of -8.8‰ VPDB to +0.5‰ VPDB. The higher pCO2 waters precipitated calcite very early during evaporation, and thus the ?18O and ?13C calcite values are slightly enriched relative to the theoretical MCL. The lower pCO2 conditions precipitated calcite late in the evaporation of the fluids, and thus yield more enriched calcite ?18O and ?13C values. Ongoing experiments under warmer and cooler evaporation temperatures will aid in the development of a quantitative model for paleo-evaporation rates from paleosol calcretes.

Gröcke, D.; Ufnar, D.; Beddows, P. A.




SciTech Connect

Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project is in the final stages of a cost shared partnership between Maurer Technology, Noble Corporation, Anadarko Petroleum, and the U.S. Department of Energy's Methane Hydrate R&D program. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition to identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. The work scope drilled and cored a well The HOT ICE No.1 on Anadarko leases beginning in FY 2003 and completed in 2004. An on-site core analysis laboratory was built and utilized for determining the physical characteristics of the hydrates and surrounding rock. The well was drilled from a new Anadarko Arctic Platform that has a minimal footprint and environmental impact. The final efforts of the project are to correlate geology, geophysics, logs, and drilling and production data and provide this information to scientists developing reservoir models. No gas hydrates were encountered in this well; however, a wealth of information was generated and is contained in this report.

Thomas E. Williams; Keith Millheim; Buddy King




SciTech Connect

Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Oil-field engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in Arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrates agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project is a cost-shared partnership between Maurer Technology, Anadarko Petroleum, Noble Corporation, and the U.S. Department of Energy's Methane Hydrate R&D program. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition to help identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. As part of the project work scope, team members drilled and cored the HOT ICE No. 1 on Anadarko leases beginning in January 2003 and completed in March 2004. Due to scheduling constraints imposed by the Arctic drilling season, operations at the site were suspended between April 21, 2003 and January 30, 2004. An on-site core analysis laboratory was designed, constructed and used for determining physical characteristics of frozen core immediately after it was retrieved from the well. The well was drilled from a new and innovative Anadarko Arctic Platform that has a greatly reduced footprint and environmental impact. Final efforts of the project were to correlate geology, geophysics, logs, and drilling and production data and provide this information to scientists for future hydrate operations. Unfortunately, no gas hydrates were encountered in this well; however, a wealth of information was generated and is contained in the project reports.

Thomas E. Williams; Keith Millheim; Bill Liddell



Defining reactive sites on hydrated mineral surfaces: Rhombohedral carbonate minerals  

NASA Astrophysics Data System (ADS)

Despite the success of surface complexation models (SCMs) to interpret the adsorptive properties of mineral surfaces, their construct is sometimes incompatible with fundamental chemical and/or physical constraints, and thus, casts doubts on the physical-chemical significance of the derived model parameters. In this paper, we address the definition of primary surface sites (i.e., adsorption units) at hydrated carbonate mineral surfaces and discuss its implications to the formulation and calibration of surface equilibria for these minerals. Given the abundance of experimental and theoretical information on the structural properties of the hydrated (10.4) cleavage calcite surface, this mineral was chosen for a detailed theoretical analysis of critical issues relevant to the definition of primary surface sites. Accordingly, a single, generic charge-neutral surface site ( tbnd CaCO 3·H 2O 0) is defined for this mineral whereupon mass-action expressions describing adsorption equilibria were formulated. The one-site scheme, analogous to previously postulated descriptions of metal oxide surfaces, allows for a simple, yet realistic, molecular representation of surface reactions and provides a generalized reference state suitable for the calculation of sorption equilibria for rhombohedral carbonate minerals via Law of Mass Action (LMA) and Gibbs Energy Minimization (GEM) approaches. The one-site scheme is extended to other rhombohedral carbonate minerals and tested against published experimental data for magnesite and dolomite in aqueous solutions. A simplified SCM based on this scheme can successfully reproduce surface charge, reasonably simulate the electrokinetic behavior of these minerals, and predict surface speciation agreeing with available spectroscopic data. According to this model, a truly amphoteric behavior is displayed by these surfaces across the pH scale but at circum-neutral pH (5.8-8.2) and relatively high ?CO 2 (?1 mM), proton/bicarbonate co-adsorption becomes important and leads to the formation of a charge-neutral H 2CO 3-like surface species which may largely account for the surface charge-buffering behavior and the relatively wide range of pH values of isoelectric points (pH iep) reported in the literature for these minerals.

