Effect of Ionic Soil Stabilizers on Soil-Water Characteristic of Special Clay

NASA Astrophysics Data System (ADS)

Cui, D.; Xiang, W.

2011-12-01

The engineering properties of special clay are conventionally improved through the use of chemical additive such as ionic soil stabilizer (ISS). Such special clays are often referred to as stabilized or treated clays. The soil-water characteristic curves (SWCC) of special clays from Henan province and Hubei province were measured both in natural and stabilized conditions using the pressure plate apparatus in the suction range of 0-500 kPa. The SWCC results are used to interpret the special clays behavior due to stabilizer treatment. In addition, relationships were developed between the basic clay and stabilized properties such as specific surface area and pore size distribution. The analysis showed that specific surface area decreases, cumulative pore volume and average pore size diameter decrease, dehydration rate slows and the thickness of water film thins after treatment with Ionic Soil Stabilizer. The research data and interpretation analysis presented here can be extended to understand the water film change behaviors influencing the mechanical and physical properties of stabilized special clay soils. KEY WORDS: ionic soil stabilizer, special clay, pore size diameter, specific surface area, soil water characteristic curve, water film

Aluminium - Cobalt-Pillared Clay for Dye Filtration Membrane

NASA Astrophysics Data System (ADS)

Darmawan, A.; Widiarsih

2018-04-01

The manufacture of membrane support from cobalt aluminium pillared clay has been conducted. This research was conducted by mixing a clay suspension with pillared solution prepared from the mixture of Co(NO3)2.6H2O and AlCl3.6H2O. The molar ratio between Al and Co was 75:25 and the ratio of [OH-]/[metal] was 2. The clay suspension was stirred for 24 hours at room temperature, filtered and dried. The dried clay was then calcined at 200°C, 300°C and 400°C with a ramp rate of 2°C/min. Aluminium-cobalt-pillared clay was then characterized by XRD and GSA and moulded become a membrane support for subsequent tests on dye filtration. The XRD analysis showed that basal spacing (d 001) value of aluminium cobalt was 19.49 Å, which was higher than the natural clay of 15.08Å however, the basal spacing decreased with increasing calcination temperature. The result of the GSA analysis showed that the pore diameter of the aluminium cobalt pillared clay membrane was almost the same as that of natural clay that were 34.5Å and 34.2Å, respectively. Nevertheless, the pillared clay has a more uniform pore size distribution. The results of methylene blue filtration measurements demonstrated that the membrane filter support could well which shown by a clear filtrate at all concentrations tested. The value of rejection and flux decreased with the increasing concentration of methylene blue. The values of dye rejection and water flux reached 99.89% and 5. 80 x 10-6 kg min-1, respectively but they decreased with increasing concentration of methylene blue. The results of this study indicates that the aluminium-pillared clay cobalt could be used as membrane materials especially for ultrafiltration.

Three-dimensional finite elements for the analysis of soil contamination using a multiple-porosity approach

NASA Astrophysics Data System (ADS)

El-Zein, Abbas; Carter, John P.; Airey, David W.

2006-06-01

A three-dimensional finite-element model of contaminant migration in fissured clays or contaminated sand which includes multiple sources of non-equilibrium processes is proposed. The conceptual framework can accommodate a regular network of fissures in 1D, 2D or 3D and immobile solutions in the macro-pores of aggregated topsoils, as well as non-equilibrium sorption. A Galerkin weighted-residual statement for the three-dimensional form of the equations in the Laplace domain is formulated. Equations are discretized using linear and quadratic prism elements. The system of algebraic equations is solved in the Laplace domain and solution is inverted to the time domain numerically. The model is validated and its scope is illustrated through the analysis of three problems: a waste repository deeply buried in fissured clay, a storage tank leaking into sand and a sanitary landfill leaching into fissured clay over a sand aquifer.

Nanofiber Enabled, Multi - Target Passive Sampling Device for Determination of the Freely Dissolved Sediment Pore Water Concentrations of Organic Contaminants

DTIC Science & Technology

2016-06-01

foil. Nanofiber diameters were adjusted between ~100-200 nm by controlling the electrospinning solution (e.g., viscosity , dielectric constant...acetate)/ Clay Nanocomposite Fibers. J Polym Sci Pol Phys 2009, 47, (24), 2501-2508. 36. Piperno, S.; Lozzi, L.; Rastelli, R.; Passacantando, M.; Santucci

Measurement and modelling of reactive transport in geological barriers for nuclear waste containment

DOE PAGES

Xiong, Qingrong; Joseph, Claudia; Schmeide, Katja; ...

2015-10-26

Compacted clays are considered as excellent candidates for barriers to radionuclide transport in future repositories for nuclear waste due to their very low hydraulic permeability. Diffusion is the dominant transport mechanism, controlled by a nano-scale pore system. Assessment of the clays' long-term containment function requires adequate modelling of such pore systems and their evolution. Existing characterisation techniques do not provide complete pore space information for effective modelling, such as pore and throat size distributions and connectivity. Special network models for reactive transport are proposed here using the complimentary character of the pore space and the solid phase. Here, this balancesmore » the insufficient characterisation information and provides the means for future mechanical–physical–chemical coupling. The anisotropy and heterogeneity of clays is represented using different length parameters and percentage of pores in different directions. Resulting networks are described as mathematical graphs with efficient discrete calculus formulation of transport. Opalinus Clay (OPA) is chosen as an example. Experimental data for the tritiated water (HTO) and U(VI) diffusion through OPA are presented. Calculated diffusion coefficients of HTO and uranium species are within the ranges of the experimentally determined data in different clay directions. This verifies the proposed pore network model and validates that uranium complexes are diffusing as neutral species in OPA. In the case of U(VI) diffusion the method is extended to account for sorption and convection. Finally, rather than changing pore radii by coarse grained mathematical formula, physical sorption is simulated in each pore, which is more accurate and realistic.« less

Measurement and modelling of reactive transport in geological barriers for nuclear waste containment.

PubMed

Xiong, Qingrong; Joseph, Claudia; Schmeide, Katja; Jivkov, Andrey P

2015-11-11

Compacted clays are considered as excellent candidates for barriers to radionuclide transport in future repositories for nuclear waste due to their very low hydraulic permeability. Diffusion is the dominant transport mechanism, controlled by a nano-scale pore system. Assessment of the clays' long-term containment function requires adequate modelling of such pore systems and their evolution. Existing characterisation techniques do not provide complete pore space information for effective modelling, such as pore and throat size distributions and connectivity. Special network models for reactive transport are proposed here using the complimentary character of the pore space and the solid phase. This balances the insufficient characterisation information and provides the means for future mechanical-physical-chemical coupling. The anisotropy and heterogeneity of clays is represented using different length parameters and percentage of pores in different directions. Resulting networks are described as mathematical graphs with efficient discrete calculus formulation of transport. Opalinus Clay (OPA) is chosen as an example. Experimental data for the tritiated water (HTO) and U(vi) diffusion through OPA are presented. Calculated diffusion coefficients of HTO and uranium species are within the ranges of the experimentally determined data in different clay directions. This verifies the proposed pore network model and validates that uranium complexes are diffusing as neutral species in OPA. In the case of U(vi) diffusion the method is extended to account for sorption and convection. Rather than changing pore radii by coarse grained mathematical formula, physical sorption is simulated in each pore, which is more accurate and realistic.

Obtaining the porewater composition of a clay rock by modeling the in- and out-diffusion of anions and cations from an in-situ experiment.

PubMed

Appelo, C A J; Vinsot, A; Mettler, S; Wechner, S

2008-10-23

A borehole in the Callovo-Oxfordian clay rock in ANDRA's underground research facility was sampled during 1 year and chemically analyzed. Diffusion between porewater and the borehole solution resulted in concentration changes which were modeled with PHREEQC's multicomponent diffusion module. In the model, the clay rock's pore space is divided in free porewater (electrically neutral) and diffuse double layer water (devoid of anions). Diffusion is calculated separately for the two domains, and individually for all the solute species while a zero-charge flux is maintained. We explain how the finite difference formulas for radial diffusion can be translated into mixing factors for solutions. Operator splitting is used to calculate advective flow and chemical reactions such as ion exchange and calcite dissolution and precipitation. The ion exchange reaction is formulated in the form of surface complexation, which allows distributing charge over the fixed sites and the diffuse double layer. The charge distribution affects pH when calcite dissolves, and modeling of the experimental data shows that about 7% of the cation exchange capacity resides in the diffuse double layer. The model calculates the observed concentration changes very well and provides an estimate of the pristine porewater composition in the clay rock.

Effects of rock mineralogy and pore structure on stress-dependent permeability of shale samples

PubMed Central

Al Ismail, Maytham I.; Zoback, Mark D.

2016-01-01

We conducted pulse-decay permeability experiments on Utica and Permian shale samples to investigate the effect of rock mineralogy and pore structure on the transport mechanisms using a non-adsorbing gas (argon). The mineralogy of the shale samples varied from clay rich to calcite rich (i.e. clay poor). Our permeability measurements and scanning electron microscopy images revealed that the permeability of the shale samples whose pores resided in the kerogen positively correlated with organic content. Our results showed that the absolute value of permeability was not affected by the mineral composition of the shale samples. Additionally, our results indicated that clay content played a significant role in the stress-dependent permeability. For clay-rich samples, we observed higher pore throat compressibility, which led to higher permeability reduction at increasing effective stress than with calcite-rich samples. Our findings highlight the importance of considering permeability to be stress dependent to achieve more accurate reservoir simulations especially for clay-rich shale reservoirs. This article is part of the themed issue ‘Energy and the subsurface’. PMID:27597792

Porosity of the Marcellus Shale: A contrast matching small-angle neutron scattering study

USGS Publications Warehouse

Bahadur, Jitendra; Ruppert, Leslie F.; Pipich, Vitaliy; Sakurovs, Richard; Melnichenko, Yuri B.

2018-01-01

Neutron scattering techniques were used to determine the effect of mineral matter on the accessibility of water and toluene to pores in the Devonian Marcellus Shale. Three Marcellus Shale samples, representing quartz-rich, clay-rich, and carbonate-rich facies, were examined using contrast matching small-angle neutron scattering (CM-SANS) at ambient pressure and temperature. Contrast matching compositions of H2O, D2O and toluene, deuterated toluene were used to probe open and closed pores of these three shale samples. Results show that although the mean pore radius was approximately the same for all three samples, the fractal dimension of the quartz-rich sample was higher than for the clay-rich and carbonate-rich samples, indicating different pore size distributions among the samples. The number density of pores was highest in the clay-rich sample and lowest in the quartz-rich sample. Contrast matching with water and toluene mixtures shows that the accessibility of pores to water and toluene also varied among the samples. In general, water accessed approximately 70–80% of the larger pores (>80 nm radius) in all three samples. At smaller pore sizes (~5–80 nm radius), the fraction of accessible pores decreases. The lowest accessibility to both fluids is at pore throat size of ~25 nm radii with the quartz-rich sample exhibiting lower accessibility than the clay- and carbonate-rich samples. The mechanism for this behaviour is unclear, but because the mineralogy of the three samples varies, it is likely that the inaccessible pores in this size range are associated with organics and not a specific mineral within the samples. At even smaller pore sizes (~<2.5 nm radius), in all samples, the fraction of accessible pores to water increases again to approximately 70–80%. Accessibility to toluene generally follows that of water; however, in the smallest pores (~<2.5 nm radius), accessibility to toluene decreases, especially in the clay-rich sample which contains about 30% more closed pores than the quartz- and carbonate-rich samples. Results from this study show that mineralogy of producing intervals within a shale reservoir can affect accessibility of pores to water and toluene and these mineralogic differences may affect hydrocarbon storage and production and hydraulic fracturing characteristics

Development of eco-friendly porous fired clay bricks using pore-forming agents: a review.

PubMed

Bories, Cecile; Borredon, Marie-Elisabeth; Vedrenne, Emeline; Vilarem, Gerard

2014-10-01

Today, clay bricks are facing technological challenges and are uncompetitive compared to materials such as concrete. Their performance must be improved if they are to stand up to the competition. Increasing environmental concerns over the accumulation of unmanaged wastes from agricultural or industrial productions have made these good candidates for incorporation into building materials to improve their performance. This process leads to the formation of pores in the bricks, producing lightweight and sustainable building materials. This paper reviews the different pore-forming agents from renewable or mineral resources as described in the literature. It also presents the impact of pore-forming agents on the physical, mechanical and thermal properties of clay bricks. Copyright © 2014 Elsevier Ltd. All rights reserved.

Methods for pore water extraction from unsaturated zone tuff, Yucca Mountain, Nevada

USGS Publications Warehouse

Scofield, K.M.

2006-01-01

Assessing the performance of the proposed high-level radioactive waste repository at Yucca Mountain, Nevada, requires an understanding of the chemistry of the water that moves through the host rock. The uniaxial compression method used to extract pore water from samples of tuffaceous borehole core was successful only for nonwelded tuff. An ultracentrifugation method was adopted to extract pore water from samples of the densely welded tuff of the proposed repository horizon. Tests were performed using both methods to determine the efficiency of pore water extraction and the potential effects on pore water chemistry. Test results indicate that uniaxial compression is most efficient for extracting pore water from nonwelded tuff, while ultracentrifugation is more successful in extracting pore water from densely welded tuff. Pore water splits collected from a single nonwelded tuff core during uniaxial compression tests have shown changes in pore water chemistry with increasing pressure for calcium, chloride, sulfate, and nitrate. Pore water samples collected from the intermediate pressure ranges should prevent the influence of re-dissolved, evaporative salts and the addition of ion-deficient water from clays and zeolites. Chemistry of pore water splits from welded and nonwelded tuffs using ultracentrifugation indicates that there is no substantial fractionation of solutes.

Hydraulic and mechanical behavior of landfill clay liner containing SSA in contact with leachate.

PubMed

Zhang, Qian; Lu, Haijun; Liu, Junzhu; Wang, Weiwei; Zhang, Xiong

2018-05-01

Sewage sludge ash (SSA) produced by municipal sludge can be used as a modified additive for clay liner, and improves the working performance of landfill clay liner in contact with leachate. Under the action of landfill leachate, the permeability, shear strength, phase composition, and pore structure of the modified clay are investigated through the flexible wall permeability test, triaxial shear test, thermal gravimetric and differential thermal analysis, and low-temperature nitrogen adsorption test, respectively. The hydraulic conductivity of the modified clay containing 0-5% SSA is in the range of 3.94 × 10 -8 -1.16 × 10 -7  cm/s, and the pollutant concentration of the sample without SSA was higher than others. The shear strength of the modified clay is more than that of the traditional clay liner, the cohesion rate of modified clay increases from 32.5 to 199.91 kPa, and the internal friction angle decreases from 32.5° to 15.6°. Furthermore, the weight loss rates of the samples are 15.69%, 17.92%, 18.06%, and 20.68%, respectively, when the SSA content increases from 0% to 5%. The total pore volume and average pore diameter of the modified clay decrease with the increase in the SSA content, respectively. However, the specific area of the modified clay increases with the increase in the SSA content.

Characterization and adsorption properties of diatomaceous earth modified by hydrofluoric acid etching.

PubMed

Tsai, Wen-Tien; Lai, Chi-Wei; Hsien, Kuo-Jong

2006-05-15

This work was a study of the chemical modification of diatomaceous earth (DE) using hydrofluoric acid (HF) solution. Under the experimental conditions investigated, it was found that HF under controlled conditions significantly etched inward into the interior of the existing pore structure in the clay mineral due to its high content of silica, leaving a framework possessing a larger BET surface area (ca. 10 m2 g(-1)) in comparison with that (ca. 4 m2 g(-1)) of its precursor (i.e., DE). Further, the results indicated that the HF concentration is a more determining factor in creating more open pores than other process parameters (temperature, holding time, and solid/liquid ratio). This observation was also in close agreement with the examinations by the silicon analysis, scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The adsorption kinetics and the adsorption isotherm of methylene blue onto the resulting clay adsorbent can be well described by a pseudo-second-order reaction model and the Freundlich model, respectively.

Paleohydrological Information from Profiles in Pore Water of Holocene Low-Permeability Cores and Groundwater Flow Simulation, Lake Kasumigaura, Japan

NASA Astrophysics Data System (ADS)

Takamoto, N.; Shimada, J.

2014-12-01

The paleohydrological information can become important to predict hydrological conditions in the future. In Japan, which hydrologically is characterized by relatively small catchment scales with steep relief of topography under humid temperate climatic conditions, the residence time of the groundwater should be relatively short. Thus the paleohydrological information preserved in the groundwater aquifer should also be limited compared with the continental aquifer. However, regarding groundwater in clay and silt sediments have low-permeability characteristic, archiving the paleohydrologic information at the time of deposition is expected. 　Therefore, in this study, cores were drilled into Holocene clay and silt deposits (Site K-1 and Site K-2) in the Lake Kasumigaurain Japan, where the depositional rate 10,000 years ago was rapid and it has been affected strongly by sea level changes including transgression and regression. By using the obtained core samples and extracted pore water from the cores, paleohydrologic information was investigated, and it was tried to understand hydrologic environments at the study area during a Holocene. In addition, groundwater flow and solute transport simulation were conducted to reproduce profiles of pore water. 　Results of investigation show that the profiles of pore water contents reflect sea level change and the difference in hydrological environment at that time at each site. The content of the paleo-brackish water in the culmination of transgression was about 14,000 mg/l in Cl-, -13.0‰ in δD and -2.6‰ in δ18O. It is allowed better understanding paleohydrological information by studying not only inorganic chemistry contents and stable isotopes of pore water and also the diatom fossils and groundwater flow and solute transport simulation. We will characterize the paleohydrological information of the study area acquired by those investigations and analysis.

The synthesis and application of pillared clays prepared from charge reduced montmorillonite

NASA Astrophysics Data System (ADS)

Engwall, Erik Edwin

The synthesis of pillared interlayered clays (PILCs) makes use of the cation exchange capacity (CEC) of clay minerals to prop their structures open with large hydroxy-metal cations. Homo-ionic Ca-Montmorillonite with a CEC of 83.9 meq/100 g has been partially exchanged with varied amounts of Li+ and heated to 200°C for 24 hours. These have been used to produce Zr and Al PILCs making use of ethanol/water synthesis solutions to overcome the hydrophobic nature of the clay. For the Zr-PILC system, the d(001) spacings determined by x-ray diffraction (XRD) were relatively constant at 19.0--20.1 A with respect to changing the unpillared CEC. The Zr-PILCs had type I isotherms for argon at 87 K and for benzene, p-xylene and 1,3,5-trimethylbenzene adsorption at 30°C. Several Al-PILC synthesis procedures were evaluated and all produced materials whose adsorption capacity decreased with decreasing unpillared CEC. This reduction in adsorption capacity with unpillared CEC could be partially overcome by the combined use of ethanol/water pillaring solutions with ethanol/water washing. Previously unreported d(001) values in the range of 26.8 to 29.8 A were observed in Al-PILCs and were often bimodal with the expected values of about 18 A. These larger d(001) values were most prevalent at lower CEC values, if pillaring conditions favored the formation of polymeric species other than the Keggin cation. A new micropore size distribution model was developed to better understand PILC pore structure. The new model was compared to the Horvath and Kawazoe (1983) model (HK) and the Cheng and Yang (1994) model (CY) using argon adsorption at 87 K on Zr and Al-PILCs. The interlayer spacings determined by XRD for the test PILCs were 9.5 and 8.5 A for Zr and Al-PILCs respectively. Pore sizes predicted by the new model were 7.5 and 7.3 A for Zr and Al-PILCs respectively. The new model consistently predicts values that are closer to the interlayer spacing than either the HK or CY models. The new model showed little change in pore size with changes in unpillared CEC for the Zr-PILC system. These results indicate that the limiting dimension in the PILC pore system is the inter-layer spacing and not the inter-pillar spacing. (Abstract shortened by UMI.)

Studying methane migration mechanisms at Walker Ridge, Gulf of Mexico, via 3D methane hydrate reservoir modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nole, Michael; Daigle, Hugh; Mohanty, Kishore

We have developed a 3D methane hydrate reservoir simulator to model marine methane hydrate systems. Our simulator couples highly nonlinear heat and mass transport equations and includes heterogeneous sedimentation, in-situ microbial methanogenesis, the influence of pore size contrast on solubility gradients, and the impact of salt exclusion from the hydrate phase on dissolved methane equilibrium in pore water. Using environmental parameters from Walker Ridge in the Gulf of Mexico, we first simulate hydrate formation in and around a thin, dipping, planar sand stratum surrounded by clay lithology as it is buried to 295mbsf. We find that with sufficient methane beingmore » supplied by organic methanogenesis in the clays, a 200x pore size contrast between clays and sands allows for a strong enough concentration gradient to significantly drop the concentration of methane hydrate in clays immediately surrounding a thin sand layer, a phenomenon that is observed in well log data. Building upon previous work, our simulations account for the increase in sand-clay solubility contrast with depth from about 1.6% near the top of the sediment column to 8.6% at depth, which leads to a progressive strengthening of the diffusive flux of methane with time. By including an exponentially decaying organic methanogenesis input to the clay lithology with depth, we see a decrease in the aqueous methane supplied to the clays surrounding the sand layer with time, which works to further enhance the contrast in hydrate saturation between the sand and surrounding clays. Significant diffusive methane transport is observed in a clay interval of about 11m above the sand layer and about 4m below it, which matches well log observations. The clay-sand pore size contrast alone is not enough to completely eliminate hydrate (as observed in logs), because the diffusive flux of aqueous methane due to a contrast in pore size occurs slower than the rate at which methane is supplied via organic methanogenesis. Therefore, it is likely that additional mechanisms are at play, notably bound water activity reduction in clays. Three-dimensionality allows for inclusion of lithologic heterogeneities, which focus fluid flow and subsequently allow for heterogeneity in the methane migration mechanisms that dominate in marine sediments at a local scale. Incorporating recently acquired 3D seismic data from Walker Ridge to inform the lithologic structure of our modeled reservoir, we show that even with deep adjective sourcing of methane along highly permeable pathways, local hydrate accumulations can be sourced either by diffusive or advective methane flux; advectively-sourced hydrates accumulate evenly in highly permeable strata, while diffusively-sourced hydrates are characterized by thin strata-bound intervals with high clay-sand pore size contrasts.« less

Ultrafiltration by a compacted clay membrane-II. Sodium ion exclusion at various ionic strengths

USGS Publications Warehouse

Hanshaw, B.B.; Coplen, T.B.

1973-01-01

Several recent laboratory studies and field investigations have indicated that shales and compacted clay minerals behave as semipermeable membranes. One of the properties of semipermeable membranes is to retard or prevent the passage of charged ionic species through the membrane pores while allowing relatively free movement of uncharged species. This phenomenon is termed salt filtering, reverse osmosis, or ultrafiltration. This paper shows how one can proceed from the ion exchange capacity of clay minerals and, by means of Donnan membrane equilibrium concept and the Teorell-Meyer-Siever theory, develop a theory to explain why and to what extent ultrafiltration occurs when solutions of known concentration are forced to flow through a clay membrane. Reasonable agreement between theory and laboratory results were found. The concentration of the ultrafiltrate was always greater than predicted because of uncertainty in values of some parameters in the equations. Ultrafiltration phenomena may be responsible for the formation of some subsurface brines and mineral deposits. The effect should also be taken into consideration in any proposal for subsurface waste emplacement in an environment containing large quantities of clay minerals. ?? 1973.

Atomistic Structure of Mineral Nano-aggregates from Simulated Compaction and Dewatering.

PubMed

Ho, Tuan Anh; Greathouse, Jeffery A; Wang, Yifeng; Criscenti, Louise J

2017-11-10

The porosity of clay aggregates is an important property governing chemical reactions and fluid flow in low-permeability geologic formations and clay-based engineered barrier systems. Pore spaces in clays include interlayer and interparticle pores. Under compaction and dewatering, the size and geometry of such pore spaces may vary significantly (sub-nanometer to microns) depending on ambient physical and chemical conditions. Here we report a molecular dynamics simulation method to construct a complex and realistic clay-like nanoparticle aggregate with interparticle pores and grain boundaries. The model structure is then used to investigate the effect of dewatering and water content on micro-porosity of the aggregates. The results suggest that slow dewatering would create more compact aggregates compared to fast dewatering. Furthermore, the amount of water present in the aggregates strongly affects the particle-particle interactions and hence the aggregate structure. Detailed analyses of particle-particle and water-particle interactions provide a molecular-scale view of porosity and texture development of the aggregates. The simulation method developed here may also aid in modeling the synthesis of nanostructured materials through self-assembly of nanoparticles.

Atomistic Structure of Mineral Nano-aggregates from Simulated Compaction and Dewatering

DOE PAGES

Ho, Tuan Anh; Greathouse, Jeffery A.; Wang, Yifeng; ...

2017-11-10

The porosity of clay aggregates is an important property governing chemical reactions and fluid flow in low-permeability geologic formations and clay-based engineered barrier systems. Pore spaces in clays include interlayer and interparticle pores. Under compaction and dewatering, the size and geometry of such pore spaces may vary significantly (sub-nanometer to microns) depending on ambient physical and chemical conditions. Here we report a molecular dynamics simulation method to construct a complex and realistic clay-like nanoparticle aggregate with interparticle pores and grain boundaries. The model structure is then used to investigate the effect of dewatering and water content on micro-porosity of themore » aggregates. The results suggest that slow dewatering would create more compact aggregates compared to fast dewatering. Furthermore, the amount of water present in the aggregates strongly affects the particle-particle interactions and hence the aggregate structure. Detailed analyses of particle-particle and water-particle interactions provide a molecular-scale view of porosity and texture development of the aggregates. The simulation method developed here may also aid in modeling the synthesis of nanostructured materials through self-assembly of nanoparticles.« less

A three-scale model for ionic solute transport in swelling clays incorporating ion-ion correlation effects

NASA Astrophysics Data System (ADS)

Le, Tien Dung; Moyne, Christian; Murad, Marcio A.

2015-01-01

A new three-scale model is proposed to describe the movement of ionic species of different valences in swelling clays characterized by three separate length scales (nano, micro, and macro) and two levels of porosity (nano- and micropores). At the finest (nano) scale the medium is treated as charged clay particles saturated by aqueous electrolyte solution containing monovalent and divalent ions forming the electrical double layer. A new constitutive law is constructed for the disjoining pressure based on the numerical resolution of non-local problem at the nanoscale which, in contrast to the Poisson-Boltzmann theory for point charge ions, is capable of capturing the short-range interactions between the ions due to their finite size. At the intermediate scale (microscale), the two-phase homogenized particle/electrolyte solution system is represented by swollen clay clusters (or aggregates) with the nanoscale disjoining pressure incorporated in a modified form of Terzaghi's effective principle. At the macroscale, the electro-chemical-mechanical couplings within clay clusters is homogenized with the ion transport in the bulk fluid lying in the micro pores. The resultant macroscopic picture is governed by a three-scale model wherein ion transport takes place in the bulk solution strongly coupled with the mechanics of the clay clusters which play the role of sources/sinks of mass to the bulk fluid associated with ion adsorption/desorption in the electrical double layer at the nanoscale. Within the context of the quasi-steady version of the multiscale model, wherein the electrolyte solution in the nanopores is assumed at instantaneous thermodynamic equilibrium with the bulk fluid in the micropores, we build-up numerically the ion-adsorption isotherms along with the constitutive law of the retardation coefficients of monovalent and divalent ions. In addition, the constitutive law for the macroscopic swelling pressure is reconstructed numerically showing patterns of attractive forces between particles for bivalent ions for particular ranges of bulk concentrations. The three-scale model is applied to numerically simulate ion diffusion in a compacted clay liner underneath a sanitary landfill. Owing to the distinct constitutive behavior of the swelling pressure and partition coefficient for each ionic species, different compaction regimes and diffusion/adsorption patterns, with totally different characteristic time scales, are observed for sodium and calcium migration in the clay liner.

A Comparative Study of T1 and T2 Relaxation in Shale

NASA Astrophysics Data System (ADS)

Keating, K.; Obasi, C. C.; Pashin, J. C.

2015-12-01

Nuclear magnetic resonance (NMR) relaxation measurement have been used extensively in petroleum and, more recently, in groundwater resource evaluation to estimate the porosity, pore-size distributions, permeability, fluid saturation, and fluid mobility. In shale, the transverse decay rate of NMR signal is sensitive to the microporosity, but is also affected by the paramagnetic contributions of clay and other iron-bearing minerals. Furthermore, contrasts in the magnetic susceptibility of the mineral matrix and pore fluids that result in an inhomogeneous magnetic field within the pore space results in an extra term in transverse relaxation. These issues can cause errors in NMR-based estimates of pore-size distribution and permeability. In this study we compare T1 and T2 relaxation time distributions in order to study the molecular mechanism of relaxation in brine-saturated mixtures of clay and other common minerals. We collected measurements on a range of mixtures of clay minerals common in shale (illite, glauconite, celadonite, chamosite, montmorillonite and kaolinite) and pyrite. To constrain the interpretation of the NMR data, we measured the magnetic susceptibility and surface area of all samples. We are confident that by accounting for the presence and variations of clay and pyrite in shale, we can substantially improve both the NMR estimate of pore-size distribution and permeability.

The origin of high sulfate concentrations in a coastal plain aquifer, Long Island, New York

USGS Publications Warehouse

Brown, C.J.; Schoonen, M.A.A.

2004-01-01

Ion-exchange batch experiments were run on Cretaceous (Magothy aquifer) clay cores from a nearshore borehole and an inland borehole on Long Island, NY, to determine the origin of high SO42- concentrations in ground water. Desorption batch tests indicate that the amounts of SO 42- released from the core samples are much greater (980-4700 ??g/g of sediment) than the concentrations in ground-water samples. The locally high SO42- concentrations in pore water extracted from cores are consistent with the overall increase in SO 42- concentrations in ground water along Magothy flow paths. Results of the sorption batch tests indicate that SO42- sorption onto clay is small but significant (40-120 ??g/g of sediment) in the low-pH (<5) pore water of clays, and a significant part of the SO42- in Magothy pore water may result from the oxidation of FeS2 by dissolved Fe(III). The acidic conditions that result from FeS2 oxidation in acidic pore water should result in greater sorption of SO42- and other anions onto protonated surfaces than in neutral-pH pore water. Comparison of the amounts of Cl- released from a clay core sample in desorption batch tests (4 ??g/g of sediment) with the amounts of Cl- sorbed to the same clay in sorption tests (3.7-5 ??g/g) indicates that the high concentrations of Cl- in pore water did not originate from connate seawater but were desorbed from sediment that was previously in contact with seawater. Furthermore, a hypothetical seawater transgression in the past is consistent with the observed pattern of sorbed cation complexes in the Magothy cores and could be a significant source of high SO42- concentrations in Magothy ground water.

Alteration, adsorption and nucleation processes on clay-water interfaces: Mechanisms for the retention of uranium by altered clay surfaces on the nanometer scale

NASA Astrophysics Data System (ADS)

Schindler, Michael; Legrand, Christine A.; Hochella, Michael F.

2015-03-01

Nano-scale processes on the solid-water interface of clay minerals control the mobility of metals in the environment. These processes can occur in confined pore spaces of clay buffers and barriers as well as in contaminated sediments and involve a combination of alteration, adsorption and nucleation processes of multiple species and phases. This study characterizes nano-scale processes on the interface between clay minerals and uranyl-bearing solution near neutral pH. Samples of clay minerals with a contact pH of ∼6.7 are collected from a U mill and mine tailings at Key Lake, Saskatchewan, Canada. The tailings material contains Cu-, As-, Co-, Mo-, Ni-, Se-bearing polymetallic phases and has been deposited with a surplus of Ca(OH)2 and Na2CO3 slaked lime. Small volumes of mill-process solutions containing sulfuric acid and U are occasionally discharged onto the surface of the tailings and are neutralized after discharge by reactions with the slaked lime. Transmission electron microscopy (TEM) in combination with the focused ion beam (FIB) technique and other analytical methods (SEM, XRD, XRF and ICP-OES) are used to characterize the chemical and mineralogical composition of phases within confined pore spaces of the clay minerals montmorillonite and kaolinite and in the surrounding tailings material. Alteration zones around the clay minerals are characterized by different generations of secondary silicates containing variable proportions of adsorbed uranyl- and arsenate-species and by the intergrowth of the silicates with the uranyl-minerals cuprosklodowskite, Cu[(UO2)2(SiO3OH)2](H2O)6 and metazeunerite, Cu[(UO2)(AsO4)2](H2O)8. The majority of alteration phases such as illite, illite-smectite, kaolinite and vermiculite have been most likely formed in the sedimentary basin of the U-ore deposit and contain low amounts of Fe (<5 at.%). Iron-enriched Al-silicates or illite-smectites (Fe >10 at.%) formed most likely in the limed tailings at high contact pH (∼10.5) and their structure is characterized by a low degree of long-range order. Adsorption of U and nucleation of metazeunerite and cuprosklodowskite are strongly controlled by the presence of the adsorbed oxy-anion species arsenate and silica on the Fe-enriched silicates. Heterogeneous nucleation of nano-crystals of the uranyl minerals occurs most likely on adsorption sites of binary uranyl-, arsenate- and silica-complexes as well as on ternary uranyl-arsenate or uranyl-silicate complexes. The uranyl minerals occur as aggregates of misoriented nano-size crystals and are the result of supersaturated solutions and a high number of nucleation sites that prevented the formation of larger crystals through Oswald ripening. The results of this study provide an understanding of interfacial nano-scale processes between uranyl species and altered clay buffers in a potential Nuclear Waste repository as similar alteration conditions of clays may occur in a multi-barrier system.

On the Theory of Solitons of Fluid Pressure and Solute Density in Geologic Porous Media, with Applications to Shale, Clay and Sandstone

NASA Astrophysics Data System (ADS)

Caserta, A.; Kanivetsky, R.; Salusti, E.

2017-11-01

We here analyze a new model of transients of pore pressure p and solute density ρ in geologic porous media. This model is rooted in the nonlinear wave theory, its focus is on advection and effect of large pressure jumps on strain. It takes into account nonlinear and also time-dependent versions of the Hooke law about stress, rate and strain. The model solutions strictly relate p and ρ evolving under the effect of a strong external stress. As a result, the presence of quick and sharp transients in low permeability rocks is unveiled, i.e., the nonlinear "Burgers solitons". We, therefore, show that the actual transport process in porous rocks for large signals is not only the linear diffusion, but also a solitons presence could control the process. A test of a presence of solitons is applied to Pierre shale, Bearpaw shale, Boom clay and Oznam-Mugu silt and clay. An application about the presence of solitons for nuclear waste disposal and salt water intrusions is also discussed. Finally, in a kind of "theoretical experiment" we show that solitons could also be present in higher permeability rocks (Jordan and St. Peter sandstones), thus supporting the idea of a possible occurrence of osmosis also in sandstones.

The nature of porosity in organic-rich mudstones of the Upper Jurassic Kimmeridge Clay Formation, North Sea, offshore United Kingdom

USGS Publications Warehouse

Fishman, Neil S.; Hackley, Paul C.; Lowers, Heather; Hill, Ronald J.; Egenhoff, Sven O.; Eberl, Dennis D.; Blum, Alex E.

2012-01-01

Analyses of organic-rich mudstones from wells that penetrated the Upper Jurassic Kimmeridge Clay Formation, offshore United Kingdom, were performed to evaluate the nature of both organic and inorganic rock constituents and their relation to porosity in this world-class source rock. The formation is at varying levels of thermal maturity, ranging from immature in the shallowest core samples to mature in the deepest core samples. The intent of this study was to evaluate porosity as a function of both organic macerals and thermal maturity. At least four distinct types of organic macerals were observed in petrographic and SEM analyses and they all were present across the study area. The macerals include, in decreasing abundance: 1) bituminite admixed with clays; 2) elongate lamellar masses (alginite or bituminite) with small quartz, feldspar, and clay entrained within it; 3) terrestrial (vitrinite, fusinite, semifusinite) grains; and 4) Tasmanites microfossils. Although pores in all maceral types were observed on ion-milled surfaces of all samples, the pores (largely nanopores with some micropores) vary as a function of maceral type. Importantly, pores in the macerals do not vary systematically as a function of thermal maturity, insofar as organic pores are of similar size and shape in both the immature and mature Kimmeridge rocks. If any organic pores developed during the generation of hydrocarbons, they were apparently not preserved, possibly because of the highly ductile nature of much of the rock constituents of Kimmeridge mudstones (clays and organic material). Inorganic pores (largely micropores with some nanopores) have been observed in all Kimmeridge mudstones. These pores, particularly interparticle (i.e., between clay platelets), and intraparticle (i.e., in framboidal pyrite, in partially dissolved detrital K-feldspar, and in both detrital and authigenic dolomite) are noteworthy because they compose much of the observable porosity in the shales in both immature and mature samples. The absence of a systematic increase in organic porosity as a function of either maceral type or thermal maturity indicates that such porosity was probably unrelated to hydrocarbon generation. Instead, much of the porosity within mudstones of the Kimmeridge appears to be largely intraparticle and interparticle (adjacent to inorganic constituents), so the petroleum storage potential in these organic-rich mudstones largely resides in inorganic pores.

Morphology of the pore space in claystones - evidence from BIB/FIB ion beam sectioning and cryo-SEM observations

NASA Astrophysics Data System (ADS)

Desbois, G.; Urai, J. L.; Kukla, P. A.

2009-12-01

Mudrocks and clay-rich fault gouges are important mechanical elements in the Earth’s crust and form seals for crustal fluids such as groundwater and hydrocarbons. Other fields of interest are the storage of anthropogenic carbon dioxide and radioactive waste in geologic formations. In addition, coupled flows, capillary processes, and associated deformation are of importance in many applied fields. A key factor to understanding these processes is a detailed understanding of the morphology of the pore space. Classic studies of porosity in fine grained materials are performed on dried or freeze dried samples and include metal injection methods, magnetic susceptibility measurement, SEM and TEM imaging, neutron scattering, NMR spectroscopy, and ESEM. Confocal microscopy and X-ray tomography are used to image porosity in coarse grained sediments but the resolution of these techniques is not sufficient at present for applications to mudrocks or clay-rich fault gouges. Therefore, observations and interpretations remain difficult because none of these approaches is able to directly describe the in-situ porosity at the pore scale. In addition, some methods require dried samples in which the natural structure of pores may have been damaged to some extent due to desiccation and dehydration of the clay minerals. A recently developed alternative is to study wet samples using a cryo-SEM, which allows stabilization of wet media at cryo-temperature, in-situ sample preparation by ion beam cross-sectioning (BIB, FIB) and observations of the stabilized microstructure at high resolution. We report on a study of Boom clay from a proposed disposal site of radioactive waste (Mol site, Belgium) using cryo-SEM at cryogenic temperature, with ion beam cross-sectioning to prepare smooth, damage free surfaces. Pores commonly have crack-like tips, preferred orientation parallel to bedding and power law size distribution. We define a number of pore types depending on shape and location in the microstructure. 3-D reconstruction by serial cross-sectioning shows 3-D connectivity of the pore space. These findings offer a new insight into the morphology of pores down to nano-scale and provide the basis for microstructure-based models of transport in clays. SEM image (SE) of a Broad Ion Beam polished cross-section performed on dry Boom clay (Mol site, Belgium) showing the 2D apparent porosity (26.3%). The cross-section is perpendicular to the bedding.

Effects of a thermal perturbation on mineralogy and pore water composition in a clay-rock: An experimental and modeling study

NASA Astrophysics Data System (ADS)

Gailhanou, H.; Lerouge, C.; Debure, M.; Gaboreau, S.; Gaucher, E. C.; Grangeon, S.; Grenèche, J.-M.; Kars, M.; Madé, B.; Marty, N. C. M.; Warmont, F.; Tournassat, C.

2017-01-01

The physical and chemical properties of clay-rocks are, at least partly, controlled by the chemical composition of their pore water. In evaluating the concept of disposing of radioactive waste in clay-rock formations, determining pore water composition is an important step in predicting how a clay-rock will behave over time and as a function of external forces, such as chemical and thermal perturbations. This study aimed to assess experimental and modeling methodology to calculate pore water composition in a clay-rock as a function of temperature (up to 80 °C). Hydrothermal alteration experiments were carried out on clay-rock samples. We conducted comprehensive chemical and mineralogical characterization of the material before and after reaction, and monitored how the chemical parameters in the liquid and gas phases changed. We compared the experimental results with the a priori predictions made by various models that differed in their hypotheses on the reactivity of the minerals present in the system. Thermodynamic equilibrium could not be assessed unequivocally in these experiments and most of the predicted mineralogy changes were too subtle to be tracked quantitatively. However, from observing the neo-formation of minerals such as goethite we were able to assess the prominent role of Fe-bearing phases in the outcome of the experiments, especially for the measured pH and pCO2 values. After calibrating the amount of reacting Fe-bearing phases with our data, we proposed a thermodynamic model that was capable of predicting the chemical evolution of the systems under investigation as well as the evolution of other systems already published in the literature, with the same clay-rock material but with significant differences in experimental conditions.

Characterizing the capacity of hyporheic sediments to attenuate groundwater nitrate loads by adsorption.

PubMed

Meghdadi, Aminreza

2018-05-02

Nitrate has been recognized as a global threat to environmental health. In this regard, the hyporheic zone (saturated media beneath and adjacent to the stream bed) plays a crucial role in attenuating groundwater nitrate, prior to discharge into surface water. While different nitrate removal pathways have been investigated over recent decades, the adsorption capacity of hyporheic sediments under natural conditions has not yet been identified. In this study, the natural attenuation capacity of the hyporheic-sediments of the Ghezel-Ozan River, located in the north-west of Iran, was determined. The sampled sediments (from 1 m below the stream bed) were characterized via XRD, FT-IR, BET, SEM, BJH, and Zeta potential. Nitrate adsorption was evaluated using a batch experiment with hyporheic pore-water from each study site. The study was performed in the hyporheic sediments of two morphologically different zones, including Z 1 located in the parafluvial zone having the clay sediment texture (57.8% clay) with smectite/Illite mixed layer clay type and Z 2 located in the river confluence area containing silty clay sediment texture (47.6% clay) with smectite/kaolinite mixed layer clay type. Data obtained from the batch experiment were subjected to pseudo-first order, pseudo-second order, intra-particle diffusion, and Elovich mass transfer kinetic models to characterize the nitrate adsorption mechanism. Furthermore, to replicate nitrate removal efficiencies of the hyporheic sediments under natural conditions, the sampled hyporheic pore-waters were applied as initial solutions to run the batch experiment. The results of the artificial nitrate solution correlated well with pseudo-second order (R 2 >95%; in both Z 1 and Z 2 ) and maximum removal efficiencies of 85.3% and 71.2% (adsorbent dosage 90 g/L, pH = 5.5, initial adsorbate concentration of 90 mg/L) were achieved in Z 1 and Z 2 , respectively. The results of the nitrate adsorption analysis revealed that the nitrate removal efficiencies varied from 17.24 ± 1.86% in Z 1 during the wet season to 28.13 ± 0.89% in Z 2 during the dry season. The results obtained by this study yielded strong evidence of the potential of hyporheic sediments to remove nitrate from an aqueous environment with great efficiency. Crown Copyright © 2018. Published by Elsevier Ltd. All rights reserved.

Behavior of nonplastic silty soils under cyclic loading.

PubMed

Ural, Nazile; Gunduz, Zeki

2014-01-01

The engineering behavior of nonplastic silts is more difficult to characterize than is the behavior of clay or sand. Especially, behavior of silty soils is important in view of the seismicity of several regions of alluvial deposits in the world, such as the United States, China, and Turkey. In several hazards substantial ground deformation, reduced bearing capacity, and liquefaction of silty soils have been attributed to excess pore pressure generation during dynamic loading. In this paper, an experimental study of the pore water pressure generation of silty soils was conducted by cyclic triaxial tests on samples of reconstituted soils by the slurry deposition method. In all tests silty samples which have different clay percentages were studied under different cyclic stress ratios. The results have showed that in soils having clay content equal to and less than 10%, the excess pore pressure ratio buildup was quicker with an increase in different cyclic stress ratios. When fine and clay content increases, excess pore water pressure decreases constant cyclic stress ratio in nonplastic silty soils. In addition, the applicability of the used criteria for the assessment of liquefaction susceptibility of fine grained soils is examined using laboratory test results.

Behavior of Nonplastic Silty Soils under Cyclic Loading

PubMed Central

Ural, Nazile; Gunduz, Zeki

2014-01-01

The engineering behavior of nonplastic silts is more difficult to characterize than is the behavior of clay or sand. Especially, behavior of silty soils is important in view of the seismicity of several regions of alluvial deposits in the world, such as the United States, China, and Turkey. In several hazards substantial ground deformation, reduced bearing capacity, and liquefaction of silty soils have been attributed to excess pore pressure generation during dynamic loading. In this paper, an experimental study of the pore water pressure generation of silty soils was conducted by cyclic triaxial tests on samples of reconstituted soils by the slurry deposition method. In all tests silty samples which have different clay percentages were studied under different cyclic stress ratios. The results have showed that in soils having clay content equal to and less than 10%, the excess pore pressure ratio buildup was quicker with an increase in different cyclic stress ratios. When fine and clay content increases, excess pore water pressure decreases constant cyclic stress ratio in nonplastic silty soils. In addition, the applicability of the used criteria for the assessment of liquefaction susceptibility of fine grained soils is examined using laboratory test results. PMID:24672343

Removal of nitrobenzene by immobilized nanoscale zero-valent iron: Effect of clay support and efficiency optimization

NASA Astrophysics Data System (ADS)

Li, Xiaoguang; Zhao, Ying; Xi, Beidou; Mao, Xuhui; Gong, Bin; Li, Rui; Peng, Xing; Liu, Hongliang

2016-05-01

In this study, natural clays were used as the support for nanoscale zero-valent iron (nZVI) to fulfill affordable and efficient decontamination materials. In comparison with the kaolinite (K) and montmorillonite (M) supported nZVI materials (K-nZVI and M-nZVI), Hangjin clay supported nZVI (HJ-nZVI) exhibited the best performance for nitrobenzene (NB) removal because of its favorable characteristics, such as higher specific surface area (SSA, 82.0 m2 g-1), larger pore volume (0.1198 cm3 g-1) and bigger average pore diameter (6.2 nm). The NB removal efficiency achieved by HJ-nZVI (93.2 ± 2.8%) was much higher than these achieved by HJ clay alone (38.2 ± 2.3%), nZVI alone (52.3 ± 2.5%) and by the combined use of nZVI and HJ clay (70.2 ± 1.3%). The superior performance of HJ-nZVI was associated with three aspects: the even distribution of nZVIs onto HJ clay, higher payload efficiency of nZVIs and the stronger adsorption capability of HJ clay support. Higher SSA, larger pore volume, favorable cation exchange capacity and structural negative charges all facilitated the payload of iron onto HJ clay. The adsorption process accelerated the reduction via increasing the local concentration of aqueous NB. The high efficiency of HJ-nZVI for decontamination warranted its promising prospect in remediation applications.

Assessing the role of clay authigenesis in the seawater potassium cycle: A paired K and Mg isotope study of deep-sea pore fluids

NASA Astrophysics Data System (ADS)

Santiago Ramos, D. P.; Higgins, J. A.

2017-12-01

In situ formation of clays (clay authigenesis) in marine sediments and altered oceanic crust is an important sink of a number of seawater cations. In particular, clay authigenesis is a major, and yet unconstrained, flux in the global seawater potassium cycle. Potassium is the fourth most abundant cation in the ocean, which constitutes an isotopically enriched K reservoir (δ41K 0‰) compared to the solid Earth (δ41K -0.5‰). Understanding what processes control this isotopic offset is the main goal of this study. Here we use a multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS) to measure the K and Mg isotope ratios (41K/39K and 26Mg/24Mg) of deep-sea pore fluids in order to assess the effects of clay formation in the K isotope composition of seawater. Mg isotopes are used as an independent proxy for clay formation, since marine authigenic clays are isotopically distinct from their detrital counterpart, an abundant component of marine sediments. Our study sites (ODP/IODP 1052, U1378, U1395, U1403) vary in location, lithology, age and sedimentation rates; however, pore-fluids from all sites show decreasing K concentrations with depth, suggesting potassium uptake into the sediments. We find that although K concentration trends are similar across all sites, measured δ41K values vary significantly. Results from 1-D diffusion-advection-reaction models suggest that these differences in isotopic profiles arise from a complex interplay between sedimentation rate and K isotopic fractionation during clay formation, aqueous K diffusion and ion exchange reactions. Further, model simulations yield fractionation factors between 0.9980 and 1.0000 for clay formation in deep-sea sediments. Despite the minor contribution of these deep-sea pore-fluids as sinks of seawater K, the processes responsible for K isotope fractionation in our study sites (clay formation and aqueous K diffusion) are also observed at shallow marine systems (major K sinks) and are thus likely responsible for setting the K isotopic composition of seawater.

Direct visualization of clay microfabric signatures driving organic matter preservation in fine-grained sediment

NASA Astrophysics Data System (ADS)

Curry, Kenneth J.; Bennett, Richard H.; Mayer, Lawrence M.; Curry, Ann; Abril, Maritza; Biesiot, Patricia M.; Hulbert, Matthew H.

2007-04-01

We employed direct visualization of organic matter (OM) sequestered by microfabric signatures in organo-clay systems to study mechanisms of OM protection. We studied polysaccharides, an abundant class of OM in marine sediments, associated with the nano- and microfabric of clay sediment using a novel application of transmission electron microscopy, histochemical staining (periodic acid-thiosemicarbazide-silver proteinate), and enzymatic digestion techniques. We used two experimental organo-clay sediment environments. First, laboratory-consolidated sediment with 10% chitin (w/w) added was probed for chitin before and after digestion with chitinase. Second, fecal pellets from the polychaete Heteromastus filiformis were used as a natural environment rich in clay and polysaccharides. Sections of this material were probed with silver proteinate for polysaccharides before and after digestion with a mixture of enzymes (amylase, cellulase, chitinase, dextranase, and pectinase). In both environments, chitin or other polysaccharides were found within pores, bridging clay domains, and attached to clay surfaces in undigested samples. Digested samples showed chitin or polysaccharides more closely associated with clay surfaces and in small pores. Our results imply protective roles for both sorption to clay surfaces and encapsulation within clay microfabric signatures.

Simulating Donnan equilibria based on the Nernst-Planck equation

NASA Astrophysics Data System (ADS)

Gimmi, Thomas; Alt-Epping, Peter

2018-07-01

Understanding ion transport through clays and clay membranes is important for many geochemical and environmental applications. Ion transport is affected by electrostatic forces exerted by charged clay surfaces. Anions are partly excluded from pore water near these surfaces, whereas cations are enriched. Such effects can be modeled by the Donnan approach. Here we introduce a new, comparatively simple way to represent Donnan equilibria in transport simulations. We include charged surfaces as immobile ions in the balance equation and calculate coupled transport of all components, including the immobile charges, with the Nernst-Planck equation. This results in an additional diffusion potential that influences ion transport, leading to Donnan ion distributions while maintaining local charge balance. The validity of our new approach was demonstrated by comparing Nernst-Planck simulations using the reactive transport code Flotran with analytical solutions available for simple Donnan systems. Attention has to be paid to the numerical evaluation of the electrochemical migration term in the Nernst-Planck equation to obtain correct results for asymmetric electrolytes. Sensitivity simulations demonstrate the influence of various Donnan model parameters on simulated anion accessible porosities. It is furthermore shown that the salt diffusion coefficient in a Donnan pore depends on local concentrations, in contrast to the aqueous salt diffusion coefficient. Our approach can be easily implemented into other transport codes. It is versatile and facilitates, for instance, assessing the implications of different activity models for the Donnan porosity.

Bulk Moisture and Salinity Sensor

NASA Technical Reports Server (NTRS)

Nurge, Mark; Monje, Oscar; Prenger, Jessica; Catechis, John

2013-01-01

Measurement and feedback control of nutrient solutions in plant root zones is critical to the development of healthy plants in both terrestrial and reduced-gravity environments. In addition to the water content, the amount of fertilizer in the nutrient solution is important to plant health. This typically requires a separate set of sensors to accomplish. A combination bulk moisture and salinity sensor has been designed, built, and tested with different nutrient solutions in several substrates. The substrates include glass beads, a clay-like substrate, and a nutrient-enriched substrate with the presence of plant roots. By measuring two key parameters, the sensor is able to monitor both the volumetric water content and salinity of the nutrient solution in bulk media. Many commercially available moisture sensors are point sensors, making localized measurements over a small volume at the point of insertion. Consequently, they are more prone to suffer from interferences with air bubbles, contact area of media, and root growth. This makes it difficult to get an accurate representation of true moisture content and distribution in the bulk media. Additionally, a network of point sensors is required, increasing the cabling, data acquisition, and calibration requirements. measure the dielectric properties of a material in the annular space of the vessel. Because the pore water in the media often has high salinity, a method to measure the media moisture content and salinity simultaneously was devised. Characterization of the frequency response for capacitance and conductance across the electrodes was completed for 2-mm glass bead media, 1- to 2-mm Turface (a clay like media), and 1- to 2-mm fertilized Turface with the presence of root mass. These measurements were then used to find empirical relationships among capacitance (C), the dissipation factor (D), the volumetric water content, and the pore water salinity.

Micro-fabric damages in Boom Clay inferred from cryo-BIB-SEM experiment: recent results

NASA Astrophysics Data System (ADS)

Desbois, Guillaume; Schmatz, Joyce; Klaver, Jop; Urai, Janos L.

2017-04-01

The Boom Clay is considered as a potential host rock in Belgium for nuclear waste disposal in a deep geological formation. One of the keys to understand the long-term performance of such a host rock is the fundamental understanding of coupling between microstructural evolution, poromechanical behaviour and the state of hydration of the system. At in situ conditions, Boom Clay is a nearly water-saturated (>94%) clay-rich geomaterial. Subsequently, for measurement of mechanical and transport properties in laboratory, cores of Boom Clay are vacuum-packed in Al-coated-poly-ethylene barrier foil to be best preserved at original hydric state. Because clay microstructures are very sensitive to dehydration, the validity of investigations done on such preserved or/and dried samples is often questionable. Desbois et al. (2009, 2013, 2014) showed the possibility to image fluid-filled porosity in Boom Clay, by using the FIB-cryo-SEM (FIB: Focussed Ion Beam) and FIB-cryo-SEM (BIB: Broad Ion Beam) techniques. However, surprisingly in Desbois et al. (2014), BIB-cryo-SEM experiments on Boom Clay, shown that the majority of the pores were fluid-free, contrasting with result in Desbois et al. (2009). In Desbois et al. (2014), several reasons were discussed to explain such discrepancies. The likely ones are the sealing efficiency of the Al-barrier foil at long term and the volume expansion due to the release of in-situ stress after core extraction, contributing both to dehydration and microfabric damage. This contribution presents the newest results based on cryo-BIB-SEM. Small pieces (30 mm3) of Boom Clay were preserved in liquid nitrogen after the core extraction at the MOL/Dessel Underground Research Laboratory in Belgium. A maximum of ten minutes time span was achieved between opening the core, the sub-sample extraction and the quenching of sub-samples in liquid nitrogen. First results show that all pores visible at cryo-SEM resolution are water saturated. However, water-filled micro-cracks are also present and they are interpreted to result from the releasing of in-situ stress after the core extraction. Moreover, the comparison of the clay micro-fabrics in the same preserved and dried sample suggests collapsing of the clay aggregates' pores in dried sample. These newest results are still preliminary and they need to be analysed in more details. However, if they are confirmed they may be important input to discuss about the validity of measurement of mechanical and transport properties done in laboratory. Desbois G., Urai J.L. and Kukla P.A. (2009). Morphology of the pore space in claystones - evidence from BIB/FIB ion beam sectioning and cryo-SEM observations. E-Earth, 4 :15-22. Desbois G., J.L. Urai, F. Pérez-Willard, Z. Radi, S. van Offern, I. Burkart, P.A. Kukla, U. Wollenberg (2013). Argon broad ion beam tomography in a cryogenic scanning electron microscope: a novel tool for the investigation of representative microstructures in sedimentary rocks containing pore fluid. Journal of Microscopy, 249(3): 215-235. Desbois G., Urai J.L., Hemes S., Brassinnes S., De Craen M., Sillen X. (2014). Nanometer-scale pore fluid distribution and drying damage in preserved clay cores from Belgian clay formations inferred by BIB-cryo-SEM. Engineering Geology, 170:117-131.

Hyporheic less-mobile porosity and solute transport in porous media

NASA Astrophysics Data System (ADS)

MahmoodPoorDehkordy, F.; Briggs, M. A.; Day-Lewis, F. D.; Scruggs, C.; Singha, K.; Zarnetske, J. P.; Lane, J. W., Jr.; Bagtzoglou, A. C.

2017-12-01

Solute transport and reactive processes are strongly influenced by hydrodynamic exchange with the hyporheic zone. Contaminant transport and redox zonation in the hyporheic zone and near-stream aquifer can be impacted by the exchange between mobile and less-mobile porosity zones in heterogeneous porous media. Less-mobile porosity zones can be created by fine materials with tight pore throats (e.g. clay, organics) and in larger, well-connected pores down gradient of flow obstructions (e.g. sand behind cobbles). Whereas fluid sampling is primarily responsive to the more-mobile domain, tracking solute tracer dynamics by geoelectrical methods provides direct information about both more- and less-mobile zones. During tracer injection through porous media of varied pore connectivity, a lag between fluid and bulk electrical conductivity is observed, creating a hysteresis loop when plotted in conductivity space. Thus, the combination of simultaneous fluid and bulk electrical conductivity measurements enables a much improved quantification of less-mobile solute dynamics compared to traditional fluid-only sampling approaches. We have demonstrated the less-mobile porosity exchange in laboratory-scale column experiments verified by simulation models. The experimental approach has also been applied to streambed sediments in column and reach-scale field experiments and verified using numerical simulation. Properties of the resultant hysteresis loops can be used to estimate exchange parameters of less-mobile porosity. Our integrated approach combining field experiments, laboratory experiments, and numerical modeling provides new insights into the effect of less-mobile porosity on solute transport in the hyporheic zone.

Deposition of Suspended Clay to Open and Sand-Filled Framework Gravel Beds in a Laboratory Flume

NASA Astrophysics Data System (ADS)

Mooneyham, Christian; Strom, Kyle

2018-01-01

Pulses of fine sediment composed of sand, silt, and clay can be introduced to gravel bed rivers through runoff from burn-impacted hillslopes, landslides, bank failure, or the introduction of reservoir sediment as a result of sluicing or dam decommissioning. Here we present a study aimed at quantifying exchange between suspensions of clay and gravel beds. The questions that motivate the work are: how do bed roughness and pore space characteristics, shear velocity (u∗), and initial concentration (C0) affect clay deposition on or within gravel beds? Where does deposition within these beds occur, and can deposited clay be resuspended while the gravel is immobile? We examine these questions in a laboratory flume using acrylic, open-framework gravel, and armored sand-gravel beds under conditions of varying u∗ and C0. Deposition of clay occurred to all beds (even with Rouse numbers ˜ 0.01). We attribute deposition under full suspension conditions to be an outcome of localized protected zones where clay can settle and available pore space in the bed. For smooth wall cases, protection came from the viscous wall region and the development of bed forms; for the rough beds, protection came from separation zones and low-velocity pore spaces. Bed porosity was the strongest influencer of nondimensional deposition rate; deposition increased with porosity. Deposition was inversely related to u∗ for the acrylic bed runs; no influence of u∗ was found for the porous bed runs. Increases in discharge resulted in resuspension of clay from acrylic beds; no resuspension was observed in the porous bed runs.

Molecular dynamics simulations of the electrical double layer on smectite surfaces contacting concentrated mixed electrolyte (NaCl-CaCl2) solutions.

PubMed

Bourg, Ian C; Sposito, Garrison

2011-08-15

We report new molecular dynamics results elucidating the structure of the electrical double layer (EDL) on smectite surfaces contacting mixed NaCl-CaCl(2) electrolyte solutions in the range of concentrations relevant to pore waters in geologic repositories for CO(2) or high-level radioactive waste (0.34-1.83 mol(c) dm(-3)). Our results confirm the existence of three distinct ion adsorption planes (0-, β-, and d-planes), often assumed in EDL models, but with two important qualifications: (1) the location of the β- and d-planes are independent of ionic strength or ion type and (2) "indifferent electrolyte" ions can occupy all three planes. Charge inversion occurred in the diffuse ion swarm because of the affinity of the clay surface for CaCl(+) ion pairs. Therefore, at concentrations ≥0.34 mol(c) dm(-3), properties arising from long-range electrostatics at interfaces (electrophoresis, electro-osmosis, co-ion exclusion, colloidal aggregation) will not be correctly predicted by most EDL models. Co-ion exclusion, typically neglected by surface speciation models, balanced a large part of the clay mineral structural charge in the more concentrated solutions. Water molecules and ions diffused relatively rapidly even in the first statistical water monolayer, contradicting reports of rigid "ice-like" structures for water on clay mineral surfaces. Published by Elsevier Inc.

Aquitard characteristics of clay-rich till deposits in East Anglia, Eastern England

NASA Astrophysics Data System (ADS)

Hiscock, K. M.; Tabatabai Najafi, M.

2011-08-01

SummaryAn extensive area of Quaternary glacial deposits (Lowestoft Till) of Elsterian (Anglian) age overlies the regionally important Cretaceous Chalk aquifer in East Anglia in Eastern England. The glacial deposits act as an aquitard potentially affording protection from surface-derived, mainly agricultural contaminants. However, there has been little previous research on the physical and chemical characteristics of the glacial tills and contained pore waters in East Anglia to demonstrate this benefit. Hence, this study presents the results from the drilling of two boreholes in northern and southern East Anglia (at Morley and Cowlinge, respectively) and the construction of a high-pressure squeezing rig to obtain pore water for major and minor ion, stable isotope (δ 18O, δ 2H) and dissolved organic carbon analysis. Special features of the mechanical squeezing rig included a high diameter-to-length ratio of the squeezer, dual seepage faces and a unique pore water collection system designed to eliminate the risk of alteration of in situ pore water redox characteristics. The hydrochemistry of the pore waters is found to be controlled by: (i) incongruent carbonate dissolution given the high proportion of chalk clasts contained in the till; (ii) cation exchange in the unweathered, clay-rich till; and (iii) pyrite oxidation associated with the mineralogy of both the chalk and clay material content that comprises the till matrix. The clay material is sourced from Upper Jurassic clays (Oxford and Kimmeridge Clay Formations) found to the west of the region. These clays are also considered to be the source of organic material contributing relatively high concentrations of dissolved organic carbon (above 2 mg/L) found in till pore waters below the soil zone. Concentrations of dissolved inorganic constituents increase with depth with a high total dissolved solids (TDS) content in excess of 1500 mg/L measured in the unweathered till below a depth of 5 m below ground level, with the highest concentrations (maximum of 3738 mg/L) associated with low-permeability, clay-rich till. The stable isotope composition of the pore waters, with mean values for δ 18O and δ 2H of -7.01‰ and -51.7‰ at Cowlinge and -6.44‰ and 49.9‰ at Morley, respectively, are similar to local meteoric water and indicate that groundwater recharge of the tills has occurred during the Holocene in the last 10,000 years. Overall, the physical and chemical characteristics of the Lowestoft Till suggest only limited groundwater recharge of the order of 10 mm/a or less in interfluve areas where the till deposits are greater than 15 m thick; although higher rates are expected where the till becomes more sand-rich, for example at valley margins and also northwards in East Anglia where the Lowestoft Till is influenced by the component of Anglian ice that advanced from the north, containing sand material derived from the floor of the North Sea Basin.

Clays causing adhesion with tool surfaces during mechanical tunnel driving

NASA Astrophysics Data System (ADS)

Spagnoli, G.; Fernández-Steeger, T.; Stanjek, H.; Feinendegen, M.; Post, C.; Azzam, R.

2009-04-01

During mechanical excavation with a tunnel boring machine (TBM) it is possible that clays stick to the cutting wheel and to other metal parts. The resulting delays in the progress of construction work, cause great economic damage and often disputes between the public awarding authorities and executing companies. One of the most important factors to reduce successfully the clay adhesion is the use of special polymers and foams. But why does the clay stick to the metal parts? A first step is to recognize which kind of clay mineralogy shows serious adhesion problems. The mechanical properties of clay and clay suspensions are primarily determined by surface chemistry and charge distribution at the interfaces, which in turn affect the arrangement of the clay structure. As we know, clay is a multi-phase material and its behaviour depends on numerous parameters such as: clay mineralogy, clay fraction, silt fraction, sand fraction, water content, water saturation, Atterberg limits, sticky limit, activity, cation exchange capacity, degree of consolidation and stress state. It is therefore likely that adhesion of clay on steel is also affected by these clay parameters. Samples of clay formations, which caused problems during tunnel driving, will be analyzed in laboratory. Mineralogical analyses (diffractometry, etc.) will be carried out to observe which minerals are responsible for adherence problems. To manipulate the physical properties, batch tests will be carried out in order to eliminate or reduce the adhesion on tool surfaces through variation of the zeta potential. Second step is the performance of vane shear tests on clay samples. Different pore fluid (distilled water, pure NaCl solution, ethanol and methanol) will be used to study the variation of the mechanical behaviour of clay depending on the dielectric constant of the fluids. This project is funded by the German Federal Ministry of Education and Research (BMBF) and the DFG (German Research Foundation) in the frame of the programme GEOTECHNOLOGIEN.

Thermal Transmittance of Porous Hollow Clay Brick by Guarded Hot Box Method

NASA Astrophysics Data System (ADS)

Kim, Joonsoo

2018-03-01

The thermal property of a porous hollow clay brick was determined by measuring the thermal transmittance of the wall made of porous hollow clay bricks. Prior to the production of porous hollow clay bricks, nonporous and porous tiny clay bricks were prepared to determine the physico-mechanical properties by modifying the amount of wood flour and firing temperature. The bricks were produced by uniaxial pressing and then fired in an electric furnace. Their physico-mechanical properties were measured by water absorption, apparent porosity, bulk density, and compressive strength. The porous tiny clay bricks were produced with three types of wood flour: coarse wood flour (1-0.36 mm), medium-sized wood flour (0.36-0.15 mm), and fine wood flour (< 0.08 mm). The thermal transmittance of porous hollow clay bricks was determined through the guarded hot box method, which measures the wall made of porous hollow clay bricks and nonporous cement bricks. The two walls had a thermal transmittance of 1.42 and 2.72 W\\cdot m^{-2}\\cdot K^{-1}, respectively. The difference in thermal transmittance was due to the pores created with fine wood flour (< 0.08 mm) as a pore-forming agent.

Permeability changes induced by microfissure closure and opening in tectonized materials. Effect on slope pore pressure regime.

NASA Astrophysics Data System (ADS)

De la Fuente, Maria; Vaunat, Jean; Pedone, Giuseppe; Cotecchia, Federica; Sollecito, Francesca; Casini, Francesca

2015-04-01

Tectonized clays are complex materials characterized by several levels of structures that may evolve during load and wetting/drying processes. Some microstructural patterns, as microfissures, have a particular influence on the value of permeability which is one of the main factors controlling pore pressure regime in slopes. In this work, the pore pressure regime measured in a real slope of tectonized clay in Southern Italy is analyzed by a numerical model that considers changes in permeability induced by microfissure closure and opening during the wetting and drying processes resulting from climatic actions. Permeability model accounts for the changes in Pore Size Distribution observed by Microscopy Intrusion Porosimetry. MIP tests are performed on representative samples of ground in initial conditions ("in situ" conditions) and final conditions (deformed sample after applying a wetting path that aims to reproduce the saturation of the soil under heavy rains). The resulting measurements allow for the characterization at microstructural level of the soil, identifying the distribution of dominant families pores in the sample and its evolution under external actions. Moreover, comparison of pore size density functions allows defining a microstructural parameter that depends on void ratio and degree of saturation and controls the variation of permeability. Model has been implemented in a thermo-hydro-mechanical code provided with a special boundary condition for climatic actions. Tool is used to analyze pore pressure measurements obtained in the tectonized clay slope. Results are analyzed at the light of the effect that permeability changes during wetting and drying have on the pore pressure regime.

Study of sorption-retarded U(VI) diffusion in Hanford silt/clay material.

PubMed

Bai, Jing; Liu, Chongxuan; Ball, William P

2009-10-15

A diffusion cell method was applied to measure the effective pore diffusion coefficient (Dp) for U(VI) under strictly controlled chemical conditions in a silt/clay sediment from the U.S. Department of Energy Hanford site, WA. "Inward-flux" diffusion studies were conducted in which [U(VI)] in both aqueous and solid phases was measured as a function of distance in the diffusion cell under conditions of constant concentration at the cell boundaries. A sequential extraction method was developed to measure sorbed contaminant U(VI) in the solid phase containing extractable background U(VI). The effect of sorption kinetics on U(VI) interparticle diffusion was evaluated by comparing sorption-retarded diffusion models with sorption described either as equilibrium or intraparticle diffusion-limited processes. Both experimental and modeling results indicated that (1) a single pore diffusion coefficient can simulate the diffusion of total aqueous U(VI), and (2) the local equilibrium assumption (LEA) is appropriate for modeling sorption-retarded diffusion under the given experimental conditions. Dp of 1.6-1.7 x 10(-6) cm2/s was estimated in aqueous solution at pH 8.0 and saturated with respect to calcite, as relevant to some subsurface regions of the Hanford site.

Paired measurements of K and Mg isotopes and clay authigenesis in marine sediments

NASA Astrophysics Data System (ADS)

Santiago Ramos, D. P.; Dunlea, A. G.; Higgins, J. A.

2016-12-01

Despite its importance as a major sink for seawater K and Mg, estimates of clay authigenesis in marine sediments remain poorly constrained. Previous work on Mg isotope fractionation during clay formation has revealed a preferential uptake of 26Mg, yielding authigenic clay products with potentially distinct δ26Mg compared to the detrital component. In a similar manner, we aim to quantify the K isotope fractionation during authigenic clay formation and to use paired δ26Mg and δ41K measurements as proxies for the identification and quantification of authigenic clays in shallow and deep marine sedimentary systems. To better understand the behavior of paired Mg and K isotopes during authigenic clay formation in marine sediments, we measured δ26Mg and δ41K values of pore-fluids and sediments from ODP/IODP sites 1052, U1395, U1403 and U1366. We find that while pore-fluid K concentrations at sites 1052, U1395 and U1403 all decline with depth, δ41K profiles differ significantly. These differences might be a result of a complex interplay between clay authigenesis, sedimentation rate, and fractionation of K isotopes during diffusion. Results from 1-D diffusion-advection-reaction models suggest that, in contrast to Mg, diffusion may play an important role in determining the overall K isotope fractionation during clay authigenesis in sites with low-sedimentation rates. Sites with high sedimentation rates may act as close systems where diffusion is negligible. In such cases, K uptake can be modeled as a Rayleigh distillation process and K isotope fractionation can be estimated. Measurements of δ26Mg and δ41K of pore-fluids from site U1395 and bulk sediments from U1366 suggest that paired measurements of these isotopic systems in siliciclastic marine sediments can provide new insights into rates of marine clay authigenesis, a globally important but understudied component of many geochemical cycles.

Micro- and Nanostructures of SAFOD Core Samples - First Results

NASA Astrophysics Data System (ADS)

Janssen, C.; Wirth, R.; Rybacki, E.; Naumann, R.; Kemnitz, H.; Wenk, H.; Dresen, G. H.

2009-12-01

Microstructures and chemical composition of ultra-cataclastic rocks from the San Andreas Fault drill hole (SAFOD) were examined using TEM, SEM and XRD analyses. The ultra-cataclasites are mainly composed of quartz, clay minerals (illite/smectite, chlorite), feldspar (plagioclase) and calcite with grain sizes between 200 nm and 500 μm. In particular we found: (1) amorphous materials, identified by transmission electron microscopy. Chemical analyses suggest that all amorphous material was formed by comminution (crush-origin) of fragments rather than by melting (melt-origin) and that the observed amorphous phases may act as hydrodynamic lubricating layers that reduce friction in the San Andreas Fault. (2) Pressure solution seams and localized precipitation of hydrous mixed-layered clay minerals suggest intensive dissolution-precipitation processes. These may lead to a thin film covering slip surfaces. (3) Authigenic clay minerals forming a flocculated fabric. (4) The fine-grained (< 1μm) gouge matrix contains clasts (feldspar, quartz) and is frequently cut by fault-related veins. The veins are filled with calcite or quartz. Observed micorstructures in the fine-grained matrix suggest comminution and sliding of the nanoscale grains. Open pore spaces up to 2.25 μm3 have been formed during and after deformation within the gouge matrix. These were possibly filled with hydrothermal fluids at elevated pore fluid pressure preventing closure. (5) Detrital quartz and feldspar grains are partly dissolved and replaced by authigenic illite-smectite (I-S) mixed-layer clay minerals. TEM imaging of these grains reveal that initial alteration processes started within pores and small fissures of grains. The crystallographic-preferred orientation of illite and I/S grains is rather weak with a maximum m.r.d. (multiples of random orientation) of 2.3. (6) Some older fault-related vein-calcites show evidence for intense intracrystalline plasticity (deformation twins and dislocation creep). Dislocation densities in calcite grains indicate a local maximum stress of about 40 MPa. The younger fault-related vein-calcite generation with elongated to fibrous habit suggests slow opening by aseismic slip. These crystals are not fractured or twinned (or only less); indicating that healing processes (cementation) outlasted deformation.

Interstitial water studies on small core samples, Leg 15

USGS Publications Warehouse

Sayles, Fred L.; Manheim, Frank T.; Waterman, Lee S.

1973-01-01

Analyses of pore fluids from reducing environments demonstrate that reduction of SO4 is accompanied by large increases in alkalinity and strong depletion of Ca and Mg. The data are compatible with a model of replacement of Fe3+ in clay lattices by Mg from the interstitial solutions and the precipitation of pyrite. Depletions of Na in the interstitial solutions are related to Mg losses by a ratio of approximately 1:3. Pore fluids from oxidizing pelagic sediments exhibit little SO4 depletion. Losses of Mg are accompanied by the addition of Ca to the pore solutions on a nearly 1:1 basis. Strong Sr enrichment is also found in these solutions. The magnitude of the Sr increase suggests that considerable carbonate recrystallization has occurred. As part of an extensive interlaboratory and analytical calibration, the effect of squeezing sediment at different temperatures has been studied in depth. Samples of a variety of lithologies have been included. Enrichment of K by as much as 24 percent and depletion of Mg and Ca by up to 7 percent occurs during warming. However, no significant effect upon Cl and SO4 could be detected. The strongest effects are seen in the minor constituents studied. On warming, Sr, Si, and B are enriched as much as 19, 40, and 60 percent, respectively. The size of the observed concentration changes varies with the mineralogy of the sediment, but is significant in all types studied, particularly with regards to Mg and K.

Effects of biochar on hydraulic conductivity of compacted kaolin clay.

PubMed

Wong, James Tsz Fung; Chen, Zhongkui; Wong, Annie Yan Yan; Ng, Charles Wang Wai; Wong, Ming Hung

2018-03-01

Compacted clay is widely used as capillary barriers in landfill final cover system. Recently, biochar amended clay (BAC) has been proposed as a sustainable alternative cover material. However, the effects of biochar on saturated hydraulic conductivity (k sat ) of clay with high degree of compaction is not yet understood. The present study aims to investigate the effects of biochar on k sat of compacted kaolin clay. Soil specimens were prepared by amending kaolin clay with biochar derived from peanut-shell at 0, 5 and 20% (w/w). The k sat of soil specimens was measured using a flexible water permeameter. The effects of biochar on the microstructure of the compacted clay was also investigated using MIP. Adding 5% and 20% of biochar increased the k sat of compacted kaolin clay from 1.2 × 10 -9 to 2.1 × 10 -9 and 1.3 × 10 -8 ms -1 , respectively. The increase in k sat of clay was due to the shift in pore size distribution of compacted biochar-amended clay (BAC). MIP results revealed that adding 20% of biochar shifted the dominant pore diameter of clay from 0.01-0.1 μm (meso- and macropores) to 0.1-4 μm (macropores). Results reported in this communication revealed that biochar application increased the k sat of compacted clay, and the increment was positively correlated to the biochar percentage. Copyright © 2017 Elsevier Ltd. All rights reserved.

Specification of matrix cleanup goals in fractured porous media.

PubMed

Rodríguez, David J; Kueper, Bernard H

2013-01-01

Semianalytical transient solutions have been developed to evaluate what level of fractured porous media (e.g., bedrock or clay) matrix cleanup must be achieved in order to achieve compliance of fracture pore water concentrations within a specified time at specified locations of interest. The developed mathematical solutions account for forward and backward diffusion in a fractured porous medium where the initial condition comprises a spatially uniform, nonzero matrix concentration throughout the domain. Illustrative simulations incorporating the properties of mudstone fractured bedrock demonstrate that the time required to reach a desired fracture pore water concentration is a function of the distance between the point of compliance and the upgradient face of the domain where clean groundwater is inflowing. Shorter distances correspond to reduced times required to reach compliance, implying that shorter treatment zones will respond more favorably to remediation than longer treatment zones in which back-diffusion dominates the fracture pore water response. For a specified matrix cleanup goal, compliance of fracture pore water concentrations will be reached sooner for decreased fracture spacing, increased fracture aperture, higher matrix fraction organic carbon, lower matrix porosity, shorter aqueous phase decay half-life, and a higher hydraulic gradient. The parameters dominating the response of the system can be measured using standard field and laboratory techniques. © 2012, The Author(s). Ground Water © 2012, National Ground Water Association.

Smectite Dehydration, Membrane Filtration, and Pore-Water Freshening in Deep Ultra-Low Permeability Formations: Deep Processes in the Nankai Accretionary Wedge

NASA Astrophysics Data System (ADS)

Brown, K. M.; Sample, J. C.; Even, E.; Poeppe, D.; Henry, P.; Tobin, H. J.; Saffer, D. M.; Hirose, T.; Toczko, S.; Maeda, L.

2014-12-01

We address the fundamental questions surrounding the nature of water and chemical transport processes deep within sedimentary basin and accretionary-wedge environments. Consolidation and permeability studies conducted to 165 MPa (~10km depth) indicate that ultra-tight clay formations (10-18 m2 to10-21 m2) can substantially modify the fluids migrating through then. Pore-water extractions conducted on smectite/illite rich core samples obtained from 1-3 km depths at IODP (NanTroSEIZE, Chikyu) deep-riser drilling Site C0002, at the elevated loads required to squeeze waters from such deeply buried sediment (stresses up to 100 MPa),resulted in anomalous patterns of sequential freshening with progressive loading. More accurate laboratory investigations (both incremental loading and Constant Rate of Strain test) revealed that such freshening initiates above 20 MPa and progresses with consolidation to become greater than 20% by effective normal load of 165 MPa. Log-log plots of stress vs. hydraulic conductivity reveal that trends remain linear to elevated stresses and total porosities as low at 14%. The implications are that stress induced smectite dehydration and/or membrane filtration effects cause remarkable changes in pore water chemistry with fluid migration through deep, tight, clay-rich formations. These changes should occur in addition to any thermally induced diagenetic and clay-dehydration effects on pore water chemistry. Work is progressing to evaluate the impact of clay composition and temperature to ascertain if purely illitic compositions show similar trends and if the mass fractionation of water and other isotopes also occurs. Such studies will ascertain if the presence of smectite is a prerequisite for freshening or if membrane filtration is a major process in earth systems containing common clay minerals. The results have major implications for interpretations of mass chemical balances, pore water profiles, and the hydrologic, geochemical, and stress state controls on deep system behavior in all deep accretionary wedge and basin environments where clays are abundant. This research used samples provided by the International Ocean Discovery Program (IODP).

Effects of exchanged cation on the microporosity of montmorillonite

USGS Publications Warehouse

Rutherford, David W.; Chiou, Cary T.; Eberl, Dennis D.

1997-01-01

The micropore volumes of 2 montmorillonites (SAz-1 and SWy-1), each exchanged with Ca, Na, K, Cs and tetramethylammonium (TMA) ions, were calculated from the measured vapor adsorption data of N2 and neo-hexane by use of t- and αs-plots. The corresponding surface areas of the exchanged clays were determined from Brunauer-Emmett-Teller (BET) plots of N2 adsorption data. Micropore volumes and surface areas of the samples increased with the size of exchanged cation: TMA > Cs > K > Ca > Na. The SAz-1 exchanged clays showed generally greater micropore volumes and surface areas than the corresponding SWy-1 clays. The vapor adsorption data and d(001) measurements for dry clay samples were used together to evaluate the likely locations and accessibility of clay micropores, especially the relative accessibility of their interlayer spacing. For both source clays exchanged with Na, Ca and K ions, the interlayer spacing appeared to be too small to admit nonpolar gases and the accessible micropores appeared to have dimensions greater than 5.0 Å, the limiting molecular dimension of neo-hexane. In these systems, there was a good consistency of micropore volumes detected by N2 and neo-hexane. When the clays were intercalated with relatively large cations (TMA and possibly Cs), the large layer expansion created additional microporosity, which was more readily accessible to small N2 than to relatively large neo-hexane. Hence, the micropore volume as detected by N2 was greater than that detected by neo-hexane. The micropore volumes with pore dimensions greater than 5 Å determined for clays exchanged with Na, Ca and K likely resulted from the pores on particle edges and void created by overlap regions of layers. The increase in micropore volumes with pore dimensions less than 5 Å determined for clays exchanged with TMA and possibly Cs could be caused by opening of the interlayer region by the intercalation of these large cations.

Crystallization and textural porosity of synthetic clay minerals.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carrado, K. A.; Csencsits, R.; Thiyagarajan, P.

2002-12-01

The crystallization of synthetic layered magnesium silicate hectorite clays from both silica sol and organosilane sources is compared. For the silica sol-derived clays, a templating method is employed wherein organic or polymeric molecules are included during clay crystallization that are then removed from the composites via calcination. The mechanism of silane-derived hectorite formation is followed by XRD, TGA, 29Si MAS NMR, and small angle X-ray scattering (SAXS), and results are compared to those obtained for the sol-derived hectorite. The mechanism appears to be similar but the rate is approximately doubled when the silane is used rather than silica sol. Analyticalmore » transmission electron microscopy (TEM) is exploited to glean structural morphology information towards resolving the nature of the resulting pore network structures. Results are compared with nitrogen adsorption-desorption isotherm behavior; dominant hysteresis loops are present in the type IV isotherms. Pore size distributions based on both the adsorption and desorption isotherms are compared. Small angle neutron scattering (SANS) experiments reveal that the average particle size increases as synthetic laponite < sol-derived hectorite < silane-derived hectorite < natural hectorite. Contrast matching SANS studies in aqueous and organic solvents are carried out to extract information about pore accessibility.« less

Regulation of landslide motion by dilatancy and pore pressure feedback

USGS Publications Warehouse

Iverson, R.M.

2005-01-01

A new mathematical model clarifies how diverse styles and rates of landslide motion can result from regulation of Coulomb friction by dilation or contraction of water-saturated basal shear zones. Normalization of the model equations shows that feedback due to coupling between landslide motion, shear zone volume change, and pore pressure change depends on a single dimensionless parameter ??, which, in turn, depends on the dilatancy angle ?? and the intrinsic timescales for pore pressure generation and dissipation. If shear zone soil contracts during slope failure, then ?? 0, and negative feedback permits slow, steady landslide motion to occur while positive pore pressure is supplied by rain infiltration. Steady state slip velocities v0 obey v0 = -(K/??) p*e, where K is the hydraulic conductivity and p*e is the normalized (dimensionless) negative pore pressure generated by dilation. If rain infiltration and attendant pore pressure growth continue unabated, however, their influence ultimately overwhelms the stabilizing influence of negative p*e. Then, unbounded landslide acceleration occurs, accentuated by an instability that develops if ?? diminishes as landslide motion proceeds. Nonetheless, numerical solutions of the model equations show that slow, nearly steady motion of a clay-rich landslide may persist for many months as a result of negative pore pressure feedback that regulates basal Coulomb friction. Similarly stabilized motion is less likely to occur in sand-rich landslides that are characterized by weaker negative feedback.

Marine geochemical cycles of the alkali elements and boron: the role of sediments

NASA Astrophysics Data System (ADS)

James, Rachael H.; Palmer, Martin R.

2000-09-01

We have analysed the concentrations of Li, K, Rb, Cs, and B, and the isotopic ratios of Li and B of a suite of pore fluids recovered from ODP Sites 1037 (Leg 169; Escanaba Trough) and 1034 (Leg 169S; Saanich Inlet). In addition, we have analysed dissolved K, Rb, and Cs concentrations for estuarine mixing of the Ganges-Brahmaputra river system. Together, these data sets have been used to assess the role of sediments in the marine geochemical cycles of the alkali elements and boron. Uptake onto clay minerals during estuarine mixing removes 20-30% of the riverine input of dissolved Cs and Rb to the oceans. Prior to this study, the only other recognised sink of Rb and Cs was uptake during low-temperature alteration of the oceanic crust. Even with this additional sink there is an excess of inputs over outputs in their modern oceanic mass balance. Pore fluid data show that Li and Rb are transferred into marine sediments during early diagenesis. However, modeling of the Li isotope systematics of the pore fluids from Site 1037 shows that seawater Li taken up during marine sedimentation can be readily returned to solution in the presence of less hydrated cations, such as NH 4+. This process also appears to result in high concentrations of pore fluid Cs (relative to local seawater) due to expulsion of adsorbed Cs from cation exchange sites. Flux calculations based on pore fluid data for a series of ODP sites indicate that early diagenesis of clay sediments removes around 8% of the modern riverine input of dissolved Li. Although NH 4+-rich fluids do result in a flux of Cs to the oceans, on the global scale this input only augments the modern riverine Cs flux by ˜3%. Nevertheless, this may have implications for the fate of radioactive Cs in the natural environment and waste repositories.

Deposition nucleation viewed as homogeneous or immersion freezing in pores and cavities

NASA Astrophysics Data System (ADS)

Marcolli, C.

2013-06-01

Heterogeneous ice nucleation is an important mechanism for the glaciation of mixed phase clouds and may also be relevant for cloud formation and dehydration at the cirrus cloud level. It is thought to proceed through different mechanisms, namely contact, condensation, immersion and deposition nucleation. Supposedly, deposition nucleation is the only pathway which does not involve liquid water but occurs by direct water vapor deposition on a surface. This study challenges this classical view by putting forward the hypothesis that what is called deposition nucleation is in fact homogeneous or immersion nucleation occurring in pores and cavities that may form between aggregated primary particles and fill with water at relative humidity RHw < 100% because of the inverse Kelvin effect. Evidence for this hypothesis of pore condensation and freezing (PCF) originates from a number of only loosely connected scientific areas. The prime example for PCF is ice nucleation in clay minerals and mineral dusts, for which the data base is best. Studies on freezing in confinement carried out on mesoporous silica materials such as SBA-15, SBA-16, MCM-41, zeolites and KIT have shown that homogeneous ice nucleation occurs abruptly at T=230-235 K in pores with diameters (D) of 3.5-4 nm or larger but only gradually at T=210-230 K in pores with D=2.5-3.5 nm. Melting temperatures in pores are depressed by an amount that can be described by the Gibbs-Thomson equation. Water adsorption isotherms of MCM-41 show that pores with D=3.5-4 nm fill with water at RHw = 56-60% in accordance with an inverse Kelvin effect. Water in such pores should freeze homogeneously for T < 235 K even before relative humidity with respect to ice (RHi) reaches ice saturation. Ice crystal growth by water vapor deposition from the gas phase is therefore expected to set in as soon as RHw > 100%. Pores with D > 7.5 nm fill with water at RHi > 100% for T < 235 K and are likely to freeze homogeneously as soon as they are filled with water. Water in pores can freeze in immersion mode at T > 235 K if the pore walls contain an active site. Pore analysis of clay minerals shows that kaolinites exhibit pore structures with pore diameters of 20-50 nm. The mesoporosity of illites and montmorillonites is characterized by pores with T = 2-5 nm. The number and size of pores is distinctly increased in acid treated montmorillonites like K10. Many clay minerals and mineral dusts show a strong increase in ice nucleation efficiency when temperature is decreased below 235 K. Such an increase is difficult to explain when ice nucleation is supposed to occur by a deposition mechanism, but evident when assuming freezing in pores, because for homogeneous ice nucleation only small pore volumes are needed, while heterogeneous ice nucleation requires larger pore structures to contain at least one active site for immersion nucleation. Together, these pieces of evidence strongly suggest that ice nucleation within pores should be the prevailing freezing mechanism of clay minerals for RHw below water saturation. Extending the analysis to other types of ice nuclei shows that freezing in pores and cracks is probably the prevailing ice nucleation mechanism for glassy and volcanic ash aerosols at RHw below water saturation. Freezing of water in carbon nanotubes might be of significance for ice nucleation by soot aerosols. No case could be identified that gives clear evidence of ice nucleation by water vapor deposition on a solid surface. Inspection of ice nuclei with a close lattice match to ice, such as silver iodide or SnomaxTM, show that for high ice nucleation efficiency below water saturation the presence of impurities or cracks on the surface may be essential. Soluble impurities promote the formation of a liquid phase below water saturation in patches on the surface or as a complete surface layer that offers an environment for immersion freezing. If porous aerosol particles come in contact with semivolatile vapors, these will condense preferentially in pores before a coating on the surface of the particles is formed. A pore partially filled with condensed species attracts water at lower RHw than an empty pore, but the aqueous solution that forms in the pore will freeze at a higher RHi than pure water. The ice nucleation ability of pores completely filled with condensed organic species might be totally impeded. Pores might also be important for preactivation, the capability of a particle to nucleate ice at lower RHi in subsequent experiments when compared to the first initial ice nucleation event. Preactivation has often been explained by persistence of ice embryos at specific sites like dislocations, steps, kinks or pores. However, it is not clear how such features can preserve an ice embryo at RHi < 100%. Rather, ice embryos could be preserved when embedded in water. To keep liquid water at RHw well below 100%, narrow pores are needed but to avoid a strong melting point depression large pores are favorable. A narrow pore opening and a large inner volume are combined in "ink bottle" pores. Such "ink bottle" pores would be suited to preserve ice at RHi < 100% and can arise e.g. in spaces between aggregated particles.

Illitization of Potassium, Cesium, and Ammonium Exchanged Smectite

NASA Astrophysics Data System (ADS)

Mills, M. M.; Wang, Y.; Payne, C.; Sanchez, A. C.; Boisvert, L.; Matteo, E. N.

2017-12-01

Bentonite clay is a primary choice for engineered barrier systems within geologic repositories for disposal of radioactive wastes due to its low permeability at saturated states, warranting diffusion as the dominant transport mechanism, and large swelling pressures that promote sealing. In order to predict how well the barrier will function over time at repository relevant temperatures, it is important to understand thermal alteration effects on montmorillonite, better known as smectite, a main constituent of bentonite. One type of thermal alteration is the conversion to illite, when exposed to elevated temperatures and a sufficient amount of potassium ions, thereby weakening barrier functions. To facilitate the conversion of smectite to illite and examine the influence of interlayer cations, illitization experiments on cation exchanged smectite were performed within hydrothermal reaction vessels over one week timescales. The <2um fraction of a Na-rich smectite clay was first exchanged with 1M Cs, K, and NH4 salt solutions and further exposed to hydrous pyrolysis using a 1M KCl solution with various solid to liquid ratios at 200°C. Multiple analysis techniques were used to characterize the altered clay and identify extent of conversion, such as XRD, cation exchange capacity, and morphology changes by SEM. The pore-water chemistry was also analyzed by ICP-OES to detect any dissolved products and silica content. Results suggest the conversion rate is relatively fast, occurring within days, and is dependent on not only the amount of K, but also dissolved silica concentration related to total solid in solution. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525. SAND2017-7856A

Linking pore-scale and basin-scale effects on diffusive methane transport in hydrate bearing environments through multi-scale reservoir simulations

NASA Astrophysics Data System (ADS)

Nole, M.; Daigle, H.; Cook, A.; Malinverno, A.; Hillman, J. I. T.