Villegas-Jiménez, Adrián; Mucci, Alfonso; Pokrovsky, Oleg S.; Schott, Jacques



Methane Recovery from Hydrate-bearing Sediments  

SciTech Connect

Gas hydrates are crystalline compounds made of gas and water molecules. Methane hydrates are found in marine sediments and permafrost regions; extensive amounts of methane are trapped in the form of hydrates. Methane hydrate can be an energy resource, contribute to global warming, or cause seafloor instability. This study placed emphasis on gas recovery from hydrate bearing sediments and related phenomena. The unique behavior of hydrate-bearing sediments required the development of special research tools, including new numerical algorithms (tube- and pore-network models) and experimental devices (high pressure chambers and micromodels). Therefore, the research methodology combined experimental studies, particle-scale numerical simulations, and macro-scale analyses of coupled processes. Research conducted as part of this project started with hydrate formation in sediment pores and extended to production methods and emergent phenomena. In particular, the scope of the work addressed: (1) hydrate formation and growth in pores, the assessment of formation rate, tensile/adhesive strength and their impact on sediment-scale properties, including volume change during hydrate formation and dissociation; (2) the effect of physical properties such as gas solubility, salinity, pore size, and mixed gas conditions on hydrate formation and dissociation, and it implications such as oscillatory transient hydrate formation, dissolution within the hydrate stability field, initial hydrate lens formation, and phase boundary changes in real field situations; (3) fluid conductivity in relation to pore size distribution and spatial correlation and the emergence of phenomena such as flow focusing; (4) mixed fluid flow, with special emphasis on differences between invading gas and nucleating gas, implications on relative gas conductivity for reservoir simulations, and gas recovery efficiency; (5) identification of advantages and limitations in different gas production strategies with emphasis; (6) detailed study of CH4-CO2 exchange as a unique alternative to recover CH4 gas while sequestering CO2; (7) the relevance of fines in otherwise clean sand sediments on gas recovery and related phenomena such as fines migration and clogging, vuggy structure formation, and gas-driven fracture formation during gas production by depressurization.

J. Carlos Santamarina; Costas Tsouris



77 FR 45715 - Application of Key Lime Air Corporation for Commuter Authority  

Federal Register 2010, 2011, 2012, 2013

The Department of Transportation is directing all interested persons to show cause why it should not issue an order finding Key Lime Air Corporation fit, willing, and able, and awarding it a Commuter Air Carrier...



The ultra-high lime with aluminum process for removing chloride from recirculating cooling water  

E-print Network

Chloride is a deleterious ionic species in cooling water systems because it is important in promoting corrosion. Chloride can be removed from cooling water by precipitation as calcium chloroaluminate using ultra-high lime with aluminum process (UHLA...

Abdel-wahab, Ahmed Ibraheem Ali



Validation of the new mixture design and testing protocol for lime stabilization  

E-print Network

describes some pertinent findings of the study. In situ properties of lime stabilized subgrades are identified based on Falling Weight Deflectometer (FWD) deflection measurements, Ground Penetration Radar (GPR) profiles, and Dynamic Cone Penetrometer (DCP...

Yusuf, Fateh Ul Anam Muhammad Shafee



Upgrading unpaved roads: Road base stabilization using lime and fly ash  

NASA Astrophysics Data System (ADS)

A cost-effective alternative to upgrading unpaved roads using asphalt which may cost $100,000 per mile is proposed. In lime-fly ash stabilization, road aggregate is thoroughly mixed with lime, fly ash and water to form a new road base to a depth of five or more inches; this new road base is then compacted and covered with a minimum asphaltic surface layer such as a double chip seal. Guidelines are given for evaluating whether road base stabilization using lime and fly ash (an in-expensive waste product of coal-burning power plants) is an economical alternative to asphalt in upgrading a particular road. Detailed guidelines are presented for estimating the cost of materials for a lime-flyash project as well as a description of the necessary construction and maintenance procedures.

Howley, J.; Wohlers, C.



Unusual Graphite Crystals: From the Lime Crest Quarry, Sparta, New Jersey  

Microsoft Academic Search

Microcrystals of graphite occurring in the Franklin Marble at the Lime Crest quarry, Sparta, New Jersey, exhibit a variety of unusual and interesting morphologies that range from sharp hexagonal crystals to nearly spherical aggregates.

John A. Jaszczak



Timing and mechanism of late-Pleistocene calcite vein formation across the Dead Sea Fault Zone, northern Israel  

NASA Astrophysics Data System (ADS)

The emplacement of calcite-filled veins perpendicular to the Dead Sea Fault Zone in northern Israel reflects strain partitioning during transpression. We present structural, geochemical, and U-Th geochronological data that constrain the mechanism, conditions and timing of vein formation. Vein walls are strongly brecciated and commonly cemented with coarsely crystalline calcite, whereas calcite-filled veins are composed of wall-parallel bands of calcite crystals. Elongated blocky and fibrous calcite crystals grew perpendicular to the vein walls and are characterised by a truncate sealing-hiatus morphology, indicating episodes of partial or complete sealing of the fractures during calcite precipitation. Stable isotope and rare-earth element and yttrium (REY) analyses indicate that calcite-filled veins precipitated by karst processes, involving meteoric water and limited fluid-rock interactions. U-Th dating results show a prolonged history of vein growth. While some veins initiated prior to 500 ka, the majority of the veins were active between 358 and 17 ka. Age constraints on vein activity correspond to an ˜E-W regional shortening phase in this sector of the Dead Sea Fault Zone, associated with an increased component of convergence during the late-Pleistocene.