2016-12-01

We explore the gas hydrate-generating capacity of diffusive methane transport induced by solubility gradients due to pore size contrasts in lithologically heterogeneous marine sediments. Through the use of 1D, 2D, and 3D reactive transport simulations, we investigate scale-dependent processes in diffusion-dominated gas hydrate systems. These simulations all track a sand body, or series of sands, surrounded by clays as they are buried through the gas hydrate stability zone. Methane is sourced by microbial methanogenesis in the clays surrounding the sand layers. In 1D, simulations performed in a Lagrangian reference frame demonstrate that gas hydrate in thin sands (3.6 m thick) can occur in high saturations (upward of 70%) at the edges of sand bodies within the upper 400 meters below the seafloor. Diffusion of methane toward the center of the sand layer depends on the concentration gradient within the sand: broader sand pore size distributions with smaller median pore sizes enhance diffusive action toward the sand's center. Incorporating downhole log- and laboratory-derived sand pore size distributions, gas hydrate saturations in the center of the sand can reach 20% of the hydrate saturations at the sand's edges. Furthermore, we show that hydrate-free zones exist immediately above and below the sand and are approximately 5 m thick, depending on the sand-clay solubility contrast. A moving reference frame is also adopted in 2D, and the angle of gravity is rotated relative to the grid system to simulate a dipping sand layer. This is important to minimize diffusive edge effects or numerical diffusion that might be associated with a dipping sand in an Eulerian grid system oriented orthogonal to gravity. Two-dimensional simulations demonstrate the tendency for gas hydrate to accumulate downdip in a sand body because of greater methane transport at depth due to larger sand-clay solubility contrasts. In 3D, basin-scale simulations illuminate how convergent sand layers in a multilayered system can compete for diffusion from clays between them, resulting in relatively low hydrate saturations. All simulations suggest that when hydrate present in clays dissociates with burial, the additional dissolved methane is soaked up by nearby sands preserving high hydrate saturations.

Linking pore-scale and basin-scale effects on diffusive methane transport in hydrate bearing environments through multi-scale reservoir simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nole, Michael; Daigle, Hugh; Cook, Ann

We explore the gas hydrate-generating capacity of diffusive methane transport induced by solubility gradients due to pore size contrasts in lithologically heterogeneous marine sediments. Through the use of 1D, 2D, and 3D reactive transport simulations, we investigate scale-dependent processes in diffusion-dominated gas hydrate systems. These simulations all track a sand body, or series of sands, surrounded by clays as they are buried through the gas hydrate stability zone. Methane is sourced by microbial methanogenesis in the clays surrounding the sand layers. In 1D, simulations performed in a Lagrangian reference frame demonstrate that gas hydrate in thin sands (3.6 m thick)more » can occur in high saturations (upward of 70%) at the edges of sand bodies within the upper 400 meters below the seafloor. Diffusion of methane toward the center of the sand layer depends on the concentration gradient within the sand: broader sand pore size distributions with smaller median pore sizes enhance diffusive action toward the sand’s center. Incorporating downhole log- and laboratory-derived sand pore size distributions, gas hydrate saturations in the center of the sand can reach 20% of the hydrate saturations at the sand’s edges. Furthermore, we show that hydrate-free zones exist immediately above and below the sand and are approximately 5 m thick, depending on the sand-clay solubility contrast. A moving reference frame is also adopted in 2D, and the angle of gravity is rotated relative to the grid system to simulate a dipping sand layer. This is important to minimize diffusive edge effects or numerical diffusion that might be associated with a dipping sand in an Eulerian grid system oriented orthogonal to gravity. Two-dimensional simulations demonstrate the tendency for gas hydrate to accumulate downdip in a sand body because of greater methane transport at depth due to larger sand-clay solubility contrasts. In 3D, basin-scale simulations illuminate how convergent sand layers in a multilayered system can compete for diffusion from clays between them, resulting in relatively low hydrate saturations. All simulations suggest that when hydrate present in clays dissociates with burial, the additional dissolved methane is soaked up by nearby sands preserving high hydrate saturations.« less

A free software for pore-scale modelling: solving Stokes equation for velocity fields and permeability values in 3D pore geometries

NASA Astrophysics Data System (ADS)

Gerke, Kirill; Vasilyev, Roman; Khirevich, Siarhei; Karsanina, Marina; Collins, Daniel; Korost, Dmitry; Mallants, Dirk

2015-04-01

In this contribution we introduce a novel free software which solves the Stokes equation to obtain velocity fields for low Reynolds-number flows within externally generated 3D pore geometries. Provided with velocity fields, one can calculate permeability for known pressure gradient boundary conditions via Darcy's equation. Finite-difference schemes of 2nd and 4th order of accuracy are used together with an artificial compressibility method to iteratively converge to a steady-state solution of Stokes' equation. This numerical approach is much faster and less computationally demanding than the majority of open-source or commercial softwares employing other algorithms (finite elements/volumes, lattice Boltzmann, etc.) The software consists of two parts: 1) a pre and post-processing graphical interface, and 2) a solver. The latter is efficiently parallelized to use any number of available cores (the speedup on 16 threads was up to 10-12 depending on hardware). Due to parallelization and memory optimization our software can be used to obtain solutions for 300x300x300 voxels geometries on modern desktop PCs. The software was successfully verified by testing it against lattice Boltzmann simulations and analytical solutions. To illustrate the software's applicability for numerous problems in Earth Sciences, a number of case studies have been developed: 1) identifying the representative elementary volume for permeability determination within a sandstone sample, 2) derivation of permeability/hydraulic conductivity values for rock and soil samples and comparing those with experimentally obtained values, 3) revealing the influence of the amount of fine-textured material such as clay on filtration properties of sandy soil. This work was partially supported by RSF grant 14-17-00658 (pore-scale modelling) and RFBR grants 13-04-00409-a and 13-05-01176-a.

Direct pore-scale reactive transport modelling of dynamic wettability changes induced by surface complexation

NASA Astrophysics Data System (ADS)

Maes, Julien; Geiger, Sebastian

2018-01-01

Laboratory experiments have shown that oil production from sandstone and carbonate reservoirs by waterflooding could be significantly increased by manipulating the composition of the injected water (e.g. by lowering the ionic strength). Recent studies suggest that a change of wettability induced by a change in surface charge is likely to be one of the driving mechanism of the so-called low-salinity effect. In this case, the potential increase of oil recovery during waterflooding at low ionic strength would be strongly impacted by the inter-relations between flow, transport and chemical reaction at the pore-scale. Hence, a new numerical model that includes two-phase flow, solute reactive transport and wettability alteration is implemented based on the Direct Numerical Simulation of the Navier-Stokes equations and surface complexation modelling. Our model is first used to match experimental results of oil droplet detachment from clay patches. We then study the effect of wettability change on the pore-scale displacement for simple 2D calcite micro-models and evaluate the impact of several parameters such as water composition and injected velocity. Finally, we repeat the simulation experiments on a larger and more complex pore geometry representing a carbonate rock. Our simulations highlight two different effects of low-salinity on oil production from carbonate rocks: a smaller number of oil clusters left in the pores after invasion, and a greater number of pores invaded.

Role of microbial Fe(III) reduction and solution chemistry in aggregation and settling of suspended particles in the Mississippi River Delta plain, Louisiana, USA

USGS Publications Warehouse

Jaisi, Deb P.; Ji, Shanshan; Dong, Hailiang; Blake, Ruth E.; Eberl, Dennis D.; Kim, Jinwook

2008-01-01

River-dominated delta areas are primary sites of active biogeochemical cycling, with productivity enhanced by terrestrial inputs of nutrients. Particle aggregation in these areas primarily controls the deposition of suspended particles, yet factors that control particle aggregation and resulting sedimentation in these environments are poorly understood. This study was designed to investigate the role of microbial Fe(III) reduction and solution chemistry in aggregation of suspended particles in the Mississippi Delta. Three representative sites along the salinity gradient were selected and sediments were collected from the sediment-water interface. Based on quantitative mineralogical analyses 88–89 wt.% of all minerals in the sediments are clays, mainly smectite and illite. Consumption of SO42− and the formation of H2S and pyrite during microbial Fe(III) reduction of the non-sterile sediments by Shewanella putrefaciens CN32 in artificial pore water (APW) media suggest simultaneous sulfate and Fe(III) reduction activity. The pHPZNPC of the sediments was ≤3.5 and their zeta potentials at the sediment-water interface pH (6.9–7.3) varied from −35 to −45 mV, suggesting that both edges and faces of clay particles have negative surface charge. Therefore, high concentrations of cations in pore water are expected to be a predominant factor in particle aggregation consistent with the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Experiments on aggregation of different types of sediments in the same APW composition revealed that the sediment with low zeta potential had a high rate of aggregation. Similarly, addition of external Fe(II) (i.e. not derived from sediments) was normally found to enhance particle aggregation and deposition in all sediments, probably resulting from a decrease in surface potential of particles due to specific Fe(II) sorption. Scanning and transmission electron microscopy (SEM, TEM) images showed predominant face-to-face clay aggregation in native sediments and composite mixtures of biopolymer, bacteria, and clay minerals in the bioreduced sediments. However, a clear need remains for additional information on the conditions, if any, that favor the development of anoxia in deep- and bottom-water bodies supporting Fe(III) reduction and resulting in particle aggregation and sedimentation.

Comparison of Pore Fractal Characteristics Between Marine and Continental Shales

NASA Astrophysics Data System (ADS)

Liu, Jun; Yao, Yanbin; Liu, Dameng; Cai, Yidong; Cai, Jianchao

Fractal characterization offers a quantitative evaluation on the heterogeneity of pore structure which greatly affects gas adsorption and transportation in shales. To compare the fractal characteristics between marine and continental shales, nine samples from the Lower Silurian Longmaxi formation in the Sichuan basin and nine from the Middle Jurassic Dameigou formation in the Qaidam basin were collected. Reservoir properties and fractal dimensions were characterized for all the collected samples. In this study, fractal dimensions were originated from the Frenkel-Halsey-Hill (FHH) model with N2 adsorption data. Compared to continental shale, marine shale has greater values of quartz content, porosity, specific surface area and total pore volume but lower level of clay minerals content, permeability, average pore diameter and methane adsorption capacity. The quartz in marine shale is mostly associated with biogenic origin, while that in continental shale is mainly due to terrigenous debris. The N2 adsorption-desorption isotherms exhibit that marine shale has fewer inkbottle-shaped pores but more plate-like and slit-shaped pores than continental shale. Two fractal dimensions (D1 and D2) were obtained at P/Po of 0-0.5 and 0.5-1. The dimension D2 is commonly greater than D1, suggesting that larger pores (diameter >˜ 4nm) have more complex structures than small pores (diameter <˜ 4nm). The fractal dimensions (both D1 and D2) positively correlate to clay minerals content, specific surface area and methane adsorption capacity, but have negative relationships with porosity, permeability and average pore diameter. The fractal dimensions increase proportionally with the increasing quartz content in marine shale but have no obvious correlation with that in continental shale. The dimension D1 is correlative to the TOC content and permeability of marine shale at a similar degree with dimension D2, while the dimension D1 is more sensitive to those of continental shale than dimension D2. Compared with dimension D2, for two shales, dimension D1 is better associated with the content of clay minerals but has worse correlations with the specific surface area and average pore diameter.

The surface-pore integrated effect of soil organic matter on retention and transport of pharmaceuticals and personal care products in soils.

PubMed

Qin, Qin; Chen, Xijuan; Zhuang, Jie

2017-12-01

This study examines a surface-pore integrated mechanism that allows soil organic matter (SOM) to influence the retention and transport of three representative pharmaceuticals and personal care products (PPCPs)-ibuprofen, carbamazepine, and bisphenol A-in agricultural soil. A series of sorption-desorption batch tests and breakthrough column experiments were conducted using manured and non-manured soils. Results show that SOM could substantially influence the environmental behaviors of PPCPs via two mechanisms: surface-coating and pore-filling. Surface-coating with molecular SOM decreases the sorption of dissociated PPCPs (e.g., ibuprofen) but increases the sorption of non-dissociated PPCPs (e.g., carbamazepine and bisphenol A), while pore-filling with colloidal SOM enhances the retention of all the PPCPs by providing nano-/micro-pores that limit diffusion. The higher retention and lower mobility of PPCPs in soil microaggregates than in bulk soils suggest that SOM content and SOM-altered soil pore structure could exert a coupled effect on PPCP retention. Differences in the elution of PPCPs with low surface tension solution (i.e., 20% ethanol) in the presence and absence of SOM indicate that PPCPs prefer to remain in SOM-filled pores. Overall, ibuprofen has a high environmental risk, whereas carbamazepine and bisphenol A could be readily retarded in agricultural soils (with a loamy clay texture). This study implies that SOM accrual (particularly pore-filling SOM) has a high potential for reducing the off-site risks of PPCPs by increasing soil nano-/micro-porosity. Copyright © 2017 Elsevier B.V. All rights reserved.

Reactive Transport Modeling and Changes in Porosity at Reactive Interfaces in a HLW repository in Clay

NASA Astrophysics Data System (ADS)

Samper, J.; Mon, A.; Montenegro, L.; Naves, A.; Fernández, J.

2016-12-01

High-level radioactive waste disposal in a deep geological repository is based on a multibarrier concept which combines natural barriers such as the geological formation and artificial barriers such as metallic containers, bentonite and concrete buffers and sealing materials. The stability and performance of the bentonite barrier could be affected by the corrosion products at the canister-bentonite interface and the hyperalkaline conditions caused by the degradation of concrete at the bentonite-concrete interface. Additionally, the host clay formation could also be affected by the hyperalkaline plume at the concrete-clay interface. Here we present a nonisothermal reactive transport model of the long-term interactions of the compacted bentonite with the corrosion products of a carbon-steel canister and the concrete liner of the engineered barrier of a high-level radioactive waste repository in clay. This problem involves large pH changes with a hyperalkaline high-pH plume, complex mineral dissolution/precipitation patterns, cation exchange reactions and proton surface complexation. These reactions lead to large changes in porosity which can even lead to pore clogging. Model results show that magnetite, the main corrosion product, precipitates and reduces significantly the porosity of the bentonite near the canister. The degradation of the concrete liner leads to the precipitation of secondary minerals and the reduction of the porosity of the bentonite and the clay formation at their interfaces with the concrete liner. The zones affected by pore clogging at the canister-bentonite, bentonite-concrete and concrete-clay interfaces at 1 Ma are equal to 10, 25 and 25 mm thick, respectively. The results of our simulations share many of the features of the models reported by others for engineered barrier systems at similar chemical conditions, including: 1) Narrow alteration zones; and 2) Pore clogging at the canister-bentonite, bentonite-concrete and concrete-clay interfaces.

Laboratory Study of Quaternary Sediment Resistivity Related to Groundwater Contamination at Mae-Hia Landfill, Mueang District, Chiang Mai Province

NASA Astrophysics Data System (ADS)

Sichan, N.

2007-12-01

This study was aimed to understand the nature of the resistivity value of the sediment when it is contaminated, in order to use the information solving the obscure interpretation in the field. The pilot laboratory experiments were designed to simulate various degree of contamination and degree of saturation then observe the resulting changes in resistivity. The study was expected to get a better understanding of how various physical parameters effect the resistivity values in term of mathematic function. And also expected to apply those obtained function to a practical quantitatively interpretation. The sediment underlying the Mae-Hia Landfill consists of clay-rich material, with interfingerings of colluvium and sandy alluvium. A systematic study identified four kinds of sediment, sand, clayey sand, sandy clay, and clay. Representative sediment and leachate samples were taken from the field and returned to the laboratory. Both the physical and chemical properties of the sediments and leachate were analyzed to delineate the necessary parameters that could be used in Archie's equation. Sediment samples were mixed with various concentration of leachate solutions. Then the resistivity values were measured at various controlled steps in the saturation degree in a well- calibrated six-electrode model resistivity box. The measured resistivity values for sand, clayey sand, sandy clay when fully and partly saturated were collected, then plotted and fitted to Archie's equation, to obtain a mathematical relationship between bulk resistivity, porosity, saturation degree and resistivity of pore fluid. The results fit well to Archie's equation, and it was possible to determine all the unknown parameters representative of the sediment samples. For sand, clayey sand, sandy clay, and clay, the formation resistivity factors (F) are 2.90, 5.77, 7.85, and 7.85 with the products of cementation factor (m) and the pore geometry factors (a) (in term of -am) are 1.49, -1.63, -1.92, -2.24 and the saturation exponents (n) are 2.06, 2.58, 3.52, and 2.46, respectively. These results were used to reinterpret the existing resistivity data of this area. The result of this reinterpretation is a map showing the quantitative distribution of the contaminant plume in the vicinity of the Mae-Hia Landfill.

Implications of contact metamorphism of Mancos Shale for critical zone processes

NASA Astrophysics Data System (ADS)

Navarre-Sitchler, A.

2016-12-01

Bedrock lithology imparts control on some critical zone processes, for example rates and extent of chemical weathering, solute release though mineral dissolution, and water flow. Bedrock can be very heterogeneous resulting in spatial variability of these processes throughout a catchment. In the East River watershed outside of Crested Butte, Colorado, bedrock is dominantly comprised of the Mancos Shale; a Cretaceous aged, organic carbon rich marine shale. However, in some areas the Mancos Shale appears contact metamorphosed by nearby igneous intrusions resulting in a potential gradient in lithologic change in part of the watershed where impacts of lithology on critical zone processes can be evaluated. Samples were collected in the East River valley along a transect from the contact between the Tertiary Gothic Mountain laccolith of the Mount Carbon igneous system and the underlying Manocs shale. Porosity of these samples was analyzed by small-angle and ultra small-angle neutron scattering. Results indicate contact metamorphism decreases porosity of the shale and changes the pore shape from slightly anisotropic pores aligned with bedding in the unmetamorphosed shale to isotropic pores with no bedding alignment in the metamorphosed shales. The porosity analysis combined with clay mineralogy, surface area, carbon content and oxidation state, and solute release rates determined from column experiments will be used to develop a full understanding of the impact of contact metamorphism on critical zone processes in the East River.

Investigating the Thermal Limit of Clay Minerals for Applications in Nuclear Waste Repository Design

NASA Astrophysics Data System (ADS)

Matteo, E. N.; Miller, A. W.; Kruichak, J.; Mills, M.; Tellez, H.; Wang, Y.

2013-12-01

Clay minerals are likely candidates to aid in nuclear waste isolation due to their low permeability, favorable swelling properties, and high cation sorption capacities. Establishing the thermal limit for clay minerals in a nuclear waste repository is a potentially important component of repository design, as flexibility of the heat load within the repository can have a major impact on the selection of repository design. For example, the thermal limit plays a critical role in the time that waste packages would need to cool before being transferred to the repository. Understanding the chemical and physical changes that occur in clay minerals at various temperatures above the current thermal limit (of 100 °C) can enable decision-makers with information critical to evaluating the potential trade-offs of increasing the thermal limit within the repository. Most critical is gaining understanding of how varying thermal conditions in the repository will impact radionuclide sorption and transport in clay materials either as engineered barriers or as disposal media. A variety of clays (illite, mixed layer illite/smectite, montmorillonite, and palygorskite) were heated for a range of temperatures between 100-500 °C. These samples were characterized by a variety of methods, including nitrogen adsorption, x-ray diffraction, thermogravimetric analysis, barium chloride exchange for cation exchange capacity (CEC), and iodide sorption. The nitrogen porosimetry shows that for all the clays, thermally-induced changes in BET surface area are dominated by collapse/creation of the microporosity, i.e. pore diameters < 17 angstroms. Changes in micro porosity (relative to no heat treatment) are most significant for heat treatments 300 °C and above. Alterations are also seen in the chemical properties (CEC, XRD, iodide sorption) of clays, and like pore size distribution changes, are most significant above 300 °C. Overall, the results imply that changes seen in pores size distribution correlate with cation exchange capacity and cation exchange processes. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's Nation Nuclear Security Administration under contract DE-AC04-94AL85000. SAND Number: 2013-6352A.

Understanding Potassium Isotope Fractionation During Authigenic Clay Formation in Pore-fluid Systems: Implications for the δ41K of Seawater

NASA Astrophysics Data System (ADS)

Santiago Ramos, D. P.; Higgins, J. A.

2015-12-01

Improvements in analytical precision on the latest generation multi-collector inductively coupled plasma mass spectrometers (MC-ICP-MS) have revealed a ~2‰ range in the ratios of stable potassium isotopes (41K/39K) in terrestrial materials (Morgan et al., in prep). Preliminary measurements of δ41K values indicate that seawater and silicate rocks are isotopically distinct reservoirs, with seawater having a δ41K value that is ~0.5‰ heavier than the silicate average (-0.5‰; Morgan et al., in prep). The heavy δ41K character of seawater might be related to 1) an isotopically enriched input flux (rivers and high-temperature hydrothermal reactions); or 2) a 41K-depleted sink associated with authigenic clay formation during low-temperature alteration of volcanic rocks. Here we present measurements of the δ41K values of pore-fluids from ODP site 1052 in order to constrain potassium isotope fractionation during secondary clay formation. We find that δ41K values and K concentrations both decline systematically with depth. Results from 1-D diffusion-advection-reaction modeling of potassium concentrations and isotopic compositions indicate that fractionation of K isotopes during diffusion (Bourg et al., 2010) can explain all of the change in δ41K values of the pore-fluid with depth. Although the size of the K sink at site 1052 is a trivial fraction of the global K sink in clay minerals, our results suggest that diffusive fractionation of K isotopes in shallow pore-fluids may be, in part, responsible for the elevated δ41K value of seawater.

Calcium isotope evidence for suppression of carbonate dissolution in carbonate-bearing organic-rich sediments

NASA Astrophysics Data System (ADS)

Turchyn, Alexandra V.; DePaolo, Donald J.

2011-11-01

Pore fluid calcium isotope, calcium concentration and strontium concentration data are used to measure the rates of diagenetic dissolution and precipitation of calcite in deep-sea sediments containing abundant clay and organic material. This type of study of deep-sea sediment diagenesis provides unique information about the ultra-slow chemical reactions that occur in natural marine sediments that affect global geochemical cycles and the preservation of paleo-environmental information in carbonate fossils. For this study, calcium isotope ratios (δ 44/40Ca) of pore fluid calcium from Ocean Drilling Program (ODP) Sites 984 (North Atlantic) and 1082 (off the coast of West Africa) were measured to augment available pore fluid measurements of calcium and strontium concentration. Both study sites have high sedimentation rates and support quantitative sulfate reduction, methanogenesis and anaerobic methane oxidation. The pattern of change of δ 44/40Ca of pore fluid calcium versus depth at Sites 984 and 1082 differs markedly from that of previously studied deep-sea Sites like 590B and 807, which are composed of nearly pure carbonate sediment. In the 984 and 1082 pore fluids, δ 44/40Ca remains elevated near seawater values deep in the sediments, rather than shifting rapidly toward the δ 44/40Ca of carbonate solids. This observation indicates that the rate of calcite dissolution is far lower than at previously studied carbonate-rich sites. The data are fit using a numerical model, as well as more approximate analytical models, to estimate the rates of carbonate dissolution and precipitation and the relationship of these rates to the abundance of clay and organic material. Our models give mutually consistent results and indicate that calcite dissolution rates at Sites 984 and 1082 are roughly two orders of magnitude lower than at previously studied carbonate-rich sites, and the rate correlates with the abundance of clay. Our calculated rates are conservative for these sites (the actual rates could be significantly slower) because other processes that impact the calcium isotope composition of sedimentary pore fluid have not been included. The results provide direct geochemical evidence for the anecdotal observation that the best-preserved carbonate fossils are often found in clay or organic-rich sedimentary horizons. The results also suggest that the presence of clay minerals has a strong passivating effect on the surfaces of biogenic carbonate minerals, slowing dissolution dramatically even in relation to the already-slow rates typical of carbonate-rich sediments.

Understanding fluid transport through the multiscale pore network of a natural shale

NASA Astrophysics Data System (ADS)

Davy, Catherine; Adler, Pierre; Song, Yang; Nguyen, Thang Kim; Troadec, David; Dhénin, Jean-Francois

2017-04-01

Natural shales have a complex pore structure, which is only partly understood today. In the present contribution, a combination of different techniques is used to get information on three different scales. On each scale, the relevant flow equation is solved and provides input for the flow equation of the next higher scale. More precisely, micro-CT, FIB/SEM (Focused Ion Beam/Scanning Electron Microscopy) and TEM (Transmission Electron Microscopy) provide a full representative 3D pore space on the macroscopic scale, the mesoscale and the nanoscale. The corresponding typical voxel sizes are 0.7 μm, 10 nm and 1 nm, respectively. The porosity on the micro-CT images is 0.5 %, and it is not connected. One can distinguish between the pores, the porous clay matrix and non porous minerals; the volume percentages of these last two phases are 0.6 and 0.395, respectively. Samples of the porous clay matrix were analyzed by FIB/SEM which yields 3D information. They have a porosity ranging from 2 to 6 %. In some of them, the pore space is connected. Finally, TEM provides 2D images with a porosity of about 10 to 25 %. These information were used in the following way to estimate the macroscopic permeability which has been measured independently and found equal to 6 x10-20 m2. At the nanoscopic scale analyzed by 2D TEM, in the absence of 3D images, the pore structure is reconstructed by using a technique based on truncated Gaussian fields. Then, the Stokes equations are solved by using a 3D Lattice Boltzmann method. The resulting velocity field is averaged and this provides the permeability K_n. The permeability of the nanoscale structure varies between 0.7x 10-20 and 1.8x10-19 m2. As expected, the material is anisotropic. At the mesoscale, percolation of the FIB/SEM pore volume occurs only along a single direction. The Stokes equations are again solved by the same method and the mesoscopic permeability Km varies between 3.3 10-20 and 1.20 10-18 m2, depending on the nature of the percolating volume. The influence of the nanoscale porosity on the mesoscopic permeability is also studied. Two examples show that despite the scale ratio between the mesoscopic and nanoscopic pores, the nanoscopic pore structure cannot be neglected to estimate the permeability of the pore clay matrix. Finally, the sample provided by micro-CT is considered as a porous medium composed of three phases with permeabilities 0 (for the non porous minerals), 1 (for the porous clay matrix) and infinity (for the macroscopic pores). The overall permeability Kmacro is obtained by solving the Darcy's equation with a variable local permeability with spatially periodic boundary conditions. Kmacro is found of the order of 0.4 and the medium is relatively isotropic on this scale. This estimation of Kmacro is in agreement with the measured value.

An analytical solution for two-dimensional vacuum preloading combined with electro-osmosis consolidation using EKG electrodes

PubMed Central

Qiu, Chenchen; Li, Yande

2017-01-01

China is a country with vast territory, but economic development and population growth have reduced the usable land resources in recent years. Therefore, reclamation by pumping and filling is carried out in eastern coastal regions of China in order to meet the needs of urbanization. However, large areas of reclaimed land need rapid drainage consolidation treatment. Based on past researches on how to improve the treatment efficiency of soft clay using vacuum preloading combined with electro-osmosis, a two-dimensional drainage plane model was proposed according to the Terzaghi and Esrig consolidation theory. However, the analytical solution using two-dimensional plane model was never involved. Current analytical solutions can’t have a thorough theoretical analysis of practical engineering and give relevant guidance. Considering the smearing effect and the rectangle arrangement pattern, an analytical solution is derived to describe the behavior of pore-water and the consolidation process by using EKG (electro-kinetic geo synthetics) materials. The functions of EKG materials include drainage, electric conduction and corrosion resistance. Comparison with test results is carried out to verify the analytical solution. It is found that the measured value is larger than the applied vacuum degree because of the stacking effect of the vacuum preloading and electro-osmosis. The trends of the mean measured value and the mean analytical value processes are comparable. Therefore, the consolidation model can accurately assess the change in pore-water pressure and the consolidation process during vacuum preloading combined with electro-osmosis. PMID:28771496

Effects of exchanged cation and layer charge on the sorption of water and EGME vapors on montmorillonite clays

USGS Publications Warehouse

Chiou, Cary T.; Rutherford, David W.

1997-01-01

The effects of exchanged cation and layer charge on the sorption of water and ethylene glycol monoethyl ether (EGME) vapors on montmorillonite have been studied on SAz-1 and SWy-1 source clays, each exchanged respectively with Ca, Na, K, Cs and tetramethylammonium (TMA) cations. The corresponding lattice expansions were also determined, and the corresponding N2 adsorption data were provided for comparison. For clays exchanged with cations of low hydrating powers (such as K, Cs and TMA), water shows a notably lower uptake than does N2 at low relative pressures (P/P0). By contrast, EGME shows higher uptakes than N2 on all exchanged clays at all P/P0. The anomaly for water is attributed to its relatively low attraction for siloxane surfaces of montmorillonite because of its high cohesive energy density. In addition to solvating cations and expanding interlayers, water and EGME vapors condense into small clay pores and interlayer voids created by interlayer expansion. The initial (dry) interlayer separation varies more significantly with cation type than with layer charge; the water-saturated interlayer separation varies more with cation type than the EGME-saturated interlayer separation. Because of the differences in surface adsorption and interlayer expansion for water and EGME, no general correspondence is found between the isotherms of water and EGME on exchanged clays, nor is a simple relation observed between the overall uptake of either vapor and the cation solvating power. The excess interlayer capacities of water and of EGME that result from lattice expansion of the exchanged clays are estimated by correcting for amounts of vapor adsorption on planar clay surfaces and of vapor condensation into intrinsic clay pores. The resulting data follow more closely the relative solvating powers of the exchanged cations.

Effect of excess pore pressure on the long runout of debris flows over low gradient channels: A case study of the Dongyuege debris flow in Nu River, China

NASA Astrophysics Data System (ADS)

Zhou, Zhen-Hua; Ren, Zhe; Wang, Kun; Yang, Kui; Tang, Yong-Jun; Tian, Lin; Xu, Ze-Min

2018-05-01

Debris flows with long reaches are one of the major natural hazards to human life and property on alluvial fans, as shown by the debris flow that occurred in the Dongyuege (DYG) Gully in August 18, 2010, and caused 96 deaths. The travel distance and the runout distance of the DYG large-scale tragic debris flow were 11 km and 9 km, respectively. In particular, the runout distance over the low gradient channel (channel slope < 5°) upstream of the depositional fan apex reached up to 3.3 km. The build-up and maintenance of excess pore pressure in the debris-flow mass might have played a crucial role in the persistence and long runout of the bouldery viscous debris flow. Experiments to measure pore pressure and pore water escape have been carried out by reconstituting the debris flow bodies with the DYG debris flow deposit. The slurrying of the debris is governed by solid volumetric concentration (SVC), and the difference between the lower SVC limit and the upper SVC limit can be defined as debris flow index (Id). Peak value (Kp) and rate of dissipation (R) of relative excess pore pressure are dependent on SVC. Further, the SVC that gives the lowest rate of dissipation is regarded as the optimum SVC (Cvo). The dissipation response of excess pore pressure can be characterized by the R value under Cvo at a given moment (i.e., 0.5 h, 1 h or 2 h later after peak time). The results reveal that a relatively high level of excess pore pressure developed within the DYG debris-flow mass and had a strong persistence capability. Further research shows that the development, peak value and dissipation of excess pore pressure in a mixture of sediment and water are related to the maximum grain size (MGS), gradation and mineralogy of clay-size particles of the sediment. The layer-lattice silicates in clay particles can be the typical clay minerals, including kaolinite, montmorillonite and illite, and also the unrepresentative clay minerals such as muscovite and chlorite. Moreover, small woody debris can also contribute to the slurrying of sediments and maintenance of debris flows in well vegetated mountainous areas and the boulders suspended in debris flows can elevate excess pore pressure and extend debris-flow mobility. The parameters, including Id, Kp, R and etc., are affected by the intrinsic properties of debris. They, therefore, can reflect the slurrying susceptibility of sediments, and can also be applied to the research on the occurrence mechanisms and risk assessment of other debris flows.

Fractal Characteristics of Pores in Taiyuan Formation Shale from Hedong Coal Field, China

NASA Astrophysics Data System (ADS)

Li, Kunjie; Zeng, Fangui; Cai, Jianchao; Sheng, Guanglong; Xia, Peng; Zhang, Kun

For the purpose of investigating the fractal characteristics of pores in Taiyuan formation shale, a series of qualitative and quantitative experiments were conducted on 17 shale samples from well HD-1 in Hedong coal field of North China. The results of geochemical experiments show that Total organic carbon (TOC) varies from 0.67% to 5.32% and the organic matters are in the high mature or over mature stage. The shale samples consist mainly of clay minerals and quartz with minor pyrite and carbonates. The FE-SEM images indicate that three types of pores, organic-related pores, inorganic-related pores and micro-fractures related pores, are developed well, and a certain number of intragranular pores are found inside quartz and carbonates formed by acid liquid corrosion. The pore size distributions (PSDs) broadly range from several to hundreds nanometers, but most pores are smaller than 10nm. As the result of different adsorption features at relative pressure (0-0.5) and (0.5-1) on the N2 adsorption isotherm, two fractal dimensions D1 and D2 were obtained with the Frenkel-Halsey-Hill (FHH) model. D1 and D2 vary from 2.4227 to 2.6219 and from 2.6049 to 2.7877, respectively. Both TOC and brittle minerals have positive effect on D1 and D2, whereas clay minerals, have a negative influence on them. The fractal dimensions are also influenced by the pore structure parameters, such as the specific surface area, BJH pore volume, etc. Shale samples with higher D1 could provide more adsorption sites leading to a greater methane adsorption capacity, whereas shale samples with higher D2 have little influence on methane adsorption capacity.

Enhancement of the bentonite sorption properties.

PubMed

Mockovciaková, Annamária; Orolínová, Zuzana; Skvarla, Jirí

2010-08-15

The almost monomineral fraction of bentonite rock-montmorillonite was modified by magnetic particles to enhance its sorption properties. The method of clay modification consists in the precipitation of magnetic nanoparticles, often used in preparing of ferrofluids, on the surface of clay. The influence of the synthesis temperature (20 and 85 degrees C) and the weight ratio of bentonite/iron oxides (1:1 and 5:1) on the composite materials properties were investigated. The obtained materials were characterized by the X-ray diffraction method and Mössbauer spectroscopy. Changes in the surface and pore properties of the magnetic composites were studied by the low nitrogen adsorption method and the electrokinetic measurements. The natural bentonite and magnetic composites were used in sorption experiments. The sorption of toxic metals (zinc, cadmium and nickel) from the model solutions was well described by the linearized Langmuir and Freundlich sorption model. The results show that the magnetic bentonite is better sorbent than the unmodified bentonite if the initial concentration of studied metals is very low. Copyright 2010 Elsevier B.V. All rights reserved.

Organic Control of Dioctahedral and Trioctahedral Clay Formation in an Alkaline Soil System in the Pantanal Wetland of Nhecolândia, Brazil.

PubMed

Barbiero, Laurent; Berger, Gilles; Rezende Filho, Ary T; Meunier, Jean-François; Martins-Silva, Elisângela R; Furian, Sonia

2016-01-01

Recent studies have focused on the formation of authigenic clays in an alkaline soil system surrounding lakes of the Nhecolândia region, Pantanal wetland. The presence of trioctahedral Mg-smectites (stevensite and saponite types), which requires low Al and Fe contents in the soil solution for its formation, contrasts with the neoformation of dioctahedral Fe-mica (glauconite, and Fe-illite), which instead requires solutions relatively enriched in Al and Fe. This study aims to understand the conditions of co-existence of both, Mg-smectite and Fe-mica a common clay association in former or modern alkaline soil systems and sediments. The study was carried out along an alkaline soil catena representative of the region. The soil organization revealed that Mg-smectite occur in top soil close to the lake, whereas Fe-mica dominate in the clay fraction of deeper greenish horizons a few meters apart. We propose here that this spatial distribution is controlled by the lateral transfer of Fe and Al with organic ligands. Alkaline organic rich solutions (DOC up to 738 mg L-1) collected in the watertable were centrifuged and filtered through membranes of decreasing pore size (0.45 μm, 0.2 μm, 30 KDa, 10 KDa, 3 KDa) to separate colloidal and dissolved fractions. Fe, Al, Si, Mg and K were analysed for each fraction. Although the filtration had no influence on Si and K contents, almost 90% of Fe (up to 2.3 mg L-1) and Al (up to 7 mg L-1) are retained at the first cutoff threshold of 0.45μm. The treatment of the same solutions by oxygen peroxide before filtration shows that a large proportion of Fe and Al were bonded to organic colloids in alkaline soil solution at the immediate lake border, allowing Mg-smectite precipitation. The fast mineralization of the organic matter a few meters apart from the lake favors the release of Fe and Al necessary for Fe-mica neoformation. In comparison with chemical and mineralogical characteristics of alkaline environments described in the literature, the study suggests that the co-existence of trioctahedral Mg-smectite and dioctahedral Fe-mica should be regarded as a standard occurrence in alkaline soil systems with organic rich waters.

Organic Control of Dioctahedral and Trioctahedral Clay Formation in an Alkaline Soil System in the Pantanal Wetland of Nhecolândia, Brazil

PubMed Central

Meunier, Jean-François; Martins-Silva, Elisângela R.; Furian, Sonia

2016-01-01

Recent studies have focused on the formation of authigenic clays in an alkaline soil system surrounding lakes of the Nhecolândia region, Pantanal wetland. The presence of trioctahedral Mg-smectites (stevensite and saponite types), which requires low Al and Fe contents in the soil solution for its formation, contrasts with the neoformation of dioctahedral Fe-mica (glauconite, and Fe-illite), which instead requires solutions relatively enriched in Al and Fe. This study aims to understand the conditions of co-existence of both, Mg-smectite and Fe-mica a common clay association in former or modern alkaline soil systems and sediments. The study was carried out along an alkaline soil catena representative of the region. The soil organization revealed that Mg-smectite occur in top soil close to the lake, whereas Fe-mica dominate in the clay fraction of deeper greenish horizons a few meters apart. We propose here that this spatial distribution is controlled by the lateral transfer of Fe and Al with organic ligands. Alkaline organic rich solutions (DOC up to 738 mg L-1) collected in the watertable were centrifuged and filtered through membranes of decreasing pore size (0.45 μm, 0.2 μm, 30 KDa, 10 KDa, 3 KDa) to separate colloidal and dissolved fractions. Fe, Al, Si, Mg and K were analysed for each fraction. Although the filtration had no influence on Si and K contents, almost 90% of Fe (up to 2.3 mg L-1) and Al (up to 7 mg L-1) are retained at the first cutoff threshold of 0.45μm. The treatment of the same solutions by oxygen peroxide before filtration shows that a large proportion of Fe and Al were bonded to organic colloids in alkaline soil solution at the immediate lake border, allowing Mg-smectite precipitation. The fast mineralization of the organic matter a few meters apart from the lake favors the release of Fe and Al necessary for Fe-mica neoformation. In comparison with chemical and mineralogical characteristics of alkaline environments described in the literature, the study suggests that the co-existence of trioctahedral Mg-smectite and dioctahedral Fe-mica should be regarded as a standard occurrence in alkaline soil systems with organic rich waters. PMID:27463379

Clay, Water, and Salt: Controls on the Permeability of Fine-Grained Sedimentary Rocks.

PubMed

Bourg, Ian C; Ajo-Franklin, Jonathan B

2017-09-19

The ability to predict the permeability of fine-grained soils, sediments, and sedimentary rocks is a fundamental challenge in the geosciences with potentially transformative implications in subsurface hydrology. In particular, fine-grained sedimentary rocks (shale, mudstone) constitute about two-thirds of the sedimentary rock mass and play important roles in three energy technologies: petroleum geology, geologic carbon sequestration, and radioactive waste management. The problem is a challenging one that requires understanding the properties of complex natural porous media on several length scales. One inherent length scale, referred to hereafter as the mesoscale, is associated with the assemblages of large grains of quartz, feldspar, and carbonates over distances of tens of micrometers. Its importance is highlighted by the existence of a threshold in the core scale mechanical properties and regional scale energy uses of shale formations at a clay content X clay ≈ 1/3, as predicted by an ideal packing model where a fine-grained clay matrix fills the gaps between the larger grains. A second important length scale, referred to hereafter as the nanoscale, is associated with the aggregation and swelling of clay particles (in particular, smectite clay minerals) over distances of tens of nanometers. Mesoscale phenomena that influence permeability are primarily mechanical and include, for example, the ability of contacts between large grains to prevent the compaction of the clay matrix. Nanoscale phenomena that influence permeability tend to be chemomechanical in nature, because they involve strong impacts of aqueous chemistry on clay swelling. The second length scale remains much less well characterized than the first, because of the inherent challenges associated with the study of strongly coupled nanoscale phenomena. Advanced models of the nanoscale properties of fine-grained media rely predominantly on the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, a mean field theory of colloidal interactions that accurately predicts clay swelling in a narrow range of conditions (low salinity, low compaction, Na + counterion). An important feature of clay swelling that is not predicted by these models is the coexistence, in most conditions of aqueous chemistry and dry bulk density, of two types of pores between parallel smectite particles: mesopores with a pore width of >3 nm that are controlled by long-range interactions (the osmotic swelling regime) and nanopores with a pore width <1 nm that are controlled by short-range interactions (the crystalline swelling regime). Nanogeochemical characterization and simulation techniques, including coarse-grained and all-atom molecular dynamics simulations, hold significant promise for the development of advanced constitutive relations that predict this coexistence and its dependence on aqueous chemistry.

Changes in the composition and properties of Ashalchinskoye bitumen-saturated sandstones when exposed to water vapor

NASA Astrophysics Data System (ADS)

Korolev, E.; Eskin, A.; Kolchugin, A.; Morozov, V.; Khramchenkov, M.; Gabdelvalieva, R.

2018-05-01

Ashalchinskoye bitumen deposit is an experimental platform for testing technology of high-viscosity oil extraction from reservoir rocks. Last time for enhanced of oil recovery in reservoir used pressurization a water vapor with a temperature of ∼ 180 ° C (SAGD technology). However, what happens in sandstone reservoir is little known. We did a study of the effects of water vapor on the structural components of bitumen saturated sandstone. In paper were studied the rock samples at base condition and after one week exposure by water vapour. The thermal analysis showed that steaming helps to removes light and middle oil fractions with a boiling point up to 360 ° C from oil saturated sandstones. Content of heavy oil fractions virtually unchanged. Studying the composition of water extractions of samples showed that the process of aquathermolysis of oil is accompanied by a lowering of the pH of the pore solution from 7.4 to 6.5 and rise content in several times of mobile cations Ca2+, Mg2+ and HCO3 -, SO4 2- anions. Follows from this that the thermal steam effect by bitumen saturated sandstones leads to partial oxidation of hydrocarbons with to form a carbon dioxide. The source of sulfate ions were oxidized pyrite aggregates. Due to the increasing acidity of condensed water, which fills the pore space of samples, pore fluid becomes aggressive to calcite and dolomite cement of bitumen saturated sandstones. As a result of the dissolution of carbonate cement the pore fluid enriched by calcium and magnesium cations. Clearly, that the process is accompanied by reduction of contact strength between fragments of minerals and rocks. Resulting part of compounds is separated from the outer side of samples and falls to bottom of water vapor container. Decreasing the amount of calcite and dolomite anions in samples in a steam-treated influence is confirmed by X-Ray analysis. X-Ray analysis data of study adscititious component of rocks showed that when influenced of water vapor to bitumen saturated sandstones there are the processes of transformation of clay minerals. Mixed-illite-montmorillonite phase is primarily exposed to changes. In this case we fix initial stage of the destruction of polycrystalline particles mixed-mineral. Reducing the size of clay minerals particles along the normal to the layers (L001) is the result from lower energy costs of delamination and disintegration the crystallites along this direction, in comparison with others. Thus, using of SAGD technology at exploitation of Ashalchinskoye bitumen saturated reservoir will be followed by acidification of the pore fluid, activation processes of dissolution calcite cement and transformation of mixed-layers clays minerals.

Spatial Persistence of Macropores and Authigenic Clays in a Reservoir Sandstone: Implications for Enhanced Oil Recovery and CO2 Storage

NASA Astrophysics Data System (ADS)

Dewers, T. A.

2015-12-01

Multiphase flow in clay-rich sandstone reservoirs is important to enhanced oil recovery (EOR) and the geologic storage of CO2. Understanding geologic controls on pore structure allows for better identification of lithofacies that can contain, storage, and/or transmit hydrocarbons and CO2, and may result in better designs for EOR-CO2 storage. We examine three-dimensional pore structure and connectivity of sandstone samples from the Farnsworth Unit, Texas, the site of a combined EOR-CO2 storage project by the Southwest Regional Partnership on Carbon Sequestration (SWP). We employ a unique set of methods, including: robotic serial polishing and reflected-light imaging for digital pore-structure reconstruction; electron microscopy; laser scanning confocal microscopy; mercury intrusion-extrusion porosimetry; and relative permeability and capillary pressure measurements using CO2 and synthetic formation fluid. Our results link pore size distributions, topology of porosity and clay-rich phases, and spatial persistence of connected flow paths to multiphase flow behavior. The authors gratefully acknowledge the U.S. Department of Energy's National Energy Technology Laboratory for sponsoring this project through the SWP under Award No. DE-FC26-05NT42591. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Stochastic modeling of filtrate alkalinity in water filtration devices: Transport through micro/nano porous clay based ceramic materials

USDA-ARS?s Scientific Manuscript database

Clay and plant materials such as wood are the raw materials used in manufacture of ceramic water filtration devices around the world. A step by step manufacturing procedure which includes initial mixing, molding and sintering is used. The manufactured ceramic filters have numerous pores which help i...

Long-term non-isothermal reactive transport model of compacted bentonite, concrete and corrosion products in a HLW repository in clay

NASA Astrophysics Data System (ADS)

Mon, Alba; Samper, Javier; Montenegro, Luis; Naves, Acacia; Fernández, Jesús

2017-02-01

Radioactive waste disposal in deep geological repositories envisages engineered barriers such as carbon-steel canisters, compacted bentonite and concrete liners. The stability and performance of the bentonite barrier could be affected by the corrosion products at the canister-bentonite interface and the hyper-alkaline conditions caused by the degradation of concrete at the bentonite-concrete interface. Additionally, the host clay formation could also be affected by the hyper-alkaline plume at the concrete-clay interface. Here we present a non-isothermal multicomponent reactive transport model of the long-term (1 Ma) interactions of the compacted bentonite with the corrosion products of a carbon-steel canister and the concrete liner of the engineered barrier of a high-level radioactive waste repository in clay. Model results show that magnetite is the main corrosion product. Its precipitation reduces significantly the porosity of the bentonite near the canister. The degradation of the concrete liner leads to the precipitation of secondary minerals and the reduction of the porosity of the bentonite and the clay formation at their interfaces with the concrete liner. The reduction of the porosity becomes especially relevant at t = 104 years. The zones affected by pore clogging at the canister-bentonite and concrete-clay interfaces at 1 Ma are approximately equal to 1 and 3.3 cm thick, respectively. The hyper-alkaline front (pH > 8.5) spreads 2.5 cm into the clay formation after 1 Ma. Our simulation results share the key features of the models reported by others for engineered barrier systems at similar chemical conditions, including: 1) Pore clogging at the canister-bentonite and concrete-clay interfaces; 2) Narrow alteration zones; and 3) Limited smectite dissolution after 1 Ma.

Long-term non-isothermal reactive transport model of compacted bentonite, concrete and corrosion products in a HLW repository in clay.

PubMed

Mon, Alba; Samper, Javier; Montenegro, Luis; Naves, Acacia; Fernández, Jesús

2017-02-01

Radioactive waste disposal in deep geological repositories envisages engineered barriers such as carbon-steel canisters, compacted bentonite and concrete liners. The stability and performance of the bentonite barrier could be affected by the corrosion products at the canister-bentonite interface and the hyper-alkaline conditions caused by the degradation of concrete at the bentonite-concrete interface. Additionally, the host clay formation could also be affected by the hyper-alkaline plume at the concrete-clay interface. Here we present a non-isothermal multicomponent reactive transport model of the long-term (1Ma) interactions of the compacted bentonite with the corrosion products of a carbon-steel canister and the concrete liner of the engineered barrier of a high-level radioactive waste repository in clay. Model results show that magnetite is the main corrosion product. Its precipitation reduces significantly the porosity of the bentonite near the canister. The degradation of the concrete liner leads to the precipitation of secondary minerals and the reduction of the porosity of the bentonite and the clay formation at their interfaces with the concrete liner. The reduction of the porosity becomes especially relevant at t=10 4 years. The zones affected by pore clogging at the canister-bentonite and concrete-clay interfaces at 1Ma are approximately equal to 1 and 3.3cm thick, respectively. The hyper-alkaline front (pH>8.5) spreads 2.5cm into the clay formation after 1Ma. Our simulation results share the key features of the models reported by others for engineered barrier systems at similar chemical conditions, including: 1) Pore clogging at the canister-bentonite and concrete-clay interfaces; 2) Narrow alteration zones; and 3) Limited smectite dissolution after 1Ma. Copyright © 2016 Elsevier B.V. All rights reserved.

Clay with Desiccation Cracks is an Advection Dominated Environment

NASA Astrophysics Data System (ADS)

Baram, S.; Kurtzman, D.; Sher, Y.; Ronen, Z.; Dahan, O.

2012-04-01

Heavy clay sediments are regarded "safe" from the hydrological point of view due to their low hydraulic conductivities. However, the formation of desiccation cracks in dispersive clays may dramatically change their bulk hydraulic properties. The impact of desiccation cracks on water percolation, dissolved salts and contaminants transport and redox related reactions (microbial ammonium oxidation and denitrification) were investigated in 6 -12 m clay layer near a diary farm waste lagoon. The study implemented unique vadose-zone monitoring systems that enable in-situ measurements of the temporal variation of the sediment's water content along with frequent sampling of the sediment's pore water along the entire vadose zone (> 30 m). Results from four years of continuous measurements showed quick rises in sediment water content following rain events and temporal wastewater overflows. The percolation pattern indicated dominance of preferential flow through a desiccation-cracks network crossing the entire clay sediment layer. High water-propagation velocities (0.4 - 23.6 m h-1) were observed, indicating that the desiccation-crack network remains open and serves as a preferential flow pathway year-round, even at high sediment water content (~0.50 m3 m-3). The rapid percolation bypassed the most bio-geo-active parts of the soil, transporting even highly sorptive contaminants (testosterone and estrogen) in to the deep sections of the vadose zone, accelerating the underlying groundwater contamination. The ammonium and nitrate concentrations in the vadose zone and the high number of nitrifying and denitrifying bacteria (~108 gene copies gdry-sediemt-1, each) found in the sediment indicated that the entire vadose zone is aerated even at high water content conditions (~0.55 m3 m-3). The dissolved salts concentration in the pore-water and the δ2H-H2O and δ18O-H2O values of the pore-water substantially increased with depth (becoming less depleted) in the clay sediment, indicating deep soil evaporation. Daily fluctuation of the air temperature in the desiccation cracks supported thermally induced air convection within the cracks void and could explain the deep soil salinization process. Combination of all the abovementioned observations demonstrated that the formation of desiccation cracks network in dispersive clay sediments generates a bulk advection dominated environment for both air and water flow, and that the reference to clay sediments as "hydrologically safe" should to be reconsidered.

Intercalated layered clay composites and their applications

NASA Astrophysics Data System (ADS)

Phukan, Anjali

Supported inorganic reagents are rapidly emerging as new and environmentally acceptable reagents and catalysts. The smectite group of layered clay minerals, such as, Montmorillonite, provides promising character for adsorption, catalytic activity, supports etc. for their large surface area, swelling behavior and ion exchange properties. Aromatic compounds intercalated in layered clays are useful in optical molecular devices. Clay is a unique material for adsorption of heavy metals and various toxic substances. Clay surfaces are known to be catalytically active due to their surface acidity. Acid activated clays possess much improved surface areas and acidities and have higher pore volumes so that can absorb large molecules in the pores. The exchangeable cations in clay minerals play a key role in controlling surface acidity and catalytic activity. Recently, optically active metal-complex-Montmorillonite composites are reported to be active in antiracemization purposes. In view of the above, a research work, relating to the preparation of different modified clay composites and their catalytic applications were carried out. The different aspects and results of the present work have been reported in four major chapters. Chapter I: This is an introductory chapter, which contains a review of the literature regarding clay-based materials. Clay minerals are phyllosilicates with layer structure. Montmorillonite, a member of smectite group of clay, is 2:1 phyllosilicate, where a layer is composed of an octahedral sheet sandwiched by two tetrahedral sheets. Such clay shows cation exchange capacity (CEC) and is expressed in milli-equivalents per 100 gm of dry clay. Clays can be modified by interaction with metal ion, metal complexes, metal cluster and organic cations for various applications. Clays are also modified by treating with acid followed by impregnation with metal salts or ions. Montmorillonite can intercalate suitable metal complexes in excess of CEC to form double or pseudo-trilayer composites. Metal ion and metal ion metal salts intercalated on Montmorillonite are efficient catalysts for Friedel-Crafts (FC) reactions, such as benzylation of benzene, synthesis of Raspberry ketone [4-(4'-hydroxyphenyl)butan-2-one] etc. Montmorillonite clay can be used as a good support for controlled release of pesticides and medicinal drugs, adsorbent for cationic dyes, toxic substances and heavy metals effective adsorbent for radioactive and toxic industrial wastes,...

Molecular dynamics simulation of the diffusion of uranium species in clay pores.

PubMed

Liu, Xiao-yu; Wang, Lu-hua; Zheng, Zhong; Kang, Ming-liang; Li, Chun; Liu, Chun-li

2013-01-15

Molecular dynamics simulations were carried out to investigate the diffusive behavior of aqueous uranium species in montmorillonite pores. Three uranium species (UO(2)(2+), UO(2)CO(3), UO(2)(CO(3))(2)(2-)) were confirmed in both the adsorbed and diffuse layers. UO(2)(CO(3))(3)(4-) was neglected in the subsequent analysis due to its scare occurrence. The species-based diffusion coefficients in montmorillonite pores were then calculated, and compared with the water mobility and their diffusivity in aqueous solution/feldspar nanosized fractures. Three factors were considered that affected the diffusive behavior of the uranium species: the mobility of water, the self-diffusion coefficient of the aqueous species, and the electrostatic forces between the negatively charged surface and charged molecules. The mobility of U species in the adsorbed layer decreased in the following sequence: UO(2)(2+)>UO(2)CO(3)>UO(2)(CO(3))(2)(2-). In the diffuse layer, we obtained the highest diffusion coefficient for UO(2)(CO(3))(2)(2-) with the value of 5.48×10(-10) m(2) s(-1), which was faster than UO(2)(2+). For these two charged species, the influence of electrostatic forces on the diffusion of solutes in the diffuse layer is overwhelming, whereas the influence of self-diffusion and water mobility is minor. Our study demonstrated that the negatively charged uranyl carbonate complex must be addressed in the safety assessment of potential radioactive waste disposal systems. Copyright © 2012 Elsevier B.V. All rights reserved.

Characterization of Zeolite in Zeolite-Geopolymer Hybrid Bulk Materials Derived from Kaolinitic Clays

PubMed Central

Takeda, Hayami; Hashimoto, Shinobu; Yokoyama, Hiroaki; Honda, Sawao; Iwamoto, Yuji

2013-01-01

Zeolite-geopolymer hybrid materials have been formed when kaolin was used as a starting material. Their characteristics are of interest because they can have a wide pore size distribution with micro- and meso-pores due to the zeolite and geopolymer, respectively. In this study, Zeolite-geopolymer hybrid bulk materials were fabricated using four kinds of kaolinitic clays (a halloysite and three kinds of kaolinite). The kaolinitic clays were first calcined at 700 °C for 3 h to transform into the amorphous aluminosilicate phases. Alkali-activation treatment of the metakaolin yielded bulk materials with different amounts and types of zeolite and different compressive strength. This study investigated the effects of the initial kaolinitic clays on the amount and types of zeolite in the resultant geopolymers as well as the strength of the bulk materials. The kaolinitic clays and their metakaolin were characterized by XRD analysis, chemical composition, crystallite size, 29Si and 27Al MAS NMR analysis, and specific surface area measurements. The correlation between the amount of zeolite formed and the compressive strength of the resultant hybrid bulk materials, previously reported by other researchers was not positively observed. In the studied systems, the effects of Si/Al and crystalline size were observed. When the atomic ratio of Si/Al in the starting kaolinitic clays increased, the compressive strength of the hybrid bulk materials increased. The crystallite size of the zeolite in the hybrid bulk materials increased with decreasing compressive strength of the hybrid bulk materials. PMID:28809241

An experimental study of the effects of adsorbing and non-adsorbing gases on friction and permeability evolution in clay-rich fault gouge

NASA Astrophysics Data System (ADS)

Lisabeth, H. P.; Zoback, M. D.

2017-12-01

Understanding the flow of fluids through fractures in clay-rich rocks is fundamental to a number of geoengineering enterprises, including development of unconventional hydrocarbon resources, nuclear waste storage and geological carbon sequestration. High clay content tends to make rocks plastic, low-porosity and anisotropic. In addition, some gasses adsorb to clay mineral surfaces, resulting in swelling and concomitant changes in physical properties. These complexities can lead to coupled behaviors that render prediction of fluid behavior in the subsurface difficult. We present the results of a suite of triaxial experiments on binary mixtures of quartz and illite grains to separate and quantify the effects of hydrostatic pressure, differential stress, clay content and gas chemistry on the evolution of mechanical and hydraulic characteristics of the gouge material during deformation. Tests are run on saw-cut samples prepared with gouge at 20 MPa confining pressure, 10 MPa pore pressure and at room temperature. Argon or carbon dioxide is used as pore fluid. Sample permeability, stress and strain are monitored continuously during hydrostatic and axial deformation. We find that pressure and shearing both lead to reductions in permeability. Adsorbing gas leads to swelling and promotes permeability reduction, but appears to have no effect on frictional properties. These results indicate that the seal integrity of clay-rich caprocks may not be compromised by shear deformation, and that depletion and shear deformation of unconventional reservoirs is expected to result in production declines.

Microstructures and deformation mechanisms in Opalinus Clay: insights from scaly clay from the Main Fault in the Mont Terri Rock Laboratory (CH)

NASA Astrophysics Data System (ADS)

Laurich, Ben; Urai, Janos L.; Nussbaum, Christophe

2017-01-01

The Main Fault in the shaly facies of Opalinus Clay is a small reverse fault formed in slightly overconsolidated claystone at around 1 km depth. The fault zone is up to 6 m wide, with micron-thick shear zones, calcite and celestite veins, scaly clay and clay gouge. Scaly clay occurs in up to 1.5 m wide lenses, providing hand specimens for this study. We mapped the scaly clay fabric at 1 m-10 nm scale, examining scaly clay for the first time using broad-ion beam polishing combined with scanning electron microscopy (BIB-SEM). Results show a network of thin shear zones and microveins, separating angular to lensoid microlithons between 10 cm and 10 µm in diameter, with slickensided surfaces. Our results show that microlithons are only weakly deformed and that strain is accumulated by fragmentation of microlithons by newly formed shear zones, by shearing in the micron-thick zones and by rearrangement of the microlithons.The scaly clay aggregates can be easily disintegrated into individual microlithons because of the very low tensile strength of the thin shear zones. Analyses of the microlithon size by sieving indicate a power-law distribution model with exponents just above 2. From this, we estimate that only 1 vol % of the scaly clay aggregate is in the shear zones.After a literature review of the hypotheses for scaly clay generation, we present a new model to explain the progressive formation of a self-similar network of anastomosing thin shear zones in a fault relay. The relay provides the necessary boundary conditions for macroscopically continuous deformation. Localization of strain in thin shear zones which are locally dilatant, and precipitation of calcite veins in dilatant shear fractures, evolve into complex microscale re-partitioning of shear, forming new shear zones while the microlithons remain much less deformed internally and the volume proportion of the µm-thick shear zones slowly increases. Grain-scale deformation mechanisms are microfracturing, boudinage and rotation of mica grains, pressure solution of carbonate fossils and pore collapse during ductile flow of the clay matrix. This study provides a microphysical basis to relate microstructures to macroscopic observations of strength and permeability of the Main Fault, and extrapolating fault properties in long-term deformation.

Diffusion Dominant Solute Transport Modelling In Deep Repository Under The Effect of Emplacement Media Degradation - 13285

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kwong, S.; Jivkov, A.P.

2013-07-01

Deep geologic disposal of high activity and long-lived radioactive waste is being actively considered and pursued in many countries, where low permeability geological formations are used to provide long term waste contaminant with minimum impact to the environment and risk to the biosphere. A multi-barrier approach that makes use of both engineered and natural barriers (i.e. geological formations) is often used to further enhance the containment performance of the repository. As the deep repository system subjects to a variety of thermo-hydro-chemo-mechanical (THCM) effects over its long 'operational' lifespan (e.g. 0.1 to 1.0 million years, the integrity of the barrier systemmore » will decrease over time (e.g. fracturing in rock or clay)). This is broadly referred as media degradation in the present study. This modelling study examines the effects of media degradation on diffusion dominant solute transport in fractured media that are typical of deep geological environment. In particular, reactive solute transport through fractured media is studied using a 2-D model, that considers advection and diffusion, to explore the coupled effects of kinetic and equilibrium chemical processes, while the effects of degradation is studied using a pore network model that considers the media diffusivity and network changes. Model results are presented to demonstrate the use of a 3D pore-network model, using a novel architecture, to calculate macroscopic properties of the medium such as diffusivity, subject to pore space changes as the media degrade. Results from a reactive transport model of a representative geological waste disposal package are also presented to demonstrate the effect of media property change on the solute migration behaviour, illustrating the complex interplay between kinetic biogeochemical processes and diffusion dominant transport. The initial modelling results demonstrate the feasibility of a coupled modelling approach (using pore-network model and reactive transport model) to examine the long term behaviour of deep geological repositories with media property change under complex geochemical conditions. (authors)« less

All-into-one strategy to synthesize mesoporous hybrid silicate microspheres from naturally rich red palygorskite clay as high-efficient adsorbents

PubMed Central

Wang, Wenbo; Tian, Guangyan; Wang, Dandan; Zhang, Zhifang; Kang, Yuru; Zong, Li; Wang, Aiqin

2016-01-01

A mesoporous hybrid silicate microsphere with superior adsorption performance has been successfully synthesized by employing an “all-into-one” strategy and a simple one-pot hydrothermal process using naturally abundant low-grade red palygorskite (PAL) clay as raw material in the presence of non-toxic SiO32− and Mg2+ ions. As is expected, both the PAL and associated minerals transformed into a new amorphous mesoporous hybrid silicate microsphere without using any additional pore-forming template. The mesoporous silicate microsphere shows a large pore size of 37.74 nm, high specific surface area of 489.81 m2/g (only 54.67 m2/g for raw PAL) and negative surface potential of −43.3 mV, and its maximum adsorption capabilities for Methylene bule (MB) and Crystal violet (CV) reach 407.95 mg/g and 397.22 mg/g, respectively. Meanwhile, 99.8% of MB (only 53% for raw PAL) and 99.7% of CV (only 43% for raw PAL) were sucessfully removed from 200 mg/L of initial dye solution by only using 1 g/L of the adsorbent. In addition, the spent adsorbent can be easily regenerated and repeatly reused for muptiple cycles. The study on adsorption mechanism revealed that electrostatic attraction, hydrogen bonding and chemical complexing interactions are the main factors contributed to the high dye adsorption. PMID:28000784

Extraction of an urease-active organo-complex from soil.

NASA Technical Reports Server (NTRS)

Burns, R. G.; El-Sayed, M. H.; Mclaren, A. D.

1972-01-01

Description of an extraction from a Dublin clay loam soil of a colloidal organic matter complex that is urease active and, by X-ray analysis, free of clays. Urease activity in the clay-free precipitates, as in the soil, was not destroyed by the activity of an added proteolytic enzyme, pronase. This is attributed to the circumstance that native soil urease resides in organic colloidal particles with pores large enough for water, urea, ammonia, and carbon dioxide to pass freely, but nevertheless small enough to exclude pronase.

Impact of pore-water freshening on clays and the compressibility of hydrate-bearing reservoirs during production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jang, Junbong; Cao, Shuang; Waite, William

Gas production efficiency from natural hydrate-bearing sediments depends in part on geotechnical properties of fine-grained materials, which are ubiquitous even in sandy hydrate-bearing sediments. The responses of fine-grained material to pore fluid chemistry changes due to freshening during hydrate dissociation could alter critical sediment characteristics during gas production activities. We investigate the electrical sensitivity of fine grains to pore fluid freshening and the implications of freshening on sediment compression and recompression parameters.

Degradation kinetics of ptaquiloside in soil and soil solution.

PubMed

Ovesen, Rikke Gleerup; Rasmussen, Lars Holm; Hansen, Hans Christian Bruun

2008-02-01

Ptaquiloside (PTA) is a carcinogenic norsesquiterpene glycoside produced in bracken (Pteridium aquilinum (L.) Kuhn), a widespread, aggressive weed. Transfer of PTA to soil and soil solution eventually may contaminate groundwater and surface water. Degradation rates of PTA were quantified in soil and soil solutions in sandy and clayey soils subjected to high natural PTA loads from bracken stands. Degradation kinetics in moist soil could be fitted with the sum of a fast and a slow first-order reaction; the fast reaction contributed 20 to 50% of the total degradation of PTA. The fast reaction was similar in all horizons, with the rate constant k(1F) ranging between 0.23 and 1.5/h. The slow degradation, with the rate constant k(1S) ranging between 0.00067 and 0.029/ h, was more than twice as fast in topsoils compared to subsoils, which is attributable to higher microbial activity in topsoils. Experiments with sterile controls confirmed that nonmicrobial degradation processes constituted more than 90% of the fast degradation and 50% of the slow degradation. The lower nonmicrobial degradation rate observed in the clayey compared with the sandy soil is attributed to a stabilizing effect of PTA by clay silicates. Ptaquiloside appeared to be stable in all soil solutions, in which no degradation was observed within a period of 28 d, in strong contrast to previous studies of hydrolysis rates in artificial aqueous electrolytes. The present study predicts that the risk of PTA leaching is controlled mainly by the residence time of pore water in soil, soil microbial activity, and content of organic matter and clay silicates.

Pyrolysis of attapulgite clay blended with yak dung enhances pasture growth and soil health: Characterization and initial field trials.

PubMed

Rafiq, Muhammad Khalid; Joseph, Stephen D; Li, Fei; Bai, Yanfu; Shang, Zhanhuan; Rawal, Aditya; Hook, James M; Munroe, Paul R; Donne, Scott; Taherymoosavi, Sara; Mitchell, David R G; Pace, Ben; Mohammed, Mohanad; Horvat, Joseph; Marjo, Christopher E; Wagner, Avital; Wang, Yanlong; Ye, Jun; Long, Rui-Jun

2017-12-31

Recent studies have shown that the pyrolysis of biomass combined with clay can result in both lower cost and increase in plant yields. One of the major sources of nutrients for pasture growth, as well as fuel and building materials in Tibet is yak dung. This paper reports on the initial field testing in a pasture setting in Tibet using yak dung, biochar, and attapulgite clay/yak dung biochars produced at ratios of 10/90 and 50/50 clay to dung. We found that the treatment with attapulgite clay/yak dung (50/50) biochar resulted in the highest pasture yields and grass nutrition quality. We also measured the properties and yields of mixtures of clay/yak dung biochar used in the field trials produced at 400°C and 500°C to help determine a possible optimum final pyrolysis temperature and dung/clay ratio. It was observed that increasing clay content increased carbon stability, overall biochar yield, pore size, carboxyl and ketone/aldehyde functional groups, hematite and ferrous/ferric sulphate/thiosulphate concentration, surface area and magnetic moment. Decreasing clay content resulted in higher pH, CEC, N content and an enhanced ability to accept and donate electrons. The resulting properties were a complex function of both processing temperature and the percentage of clay for the biochars processed at both 400°C and 500°C. It is possible that the increase in yield and nutrient uptake in the field trial is related to the higher concentration of C/O functional groups, higher surface area and pore volume and higher content of Fe/O/S nanoparticles of multiple oxidation state in the 50/50 clay/dung. These properties have been found to significantly increase the abundance of beneficial microorganisms and hence improve the nutrient cycling and availability in soil. Further field trials are required to determine the optimum pyrolysis production conditions and application rate on the abundance of beneficial microorganisms, yields and nutrient quality. Copyright © 2017 Elsevier B.V. All rights reserved.

Snowball gouge-aggregates formed in experimental fault gouges at seismic slip rates

NASA Astrophysics Data System (ADS)

Kim, J. H.; Ree, J. H.; Hirose, T.; Yang, K.; Kim, J. W.

2015-12-01

Clay-clast aggregates (CCA) have commonly been reported from experimental and natural fault gouges, but their formation process and mechanical meaning are not so clear. We call CCA snowball gouge aggregate (SGA) since its formation process is similar to that of snowball (see below) and CCA-like structure has been reported also from pure quartz and pure calcite gouges. Here, we discuss the formation process of SGA and its implication for faulting from experimental results of simulated gouges. We conducted high-velocity rotary shear experiments on Ca-bentonite gouges at a normal stress of 1 MPa, slip rate of 1.31 m/s, room temperature and room humidity conditions. Ca-bentonite gouge consists of montmorillonite (>95%) and other minor minerals including quartz and plagioclase. Upon displacement, the friction abruptly increases to the 1st peak (friction coefficient μ≈ 0.7) followed by slip weakening to reach a steady state (μ≈ 0.25~0.3). The simulated fault zone can be divided into slip-localization zone (SLZ) and low-slip-rate zone (LSZ) based on grain size. Spherical SGAs with their size ranging from 1 to 100 μm occur only in LSZ, and their proportion is more than 90%. Two types of SGA occur; SGA with and without a central clast. Both types of SGA show a concentric layering defined by the alternation of pore-rich (1-1.5 μm thick) and pore-poor layers (1.5-2 μm thick). Clay minerals locally exhibit a preferred orientation with their basal plane parallel to the layer boundary. We interpret that the pore-poor layers are clay-accumulated layers formed by rolling of SGA nuclei, and pore-rich layers correspond to the boundary between accumulated clay layers. Water produced from dehydration of clays due to frictional heating presumably acts as an adhesion agent of clay minerals during rolling of SGA. Since the number of layers within each SGA represents the number of rolling, the minimum displacement estimated from the number of layers and layer thickness of the largest SGA (with a diameter of 100 μm) is about 2.7 mm (slip rate≈ 170 μm/s) which is much less than the total displacement of 20 m, suggesting that most of the displacement occurred along the SLZ. Our results imply that SGA can be formed only in subseismic slip-rate zones and that minimum displacement and slip rate can be estimated from SGA.

Adsorptive potential of cationic Basic Yellow 2 (BY2) dye onto natural untreated clay (NUC) from aqueous phase: Mass transfer analysis, kinetic and equilibrium profile

NASA Astrophysics Data System (ADS)

Öztürk, A.; Malkoc, E.

2014-04-01

In this work, natural untreated clay (NUC) was studied for the removal of Basic Yellow 2 (BY2) from aqueous solution in batch system. The effects of initial BY2 concentration, contact time, solution temperature and solution pH on BY2 adsorption were investigated. Nitrogen sorption measurements were employed to investigate the variation in surface and pore properties after dye adsorption. The adsorbent was characterized by means of FTIR, PSD, TEM, XRD and BET analysis. The equilibrium adsorption data were analyzed by Langmuir, Freundlich, Temkin and Scatchard isotherm models. The maximum monolayer adsorption capacity was found to be 833.33 mg/g at 25 °C (at room temperature). The pseudo-second-order kinetic model provided the best fit to the experimental datas compared with pseudo-first-order kinetic adsorption models. To explain mass transfer mechanism of BY2 adsorption, obtained experimental datas were applied Weber and Morris model, Body and Frusawa and Smith models. The results show that the adsorption process is controlled by film diffusion. The thermodynamic parameters such as, Gibbs free energy changes (ΔG°), standard enthalpy change (ΔH°) and standard entropy change (ΔS°) were determined. Adsorption of BY2 on NUC is exothermic and spontaneous in nature. The calculated activation energy of adsorption was found to be 5.24 kJ/mol for BY2. This value indicates that the adsorption process is a physisorption.

Solute profiles in soils, weathering gradients and exchange equilibrium/disequilibrium

USGS Publications Warehouse

White, A.F.; Schulz, M.S.; Stonestrom, David A.; Vivit, D.V.; Fitzpatrick, J.; Bullen, T.

2008-01-01

The spatial and temporal changes in hydrology and pore water elemental and 87/86Sr compositions were used to determine contemporary weathering rates in a 65 to 226 ky old soil chronosequence formed from granitic sediments deposited on marine terraces along coastal California. Cl-corrected Na, K and Si increased with depth denoting inputs from the weathering of plagioclase and K-feldspar. Solute 87/86Sr exhibited progressive mixing of sea water-dominated precipitation with inputs from less radiogenic plagioclase. Linear approximations to these weathering gradients were used to determine plagioclase weathering rates of between 0.38 and 8.9×10−15 moles m−2 s−1. The lack of corresponding weathering gradients for Ca and Sr indicated short-term equilibrium with the clay ion exchange pool which requires periodic resetting by natural perturbations to maintain continuity, in spite of soil composition changes reflecting the effects of long-term weathering.

An evaluation of the mobility of pathogen indicators, Escherichia coli and bacteriophage MS-2, in a highly weathered tropical soil under unsaturated conditions

USGS Publications Warehouse

Wong, T.-P.; Byappanahalli, M.; Yoneyama, B.; Ray, C.

2008-01-01

Laboratory column experiments were conducted to study the effects of anionic polyacrylamide (PAM) polymer and surfactant linear alkylbenzene sulfonate (LAS) on the movement of Escherichia coli and the FRNA phage MS-2. The study was designed to evaluate if PAM or PAM + LAS would enhance the mobility of human pathogens in tropical soils under unsaturated conditions. No breakthrough of phage was observed in a 10 cm column after passing 100 pore volumes of solution containing 1 ?? 108 plaque-forming units (PFU)/ml. In later experiments, after passing 10-20 pore volumes of influent containing 1 ?? 108/ml MS-2 or E. coli through 15 cm columns, the soil was sliced and the organisms eluted. Phage moved slightly deeper in the polymer-treated column than in the control column. There was no measurable difference in the movement of E. coli in either polymer-treated or control columns. The properties of the soil (high amounts of metal oxides, kaolinitic clay), unsaturated flow conditions, and relatively high ionic strengths of the leaching solution attributed to significant retention of these indicators. The impacts of PAM and LAS on the mobility of E. coli or MS-2 phage in the chosen soils were not significant. ?? IWA Publishing 2008.

Colloid release and clogging in porous media: Effects of solution ionic strength and flow velocity.

PubMed

Torkzaban, Saeed; Bradford, Scott A; Vanderzalm, Joanne L; Patterson, Bradley M; Harris, Brett; Prommer, Henning

2015-10-01

The release and retention of in-situ colloids in aquifers play an important role in the sustainable operation of managed aquifer recharge (MAR) schemes. The processes of colloid release, retention, and associated permeability changes in consolidated aquifer sediments were studied by displacing native groundwater with reverse osmosis-treated (RO) water at various flow velocities. Significant amounts of colloid release occurred when: (i) the native groundwater was displaced by RO-water with a low ionic strength (IS), and (ii) the flow velocity was increased in a stepwise manner. The amount of colloid release and associated permeability reduction upon RO-water injection depended on the initial clay content of the core. The concentration of released colloids was relatively low and the permeability reduction was negligible for the core sample with a low clay content of about 1.3%. In contrast, core samples with about 6 and 7.5% clay content exhibited: (i) close to two orders of magnitude increase in effluent colloid concentration and (ii) more than 65% permeability reduction. Incremental improvement in the core permeability was achieved when the flow velocity increased, whereas a short flow interruption provided a considerable increase in the core permeability. This dependence of colloid release and permeability changes on flow velocity and colloid concentration was consistent with colloid retention and release at pore constrictions due to the mechanism of hydrodynamic bridging. A mathematical model was formulated to describe the processes of colloid release, transport, retention at pore constrictions, and subsequent permeability changes. Our experimental and modeling results indicated that only a small fraction of the in-situ colloids was released for any given change in the IS or flow velocity. Comparison of the fitted and experimentally measured effluent colloid concentrations and associated changes in the core permeability showed good agreement, indicating that the essential physics were accurately captured by the model. Copyright © 2015 Elsevier B.V. All rights reserved.

Microtomographic quantification of hydraulic clay mineral displacement effects during a CO2 sequestration experiment with saline aquifer sandstone.

PubMed

Sell, Kathleen; Enzmann, Frieder; Kersten, Michael; Spangenberg, Erik

2013-01-02

We combined a noninvasive tomographic imaging technique with an invasive open-system core-flooding experiment and compared the results of the pre- and postflooded states of an experimental sandstone core sample from an ongoing field trial for carbon dioxide geosequestration. For the experiment, a rock core sample of 80 mL volume was taken from the 629 m Stuttgart Formation storage domain of a saline sandstone aquifer at the CCS research pilot plant Ketzin, Germany. Supercritical carbon dioxide and synthetical brine were injected under in situ reservoir p/T-conditions at an average flow rate of 0.1 mL/min for 256 h. X-ray computed microtomographic imaging was carried out before and after the core-flooding experiment at a spatial voxel resolution of 27 μm. No significant changes in microstructure were found at the tomographic imaging resolution including porosity and pore size distribution, except of an increase of depositional heterogeneous distribution of clay minerals in the pores. The digitized rock data were used as direct real microstructure input to the GeoDict software package, to simulate Navier-Stokes flow by a lattice Boltzmann equation solver. This procedure yielded 3D pressure and flow velocity fields, and revealed that the migration of clay particles decreased the permeability tensor probably due to clogging of pore openings.

Diagenesis and reservoir quality of Bhuban sandstones (Neogene), Titas Gas Field, Bengal Basin, Bangladesh

NASA Astrophysics Data System (ADS)

Aminul Islam, M.

2009-06-01

This study deals with the diagenesis and reservoir quality of sandstones of the Bhuban Formation located at the Titas Gas Field of Bengal Basin. Petrographic study including XRD, CL, SEM and BSE image analysis and quantitative determination of reservoir properties were carried out for this study. The sandstones are fine to medium-grained, moderately well to well sorted subfeldspathic arenites with subordinate feldspathic and lithic arenites. The diagenetic processes include clay infiltration, compaction and cementation (quartz overgrowth, chlorite, kaolinite, calcite and minor amount of pyrite, dolomite and K-feldspar overgrowth). Quartz is the dominant pore occluding cement and generally occurred as small euhedral crystals, locally as large pyramidal crystals in the primary pores. Pressure solution derived from grain contact is the main contributor of quartz overgrowths. Chlorite occurs as pore-lining and pore filling cement. In some cases, chlorite helps to retain porosity by preventing quartz overgrowth. In some restricted depth interval, pore-occlusion by calcite cement is very much intense. Kaolinite locally developed as vermiform and accelerated the minor porosity loss due to pore-occlusion. Kaolinite/chlorite enhances ineffective microporosity. Kaolinite is a by-product of feldspar leaching in the presence of acidic fluid produced during the maturation of organic matter in the adjacent Miocene or deeper Oligocene source rocks. The relation between diagenesis and reservoir quality is as follows: the initial porosity was decreased by compaction and cementation and then increased by leaching of the metastable grains and dissolution of cement. Good quality reservoir rocks were deposited in fluvial environment and hence quality of reservoir rocks is also environment selective. Porosity and permeability data exhibit good inverse correlation with cement. However, some data points indicate multiple controls on permeability. Reservoir quality is thus controlled by pore occluding cement, textural parameters (grain size, pore size and sorting) and depositional environment. The reservoir finally resumed partly its pre-cementation quality after development of secondary porosity.

Extraction of water and solutes from argillaceous rocks for geochemical characterisation: Methods, processes and current understanding

NASA Astrophysics Data System (ADS)

Sacchi, Elisa; Michelot, Jean-Luc; Pitsch, Helmut; Lalieux, Philippe; Aranyossy, Jean-François

2001-01-01

This paper summarises the results of a comprehensive critical review, initiated by the OECD/NEA "Clay Club," of the extraction techniques available to obtain water and solutes from argillaceous rocks. The paper focuses on the mechanisms involved in the extraction processes, the consequences on the isotopic and chemical composition of the extracted pore water and the attempts made to reconstruct its original composition. Finally, it provides some examples of reliable techniques and information, as a function of the purpose of the geochemical study. Résumé. Cet article résume les résultats d'une synthèse critique d'ensemble, lancée par le OECD/NEA "Clay Club", sur les techniques d'extraction disponibles pour obtenir l'eau et les solutés de roches argileuses. L'article est consacré aux mécanismes impliqués dans les processus d'extraction, aux conséquences sur la composition isotopique et chimique de l'eau porale extraite et aux tentatives faites pour reconstituer sa composition originelle. Finalement, il donne quelques exemples de techniques fiables et d'informations, en fonction du but de l'étude géochimique. Resúmen. Este artículo resume los resultados de una revisión crítica exhaustiva (iniciada por el "Clay Club" OECD/NEA) de las técnicas de extracción disponibles para obtener agua y solutos en rocas arcillosas. El artículo se centra en los mecanismos involucrados en los procesos extractivos, las consecuencias en la composición isotópica y química del agua intersticial extraída, y en los intentos realizados para reconstruir su composición original. Finalmente, se presentan algunos ejemplos de técnicas fiables e información, en función del propósito del estudio geoquímico.

Interstitial Water Geochemistry and Low Temperature Alteration in Volcaniclastic Sediments from the Amami Sankaku Basin at IODP Site U1438 (Expedition 351)

NASA Astrophysics Data System (ADS)

Loudin, L. C.; Yogodzinski, G. M.; Sena, C.; van der Land, C.; Zhang, Z.; Marsaglia, K. M.; Meffre, S.

2014-12-01

Interstitial water (IW) geochemistry provides insight into the diagenetic transformation of sediment to rock by component dissolution/alteration and precipitation of new mineral phases as pore-filling cements, as well as providing insight into ion exchange reactions with secondary minerals. At Site U1438, 67 IW samples were collected within a ~950 m section of volcaniclastic sediments. These were analyzed for pH as well as major and trace elements. The corresponding host sediments were mineralogically characterized by XRD and petrographic observations. Three alteration zones are inferred: 1) the upper alteration zone (~0-300 mbsf) characterized by maximum IW concentrations of Si (790.1 μM), Sr (138.5 μM) and Mn (279.5 μM), consistent with volcanic glass and siliceous microfossil dissolution, enhanced reduction of Mn oxides, and carbonate recrystallization. Maximum concentrations in Li and B coupled with the lowest pH (6.7) imply that Li and B are released into the IW due to silicate dissolution and clay desorption. 2) At intermediate depths (~300 to ~550 mbsf) Mg, K, Sr, Si, Mn, Li, and B are at concentration minima, possibly due to growth of authigenic minerals. B and Li minimum concentrations occur at high pH (~9) suggesting that these elements are preferentially removed from high pH waters during the precipitation of clay mineral and zeolite cements in primary and secondary (dissolution) pores. The mineralogy of these phases is confirmed by XRD data, and their pore-filling nature is seen in thin sections of the coarser lithologies. 3) The deep alteration zone (>~550m) is characterized by an increase in B, Li, Sr and Ca. At ~650 mbsf, Ca becomes the dominant cation in solution consistent with either mineral interaction with the IW, or diffusive input from underlying igneous basement (~1400 mbsf).

Semianalytical solutions for transport in aquifer and fractured clay matrix system

NASA Astrophysics Data System (ADS)

Huang, Junqi; Goltz, Mark N.

2015-09-01

A three-dimensional mathematical model that describes transport of contaminant in a horizontal aquifer with simultaneous diffusion into a fractured clay formation is proposed. A group of semianalytical solutions is derived based on specific initial and boundary conditions as well as various source functions. The analytical model solutions are evaluated by numerical Laplace inverse transformation and analytical Fourier inverse transformation. The model solutions can be used to study the fate and transport in a three-dimensional spatial domain in which a nonaqueous phase liquid exists as a pool atop a fractured low-permeability clay layer. The nonaqueous phase liquid gradually dissolves into the groundwater flowing past the pool, while simultaneously diffusing into the fractured clay formation below the aquifer. Mass transfer of the contaminant into the clay formation is demonstrated to be significantly enhanced by the existence of the fractures, even though the volume of fractures is relatively small compared to the volume of the clay matrix. The model solution is a useful tool in assessing contaminant attenuation processes in a confined aquifer underlain by a fractured clay formation.

Boron desorption in subduction forearcs: Systematics and implications for the origin and transport of deeply-sourced fluids

NASA Astrophysics Data System (ADS)

Saffer, D. M.; Kopf, A.

2015-12-01

At many subduction zones, pore water geochemical anomalies at seafloor seeps and in shallow boreholes indicate upward fluid flow and chemical transport from depths of several km. Identifying the source regions and flow pathways of these fluids is a key step toward quantifying volatile fluxes through forearcs, and in understanding their potential connection to loci of excess pore pressure along the plate boundary. Here, we focus on observations of pore water freshening (reported in terms of [Cl]), elevated [B], and light δ11B. Pore water freshening is generally thought to result from clay dehydration, whereas the B and δ11B signatures are interpreted to reflect desorption of isotopically light B from pelitic sediments with increasing temperature. We develop a model to track the coupled effects of B desorption, smectite dehydration, and progressive consolidation within the underthrusting sediment section. Our model incorporates established kinetic models of clay dehydration, and experimental data that define the temperature-dependent distribution coefficient (Kd) and fractionation of B in marine sediments. A generic sensitivity analysis demonstrates that the relative timing of heating and consolidation is a dominant control on pore water composition. For cold slabs, freshening is maximized because dehydration releases bound water into low porosity sediment, whereas B concentrations and isotopic signatures are modest because desorption is only partially complete. For warmer slabs, [B] and [Cl] signals are smaller, because heating and desorption occur shallower and into larger porosities, but the predicted δ11B signal is larger. The former scenario is typical of non-accretionary margins where the insulating sediment layer on the subducting plate is commonly <1 km thick. This result provides a quantitative explanation for the global observation that [Cl] depletion and [B] enrichment signals are generally strongest at non-accretionary margins. Application of our multi-tracer approach to the Costa Rica, N. Japan, N. Barbados, and Mediterranean Ridge subduction zones illustrates that clay dehydration and B desorption are viable mechanisms for the generation of observed geochemical signatures, including pore water freshening of over 50%, [B] up to 10x seawater values, and δ11B as low as 17‰.

New Tubular Ceramic Membranes from Natural Moroccan Clay for Microfiltration Application

NASA Astrophysics Data System (ADS)

Ait Taleb, A.; El Baraka, N.; Saffaj, N.; Laknifli, A.; Mamouni, R.; Fatni, A.; El Hammadi, A.; El Qacimi, N.

2018-05-01

This paper is devoted the preparation of low cost microfiltration membranes using Moroccan clay powder. The preparation of membrane was composed with two steps: First a macroporous tubular support with a pore diameter 10 μm and porosity 43%. Secondly a microfiltration layer was performed by the slip casting method. A deflocculated slip was obtained by mixing mineral powder of ZrO2, PVA (polyvinyl alcohol) and water, after drying at room temperature for 24 h, the microfiltration layer was heated to 800°C for consolidation. Scanning electron microscopy observation showed homogeneous layers without cracks with an average pore diameter of 0.19 μm for the active layer. Water permeability obtained is about 841 L/h.m2.bar. The membranes have been tested to cleaning of colored wastewater.

The action of water films at Å-scales in the Earth: Implications for the Nankai subduction system

NASA Astrophysics Data System (ADS)

Brown, Kevin M.; Poeppe, Dean; Josh, Matthew; Sample, James; Even, Emilie; Saffer, Demian; Tobin, Harold; Hirose, Takehiro; Kulongoski, J. T.; Toczko, Sean; Maeda, Lena; IODP Expedition 348 Shipboard Party

2017-04-01

Water properties change with confinement within nanofilms trapped between natural charged clay particles. We investigated nanofilm characteristics through high-stress laboratory compression tests in combination with analyses of expelled pore fluids. We utilized sediments obtained from deep drilling of the Nankai subduction zone at Site C0002 of the Integrated Ocean Drilling Program (IODP). We show that below 1-2 km, there should be widespread ultrafiltration of migrating fluids. Experiments to > ∼ 100 MPa normal compression collapse pores below a few ion monofilm thicknesses. A reduction towards a single condensing/dehydrating ion monofilm occurs as stresses rise >100-200 MPa and clay separations are reduced to <10-20 Å. Thus, porosity in high mineral surface area systems only consists of double and single monofilms at depths below a few km leaving little room for either bulk water or the deep biosphere. The resulting semipermeable properties result in variable segregation of ions and charged isotopes and water during active flow. The ultrafiltration and ion dehydration processes are coupled in that both require the partial immobilization of ions between the charged clay surfaces. The general effect is to increase salinities in residual pore fluids at depth and freshen fluids expelled during consolidation. Cessation of nanofilm collapse to a near constant ∼17 Å below 2 km depth at Nankai supports the contention for the onset of substantial geopressuring on the deeper seismogenic fault. The properties of monofilm water, thus, have considerable implications for the deep water properties of subduction zones generating major tremor and Mw 8+ earthquakes. Indeed, the combined effects of advective flow, ultrafiltration, diffusion, and diagenesis could provide a unifying explanation for the origins of overpressuring and pore water geochemical signals observed in many natural systems.

Mechanisms governing brittle fault mechanics - a multi-scale study from the Permian Khao-Kwang fold-and-thrust belt, Thailand

NASA Astrophysics Data System (ADS)

von Hagke, Christoph; Morley, Chris; Kanitpanyacharoen, Waruntorn

2017-04-01

Despite our qualitative understanding of factors contributing to thrust and detachment weakness such as mineralogy, pore fluid pressure, or efficiency of structure localization, it is difficult to assess the contribution of the individual factors. Here we present multi-scale analysis of a mixed clay / carbonate high displacement (kms of heave) thrust zone, where it is possible to study structures formed within a similar temperature and pressure regime, and thus only varying due to lithological contrasts. We mapped the well-exposed thrust zone in a large quarry at outcrop scale in five separate sections present along a strike-distance of 1 km. The thrust zone shows considerable variations in structural style, as well as localization within different clay and limestone horizons. Zones of low and high strain have been identified. We investigate these changes in macroscopic deformation style using Virtual Polarizing Microscopy, and the combined methods of Broad Ion Beam milling and Scanning Electron Microscopy in addition with XRD analysis. We characterize structural and mineralogical variations in the thrust zone at all scales, from outcrop down to nano-meters. Results show strain localization is heterogeneous, with strong variations along strike. Within the clay package, strain localizes along zones rich in organic matter. Microstructures are complex, and show multiple deformation events, including crack-seal processes and reworking of vein material. Pressure solution is dominant. XRD analysis shows mineralogical differences between zones of high and low strain within the shale-dominated package. However, highest strain does not only occur in the clay units, but partly is accommodated in the surrounding limestone.

Influence of clay minerals on curcumin properties: Stability and singlet oxygen generation

NASA Astrophysics Data System (ADS)

Gonçalves, Joyce L. S.; Valandro, Silvano R.; Poli, Alessandra L.; Schmitt, Carla C.

2017-09-01

Curcumin (CUR) has showed promising photophysical properties regarding to biological and chemical sciences. However, the main barrier for those applications are their low solubility and stability in aqueous solution. The effects of two different clay minerals, the montmorillonite (SWy-2) and the Laponite RD (Lap) nanoclay, on the stabilization of Curcumin were investigated. Their effects were compared with two well-established environments (acidic and neutral aqueous media). CUR/clay hybrids were prepared using a simple and fast method, where CUR solution was added into clay suspensions, to obtain well dispersed hybrids in water. The degradation process of CUR and CUR/clays hybrids was investigated using UV-Vis spectroscopic. For both studied hybrids, the CUR degradation process was suppressed by the presence of the clay particles. Furthermore, the Lap showed a great stabilization effect than SWy-2. This behavior was due to the smaller particle size and higher exfoliation ability of Lap, providing a large surface for CUR adsorption compared to SWy-2. The degradation process of CUR solutions and CUR/clay hybrids was also studied in the presence of light. CUR photodegradation process was faster not only in the aqueous solution but also in the clay suspension compared to those studied in the dark. The presence of clay particles accelerated the photodegradation of CUR due to the products formation in the reactions between CUR and oxygen radicals. Our results showed that the singlet oxygen quantum yield (ΦΔ) of CUR were about 59% higher in the clay suspensions than CUR in aqueous solution. Therefore, the formation of CUR/clay hybrids, in particularly with Lap, suppressed the degradation in absence light of CUR and increased the singlet oxygen generation, which makes this hybrids of CUR/clay a promising material to enlarge the application of CUR in the biological sciences.

Sructure and dynamics of fluids in micropous and mesoporous earth and engineered materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cole, David R; Mamontov, Eugene; Rother, Gernot

2009-01-01

The behavior of liquids in confined geometries (pores, fractures) typically differs, due to the effects of large internal surfaces and geometri-cal confinement, from their bulk behavior in many ways. Phase transitions (i.e., freezing and capillary condensation), sorption and wetting, and dy-namical properties, including diffusion and relaxation, may be modified, with the strongest changes observed for pores ranging in size from <2 nm to 50 nm the micro- and mesoporous regimes. Important factors influ-encing the structure and dynamics of confined liquids include the average pore size and pore size distribution, the degree of pore interconnection, and the character of the liquid-surfacemore » interaction. While confinement of liq-uids in hydrophobic matrices, such as carbon nanotubes, or near the sur-faces of mixed character, such as many proteins, has also been an area of rapidly growing interest, the confining matrices of interest to earth and ma-terials sciences usually contain oxide structural units and thus are hydro-philic. The pore size distribution and the degree of porosity and inter-connection vary greatly amongst porous matrices. Vycor, xerogels, aerogels, and rocks possess irregular porous structures, whereas mesopor-ous silicas (e.g., SBA-15, MCM-41, MCM-48), zeolites, and layered sys-tems, for instance clays, have high degrees of internal order. The pore type and size may be tailored by means of adjusting the synthesis regimen. In clays, the interlayer distance may depend on the level of hydration. Al-though studied less frequently, matrices such as artificial opals and chry-sotile asbestos represent other interesting examples of ordered porous structures. The properties of neutrons make them an ideal probe for com-paring the properties of bulk fluids with those in confined geometries. In this chapter, we provide a brief review of research performed on liquids confined in materials of interest to the earth and material sciences (silicas, aluminas, zeolites, clays, rocks, etc.), emphasizing those neutron scattering techniques which assess both structural modification and dynamical behav-ior. Quantitative understanding of the complex solid-fluid interactions under different thermodynamic situations will impact both the design of bet-ter substrates for technological applications (e.g., chromatography, fluid capture, storage and release, and heterogeneous catalysis) as well as our fundamental understanding of processes encountered in the environment (i.e., fluid and waste mitigation, carbon sequestration, etc.).« less

Thermally-driven Coupled THM Processes in Shales

NASA Astrophysics Data System (ADS)

Rutqvist, J.

2017-12-01

Temperature changes can trigger strongly coupled thermal-hydrological-mechanical (THM) processes in shales that are important to a number of subsurface energy applications, including geologic nuclear waste disposal and hydrocarbon extraction. These coupled processes include (1) direct pore-volume couplings, by thermal expansion of trapped pore-fluid that triggers instantaneous two-way couplings between pore fluid pressure and mechanical deformation, and (2) indirect couplings in terms of property changes, such as changes in mechanical stiffness, strength, and permeability. Direct pore-volume couplings have been studied in situ during borehole heating experiments in shale (or clay stone) formations at Mont Terri and Bure underground research laboratories in Switzerland and France. Typically, the temperature changes are accompanied with a rapid increase in pore pressure followed by a slower decrease towards initial (pre-heating) pore pressure. Coupled THM modeling of these heater tests shows that the pore pressure increases because the thermal expansion coefficient of the fluid is much higher than that of the porous clay stone. Such thermal pressurization induces fluid flow away from the pressurized area towards areas of lower pressure. The rate of pressure increase and magnitude of peak pressure depends on the rate of heating, pore-compressibility, and permeability of the shale. Modeling as well as laboratory experiments have shown that if the pore pressure increase is sufficiently large it could lead to fracturing of the shale or shear slip along pre-existing bedding planes. Another set of data and observations have been collected associated with studies related to concentrated heating and cooling of oil-shales and shale-gas formations. Heating may be used to enhance production from tight oil-shale, whereas thermal stimulation has been attempted for enhanced shale-gas extraction. Laboratory experiments on shale have shown that strength and elastic deformation modulus decreases with temperature while the rate creep deformations increase with temperature. Such temperature dependency also affects the well stability and zonal sealing across shale layers.

Early containment of high-alkaline solution simulating low-level radioactive waste stream in clay-bearing blended cement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kruger, A.A.; Olson, R.A.; Tennis, P.D.

1995-04-01

Portland cement blended with fly ash and attapulgite clay was mixed with high-alkaline solution simulating low-level radioactive waste stream at a one-to-one weight ratio. Mixtures were adiabatically and isothermally cured at various temperatures and analyzed for phase composition, total alkalinity, pore solution chemistry, and transport properties as measured by impedance spectroscopy. Total alkalinity is characterized by two main drops. The early one corresponds to a rapid removal of phosphorous, aluminum, sodium, and to a lesser extent potassium solution. The second drop from about 10 h to 3 days is mainly associated with the removal of aluminum, silicon, and sodium. Thereafter,more » the total alkalinity continues descending, but at a lower rate. All pastes display a rapid flow loss that is attributed to an early precipitation of hydrated products. Hemicarbonate appears as early as one hour after mixing and is probably followed by apatite precipitation. However, the former is unstable and decomposes at a rate that is inversely related to the curing temperature. At high temperatures, zeolite appears at about 10 h after mixing. At 30 days, the stabilized crystalline composition Includes zeolite, apatite and other minor amounts of CaCO{sub 3}, quartz, and monosulfate Impedance spectra conform with the chemical and mineralogical data. The normalized conductivity of the pastes shows an early drop, which is followed by a main decrease from about 12 h to three days. At three days, the permeability of the cement-based waste as calculated by Katz-Thompson equation is over three orders of magnitude lower than that of ordinary portland cement paste. However, a further decrease in the calculated permeability is questionable. Chemical stabilization is favorable through incorporation of waste species into apatite and zeolite.« less

Comparison of soil solution sampling techniques to assess metal fluxes from contaminated soil to groundwater.

PubMed

Coutelot, F; Sappin-Didier, V; Keller, C; Atteia, O

2014-12-01

The unsaturated zone plays a major role in elemental fluxes in terrestrial ecosystems. A representative chemical analysis of soil pore water is required for the interpretation of soil chemical phenomena and particularly to assess Trace Elements (TEs) mobility. This requires an optimal sampling system to avoid modification of the extracted soil water chemistry and allow for an accurate estimation of solute fluxes. In this paper, the chemical composition of soil solutions sampled by Rhizon® samplers connected to a standard syringe was compared to two other types of suction probes (Rhizon® + vacuum tube and Rhizon® + diverted flow system). We investigated the effects of different vacuum application procedures on concentrations of spiked elements (Cr, As, Zn) mixed as powder into the first 20 cm of 100-cm columns and non-spiked elements (Ca, Na, Mg) concentrations in two types of columns (SiO2 sand and a mixture of kaolinite + SiO2 sand substrates). Rhizon® was installed at different depths. The metals concentrations showed that (i) in sand, peak concentrations cannot be correctly sampled, thus the flux cannot be estimated, and the errors can easily reach a factor 2; (ii) in sand + clay columns, peak concentrations were larger, indicating that they could be sampled but, due to sorption on clay, it was not possible to compare fluxes at different depths. The different samplers tested were not able to reflect the elemental flux to groundwater and, although the Rhizon® + syringe device was more accurate, the best solution remains to be the use of a lysimeter, whose bottom is kept continuously at a suction close to the one existing in the soil.

PES-Kaolin Mixed Matrix Membranes for Arsenic Removal from Water

PubMed Central

Russo, Francesca; Rezzouk, Lina

2017-01-01

The aim of this work was the fabrication and the characterization of mixed matrix membranes (MMMs) for arsenic (As) removal from water. Membrane separation was combined with an adsorption process by incorporating the kaolin (KT2) Algerian natural clay in polymeric membranes. The effects of casting solution composition was explored using different amounts of polyethersufone (PES) as a polymer, polyvinyl-pyrrolidone (PVP K17) and polyethylene glycol (PEG 200) as pore former agents, N-methyl pyrrolidone (NMP) as a solvent, and kaolin. Membranes were prepared by coupling Non-solvent Induced Phase Separation and Vapour Induced Phase Separation (NIPS and VIPS, respectively). The influence of the exposure time to controlled humid air and temperature was also investigated. The MMMs obtained were characterized in terms of morphology, pore size, porosity, thickness, contact angle and pure water permeability. Adsorption membrane-based tests were carried out in order to assess the applicability of the membranes produced for As removal from contaminated water. Among the investigated kaolin concentrations (ranging from 0 wt % to 5 wt %), a content of 1.25 wt % led to the MMM with the most promising performance. PMID:28974009

Influence of clay particles on the transport and retention of titanium dioxide nanoparticles in quartz sand.

PubMed

Cai, Li; Tong, Meiping; Wang, Xueting; Kim, Hyunjung

2014-07-01

This study investigated the influence of two representative suspended clay particles, bentonite and kaolinite, on the transport of titanium dioxide nanoparticles (nTiO2) in saturated quartz sand in both NaCl (1 and 10 mM ionic strength) and CaCl2 solutions (0.1 and 1 mM ionic strength) at pH 7. The breakthrough curves of nTiO2 with bentonite or kaolinite were higher than those without the presence of clay particles in NaCl solutions, indicating that both types of clay particles increased nTiO2 transport in NaCl solutions. Moreover, the enhancement of nTiO2 transport was more significant when bentonite was present in nTiO2 suspensions relative to kaolinite. Similar to NaCl solutions, in CaCl2 solutions, the breakthrough curves of nTiO2 with bentonite were also higher than those without clay particles, while the breakthrough curves of nTiO2 with kaolinite were lower than those without clay particles. Clearly, in CaCl2 solutions, the presence of bentonite in suspensions increased nTiO2 transport, whereas, kaolinite decreased nTiO2 transport in quartz sand. The attachment of nTiO2 onto clay particles (both bentonite and kaolinite) were observed under all experimental conditions. The increased transport of nTiO2 in most experimental conditions (except for kaolinite in CaCl2 solutions) was attributed mainly to the clay-facilitated nTiO2 transport. The straining of larger nTiO2-kaolinite clusters yet contributed to the decreased transport (enhanced retention) of nTiO2 in divalent CaCl2 solutions when kaolinite particles were copresent in suspensions.

Effects of clay minerals on diethyl phthalate degradation in Fenton reactions.

PubMed

Chen, Ning; Fang, Guodong; Zhou, Dongmei; Gao, Juan

2016-12-01

Phthalate esters are a group of plasticizers, which are commonly detected in China's soils and surface water. Fenton reactions are naturally occurring and widely applied in the degradation of contaminants. However, limited research was considered the effects of clay minerals on contaminants degradation with OH oxidation. In this study, batch experiments were conducted to investigate the degradation of diethyl phthalate (DEP) in Fenton reactions in the presence of clay minerals, and the effects of clay type, Fe content in clay structure. The results showed the clay adsorption inhibited total degradation of DEP, and Fe content in clay structure played an important role in DEP degradation, including in solution and adsorbed in clay minerals. Clay minerals with less Fe content (<3%) quenched OH radical, while nontronite with Fe content 19.2% improved OH radical generation and accelerated DEP degradation in solution. The degradation of clay-adsorbed DEP was much slower than DEP in solution. Six main products of DEP degradation were identified, including monoethyl phthalate, phthalate acid, hydroxyl diethyl phthalate, etc. This study implied that phthalate ester's degradation would be much slower in natural water than expected in the presence of clay minerals. Copyright © 2016 Elsevier Ltd. All rights reserved.

Direct numerical simulation of supercritical gas flow in complex nanoporous media: Elucidating the relationship between permeability and pore space geometry

NASA Astrophysics Data System (ADS)

Landry, C. J.; Prodanovic, M.; Eichhubl, P.

2015-12-01

Mudrocks and shales are currently a significant source of natural gas and understanding the basic transport properties of these formations is critical to predicting long-term production, however, the nanoporous nature of mudrocks presents a unique challenge. Mudrock pores are predominantly in the range of 1-100 nm, and within this size range the flow of gas at reservoir conditions will fall within the slip-flow and early transition-flow regime (0.001 < Kn < 1.0). Therefore, flow-rates will significantly deviate from Navier-Stokes predictions. Currently, the study of slip-flows is mostly limited to simple tube and channel geometries, but the geometry of mudrock pores is often sponge-like (organic matter) and/or platy (clays). Here we present a local effective viscosity lattice Boltzmann model (LEV-LBM) constructed for flow simulation in the slip- and early-transition flow regimes, adapted here for complex geometries. At the macroscopic scale the LEV-LBM is parameterized with local effective viscosities at each node to capture the variance of the mean free path of gas molecules in a bounded system. The LEV-LBM is first validated in simple tube geometries, where excellent agreement with linearized Boltzmann solutions is found for Knudsen numbers up to 1.0. The LEV-LBM is then employed to quantify the length effect on the apparent permeability of tubes, which suggests pore network modeling of flow in the slip and early-transition regime will result in overestimation unless the length effect is considered. Furthermore, the LEV-LBM is used to evaluate the predictive value of commonly measured pore geometry characteristics such as porosity, pore size distribution, and specific solid surface area for the calculation of permeability. We show that bundle of tubes models grossly overestimate apparent permeability, as well as underestimate the increase in apparent permeability with decreasing pressure as a result of excluding topology and pore shape from calculations.

Size effects of pore density and solute size on water osmosis through nanoporous membrane.

PubMed

Zhao, Kuiwen; Wu, Huiying

2012-11-15

Understanding the behavior of osmotic transport across nanoporous membranes at molecular level is critical to their design and applications, and it is also beneficial to the comprehension of the mechanism of biological transmembrane transport processes. Pore density is an important parameter for nanoporous membranes. To better understand the influence of pore density on osmotic transport, we have performed systematic molecular dynamics simulations on water osmosis across nanoporous membranes with different pore densities (i.e., number of pores per unit area of membrane). The simulation results reveal that significant size effects occur when the pore density is so high that the center-to-center distance between neighboring nanopores is comparable to the solute size. The size effects are independent of the pore diameter and solute concentration. A simple quantitative correlation between pore density, solute size, and osmotic flux has been established. The results are excellently consistent with the theoretical predictions. It is also shown that solute hydration plays an important role in real osmotic processes. Solute hydration strengthens the size effects of pore density on osmotic processes due to the enlarged effective solute size induced by hydration. The influence of pore density, solute size, and solute hydration on water osmosis through nanoporous membranes can be introduced to eliminate the deviations of real osmotic processes from ideal behavior.

Numerical simulation of mechanical compaction of deepwater shallow sediments

NASA Astrophysics Data System (ADS)

Sun, Jin; Wu, Shiguo; Deng, Jingen; Lin, Hai; Zhang, Hanyu; Wang, Jiliang; Gao, Jinwei

2018-02-01

To study the compaction law and overpressure evolution in deepwater shallow sediments, a large-strain compaction model that considers material nonlinearity and moving boundary is formulated. The model considers the dependence of permeability and material properties on void ratio. The modified Cam-Clay model is selected as the constitutive relations of the sediments, and the deactivation/reactivation method is used to capture the moving top surface during the deposition process. A one-dimensional model is used to study the compaction law of the shallow sediments. Results show that the settlement of the shallow sediments is large under their own weight during compaction. The void ratio decreases strictly with burial depth and decreases more quickly near the seafloor than in the deeper layers. The generation of abnormal pressure in the shallow flow sands is closely related to the compaction law of shallow sediments. The two main factors that affect the generation of overpressure in the sands are deposition rate and permeability of overlying clay sediments. Overpressure increases with an increase in deposition rate and a decrease in the permeability of the overlying clay sediment. Moreover, an upper limit for the overpressure exists. A two-dimensional model is used to study the differential compaction of the shallow sediments. The pore pressure will still increase due to the inflow of the pore fluid from the neighboring clay sediment even though the deposition process is interrupted.

Effects of fluid-rock interactions on faulting within active fault zones - evidence from fault rock samples retrieved from international drilling projects

NASA Astrophysics Data System (ADS)

Janssen, C.; Wirth, R.; Kienast, M.; Yabe, Y.; Sulem, J.; Dresen, G. H.

2015-12-01

Chemical and mechanical effects of fluids influence the fault mechanical behavior. We analyzed fresh fault rocks from several scientific drilling projects to study the effects of fluids on fault strength. For example, in drill core samples on a rupture plane of an Mw 2.2 earthquake in a deep gold mine in South Africa the main shock occurred on a preexisting plane of weakness that was formed by fluid-rock interaction (magnesiohornblende was intensively altered to chlinochlore). The plane acted as conduit for hydrothermal fluids at some time in the past. The chemical influence of fluids on mineralogical alteration and geomechanical processes in fault core samples from SAFOD (San Andreas Fault Observatory at Depth) is visible in pronounced dissolution-precipitation processes (stylolites, solution seams) as well as in the formation of new phases. Detrital quartz and feldspar grains are partially dissolved and replaced by authigenic illite-smectite (I-S) mixed-layer clay minerals. Transmission Electron Microscopy (TEM) imaging of these grains reveals that the alteration processes and healing were initiated within pores and small intra-grain fissures. Newly formed phyllosilicates growing into open pore spaces likely reduced the fluid permeability. The mechanical influence of fluids is indicated by TEM observations, which document open pores that formed in-situ in the gouge material during or after deformation. Pores were possibly filled with formation water and/or hydrothermal fluids suggesting elevated fluid pressure preventing pore collapse. Fluid-driven healing of fractures in samples from SAFOD and the DGLab Gulf of Corinth project is visible in cementation. Cathodoluminescence microscopy (CL) reveals different generations of calcite veins. Differences in CL-colors suggest repeated infiltration of fluids with different chemical composition from varying sources (formation and meteoric water).

The Influence of Syndepositional Macropores on the Hydraulic Integrity of Thick Alluvial Clay Aquitards

NASA Astrophysics Data System (ADS)

Timms, Wendy A.; Acworth, R. Ian; Crane, Richard A.; Arns, Christoph H.; Arns, Ji-Youn; McGeeney, Dayna E.; Rau, Gabriel C.; Cuthbert, Mark O.

2018-04-01

Clay-rich deposits are commonly assumed to be aquitards which act as natural hydraulic barriers due to their low hydraulic connectivity. Postdepositional weathering processes are known to increase the permeability of aquitards in the near surface but not impact on deeper parts of relatively thick formations. However, syndepositional processes affecting the hydraulic properties of aquitards have previously received little attention in the literature. Here, we analyze a 31 m deep sediment core recovered from an inland clay-rich sedimentary sequence using a combination of techniques including particle size distribution and microscopy, centrifuge dye tracer testing and micro X-ray CT imaging. Subaerial deposition of soils within these fine grained alluvial deposits has led to the preservation of considerable macropores (root channels or animal burrows). Connected pores and macropores thus account for vertical hydraulic conductivity (K) of 4.2×10-9 m/s (geometric mean of 13 samples) throughout the thick aquitard, compared to a matrix K that is likely <10-10 m/s, the minimum K value that was measured. Our testing demonstrates that such syndepositional features may compromise the hydraulic integrity of what otherwise appears to have the characteristics of a much lower permeability aquitard. Heterogeneity within a clay-rich matrix could also enhance vertical connectivity, as indicated by digital analysis of pore morphology in CT images. We highlight that the paleo-environment under which the sediment was deposited must be considered when aquitards are investigated as potential natural hydraulic barriers and illustrate the value of combining multiple investigation techniques for characterizing clay-rich deposits.

Problems of the theory of the consolidation solved in the special functions

NASA Astrophysics Data System (ADS)

Dasibekov, Azhibek; Abzhapbarov, Azimkhan; Duisebayeva, Peruza; Polatbek, Aigul

2016-08-01

The soil, which deformation modulus is continuously increased with depth is called continuously heterogeneous. In this paper, this heterogeneity is presented in the form of: E =Em(α+β z ) m (α >0 ,Em>0 ,α +βz>0 ), wher Em, α, β, m are experimental parameters. On the basis of this dependence the consolidation problems of elastic and elastically creeping inhomogeneous soils are solved in relation to the restricted area of the consolidation. These solutions make it possible to calculate the values of the pore pressure, the amount of the main stresses and vertical displacements of upper surface points of the condensed inhomogeneous soil mass. In these solutions for highly compressed water-saturated clay soils is also taken into account that at the initial time the part of loading, instantly enclosed load q to the soil which is equal in value of the structural strength of the compression pstr, is immediately perceived by a matrix. In addition, Darcy's law is broken, i.e. the initial gradient of pressure is considered. The resulting calculation formulas are presented as a combination of Bessel functions of the first and second kinds. Taking into account that currently one can define any values of the Bessel functions, it is possible to calculate the pressure in the pore fluids and predict the speed of sediments of the compacting mass.

Chitosan composite hydrogels reinforced with natural clay nanotubes.

PubMed

Huang, Biao; Liu, Mingxian; Zhou, Changren

2017-11-01

Here, chitosan composites hydrogels were prepared by addition of halloysite nanotubes (HNTs) in the chitosan KOH/LiOH/urea solution. The raw chitosan and chitosan/HNTs composite hydrogels were obtained by heat treatment at 60°C for 8h and then regeneration in ethanol solution. The viscosity of the composite solution is increased with HNTs content. The Fourier transform infrared spectroscopy (FT-IR) shows that the hydrogen bonds interactions exist between the HNTs and the chitosan. X-ray diffraction (XRD) results show that the crystal structure of HNT is not changed in the composite hydrogels. The compressive property test and storage modulus determination show that the mechanical properties and anti-deformation ability of the composite hydrogel significantly increase owing to the reinforcing effect of HNTs. The composites hydrogel with 66.7% HNTs can undergo 7 times compression cycles without breaking with compressive strength of 0.71MPa at 70% deformation, while pure chitosan hydrogel is broken after bearing 5 compression cycles with compressive strength of 0.14MPa and a maximum deformation of 59%. A porous structure with pore size of 100-500μm is found in the composite hydrogels by scanning electron microscopy (SEM), and the pore size and the swelling ratio in NaCl solution decrease by the addition of HNTs and the immersing of ethanol. Chitosan/HNTs composite hydrogels show low cytotoxicity towards MC3T3-E1 cells. Also, the composite hydrogels show a maximum drug entrapment efficiency of 45.7% for doxorubicin (DOX) which is much higher than that of pure chitosan hydrogel (27.5%). All the results illustrate that the chitosan/HNTs composite hydrogels show promising applications as biomaterials. Copyright © 2017 Elsevier Ltd. All rights reserved.

Integrating SANS and fluid-invasion methods to characterize pore structure of typical American shale oil reservoirs.

PubMed

Zhao, Jianhua; Jin, Zhijun; Hu, Qinhong; Jin, Zhenkui; Barber, Troy J; Zhang, Yuxiang; Bleuel, Markus

2017-11-13

An integration of small-angle neutron scattering (SANS), low-pressure N 2 physisorption (LPNP), and mercury injection capillary pressure (MICP) methods was employed to study the pore structure of four oil shale samples from leading Niobrara, Wolfcamp, Bakken, and Utica Formations in USA. Porosity values obtained from SANS are higher than those from two fluid-invasion methods, due to the ability of neutrons to probe pore spaces inaccessible to N 2 and mercury. However, SANS and LPNP methods exhibit a similar pore-size distribution, and both methods (in measuring total pore volume) show different results of porosity and pore-size distribution obtained from the MICP method (quantifying pore throats). Multi-scale (five pore-diameter intervals) inaccessible porosity to N 2 was determined using SANS and LPNP data. Overall, a large value of inaccessible porosity occurs at pore diameters <10 nm, which we attribute to low connectivity of organic matter-hosted and clay-associated pores in these shales. While each method probes a unique aspect of complex pore structure of shale, the discrepancy between pore structure results from different methods is explained with respect to their difference in measurable ranges of pore diameter, pore space, pore type, sample size and associated pore connectivity, as well as theoretical base and interpretation.

46 CFR Table II to Part 150 - Grouping of Cargoes

Code of Federal Regulations, 2013 CFR

2013-10-01

... solutions Clay slurry Corn syrup Dextrose solution 2,4-Dichlorophenoxyacetic acid, Diethanolamine salt...) Caramel solutions Clay slurry Coal slurry Corn syrup Dextrose solution 2,4-Dichlorophenoxyacetic acid... Coal tar, high temperature Coal tar pitch Decahydronaphthalene Degummed C9 (DOW) Diphenyl, Diphenyl...

46 CFR Table II to Part 150 - Grouping of Cargoes

Code of Federal Regulations, 2014 CFR

2014-10-01

... solutions Clay slurry Corn syrup Dextrose solution 2,4-Dichlorophenoxyacetic acid, Diethanolamine salt... lignosulfonate solution (free alkali content 1% or less) Caramel solutions Clay slurry Coal slurry Corn syrup... Coal tar, high temperature Coal tar pitch Decahydronaphthalene Degummed C9 (DOW) Diphenyl, Diphenyl...

Evolution of Micro-Pores in a Single-Crystal Nickel-Based Superalloy During Solution Heat Treatment

NASA Astrophysics Data System (ADS)

Li, Xiangwei; Wang, Li; Dong, Jiasheng; Lou, Langhong; Zhang, Jian

2017-06-01

Evolution of micro-pores in a third-generation single-crystal nickel-based superalloy during solution heat treatment at 1603 K (1330 °C) was investigated by X-ray computed tomography. 3D information including morphology, size, number, and volume fraction of micro-pores formed during solidification (S-pores) and solution (H-pores) was analyzed. The growth behaviors of both S-pores and H-pores can be related to the vacancy formation and diffusion during heat treatment.

Implementation into earthquake sequence simulations of a rate- and state-dependent friction law incorporating pressure solution creep

NASA Astrophysics Data System (ADS)

Noda, H.

2016-05-01

Pressure solution creep (PSC) is an important elementary process in rock friction at high temperatures where solubilities of rock-forming minerals are significantly large. It significantly changes the frictional resistance and enhances time-dependent strengthening. A recent microphysical model for PSC-involved friction of clay-quartz mixtures, which can explain a transition between dilatant and non-dilatant deformation (d-nd transition), was modified here and implemented in dynamic earthquake sequence simulations. The original model resulted in essentially a kind of rate- and state-dependent friction (RSF) law, but assumed a constant friction coefficient for clay resulting in zero instantaneous rate dependency in the dilatant regime. In this study, an instantaneous rate dependency for the clay friction coefficient was introduced, consistent with experiments, resulting in a friction law suitable for earthquake sequence simulations. In addition, a term for time-dependent strengthening due to PSC was added which makes the friction law logarithmically rate-weakening in the dilatant regime. The width of the zone in which clasts overlap or, equivalently, the interface porosity involved in PSC plays a role as the state variable. Such a concrete physical meaning of the state variable is a great advantage in future modelling studies incorporating other physical processes such as hydraulic effects. Earthquake sequence simulations with different pore pressure distributions demonstrated that excess pore pressure at depth causes deeper rupture propagation with smaller slip per event and a shorter recurrence interval. The simulated ruptures were arrested a few kilometres below the point of pre-seismic peak stress at the d-nd transition and did not propagate spontaneously into the region of pre-seismic non-dilatant deformation. PSC weakens the fault against slow deformation and thus such a region cannot produce a dynamic stress drop. Dynamic rupture propagation further down to brittle-plastic transition, evidenced by geological observations, would require even smaller frictional resistance at coseismic slip rate, suggesting the importance of implementation of dynamic weakening activated at coseismic slip rates for more realistic simulation of earthquake sequences. The present models produced much smaller afterslip at deeper parts of arrested ruptures than those with logarithmic RSF laws because of a more significant rate-strengthening effect due to linearly viscous PSC. Detailed investigation of afterslip would give a clue to understand the deformation mechanism which controls shear resistance of the fault in a region of arrest of earthquake ruptures.

Effects of clay dispersion on aquifer storage and recovery in coastal aquifers

USGS Publications Warehouse

Konikow, Leonard F.; August, L.L.; Voss, C.I.

2001-01-01

Cyclic injection, storage, and withdrawal of freshwater in brackish aquifers is a form of aquifer storage and recovery (ASR) that can beneficially supplement water supplies in coastal areas. A 1970s field experiment in Norfolk, Virginia, showed that clay dispersion in the unconsolidated sedimentary aquifer occurred because of cation exchange on clay minerals as freshwater displaced brackish formation water. Migration of interstitial clay particles clogged pores, reduced permeability, and decreased recovery efficiency, but a calcium preflush was found to reduce clay dispersion and lead to a higher recovery efficiency. Column experiments were performed in this study to quantify the relations between permeability changes and clay mineralogy, clay content, and initial water salinity. The results of these experiments indicate that dispersion of montmorillonite clay is a primary contributor to formation damage. The reduction in permeability by clay dispersion may be expressed as a linear function of chloride content. Incorporating these simple functions into a radial, cross-sectional, variable-density, ground-water flow and transport model yielded a satisfactory simulation of the Norfolk field test - and represented an improvement over the model that ignored changes in permeability. This type of model offers a useful planning and design tool for ASR operations in coastal clastic aquifer systems.

46 CFR Table 2 to Part 153 - Cargoes Not Regulated Under Subchapters D or O of This Chapter When Carried in Bulk on Non...

Code of Federal Regulations, 2013 CFR

2013-10-01

...-ethylamino-6-isopropylamino-5-triazine solution # Choline chloride solution D Clay slurry III Coal slurry III... acid, dimethylamine salt solution * Y Choline chloride solutions Z Clay slurry OS Coal slurry OS...

Re-evaluating the oceanic magnesium and magnesium isotope budgets - the contribution of authigenic mineral formation in marine sediments

NASA Astrophysics Data System (ADS)

Berg, R. D.; Solomon, E. A.

2016-12-01

Formation of authigenic minerals in marine sediments is a globally significant geochemical process for several major element cycles in the ocean on the 105-107 year time scale, including the sulfur, potassium, and calcium cycles. However, the significance of these processes to the magnesium (Mg) cycle have not yet been well constrained, and thus are not typically included in global oceanic Mg budgets. Exclusion of this authigenic sink for Mg affects work derived from the existing Mg and Mg isotope budgets in the fields of paleo-oceanography and global geochemical cycling. To robustly constrain the magnitude of this sedimentary Mg sink in continental slope, rise, and abyssal environments, we estimate rates of Mg uptake in marine sediments using reactive-transport modeling of 200 pore water solute concentration profiles measured during scientific ocean drilling expeditions. The depth-integrated rates of Mg uptake are extrapolated globally using statistical machine learning methods, which are particularly well-suited for using with the wide variety of environments represented in the ocean drilling dataset. Due to the differences in Mg isotope fractionation during formation of authigenic clays versus carbonates, the relative proportion of the Mg flux being sequestered by these minerals may have a major effect on the oceanic Mg isotope record. We evaluate the processes controlling Mg uptake (authigenic clay and carbonate formation) at representative continental margin locations using pore water Mg isotope measurements. Results indicate that rates of Mg uptake are over an order of magnitude higher in continental margin settings than in the abyssal environment, likely due to greater organic matter degradation resulting in higher rates of carbonate formation and in situ weathering of primary silicates to authigenic clays. Preliminary results show that authigenic mineral formation in marine sediments is a major sink for Mg in the ocean, rivaling the ridge-crest hydrothermal sink. The quantification of this Mg sink and associated Mg isotope fractionation provides more accurate constraints on the modern global Mg budget, and provides a benchmark for models and interpretations of the paleooceanographic Mg isotope record.

Preparation and characterization of chitosan-clay nanocomposites for the removal of Cu(II) from aqueous solution.

PubMed

Azzam, Eid M S; Eshaq, Gh; Rabie, A M; Bakr, A A; Abd-Elaal, Ali A; El Metwally, A E; Tawfik, Salah M

2016-08-01

In the present study, chitosan assembled on gold and silver nanoparticles were prepared and characterized by UV-vis, TEM, EDX and DLS techniques. The nanocomposites chitosan (Ch)/clay, chitosan (Ch)/AgNPs/clay and chitosan (Ch)/AuNPs/clay were prepared by solution mixing method and characterized by FTIR, XRD, and SEM techniques. The adsorption of copper(II) ions onto the prepared hybrid composites from an aqueous solution using batch adsorption was examined. The results showed that benefiting from the surface property of clay, the abundant amino and hydroxyl functional groups of chitosan, the adsorbent provides adequate and versatile adsorption for the Cu(II) ions under investigation. The batch adsorption experiments showed that the adsorption of the Cu(II) is considerably dependent on pH of milieu, the amount of adsorbent, and contact time. Batch adsorption studies revealed that the adsorption capacity of Cu(II) increased with increase in initial concentration and contact time with optimum pH in the range around neutral. The maximum uptake of Cu(II) ions by (Ch)/AgNPs/clay composite was found to be 181.5mg/g. The adsorption efficiency of Cu(II) ions by prepared (Ch)/AgNPs/clay and (Ch)/AuNPs/clay is bigger than that the individual chitosan (Ch)/clay composite which clarifies the role of metal nanoparticles in enhancement the adsorption characters. The study suggests that the (Ch)/AgNPs/clay hybrid composite is a promising nano-adsorbent for the removal of Cu(II) ions from aqueous solution. Copyright © 2016 Elsevier B.V. All rights reserved.

Xiphinema americanum as Affected by Soil Organic Matter and Porosity.

PubMed

Ponchillia, P E

1972-07-01

The effects of four soil types, soil porosity, particle size, and organic matter were tested on survival and migration of Xiphinema americanum. Survival and migration were significantly greater in silt loam than in clay loam and silty clay soils. Nematode numbers were significantly greater in softs planted with soybeans than in fallow softs. Nematode survival was greatest at the higher of two pore space levels in four softs. Migration of X. americanum through soft particle size fractions of 75-150, 150-250, 250-500, 500-700, and 700-1,000 mu was significantly greater in the middle three fractions, with the least occurring in the smallest fraction. Additions of muck to silt loam and loamy sand soils resulted in reductions in survival and migration of the nematode. The fulvic acid fraction of muck, extracted with sodium hydroxide, had a deleterious effect on nematode activity. I conclude that soils with small amounts of air-filled pore space, extremes in pore size, or high organic matter content are deleterious to the migration and survival of X. americanum, and that a naturally occurring toxin affecting this species may be present in native soft organic matter.

U.S. Geological survey program on toxic waste--ground-water contamination; proceedings of the Second technical meeting, Cape Cod, Massachusetts, October 21-25, 1985

USGS Publications Warehouse

Ragone, S.E.

1988-01-01

This study characterizes the clay minerals in sediments associated with a plume of creosote-contaminated groundwater. The plume of contaminated groundwater near Pensacola, FL, is in shallow, permeable, Miocene to Holocene quartz sand and flows southward toward Pensacola Bay. Clay-size fractions were separated from 41 cores, chiefly split-spoon samples at 13 drill sites. The most striking feature of the chemical analyses of the clay fractions from uncontaminated site 2 and contaminated sites 4,5,6, and 7 is the variability of iron oxide (species in some samples as Fe2O3); total iron oxide abundance is lowest (2.5%) in uncontaminated sample 2-40, but is > 4.5% (4.5 to 8.5%) in the remaining assemblages. One feature suggesting interaction between the indigenous clays and the waste plume is the presence of nontronite-rich smectite. Nontronite commonly has been identified as the product of hydrothermal alteration and deep-sea weathering of submarine basalts; it is not a common constituent of Cenozoic Gulf Coast sediments. At the Pensacola site, relatively abundant nontronitic smectite is confined to contaminated sands or associated muds; it is least abundant or absent in sands and muds peripheral to the waste plume. The geochemistry of the waste plume, its substantial dissolved, (chiefly ferrous iron), mildly acidic (pH 5-6), and low redox composition, provides an environment similar to that previously determined for the low-temperature synthesis of nontronite. Data from clay-size fractions confirm conclusions that neoformed pyrite in some grain coatings occurs in an assemblage with excess iron over that required in the pyrite. Continuing studies to evaluate these tentative conclusions include: (1) chemical analysis of clay fractions from remaining sites to further examine the apparent relation between iron content and abundance of nontronitic smectite; (2) clay separation and analysis, and pore fluid extraction (squeezing or ultracentrifugation) and analysis from a continuous core through the mud lens to determine pore fluid composition (presence or absence of waste fluid), and character of associated clay minerals; and (3) clay separation and analysis in both permeable sands and the intervening mud lens that are clearly outside the limits of the waste plume to further document the effects of the plume. (See also W90-00022) (Lantz-PTT)

Pore water colloid properties in argillaceous sedimentary rocks.

PubMed

Degueldre, Claude; Cloet, Veerle

2016-11-01

The focus of this work is to evaluate the colloid nature, concentration and size distribution in the pore water of Opalinus Clay and other sedimentary host rocks identified for a potential radioactive waste repository in Switzerland. Because colloids could not be measured in representative undisturbed porewater of these host rocks, predictive modelling based on data from field and laboratory studies is applied. This approach allowed estimating the nature, concentration and size distributions of the colloids in the pore water of these host rocks. As a result of field campaigns, groundwater colloid concentrations are investigated on the basis of their size distribution quantified experimentally using single particle counting techniques. The colloid properties are estimated considering data gained from analogue hydrogeochemical systems ranging from mylonite features in crystalline fissures to sedimentary formations. The colloid concentrations were analysed as a function of the alkaline and alkaline earth element concentrations. Laboratory batch results on clay colloid generation from compacted pellets in quasi-stagnant water are also reported. Experiments with colloids in batch containers indicate that the size distribution of a colloidal suspension evolves toward a common particle size distribution independently of initial conditions. The final suspension size distribution was found to be a function of the attachment factor of the colloids. Finally, calculations were performed using a novel colloid distribution model based on colloid generation, aggregation and sedimentation rates to predict under in-situ conditions what makes colloid concentrations and size distributions batch- or fracture-size dependent. The data presented so far are compared with the field and laboratory data. The colloid occurrence, stability and mobility have been evaluated for the water of the considered potential host rocks. In the pore water of the considered sedimentary host rocks, the clay colloid concentration is expected to be very low (<1ppb, for 10-100nm) which restricts their relevance for radionuclide transport. Copyright © 2016. Published by Elsevier B.V.

DOE Office of Scientific and Technical Information (OSTI.GOV)

DiStefano, Victoria H.; McFarlane, Joanna; Anovitz, Lawrence M.

This study is an attempt to understand how native organics are distributed with respect to pore size to determine the relationship between hydrocarbon chemistry and pore structure in shales, as the location and accessibility of hydrocarbons is key to understanding and improving the extractability of hydrocarbons in hydraulic fracturing. Selected shale cores from the Eagle Ford and Marcellus formations were subjected to pyrolysis gas chromatography (GC), thermogravimetric analysis, and organic solvent extraction with the resulting effluent analyzed by GC-mass spectrometry (MS). Organics representing the oil and gas fraction (0.1 to 1 wt. %) were observed by GC-MS. For most ofmore » the samples, the amount of native organic extracted directly related to the percentage of clay in the shale. The porosity and pore size distribution (0.95 nm to 1.35 m) in the Eagle Ford and Marcellus shales was measured before and after solvent extraction using small angle neutron scattering (SANS). An unconventional method was used to quantify the background from incoherent scattering as the Porod transformation obscures the Bragg peak from the clay minerals. Furthermore, the change in porosity from SANS is indicative of the extraction or breakdown of higher molecular weight bitumen with high C/H ratios (asphaltenes and resins). This is mostly likely attributed to complete dissolution or migration of asphaltenes and resins. These longer carbon chain lengths, C30-C40, were observed by pyrolysis GC, but either were too heavy to be analyzed in the extracts by GC-MS or were not effectively leached into the organic solvents. Thus, experimental limitations meant that the amount of extractable material could not be directly correlated to the changes in porosity measured by SANS. But, the observable porosity generally increased with solvent extraction. A decrease in porosity after extraction as observed in a shale with high clay content and low maturity was attributed to swelling of pores with solvent uptake or migration of resins and asphaltenes.« less

Extraction of organic compounds from representative shales and the effect on porosity

DOE PAGES

DiStefano, Victoria H.; McFarlane, Joanna; Anovitz, Lawrence M.; ...

2016-09-01

This study is an attempt to understand how native organics are distributed with respect to pore size to determine the relationship between hydrocarbon chemistry and pore structure in shales, as the location and accessibility of hydrocarbons is key to understanding and improving the extractability of hydrocarbons in hydraulic fracturing. Selected shale cores from the Eagle Ford and Marcellus formations were subjected to pyrolysis gas chromatography (GC), thermogravimetric analysis, and organic solvent extraction with the resulting effluent analyzed by GC-mass spectrometry (MS). Organics representing the oil and gas fraction (0.1 to 1 wt. %) were observed by GC-MS. For most ofmore » the samples, the amount of native organic extracted directly related to the percentage of clay in the shale. The porosity and pore size distribution (0.95 nm to 1.35 m) in the Eagle Ford and Marcellus shales was measured before and after solvent extraction using small angle neutron scattering (SANS). An unconventional method was used to quantify the background from incoherent scattering as the Porod transformation obscures the Bragg peak from the clay minerals. Furthermore, the change in porosity from SANS is indicative of the extraction or breakdown of higher molecular weight bitumen with high C/H ratios (asphaltenes and resins). This is mostly likely attributed to complete dissolution or migration of asphaltenes and resins. These longer carbon chain lengths, C30-C40, were observed by pyrolysis GC, but either were too heavy to be analyzed in the extracts by GC-MS or were not effectively leached into the organic solvents. Thus, experimental limitations meant that the amount of extractable material could not be directly correlated to the changes in porosity measured by SANS. But, the observable porosity generally increased with solvent extraction. A decrease in porosity after extraction as observed in a shale with high clay content and low maturity was attributed to swelling of pores with solvent uptake or migration of resins and asphaltenes.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Joseph, Claudia; Mibus, Jens; Trepte, Paul

As a contribution to the safety assessment of nuclear waste repositories, U(VI) diffusion through the potential buffer material MX-80 bentonite was investigated at three clay dry densities over six years. Synthetic MX-80 model pore water was used as background electrolyte. Speciation calculations showed that Ca 2UO 2(CO 3) 3(aq) was the main U(VI) species. The in- and out-diffusion of U(VI) was investigated separately. U(VI) diffused about 3 mm, 1.5 mm, and 1 mm into the clay plug at ρ = 1.3, 1.6, and 1.9 g/cm 3, respectively. No through-diffusion of the U(VI) tracer was observed. However, leaching of natural uraniummore » contained in the clay occurred and uranium was detected in all receiving reservoirs. As expected, the effective and apparent diffusion coefficients, D e and D a, decreased with increasing dry density. The D a values for the out-diffusion of natural U(VI) were in good agreement with previously determined values. Surprisingly, D a values for the in-diffusion of U(VI) were about two orders of magnitude lower than values obtained in short-term in-diffusion experiments reported in the literature. Some potential reasons for this behavior that were evaluated are changes of the U(VI) speciation within the clay (precipitation, reduction) or changes of the clay porosity and pore connectivity with time. By applying Archie's law and the extended Archie's law, it was estimated that a significantly smaller effective porosity must be present for the long-term in-diffusion of U(VI). Finally, the results suggest that long-term studies of key transport phenomena may reveal additional processes that can directly impact long-term repository safety assessments.« less

Long-term diffusion of U(VI) in bentonite: Dependence on density

DOE PAGES

Joseph, Claudia; Mibus, Jens; Trepte, Paul; ...

2016-10-12

As a contribution to the safety assessment of nuclear waste repositories, U(VI) diffusion through the potential buffer material MX-80 bentonite was investigated at three clay dry densities over six years. Synthetic MX-80 model pore water was used as background electrolyte. Speciation calculations showed that Ca 2UO 2(CO 3) 3(aq) was the main U(VI) species. The in- and out-diffusion of U(VI) was investigated separately. U(VI) diffused about 3 mm, 1.5 mm, and 1 mm into the clay plug at ρ = 1.3, 1.6, and 1.9 g/cm 3, respectively. No through-diffusion of the U(VI) tracer was observed. However, leaching of natural uraniummore » contained in the clay occurred and uranium was detected in all receiving reservoirs. As expected, the effective and apparent diffusion coefficients, D e and D a, decreased with increasing dry density. The D a values for the out-diffusion of natural U(VI) were in good agreement with previously determined values. Surprisingly, D a values for the in-diffusion of U(VI) were about two orders of magnitude lower than values obtained in short-term in-diffusion experiments reported in the literature. Some potential reasons for this behavior that were evaluated are changes of the U(VI) speciation within the clay (precipitation, reduction) or changes of the clay porosity and pore connectivity with time. By applying Archie's law and the extended Archie's law, it was estimated that a significantly smaller effective porosity must be present for the long-term in-diffusion of U(VI). Finally, the results suggest that long-term studies of key transport phenomena may reveal additional processes that can directly impact long-term repository safety assessments.« less

Probing Contaminant Transport to and from Clay Surfaces in Organic Solvents and Water Using Solution Calorimetry.

PubMed

Pourmohammadbagher, Amin; Shaw, John M

2015-09-15

Clays, in tailings, are a significant ongoing environmental concern in the mining and oilsands production industries, and clay rehabilitation following contamination poses challenges episodically. Understanding the fundamentals of clay behavior can lead to better environmental impact mitigation strategies. Systematic calorimetric measurements are shown to provide a framework for parsing the synergistic and antagonistic impacts of trace (i.e., parts per million level) components on the surface compositions of clays. The enthalpy of solution of as-received and "contaminated" clays, in as-received and "contaminated" organic solvents and water, at 60 °C and atmospheric pressure, provides important illustrative examples. Clay contamination included pre-saturation of clays with water and organic liquids. Solvent contamination included the addition of trace water to organic solvents and trace organic liquids to water. Enthalpy of solution outcomes are interpreted using a quantitative mass and energy balance modeling framework that isolates terms for solvent and trace contaminant sorption/desorption and surface energy effects. Underlying surface energies are shown to dominate the energetics of the solvent-clay interaction, and organic liquids as solvents or as trace contaminants are shown to displace water from as-received clay surfaces. This approach can be readily extended to include pH, salts, or other effects and is expected to provide mechanistic and quantitative insights underlying the stability of clays in tailings ponds and the behaviors of clays in diverse industrial and natural environments.

Microstructure and permeability of the Whitby Mudstone (UK) as an analogue for the Posidonia shale (NL)

NASA Astrophysics Data System (ADS)

Houben, Maartje; Barnhoorn, Auke; Drury, Martyn; Peach, Colin; Spiers, Christopher

2015-04-01

In order to make gas productivity from a shale economically interesting we should find ways to better connect the in-situ pore network to the natural occurring and mechanical induced fractures in the rock. When trying to improve gas productivity a first aim is to understand gas storage and gas flow potential through the rock by investigating the microstructure and measure the matrix porosity and permeability of the unfractured shales. Using a combination of methods we have characterized the porosity and permeability of the Jet Dogger section of the Whitby Mudstone Formation (UK), which we use as an analogue for the Posidonia Shale (NL). The Posidonia shale is a possible unconventional source for gas in Northern Europe. A combination of Precision Ion Polishing (PIPS) and Scanning Electron Microscopy (SEM) has been used to investigate the microstructure and the pores. Microstructurally the circa 8 meter thick Jet section of the Whitby Mudstone Formation can be subdivided into a fossil rich (>15 %) top half with an organic matter content of 7-10% and a sub-mm laminated (alternating clay-rich, carbonate-rich, not necessarily fossils, layers) lower half were the organic matter content varies from 0.3-16%. In addition, any possible flow in the rock has to go through the fine-grained clay matrix (all grains < 2 μm) due to the fact that all larger grains are completely surround by this matrix. Visible PIPS-SEM porosity (pore diameter > 100 nm) is in the order of 0.5-2.5% and is not connected in 2D. Furthermore, overall more than 40% of the visible porosity is present within the clay matrix (sometimes even up to 80%). Porosity and pore size distributions for pores with smaller diameters (2 < diameter < 100 nm) were determined using Ar and N2 gas adsorption. The adsorption porosity was in the order of 1-5%, were we found 1-2.5% porosity for the top half of the section and 2-5% porosity for the bottom half. Ar gas permeability of the samples was measured on 1-inch diameter cores using Ar-gas-permeametry with a pressure step of 0.2 MPa. The permeability measured was in the order of 2•10-19 - 1•10-17 m2 at a confining pressure of 0.8 MPa. The top half of the section (less porous) showed a slightly lower permeability (2•10-19 -3•10-18 m2) than the lower half of the Jet Dogger section (1•10-18 - 1•10-17m2). The PIPS-SEM porosity is apparently unconnected on the scale used for imaging and any flow through these rocks has to go through the clay matrix. A connected network of nano-scale pores connected to the micro-scale (PIPS-SEM) pores should be present because of the fact that we measured a through flow of gas. Relationships between the permeability and Ar-porosity and permeability and microstructure were, however, not systematic.

Shape matters: pore geometry and orientation influences the strength and stiffness of porous rocks

NASA Astrophysics Data System (ADS)

Griffiths, Luke; Heap, Michael; Xu, Tao; Chen, Chong-Feng; Baud, Patrick

2017-04-01

The geometry of voids in porous rock fall between two end-members: very low aspect ratio (the ratio of the minor to the major semi-axis) microcracks and perfectly spherical pores with an aspect ratio of unity. Although the effect of these end-member geometries on the mechanical behaviour of porous rock has received considerable attention, our understanding of the influence of voids with an intermediate aspect ratio is much less robust. Here we perform two-dimensional numerical simulations (Rock Failure Process Analysis, RFPA2D) to better understand the influence of pore aspect ratio (from 0.2 to 1.0) and the angle between the pore major axis and the applied stress (from 0 to 90°) on the mechanical behaviour of porous rock. Our numerical simulations show that, for a fixed aspect ratio (0.5) the uniaxial compressive strength and Young's modulus of porous rock can be reduced by a factor of 2.4 and 1.3, respectively, as the angle between the major axis of the elliptical pores and the applied stress is rotated from 0 to 90°. This weakening effect is accentuated at higher porosities. The influence of pore aspect ratio (which we vary from 0.2 to 1.0) on strength and Young's modulus depends on the pore angle. At low angles ( 0-10°) an increase in aspect ratio reduces the strength and Young's modulus. At higher angles ( 40-90°), however, strength and Young's modulus increase as aspect ratio is increased. At intermediate angles ( 20-30°), strength and Young's modulus first increase and then decrease as pore aspect ratio approaches unity. We find that the analytical solutions for the stress and Young's modulus at the boundary of a single elliptical pore are in excellent agreement with our numerical simulations. The results of our numerical modelling are also in agreement with recent experimental data for porous basalt, but fail to capture the strength anisotropy observed in experiments on sandstone. The alignment of grains or platy minerals such as clays may play an important role in controlling strength anisotropy in porous sandstones. The modelling presented herein shows that porous rocks containing elliptical pores can display a strength and stiffness anisotropy, with implications for the preservation and destruction of porosity and permeability, as well as the distribution of stress and strain within the Earth's crust.

Effect of Electric Field on Gas Hydrate Nucleation Kinetics: Evidence for the Enhanced Kinetics of Hydrate Nucleation by Negatively Charged Clay Surfaces.

PubMed

Park, Taehyung; Kwon, Tae-Hyuk

2018-03-06

Natural gas hydrates are found widely in oceanic clay-rich sediments, where clay-water interactions have a profound effect on the formation behavior of gas hydrates. However, it remains unclear why and how natural gas hydrates are formed in clay-rich sediments in spite of factors that limit gas hydrate formation, such as small pore size and high salinity. Herein, we show that polarized water molecules on clay surfaces clearly promote gas hydrate nucleation kinetics. When water molecules were polarized with an electric field of 10 4 V/m, gas hydrate nucleation occurred significantly faster with an induction time reduced by 5.8 times. Further, the presence of strongly polarized water layers at the water-gas interface hindered gas uptake and thus hydrate formation, when the electric field was applied prior to gas dissolution. Our findings expand our understanding of the formation habits of naturally occurring gas hydrates in clay-rich sedimentary deposits and provide insights into gas production from natural hydrate deposits.

Bentonite modification with pillarization method using metal stannum

NASA Astrophysics Data System (ADS)

Widjaya, Robert R.; Juwono, Ariadne L.; Rinaldi, Nino

2017-11-01

Clay minerals have received considerable attention in the last years because of their environmental compatibility, low cost, high selectivity, and operational simplicity. Although clays are very useful for many application in the field of catalysis, they have main disadvantage: their lack of pore volume and spesific surface area. Porosity and stability of these materials are improved by pillaring the clay layers with SnCl4, which leads to materials known as pillared clays (PILC). This research aims were to characterize the Bentonite and Sn-Bentonite as catalysts for cracking and oligomerization. The Sn-Bentonite was prepared by pillarization method with a variation in metal ratio of 5 mmol dan 10 mmol.gr-1 of bentonit. The catalyst characterized by X-ray Diffraction, X-ray Fluorescence, Fourier Transform Infra Red, Brunauer Emmett Teller, Thermogravimetric Analysis. The results showed that the Sn-Bentonite catalyst had large basal spacing and good porous structure, and the specific surface areas increased. XRF detected the Sn in the Bentonite and TGA results showed the ability Sn-Bentonite in receiving heat. FTIR test showed two type of acidity, broansted and lewis acid. The characterized results indicated that Sn-Bentonite with metal ratio 5 mmol.gr-1 better than Sn-Bentonite with metal ratio 10 mmol.gr-1, in which there was a significant increase the basal spacings, specific surface area, and pore volume. The TGA results for Sn-Bentonite appeared to be more thermally stable than Bentonite.

Physicochemical of pillared clays prepared by several metal oxides

NASA Astrophysics Data System (ADS)

Rinaldi, Nino; Kristiani, Anis

2017-03-01

Natural clays could be modified by the pillarization method, called as Pillared Clays (PILCs). PILCs have been known as porous materials that can be used for many applications, one of the fields is catalysis. PILCs as two dimensional materials are interesting because their structures and textural properties can be controlled by using a metal oxide as the pillar. Different metal oxide used as the pillar causes different properties results of pillared clays. Usually, natural smectite clays/bentonites are used as a raw material. Therefore, a series of bentonite pillared by metal oxides was prepared through pillarization method. Variation of metals pillared into bentonite are aluminium, chromium, zirconium, and ferro. The physicochemical properties of catalysts were characterized by using X-ray Diffraction (XRD), Thermo Gravimetric Analysis (TGA), Brunauer-Emmett-Teller (BET) and Barret-Joyner-Halenda (BJH) analysis, and Fourier transform infrared spectroscopy (FTIR) measurement. Noteworthy characterization results showed that different metals pillared into bentonite affected physical and chemical properties, i.e. basal spacing, surface area, pore size distribution, thermal stability and acidity.

RADIOACTIVE CONCENTRATOR AND RADIATION SOURCE

DOEpatents

Hatch, L.P.

1959-12-29

A method is presented for forming a permeable ion exchange bed using Montmorillonite clay to absorb and adsorb radioactive ions from liquid radioactive wastes. A paste is formed of clay, water, and a material that fomns with clay a stable aggregate in the presence of water. The mixture is extruded into a volume of water to form clay rods. The rods may then be used to remove radioactive cations from liquid waste solutions. After use, the rods are removed from the solution and heated to a temperature of 750 to 1000 deg C to fix the ratioactive cations in the clay.

Influence of Polymer-Clay Interfacial Interactions on the Ignition Time of Polymer/Clay Nanocomposites

PubMed Central

Zope, Indraneel S.; Yu, Zhong-Zhen

2017-01-01

Metal ions present on smectite clay (montmorillonite) platelets have preferential reactivity towards peroxy/alkoxy groups during polyamide 6 (PA6) thermal decomposition. This changes the decomposition pathway and negatively affects the ignition response of PA6. To restrict these interfacial interactions, high-temperature-resistant polymers such as polyetherimide (PEI) and polyimide (PI) were used to coat clay layers. PEI was deposited on clay by solution-precipitation, whereas PI was deposited through a solution-imidization-precipitation technique before melt blending with PA6. The absence of polymer-clay interfacial interactions has resulted in a similar time-to-ignition of PA6/PEI-clay (133 s) and PA6/PI-clay (139 s) composites as neat PA6 (140 s). On the contrary, PA6 with conventional ammonium-based surfactant modified clay has showed a huge drop in time-to-ignition (81 s), as expected. The experimental evidences provided herein reveal the role of the catalytic activity of clay during the early stages of polymer decomposition. PMID:28800095

Influence of Polymer-Clay Interfacial Interactions on the Ignition Time of Polymer/Clay Nanocomposites.

PubMed

Zope, Indraneel S; Dasari, Aravind; Yu, Zhong-Zhen

2017-08-11

Metal ions present on smectite clay (montmorillonite) platelets have preferential reactivity towards peroxy/alkoxy groups during polyamide 6 (PA6) thermal decomposition. This changes the decomposition pathway and negatively affects the ignition response of PA6. To restrict these interfacial interactions, high-temperature-resistant polymers such as polyetherimide (PEI) and polyimide (PI) were used to coat clay layers. PEI was deposited on clay by solution-precipitation, whereas PI was deposited through a solution-imidization-precipitation technique before melt blending with PA6. The absence of polymer-clay interfacial interactions has resulted in a similar time-to-ignition of PA6/PEI-clay (133 s) and PA6/PI-clay (139 s) composites as neat PA6 (140 s). On the contrary, PA6 with conventional ammonium-based surfactant modified clay has showed a huge drop in time-to-ignition (81 s), as expected. The experimental evidences provided herein reveal the role of the catalytic activity of clay during the early stages of polymer decomposition.

Study into the correlation of dominant pore throat size and SIP relaxation frequency

NASA Astrophysics Data System (ADS)

Kruschwitz, Sabine; Prinz, Carsten; Zimathies, Annett

2016-12-01

There is currently a debate within the SIP community about the characteristic textural length scale controlling relaxation time of consolidated porous media. One idea is that the relaxation time is dominated by the pore throat size distribution or more specifically the modal pore throat size as determined in mercury intrusion capillary pressure tests. Recently new studies on inverting pore size distributions from SIP data were published implying that the relaxation mechanisms and controlling length scale are well understood. In contrast new analytical model studies based on the Marshall-Madden membrane polarization theory suggested that two relaxation processes might compete: the one along the short narrow pore (the throat) with one across the wider pore in case the narrow pores become relatively long. This paper presents a first systematically focused study into the relationship of pore throat sizes and SIP relaxation times. The generality of predicted trends is investigated across a wide range of materials differing considerably in chemical composition, specific surface and pore space characteristics. Three different groups of relaxation behaviors can be clearly distinguished. The different behaviors are related to clay content and type, carbonate content, size of the grains and the wide pores in the samples.

Stochastic modeling of the migration of Cs-137 in the soil considering a power law tailing in space

NASA Astrophysics Data System (ADS)

Oka, Hiroki; Hatano, Yuko

2016-04-01

We develop a theoretical model to reproduce the measured data of Cs-137 in the soil due to the Fukushima Daiichi NPP accident. In our past study, we derived the analytic solution under the generalized Robin boundary condition (Oka-Yamamoto solution). This is a generalization of the He-Walling solution (1996). We compared our solution with the Fukushima soil data of for 3 years after the accident and found that the concentration of Cs-137 has a discrepancy from our solution, specifically in a deep part because the depth profiles have a power law tailing. Therefore, we improved our model in the following aspect. When Cs particle (or Cs solution) migrate in the soil, the diffusion coefficient should be the results of many processes in the soil. These processes include the effect of various materials which constitute the soil (clay, litter, sand), or the variations of pore size in the soil. Hence we regard the diffusion coefficient as the stochastic variable, we derive the model. Specifically, we consider the solution of ADE to be the conditional probability C(x,t|D) in terms of the diffusion coefficient D and calculate C(x,t)=∫_(0~∞) C(x,t|D)*f(D)*dD, where f(D) is the probability density function of D. This model has a power law tailing in space like the space-fractional ADE.

Leaching of Conductive Species: Implications to Measurements of Electrical Resistivity

PubMed Central

Spragg, R; Jones, S; Bu, Y; Lu, Y; Bentz, D; Snyder, K; Weiss, J

2017-01-01

Electrical tests have been used to characterize the microstructure of porous materials, the measured electrical response being determined by the contribution of the microstructure (porosity and tortuosity) and the electrical properties of the solution (conductivity of the pore solution) inside the pores of the material. This study has shown how differences in concentration between the pore solution (i.e., the solution in the pores) and the storage solution surrounding the test specimen leads to significant transport (leaching) of the conductive ionic species between the pore solution and the storage solution. Leaching influences the resistivity of the pore solution, thereby influencing electrical measurements on the bulk material from either a surface or uniaxial bulk resistance test. This paper has three main conclusions: 1.) Leaching of conductive species does occur with concentration gradients and that a diffusion based approach can be used to estimate the time scale associated with this change. 2.) Leaching of ions in the pore solution can influence resistivity measurements, and the ratio of surface to uniaxial resistivity can be used as a method to assess the presence of leaching and 3.) An estimation of the magnitude of leaching for standardized tests of cementitious materials. PMID:28584407

Leaching of Conductive Species: Implications to Measurements of Electrical Resistivity.

PubMed

Spragg, R; Jones, S; Bu, Y; Lu, Y; Bentz, D; Snyder, K; Weiss, J

2017-05-01

Electrical tests have been used to characterize the microstructure of porous materials, the measured electrical response being determined by the contribution of the microstructure (porosity and tortuosity) and the electrical properties of the solution (conductivity of the pore solution) inside the pores of the material. This study has shown how differences in concentration between the pore solution (i.e., the solution in the pores) and the storage solution surrounding the test specimen leads to significant transport (leaching) of the conductive ionic species between the pore solution and the storage solution. Leaching influences the resistivity of the pore solution, thereby influencing electrical measurements on the bulk material from either a surface or uniaxial bulk resistance test. This paper has three main conclusions: 1.) Leaching of conductive species does occur with concentration gradients and that a diffusion based approach can be used to estimate the time scale associated with this change. 2.) Leaching of ions in the pore solution can influence resistivity measurements, and the ratio of surface to uniaxial resistivity can be used as a method to assess the presence of leaching and 3.) An estimation of the magnitude of leaching for standardized tests of cementitious materials.

Clay mineral formation and transformation in rocks and soils

USGS Publications Warehouse

Eberl, D.D.

1983-01-01

Three mechanisms for clay mineral formation (inheritance, neoformation, and transformation) operating in three geological environments (weathering, sedimentary, and diagenetic-hydrothermal) yield nine possibilities for the origin of clay minerals in nature. Several of these possibilities are discussed in terms of the rock cycle. The mineralogy of clays neoformed in the weathering environment is a function of solution chemistry, with the most dilute solutions favoring formation of the least soluble clays. After erosion and transportation, these clays may be deposited on the ocean floor in a lateral sequence that depends on floccule size. Clays undergo little reaction in the ocean, except for ion exchange and the neoformation of smectite; therefore, most clays found on the ocean floor are inherited from adjacent continents. Upon burial and heating, however, dioctahedral smectite reacts in the diagenetic environment to yield mixed-layer illite-smectite, and finally illite. With uplift and weathering, the cycle begins again. Refs.

Removal of Cr(VI) from Aqueous Environments Using Micelle-Clay Adsorption

PubMed Central

Qurie, Mohannad; Khamis, Mustafa; Manassra, Adnan; Ayyad, Ibrahim; Nir, Shlomo; Scrano, Laura; Bufo, Sabino A.; Karaman, Rafik

2013-01-01

Removal of Cr(VI) from aqueous solutions under different conditions was investigated using either clay (montmorillonite) or micelle-clay complex, the last obtained by adsorbing critical micelle concentration of octadecyltrimethylammonium ions onto montmorillonite. Batch experiments showed the effects of contact time, adsorbent dosage, and pH on the removal efficiency of Cr(VI) from aqueous solutions. Langmuir adsorption isotherm fitted the experimental data giving significant results. Filtration experiments using columns filled with micelle-clay complex mixed with sand were performed to assess Cr(VI) removal efficiency under continuous flow at different pH values. The micelle-clay complex used in this study was capable of removing Cr(VI) from aqueous solutions without any prior acidification of the sample. Results demonstrated that the removal effectiveness reached nearly 100% when using optimal conditions for both batch and continuous flow techniques. PMID:24222757

Macropore system characteristics controls on non-reactive solute transport at different flow rates

NASA Astrophysics Data System (ADS)

Larsbo, Mats; Koestel, John

2014-05-01

Preferential flow and transport in macroporous soils are important pathways for the leaching of agrochemicals through soils. Preferential solute transport in soil is to a large extent determined by the macropore system characteristics and the water flow conditions. The importance of different characteristics of the macropore system is likely to vary with the flow conditions. The objective of this study was to determine which properties of the macropore system that control the shape of non-reactive tracer solute breakthrough curves at different steady-state flow rates. We sampled five undisturbed columns (20 cm high, 20 cm diameter) from the soil surface of four soils with clay contents between 21 and 50 %. Solute transport experiments were carried out under unsaturated conditions at 2, 4, 6, 8 and 12 mm h-1 flow rates. For each flow rate a pulse of potassium bromide solution was applied at the soil surface and the electrical conductivity was measured with high temporal resolution in the column effluent. We used the 5 % arrival time and the holdback factor to estimate the degree of preferential transport from the resulting breakthrough curves. Unsaturated hydraulic conductivities were measured at the soil surface of the columns using a tension disc infiltrometer. The macropore system was imaged by industrial X-ray computed tomography at a resolution of 125 μm in all directions. Measures of the macropore system characteristics including measures of pore continuity were calculated from these images using the ImageJ software. Results show that the degree of preferential transport is generally increasing with flow rate when larger pores become active in the transport. The degree of preferential flow was correlated to measures of macropore topology. This study show that conclusions drawn from experiments carried out at one flow rate should generally not be extrapolated to other flow rates.

A new challenge: in-situ investigation of the elusive nanostructures in wet halite and clay using BIB/FIB-cryo-SEM methods

NASA Astrophysics Data System (ADS)

Desbois, G.; Urai, J. L.

2009-04-01

Mudrocks and saltrocks form seals for hydrocarbon accumulations, aquitards and chemical barriers. The sealing capacity is controlled either by the rock microstructure or by chemical interactions between minerals and the permeating fluid. A detailed knowledge about the sealing characteristics is of particular interest in Petroleum Sciences. Other fields of interest are the storage of anthropogenic carbon dioxide and radioactive waste in geologic formations. A key factor to the understanding of sealing by mudstones and saltrocks is the study of their porosity. However, Halite and clay are so fluids sensitive that investigation on dried samples required by traditional methods of investigations (metal injection methods [6],[3]; magnetic susceptibility measurement [4]; SEM imaging of broken surfaces [5] and CT scanner computing [7]) are critical for robust interpretation. In one hand, none of these methods is able to directly describe the in-situ porosity at the pore scale and on the other hand, most of these methods require dried samples in which the natural structure of pores could be damaged due to the desiccation, dehydration and dissolution-recrystallisation of the fabric. SEM imaging is certainly the most direct approach to investigate the porosity but it is generally limited by the poor quality of the mechanically prepared surfaces. This problem is solved by the recent development of ion milling tools (FIB: Focussed Ion Beam or BIB: Broad Ion Beam, which allows producing in-situ high quality polished cross-sections suitable for high resolution pores SEM imaging at nano-scale. More over, new and innovative developments of the cryo-SEM approach in the Geosciences allow investigating samples under wet natural conditions. Thus, we are developing the combination of FIB/BIB-cryo-SEM methods ([1],[2]), which combine in one machine the vitrification of the pore fluids by very rapid cooling, the excavation of the sample by ion milling tool and SEM imaging. By these, we are able to stabilize the in-situ fluids in grain boundaries or pores, preserve the natural structures at nano scale, produce high quality polished cross-sections for high resolution SEM imaging and reconstruct accurately the grain boundary and the pore space networks in 3D by serial cross sectioning. Our first investigations on wet halite and wet clay materials produced unprecedented high quality images of fully preserved fluid-filled pore space as appear in nature. We have thus validated the use of the FIB/BIB-cryo-SEM technology for the in-situ investigations of the elusive structures in wet geomaterials paving the way towards a fuller understanding of how pore geometry can affect physical properties of rocks. [1] Desbois G. And Urai J.L. (submitted). In-situ morphology of meso-porosity in Boom clay (Mol site, Belgium) inferred by the innovative FIB-cryo-SEM method. E-earth. [2] Desbois G., Urai J.L., Burkhardt C., Drury M., Hayles M. and Humbel B. (2008). Cryogenic vitrification and 3D serial sectioning using high resolution cryo-FIB-SEM technology for brine-filled grain boundaries in halite: first results. Geofluids, 8: 60-72 [3] Esteban L., Géraud Y. And Bouchez J.L. (2006). Pore network geometry in low permeability argillites from magnetic fabric data and oriented mercury injections. Geophysical Research Letters, vol. 33, L18311, doi : 10.1029/2006GL026908. [4] Esteban L., Géraud Y. And Bouchez J.L. (2007). Pore network connectivity anisotropy in Jurassic argillite specimens from eastern Paris Basin (France). Physics and Chemistry of the Earth, 32(1) :161-169. [5] Hildenbrand A., Krooss B. M. and Urai J. L. (2005). Relationship between pore structure and fluid transport in argillaceous rocks. Solid Mechanics and Its Applications, IUTAM Symposium on Physicochemical and Electromechanical Interactions in Porous Media, 125 : 231-237, doi : 10.1007/1-4020-3865-8_26. [6] Hildenbrand A. and Urai J.L. (2003) Investigation of the morphology of pore space in mudstones—first results. Marine and Petroleum Geology, 20(10):1185-1200. [7] H. Taud H., Martinez-Angeles R., Parrot J.F., Hernandez-Escobedo L. (2005). Porosity estimation method by X-ray computed tomography. Journal of Petroleum Science and Engineering, (47), 3-4, 30: 209-217

Fractal Characteristics of Continental Shale Pores and its Significance to the Occurrence of Shale Oil in China: a Case Study of Biyang Depression

NASA Astrophysics Data System (ADS)

Li, Jijun; Liu, Zhao; Li, Junqian; Lu, Shuangfang; Zhang, Tongqian; Zhang, Xinwen; Yu, Zhiyuan; Huang, Kaizhan; Shen, Bojian; Ma, Yan; Liu, Jiewen

Samples from seven major exploration wells in Biyang Depression of Henan Oilfield were compared using low-temperature nitrogen adsorption and shale oil adsorption experiments. Comprehensive analysis of pore development, oiliness and shale oil flowability was conducted by combining fractal dimension. The results show that the fractal dimension of shale in Biyang Depression of Henan Oilfield was negatively correlated with the average pore size and positively correlated with the specific surface area. Compared with the large pore, the small pore has great fractal dimension, indicating the pore structure is more complicated. Using S1 and chloroform bitumen A to evaluate the relationship between shale oiliness and pore structure, it was found that the more heterogeneous the shale pore structure, the higher the complexity and the poorer the oiliness. Clay minerals are the main carriers involved in crude oil adsorption, affecting the mobility of shale oil. When the pore complexity of shale was high, the content of micro- and mesopores was high, and the high specific surface area could enhance the adsorption and reduce the mobility of shale oil.

Intercomparison of 3D pore-scale flow and solute transport simulation methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Xiaofan; Mehmani, Yashar; Perkins, William A.

2016-09-01

Multiple numerical approaches have been developed to simulate porous media fluid flow and solute transport at the pore scale. These include methods that 1) explicitly model the three-dimensional geometry of pore spaces and 2) those that conceptualize the pore space as a topologically consistent set of stylized pore bodies and pore throats. In previous work we validated a model of class 1, based on direct numerical simulation using computational fluid dynamics (CFD) codes, against magnetic resonance velocimetry (MRV) measurements of pore-scale velocities. Here we expand that validation to include additional models of class 1 based on the immersed-boundary method (IMB),more » lattice Boltzmann method (LBM), smoothed particle hydrodynamics (SPH), as well as a model of class 2 (a pore-network model or PNM). The PNM approach used in the current study was recently improved and demonstrated to accurately simulate solute transport in a two-dimensional experiment. While the PNM approach is computationally much less demanding than direct numerical simulation methods, the effect of conceptualizing complex three-dimensional pore geometries on solute transport in the manner of PNMs has not been fully determined. We apply all four approaches (CFD, LBM, SPH and PNM) to simulate pore-scale velocity distributions and nonreactive solute transport, and intercompare the model results with previously reported experimental observations. Experimental observations are limited to measured pore-scale velocities, so solute transport comparisons are made only among the various models. Comparisons are drawn both in terms of macroscopic variables (e.g., permeability, solute breakthrough curves) and microscopic variables (e.g., local velocities and concentrations).« less

PORE SPACE ANALYSIS OF NAPL DISTRIBUTION IN SAND-CLAY MEDIA. (R827120)

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

δ30Si systematics in a granitic saprolite, Puerto Rico

USGS Publications Warehouse

Ziegler, Karen; Chadwick, Oliver A.; White, Arthur F.; Brzezinski, Mark A.

2005-01-01

Granite weathering and clay mineral formation impart distinct and interpretable stable Si isotope (δ30Si) signatures to their solid and aqueous products. Within a saprolite, clay minerals have δ30Si values ∼2.0‰ more negative than their parent mineral and the δ30Si signature of the bulk solid is determined by the ratio of primary to secondary minerals. Mineral-specific weathering reactions predominate at different depths, driving changes in differing δ30Sipore watervalues. At the bedrock-saprolite interface, dissolution of plagioclase and hornblende creates δ30Sipore water signatures more positive than granite by up to 1.2‰; these reactions are the main contributor of Si to stream water and determine its δ30Si value. Throughout the saprolite, biotite weathering releases Si to pore waters but kaolinite overgrowth formation modulates its contribution to pore-water Si. The influence of biotite on δ30Sipore water is greatest near the bedrock where biotite-derived Si mixes with bulk pore water prior to kaolinite formation. Higher in the saprolite, biotite grains have become more isolated by kaolinite overgrowth, which consumes biotite-derived Si that would otherwise influence δ30Sipore water. Because of this isolation, which shifts the dominant source of pore-water Si from biotite to quartz, δ30Sipore water values are more negative than granite by up to 1.3‰ near the top of the saprolite.

Laboratory experiments simulating poroelastic stress changes associated with depletion and injection in low-porosity sedimentary rocks

NASA Astrophysics Data System (ADS)

Ma, Xiaodong; Zoback, Mark D.

2017-04-01

We characterized the poroelastic deformation of six cores from three formations associated with the Bakken play in the Williston Basin (the Lodgepole, Middle Bakken, and Three Forks formations). All are low-porosity, low-permeability formations, but vary considerably in clay, kerogen, and carbonate content. The experimental program simulated reservoir stress changes associated with depletion and injection via cycling both the confining pressure (Pc) and pore pressure (Pp). We measured volumetric strain, derived the corresponding bulk modulus, and calculated the Biot coefficient (α). We found α, which generally ranges between 0.3 and 0.9, to vary systematically with Pc and Pp for each of the specimens tested. The effect of pore pressure on α is much larger at low simple effective stress (σ = Pc-Pp) during depletion than injection. The α decreases with σ for all pore pressures. For the same Pc and Pp, the Biot coefficient is consistently higher during injection than during depletion. Given the observed variations of α with Pc and Pp, the modeling of reservoir stress changes using a constant α could be problematic as poroelastic stress changes during depletion and injection are not likely to follow the same path. Scanning electron microscope examination of microstructures suggests that the variations of the bulk modulus and the Biot coefficient can be attributed to the abundance of compliant components (pores, microcracks, clays, and organic matter) and how they are distributed throughout the rock matrix.

Macro-scale deformation behavior and characterization of deformation mechanisms below µm-scale in experimentally deformed Boom Clay by using the combination of triaxial compression, X-ray µ-CT imaging, DIC, BIB cross sectioning, and SEM

NASA Astrophysics Data System (ADS)

Oelker, Anne; Desbois, Guillaume; Urai, Janos L.; Bésuelle, Pierre; Viggiani, Gioacchino; Levasseur, Séverine

2017-04-01

Boom Clay is one formation being studied in Belgium as a potential host rock for deep geological disposal of radioactive waste. This poorly indurated clay presents in its natural state favorable properties against the migration of radionuclides: low permeability, low solute diffusion rates, good retention and sorption capacity for many radionuclides and good self-sealing capacity. During construction of disposal galleries, stress redistribution will lead to perturbation of the clay and the formation around galleries of the so-called "Excavation disturbed Zone" (EdZ). The study of deformation mechanisms and evolution of Boom Clay properties at macro but also micro scale allows to assess in a more mechanistic way the evolution of Boom Clay properties in this EdZ. In this work, we show microstructural investigations of Boom Clay deformed in undrained triaxial compression by linking conventional stress/strain curves with Digital Image Correlation (DIC) and scanning electron microscopy (SEM) imaging of broad-ion-beam (BIB) milled cross-sections to deduce deformation mechanisms based on microstructures at sub-micron resolution. Two specimens, collected in Mol (Belgium) at the European Underground Laboratories (URL) on HADES level, were analyzed: The major principal stress σ1 was applied parallel as well as perpendicular to the bedding direction with an initial mean normal effective stress of 4.5 MPa and an initial pore water pressure of 2.3 MPa, which are equal to the in-situ values. Linking the resulting DIC-derived maps of incremental strains with the corresponding stress/strain curve give not only information about the moment of the shear band development, but also on the way strain evolves within the specimen throughout the rest. Incremental DIC analysis of X-ray tomographic scans performed during loading tests give a time evolution of the strain field, and subsequently allow to detect strain localization which appears close to the stress peak. Regions with a comparable high and low shear strain were chosen and prepared for BIB-SEM investigations. In this case, shear bands show typical characteristics of uncemented small-grained clay-rich materials deformed at high shear strains including anastomosing shears. At nano-scale, the preferential orientation of clay particles in the anastomosing shears are construed to be responsible for the shear weakness. In addition, the reorientation of clay particles during the deformation leads to the strong reduction of porosity in the shear band. Ductile deformation mechanisms represented by grain-rotation, grain-sliding, bending, and granular flow are strongly involved for the development of the shear band.

Influence of Clay Content, Mineralogy and Fabric On Radar Frequency Response of Aquifer Materials

NASA Astrophysics Data System (ADS)

West, L. J.; Handley, K.

High frequency electromagnetic methods such as ground penetrating radar (GPR) and time domain reflectometry (TDR) are widely employed to measure water saturation in the vadose zone and water filled porosity in the saturated zone. However, previous work has shown that radar frequency dielectric properties are strongly influenced by clay as well as by water content. They have also shown that that the dielectric response of clay minerals is strongly frequency dependent, and that even a small proportion of clay such as that present in many sandstone aquifers can have a large effect at typi- cal GPR frequencies (around 100MHz). Hence accurate water content/porosity deter- mination requires clay type and content to be taken into account. Reported here are dielectric measurements on clay-sand mixtures, aimed at investigating the influence of clay mineralogy, particle shape, and the geometrical arrangement of the mixture constituents on GPR and TDR response. Dielectric permittivity (at 50-1000MHz) was measured for mixtures of Ottawa Sand and various clay minerals or clay size quartz rock flour, using a specially constructed dielectric cell. Both homogeneous and layered mixtures were tested. The influence of pore water salinity, clay type, and particle arrangement on the dielectric response is interpreted in terms of dielectric dispersion mechanisms. The appropriateness of var- ious dielectric mixing rules such as the Complex Refractive Index Method (CRIM) for determination of water content or porosity from field GPR and TDR data are dis- cussed.

Fluorescent Lamp Glass Waste Incorporation into Clay Ceramic: A Perfect Solution

NASA Astrophysics Data System (ADS)

Morais, Alline Sardinha Cordeiro; Vieira, Carlos Maurício Fontes; Rodriguez, Rubén Jesus Sanchez; Monteiro, Sergio Neves; Candido, Veronica Scarpini; Ferreira, Carlos Luiz

2016-09-01

The mandatory use of fluorescent lamps as part of a Brazilian energy-saving program generates a huge number of spent fluorescent lamps (SFLs). After operational life, SFLs cannot be disposed as common garbage owing to mercury and lead contamination. Recycling methods separate contaminated glass tubes and promote cleaning for reuse. In this work, glass from decontaminated SFLs was incorporated into clay ceramics, not only as an environmental solution for such glass wastes and clay mining reduction but also due to technical and economical advantages. Up to 30 wt.% of incorporation, a significant improvement in fired ceramic flexural strength and a decrease in water absorption was observed. A prospective analysis showed clay ceramic incorporation as an environmentally correct and technical alternative for recycling the enormous amount of SFLs disposed of in Brazil. This could also be a solution for other world clay ceramic producers, such as US, China and some European countries.

Pore-Water Quality in the Clay-Silt Confining Units of the Lower Miocene Kirkwood Formation and Hypothetical Effects on Water Quality in the Atlantic City 800-Foot Sand, Northeastern Cape May County, New Jersey, 2001

USGS Publications Warehouse

Szabo, Zoltan; Keller, Elizabeth A.; Defawe, Rose M.

2006-01-01

Pore water was extracted from clay-silt core samples collected from a borehole at Ocean View, west of Sea Isle City, in northeastern Cape May County, New Jersey. The borehole intersects the lower Miocene Kirkwood Formation, which includes a thick sand and gravel unit between two clay-silt units. The sand and gravel unit forms a major confined aquifer in the region, known as the Atlantic City 800-foot sand, the major source of potable water along the Atlantic Coast of southern New Jersey. The pore water from the core is of interest because the borehole intersects the aquifer in an area where the ground water is sodium-rich and sulfidic. Locally in the aquifer in central and southern Cape May County, sodium concentrations are near the New Jersey secondary drinking-water standard of 50 mg/L (milligrams per liter), and typically are greater than 30 mg/L, but chloride and sulfate do not approach their respective secondary drinking-water standards except in southernmost Cape May County. Pore waters from the confining units are suspected to be a source of sodium, sulfur, and chloride to the aquifer. Constituent concentrations in filtered pore-water samples were determined using the inductively coupled plasma-mass spectrometry analytical technique to facilitate the determination of low-level concentrations of many trace constituents. Calcium-sodium-sulfate-bicarbonate, calcium-chloride-sulfate, calcium-sulfate, and sodium-sulfate-chloride-bicarbonate type waters characterize samples from the deepest part of the confining unit directly overlying the aquifer (termed the 'lower' confining unit). A sodium-chloride-sulfate type water is dominant in the composite confining unit below the aquifer. Sodium, chloride, and sulfate became increasingly dominant with depth. Pore water from the deepest sample recovered (1,390 ft (feet) below land surface) was brackish, with concentrations of sodium, chloride, and sulfate of 5,930, 8,400, and 5,070 mg/L, respectively. Pore-water samples from 900 ft or less below land surface, although mineralized, were fresh, not brackish. Sodium concentrations ranged from 51.3 to 513 mg/L, with the maximum concentration found at 882 ft below land surface in the composite confining unit below the aquifer. Chloride concentrations ranged from 46.4 to 757 mg/L, with the maximum concentration found at 596 ft below land surface in the 'lower' confining unit, and were higher than those in pore water from the same units at Atlantic City, N.J. Concentrations of chloride in the composite confining unit below the aquifer were consistently greater than 250 mg/L, indicating that the confining unit can be a source of chloride at depth. Of the major anions, sulfate was the constituent whose concentration varied most, ranging from 42 to 799 mg/L. The maximum concentration was found at 406 ft below land surface, in the upper part of the confining unit overlying the aquifer and the Rio Grande water-bearing zone (termed the 'upper' confining unit). Sulfide was not detected in any pore-water sample despite the presence of abundant quantities of sulfate and sulfide in the aquifer. The absence of sulfide in the pore waters is consistent with the hypothesis that sulfate is reduced in the aquifer. The presence of arsenic, at concentrations ranging from 0.0062 to 0.0374 mg/L, is consistent with the absence of sulfide and the possible presence of iron in the pore water.

Effect of confinement in nano-porous materials on the solubility of a supercritical gas

NASA Astrophysics Data System (ADS)

Hu, Yaofeng; Huang, Liangliang; Zhao, Shuangliang; Liu, Honglai; Gubbins, Keith E.

2016-11-01

By combining Gibbs Ensemble Monte Carlo simulations and density functional theory, we investigate the influence of confinement in a slit-shaped carbon pore on the solubility of a supercritical solute gas in a liquid solvent. In the cases studied here, competing adsorption of the solvent and solute determines whether the solubility is enhanced or suppressed for larger pores. We find that the solubility in the confined system is strongly dependent on pore width, and that molecular packing effects are important for small pore widths. In addition, the solubility decreases on increase in the temperature, as for the bulk mixture, but the rate of decrease is greater in the pore due to a decrease in the partial molar enthalpy of the solute in the pore; this effect becomes greater as pore width is decreased. The solubility is increased on increasing the bulk pressure of the gas in equilibrium with the pore, and obeys Henry's law at lower pressures. However, the Henry constant differs significantly from that for the bulk mixture, and the range of pressure over which Henry's law applies is reduced relative to that for the bulk mixture. The latter observation indicates that solute-solute interactions become more important in the pore than for the bulk at a given bulk pressure. Finally, we note that different authors use different definitions of the solubility in pores, leading to some confusion over the reported phenomenon of 'oversolubility'. We recommend that solubility be defined as the overall mole fraction of solute in the pores, since it takes into account the increase in density of the solvent in the pores, and avoids ambiguity in the definition of the pore volume.

Removal of diphenhydramine from water by swelling clay minerals.

PubMed

Li, Zhaohui; Chang, Po-Hsiang; Jiang, Wei-Teh; Jean, Jiin-Shuh; Hong, Hanlie; Liao, Libing

2011-08-01

Frequent detection of pharmaceuticals in surface water and wastewater attracted renewed attention on studying interactions between pharmaceuticals and sludge or biosolids generated from wastewater treatment. Less attention was focused on studying interactions between pharmaceuticals and clay minerals, important soil and sediment components. This research targeted on investigating interactions between diphenhydramine (DPH), an important antihistamine drug, and a montmorillonite, a swelling clay, in aqueous solution. Stoichiometric desorption of exchangeable cations accompanying DPH adsorption confirmed that cation exchange was the most important mechanism of DPH uptake by the swelling clay. When the solution pH was below the pK(a) of DPH, its adsorption on the swelling clay was less affected by pH. Increasing solution pH above the pK(a) value resulted in a decrease in DPH adsorption by the clay. An increase in d(001) spacing at a high DPH loading level suggested interlayer adsorption, thus, intercalation of DPH. The results from this study showed that swelling clays are a good environmental sink for weak acidic drugs like DPH. In addition, the large cation exchange capacity and surface area make the clay a good candidate to remove cationic pharmaceuticals from the effluent of wastewater treatment facilities. Copyright © 2011 Elsevier Inc. All rights reserved.

The influence of pore geometry and orientation on the strength and stiffness of porous rock

NASA Astrophysics Data System (ADS)

Griffiths, Luke; Heap, Michael J.; Xu, Tao; Chen, Chong-feng; Baud, Patrick

2017-03-01

The geometry of voids in porous rock falls between two end-members: very low aspect ratio (the ratio of the minor to the major axis) microcracks and perfectly spherical pores with an aspect ratio of unity. Although the effect of these end-member geometries on the mechanical behaviour of porous rock has received considerable attention, our understanding of the influence of voids with an intermediate aspect ratio is much less robust. Here we perform two-dimensional numerical simulations (Rock Failure Process Analysis, RFPA2D) to better understand the influence of pore aspect ratio (from 0.2 to 1.0) and the angle between the pore major axis and the applied stress (from 0 to 90°) on the mechanical behaviour of porous rock under uniaxial compression. Our numerical simulations show that, for a fixed aspect ratio (0.5) the uniaxial compressive strength and Young's modulus of porous rock can be reduced by a factor of ∼2.4 and ∼1.3, respectively, as the angle between the major axis of the elliptical pores and the applied stress is rotated from 0 to 90°. The influence of pore aspect ratio on strength and Young's modulus depends on the pore angle. At low angles (∼0-10°) an increase in aspect ratio reduces the strength and Young's modulus. At higher angles (∼40-90°), however, strength and Young's modulus increase as aspect ratio is increased. At intermediate angles (∼20-30°), strength and Young's modulus first increase and then decrease as pore aspect ratio approaches unity. These simulations also highlight that the influence of pore angle on compressive strength and Young's modulus decreases as the pore aspect ratio approaches unity. We find that the analytical solution for the stress concentration around a single elliptical pore, and its contribution to elasticity, are in excellent qualitative agreement with our numerical simulations. The results of our numerical modelling are also in agreement with recent experimental data for porous basalt, but fail to capture the strength anisotropy observed in experiments on sandstone. We conclude that the alignment of grains or platy minerals such as clays exerts a greater influence on strength anisotropy in porous sandstones than pore geometry. Finally, we show that the strength anisotropy that arises as a result of preferentially aligned elliptical pores is of a similar magnitude to that generated by bedding in porous sandstones and foliation in low-porosity metamorphic rocks. The modelling presented herein shows that porous rocks containing elliptical pores can display a strength and stiffness anisotropy, with implications for the preservation and destruction of porosity and permeability, as well as the distribution of stress and strain within the Earth's crust.

Measurement of variation in soil solute tracer concentration across a range of effective pore sizes

USGS Publications Warehouse

Harvey, Judson W.

1993-01-01

Solute transport concepts in soil are based on speculation that solutes are distributed nonuniformly within large and small pores. Solute concentrations have not previously been measured across a range of pore sizes and examined in relation to soil hydrological properties. For this study, modified pressure cells were used to measure variation in concentration of a solute tracer across a range of pore sizes. Intact cores were removed from the site of a field tracer experiment, and soil water was eluted from 10 or more discrete classes of pore size. Simultaneous changes in water content and unsaturated hydraulic conductivity were determined on cores using standard pressure cell techniques. Bromide tracer concentration varied by as much as 100% across the range of pore sizes sampled. Immediately following application of the bromide tracer on field plots, bromide was most concentrated in the largest pores; concentrations were lower in pores of progressively smaller sizes. After 27 days, bromide was most dilute in the largest pores and concentrations were higher in the smaller pores. A sharp, threefold decrease in specific water capacity during elution indicated separation of two major pore size classes at a pressure of 47 cm H2O and a corresponding effective pore diameter of 70 μm. Variation in tracer concentration, on the other hand, was spread across the entire range of pore sizes investigated in this study. A two-porosity characterization of the transport domain, based on water retention criteria, only broadly characterized the pattern of variation in tracer concentration across pore size classes during transport through a macroporous soil.

Method of preparation of a CO.sub.2 removal sorbent with high chemical stability during multiple cycles

DOEpatents

Siriwardane, Ranjani V.; Rosencwaig, Shira

2015-07-14

Method for the production of a clay-alkali-amine CO.sub.2 sorbent prepared by integrating a clay substrate, basic alkali salt, and amine liquid. The basic alkali salt is present relative to the clay substrate in a weight ratio of from about 1 part to about 50 parts per 100 parts of the clay substrate. The amine liquid is present relative to a clay-alkali combination in a weight ratio of from about 1 part to about 10 parts per 10 parts of the clay-alkali combination. The clay substrate and basic alkali salt may be combined in a solid-solid heterogeneous mixture and followed by introduction of the amine liquid. Alternatively, an alkaline solution may be blended with the amine solution prior to contacting the clay substrate. The clay-alkali-amine CO.sub.2 sorbent is particularly advantageous for low temperature CO.sub.2 removal cycles in a gas stream having a CO.sub.2 concentration less than around 2000 ppm and an oxygen concentration around 21%, such as air. Results are presented illustrating the performance of the clay-alkali-amine CO.sub.2 sorbent compared to a clay-amine sorbent lacking the alkali inclusion.

Effects of waste glass additions on quality of textile sludge-based bricks.

PubMed

Rahman, Ari; Urabe, Takeo; Kishimoto, Naoyuki; Mizuhara, Shinji

2015-01-01

This research investigated the utilization of textile sludge as a substitute for clay in brick production. The addition of textile sludge to a brick specimen enhanced its pores, thus reducing the quality of the product. However, the addition of waste glass to brick production materials improved the quality of the brick in terms of both compressive strength and water absorption. Maximum compressive strength was observed with the following composition of waste materials: 30% textile sludge, 60% clay and 10% waste glass. The melting of waste glass clogged up pores on the brick, which improved water absorption performance and compressive strength. Moreover, a leaching test on a sludge-based brick to which 10% waste glass did not detect significant heavy metal compounds in leachates, with the product being in conformance with standard regulations. The recycling of textile sludge for brick production, when combined with waste glass additions, may thus be promising in terms of both product quality and environmental aspects.

Influences of composted hazelnut husk on some physical properties of soils.

PubMed

Zeytin, Serhat; Baran, Abdullah

2003-07-01

Some physical properties of clay loam and sandy loam soils amended with hazelnut husk (HH) were investigated. HH collected from hazelnut trees were dried, ground and composted for four months. Before use the composted material obtained was separated to three different aggregate sizes, smaller than 0.84 mm, 0.84-2.38 mm and bigger than 2.38 mm. Then these fractions were mixed with soil samples, at 0%, 1%, 2%, 4% and 8% by weight. Huzelnut husk compost-soil mixtures were placed to plastic pots and kept in an incubator at 25+/-5 degrees C for 45 and 90 days. At the end of incubation periods, water stable aggregate (WSA), hydraulic conductivity, total porosity, aeration porosity and macro- and micro-pore percentages of the mixtures were determined. Results obtained showed that composted HH increased the WSA, hydraulic conductivity, total porosity and macro-pore percentage in both clay loam and sandy loam soils depending on the incubation time and aggregate sizes.

Solute mixing regulates heterogeneity of mineral precipitation in porous media: Effect of Solute Mixing on Precipitation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cil, Mehmet B.; Xie, Minwei; Packman, Aaron I.