Nuriel, Perach; Weinberger, Ram; Rosenbaum, Gideon; Golding, Suzanne D.; Zhao, Jian-xin; Tonguc Uysal, I.; Bar-Matthews, Miryam; Gross, Michael R.



Mass fractionation of noble gases in synthetic methane hydrate: Implications for naturally occurring gas hydrate dissociation  

USGS Publications Warehouse

As a consequence of contemporary or longer term (since 15 ka) climate warming, gas hydrates in some settings may presently be dissociating and releasing methane and other gases to the ocean-atmosphere system. A key challenge in assessing the impact of dissociating gas hydrates on global atmospheric methane is the lack of a technique able to distinguish between methane recently released from gas hydrates and methane emitted from leaky thermogenic reservoirs, shallow sediments (some newly thawed), coal beds, and other sources. Carbon and deuterium stable isotopic fractionation during methane formation provides a first-order constraint on the processes (microbial or thermogenic) of methane generation. However, because gas hydrate formation and dissociation do not cause significant isotopic fractionation, a stable isotope-based hydrate-source determination is not possible. Here, we investigate patterns of mass-dependent noble gas fractionation within the gas hydrate lattice to fingerprint methane released from gas hydrates. Starting with synthetic gas hydrate formed under laboratory conditions, we document complex noble gas fractionation patterns in the gases liberated during dissociation and explore the effects of aging and storage (e.g., in liquid nitrogen), as well as sampling and preservation procedures. The laboratory results confirm a unique noble gas fractionation pattern for gas hydrates, one that shows promise in evaluating modern natural gas seeps for a signature associated with gas hydrate dissociation.

Hunt, Andrew G.; Stern, Laura; Pohlman, John W.; Ruppel, Carolyn; Moscati, Richard J.; Landis, Gary P.



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

NASA Astrophysics Data System (ADS)

In low-grade metamorphic terrains at temperatures < 300° C e-twinning of calcite is common. The width and density 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. 14 experiments were performed at 100-400 MPa confining pressure and T < 350° C in a Paterson-type gas deformation apparatus. Seven samples were deformed in axial compression test at strain rates from 10-4 -10-6s-1. Seven samples were deformed in torsion tests to shear strains ? < 1.8. After testing, thin sections of all samples were prepared for optical inspection of twin density and twin width. Twin density varied between 10 and 500 [twins/mm] at stresses up to 280 MPa. At given conditions and with increasing strain twin density increased significantly. No clear dependence of twin density on temperatures up to 300° C was found in experiments. The experimentally deformed samples were compared to naturally-deformed low-grade calcite rocks from different fault zones. From optical thin sections of 20 samples deformation temperatures were estimated based on twin width and fluid inclusion data. These samples were subsequently used for optical measurements of twin density. Twin density varied between 10 and 100 [twins/mm] up to temperatures of 300° C. Using published calcite piezometers (Rowe and Rutter 1990) we estimated paleostresses. From our experiments and field data we did not observe a clear relation between twin width and temperature up to 250° C. Above 250° C, temperatures estimated from calcite twin widths in naturally deformed calcite samples do correspond to temperatures estimated using other methods (e.g. fluid inclusion analysis, vitrinite reflection, conodont colour alteration index). Using the existing paleopiezometres, differential stresses inferred from twin density in the experimentally deformed samples are commonly overestimated by up to a factor of 2 at low stress. Towards higher stresses > 150 MPa predicted and experimental values converge for samples deformed to similar strains. The experimental data clearly shows a strong dependence of twin density on strain for all tested temperatures.

Rybacki, E.; Janssen, C.; Dresen, G.



Organic Surfaces Promote Calcite Nucleation Through Biomolecule-Specific Reductions in Interfacial Free Energy  

NASA Astrophysics Data System (ADS)