Synchrotron X-ray microtomography was used to track the spatiotemporal evolution of mineral precipitation and the consequent alteration of the pore structure. Column experiments were conducted by injecting CaCl2 and NaHCO3 solutions into granular porous media either as a premixed supersaturated solution (external mixing) or as separate solutions that mixed within the specimen (internal mixing). The two mixing modes produced distinct mineral growth patterns. While internal mixing promoted transverse heterogeneity with precipitation at the mixing zone, external mixing favored relatively homogeneous precipitation along the flow direction. The impact of precipitation on pore water flow and permeability was assessed via 3-D flowmore » simulations, which indicated anisotropic permeability evolution for both mixing modes. Under both mixing modes, precipitation decreased the median pore size and increased the skewness of the pore size distribution. Such similar pore-scale evolution patterns suggest that the clogging of individual pores depends primarily on local supersaturation state and pore geometry.« less

One-dimensional pore pressure diffusion of different grain-fluid mixtures

NASA Astrophysics Data System (ADS)

von der Thannen, Magdalena; Kaitna, Roland

2015-04-01

During the release and the flow of fully saturated debris, non-hydrostatic fluid pressure can build up and probably dissipate during the event. This excess fluid pressure has a strong influence on the flow and deposition behaviour of debris flows. Therefore, we investigate the influence of mixture composition on the dissipation of non-hydrostatic fluid pressures. For this we use a cylindrical pipe of acrylic glass with installed pore water pressure sensors in different heights and measure the evolution of the pore water pressure over time. Several mixtures with variable content of fine sediment (silt and clay) and variable content of coarse sediment (with fixed relative fractions of grains between 2 and 32 mm) are tested. For the fines two types of clay (smectite and kaolinite) and loam (Stoober Lehm) are used. The analysis is based on the one-dimensional consolidation theory which uses a diffusion coefficient D to model the decay of excess fluid pressure over time. Starting from artificially induced super-hydrostatic fluid pressures, we find dissipation coefficients ranging from 10-5 m²/s for liquid mixtures to 10-8 m²/s for viscous mixtures. The results for kaolinite and smectite are quite similar. For our limited number of mixtures the effect of fines content is more pronounced than the effect of different amounts of coarse particles.

Critical parameters in the production of ceramic pot filters for household water treatment in developing countries.

PubMed

Soppe, A I A; Heijman, S G J; Gensburger, I; Shantz, A; van Halem, D; Kroesbergen, J; Wubbels, G H; Smeets, P W M H

2015-06-01

The need to improve the access to safe water is generally recognized for the benefit of public health in developing countries. This study's objective was to identify critical parameters which are essential for improving the performance of ceramic pot filters (CPFs) as a point-of-use water treatment system. Defining critical production parameters was also relevant to confirm that CPFs with high-flow rates may have the same disinfection capacity as pots with normal flow rates. A pilot unit was built in Cambodia to produce CPFs under controlled and constant conditions. Pots were manufactured from a mixture of clay, laterite and rice husk in a small-scale, gas-fired, temperature-controlled kiln and tested for flow rate, removal efficiency of bacteria and material strength. Flow rate can be increased by increasing pore sizes and by increasing porosity. Pore sizes were increased by using larger rice husk particles and porosity was increased with larger proportions of rice husk in the clay mixture. The main conclusions: larger pore size decreases the removal efficiency of bacteria; higher porosity does not affect the removal efficiency of bacteria, but does influence the strength of pots; flow rates of CPFs can be raised to 10-20 L/hour without a significant decrease in bacterial removal efficiency.

A minimalistic microbial food web in an excavated deep subsurface clay rock.

PubMed

Bagnoud, Alexandre; de Bruijn, Ino; Andersson, Anders F; Diomidis, Nikitas; Leupin, Olivier X; Schwyn, Bernhard; Bernier-Latmani, Rizlan

2016-01-01

Clay rocks are being considered for radioactive waste disposal, but relatively little is known about the impact of microbes on the long-term safety of geological repositories. Thus, a more complete understanding of microbial community structure and function in these environments would provide further detail for the evaluation of the safety of geological disposal of radioactive waste in clay rocks. It would also provide a unique glimpse into a poorly studied deep subsurface microbial ecosystem. Previous studies concluded that microorganisms were present in pristine Opalinus Clay, but inactive. In this work, we describe the microbial community and assess the metabolic activities taking place within borehole water. Metagenomic sequencing and genome-binning of a porewater sample containing suspended clay particles revealed a remarkably simple heterotrophic microbial community, fueled by sedimentary organic carbon, mainly composed of two organisms: a Pseudomonas sp. fermenting bacterium growing on organic macromolecules and releasing organic acids and H2, and a sulfate-reducing Peptococcaceae able to oxidize organic molecules to CO(2). In Opalinus Clay, this microbial system likely thrives where pore space allows it. In a repository, this may occur where the clay rock has been locally damaged by excavation or in engineered backfills. © FEMS 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Preparation of surface-functionalized porous clay heterostructures via carbonization of soft-template and their adsorption performance for toluene

NASA Astrophysics Data System (ADS)

Wang, Yuebo; Su, Xiaoli; Xu, Zhen; Wen, Ke; Zhang, Ping; Zhu, Jianxi; He, Hongping

2016-02-01

A new type of surface-functionalized porous clay heterostructures (SF-PCH) was synthesized via carbonization of the template agents with sulfuric acid. The converted carbons deposited on the porous surface of the SF-PCH samples and changed their surface chemical properties. The composites possessed a maximum carbon content of 5.35%, a large specific surface area of 428 m2/g and micropore volume of approximately 0.2 cm3/g. The layered and porous structure of SF-PCH was retained after carbonization and calcination when sulfuric acid solution with a mild concentration was used. Analysis by XPS confirmed that the carbonaceous matter in the pore channels was functionalized with various organic groups, including carbonaceous, nitrogenous, and sulfated groups. Both the surface chemical property and structural characteristic of adsorbents have effects on the adsorption properties of SF-PCH for toluene. The SF-PCH samples exhibited a stronger adsorption affinity to toluene compared with untreated PCH in the low pressure region, which is more valuable in the practical applications. These results demonstrate that carbonization of soft-template is a feasible process for the surface modification of PCH, enabling the resulting composites to become promising candidates for application in toluene emission control.

Chemical and microstructural analyses for heavy metals removal from water media by ceramic membrane filtration.

PubMed

Ali, Asmaa; Ahmed, Abdelkader; Gad, Ali

2017-01-01

This study aims to investigate the ability of low cost ceramic membrane filtration in removing three common heavy metals namely; Pb 2+ , Cu 2+ , and Cd 2+ from water media. The work includes manufacturing ceramic membranes with dimensions of 15 by 15 cm and 2 cm thickness. The membranes were made from low cost materials of local clay mixed with different sawdust percentages of 0.5%, 2.0%, and 5.0%. The used clay was characterized by X-ray diffraction (XRD) and X-ray fluorescence analysis. Aqueous solutions of heavy metals were prepared in the laboratory and filtered through the ceramic membranes. The influence of the main parameters such as pH, initial driving pressure head, and concentration of heavy metals on their removal efficiency by ceramic membranes was investigated. Water samples were collected before and after the filtration process and their heavy metal concentrations were determined by chemical analysis. Moreover, a microstructural analysis using scanning electronic microscope (SEM) was performed on ceramic membranes before and after the filtration process. The chemical analysis results showed high removal efficiency up to 99% for the concerned heavy metals. SEM images approved these results by showing adsorbed metal ions on sides of the internal pores of the ceramic membranes.

Stress fields around two pores in an elastic body: exact quadrature domain solutions.

PubMed

Crowdy, Darren

2015-08-08

Analytical solutions are given for the stress fields, in both compression and far-field shear, in a two-dimensional elastic body containing two interacting non-circular pores. The two complex potentials governing the solutions are found by using a conformal mapping from a pre-image annulus with those potentials expressed in terms of the Schottky-Klein prime function for the annulus. Solutions for a three-parameter family of elastic bodies with two equal symmetric pores are presented and the compressibility of a special family of pore pairs is studied in detail. The methodology extends to two unequal pores. The importance for boundary value problems of plane elasticity of a special class of planar domains known as quadrature domains is also elucidated. This observation provides the route to generalization of the mathematical approach here to finding analytical solutions for the stress fields in bodies containing any finite number of pores.

Effect of ten quaternary ammonium cations on tetrachloromethane sorption to clay from water

USGS Publications Warehouse

Smith, J.A.

1990-01-01

The mineral surface of Wyoming bentonite (clay) was modified by replacing inorganic ions by each of 10 quaternary ammonium compounds, and tetrachloromethane sorption to the modified sorbents from water was studied. Tetrachloromethane sorption from solution to clay modified with tetramethyl-, tetraethyl-, benzyltrimethyl-, or benzyltriethylammonium cations generally is characterized by relatively high solute uptake, isotherm nonlinearity, and competitive sorption (with trichloroethene as the competing sorbate). For these sorbents, the ethyl functional groups yield reduced sorptive capacity relative to methyl groups, whereas the benzyl group appears to have a similar effect on sorbent capacity as the methyl group. Sorption of tetrachloromethane to clay modified with dodecyldimethyl(2-phenoxyethyl)-, dodecyltrimethyl-, tetradecyltrimethyl-, hexadecyltrimethyl-, or benzyldimethylhexadecylammonium bromide is characterized by relatively low solute uptake, isotherm linearity, and noncompetitive sorption. For these sorbents, an increase in the size of the nonpolar functional group(s) causes an increase in the organic carbon normalized sorption coefficient (Koc). No measurable uptake of tetrachloromethane sorption by the unmodified clay or clay modified by ammonium bromide was observed. ?? 1990 American Chemical Society.

Clay-enhanced DNA separation in low-molecular-weight poly(N,N-dimethylacrylamide) solution by capillary electrophoresis.

PubMed

Liang, D; Song, L; Chen, Z; Chu, B

2001-06-01

The effect of the separation medium in capillary electrophoresis consisting of a low-molecular-mass poly(N,N-dimethylacrylamide) (PDMA) solution on the DNA separation by adding a small amount of montmorillonite clay into the polymer matrix is presented. On the separation of the pBR322/HaeIII digest, both the resolution and the efficiency were increased by adding 2.5-5.0 x 10(-5) g/mL clay into the 5% w/v PDMA with a molecular mass of only 100 K. Moreover, there was no increase in the migration time of DNA fragments. Similar results were observed by using a C-terminated pGEM-3Zf(+) sequencing DNA sample in a sequencing buffer. Experimental data also showed that the addition of clay increased the viscosity of the polymer solution. We attribute this effect to the structural change of the polymer matrix caused by the exfoliated clay sheets, whereby the thin clay sheets function like a "dynamic cross-linking plate" for the PDMA chains and effectively increase the apparent molecular mass of PDMA.

Nanometer-Scale Pore Characteristics of Lacustrine Shale, Songliao Basin, NE China

PubMed Central

Wang, Min; Yang, Jinxiu; Wang, Zhiwei; Lu, Shuangfang

2015-01-01

In shale, liquid hydrocarbons are accumulated mainly in nanometer-scale pores or fractures, so the pore types and PSDs (pore size distributions) play a major role in the shale oil occurrence (free or absorbed state), amount of oil, and flow features. The pore types and PSDs of marine shale have been well studied; however, research on lacustrine shale is rare, especially for shale in the oil generation window, although lacustrine shale is deposited widely around the world. To investigate the relationship between nanometer-scale pores and oil occurrence in the lacustrine shale, 10 lacustrine shale core samples from Songliao Basin, NE China were analyzed. Analyses of these samples included geochemical measurements, SEM (scanning electron microscope) observations, low pressure CO2 and N2 adsorption, and high-pressure mercury injection experiments. Analysis results indicate that: (1) Pore types in the lacustrine shale include inter-matrix pores, intergranular pores, organic matter pores, and dissolution pores, and these pores are dominated by mesopores and micropores; (2) There is no apparent correlation between pore volumes and clay content, however, a weak negative correlation is present between total pore volume and carbonate content; (3) Pores in lacustrine shale are well developed when the organic matter maturity (Ro) is >1.0% and the pore volume is positively correlated with the TOC (total organic carbon) content. The statistical results suggest that oil in lacustrine shale mainly occurs in pores with diameters larger than 40 nm. However, more research is needed to determine whether this minimum pore diameter for oil occurrence in lacustrine shale is widely applicable. PMID:26285123

Nanometer-Scale Pore Characteristics of Lacustrine Shale, Songliao Basin, NE China.

PubMed

Wang, Min; Yang, Jinxiu; Wang, Zhiwei; Lu, Shuangfang

2015-01-01

In shale, liquid hydrocarbons are accumulated mainly in nanometer-scale pores or fractures, so the pore types and PSDs (pore size distributions) play a major role in the shale oil occurrence (free or absorbed state), amount of oil, and flow features. The pore types and PSDs of marine shale have been well studied; however, research on lacustrine shale is rare, especially for shale in the oil generation window, although lacustrine shale is deposited widely around the world. To investigate the relationship between nanometer-scale pores and oil occurrence in the lacustrine shale, 10 lacustrine shale core samples from Songliao Basin, NE China were analyzed. Analyses of these samples included geochemical measurements, SEM (scanning electron microscope) observations, low pressure CO2 and N2 adsorption, and high-pressure mercury injection experiments. Analysis results indicate that: (1) Pore types in the lacustrine shale include inter-matrix pores, intergranular pores, organic matter pores, and dissolution pores, and these pores are dominated by mesopores and micropores; (2) There is no apparent correlation between pore volumes and clay content, however, a weak negative correlation is present between total pore volume and carbonate content; (3) Pores in lacustrine shale are well developed when the organic matter maturity (Ro) is >1.0% and the pore volume is positively correlated with the TOC (total organic carbon) content. The statistical results suggest that oil in lacustrine shale mainly occurs in pores with diameters larger than 40 nm. However, more research is needed to determine whether this minimum pore diameter for oil occurrence in lacustrine shale is widely applicable.

Soil-Structural Stability as Affected by Clay Mineralogy, Soil Texture and Polyacrylamide Application

USDA-ARS?s Scientific Manuscript database

Soil-structural stability (expressed in terms of aggregate stability and pore size distribution) depends on (i) soil inherent properties, (ii) extrinsic condition prevailing in the soil that may vary temporally and spatially, and (iii) addition of soil amendments. Different soil management practices...

Modelling of clay diagenesis using a combined approach of crystalchemistry and thermochemistry: a case study in the smectite illitization.

NASA Astrophysics Data System (ADS)

Geloni, Claudio; Previde Massara, Elisabetta; Di Paola, Eleonora; Ortenzi, Andrea; Gherardi, Fabrizio; Blanc, Philippe

2017-04-01

Diagenetic transformations occurring in clayey and arenaceous sediments is investigated in a number of hydrocarbon reservoirs with an integrated approach that combines mineralogical analysis, crystalchemistry, estimation of thermochemical parameters of clay minerals, and geochemical modelling. Because of the extremely variable crystalchemistry of clays, especially in the smectite - illite compositional range, the estimation of thermochemical parameters of site-specific clay-rich rocks is crucial to investigate water-rock equilibria and to predict mineralogical evolutionary patterns at the clay-sandstone interface. The task of estimating the thermochemical properties of clay minerals and predicting diagenetic reactions in natural reservoirs is accomplished through the implementation of an informatized, procedure (IP) that consists of: (i) laboratory analysis of smectite, illite and mixed layers (I/S) for the determination of their textural characteristics and chemical composition; (ii) estimation of the thermodynamic and structural parameters (enthalpy, entropy, and free energy of formation, thermal capacity, molar volume, molar weight) with a MS Excel tool (XLS) specifically developed at the French Bureau of Geological and Mining Researches (BRGM); (iii) usage of the SUPCRT (Johnson et al., 1992) software package (thereinafter, SSP) to derive log K values to be incorporated in thermodynamic databases of the standard geochemical codes; (iv) check of the consistency of the stability domains calculated with these log K values with relevant predominance diagrams; (v) final application of geochemical and reactive transport models to investigate the reactive mechanisms under different thermal conditions (40-150°C). All the simulations consider pore waters having roughly the same chemical composition of reservoir pore waters, and are performed with The Geochemist Workbench (Bethke and Yeakel, 2015), PHREEQC (Parkhurst, 1999) and TOUGHREACT (Xu, 2006). The overall procedure benefits from: (i) (minor) improvements of the I/O structure of the SSP; (ii) the development of a suite of python scripts to automate the steps needed to augment the thermodynamic database by integrating the external information provided by potential users with the XLS tool and the SSP; (iii) the creation of specific outputs to allow for more convenient handling and inspection of computed parameters of the thermodynamic database. A case study focused on non-isothermal smectite-illite transformation is presented to show the capability of our numerical models to account for clay compaction under 1D geometry conditions. This model considers fluid flow driven by the compaction of a clay layer, and chemistry-fluid flow mutual feedback with the underlying sandstone during the advancement of the diagenesis. Due to this complex interaction, as a result of the smectite-illite transformation in the clays, significant quartz cementation affects the sandstone adjacent to the compacting clay.

Using Neutrons to Study Fluid-Rock Interactions in Shales

NASA Astrophysics Data System (ADS)

DiStefano, V. H.; McFarlane, J.; Anovitz, L. M.; Gordon, A.; Hale, R. E.; Hunt, R. D.; Lewis, S. A., Sr.; Littrell, K. C.; Stack, A. G.; Chipera, S.; Perfect, E.; Bilheux, H.; Kolbus, L. M.; Bingham, P. R.

2015-12-01

Recovery of hydrocarbons by hydraulic fracturing depends on complex fluid-rock interactions that we are beginning to understand using neutron imaging and scattering techniques. Organic matter is often thought to comprise the majority of porosity in a shale. In this study, correlations between the type of organic matter embedded in a shale and porosity were investigated experimentally. Selected shale cores from the Eagle Ford and Marcellus formations were subjected to pyrolysis-gas chromatography, Differential Thermal Analysis/Thermogravimetric analysis, and organic solvent extraction with the resulting affluent analyzed by gas chromatography-mass spectrometry. The pore size distribution of the microporosity (~1 nm to 2 µm) in the Eagle Ford shales was measured before and after solvent extraction using small angle neutron scattering. Organics representing mass fractions of between 0.1 to 1 wt.% were removed from the shales and porosity generally increased across the examined microporosity range, particularly at larger pore sizes, approximately 50 nm to 2 μm. This range reflects extraction of accessible organic material, including remaining gas molecules, bitumen, and kerogen derivatives, indicating where the larger amount of organic matter in shale is stored. An increase in porosity at smaller pore sizes, ~1-3 nm, was also present and could be indicative of extraction of organic material stored in the inter-particle spaces of clays. Additionally, a decrease in porosity after extraction for a sample was attributed to swelling of pores with solvent uptake. This occurred in a shale with high clay content and low thermal maturity. The extracted hydrocarbons were primarily paraffinic, although some breakdown of larger aromatic compounds was observed in toluene extractions. The amount of hydrocarbon extracted and an overall increase in porosity appeared to be primarily correlated with the clay percentage in the shale. This study complements fluid transport neutron imaging studies, to explain the physics and chemistry of fluid-rock behavior. Research supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division and the Bredesen Center at the University of Tennessee.

In situ chemical osmosis experiment in the Boom Clay at the Mol underground research laboratory

NASA Astrophysics Data System (ADS)

Garavito, A. M.; De Cannière, P.; Kooi, H.

Studies on the compatibility of Boom Clay with large amounts of nitrate- bearing bituminized radioactive waste have recently raised a particular interest for osmosis-induced effects in this reference formation in Belgium. Indeed, water flow and solute transport may be associated with several types of driving forces, or gradients (chemical, electrical, thermal), in addition to the hydraulic forces, resulting in the so-called coupled flows. Fluid flow caused by driving forces different than hydraulic gradients is referred to as osmosis. Chemical osmosis, the water flow induced by a chemical gradient across a semi-permeable membrane, can generate pressure increase. The question thus arises if there is a risk to create high pore pressures that could damage the near-field of medium-level waste (MLW) galleries, if osmotically driven water flows towards the galleries are produced by the release of large amounts of NaNO 3 (750 t) in the formation. To what extent a low-permeability clay formation such as the Boom Clay acts as an osmotic membrane is thus a key issue to assess the relevance of osmosis phenomena for the disposal of medium-level waste. An in situ osmosis experiment has been conducted at the H ADES underground research laboratory to determine the osmotic efficiency of Boom Clay at the field scale. A recently developed chemical osmosis flow continuum model has been used to design the osmosis experiment, and to interpret the water pressure measurements. Experimental data could be reproduced quite accurately by the model, and the inferred parameter values are consistent with independent determinations for Boom Clay. A rapid water pressure increase (but limited to about a 2 m water column) was observed after 12 h in the filter containing the more saline water. Then, the osmotically induced water pressure slowly decays on several months. So, the experimental results obtained in situ confirm the occurrence of non-hydraulic flow phenomena (chemical osmosis) in a low-permeability plastic formation such as the Boom Clay. The osmotic efficiency of Boom Clay is high under undisturbed chemical conditions ( σ = 0.41 at 0.014 M NaHCO 3), but rapidly decreases when the dissolved salts concentration increases ( σ = 0.07 at 0.14 M NaHCO 3). A semi-permeable membrane behaviour of the Boom Clay (high efficiencies) may be expected for the disposal of nitrate-bearing radioactive waste. However, the presently observed osmotically induced pressure is too low to have a significant mechanical impact on the host rock. Finally, the short duration of the osmosis test performed suggests that the shut-in test method used is effective for osmosis testing.

Effects of preparation methods on the structure and mechanical properties of wet conditioned starch/montmorillonite nanocomposite films.

PubMed

Müller, Péter; Kapin, Éva; Fekete, Erika

2014-11-26

TPS/Na-montmorillonite nanocomposite films were prepared by solution and melt blending. Clay content changed between 0 and 25 wt% based on the amount of dry starch. Structure, tensile properties, and water content of wet conditioned films were determined as a function of clay content. Intercalated structure and VH-type crystallinity of starch were found for all the nanocomposites independently of clay and plasticizer content or preparation method, but at larger than 10 wt% clay content nanocomposites prepared by melt intercalation contained aggregated particles as well. In spite of the incomplete exfoliation clay reinforces TPS considerably. Preparation method has a strong influence on mechanical properties of wet conditioned films. Mechanical properties of the conditioned samples prepared by solution homogenization are much better than those of nanocomposites prepared by melt blending. Water, which was either adsorbed or bonded in the composites in conditioning or solution mixing process, respectively, has different effect on mechanical properties. Copyright © 2014 Elsevier Ltd. All rights reserved.

Role of interlayer hydration in lincomycin sorption by smectite clays.

PubMed

Wang, Cuiping; Ding, Yunjie; Teppen, Brian J; Boyd, Stephen A; Song, Cunyi; Li, Hui

2009-08-15

Lincomycin, an antibiotic widely administered as a veterinary medicine, is frequently detected in water. Little is known about the soil-water distribution of lincomycin despite the fact that this is a major determinant of its environmental fate and potential for exposure. Cation exchange was found to be the primary mechanism responsible for lincomycin sorption by soil clay minerals. This was evidenced by pH-dependent sorption, and competition with inorganic cations for sorptive sites. As solution pH increased, lincomycin sorption decreased. The extent of reduction was consistent with the decrease in cationic lincomycin species in solution. The presence of Ca2+ in solution diminished lincomycin sorption. Clay interlayer hydration status strongly influenced lincomycin adsorption. Smectites with the charge deficit from isomorphic substitution in tetrahedral layers (i.e., saponite) manifest a less hydrated interlayer environment resulting in greater sorption than that by octahedrally substituted clays (i.e., montmorillonite). Strongly hydrated exchangeable cations resulted in a more hydrated clay interlayer environment reducing sorption in the order of Ca- < K- < Cs-smectite. X-ray diffraction revealed that lincomycin was intercalated in smectite clay interlayers. Sorption capacity was limited by clay surface area rather than by cation exchange capacity. Smectite interlayer hydration was shown to be a major, yet previously unrecognized, factor influencing the cation exchange process of lincomycin on aluminosilicate mineral surfaces.

Origins of saline fluids at convergent margins

NASA Astrophysics Data System (ADS)

Martin, Jonathan B.; Kastner, Miriam; Egeberg, Per Kr.

The compositions of pore and venting fluids at convergent margins differ from seawater values, reflecting mixing and diagenesis. Most significantly, the concentration of Cl-, assumed to be a conservative ion, differs from its seawater value. Chloride concentrations could be elevated by four processes, although two, the formation of gas hydrate and ion filtration by clay membranes, are insignificant in forming saline fluids at convergent margins. During the formation of gas hydrate, the resulting Cl--rich fluids, estimated to contain an average excess of ˜140 mM Cl- over seawater value, probably would be flushed from the sediment when the pore fluids vent to seawater. Ion filtration by clay membranes requires compaction pressures typical of >2 km burial depths. Even at these depths, the efficiency of ion filtration will be negligible because (1) fluids will flow through fractures, thereby bypassing clay membranes, (2) concentrations of clay minerals are diluted by other phases, and (3) during burial, smectite converts to illite, which has little capacity for ion filtration. A third process, mixing with subaerially evaporated seawater, elevates Cl- concentrations to 1043 mM in forearc basins along the Peru margin. Evaporation of seawater, however, will be important only in limited geographic regions that are characterized by enclosed basins, arid climates, and permeable sediments. At the New Hebrides and Izu-Bonin margins, Cl- concentrations are elevated to a maximum of 1241 mM. The process responsible for this increase is the alteration of volcanic ash to hydrous clay and zeolite minerals. Mass balance calculations, based on the decrease in δ18O values to -9.5‰ (SMOW), suggest that the Cl- concentrations could increase solely from the formation of smectite in a closed system. The diagenesis of volcanic ash also alters the concentrations of most dissolved species in addition to Cl-. Depending on the volume of this altered fluid, it could influence seawater chemistry when vented from the sediment.

Modification of Lightweight Aggregates' Microstructure by Used Motor Oil Addition.

PubMed

Franus, Małgorzata; Jozefaciuk, Grzegorz; Bandura, Lidia; Lamorski, Krzysztof; Hajnos, Mieczysław; Franus, Wojciech

2016-10-18

An admixture of lightweight aggregate substrates (beidellitic clay containing 10 wt % of natural clinoptilolite or Na-P1 zeolite) with used motor oil (1 wt %-8 wt %) caused marked changes in the aggregates' microstructure, measured by a combination of mercury porosimetry (MIP), microtomography (MT), and scanning electron microscopy. Maximum porosity was produced at low (1%-2%) oil concentrations and it dropped at higher concentrations, opposite to the aggregates' bulk density. Average pore radii, measured by MIP, decreased with an increasing oil concentration, whereas larger (MT) pore sizes tended to increase. Fractal dimension, derived from MIP data, changed similarly to the MIP pore radius, while that derived from MT remained unaltered. Solid phase density, measured by helium pycnometry, initially dropped slightly and then increased with the amount of oil added, which was most probably connected to changes in the formation of extremely small closed pores that were not available for He atoms.

Modification of Lightweight Aggregates’ Microstructure by Used Motor Oil Addition

PubMed Central

Franus, Małgorzata; Jozefaciuk, Grzegorz; Bandura, Lidia; Lamorski, Krzysztof; Hajnos, Mieczysław; Franus, Wojciech

2016-01-01

An admixture of lightweight aggregate substrates (beidellitic clay containing 10 wt % of natural clinoptilolite or Na-P1 zeolite) with used motor oil (1 wt %–8 wt %) caused marked changes in the aggregates’ microstructure, measured by a combination of mercury porosimetry (MIP), microtomography (MT), and scanning electron microscopy. Maximum porosity was produced at low (1%–2%) oil concentrations and it dropped at higher concentrations, opposite to the aggregates’ bulk density. Average pore radii, measured by MIP, decreased with an increasing oil concentration, whereas larger (MT) pore sizes tended to increase. Fractal dimension, derived from MIP data, changed similarly to the MIP pore radius, while that derived from MT remained unaltered. Solid phase density, measured by helium pycnometry, initially dropped slightly and then increased with the amount of oil added, which was most probably connected to changes in the formation of extremely small closed pores that were not available for He atoms. PMID:28773964

Cyclic deformation-induced solute transport in tissue scaffolds with computer designed, interconnected, pore networks: experiments and simulations.

PubMed

Den Buijs, Jorn Op; Dragomir-Daescu, Dan; Ritman, Erik L

2009-08-01

Nutrient supply and waste removal in porous tissue engineering scaffolds decrease from the periphery to the center, leading to limited depth of ingrowth of new tissue into the scaffold. However, as many tissues experience cyclic physiological strains, this may provide a mechanism to enhance solute transport in vivo before vascularization of the scaffold. The hypothesis of this study was that pore cross-sectional geometry and interconnectivity are of major importance for the effectiveness of cyclic deformation-induced solute transport. Transparent elastic polyurethane scaffolds, with computer-programmed design of pore networks in the form of interconnected channels, were fabricated using a 3D printing and injection molding technique. The scaffold pores were loaded with a colored tracer for optical contrast, cyclically compressed with deformations of 10 and 15% of the original undeformed height at 1.0 Hz. Digital imaging was used to quantify the spatial distribution of the tracer concentration within the pores. Numerical simulations of a fluid-structure interaction model of deformation-induced solute transport were compared to the experimental data. The results of experiments and modeling agreed well and showed that pore interconnectivity heavily influences deformation-induced solute transport. Pore cross-sectional geometry appears to be of less relative importance in interconnected pore networks. Validated computer models of solute transport can be used to design optimal scaffold pore geometries that will enhance the convective transport of nutrients inside the scaffold and the removal of waste, thus improving the cell survivability deep inside the scaffold.

A note on the effect of fault gouge composition on the stability of frictional sliding

USGS Publications Warehouse

Summers, R.; Byerlee, J.

1977-01-01

The frictional properties of fault gouge have been studied at confining pressures to 6 kbars. If the gouge is composed of strong materials such as crushed granite or quartz sand, the frictional strength is high, and violent stick-slip occurs at confining pressures above approximately 1.5 kbars. If the gouge is composed of minerals such as illite, kaolinite, chlorite, or antigorite, which have weak bonding forces between the structural layers, the frictional strength is slightly lower, but violent stick-slip still occurs under high confining pressure. The expanding clays, montmorillonite and vermiculite, which have free water between their structural layers, slide stably at confining pressures as high as 6.25 kbars and exhibit low friction. A similar stable behavior with lowered strength is observed in water-saturated quartz sand when the water is confined within the fault zone during deformation. The results of this series of experiments support water being the stabilizing influence when it is either (1) trapped within or between rocks of low permeability and can provide a high pore pressure when the rocks are deformed, or (2) loosely bonded in a mineral structure, as in the hydrated clays, where it can produce a pseudo-pore pressure when the clay is compressed. In both these cases, the effective stress can be reduced and the deformation stabilized. ?? 1977.

Preparation of sorbent pellets with high integrity for sorption of CO.sub.2 from gas streams

DOEpatents

Siriwardane, Ranjani V.

2016-05-10

Method for the production of a CO.sub.2 sorbent prepared by integrating a clay substrate, basic alkali salt, amine liquid, hydraulic binder, and a liquid binder. The basic alkali salt is present relative to the clay substrate in a weight ratio of from about 1 part to about 50 parts per 100 parts of the clay substrate. The amine liquid is present relative to a clay-alkali combination in a weight ratio of from about 1 part to about 10 parts per 10 parts of the clay-alkali combination. The clay substrate and basic alkali salt may be combined in a solid-solid heterogeneous mixture and followed by introduction of the amine liquid. Alternatively, an alkaline solution may be blended with the amine solution prior to contacting the clay substrate. The clay-alkali-amine CO.sub.2 sorbent is particularly advantageous for low temperature CO.sub.2 removal cycles in a gas stream having a CO.sub.2 concentration less than around 2000 ppm and an oxygen concentration around 21%, such as air.

Pre-activation of aerosol particles by ice preserved in pores

NASA Astrophysics Data System (ADS)

Marcolli, Claudia

2017-02-01

Pre-activation denotes the capability of particles or materials to nucleate ice at lower relative humidities or higher temperatures compared to their intrinsic ice nucleation efficiency after having experienced an ice nucleation event or low temperature before. This review presumes that ice preserved in pores is responsible for pre-activation and analyses pre-activation under this presumption. Idealized trajectories of air parcels are used to discuss the pore characteristics needed for ice to persist in pores and to induce macroscopic ice growth out of the pores. The pore width needed to keep pores filled with water decreases with decreasing relative humidity as described by the inverse Kelvin equation. Thus, narrow pores remain filled with ice well below ice saturation. However, the smaller the pore width, the larger the melting and freezing point depressions within the pores. Therefore, pre-activation due to pore ice is constrained by the melting of ice in narrow pores and the sublimation of ice from wide pores imposing restrictions on the temperature and relative humidity range of pre-activation for cylindrical pores. Ice is better protected in ink-bottle-shaped pores with a narrow opening leading to a large cavity. However, whether pre-activation is efficient also depends on the capability of ice to grow macroscopically, i.e. out of the pore. A strong effect of pre-activation is expected for swelling pores, because at low relative humidity (RH) their openings narrow and protect the ice within them against sublimation. At high relative humidities, they open up and the ice can grow to macroscopic size and form an ice crystal. Similarly, ice protected in pockets is perfectly sheltered against sublimation but needs the dissolution of the surrounding matrix to be effective. Pores partially filled with condensable material may also show pre-activation. In this case, complete filling occurs at lower RH than for empty pores and freezing shifts to lower temperatures.Pre-activation experiments confirm that materials susceptible to pre-activation are indeed porous. Pre-activation was observed for clay minerals like illite, kaolinite, and montmorillonite with inherent porosity. The largest effect was observed for the swelling clay mineral montmorillonite. Some materials may acquire porosity, depending on the formation and processing conditions. Particles of CaCO3, meteoritic material, and volcanic ash showed pre-activation for some samples or in some studies but not in other ones. Quartz and silver iodide were not susceptible to pre-activation.Atmospheric relevance of pre-activation by ice preserved in pores may not be generally given but depend on the atmospheric scenario. Lower-level cloud seeding by pre-activated particles released from high-level clouds crucially depends on the ability of pores to retain ice at the relative humidities and temperatures of the air masses they pass through. Porous particles that are recycled in wave clouds may show pre-activation with subsequent ice growth as soon as ice saturation is exceeded after having passed a first cloud event. Volcanic ash particles and meteoritic material likely influence ice cloud formation by pre-activation. Therefore, the possibility of pre-activation should be considered when ice crystal number densities in clouds exceed the number of ice-nucleating particles measured at the cloud forming temperature.

Filtration performance of microporous ceramic supports.

PubMed

Belouatek, Aissa; Ouagued, Abdellah; Belhakem, Mustapha; Addou, Ahmed

2008-04-24

The use of inorganic membranes in pollution treatment is actually limited by the cost of such membranes. Advantages of inorganic membranes are their chemical, thermal and pH properties. The purpose of this work was the development of microporous ceramic materials based on clay for liquid waste processing. The supports or ceramic filters having various compositions were prepared and thermally treated at 1100 degrees C. The results show that, at the temperature studied, porosity varied according to the support composition from 12% for the double-layered (ceramic) support to 47% for the activated carbon- filled support with a mean pore diameter between 0.8 and 1.3 microm, respectively. Volumes of 5 l of distilled water were filtered tangentially for 3 h under an applied pressure of 3.5 and 5.5 bar. The retention of tubular supports prepared was tested with molecules of varying size (Evans blue, NaCl and Sacharose). The study of the liquid filtration and flow through these supports showed that the retention rate depends on support composition and pore diameter, and solute molecular weight. The S1 support (mixture of barbotine and 1% (w/w) activated carbon) gave a flux for distilled water of 68 L/m2 h while the double-layered support resulted in a flux of 8 L/m2 h for the same solution at the pressure of 3.5 bar. At a pressure of 5.5 bar an increase in the distilled water flux through the various supports was observed. It was significant for the S1 support (230 L/m h).

Semianalytical Solutions for Transport in Aquifer and Fractured Clay Matrix System

EPA Science Inventory

A three-dimensional mathematical model that describes transport of contaminant in a horizontal aquifer with simultaneous diffusion into a fractured clay formation is proposed. A group of analytical solutions is derived based on specific initial and boundary conditions as well as ...

MODIFIED REVERSE OSMOSIS SYSTEM FOR TREATMENT OF PRODUCED WATERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

T.M. Whitworth; Liangxiong Li

2002-09-15

This report describes work performed during the second year of the project ''Modified reverse osmosis system for treatment of produced waters.'' We performed two series of reverse osmosis experiments using very thin bentonite clay membranes compacted to differing degrees. The first series of 10 experiments used NaCl solutions with membranes that ranged between 0.041 and 0.064mm in thickness. Our results showed compaction of such ultra-thin clay membranes to be problematic. The thickness of the membranes was exceeded by the dimensional variation in the machined experimental cell and this is believed to have resulted in local bypassing of the membrane withmore » a resultant decrease in solute rejection efficiency. In two of the experiments, permeate flow was varied as a percentage of the total flow to investigate results of changing permeate flow on solute rejection. In one experiment, the permeate flow was varied between 2.4 and 10.3% of the total flow with no change in solute rejection. In another experiment, the permeate flow was varied between 24.6 and 52.5% of the total flow. In this experiment, the solute rejection rate decreased as the permeate occupied greater fractions of the total flow. This suggests a maximum solute rejection efficiency for these clay membranes for a permeate flow of between 10.3 and 24.6% of the total; flow. Solute rejection was found to decrease with increasing salt concentration and ranged between 62.9% and 19.7% for chloride and between 61.5 and 16.8% for sodium. Due to problems with the compaction procedure and potential membrane bypassing, these rejection rates are probably not the upper limit for NaCl rejection by bentonite membranes. The second series of four reverse osmosis experiments was conducted with a 0.057mm-thick bentonite membrane and dilutions of a produced water sample with an original TDS of 196,250 mg/l obtained from a facility near Loco Hill, New Mexico, operated by an independent. These experiments tested the separation efficiency of the bentonite membrane for each of the dilutions. We found that membrane efficiency decreased with increasing solute concentration and with increasing TDS. The rejection of SO{sub 4}{sup 2-} was greater than Cl{sup -}. This may be because the SO{sub 4}{sup 2-} concentration was much lower than the Cl{sup -} concentration in the waters tested. The cation rejection sequence varied with solute concentration and TDS. The solute rejection sequence for multi-component solutions is difficult to predict for synthetic membranes; it may not be simple for clay membranes either. The permeate flows in our experiments were 4.1 to 5.4% of the total flow. This suggests that very thin clay membranes may be useful for some separations. Work on development of a spiral-wound clay membrane module found that it is difficult to maintain compaction of the membrane if the membrane is rolled and then inserted in the outer tube. A different design was tried using a cylindrical clay membrane and this also proved difficult to assemble with adequate membrane compaction. The next step is to form the membrane in place using hydraulic pressure on a thin slurry of clay in either water or a nonpolar organic solvent such as ethanol. Technology transfer efforts included four manuscripts submitted to peer-reviewed journals, two abstracts, and chairing a session on clays as membranes at the Clay Minerals Society annual meeting.« less

Diffusional Transport of Organic Solutes in Subsurface Clay Lenses and Layers

NASA Astrophysics Data System (ADS)

Demond, A. H.; Ayral, D.; Goltz, M. N.

2009-12-01

The storage of organic solvents in clay lenses and layers in the subsurface creates long-term contaminant sources. Because of the low hydraulic conductivities of clay, it is thought that organic movement into clay lenses occurs through the process of diffusion. The ratio of the effective diffusion coefficient in the porous medium and the diffusion coefficient in bulk water is usually given by the tortuosity factor which accounts for the reduced area and the increased path length in the porous medium. However, there is field evidence which suggests that the concentrations in these lenses exceed that which can be accounted for by simple diffusion. There are reports, for example, of tortuosity factors greater than 1.0, which theoretically is not possible. Clays such as montmorillonite or bentonite shrink and swell depending on water content, and similar behavior can occur in the presence of organic solvents. In fact, research has shown that the basal spacing of bentonite can decrease by 50% when permeated with heptane. Such contraction of the clay structure can lead to the formation of cracks and macropores, with a concomitant alteration of the diffusional pathways that solutes follow. Models formulated for diffusional transport in soil are available to calculate the tortuosity factor as a function of water content. In addition, models are available to simulate phenomena in which the diffusion coefficient is concentration dependent. However, calculations of diffusional transport using such models show that they may not adequately reflect the impact of the alteration of the clay structure. However, modeling the transport of organic solutes in clay as a dual-domain system with some minimal advective transport in macropores can yield tortuosity factors greater than 1.0. Thus, it appears the cracking of clay in contact with organic solvents and a resultant advective component to transport of the solute may be an explanation of field observations.

Compositional controls on early diagenetic pathways in fine-grained sedimentary rocks: Implications for predicting unconventional reservoir attributes of mudstones

USGS Publications Warehouse

Keller, Margaret A.; Macquaker, Joe H.S.; Taylor, Kevin G.; Polya, David

2014-01-01

Diagenesis significantly impacts mudstone lithofacies. Processes operating to control diagenetic pathways in mudstones are poorly known compared to analogous processes occurring in other sedimentary rocks. Selected organic-carbon-rich mudstones, from the Kimmeridge Clay and Monterey Formations, have been investigated to determine how varying starting compositions influence diagenesis.The sampled Kimmeridge Clay Formation mudstones are organized into thin homogenous beds, composed mainly of siliciclastic detritus, with some constituents derived from water-column production (e.g., coccoliths, S-depleted type-II kerogen, as much as 52.6% total organic carbon [TOC]) and others from diagenesis (e.g., pyrite, carbonate, and kaolinite). The sampled Monterey Formation mudstones are organized into thin beds that exhibit pelleted wavy lamination, and are predominantly composed of production-derived components including diatoms, coccoliths, and foraminifera, in addition to type-IIS kerogen (as much as 16.5% TOC), and apatite and silica cements.During early burial of the studied Kimmeridge Clay Formation mudstones, the availability of detrital Fe(III) and reactive clay minerals caused carbonate- and silicate-buffering reactions to operate effectively and the pore waters to be Fe(II) rich. These conditions led to pyrite, iron-poor carbonates, and kaolinite cements precipitating, preserved organic carbon being S-depleted, and sweet hydrocarbons being generated. In contrast, during the diagenesis of the sampled Monterey Formation mudstones, sulfide oxidation, coupled with opal dissolution and the reduced availability of both Fe(III) and reactive siliciclastic detritus, meant that the pore waters were poorly buffered and locally acidic. These conditions resulted in local carbonate dissolution, apatite and silica cements precipitation, natural kerogen sulfurization, and sour hydrocarbons generation.Differences in mud composition at deposition significantly influence subsequent diagenesis. These differences impact their source rock attributes and mechanical properties.

Mucilage from seeds of chia (Salvia hispanica L.) used as soil conditioner; effects on the sorption-desorption of four herbicides in three different soils.

PubMed

Di Marsico, A; Scrano, L; Amato, M; Gàmiz, B; Real, M; Cox, L

2018-06-01

The objective of this work was to determine the effect of the mucilage extracted from Chia seeds (Salvia hispanica L.) as soil amendment on soil physical properties and on the sorption-desorption behaviour of four herbicides (MCPA, Diuron, Clomazone and Terbuthylazine) used in cereal crops. Three soils of different texture (sandy-loam, loam and clay-loam) were selected, and mercury intrusion porosimetry and surface area analysis were used to examine changes in the microstructural characteristics caused by the reactions that occur between the mucilage and soil particles. Laboratory studies were conducted to characterise the selected herbicides with regard their sorption on tested soils added or not with the mucilage. Mucilage amendment resulted in a reduction in soil porosity, basically due to a reduction in larger pores (radius>10μm) and an important increase in finer pores (radius<10μm) and in partcles' surface. A higher herbicide sorption in the amended soils was ascertained when compared to unamended soils. The sorption percentage of herbicides in soils treated with mucilage increased in the order; sandy-loam

Intercomparison of 3D pore-scale flow and solute transport simulation methods

DOE PAGES

Mehmani, Yashar; Schoenherr, Martin; Pasquali, Andrea; ...

2015-09-28

Multiple numerical approaches have been developed to simulate porous media fluid flow and solute transport at the pore scale. These include 1) methods that explicitly model the three-dimensional geometry of pore spaces and 2) methods that conceptualize the pore space as a topologically consistent set of stylized pore bodies and pore throats. In previous work we validated a model of the first type, using computational fluid dynamics (CFD) codes employing a standard finite volume method (FVM), against magnetic resonance velocimetry (MRV) measurements of pore-scale velocities. Here we expand that validation to include additional models of the first type based onmore » the lattice Boltzmann method (LBM) and smoothed particle hydrodynamics (SPH), as well as a model of the second type, a pore-network model (PNM). The PNM approach used in the current study was recently improved and demonstrated to accurately simulate solute transport in a two-dimensional experiment. While the PNM approach is computationally much less demanding than direct numerical simulation methods, the effect of conceptualizing complex three-dimensional pore geometries on solute transport in the manner of PNMs has not been fully determined. We apply all four approaches (FVM-based CFD, LBM, SPH and PNM) to simulate pore-scale velocity distributions and (for capable codes) nonreactive solute transport, and intercompare the model results. Comparisons are drawn both in terms of macroscopic variables (e.g., permeability, solute breakthrough curves) and microscopic variables (e.g., local velocities and concentrations). Generally good agreement was achieved among the various approaches, but some differences were observed depending on the model context. The intercomparison work was challenging because of variable capabilities of the codes, and inspired some code enhancements to allow consistent comparison of flow and transport simulations across the full suite of methods. This paper provides support for confidence in a variety of pore-scale modeling methods and motivates further development and application of pore-scale simulation methods.« less

Intercomparison of 3D pore-scale flow and solute transport simulation methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Xiaofan; Mehmani, Yashar; Perkins, William A.

2016-09-01

Multiple numerical approaches have been developed to simulate porous media fluid flow and solute transport at the pore scale. These include 1) methods that explicitly model the three-dimensional geometry of pore spaces and 2) methods that conceptualize the pore space as a topologically consistent set of stylized pore bodies and pore throats. In previous work we validated a model of the first type, using computational fluid dynamics (CFD) codes employing a standard finite volume method (FVM), against magnetic resonance velocimetry (MRV) measurements of pore-scale velocities. Here we expand that validation to include additional models of the first type based onmore » the lattice Boltzmann method (LBM) and smoothed particle hydrodynamics (SPH), as well as a model of the second type, a pore-network model (PNM). The PNM approach used in the current study was recently improved and demonstrated to accurately simulate solute transport in a two-dimensional experiment. While the PNM approach is computationally much less demanding than direct numerical simulation methods, the effect of conceptualizing complex three-dimensional pore geometries on solute transport in the manner of PNMs has not been fully determined. We apply all four approaches (FVM-based CFD, LBM, SPH and PNM) to simulate pore-scale velocity distributions and (for capable codes) nonreactive solute transport, and intercompare the model results. Comparisons are drawn both in terms of macroscopic variables (e.g., permeability, solute breakthrough curves) and microscopic variables (e.g., local velocities and concentrations). Generally good agreement was achieved among the various approaches, but some differences were observed depending on the model context. The intercomparison work was challenging because of variable capabilities of the codes, and inspired some code enhancements to allow consistent comparison of flow and transport simulations across the full suite of methods. This study provides support for confidence in a variety of pore-scale modeling methods and motivates further development and application of pore-scale simulation methods.« less

Geophysical characterization of areas prone to quick-clay landslides using radio-magnetotelluric and seismic methods

NASA Astrophysics Data System (ADS)

Wang, Shunguo; Malehmir, Alireza; Bastani, Mehrdad

2016-05-01

Landslides attributed to quick clays have not only considerable influences on surface geomorphology, they have caused delays in transportation systems, environmental problems and human fatalities, especially in Scandinavia and North America. If the subsurface distributions of quick clays are known, potential damages can be mitigated and the triggers of landslides can better be studied and understood. For this purpose, new radio-magnetotelluric (RMT) and seismic data were acquired in an area near the Göta River in southwest Sweden that contains quick clays and associated landslides. High-resolution data along 4 new lines, in total 3.8 km long, were acquired and merged with earlier acquired data from the site. Velocity and resistivity models derived from first breaks and RMT data were used to delineate subsurface geology, in particular the bedrock surface and coarse-grained materials that overlay the bedrock. The latter often are found underlying quick clays at the site. Comparably high-resistivity and sometimes high-velocity regions within marine clays are attributed to a combination of leached salt from marine clays or potential quick clays and coarse-grained materials. The resistivity and tomographic velocity models suggest a much larger role of the coarse-grained materials at the site than previously thought, but they also suggest two different scenarios for triggering quick-clay landslides at the site. These scenarios are related to the erosion of the riverbank, increased pore-pressure and surface topography when close to the river and human activity when away from the river and where bowl-shaped bedrock surrounds the sediments.

Identification of remagnetization processes in Paleozoic sedimentary rocks of the northeast Rhenish Massif in Germany by K-Ar dating and REE tracing of authigenic illite and Fe oxides

NASA Astrophysics Data System (ADS)

Zwing, A.; Clauer, N.; Liewig, N.; Bachtadse, V.

2009-06-01

This study combines mineralogical, chemical (rare earth elemental (REE)) and isotopic (K-Ar) data of clay minerals as well as chemical compositions (major and REE) of Fe oxide leachates from remagnetized Palaeozoic sedimentary rocks from NE Rhenish Massif in Germany, for which the causes of remagnetization are not yet clear. The dominant carrier of the syntectonic, pervasive Carboniferous magnetization is magnetite. The Middle Devonian clastic rocks record an illitization event at 348 ± 7 Ma probably connected to a major magmatic event in the Mid-German Crystalline Rise, whereas a second illitization episode at 324 ± 3 Ma is coeval to the northward migrating deformation through the Rhenish Massif, being only detected in Upper Devonian and Lower Carboniferous rocks. The age of that younger illitization is not significantly different from that of the remagnetization, which, however, is not restricted to the upper part of the orogenic belt, but affects also the Middle Devonian strata. The REE patterns of the Fe-enriched leachates support two mineralization episodes with varied oxidation-reduction conditions outlined by varied Eu and Ce anomalies. This is not compatible with a unique, pervasive migration of orogenic fluids on a regional scale to explain the remagnetization in the studied region. While clay diagenesis and remagnetization are time-equivalent in Upper Devonian and Lower Carboniferous rocks, they are not so in Middle Devonian rocks. Transformation of smectite into illite cannot, therefore, account for the growth of associated authigenic magnetite, which must have been triggered by a different process. Since remagnetization and deformation ages are similar, the mechanism could relate to local physical conditions such as pressure solution and changing pore fluid pressure due to tectonic stress as well as to chemical conditions such as changing composition of the pore fluids.

Quantitative experimental monitoring of molecular diffusion in clay with positron emission tomography

NASA Astrophysics Data System (ADS)

Kulenkampff, Johannes; Zakhnini, Abdelhamid; Gründig, Marion; Lippmann-Pipke, Johanna

2016-08-01

Clay plays a prominent role as barrier material in the geosphere. The small particle sizes cause extremely small pore sizes and induce low permeability and high sorption capacity. Transport of dissolved species by molecular diffusion, driven only by a concentration gradient, is less sensitive to the pore size. Heterogeneous structures on the centimetre scale could cause heterogeneous effects, like preferential transport zones, which are difficult to assess. Laboratory measurements with diffusion cells yield limited information on heterogeneity, and pore space imaging methods have to consider scale effects. We established positron emission tomography (PET), applying a high-resolution PET scanner as a spatially resolved quantitative method for direct laboratory observation of the molecular diffusion process of a PET tracer on the prominent scale of 1-100 mm. Although PET is rather insensitive to bulk effects, quantification required significant improvements of the image reconstruction procedure with respect to Compton scatter and attenuation. The experiments were conducted with 22Na and 124I over periods of 100 and 25 days, respectively. From the images we derived trustable anisotropic diffusion coefficients and, in addition, we identified indications of preferential transport zones. We thus demonstrated the unique potential of the PET imaging modality for geoscientific process monitoring under conditions where other methods fail, taking advantage of the extremely high detection sensitivity that is typical of radiotracer applications.

A study of clay pore water and sporopollens for characterizing paleoenvironments in the Hebei Plain, Northern China

NASA Astrophysics Data System (ADS)

Niu, Hong; Liang, Xing; Lu, Guoping; Peng, Fei; Jin, Menggui; Gu, Yansheng

2017-08-01

We developed a clay pore water (CPW) isotopic method for tracing paleoenvironments characterized by sporopollens. The thick clayey layers have the advantage of preserving pore water regardless of whether the water is inherent in the clayey layers or not. Therefore, the clayey layers are a suitable target from which paleoenvironmental information can be extracted. Sediment sporopollens as well as CPW deuterium and oxygen isotopes were investigated in drilling cores obtained from a 130-m borehole at a field site in Hengshui in the North China Plain. Our interpretation of δ18O in CPW was consistent with sporopollens climate indices, indicating that CPW was an effective proxy for obtaining paleoenvironmental information. Sporopollens species were abundant in the cores, but the quantity of each species was low. Furthermore, mean annual temperature and precipitation curves were established using a pollen-climatic response surface model. The results indicated two warm-humid periods (5.2-0 m, 22.6-11 m) and one cold-dry period (8.8-6.4 m) in the Holocene as well as two warm-humid periods (90.6-83 m, 110.6-108.2 m) and three cold-dry periods (approximately 40 m, 66.4-56.8 m, approximately 100 m) in the Late Pleistocene. Data derived from the sporopollens and CPW cumulatively elucidate the environmental change in Northern China.

Cyclic Deformation-Induced Solute Transport in Tissue Scaffolds with Computer Designed, Interconnected, Pore Networks: Experiments and Simulations

PubMed Central

Op Den Buijs, Jorn; Dragomir-Daescu, Dan; Ritman, Erik L.

2014-01-01

Nutrient supply and waste removal in porous tissue engineering scaffolds decrease from the periphery to the center, leading to limited depth of ingrowth of new tissue into the scaffold. However, as many tissues experience cyclic physiological strains, this may provide a mechanism to enhance solute transport in vivo before vascularization of the scaffold. The hypothesis of this study was that pore cross-sectional geometry and interconnectivity are of major importance for the effectiveness of cyclic deformation-induced solute transport. Transparent elastic polyurethane scaffolds, with computer-programmed design of pore networks in the form of interconnected channels, were fabricated using a 3D printing and injection molding technique. The scaffold pores were loaded with a colored tracer for optical contrast, cyclically compressed with deformations of 10 and 15% of the original undeformed height at 1.0 Hz. Digital imaging was used to quantify the spatial distribution of the tracer concentration within the pores. Numerical simulations of a fluid–structure interaction model of deformation-induced solute transport were compared to the experimental data. The results of experiments and modeling agreed well and showed that pore interconnectivity heavily influences deformation-induced solute transport. Pore cross-sectional geometry appears to be of less relative importance in interconnected pore networks. Validated computer models of solute transport can be used to design optimal scaffold pore geometries that will enhance the convective transport of nutrients inside the scaffold and the removal of waste, thus improving the cell survivability deep inside the scaffold. PMID:19466547

Thermal conductivity of hydrate-bearing sediments

USGS Publications Warehouse

Cortes, Douglas D.; Martin, Ana I.; Yun, Tae Sup; Francisca, Franco M.; Santamarina, J. Carlos; Ruppel, Carolyn D.

2009-01-01

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

Remagnetization and Cementation of Unconsolidated Sediments in the Mallik 5L-38 Well (Canadian Arctic) by Solute Exclusion During Gas Hydrate Formation

NASA Astrophysics Data System (ADS)

Hamilton, T. S.; Enkin, R. J.; Esteban, L.

2007-05-01

Bulk magnetic properties provide a sensitive measure of sedimentary diagenesis related to the stability and growth of gas hydrates. The deposit at Mallik (Mackenzie Delta, Canadian Arctic) occurs in unconsolidated Tertiary sands, but is absent in interstratified silt layers. A detailed sampling of the JAPEX/JNOC/GSC Mallik 5L-38 core tested the use of magnetic properties for detecting diagenetic changes related to the hydrate. Petrographic studies reveal that the sands are well sorted and clean, with quartz > chert >> muscovite and little fines content. Excepting a few rare bands of indurated dolomite in the midst of the gas hydrate zone, there is little or no cementation in the sands. Detrital magnetite is the dominant magnetic mineral, comprising up to a few percent of the sand grain population. In contrast, the muddier layers have a somewhat different detrital grain composition, richer in lithic (sedimentary and metamorphic) grains, feldspar, and clays. They are extensively diagenetically altered (to as much as 30- 40%) and cemented with carbonates, clays, chlorite and the iron sulphide greigite (the dominant magnetic mineral). The greigite is recognized by its isotropic creamy-white reflectance, cubic to prismatic habit, and characteristic tarnish to faintly bluish bireflectant mackinawite. Habits range from disseminated cubes and colliform masses to inflationary massive sulphide veins and clots. Rare detrital grains of magnetite were observed among the silt grains, but never in a reaction relationship or overgrown. Instead the greigite has nucleated separately, in tensional fractures and granular masses up to 4 mm across. In this particular sediment sequence, being so quartz and chert rich, there is insufficient local source for the introduced cements (calcite, dolomite, greigite, clays, jarosite), so ions must have been introduced by fluid flow. Magnetic studies reveal a bi-modal character related to the lithology (sands versus silts) and their magnetic mineralogy. Silt samples are significantly stronger than sand samples in saturation magnetization and magnetic susceptibility. The silt samples have single-domain to pseudo-single domain coercivity ratios whereas the gas hydrate bearing sands have a more multi-domain nature. Sands with current gas hydrate concentrations > 80% have less magnetic material and single domain characteristics. The source of the greigite, carbonates, and other diagenetic minerals was apparently concentrated solutes excluded from formation waters by the freezing and formation of the water dominated gas hydrate. The hydrates served as a cementing agent for the unconsolidated sediments, allowing them to fracture. Some layers have been so inflated by the introduction carbonate and sulfide cements that they resemble hydrothermal tufa and skarns with floating sand grains. In the silts, the magnetic properties reflect the mixture of primary detrital magnetite and diagenetic greigite in various grain sizes and concentrations. At Mallik, the magnetic properties are sensitive to the diagenetic mineralogy and redox state associated with the transport of methane and pore fluids and the creation of gas hydrates. Hypersaline brines, produced by solute exclusion from pore waters, fractured and inflated less permeable sediments and forced rapid disequilibrium growth of greigite without dissolving primary detrital magnetite grains.

Direct shear characterisation of simulated clay-bearing gouges: a case study from the Pernicana Fault System (Mount Etna, Sicily)

NASA Astrophysics Data System (ADS)

Ougier-Simonin, Audrey; Castagna, Angela; Benson, Philip; Walker, Richard

2017-04-01

Fault stability and shear strength are strongly controlled by the mechanical and frictional properties of the rocks and gouges involved. The Pernicana Fault System (PFS) is a first order bounding fault of the unstable sector of Mount Etna volcano (Italy). The PFS is a mature fault zone and one of the most active amongst the fault systems of the eastern sliding flank, showing transition from seismic in the upper part, to aseismic behaviour in the lower part toward the Ionian Sea. The PFS is expressed intermittently at the surface as a steeply-dipping fault, but the location at depth within the sedimentary basement beneath Etna remains highly debated. The basement is complex, comprising flyschoid formations of mostly carbonate, sandstone and claystone belonging to the Appenninic-Maghrebian Chain (AMC), which lie above foreland carbonate sequences from the Hyblean Plateau (HP) belonging to the African plate. Furthermore, the south-eastern sector of Mount Etna lies on quaternary foredeep deposits of silt and clay. Recent studies have highlighted the presence of water in the system that may play a major role as a triggering mechanism of sliding. In this study, we perform triaxial tests using synthetic gouges in direct shear sliding holders to explore the frictional properties of the main lithology types (namely carbonate, sandstone and clays) identified and collected in the AMC and HP units. Samples of carbonate ( 98% CaCO3) and sandstone ( 98% SiO2) were manually crushed and then milled using a planetary mill, while clays (clay fraction composed by chlorite, smectite, mica, and kaolinite) were worked manually to preserve clay minerals. Powders of carbonate and sandstone were sieved and selected in a range between <180 µm and >63 µm, while natural clay were sieved to <45 µm (fine silt-clay) for the experiments. The holders, specifically designed and built for this project, allow for up to 10 mm of total displacement over a surface of 54 mm width and 98 mm length, and are equipped with pore fluid inserts for experiments in water-saturated conditions. The triaxial cell has a confining pressure capacity of 0-140 MPa and temperature capacity of 20-200°C. Here we present the results of a first set of experiments conducted at a displacement rate of 0.001 mm/s, using gouges prepared to represent the end-members of each lithology, and as mixtures of carbonate and sandstone gouges with 10%-25%-50% clays. Overall, this study aims to determine the control of pore fluids on the frictional properties of simulated gouges for the Etnean basement under representative stress conditions and to inform numerical modelling of the likely development of the PFS at depth.

Connection equation and shaly-sand correction for electrical resistivity

USGS Publications Warehouse

Lee, Myung W.

2011-01-01

Estimating the amount of conductive and nonconductive constituents in the pore space of sediments by using electrical resistivity logs generally loses accuracy where clays are present in the reservoir. Many different methods and clay models have been proposed to account for the conductivity of clay (termed the shaly-sand correction). In this study, the connectivity equation (CE), which is a new approach to model non-Archie rocks, is used to correct for the clay effect and is compared with results using the Waxman and Smits method. The CE presented here requires no parameters other than an adjustable constant, which can be derived from the resistivity of water-saturated sediments. The new approach was applied to estimate water saturation of laboratory data and to estimate gas hydrate saturations at the Mount Elbert well on the Alaska North Slope. Although not as accurate as the Waxman and Smits method to estimate water saturations for the laboratory measurements, gas hydrate saturations estimated at the Mount Elbert well using the proposed CE are comparable to estimates from the Waxman and Smits method. Considering its simplicity, it has high potential to be used to account for the clay effect on electrical resistivity measurement in other systems.

Development of a Design Technology for Ground Support for Tunnels in Soil : Vol. I. Time Dependent Response Due to Consolidation in Clays

DOT National Transportation Integrated Search

1983-02-01

The report presents an investigation of the phenomenon of tunnel related movements, due to consolidation in clayey or silty soils, as a result of dissipation of excess pore pressures induced during construction. A review of field data showing time de...

Reactive Fe(II) layers in deep-sea sediments

NASA Astrophysics Data System (ADS)

König, Iris; Haeckel, Matthias; Drodt, Matthias; Suess, Erwin; Trautwein, Alfred X.

1999-05-01

The percentage of the structural Fe(II) in clay minerals that is readily oxidized to Fe(III) upon contact with atmospheric oxygen was determined across the downcore tan-green color change in Peru Basin sediments. This latent fraction of reactive Fe(II) was only found in the green strata, where it proved to be large enough to constitute a deep reaction layer with respect to the pore water O 2 and NO 3-. Large variations were detected in the proportion of the reactive Fe(II) concentration to the organic matter content along core profiles. Hence, the commonly observed tan-green color change in marine sediments marks the top of a reactive Fe(II) layer, which may represent the major barrier to the movement of oxidation fronts in pelagic subsurface sediments. This is also demonstrated by numerical model simulations. The findings imply that geochemical barriers to pore water oxidation fronts form diagenetically in the sea floor wherever the stage of iron reduction is reached, provided that the sediments contain a significant amount of structural iron in clay minerals.

Relationship between mineralogy and porosity in seals relevant to geologic CO2 Sequestration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Swift, Alexander; Anovitz, Lawrence; Sheets, Julia

2014-01-01

Porosity and permeability are key petrophysical variables that link the thermal, hydrological, geochemical, and geomechanical properties of subsurface formations. The size, shape, distribution, and connectivity of rock pores dictate how fluids migrate into and through micro- and nano-environments, then wet and react with accessible solids. Three representative samples of cap rock from the Eau Claire Formation, the prospective sealing unit that overlies the Mount Simon Sandstone, a potential CO 2 storage formation, were interrogated with an array of complementary methods. neutron scattering, backscattered-electron imaging, energydispersive spectroscopy, and mercury porosimetry. Results are presented that detail variations between lithologic types in totalmore » and connected nano- to microporosity across more than five orders of magnitude. Pore types are identified and then characterized according to presence in each rock type, relative abundance, and surface area of adjacent minerals, pore and pore-throat diameters, and degree of connectivity. We observe a bimodal distribution of porosity as a function of both pore diameter and pore-throat diameter. The contribution of pores at the nano- and microscales to the total and the connected porosity is a distinguishing feature of each lithology observed. Pore:pore-throat ratios at each of these two scales diverge markedly, being almost unity at the nanoscale regime (dominated by illitic clay and micas), and varying by one and a half orders of magnitude at the microscale within a clastic mudstone.« less

The electrochemistry of carbon steel in simulated concrete pore water in boom clay repository environments

NASA Astrophysics Data System (ADS)

MacDonald, D. D.; Saleh, A.; Lee, S. K.; Azizi, O.; Rosas-Camacho, O.; Al-Marzooqi, A.; Taylor, M.

2011-04-01

The prediction of corrosion damage of canisters to experimentally inaccessible times is vitally important in assessing various concepts for the disposal of High Level Nuclear Waste. Such prediction can only be made using deterministic models, whose predictions are constrained by the time-invariant natural laws. In this paper, we describe the measurement of experimental electrochemical data that will allow the prediction of damage to the carbon steel overpack of the super container in Belgium's proposed Boom Clay repository by using the Point Defect Model (PDM). PDM parameter values are obtained by optimizing the model on experimental, wide-band electrochemical impedance spectroscopy data.

Pore shape of honeycomb-patterned films: modulation and interfacial behavior.

PubMed

Wan, Ling-Shu; Ke, Bei-Bei; Zhang, Jing; Xu, Zhi-Kang

2012-01-12

The control of the pore size of honeycomb-patterned films has been more or less involved in most work on the topic of breath figures. Modulation of the pore shape was largely ignored, although it is important to applications in replica molding, filtration, particle assembly, and cell culture. This article reports a tunable pore shape for patterned films prepared from commercially available polystyrene (PS). We investigated the effects of solvents including tetrahydrofuran (THF) and chloroform (CF) and hydrophilic additives including poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA), poly(ethylene glycol) (PEG), and poly(N-vinyl pyrrolidone) (PVP). Water droplets on/in the polymer solutions were observed and analyzed for simulating the formation and stabilization of breath figures. Interfacial tensions of the studied systems were measured and considered as a main factor to modulate the pore shape. Results indicate that the pores gradually change from near-spherical to ellipsoidal with the increase of additive content when using CF as the solvent; however, only ellipsoidal pores are formed from the THF solution. It is demonstrated that the aggregation of the additives at the water/polymer solution interface is more efficient in the THF solution than that in the CF solution. This aggregation decreases the interfacial tension, stabilizes the condensed water droplets, and shapes the pores of the films. The results may facilitate our understanding of the dynamic breath figure process and provide a new pathway to prepare patterned films with different pore structures.

Diffusion of U(VI) in Opalinus Clay: Influence of temperature and humic acid

NASA Astrophysics Data System (ADS)

Joseph, C.; Van Loon, L. R.; Jakob, A.; Steudtner, R.; Schmeide, K.; Sachs, S.; Bernhard, G.

2013-05-01

The diffusion of U(VI) (c0 = 1 × 10-6 mol/L) in compacted Opalinus Clay from the Mont Terri underground laboratory, Switzerland, was studied in the absence and presence of humic acid (10 mg/L) at two different temperatures (25 °C, 60 °C) under anaerobic conditions. As background electrolyte synthetic Opalinus Clay pore water (pH 7.6, I = 0.36 mol/L) was used. The diffusion-accessible porosity, ɛ, was determined for each Opalinus Clay bore core sample by through-diffusion experiments with tritiated water (HTO) before the U(VI) diffusion experiments were carried out. The values for the effective diffusion and distribution coefficients De and Kd obtained for U(VI) and humic acid at 25 °C as well as at 60 °C showed that humic acid has no significant influence on the U(VI) diffusion. The diffusion profiles of humic acid in Opalinus Clay at 25 and 60 °C indicate the contributions of two different humic acid particle size fractions (<1 kDa and 10-100 kDa). The small-sized humic acid fraction diffused through the whole Opalinus Clay samples at both temperatures within the 3 month duration of the U(VI) diffusion experiments. At 60 °C, diffusion profiles of two different U(VI) species were observed. In a separate experiment the U(VI) speciation in the source reservoir solution at 60 °C was analyzed by laser-induced fluorescence spectroscopy, photon correlation spectroscopy and scanning electron microscopy with an energy dispersive X-ray detector. The two diffusion profiles could be attributed to an unknown colloidal and a known aquatic U(VI) species (Ca2UO2(CO3)3(aq)). The diffusion results showed that the interaction of U(VI) and of the large-sized humic acid colloid fraction with the clay is stronger at 60 °C. An increase of Kd from 0.025 ± 0.003 m3/kg at 25 °C to 0.25 ± 0.05 m3/kg for U(VI)colloidal at 60 °C was determined. In addition, the value for De of U(VI) increased with increasing temperature. Using the De values at 25 and 60 °C, a preliminary activation energy for the diffusion of U(VI) through Opalinus Clay of 10 kJ/mol was calculated. The observed increased Kd and De values for U(VI)aqueous at 60 °C compensated each other to almost equal values of the apparent diffusion coefficient Da at 25 and 60 °C. Hence, an elevated temperature of 60 °C does not impact the migration of U(VI) through OPA significantly.

Comparison of tetrachloromethane sorption to an alkylammonium-clay and an alkyldiammonium-clay

USGS Publications Warehouse

Smith, J.A.; Jaffe, P.R.

1991-01-01

The interlamellar space of Wyoming bentonite (clay) was modified by exchanging either decyltrimethyl-ammonium (DTMA) or decyltrimethyldiammonium (DTMDA) cations for inorganic ions, and tetrachloromethane sorption to the resulting two organoclays from water was studied at 10, 20, and 35??C. Only one end of the 10-carbon alkyl chain of the DTMA cation is attached to the silica surface of the clay mineral, and tetrachloromethane sorption of DTMA-clay is characterized by isotherm linearity, noncompetitive sorption, weak solute uptake, and a relatively low heat of sorption. Both ends of the 10-carbon chain of the DTMDA cation are attached to the silica surface of the clay mineral, and tetrachloromethane sorption to DTMDA-clay is characterized by nonlinear isotherms, competitive sorption, strong solute uptake, and a relatively high, exothermic heat of sorption that varies as a function of the mass of tetrachloromethane sorbed. Therefore, the attachment of both ends of the alkyl chain to the interlamellar mineral surface appears to change the sorption mechanism from a partition-dominated process to an adsorption-dominated process. ?? 1991 American Chemical Society.

Seasonal Effects on the Relationships Between Soil Water Content, Pore Water Pressure and Shear Strength and Their Implications for Slope Stability

NASA Astrophysics Data System (ADS)

Hughes, P. N.

2015-12-01

A soil's shear resistance is mainly dependent upon the magnitude of effective stress. For small to medium height slopes (up to 10m) in clay soils the total stress acting along potential failure planes will be low, therefore the magnitude of effective stress (and hence soil shear strength) will be dominated by the pore-water pressure. The stability of slopes on this scale through periods of increased precipitation is improved by the generation of negative pore pressures (soil suctions) during preceding, warmer, drier periods. These negative pore water pressures increase the effective stress within the soil and cause a corresponding increase in shearing resistance. The relationships between soil water content and pore water pressure (soil water retention curves) are known to be hysteretic, but for the purposes of the majority of slope stability assessments in partially saturated clay soils, these are assumed to be consistent with time. Similarly, the relationship between shear strength and water content is assumed to be consistent over time. This research presents a laboratory study in which specimens of compacted Glacial Till (typical of engineered slopes within the UK) were subjected to repeated cycles of wetting and drying to simulate seasonal cycles. At predetermined water contents, measurements of soil suction were made using tensiometer and dewpoint potentiometer methods. The undrained shear strength of the specimens was then measured using triaxial strength testing equipment. Results indicate that repeated wetting and drying cycles caused a change in the soil water retention behaviour. A reduction in undrained shear strength at corresponding water contents along the wetting and drying paths was also observed. The mechanism for the change in the relationship is believed to be a deterioration in the soil physical structure due to shrink/swell induced micro-cracking. The non-stationarity of these relationships has implications for slope stability assessment.

Impact of monovalent cations on soil structure. Part II. Results of two Swiss soils

NASA Astrophysics Data System (ADS)

Farahani, Elham; Emami, Hojat; Keller, Thomas

2018-01-01

In this study, we investigated the impact of adding solutions with different potassium and sodium concentrations on dispersible clay, water retention characteristics, air permeability, and soil shrinkage behaviour using two agricultural soils from Switzerland with different clay content but similar organic carbon to clay ratio. Three different solutions (including only Na, only K, and the combination of both) were added to soil samples at three different cation ratio of soil structural stability levels, and the soil samples were incubated for one month. Our findings showed that the amount of readily dispersible clay increased with increasing Na concentrations and with increasing cation ratio of soil structural stability. The treatment with the maximum Na concentration resulted in the highest water retention and in the lowest shrinkage capacity. This was was associated with high amounts of readily dispersible clay. Air permeability generally increased during incubation due to moderate wetting and drying cycles, but the increase was negatively correlated with readily dispersible clay. Readily dispersible clay decreased with increasing K, while readily dispersible clay increased with increasing K in Iranian soil (Part I of our study). This can be attributed to the different clay mineralogy of the studied soils (muscovite in Part I and illite in Part II).

Self-consistent Modeling of Elastic Anisotropy in Shale

NASA Astrophysics Data System (ADS)

Kanitpanyacharoen, W.; Wenk, H.; Matthies, S.; Vasin, R.

2012-12-01

Elastic anisotropy in clay-rich sedimentary rocks has increasingly received attention because of significance for prospecting of petroleum deposits, as well as seals in the context of nuclear waste and CO2 sequestration. The orientation of component minerals and pores/fractures is a critical factor that influences elastic anisotropy. In this study, we investigate lattice and shape preferred orientation (LPO and SPO) of three shales from the North Sea in UK, the Qusaiba Formation in Saudi Arabia, and the Officer Basin in Australia (referred to as N1, Qu3, and L1905, respectively) to calculate elastic properties and compare them with experimental results. Synchrotron hard X-ray diffraction and microtomography experiments were performed to quantify LPO, weight proportions, and three-dimensional SPO of constituent minerals and pores. Our preliminary results show that the degree of LPO and total amount of clays are highest in Qu3 (3.3-6.5 m.r.d and 74vol%), moderately high in N1 (2.4-5.6 m.r.d. and 70vol%), and lowest in L1905 (2.3-2.5 m.r.d. and 42vol%). In addition, porosity in Qu3 is as low as 2% while it is up to 6% in L1605 and 8% in N1, respectively. Based on this information and single crystal elastic properties of mineral components, we apply a self-consistent averaging method to calculate macroscopic elastic properties and corresponding seismic velocities for different shales. The elastic model is then compared with measured acoustic velocities on the same samples. The P-wave velocities measured from Qu3 (4.1-5.3 km/s, 26.3%Ani.) are faster than those obtained from L1905 (3.9-4.7 km/s, 18.6%Ani.) and N1 (3.6-4.3 km/s, 17.7%Ani.). By making adjustments for pore structure (aspect ratio) and single crystal elastic properties of clay minerals, a good agreement between our calculation and the ultrasonic measurement is obtained.

Conceptual model analysis of interaction at a concrete-Boom Clay interface

NASA Astrophysics Data System (ADS)

Liu, Sanheng; Jacques, Diederik; Govaerts, Joan; Wang, Lian

In many concepts for deep disposal of high-level radioactive waste, cementitious materials are used in the engineered barriers. For example, in Belgium the engineered barrier system is based on a considerable amount of cementitious materials as buffer and backfill in the so-called supercontainer embedded in the hosting geological formation. A potential hosting formation is Boom Clay. Insight in the interaction between the high-pH pore water of the cementitious materials and neutral-pH Boom Clay pore water is required. Two problems are quite common for modeling of such a system. The first one is the computational cost due to the long timescale model assessments envisaged for the deep disposal system. Also a very fine grid (in sub-millimeter), especially at interfaces has to be used in order to accurately predict the evolution of the system. The second one is whether to use equilibrium or kinetic reaction models. The objectives of this paper are twofold. First, we develop an efficient coupled reactive transport code for this diffusion-dominated system by making full use of multi-processors/cores computers. Second, we investigate how sensitive the system is to chemical reaction models especially when pore clogging due to mineral precipitation is considered within the cementitious system. To do this, we selected two portlandite dissolution models, i.e., equilibrium (fastest) and diffusion-controlled model with precipitation of a calcite layer around portlandite particles (diffusion-controlled dissolution). The results show that with shrinking core model portlandite dissolution and calcite precipitation are much slower than with the equilibrium model. Also diffusion-controlled dissolution smooths out dissolution fronts compared to the equilibrium model. However, only a slight difference with respect to the clogging time can be found even though we use a very small diffusion coefficient (10-20 m2/s) in the precipitated calcite layer.

Elevated gas hydrate saturation within silt and silty clay sediments in the Shenhu area, South China Sea

USGS Publications Warehouse

Wang, Xiujuan; Hutchinson, Deborah R.; Wu, Shiguo; Yang, Shengxiong; Guo, Yiqun

2011-01-01

Gas hydrate saturations were estimated using five different methods in silt and silty clay foraminiferous sediments from drill hole SH2 in the South China Sea. Gas hydrate saturations derived from observed pore water chloride values in core samples range from 10 to 45% of the pore space at 190–221 m below seafloor (mbsf). Gas hydrate saturations estimated from resistivity (Rt) using wireline logging results are similar and range from 10 to 40.5% in the pore space. Gas hydrate saturations were also estimated by P wave velocity obtained during wireline logging by using a simplified three-phase equation (STPE) and effective medium theory (EMT) models. Gas hydrate saturations obtained from the STPE velocity model (41.0% maximum) are slightly higher than those calculated with the EMT velocity model (38.5% maximum). Methane analysis from a 69 cm long depressurized core from the hydrate-bearing sediment zone indicates that gas hydrate saturation is about 27.08% of the pore space at 197.5 mbsf. Results from the five methods show similar values and nearly identical trends in gas hydrate saturations above the base of the gas hydrate stability zone at depths of 190 to 221 mbsf. Gas hydrate occurs within units of clayey slit and silt containing abundant calcareous nannofossils and foraminifer, which increase the porosities of the fine-grained sediments and provide space for enhanced gas hydrate formation. In addition, gas chimneys, faults, and fractures identified from three-dimensional (3-D) and high-resolution two-dimensional (2-D) seismic data provide pathways for fluids migrating into the gas hydrate stability zone which transport methane for the formation of gas hydrate. Sedimentation and local canyon migration may contribute to higher gas hydrate saturations near the base of the stability zone.

Tracing mineral weathering reactions in the critical zone using Mg, Ca, and Sr isotopes, Luquillo Mountains, Puerto Rico

NASA Astrophysics Data System (ADS)

Buss, H. L.; White, A. F.; Vivit, D.; Bullen, T. D.; Blum, A. E.; Dessert, C.; Gaillardet, J.

2008-12-01

Mineral weathering in the critical zone directly impacts the availability of many important soil nutrients. As part of the USGS Water Energy and Biogeochemical Budgets (WEBB) program and the Critical Zone Exploration Network, we are investigating mineral nutrient distributions and fluxes in depth profiles (to 16 m) at five sites in the Bisley 1 catchment in the Luquillo Mountains of Puerto Rico. The Bisley 1 catchment contains a thick regolith developed on marine bedded, andesitic, volcaniclastic bedrock. Pore waters were sampled as a function of depth from nested suction water samplers. Pore water chemistry was analyzed and compared to total chemistry of solid samples taken from augered cores. Mg, Ca and Sr isotope ratios were measured of the pore waters at the Institut de Physique du Globe de Paris (Mg) and at the USGS in Menlo Park, CA (Ca, Sr). The Mg isotope ratios increase with increasing depth from δ26Mg = -0.772 at the surface to - 0.267 at depth, relative to the DSM3 standard. Sr isotope ratios vary from 0.70922 to 0.71016 87Sr/86Sr, with no discernible depth trend. The regolith is highly weathered and is depleted in primary minerals (except quartz) with respect to bedrock. Volumetric strain, calculated with respect to quartz, indicates approximately 25% volume collapse occurred relative to the original volume of the bedrock. Plagioclase, chlorite, pyroxene, and amphibole weather at the bedrock-regolith interface. The regolith contains quartz, kaolinite, other clays, and iron and manganese oxides. Increasing solid and pore water Mg concentrations and δ26Mg with depth likely indicate a two step weathering process wherein high-Mg chlorite dissolves at the bedrock-regolith interface and forms Mg-containing secondary clays and oxides, which then dissolve within the regolith profile.

Desorption of intrinsic cesium from smectite: inhibitive effects of clay particle organization on cesium desorption.

PubMed

Fukushi, Keisuke; Sakai, Haruka; Itono, Taeko; Tamura, Akihiro; Arai, Shoji

2014-09-16

Fine clay particles have functioned as transport media for radiocesium in terrestrial environments after nuclear accidents. Because radiocesium is expected to be retained in clay minerals by a cation-exchange reaction, ascertaining trace cesium desorption behavior in response to changing solution conditions is crucially important. This study systematically investigated the desorption behavior of intrinsic Cs (13 nmol/g) in well-characterized Na-montmorillonite in electrolyte solutions (NaCl, KCl, CaCl2, and MgCl2) under widely differing cation concentrations (0.2 mM to 0.2 M). Batch desorption experiments demonstrated that Cs(+) desorption was inhibited significantly in the presence of the environmental relevant concentrations of Ca(2+) and Mg(2+) (>0.5 mM) and high concentrations of K(+). The order of ability for Cs desorption was Na(+) = K(+) > Ca(2+) = Mg(2+) at the highest cation concentration (0.2 M), which is opposite to the theoretical prediction based on the cation-exchange selectivity. Laser diffraction grain-size analyses revealed that the inhibition of Cs(+) desorption coincided with the increase of the clay tactoid size. Results suggest that radiocesium in the dispersed fine clay particles adheres on the solid phase when the organization of swelling clay particles occurs because of changes in solution conditions caused by both natural processes and artificial treatments.

MODIFIED REVERSE OSMOSIS SYSTEM FOR TREATMENT OF PRODUCED WATERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

T.M. Whitworth; Liangxiong Li

2002-09-15

This report describes work performed during the first year of the project ''Modified Reverse Osmosis System for Treatment of Produced Waters.'' This research project has two objectives. The first objective is to test the use of clay membranes in the treatment of produced waters by reverse osmosis. The second objective is to test the ability of a system patented by the New Mexico Tech Research Foundation to remove salts from reverse osmosis waste streams as a solid. We performed 12 experiments using clay membranes in cross-flow experimental cells. We found that, due to dispersion in the porous frit used adjacentmore » to the membrane, the concentration polarization layer seems to be completely (or nearly completely) destroyed at low flow rates. This observation suggests that clay membranes used with porous frit material many reach optimum rejection rates at lower pumping rates than required for use with synthetic membranes. The solute rejection efficiency decreases with increasing solution concentration. For the membranes and experiments reported here, the rejection efficiency ranged from 71% with 0.01 M NaCl solution down to 12% with 2.3 M NaCl solution. More compacted clay membranes will have higher rejection capabilities. The clay membranes used in our experiments were relatively thick (approximately 0.5 mm). The active layer of most synthetic membranes is only 0.04 {micro}m (0.00004 mm), approximately 1250 times thinner than the clay membranes used in these experiments. Yet clay membranes as thin as 12 {micro}m have been constructed (Fritz and Eady, 1985). Since Darcy's law states that the flow through a material of constant permeability is inversely proportional to it's the material's thickness, then, based on these experimental observations, a very thin clay membrane would be expected to have much higher flow rates than the ones used in these experiments. Future experiments will focus on testing very thin clay membranes. The membranes generally exhibited reasonable stable rejection rates over time for chloride for a range of concentrations between 0.01 and 2.5 M. One membrane ran in excess of three months with no apparent loss of usability. This suggests that clay membranes may have a long useable life. Twenty different hyperfiltration-induced solute precipitation experiments were either attempted or completed and are reported here. The results of these experiments suggest that hyperfiltration-induced solute precipitation is possible, even for very soluble substances such as NaCl. However, the precipitation rates obtained in the laboratory do not appear to be adequate for commercial application at this time. Future experiments will focus on making the clay membranes more compact and thinner in order to obtain higher flux rates. Two alternative methods of removing solutes from solution, for which the New Mexico Tech Research Foundation is preparing patent applications, are also being investigated. These methods will be described in the next annual report after the patent applications are filed. Technology transfer efforts included two meetings (one in Farmington NM, and one in Hobbs, NM) where the results of this research were presented to independent oil producers and other interested parties. In addition, members of the research team gave seven presentations concerning this research and because of this research project T. M. (Mike) Whitworth was asked to sit on the advisory board for development of a new water treatment facility for the City of El Paso, Texas. Several papers are in preparation for submission to peer-reviewed journals based on the data presented in this report.« less

Saturation-dependent solute dispersivity in porous media: Pore-scale processes

NASA Astrophysics Data System (ADS)

Raoof, A.; Hassanizadeh, S. M.

2013-04-01

It is known that in variably saturated porous media, dispersion coefficient depends on Darcy velocity and water saturation. In one-dimensional flow, it is commonly assumed that the dispersion coefficient is a linear function of velocity. The coefficient of proportionality, called the dispersivity, is considered to depend on saturation. However, there is not much known about its dependence on saturation. In this study, we investigate, using a pore network model, how the longitudinal dispersivity varies nonlinearly with saturation. We schematize the porous medium as a network of pore bodies and pore throats with finite volumes. The pore space is modeled using the multidirectional pore-network concept, which allows for a distribution of pore coordination numbers. This topological property together with the distribution of pore sizes are used to mimic the microstructure of real porous media. The dispersivity is calculated by solving the mass balance equations for solute concentration in all network elements and averaging the concentrations over a large number of pores. We have introduced a new formulation of solute transport within pore space, where we account for different compartments of residual water within drained pores. This formulation makes it possible to capture the effect of limited mixing due to partial filling of the pores under variably saturated conditions. We found that dispersivity increases with the decrease in saturation, it reaches a maximum value, and then decreases with further decrease in saturation. To show the capability of our formulation to properly capture the effect of saturation on solute dispersion, we applied it to model the results of a reported experimental study.

Lithotype characterizations by Nuclear Magnetic Resonance (NMR): A case study on limestone and associated rocks from the eastern Dahomey Basin, Nigeria

NASA Astrophysics Data System (ADS)

Olatinsu, O. B.; Olorode, D. O.; Clennell, B.; Esteban, L.; Josh, M.

2017-05-01

Three representative rock types (limestone, sandstone, and shale) and glauconite samples collected from Ewekoro Quarry, eastern Dahomey Basin in Nigeria were characterized using low field 2 MHz and 20 MHz Nuclear Magnetic Resonance (NMR) techniques. NMR T2 relaxation time decay measurement was conducted on disc samples under partial water-saturation and full water-saturation conditions using CPMG spin-echo routine. The T2 relaxation decay was converted into T2 distribution in the time domain to assess and evaluate the pore size distribution of the samples. Good agreement exists between water content from T2 NMR distributions and water imbibition porosity (WIP) technique. Results show that the most useful characteristics to discriminate the different facies come from full saturation NMR 2 MHz pore size distribution (PSD). Shale facies depict a quasi-unimodal distribution with greater than 90% contribution from clay bound water component (T2s) coupled to capillary bound water component (T2i) centred on 2 ms. The other facies with well connected pore structure show either bimodal or trimodal T2 distribution composed of the similar clay bound water component centred on 0.3 ms and quasi-capillary bound water component centred on 10 ms. But their difference depends on the movable water T2 component (T2l) that does not exist in the glauconite facies (bimodal distribution) while it exists in both the sandstone and limestone facies. The basic difference between the limestone and sandstone facies is related to the longer T2 coupling: T2i and T2l populations are coupled in sandstone generating a single population which convolves both populations (bimodal distribution). Limestone with a trimodal distribution attests to the fact that carbonate rocks have more complex pore system than siliclastic rocks. The degree of pore connectivity is highest in sandstone, followed by limestone and least in glauconite. Therefore a basic/quick NMR log run on samples along a geological formation can provide precise lithofacies characterization with quantitative information on pore size, structure and distributions.

Slip-flow in complex porous media as determined by a multi-relaxation-time lattice Boltzmann model

NASA Astrophysics Data System (ADS)

Landry, C. J.; Prodanovic, M.; Eichhubl, P.

2014-12-01

The pores and throats of shales and mudrocks are predominantly found within a range of 1-100 nm, within this size range the flow of gas at reservoir conditions will fall within the slip-flow and low transition-flow regime (0.001 < Kn < 0.5). Currently, the study of slip-flows is for the most part limited to simple tube and channel geometries, however, the geometry of mudrock pores is often sponge-like (organic matter) and/or platy (clays). Molecular dynamics (MD) simulations can be used to predict slip-flow in complex geometries, but due to prohibitive computational demand are generally limited to small volumes (one to several pores). Here we present a multi-relaxation-time lattice Boltzmann model (LBM) parameterized for slip-flow (Guo et al. 2008) and adapted here to complex geometries. LBMs are inherently parallelizable, such that flow in complex geometries of significant (near REV-scale) volumes can be readily simulated at a fraction of the computational cost of MD simulations. At the macroscopic-scale the LBM is parameterized with local effective viscosities at each node to capture the variance of the mean-free-path of gas molecules in a bounded system. The corrected mean-free-path for each lattice node is determined using the mean distance of the node to the pore-wall and Stop's correction for mean-free-paths in an infinite parallel-plate geometry. At the microscopic-scale, a combined bounce-back specular-reflection boundary condition is applied to the pore-wall nodes to capture Maxwellian-slip. The LBM simulation results are first validated in simple tube and channel geometries, where good agreement is found for Knudsen numbers below 0.1, and fair agreement is found for Knudsen numbers between 0.1 and 0.5. More complex geometries are then examined including triangular-ducts and ellipsoid-ducts, both with constant and tapering/expanding cross-sections, as well as a clay pore-network imaged from a hydrocarbon producing shale by sequential focused ion-beam scanning electron microscopy. These results are analyzed to determine grid-independent resolutions, and used to explore the relationship between effective permeability and Knudsen number in complex geometries.

A forward analysis on the applicability of tracer breakthrough profiles in revealing the pore structure of tight gas sandstone and carbonate rocks

NASA Astrophysics Data System (ADS)

Mehmani, Ayaz; Mehmani, Yashar; Prodanović, Maša.; Balhoff, Matthew

2015-06-01

We explore tracer breakthrough profiles (TBP) as a macroscopic property to infer the pore-space topology of tight gas sandstone and carbonate rocks at the core scale. The following features were modeled via three-dimensional multiscale networks: microporosity within dissolved grains and pore-filling clay, cementation in the absence and presence of microporosity (each classified into uniform, pore-preferred, and throat-preferred modes), layering, vug, and microcrack inclusion. A priori knowledge of the extent and location of each process was assumed to be known. With the exception of an equal importance of macropores and pore-filling micropores, TBPs show little sensitivity to the fraction of micropores present. In general, significant sensitivity of the TBPs was observed for uniform and throat-preferred cementation. Layering parallel to the fluid flow direction had a considerable impact on TBPs whereas layering perpendicular to flow did not. Microcrack orientations seemed of minor importance in affecting TBPs. This article was corrected on 9 Nov 2015. See the end of the full text for details.

Single and multi-component adsorption of salicylic acid, clofibric acid, carbamazepine and caffeine from water onto transition metal modified and partially calcined inorganic-organic pillared clay fixed beds.

PubMed

Cabrera-Lafaurie, Wilman A; Román, Félix R; Hernández-Maldonado, Arturo J

2015-01-23

Fixed-beds of transition metal (Co(2+), Ni(2+) or Cu(2+)) inorganic-organic pillared clays (IOCs) were prepared to study single- and multi-component non-equilibrium adsorption of a set of pharmaceutical and personal care products (PPCPs: salicylic acid, clofibric acid, carbamazepine and caffeine) from water. Adsorption capacities for single components revealed that the copper(II) IOCs have better affinity toward salicylic and clofibric acid. However, multi-component adsorption tests showed a considerable decrease in adsorption capacity for the acids and an unusual selectivity toward carbamazepine depending on the transition metal. This was attributed to a combination of competition between PPCPs for adsorption sites, adsorbate-adsorbate interactions, and plausible pore blocking caused by carbamazepine. The cobalt(II) IOC bed that was partially calcined to fractionate the surfactant moiety showcased the best selectivity toward caffeine, even during multi-component adsorption. This was due to a combination of a mildly hydrophobic surface and interaction between the PPCP and cobalt(II). In general, the tests suggest that these IOCs may be a potential solution for the removal of PPCPs if employed in a layered-bed configuration, to take care of families of adsorbates in a sequence that would produce sharpened concentration wavefronts. Copyright © 2014 Elsevier B.V. All rights reserved.

Modeling the acid-base surface chemistry of montmorillonite.

PubMed

Bourg, Ian C; Sposito, Garrison; Bourg, Alain C M

2007-08-15

Proton uptake on montmorillonite edge surfaces can control pore water pH, solute adsorption, dissolution kinetics and clay colloid behavior in engineered clay barriers and natural weathering environments. Knowledge of proton uptake reactions, however, is currently limited by strong discrepancies between reported montmorillonite titration data sets and by conflicting estimates of edge structure, reactivity and electrostatics. In the present study, we show that the apparent discrepancy between titration data sets results in large part from the widespread use of an erroneous assumption of zero specific net proton surface charge at the onset of titration. Using a novel simulation scheme involving a surface chemistry model to simulate both pretreatment and titration, we find that montmorillonite edge surface chemistry models that account for the "spillover" of electrostatic potential from basal onto edge surfaces and for the stabilization of deprotonated Al-Si bridging sites through bond-length relaxation at the edge surface can reproduce key features of the best available experimental titration data (the influence of pretreatment conditions on experimental results, the absence of a point of zero salt effect, buffer capacity in the acidic pH range). However, no combination of current models of edge surface structure, reactivity and electrostatics can quantitatively predict, without fitted parameters, the experimental titration data over the entire range of pH (4.5 to 9) and ionic strength (0.001 to 0.5 mol dm(-3)) covered by available data.

Origin and diagenesis of clay minerals in relation to sandstone paragenesis: An example in eolian dune reservoirs and associated rocks, Permian upper part of the Minnelusa Formation, Powder River basin, Wyoming

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pollastro, R.M.; Schenk, C.J.

Eolian dune sandstones are the principal reservoir rocks in the Permian upper part of the Minnelusa Formation, Powder River basin, Wyoming. These sandstones formed as shorelines retreated and dunes migrated across siliciclastic sabkhas. Sandstones are mainly quartzarenites; on average, clay minerals constitute about 5 wt.% the whole rock. Although present in minor amounts, clay minerals play an important role in the diagenetic evolution of these sandstones. Allogenic clay minerals are present in shaly rock fragments and laminae. Early infiltration of clays into porous sabkha sands commonly form characteristic menisei or bridges between framework grains or, when more extensive, form coatingsmore » or rims on grain surfaces. Authigenic clays include nearly pure smectite, mixed-layer illite/smectite (I/S), and late diagenetic illite and corrensite; these clay minerals are present as pore-lining cements. In addition to the deposition and neoformation of clay minerals throughout sandstone paragenesis, the conversion of smectite to illite occurred as temperatures increased with progressive burial. A temperature of 103C is calculated at a present depth of 3,200 m using a geothermal gradient of 30C/km and a mean annual surface temperature of 7C. After correction for uplift and erosion (250 m), the maximum calculated temperature for the conversion of all random I/S to ordered I/S is 100C. This calculated temperature is in excellent agreement with temperatures of 100-110C implied from I/S geothermometry.« less

Can the three pore model correctly describe peritoneal transport of protein?

PubMed

Waniewski, Jacek; Poleszczuk, Jan; Antosiewicz, Stefan; Baczynński, Daniel; Gałach, Magda; Pietribiasi, Mauro; Wanńkowicz, Zofia

2014-01-01

The three pore model (3PM) includes large pores for the description of protein leak to the peritoneal cavity during peritoneal dialysis. However, the reliability of this description has been not fully tested against clinical data yet. Peritoneal transport parameters were estimated using 3PM, extended 3p model (with estimation of fraction of large pores, ext3PM), ext3PM with modified size of pores and proteins (mext3PM), and simplified two pore (2PM, small and ultrasmall pores) models for 32 patients on peritoneal dialysis investigated using the sequential peritoneal equilibration test (consecutive peritoneal equilibration test [PET]: glucose 2.27%, 4 h, and miniPET: glucose 3.86%, 1 h). Urea, creatinine, glucose, sodium, phosphate, albumin, and IgM concentrations were measured in dialysis fluid and plasma. Ext3PM and mext3PM, with large pore fraction of about 0.14, provided a good description of fluid and small solute kinetics, but their predictions for albumin transport were less accurate. Two pore model precisely described the data on fluid and small solute transport. The 3p models could not describe the diffusive-convective transport of albumin as precisely as the transport of fluid, small solutes, and IgM. The 2p model (not applicable for proteins) was an efficient tool for modeling fluid and small solute transport.

CO 2 Sorption to Subsingle Hydration Layer Montmorillonite Clay Studied by Excess Sorption and Neutron Diffraction Measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rother, Gernot; Ilton, Eugene S.; Wallacher, Dirk

2013-01-02

Geologic storage of CO 2 requires that the caprock sealing the storage rock is highly impermeable to CO 2. Swelling clays, which are important components of caprocks, may interact with CO 2 leading to volume change and potentially impacting the seal quality. The interactions of supercritical (sc) CO 2 with Na saturated montmorillonite clay containing a subsingle layer of water in the interlayer region have been studied by sorption and neutron diffraction techniques. The excess sorption isotherms show maxima at bulk CO2 densities of ≈0.15 g/cm 3, followed by an approximately linear decrease of excess sorption to zero and negativemore » values with increasing CO 2 bulk density. Neutron diffraction experiments on the same clay sample measured interlayer spacing and composition. The results show that limited amounts of CO 2 are sorbed into the interlayer region, leading to depression of the interlayer peak intensity and an increase of the d(001) spacing by ca. 0.5 Å. The density of CO 2 in the clay pores is relatively stable over a wide range of CO 2 pressures at a given temperature, indicating the formation of a clay-CO 2 phase. Finally, at the excess sorption maximum, increasing CO 2 sorption with decreasing temperature is observed while the high-pressure sorption properties exhibit weak temperature dependence.« less

Rainfall-soil moisture relations in landslide-prone areas of a tropical rain forest, Puerto Rico

USGS Publications Warehouse

Larsen, Matthew C.; Torres-Sanchez, Angel J.; Krishna, J.H.; Quinones-Aponte, Vicente; Gomez-Gomez, Fernando; Morris, G.L.

1990-01-01

Detailed studies of the relation between rainfall and soil moisture are underway at two forested sites on slopes in the CNF. Soil at the sites is characterized by a layer of silty-clay colluvial soil about 1 m thick, which is underlain by up to 10 m of saprolite, and overlies weathered volcaniclastic or quartz-diorite bedrock. Although considerable surface runoff has been observed at the study sites, data show moderate to rapid increases in pore pressure in repsonse to short duration storm events. Pore-pressure increases are greatest in the lower sections of concave slopes apparently due to convergent flow. It is anticipated that these pore-pressure data will provide a means of assessing rainfall characteristics leading to landslide initiation as well as insight to the mechanics of shallow landslides

Electrical resistivity characteristics of diesel oil-contaminated kaolin clay and a resistivity-based detection method.

PubMed

Liu, Zhibin; Liu, Songyu; Cai, Yi; Fang, Wei

2015-06-01

As the dielectric constant and conductivity of petroleum products are different from those of the pore water in soil, the electrical resistivity characteristics of oil-contaminated soil will be changed by the corresponding oil type and content. The contaminated soil specimens were manually prepared by static compaction method in the laboratory with commercial kaolin clay and diesel oil. The water content and dry density of the first group of soil specimens were controlled at 10 % and 1.58 g/cm(3). Corresponding electrical resistivities of the contaminated specimens were measured at the curing periods of 7, 14, and 28 and 90, 120, and 210 days on a modified oedometer cell with an LCR meter. Then, the electrical resistivity characteristics of diesel oil-contaminated kaolin clay were discussed. In order to realize a resistivity-based oil detection method, the other group of oil-contaminated kaolin clay specimens was also made and tested, but the initial water content, oil content, and dry density were controlled at 0~18 %, 0~18 %, 1.30~1.95 g/cm(3), respectively. Based on the test data, a resistivity-based artificial neural network (ANN) was developed. It was found that the electrical resistivity of kaolin clay decreased with the increase of oil content. Moreover, there was a good nonlinear relationship between electrical resistivity and corresponding oil content when the water content and dry density were kept constant. The decreasing velocity of the electrical resistivity of oil-contaminated kaolin clay was higher before the oil content of 12 % than after 12 %, which indicated a transition of the soil from pore water-controlled into oil-controlled electrical resistivity characteristics. Through microstructural analysis, the decrease of electrical resistivity could be explained by the increase of saturation degree together with the collapse of the electrical double layer. Environmental scanning electron microscopy (ESEM) photos indicated that the diesel oil in kaolin clay normally had three kinds of effects including oil filling, coating, and bridging. Finally, a resistivity-based ANN model was established based on the database collected from the experiment data. The performance of the model was proved to be reasonably accepted, which puts forward a possible simple, economic, and effective tool to detect the oil content in contaminated clayey soils just with four basic parameters: wet density, dry density, measured moisture content, and electrical resistivity.

Molecular simulation of structure and diffusion at smectite-water interfaces: Using expanded clay interlayers as model nanopores

DOE PAGES

Greathouse, Jeffery A.; Hart, David; Bowers, Geoffrey M.; ...

2015-07-20

In geologic settings relevant to a number of extraction and potential sequestration processes, nanopores bounded by clay mineral surfaces play a critical role in the transport of aqueous species. Solution structure and dynamics at clay–water interfaces are quite different from their bulk values, and the spatial extent of this disruption remains a topic of current interest. We have used molecular dynamics simulations to investigate the structure and diffusion of aqueous solutions in clay nanopores approximately 6 nm thick, comparing the effect of clay composition with model Na-hectorite and Na-montmorillonite surfaces. In addition to structural properties at the interface, water andmore » ion diffusion coefficients were calculated within each aqueous layer at the interface, as well as in the central bulk-like region of the nanopore. The results show similar solution structure and diffusion properties at each surface, with subtle differences in sodium adsorption complexes and water structure in the first adsorbed layer due to different arrangements of layer hydroxyl groups in the two clay models. Interestingly, the extent of surface disruption on bulk-like solution structure and diffusion extends to only a few water layers. Additionally, a comparison of sodium ion residence times confirms similar behavior of inner-sphere and outer-sphere surface complexes at each clay surface, but ~1% of sodium ions adsorb in ditrigonal cavities on the hectorite surface. Thus, the presence of these anhydrous ions is consistent with highly immobile anhydrous ions seen in previous nuclear magnetic resonance spectroscopic measurements of hectorite pastes.« less

Alkali-Activated Aluminium-Silicate Composites as Insulation Materials for Industrial Application

NASA Astrophysics Data System (ADS)

Dembovska, L.; Bajare, D.; Pundiene, I.; Bumanis, G.

2015-11-01

The article reports on the study of thermal stability of alkali-activated aluminium- silicate composites (ASC) at temperature 800-1100°C. ASC were prepared by using calcined kaolinite clay, aluminium scrap recycling waste, lead-silicate glass waste and quartz sand. As alkali activator, commercial sodium silicate solution modified with an addition of sodium hydroxide was used. The obtained alkali activation solution had silica modulus Ms=1.67. Components of aluminium scrap recycling waste (aluminium nitride (AlN) and iron sulphite (FeSO3)) react in the alkali media and create gases - ammonia and sulphur dioxide, which provide the porous structure of the material [1]. Changes in the chemical composition of ASC during heating were identified and quantitatively analysed by using DTA/TG, dimension changes during the heating process were determined by using HTOM, pore microstructure was examined by SEM, and mineralogical composition of ASC was determined by XRD. The density of ASC was measured in accordance with EN 1097-7. ASC with density around 560 kg/m3 and heat resistance up to 1100°C with shrinkage less than 5% were obtained. The intended use of this material is the application as an insulation material for industrial purposes at elevated temperatures.

Vertical Migration Potential of Metal Contaminants at Small Arms Firing Ranges, Camp Edwards Military Reservation, Massachusetts.

DTIC Science & Technology

1998-03-01

halloysite on lead concentration in solution 57 Figure 41. Solubility of lead carbonate as a function of pH for a total activity aH2C03...Effects of adsorption by halloysite (a clay) on lead concentration in solution. Contours are equilibrium lead concentrations at different clay

Parametric study of the physical properties of hydrate-bearing sand, silt, and clay sediments: 1. Electromagnetic properties

USGS Publications Warehouse

Lee, J.Y.; Santamarina, J.C.; Ruppel, C.

2010-01-01

The marked decrease in bulk electrical conductivity of sediments in the presence of gas hydrates has been used to interpret borehole electrical resistivity logs and, to a lesser extent, the results of controlled source electromagnetic surveys to constrain the spatial distribution and predicted concentration of gas hydrate in natural settings. Until now, an exhaustive laboratory data set that could be used to assess the impact of gas hydrate on the electromagnetic properties of different soils (sand, silt, and clay) at different effective stress and with different saturations of hydrate has been lacking. The laboratory results reported here are obtained using a standard geotechnical cell and the hydrate-formed tetrahydrofuran (THF), a liquid that is fully miscible in water and able to produce closely controlled saturations of hydrate from dissolved phase. Both permittivity and electrical conductivity are good indicators of the volume fraction of free water in the sediment, which is in turn dependent on hydrate saturation. Permittivity in the microwave frequency range is particularly predictive of free water content since it is barely affected by ionic concentration, pore structure, and surface conduction. Electrical conductivity (or resistivity) is less reliable for constraining water content or hydrate saturation: In addition to fluid-filled porosity, other factors, such as the ionic concentration of the pore fluid and possibly other conduction effects (e.g., surface conduction in high specific surface soils having low conductivity pore fluid), also influence electrical conductivity.

Hydrocarbon generation and expulsion in shale Vs. carbonate source rocks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leythaeuser, D.; Krooss, B.; Hillebrand, T.

1993-09-01

For a number of commercially important source rocks of shale and of carbonate lithologies, which were studied by geochemical, microscopical, and petrophysical techniques, a systematic comparison was made of the processes on how hydrocarbon generation and migration proceed with maturity progress. In this way, several fundamental differences between both types of source rocks were recognized, which are related to differences of sedimentary facies and, more importantly, of diagenetic processes responsible for lithification. Whereas siliciclastic sediments lithify mainly by mechanical compaction, carbonate muds get converted into lithified rocks predominantly by chemical diagenesis. With respect to their role as hydrocarbon source rocks,more » pressure solution processes appear to be key elements. During modest burial stages and prior to the onset of hydrocarbon generation reactions by thermal decomposition of kerogen, pressure solution seams and stylolites. These offer favorable conditions for hydrocarbon generation and expulsion-a three-dimensional kerogen network and high organic-matter concentrations that lead to effective saturation of the internal pore fluid system once hydrocarbon generation has started. As a consequence, within such zones pore fluids get overpressured, leading ultimately to fracturing. Petroleum expulsion can then occur at high efficiencies and in an explosive fashion, whereby clay minerals and residual kerogen particles are squeezed in a toothpaste-like fashion into newly created fractures. In order to elucidate several of the above outlined steps of hydrocarbon generation and migration processes, open-system hydrous pyrolysis experiments were performed. This approach permits one to monitor changes in yield and composition of hydrocarbon products generated and expelled at 10[degrees]C temperature increments over temperature range, which mimics in the laboratory the conditions prevailing in nature over the entire liquid window interval.« less

Diagenesis in tephra-rich sediments from the Lesser Antilles Volcanic Arc: Pore fluid constraints

NASA Astrophysics Data System (ADS)

Murray, Natalie A.; McManus, James; Palmer, Martin R.; Haley, Brian; Manners, Hayley

2018-05-01

We present sediment pore fluid and sediment solid phase results obtained during IODP Expedition 340 from seven sites located within the Grenada Basin of the southern Lesser Antilles Volcanic Arc region. These sites are generally characterized as being low in organic carbon content and rich in calcium carbonate and volcanogenic material. In addition to the typical reactions related to organic matter diagenesis, pore fluid chemistry indicates that the diagenetic reactions fall within two broad categories; (1) reactions related to chemical exchange with volcanogenic material and (2) reactions related to carbonate dissolution, precipitation, or recrystallization. For locations dominated by reaction with volcanogenic material, these sites exhibit increases in dissolved Ca with coeval decreases in Mg. We interpret this behavior as being driven by sediment-water exchange reactions from the alteration of volcanic material that is dispersed throughout the sediment package, which likely result in formation of Mg-rich secondary authigenic clays. In contrast to this behavior, sediment sequences that exhibit decreases in Ca, Mg, Mn, and Sr with depth suggest that carbonate precipitation is an active diagenetic process affecting solute distributions. The distributions of pore fluid 87Sr/86Sr reflect these competitive diagenetic reactions between volcanic material and carbonate, which are inferred by the major cation distributions. From one site where we have solid phase 87Sr/86Sr (site U1396), the carbonate fraction is found to be generally consistent with the contemporaneous seawater isotope values. However, the 87Sr/86Sr of the non-carbonate fraction ranges from 0.7074 to 0.7052, and these values likely represent a mixture of local arc volcanic sources and trans-Atlantic eolian sources. Even at this site where there is clear evidence for diagenesis of volcanogenic material, carbonate diagenesis appears to buffer pore fluid 87Sr/86Sr from the larger changes that might be expected given the high abundance of tephra in these sediments. Part of this carbonate buffering, at this site as well as throughout the region, derives from the fact that the Sr concentration in the non-carbonate fraction is generally low (<200 ppm), whereas the carbonate fraction has Sr concentrations approaching ∼1000 ppm.

Determination of pore size distributions of porous chromatographic adsorbents by inverse size-exclusion chromatography.

PubMed

Yao, Yan; Lenhoff, Abraham M

2004-05-28

The macroscopic properties of porous chromatographic adsorbents are directly influenced by the pore structure, with the pore size distribution (PSD) playing a major role beyond simply the mean pore size. Inverse size-exclusion chromatography (ISEC), a widely used chromatographic method for determining the PSD of porous media, provides more relevant information on liquid chromatographic materials in situ than traditional methods, such as gas sorption and mercury intrusion. The fundamentals and applications of ISEC in the characterization of the pore structure are reviewed. The description of the probe solutes and the pore space, as well as theoretical models for deriving the PSD from solute partitioning behavior, are discussed. Precautions to ensure integrity of the experiments are also outlined, including accounting for probe polydispersity and minimization of solute-adsorbent interactions. The results that emerge are necessarily model-dependent, but ISEC nonetheless represents a powerful and non-destructive source of quantitative pore structure information that can help to elucidate chromatographic performance observations covering both retention and rate aspects.

Influence of clay particles on microfluidic-based preparation of hydrogel composite microsphere

NASA Astrophysics Data System (ADS)

Hong, Joung Sook

2016-05-01

For the successful fabrication of a hydrogel composite microsphere, this study aimed to investigate the influence of clay particles on microsphere formation in a microfluidic device which has flow focusing and a 4.5:1 contraction channel. A poly alginic acid solution (2.0 wt.%) with clay particles was used as the dispersed phase to generate drops in an oil medium, which then merged with drops of a CaCl2 solution for gelation. Drop generations were observed with different flow rates and particles types. When the flow rate increased, drop generation was enhanced and drop size decreased by the build-up of more favorable hydrodynamic flow conditions to detach the droplets. The addition of a small amount of particles insignificantly changed the drop generation behavior even though it reduced interfacial tension and increased the viscosity of the solution. Instead, clays particles significantly affected hydro-gelation depending on the hydrophobicity of particles, which produced further heterogeneity in the shape and size of microsphere.

Evaluation of White Bentonite Modified by Acid Attack

NASA Astrophysics Data System (ADS)

Andrade, C. G. Bastos; Fermino, D. M.; Fernandes, M. G.; Valenzuela-Diaz, F. R.

For industrial use, the smectite clays must be cleared of impurities, usually obtained by acid modification, using a high concentration solution of inorganic acid at temperatures under boiling point. In the present paper, a sample of white bentonite from Paraiba, Brazil, was modified by hydrochloric acid under moderate conditions (90°C, reaction times of 1, 6, 12, 18 and 24hours in close reactor, concentration of the aqueous solution of hydrochloric acid 1.5 M, acid solution/clay ratio of 1g/10mL). The purpose of these attacks is to reduce the concentration of impurities with minimal change in the clay minerals structure. The modified samples were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF), Cation Exchange Capacity (CEC), Stereomicroscopy, Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Detector (EDS). Thus, this modified bentonite tends to be a good economic and environmental alternative in manufacturing of products with high added value such as cosmetics and polymer/clay nanocomposites.

Effect of pore water velocities and solute input methods on chloride transport in the undisturbed soil columns of Loess Plateau

NASA Astrophysics Data System (ADS)

Zhou, BeiBei; Wang, QuanJiu

2017-09-01

Studies on solute transport under different pore water velocity and solute input methods in undisturbed soil could play instructive roles for crop production. Based on the experiments in the laboratory, the effect of solute input methods with small pulse input and large pulse input, as well as four pore water velocities, on chloride transport in the undisturbed soil columns obtained from the Loess Plateau under controlled condition was studied. Chloride breakthrough curves (BTCs) were generated using the miscible displacement method under water-saturated, steady flow conditions. Using the 0.15 mol L-1 CaCl2 solution as a tracer, a small pulse (0.1 pore volumes) was first induced, and then, after all the solution was wash off, a large pulse (0.5 pore volumes) was conducted. The convection-dispersion equation (CDE) and the two-region model (T-R) were used to describe the BTCs, and their prediction accuracies and fitted parameters were compared as well. All the BTCs obtained for the different input methods and the four pore water velocities were all smooth. However, the shapes of the BTCs varied greatly; small pulse inputs resulted in more rapid attainment of peak values that appeared earlier with increases in pore water velocity, whereas large pulse inputs resulted in an opposite trend. Both models could fit the experimental data well, but the prediction accuracy of the T-R was better. The values of the dispersivity, λ, calculated from the dispersion coefficient obtained from the CDE were about one order of magnitude larger than those calculated from the dispersion coefficient given by the T-R, but the calculated Peclet number, Pe, was lower. The mobile-immobile partition coefficient, β, decreased, while the mass exchange coefficient increased with increases in pore water velocity.

The effect of clay on the dissolution of nuclear waste glass

NASA Astrophysics Data System (ADS)

Lemmens, K.

2001-09-01

In a nuclear waste repository, the waste glass can interact with metals, backfill materials (if present) and natural host rock. Of the various host rocks considered, clays are often reported to delay the onset of the apparent glass saturation, where the glass dissolution rate becomes very small. This effect is ascribed to the sorption of silica or other glass components on the clay. This can have two consequences: (1) the decrease of the silica concentration in solution increases the driving force for further dissolution of glass silica, and (2) the transfer of relatively insoluble glass components (mainly silica) from the glass surface to the clay makes the alteration layer less protective. In recent literature, the latter explanation has gained credibility. The impact of the environmental materials on the glass surface layers is however not well understood. Although the glass dissolution can initially be enhanced by clay, there are arguments to assume that it will decrease to very low values after a long time. Whether this will indeed be the case, depends on the fate of the released glass components in the clay. If they are sorbed on specific sites, it is likely that saturation of the clay will occur. If however the released glass components are removed by precipitation (growth of pre-existing or new secondary phases), saturation of the clay is less likely, and the process can continue until exhaustion of one of the system components. There are indications that the latter mechanism can occur for varying glass compositions in Boom Clay and FoCa clay. If sorption or precipitation prevents the formation of protective surface layers, the glass dissolution can in principle proceed at a high rate. High silica concentrations are assumed to decrease the dissolution rate (by a solution saturation effect or by the impact on the properties of the glass alteration layer). In glass corrosion tests at high clay concentrations, silica concentrations are, however, often higher than the silica concentrations in equilibrium with the glass surface ( C ∗Si, saturation) that are found in absence of clay. Nevertheless, the glass dissolution proceeds at relatively high rate. C ∗Si, saturation seems to be increased by the presence of clay. To understand this, more knowledge is necessary concerning the fate of the released silica and the silica speciation in solution.

Organic matter and the geotechnical properties of submarine sediments

NASA Astrophysics Data System (ADS)

Keller, George H.

1982-09-01

Continental slope deposits off Peru and Oregon where coastal upwelling is a pronounced oceanographic process possess significant concentrations of organic carbon. Geotechnical properties are altered to varying degrees by the organic matter. Organic matter absorbs water and causes clay-size particles to aggregate forming an open fabric. This causes unusually high water contents and plasticity and exceptionally low wet bulk densities. Some of these deposits show notable increases in shear strength, sensitivity and degree of apparent overconsolidation. Owing to the unique geotechnical properties, sediment stability characteristics are considered to be poor in situations of excess pore pressures. Failure appears to take the form of a fluidized flow somewhat similar to the quick clays of Scandinavia.

The Point Lookout Sandstone: a tale of two cores, or petrology, diagenesis, and reservoir properties of Point Lookout Sandstone, Southern Ute Indian Reservation, San Juan Basin, Colorado

USGS Publications Warehouse

Keighin, C.W.; Zech, R.S.; Dunbar, R.W.

1993-01-01

The Point Lookout sandstones are quartz-rich, fine to very-fine grained, and contain moderately variable quantities of potassium feldspar (2 to 20 modal percent) and lithic fragments (9 to 20 modal percent). Locally, sandstone is tightly cemented by carbonate cement; clays are not important as cementing agents, although they significantly reduce permeability of some samples. Pores are small; many are intergranular micropores between crystals of authigenic clay. Depositional environments are highly variable and range from lower shoreface to coastal plain and include minor deltaic environments. The best reservoir characteristics are generally in the upper shoreface sandstones. -from Authors

Visualizing and Quantifying Bioaccessible Pores in Field-Aged Petroleum Hydrocarbon-Contaminated Clay Soils Using Synchrotron-based X-ray Computed Tomography

NASA Astrophysics Data System (ADS)

Chang, W.; Kim, J.; Zhu, N.; McBeth, J. M.

2015-12-01

Microbial hydrocarbon degradation is environmentally significant and applicable to contaminated site remediation practices only when hydrocarbons (substrates) are physically bioaccessible to bacteria in soil matrices. Powerful X-rays are produced by synchrotron radiation, allowing for bioaccessible pores in soil (larger than 4 microns), where bacteria can be accommodated, colonize and remain active, can be visualized at a much higher resolution. This study visualized and quantified such bioaccessible pores in intact field-aged, oil-contaminated unsaturated soil fractions, and examined the relationship between the abundance of bioaccessible pores and hydrocarbon biodegradation. Using synchrotron-based X-ray Computed Tomography (CT) at the Canadian Light Source, a large dataset of soil particle characteristics, such as pore volumes, surface areas, number of pores and pore size distribution, was generated. Duplicate samples of five different soil fractions with different soil aggregate sizes and water contents (13, 18 and 25%) were examined. The method for calculating the number and distribution of bioaccessible pores using CT images was validated using the known porosity of Ottawa sand. This study indicated that the distribution of bioaccessible pore sizes in soil fractions are very closely related to microbial enhancement. A follow-up aerobic biodegradation experiment for the soils at 17 °C (average site temperature) over 90 days confirmed that a notable decrease in hydrocarbon concentrations occurred in soils fractions with abundant bioaccessible pores and with a larger number of pores between 10 and 100 μm. The hydrocarbon degradation in bioactive soil fractions was extended to relatively high-molecular-weight hydrocarbons (C16-C34). This study provides quantitative information about how internal soil pore characteristics can influence bioremediation performance.

Polymer based nanocomposites with nanofibers and exfoliated clay

NASA Technical Reports Server (NTRS)

Meador, Michael A.; Reneker, Darrell H.

2005-01-01

Polymer solutions, containing clay sheets, were electrospun into nanofibers and microfibers that contained clay sheets inside. Controllable removal of polymer by plasma etching from the surface of fibers revealed the arrangement of clay. The shape, flexibility, size distribution and arrangement of clay sheets were observed by transmission and scanning electron microscopy. The clay sheets were partially aligned in big fibers with normal direction of clay sheets perpendicular to fiber axis. Crumpling of clay sheets inside fibers was observed when the fiber diameter was comparable to the lateral size of clay sheets. Single sheets of clay were observed both by catching clay sheets dispersed in water with electrospun nanofiber mats and by the deliberate removal of most of the polymer in the fibers. Thin, flexible gas barrier films, that are reasonably strong, were assembled from clay sheets and polymer nanofibers. Structure of composite films was characterized with scanning electron microscopy. Continuous film of clay sheets were physically attached to the surface of fiber mats. Spincoating film of polymer and clay sheets was reinforced by electrospun fiber scaffold. Certain alignment of clay sheets was observed in the vicinity of fibers.

Shales and geological waste repositories: from microstructure description to macro-scale properties

NASA Astrophysics Data System (ADS)

Tournassat, C.; Steefel, C. I.; Gaboreau, S.

2017-12-01

The mineralogical and chemical properties of clays have been the subject of longstanding study for the long-term disposal of nuclear wastes in geological repositories. The low permeability of clay materials, including shales, provides at least part of the safety functions for radionuclide contaminants confinement. From a geochemical and mineralogical point of view, the high adsorption capacity of clay minerals adds to the effect of low hydraulic conductivities by greatly increasing the retardation of radionuclides and other contaminants, making clays ideal where isolation from the biosphere is desired. While their low permeability and high adsorption capacity are widely acknowledged, it is clear nonetheless that there is a need for an improved understanding of how the chemical and mineralogical properties of shales impact their macroscopic properties. It is at the pore-scale that the chemical properties of clay minerals become important since their electrostatic properties can play a large role. The negative electrostatic potential field at the clay mineral surfaces results in the presence of porosity domains where electroneutrality is not achieved: cations are attracted by the surfaces while anions are repulsed from them, resulting in the presence of a diffuse ion swarm - or diffuse layer. Numerical methods for modeling macroscopic properties of clay media with the consideration of the presence of a diffuse ion swarm have met a growing interest in diverse communities in the past years. In this presentation we will highlight the complex interplays of mineralogical, chemical and microstructural characteristics of clay materials that are ultimately responsible for a remarkable array of macro-scale properties such as specific adsorption, high swelling pressure, semi-permeable membrane properties, and non-Fickian diffusional behavior.

[Interaction of clay minerals with microorganisms: a review of experimental data].

PubMed

Naĭmark, E B; Eroshchev-Shak, V A; Chizhikova, N P; Kompantseva, E I

2009-01-01

A review of publications containing results of experiments on the interaction of microorganisms with clay minerals is presented. Bacteria are shown to be involved in all processes related to the transformation of clay minerals: formation of clays from metamorphic and sedimentary rocks, formation of clays from solutions, reversible transitions of different types of clay minerals, and consolidation of clay minerals into sedimentary rocks. Integration of these results allows to conclude that bacteria reproduced all possible abiotic reactions associated with the clay minerals, these reactions proceed much faster with the bacteria being involved. Thus, bacteria act as a living catalyst in the geochemical cycle of clay minerals. The ecological role of bacteria can be considered as a repetition of a chemical process of the abiotic world, but with the use of organic catalytic innovation.

Hydraulic performance of Compacted Clay Liners (CCLs) under combined temperature and leachate exposures.

PubMed

Aldaeef, A A; Rayhani, M T

2014-12-01

Experimental investigations were carried out to investigate the effect of thermo-chemical exposures on the hydraulic performance of Compacted Clay Liners (CCLs) in landfills. Hydraulic conductivity of most CCL specimens was increased by two to three times their initial values when exposed to 55 °C for 75 days. CCL specimens also experienced increases in their hydraulic conductivities when exposed to leachate at room temperature. This behaviour could be due to the decrease in viscosity when the permeant was changed from tap water to leachate. However, as the leachate exposure time exceeded the first 15 days, hydraulic conductivity readings decreased to as much as one order of magnitude after 75 days of leachate permeation at room temperature. The gradual decrease in the CCLs hydraulic conductivities was most likely due to chemical precipitation and clogging of pore voids within the soils which seemed to reduce the effective pore volume. The rate of hydraulic conductivity reduction due to leachate permeation was slower at higher temperatures, which was attributed to the lower permeant viscosity and lower clogging occurrence. The observed hydraulic behaviours were correlated to the physical, mineral, and chemical properties of the CCLs and described below. Copyright © 2014 Elsevier Ltd. All rights reserved.

Clay-mediated reactions of HCN oligomers - The effect of the oxidation state of the clay

NASA Technical Reports Server (NTRS)

Ferris, J. P.; Alwis, K. W.; Edelson, E. H.; Mount, N.; Hagan, W. J., Jr.

1981-01-01

Montmorillonite clays which contain Fe(III) inhibit the oligomerization of aqueous solutions of HCN. The inhibitory effect is due to the rapid oxidation of diaminomaleonitrile, a key intermediate in HCN oligomerization, by the Fe(III) incorporated into the aluminosilicate lattice of the clay. The Fe(III) oxidizes diaminomaleonitrile to diiminosuccinonitrile, a compound which is rapidly hydrolyzed to HCN and oxalic acid derivatives. Diaminomaleonitrile is not oxidized when Fe(III) in the montmorillonite is reduced with hydrazine. The oxidation state of the clay is an important variable in experiments designed to simulate clay catalysis on the primitive earth.

Research of CO2 and N2 Adsorption Behavior in K-Illite Slit Pores by GCMC Method

PubMed Central

Chen, Guohui; Lu, Shuangfang; Zhang, Junfang; Xue, Qingzhong; Han, Tongcheng; Xue, Haitao; Tian, Shansi; Li, Jinbu; Xu, Chenxi; Pervukhina, Marina; Clennell, Ben

2016-01-01

Understanding the adsorption mechanisms of CO2 and N2 in illite, one of the main components of clay in shale, is important to improve the precision of the shale gas exploration and development. We investigated the adsorption mechanisms of CO2 and N2 in K-illite with varying pore sizes at the temperature of 333, 363 and 393 K over a broad range of pressures up to 30 MPa using the grand canonical Monte Carlo (GCMC) simulation method. The simulation system is proved to be reasonable and suitable through the discussion of the impact of cation dynamics and pore wall thickness. The simulation results of the excess adsorption amount, expressed per unit surface area of illite, is in general consistency with published experimental results. It is found that the sorption potential overlaps in micropores, leading to a decreasing excess adsorption amount with the increase of pore size at low pressure, and a reverse trend at high pressure. The excess adsorption amount increases with increasing pressure to a maximum and then decreases with further increase in the pressure, and the decreasing amount is found to increase with the increasing pore size. For pores with size greater larger than 2 nm, the overlap effect disappears. PMID:27897232

Removal of a hazardous heavy metal from aqueous solution using functionalized graphene and boron nitride nanosheets: Insights from simulations.

PubMed

Azamat, Jafar; Sattary, Batoul Shirforush; Khataee, Alireza; Joo, Sang Woo

2015-09-01

A computer simulation was performed to investigate the removal of Zn(2+) as a heavy metal from aqueous solution using the functionalized pore of a graphene nanosheet and boron nitride nanosheet (BNNS). The simulated systems were comprised of a graphene nanosheet or BNNS with a functionalized pore containing an aqueous ionic solution of zinc chloride. In order to remove heavy metal from an aqueous solution using the functionalized pore of a graphene nanosheet and BNNS, an external voltage was applied along the z-axis of the simulated box. For the selective removal of zinc ions, the pores of graphene and BNNS were functionalized by passivating each atom at the pore edge with appropriate atoms. For complete analysis systems, we calculated the potential of the mean force of ions, the radial distribution function of ion-water, the residence time of ions, the hydrogen bond, and the autocorrelation function of the hydrogen bond. Copyright © 2015 Elsevier Inc. All rights reserved.

Biogeochemical Factors Influencing the Transport and Fate of Colloids and Colloid-Associated Contaminants in the Vadose Zone

NASA Astrophysics Data System (ADS)

Bradford, S. A.

2016-12-01

The vadose zone exhibits large spatial and temporal variability in many physical, chemical, and biological factors that strongly influence the transport and fate of colloids (e.g., microbes, nanoparticles, clays, and dissolved organic matter) and colloid-associated contaminants (e.g., heavy metals, radionuclides, pesticides, and antibiotics). This presentation highlights our research activities to better understand and predict the influence of specific biogeochemical processes on colloid and colloid-facilitated transport. Results demonstrate the sensitivity of colloid transport, retention, release, and clogging to transients in solution chemistry (e.g., ionic strength, pH, cation and anion type, and surfactants), water velocity and saturation, and preferential flow. Mathematical modeling at interface-, pore-, and continuum-scales is shown to be a critical tool to quantify the relative importance and coupling of these biogeochemical factors on colloid and contaminant transport and fate, which otherwise might be experimentally intractable. Existing gaps in knowledge and model limitations are identified.

An investigation into the effects of pore connectivity on T2 NMR relaxation

NASA Astrophysics Data System (ADS)

Ghomeshi, Shahin; Kryuchkov, Sergey; Kantzas, Apostolos

2018-04-01

Nuclear Magnetic Resonance (NMR) is a powerful technique used to characterize fluids and flow in porous media. The NMR relaxation curves are closely related to pore geometry, and the inversion of the NMR relaxometry data is known to give useful information with regards to pore size distribution (PSD) through the relative amplitudes of the fluids stored in the small and large pores. While this information is crucial, the main challenge for the successful use of the NMR measurements is the proper interpretation of the measured signals. Natural porous media patterns consist of complex pore structures with many interconnected or "coupled" regions, as well as isolated pores. This connectivity along the throats changes the relaxation distribution and in order to properly interpret this data, a thorough understanding of the effects of pore connectivity on the NMR relaxation distribution is warranted. In this paper we address two main points. The first pertains to the fact that there is a discrepancy between the relaxation distribution obtained from experiments, and the ones obtained from solving the mathematical models of diffusion process in the digitized images of the pore space. There are several reasons that may attribute to this such as the lack of a proper incorporation of surface roughness into the model. However, here we are more interested in the effects of pore connectivity and to understand why the typical NMR relaxation distribution obtained from experiments are wider, while the numerical simulations predict that a wider NMR relaxation distribution may indicate poor connectivity. Secondly, by not taking into account the pore coupling effects, from our experience in interpreting the data, we tend to underestimate the pore volume of small pores and overestimate the amplitudes in the large pores. The role of pore coupling becomes even more prominent in rocks with small pore sizes such as for example in shales, clay in sandstones, and in the microstructures of carbonates.

Desorption and mobility mechanisms of co-existing polycyclic aromatic hydrocarbons and heavy metals in clays and clay minerals.

PubMed

Saeedi, Mohsen; Li, Loretta Y; Grace, John R

2018-05-15

The effects of soil components such as clay minerals and as humic acids, as well as co-existing metals and polycyclic aromatic hydrocarbons, on desorption and mobility are examined. Three types of artificially blended clay and clay mineral mixtures (pure kaolinite, kaolinite + sand and kaolinite + sand + bentonite), each with different humic acid content, were tested for desorption and mobility of acenaphthene, fluorene and fluoranthene by three extracting solutions CaCl 2 (0.01 M) and EDTA (0.01M) with non-ionic surfactants (Tween 80 and Triton X100). Heavy metals (Ni, Pb and Zn) were also studied for desorption and mobility. The influence of co-present metals on simultaneous desorption and mobility of PAHs was investigated as well. The results showed that <10% of metals in the clay mineral mixtures were mobile. Combined EDTA and non-ionic solutions can enhance the desorption and mobility of PAHs to >80% in clay mineral mixtures containing no sand, while in the same soils containing ∼40% sand, the desorption exceeded 90%. Heavy metals, as well as increasing humic acids content in the clay mineral mixtures, decreased the desorption and mobility of PAHs, especially for soils containing no sand, and for fluoranthene compared with fluorene and acenaphthene. Copyright © 2018 Elsevier Ltd. All rights reserved.

Bubble Formation Modeling in IE-911

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fondeur, F.F.

2000-09-27

The author used diffusion modeling to determine the hydrogen and oxygen concentration inside IE-911. The study revealed gas bubble nucleation will not occur in the bulk solution inside the pore or on the pore wall. This finding results from the fast oxygen and hydrogen gas molecular diffusion and a very confined pore space. The net steady state concentration of these species inside the pore proves too low to drive bubble nucleation. This study did not investigate other gas bubble nucleating mechanism such as suspended particles in solution.

Understanding fluid transport through the multiscale pore network of a natural shale

NASA Astrophysics Data System (ADS)

Davy, Catherine A.; Nguyen Kim, Thang; Song, Yang; Troadec, David; Blanchenet, Anne-Marie; Adler, Pierre M.

2017-06-01

The pore structure of a natural shale is obtained by three imaging means. Micro-tomography results are extended to provide the spatial arrangement of the minerals and pores present at a voxel size of 700 nm (the macroscopic scale). FIB/SEM provides a 3D representation of the porous clay matrix on the so-called mesoscopic scale (10-20 nm); a connected pore network, devoid of cracks, is obtained for two samples out of five, while the pore network is connected through cracks for two other samples out of five. Transmission Electron Microscopy (TEM) is used to visualize the pore space with a typical pixel size of less than 1 nm and a porosity ranging from 0.12 to 0.25. On this scale, in the absence of 3D images, the pore structure is reconstructed by using a classical technique, which is based on truncated Gaussian fields. Permeability calculations are performed with the Lattice Boltzmann Method on the nanoscale, on the mesoscale, and on the combination of the two. Upscaling is finally done (by a finite volume approach) on the bigger macroscopic scale. Calculations show that, in the absence of cracks, the contribution of the nanoscale pore structure on the overall permeability is similar to that of the mesoscale. Complementarily, the macroscopic permeability is measured on a centimetric sample with a neutral fluid (ethanol). The upscaled permeability on the macroscopic scale is in good agreement with the experimental results.

Osmotic water transport in aquaporins: evidence for a stochastic mechanism

PubMed Central

Zeuthen, Thomas; Alsterfjord, Magnus; Beitz, Eric; MacAulay, Nanna

2013-01-01

We test a novel, stochastic model of osmotic water transport in aquaporins. A solute molecule present at the pore mouth can either be reflected or permeate the pore. We assume that only reflected solute molecules induce osmotic transport of water through the pore, while permeating solute molecules give rise to no water transport. Accordingly, the rate of water transport is proportional to the reflection coefficient σ, while the solute permeability, PS, is proportional to 1 –σ. The model was tested in aquaporins heterologously expressed in Xenopus oocytes. A variety of aquaporin channel sizes and geometries were obtained with the two aquaporins AQP1 and AQP9 and mutant versions of these. Osmotic water transport was generated by adding 20 mm of a range of different-sized osmolytes to the outer solution. The osmotic water permeability and the reflection coefficient were measured optically at high resolution and compared to the solute permeability obtained from short-term uptake of radio-labelled solute under isotonic conditions. For each type of aquaporin there was a linear relationship between solute permeability and reflection coefficient, in accordance with the model. We found no evidence for coupling between water and solute fluxes in the pore. In confirmation of molecular dynamic simulations, we conclude that the magnitude of the osmotic water permeability and the reflection coefficient are determined by processes at the arginine selectivity filter located at the outward-facing end of the pore. PMID:23959676

Diagenetic contrast of sandstones in hydrocarbon prospective Mesozoic rift basins (Ethiopia, UK, USA)

NASA Astrophysics Data System (ADS)

Wolela, A.

2014-11-01

Diagenetic studied in hydrocarbon-prospective Mesozoic rift basins were carried out in the Blue Nile Basin (Ethiopia), Ulster Basin (United Kingdom) and Hartford Basin (United States of America). Alluvial fan, single and amalgamated multistorey meandering and braided river, deep and shallow perennial lake, shallow ephemeral lake, aeolian and playa mud-flat are the prominent depositional environments. The studied sandstones exhibit red bed diagenesis. Source area geology, depositional environments, pore-water chemistry and circulation, tectonic setting and burial history controlled the diagenetic evolution. The diagenetic minerals include: facies-related minerals (calcrete and dolocrete), grain-coating clay minerals and/or hematite, quartz and feldspar overgrowths, carbonate cements, hematite, kaolinite, illite-smectite, smectite, illite, chlorite, actinolite, laumontite, pyrite and apatite. Diversity of diagenetic minerals and sequence of diagenetic alteration can be directly related to depositional environment and burial history of the basins. Variation in infiltrated clays, carbonate cements and clay minerals observed in the studied sandstones. The alluvial fan and fluviatile sandstones are dominated by kaolinite, illite calcite and ferroan calcite, whereas the playa and lacustrine sandstones are dominated by illite-smectite, smectite-chlorite, smectite, chlorite, dolomite ferroan dolomite and ankerite. Albite, pyrite and apatite are predominantly precipitated in lacustrine sandstones. Basaltic eruption in the basins modified mechanically infiltrated clays to authigenic clays. In all the studied sandstones, secondary porosity predominates over primary porosity. The oil emplacement inhabited clay authigenesis and generation of secondary porosity, whereas authigenesis of quartz, pyrite and apatite continued after oil emplacement.

The Effects of Air-Cooled Blast Furnace Slag (ACBFS) Aggregate on the Chemistry of Pore Solution and the Interfacial Transition Zone

NASA Astrophysics Data System (ADS)

Panchmatia, Parth

Numerous laboratory and field studies have demonstrated that concrete incorporating air cooled blast furnace slag (ACBFS) aggregate showed a higher degree of infilling of voids with ettringite as opposed to concrete prepared using naturally mined carbonate aggregates when exposed to similar environmental conditions. This observation prompted some to link the deterioration observed in the ACBFS aggregate concrete structures to the compromised freeze-thaw resistance due to infilling of air voids. Concerns about the release of sulfur from ACBFS aggregate into the pore solution of concrete had been presented as the reason for the observed ettringite deposits in the air voids. However, literature quantifying the influence of ACBFS aggregate on the chemistry of the pore solution of concrete is absent. Therefore, the main purpose of this research was to quantify the effects of ACBFS aggregate on the chemistry of the pore solution of mortars incorporating them. Coarse and crushed ACBFS aggregates were submerged in artificial pore solutions (APSs) representing pore solutions of 3-day, 7-day, and 28-day hydrated plain, binary, and ternary paste systems. The change in the chemistry of these artificial pore solutions was recorded to quantify the chemical contribution of ACBFS aggregate to the pore solution of concrete. It was observed that the sulfate concentration of all APSs increased once they were in contact with either coarse or crushed ACBFS aggregate. After 28 days of contact, the increase in sulfate concentration of the APSs ranged from 4.85 - 12.23 mmol/L and 14.21 - 16.87 mmol/L for contact with coarse and crushed ACBFS aggregate, respectively. More than 40% of the total sulfate that was released by the ACBFS aggregate occurred during the first 72 hours (3 days) of its contact with the APSs. There was little or no difference in the amount of sulfate released from ACBFS aggregate in the different types of APSs. In other words, the type of binder solution from which pore solution was extracted had no effect on the amount of sulfate that was released when it was in contact with ACBFS aggregate. The relatively quick release of sulfur from ACBFS aggregate into the APSs prompted investigation of the chemical composition of the pore solution of mortar (at early stages of hydration) incorporating ACBFS aggregate. The chemical composition of the pore solutions obtained from mortars prepared using ACBFS aggregate and plain and binary paste matrices was compared those of mortars prepared using Ottawa sand and plain and binary paste matrices. After 7 days of hydration, the sulfur (S) concentration of the pore solution extracted from mortars prepared using ACBFS aggregate was 3.4 - 5.6 times greater than that obtained from corresponding mortars (i.e. mortars with the same paste matrix) prepared using Ottawa sand. Binary mortars containing fly ash (FA) showed the lowest S content after 7 days of hydration amongst all mortars prepared using ACBFS aggregate. On the other hand, binary mortars prepared using slag cement (SC) and ACBFS aggregate had the highest S concentration after 7 days of hydration. These effects on the S concentration in the pore solutions can be explained by the difference in the chemical makeup of the binders, and not because of different rate of release of S from ACBFS into the pore solution. In addition, TGA analysis of 7-day hydrated mortars revealed that the ettringite, monosulfate, and calcium hydroxide content was lower in mortars prepared using ACBFS aggregate as opposed to those prepared using Ottawa sand. This could be because of the low degree of hydration in mortars with ACBFS aggregate because of the high sulfate concentration in its pore solution. The properties of the interfacial transition zone (ITZ), i.e. the zone in the vicinity of the aggregate surface, depends on the property of the aggregate such as its porosity and texture. Therefore, it is expected that the properties of ITZ around the ACBFS particle, which is porous and proven to contribute sulfate, be different from the ITZ around the naturally mined siliceous aggregate. Image analysis conducted on backscattered images obtained using scanning electron microscope revealed that the ITZ of naturally mined siliceous aggregate was more porous compared to the ITZ of ACBFS aggregate. In addition, calcium hydroxide deposits were more frequent and larger in size in the ITZ around siliceous sand than in the case of the ITZ around the ACBFS aggregate.

Evaluation of accessible mineral surface areas for improved prediction of mineral reaction rates in porous media

NASA Astrophysics Data System (ADS)

Beckingham, Lauren E.; Steefel, Carl I.; Swift, Alexander M.; Voltolini, Marco; Yang, Li; Anovitz, Lawrence M.; Sheets, Julia M.; Cole, David R.; Kneafsey, Timothy J.; Mitnick, Elizabeth H.; Zhang, Shuo; Landrot, Gautier; Ajo-Franklin, Jonathan B.; DePaolo, Donald J.; Mito, Saeko; Xue, Ziqiu

2017-05-01

The rates of mineral dissolution reactions in porous media are difficult to predict, in part because of a lack of understanding of mineral reactive surface area in natural porous media. Common estimates of mineral reactive surface area used in reactive transport models for porous media are typically ad hoc and often based on average grain size, increased to account for surface roughness or decreased by several orders of magnitude to account for reduced surface reactivity of field as opposed to laboratory samples. In this study, accessible mineral surface areas are determined for a sample from the reservoir formation at the Nagaoka pilot CO2 injection site (Japan) using a multi-scale image analysis based on synchrotron X-ray microCT, SEM QEMSCAN, XRD, SANS, and FIB-SEM. This analysis not only accounts for accessibility of mineral surfaces to macro-pores, but also accessibility through connected micro-pores in smectite, the most abundant clay mineral in this sample. While the imaging analysis reveals that most of the micro- and macro-pores are well connected, some pore regions are unconnected and thus inaccessible to fluid flow and diffusion. To evaluate whether mineral accessible surface area accurately reflects reactive surface area a flow-through core experiment is performed and modeled at the continuum scale. The core experiment is performed under conditions replicating the pilot site and the evolution of effluent solutes in the aqueous phase is tracked. Various reactive surface area models are evaluated for their ability to capture the observed effluent chemistry, beginning with parameter values determined as a best fit to a disaggregated sediment experiment (Beckingham et al., 2016) described previously. Simulations that assume that all mineral surfaces are accessible (as in the disaggregated sediment experiment) over-predict the observed mineral reaction rates, suggesting that a reduction of RSA by a factor of 10-20 is required to match the core flood experimental data. While the fit of the effluent chemistry (and inferred mineral dissolution rates) greatly improve when the pore-accessible mineral surface areas are used, it was also necessary to include highly reactive glass phases to match the experimental observations, in agreement with conclusions from the disaggregated sediment experiment. It is hypothesized here that the 10-20 reduction in reactive surface areas based on the limited pore accessibility of reactive phases in core flood experiment may be reasonable for poorly sorted and cemented sediments like those at the Nagaoka site, although this reflects pore rather than larger scale heterogeneity.

Morphology and Fractal Characterization of Multiscale Pore Structures for Organic-Rich Lacustrine Shale Reservoirs

NASA Astrophysics Data System (ADS)

Wang, Yang; Wu, Caifang; Zhu, Yanming; Chen, Shangbin; Liu, Shimin; Zhang, Rui

Lacustrine shale gas has received considerable attention and has been playing an important role in unconventional natural gas production in China. In this study, multiple techniques, including total organic carbon (TOC) analysis, X-ray diffraction (XRD) analysis, field emission scanning electron microscopy (FE-SEM), helium pycnometry and low-pressure N2 adsorption have been applied to characterize the pore structure of lacustrine shale of Upper Triassic Yanchang Formation from the Ordos Basin. The results show that organic matter (OM) pores are the most important type dominating the pore system, while interparticle (interP) pores, intraparticle (intraP) and microfractures are also usually observed between or within different minerals. The shapes of OM pores are less complex compared with the other two pore types based on the Image-Pro Plus software analysis. In addition, the specific surface area ranges from 2.76m2/g to 10.26m2/g and the pore volume varies between 0.52m3/100g and 1.31m3/100g. Two fractal dimensions D1 and D2 were calculated using Frenkel-Halsey-Hill (FHH) method, with D1 varying between 2.510 and 2.632, and D2 varying between 2.617 and 2.814. Further investigation indicates that the fractal dimensions exhibit positive correlations with TOC contents, whereas there is no definite relationship observed between fractal dimensions and clay minerals. Meanwhile, the fractal dimensions increase with the increase in specific surface area, and is negatively correlated with the pore size.

Acoustics of marine sediment under compaction: binary grain-size model and viscoelastic extension of Biot's theory.

PubMed

Leurer, Klaus C; Brown, Colin

2008-04-01

This paper presents a model of acoustic wave propagation in unconsolidated marine sediment, including compaction, using a concept of a simplified sediment structure, modeled as a binary grain-size sphere pack. Compressional- and shear-wave velocities and attenuation follow from a combination of Biot's model, used as the general framework, and two viscoelastic extensions resulting in complex grain and frame moduli, respectively. An effective-grain model accounts for the viscoelasticity arising from local fluid flow in expandable clay minerals in clay-bearing sediments. A viscoelastic-contact model describes local fluid flow at the grain contacts. Porosity, density, and the structural Biot parameters (permeability, pore size, structure factor) as a function of pressure follow from the binary model, so that the remaining input parameters to the acoustic model consist solely of the mass fractions and the known mechanical properties of each constituent (e.g., carbonates, sand, clay, and expandable clay) of the sediment, effective pressure, or depth, and the environmental parameters (water depth, salinity, temperature). Velocity and attenuation as a function of pressure from the model are in good agreement with data on coarse- and fine-grained unconsolidated marine sediments.

Sensitive strata in Bootlegger Cove Formation

USGS Publications Warehouse

Olsen, Harold W.

1989-01-01

Sensitivity magnitudes are interpreted from remolded strength values in recent subsurface geologic, geotechnical, and geochemical data from the Bootlegger Cove Formation adjacent to the Turnagain Heights Landslide. The results show that strata composed of highly sensitive clays occur in both the middle and lower zones of the formation, and that between these strata the clays are generally of low-to-medium sensitivity. The most sensitive stratum is in the middle zone between two sand layers, and its sensitivity increases from both clay-sand interfaces to a maximum at the center of the stratum. The pore fluid chemistry of the highly sensitive materials differs from that in the materials of low to medium sensitivity only in their concentrations of organic carbon, chloride, bicarbonate, and sulfate. The total dissolved solids concentration is low, and the ratio of monovalent to divalent cations is very high throughout the middle and lower zones of the formation. Of the known causes of high and extremely high sensitivities, only organic and/or anionic dispersants are consistent with these findings.

Models for Gas Hydrate-Bearing Sediments Inferred from Hydraulic Permeability and Elastic Velocities

USGS Publications Warehouse

Lee, Myung W.

2008-01-01

Elastic velocities and hydraulic permeability of gas hydrate-bearing sediments strongly depend on how gas hydrate accumulates in pore spaces and various gas hydrate accumulation models are proposed to predict physical property changes due to gas hydrate concentrations. Elastic velocities and permeability predicted from a cementation model differ noticeably from those from a pore-filling model. A nuclear magnetic resonance (NMR) log provides in-situ water-filled porosity and hydraulic permeability of gas hydrate-bearing sediments. To test the two competing models, the NMR log along with conventional logs such as velocity and resistivity logs acquired at the Mallik 5L-38 well, Mackenzie Delta, Canada, were analyzed. When the clay content is less than about 12 percent, the NMR porosity is 'accurate' and the gas hydrate concentrations from the NMR log are comparable to those estimated from an electrical resistivity log. The variation of elastic velocities and relative permeability with respect to the gas hydrate concentration indicates that the dominant effect of gas hydrate in the pore space is the pore-filling characteristic.

Pore Structure and Diagenetic Controls on Relative Permeability: Implications for Enhanced Oil Recovery and CO2 Storage

NASA Astrophysics Data System (ADS)

Feldman, J.; Dewers, T. A.; Heath, J. E.; Cather, M.; Mozley, P.

2016-12-01

Multiphase flow in clay-bearing sandstones of the Morrow Sandstone governs the efficiency of CO2 storage and enhanced oil recovery at the Farnsworth Unit, Texas. This formation is the target for enhanced oil recovery and injection of one million metric ton of anthropogenically-sourced CO2. The sandstone hosts eight major flow units that exhibit distinct microstructural characteristics due to diagenesis, including: "clean" macro-porosity; quartz overgrowths constricting some pores; ghost grains; intergranular porosity filled by microporous authigenic clay; and feldspar dissolution. We examine the microstructural controls on macroscale (core scale) relative permeability and capillary pressure behavior through: X-ray computed tomography, Robomet.3d, and focused ion beam-scanning electron microscopy imaging of the pore structure of the major flow units of the Morrow Sandstone; relative permeability and capillary pressure in the laboratory using CO2, brine, and oil at reservoir pressure and effective stress conditions. The combined data sets inform links between patterns of diagenesis and multiphase flow. These data support multiphase reservoir simulation and performance assessment by the Southwest Regional Partnership on Carbon Sequestration (SWP). Funding for this project is provided by the U.S. Department of Energy's National Energy Technology Laboratory through the SWP under Award No. DE-FC26-05NT42591. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Pore-Lining Composition and Capillary Breakthrough Pressure of Mudstone Caprocks: Sealing Efficiency of Geologic CO2 Storage Sites

NASA Astrophysics Data System (ADS)

Heath, J. E.; Dewers, T. A.; McPherson, B. J.; Kotula, P. G.

2010-12-01

Subsurface containment of CO2 is predicated on effective caprock sealing. Many previous studies have relied on macroscopic measurements of capillary breakthrough pressure and other petrophysical properties without direct examination of solid phases that line pore networks and directly contact fluids. However, pore-lining phases strongly contribute to sealing behavior through interfacial interactions among CO2, brine, and the mineral or non-mineral phases. Our high resolution (i.e., sub-micron) examination of the composition of pore-lining phases of several continental and marine mudstones indicates that sealing efficiency (i.e., breakthrough pressure) is governed by pore shapes and pore-lining phases that are not identifiable except through direct characterization of pores. Bulk X-ray diffraction data does not indicate which phases line the pores and may be especially lacking for mudstones with organic material. Organics can line pores and may represent once-mobile phases that modify the wettability of an originally clay-lined pore network. For shallow formations (i.e., < ~800 m depth), interfacial tension and contact angles result in breakthrough pressures that may be as high as those needed to fracture the rock—thus, in the absence of fractures, capillary sealing efficiency is indicated. Deeper seals have poorer capillary sealing if mica-like wetting dominates the wettability. We thank the U.S. Department of Energy’s National Energy Technology Laboratory and the Office of Basic Energy Sciences, and the Southeast and Southwest Carbon Sequestration Partnerships for supporting this work. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

Mild acid and alkali treated clay minerals enhance bioremediation of polycyclic aromatic hydrocarbons in long-term contaminated soil: A 14C-tracer study.

PubMed

Biswas, Bhabananda; Sarkar, Binoy; Rusmin, Ruhaida; Naidu, Ravi

2017-04-01

Bioremediation of polycyclic aromatic hydrocarbon (PAH)-contaminated soils requires a higher microbial viability and an increased PAH bioavailability. The clay/modified clay-modulated bacterial degradation could deliver a more efficient removal of PAHs in soils depending on the bioavailability of the compounds. In this study, we modified clay minerals (smectite and palygorskite) with mild acid (HCl) and alkali (NaOH) treatments (0.5-3 M), which increased the surface area and pore volume of the products, and removed the impurities without collapsing the crystalline structure of clay minerals. In soil incubation studies, supplements with the clay products increased bacterial growth in the order: 0.5 M HCl ≥ unmodified ≥ 0.5 M NaOH ≥ 3 M NaOH ≥ 3 M HCl for smectite, and 0.5 M HCl ≥ 3 M NaOH ≥ 0.5 M NaOH ≥ 3 M HCl ≥ unmodified for palygorskite. A 14 C-tracing study showed that the mild acid/alkali-treated clay products increased the PAH biodegradation (5-8%) in the order of 0.5 M HCl ≥ unmodified > 3 M NaOH ≥ 0.5 M NaOH for smectite, and 0.5 M HCl > 0.5 M NaOH ≥ unmodified ≥ 3 M NaOH for palygorskite. The biodegradation was correlated (r = 0.81) with the bioavailable fraction of PAHs and microbial growth as affected particularly by the 0.5 M HCl and 0.5 M NaOH-treated clay minerals. These results could be pivotal in developing a clay-modulated bioremediation technology for cleaning up PAH-contaminated soils and sediments in the field. Copyright © 2017 Elsevier Ltd. All rights reserved.

Multiscale Analysis of Soil Porosity from Hg Injection Curves in Soils from Minas Gerais, Brazil

NASA Astrophysics Data System (ADS)

Vidal Vázquez, E.; Miranda, J. G. V.; Paz-Ferreiro, J.

2012-04-01

The soil pore space is a continuum extremely variable in size, including structures smaller than nanometres and as large as macropores or cracks with millimetres or even centimetres size. Pore size distributions (PSDs) affects important soil functions, such as transmission and storage of water, and root growth. Direct and indirect measurements of PSDs are currently used to characterize soil structure. Mercury injection porosimetry is useful for assessing equivalent pore size diameters in the range from about 0,5 nm to 100 μm. Here, the multifractal formalism was employed to describe Hg injection curves measured in duplicate samples collected on 54 horizons from 19 profiles in Minas Gerais state, Brazil. Ten of the studied profiles were classified as Ferralsols (Latosols, Oxisols). Besides these, other wide different soil groups were sampled, including Nitisol, Acrisol, Alisol, Luvisol, Planosol, Cambisol, Andosol and Leptosol. Clay content varied from 4 to 86% and pore volume in the range from 100 to 0.005 μm was between 5.52 a 53.76 cm3100g-1. All the horizons taken on Ferralsols and Nitisols as well as in Bt argic horizons from Acrisol Alisol, Luvisol and Planosol clearly showed a bimodal pore size distribution. Pore volume in the range from 100 to 0.005 μm and microporosity (0,2-0.005 μm) showed a significant relationship with clay content an Al2O3. All the Hg injection data sets studied soil showed remarkably good scaling trends and could be fitted reasonably well with multifractal models. The capacity dimensions, D0, was not significantly different from the Euclidean dimension. The entropy dimension, D1, varied from 0.590 to 0.946 , whereas the Hölder exponent of order zero, α0was between 1.027 and 1.451, and these two parameters showed a lineal negatives relationship, as expected. The highest D1 values, ranging from 0.913 to 0.980, were obtained for the Leptosol, whereas the lowest D1 values, ranging from 0.641 to 0.766 corresponded to the Nitisol. This results reflect that most of the measure concentrated in a small size domain for the horizons sampled from the Nitisol, whereas for the Leptosol the measure was more evenly distributed. In general, multifractal indices have been found to be useful for assessing differences in pore size distributions of the studied soil types.

Natural and synthetic mineral silicates as functional nanoparticles in polymer composites

NASA Astrophysics Data System (ADS)

Shao, Hua

A new strategy is described for the substantial enhancement of the barrier properties for both a thermoset epoxy polymer and a thermoplastic polyolefin by sandwiching a novel self-supported clay fabric film between thin polymer sheets. The success of this strategy is attributed to the high orientation of clay nanolayers in the paper-like clay fabric films and to the filling of the micro- or sub-micro sized voids between imperfectly tiled clay platelet edges by the polymer chains. Thermoplastic polyolefin-clay fabric film composites were fabricated by hot-pressing the clay films between two sheets of high density polyethylene (HDPE) films. The sandwiched composites exhibit more than a 30-fold decrease in O2 transmission rate with respect to the pure HDPE film. Impregnating the self-supported clay papers with epoxy pre-polymers successfully leads to thermoset composite films with more than 2-3 orders of magnitude reduction in O2 permeability in comparison to the pristine epoxy matrix. Owing to the promising use of synthetic Mg-saponite (denoted SAP) as epoxy polymer reinforcing agents, we investigated the cost-effective synthesis of SAP by replacing urea with sodium hydroxide as base source. Co-crystallization of new zeolite phases, such as garronite (denoted GIS) and cancrinite (denoted CAN), occurred along with SAP upon increasing the alkalinity of the reaction mixture. This finding represents the first example of the preparation of a CAN/SAP phase mixture. Moreover, pure-phase cancrinite with rod-like morphology up to several mum in length was synthesized under Mg-free conditions. Also, the Si/AI ratio within the synthesis gel has an influence on the chemical composition and textural properties of pure CAN crystals. Microporous cancrinite is a promising candidate for reinforcing epoxy polymers, considering that CAN represents a substantial fraction of the mixed CAN-SAP phase formed during the synthesis of saponite. Therefore, the reaction conditions (e.g. alkalinity, reaction temperature, and duration) were further expored in order to optimize the formation of small crystals of CAN (˜ 100 nm) with large external surface area and high pore volume. These textural features facilitate the homogeneous dispersion of cancrinite particles in epoxy matrices. In addition, a new phase sodalite (denoted SOD) was co-crystallized along with CAN in some cases, depending on reaction conditions. The synthetic zeolites CAN and SOD act as reinforcing agents for thermoset epoxy polymers owing in part to their small particle size, large surface area and high pore volume. The tensile strength, modulus and toughness of an epoxy matrix are simultaneously enhanced without the need for organic surface modification of zeolites. This finding represents the first example for which the mechanical properties of glassy epoxy composite are all improved through the use of a microporous zeolite as a functional inorganic nanoparticle.

Diagenetic history of the Surma Group sandstones (Miocene) in the Surma Basin, Bangladesh

NASA Astrophysics Data System (ADS)

Rahman, M. Julleh Jalalur; McCann, Tom

2012-02-01

This study examines the various diagenetic controls of the Miocene Surma Group sandstones encountered in petroleum exploration wells from the Surma Basin, which is situated in the northeastern part of the Bengal Basin, Bangladesh. The principal diagenetic minerals/cements in the Surma Group sandstones are Fe-carbonates (with Fe-calcite dominating), quartz overgrowths and authigenic clays (predominantly chlorite, illite-smectite and minor kaolin). The isotopic composition of the carbonate cement revealed a narrow range of δ 18O values (-10.3‰ to -12.4‰) and a wide range of δ 13C value (+1.4‰ to -23.1‰). The δ 13C VPDB and δ 18O VPDB values of the carbonate cements reveal that carbon was most likely derived from the thermal maturation of organic matter during burial, as well as from the dissolution of isolated carbonate clasts and precipitated from mixed marine-meteoric pore waters. The relationship between the intergranular volume (IGV) versus cement volume indicates that compaction played a more significant role than cementation in destroying the primary porosity. However, cementation also played a major role in drastically reducing porosity and permeability in sandstones with poikilotopic, pore-filling blocky cements formed in early to intermediate and deep burial areas. In addition to Fe-carbonate cements, various clay minerals including illite-smectite and chlorite occur as pore-filling and pore-lining authigenic phases. Significant secondary porosity has been generated at depths from 2500 m to 4728 m. The best reservoir rocks found at depths of 2500-3300 m are well sorted, relatively coarse grained; more loosely packed and better rounded sandstones having good porosities (20-30%) and high permeabilities (12-6000 mD). These good quality reservoir rocks are, however, not uniformly distributed and can be considered to be compartmentalized as a result of interbedding with sandstone layers of low to moderate porosities, low permeabilities owing to poor sorting and extensive compaction and cementation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bihani, Abhishek; Daigle, Hugh; Cook, Ann

Coexistence of three methane phases (liquid (L), gas (G), hydrate (H)) in marine gas hydrate systems may occur according to in-situ pressure, temperature, salinity and pore size. In sediments with salinity close to seawater, a discrete zone of three-phase (3P) equilibrium may occur near the base of the regional hydrate stability zone (RHSZ) due to capillary effects. The existence of a 3P zone influences the location of the bottom-simulating reflection (BSR) and has implications for methane fluxes at the base of the RHSZ. We studied hydrate stability conditions in two wells, WR313-G and WR313-H, at Walker Ridge Block 313 inmore » the northern Gulf of Mexico. We determined pore size distributions (PSD) by constructing a synthetic nuclear magnetic resonance (NMR) relaxation time distribution. Correlations were obtained by non-linear regression on NMR, gamma ray, and bulk density logs from well KC-151 at Keathley Canyon. The correlations enabled construction of relaxation time distributions for WR313-G and WR313-H, which were used to predict PSD through comparison with mercury injection capillary pressure measurements. With the computed PSD, L+H and L+G methane solubility was determined from in-situ pressure and temperature. The intersection of the L+G and L+H curves for various pore sizes allowed calculation of the depth range of the 3P equilibrium zone. As in previous studies at Blake Ridge and Hydrate Ridge, the top of the 3P zone moves upwards with increasing water depth and overlies the bulk 3P equilibrium depth. In clays at Walker Ridge, the predicted thickness of the 3P zone is approximately 35 m, but in coarse sands it is only a few meters due to the difference in absolute pore sizes and the width of the PSD. The thick 3P zone in the clays may explain in part why the BSR is only observed in the sand layers at Walker Ridge, although other factors may influence the presence or absence of a BSR.« less

Elevated gas hydrate saturation within silt and silty clay sediments in the Shenhu area, South China Sea

USGS Publications Warehouse

Wang, X.; Hutchinson, D.R.; Wu, S.; Yang, S.; Guo, Y.

2011-01-01

Gas hydrate saturations were estimated using five different methods in silt and silty clay foraminiferous sediments from drill hole SH2 in the South China Sea. Gas hydrate saturations derived from observed pore water chloride values in core samples range from 10 to 45% of the pore space at 190-221 m below seafloor (mbsf). Gas hydrate saturations estimated from resistivity (Rt) using wireline logging results are similar and range from 10 to 40.5% in the pore space. Gas hydrate saturations were also estimated by P wave velocity obtained during wireline logging by using a simplified three-phase equation (STPE) and effective medium theory (EMT) models. Gas hydrate saturations obtained from the STPE velocity model (41.0% maximum) are slightly higher than those calculated with the EMT velocity model (38.5% maximum). Methane analysis from a 69 cm long depressurized core from the hydrate-bearing sediment zone indicates that gas hydrate saturation is about 27.08% of the pore space at 197.5 mbsf. Results from the five methods show similar values and nearly identical trends in gas hydrate saturations above the base of the gas hydrate stability zone at depths of 190 to 221 mbsf. Gas hydrate occurs within units of clayey slit and silt containing abundant calcareous nannofossils and foraminifer, which increase the porosities of the fine-grained sediments and provide space for enhanced gas hydrate formation. In addition, gas chimneys, faults, and fractures identified from three-dimensional (3-D) and high-resolution two-dimensional (2-D) seismic data provide pathways for fluids migrating into the gas hydrate stability zone which transport methane for the formation of gas hydrate. Sedimentation and local canyon migration may contribute to higher gas hydrate saturations near the base of the stability zone. Copyright 2011 by the American Geophysical Union.

Use of natural clays as sorbent materials for rare earth ions: Materials characterization and set up of the operative parameters.

PubMed

Iannicelli-Zubiani, Elena Maria; Cristiani, Cinzia; Dotelli, Giovanni; Gallo Stampino, Paola; Pelosato, Renato; Mesto, Ernesto; Schingaro, Emanuela; Lacalamita, Maria

2015-12-01

Two mineral clays of the montmorillonite group were tested as sorbents for the removal of Rare Earths (REs) from liquid solutions. Lanthanum and neodymium model solutions were used to perform uptake tests in order to: (a) verify the clays sorption capability, (b) investigate the sorption mechanisms and (c) optimize the experimental parameters, such as contact time and pH. The desorption was also studied, in order to evaluate the feasibility of REs recovery from waters. The adsorption-desorption procedure with the optimized parameters was also tested on a leaching solution obtained by dissolution of a dismantled NdFeB magnet of a hard-disk. The clays were fully characterized after REs adsorption and desorption by means of X-ray powder diffraction (XRPD) and X-ray photoelectron spectroscopy (XPS); the liquid phase was characterized via Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) analyses. The experimental results show that both clays are able to capture and release La and Nd ions, with an ion exchange mechanism. The best total efficiency (capture ≈ 50%, release ≈ 70%) is obtained when the uptake and release processes are performed at pH=5 and pH=1 respectively; in real leached scrap solutions, the uptake is around 40% but release efficiency is strongly decreased passing from a mono-ion system to a real system (from 80% to 5%). Furthermore, a strong matrix effect is found, with the matrix largely affecting both the uptake and the release of neodymium. Copyright © 2015 Elsevier Ltd. All rights reserved.

A new approximation for pore pressure accumulation in marine sediment due to water waves

NASA Astrophysics Data System (ADS)

Jeng, D.-S.; Seymour, B. R.; Li, J.

2007-01-01

The residual mechanism of wave-induced pore water pressure accumulation in marine sediments is re-examined. An analytical approximation is derived using a linear relation for pore pressure generation in cyclic loading, and mistakes in previous solutions (Int. J. Numer. Anal. Methods Geomech. 2001; 25:885-907; J. Offshore Mech. Arctic Eng. (ASME) 1989; 111(1):1-11) are corrected. A numerical scheme is then employed to solve the case with a non-linear relation for pore pressure generation. Both analytical and numerical solutions are verified with experimental data (Laboratory and field investigation of wave-sediment interaction. Joseph H. Defrees Hydraulics Laboratory, School of Civil and Environmental Engineering, Cornell University, Ithaca, NY, 1983), and provide a better prediction of pore pressure accumulation than the previous solution (J. Offshore Mech. Arctic Eng. (ASME) 1989; 111(1):1-11). The parametric study concludes that the pore pressure accumulation and use of full non-linear relation of pore pressure become more important under the following conditions: (1) large wave amplitude, (2) longer wave period, (3) shallow water, (4) shallow soil and (5) softer soils with a low consolidation coefficient. Copyright

Long-term geochemical evolution of the near field repository: Insights from reactive transport modelling and experimental evidences

NASA Astrophysics Data System (ADS)

Arcos, David; Grandia, Fidel; Domènech, Cristina; Fernández, Ana M.; Villar, María V.; Muurinen, Arto; Carlsson, Torbjörn; Sellin, Patrik; Hernán, Pedro

2008-12-01

The KBS-3 underground nuclear waste repository concept designed by the Swedish Nuclear Fuel and Waste Management Co. (SKB) includes a bentonite buffer barrier surrounding the copper canisters and the iron insert where spent nuclear fuel will be placed. Bentonite is also part of the backfill material used to seal the access and deposition tunnels of the repository. The bentonite barrier has three main safety functions: to ensure the physical stability of the canister, to retard the intrusion of groundwater to the canisters, and in case of canister failure, to retard the migration of radionuclides to the geosphere. Laboratory experiments (< 10 years long) have provided evidence of the control exerted by accessory minerals and clay surfaces on the pore water chemistry. The evolution of the pore water chemistry will be a primordial factor on the long-term stability of the bentonite barrier, which is a key issue in the safety assessments of the KBS-3 concept. In this work we aim to study the long-term geochemical evolution of bentonite and its pore water in the evolving geochemical environment due to climate change. In order to do this, reactive transport simulations are used to predict the interaction between groundwater and bentonite which is simulated following two different pathways: (1) groundwater flow through the backfill in the deposition tunnels, eventually reaching the top of the deposition hole, and (2) direct connection between groundwater and bentonite rings through fractures in the granite crosscutting the deposition hole. The influence of changes in climate has been tested using three different waters interacting with the bentonite: present-day groundwater, water derived from ice melting, and deep-seated brine. Two commercial bentonites have been considered as buffer material, MX-80 and Deponit CA-N, and one natural clay (Friedland type) for the backfill. They show differences in the composition of the exchangeable cations and in the accessory mineral content. Results from the simulations indicate that pore water chemistry is controlled by the equilibrium with the accessory minerals, especially carbonates. pH is buffered by precipitation/dissolution of calcite and dolomite, when present. The equilibrium of these minerals is deeply influenced by gypsum dissolution and cation exchange reactions in the smectite interlayer. If carbonate minerals are initially absent in bentonite, pH is then controlled by surface acidity reactions in the hydroxyl groups at the edge sites of the clay fraction, although its buffering capacity is not as strong as the equilibrium with carbonate minerals. The redox capacity of the bentonite pore water system is mainly controlled by Fe(II)-bearing minerals (pyrite and siderite). Changes in the groundwater composition lead to variations in the cation exchange occupancy, and dissolution-precipitation of carbonate minerals and gypsum. The most significant changes in the evolution of the system are predicted when ice-melting water, which is highly diluted and alkaline, enters into the system. In this case, the dissolution of carbonate minerals is enhanced, increasing pH in the bentonite pore water. Moreover, a rapid change in the population of exchange sites in the smectite is expected due to the replacement of Na for Ca.

Long-term geochemical evolution of the near field repository: insights from reactive transport modelling and experimental evidences.

PubMed

Arcos, David; Grandia, Fidel; Domènech, Cristina; Fernández, Ana M; Villar, María V; Muurinen, Arto; Carlsson, Torbjörn; Sellin, Patrik; Hernán, Pedro

2008-12-12

The KBS-3 underground nuclear waste repository concept designed by the Swedish Nuclear Fuel and Waste Management Co. (SKB) includes a bentonite buffer barrier surrounding the copper canisters and the iron insert where spent nuclear fuel will be placed. Bentonite is also part of the backfill material used to seal the access and deposition tunnels of the repository. The bentonite barrier has three main safety functions: to ensure the physical stability of the canister, to retard the intrusion of groundwater to the canisters, and in case of canister failure, to retard the migration of radionuclides to the geosphere. Laboratory experiments (< 10 years long) have provided evidence of the control exerted by accessory minerals and clay surfaces on the pore water chemistry. The evolution of the pore water chemistry will be a primordial factor on the long-term stability of the bentonite barrier, which is a key issue in the safety assessments of the KBS-3 concept. In this work we aim to study the long-term geochemical evolution of bentonite and its pore water in the evolving geochemical environment due to climate change. In order to do this, reactive transport simulations are used to predict the interaction between groundwater and bentonite which is simulated following two different pathways: (1) groundwater flow through the backfill in the deposition tunnels, eventually reaching the top of the deposition hole, and (2) direct connection between groundwater and bentonite rings through fractures in the granite crosscutting the deposition hole. The influence of changes in climate has been tested using three different waters interacting with the bentonite: present-day groundwater, water derived from ice melting, and deep-seated brine. Two commercial bentonites have been considered as buffer material, MX-80 and Deponit CA-N, and one natural clay (Friedland type) for the backfill. They show differences in the composition of the exchangeable cations and in the accessory mineral content. Results from the simulations indicate that pore water chemistry is controlled by the equilibrium with the accessory minerals, especially carbonates. pH is buffered by precipitation/dissolution of calcite and dolomite, when present. The equilibrium of these minerals is deeply influenced by gypsum dissolution and cation exchange reactions in the smectite interlayer. If carbonate minerals are initially absent in bentonite, pH is then controlled by surface acidity reactions in the hydroxyl groups at the edge sites of the clay fraction, although its buffering capacity is not as strong as the equilibrium with carbonate minerals. The redox capacity of the bentonite pore water system is mainly controlled by Fe(II)-bearing minerals (pyrite and siderite). Changes in the groundwater composition lead to variations in the cation exchange occupancy, and dissolution-precipitation of carbonate minerals and gypsum. The most significant changes in the evolution of the system are predicted when ice-melting water, which is highly diluted and alkaline, enters into the system. In this case, the dissolution of carbonate minerals is enhanced, increasing pH in the bentonite pore water. Moreover, a rapid change in the population of exchange sites in the smectite is expected due to the replacement of Na for Ca.

The radiolysis and radioracemization of amino acids on clays

NASA Technical Reports Server (NTRS)

Bonner, W. A.; Hall, H.; Chow, G.; Yi, L.; Lemmon, R. M.

1985-01-01

The effects of the surfaces of kaolinite and bentonite clays on the radiolysis and radioracemization of L-leucine and its hydrochloride salt have been investigated experimentally. L-leucine and its hydrochloride salt were deposited on the clays and the amino acid/clay preparations were irradiated by a Co-60 gamma-ray source which induced 2-89 percent radiolysis. The efficiency of radiolysis and radioracemization were measured using gas chromatography. Results were obtained for leucine in 0.1 M aqueous solution for comparison with the clay-deposted leucine and leucine hydrochloride. It is found that radiolysis and radioracemization in the samples occurred according to a pseudo-first-order rate law. Comparison of the specific rate constants showed that leucine and its hydrochloride salt were the most resistant to both radiolysis and radioracemization, followed by leucine and its hydrochloride salt on kaolin. Leucine and its HCl salt on bentonite, and leucine in aqueous solution were found to be the least resistant to radiolysis and radioracemization. The experimental results are intepreted with respect to the Vester-Ulbricht mechanism for the origin of optical activity.

Non-perturbative Quantification of Ionic Charge Transfer through Nm-Scale Protein Pores Using Graphene Microelectrodes

NASA Astrophysics Data System (ADS)

Ping, Jinglei; Johnson, A. T. Charlie; A. T. Charlie Johnson Team

Conventional electrical methods for detecting charge transfer through protein pores perturb the electrostatic condition of the solution and chemical reactivity of the pore, and are not suitable to be used for complex biofluids. We developed a non-perturbative methodology ( fW input power) for quantifying trans-pore electrical current and detecting the pore status (i.e., open vs. closes) via graphene microelectrodes. Ferritin was used as a model protein featuring a large interior compartment, well-separated from the exterior solution with discrete pores as charge commuting channels. The charge flowing through the ferritin pores transfers into the graphene microelectrode and is recorded by an electrometer. In this example, our methodology enables the quantification of an inorganic nanoparticle-protein nanopore interaction in complex biofluids. The authors acknowledge the support from the Defense Advanced Research Projects Agency (DARPA) and the U.S. Army Research Office under Grant Number W911NF1010093.

Welded tuff porosity characterization using mercury intrusion, nitrogen and ethylene glycol monoethyl ether sorption and epifluorescence microscopy

USGS Publications Warehouse

Reddy, M.M.; Claassen, H.C.; Rutherford, D.W.; Chiou, C.T.

1994-01-01

Porosity of welded tuff from Snowshoe Mountain, Colorado, was characterized by mercury intrusion porosimetry (MIP), nitrogen sorption porosimetry, ethylene glycol monoethyl ether (EGME) gas phase sorption and epifluorescence optical microscopy. Crushed tuff of two particle-size fractions (1-0.3 mm and less than 0.212 mm), sawed sections of whole rock and crushed tuff that had been reacted with 0.1 N hydrochloric acid were examined. Average MIP pore diameter values were in the range of 0.01-0.02??m. Intrusion volume was greatest for tuff reacted with 0.1 N hydrochloric acid and least for sawed tuff. Cut rock had the smallest porosity (4.72%) and crushed tuff reacted in hydrochloric acid had the largest porosity (6.56%). Mean pore diameters from nitrogen sorption measurements were 0.0075-0.0187 ??m. Nitrogen adsorption pore volumes (from 0.005 to 0.013 cm3/g) and porosity values (from 1.34 to 3.21%) were less than the corresponding values obtained by MIP. More than half of the total tuff pore volume was associated with pore diameters < 0.05??m. Vapor sorption of EGME demonstrated that tuff pores contain a clay-like material. Epifluorescence microscopy indicated that connected porosity is heterogeneously distributed within the tuff matix; mineral grains had little porosity. Tuff porosity may have important consequences for contaminant disposal in this host rock. ?? 1994.

Porous synthetic hectorite clay-alginate composite beads for effective adsorption of methylene blue dye from aqueous solution.

PubMed

Pawar, Radheshyam R; Lalhmunsiama; Gupta, Prabuddha; Sawant, Sandesh Y; Shahmoradi, B; Lee, Seung-Mok

2018-07-15

The present study deals with the preparation and characterization of mesoporous synthetic hectorite (MSH) clay which further encapsulated with Na-alginate for the preparation of mesoporous synthetic hectorite-alginate beads (MSH-AB) where Ca 2+ act as a cross-linking agent. The detail characterization of MSH and MSH-AB were carried out by various physicochemical techniques. The thermogravimetric analysis study showed better thermal stability results for MSH-AB. The textural properties results of MSH and MSH-AB showed the high surface area 468, 205m 2 /g, and the pore volume of 0.34, 0.29cm 3 /g respectively. The applicability of powder MSH and MSH-AB in wet (W) and dry (D) forms were assessed for the removal of cationic dye, methylene blue (MB) by optimizing various batch adsorption parameters. The Langmuir monolayer adsorption capacity obtained for MSH-AB-W showed significant high adsorption efficacy (i.e., 785.45mgMB/g) compared to the MSH-AB-D (357.14mgMB/g) and powder MSH materials (196.00mgMB/g). The adsorption isotherm studies showed that the Langmuir isotherm model was best suitable for MSH, whereas the Freundlich model was utilised to describe the adsorption behavior of organized hydrogel composite beads. The pseudo-second-order kinetics model was observed best for MB sorption onto MSH, whereas pseudo-first order useful to describe the kinetic behavior of MSH-AB. The regeneration experimental results revealed that MSH-AB-W could be recycled more than six cycles with high MB removal efficiency. Furthermore, the adsorption property of the MSH-AB-W was examined for the binary mixture of MB with other dye solutions such as Methyl Red (MR), Methyl Orange (MO), Alizarine Yellow (AY), and Remazol Brilliant Blue (RBB) to evaluate the selective adsorption efficiency. The MSH composite beads were found potentially suitable as an efficient, selective and recyclable adsorbent for the removal of MB from the aqueous solutions. Copyright © 2018 Elsevier B.V. All rights reserved.

Thallium (Tl) sorption onto illite and smectite: Implications for Tl mobility in the environment

NASA Astrophysics Data System (ADS)

Martin, Loïc A.; Wissocq, Aubéry; Benedetti, M. F.; Latrille, Christelle

2018-06-01

Clay minerals play a relevant role in the transport and fate of trace elements in the environment. Though illite has been referred as an important Thallium (Tl) bearing phase in soils, mechanisms and affinity of thallium for clay minerals remain poorly known. This study investigated the sorption behavior of thallium as Tl(I) onto illite and smectite, two clay minerals occurring mainly in soils and sediments. Different sorption experiments were carried out under various pH conditions and Tl concentrations, in competition with sodium and calcium at a constant ionic strength of 0.01 mol L-1. Our results showed that illite displayed more affinity than smectite for thallium. With illite, the distribution coefficients (Kd in L kg-1) varied between 102.75 ± 0.17 and 104.0 ± 0.17 in Na solutions versus between 102.25 ± 0.17 and 103.0 ± 0.17 in Ca solutions, depending on pH. With smectite, Kd (in L kg-1) ranged between 102.50 ± 0.16 and 103.20 ± 0.16 and between 101.25 ± 0.16 and 101.95 ± 0.16 in Na and Ca solutions, respectively. Sorption behavior was described with the Multi-Site Ion Exchanger model and selectivity coefficients with respect to protons were calculated for the first time. In all cases, independently of clay mineral and background electrolyte, low capacity but highly reactive sites were dominant in thallium uptake, highlighting Tl affinity for those sites. Moreover, the exchangeable and reversible interactions between Tl+ and clays reactive sites suggested that in changing conditions, thallium could be released in solution. The role of clay minerals in thallium environmental cycle is evident and confirmed illite to be a dominant Tl bearing phase, in some environment competing with manganese oxides. Compared to others Tl bearing mineral phases, clays are ranked as follows: MnO2 > illite > smectite ∼ ferrihydrite ≥ Al2O3 ∼ goethite > SiO2. Finally, over the three monovalent cations (Tl, Rb, Cs) Tl is the one less sorbed on illite independently of the background cations.

Anisotropic Behaviour of Opalinus Clay Through Consolidated and Drained Triaxial Testing in Saturated Conditions

NASA Astrophysics Data System (ADS)

Favero, Valentina; Ferrari, Alessio; Laloui, Lyesse

2018-05-01

This paper investigates the anisotropic hydro-mechanical behaviour of Opalinus Clay shale, the host material currently being considered for the construction of a nuclear waste repository in Switzerland. Consolidated and drained triaxial tests on Opalinus Clay from the Mont Terri URL have been conducted in order to derive information on its strength and stiffness properties. Opalinus Clay specimens were tested both parallel to bedding (P-specimens) and perpendicular to bedding (S-specimens). The considered effective confining stress range (from 2 to 12 MPa) has been selected in order to reproduce possible in situ stress conditions for the repository. In this work, particular attention has been paid to the experimental procedure in order to ensure consolidated conditions and avoid generation of unwanted excess pore water pressure during drained shearing. The Skempton B parameter has been determined for all the tested specimens in order to ensure saturation. Both single-stage and multistage triaxial testing procedures were adopted in the experimental campaign. The results of the triaxial tests highlight an anisotropic elastic response of Opalinus Clay: S-specimens present a more compliant behaviour than P-specimens. The values of the Young modulus are found to increase with the increase in mean effective stress. The analysis of the peak and ultimate shear strength results reveals that the material behaves in a similar manner regardless of the considered direction of loading (P and S directions) with respect to the bedding orientation. Peak and ultimate failure envelopes for Opalinus Clay were derived for the investigated stress range.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mouzakis, Katherine M.; Navarre-Sitchler, Alexis K.; Rother, Gernot

Carbon capture, utilization, and storage, one proposed method of reducing anthropogenic emissions of CO 2, relies on low permeability formations, such as shales, above injection formations to prevent upward migration of the injected CO 2. Porosity in caprocks evaluated for sealing capacity before injection can be altered by geochemical reactions induced by dissolution of injected CO 2 into pore fluids, impacting long-term sealing capacity. Therefore, long-term performance of CO 2 sequestration sites may be dependent on both initial distribution and connectivity of pores in caprocks, and on changes induced by geochemical reaction after injection of CO 2, which are currentlymore » poorly understood. This paper presents results from an experimental study of changes to caprock porosity and pore network geometry in two caprock formations under conditions relevant to CO 2 sequestration. Pore connectivity and total porosity increased in the Gothic Shale; while total porosity increased but pore connectivity decreased in the Marine Tuscaloosa. Gothic Shale is a carbonate mudstone that contains volumetrically more carbonate minerals than Marine Tuscaloosa. Carbonate minerals dissolved to a greater extent than silicate minerals in Gothic Shale under high CO 2 conditions, leading to increased porosity at length scales <~200 nm that contributed to increased pore connectivity. In contrast, silicate minerals dissolved to a greater extent than carbonate minerals in Marine Tuscaloosa leading to increased porosity at all length scales, and specifically an increase in the number of pores >~1 μm. Mineral reactions also contributed to a decrease in pore connectivity, possibly as a result of precipitation in pore throats or hydration of the high percentage of clays. Finally, this study highlights the role that mineralogy of the caprock can play in geochemical response to CO 2 injection and resulting changes in sealing capacity in long-term CO 2 storage projects.« less

Sediment composition and texture of Pleistocene deep-sea turbidites in the eastern Nankai Trough gas hydrate field

NASA Astrophysics Data System (ADS)

Egawa, K.; Nishimura, O.; Izumi, S.; Ito, T.; Konno, Y.; Yoneda, J.; Jin, Y.; Kida, M.; Suzuki, K.; Nakatsuka, Y.; Nagao, J.

2013-12-01

In the 2012 JOGMEC/JAPEX pressure coring operation, we collected a totally 60-m-long core sample from the interval of gas hydrate concentration zone at the planned site of the world's first offshore production test of natural gas hydrates in the eastern Nankai Trough area. In this contribution, the cored sediments were sedimentologically, mineralogically, and paleontologically analyzed to know sediment composition and texture of reservoir formation, which are known to provide useful geological information to discuss sedimentation, diagenesis, and permeability. The targeted interval belongs to a Middle Pleistocene deep-sea turbidite sequence distributed around the Daini Atsumi Knoll, east of the Kumano forearc basin, and consists of the lower (thick sand-dominant), middle (thin-bedded sand-and-mud alteration), and upper (mud-dominant) formations in ascending order. X-ray powder diffraction analysis and scanning electron microscopic observation revealed that pore space in turbidite sands is commonly filled with clay fractions (mostly phyllosilicates) in the lower formation. Such a pore filling of clay fractions is reflected in particle size distribution showing high standard deviation and clay content, and thus is expected to have an impact on permeability. There is the older Pliocene to Early Pleistocene fossil coccolith record in the middle formation, indicating sediment reworking probably induced by submarine landslide. The coexistence of authigenic siderite and framboidal pyrite in the middle formation strongly suggests anoxic microbial activity under methane oxidation and sulfide reduction conditions at least before the hydrate cementation. This contribution was financially supported by the Research Consortium for Methane Hydrate Resources in Japan (MH21 Research Consortium) planned by the Ministry of Economy, Trade and Industry (METI).