Sites of biogenic calcification are comprised of complex macromolecular assemblages that are implicated in regulating the onset of mineralization. Classical nucleation theory predicts that the organic templates provided by these proteins and polysaccharides significantly affect nucleation rate by modulating interfacial free energy, which determines the thermodynamic barrier to nucleation. Recent evidence suggests that calcium carbonate (CaCO3) formation often involves pre-nucleation clusters and transient precursor phases, which raises the question of how biomolecular controls on crystallization are related to emerging concepts in non-classical mineralization. While previous studies qualitatively demonstrate that the chemical functionalities of biomolecules influence the nucleating mineral phase and morphology, a mechanistic understanding of their control over nucleation kinetics and thermodynamics is not well established. Here we test the hypothesis that specific chemical functional groups regulate the kinetics and thermodynamics of CaCO3 formation by using self-assembled monolayers (SAMs) as substrates for calcite nucleation. We measured nucleation rates on substrates with different termini (-COOH, -PO4, and -SH) and alkanethiol chain lengths (16-C and 11-C) at a variety of chemical driving forces, both above and below the reported solubility of amorphous calcium carbonate (ACC). Using classical nucleation theory to interpret the kinetic data, we calculated calcite-substrate interfacial energies and estimated substrate-specific effects on the thermodynamic barrier to nucleation. Calcite - substrate interaction forces were quantified with independent dynamic force spectroscopy (DFS) measurements. The nucleation rate measurements show that organic templates reduce the thermodynamic barrier to calcite nucleation compared to homogeneous nucleation through reductions in interfacial free energy. These free energies are correlated with independent DFS measurements of calcite-substrate interaction force by a systematic relationship that is general to chemistry and chain length. Calcite nucleation in these systems is accurately described with classical models of nucleation. The findings demonstrate a physical basis for how organic surfaces reduce the thermodynamic barrier to nucleation and show that precursor phases and pre-nucleation clusters are not required for template-directed mineralization.

Hamm, L. M.; Han, N.; Giuffre, A. J.; De Yoreo, J.; Dove, P. M.



Calibration of the calcite-water oxygen-isotope geothermometer at Devils Hole, Nevada, a natural laboratory  

USGS Publications Warehouse

The ??18O of ground water (-13.54 ?? 0.05 ???) and inorganically precipitated Holocene vein calcite (+14.56 ?? 0.03 ???) from Devils Hole cave #2 in southcentral Nevada yield an oxygen isotopic fractionation factor between calcite and water at 33.7 ??C of 1.02849 ?? 0.00013 (1000 ln ??calcite-water = 28.09 ?? 0.13). Using the commonly accepted value of ???(??calcite-water)/???T of -0.00020 K-1, this corresponds to a 1000 ln ??calcite-water value at 25 ??C of 29.80, which differs substantially from the current accepted value of 28.3. Use of previously published oxygen isotopic fractionation factors would yield a calcite precipitation temperature in Devils Hole that is 8 ??C lower than the measured ground water temperature. Alternatively, previously published fractionation factors would yield a ??18O of water, from which the calcite precipitated, that is too negative by 1.5 ??? using a temperature of 33.7 ??C. Several lines of evidence indicate that the geochemical environment of Devils Hole has been remarkably constant for at least 10 ka. Accordingly, a re-evaluation of calcite-water oxygen isotopic fractionation factor may be in order. Assuming the Devils Hole oxygen isotopic value of ??calcite-water represents thermodynamic equilibrium, many marine carbonates are precipitated with a ??18O value that is too low, apparently due to a kinetic isotopic fractionation that preferentially enriches 16O in the solid carbonate over 18O, feigning oxygen isotopic equilibrium.

Coplen, T.B.



Experimental fracture study for a V-notched soda-lime glass specimen  

Microsoft Academic Search

Engineering components made of soda-lime glass sometimes contain notches with different shapes, particularly V-shaped notches. A V-notch plays the role of a stress concentrator that dramatically decreases the load bearing capacity of the component. Since fracture in soda-lime glass occurs suddenly due to its brittleness, it is necessary to estimate the fracture resistance of V-notched glass components under different loading

M. R. Ayatollahi; A. R. Torabi



Evaluation of lime-fly ash stabilized bases and subgrades using static and dynamic deflection systems  

E-print Network

EVALUATION OF LIME-FLY ASH STABILIZED BASFS AND SUBGRADES USING STATIC AND DYNAMIC DEFLECTION SYSTEMS A Thesis GARY W. RABA Submitted to the Graduate College of Texas AIIM University in partial fulfillment of the requirements for the degree... of MASTER OF SCIENCE December 1982 Major Subject: Civil Engineering EVALUATION OF LIME-FLY ASH STABILIZED BASES AND SUBGRADES USING STATIC AND DYNAMIC DEFLECTION SYSTEMS A Thesis by Gary Nl. Raba Approved as to style and content by: !Chairman...

Raba, Gary W.