Experimental Study on Vacuum Dynamic Consolidation Treatment of Soft Soil Foundation

NASA Astrophysics Data System (ADS)

Fu-lai, Ni; Xin, Wen; Xiao-bin, Zhang; Wei, Li

2017-11-01

In view of the deficiency of the saturated silt clay foundation reinforced by the dynamic consolidation method, combination the project of soft foundation treatment test area in Tangshan, the reaserch analysed indexes, included groundwater level, pore water pressure, settlement about soil layer and so on, by use of field tests and indoor geotechnical tests, The results showed that the whole reinforcement effect with vacuum dynamic compaction method to blow fill foundation is obvious, due to the result of vacuum precipitation, generally, the excess pore water pressure can be dissipated by 90% above in 2 days around and the effective compaction coefficient can reached more than 0.9,the research work in soft foundation treatment engineering provide a new method and thought to similar engineering.

Engineering and Design: Geotechnical Analysis by the Finite Element Method

DTIC Science & Technology

1995-07-31

of an Idealized ’Wet Clay’.” Nobari, E. S., Lee, K. L., and Duncan, J. M. Soil Mechanics, Wiesbaden I, 47-54. (1973). “ Hydraulic Fracturing in Zoned...nonsteady flow conditions - Pore pressures induced by loading under undrained conditions - Potential for cracking in embankment dams - Potential for hydraulic ... fracturing in embankment dams - Potential for hydraulic separation between concrete and soil - Settlements and horizontal movements b. Comparing

Modelling the Mont Terri HE-D experiment for the Thermal–Hydraulic–Mechanical response of a bedded argillaceous formation to heating

DOE PAGES

Garitte, B.; Nguyen, T. S.; Barnichon, J. D.; ...

2017-05-09

Coupled thermal–hydrological–mechanical (THM) processes in the near field of deep geological repositories can influence several safety features of the engineered and geological barriers. Among those features are: the possibility of damage in the host rock, the time for re-saturation of the bentonite, and the perturbations in the hydraulic regime in both the rock and engineered seals. Within the international cooperative code-validation project DECOVALEX-2015, eight research teams developed models to simulate an in situ heater experiment, called HE-D, in Opalinus Clay at the Mont Terri Underground Research Laboratory in Switzerland. The models were developed from the theory of poroelasticity in ordermore » to simulate the coupled THM processes that prevailed during the experiment and thereby to characterize the in situ THM properties of Opalinus Clay. The modelling results for the evolution of temperature, pore water pressure, and deformation at different points are consistent among the research teams and compare favourably with the experimental data in terms of trends and absolute values. The models were able to reproduce the main physical processes of the experiment. In particular, most teams simulated temperature and thermally induced pore water pressure well, including spatial variations caused by inherent anisotropy due to bedding.« less

Modelling the Mont Terri HE-D experiment for the Thermal–Hydraulic–Mechanical response of a bedded argillaceous formation to heating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garitte, B.; Nguyen, T. S.; Barnichon, J. D.

Coupled thermal–hydrological–mechanical (THM) processes in the near field of deep geological repositories can influence several safety features of the engineered and geological barriers. Among those features are: the possibility of damage in the host rock, the time for re-saturation of the bentonite, and the perturbations in the hydraulic regime in both the rock and engineered seals. Within the international cooperative code-validation project DECOVALEX-2015, eight research teams developed models to simulate an in situ heater experiment, called HE-D, in Opalinus Clay at the Mont Terri Underground Research Laboratory in Switzerland. The models were developed from the theory of poroelasticity in ordermore » to simulate the coupled THM processes that prevailed during the experiment and thereby to characterize the in situ THM properties of Opalinus Clay. The modelling results for the evolution of temperature, pore water pressure, and deformation at different points are consistent among the research teams and compare favourably with the experimental data in terms of trends and absolute values. The models were able to reproduce the main physical processes of the experiment. In particular, most teams simulated temperature and thermally induced pore water pressure well, including spatial variations caused by inherent anisotropy due to bedding.« less

Do acid volatile sulfides (AVS) influence the accumulation of sediment-bound metals to benthic invertebrates under natural field conditions?

PubMed

De Jonge, Maarten; Dreesen, Freja; De Paepe, Josefina; Blust, Ronny; Bervoets, Lieven

2009-06-15

The present study evaluates the influence of acid volatile sulfides (AVS) on accumulation of sediment-bound metals in benthic invertebrates under natural field conditions. Natural sediments, pore water, surface water, and two species of widespread benthic invertebrates (Chironomus gr. thummi and Tubifex tubifex) were collected from 17 historical polluted Flemish lowland rivers and measured for metal concentrations. Different sediment characteristics were determined (AVS, organic matter, clay content) and multiple regression was used to study their relationship with accumulated metals in the invertebrates. Physical and chemical analysis of the field samples indicated low metal concentrations in the water and pore water, but very high metal concentrations in the sediment and the invertebrates, especially for Pb (5.99 micromol/ g). In general, metal accumulation in chironomids and tubificid worms was most strongly correlated with total metal concentrations in the sediment and sediment metal concentrations normalized for organic matter and clay content. Following the results of the linear regression model, AVS did not turn out to be a significant variable in describing variation in metal accumulation. Our study clearly demonstrates that, in addition to the results gained from experiments under lab conditions, benthic invertebrates can accumulate metals from unspiked field sediments even when there's an excess of AVS.

Impact of Oxidative Dissolution on Black Shale Fracturing: Implication for Shale Fracturing Treatment Design

NASA Astrophysics Data System (ADS)

You, L.; Chen, Q.; Kang, Y.; Cheng, Q.; Sheng, J.

2017-12-01

Black shales contain a large amount of environment-sensitive compositions, e.g., clay minerals, carbonate, siderite, pyrite, and organic matter. There have been numerous studies on the black shales compositional and pore structure changes caused by oxic environments. However, most of the studies did not focus on their ability to facilitate shale fracturing. To test the redox-sensitive aspects of shale fracturing and its potentially favorable effects on hydraulic fracturing in shale gas reservoirs, the induced microfractures of Longmaxi black shales exposed to deionized water, hydrochloric acid, and hydrogen peroxide at room-temperature for 240 hours were imaged by scanning electron microscopy (SEM) and CT-scanning in this paper. Mineral composition, acoustic emission, swelling, and zeta potential of the untreated and oxidative treatment shale samples were also recorded to decipher the coupled physical and chemical effects of oxidizing environments on shale fracturing processes. Results show that pervasive microfractures (Fig.1) with apertures ranging from tens of nanometers to tens of microns formed in response to oxidative dissolution by hydrogen peroxide, whereas no new microfracture was observed after the exposure to deionized water and hydrochloric acid. The trajectory of these oxidation-induced microfractures was controlled by the distribution of phyllosilicate framework and flaky or stringy organic matter in shale. The experiments reported in this paper indicate that black shales present the least resistance to crack initiation and subcritical slow propagation in hydrogen peroxide, a process we refer to as oxidation-sensitive fracturing, which are closely related to the expansive stress of clay minerals, dissolution of redox-sensitive compositions, destruction of phyllosilicate framework, and the much lower zeta potential of hydrogen peroxide solution-shale system. It could mean that the injection of fracturing water with strong oxidizing aqueous solution may play an important role in improving hydraulic fracturing of shale formation by reducing the energy requirements for crack growth. However, additional work is needed to the selection of highly-effective, economical, and environmentally friendly oxidants.

Lysimeter study to investigate the effect of rainfall patterns on leaching of isoproturon.

PubMed

Beulke, Sabine; Brown, Colin D; Fryer, Christopher J; Walker, Allan

2002-01-01

The influence of five rainfall treatments on water and solute leaching through two contrasting soil types was investigated. Undisturbed lysimeters (diameter 0.25 m, length 0.5 m) from a sandy loam (Wick series) and a moderately structured clay loam (Hodnet series) received autumn applications of the radio-labelled pesticide isoproturon and bromide tracer. Target rainfall plus irrigation from the end of November 1997 to May 1998 ranged from drier to wetter than average (235 to 414 mm); monthly rainfall was varied according to a pre-selected pattern or kept constant (triplicate lysimeters per regime). Leachate was collected at intervals and concentrations of the solutes were determined. Total flow (0.27-0.94 pore volumes) and losses of bromide (3-80% of applied) increased with increasing inputs of water and were larger from the Wick sandy loam than from the Hodnet clay loam soil. Matrix flow appeared to be the main mechanism for transport of isoproturon through the Wick soil whereas there was a greater influence of preferential flow for the Hodnet lysimeters. The total leached load of isoproturon from the Wick lysimeters was 0.02-0.26% of that applied. There was no clear variation in transport processes between the rainfall treatments investigated for this soil and there was an approximately linear relationship (r2 = 0.81) between leached load and total flow. Losses of isoproturon from the Hodnet soil were 0.03-0.39% of applied and there was evidence of enhanced preferential flow in the driest and wettest treatments. Leaching of isoproturon was best described by an exponential relationship between load and total flow (r2 = 0.62). A 45% increase in flow between the two wettest treatments gave a 100% increase in leaching of isoproturon from the Wick soil. For the Hodnet lysimeters, a 35% increase in flow between the same treatments increased herbicide loss by 325%.

A multi-scale Lattice Boltzmann model for simulating solute transport in 3D X-ray micro-tomography images of aggregated porous materials

NASA Astrophysics Data System (ADS)

Zhang, Xiaoxian; Crawford, John W.; Flavel, Richard J.; Young, Iain M.

2016-10-01

The Lattice Boltzmann (LB) model and X-ray computed tomography (CT) have been increasingly used in combination over the past decade to simulate water flow and chemical transport at pore scale in porous materials. Because of its limitation in resolution and the hierarchical structure of most natural soils, the X-ray CT tomography can only identify pores that are greater than its resolution and treats other pores as solid. As a result, the so-called solid phase in X-ray images may in reality be a grey phase, containing substantial connected pores capable of conducing fluids and solute. Although modified LB models have been developed to simulate fluid flow in such media, models for solute transport are relatively limited. In this paper, we propose a LB model for simulating solute transport in binary soil images containing permeable solid phase. The model is based on the single-relaxation time approach and uses a modified partial bounce-back method to describe the resistance caused by the permeable solid phase to chemical transport. We derive the relationship between the diffusion coefficient and the parameter introduced in the partial bounce-back method, and test the model against analytical solution for movement of a pulse of tracer. We also validate it against classical finite volume method for solute diffusion in a simple 2D image, and then apply the model to a soil image acquired using X-ray tomography at resolution of 30 μm in attempts to analyse how the ability of the solid phase to diffuse solute at micron-scale affects the behaviour of the solute at macro-scale after a volumetric average. Based on the simulated results, we discuss briefly the danger in interpreting experimental results using the continuum model without fully understanding the pore-scale processes, as well as the potential of using pore-scale modelling and tomography to help improve the continuum models.

The influence of shale depositional fabric on the kinetics of hydrocarbon generation through control of mineral surface contact area on clay catalysis

NASA Astrophysics Data System (ADS)

Rahman, Habibur M.; Kennedy, Martin; Löhr, Stefan; Dewhurst, David N.; Sherwood, Neil; Yang, Shengyu; Horsfield, Brian

2018-01-01

Accurately assessing the temperature and hence the depth and timing of hydrocarbon generation is a critical step in the characterization of a petroleum system. Clay catalysis is a potentially significant modifier of hydrocarbon generation temperature, but experimental studies of clay catalysis show inconsistent or contradictory results. This study tests the hypothesis that source rock fabric itself is an influence on clay mineral catalysis as it controls the extent to which organic matter and clay minerals are physically associated. Two endmember clay-organic fabrics distinguish the source rocks studied: (1) a particulate fabric where organic matter is present as discrete, >5 μm particles and (2) a nanocomposite fabric in which amorphous organic matter is associated with clay mineral surfaces at sub-micron scale. High-resolution electron imaging and bulk geochemical characterisation confirm that samples of the Miocene Monterey Formation (California) are representative of the nanocomposite source rock endmember, whereas samples from the Permian Stuart Range Formation (South Australia) represent the particulate source rock endmember. Kinetic experiments are performed on paired whole rock and kerogen isolate samples from these two formations using open system, non-isothermal pyrolysis at three different heating rates (0.7, 2 and 5 K/min) to determine the effects of the different shale fabrics on hydrocarbon generation kinetics. Extrapolation to a modelled geological heating rate shows a 20 °C reduction in the onset temperature of hydrocarbon generation in Monterey Formation whole rock samples relative to paired kerogen isolates. This result is consistent with the Monterey Formations's nanocomposite fabric where clay catalysis can proceed because reactive clay minerals are intimately associated with organic matter. By contrast, there is no significant difference in the modelled hydrocarbon generation temperature of paired whole rock and kerogen isolates from the Stuart Range Formation. This is consistent with its particulate fabric, where relatively large, discrete organic particles have limited contact with the mineral matrix and the clay minerals are mainly diagenetic and physically segregated within pores. While heating rate may have a control on mineral matrix effects, this result shows that the extent to which organic matter and clay minerals are physically associated could have a significant effect on the timing of hydrocarbon generation, and is a function of the depositional environment and detrital vs diagenetic origin of clay minerals in source rocks.

Heavy metal contamination of the soils used for stocking raw materials in the former ILVA iron-steel industrial plant of Bagnoli (southern Italy).

PubMed

Adamo, P; Arienzo, M; Bianco, M R; Terribile, F; Violante, P

2002-08-05

The total contents and the chemical and mineralogical forms of the metals Fe, Al, Cu, Co, Cr, Pb, Zn, Ni and Mn in the horizons of a soil profile, representative of an area devoted to stocking raw materials in the dismantled iron-steel industrial plant of ILVA of Bagnoli (Naples), were studied by physical and chemical methods. The geological setting of the study area is the result of volcanic activity in the Phlegrean Fields, a group of polygenic volcanoes to the west of Naples, which give rise to the parent soil material. Soil morphology appeared to be strongly disturbed by the occurrence and stratification of materials used in the industrial process. Fine sediments illuviation down the profile resulted in the occurrence of silt and clay coatings. The total contents of Cu, Co, Cr, Pb, Zn and Ni, in the whole soil samples, especially in the surface layers, were above the regulatory levels (Cu 120, Co 20, Cr 150, Pb 100, Zn 150, Ni 120 mg kg(-1)) stated by the Italian Ministry of Environment for soils in public, private and residential areas, and below the levels (Cu 600, Co 250, Cr 800, Pb 1000, Zn 1500, Ni 500 mg kg(-1)) outlined for soils and subsoils of industrial and commercial areas (Gazzetta Ufficiale della Repubblica Italiana, 1999). Speciation of heavy metals and the determination of the different chemical pools in the fraction < 2 mm identified the large presence of elements trapped in the mineralogical structure of oxides and silicates and occluded in easily reducible manganese or iron oxides. A constant amount of Cu was associated with organic compounds. A significant amount of Zn (> 20%) was extracted in diluted acetic acid solution, indicating that the element was present in a more readily and potentially available form. In the clay fraction (< 2 microm) heavy metals were associated with both amorphous and crystalline iron forms. The presence of iron-rich clay coatings was evident in the illuvial pores of deeper horizons. Enrichment in Cu, Co, Cr and Zn of the coatings was observed. Possible translocation of metals down through the soil profile mainly bound to fine particles of relatively inert forms of iron is hypothesised. The dispersion in water of the clay fraction resulted in an average percentage dispersion of approximately 20% with a peak of 41.7% at 68-72 cm depth. Magnetite, goethite, hematite, calcite and quartz mixed with K-feldspars, clynopyroxenes and mica occurred in the coarse sand fractions (2-0.2 mm) of the soil samples from all the surface horizons. Talcum and goethite together with clay minerals at 1.4 nm, kaolinite and illite were found in the clays (< 2 microm).

Relating salt marsh pore water geochemistry patterns to vegetation zones and hydrologic influences

NASA Astrophysics Data System (ADS)

Moffett, Kevan B.; Gorelick, Steven M.

2016-03-01

Physical, chemical, and biological factors influence vegetation zonation in salt marshes and other wetlands, but connections among these factors could be better understood. If salt marsh vegetation and marsh pore water geochemistry coorganize, e.g., via continuous plant water uptake and persistently unsaturated sediments controlling vegetation zone-specific pore water geochemistry, this could complement known physical mechanisms of marsh self-organization. A high-resolution survey of pore water geochemistry was conducted among five salt marsh vegetation zones at the same intertidal elevation. Sampling transects were arrayed both parallel and perpendicular to tidal channels. Pore water geochemistry patterns were both horizontally differentiated, corresponding to vegetation zonation, and vertically differentiated, relating to root influences. The geochemical patterns across the site were less broadly related to marsh hydrology than to vegetation zonation. Mechanisms contributing to geochemical differentiation included: root-induced oxidation and nutrient (P) depletion, surface and creek-bank sediment flushing by rainfall or tides, evapotranspiration creating aerated pore space for partial sediment flushing in some areas while persistently saturated conditions hindered pore water renewal in others, and evapoconcentration of pore water solutes overall. The concentrated pore waters draining to the tidal creeks accounted for 41% of ebb tide solutes (median of 14 elements), including being a potentially toxic source of Ni but a slight sink for Zn, at least during the short, winter study period in southern San Francisco Bay. Heterogeneous vegetation effects on pore water geochemistry are not only significant locally within the marsh but may broadly influence marsh-estuary solute exchange and ecology.

Multiscale modelling of dual-porosity porous media; a computational pore-scale study for flow and solute transport

NASA Astrophysics Data System (ADS)

de Vries, Enno T.; Raoof, Amir; van Genuchten, Martinus Th.

2017-07-01

Many environmental and agricultural applications involve the transport of water and dissolved constituents through aggregated soil profiles, or porous media that are structured, fractured or macroporous in other ways. During the past several decades, various process-based macroscopic models have been used to simulate contaminant transport in such media. Many of these models consider advective-dispersive transport through relatively large inter-aggregate pore domains, while exchange with the smaller intra-aggregate pores is assumed to be controlled by diffusion. Exchange of solute between the two domains is often represented using a first-order mass transfer coefficient, which is commonly obtained by fitting to observed data. This study aims to understand and quantify the solute exchange term by applying a dual-porosity pore-scale network model to relatively large domains, and analysing the pore-scale results in terms of the classical dual-porosity (mobile-immobile) transport formulation. We examined the effects of key parameters (notably aggregate porosity and aggregate permeability) on the main dual-porosity model parameters, i.e., the mobile water fraction (ϕm) and the mass transfer coefficient (α). Results were obtained for a wide range of aggregate porosities (between 0.082 and 0.700). The effect of aggregate permeability was explored by varying pore throat sizes within the aggregates. Solute breakthrough curves (BTCs) obtained with the pore-scale network model at several locations along the domain were analysed using analytical solutions of the dual-porosity model to obtain estimates of ϕm and α. An increase in aggregate porosity was found to decrease ϕm and increase α, leading to considerable tailing in the BTCs. Changes in the aggregate pore throat size affected the relative flow velocity between the intra- and inter-aggregate domains. Higher flow velocities within the aggregates caused a change in the transport regime from diffusion dominated to more advection dominated. This change increased the exchange rate of solutes between the mobile and immobile domains, with a related increase in the value of the mass transfer coefficient and less tailing in the BTCs.

Single clay sheets inside electrospun polymer nanofibers

NASA Astrophysics Data System (ADS)

Sun, Zhaohui

2005-03-01

Nanofibers were prepared from polymer solution with clay sheets by electrospinning. Plasma etching, as a well controlled process, was used to supply electrically excited gas molecules from a glow discharge. To reveal the structure and arrangement of clay layers in the polymer matrix, plasma etching was used to remove the polymer by controlled gasification to expose the clay sheets due to the difference in reactivity. The shape, flexibility, and orientation of clay sheets were studied by transmission and scanning electron microscopy. Additional quantitative information on size distribution and degree of exfoliation of clay sheets were obtained by analyzing electron micrograph of sample after plasma etching. Samples in various forms including fiber, film and bulk, were thinned by plasma etching. Morphology and dispersion of inorganic fillers were studied by electron microscopy.

Geochemical evolution of Great Salt Lake, Utah, USA

USGS Publications Warehouse

Jones, B.F.; Naftz, D.L.; Spencer, R.J.; Oviatt, Charles G.

2009-01-01

The Great Salt Lake (GSL) of Utah, USA, is the largest saline lake in North America, and its brines are some of the most concentrated anywhere in the world. The lake occupies a closed basin system whose chemistry reflects solute inputs from the weathering of a diverse suite of rocks in its drainage basin. GSL is the remnant of a much larger lacustrine body, Lake Bonneville, and it has a long history of carbonate deposition. Inflow to the lake is from three major rivers that drain mountain ranges to the east and empty into the southern arm of the lake, from precipitation directly on the lake, and from minor groundwater inflow. Outflow is by evaporation. The greatest solute inputs are from calcium bicarbonate river waters mixed with sodium chloride-type springs and groundwaters. Prior to 1930 the lake concentration inversely tracked lake volume, which reflected climatic variation in the drainage, but since then salt precipitation and re-solution, primarily halite and mirabilite, have periodically modified lake-brine chemistry through density stratification and compositional differentiation. In addition, construction of a railway causeway has restricted circulation, nearly isolating the northern from the southern part of the lake, leading to halite precipitation in the north. These and other conditions have created brine differentiation, mixing, and fractional precipitation of salts as major factors in solute evolution. Pore fluids and diagenetic reactions have been identified as important sources and especially sinks for CaCO3, Mg, and K in the lake, depending on the concentration gradient and clays. ?? U.S. Geological Survey 2008.

Phosphates in some Missouri refractory clays

USGS Publications Warehouse

Halley, Robert B.; Foord, Eugene E.; Keller, David J.; Keller, Walter D.

1997-01-01

This paper describes in detail phosphate minerals occurring in refractory clays of Missouri and their effect on the refractory degree of the clays. The minerals identified include carbonate-fluorapatite (francolite), crandallite, goyazite, wavellite, variscite and strengite. It is emphasized that these phosphates occur only in local isolated concentrations, and not generally in Missouri refractory clays.The Missouri fireclay region comprises 2 districts, northern and southern, separated by the Missouri River. In this region, clay constitutes a major part of the Lower Pennsylvanian Cheltenham Formation. The original Cheltenham mud was an argillic residue derived from leaching and dissolution of pre-Pennsylvanian carbonates. The mud accumulated on a karstic erosion surface truncating the pre-Cheltenham rocks. Fireclays of the northern district consist mainly of poorly ordered kaolinite, with variable but minor amounts of illite, chlorite and fine-grained detrital quartz. Clays of the southern district were subjected to extreme leaching that produced well-ordered kaolinite flint clays. Local desilication formed pockets of diaspore, or more commonly, kaolinite, with oolite-like nubs or burls of diaspore (“burley”" clay).The phosphate-bearing materials have been studied by X-ray diffraction (XRD), scanning electron microscopy-energy dispersive spectral analysis (SEM-EDS) and chemical analysis. Calcian goyazite was identified in a sample of diaspore, and francolite in a sample of flint clay. A veinlet of wavellite occurs in flint clay at one locality, and a veinlet of variscite-strengite at another locality.The Missouri flint-clay-hosted francolite could not have formed in the same manner as marine francolite. The evidence suggests that the Cheltenham francolite precipitated from ion complexes in pore water, nearly simultaneously with crystallization of kaolinite flint clay from an alumina-silica gel. Calcian goyazite is an early diagenetic addition to its diaspore host. The wavellite and variscite-strengite veinlets are secondary, precipitated from ion complexes in ground water percolating along cracks in the flint clay. The flint clay host of the variscite-strengite veinlet contains strontian crandallite. All of the phosphates contain significant amounts of strontium. The source of P, Ca and Sr was the marine carbonates. Dissolution of these carbonates produced the argillic residue that became the primordial Cheltenham paludal mud, which ultimately altered to fireclay.Preliminary firing tests show that the presence of phosphates lowers fusion temperature. However, it is not clear whether poor refractoriness is due to the presence of phosphates, per se, or to Ca, Sr and other alkaline elements present in the phosphates.

Ultimate Lateral Capacity of Rigid Pile in c- φ Soil

NASA Astrophysics Data System (ADS)

Zhang, Wei-min

2018-03-01

To date no analytical solution of the pile ultimate lateral capacity for the general c- φ soil has been obtained. In the present study, a new dimensionless embedded ratio was proposed and the analytical solutions of ultimate lateral capacity and rotation center of rigid pile in c- φ soils were obtained. The results showed that both the dimensionless ultimate lateral capacity and dimensionless rotation center were the univariate functions of the embedded ratio. Also, the ultimate lateral capacity in the c- φ soil was the combination of the ultimate lateral capacity ( f c ) in the clay, and the ultimate lateral capacity ( f φ ) in the sand. Therefore, the Broms chart for clay, solution for clay ( φ=0) put forward by Poulos and Davis, solution for sand ( c=0) obtained by Petrasovits and Awad, and Kondner's ultimate bending moment were all proven to be the special cases of the general solution in the present study. A comparison of the field and laboratory tests in 93 cases showed that the average ratios of the theoretical values to the experimental value ranged from 0.85 to 1.15. Also, the theoretical values displayed a good agreement with the test values.

Quantifying the clay content with borehole depth and impact on reservoir flow

NASA Astrophysics Data System (ADS)

Sarath Kumar, Aaraellu D.; Chattopadhyay, Pallavi B.

2017-04-01

This study focuses on the application of reservoir well log data and 3D transient numerical model for proper optimization of flow dynamics and hydrocarbon potential. Fluid flow through porous media depends on clay content that controls porosity, permeability and pore pressure. The pressure dependence of permeability is more pronounced in tight formations. Therefore, preliminary clay concentration analysis and geo-mechanical characterizations have been done by using wells logs. The assumption of a constant permeability for a reservoir is inappropriate and therefore the study deals with impact of permeability variation for pressure-sensitive formation. The study started with obtaining field data from available well logs. Then, the mathematical models are developed to understand the efficient extraction of oil in terms of reservoir architecture, porosity and permeability. The fluid flow simulations have been done using COMSOL Multiphysics Software by choosing time dependent subsurface flow module that is governed by Darcy's law. This study suggests that the reservoir should not be treated as a single homogeneous structure with unique porosity and permeability. The reservoir parameters change with varying clay content and it should be considered for effective planning and extraction of oil. There is an optimum drawdown for maximum production with varying permeability in a reservoir.

Transport of Organic Solutes in Clay Formations

EPA Science Inventory

The research is a pilot investigation for the SERDP (Strategic Environmental Research and Development Program, DoD) founded project, Impact of Clay-DNAPL Interactions on Transport and Storage of Chlorinated Solvents in Low Permeability Zones, from 2010-2012. The report tries to s...

Experimental Study of Porosity Changes in Shale Caprocks Exposed to CO 2-Saturated Brines I: Evolution of Mineralogy, Pore Connectivity, Pore Size Distribution, and Surface Area

DOE PAGES

Mouzakis, Katherine M.; Navarre-Sitchler, Alexis K.; Rother, Gernot; ...

2016-07-18

Carbon capture, utilization, and storage, one proposed method of reducing anthropogenic emissions of CO 2, relies on low permeability formations, such as shales, above injection formations to prevent upward migration of the injected CO 2. Porosity in caprocks evaluated for sealing capacity before injection can be altered by geochemical reactions induced by dissolution of injected CO 2 into pore fluids, impacting long-term sealing capacity. Therefore, long-term performance of CO 2 sequestration sites may be dependent on both initial distribution and connectivity of pores in caprocks, and on changes induced by geochemical reaction after injection of CO 2, which are currentlymore » poorly understood. This paper presents results from an experimental study of changes to caprock porosity and pore network geometry in two caprock formations under conditions relevant to CO 2 sequestration. Pore connectivity and total porosity increased in the Gothic Shale; while total porosity increased but pore connectivity decreased in the Marine Tuscaloosa. Gothic Shale is a carbonate mudstone that contains volumetrically more carbonate minerals than Marine Tuscaloosa. Carbonate minerals dissolved to a greater extent than silicate minerals in Gothic Shale under high CO 2 conditions, leading to increased porosity at length scales <~200 nm that contributed to increased pore connectivity. In contrast, silicate minerals dissolved to a greater extent than carbonate minerals in Marine Tuscaloosa leading to increased porosity at all length scales, and specifically an increase in the number of pores >~1 μm. Mineral reactions also contributed to a decrease in pore connectivity, possibly as a result of precipitation in pore throats or hydration of the high percentage of clays. Finally, this study highlights the role that mineralogy of the caprock can play in geochemical response to CO 2 injection and resulting changes in sealing capacity in long-term CO 2 storage projects.« less

Corrosion protection performance of corrosion inhibitors and epoxy-coated reinforcing steel in a simulated concrete pore water solution.

DOT National Transportation Integrated Search

1998-06-01

We used a simulated concrete pore water solution to evaluate the corrosion protection performance of concrete corrosion-inhibiting admixtures and epoxy-coated reinforcing bars (ECR). We evaluated three commercial corrosion inhibitors, ECR from three ...

Sustainable colloidal-silver-impregnated ceramic filter for point-of-use water treatment.

PubMed

Oyanedel-Craver, Vinka A; Smith, James A

2008-02-01

Cylindrical colloidal-silver-impregnated ceramic filters for household (point-of-use) water treatment were manufactured and tested for performance in the laboratory with respect to flow rate and bacteria transport. Filters were manufactured by combining clay-rich soil with water, grog (previously fired clay), and flour, pressing them into cylinders, and firing them at 900 degrees C for 8 h. The pore-size distribution of the resulting ceramic filters was quantified by mercury porosimetry. Colloidal silver was applied to filters in different quantities and ways (dipping and painting). Filters were also tested without any colloidal-silver application. Hydraulic conductivity of the filters was quantified using changing-head permeability tests. [3H]H2O water was used as a conservative tracer to quantify advection velocities and the coefficient of hydrodynamic dispersion. Escherichia coli (E. coli) was used to quantify bacterial transport through the filters. Hydraulic conductivity and pore-size distribution varied with filter composition; hydraulic conductivities were on the order of 10(-5) cm/s and more than 50% of the pores for each filter had diameters ranging from 0.02 to 15 microm. The filters removed between 97.8% and 100% of the applied bacteria; colloidal-silver treatments improved filter performance, presumably by deactivation of bacteria. The quantity of colloidal silver applied per filter was more important to bacteria removal than the method of application. Silver concentrations in effluent filter water were initially greater than 0.1 mg/L, but dropped below this value after 200 min of continuous operation. These results indicate that colloidal-silver-impregnated ceramic filters, which can be made using primarily local materials and labor, show promise as an effective and sustainable point-of-use water treatment technology for the world's poorest communities.

Reactivity of clay minerals with acids and alkalies

USGS Publications Warehouse

Carroll, Dorothy; Starkey, Harry C.

1971-01-01

One-g samples of a montmorillonite, a metabentonite, an illite, two kaolinites, and three halloysites were treated with 50 ml of hydrochloric acid (6⋅45 N, 1:1), acetic acid (4⋅5 N, 1:3), sodium hydroxide (2⋅8 N), sodium chloride solution (pH 6⋅10; Na = 35‰; Cl = 21⋅5‰), and natural sea water (pH 7⋅85; Na = 35⋅5‰; Cl = 21⋅ 5‰) for a 10-day period in stoppered plastic vials. The supernatant solutions were removed from the clay minerals and analyzed for SiO2, Al2O3, CaO, MgO, Na2O, and K2O. All the solutions removed some SiO2, Al2O3, and Fe2O3 from the samples, but the quantities were small. Sodium hydroxide attacked the kaolin group minerals more strongly than it did montmorillonite, metabentonite, or illite. Halloysite was more strongly attacked by hydrochloric acid than was any of the other experimental minerals. Hydrochloric acid removed iron oxide coatings from soil clay minerals, but acetic acid did not remove them completely. The samples most strongly attacked by HCl and NaOH were examined by X-ray diffraction. Acid treatment did not destroy the structure of the clays, but the halloysite structure was partially destroyed. Sodium hydroxide attacked the halloysite structure, as shown by chemical analysis and X-ray diffraction. These experiments show that treatment in dilute acids has no harmful effect in the preparation of clays for X-ray diffraction. Acetic acid is preferred to hydrochloric acid for this purpose. Hydrochloric acid cleans clay minerals by removing free iron oxide from the surface; acetic acid is less effective.

Quantifying structural states of soft mudrocks

NASA Astrophysics Data System (ADS)

Li, B.; Wong, R. C. K.

2016-05-01

In this paper, a cm model is proposed to quantify structural states of soft mudrocks, which are dependent on clay fractions and porosities. Physical properties of natural and reconstituted soft mudrock samples are used to derive two parameters in the cm model. With the cm model, a simplified homogenization approach is proposed to estimate geomechanical properties and fabric orientation distributions of soft mudrocks based on the mixture theory. Soft mudrocks are treated as a mixture of nonclay minerals and clay-water composites. Nonclay minerals have a high stiffness and serve as a structural framework of mudrocks when they have a high volume fraction. Clay-water composites occupy the void space among nonclay minerals and serve as an in-fill matrix. With the increase of volume fraction of clay-water composites, there is a transition in the structural state from the state of framework supported to the state of matrix supported. The decreases in shear strength and pore size as well as increases in compressibility and anisotropy in fabric are quantitatively related to such transition. The new homogenization approach based on the proposed cm model yields better performance evaluation than common effective medium modeling approaches because the interactions among nonclay minerals and clay-water composites are considered. With wireline logging data, the cm model is applied to quantify the structural states of Colorado shale formations at different depths in the Cold Lake area, Alberta, Canada. Key geomechancial parameters are estimated based on the proposed homogenization approach and the critical intervals with low strength shale formations are identified.

The effect of switchable water additives on clay settling.

PubMed

Chen, Chien-Shun; Lau, Ying Yin; Mercer, Sean M; Robert, Tobias; Horton, J Hugh; Jessop, Philip G

2013-01-01

The recycling of process water from strip mining extractions is a very relevant task both industrially and environmentally. The sedimentation of fine tailings during such processes, however, can often require long periods of time and/or the addition of flocculants which make later water recycling difficult. We propose the use of switchable water additives as reversible flocculants for clay/water suspensions. Switchable water additives are compounds such as diamines that make it possible to reversibly control the ionic strength of an aqueous solution. Addition of CO(2) to such an aqueous solution causes the ionic strength to rise dramatically, and the change is reversed upon removal of the CO(2). These additives, while in the presence of CO(2), promote the aggregation of clay tailings, reduce settling times, and greatly increase the clarity of the liberated water. The removal of CO(2) from the liberated water regenerates a low ionic strength solution that does not promote clay aggregation and settling until CO(2) is added again. Such reversible behavior would be useful in applications such as oil sands separations in which the recycled water must not promote aggregation. When added to kaolinite and montmorillonite clay suspensions, switchable water provided process waters of lower turbidity than those additives from inorganic salts or by CO(2)-treatment alone. When recollected, the switchable water supernatant was shown to be recyclable over three cycles for enhanced settling of kaolinite. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Microbial metabolism alters pore water chemistry and increases consolidation of oil sands tailings.

PubMed

Arkell, Nicholas; Kuznetsov, Petr; Kuznetsova, Alsu; Foght, Julia M; Siddique, Tariq

2015-01-01

Tailings produced during bitumen extraction from surface-mined oil sands ores (tar sands) comprise an aqueous suspension of clay particles that remain dispersed for decades in tailings ponds. Slow consolidation of the clays hinders water recovery for reuse and retards volume reduction, thereby increasing the environmental footprint of tailings ponds. We investigated mechanisms of tailings consolidation and revealed that indigenous anaerobic microorganisms altered porewater chemistry by producing CO and CH during metabolism of acetate added as a labile carbon amendment. Entrapped biogenic CO decreased tailings pH, thereby increasing calcium (Ca) and magnesium (Mg) cations and bicarbonate (HCO) concentrations in the porewater through dissolution of carbonate minerals. Soluble ions increased the porewater ionic strength, which, with higher exchangeable Ca and Mg, decreased the diffuse double layer of clays and increased consolidation of tailings compared with unamended tailings in which little microbial activity was observed. These results are relevant to effective tailings pond management strategies. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Permeability of Granite Including Macro-Fracture Naturally Filled with Fine-Grained Minerals

NASA Astrophysics Data System (ADS)

Nara, Yoshitaka; Kato, Masaji; Niri, Ryuhei; Kohno, Masanori; Sato, Toshinori; Fukuda, Daisuke; Sato, Tsutomu; Takahashi, Manabu

2018-03-01

Information on the permeability of rock is essential for various geoengineering projects, such as geological disposal of radioactive wastes, hydrocarbon extraction, and natural hazard risk mitigation. It is especially important to investigate how fractures and pores influence the physical and transport properties of rock. Infiltration of groundwater through the damage zone fills fractures in granite with fine-grained minerals. However, the permeability of rock possessing a fracture naturally filled with fine-grained mineral grains has yet to be investigated. In this study, the permeabilities of granite samples, including a macro-fracture filled with clay and a mineral vein, are investigated. The permeability of granite with a fine-grained mineral vein agrees well with that of the intact sample, whereas the permeability of granite possessing a macro-fracture filled with clay is lower than that of the macro-fractured sample. The decrease in the permeability is due to the filling of fine-grained minerals and clay in the macro-fracture. It is concluded that the permeability of granite increases due to the existence of the fractures, but decreases upon filling them with fine-grained minerals.

Study on characteristics of PVDF/nano-clay composite polymer electrolyte using PVP as pore-forming agent

NASA Astrophysics Data System (ADS)

Dyartanti, Endah R.; Purwanto, Agus; Widiasa, I. Nyoman; Susanto, Heru

2016-02-01

Polyvinylidene fluoride (PVDF) based polymer electrolytes have a high dielectric constant, which can assist in greater ionization of lithium salts. The main advantages of PVDF are its durability in long battery operation and its ability to be a good ion conductor. However, the limitation of this polymer is its crystalline molecular structure. Dispersing nano-particles in the polymer matrix may improve the characteristics of the PVDF polymer. This paper aims to investigate the impact of nano-clay addition on the characteristics of PVDF polymer to be used as a polymer electrolyte membrane. In addition, the effect of poly(vinyl pyrrolidone) (PVP) is also investigated. The membrane was prepared by phase separation method whereas the polymer electrolyte membranes was prepared by immersing into 1 M lithium hexafluorophosphate (LiPF6) in ethylene carbonate/dimethyl carbonate (EC/DMC) electrolytes for 1 h. The membranes were characterized by scanning electron microscope (SEM), porosity and electrolyte uptake and performance in battery cell. The results showed that both nano-clay and PVP have significant impacts on the improvement of PVDF membranes to be used as polymer electrolyte.

Land subsidence of clay deposits after the Tohoku-Pacific Ocean Earthquake

NASA Astrophysics Data System (ADS)

Yasuhara, K.; Kazama, M.

2015-11-01

Extensive infrastructure collapse resulted from the cataclysmic earthquake that struck off the eastern coast of Japan on 11 March 2011 and from its consequent gigantic tsunami, affecting not only the Tohoku region but also the Kanto region. Among the geological and geotechnical processes observed, land subsidence occurring in both coastal and inland areas and from Tohoku to Kanto is an extremely important issue that must be examined carefully. This land subsidence is classifiable into three categories: (i) land sinking along the coastal areas because of tectonic movements, (ii) settlement of sandy deposits followed by liquefaction, and (iii) long-term post-earthquake recompression settlement in soft clay caused by dissipation of excess pore pressure. This paper describes two case histories of post-earthquake settlement of clay deposits from among the three categories of ground sinking and land subsidence because such settlement has been frequently overlooked in numerous earlier earthquakes. Particularly, an attempt is made to propose a methodology for predicting such settlement and for formulating remedial or responsive measures to mitigate damage from such settlement.

High temperature ion channels and pores

NASA Technical Reports Server (NTRS)

Cheley, Stephen (Inventor); Gu, Li Qun (Inventor); Bayley, Hagan (Inventor); Kang, Xiaofeng (Inventor)

2011-01-01

The present invention includes an apparatus, system and method for stochastic sensing of an analyte to a protein pore. The protein pore may be an engineer protein pore, such as an ion channel at temperatures above 55.degree. C. and even as high as near 100.degree. C. The analyte may be any reactive analyte, including chemical weapons, environmental toxins and pharmaceuticals. The analyte covalently bonds to the sensor element to produce a detectable electrical current signal. Possible signals include change in electrical current. Detection of the signal allows identification of the analyte and determination of its concentration in a sample solution. Multiple analytes present in the same solution may also be detected.

Effects of pore-scale dispersion, degree of heterogeneity, sampling size, and source volume on the concentration moments of conservative solutes in heterogeneous formations

Treesearch

Daniele Tonina; Alberto Bellin

2008-01-01

Pore-scale dispersion (PSD), aquifer heterogeneity, sampling volume, and source size influence solute concentrations of conservative tracers transported in heterogeneous porous formations. In this work, we developed a new set of analytical solutions for the concentration ensemble mean, variance, and coefficient of variation (CV), which consider the effects of all these...

Adsorption of DDT and PCB by Nanomaterials from Residual Soil.

PubMed

Taha, Mohd Raihan; Mobasser, Shariat

2015-01-01

This paper presents the findings of a study on adsorption of dichlorodiphenythreechloroethen (DDT) and polychlorinated biphenyls (PCBs) on three nanomaterials including Multi walled Carbon Nanotube (MWNT), nano-clay and nano-alumina. DDT and PCBs are of significant concern due their high toxicity and long environmental half-lives. Experiments were conducted using batch adsorption procedures at different DDT and PCBs concentrations, from 10 to 60 mg/L. The amounts of MWNT, nano-clay and Nano-alumina used were 0.25%, 0.50%, 0.75%, 1%, 2% and 10%. The adsorption of PCBs solution onto the MWNT, nano-clay and nano-alumina was characterized by an initial rapid adsorption which eventually became constant within 22, 20, and 17 hours, respectively. The adsorption of DDT solution onto the MWNT, nano-clay and nano-alumina was also characterized by an initial rapid adsorption which gradually became constant within 22, 22 and 16 hours, respectively. Results of this study indicated that MWNT was a better adsorbent material compared to nano-clay and nano-alumina for both contaminants in this study. While at 10% of MWNT 88.9% and 77% of DDT and PCB were removed by MWNT, respectively. The effect of pH and temperature were also investigated.

Adsorption of DDT and PCB by Nanomaterials from Residual Soil

PubMed Central

Taha, Mohd Raihan; Mobasser, Shariat

2015-01-01

This paper presents the findings of a study on adsorption of dichlorodiphenythreechloroethen (DDT) and polychlorinated biphenyls (PCBs) on three nanomaterials including Multi walled Carbon Nanotube (MWNT), nano-clay and nano-alumina. DDT and PCBs are of significant concern due their high toxicity and long environmental half-lives. Experiments were conducted using batch adsorption procedures at different DDT and PCBs concentrations, from 10 to 60 mg/L. The amounts of MWNT, nano-clay and Nano-alumina used were 0.25%, 0.50%, 0.75%, 1%, 2% and 10%. The adsorption of PCBs solution onto the MWNT, nano-clay and nano-alumina was characterized by an initial rapid adsorption which eventually became constant within 22, 20, and 17 hours, respectively. The adsorption of DDT solution onto the MWNT, nano-clay and nano-alumina was also characterized by an initial rapid adsorption which gradually became constant within 22, 22 and 16 hours, respectively. Results of this study indicated that MWNT was a better adsorbent material compared to nano-clay and nano-alumina for both contaminants in this study. While at 10% of MWNT 88.9% and 77% of DDT and PCB were removed by MWNT, respectively. The effect of pH and temperature were also investigated. PMID:26659225

Petrophysical laboratory invertigations of carbon dioxide storage in a subsurface saline aquifer in Ketzin/Germany within the scope of CO2SINK

NASA Astrophysics Data System (ADS)

Zemke, K.; Kummmerow, J.; Wandrey, M.; Co2SINK Group

2009-04-01

Since June of 2008 carbon dioxide has been injected into a saline aquifer at the Ketzin test site [Würdemann et al., this volume]. The food grade CO2 is injected into a sandstone zone of the Stuttgart formation at ca. 650 m depth at 35°C reservoir temperature and 62 bar reservoir pressure. With the injection of CO2 into the geological formation, chemical and physical reservoir characteristics are changed depending on pressure, temperature, fluid chemistry and rock composition. Fluid-rock interaction could comprise dissolution of non-resistant minerals in CO2-bearing pore fluids, cementing of the pore space by precipitating substances from the pore fluid, drying and disintegration of clay minerals and thus influence of the composition and activities of the deep biosphere. To testing the injection behaviour of CO2 in water saturated rock and to evaluate the geophysical signature depending on the thermodynamic conditions, flow experiments with water and CO2 have been performed on cores of the Stuttgart formation from different locations including new wells of ketzin test site. The studied core material is an unconsolidated fine-grained sandstone with porosity values from 15 to 32 %. Permeability, electrical resistivity, and sonic wave velocities and their changes with pressure, saturation and time have been studied under simulated in situ conditions. The flow experiments conducted over several weeks with brine and CO2 showed no significant changes of resistivity and velocity and a slightly decreasing permeability. Pore fluid analysis showed mobilization of clay and some other components. A main objective of the CO2Sink laboratory program is the assessment of the effect of long-term CO2 exposure on reservoir rocks to predict the long-term behaviour of geological CO2 storage. For this CO2 exposure experiments reservoir rock samples were exposed to CO2 saturated reservoir fluid in corrosion-resistant high pressure vessels under in situ temperature and pressure conditions over a period of several months. Before and after the CO2 exposure experiment cyclic measurements of physical properties were carried out on these cores in a mechanical testing system. After experimental runs of up to 3 months no significant changes in flow and petrophysical data were observed. [For the microbilogical studies see Wandrey et al., this volume.] To study the impact of fluid-rock interactions on petrophysical parameters, porosity and pore radii distribution have been investigated before and after the experiment by NMR relaxation and mercury-injection. NMR measurements on rock core plugs saturated with brine may return valuable information on the porous structure of the rock core. The distribution of NMR-T2 values (CPMG) reflects the pore sizes within the rock core. NMR pore size is a derivative of the ratio pore surface/volume. The mercury injection pore size is an area-equivalent diameter of the throats connecting the pore system. Most of the tested samples show in the NMR measurements a slightly increasing porosity and a higher part of large pores. The mercury measurements and thin- section for microstructural characterisation after the CO2 exposure will be done at a later date.

The physics of debris flows

NASA Astrophysics Data System (ADS)

Iverson, Richard M.

1997-08-01

Recent advances in theory and experimentation motivate a thorough reassessment of the physics of debris flows. Analyses of flows of dry, granular solids and solid-fluid mixtures provide a foundation for a comprehensive debris flow theory, and experiments provide data that reveal the strengths and limitations of theoretical models. Both debris flow materials and dry granular materials can sustain shear stresses while remaining static; both can deform in a slow, tranquil mode characterized by enduring, frictional grain contacts; and both can flow in a more rapid, agitated mode characterized by brief, inelastic grain collisions. In debris flows, however, pore fluid that is highly viscous and nearly incompressible, composed of water with suspended silt and clay, can strongly mediate intergranular friction and collisions. Grain friction, grain collisions, and viscous fluid flow may transfer significant momentum simultaneously. Both the vibrational kinetic energy of solid grains (measured by a quantity termed the granular temperature) and the pressure of the intervening pore fluid facilitate motion of grains past one another, thereby enhancing debris flow mobility. Granular temperature arises from conversion of flow translational energy to grain vibrational energy, a process that depends on shear rates, grain properties, boundary conditions, and the ambient fluid viscosity and pressure. Pore fluid pressures that exceed static equilibrium pressures result from local or global debris contraction. Like larger, natural debris flows, experimental debris flows of ˜10 m³ of poorly sorted, water-saturated sediment invariably move as an unsteady surge or series of surges. Measurements at the base of experimental flows show that coarse-grained surge fronts have little or no pore fluid pressure. In contrast, finer-grained, thoroughly saturated debris behind surge fronts is nearly liquefied by high pore pressure, which persists owing to the great compressibility and moderate permeability of the debris. Realistic models of debris flows therefore require equations that simulate inertial motion of surges in which high-resistance fronts dominated by solid forces impede the motion of low-resistance tails more strongly influenced by fluid forces. Furthermore, because debris flows characteristically originate as nearly rigid sediment masses, transform at least partly to liquefied flows, and then transform again to nearly rigid deposits, acceptable models must simulate an evolution of material behavior without invoking preternatural changes in material properties. A simple model that satisfies most of these criteria uses depth-averaged equations of motion patterned after those of the Savage-Hutter theory for gravity-driven flow of dry granular masses but generalized to include the effects of viscous pore fluid with varying pressure. These equations can describe a spectrum of debris flow behaviors intermediate between those of wet rock avalanches and sediment-laden water floods. With appropriate pore pressure distributions the equations yield numerical solutions that successfully predict unsteady, nonuniform motion of experimental debris flows.

The physics of debris flows

USGS Publications Warehouse

Iverson, R.M.

1997-01-01

Recent advances in theory and experimentation motivate a thorough reassessment of the physics of debris flows. Analyses of flows of dry, granular solids and solid-fluid mixtures provide a foundation for a comprehensive debris flow theory, and experiments provide data that reveal the strengths and limitations of theoretical models. Both debris flow materials and dry granular materials can sustain shear stresses while remaining static; both can deform in a slow, tranquil mode characterized by enduring, frictional grain contacts; and both can flow in a more rapid, agitated mode characterized by brief, inelastic grain collisions. In debris flows, however, pore fluid that is highly viscous and nearly incompressible, composed of water with suspended silt and clay, can strongly mediate intergranular friction and collisions. Grain friction, grain collisions, and viscous fluid flow may transfer significant momentum simultaneously. Both the vibrational kinetic energy of solid grains (measured by a quantity termed the granular temperature) and the pressure of the intervening pore fluid facilitate motion of grains past one another, thereby enhancing debris flow mobility. Granular temperature arises from conversion of flow translational energy to grain vibrational energy, a process that depends on shear rates, grain properties, boundary conditions, and the ambient fluid viscosity and pressure. Pore fluid pressures that exceed static equilibrium pressures result from local or global debris contraction. Like larger, natural debris flows, experimental debris flows of ???10 m3 of poorly sorted, water-saturated sediment invariably move as an unsteady surge or series of surges. Measurements at the base of experimental flows show that coarse-grained surge fronts have little or no pore fluid pressure. In contrast, finer-grained, thoroughly saturated debris behind surge fronts is nearly liquefied by high pore pressure, which persists owing to the great compressibility and moderate permeability of the debris. Realistic models of debris flows therefore require equations that simulate inertial motion of surges in which high-resistance fronts dominated by solid forces impede the motion of low-resistance tails more strongly influenced by fluid forces. Furthermore, because debris flows characteristically originate as nearly rigid sediment masses, transform at least partly to liquefied flows, and then transform again to nearly rigid deposits, acceptable models must simulate an evolution of material behavior without invoking preternatural changes in material properties. A simple model that satisfies most of these criteria uses depth-averaged equations of motion patterned after those of the Savage-Hutter theory for gravity-driven flow of dry granular masses but generalized to include the effects of viscous pore fluid with varying pressure. These equations can describe a spectrum of debris flow behaviors intermediate between those of wet rock avalanches and sediment-laden water floods. With appropriate pore pressure distributions the equations yield numerical solutions that successfully predict unsteady, nonuniform motion of experimental debris flows.

Synchrotron X-ray Applications Toward an Understanding of Elastic Anisotropy

NASA Astrophysics Data System (ADS)

Kanitpanyacharoen, Waruntorn

The contribution of this dissertation is to expand the current knowledge of factors and mechanisms that influence the development of preferred orientation of minerlas and pores in different materials, ranging from rocks in Earth's crust to minerals in the deep Earth. Preferred orientation--a main contributing component to elastic anisotropy--is however very challenging to quantify. The overall focus of this thesis thus aims to (1) apply the capabilities of synchrotron X-ray techniques to determine preferred orientations of hexagonal metals and shales under different conditions and (2) enhance our understanding of their relationships to the elastic properties. Lattice preferred orientation (LPO) or 'texture' of hexagonal close-packed iron (hcp- Fe) crystals during deformation has been suggested as the cause of the elastic anisotropy observed in Earth's inner core. However, relatively little is known about LPO of other hcp metals. An investigation of a wide range of hcp metals (Cd, Zn, Os, and Hf) as analogs to hcp-Fe was thus undertaken to better understand deformation mechanisms at high pressure and temperature in Chapter 2. Results show that all hcp metals preferentially align their c-axes near the compression axis during deformation but with considerable differences. The gradual texture evolution in Cd and Zn is mainly controlled by basal slip systems while a rapid texture development in Os and Hf at ambient temperature is due to a dominant role of tensile twinning, with some degree of basal slip. At elevated temperature, tensile twinning is suppressed and texturing is governed by combined basal and prismatic slip. Under all conditions, basal slip appears to be the main deformation mechanism in hcp metals at high pressure and temperature. These findings are similar to those of hcp-Fe and useful to better understand the deformation mechanisms of hcp metals and their implications for elastic anisotropy. In Chapter 3, a high-energy synchrotron X-ray diffraction technique was applied to characterize LPO and phase proportions of Posidonia Shale collected in the Hils Syncline from Germany, in order to examine the influence of clay content, burial depth, and thermal history. The samples used in this study had experienced different local temperatures during burial and uplifting, as established by the maturity of kerogen (0.68-1.45% vitrinite reflectance, Ro), but their constituent clay minerals, including kaolinite, illite-mica, and illite-smectite, show similar degrees of LPO in all samples, ranging between 3.7 and 6.3 multiple of random distribution (m.r.d.). These observations imply that the difference in local thermal history, which significantly affects the maturity of kerogen, at most marginally influences LPO of clays, as the alignment of clays was established early in the history. In Chapter 4, the SPO of constituents phases in Kimmeridge Shale (North Sea, UK) and Barnett Shale (Gulf of Mexico, USA) was quantified to a resolution of ˜1 mum by using synchrotron X-ray microtomography (SXMT) technique. Measurements were done at different facilities (ALS, APS, and SLS) to characterize 3D microstructures, explore resolution limitations, and develop satisfactory procedures for data quantification. Segmentation images show that the SPO of low density features, including pores, fractures, and kerogen, is mostly anisotropic and oriented parallel to the bedding plane. Small pores are generally dispersed, whereas some large fractures and kerogen have irregular shapes and remain aligned horizontally. In contrast, pyrite exhibits no SPO. The volume fractions and aspect ratios of low density features extracted from three synchrotron sources show excellent agreement with 6.3(6)% for Kimmeridge Shale and 4.5(4)% for Barnett Shale. A small variation is mainly due to differences of optical instruments and technical setups. The SXMT is proven to be a crucial technique to investigate 3D internal structures of fine-grained materials at high-resolution. A relationship between LPO, SPO, and elastic anisotropy of the Qusaiba Shale from the Rub'al-Khali basin in Saudi Arabia is established in Chapter 5. The Qusaiba samples exhibit strong LPO of clay minerals (2.4-6.8 m.r.d.) due to their high total clay content and high degree of compaction. The SPO of pores, fractures, and kerogen here are also anisotropic and organized mainly parallel to bedding, with little connectivity of the flat pores normal to the bedding. The microscopic information (LPO) extracted from different synchrotron X-ray techniques is then applied in different averaging approaches (Voigt, Reuss, Hill, and Geometric mean) to calculate macroscopic properties of shales. (Abstract shortened by UMI.)

Suitability of the methylene blue test for determination of cation exchange capacity of clay minerals related to ammonium acetate method

NASA Astrophysics Data System (ADS)

Milošević, Maja; Logar, Mihovil; Dojčinović, Biljana; Erić, Suzana

2015-04-01

Cation exchange capacity (CEC) represents one of the most important parameters of clay minerals which reflects their ability to exchange cations with liquid phases in near contact. Measurement of CEC is used for characterizing sample plasticity, adsorbing and swelling properties which later define their usage in industrial purposes. Several methods have been developed over the years for determination of layer charge, charge density, charge distribution, etc. and have been published in numerous papers (Czimerova et al., 2006; Yukselen and Kaya, 2008). The main goal of present study is comparison of suitability of more recent method - methylene blue test in regard to older method - ammonium acetate for determination of CEC. For this study, we selected one montmorillonite clay (Bogovina, Serbia) and two mainly kaolinite clays (Miličinica, Serbia). Chemicals used for CEC determinations were solution of methylene blue (MB)(14*10-6M/ml) and ammonium acetate (AA) solution (1M). The obtained results are showing generally lower values in case of MB method. The main difference is due to molecular aggregation of MB on the clay surface. AA method is highly sensitive to the presence of CaO. Release of Ca ion from the sample into the solution can limit the saturation of exchange sites by the ammonium ion. This is clearly visible in case of montmorillonite clay. Fe2+ and Mg ions are difficult to move by the ammonium ion because of their ion radius, but in case of MB molecule there is no such restriction in removing them from the exchange sites. MB solution, even in a low concentration (2*10-6M/ml), is showing preferable results in moving the ions from their positions which is already visible after adding a small quantity of solution (25cm3). Both MB-titration and MB-spot test yield similar results and are much simpler methods than AA and they also give other information such as specific surface area (external and internal) whereas AA method only provides information about cations in exchangeable positions. Both methods, methylene blue test and ammonium acetate method, have advantages and disadvantages and differ in their requirements for the sample preparations but in general method selection is depending on the specific application of the given sample. References: - Yukselen, Y. and Kaya, A., Engineering Geology 102 (2008) 38-45 - Czimerova, A., Bujdak, J. and Dohrmann, R., Applied Clay Science 34 (2006) 2-13

Soil transport parameters of potassium under a tropical saline soil condition using STANMOD

NASA Astrophysics Data System (ADS)

Suzanye da Silva Santos, Rafaelly; Honorio de Miranda, Jarbas; Previatello da Silva, Livia

2015-04-01

Environmental responsibility and concerning about the final destination of solutes in soil, so more studies allow a better understanding about the solutes behaviour in soil. Potassium is a macronutrient that is required in high concentrations, been an extremely important nutrient for all agricultural crops. It plays essential roles in physiological processes vital for plant growth, from protein synthesis to maintenance of plant water balance, and is available to plants dissolved in soil water while exchangeable K is loosely held on the exchange sites on the surface of clay particles. K will tend to be adsorbed onto the surface of negatively charged soil particles. Potassium uptake is vital for plant growth but in saline soils sodium competes with potassium for uptake across the plasma membrane of plant cells. This can result in high Na+:K+ ratios that reduce plant growth and eventually become toxic. This study aimed to obtain soil transport parameters of potassium in saline soil, such as: pore water velocity in soil (v), retardation factor (R), dispersivity (λ) and dispersion coefficient (D), in a disturbed sandy soil with different concentrations of potassium chlorate solution (KCl), which is one of the most common form of potassium fertilizer. The experiment was carried out using soil samples collected in a depth of 0 to 20 cm, applying potassium chlorate solution containing 28.6, 100, 200 and 500 mg L-1 of K. To obtain transport parameters, the data were adjusted with the software STANMOD. At low concentrations, interaction between potassium and soil occur more efficiently. It was observed that only the breakthrough curve prepared with solution of 500 mg L-1 reached the applied concentration, and the solution of 28.6 mg L-1 overestimated the parameters values. The STANMOD proved to be efficient in obtaining potassium transport parameters; KCl solution to be applied should be greater than 500 mg L-1; solutions with low concentrations tend to overestimate parameters values.

Characterization of the porins of Campylobacter jejuni and Campylobacter coli and implications for antibiotic susceptibility.

PubMed Central

Page, W J; Huyer, G; Huyer, M; Worobec, E A

1989-01-01

The major outer membrane protein was extracted from Campylobacter coli by Triton X-100/EDTA fractionation of cell envelopes. This heat-modifiable protein was shown to have pore-forming activity in black lipid bilayers. The C. coli porin formed a relatively small cation-selective pore with a mean single-channel conductance of 0.53 +/- 0.16 nS in 1.0 M KCl. There was no evidence of oligomer formation, which suggested that each protein monomer formed a pore. Pore-forming activity of the C. coli porin and similarly prepared Campylobacter jejuni porin was also measured in liposome-swelling assays. These results confirmed the cation selectivity of both pores. The C. coli porin formed a small pore, which hindered the penetration of solutes with a molecular weight of 262, and a larger pore, which hindered the penetration of solutes with a molecular weight of 340, in a protein-concentration-dependent manner. C. jejuni formed one size of pore that was slightly larger than the C. coli pore and just permitted the passage of solutes, with a molecular weight of 340. A review of the literature concerning in vitro screening of antimicrobial agents tended to confirm the low permeability of the C. jejuni outer membrane to hydrophilic antimicrobial agents except when the molecules had molecular weights of less than 360. The porins of C. jejuni and C. coli may contribute to intrinsic resistance to antimicrobial agents, whereas alternative (nonporin) routes of antimicrobial agent uptake may be more important determinants of susceptibility to antimicrobial agents. Images PMID:2543277

Characterization of the porins of Campylobacter jejuni and Campylobacter coli and implications for antibiotic susceptibility.

PubMed

Page, W J; Huyer, G; Huyer, M; Worobec, E A

1989-03-01

The major outer membrane protein was extracted from Campylobacter coli by Triton X-100/EDTA fractionation of cell envelopes. This heat-modifiable protein was shown to have pore-forming activity in black lipid bilayers. The C. coli porin formed a relatively small cation-selective pore with a mean single-channel conductance of 0.53 +/- 0.16 nS in 1.0 M KCl. There was no evidence of oligomer formation, which suggested that each protein monomer formed a pore. Pore-forming activity of the C. coli porin and similarly prepared Campylobacter jejuni porin was also measured in liposome-swelling assays. These results confirmed the cation selectivity of both pores. The C. coli porin formed a small pore, which hindered the penetration of solutes with a molecular weight of 262, and a larger pore, which hindered the penetration of solutes with a molecular weight of 340, in a protein-concentration-dependent manner. C. jejuni formed one size of pore that was slightly larger than the C. coli pore and just permitted the passage of solutes, with a molecular weight of 340. A review of the literature concerning in vitro screening of antimicrobial agents tended to confirm the low permeability of the C. jejuni outer membrane to hydrophilic antimicrobial agents except when the molecules had molecular weights of less than 360. The porins of C. jejuni and C. coli may contribute to intrinsic resistance to antimicrobial agents, whereas alternative (nonporin) routes of antimicrobial agent uptake may be more important determinants of susceptibility to antimicrobial agents.

A microstructural study of SAFOD gouge from actively creeping San Andreas Fault zone; Implications for shear localization models

NASA Astrophysics Data System (ADS)

Blackburn, E. D.; Hadizadeh, J.; Babaie, H. A.

2009-12-01

The prevailing models of shear localization in fault gouges are mainly based on experimental aggregates that necessarily neglect the effects of chemical and mechanical maturation with time. The SAFOD cores have provided a chance to test whether cataclasis as a deformation mechanism and factors such as porosity and particle size, critical in some existing shear localization models continue to be critical in mature gouges. We studied a core sample from 3194m MD in the SAFOD phase 3, which consists of intensely foliated shale-siltstone cataclasites in contact with less deformed shale. Microstructures were studied in 3 perpendicular planes with reference to foliation using high resolution scanning electron microscopy, cathodoluminescence imaging, X-ray fluorescence mapping, and energy dispersive X-ray spectroscopy. The cataclastic foliation, recognizable at length scales >100 μm, is primarily defined by bands of clay gouge with distinct microstructure, clay content, and porosity. Variations in elemental composition and porosity of the clay gouge were measured continuously across the foliation. Prominent features within the foliation bands include lens-shaped clusters of highly brecciated and veined siltstone fragments, pyrite smears, and pyrite-cemented cataclasites. The microstructural relations and chemical data provide clear evidence of multiple episodes of veining and deformation with some possibility of relative age determination for the episodes. There is evidence of syn-deformation hydrothermal changes including growth and brittle shear of pyrite, alteration of host shale clays to illite-smectite clays and Fe-rich smectite. Evidence of grain-boundary corrosion of non-clay mineral fragments suggests pressure solution creep. The gouge porosity estimates varied from 0-18% (about 3% in less deformed shale) with the highest value in the bands with abundant siltstone fragments. The banding is mechanically significant since it pervasively segregates the gouge into regions of low clay content, high-porosity and regions of low-porosity, high clay content. It appears from our data that shear localization in the gouge involves pressure solution as well as cataclastic flow assisted by alteration-softening. While the porous bands are potential conduits for fluid flow and could be sites for pressure solution creep, the clay-rich bands could serve as sites of shear localization due to their lower dilatancy rate. A better understanding of interaction between the two deformation mechanisms might shed light on the nature of microearthquake activity in the creeping segment of the SAF.

Rheological properties of purified illite clays in glycerol/water suspensions

NASA Astrophysics Data System (ADS)

Dusenkova, I.; Malers, J.; Berzina-Cimdina, L.

2015-04-01

There are many studies about rheological properties of clay-water suspensions, but no published investigations about clay-glycerol suspensions. In this work apparent viscosity of previously purified illite containing clay fraction < 2 μm and glycerol/water suspensions were investigated. Carbonates were removed by dissolution in hydrochloric and citric acids and other non-clay minerals were almost totally removed by centrifugation. All obtained suspensions behaved as shear-thinning fluids with multiple times higher viscosity than pure glycerol/water solutions. Reduction of clay fraction concentration by 5% decreased the apparent viscosity of 50% glycerol/water suspensions approximately 5 times. There was basically no difference in apparent viscosity between all four 50% glycerol/water suspensions, but in 90% glycerol/water suspensions samples from Iecava deposit showed slightly higher apparent viscosity, which could be affected by the particle size distribution.

Water saturation of hydrothermal smectite-rich clay might have promoted slope instability prior to the 1998 debris avalanche at Casita volcano, Nicaragua

NASA Astrophysics Data System (ADS)

Delmelle, P.; Opfergelt, S.; Boivin, P.; Delvaux, B.

2006-12-01

In October 1998, a relatively small collapse (1 600 000 cubic meters) of a pre-existing scarp occurred on the southern flank of the dormant Casita volcano, Nicaragua. It resulted in a debris avalanche, which quickly transformed into a disastrous debris flow that destroyed two towns and killed more than 2500 people. The failure was shown to be triggered by an excess pore water pressure within highly fractured rocks, following prolonged seasonal rains and precipitations from Hurricane Mitch. This pressure was linked to the water saturation of a hydrothermally-altered clay bedrock impeding in-depth infiltration. Yet, the nature and amounts of the clay material involved in the slope failure were still unknown. Here we report on physical, chemical and mineralogical investigations aimed at quantifying the clay content, and identifying the layer silicates of the hydrothermally-altered clays uncovered by the 1998 debris avalanche. The fine clay material was exceptionally rich in smectite (up to 50 wt. percent), which swells upon wetting and shrinks during dry conditions (Opfergelt et al., 2006, Geophys. Res. Lett., 33 (15), L15305). The smectite belonged to the beidellite-montmorillonite series. The pervasive presence of water-saturated smectitic clay strongly reduced the permeability in depth, and also altered the rheological and mechanical properties of both the pre-failure rock mass and flow materials. The shrink-swell behavior progressively decreased the rock's shear strength, and gradually destabilized the overlying rock mass in the decades and centuries before the landslide, thereby contributing to slope instability. Prolonged intense rainfall led to the formation of incipient weak failure surfaces in the superficial rock mass. As provoked by water saturation, this process was likely favored by the rapid change of the mechanical properties of smectite-rich clays deposited in fracture, joint and gouge interfaces. We suggest that hazard assessments associated with unstable volcanic slopes, especially on volcanoes hosting a long-lived hydrothermal system, should include the potential long and short-term impacts of swelling clays.

Silicon-based Porous Ceramics via Freeze Casting of Preceramic Polymers

NASA Astrophysics Data System (ADS)

Naviroj, Maninpat

Freeze casting is a technique for processing porous materials that has drawn significant attention for its effectiveness in producing a variety of tailorable pore structures for ceramics, metals, and polymers. With freeze casting, pores are generated based on a solidification process where ice crystals act as a sacrificial template which can eventually be sublimated to create pores. While the majority of freeze-casting studies have been performed using conventional ceramic suspensions, this work explores an alternative processing route by freeze casting with preceramic polymer solutions. Significant differences exist between freeze casting of a particulate suspension and a polymeric solution. These changes affect the processing method, solidification behavior, and pore structure, thereby introducing new challenges and possibilities for the freeze-casting technique. The first part of this study explored the processing requirements involved with freeze casting of preceramic polymers, along with methods to control the resulting pore structure. Solvent choice, freezing front velocity, and polymer concentration were used as processing variables to manipulate the pore structures. A total of seven organic solvents were freeze cast with a polymethylsiloxane preceramic polymer to produce ceramics with isotropic, dendritic, prismatic, and lamellar pore morphologies. Changes in freezing front velocity and polymer concentration were shown to influence pore size, shape, and connectivity. Differences between suspension- and solution-based samples freeze cast under equivalent conditions were also investigated. Certain solidification microstructures were strongly affected by the presence of suspended particles, creating differences between pore structures generated from the same solvents. Additionally, processing of solution-based samples were found to be the more facile technique. Compressive strength and water permeability of dendritic and lamellar structures were analyzed to determine functional differences between the pore structures. Results show that dendritic structures were up to 30 times stronger, while lamellar structures provided higher permeability constants. A change in freezing front velocity was shown to significantly affect permeability but not compressive strength. Finally, improved pore alignment along the freezing direction was achieved by controlling the nucleation and growth of solvent crystals through the use of a grain-selection template. Dendritic samples freeze cast with a template showed substantial increase in pore alignment, as determined by image analysis and permeability tests, with the permeability constant increasing by up to 6-fold when compared to a control sample.

Geothermal alteration of basaltic core from the Snake River Plain, Idaho

NASA Astrophysics Data System (ADS)

Sant, Christopher J.

The Snake River Plain is located in the southern part of the state of Idaho. The eastern plain, on which this study focuses, is a trail of volcanics from the Yellowstone hotspot. Three exploratory geothermal wells were drilled on the Snake River Plain. This project analyzes basaltic core from the first well at Kimama, north of Burley, Idaho. The objectives of this project are to establish zones of geothermal alteration and analyze the potential for geothermal power production using sub-aquifer resources on the axial volcanic zone of the Snake River Plain. Thirty samples from 1,912 m of core were sampled and analyzed for clay content and composition using X-ray diffraction. Observations from core samples and geophysical logs are also used to establish alteration zones. Mineralogical data, geophysical log data and physical characteristics of the core suggest that the base of the Snake River Plain aquifer at the axial zone is located 960 m below the surface, much deeper than previously suspected. Swelling smectite clay clogs pore spaces and reduces porosity and permeability to create a natural base to the aquifer. Increased temperatures favor the formation of smectite clay and other secondary minerals to the bottom of the hole. Below 960 m the core shows signs of alteration including color change, formation of clay, and filling of other secondary minerals in vesicles and fractured zones of the core. The smectite clay observed is Fe-rich clay that is authigenic in some places. Geothermal power generation may be feasible using a low temperature hot water geothermal system if thermal fluids can be attained near the bottom of the Kimama well.

Investigation of quartz diagenesis in mudstones of the Spraberry and Wolfcamp Formations

NASA Astrophysics Data System (ADS)

Eakin, A.; Reece, J. S.

2016-12-01

Here we present preliminary core analysis of the diagenetic variability existing within a siliceous mudstone facies of the Permian Spraberry and Wolfcamp Formations in the Midland Basin, Texas. Within this mudstone facies, the carbonate content varies from absent in several Wolfcamp Formation samples to >40 wt. % in the Spraberry Formation. A normalized ratio of quartz to clay content with carbonate removed reveals a systematic decrease in quartz content with increasing clay content. This relationship is typical of rocks with variable amounts of detrital quartz content. However, in this siliceous mudstone facies, the abundance of detrital quartz silt grains does not vary widely. Additionally, for the same clay content, the Wolfcamp Formation shows a higher concentration of quartz than the Spraberry Formation. Scanning electron microscopy (SEM) reveals the presence of microcrystalline quartz cement that likely accounts for the increased quartz content in the Wolfcamp Formation. This research tests the hypothesis that the increased quartz cement in the Wolfcamp Formation may occur at the expense of the carbonate cement present in the overlying Spraberry Formation. Furthermore, the deviation in quartz content for the same clay concentration only occurs once the ratio of quartz to clay content increases beyond 1.2. This ratio may represent a threshold of detrital quartz in the clay matrix required to have enough porosity and nucleation surface area for authigenic quartz growth. The presence of matrix cement may impact the mechanical properties to favor fracturing and cataclasis over more ductile deformation. This would enhance development of secondary porosity, while also increasing permeability through the connection of primary pores. Acquiring a fundamental understanding of diagenesis in the Spraberry and Wolfcamp Formations will aid in better prediction of mechanical behavior during drilling and optimized resource recovery.

Permeability-porosity relationships in sedimentary rocks

USGS Publications Warehouse

Nelson, Philip H.

1994-01-01

In many consolidated sandstone and carbonate formations, plots of core data show that the logarithm of permeability (k) is often linearly proportional to porosity (??). The slope, intercept, and degree of scatter of these log(k)-?? trends vary from formation to formation, and these variations are attributed to differences in initial grain size and sorting, diagenetic history, and compaction history. In unconsolidated sands, better sorting systematically increases both permeability and porosity. In sands and sandstones, an increase in gravel and coarse grain size content causes k to increase even while decreasing ??. Diagenetic minerals in the pore space of sandstones, such as cement and some clay types, tend to decrease log(k) proportionately as ?? decreases. Models to predict permeability from porosity and other measurable rock parameters fall into three classes based on either grain, surface area, or pore dimension considerations. (Models that directly incorporate well log measurements but have no particular theoretical underpinnings from a fourth class.) Grain-based models show permeability proportional to the square of grain size times porosity raised to (roughly) the fifth power, with grain sorting as an additional parameter. Surface-area models show permeability proportional to the inverse square of pore surface area times porosity raised to (roughly) the fourth power; measures of surface area include irreducible water saturation and nuclear magnetic resonance. Pore-dimension models show permeability proportional to the square of a pore dimension times porosity raised to a power of (roughly) two and produce curves of constant pore size that transgress the linear data trends on a log(k)-?? plot. The pore dimension is obtained from mercury injection measurements and is interpreted as the pore opening size of some interconnected fraction of the pore system. The linear log(k)-?? data trends cut the curves of constant pore size from the pore-dimension models, which shows that porosity reduction is always accompanied by a reduction in characteristic pore size. The high powers of porosity of the grain-based and surface-area models are required to compensate for the inclusion of the small end of the pore size spectrum.

Source and sink of fluid in pelagic siliceous sediments along a cold subduction plate boundary

NASA Astrophysics Data System (ADS)

Yamaguchi, Asuka; Hina, Shoko; Hamada, Yohei; Kameda, Jun; Hamahashi, Mari; Kuwatani, Tatsu; Shimizu, Mayuko; Kimura, Gaku

2016-08-01

Subduction zones where old oceanic plate underthrusting occurs are characterized by thick pelagic sediments originating from planktonic ooze as well as cold thermal conditions. For a better understanding of dehydration from pelagic sediments and fluid behavior, which would play a key role in controlling the dynamics in the shallow portion of the subduction zone, as observed in the 2011 Tohoku earthquake and tsunami, we investigate cherts in a Jurassic accretionary complex in Japan. The microstructure and microchemistry of these cherts indicate dissolution of SiO2 from a pressure solution seam and precipitation of SiO2 to the ;white chert layer,; which would act as a fluid conduit. The amount of water necessary to precipitate SiO2 in the white chert is 102 times larger than that produced by compaction and silica/clay diagenesis. Other fluid sources, such as hydrated oceanic crust or oceanic mantle, are necessary to account for this discrepancy in the fluid budget. A large amount of external fluid likely contributed to rising pore pressure along cold plate boundaries.

Method of fabrication of supported liquid membranes

DOEpatents

Luebke, David R.; Hong, Lei; Myers, Christina R.

2015-11-17

Method for the fabrication of a supported liquid membrane having a dense layer in contact with a porous layer, and a membrane liquid layer within the interconnected pores of the porous layer. The dense layer is comprised of a solidified material having an average pore size less than or equal to about 0.1 nanometer, while the porous layer is comprised of a plurality of interconnected pores and has an average pore size greater than 10 nanometers. The supported liquid membrane is fabricated through the preparation of a casting solution of a membrane liquid and a volatile solvent. A pressure difference is established across the dense layer and porous layer, the casting solution is applied to the porous layer, and the low viscosity casting solution is drawn toward the dense layer. The volatile solvent is evaporated and the membrane liquid precipitates, generating a membrane liquid layer in close proximity to the dense layer.

Application of Mortar Coupling in Multiscale Modelling of Coupled Flow, Transport, and Biofilm Growth in Porous Media

NASA Astrophysics Data System (ADS)

Laleian, A.; Valocchi, A. J.; Werth, C. J.

2017-12-01

Multiscale models of reactive transport in porous media are capable of capturing complex pore-scale processes while leveraging the efficiency of continuum-scale models. In particular, porosity changes caused by biofilm development yield complex feedbacks between transport and reaction that are difficult to quantify at the continuum scale. Pore-scale models, needed to accurately resolve these dynamics, are often impractical for applications due to their computational cost. To address this challenge, we are developing a multiscale model of biofilm growth in which non-overlapping regions at pore and continuum spatial scales are coupled with a mortar method providing continuity at interfaces. We explore two decompositions of coupled pore-scale and continuum-scale regions to study biofilm growth in a transverse mixing zone. In the first decomposition, all reaction is confined to a pore-scale region extending the transverse mixing zone length. Only solute transport occurs in the surrounding continuum-scale regions. Relative to a fully pore-scale result, we find the multiscale model with this decomposition has a reduced run time and consistent result in terms of biofilm growth and solute utilization. In the second decomposition, reaction occurs in both an up-gradient pore-scale region and a down-gradient continuum-scale region. To quantify clogging, the continuum-scale model implements empirical relations between porosity and continuum-scale parameters, such as permeability and the transverse dispersion coefficient. Solutes are sufficiently mixed at the end of the pore-scale region, such that the initial reaction rate is accurately computed using averaged concentrations in the continuum-scale region. Relative to a fully pore-scale result, we find accuracy of biomass growth in the multiscale model with this decomposition improves as the interface between pore-scale and continuum-scale regions moves downgradient where transverse mixing is more fully developed. Also, this decomposition poses additional challenges with respect to mortar coupling. We explore these challenges and potential solutions. While recent work has demonstrated growing interest in multiscale models, further development is needed for their application to field-scale subsurface contaminant transport and remediation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ahmed, K.; Tonks, M.; Zhang, Y.

A detailed phase field model for the effect of pore drag on grain growth kinetics was implemented in MARMOT. The model takes into consideration both the curvature-driven grain boundary motion and pore migration by surface diffusion. As such, the model accounts for the interaction between pore and grain boundary kinetics, which tends to retard the grain growth process. Our 2D and 3D simulations demonstrate that the model capture all possible pore-grain boundary interactions proposed in theoretical models. For high enough surface mobility, the pores move along with the migrating boundary as a quasi-rigid-body, albeit hindering its migration rate compared tomore » the pore-free case. For less mobile pores, the migrating boundary can separate from the pores. For the pore-controlled grain growth kinetics, the model predicts a strong dependence of the growth rate on the number of pores, pore size, and surface diffusivity in agreement with theroretical models. An evolution equation for the grain size that includes these parameters was derived and showed to agree well with numerical solution. It shows a smooth transition from boundary-controlled kinetics to pore-controlled kinetics as the surface diffusivity decreases or the number of pores or their size increases. This equation can be utilized in BISON to give accurate estimate for the grain size evolution. This will be accomplished in the near future. The effect of solute drag and anisotropy of grain boundary on grain growth will be investigated in future studies.« less

Accumulation of Colloidal Particles in Flow Junctions Induced by Fluid Flow and Diffusiophoresis

NASA Astrophysics Data System (ADS)

Shin, Sangwoo; Ault, Jesse T.; Warren, Patrick B.; Stone, Howard A.

2017-10-01

The flow of solutions containing solutes and colloidal particles in porous media is widely found in systems including underground aquifers, hydraulic fractures, estuarine or coastal habitats, water filtration systems, etc. In such systems, solute gradients occur when there is a local change in the solute concentration. While the effects of solute gradients have been found to be important for many applications, we observe an unexpected colloidal behavior in porous media driven by the combination of solute gradients and the fluid flow. When two flows with different solute concentrations are in contact near a junction, a sharp solute gradient is formed at the interface, which may allow strong diffusiophoresis of the particles directed against the flow. Consequently, the particles accumulate near the pore entrance, rapidly approaching the packing limit. These colloidal dynamics have important implications for the clogging of a porous medium, where particles that are orders of magnitude smaller than the pore width can accumulate and block the pores within a short period of time. We also show that this effect can be exploited as a useful tool for preconcentrating biomolecules for rapid bioassays.

Sedimentary controls on modern sand grain coat formation

NASA Astrophysics Data System (ADS)

Dowey, Patrick J.; Worden, Richard H.; Utley, James; Hodgson, David M.

2017-05-01

Coated sand grains can influence reservoir quality evolution during sandstone diagenesis. Porosity can be reduced and fluid flow restricted where grain coats encroach into pore space. Conversely pore-lining grain coats can restrict the growth of pore-filling quartz cement in deeply buried sandstones, and thus can result in unusually high porosity in deeply buried sandstones. Being able to predict the distribution of coated sand grains within petroleum reservoirs is thus important to help find good reservoir quality. Here we report a modern analogue study of 12 sediment cores from the Anllóns Estuary, Galicia, NW Spain, collected from a range of sub-environments, to help develop an understanding of the occurrence and distribution of coated grains. The cores were described for grain size, bioturbation and sedimentary structures, and then sub-sampled for electron and light microscopy, laser granulometry, and X-ray diffraction analysis. The Anllóns Estuary is sand-dominated with intertidal sand flats and saltmarsh environments at the margins; there is a shallowing/fining-upwards trend in the estuary-fill succession. Grain coats are present in nearly every sample analysed; they are between 1 μm and 100 μm thick and typically lack internal organisation. The extent of grain coat coverage can exceed 25% in some samples with coverage highest in the top 20 cm of cores. Samples from muddy intertidal flat and the muddy saltmarsh environments, close to the margins of the estuary, have the highest coat coverage (mean coat coverage of 20.2% and 21.3%, respectively). The lowest mean coat coverage occurs in the sandy saltmarsh (10.4%), beyond the upper tidal limit and sandy intertidal flat environments (8.4%), close to the main estuary channel. Mean coat coverage correlates with the concentration of clay fraction. The primary controls on the distribution of fine-grained sediment, and therefore grain coat distribution, are primary sediment transport and deposition processes that concentrate the clay fraction in the sediment towards the margins of the estuary. Bioturbation and clay illuviation/mechanical infiltration are secondary processes that may redistribute fine-grained sediment and produce grain coats. Here we have shown that detrital grain coats are more likely in marginal environments of ancient estuary-fills, which are typically found in the fining-upward part of progradational successions.

Modeling selenate adsorption behavior on oxides, clay minerals, and soils using the triple layer model

USDA-ARS?s Scientific Manuscript database

Selenate adsorption behavior was investigated on amorphous aluminum oxide, amorphous iron oxide, goethite, clay minerals: kaolinites, montmorillonites, illite, and 18 soil samples from Hawaii, and the Southwestern and the Midwestern regions of the US as a function of solution pH. Selenate adsorpti...

Modeling selenite adsorption envelopes on oxides, clay minerals, and soils using the triple layer model

USDA-ARS?s Scientific Manuscript database

Selenite adsorption behavior was investigated on amorphous aluminum and iron oxides, clay minerals: kaolinite, montmorillonite, and illite, and 45 surface and subsurface soil samples from the Southwestern and Midwestern regions of the USA as a function of solution pH. Selenite adsorption decreased ...

Picloram and Aminopyralid Sorption to Soil and Clay Minerals

USDA-ARS?s Scientific Manuscript database

Aminopyralid sorption data are lacking, and these data are needed to predict off-target transport and plant available herbicide in soil solution. The objective of this research was to determine the sorption of picloram and aminopyralid to five soils and three clay minerals and determine if the pote...

Near-Sea Floor Compaction and Shallow Overpressures: Constrains From High Strain Consolidation Tests on ODP Sediments

NASA Astrophysics Data System (ADS)

Olgaard, D. L.; Dugan, B. E.; Gooch, M. J.

2001-12-01

Before launching into the title topic, I will share a few ``memories of torsion testing'' that exemplify one of the breakthrough contributions Mervyn Paterson has made to Geodynamics. Mervyn and his machines, the torsion apparatus in particular, have revolutionized structural geology by providing the means to quantify crustal and mantle deformation processes up to and beyond the high shear strains observed in the field. High strain is also important in basin evolution. High strain consolidation tests are used to help understand mechanical and fluid flow processes in deforming sediments on continental slopes. Clay-rich sediments compact from 70% to less than 40% porosity within 1000m below the sea floor [mbsf]. Clay-rich sediments have notoriously low permeabilities and, when combined with rapid deposition rates, can cause pore-fluid pressures greatly in excess of hydrostatic at shallow depths. Such high overpressures are particularly hazardous to slope stability and to deepwater drilling. Recently, Dugan and Flemings [Science, 289, 2000] used forward sedimentation models for the New Jersey continental slope calibrated with ODP data, to predict fluid pressures near lithostatic to depths of 640m. In the current study we use consolidation tests to verify these model predictions. Silty-clay cores were collected from depths of 60 to 650mbsf during ODP Leg 1073. Five samples were tested under drained, uniaxial strain conditions, i.e. zero radial displacement. Cylindrical samples were first subjected to a hydrostatic effective stress of ~0.2MPa, then axially loaded at a constant rate of 0.7kPa/min to maintain drained conditions. Pore pressure [brine] was held constant at 3.5MPa. Confining pressure was increased to maintain the uniaxial strain condition. P-wave velocities and permeabilities were measured at various stress conditions on two samples. The samples compacted rapidly at low stresses, then at decreasing rates as stress increased. A total compaction of 22% volumetric strain was achieved at the maximum axial stress of 22 MPa. The in situ pore pressures for each depth were calculated from the ``maximum effective stress'' determined from the break in slope of the data in log[effective stress] vs. void ratio plots. Test results confirm that pore pressure gradients exceed hydrostatic, approaching lithostatic, from about 60m to the base of the Pleistocene [~550m], then decrease within the underlying Miocene sandy silt. The confining-to-axial effective stress ratio increased asymptotically during loading to a value of 0.6; similar to that expected for silty shales. P-wave velocity-porosity-effective stress trends are used to predict overpressures, and thus anticipate hazards in near-seafloor sediments.

Hydrologic exchange and chemical weathering in a proglacial watershed near Kangerlussuaq, west Greenland

NASA Astrophysics Data System (ADS)

Deuerling, Kelly M.; Martin, Jonathan B.; Martin, Ellen E.; Scribner, Cecilia A.

2018-01-01

The exchange of proglacial river water with active layer pore water could alter water chemical compositions in glacial outwash plains and oceanic solute fluxes. To evaluate effects of this exchange, we sampled Watson River and adjacent pore water during the 2013 melt season at two sandurs in western Greenland; one in Sandflugtdalen and the other near the confluence with Søndre Strømfjord. We measured temperature, specific conductivity, and head gradients between the river and bank over a week-long period at Sandflugtdalen, as well as sediment hydraulic conductivity and chemical compositions of waters from both sites. Specific conductivity of pore water is four to ten times greater than river water as solutes are concentrated from weathering reactions, cryoconcentration, and evaporation. Pore water compositions are predominantly altered by carbonate dissolution and sulfide mineral oxidation. High concentrations of HCO3 and SO4 result from solute recycling and dissolution of secondary Ca-Mg carbonate/sulfate salts initially formed by near-surface evaporation in the summer and at depth by freeze-in of the active layer and cryoconcentration in the winter. High hydraulic conductivity (10-5 to 10-4 m/s) and diurnal fluctuations of river stage during our study caused exchange of river and pore water immediately adjacent to the river channel, with a net loss of river water to the bank. Pore water >6 m from the river continuously flowed away from the river. Approximately 1-8% of the river discharge through the Sandflugtdalen was lost to the river bank during our 6.75 day study based on calculations using Darcy's Law. Although not sampled, some of this water should discharge to the river during low river stage early and late in the melt season. Elevated pore water solute concentrations in sandurs and water exchange at diurnal and seasonal frequency should impact fluxes of solutes to the ocean, although understanding the magnitude of this effect will require long-term evaluation throughout the melt season.

Investigating Hydrophilic Pores in Model Lipid Bilayers using Molecular Simulations: Correlating Bilayer Properties with Pore Formation Thermodynamics

PubMed Central

Hu, Yuan; Sinha, Sudipta Kumar

2015-01-01

Cell-penetrating and antimicrobial peptides show remarkable ability to translocate across physiological membranes. Along with factors such as electric potential induced-perturbations of membrane structure and surface tension effects, experiments invoke pore-like membrane configurations during the solute transfer process into vesicles and cells. The initiation and formation of pores are associated with a non-trivial free energy cost, thus necessitating consideration of the factors associated with pore formation and attendant free energetics. Due to experimental and modeling challenges related to the long timescales of the translocation process, we use umbrella-sampling molecular dynamics simulations with a lipid-density based order parameter to investigate membrane pore-formation free energy employing Martini coarse-grained models. We investigate structure and thermodynamic features of the pore in 18 lipids spanning a range of head-groups, charge states, acyl chain lengths and saturation. We probe the dependence of pore-formation barriers on area per lipid, lipid bilayer thickness, membrane bending rigidities in three different lipid classes. The pore formation free energy in pure bilayers and peptide translocating scenarios are significantly coupled with bilayer thickness. Thicker bilayers require more reversible work to create pores. Pore formation free energy is higher in peptide-lipid systems relative to the peptide-free lipid systems due to penalties to maintain solvation of charged hydrophilic solutes within the membrane environment. PMID:25614183

Numerical Simulation of the Freeze-Thaw Behavior of Mortar Containing Deicing Salt Solution

PubMed Central

Esmaeeli, Hadi S.; Farnam, Yaghoob; Bentz, Dale P.; Zavattieri, Pablo D.; Weiss, Jason

2016-01-01

This paper presents a one-dimensional finite difference model that is developed to describe the freeze-thaw behavior of an air-entrained mortar containing deicing salt solution. A phenomenological model is used to predict the temperature and the heat flow for mortar specimens during cooling and heating. Phase transformations associated with the freezing/melting of water/ice or transition of the eutectic solution from liquid to solid are included in this phenomenological model. The lever rule is used to calculate the quantity of solution that undergoes the phase transformation, thereby simulating the energy released/absorbed during phase transformation. Undercooling and pore size effects are considered in the numerical model. To investigate the effect of pore size distribution, this distribution is considered using the Gibbs-Thomson equation in a saturated mortar specimen. For an air-entrained mortar, the impact of considering pore size (and curvature) on freezing was relatively insignificant; however the impact of pore size is much more significant during melting. The fluid inside pores smaller than 5 nm (i.e., gel pores) has a relatively small contribution in the macroscopic freeze-thaw behavior of mortar specimens within the temperature range used in this study (i.e., +24 °C to −35 °C), and can therefore be neglected for the macroscopic freeze-thaw simulations. A heat sink term is utilized to simulate the heat dissipation during phase transformations. Data from experiments performed using a low-temperature longitudinal guarded comparative calorimeter (LGCC) on mortar specimens fully saturated with various concentration NaCl solutions or partially saturated with water is compared to the numerical results and a promising agreement is generally obtained. PMID:28082830

Numerical Simulation of the Freeze-Thaw Behavior of Mortar Containing Deicing Salt Solution.

PubMed

Esmaeeli, Hadi S; Farnam, Yaghoob; Bentz, Dale P; Zavattieri, Pablo D; Weiss, Jason

2017-02-01

This paper presents a one-dimensional finite difference model that is developed to describe the freeze-thaw behavior of an air-entrained mortar containing deicing salt solution. A phenomenological model is used to predict the temperature and the heat flow for mortar specimens during cooling and heating. Phase transformations associated with the freezing/melting of water/ice or transition of the eutectic solution from liquid to solid are included in this phenomenological model. The lever rule is used to calculate the quantity of solution that undergoes the phase transformation, thereby simulating the energy released/absorbed during phase transformation. Undercooling and pore size effects are considered in the numerical model. To investigate the effect of pore size distribution, this distribution is considered using the Gibbs-Thomson equation in a saturated mortar specimen. For an air-entrained mortar, the impact of considering pore size (and curvature) on freezing was relatively insignificant; however the impact of pore size is much more significant during melting. The fluid inside pores smaller than 5 nm (i.e., gel pores) has a relatively small contribution in the macroscopic freeze-thaw behavior of mortar specimens within the temperature range used in this study (i.e., +24 °C to -35 °C), and can therefore be neglected for the macroscopic freeze-thaw simulations. A heat sink term is utilized to simulate the heat dissipation during phase transformations. Data from experiments performed using a low-temperature longitudinal guarded comparative calorimeter (LGCC) on mortar specimens fully saturated with various concentration NaCl solutions or partially saturated with water is compared to the numerical results and a promising agreement is generally obtained.

A mini drivepoint sampler for measuring pore water solute concentrations in the hyporheic zone of sand-bottom streams

USGS Publications Warehouse

Duff, J.H.; Murphy, F.; Fuller, C.C.; Triska, F.J.

1998-01-01

A new method for collecting pore-water samples in sand and gravel streambeds is presented. We developed a mini drivepoint solution sampling (MINIPOINT) technique to collect pore-water samples at 2.5-cm vertical resolution. The sampler consisted of six small-diameter stainless steel drivepoints arranged in a 10-cm-diameter circular array. In a simple procedure, the sampler was installed in the streambed to preset drivepoint depths of 2.5, 5.0, 7.5, 10.0, 12.5, and 15.0 cm. Sampler performance was evaluated in the Shingobee River, Minnesota, and Pinal Creek, Arizona, by measuring the vertical gradient of chloride concentration in pore water beneath the streambed that was established by the uninterrupted injection to the stream for 3 d. Pore-water samples were withdrawn from all drivepoints simultaneously. In the first evaluation, the vertical chloride gradient was unchanged at withdrawal rates between 0.3 and 4.0 ml min-1 but was disturbed at higher rates. In the second evaluation, up to 70 ml of pore water was withdrawn from each drivepoint at a withdrawal rate of 2.5 ml min-1 without disturbing the vertical chloride gradient. Background concentrations of other solutes were also determined with MINIPOINT sampling. Steep vertical gradients were present for biologically reactive solutes such as DO, NH4/+, NO3/-, and dissolved organic C in the top 20 cm of the streambed. These detailed solute profiles in the hyporheic zone could not have been determined without a method for close interval vertical sampling that does not disturb natural hydrologic mixing between stream water and groundwater.

Solute location in a nanoconfined liquid depends on charge distribution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harvey, Jacob A.; Thompson, Ward H., E-mail: wthompson@ku.edu

2015-07-28

Nanostructured materials that can confine liquids have attracted increasing attention for their diverse properties and potential applications. Yet, significant gaps remain in our fundamental understanding of such nanoconfined liquids. Using replica exchange molecular dynamics simulations of a nanoscale, hydroxyl-terminated silica pore system, we determine how the locations explored by a coumarin 153 (C153) solute in ethanol depend on its charge distribution, which can be changed through a charge transfer electronic excitation. The solute position change is driven by the internal energy, which favors C153 at the pore surface compared to the pore interior, but less so for the more polar,more » excited-state molecule. This is attributed to more favorable non-specific solvation of the large dipole moment excited-state C153 by ethanol at the expense of hydrogen-bonding with the pore. It is shown that a change in molecule location resulting from shifts in the charge distribution is a general result, though how the solute position changes will depend upon the specific system. This has important implications for interpreting measurements and designing applications of mesoporous materials.« less

Native, acidic pre-treated and composite clay efficiency for the adsorption of dicationic dye in aqueous medium.

PubMed

Ehsan, Asma; Bhatti, Haq Nawaz; Iqbal, Munawar; Noreen, Saima

2017-02-01

Environmental applications of composites have attracted the interests of researchers due to their excellent adsorption efficiency for pollutants. Native, HCl pre-treated clay and MnFe 2 O 4 /clay composite were investigated as an adsorbent for removal of methyl green from aqueous solution. The adsorption behaviors of dye onto native, HCl pre-treated and composite clays were studied as a function of contact time, adsorbent dose, pH, initial dye concentration and temperature. Maximum dye adsorption of 44 mg/g was achieved at pH of 8, contact time 40 min, adsorbent dose 0.20 g/L and initial dye concentration of 125 mg/L using clay composite. The Langmuir isotherm and pseudo-second-order kinetic model best explained the methyl green dye adsorption onto clay adsorbents. Thermodynamic parameters revealed the endothermic and spontaneous adsorption nature of dye. From results, it is concluded that clay has potential for adsorbing methyl green and can be used for the removal of dyes from industrial effluents.

Chemical models for martian weathering profiles: Insights into formation of layered phyllosilicate and sulfate deposits

NASA Astrophysics Data System (ADS)

Zolotov, Mikhail Yu.; Mironenko, Mikhail V.

2016-09-01

Numerical chemical models for water-basalt interaction have been used to constrain the formation of stratified mineralogical sequences of Noachian clay-bearing rocks exposed in the Mawrth Vallis region and in other places on cratered martian highlands. The numerical approaches are based on calculations of water-rock type chemical equilibria and models which include rates of mineral dissolution. Results show that the observed clay-bearing sequences could have formed through downward percolation and neutralization of acidic H2SO4-HCl solutions. A formation of weathering profiles by slightly acidic fluids equilibrated with current atmospheric CO2 requires large volumes of water and is inconsistent with observations. Weathering by solutions equilibrated with putative dense CO2 atmospheres leads to consumption of CO2 to abundant carbonates which are not observed in clay stratigraphies. Weathering by H2SO4-HCl solutions leads to formation of amorphous silica, Al-rich clays, ferric oxides/oxyhydroxides, and minor titanium oxide and alunite at the top of weathering profiles. Mg-Fe phyllosilicates, Ca sulfates, zeolites, and minor carbonates precipitate from neutral and alkaline solutions at depth. Acidic weathering causes leaching of Na, Mg, and Ca from upper layers and accumulation of Mg-Na-Ca sulfate-chloride solutions at depth. Neutral MgSO4 type solutions dominate in middle parts of weathering profiles and could occur in deeper layers owing to incomplete alteration of Ca minerals and a limited trapping of Ca to sulfates. Although salts are not abundant in the Noachian geological formations, the results suggest the formation of Noachian salty solutions and their accumulation at depth. A partial freezing and migration of alteration solutions could have separated sulfate-rich compositions from low-temperature chloride brines and contributed to the observed diversity of salt deposits. A Hesperian remobilization and release of subsurface MgSO4 type solutions into newly-formed depressions could account for formation of some massive layered sulfate deposits through freezing or evaporation. This scenario explains the observed deficiency of salts in Noachian formations, a paucity of Hesperian phyllosilicates, and the occurrence of sulfate deposits in Valles Marineris troughs, chaotic terrains, and some craters of the Hesperian age.

Compaction and Permeability Reduction of Castlegate Sandstone under Pore Pressure Cycling

NASA Astrophysics Data System (ADS)

Bauer, S. J.

2014-12-01

We investigate time-dependent compaction and permeability changes by cycling pore pressure with application to compressed air energy storage (CAES) in a reservoir. Preliminary experiments capture the impacts of hydrostatic stress, pore water pressure, pore pressure cycling, chemical, and time-dependent considerations near a borehole in a CAES reservoir analog. CAES involves creating an air bubble in a reservoir. The high pressure bubble serves as a mechanical battery to store potential energy. When there is excess grid energy, bubble pressure is increased by air compression, and when there is energy needed on the grid, stored air pressure is released through turbines to generate electricity. The analog conditions considered are depth ~1 km, overburden stress ~20 MPa and a pore pressure ~10MPa. Pore pressure is cycled daily or more frequently between ~10 MPa and 6 MPa, consistent with operations of a CAES facility at this depth and may continue for operational lifetime (25 years). The rock can vary from initially fully-to-partially saturated. Pore pressure cycling changes the effective stress.Jacketed, room temperature tap water-saturated samples of Castlegate Sandstone are hydrostatically confined (20 MPa) and subjected to a pore pressure resulting in an effective pressure of ~10 MPa. Pore pressure is cycled between 6 to 10 MPa. Sample displacement measurements yielded determinations of volumetric strain and from water flow measurements permeability was determined. Experiments ran for two to four weeks, with 2 to 3 pore pressure cycles per day. The Castlegate is a fluvial high porosity (>20%) primarily quartz sandstone, loosely calcite cemented, containing a small amount of clay.Pore pressure cycling induces compaction (~.1%) and permeability decreases (~20%). The results imply that time-dependent compactive processes are operative. The load path, of increasing and decreasing pore pressure, may facilitate local loosening and grain readjustments that results in the compaction and permeability decreases observed. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Dept. of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.SAND2014-16586A

DOE Office of Scientific and Technical Information (OSTI.GOV)

Viani, Alberto, E-mail: viani@itam.cas.cz; Sotiriadis, Konstantinos; Len, Adél

Full characterization of fired-clay bricks is crucial for the improvement of process variables in manufacturing and, in case of old bricks, for restoration/replacement purposes. To this aim, five bricks produced in a plant in Czech Republic in the past have been investigated with a combination of analytical techniques in order to derive information on the firing process. An additional old brick from another brickyard was also used to study the influence of different raw materials on sample microstructure. The potential of X-ray diffraction with the Rietveld method and small angle neutron scattering technique has been exploited to describe the phasemore » transformations taking place during firing and characterize the brick microstructure. Unit-cell parameter of spinel and amount of hematite are proposed as indicators of the maximum firing temperature, although for the latter, limited to bricks produced from the same raw material. The fractal quality of the surface area of pores obtained from small angle neutron scattering is also suggested as a method to distinguish between bricks produced from different raw clays. - Highlights: • Rietveld method helps in describing microstructure and physical properties of bricks. • XRPD derived cell parameter of spinel is proposed as an indicator of firing temperature. • SANS effectively describes brick micro and nanostructure, including closed porosity. • Fractal quality of pore surface is proposed as ‘fingerprint’ of brick manufacturing.« less

Spatio-Temporal Self-Organization in Mudstones (Invited)

NASA Astrophysics Data System (ADS)

Dewers, T. A.

2010-12-01

Shales and other mudstones are the most abundant rock types in sedimentary basins, yet have received comparatively little attention. Common as hydrocarbon seals, these are increasingly being targeted as unconventional gas reservoirs, caprocks for CO2 sequestration, and storage repositories for waste. The small pore and grain size, large specific surface areas, and clay mineral structures lend themselves to rapid reaction rates, high capillary pressures, and semi-permeable membrane behavior accompanying changes in stress, pressure, temperature and chemical conditions. Under far from equilibrium conditions, mudrocks display a variety of spatio-temporal self-organized phenomena arising from nonlinear thermo-mechano-chemo-hydro coupling. Beginning with a detailed examination of nano-scale pore network structures in mudstones, we discuss the dynamics behind such self-organized phenomena as pressure solitons in unconsolidated muds, chemically-induced flow self focusing and permeability transients, localized compaction, time dependent well-bore failure, and oscillatory osmotic fluxes as they occur in clay-bearing sediments. Examples are draw from experiments, numerical simulation, and the field. These phenomena bear on the ability of these rocks to serve as containment barriers. This work is funded by the US Department of Energy, Office of Basic Energy Sciences. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000

Preliminary investigation of the elemental variation and diagenesis of a tabular uranium deposit, La Sal Mine, San Juan County, Utah

USGS Publications Warehouse

Brooks, Robert A.; Campbell, John A.

1976-01-01

Ore in the La Sal mine, San Juan County, Utah, occurs as a typical tabular-type uranium deposit of the-Colorado Plateau. Uranium-vanadium occurs in the Salt Wash Member of the Jurassic Morrison Formation. Chemical and petrographic analyses were used to determine elemental variation and diagenetic aspects across the orebody. Vanadium is concentrated in the dark clay matrix, which constitutes visible ore. Uranium content is greater above the vanadium zone. Calcium, carbonate carbon, and lead show greater than fifty-fold increase across the ore zone, whereas copper and organic carbon show only a several-fold increase. Large molybdenum concentrations are present in and above the tabular layer, and large selenium concentrations occur below the uranium zone within the richest vanadium zone. Iron is enriched in the vanadium horizon. Chromium is depleted from above the ore and strongly enriched below. Elements that vary directly with the vanadium content include magnesium, iron, selenium, zirconium, strontium, titanium, lead, boron, yttrium, and scandium. The diagenetic sequence is as follows: (1) formation of secondary quartz overgrowths as cement; (2) infilling and lining of remaining pores with amber opaline material; (3) formation of vanadium-rich clay matrix, which has replaced overgrowths as well as quartz grains; (4) replacement of overgrowths and detrital grains by calcite; (5) infilling of pores with barite and the introduction of pyrite and marcasite.

Pathways of fluid transport and reabsorption across the peritoneal membrane.

PubMed

Asghar, R B; Davies, S J

2008-05-01

The three-pore model of peritoneal fluid transport predicts that once the osmotic gradient has dissipated, fluid reabsorption will be due to a combination of small-pore reabsorption driven by the intravascular oncotic pressure, and an underlying disappearance of fluid from the cavity by lymphatic drainage. Our study measured fluid transport by these pathways in the presence and absence of an osmotic gradient. Paired hypertonic and standard glucose-dwell studies were performed using radio-iodinated serum albumin as an intraperitoneal volume marker and changes in intraperitoneal sodium mass to determine small-pore versus transcellular fluid transport. Disappearance of iodinated albumin was considered to indicate lymphatic drainage. Variability in transcellular ultrafiltration was largely explained by the rate of small-solute transport across the membrane. In the absence of an osmotic gradient, fluid reabsorption occurred via the small-pore pathway, the rate being proportional to the small-solute transport characteristics of the membrane. In most cases, fluid removal from the peritoneal cavity by this pathway was faster than by lymphatic drainage. Our study shows that the three-pore model describes the pathways of peritoneal fluid transport well. In the presence of high solute transport, poor transcellular ultrafiltration was due to loss of the osmotic gradient and an enhanced small-pore reabsorption rate after this gradient dissipated.

Mesoporous Silica Gel-Based Mixed Matrix Membranes for Improving Mass Transfer in Forward Osmosis: Effect of Pore Size of Filler.

PubMed

Lee, Jian-Yuan; Wang, Yining; Tang, Chuyang Y; Huo, Fengwei

2015-11-23

The efficiency of forward osmosis (FO) process is generally limited by the internal concentration polarization (ICP) of solutes inside its porous substrate. In this study, mesoporous silica gel (SG) with nominal pore size ranging from 4-30 nm was used as fillers to prepare SG-based mixed matrix substrates. The resulting mixed matrix membranes had significantly reduced structural parameter and enhanced membrane water permeability as a result of the improved surface porosity of the substrates. An optimal filler pore size of ~9 nm was observed. This is in direct contrast to the case of thin film nanocomposite membranes, where microporous nanoparticle fillers are loaded to the membrane rejection layer and are designed in such a way that these fillers are able to retain solutes while allowing water to permeate through them. In the current study, the mesoporous fillers are designed as channels to both water and solute molecules. FO performance was enhanced at increasing filler pore size up to 9 nm due to the lower hydraulic resistance of the fillers. Nevertheless, further increasing filler pore size to 30 nm was accompanied with reduced FO efficiency, which can be attributed to the intrusion of polymer dope into the filler pores.

Mesoporous Silica Gel–Based Mixed Matrix Membranes for Improving Mass Transfer in Forward Osmosis: Effect of Pore Size of Filler

PubMed Central

Lee, Jian-Yuan; Wang, Yining; Tang, Chuyang Y.; Huo, Fengwei

2015-01-01

The efficiency of forward osmosis (FO) process is generally limited by the internal concentration polarization (ICP) of solutes inside its porous substrate. In this study, mesoporous silica gel (SG) with nominal pore size ranging from 4–30 nm was used as fillers to prepare SG-based mixed matrix substrates. The resulting mixed matrix membranes had significantly reduced structural parameter and enhanced membrane water permeability as a result of the improved surface porosity of the substrates. An optimal filler pore size of ~9 nm was observed. This is in direct contrast to the case of thin film nanocomposite membranes, where microporous nanoparticle fillers are loaded to the membrane rejection layer and are designed in such a way that these fillers are able to retain solutes while allowing water to permeate through them. In the current study, the mesoporous fillers are designed as channels to both water and solute molecules. FO performance was enhanced at increasing filler pore size up to 9 nm due to the lower hydraulic resistance of the fillers. Nevertheless, further increasing filler pore size to 30 nm was accompanied with reduced FO efficiency, which can be attributed to the intrusion of polymer dope into the filler pores. PMID:26592565

Depressurization-induced fines migration in hydrate-bearing clayey sands: X-ray CT imaging and quantification

NASA Astrophysics Data System (ADS)

Han, G.; Kwon, T. H.; Lee, J. Y.

2016-12-01

As gas and water flows induced by depressurization of hydrate-bearing sediments exert seepage forces on fines in sediments, such as clay particles, depressurization is reported to accompany the transport of fine particles through sediment pores, i.e., fines migration. Because such fines migration can cause pore clogging, the fines migration is considered as one of the critical phenomena contributing to the transport of fluids among various pore-scale processes associated with depressurization. However, quantification of fines migration during depressurization still remains poorly understood. This study thus investigated fines migration caused by depressurization using X-ray computerized tomography(X-ray CT) imaging. A host sediment was prepared by mixing fine sand with kaolinite clay minerals to achieve 10% mass fraction of fines (less than 75 um). Then, methane hydrate was synthesized in the host clayey sand, and thereafter water was injected to saturate the hydrate-bearing sediment sample. Step-wise depressurization was applied while the produced gas was collected through an outlet fluid port. X-ray CT imaging was conducted on the sediment sample over the courses of the experiment to monitor the sample preparation, hydrate formation, depressurization, and fines migration. Based on the calibration tests, the amount and locations of methane hydrate formed in the sample was estimated, and the gas migration path was also identified. Finally, the spatial distribution of fines after completion of depressurization was first assessed using the obtained X-ray images and then compared with the post-mortem mine-back results.Notably, we found that the middle part of the sample was clogged possibly by fines or by re-formed hydrate, leading to a big pressure difference between the inlet and outlet fluid port of the sample by 3 MPa. Owing to this clogging and the lost in pressure communication, hydrate dissociation first occurred at the bottom half and the hydrate dissociation in the top half part followed later. Our study demonstrates that X-ray CT imaging can be a useful tool to visualize and quantify the fines migration during hydrate depressurization, and our results present an experimental evidence that depressurization can cause pore clogging in sediments containing more than 10% fines fraction.

Effect of heterocyclic based organoclays on the properties of polyimide-clay nanocomposites.

PubMed

Krishnan, P Santhana Gopala; Joshi, Mangala; Bhargava, Prachur; Valiyaveettil, Suresh; He, Chaobin

2005-07-01

Polyimide-clay nanocomposites were prepared from their precursor, namely, polyamic acid, by the solution-casting method. Organomodified montmorillonite (MMT) clay was prepared by treating Na+MMT (Kunipia F) with three different intercalating agents, namely, piperazine dihydrochloride, 1,3-bis(4-piperidinylpropane) dihydrochloride and 4,4'-bipiperidine dihydrochloride at 80 degrees C. Polyamic acid solutions containing various weight percentages of organomodified MMT were prepared by reacting 4,4'-(1,1'-biphenyl-4,4'-diyldioxy)dianiline with bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride in N-methyl-2-pyrrolidinone containing dispersed particles of organomodified MMT at 20 degrees C. Nanocomposite films were prepared from these solutions by solution casting and heated subsequently at a programmed heating rate. These films were transparent and brown in color. The extent of layer separation in nanocomposite films depends upon the chemical structure of the organoclay. These films were characterized by inherent viscosity, FT-IR, DSC, TMA, WAXD, TEM, UV, and TGA. The tensile behavior and surface energy studies were also investigated. The nanocomposite films had superior tensile properties, thermal behavior, and solvent resistance. Among the three organoclays, piperazine dihydrochloride was the best modifier.

Factors affecting plant growth in membrane nutrient delivery

NASA Technical Reports Server (NTRS)

Dreschel, T. W.; Wheeler, R. M.; Sager, J. C.; Knott, W. M.

1990-01-01

The development of the tubular membrane plant growth unit for the delivery of water and nutrients to roots in microgravity has recently focused on measuring the effects of changes in physical variables controlling solution availability to the plants. Significant effects of membrane pore size and the negative pressure used to contain the solution were demonstrated. Generally, wheat grew better in units with a larger pore size but equal negative pressure and in units with the same pore size but less negative pressure. Lettuce also exhibited better plant growth at less negative pressure.

The effect of natural and anthropogenic factors on sorption of copper in chernozem

NASA Astrophysics Data System (ADS)

Bauer, Tatiana; Minkina, Tatiana; Mandzhieva, Saglara; Pinskii, David; Linnik, Vitaly; Sushkova, Svetlana

2016-04-01

The aim of this work was to study the effect of the attendant anions and particle-size distribution on the adsorption of copper by ordinary chernozem. Solutions of HM nitrates, acetates, chlorides, and sulfates were used to study the effect of the chemical composition of added copper salts on the adsorption of copper by an ordinary chernozem. Samples of the soil sieved through a 1-mm sieve in the natural ionic form and soil fraction with different particle size (clay - the particle with size < 1μm and physical clay < 10 μm) were treated with solutions of the corresponding copper salts at a soil : solution ratio of 1:10. The concentrations of the initial copper solutions were 0.02, 0.05, 0.08, 0.1, 0.3, 0.5, and 1.0 mM/L. The range of Cu2+ concentrations in the studied system covers different geochemical situations corresponding to the actual levels of soil contamination with the metal under study. The suspensions were shaken for 1 h, left to stand for 24 h, and then filtered. The contents of the HM in the filtrates were determined by atomic absorption spectrometry (AAS). The contents of the adsorbed copper cations were calculated from the difference between the metal concentrations in the initial and equilibrium solutions. The isotherms of copper adsorption from the metal nitrate, chloride, and sulfate solutions have near linear shapes and, hence, can be satisfactorily described by a Henry or Freundlich equation: Cads = KH •Ceq.(1) Cads = KF •Ceqn,(2) where Cadsis the content of the adsorbed cations, mM/kg soil;Ceq is the concentration of copper in the equilibrium solution, mM/L; KH and KF denote the Henry and Freundlich adsorption coefficients, respectively, kg/L. The isotherm of Cu2+ adsorption by ordinary chernozem from acetate solutions is described by the Langmuir equation: Cads = C∞ÊLC / (1 + ÊLC), (3) where Cadsis the content of the adsorbed cations, mM/kg soil;C∞ is the maximum adsorption of the HM, mM/kg soil; ÊL is the affinity constant, L/mM; C is the concentration of the HM in the equilibrium solution, mM/L. According to the values of KH, the binding strength of the copper cations adsorbed from different salt solutions decreases in the series: Cu(Ac)2(1880,5± 76,2) > CuCl2(1442,8±113,5) > Cu(NO3)2(911,4 ± 31,1) >> CuSO4(165,3 ± 12,9). Thus, copper is most strongly adsorbed from the acetate solution and least strongly from the sulfate solution. The adsorption of copper by clay and physical clay fractions from the ordinary chernozem was of limited character and followed the (3) equation. In the particle-size fractions separated from the soils, the concentrations of copper decreased with the decreasing particle size. The values of ÊL and C∞characterizing the HM adsorption by the chernozem and its particle-size fractions formed the following sequence: clay (80,20±20,29 and 28,45±0,46 > physical clay (58,20±14,54 and 22,15±1,22) > entire soil (38,80±12,33 and 17,58±3,038). This work was supported by the Russian Ministry of Education and Science, project no. 5.885.2014/K, Russian Foundation for Basic Research, projects no. 14-05-00586 À

Deformation mechanisms and resealing of damage zones in experimentally deformed cemented and un-cemented clay-rich geomaterials, at low bulk strain

NASA Astrophysics Data System (ADS)

Desbois, Guillaume; Urai, Janos L.; Schuck, Bernhardt; Hoehne, Nadine; Oelker, Anne; Bésuelle, Pierre; Viggiani, Gioacchino; Schmatz, Joyce; Klaver, Jop

2017-04-01

A microphysics-based understanding of mechanical and fluid flow properties in clay-rich geomaterials is required for extrapolating better constitutive equations beyond the laboratory's time scales, so that predictions over the long term can be made less uncertain. In this contribution, we present microstructural investigations of rocks specimens sheared in triaxial compression at low bulk strain, by using the combination of broad-ion-beam (BIB) milling and scanning electron microscopy (SEM) to infer deformation mechanisms based on microstructures imaged at sub-micron resolution. Two end-member clay-rich geomaterials from European Underground Laboratories (URL) were analysed: (i) the poorly cemented Boom Clay sediment (BC from URL at Mol/Dessel, Belgium; confining pressure [CP] = 0.375 & 1.5 MPa) and (ii) the Callovo-Oxfordian claystone (COx from the URL at Bure, France; CP = 2 & 10 MPa). Although as a first approximation the inelastic bahvior of cemented and uncemented clay-rich geomaterials can be described by similar pressure-dependent hardening plasticity models, deformed samples in this contribution show very contrasting micro-scale behaviour: microstructures reveal brittle-ductile transitional behaviour in BC, whereas deformation in COx is dominantly cataclastic. In Boom Clay, at meso-scale, shear bands exhibit characteristics that are typical of uncemented small-grained clay-rich materials deformed at high shear strains, consisting of anastomosing shears interpreted as Y- and B-shears, which bound the passively deformed microlithons. At micro- down to nano-scale, the strong shape preferential orientation of clay aggregates in the anastomosing shears is interpreted to be responsible of the shear weakness. More over, the reworking of clay aggregates during deformation contributes to the collapsing of porosity in the shear band. Ductile deformation mechanisms represented by grain-rotation, grain-sliding, bending and granular flow mechanisms are strongly involved for the development of the shear band. At the same time, evidence for dilatancy at low confining pressure indicates that deformation involves also brittle deformation. Our observations strongly suggest that the deformation mostly localizes in those regions of the specimen, where the original grain sizes are smaller. In COx, microstructures show evidence for dominantly cataclastic deformation involving intergranular - transgranular - and - intragranular micro fracturing, grain rotation and clay particle bending mechanisms, down to nm- scale. Micro fracturing of the original fabric results in fragments at a range of scales, which are reworked into a clay-rich cataclastic gouge during frictional flow. Intergranular and minor intragranular micro fracturing occur in regions of non localized deformation, whereas transgranular micro fracturing occurs at regions of localized deformation. These processes are accompanied by dilatancy, but also by progressive decrease of porosity and pore size in the gouge with the non-clay particles embedded in reworked clay. The mechanism of this compaction during shearing is interpreted to be a combination of cataclasis of the cemented clay matrix, and shear-induced rearrangement of clay particles around the fragments of non-clay particles.

Evaluation of the predictive capability of coupled thermo-hydro-mechanical models for a heated bentonite/clay system (HE-E) in the Mont Terri Rock Laboratory

DOE PAGES

Garitte, B.; Shao, H.; Wang, X. R.; ...

2017-01-09

Process understanding and parameter identification using numerical methods based on experimental findings are a key aspect of the international cooperative project DECOVALEX. Comparing the predictions from numerical models against experimental results increases confidence in the site selection and site evaluation process for a radioactive waste repository in deep geological formations. In the present phase of the project, DECOVALEX-2015, eight research teams have developed and applied models for simulating an in-situ heater experiment HE-E in the Opalinus Clay in the Mont Terri Rock Laboratory in Switzerland. The modelling task was divided into two study stages, related to prediction and interpretation ofmore » the experiment. A blind prediction of the HE-E experiment was performed based on calibrated parameter values for both the Opalinus Clay, that were based on the modelling of another in-situ experiment (HE-D), and modelling of laboratory column experiments on MX80 granular bentonite and a sand/bentonite mixture .. After publication of the experimental data, additional coupling functions were analysed and considered in the different models. Moreover, parameter values were varied to interpret the measured temperature, relative humidity and pore pressure evolution. The analysis of the predictive and interpretative results reveals the current state of understanding and predictability of coupled THM behaviours associated with geologic nuclear waste disposal in clay formations.« less

Nanoporous clay with carbon sink and pesticide trapping properties

NASA Astrophysics Data System (ADS)

Woignier, T.; Duffours, L.; Colombel, P.; Dieudonné, P.

2015-07-01

A thorough understanding of the mechanisms and factors involved in the dynamics of organic carbon in soils is required to identify and enhance natural sinks for greenhouse gases. Some tropical soils, such as Andosols, have 3-6 fold higher concentrations of organic carbon than other kinds of soils containing classical clays. In the tropics, toxic pesticides permanently pollute soils and contaminate crops, water resources, and ecosystems. However, not all soils are equal in terms of pesticide contamination or in their ability to transfer pollution to the ecosystem. Andosols are generally more polluted than the other kinds of soils but, surprisingly, they retain and trap more pesticides, thereby reducing the transfer of pesticides to ecosystems, water resources, and crops. Andosols thus have interesting environmental properties in terms of soil carbon sequestration and pesticide retention. Andosols contain a nano porous clay (allophane) with unique structures and physical properties compared to more common clays; these are large pore volume, specific surface area, and a tortuous and fractal porous arrangement. The purpose of this mini review is to discuss the importance of the allophane fractal microstructure for carbon sequestration and pesticide trapping in the soil. We suggest that the tortuous microstructure (which resembles a labyrinths) of allophane aggregates and the associated low accessibility partly explain the poor availability of soil organic matter and of any pesticides trapped in andosols.

Evaluation of the predictive capability of coupled thermo-hydro-mechanical models for a heated bentonite/clay system (HE-E) in the Mont Terri Rock Laboratory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garitte, B.; Shao, H.; Wang, X. R.

Process understanding and parameter identification using numerical methods based on experimental findings are a key aspect of the international cooperative project DECOVALEX. Comparing the predictions from numerical models against experimental results increases confidence in the site selection and site evaluation process for a radioactive waste repository in deep geological formations. In the present phase of the project, DECOVALEX-2015, eight research teams have developed and applied models for simulating an in-situ heater experiment HE-E in the Opalinus Clay in the Mont Terri Rock Laboratory in Switzerland. The modelling task was divided into two study stages, related to prediction and interpretation ofmore » the experiment. A blind prediction of the HE-E experiment was performed based on calibrated parameter values for both the Opalinus Clay, that were based on the modelling of another in-situ experiment (HE-D), and modelling of laboratory column experiments on MX80 granular bentonite and a sand/bentonite mixture .. After publication of the experimental data, additional coupling functions were analysed and considered in the different models. Moreover, parameter values were varied to interpret the measured temperature, relative humidity and pore pressure evolution. The analysis of the predictive and interpretative results reveals the current state of understanding and predictability of coupled THM behaviours associated with geologic nuclear waste disposal in clay formations.« less

In situ clay formation : evaluation of a proposed new technology for stable containment barriers.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nagy, Kathryn L.; DiGiovanni, Anthony Albert; Fredrich, Joanne T.

2004-03-01

Containment of chemical wastes in near-surface and repository environments is accomplished by designing engineered barriers to fluid flow. Containment barrier technologies such as clay liners, soil/bentonite slurry walls, soil/plastic walls, artificially grouted sediments and soils, and colloidal gelling materials are intended to stop fluid transport and prevent plume migration. However, despite their effectiveness in the short-term, all of these barriers exhibit geochemical or geomechanical instability over the long-term resulting in degradation of the barrier and its ability to contain waste. No technologically practical or economically affordable technologies or methods exist at present for accomplishing total remediation, contaminant removal, or destruction-degradationmore » in situ. A new type of containment barrier with a potentially broad range of environmental stability and longevity could result in significant cost-savings. This report documents a research program designed to establish the viability of a proposed new type of containment barrier derived from in situ precipitation of clays in the pore space of contaminated soils or sediments. The concept builds upon technologies that exist for colloidal or gel stabilization. Clays have the advantages of being geologically compatible with the near-surface environment and naturally sorptive for a range of contaminants, and further, the precipitation of clays could result in reduced permeability and hydraulic conductivity, and increased mechanical stability through cementation of soil particles. While limited success was achieved under certain controlled laboratory conditions, the results did not warrant continuation to the field stage for multiple reasons, and the research program was thus concluded with Phase 2.« less

Restore the change process of Longmaxi shale pore structure during the diagenesis by the potassium and the magnesium

NASA Astrophysics Data System (ADS)

Zhou, W.

2016-12-01

The pore structure of Longmaxi shale was changing during the diagenetic process, mainly caused by the illitization and serpentinzation. The evolution of shale pore structure mainly relates to the element migration. Based on the result of electron microprobe analyser (EMPA), it is possible to find the distribution of element in shale directly and to distinguish the destroyed primary pore structure as element will remain in the migration way. The migration of potassium in Longmaxi shale mainly happened during early diagenesis phase to middle diagenesis phase (Geothermal temperature: 60°-140°). During the illitization, potassium mainly came from potassium feldspar, migrated though the connected pore structure and reacted with smectite. Illite and illite/smectite in Longmaxi shale distribute continuously in 10micron-level flocculent formation, which means that primary connective pore structure in Longmaxi shale has a same scale. The concentration of potassium has an obvious gradient that potassium content in middle of flocculation of Illite/smectite is about 6.8% and 4.8% in the boundary parts (Fig.). In addition, as SiO2 was generated during the illitization, which makes Longmaxi shale very compacted. The migration of magnesium in Longmaxi shale happened during low temperature serpentinization (Geothermal temperature: 140°-350°). Magnesium mainly came from dolomite and migrated in primary pores. According to the result of EMPA, it can be recognized that the migration path of magnesium is much simpler than potassium, which is caused as serpentinization do not have much reaction with clay minerals around (Fig.). Serpentine jams the primary pores of Longmaxi shale too. As reaction temperature of serpentinization is higher than illitization and serpentine is inserts in illite/smectite, the formation process of Longmaxi shale pore structure can be mainly divided into two phases: geothermal temperature˜140° and˜140°.

Pore-scale investigation on the response of heterotrophic respiration to moisture conditions in heterogeneous soils

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Zhifeng; Liu, Chongxuan; Todd-Brown, Katherine E.

The relationship between microbial respiration rate and soil moisture content is an important property for understanding and predicting soil organic carbon degradation, CO 2 production and emission, and their subsequent effects on climate change. This paper reports a pore-scale modeling study to investigate the response of heterotrophic respiration to moisture conditions in soils and to evaluate various factors that affect this response. X-ray computed tomography was used to derive soil pore structures, which were then used for pore-scale model investigation. The pore-scale results were then averaged to calculate the effective respiration rates as a function of water content in soils.more » The calculated effective respiration rate first increases and then decreases with increasing soil water content, showing a maximum respiration rate at water saturation degree of 0.75 that is consistent with field and laboratory observations. The relationship between the respiration rate and moisture content is affected by various factors, including pore-scale organic carbon bioavailability, the rate of oxygen delivery, soil pore structure and physical heterogeneity, soil clay content, and microbial drought resistivity. Simulations also illustrates that a larger fraction of CO 2 produced from microbial respiration can be accumulated inside soil cores under higher saturation conditions, implying that CO 2 flux measured on the top of soil cores may underestimate or overestimate true soil respiration rates under dynamic moisture conditions. Overall, this study provides mechanistic insights into the soil respiration response to the change in moisture conditions, and reveals a complex relationship between heterotrophic microbial respiration rate and moisture content in soils that is affected by various hydrological, geochemical, and biophysical factors.« less

Investigating Hydrophilic Pores in Model Lipid Bilayers Using Molecular Simulations: Correlating Bilayer Properties with Pore-Formation Thermodynamics.

PubMed

Hu, Yuan; Sinha, Sudipta Kumar; Patel, Sandeep

2015-06-23

Cell-penetrating and antimicrobial peptides show a remarkable ability to translocate across physiological membranes. Along with factors such as electric-potential-induced perturbations of membrane structure and surface tension effects, experiments invoke porelike membrane configurations during the solute transfer process into vesicles and cells. The initiation and formation of pores are associated with a nontrivial free-energy cost, thus necessitating a consideration of the factors associated with pore formation and the attendant free energies. Because of experimental and modeling challenges related to the long time scales of the translocation process, we use umbrella sampling molecular dynamics simulations with a lipid-density-based order parameter to investigate membrane-pore-formation free energy employing Martini coarse-grained models. We investigate structure and thermodynamic features of the pore in 18 lipids spanning a range of headgroups, charge states, acyl chain lengths, and saturation. We probe the dependence of pore-formation barriers on the area per lipid, lipid bilayer thickness, and membrane bending rigidities in three different lipid classes. The pore-formation free energy in pure bilayers and peptide translocating scenarios are significantly coupled with bilayer thickness. Thicker bilayers require more reversible work to create pores. The pore-formation free energy is higher in peptide-lipid systems than in peptide-free lipid systems due to penalties to maintain the solvation of charged hydrophilic solutes within the membrane environment.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yanping Guo; Abhishek Yadav; Tanju Karanfil

Adsorption of trichloroethylene (TCE) and atrazine, two synthetic organic contaminants (SOCs) having different optimum adsorption pore regions, by four activated carbons and an activated carbon fiber (ACF) was examined. Adsorbents included two coconut-shell based granular activated carbons (GACs), two coal-based GACs (F400 and HD4000) and a phenol formaldehyde-based activated carbon fiber. The selected adsorbents had a wide range of pore size distributions but similar surface acidity and hydrophobicity. Single solute and preloading (with a dissolved organic matter (DOM)) isotherms were performed. Single solute adsorption results showed that (i) the adsorbents having higher amounts of pores with sizes about the dimensionsmore » of the adsorbate molecules exhibited higher uptakes, (ii) there were some pore structure characteristics, which were not completely captured by pore size distribution analysis, that also affected the adsorption, and (iii) the BET surface area and total pore volume were not the primary factors controlling the adsorption of SOCs. The preloading isotherm results showed that for TCE adsorbing primarily in pores <10 {angstrom}, the highly microporous ACF and GACs, acting like molecular sieves, exhibited the highest uptakes. For atrazine with an optimum adsorption pore region of 10-20 {angstrom}, which overlaps with the adsorption region of some DOM components, the GACs with a broad pore size distribution and high pore volumes in the 10-20 {angstrom} region had the least impact of DOM on the adsorption. 25 refs., 3 figs., 3 tabs.« less

In Situ Clay Formation: Evaluation of a Proposed New Technology for Stable Containment Barriers

DTIC Science & Technology

2004-03-01

situ layered double hydroxide precipitation........... 23 4.2.1 Solution preparation and column mixing...22 Table 4.2 Summary of in situ precipitation of layered double hydroxide (LDH...effect on permeability for the smallest volume precipitated is sheet silicates or layered -clay phases (hereafter called “clays”). In natural

Preparation of alpha-alumina-supported mesoporous bentonite membranes for reverse osmosis desalination of aqueous solutions.

PubMed

Li, Liangxiong; Dong, Junhang; Lee, Robert

2004-05-15

In this study, mesoporous bentonite clay membranes approximately 2 microm thick were prepared on porous alpha-alumina substrates by a sol-gel method. Nanosized clay particles were obtained from commercial Na-bentonite powders (Wyoming) by a process of sedimentation, washing, and freeze-drying. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption-desorption were employed for membrane characterization. It was found that the content of solids, concentration of polymer binder, and pH value of the clay colloidal suspension had critical influences on membrane formation during the dip-coating process. The membranes were tested for reverse osmosis separation of a 0.1 M NaCl solution. Both water permeability and Na(+) rejection rate of the supported membranes were comparable to those of the compacted thick membranes reported in the literature. However, due to the drastically reduced membrane thickness, water permeance and flux of the supported membranes were significantly higher than those of the compacted thick membranes. It was also observed that the calcination temperature played a critical role in determining structural stability in water and desalination performance of the clay membrane.

Clay-mineral assemblages from some levels of K-118 drill core of Maha Sarakham evaporites, northeastern Thailand

NASA Astrophysics Data System (ADS)

Suwanich, Parkorn

Clay-mineral assemblages in Middle Clastic, Middle Salt, Lower Clastic, Potash Zone, and Lower Salt, totalling 13 samples from K-118 drill core, in the Maha Sarakham Formation, Khorat Basin, northeastern Thailand were studied. The clay-size particles were separated from the water-soluble salt by water leaching. Then the samples were leached again in the EDTA solution and separated into clay-size particles by using the timing sedimentation. The EDTA-clay residues were divided and analyzed by using the XRD and XRF method. The XRD peaks show that the major-clay minerals are chlorite, illite, and mixed-layer corrensite including traces of rectorite? and paragonite? The other clay-size particles are quartz and potassium feldspar. The XRF results indicate Mg-rich values and moderate MgAl atom ratio values in those clay minerals. The variable Fe, Na, and K contents in the clay-mineral assemblages can explain the environment of deposition compared to the positions of the samples from the core. Hypothetically, mineralogy and the chemistry of the residual assemblages strongly indicate that severe alteration and Mg-enrichment of normal clay detritus occurred in the evaporite environment through brine-sediment interaction. The various Mg-enrichment varies along the various members reflecting whether sedimentation is near or far from the hypersaline brine.

Improved Yield of High Molecular Weight DNA Coincides with Increased Microbial Diversity Access from Iron Oxide Cemented Sub-Surface Clay Environments

DOE PAGES

Hurt, Jr., Richard A.; Robeson II, Michael S.; Shakya, Migun; ...

2014-07-14

Despite more than three decades of progress, efficient nucleic acid extraction from microbial communities has remained difficult, particularly from clay environments. Lysis with concentrated guanidine followed by concentrated sodium phosphate extraction supported DNA and RNA recovery from high iron, low humus content clay. Alterating the extraction pH or using other ionic solutions (Na 2SO 4 and NH 4H 2PO 4) yielded no detectable nucleic acid. DNA recovered using a lysis solution with 500 mM phosphate buffer (PB) followed by a 1 M PB wash was 15.22±2.33 g DNA/g clay, with most DNA consisting of >20 Kb fragments, compared to 2.46±0.25more » g DNA/g clay with the Powerlyzer soil DNA system (MoBio). Increasing [PB] in the lysis reagent coincided with increasing DNA fragment length. Rarefaction plots based on16S rRNA (V1/V3 region) pyrosequencing libraries from A-horizon and clay soils showed an ~80% and ~400% larger accessed diversity compared to a previous grinding protocol or the Powerlyzer soil DNA system, respectively. The observed diversity from the Firmicutes showed the strongest increase with >3-fold more bacterial species recovered using this system. Additionally, some OTU's having more than 100 sequences in these libraries were absent in samples extracted using the PowerLyzer reagents or the previous lysis method.« less

Improved Yield of High Molecular Weight DNA Coincides with Increased Microbial Diversity Access from Iron Oxide Cemented Sub-Surface Clay Environments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hurt, Jr., Richard A.; Robeson II, Michael S.; Shakya, Migun

Despite more than three decades of progress, efficient nucleic acid extraction from microbial communities has remained difficult, particularly from clay environments. Lysis with concentrated guanidine followed by concentrated sodium phosphate extraction supported DNA and RNA recovery from high iron, low humus content clay. Alterating the extraction pH or using other ionic solutions (Na 2SO 4 and NH 4H 2PO 4) yielded no detectable nucleic acid. DNA recovered using a lysis solution with 500 mM phosphate buffer (PB) followed by a 1 M PB wash was 15.22±2.33 g DNA/g clay, with most DNA consisting of >20 Kb fragments, compared to 2.46±0.25more » g DNA/g clay with the Powerlyzer soil DNA system (MoBio). Increasing [PB] in the lysis reagent coincided with increasing DNA fragment length. Rarefaction plots based on16S rRNA (V1/V3 region) pyrosequencing libraries from A-horizon and clay soils showed an ~80% and ~400% larger accessed diversity compared to a previous grinding protocol or the Powerlyzer soil DNA system, respectively. The observed diversity from the Firmicutes showed the strongest increase with >3-fold more bacterial species recovered using this system. Additionally, some OTU's having more than 100 sequences in these libraries were absent in samples extracted using the PowerLyzer reagents or the previous lysis method.« less

Investigating the behaviour of Mg isotopes during the formation of clay minerals

NASA Astrophysics Data System (ADS)

Wimpenny, Joshua; Colla, Christopher A.; Yin, Qing-Zhu; Rustad, James R.; Casey, William H.

2014-03-01

We present elemental and isotopic data detailing how the Mg isotope system behaves in natural and experimentally synthesized clay minerals. We show that the bulk Mg isotopic composition (δ26Mg) of a set of natural illite, montmorillonite and kaolinite spans a 2‰ range, and that their isotopic composition depends strongly on a balance between the relative proportions of structural and exchangeable Mg. After acid leaching, these natural clays become relatively enriched in isotopically heavy Mg by between 0.2‰ and 1.6‰. Results of exchange experiments indicate that the Mg that has adsorbed to interlayer spaces and surface charged sites is relatively enriched in isotopically light Mg compared to the residual clay. The isotopic composition of this exchangeable Mg (-1.49‰ to -2.03‰) is characteristic of the isotopic composition of Mg found in many natural waters. Further experiments with an isotopically characterized MgCl2 solution shows that the clay minerals adsorb this exchangeable Mg with little or no isotopic fractionation, although we cannot discount the possibility that the uptake of exchangeable Mg does so with a slight preference for 24Mg. To characterize the behaviour of Mg isotopes during clay mineral formation we synthesized brucite (Mg(OH)2), which we consider to be a good analogue for the incorporation of Mg into the octahedral sheet of Mg-rich clay minerals or into the brucitic layer of clays such as chlorite. In our experiment the brucite mineral becomes enriched in the heavy isotopes of Mg while the corresponding solution is always relatively enriched in isotopically light Mg. The system reaches a steady state after 10 days with a final fractionation factor (αsolid-solution) of 1.0005 at near-neutral pH. This result is consistent with the general consensus that secondary clay minerals preferentially take up isotopically heavy Mg during their formation. However our results also show that exchangeable Mg is an important component within bulk clay minerals and can have an important influence over the bulk clay δ26Mg value. Modeling shows that in certain soils or sediments where the percentage of exchangeable Mg is >30% and the isotopic composition of the exchangeable Mg is around -2‰, the generation of bulk δ26Mg values of <-0.5‰ is likely. On a broader scale, Mg-rich minerals such as smectite and illite are likely to impart a stronger control over the Mg budget in clay rich sediments, and their high structural Mg component is likely to result in bulk sediment δ26Mg values that are closer in composition to the UCC. Despite this, results of modeling, together with experimental observation suggests that the uptake of exchangeable Mg into these clay rich sediments could cause a decrease in the bulk δ26Mg value by up to ˜0.3-0.4‰. This should be accounted for when assessing the δ26Mg value of sediments on a crustal scale.

Reducement of cadmium adsorption on clay minerals by the presence of dissolved organic matter from animal manure.

PubMed

Zhou, Wenjun; Ren, Lingwei; Zhu, Lizhong

2017-04-01

Clay minerals are the most popular adsorbents/amendments for immobilizing heavy metals in contaminated soils, but the dissolved organic matter (DOM) in soil environment would potentially affect the adsorption/immobilization capacity of clay minerals for heavy metals. In this study, the effects of DOM derived from chicken manure (CM) on the adsorption of cadmium (Cd 2+ ) on two clay minerals, bentonite and zeolite, were investigated. The equilibrium data for Cd 2+ sorption in the absence or presence of CM-DOM could be well-fitted to the Langmuir equation (R 2  > 0.97). The presence of CM-DOM in the aqueous solution was found to greatly reduce the adsorption capacity of both minerals for Cd 2+ , in particular zeolite, and the percentage decreases for Cd 2+ sorption increased with increasing concentrations of Cd 2+ as well as CM-DOM in aqueous solutions. The adsorption of CM-DOM on zeolite was greater than that on bentonite in the absence of Cd 2+ , however, a sharp increase was observed for CM-DOM sorption on bentonite with increasing Cd 2+ concentrations but little change for that on zeolite, which can be attributed to the different ternary structures on mineral surface. The CM-DOM modified clay minerals were utilized to investigate the effect of mineral-adsorbed CM-DOM on Cd 2+ sorption. The adsorbed form was found to inhibit Cd 2+ sorption, and further calculation suggested it primarily responsible for the overall decrease in Cd 2+ sorption on clay minerals in the presence of CM-DOM in aqueous solutions. An investigation for the mineral surface morphology suggested that the mineral-adsorbed CM-DOM decreased Cd 2+ sorption on bentonite mainly through barrier effect, while in the case of zeolite, it was the combination of active sites occupation and barrier effect. These results can serve as a guide for evaluating the performance of clay minerals in immobilizing heavy metals when animal manure is present in contaminated soils. Copyright © 2017 Elsevier Ltd. All rights reserved.

Adsorption of polypropylene from dilute solutions on a zeolite column packing.

PubMed

Macko, Tibor; Pasch, Harald; Denayer, Joeri F

2005-01-01

Faujasite type zeolite CBV-780 was tested as adsorbent for isotactic polypropylene by liquid chromatography. When cyclohexane, cyclohexanol, n-decanol, n-dodecanol, diphenylmethane, or methylcyclohexane was used as mobile phase, polypropylene was fully or partially retained within the column packing. This is the first series of sorbent-solvent systems to show a pronounced retention of isotactic polypropylene. According to the hydrodynamic volumes of polypropylene in solution, macromolecules of polypropylene should be fully excluded from the pore volume of the sorbent. Sizes of polypropylene macromolecules in linear conformations, however, correlate with the pore size of the column packing used. It is presumed that the polypropylene chains partially penetrate into the pores and are retained due to the high adsorption potential in the narrow pores.

Superficially Porous Particles with 1000 Å Pores for Large Biomolecule High Performance Liquid Chromatography and Polymer Size Exclusion Chromatography

PubMed Central

Wagner, Brian M.; Schuster, Stephanie A.; Boyes, Barry E.; Shields, Taylor J.; Miles, William L.; Haynes, Mark J.; Moran, Robert E.; Kirkland, Joseph J.; Schure, Mark R.

2017-01-01

To facilitate mass transport and column efficiency, solutes must have free access to particle pores to facilitate interactions with the stationary phase. To ensure this feature, particles should be used for HPLC separations which have pores sufficiently large to accommodate the solute without restricted diffusion. This paper describes the design and properties of superficially porous (also called Fused-Core®, core shell or porous shell) particles with very large (1000 Å) pores specifically developed for separating very large biomolecules and polymers. Separations of DNA fragments, monoclonal antibodies, large proteins and large polystyrene standards are used to illustrate the utility of these particles for efficient, high-resolution applications. PMID:28213987

Superficially porous particles with 1000Å pores for large biomolecule high performance liquid chromatography and polymer size exclusion chromatography.

PubMed

Wagner, Brian M; Schuster, Stephanie A; Boyes, Barry E; Shields, Taylor J; Miles, William L; Haynes, Mark J; Moran, Robert E; Kirkland, Joseph J; Schure, Mark R

2017-03-17

To facilitate mass transport and column efficiency, solutes must have free access to particle pores to facilitate interactions with the stationary phase. To ensure this feature, particles should be used for HPLC separations which have pores sufficiently large to accommodate the solute without restricted diffusion. This paper describes the design and properties of superficially porous (also called Fused-Core ® , core shell or porous shell) particles with very large (1000Å) pores specifically developed for separating very large biomolecules and polymers. Separations of DNA fragments, monoclonal antibodies, large proteins and large polystyrene standards are used to illustrate the utility of these particles for efficient, high-resolution applications. Copyright © 2017 Elsevier B.V. All rights reserved.

Using nuclear magnetic resonance and transient electromagnetics to characterise water distribution beneath an ice covered volcanic crater: the case of Sherman Crater Mt. Baker Washington.

USGS Publications Warehouse

Irons, Trevor P.; Martin, Kathryn; Finn, Carol A.; Bloss, Benjamin; Horton, Robert J.

2014-01-01

Surface and laboratory Nuclear Magnetic Resonance (NMR) measurements combined with transient electromagnetic (TEM) data are powerful tools for subsurface water detection. Surface NMR (sNMR) and TEM soundings, laboratory NMR, complex resistivity, and X-Ray Diffraction (XRD) analysis were all conducted to characterise the distribution of water within Sherman Crater on Mt. Baker, WA. Clay rich rocks, particularly if water saturated, can weaken volcanoes, thereby increasing the potential for catastrophic sector collapses that can lead to far-travelled, destructive debris flows. Detecting the presence and volume of shallow groundwater is critical for evaluating these landslide hazards. The TEM data identified a low resistivity layer (<10 ohm-m), under 60 m of glacial ice related to water saturated clays. The TEM struggles to resolve the presence or absence of a plausible thin layer of bulk liquid water on top of the clay. The sNMR measurements did not produce any observable signal, indicating the lack of substantial accumulated bulk water below the ice. Laboratory analysis on a sample from the crater wall that likely represented the clays beneath the ice confirmed that the controlling factor for the lack of sNMR signal was the fine-grained nature of the media. The laboratory measurements further indicated that small pores in clays detected by the XRD contain as much as 50% water, establishing an upper bound on the water content in the clay layer. Forward modelling of geologic scenarios revealed that bulk water layers as thin as ½ m between the ice and clay layer would have been detectable using sNMR. The instrumentation conditions which would allow for sNMR detection of the clay layer are investigated. Using current instrumentation the combined analysis of the TEM and sNMR data allow for valuable characterisation of the groundwater system in the crater. The sNMR is able to reduce the uncertainty of the TEM in regards to the presence of a bulk water layer, a valuable piece of information in hazard assessment.

Effect of Stepwise Pressure Change on Porosity Evolution during Directional Solidification in Small Cylindrical Channels

NASA Technical Reports Server (NTRS)

Grugel, R.N.; Lee, C.P.; Cox, M.C.; Blandford, B.T.; Anilkumar, A.V.

2008-01-01

Controlled directional solidification experiments were performed in capillary channels, using nitrogen-saturated succinonitrile, to examine the effect of an in-situ stepwise processing pressure increase on an isolated pore evolution. Two experiments were performed using different processing pressure input profiles. The results indicate that a processing pressure increase has a transient effect on pore growth geometry characterized by an initial phase of decreasing pore diameter, followed by a recovery phase of increasing pore diameter. The experimental results also show that processing pressure can be used as a control parameter to either increase or terminate porosity formation. A theoretical model is introduced which indicates that the pore formation process is limited by the diffusion of solute-gas through the melt, and that the observed response toa pressure increase is attributed to the re-equilibration of solute concentration in the melt associated with the increased melt pressure.

Elements of an improved model of debris-flow motion

USGS Publications Warehouse

Iverson, R.M.

2009-01-01

A new depth-averaged model of debris-flow motion describes simultaneous evolution of flow velocity and depth, solid and fluid volume fractions, and pore-fluid pressure. Non-hydrostatic pore-fluid pressure is produced by dilatancy, a state-dependent property that links the depth-averaged shear rate and volumetric strain rate of the granular phase. Pore-pressure changes caused by shearing allow the model to exhibit rate-dependent flow resistance, despite the fact that the basal shear traction involves only rate-independent Coulomb friction. An analytical solution of simplified model equations shows that the onset of downslope motion can be accelerated or retarded by pore-pressure change, contingent on whether dilatancy is positive or negative. A different analytical solution shows that such effects will likely be muted if downslope motion continues long enough, because dilatancy then evolves toward zero, and volume fractions and pore pressure concurrently evolve toward steady states. ?? 2009 American Institute of Physics.

Rapid and high-precision measurement of sulfur isotope and sulfur concentration in sediment pore water by multi-collector inductively coupled plasma mass spectrometry.

PubMed

Bian, Xiao-Peng; Yang, Tao; Lin, An-Jun; Jiang, Shao-Yong

2015-01-01

We have developed a technique for the rapid, precise and accurate determination of sulfur isotopes (δ(34)S) by MC-ICP-MS applicable to a range of sulfur-bearing solutions of different sulfur content. The 10 ppm Alfa-S solution (ammonium sulfate solution, working standard of the lab of the authors) was used to bracket other Alfa-S solutions of different concentrations and the measured δ(34)SV-CDT values of Alfa-S solutions deviate from the reference value to varying degrees (concentration effect). The stability of concentration effect has been verified and a correction curve has been constructed based on Alfa-S solutions to correct measured δ(34)SV-CDT values. The curve has been applied to AS solutions (dissolved ammonium sulfate from the lab of the authors) and pore water samples successfully, validating the reliability of our analytical method. This method also enables us to measure the sulfur concentration simultaneously when analyzing the sulfur isotope composition. There is a strong linear correlation (R(2)>0.999) between the sulfur concentrations and the intensity ratios of samples and the standard. We have constructed a regression curve based on Alfa-S solutions and this curve has been successfully used to determine sulfur concentrations of AS solutions and pore water samples. The analytical technique presented here enable rapid, precise and accurate S isotope measurement for a wide range of sulfur-bearing solutions - in particular for pore water samples with complex matrix and varying sulfur concentrations. Also, simultaneous measurement of sulfur concentrations is available. Copyright © 2014 Elsevier B.V. All rights reserved.

Preparation of Microcrystals of Piroxicam Monohydrate by Antisolvent Precipitation via Microfabricated Metallic Membranes with Ordered Pore Arrays.

PubMed

Othman, Rahimah; Vladisavljević, Goran T; Simone, Elena; Nagy, Zoltan K; Holdich, Richard G

2017-12-06

Microcrystals of piroxicam (PRX) monohydrate with a narrow size distribution were prepared from acetone/PRX solutions by antisolvent crystallization via metallic membranes with ordered pore arrays. Crystallization was achieved by controlled addition of the feed solution through the membrane pores into a well-stirred antisolvent. A complete transformation of an anhydrous form I into a monohydrate form of PRX was confirmed by Raman spectroscopy and differential scanning calorimetry. The size of the crystals was 7-34 μm and was controlled by the PRX concentration in the feed solution (15-25 g L -1 ), antisolvent/solvent volume ratio (5-30), and type of antisolvent (Milli-Q water or 0.1-0.5 wt % aqueous solutions of hydroxypropyl methyl cellulose (HPMC), poly(vinyl alcohol) or Pluronic P-123). The smallest crystals were obtained by injecting 25 g L -1 PRX solution through a stainless-steel membrane with a pore size of 10 μm into a 0.06 wt % HPMC solution stirred at 1500 rpm using an antisolvent/solvent ratio of 20. HPMC provided better steric stabilization of microcrystals against agglomeration than poly(vinyl alcohol) and Pluronic P-123, due to hydrogen bonding interactions with PRX and water. A continuous production of large PRX monohydrate microcrystals with a volume-weighted mean diameter above 75 μm was achieved in a continuous stirred membrane crystallizer. Rapid pouring of Milli-Q water into the feed solution resulted in a mixture of highly polydispersed prism-shaped and needle-shaped crystals.

An Image-based Micro-continuum Pore-scale Model for Gas Transport in Organic-rich Shale

NASA Astrophysics Data System (ADS)

Guo, B.; Tchelepi, H.

2017-12-01

Gas production from unconventional source rocks, such as ultra-tight shales, has increased significantly over the past decade. However, due to the extremely small pores ( 1-100 nm) and the strong material heterogeneity, gas flow in shale is still not well understood and poses challenges for predictive field-scale simulations. In recent years, digital rock analysis has been applied to understand shale gas transport at the pore-scale. An issue with rock images (e.g. FIB-SEM, nano-/micro-CT images) is the so-called "cutoff length", i.e., pores and heterogeneities below the resolution cannot be resolved, which leads to two length scales (resolved features and unresolved sub-resolution features) that are challenging for flow simulations. Here we develop a micro-continuum model, modified from the classic Darcy-Brinkman-Stokes framework, that can naturally couple the resolved pores and the unresolved nano-porous regions. In the resolved pores, gas flow is modeled with Stokes equation. In the unresolved regions where the pore sizes are below the image resolution, we develop an apparent permeability model considering non-Darcy flow at the nanoscale including slip flow, Knudsen diffusion, adsorption/desorption, surface diffusion, and real gas effect. The end result is a micro-continuum pore-scale model that can simulate gas transport in 3D reconstructed shale images. The model has been implemented in the open-source simulation platform OpenFOAM. In this paper, we present case studies to demonstrate the applicability of the model, where we use 3D segmented FIB-SEM and nano-CT shale images that include four material constituents: organic matter, clay, granular mineral, and pore. In addition to the pore structure and the distribution of the material constituents, we populate the model with experimental measurements (e.g. size distribution of the sub-resolution pores from nitrogen adsorption) and parameters from the literature and identify the relative importance of different physics on gas production. Overall, the micro-continuum model provides a novel tool for digital rock analysis of organic-rich shale.

Calibration-free quantification of interior properties of porous media with x-ray computed tomography.

PubMed

Hussein, Esam M A; Agbogun, H M D; Al, Tom A

2015-03-01

A method is presented for interpreting the values of x-ray attenuation coefficients reconstructed in computed tomography of porous media, while overcoming the ambiguity caused by the multichromatic nature of x-rays, dilution by void, and material heterogeneity. The method enables determination of porosity without relying on calibration or image segmentation or thresholding to discriminate pores from solid material. It distinguishes between solution-accessible and inaccessible pores, and provides the spatial and frequency distributions of solid-matrix material in a heterogeneous medium. This is accomplished by matching an image of a sample saturated with a contrast solution with that saturated with a transparent solution. Voxels occupied with solid-material and inaccessible pores are identified by the fact that they maintain the same location and image attributes in both images, with voxels containing inaccessible pores appearing empty in both images. Fully porous and accessible voxels exhibit the maximum contrast, while the rest are porous voxels containing mixtures of pore solutions and solid. This matching process is performed with an image registration computer code, and image processing software that requires only simple subtraction and multiplication (scaling) processes. The process is demonstrated in dolomite (non-uniform void distribution, homogeneous solid matrix) and sandstone (nearly uniform void distribution, heterogeneous solid matrix) samples, and its overall performance is shown to compare favorably with a method based on calibration and thresholding. Copyright © 2014 Elsevier Ltd. All rights reserved.

Cracking of Clay Due to Contact with Waste Chlorinated Solvents

NASA Astrophysics Data System (ADS)

Otero, M.; Ayral, D.; Shipan, J.; Goltz, M. N.; Huang, J.; Demond, A. H.

2012-12-01

Clays are known to crack upon desiccation. Desiccation cracks of up to 3 cm wide have been reported in natural soils. This raises the question if a similar behavior is seen when a dense non-aqueous phase liquids (DNAPL) waste is in contact with clay. The contact with organic liquids causes the clay structure to shrink, leading to the formation of cracks. Moreover, DNAPL waste not only contains the organic liquid solvent but also includes surface-active solutes or surfactants. Such solutes can enhance the interaction of the organic solvents with the clay. This research will assess whether or not contact with chlorinated organic waste causes cracking. In order to evaluate the possibility of cracking in the clay, microcosms have been constructed that mimic aquifer systems, consisting of a saturated layer of sand, a saturated layer of bentonite clay and a 2.5 cm layer of either pure chlorinated solvents or DNAPL waste. The onset of cracking for the microcosm with tetrachloroethylene (PCE) waste as the DNAPL layer occurred after ten days of contact. Similarly, at eight days, cracks were observed in a microcosm containing trichloroethylene (TCE) waste . Forty-four days later, the length and number of cracks have grown considerably; with a total crack length of 50 cm on a surface of 80 cm2 in the microcosm containing PCE waste. On the other hand it took approximately 161 days for the clay layer in the microcosm containing pure PCE to crack. To quantity the degree of cracking, crack maps were developed using the image software, Image J. Characteristics like crack length, crack aperture, and the percentage of total length for a range of apertures were calculated using this software. For example, for the PCE waste microcosm, it was calculated that 3.7% of the crack length had an aperture of 100-300 microns, 15.1% of the crack length had an aperture of 300-500 microns, 29.7% of the crack length had an aperture of 500-700 microns, 40.1% of the crack length had an aperture of 700-900 microns, 6.3% had an aperture of 900-1,100 microns and 5.1% had an aperture of over 1,100 microns. These data suggest that aquitards in the field might crack when in contact with the DNAPL waste. Moreover, it is apparent that the waste contains solutes that accelerate the cracking of the clay layer. Thus, models examining the impact of storage in low permeability layers need to consider the possible impact of cracking.

Accumulation of Colloidal Particles in Flow Junctions Induced by Fluid Flow and Diffusiophoresis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shin, Sangwoo; Ault, Jesse T.; Warren, Patrick B.

The flow of solutions containing solutes and colloidal particles in porous media is widely found in systems including underground aquifers, hydraulic fractures, estuarine or coastal habitats, water filtration systems, etc. In such systems, solute gradients occur when there is a local change in the solute concentration. While the effects of solute gradients have been found to be important for many applications, we observe an unexpected colloidal behavior in porous media driven by the combination of solute gradients and the fluid flow. When two flows with different solute concentrations are in contact near a junction, a sharp solute gradient is formedmore » at the interface, which may allow strong diffusiophoresis of the particles directed against the flow. Consequently, the particles accumulate near the pore entrance, rapidly approaching the packing limit. These colloidal dynamics have important implications for the clogging of a porous medium, where particles that are orders of magnitude smaller than the pore width can accumulate and block the pores within a short period of time. As a result, we also show that this effect can be exploited as a useful tool for preconcentrating biomolecules for rapid bioassays.« less

Accumulation of Colloidal Particles in Flow Junctions Induced by Fluid Flow and Diffusiophoresis

DOE PAGES

Shin, Sangwoo; Ault, Jesse T.; Warren, Patrick B.; ...

2017-11-16

The flow of solutions containing solutes and colloidal particles in porous media is widely found in systems including underground aquifers, hydraulic fractures, estuarine or coastal habitats, water filtration systems, etc. In such systems, solute gradients occur when there is a local change in the solute concentration. While the effects of solute gradients have been found to be important for many applications, we observe an unexpected colloidal behavior in porous media driven by the combination of solute gradients and the fluid flow. When two flows with different solute concentrations are in contact near a junction, a sharp solute gradient is formedmore » at the interface, which may allow strong diffusiophoresis of the particles directed against the flow. Consequently, the particles accumulate near the pore entrance, rapidly approaching the packing limit. These colloidal dynamics have important implications for the clogging of a porous medium, where particles that are orders of magnitude smaller than the pore width can accumulate and block the pores within a short period of time. As a result, we also show that this effect can be exploited as a useful tool for preconcentrating biomolecules for rapid bioassays.« less

Review: Some low-frequency electrical methods for subsurface characterization and monitoring in hydrogeology

NASA Astrophysics Data System (ADS)

Revil, A.; Karaoulis, M.; Johnson, T.; Kemna, A.

2012-06-01

Low-frequency geoelectrical methods include mainly self-potential, resistivity, and induced polarization techniques, which have potential in many environmental and hydrogeological applications. They provide complementary information to each other and to in-situ measurements. The self-potential method is a passive measurement of the electrical response associated with the in-situ generation of electrical current due to the flow of pore water in porous media, a salinity gradient, and/or the concentration of redox-active species. Under some conditions, this method can be used to visualize groundwater flow, to determine permeability, and to detect preferential flow paths. Electrical resistivity is dependent on the water content, the temperature, the salinity of the pore water, and the clay content and mineralogy. Time-lapse resistivity can be used to assess the permeability and dispersivity distributions and to monitor contaminant plumes. Induced polarization characterizes the ability of rocks to reversibly store electrical energy. It can be used to image permeability and to monitor chemistry of the pore water-minerals interface. These geophysical methods, reviewed in this paper, should always be used in concert with additional in-situ measurements (e.g. in-situ pumping tests, chemical measurements of the pore water), for instance through joint inversion schemes, which is an area of fertile on-going research.

Diffusive transport and reaction in clay rocks: A storage (nuclear waste, CO2, H2), energy (shale gas) and water quality issue

NASA Astrophysics Data System (ADS)

Charlet, Laurent; Alt-Epping, Peter; Wersin, Paul; Gilbert, Benjamin

2017-08-01

Clay rocks are low permeability sedimentary formations that provide records of Earth history, influence the quality of water resources, and that are increasingly used for the extraction or storage of energy resources and the sequestration of waste materials. Informed use of clay rock formations to achieve low-carbon or carbon-free energy goals requires the ability to predict the rates of diffusive transport processes for chemically diverse dissolved and gaseous species over periods up to thousands of years. We survey the composition, properties and uses of clay rock and summarize fundamental science challenges in developing confident conceptual and quantitative gas and solute transport models.

Diazonium cation-exchanged clay: an efficient, unfrequented route for making clay/polymer nanocomposites.

PubMed

Salmi, Zakaria; Benzarti, Karim; Chehimi, Mohamed M

2013-11-05

We describe a simple, off-the-beaten-path strategy for making clay/polymer nanocomposites through tandem diazonium salt interface chemistry and radical photopolymerization. Prior to photopolymerization, sodium montmorillonite (MMT) was ion exchanged with N,N'-dimethylbenzenediazonium cation (DMA) from the tetrafluoroborate salt precursor. DMA acts as a hydrogen donor for benzophenone in solution; this pair of co-initiators permits us to photopolymerize glycidyl methacrylate (GMA) between the lamellae of the diazonium-modified clay, therefore providing intercalated MMT-PGMA nanocomposites with an onset of exfoliation. This work conclusively provides a new approach for bridging reactive and functional polymers to layered nanomaterials via aryl diazonium salts in a simple, fast, efficient cation-exchange approach.

A multi-scale network method for two-phase flow in porous media

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khayrat, Karim, E-mail: khayratk@ifd.mavt.ethz.ch; Jenny, Patrick

Pore-network models of porous media are useful in the study of pore-scale flow in porous media. In order to extract macroscopic properties from flow simulations in pore-networks, it is crucial the networks are large enough to be considered representative elementary volumes. However, existing two-phase network flow solvers are limited to relatively small domains. For this purpose, a multi-scale pore-network (MSPN) method, which takes into account flow-rate effects and can simulate larger domains compared to existing methods, was developed. In our solution algorithm, a large pore network is partitioned into several smaller sub-networks. The algorithm to advance the fluid interfaces withinmore » each subnetwork consists of three steps. First, a global pressure problem on the network is solved approximately using the multiscale finite volume (MSFV) method. Next, the fluxes across the subnetworks are computed. Lastly, using fluxes as boundary conditions, a dynamic two-phase flow solver is used to advance the solution in time. Simulation results of drainage scenarios at different capillary numbers and unfavourable viscosity ratios are presented and used to validate the MSPN method against solutions obtained by an existing dynamic network flow solver.« less

Pyronin Y (basic xanthene dye)-bentonite composite: A spectroscopic study

NASA Astrophysics Data System (ADS)

Tabak, A.; Kaya, M.; Yilmaz, N.; Meral, K.; Onganer, Y.; Caglar, B.; Sungur, O.

2014-02-01

The expansion by 1.43 Angstrom of basal spacing and the shift to higher frequencies of in-plane ring vibrations of the Pyronin Y molecule at 1603 and 1527 cm-1 on the formation of Pyronin Y-bentonite composite exhibited that the dye cations might be oriented as a monolayer form in the interlamellar spacing with aromatic rings parallel to clay layers. Thermal analysis results of this composite compared to those of raw bentonite signified the different outer sphere water entities associated with the replacement of inorganic cations with organic dye cations and the gradual decomposition of the organic molecule in the interlamellar spacing. Thermo-Infrared spectra of Pyronin Y-bentonite sample up to high temperatures showed the thermal stability of the dye-clay composite as a result of the presence of π interactions. The pore structure characteristics of Pyronin Y-bentonite composite exhibited the increase in the number of mesopores during formation of the composite.

Acid composition and use thereof in treating fluid-bearing geologic formations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kucera, C.H.

1972-04-04

A composition useful as a fluid-loss control additive consists of a mixture of the following ingredients in the amount of between 7% and 30% by wt of each, to make a total of 100%: (1) an aqueous dispersion for binding clay selected from the class consisting of resins, rubber, rosin acids, and natural gums; (2) a thickening agent selected from the class consisting of fatty acids having from 10 to 24 carbon atoms, rosin acids, and metal soaps thereof; (3) an anionic or nonionic surfactant; and (4) a colloid-forming material which is either clay or asbestos cement. Another optional ingredientmore » is a low- viscosity oil, which is added in amount of up to 75% by wt of the sum of ingredients (1) to (4). The present composition prevents or greatly retards the excessive loss of fluids through the connecting pores of a geologic formation. (7 claims)« less

Coupling root architecture and pore network modeling - an attempt towards better understanding root-soil interactions

NASA Astrophysics Data System (ADS)

Leitner, Daniel; Bodner, Gernot; Raoof, Amir

2013-04-01

Understanding root-soil interactions is of high importance for environmental and agricultural management. Root uptake is an essential component in water and solute transport modeling. The amount of groundwater recharge and solute leaching significantly depends on the demand based plant extraction via its root system. Plant uptake however not only responds to the potential demand, but in most situations is limited by supply form the soil. The ability of the plant to access water and solutes in the soil is governed mainly by root distribution. Particularly under conditions of heterogeneous distribution of water and solutes in the soil, it is essential to capture the interaction between soil and roots. Root architecture models allow studying plant uptake from soil by describing growth and branching of root axes in the soil. Currently root architecture models are able to respond dynamically to water and nutrient distribution in the soil by directed growth (tropism), modified branching and enhanced exudation. The porous soil medium as rooting environment in these models is generally described by classical macroscopic water retention and sorption models, average over the pore scale. In our opinion this simplified description of the root growth medium implies several shortcomings for better understanding root-soil interactions: (i) It is well known that roots grow preferentially in preexisting pores, particularly in more rigid/dry soil. Thus the pore network contributes to the architectural form of the root system; (ii) roots themselves can influence the pore network by creating preferential flow paths (biopores) which are an essential element of structural porosity with strong impact on transport processes; (iii) plant uptake depend on both the spatial location of water/solutes in the pore network as well as the spatial distribution of roots. We therefore consider that for advancing our understanding in root-soil interactions, we need not only to extend our root models, but also improve the description of the rooting environment. Until now there have been no attempts to couple root architecture and pore network models. In our work we present a first attempt to join both types of models using the root architecture model of Leitner et al., (2010) and a pore network model presented by Raoof et al. (2010). The two main objectives of coupling both models are: (i) Representing the effect of root induced biopores on flow and transport processes: For this purpose a fixed root architecture created by the root model is superimposed as a secondary root induced pore network to the primary soil network, thus influencing the final pore topology in the network generation. (ii) Representing the influence of pre-existing pores on root branching: Using a given network of (rigid) pores, the root architecture model allocates its root axes into these preexisting pores as preferential growth paths with thereby shape the final root architecture. The main objective of our study is to reveal the potential of using a pore scale description of the plant growth medium for an improved representation of interaction processes at the interface of root and soil. References Raoof, A., Hassanizadeh, S.M. 2010. A New Method for Generating Pore-Network Models. Transp. Porous Med. 81, 391-407. Leitner, D, Klepsch, S., Bodner, G., Schnepf, S. 2010. A dynamic root system growth model based on L-Systems. Tropisms and coupling to nutrient uptake from soil. Plant Soil 332, 177-192.

Study on characteristics of PVDF/nano-clay composite polymer electrolyte using PVP as pore-forming agent

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dyartanti, Endah R., E-mail: heru.susanto@undip.ac.id, E-mail: endah-rd@uns.ac.id; Department of Chemical Engineering, Diponegoro University, Semarang; Purwanto, Agus

2016-02-08

Polyvinylidene fluoride (PVDF) based polymer electrolytes have a high dielectric constant, which can assist in greater ionization of lithium salts. The main advantages of PVDF are its durability in long battery operation and its ability to be a good ion conductor. However, the limitation of this polymer is its crystalline molecular structure. Dispersing nano-particles in the polymer matrix may improve the characteristics of the PVDF polymer. This paper aims to investigate the impact of nano-clay addition on the characteristics of PVDF polymer to be used as a polymer electrolyte membrane. In addition, the effect of poly(vinyl pyrrolidone) (PVP) is alsomore » investigated. The membrane was prepared by phase separation method whereas the polymer electrolyte membranes was prepared by immersing into 1 M lithium hexafluorophosphate (LiPF{sub 6}) in ethylene carbonate/dimethyl carbonate (EC/DMC) electrolytes for 1 h. The membranes were characterized by scanning electron microscope (SEM), porosity and electrolyte uptake and performance in battery cell. The results showed that both nano-clay and PVP have significant impacts on the improvement of PVDF membranes to be used as polymer electrolyte.« less

Impact of multicomponent ionic transport on pH fronts propagation in saturated porous media

NASA Astrophysics Data System (ADS)

Muniruzzaman, Muhammad; Rolle, Massimo

2016-04-01

Multicomponent ionic interactions have been increasingly recognized as important factors for the displacement of charged species in porous media under both diffusion- [1,2] and advection-dominated flow regimes [3,4]. In this study we investigate the propagation of pH fronts during multicomponent ionic transport in saturated porous media under flow-through conditions. By performing laboratory bench-scale experiments combined with numerical modeling we show the important influence of Coulombic effects on proton transport in the presence of ionic admixtures. The experiments were performed in a quasi two-dimensional flow-through setup under steady-state flow and transport conditions. Dilute solutions of hydrochloric acid with MgCl2 (1:2 strong electrolyte) were used as tracer solutions to experimentally test the effect of electrochemical cross-coupling on the migration of diffusive/dispersive pH fronts. We focus on two experimental scenarios, with different composition of tracer solutions, causing remarkably different effects on the propagation of the acidic fronts with relative differences in the penetration depth of pH fronts of 36% between the two scenarios and of 25% and 15% for each scenario with respect to the transport of ions at liberated state (i.e., without considering the charge effects). Also significant differences in the dilution of the distinct ionic plumes, quantified using the flux-related dilution index at the laboratory bench scale [5], were measured at the outflow of the flow-through system. The dilution of the pH plumes also changed considerably (26% relative difference) in the two flow-through experiments only due to the different composition of the pore water solution and to the electrostatic coupling of the ions in the flow-through setups. Numerical transport simulations were performed to interpret the laboratory experiments. The simulations were based on a multicomponent ionic formulation accurately capturing the Coulombic interactions between the transported ions in the flow-through system. The results of purely forward simulations show a very good agreement with the high-resolution measurements performed at the outlet of the flow-through setup and illustrate the importance of charge effects on pH fronts propagation in porous media. [1] Giambalvo, E. R., C. I. Steefel, A. T. Fisher, N. D. Rosenberg, and C. G. Wheat (2002), Effect of fluid-sediment reaction on hydrothermal fluxes of major elements, eastern flank of the Juan de Fuca Ridge, Geochim. Cosmochim. Acta, 66, 1739-1757. [2] Appelo, C. A. J., and P. Wersin (2007), Multicomponent diffusion modeling in clay systems with application to the diffusion of tritium, iodide, and sodium in opalinus clay, Environ. Sci. Technol., 41, 5002-5007. [3] Rolle, M., M. Muniruzzaman, C. M. Haberer, and P. Grathwohl (2013), Coulombic effects in advection-dominated transport of electrolytes in porous media: Multicomponent ionic dispersion, Geochim. Cosmochim. Acta, 120, 195-205. [4] Muniruzzaman, M., C. M. Haberer, P. Grathwohl, and M. Rolle (2014), Multicomponent ionic dispersion during transport of electrolytes in heterogeneous porous media: Experiments and model-based interpretation, Geochim. Cosmochim. Acta, 141, 656-669. [5] Rolle, M., G. Chiogna, D. L. Hochstetler, and P. K. Kitanidis (2013), On the importance of diffusion and compound-specific mixing for groundwater transport: An investigation from pore to field scale, J. Contam. Hydrol., 153, 51-68.

Biochar-Induced Changes in Soil Hydraulic Conductivity and Dissolved Nutrient Fluxes Constrained by Laboratory Experiments

PubMed Central

Barnes, Rebecca T.; Gallagher, Morgan E.; Masiello, Caroline A.; Liu, Zuolin; Dugan, Brandon

2014-01-01

The addition of charcoal (or biochar) to soil has significant carbon sequestration and agronomic potential, making it important to determine how this potentially large anthropogenic carbon influx will alter ecosystem functions. We used column experiments to quantify how hydrologic and nutrient-retention characteristics of three soil materials differed with biochar amendment. We compared three homogeneous soil materials (sand, organic-rich topsoil, and clay-rich Hapludert) to provide a basic understanding of biochar-soil-water interactions. On average, biochar amendment decreased saturated hydraulic conductivity (K) by 92% in sand and 67% in organic soil, but increased K by 328% in clay-rich soil. The change in K for sand was not predicted by the accompanying physical changes to the soil mixture; the sand-biochar mixture was less dense and more porous than sand without biochar. We propose two hydrologic pathways that are potential drivers for this behavior: one through the interstitial biochar-sand space and a second through pores within the biochar grains themselves. This second pathway adds to the porosity of the soil mixture; however, it likely does not add to the effective soil K due to its tortuosity and smaller pore size. Therefore, the addition of biochar can increase or decrease soil drainage, and suggests that any potential improvement of water delivery to plants is dependent on soil type, biochar amendment rate, and biochar properties. Changes in dissolved carbon (C) and nitrogen (N) fluxes also differed; with biochar increasing the C flux from organic-poor sand, decreasing it from organic-rich soils, and retaining small amounts of soil-derived N. The aromaticity of C lost from sand and clay increased, suggesting lost C was biochar-derived; though the loss accounts for only 0.05% of added biochar-C. Thus, the direction and magnitude of hydraulic, C, and N changes associated with biochar amendments are soil type (composition and particle size) dependent. PMID:25251677

Reversibility of radiocaesium sorption on illite

NASA Astrophysics Data System (ADS)

de Koning, Arjan; Comans, Rob N. J.

2004-07-01

Adsorption of trace amounts of radiocaesium on NH 4-, K-, and Na-saturated Fithian illite and subsequent desorption by 1 M NH 4 showed that a substantial amount of radiocaesium (44%, 46%, and 91% for NH 4-, K-, and Na-illite, respectively) cannot be desorbed after only 5 min of adsorption. Our results suggest that this instantaneous fixation is caused by the collapse of the frayed edges of the clay mineral and the relatively high concentration of radiocaesium building up in solution in the batch desorption experiments. Consequently, commonly applied high-NH 4 extractions underestimate truly exchangeable amounts of radiocaesium in soils and sediments containing illitic clay minerals. The rate of desorption of trace amounts of radiocaesium from the solids using high NH 4 or Cs concentrations has a half-life of about 2 yr, reflecting radiocaesium desorption from (partially) collapsed interlayers. Extraction of radiocaesium from illite after 5 min of contact time with a Cs-selective adsorbent or a 1 × 10 -6 M CsCl solution shows that 100% of the bound radiocaesium is readily available. The desorption rate in the presence of a Cs-selective adsorbent has a half-life of about 0.2 yr. Desorption of radiocaesium from illite using different ammonium concentrations shows that radiocaesium partitioning follows reversible ion-exchange theory if the NH 4 concentration is below 1 × 10 -4 M, and sufficient time (weeks) is allowed for the reaction to proceed. Thus, radiocaesium sorption reversibility in the natural environment is much higher than generally assumed, and equilibrium solid/liquid partitioning may be assumed for the long-term modelling of radiocaesium mobility in the natural environment. In the particular case of anoxic freshwater sediments with very high NH 4 concentrations in the pore waters (up to several mmol.L -1), collapse of the frayed edges of illite may occur, influencing radiocaesium partitioning. If collapse occurs before radiocaesium adsorbs to illite, high caesium sorption reversibility as measured by high-NH 4 extraction can be expected because further collapse of the frayed edges during the extraction procedure will be limited. This effect has indeed been observed earlier in the extraction of radiocaesium from anoxic freshwater sediments with high-NH 4 solutions and was as yet unexplained.

Humidity sensitive polymers In solution processed adjustable pore-volume Cu(In,Ga)S2 photocathodes for solar hydrogen production

NASA Astrophysics Data System (ADS)

Zhang, Chuan; Luo, Wenjun; Wen, Xin; Guan, Zhongjie; Zou, Zhigang

2017-11-01

P-type Cu(In,Ga)S2 semiconductors are promising candidates to be used as photocathodes for solar water splitting. Porous structures have been widely used to improve the performances of photoelectrodes due to good minority carrier transport. However, a porous photoelectrode has longer transport distance of majority carriers, which limits its performance. Controlling pore volume of a photoelectrode can balance minority and majority carrier transport and improve the performance. Here, a porous Cu(In,Ga)S2 film is prepared by facile spin-coating method. The pore volume of Cu(In,Ga)S2 film is controlled by adjusting relative humidity (RH) of air during spin-coating process. Further studies suggest that polyvinyl acetate (PVAc) in precursor solution is a humidity sensitive polymer and plays a key role to form different pore volume. The 40% RH sample has the best performance due to its optimum pore volume. After further coated with CdS surface passivation layer and Pt electrocatalyst on the surface, a 40% RH Cu(In,Ga)S2 photocathode indicates a photocurrent density of 8.6 mA cm-2 at 0 V RHE, which is one of the highest photocurrents of Cu(In,Ga)S2 photocathodes. This new strategy for adjusting pore volume is also suitable to prepare other solution-processed inorganic materials.

Adverse effects of mineral-alkali reactions in alkaline flooding: Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thornton, S.D.

1988-01-01

Two slim-tube experiments and supporting bottle tests were performed for a study of sandstone-alkali reactions. The two samples of reservoir sandstone used are from oilfields in the People's Republic of China. The first sandstone contains 16 percent clay and is from the Gu-Dao oilfield. The second sandstone contains 12 percent clay and is from the Liao-He oilfield. These two sandstones were allowed to react with alkaline solutions in 6-month bottle tests. Each sandstone consumed the most alkali from 0.5 N NaOH solution, an intermediate amount of alkali from 0.5 N Na/sub 2/SiO/sub 3/ solution, and the least amount of alkalimore » from 0.5 N Na/sub 2/CO/sub 3/ solution. 59 refs., 14 figs., 20 tabs.« less

Mechanical reinforcement and environmental effects on a nylon-6/clay nanocomposite

NASA Astrophysics Data System (ADS)

Shelley, J. Stebbins

2000-10-01

Hybridization, or modifying the organic polymers with inorganic constituents, is one method of achieving mechanical property improvements in polymeric materials while preserving processing characteristics. Toyota Central Research developed, and Ube Industries commercialized, one such hybrid nanocomposite: nylon-6/montmorillonite clay. This dissertation explores mechanisms of reinforcement in these nylon-6/clay nanocomposites and studies their degradation by atmospheric pollutants. A 100% improvement in modulus, 77% improvement in yield stress, and 54°C improvement in heat distortion temperature over nylon-6 were observed in extruded 5 wt% clay nanocomposite sheets. Infrared absorption spectrography and dynamic mechanical analysis were used to investigate the mechanisms of reinforcement in these nanocomposites. The improved mechanical properties, increased heat distortion temperature, reduced diffusion rate, and lower susceptibility to degradation in NO x observed where attributed to constraint of polymer chain motion by interaction with clay lamellae. Changes in the loss tangent peak in the glass transition region of the dynamic mechanical data provide an estimate of the volume of chains constrained by complexation of their mid-chain amide oxygen groups with the charged clay lamellae. X-ray analysis, optical microscopy, and light scattering were used to study changes in crystallization due to this complexation. Photomicrographs indicate that the morphology of the crystallites change from spherulitic to planar with the addition of clay. Decreases in diffusion rates of water and total water absorption were demonstrated in immersion experiments. Complexation of nylon-6 with 5 wt% clay reduces the total absorption of water by over 16%. The plane stress fracture toughness of extruded 5 wt% clay nanocomposite was 46% greater than that of nylon-6. The degradation of the nanocomposites in calcium chloride solution and NOx was examined through post exposure residual tensile and stress cracking experiments. CaCl 2 solution degraded the mechanical responses of the nanocomposite materials in proportion to the amount of water absorbed. NOx exposure degraded the mechanical performance regardless of the constraining effect of clay lamellae and the reduced diffusion rate in the nanocomposites. The stress cracking response of the nanocomposite in NOx (apparently not diffusion driven) resulted in a 650% increase in the time to failure of 5 wt% clay nanocomposites over unmodified nylon-6 for the same normalized stress intensity factor.

Transverse Chemotactic Migration of Bacteria from High to Low Permeability Regions in a Dual Permeability Porous Microfluidic Device

NASA Astrophysics Data System (ADS)

Singh, R.; Olson, M. S.

2011-12-01

Low permeability regions sandwiched between high permeability regions such as clay lenses are difficult to treat using conventional treatment methods. Trace concentrations of contaminants such as non-aqueous phase liquids (NAPLs) remain trapped in these regions and over the time diffuse out into surrounding water thereby acting as a long term source of groundwater contamination. Bacterial chemotaxis (directed migration toward a contaminant source), may be helpful in enhancing bioremediation of such contaminated sites. This study is focused on simulating a two-dimensional dual-permeability groundwater contamination scenario using microfluidic devices and evaluating transverse chemotactic migration of bacteria from high to low permeability regions. A novel bi-layer polydimethylsiloxane (PDMS) microfluidic device was fabricated using photolithography and soft lithography techniques to simulate contamination of a dual- permeability region due to leakage from an underground storage tank into a low permeability region. This device consists of a porous channel through which a bacterial suspension (Escherchia Coli HCB33) is flown and another channel for injecting contaminant/chemo-attractant (DL-aspertic acid) into the porous channel. The pore arrangement in the porous channel contains a 2-D low permeability region surrounded by high permeability regions on both sides. Experiments were performed under chemotactic and non-chemotactic (replacing attractant with buffer solution in the non porous channel) conditions. Images were captured in transverse pore throats at cross-sections 4.9, 9.8, and 19.6 mm downstream from the attractant injection point and bacteria were enumerated in the middle of each pore throat. Bacterial chemotaxis was quantified in terms of the change in relative bacterial counts in each pore throat at cross-sections 9.8 and 19.6 mm with respect to counts at the cross-section at 4.9 mm. Under non-chemotactic conditions, relative bacterial count was observed to decrease at 9.8 mm and 19.6 mm cross-sections in low permeability regions due to dilution with the injectate from the non-porous channel (Figure 1). However, relative bacterial counts increased in the low permeability region at both downstream cross-sections under chemotactic conditions. A large increase in relative bacterial count in the pore throats just outside the low permeability region was also observed at both cross-sections (Figure 1). The bacterial chemotactic response was observed to decrease linearly with increasing Darcy velocity and at flow rate 0.220 mm/s the chemotactic effect was offset by the advective flow in the porous channel.

Arsenic, vanadium, iron, and manganese biogeochemistry in a deltaic wetland, southern Louisiana, USA

DOE PAGES

Telfeyan, Katherine; Breaux, Alexander; Kim, Jihyuk; ...

2017-04-05

Geochemical cycling of the redox-sensitive trace elements arsenic (As) and vanadium (V) was examined in shallow pore waters from a marsh in an interdistributary embayment of the lower Mississippi River Delta. In particular, we explore how redox changes with depth and distance from the Mississippi River affect As and V cycling in the marsh pore waters. Previous geophysical surveys and radon mass balance calculations suggested that Myrtle Grove Canal and bordering marsh receive fresh groundwater, derived in large part from seepage of the Mississippi River, which subsequently mixes with brackish waters of Barataria Bay. In addition, the redox geochemistry ofmore » pore waters in the wetlands is affected by Fe and S cycling in the shallow subsurface (0-20 cm). Sediments with high organic matter content undergo SO 4 2- reduction, a process ubiquitous in the shallow subsurface but largely absent at greater depths (~3 m). Instead, at depth, in the absence of organic-rich sediments, Fe concentrations are elevated, suggesting that reduction of Fe(III) oxides/oxyhydroxides buffers redox conditions. Arsenic and V cycling in the shallow subsurface are decoupled from their behavior at depth, where both V and As appear to be removed from solution by either diffusion or adsorption onto, or co-precipitation with, authigenic minerals within the deeper aquifer sediments. Pore water As concentrations are greatest in the shallow subsurface (e.g., up to 315 nmol kg -1 in the top ~20 cm of the sediment) but decrease with depth, reaching values <30 nmol kg -1 at depths between 3 and 4 m. Vanadium concentrations appear to be tightly coupled to Fe cycling in the shallow subsurface, but at depth, V may be adsorbed to clay or sedimentary organic matter (SOM). Diffusive fluxes are calculated to examine the export of trace elements from the shallow marsh pore waters to the overlying canal water that floods the marsh. The computed fluxes suggest that the shallow sediment serves as a source of Fe, Mn, and As to the surface waters, whereas the sediments act as a sink for V. Iron and Mn fluxes are substantial, ranging from 50 to 30,000 and 770 to 4,300 nmol cm -2 day -1, respectively, whereas As fluxes are much less, ranging from 2.1 to 17 nmol cm -2 day -1. Vanadium fluxes range from 3.0 nmol cm -2 day -1 directed into the sediment to 1.7 nmol cm -2 day -1 directed out of the sediment« less

Arsenic, vanadium, iron, and manganese biogeochemistry in a deltaic wetland, southern Louisiana, USA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Telfeyan, Katherine; Breaux, Alexander; Kim, Jihyuk

Geochemical cycling of the redox-sensitive trace elements arsenic (As) and vanadium (V) was examined in shallow pore waters from a marsh in an interdistributary embayment of the lower Mississippi River Delta. In particular, we explore how redox changes with depth and distance from the Mississippi River affect As and V cycling in the marsh pore waters. Previous geophysical surveys and radon mass balance calculations suggested that Myrtle Grove Canal and bordering marsh receive fresh groundwater, derived in large part from seepage of the Mississippi River, which subsequently mixes with brackish waters of Barataria Bay. In addition, the redox geochemistry ofmore » pore waters in the wetlands is affected by Fe and S cycling in the shallow subsurface (0-20 cm). Sediments with high organic matter content undergo SO 4 2- reduction, a process ubiquitous in the shallow subsurface but largely absent at greater depths (~3 m). Instead, at depth, in the absence of organic-rich sediments, Fe concentrations are elevated, suggesting that reduction of Fe(III) oxides/oxyhydroxides buffers redox conditions. Arsenic and V cycling in the shallow subsurface are decoupled from their behavior at depth, where both V and As appear to be removed from solution by either diffusion or adsorption onto, or co-precipitation with, authigenic minerals within the deeper aquifer sediments. Pore water As concentrations are greatest in the shallow subsurface (e.g., up to 315 nmol kg -1 in the top ~20 cm of the sediment) but decrease with depth, reaching values <30 nmol kg -1 at depths between 3 and 4 m. Vanadium concentrations appear to be tightly coupled to Fe cycling in the shallow subsurface, but at depth, V may be adsorbed to clay or sedimentary organic matter (SOM). Diffusive fluxes are calculated to examine the export of trace elements from the shallow marsh pore waters to the overlying canal water that floods the marsh. The computed fluxes suggest that the shallow sediment serves as a source of Fe, Mn, and As to the surface waters, whereas the sediments act as a sink for V. Iron and Mn fluxes are substantial, ranging from 50 to 30,000 and 770 to 4,300 nmol cm -2 day -1, respectively, whereas As fluxes are much less, ranging from 2.1 to 17 nmol cm -2 day -1. Vanadium fluxes range from 3.0 nmol cm -2 day -1 directed into the sediment to 1.7 nmol cm -2 day -1 directed out of the sediment« less

Organofunctionalized Amazon smectite for dye removal from aqueous medium--kinetic and thermodynamic adsorption investigations.