?????????????????????????????????????????????????????????????????????? COMBINATIONS OF LIME AND COAL FLY ASH AS STABILIZERS FOR SOFT SOIL  

Microsoft Academic Search

This research attempted to study strength development of clayey soil stabilized with lime and coal fly ash. Emphasis was placed on using fly ash with high content. Therefore, lime blended with coal fly ash by weight at ratios of 1:1, 1:3, 1:6 and 1:9 were used at stabilizer contents of 100, 150, 200 and 250 kg\\/m3 and a water to

Kamol Amornfa


Microfungi in coniferous forest soils treated with lime or wood ash  

Microsoft Academic Search

Microfungal species composition was studied in coniferous forest soils which had been treated with lime or wood ash. The pH increased by about 2.5 units at the highest rate of application. Fungi were isolated 4–5 years after the treatments using a soil washing technique. At one site, Öringe, clear differences in species composition due to liming were found. Penicillium spinulosum,

E. Bååth; K. Arnebrant



Formation of silver colloids in silver ion-exchanged soda-lime glasses during annealing  

Microsoft Academic Search

The structural and compositional changes of the soda-lime glasses during the formation of the silver colloids were analyzed by the X-ray Photoelectron Spectroscopy (XPS) in order to examine the silver colloid formation mechanism. The in situ behavior of silver and SiO2 networks on the surfaces of silver ion-exchanged soda-lime glasses during heating and cooling processes in ultra-high vaccum was monitored.

Paul W. Wang



A study of the workability of natural hydraulic lime mortars and its influence on strength  

Microsoft Academic Search

Lime mortars are currently used for both repairs to historic buildings and new construction. An important mortar property\\u000a is workability. Lime mortars are often described as highly workable, however, due to the many variables contributing to workability,\\u000a this is difficult to quantify. Workability largely depends on water content, and this will greatly affect compressive and\\u000a flexural strengths, which in turn

R. Hanley; S. Pavía



Alternative control of Aethina tumida Murray (Coleoptera: Nitidulidae) with lime and diatomaceous earth  

Microsoft Academic Search

Aiming at alternative small hive beetle control, slaked lime, powdered limestone and diatomaceous earth (Fossil Shield® FS\\u000a 95, FS 90.0 and FS 90.0s) were evaluated for their effects on pupation and adult emergence in the laboratory. Limestone, FS\\u000a 90.0 and FS 95 showed no significant effect. Slaked lime in autoclaved soil prevented pupation, but was lethal only in high\\u000a dosages

Sven Buchholz; Katharina Merkel; Sebastian Spiewok; Jeff S. Pettis; Michael Duncan; Robert Spooner-Hart; Christian Ulrichs; Wolfgang Ritter; P. Neumann



Effect of Lime on Criconemella xenoplax and Bacterial Canker in Two California Orchards 1  

Microsoft Academic Search

In a peach orchard with an initial soil pH of 4.9, preplant application of 0, 13.2, 18.2, 27.3, or 54.2 kg lime\\/tree site altered soil pH (range after 1 year = 4.8-7.3) but did not affect numbers of Criconemella xenoplax or tree circumference. Liming also failed to reduce the incidence of bacterial canker, which affected 17% of the trees by




Effect of lime on the availability of residual phosphorus and its extractability by dilute acid  

Microsoft Academic Search

The objective of this study was to determine the long-term effects of liming an acid, P-deficient Placid sand (sandy, siliceous, hyperthermic Typic Humaquept) on the availability of residual fertilizer P to potatoes (Solanum tuberosum L.). Dolomitic limestone was applied in November 1977, at rates of 0, 2240, 4480, and 8960 kg\\/ha in a split-plot design with lime as main plots

R. D. Rhue; D. R. Hensel



Sugarcane juice extraction and preservation, and long-term lime pretreatment of bagasse  

E-print Network

SUGARCANE JUICE EXTRACTION AND PRESERVATION, AND LONG-TERM LIME PRETREATMENT OF BAGASSE A Dissertation by CESAR BENIGNO GRANDA COTLEAR Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment... RESERVED SUGARCANE JUICE EXTRACTION AND PRESERVATION, AND LONG-TERM LIME PRETREATMENT OF BAGASSE A Dissertation by CESAR BENIGNO GRANDA COTLEAR Submitted to Texas A&M University in partial fulfillment of the requirements for the degree...

Granda Cotlear, Cesar Benigno



Application of Coal Fly Ash to Replace Lime in the Management of Reactive Mine Tailings  

Microsoft Academic Search

Acid mine drainage (AMD), the acidic water discharged from active, inactive, or abandoned mine sites, is probably the single\\u000a largest environmental liability facing the mining industry. Mining companies use large quantities of lime for AMD control\\u000a in daily operation. The manufacture of lime contributes significant emission of greenhouse gas (GHG). This paper presents\\u000a an innovative approach of using coal fly

H. Wang; J. Shang; Y. Xu; M. Yeheyis; E. Yanful


Volatile fatty acid fermentation of lime-treated biomass by rumen microorganisms  

E-print Network

VOLATILE FATTY ACID FERMENTATION OF LIME-TREATED BIOMASS BY RUMEN MICROORGANISMS A Thesis by CHARLES ROBERT RAPIER Submitted to the Office of Cnaduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree... of MASTER OF SCIENCE August 1995 Major Subject: Chemical Engineeriug VOLATILE FATTY ACID FERMENTATION OF LIME-TREATED BIOMASS BY RUMEN MICROORGANISMS A Thesis by CHARLES ROBERT RAPIER Submitted to Texas AkM University in partial fultillment...

Rapier, Charles Robert



Short-term responses of wetland vegetation after liming of an Adirondack watershed  

Microsoft Academic Search

Watershed liming has been suggested as a long-term mitigation strategy for lake acidity, particularly in areas subject to high levels of acidic deposition. However, virtually no information has been available on the impacts of liming on wetland vegetation. In 1989, 1100 Mg of limestone (83.5% CaCO[sub 3]) were aerially applied to 48% (100 ha) of the Woods Lake watershed in

I. R. Mackun; D. J. Leopold; D. J. Raynal



Multiphasic finite element modeling of concrete hydration  

SciTech Connect

This paper presents a model predicting the development of hydration and its consequences on temperature and water content. As it considers the effects of climatic conditions, the proposed model is a promising tool to evaluate the temperature, hydric and hydration fields of structures in situ. The hydration model predicts the hydration evolution of several main species (not only clinker but also mineral additions like fly ash or silica fume for instance). For each component, the modeling considers hydration development and chemical interaction between reactions. It also takes into account temperature and water content effects on reaction kinetics through thermal and hydric activation. Hydration development in turn modifies the thermal and hydric states of material. The result is a numerical model coupling hydration, and the thermal and hydric states of cement-based material. The model was tested on a 27 m{sup 3} concrete block in situ equipped with temperature sensors situated in the core and close to the face exposed to solar radiation.

Buffo-Lacarriere, L. [VINCI Construction Grands Projets, 5 cours Ferdinand de Lesseps, F-92851 Rueil-Malmaison Cedex (France); Laboratoire Materiaux et Durabilite des Constructions, INSA-UPS, 135 avenue de Rangueil, F-31077 Toulouse Cedex 4 (France); Sellier, A. [Laboratoire Materiaux et Durabilite des Constructions, INSA-UPS, 135 avenue de Rangueil, F-31077 Toulouse Cedex 4 (France)]. E-mail:; Escadeillas, G. [Laboratoire Materiaux et Durabilite des Constructions, INSA-UPS, 135 avenue de Rangueil, F-31077 Toulouse Cedex 4 (France); Turatsinze, A. [Laboratoire Materiaux et Durabilite des Constructions, INSA-UPS, 135 avenue de Rangueil, F-31077 Toulouse Cedex 4 (France)



Gas Hydrates Research Programs: An International Review  

SciTech Connect

Gas hydrates sediments have the potential of providing a huge amount of natural gas for human use. Hydrate sediments have been found in many different regions where the required temperature and pressure conditions have been satisfied. Resource exploitation is related to the safe dissociation of the gas hydrate sediments. Basic depressurization techniques and thermal stimulation processes have been tried in pilot efforts to exploit the resource. There is a growing interest in gas hydrates all over the world due to the inevitable decline of oil and gas reserves. Many different countries are interested in this valuable resource. Unsurprisingly, developed countries with limited energy resources have taken the lead in worldwide gas hydrates research and exploration. The goal of this research project is to collect information in order to record and evaluate the relative strengths and goals of the different gas hydrates programs throughout the world. A thorough literature search about gas hydrates research activities has been conducted. The main participants in the research effort have been identified and summaries of their past and present activities reported. An evaluation section discussing present and future research activities has also been included.

Jorge Gabitto; Maria Barrufet



Municipal sludge metal contamination of old-field ecosystems: Do liming and tilling affect remediation  

SciTech Connect

Mechanisms of ecosystem recovery following 11 years of sewage sludge disposal were addressed by examining the effects of tilling and/or liming on soil chemistry and the heavy metal (Cd, Cu, Pb, and Zn) concentrations in soil, earthworms, vegetation, spiders, and crickets. In 1989 and 1990, subplots in each of three former 0.1-ha, long-term treatments (sludge, fertilizer, and control) were either unmanipulated or manipulated via tilling and/or liming. Liming significantly increased the pH of soil from the long-term sludge and fertilizer plots, and the combination of tilling and liming affected the heavy metal concentrations in earthworms, as lower concentrations of Cd, Cu, Pb, and Zn were found in earthworms collected from subplots that had been both tilled and limed. However, most observed significant differences in heavy metal concentrations reflected the long-term treatments, as heavy metal concentrations tended to be greater in the soil and biota collected from sludge-treated plots. Thus, heavy metals remained in the soil in forms available to the biota, regardless of the cessation of sludge application or subplot manipulations (liming and/or tilling) for two years following cessation of sludge application.

Benninger-Truax, M.; Taylor, D.H. (Miami Univ., Oxford, OH (United States). Dept. of Zoology)



A Comparison between Lime and Alkaline Hydrogen Peroxide Pretreatments of Sugarcane Bagasse for Ethanol Production  

NASA Astrophysics Data System (ADS)

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 hydrolysis. Experiments were performed using the bagasse as it comes from an alcohol/ sugar factory and bagasse in the size range of 0.248 to 1.397 mm (12-60 mesh). The results show that when hexoses and pentoses are of interest, lime should be the pretreatment agent chosen, as high TRS yields are obtained for nonscreened bagasse using 0.40 g lime/g dry biomass at 70 °C for 36 h. When the product of interest is glucose, the best results were obtained with lime pretreatment of screened bagasse. However, the results for alkaline peroxide and lime pretreatments of nonscreened bagasse are not very different.

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



SciTech Connect

Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the USA have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project is in the second year of a three-year endeavor being sponsored by Maurer Technology, Noble, and Anadarko Petroleum, in partnership with the DOE. The purpose of the project is to build on previous and ongoing R&D in the area of onshore hydrate deposition. We plan to identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. We also plan to design and implement a program to safely and economically drill, core and produce gas from arctic hydrates. The current work scope is to drill and core a well on Anadarko leases in FY 2003 and 2004. We are also using an on-site core analysis laboratory to determine some of the physical characteristics of the hydrates and surrounding rock. The well is being drilled from a new Anadarko Arctic Platform that will have minimal footprint and environmental impact. We hope to correlate geology, geophysics, logs, and drilling and production data to allow reservoir models to be calibrated. Ultimately, our goal is to form an objective technical and economic evaluation of reservoir potential in Alaska.

Thomas E. Williams; Keith Millheim; Buddy King




SciTech Connect

Natural-gas hydrates have been encountered beneath the permafrost and considered a nuisance by the oil and gas industry for years. Engineers working in Russia, Canada and the US have documented numerous drilling problems, including kicks and uncontrolled gas releases, in arctic regions. Information has been generated in laboratory studies pertaining to the extent, volume, chemistry and phase behavior of gas hydrates. Scientists studying hydrate potential agree that the potential is great--on the North Slope of Alaska alone, it has been estimated at 590 TCF. However, little information has been obtained on physical samples taken from actual rock containing hydrates. This gas-hydrate project is in the second year of a three-year endeavor being sponsored by maurer Technology, noble, and Anadarko Petroleum, in partnership with the DOE. The purpose of the project is to build on previous and ongoing R and D in the area of onshore hydrate deposition. They plan to identify, quantify and predict production potential for hydrates located on the North Slope of Alaska. They also plan to design and implement a program to safely and economically drill, core and produce gas from arctic hydrates. The current work scope is to drill and core a well on Anadarko leases in FY 2003 and 2004. They are also using an on-site core analysis laboratory to determine some of the physical characteristics of the hydrates and surrounding rock. The well is being drilled from a new Anadarko Arctic Platform that will have minimal footprint and environmental impact. They hope to correlate geology, geophysics, logs, and drilling and production data to allow reservoir models to be calibrated. Ultimately, the goal is to form an objective technical and economic evaluation of reservoir potential in Alaska.

Thomas E. Williams; Keith Millheim; Buddy King



Rotifers colonising sediments with shallow gas hydrates.  


Rotifers, one of the smallest metazoans, are only seldom found in marine environments. Surprisingly, we discovered high abundances of at least two new species of rotifers settling in anoxic and highly sulphidic sediments associated with shallow gas hydrates (GH) at the southern crest of Hydrate Ridge off Oregon, NE Pacific, in a water depth of about 780 m. At basins adjacent to Hydrate Ridge, 1,285-2,304 m deep, we found rotifers co-occurring with the sulphide-oxidising bacteria Thioploca sp. PMID:12835839

Sommer, Stefan; Gutzmann, Erik; Ahlrichs, Wilko; Pfannkuche, Olaf



Carbon dioxide hydrate and floods on Mars  

NASA Technical Reports Server (NTRS)

Ground ice on Mars probably consists largely of carbon dioxide hydrate. This hydrate dissociates upon release of pressure at temperatures between 0 and 10 C. The heat capacity of the ground would be sufficient to produce up to 4% (by volume) of water at a rate equal to that at which it can be drained away. Catastrophic dissociation of carbon dioxide hydrate during some past epoch when the near-surface temperature was in this range would have produced chaotic terrain and flood channels.

Milton, D. J.



Clathrate hydrates in cometary nuclei and porosity  

NASA Technical Reports Server (NTRS)

Possible mechanisms of formation and decomposition of CO2-clathrate hydrate in cometary nuclei are discussed. As far as it is known, this is the only clathrate hydrate which is unstable at low temperatures. Calculation shows that, in accord with other evidence, neither volume nor grain boundary diffusion in the clathrate lattice can be responsible for the rate of these reactions and that a surface mechanism with the attendant sensitivity to pressure must play a crucial role. Density changes accompanying CO2-clathrate decomposition and formation can lead to microporosity and enhanced brittleness or even to fracture of cometary nuclei at low temperatures. Other clathrate hydrates and mixed clathrates are also discussed.

Smoluchowski, R.



Inhibition of gas hydrates by methanol  

SciTech Connect

A molecular-thermodynamic correlation has been developed for calculating the inhibition effect of methanol on the formation of hydrates in moist gas mixtures. Six phases are potentially present in these mixtures: gas, aqueous liquid, hydrocarbon liquid, ice, and hydrate structures I and II. For a given temperature and system composition, the molecular-thermodynamic method described allows computation of the hydrate-point pressure as well as relative amounts and compositions of all coexisting phases. Good agreement is obtained when calculated results are compared with diverse experimental data reported in the literature. The correlation given here may be useful for computer-aided design for gas processing and transportation.

Anderson, F.E.; Prausnitz, J.M.



Effects of inhibitors on hydrate formation  

SciTech Connect

This method for predicting the effect of inhibitors on natural gas hydrate-formation conditions appears to be more accurate than that currently used for injecting inhibitor into a natural gas stream. Incorporating existing hydrate parameters and data from the literature, analysts can predict the effects of KCl, CaCl/sub 2/, CH/sub 3/OH, and C/sub 2/H/sub 5/OH inhibition of pure gas hydrates. The extension to other inhibitors and gas mixtures is straightforward. Work is proceeding to extend the measurements to simulated natural gases with methanol and glycol inhibitors.

Menten, P.D.; Parrish, W.R.; Sloan, E.D.



Glass powder blended cement hydration modelling  

NASA Astrophysics Data System (ADS)

The use of waste materials in construction is among the most attractive options to consume these materials without affecting the environment. Glass is among these types of potential waste materials. In this research, waste glass in powder form, i.e. glass powder (GP) is examined for potential use in enhancing the characteristics of concrete on the basis that it is a pozzolanic material. The experimental and the theoretical components of the work are carried out primarily to prove that glass powder belongs to the "family" of the pozzolanic materials. The chemical and physical properties of the hydrated activated glass powder and the hydrated glass powder cement on the microstructure level have been studied experimentally and theoretically. The work presented in this thesis consists of two main phases. The first phase contains experimental investigations of the reaction of glass powder with calcium hydroxide (CH) and water. In addition, it includes experiments that are aimed at determining the consumption of water and CH with time. The reactivity, degree of hydration, and nature of the pore solution of the glass powder-blended cement pastes and the effect of adding different ratios of glass powder on cement hydration is also investigated. The experiments proved that glass powder has a pozzolanic effect on cement hydration; hence it enhances the chemical and physical properties of cement paste. Based on the experimental test results, it is recommended to use a glass powder-to-cement ratio (GP/C) of 10% as an optimum ratio to achieve the best hydration and best properties of the paste. Two different chemical formulas for the produced GP C-S-H gel due to the pure GP and GP-CH pozzolanic reaction hydration are proposed. For the pure GP hydration, the produced GP C-S-H gel has a calcium-to-silica ratio (C/S) of 0.164, water-to-silica ratio (H/S) of 1.3 and sodium/silica ratio (N/S) of 0.18. However, for the GP-CH hydration, the produced GP C-S-H gel has a C/S ratio of 1.17, H/S ratio of 2.5 and N/S ratio of 0.18. In the second phase of this research, theoretical models are built using a modified version of an existing cement hydration modelling code, "CEMHYD3D", to simulate the chemical reaction of the activated glass powder hydration and glass powder in cement. The modified model, which is referred to as the "MOD-model" is further used to predict the types, compositions and quantities of reaction products. Furthermore, the glass powder hydration data, which is obtained experimentally, is incorporated into the MOD-model to determine the effect of adding glass powder to the paste on the process of cement hydration and resulting paste properties. Comparisons between theoretical and experimental results are made to evaluate the developed models. The MOD-model predictions have been validated using the experimental results, and were further used to investigate various properties of the hydrated glass powder cement paste. These properties include, for example, CH content of the paste, porosity, hydration degree of the glass powder and conventional C-S-H and GP CS-H contents. The results show that the MOD-model is capable of accurately simulating the hydration process of glass powder-blended cement paste and can be used to predict various properties of the hydrating paste.

Saeed, Huda


Substrate templating guides the photoinduced reaction of C60 on calcite.  


A substrate-guided photochemical reaction of C60 fullerenes on calcite, a bulk insulator, investigated by non-contact atomic force microscopy is presented. The success of the covalent linkage is evident from a shortening of the intermolecular distances, which is clearly expressed by the disappearance of the moiré pattern. Furthermore, UV/Vis spectroscopy and mass spectrometry measurements carried out on thick films demonstrate the ability of our setup for initiating the photoinduced reaction. The irradiation of C60 results in well-oriented covalently linked domains. The orientation of these domains is dictated by the lattice dimensions of the underlying calcite substrate. Using the lattice mismat