PubMed

Guerra, Denis L; Silva, Weber L L; Oliveira, Helen C P; Viana, Rúbia R; Airoldi, Claudio

2011-02-15

The objective of this study is to examine the adsorption behavior of Sumifix Brilliant Orange 3R textile dye from aqueous solution on smectite sample, an abundant Amazon clay. The original smectite clay mineral has been collected from Amazon region, Brazil. The compound 2-aminomethylpyridine was anchored onto smectite surface by heterogeneous route. The ability of these materials to remove the Sumifix Brilliant Orange 3R textile dye from aqueous solution was followed by a series of adsorption isotherms, using a batchwise process. The maximum number of moles adsorbed was determined to be 1.26 and 2.07 mmol g(-1) for natural and modified clay samples, respectively. The energetic effects caused by dye cations adsorption were determined through calorimetric titrations. Thermodynamics indicated the existence of favorable conditions for such dye-nitrogen interactions. Copyright © 2010. Published by Elsevier B.V.

Surfactant-Modified Soil Amendments Reduce Nitrogen and Phosphorus Leaching in a Sand-Based Rootzone.

PubMed

Shaddox, Travis W; Kruse, Jason K; Miller, Grady L; Nkedi-Kizza, Peter; Sartain, Jerry B

2016-09-01

United States Golf Association putting greens are susceptible to nitrogen (N) and phosphorus (P) leaching. Inorganic soil amendments are used to increase moisture and nutrient retention and may influence N and P leaching. This study was conducted to determine whether N and P leaching could be reduced using soil amendments and surfactant-modified soil amendments. Treatments included a control (sand), sand-peat, zeolite, calcined clay, hexadecyltrimethylammonium-zeolite, and hexadecyltrimethylammonium-calcined clay. Lysimeters were filled with a 30-cm rootzone layer of sand-peat (85:15 by volume), below which a 5-cm treatment layer of amendments was placed. A solution of NO-N, NH-N, and orthophosphate-P (2300, 2480, and 4400 μg mL, respectively) was injected at the top of each lysimeter, and leachate was collected using an autocollector set to collect a 10-mL sample every min until four pore volumes were collected. Uncoated amendments, sand, and peat had no influence on NO-N retention, whereas hexadecyltrimethylammonium-coated amendments reduced NO-N leaching to below detectable limits. Both coated and uncoated amendments reduced NH-N leaching, with zeolite reducing NH-N leached to near zero regardless of hexadecyltrimethylammonium coating. Pure sand resulted in a 13% reduction of applied orthophosphate-P leaching, whereas peat contributed to orthophosphate-P leaching. Surfactant-modified amendments reduced orthophosphate-P leaching by as much as 97%. Surfactant-modified soil amendments can reduce NO-N, NH-N, and orthophosphate-P leaching and, thus, may be a viable option for removing leached N and P before they enter surface or ground waters. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Grain Size Distribution in Mudstones: A Question of Nature vs. Nurture

NASA Astrophysics Data System (ADS)

Schieber, J.

2011-12-01

Grain size distribution in mudstones is affected by the composition of the source material, the processes of transport and deposition, and post-depositional diagenetic modification. With regard to source, it does make a difference whether for example a slate belt is eroded vs a stable craton. The former setting tends to provide a broad range of detrital quartz in the sub 62 micron size range in addition to clays and greenschist grade rock fragments, whereas the latter may be biased towards coarser quartz silt (30-60 microns), in addition to clays and mica flakes. In flume experiments, when fine grained materials are transported in turbulent flows at velocities that allow floccules to transfer to bedload, a systematic shift of grain size distribution towards an increasingly finer grained suspended load is observed as velocity is lowered. This implies that the bedload floccules are initially constructed of only the coarsest clay particles at high velocities, and that finer clay particles become incorporated into floccules as velocity is lowered. Implications for the rock record are that clay beds deposited from decelerating flows should show subtle internal grading of coarser clay particles; and that clay beds deposited from continuous fast flows should show a uniform distribution of coarse clays. Still water settled clays should show a well developed lower (coarser) and upper (finer) subdivision. A final complication arises when diagenetic processes, such as the dissolution of biogenic silica, give rise to diagenetic quartz grains in the silt to sand size range. This diagenetic silica precipitates in fossil cavities and pore spaces of uncompacted muds, and on casual inspection can be mistaken for detrital quartz. In distal mudstone successions close to 100 % of "apparent" quartz silt can be of that origin, and reworking by bottom currents can further enhance a detrital perception by producing rippled and laminated silt beds. Although understanding how size distributions in mudstones evolve is considered central to problems in hillslope, fluvial, aeolian, coastal, and submarine systems, one can not simply measure distributions and hope to arrive at an answer. The complex origins of mudstones are reflected in their very broad compositional range, and multiple overprinted processes have to be considered in order to make sense out of observed grain size distributions.

Unifying Pore Network Modeling, Continuous Time Random Walk Theory and Experiment - Accomplishments and Future Directions

NASA Astrophysics Data System (ADS)

Bijeljic, B.

2008-05-01

This talk will describe and highlight the advantages offered by a methodology that unifies pore network modeling, CTRW theory and experiment in description of solute dispersion in porous media. Solute transport in a porous medium is characterized by the interplay of advection and diffusion (described by Peclet number, Pe) that cause spreading of solute particles. This spreading is traditionally described by dispersion coefficients, D, defined by σ 2 = 2Dt, where σ 2 is the variance of the solute position and t is the time. Using a pore-scale network model based on particle tracking, the rich Peclet- number dependence of dispersion coefficient is predicted from first principles and is shown to compare well with experimental data for restricted diffusion, transition, power-law and mechanical dispersion regimes in the asymptotic limit. In the asymptotic limit D is constant and can be used in an averaged advection-dispersion equation. However, it is highly important to recognize that, until the velocity field is fully sampled, the particle transport is non-Gaussian and D possesses temporal or spatial variation. Furthermore, temporal probability density functions (PDF) of tracer particles are studied in pore networks and an excellent agreement for the spectrum of transition times for particles from pore to pore is obtained between network model results and CTRW theory. Based on the truncated power-law interpretation of PDF-s, the physical origin of the power-law scaling of dispersion coefficient vs. Peclet number has been explained for unconsolidated porous media, sands and a number of sandstones, arriving at the same conclusion from numerical network modelling, analytic CTRW theory and experiment. Future directions for further applications of the methodology presented are discussed in relation to the scale- dependent solute dispersion and reactive transport. Significance of pre-asymptotic dispersion in porous media is addressed from pore-scale upwards and the impact of heterogeneity is discussed. The length traveled by solute plumes before Gaussian behaviour is reached increases with an increase in heterogeneity and/or Pe. This opens up the question on the nature of dispersion in natural systems where the heterogeneities at the larger scales will profoundly increase the range of velocities in the aquifer, thus considerably delaying the asymptotic approach to Gaussian behaviour. As a consequence, the asymptotic behaviour might not be reached at the field scale.

Clay induced aggregation of a tetra-cationic metalloporphyrin in Layer by Layer self assembled film

NASA Astrophysics Data System (ADS)

Banik, Soma; Bhattacharjee, J.; Hussain, S. A.; Bhattacharjee, D.

2015-12-01

Porphyrins have a general tendency to form aggregates in ultrathin films. Also electrostatic adsorption of cationic porphyrins onto anionic nano clay platelets results in the flattening of porphyrin moieties. The flattening is evidenced by the red-shifting of Soret band with respect to the aqueous solution. In the present communication, we have studied the clay induced aggregation behaviour of a tetra-cationic metalloporphyrin Manganese (III) 5, 10, 15, 20-tetra (4 pyridyl)-21 H, 23 H-porphine chloride tetrakis (methochloride) (MnTMPyP) in Layer-by-Layer (LbL) self assembled film. The adsorption of dye molecules onto nano clay platelets resulted in the flattening of the meso substituent groups of the dye chromophore. In Layer-by-Layer ultrathin film, the flattened porphyrin molecules tagged nano clay platelets were further associated to form porphyrin aggregates. This has been clearly demonstrated from the UV-vis absorption spectroscopic studies. Atomic Force Microscopic (AFM) studies gave visual evidence of the association of organo-clay hybrid molecules in the LbL film.

Exfoliation restacking route to Au nanoparticle-clay nanohybrids

NASA Astrophysics Data System (ADS)

Paek, Seung-Min; Jang, Jae-Up; Hwang, Seong-Ju; Choy, Jin-Ho

2006-05-01

A novel gold-pillared aluminosilicate (Au-PILC) were synthesized with positively charged gold nanoparticles capped by mercaptoammonium and exfoliated silicate layers. Gold nanoparticles were synthesized by NaBH4 reduction of AuCl4- in the presence of N,N,N-Trimethyl (11-mercaptoundecyl)ammonium (HS(CH2)11NMe3+) protecting ligand in an aqueous solution, and purified by dialysis. The resulting positively charged and water-soluble gold nanoparticles were hybridized with exfoliated silicate sheets by electrostatic interaction. The formation of Au clay hybrids could be easily confirmed by the powder X-ray diffraction with the increased basal spacing of clay upon insertion of Au nanoparticles. TEM image clearly revealed that the Au particles with an average size of 4 nm maintain their structure even after intercalation. The Au nanoparticles supported by clay matrix were found to be thermally more stable, suggesting that the Au nanoparticles were homogeneously protected with clay nanoplates. The present synthetic route could be further applicable to various hybrid systems between metal nanoparticles and clays.

Mechanisms behind injecting the combination of nano-clay particles and polymer solution for enhanced oil recovery

NASA Astrophysics Data System (ADS)

Khalili Nezhad, Seyyed Shahram; Cheraghian, Goshtasp

2016-08-01

Laboratory investigations and field applications have proved injection of polymer solution to be an effective means to improve oil recovery for reservoirs of medium oil viscosity. The incremental oil produced in this case is the result of an increase in areal and vertical sweep efficiencies. Biopolymers and synthetic polymers are the major categories used in the petroleum industry for specific reasons. Biopolymers like xanthan are limited in their application as they are more susceptible to biodegradation. Synthetic polymers like Hydrolyzed PolyAcrylaMide (HPAM) have a much wider application as they are less susceptible to biodegradation. Furthermore, development of nanotechnology has successfully provided technical and economical viable alternatives for present materials. The objective of this study is to investigate the effect of combining clay nanoparticles with polymer solution on oil recovery. This paper includes a history match of both one-dimensional and two-dimensional polymer floods using a three-dimensional numerical model for fluid flow and mass transport. Results indicated that the amount of polymer adsorption decreased when clay nanoparticles were added to the PolyAcrylaMide solution; however, mobility ratio improvement is believed to be the main contributor for the proposed method in order to enhance much oil recovery compared to xanthan flood and HPAM flood.

Modification and characterization of montmorillonite clay for the extraction of zearalenone

NASA Astrophysics Data System (ADS)

Hue, Kerri-Ann Alicia

Mycotoxins are secondary metabolites of organisms belonging to the fungus kingdom. The cost associated with mycotoxin contamination in the USA and Canada is approximately US $5 billion. Zearalenone (ZEN), a resorcylic acid lactone, is produced by various members of the genus Fusarium . These fungi often colonize a variety of foods and feedstuffs including, corn, sorghum, wheat, oats, barley, and other cereal grains. This metabolite has estrogenic effects in farm animals with pigs being the most sensitive. ZEN induces hyperestrogenism and can cause infertility, reduced sex drive, fetal mummification, and abortions. Clays have successfully been used in the animal feed industry as an adsorbent and binders for certain small, water soluble mycotoxins. These mycotoxins are attracted to the electrical imbalance between the layers of the clays caused by isomorphic substitution of structural atoms. The mycotoxins are sequestered in the clay layers and pass harmlessly through the animal. However, ZEN is water insoluble and is not extracted easily with aluminosilicate clays. Therefore the modification of hydrated sodium calcium aluminosilicate (HSCAS) clays with organic cations has been proposed to render the clays hydrophobic and increase the ZEN binding capacity. The goal of this study was to develop a safe and cost effective organophilic material able to bind and extract zearalenone, to investigate the factors most important to extraction, and to investigate the fundamental properties between the clay-surfactant-mycotoxin systems that lead to extraction. The clay was modified by cation exchange reactions with tricaprylmethylammonium (TCMA) chloride and generic corn oil. The organophilic clays were then characterized using XRD, FTIR, and TGA analytical techniques. These techniques were used to determine the change in fundamental clay properties that would lead to the extraction of ZEN. Desorption studies were performed to determine any increase in toxicity that might be caused by washing of the clays or exposure to electrolytic solutions. Statistical design of experiments was used to determine the factors most influential during ZEN extraction. Modification by TCMA resulted in an increase in intergallery spacing of ˜0.6nm. TGA and FTIR studies indicated intercalation of organic species within the clay layers. An increase in weight loss proportional to the amount of TCMA added was observed by TGA analysis. In addition to the peaks found in the natural clay, peaks at 2928 cm-1, 2852 cm -1, and 1466 cm-1, which belong to C-H asymmetric stretching, C-H symmetric stretching and -CH2 scissoring respectively characteristic of TCMA were present. The clays developed were able to extract >90% ZEN in vitro at pH 3 and pH7. The factors most important for extraction changed depending on the levels of parameters chosen. Mathematical models were developed that showed the relationship between the factors and the ZEN removal percentage. When exposed to electrolyte solutions ˜1.5pmm of surfactant desorbed from the modified clay.

Optimization of mesoporous carbons for efficient adsorption of berberine hydrochloride from aqueous solutions.

PubMed

Li, Yin; Fu, Jie; Deng, Shuguang; Lu, Xiuyang

2014-06-15

Sixteen mesoporous carbon adsorbents were synthesized by varying the ratio of soft to hard templates in order to optimize the pore textural properties of these adsorbents. The mesoporous carbon adsorbents have a high BET specific surface area (1590.3-2193.5 m(2)/g), large pore volume (1.72-2.56 cm(3)/g), and uniform pore size distribution with a median pore diameter ranging from 3.51 nm to 4.52 nm. It was observed that pore textural properties of the carbon adsorbents critically depend on the molar ratio of carbon sources to templates, and the hard template plays a more important role than the soft template in manipulating the pore textures. Adsorption isotherms of berberine hydrochloride at 303 K were measured to evaluate the adsorption efficacy of these adsorbents. The adsorption of berberine hydrochloride from aqueous solutions on the sixteen mesoporous carbon adsorbents synthesized in this work is very efficient, and the adsorption equilibrium capacities on all samples are more than double the adsorption capacities of berberine hydrochloride of the benchmark adsorbents (polymer resins and spherical activated carbons) at similar conditions. It was observed from the adsorption experiments that the equilibrium adsorption amounts of berberine hydrochloride are strongly correlated with the BET specific surface area and pore volume of the adsorbents. The adsorbent with the highest BET of 2193.5 m(2)/g displayed the largest adsorption capacity of 574 mg/g at an equilibrium concentration of 0.10mg/mL of berberine hydrochloride in an aqueous solution. Copyright © 2014 Elsevier Inc. All rights reserved.

Pore-water chemistry explains zinc phytotoxicity in soil.

PubMed

Kader, Mohammed; Lamb, Dane T; Correll, Ray; Megharaj, Mallavarapu; Naidu, Ravi

2015-12-01

Zinc (Zn) is a widespread soil contaminant arising from a numerous anthropogenic sources. However, adequately predicting toxicity of Zn to ecological receptors remains difficult due to the complexity of soil characteristics. In this study, we examined solid-solution partitioning using pore-water data and toxicity of Zn to cucumber (Cucumis sativus L.) in spiked soils. Pore-water effective concentration (ECx, x=10%, 20% and 50% reduction) values were negatively related to pH, indicating lower Zn pore water concentration were needed to cause phytotoxicity at high pH soils. Total dissolved zinc (Znpw) and free zinc (Zn(2+)) in soil-pore water successfully described 78% and 80.3% of the variation in relative growth (%) in the full dataset. When the complete data set was used (10 soils), the estimated EC50pw was 450 and 79.2 µM for Znpw and Zn(2+), respectively. Total added Zn, soil pore water pH (pHpw) and dissolve organic carbon (DOC) were the best predictors of Znpw and Zn(2+) in pore-water. The EC10 (total loading) values ranged from 179 to 5214 mg/kg, depending on soil type. Only pH measurements in soil were related to ECx total Zn data. The strongest relationship to ECx overall was pHca, although pHw and pHpw were in general related to Zn ECx. Similarly, when a solution-only model was used to predict Zn in shoot, DOC was negatively related to Zn in shoot, indicating a reduction in uptake/ translocation of Zn from solution with increasing DOC. Copyright © 2015 Elsevier Inc. All rights reserved.

Highly Transparent and Self-Extinguishing Nanofibrillated Cellulose-Monolayer Clay Nanoplatelet Hybrid Films.

PubMed

Ming, Siyi; Chen, Gang; He, Jiahao; Kuang, Yudi; Liu, Yu; Tao, Ruiqiang; Ning, Honglong; Zhu, Penghui; Liu, Yingyao; Fang, Zhiqiang

2017-08-29

A viable solution toward "green" optoelectronics is rooted in our ability to fabricate optoelectronics on transparent nanofibrillated cellulose (NFC) film substrates. However, the flammability of transparent NFC film poses a severe fire hazard in optoelectronic devices. Despite many efforts toward enhancing the fire-retardant features of transparent NFC film, making NFC film fire-retardant while maintaining its high transparency (≥90%) remains an ambitious objective. Herein, we combine NFC with NFC-dispersed monolayer clay nanoplatelets as a fire retardant to prepare highly transparent NFC-monolayer clay nanoplatelet hybrid films with a superb self-extinguishing behavior. Homogeneous and stable monolayer clay nanoplatelet dispersion was initially obtained by using NFC as a green dispersing agent with the assistance of ultrasonication and then used to blend with NFC to prepare highly transparent and self-extinguishing hybrid films by a water evaporation-induced self-assembly process. As the content of monolayer clay nanoplatelets increased from 5 wt % to 50 wt %, the obtained hybrid films presented enhanced self-extinguishing behavior (limiting oxygen index sharply increased from 21% to 96.5%) while retaining a ∼90% transparency at 600 nm. More significantly, the underlying mechanisms for the high transparency and excellent self-extinguishing behavior of these hybrid films with a clay nanoplatelet content of over 30 wt % were unveiled by a series of characterizations such as SEM, XRD, TGA, and limiting oxygen index tester. This work offers an alternative environmentally friendly, self-extinguishing, and highly transparent substrate to next-generation optoelectronics, and is aimed at providing a viable solution to environmental concerns that are caused by ever-increasing electronic waste.

Preparation of Microcrystals of Piroxicam Monohydrate by Antisolvent Precipitation via Microfabricated Metallic Membranes with Ordered Pore Arrays

PubMed Central

2017-01-01

Microcrystals of piroxicam (PRX) monohydrate with a narrow size distribution were prepared from acetone/PRX solutions by antisolvent crystallization via metallic membranes with ordered pore arrays. Crystallization was achieved by controlled addition of the feed solution through the membrane pores into a well-stirred antisolvent. A complete transformation of an anhydrous form I into a monohydrate form of PRX was confirmed by Raman spectroscopy and differential scanning calorimetry. The size of the crystals was 7–34 μm and was controlled by the PRX concentration in the feed solution (15–25 g L–1), antisolvent/solvent volume ratio (5–30), and type of antisolvent (Milli-Q water or 0.1–0.5 wt % aqueous solutions of hydroxypropyl methyl cellulose (HPMC), poly(vinyl alcohol) or Pluronic P-123). The smallest crystals were obtained by injecting 25 g L–1 PRX solution through a stainless-steel membrane with a pore size of 10 μm into a 0.06 wt % HPMC solution stirred at 1500 rpm using an antisolvent/solvent ratio of 20. HPMC provided better steric stabilization of microcrystals against agglomeration than poly(vinyl alcohol) and Pluronic P-123, due to hydrogen bonding interactions with PRX and water. A continuous production of large PRX monohydrate microcrystals with a volume-weighted mean diameter above 75 μm was achieved in a continuous stirred membrane crystallizer. Rapid pouring of Milli-Q water into the feed solution resulted in a mixture of highly polydispersed prism-shaped and needle-shaped crystals. PMID:29234241

Constraints on silicates formation in the Si-Al-Fe system: Application to hard deposits in steam generators of PWR nuclear reactors

NASA Astrophysics Data System (ADS)

Berger, Gilles; Million-Picallion, Lisa; Lefevre, Grégory; Delaunay, Sophie

2015-04-01

Introduction: The hydrothermal crystallization of silicates phases in the Si-Al-Fe system may lead to industrial constraints that can be encountered in the nuclear industry in at least two contexts: the geological repository for nuclear wastes and the formation of hard sludges in the steam generator of the PWR nuclear plants. In the first situation, the chemical reactions between the Fe-canister and the surrounding clays have been extensively studied in laboratory [1-7] and pilot experiments [8]. These studies demonstrated that the high reactivity of metallic iron leads to the formation of Fe-silicates, berthierine like, in a wide range of temperature. By contrast, the formation of deposits in the steam generators of PWR plants, called hard sludges, is a newer and less studied issue which can affect the reactor performance. Experiments: We present here a preliminary set of experiments reproducing the formation of hard sludges under conditions representative of the steam generator of PWR power plant: 275°C, diluted solutions maintained at low potential by hydrazine addition and at alkaline pH by low concentrations of amines and ammoniac. Magnetite, a corrosion by-product of the secondary circuit, is the source of iron while aqueous Si and Al, the major impurities in this system, are supplied either as trace elements in the circulating solution or by addition of amorphous silica and alumina when considering confined zones. The fluid chemistry is monitored by sampling aliquots of the solution. Eh and pH are continuously measured by hydrothermal Cormet© electrodes implanted in a titanium hydrothermal reactor. The transformation, or not, of the solid fraction was examined post-mortem. These experiments evidenced the role of Al colloids as precursor of cements composed of kaolinite and boehmite, and the passivation of amorphous silica (becoming unreactive) likely by sorption of aqueous iron. But no Fe-bearing was formed by contrast to many published studies on the Fe-clay interactions in the nuclear waste storage, and by contrast with basic thermodynamic predictions. Conclusion: The Fe-clays and steam generators contexts imply relatively close aqueous environments: hydrothermal, reduced, diluted, neutral to slightly alkaline. The main difference is the status of iron: ferric/ferrous (magnetite) in the steam generators, metallic in the Fe-clay experiments. The concentration of aqueous iron when supplied by magnetite is low and does not allow its incorporation in secondary phases. By contrast, aqueous ferrous iron released by the corrosion of steel is not limited by the source, rather by the sink, and produces Fe-rich silicates. This example illustrates the discrepancy between complex mineral reactions and oversimplified predictions when sorption/passivation and nucleation/growth constraints are ignored. Reference: [1] Lanson et al. (2012) Amer. Min. 97, 864-871. [2] Lantenois et al. (2005) Clays & Clay Min. 53, 597-612. [3] Mosser-Ruck et al. (2010) Clays & Clay Min. 58, 280-291. [4] Perronnet et al. (2008) App. Clay Sci. 38, 187-202. [5] Osacky et al. (2010) App. Clay Sci. 50, 237-244. [6] Guillaume et al. (2003) Clay Min. 38, 281-302. [7] Rivard et al. (2013) Amer. Mineral. 98, 163-180. [8] Svensson and Hansen (2013) Clays & Clay Min. 61, 566-579.

Porosity characterization of fresh and altered stones by ultrasound velocity and mercury intrusion porosimetry

NASA Astrophysics Data System (ADS)

Scrivano, Simona; Gaggero, Laura; Gisbert Aguilar, Josep

2016-04-01

Porosity is the main physical feature dealing with rocks durability and storage capacity. The analysis of this parameter is key factor in predicting rock performances (Molina et al., 2011). There are several techniques that can be applied to acquire the widest information range possible about pores (e.g. size, shape, distribution), leading to a better understanding of decay processes and trapping capacity. The coupling of a detailed minero-petrographic analysis with physical measures such as ultrasounds and mercury intrusion porosimetry (MIP) proved to be a valid tool for understanding the porous network and its evolution during weathering processes. Both fresh and salt-weathered samples were analysed to investigate the modification triggered in the porous network by crystallization. The ageing process was induced using a Na2SO4 saturated saline solution with the partial continuous immersion method (Benavente et al., 2001). The study was addressed to four sedimentary lithotypes: 1) Arenaria Macigno, a greywacke made up of thickened clasts of quartz, plagioclase and K-feldspar cemented by micritic calcite and phyllosilicates; 2) Breccia Aurora, a calcareous breccia with nodules of compact limestone and micritic cement joints; 3) Rosso Verona, a biomicrite where the compact bio-micrite matrix is cut by clay minerals veins; and 4) Vicenza Stone, an organogenic limestone rich in micro- and macro foraminifera, algae, bryozoans and remains of echinoderms, with iron oxides. An appropriate description of the porous network variation and recognition of the origin of secondary porosity was attained. The study defined that the pore shape and distribution (anisotropy coefficient K) has a fluctuation up to the 50% after weathering treatments and pore-size distribution (defined in a range between 0,0025 - 75 μm), allowing modelling the mechanisms of water transport and evaluating decay susceptibility of these lithotypes. Molina E, Cultrone G, Sebastián E, Alonso FJ, Carrizo L, Gisbert J, et al. The pore system of sedimentary rocks as a key factor in the durability of building materials. Eng Geol 118 (2011) 110-21. D. Benavente, M.A. Garcia del Cura, A. Bernabeu, S. Ordonez. Quantification of salt weathering in porous stones using an experimental continuous partial immersion method. Eng Geol 59 (2001) 313-325.

Nanofiber based triple layer hydro-philic/-phobic membrane - a solution for pore wetting in membrane distillation

PubMed Central

Prince, J. A.; Rana, D.; Matsuura, T.; Ayyanar, N.; Shanmugasundaram, T. S.; Singh, G.

2014-01-01

The innovative design and synthesis of nanofiber based hydro-philic/phobic membranes with a thin hydro-phobic nanofiber layer on the top and a thin hydrophilic nanofiber layer on the bottom of the conventional casted micro-porous layer which opens up a solution for membrane pore wetting and improves the pure water flux in membrane distillation. PMID:25377488

Modification of clay barriers with a cationic surfactant to improve the retention of pesticides in soils.

PubMed

Rodríguez-Cruz, M S; Sánchez-Martín, M J; Andrades, M S; Sánchez-Camazano, M

2007-01-10

In this work, the efficiency of reactive clay barriers in the immobilisation of organic pesticides in a sandy soil was studied. Reactive barriers were prepared by modification of montmorillonite, kaolinite and palygorskite clay minerals, and of a clayey soil with the cationic surfactant octadecyltrimethylammonium bromide (ODTMA). Percolation curves of the pesticides linuron, atrazine and metalaxyl of different hydrophobic character, were obtained in columns packed with a natural sandy soil with these barriers intercalated under saturated flow conditions. The cumulative curves in the unmodified soil indicated a leaching of pesticides greater than 85% of the total amount of compound added. After barrier intercalation, the breakthrough curves (BTC) indicated a dramatic decrease in the amounts of linuron leached in all columns and a significant modification of the leaching kinetics of atrazine and metalaxyl. Retardation factors, R, of the pesticides in the columns were significantly correlated with the organic matter content (OM) derived from the ODTMA of the organo clay/soil barriers (r2>or=0.78). Significant correlations were also found between these R factors and the pore volume values corresponding to the maximum peaks of the BTCs (r2=0.83; p<0.01) or the total volumes leached (r2=0.44; p<0.05) for the pesticides atrazine and metalaxyl. The results obtained point to the interest in the use of reactive clay barriers for almost complete immobilisation of hydrophobic pesticides or for decreasing the leaching of moderately hydrophobic pesticides coming from point-like sources of pollution. These barriers would avoid the generation of elevated concentrations of these compounds in the soils due to their rapid washing.

Modeling the arrangement of particles in natural swelling-clay porous media using three-dimensional packing of elliptic disks

NASA Astrophysics Data System (ADS)

Ferrage, Eric; Hubert, Fabien; Tertre, Emmanuel; Delville, Alfred; Michot, Laurent J.; Levitz, Pierre

2015-06-01

Swelling clay minerals play a key role in the control of water and pollutant migration in natural media such as soils. Moreover, swelling clay particles' orientational properties in porous media have significant implications for the directional dependence of fluid transfer. Herein we investigate the ability to mimic the organization of particles in natural swelling-clay porous media using a three-dimensional sequential particle deposition procedure [D. Coelho, J.-F. Thovert, and P. M. Adler, Phys. Rev. E 55, 1959 (1997), 10.1103/PhysRevE.55.1959]. The algorithm considered is first used to simulate disk packings. Porosities of disk packings fall onto a single master curve when plotted against the orientational scalar order parameter value. This relation is used to validate the algorithm used in comparison with existing ones. The ellipticity degree of the particles is shown to have a negligible effect on the packing porosity for ratios ℓa/ℓb less than 1.5, whereas a significant increase in porosity is obtained for higher values. The effect of the distribution of the geometrical parameters (size, aspect ratio, and ellipticity degree) of particles on the final packing properties is also investigated. Finally, the algorithm is used to simulate particle packings for three size fractions of natural swelling-clay mineral powders. Calculated data regarding the distribution of the geometrical parameters and orientation of particles in porous media are successfully compared with experimental data obtained for the same samples. The results indicate that the obtained virtual porous media can be considered representative of natural samples and can be used to extract properties difficult to obtain experimentally, such as the anisotropic features of pore and solid phases in a system.

Frictional and hydrologic behavior of the San Andreas Fault: Insights from laboratory experiments on SAFOD cuttings and core

NASA Astrophysics Data System (ADS)

Carpenter, B. M.; Marone, C.; Saffer, D. M.

2010-12-01

The debate concerning the apparent low strength of tectonic faults, including the San Andreas Fault (SAF), continues to focus on: 1) low intrinsic friction resulting from mineralogy and/or fabric, and 2) decreased effective normal stress due to elevated pore pressure. Here we inform this debate with laboratory measurements of the frictional behavior and permeability of cuttings and core returned from the SAF at a vertical depth of 2.7 km. We conducted experiments on cuttings and core recovered during SAFOD Phase III drilling. All samples in this study are adjacent to and within the active fault zone penetrated at 10814.5 ft (3296m) measured depth in the SAFOD borehole. We sheared gouge samples composed of drilling cuttings in a double-direct shear configuration subject to true-triaxial loading under constant effective normal stress, confining pressure, and pore pressure. Intact wafers of material were sheared in a single-direct shear configuration under similar conditions of effective stress, confining pressure, and pore pressure. We also report on permeability measurements on intact wafers of wall rock and fault gouge prior to shearing. Initial results from experiments on cuttings show: 1) a weak fault (µ=~0.21) compared to the surrounding wall rock (µ=~0.35), 2) velocity strengthening behavior, (a-b > 0), consistent with aseismic slip, and 3) near zero healing rates in material from the active fault. XRD analysis on cuttings indicates the main mineralogical difference between fault rock and wall rock, is the presence of significant amounts of smectite within the fault rock. Taken together, the measured frictional behavior and clay mineral content suggest that the clay composition exhibits a basic control on fault behavior. Our results document the first direct evidence of weak material from an active fault at seismogenic depths. In addition, our results could explain why the SAF in central California fails aseismically and hosts only small earthquakes.

Thermo-hydro-mechanical coupling in long-term sedimentary rock response

NASA Astrophysics Data System (ADS)

Makhnenko, R. Y.; Podladchikov, Y.

2017-12-01

Storage of nuclear waste or CO2 affects the state of stress and pore pressure in the subsurface and may induce large thermal gradients in the rock formations. In general, the associated coupled thermo-hydro-mechanical effect on long-term rock deformation and fluid flow have to be studied. Principles behind mathematical models for poroviscoelastic response are reviewed, and poroviscous model parameter, the bulk viscosity, is included in the constitutive equations. Time-dependent response (creep) of fluid-filled sedimentary rocks is experimentally quantified at isotropic stress states. Three poroelastic parameters are measured by drained, undrained, and unjacketed geomechanical tests for quartz-rich Berea sandstone, calcite-rich Apulian limestone, and clay-rich Jurassic shale. The bulk viscosity is calculated from the measurements of pore pressure growth under undrained conditions, which requires time scales 104 s. The bulk viscosity is reported to be on the order of 1015 Pa•s for the sandstone, limestone, and shale. It is found to be decreasing with the increase of pore pressure despite corresponding decrease in the effective stress. Additionally, increase of temperature (from 24 ºC to 40 ºC) enhances creep, where the most pronounced effect is reported for the shale with bulk viscosity decrease by a factor of 3. Viscous compaction of fluid-filled porous media allows a generation of a special type of fluid flow instability that leads to formation of high-porosity, high-permeability domains that are able to self-propagate upwards due to interplay between buoyancy and viscous resistance of the deforming porous matrix. This instability is known as "porosity wave" and its formation is possible under conditions applicable to deep CO2 storage in reservoirs and explains creation of high-porosity channels and chimneys. The reported experiments show that the formation of high-permeability pathways is most likely to occur in low-permeable clay-rich materials (caprock representatives) at elevated temperatures.

Experimental and theoretical studies of the effect of temperature on supercritical CO2 adsorption on illite

NASA Astrophysics Data System (ADS)

Joewondo, N.; Zhang, Y.; Prasad, M.

2016-12-01

Sequestration of carbon dioxide in shale has been a subject of interest as the result of the technological advancement in gas shale production. The process involves injection of CO2 to enhance methane recovery and storing CO2 in depleted shale reservoir at elevated pressures. To better understand both shale production and carbon storage one must study the physical phenomena acting at different scales that control the in situ fluid flow. Shale rocks are complex systems with heterogeneous structures and compositions. Pore structures of these systems are in nanometer scales and have significant gas storage capacity and surface area. Adsorption is prominent in nanometer sized pores due to the high attraction between gas molecules and the surface of the pores. Recent studies attempt to find correlation between storage capacity and the rock composition, particularly the clay content. This study, however, focuses on the study of supercritical adsorption of CO2 on pure clay sample. We have built an in-house manometric experimental setup that can be used to study both the equilibrium and kinetics of adsorption. The experiment is conducted at isothermal condition. The study of equilibrium of adsorption gives insight on the storage capacity of these systems, and the study of the kinetics of adsorption is essential in understanding the resistance to fluid transport. The diffusion coefficient, which can be estimated from the dynamic experimental results, is a parameter which quantify diffusion mobility, and is affected by many factors including pressure and temperature. The first part of this paper briefly discusses the study of both equilibrium and kinetics of the CO2 adsorption on illite. Both static and dynamic measurements on the system are compared to theoretical models available in the literature to estimate the storage capacity and the diffusion time constants. The main part of the paper discusses the effect of varying temperature on the static and dynamic experimental results.

Nanoparticles of nickel oxide: growth and organization on zinc-substituted anionic clay matrix by one-pot route at room temperature

NASA Astrophysics Data System (ADS)

Carja, Gabriela; Nakajima, Akira; Dranca, Cristian; Okada, Kiyoshi

2010-10-01

A room temperature nanocarving strategy is developed for the fabrication of nanoparticles of nickel oxide on zinc-substituted anionic clay matrix (Ni/ZnLDH). It is based on the growth and organization of nanoparticles of nickel oxide which occur during the structural reconstruction of the layered structure of the anionic clay in NiSO4 aqueous solution. No organic compounds are used during the fabrication. The described material was characterized by X-ray diffraction (XRD), IR spectroscopy (FTIR), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM), energy dispersive X-ray (EDX) spectroscopy, and X-ray photoelectron spectroscopy (XPS). Results show that the nickel-clay nanoarchitecture consists of small nanoparticles of nickel oxide (average size 7 nm) deposited on the larger nanoparticles (average size 90 nm) of zinc-substituted clay. The optical properties of the new nickel-zinc formulation are studied by UV-Vis.

Structure of peat soils and implications for biogeochemical processes and hydrological flow

NASA Astrophysics Data System (ADS)

Rezanezhad, F.; McCarter, C. P. R.; Gharedaghloo, B.; Kleimeier, C.; Milojevic, T.; Liu, H.; Weber, T. K. D.; Price, J. S.; Quinton, W. L.; Lenartz, B.; Van Cappellen, P.

2017-12-01

Permafrost peatlands contain globally important amounts of soil organic carbon and play major roles in global water, nutrient and biogeochemical cycles. The structure of peatland soils (i.e., peat) are highly complex with unique physical and hydraulic properties; where significant, and only partially reversible, shrinkage occurs during dewatering (including water table fluctuations), compression and/or decomposition. These distinct physical and hydraulic properties controls water flow, which in turn affect reactive and non-reactive solute transport (such as, sorption or degradation) and biogeochemical functions. Additionally, peat further attenuates solute migration through molecular diffusion into the inactive pores of Sphagnum dominated peat. These slow, diffusion-limited solute exchanges between the pore regions may give rise to pore-scale chemical gradients and heterogeneous distributions of microbial habitats and activity in peat soils. Permafrost peat plateaus have the same essential subsurface characteristics as other widely organic soil-covered peatlands, where the hydraulic conductivity is related to the degree of decomposition and soil compression. Increasing levels of decomposition correspond with a reduction of effective pore diameter and consequently restrict water and solute flow (by several orders of magnitude in hydraulic conductivity between the ground surface and a depth of 50 cm). In this presentation, we present the current knowledge of key physical and hydraulic properties related to the structure of globally available peat soils and discuss their implications for water storage, flow and the migration of solutes.

Effect of olive mill waste addition on the properties of porous fired clay bricks using Taguchi method.

PubMed

Sutcu, Mucahit; Ozturk, Savas; Yalamac, Emre; Gencel, Osman

2016-10-01

Production of porous clay bricks lightened by adding olive mill waste as a pore making additive was investigated. Factors influencing the brick manufacturing process were analyzed by an experimental design, Taguchi method, to find out the most favorable conditions for the production of bricks. The optimum process conditions for brick preparation were investigated by studying the effects of mixture ratios (0, 5 and 10 wt%) and firing temperatures (850, 950 and 1050 °C) on the physical, thermal and mechanical properties of the bricks. Apparent density, bulk density, apparent porosity, water absorption, compressive strength, thermal conductivity, microstructure and crystalline phase formations of the fired brick samples were measured. It was found that the use of 10% waste addition reduced the bulk density of the samples up to 1.45 g/cm(3). As the porosities increased from 30.8 to 47.0%, the compressive strengths decreased from 36.9 to 10.26 MPa at firing temperature of 950 °C. The thermal conductivities of samples fired at the same temperature showed a decrease of 31% from 0.638 to 0.436 W/mK, which is hopeful for heat insulation in the buildings. Increasing of the firing temperature also affected their mechanical and physical properties. This study showed that the olive mill waste could be used as a pore maker in brick production. Copyright © 2016 Elsevier Ltd. All rights reserved.

Investigating Interactions between the Silica and Carbon Cycles during Precipitation and Early Diagenesis of Authigenic Clay/Carbonate-Mineral Associations in the Carbonate Rock Record

NASA Astrophysics Data System (ADS)

McKenzie, J. A.; Francisca Martinez Ruiz, F.; Sanchez-Roman, M.; Anjos, S.; Bontognali, T. R. R.; Nascimento, G. S.; Vasconcelos, C.

2017-12-01

The study of authigenic clay/carbonate-mineral associations within carbonate sequences has important implications for the interpretation of scientific problems related with rock reservoir properties, such as alteration of potential porosity and permeability. More specifically, when clay minerals are randomly distributed within the carbonate matrix, it becomes difficult to predict reservoir characteristics. In order to understand this mineral association in the geological record, we have undertaken a comparative study of specially designed laboratory experiments with modern environments, where clay minerals have been shown to precipitate together with a range of carbonate minerals, including calcite, Mg-calcite and dolomite. Two modern dolomite-forming environments, the Coorong lakes, South Australia and Brejo do Espinho Rio de Janeiro, Brazil, were selected for this investigation. For comparative evaluation, enrichment microbial culture experiments, using natural pore water from Brejo do Espinho as the growth medium to promote mineral precipitation, were performed under both aerobic and anaerobic conditions. To establish the environmental parameters and biological processes facilitating the dual mineral association, the experimental samples have been compared with the natural minerals using HRTEM measurements. The results demonstrate that the clay and carbonate minerals apparently do not co-precipitate, but the precipitation of the different minerals in the same sample has probably occurred under different environmental conditions with variable chemistries, e.g., hypersalinity versus normal salinity resulting from the changing ratio of evaporation versus precipitation. Thus, the investigated mineral association is not a product of diagenetic processes but of sequential in situ precipitation processes related to changes in the silica and carbon availability. Implications for ancient carbonate formations will be presented and discussed in the context of a specific example of this clay/carbonate-mineral association recorded in the Lower Cretaceous Codó Formation, NE Brazil (Bahniuk et al., 2015. Sedimentology, 62, 155-181).

Microbially-accelerated consolidation of oil sands tailings. Pathway II: solid phase biogeochemistry.

PubMed

Siddique, Tariq; Kuznetsov, Petr; Kuznetsova, Alsu; Li, Carmen; Young, Rozlyn; Arocena, Joselito M; Foght, Julia M

2014-01-01

Consolidation of clay particles in aqueous tailings suspensions is a major obstacle to effective management of oil sands tailings ponds in northern Alberta, Canada. We have observed that microorganisms indigenous to the tailings ponds accelerate consolidation of mature fine tailings (MFT) during active metabolism by using two biogeochemical pathways. In Pathway I, microbes alter porewater chemistry to indirectly increase consolidation of MFT. Here, we describe Pathway II comprising significant, direct and complementary biogeochemical reactions with MFT mineral surfaces. An anaerobic microbial community comprising Bacteria (predominantly Clostridiales, Synergistaceae, and Desulfobulbaceae) and Archaea (Methanolinea/Methanoregula and Methanosaeta) transformed Fe(III) minerals in MFT to amorphous Fe(II) minerals during methanogenic metabolism of an added organic substrate. Synchrotron analyses suggested that ferrihydrite (5Fe2O3. 9H2O) and goethite (α-FeOOH) were the dominant Fe(III) minerals in MFT. The formation of amorphous iron sulfide (FeS) and possibly green rust entrapped and masked electronegative clay surfaces in amended MFT. Both Pathways I and II reduced the surface charge potential (repulsive forces) of the clay particles in MFT, which aided aggregation of clays and formation of networks of pores, as visualized using cryo-scanning electron microscopy (SEM). These reactions facilitated the egress of porewater from MFT and increased consolidation of tailings solids. These results have large-scale implications for management and reclamation of oil sands tailings ponds, a burgeoning environmental issue for the public and government regulators.

The impact of hazardous waste leachate on performance of clay liners.

PubMed

Mosavat, Nasim; Nalbantoglu, Zalihe

2013-02-01

Penetration of hazardous liquids through waste containment barriers exerts contamination and considerable alterations in geotechnical properties of clay liners. In general, these changes are attributed to the variation of the dielectric constant and the chemistry of the pore fluids which cause changes in soil structure. In the present study, a series of laboratory tests were performed on natural and contaminated clay soil permeated with different hazardous liquids: ethylene glycol and toluene which are generally found in petroleum-contaminated sites, possessing intermediate and low dielectric constants. Toluene was used in its pure form and ethylene glycol was used at various percentages of 0, 20, 40 and 60% by the volume of distilled water. In addition, natural sea water was also utilized as an inorganic fluid for permeation and salinization of the clay soil. The overall test results indicated that plasticity, sedimentation time, unconfined compressive strength, swell and compressibility generally decreased with increasing organic fluid/water concentration, while a slight increase in the permeability values was observed. Pure toluene resulted in diminution of plasticity and considerable flocculation of the particles which caused the soil to become granular. Sea water also caused particle flocculation and reduction in plasticity, swell potential and unconfined compressive strength, although it was noted that compressibility properties remained unchanged compared to distilled water. Finally, the correlation between the electrical resistivity and plasticity index values suggested that the electrical resistivity measurements can be used as a detecting technique for subsurface soil and waste barrier contamination.

Microbially-accelerated consolidation of oil sands tailings. Pathway II: solid phase biogeochemistry

PubMed Central

Siddique, Tariq; Kuznetsov, Petr; Kuznetsova, Alsu; Li, Carmen; Young, Rozlyn; Arocena, Joselito M.; Foght, Julia M.

2014-01-01

Consolidation of clay particles in aqueous tailings suspensions is a major obstacle to effective management of oil sands tailings ponds in northern Alberta, Canada. We have observed that microorganisms indigenous to the tailings ponds accelerate consolidation of mature fine tailings (MFT) during active metabolism by using two biogeochemical pathways. In Pathway I, microbes alter porewater chemistry to indirectly increase consolidation of MFT. Here, we describe Pathway II comprising significant, direct and complementary biogeochemical reactions with MFT mineral surfaces. An anaerobic microbial community comprising Bacteria (predominantly Clostridiales, Synergistaceae, and Desulfobulbaceae) and Archaea (Methanolinea/Methanoregula and Methanosaeta) transformed FeIII minerals in MFT to amorphous FeII minerals during methanogenic metabolism of an added organic substrate. Synchrotron analyses suggested that ferrihydrite (5Fe2O3. 9H2O) and goethite (α-FeOOH) were the dominant FeIII minerals in MFT. The formation of amorphous iron sulfide (FeS) and possibly green rust entrapped and masked electronegative clay surfaces in amended MFT. Both Pathways I and II reduced the surface charge potential (repulsive forces) of the clay particles in MFT, which aided aggregation of clays and formation of networks of pores, as visualized using cryo-scanning electron microscopy (SEM). These reactions facilitated the egress of porewater from MFT and increased consolidation of tailings solids. These results have large-scale implications for management and reclamation of oil sands tailings ponds, a burgeoning environmental issue for the public and government regulators. PMID:24711806

Possible pore size effects on the state of tris(8-quinolinato)aluminum(III) (Alq3) adsorbed in mesoporous silicas and their temperature dependence.

PubMed

Tagaya, Motohiro; Ogawa, Makoto

2008-12-07

The states of tris(8-quinolinato)aluminum(III) (Alq3) adsorbed in mesoporous silicas with different pore sizes (2.5, 3.1 and 5.0 nm) were investigated. Alq3 was successfully occluded into the mesoporous silicas from solution and the adsorbed amount of Alq3 per BET surface area was effectively controlled by changing the added amount Alq3 to the solution. The state of Alq3 in the mesopore varied depending on the pore size as well as the adsorbed amount of Alq3 as revealed by variation of the photoluminescence spectra. The luminescence of the adsorbed Alq3 was found to be temperature-dependent, indicating the mobility of the adsorbed Alq3 to temperature variations. The temperature-dependence also depended on the pore size. The guest-guest interactions between Alq3 molecules as well as the host-guest interactions between Alq3 and the mesopore were controlled by the pore size.

Synthesis and characterization of porous silicon as hydroxyapatite host matrix of biomedical applications.

PubMed

Dussan, A; Bertel, S D; Melo, S F; Mesa, F

2017-01-01

In this work, porous-silicon samples were prepared by electrochemical etching on p-type (B-doped) Silicon (Si) wafers. Hydrofluoric acid (HF)-ethanol (C2H5OH) [HF:Et] and Hydrofluoric acid (HF)-dimethylformamide (DMF-C3H7NO) [HF:DMF] solution concentrations were varied between [1:2]-[1:3] and [1:7]-[1:9], respectively. Effects of synthesis parameters, like current density, solution concentrations, reaction time, on morphological properties were studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements. Pore sizes varying from 20 nm to micrometers were obtained for long reaction times and [HF:Et] [1:2] concentrations; while pore sizes in the same order were observed for [HF:DMF] [1:7], but for shorter reaction time. Greater surface uniformity and pore distribution was obtained for a current density of around 8 mA/cm2 using solutions with DMF. A correlation between reflectance measurements and pore size is presented. The porous-silicon samples were used as substrate for hydroxyapatite growth by sol-gel method. X-ray diffraction (XRD) and SEM were used to characterize the layers grown. It was found that the layer topography obtained on PS samples was characterized by the evidence of Hydroxyapatite in the inter-pore regions and over the surface.

Synthesis and characterization of porous silicon as hydroxyapatite host matrix of biomedical applications

PubMed Central

Dussan, A.; Bertel, S. D.; Melo, S. F.

2017-01-01

In this work, porous-silicon samples were prepared by electrochemical etching on p-type (B-doped) Silicon (Si) wafers. Hydrofluoric acid (HF)-ethanol (C2H5OH) [HF:Et] and Hydrofluoric acid (HF)-dimethylformamide (DMF-C3H7NO) [HF:DMF] solution concentrations were varied between [1:2]—[1:3] and [1:7]—[1:9], respectively. Effects of synthesis parameters, like current density, solution concentrations, reaction time, on morphological properties were studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements. Pore sizes varying from 20 nm to micrometers were obtained for long reaction times and [HF:Et] [1:2] concentrations; while pore sizes in the same order were observed for [HF:DMF] [1:7], but for shorter reaction time. Greater surface uniformity and pore distribution was obtained for a current density of around 8 mA/cm2 using solutions with DMF. A correlation between reflectance measurements and pore size is presented. The porous-silicon samples were used as substrate for hydroxyapatite growth by sol-gel method. X-ray diffraction (XRD) and SEM were used to characterize the layers grown. It was found that the layer topography obtained on PS samples was characterized by the evidence of Hydroxyapatite in the inter-pore regions and over the surface. PMID:28291792

Accounting for sub-resolution pores in models of water and solute transport in soils based on computed tomography images: Are we there yet?

NASA Astrophysics Data System (ADS)

Baveye, Philippe C.; Pot, Valérie; Garnier, Patricia

2017-12-01

In the last decade, X-ray computed tomography (CT) has become widely used to characterize the geometry and topology of the pore space of soils and natural porous media. Regardless of the resolution of CT images, a fundamental problem associated with their use, for example as a starting point in simulation efforts, is that sub-resolution pores are not detected. Over the last few years, a particular type of modeling method, known as ;Grey; or ;Partial Bounce Back; Lattice-Boltzmann (LB), has been adopted by increasing numbers of researchers to try to account for sub-resolution pores in the modeling of water and solute transport in natural porous media. In this short paper, we assess the extent to which Grey LB methods indeed offer a workable solution to the problem at hand. We conclude that, in spite of significant computational advances, a major experimental hurdle related to the evaluation of the penetrability of sub-resolution pores, is blocking the way ahead. This hurdle will need to be cleared before Grey LB can become a credible option in the microscale modeling of soils and sediments. A necessarily interdisciplinary effort, involving both modelers and experimentalists, is needed to clear the path forward.

Characteristics and engineering properties of residual soil of volcanic deposits

NASA Astrophysics Data System (ADS)

Wibawa, Y. S.; Sugiarti, K.; Soebowo, E.

2018-02-01

Residual soil knowledge of volcanic-sedimentary rock products provides important information on the soil bearing capacity and its engineering properties. The residual soil is the result of weathering commonly found in unsaturated conditions, having varied geotechnical characteristics at each level of weathering. This paper summarizes the results of the research from the basic engineering properties of residual soil of volcanic-sedimentary rocks from several different locations. The main engineering properties of residual soil such as specific gravity, porosity, grain size, clay content (X-Ray test) and soil shear strength are performed on volcanic rock deposits. The results show that the variation of the index and engineering properties and the microstructure properties of residual soil have the correlation between the depths of weathering levels. Pore volume and pore size distribution on weathered rock profiles can be used as an indication of weathering levels in the tropics.

X-ray Computed Tomography and Pore Network Modeling to Assess the Impact of Biochar on Saturated Hydraulic Conductivity of Stormwater Infiltration Media

NASA Astrophysics Data System (ADS)

Imhoff, P. T.; Nakhli, S. A. A.; Mills, G.; Yudi, Y.; Abera, K.; Williams, R.; Manahiloh, K. N.; Willson, C. S.

2017-12-01

Biochar has been proposed as an amendment to stormwater infiltration media to enhance pollutant capture (metals, organics) or transformation (e.g., nitrate). Because stormwater media must maintain sufficient infiltration capacity, it is critical that biochar amendment not reduce saturated hydraulic conductivity. We present experimental measurements of saturated hydraulic conductivity for mixtures of wood biochar, sieved to various size fractions, and uniform sands or bioretention media (mixtures of sand, clay, and sawdust). While the influence of biochar on the inter particle pore volume of the mixtures explained most changes in hydraulic conductivity, for mixtures containing large biochar particles results were unexpected. For example, while large biochar particles (2 - 4.75 mm) increased inter particle porosity from 0.35 to 0.48 for a sand/biochar mixture, hydraulic conductivity decreased from 820 ± 90 cm/h to 323 ± 2 cm/h. To understand this and other unusual data, biochar was doped with 3% CsCl, mixed with uniform sand using different packing techniques, and analyzed with X-ray computed tomography to assess biochar distribution and pore structure. Depending on packing technique, biochar particles were either segregated or uniformly mixed, which influenced pore structure. Biochar content and inter particle pore volume determined from X-ray images were in excellent agreement with experimental data (< 5% difference). Grain-based algorithms were then used to generate physically-representative pore networks, and single-phase permeability models were employed to estimate saturated hydraulic conductivity of sand and biochar-amended sand packings for specimens prepared with different packing techniques. Results from these analyses will be presented and compared with experimental measurements to elucidate the mechanisms by which large biochar particles alter the saturated hydraulic conductivity of engineered media.

Development of a pore network simulation model to study nonaqueous phase liquid dissolution

USGS Publications Warehouse

Dillard, Leslie A.; Blunt, Martin J.

2000-01-01

A pore network simulation model was developed to investigate the fundamental physics of nonequilibrium nonaqueous phase liquid (NAPL) dissolution. The network model is a lattice of cubic chambers and rectangular tubes that represent pore bodies and pore throats, respectively. Experimental data obtained by Powers [1992] were used to develop and validate the model. To ensure the network model was representative of a real porous medium, the pore size distribution of the network was calibrated by matching simulated and experimental drainage and imbibition capillary pressure‐saturation curves. The predicted network residual styrene blob‐size distribution was nearly identical to the observed distribution. The network model reproduced the observed hydraulic conductivity and produced relative permeability curves that were representative of a poorly consolidated sand. Aqueous‐phase transport was represented by applying the equation for solute flux to the network tubes and solving for solute concentrations in the network chambers. Complete mixing was found to be an appropriate approximation for calculation of chamber concentrations. Mass transfer from NAPL blobs was represented using a corner diffusion model. Predicted results of solute concentration versus Peclet number and of modified Sherwood number versus Peclet number for the network model compare favorably with experimental data for the case in which NAPL blob dissolution was negligible. Predicted results of normalized effluent concentration versus pore volume for the network were similar to the experimental data for the case in which NAPL blob dissolution occurred with time.

Seasonal movement of the Slumgullion landslide determined from global positioning system surveys and field instrumentation, July 1998-March 2002

USGS Publications Warehouse

Coe, J.A.; Ellis, W.L.; Godt, J.W.; Savage, W.Z.; Savage, J.E.; Michael, J.A.; Kibler, J.D.; Powers, P.S.; Lidke, D.J.; Debray, S.

2003-01-01

Measurements of landslide movement made by global positioning system surveys and extensometers over a 3.5-year period show that the Slumgullion landslide in the San Juan Mountains of southwest Colorado moved throughout the monitoring period, but that daily velocities varied on a seasonal basis. Landslide velocities peaked in the early spring and summer in response to snowmelt and summer thunderstorms, respectively. Velocities were slowest in mid-winter when air and soil temperatures were coldest and precipitation was generally low and/or in the form of snow with a low water content. We hypothesize that the seasonal variability in velocities is due to ground-water levels and corresponding pore pressures that decrease when surface water is unavailable or cannot infiltrate frozen landslide material, and increase when surface water from melting snow or rainfall infiltrates unfrozen landslide material. We also suggest that patches of bouldery debris and fractures (created by continuous movement of the landslide) are conduits through which surface water can infiltrate, regardless of the frozen or unfrozen state of the landslide matrix material. Therefore, the availability of surface water is more important than landslide temperature in controlling the rate of landslide movement. This hypothesis is supported by field instrumentation data that show (1) landslide velocities coinciding with precipitation amounts regardless of the depth of freezing of landslide material, (2) spring and annual landslide velocities that were greatest when the depth of freezing was also the greatest, and (3) a rapid (several weeks or less) velocity and pore pressure response to rainfall. The persistent, but seasonally variable movement of the landslide, fits the bathtub model for landslide movement described by Baum and Reid [Baum, R.L., Reid, M.E., 2000. Ground water isolation by low-permeability clays in landslide shear zones. In: Bromhead, E.N., Dixon, N., Ibsen, M.-L. (Eds.), Landslides in Research, Theory and Practice. Proc. 8th Int. Symp. on Landslides, Cardiff, Wales, vol. 1, 139-144]. In their model, the landslide is isolated both mechanically and hydrologically from adjacent materials by low permeability clays. These clays cause the landslide to retain water. Our data support this model by suggesting that pore pressures at the basal landslide surface are always adequate to maintain landslide movement and that any infiltration of water at the surface of the landslide is adequate to rapidly increase landslide velocity. ?? 2002 Elsevier Science B.V. All rights reserved.

Micromechanics investigation of expansive reactions in chemoelastic concrete.

PubMed

Lemarchand, Eric; Dormieux, Luc; Ulm, Franz-Josef

2005-11-15

Expansive reactions damage porous materials through the formation of reaction products of a volume in excess of the available space left by the reactants and the natural porosity of the material. This leads to pressurizing the pore space accessible to the reaction products, which differs when the chemical reaction is through-solution or topochemical or both in nature. This paper investigates expansive reactions from a micromechanical point of view, which allows bridging the scale from the local chemo-mechanical mechanisms to the macroscopically observable stress-free expansion. In particular, the study of the effect of morphology of the pore space, in which the chemical expansion occurs locally, on the macroscopically observable expansion is the main focus of this paper. The first part revisits the through-solution and the topochemical reaction mechanism within the framework of micro-macro-homogenization theories, and the effect of the microscopic geometry of pores and microcracks in the solid matrix on the macroscopic chemical expansion is examined. The second part deals with the transition from a topochemical to a through-solution-like mechanism that occurs in a solid matrix with inclusions (cracks, pores) of different morphology.

Poly(vinyl acetate)/clay nanocomposite materials for organic thin film transistor application.

PubMed

Park, B J; Sung, J H; Park, J H; Choi, J S; Choi, H J

2008-05-01

Nanocomposite materials of poly(vinyl acetate) (PVAc) and organoclay were fabricated, in order to be utilized as dielectric materials of the organic thin film transistor (OTFT). Spin coating condition of the nanocomposite solution was examined considering shear viscosity of the composite materials dissolved in chloroform. Intercalated structure of the PVAc/clay nanocomposites was characterized using both wide-angle X-ray diffraction and TEM. Fracture morphology of the composite film on silicon wafer was also observed by SEM. Dielectric constant (4.15) of the nanocomposite materials shows that the PVAc/clay nanocomposites are applicable for the gate dielectric materials.

Molecular dynamics simulations of trihalomethanes removal from water using boron nitride nanosheets.

PubMed

Azamat, Jafar; Khataee, Alireza; Joo, Sang Woo

2016-04-01

Molecular dynamics simulations were performed to investigate the separation of trihalomethanes (THMs) from water using boron nitride nanosheets (BNNSs). The studied systems included THM molecules and a functionalized BNNS membrane immersed in an aqueous solution. An external pressure was applied to the z axis of the systems. Two functionalized BNNSs with large fluorinated-hydrogenated pore (F-H-pores) and small hydrogen-hydroxyl pore (H-OH-pores) were used. The pores of the BNNS membrane were obtained by passivating each nitrogen and boron atoms at the pore edges with fluorine and hydrogen atoms in the large pore or with hydroxyl and hydrogen atoms in the small pore. The results show that the BNNS with a small functionalized pore was impermeable to THM molecules, in contrast to the BNNS with a large functionalized pore. Using these membranes, water contaminants can be removed at lower cost.

Effective equations governing an active poroelastic medium

PubMed Central

2017-01-01

In this work, we consider the spatial homogenization of a coupled transport and fluid–structure interaction model, to the end of deriving a system of effective equations describing the flow, elastic deformation and transport in an active poroelastic medium. The ‘active’ nature of the material results from a morphoelastic response to a chemical stimulant, in which the growth time scale is strongly separated from other elastic time scales. The resulting effective model is broadly relevant to the study of biological tissue growth, geophysical flows (e.g. swelling in coals and clays) and a wide range of industrial applications (e.g. absorbant hygiene products). The key contribution of this work is the derivation of a system of homogenized partial differential equations describing macroscale growth, coupled to transport of solute, that explicitly incorporates details of the structure and dynamics of the microscopic system, and, moreover, admits finite growth and deformation at the pore scale. The resulting macroscale model comprises a Biot-type system, augmented with additional terms pertaining to growth, coupled to an advection–reaction–diffusion equation. The resultant system of effective equations is then compared with other recent models under a selection of appropriate simplifying asymptotic limits. PMID:28293138

Simulation of solute transport through heterogeneous networks: analysis using the method of moments and the statistics of local transport characteristics.

PubMed

Li, Min; Qi, Tao; Bernabé, Yves; Zhao, Jinzhou; Wang, Ying; Wang, Dong; Wang, Zheming

2018-02-28

We used a time domain random walk approach to simulate passive solute transport in networks. In individual pores, solute transport was modeled as a combination of Poiseuille flow and Taylor dispersion. The solute plume data were interpreted via the method of moments. Analysis of the first and second moments showed that the longitudinal dispersivity increased with increasing coefficient of variation of the pore radii CV and decreasing pore coordination number Z. The third moment was negative and its magnitude grew linearly with time, meaning that the simulated dispersion was intrinsically non-Fickian. The statistics of the Eulerian mean fluid velocities [Formula: see text], the Taylor dispersion coefficients [Formula: see text] and the transit times [Formula: see text] were very complex and strongly affected by CV and Z. In particular, the probability of occurrence of negative velocities grew with increasing CV and decreasing Z. Hence, backward and forward transit times had to be distinguished. The high-τ branch of the transit-times probability curves had a power law form associated to non-Fickian behavior. However, the exponent was insensitive to pore connectivity, although variations of Z affected the third moment growth. Thus, we conclude that both the low- and high-τ branches played a role in generating the observed non-Fickian behavior.

The use of positrons to survey alteration layers on synthetic nuclear waste glasses

NASA Astrophysics Data System (ADS)

Reiser, Joelle T.; Parruzot, Benjamin; Weber, Marc H.; Ryan, Joseph V.; McCloy, John S.; Wall, Nathalie A.

2017-07-01

In order to safeguard society and the environment, understanding radioactive waste glass alteration mechanisms in interactions with solutions and near-field materials, such as Fe, is essential to nuclear waste repository performance assessments. Alteration products are formed at the surface of glasses after reaction with solution. In this study, glass altered in the presence of Fe0 in aqueous solution formed two alteration layers: one embedded with Fe closer to the surface and one without Fe found deeper in the sample. Both layers were found to be thinner than the alteration layer found in glass altered in aqueous solution only. For the first time, Doppler Broadening Positron Annihilation Spectroscopy (DB-PAS) is used to non-destructively characterize the pore structures of glass altered in the presence of Fe0. Advantages and disadvantages of DB-PAS compared to other techniques used to analyze pore structures for altered glass samples are discussed. Ultimately, DB-PAS has shown to be an excellent choice for pore structure characterization for glasses with multiple alteration layers. Monte Carlo modeling predicted positron trajectories through the layers, and helped explain DB-PAS data, which showed that the deeper alteration layer without Fe had a similar composition and pore structure to layers on glass altered in water only.

The use of positrons to survey alteration layers on synthetic nuclear waste glasses

DOE PAGES

Reiser, Joelle T.; Parruzot, Benjamin; Weber, Marc H.; ...

2017-07-01

Here, in order to safeguard society and the environment, understanding radioactive waste glass alteration mechanisms in interactions with solutions and near-field materials, such as Fe, is essential to nuclear waste repository performance assessments. Alteration products are formed at the surface of glasses after reaction with solution. In this study, glass altered in the presence of Fe 0 in aqueous solution formed two alteration layers: one embedded with Fe closer to the surface and one without Fe found deeper in the sample. Both layers were found to be thinner than the alteration layer found in glass altered in aqueous solution only.more » For the first time, Doppler Broadening Positron Annihilation Spectroscopy (DB-PAS) is used to non-destructively characterize the pore structures of glass altered in the presence of Fe 0. Advantages and disadvantages of DB-PAS compared to other techniques used to analyze pore structures for altered glass samples are discussed. Ultimately, DB-PAS has shown to be an excellent choice for pore structure characterization for glasses with multiple alteration layers. Monte Carlo modeling predicted positron trajectories through the layers, and helped explain DB-PAS data, which showed that the deeper alteration layer without Fe had a similar composition and pore structure to layers on glass altered in water only.« less

The use of positrons to survey alteration layers on synthetic nuclear waste glasses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reiser, Joelle T.; Parruzot, Benjamin; Weber, Marc H.

Here, in order to safeguard society and the environment, understanding radioactive waste glass alteration mechanisms in interactions with solutions and near-field materials, such as Fe, is essential to nuclear waste repository performance assessments. Alteration products are formed at the surface of glasses after reaction with solution. In this study, glass altered in the presence of Fe 0 in aqueous solution formed two alteration layers: one embedded with Fe closer to the surface and one without Fe found deeper in the sample. Both layers were found to be thinner than the alteration layer found in glass altered in aqueous solution only.more » For the first time, Doppler Broadening Positron Annihilation Spectroscopy (DB-PAS) is used to non-destructively characterize the pore structures of glass altered in the presence of Fe 0. Advantages and disadvantages of DB-PAS compared to other techniques used to analyze pore structures for altered glass samples are discussed. Ultimately, DB-PAS has shown to be an excellent choice for pore structure characterization for glasses with multiple alteration layers. Monte Carlo modeling predicted positron trajectories through the layers, and helped explain DB-PAS data, which showed that the deeper alteration layer without Fe had a similar composition and pore structure to layers on glass altered in water only.« less

Smectite clays in Mars soil: evidence for their presence and role in Viking biology experimental results.

PubMed

Banin, A; Rishpon, J

1979-12-01

Various chemical, physical and geological observations indicate that smectite clays are probably the major components of the Martian soil. Satisfactory ground-based chemical simulation of the Viking biology experimental results was obtained with the smectite clays nontronite and montmorillonite when they contained iron and hydrogen as adsorbed ions. Radioactive gas was released from the medium solution used in the Viking Labeled Release (LR) experiment when interacted with the clays, at rates and quantities similar to those measured by Viking on Mars. Heating of the active clay (mixed with soluble salts) to 160 degrees C in CO2 atmosphere reduced the decomposition activity considerably, again, as was observed on Mars. The decomposition reaction in LR experiment is postulated to be iron-catalyzed formate decomposition on the clay surface. The main features of the Viking Pyrolytic Release (PR) experiment were also simulated recently (Hubbard, 1979) which the iron clays, including a relatively low '1st peak' and significant '2nd peak'. The accumulated observations on various Martian soil properties and the results of simulation experiments, thus indicate that smectite clays are major and active components of the Martian soil. It now appears that many of the results of the Viking biology experiments can be explained on the basis of their surface activity in catalysis and adsorption.

Effect of the solvent on the size of clay nanoparticles in solution as determined using an ultraviolet-visible (UV-Vis) spectroscopy methodology.

PubMed

Alin, Jonas; Rubino, Maria; Auras, Rafael

2015-06-01

Ultraviolet-visible (UV-Vis) spectroscopy methodology was developed and utilized for the in situ nanoscale measurement of the size of mineral clay agglomerates in various liquid suspensions. The clays studied were organomodified and unmodified montmorillonite clays (I.44p, Cloisite 93a, and PGN). The methodology was compared and validated against dynamic light scattering (DLS) analysis. The method was able to measure clay agglomerates in solvents in situations where DLS analysis was unsuccessful due to the shapes, polydispersity, and high aspect ratios of the clay particles and the complexity of the aggregates, or dispersion medium. The measured clay agglomerates in suspension were found to be in the nanometer range in the more compatible solvents, and their sizes correlated with the Hansen solubility parameter space distance between the clay modifiers and the solvents. Mass detection limits for size determination were in the range from 1 to 9 mg/L. The methodology thus provides simple, rapid, and inexpensive characterization of clays or particles in the nano- or microsize range in low concentrations in various liquid media, including complex mixtures or highly viscous fluids that are difficult to analyze with DLS. In addition, by combining UV-VIS spectroscopy with DLS it was possible to discern flocculation behavior in liquids, which otherwise could result in false size measurements by DLS alone.

Evaluation of physico-mechanical properties of clayey soils using electrical resistivity imaging technique

NASA Astrophysics Data System (ADS)

Kibria, Golam

Resistivity imaging (RI) is a promising approach to obtaining continuous profile of soil subsurface. This method offers simple technique to identify moisture variation and heterogeneity of the investigated area. However, at present, only qualitative information of subsurface can be obtained using RI. A study on the quantification of geotechnical properties has become important for rigorous use of this method in the evaluation of geohazard potential and construction quality control of landfill liner system. Several studies have been performed to describe electrical resistivity of soil as a function of pore fluid conductivity and surface conductance. However, characterization tests on pore water and surface charge are not typically performed in a conventional geotechnical investigation. The overall objective of this study is to develop correlations between geotechnical parameters and electrical resistivity of soil, which would provide a mean to estimate geotechnical properties from RI. As a part of the study, multiple regression analyses were conducted to develop practically applicable models correlating resistivity with influential geotechnical parameters. The soil samples considered in this study were classified as highly plastic clay (CH) and low plasticity clay (CL) according to Unified Soil Classification System (USCS). Based on the physical tests, scanning electron microscope (SEM), and energy dispersive X-ray spectroscopy (EDS) analysis, kaolinite was identified as the dominant mineral with some traces of magnesium, calcium, potassium, and iron. Electrical resistivity tests were conducted on compacted clays and undisturbed samples under varied geotechnical conditions. The experimental results indicated that the degree of saturation substantially influenced electrical resistivity. Electrical resistivity decreased as much as 11 times from initial value for the increase of degree of saturation from 23 to 100% in the laboratory tests on compacted clays. In case of undisturbed soil samples, resistivity decreased as much as sixteen fold (49.4 to 3.2 Ohm-m) for an increase of saturation from 31 to 100%. Furthermore, the resistivity results were different for the specimens at a specific degree of saturation because of varied surface activity and isomorphous substitution of clayey soils. In addition to physical properties, compressibility of clays was correlated with electrical conductivity. Based on the investigation, it was determined that the electrical conductivity vs. pressure curves followed similar trends as e vs. logp curves. Multiple linear regression (MLR) models were developed for compacted and undisturbed samples using statistical analysis software SAS (2009). During model development, degree of saturation and CEC were selected as independent variables. The proposed models were validated using experimental results on a different set of samples. Moreover, the applicability of the models in the determination of degrees of saturation was evaluated using field RI tests.

Experimental Investigation on Pore Structure Characterization of Concrete Exposed to Water and Chlorides

PubMed Central

Liu, Jun; Tang, Kaifeng; Qiu, Qiwen; Pan, Dong; Lei, Zongru; Xing, Feng

2014-01-01

In this paper, the pore structure characterization of concrete exposed to deionised water and 5% NaCl solution was evaluated using mercury intrusion porosity (MIP), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effects of calcium leaching, fly ash incorporation, and chloride ions on the evolution of pore structure characteristics were investigated. The results demonstrate that: (i) in ordinary concrete without any fly ash, the leaching effect of the cement products is more evident than the cement hydration effect. From the experimental data, Ca(OH)2 is leached considerably with the increase in immersion time. The pore structure of concrete can also be affected by the formation of an oriented structure of water in concrete materials; (ii) incorporation of fly ash makes a difference for the performance of concrete submersed in solutions as the total porosity and the pore connectivity can be lower. Especially when the dosage of fly ash is up to 30%, the pores with the diameter of larger than 100 nm show significant decrease. It demonstrates that the pore properties are improved by fly ash, which enhances the resistance against the calcium leaching; (iii) chlorides have a significant impact on microstructure of concrete materials because of the chemical interactions between the chlorides and cement hydrates. PMID:28788204

Absence of plant uptake and translocation of polybrominated biphenyls (PBBs).

PubMed

Chou, S F; Jacobs, L W; Penner, D; Tiedje, J M

1978-04-01

Studies of polybrominated biphenyl (PBB) uptake by plants have been conducted in hydroponic solutions and in greenhouse experiments with soil. Autoradiograms of corn and soybean seedlings grown in hydroponic solutions showed no translocation of 14C-PBB from 14C-PBB-treated solutions to plant tops or within the leaf from 14C-PBB-treated spots on the upper leaf surface. A significant portion of the 14C-PBB associated with the roots was removed when the roots were dipped in acetone. Three root crops (radishes, carrots, and onions) were grown in two soils, each treated with a mixture of FireMaster BP-6 (PBB) and 14C-PBB to achieve final concentrations of 100 ppm and 100 ppb. All roots showed more PBB when grown in the soil with the lower clay and organic matter content than they did when grown in the soil with more clay and organic matter. In the latter soil (clay loam) no PBB was detected in any roots from the 100 ppb treatment. More PBB was associated with roots of carrot than of radish or onion. Corn leaf whorls containing dust from a PBB contamination soil and washed radishes from a heavily contaminated garden showed no PBB.

Iodide uptake by negatively charged clay interlayers?

PubMed

Miller, Andrew; Kruichak, Jessica; Mills, Melissa; Wang, Yifeng

2015-09-01

Understanding iodide interactions with clay minerals is critical to quantifying risk associated with nuclear waste disposal. Current thought assumes that iodide does not interact directly with clay minerals due to electrical repulsion between the iodide and the negatively charged clay layers. However, a growing body of work indicates a weak interaction between iodide and clays. The goal of this contribution is to report a conceptual model for iodide interaction with clays by considering clay mineral structures and emergent behaviors of chemical species in confined spaces. To approach the problem, a suite of clay minerals was used with varying degrees of isomorphic substitution, chemical composition, and mineral structure. Iodide uptake experiments were completed with each of these minerals in a range of swamping electrolyte identities (NaCl, NaBr, KCl) and concentrations. Iodide uptake behaviors form distinct trends with cation exchange capacity and mineral structure. These trends change substantially with electrolyte composition and concentration, but do not appear to be affected by solution pH. The experimental results suggest that iodide may directly interact with clays by forming ion-pairs (e.g., NaI(aq)) which may concentrate within the interlayer space as well as the thin areas surrounding the clay particle where water behavior is more structured relative to bulk water. Ion pairing and iodide concentration in these zones is probably driven by the reduced dielectric constant of water in confined space and by the relatively high polarizability of the iodide species. Copyright © 2015 Elsevier Ltd. All rights reserved.

The Capacity for Compaction Weakening in Fault Gouge in Nature and Experiment

NASA Astrophysics Data System (ADS)

Faulkner, D.; Boulton, C. J.; Sanchez Roa, C.; Den Hartog, S. A. M.; Bedford, J. D.

2017-12-01

As faults form in low permeability rocks, the compaction of fault gouge can lead to significant pore-fluid pressure increases. The pore pressure increase results from the collapse of the porosity through shear-enhanced compaction and the low hydraulic diffusivity of the gouge that inhibits fluid flow. In experiments, the frictional properties of clay-bearing fault gouges are significantly affected by the development of locally high pore-fluid pressures when compaction rates are high due to fast displacement rates or slip in underconsolidated materials. We show how the coefficient of friction of fault gouges sheared at different slip velocities can be explained with a numerical model that is constrained by laboratory measurements of contemporaneous changes in permeability and porosity. In nature, for compaction weakening to play an important role in earthquake nucleation (and rupture propagation), a mechanism is required to reset the porosity, i.e., maintain underconsolidated gouge along the fault plane. We use the observations of structures within the principal slip zone of the Alpine Fault in New Zealand to suggest that cyclic fluidization of the gouge occurs during coseismic slip, thereby resetting the gouge porosity prior to the next seismic event. Results from confined laboratory rotary shear measurements at elevated slip rates appear to support the hypothesis that fluidization leads to underconsolidation and, thus, to potential weakening by shear-enhanced compaction-induced pore-fluid pressurization.

Chemical Mechanisms of Toxic Solute Interactions with Soil Constituents

DTIC Science & Technology

1993-04-01

been widely reported (References 125-127). However, in days such as montmorillonite and kaolinite , whose cations have been (partially) exchanged with...matrix-isolation methods were used to characterize the sorption of water and fuel compounds on a model soil consisting of montmorillonite clay. The...only under very dry conditions. 14. SUBJECT TERMS Montmorillonite clay, fuels, infrared 15 NUMBER Of PAGES spectroscopy, ultraviolet-visible

Information Control: Preserving the Advantage

DTIC Science & Technology

2015-06-01

sanitary laboratory for US forces to exploit technical solutions with minimal resistance, inevitably leading to potent and promising results on the...parity, eventually forcing decision makers to pursue bilateral and multilateral agreements in space law. See McDougall, 272. 21 James Clay Moltz, The...the discussions of human nature, control, and strategy outlined in Chapter 1. 12 James Clay Moltz, The Politics of Space Security: Strategic Restraint

Rates and time scales of clay-mineral formation by weathering in saprolitic regoliths of the southern Appalachians from geochemical mass balance

Treesearch

Jason R. Price; Michael A. Velbel; Lina C. Patino

2005-01-01

Rates of clay formation in three watersheds located at the Coweeta Hydrologic Laboratory, western North Carolina, have been determined from solute flux-based mass balance methods. A system of mass balance equations with enough equations and unknowns to allow calculation of secondary mineral formation rates as well as the more commonly determined primary-...

Sorption of Hydrophobic Organic Compounds on Natural Sorbents and Organoclays from Aqueous and Non-Aqueous Solutions: A Mini-Review

PubMed Central

Moyo, Francis; Tandlich, Roman; Wilhelmi, Brendan S.; Balaz, Stefan

2014-01-01

Renewed focus on the sorption of hydrophobic organic chemicals (HOCs) onto mineral surfaces and soil components is required due to the increased and wider range of organic pollutants being released into the environment. This mini-review examines the possibility of the contribution and mechanism of HOC sorption onto clay mineral sorbents such as kaolinite, and soil organic matter and the possible role of both in the prevention of environmental contamination by HOCs. Literature data indicates that certain siloxane surfaces can be hydrophobic. Therefore soils can retain HOCs even at low soil organic levels and the extent will depend on the structure of the pollutant and the type and concentration of clay minerals in the sorbent. Clay minerals are wettable by nonpolar solvents and so sorption of HOCs onto them from aqueous and non-aqueous solutions is possible. This is important for two reasons: firstly, the movement and remediation of soil environments will be a function of the concentration and type of clay minerals in the soil. Secondly, low-cost sorbents such as kaolinite and expandable clays can be added to soils or contaminated environments as temporary retention barriers for HOCs. Inorganic cations sorbed onto the kaolinite have a strong influence on the rate and extent of sorption of hydrophobic organic pollutants onto kaolinite. Structural sorbate classes that can be retained by the kaolinite matrix are limited by hydrogen bonding between hydroxyl groups of the octahedral alumosilicate sheet and the tetrahedral sheet with silicon. Soil organic carbon plays a key role in the sorption of HOCs onto soils, but the extent will be strongly affected by the structure of the organic soil matter and the presence of soot. Structural characterisation of soil organic matter in a particular soil should be conducted during a particular contamination event. Contamination by mining extractants and antibiotics will require renewed focus on the use of the QSAR approaches in the context of the sorption of HOCs onto clay minerals from aqueous and non-aqueous solutions. PMID:24821385

A Review of Darcy's Law: Limitations and Alternatives for Predicting Solute Transport

NASA Astrophysics Data System (ADS)

Steenhuis, Tammo; Kung, K.-J. Sam; Jaynes, Dan; Helling, Charles S.; Gish, Tim; Kladivko, Eileen

2016-04-01

Darcy's Law that was derived originally empirically 160 years ago, has been used successfully in calculating the (Darcy) flux in porous media throughout the world. However, field and laboratory experiments have demonstrated that the Darcy flux employed in the convective disperse equation could only successfully predict solute transport under two conditions: (1) uniformly or densely packed porous media; and (2) field soils under relatively dry condition. Employing the Darcy flux for solute transport in porous media with preferential flow pathways was problematic. In this paper we examine the theoretical background behind these field and laboratory observations and then provide an alternative to predict solute movement. By examining the characteristics of the momentum conservation principles on which Darcy's law is based, we show under what conditions Darcy flux can predict solute transport in porous media of various complexity. We find that, based on several case studies with capillary pores, Darcy's Law inherently merges momentum and in that way erases information on pore-scale velocities. For that reason the Darcy flux cannot predict flow in media with preferential flow conduits where individual pore velocities are essential in predicting the shape of the breakthrough curve and especially "the early arrival" of solutes. To overcome the limitations of the assumption in Darcy's law, we use Jury's conceptualization and employ the measured chemical breakthrough curve as input to characterize the impact of individual preferential flow pathways on chemical transport. Specifically, we discuss how best to take advantage of Jury's conceptualization to extract the pore-scale flow velocity to accurately predict chemical transport through soils with preferential flow pathways.

Dynamics of water in LiCl and CaCl 2 aqueous solutions confined in silica matrices: A backscattering neutron spectroscopy study

NASA Astrophysics Data System (ADS)

Mamontov, E.; Cole, D. R.; Dai, S.; Pawel, M. D.; Liang, C. D.; Jenkins, T.; Gasparovic, G.; Kintzel, E.

2008-09-01

Backscattering neutron spectroscopy was used to probe the dynamics of water molecules in LiCl and CaCl 2 aqueous solutions confined in 2.7, 1.9, and 1.4 nm diameter pores of various silica matrices. The pore size of 2.7 nm was found to be sufficiently large for the confined liquids to exhibit characteristic traits of bulk behavior, such as a freezing-melting transition and a phase separation. On the other hand, none of the fluids in the 1.4 nm pores exhibited a clear freezing-melting transition; instead, their dynamics at low temperatures gradually became too slow for the nanosecond resolution of the experiment. The greatest suppression of water mobility was observed in the CaCl 2 solutions, which suggests that cation charge and perhaps the cation hydration environment have a profound influence on the dynamics of the water molecules. Quasielastic neutron scattering measurements of pure H 2O and 1 m LiCl-H 2O solution confined in 1.9 nm pores revealed a dynamic transition in both liquids at practically the same temperature of 225-226 K, even though the dynamics of the solution at room temperature appeared to slow down by more than an order of magnitude compared to the pure water. The observation of the dynamic transition in the solution suggests that this transition may be a universal feature of water governed by processes acting on the local scale, such as a change in the hydrogen bonding.

Long-Term Changes in Chemical Weathering in the Himalayan Region from Indus Fan Sediments

NASA Astrophysics Data System (ADS)

Carter, S.; Griffith, E. M.; Scher, H.; Dellapenna, T. M.; Clift, P. D.

2017-12-01

The Asian Monsoon reflects large-scale interactions between the atmosphere, land, and ocean systems. Increasing our understanding of this system, how and why it has evolved through time, is critically important in order to understand how it may evolve in the future. The radiogenic strontium isotopic signature (87Sr/86Sr) of the clay fraction in deep sea sediment cores within submarine fans has been used as a record of riverine 87Sr/86Sr composition to gain information about Himalayan weathering intensity. Strontium exists in clay minerals primarily in interlayer sites or adsorbed onto mineral surfaces. Interlayer cation exchange is thought to be completed within rivers during recrystallization or neoformation of clays. A record of chemical weathering intensity in the Himalayas is presented by analyzing the 87Sr/86Sr signature of the clay fraction in sediments from International Ocean Discovery Program (IODP) Expedition 355 Sites U1456 and U1457, located on the Indus Fan, eastern Arabian Sea. This record will be coupled with additional records of bulk grain size and K/Al ratios of clay as potentially additional indicators of weathering intensity. The Sr isotopes in the interstitial waters at each site have also been measured (Carter et al., in press) to verify that the Sr in the treated clay fraction is not being reset by diagenesis in the sedimentary column. Initial results verify that the 87Sr/86Sr values of the clay are less than those in the bulk sediment, as expected, but are not similar to pore fluid Sr. 87Sr/86Sr values of the clays show trends suggesting fluctuations in chemical weathering intensity through time. However, bulk grain size and K/Al ratios results conflict with the 87Sr/86Sr values. If the additional proxy records continue to show conflicting results for "weathering intensity", together they may reveal more information regarding the sedimentary system. Ultimately, the various records will either agree, providing strong evidence for changes in chemical weathering and the evolution of the monsoon, or disagree, allowing for further investigation into the relationships between chemical weathering, evolution of the flood plain, and sediment deposition in the fan. These new records will aid in the correlation of Himalayan exhumation and monsoon intensity and help to constrain this dynamic system.

The Status of Water in Swelling Shales: An Insight from the Water Retention Properties of the Callovo-Oxfordian Claystone

NASA Astrophysics Data System (ADS)

Menaceur, Hamza; Delage, Pierre; Tang, Anh Minh; Talandier, Jean

2016-12-01

The Callovo-Oxfordian (COx) claystone is considered in France as a possible host rock for the disposal of high-level long-lived radioactive waste at great depth. During the operational phase, the walls of the galleries and of the disposal cells will be successively subjected to desaturation induced by ventilation followed by resaturation once the galleries are closed. To better understand this phenomenon, a sound understanding of the water retention properties of the COx claystone is necessary. Following a previous study by the same group, this paper presents an investigation of microstructure changes in COx claystone under suction changes. Microstructure was investigated by means of mercury intrusion porosimetry tests on freeze-dried specimens previously submitted to various suctions. Along the drying path, the initial microstructure, characterised by a well-classified unimodal pore population around a mean diameter value of 32 nm, slightly changed with the same shape of the PSD curve and slightly moved towards smaller diameters (27-28 nm) at suctions of 150 and 331 MPa, respectively. The infra-porosity too small to be intruded by mercury (diameter smaller than 5.5 nm) reduced from 4.3 to 3.3 %. Oven drying reduced the mean diameter to 20 nm and the infra-porosity to 1 %. Wetting up to 9 MPa suction leads to saturation with no significant change in the PSD curve, whereas wetting at zero suction gave rise to the appearance of a large pore population resulting from the development of cracks with width of several micrometres, together with an enlargement of the initial pore population above the mean diameter. The concepts describing the step hydration of smectites (by the successive placement within the clay platelets along the smectite faces of 1, 2, 3 and 4 layers of water molecules with respect to the suction applied) appeared relevant to better understand the changes in microstructure of the COx claystone under suction changes. This also allowed to better define the status of water in claystones and shales containing smectite, with a distinction made between the water adsorbed within the clay platelets, and the free inter-platelet water involved in hydromechanical couplings through changes in pore pressure and water transfers.

A general diagram for estimating pore size of ultrafiltration and reverse osmosis membranes

NASA Technical Reports Server (NTRS)

Sarbolouki, M. N.

1982-01-01

A slit sieve model has been used to develop a general correlation between the average pore size of the upstream surface of a membrane and the molecular weight of the solute which it retains by better than 80%. The pore size is determined by means of the correlation using the high retention data from an ultrafiltration (UF) or a reverse osmosis (RO) experiment. The pore population density can also be calculated from the flux data via appropriate equations.

Multisurface modeling of Ni bioavailability to wheat (Triticum aestivum L.) in various soils.

PubMed

Zhao, Xiaopeng; Jiang, Yang; Gu, Xueyuan; Gu, Cheng; Taylor, J Anita; Evans, Les J

2018-07-01

Continual efforts have been made to determine a simple and universal method of estimating heavy metal phytoavailability in terrestrial systems. In the present study, a mechanism-based multi-surface model (MSM) was developed to predict the partition of Ni(II) in soil-solution phases and its bioaccumulation in wheat (Triticum aestivum L.) in 19 Chinese soils with a wide range of soil properties. MSM successfully predicted the Ni(II) dissolution in 0.01 M CaCl 2 extracting solution (R 2  = 0.875). The two-site model for clay fraction improved the prediction, particularly for alkaline soils, because of the additional consideration of edge sites. More crucially, the calculated dissolved Ni(II) was highly correlated with the metal accumulation in wheat (R 2  = 0.820 for roots and 0.817 for shoots). The correlation coefficients for the MSM and various chemical extraction methods have the following order: soil pore water > MSM ≈ diffuse gradient technique (DGT) > soil total Ni > 0.43 M HNO 3  > 0.01 M CaCl 2 . The results suggested that the dissolved Ni(II) calculated using MSM can serve as an effective indicator of the bioavailability of Ni(II) in various soils; hence, MSM can be used as an supplement for metal risk prediction and assessment besides chemical extraction techniques. Copyright © 2018 Elsevier Ltd. All rights reserved.

Sulfur Isotope Fractionation in Marine Pore waters from the Offshore Southwestern Taiwan

NASA Astrophysics Data System (ADS)

Yu, T. L.; Chen, N. C.; Wang, B. S.; Lin, L. H.; Yang, T. F.; Chen, Y. G.; Shen, C. C.

2017-12-01

In this study, we selected two marine sediment cores, 474cm C11 and 252cm EN1, with different sulfate reduction rate due to anaerobic oxidation of methane (AOM) in offshore southwestern Taiwan, to clarify the regional sulfur biogeochemical process. Sulfur isotopic composition in pore waters was determined on a multi-collector inductively coupled mass spectrometer, Thermo NEPTUNE, with 2-sigma reproducibility of ±0.18‰. Our results show that correlation between δ34S values of 21.7-40.6‰ and 21.5-54.3‰, and sulfate contents of 7.1-26.6 and 1.2-27.6mM follows a closed system Rayleigh fractionation model above the sulfate-methane transition zone (SMTZ) at depths of 172.5 cm for core C11 and 212.5 cm for core EN1 below sea floor. At the SMTZ, δ34S reaches the summit of 40.6 ‰, followed by a decreasing trend to 16-20‰ at depth of 172.5-470.0 cm for core C11. Our results suggest that sulfur in pore fluids offshore southwestern Taiwan is controlled by multiple processes including microbial sulfate reduction, barite dissolution and clay dehydration.

Reexamining ultrafiltration and solute transport in groundwater

NASA Astrophysics Data System (ADS)

Neuzil, C. E.; Person, Mark

2017-06-01

Geologic ultrafiltration—slowing of solutes with respect to flowing groundwater—poses a conundrum: it is consistently observed experimentally in clay-rich lithologies, but has been difficult to identify in subsurface data. Resolving this could be important for clarifying clay and shale transport properties at large scales as well as interpreting solute and isotope patterns for applications ranging from nuclear waste repository siting to understanding fluid transport in tectonically active environments. Simulations of one-dimensional NaCl transport across ultrafiltering clay membrane strata constrained by emerging data on geologic membrane properties showed different ultrafiltration effects than have often been envisioned. In relatively high-permeability advection-dominated regimes, salinity increases occurred mostly within membrane units while their effluent salinity initially fell and then rose to match solute delivery. In relatively low-permeability diffusion-dominated regimes, salinity peaked at the membrane upstream boundary and effluent salinity remained low. In both scenarios, however, only modest salinity changes (up to ˜3 g L-1) occurred because of self-limiting tendencies; membrane efficiency declines as salinity rises, and although sediment compaction increases efficiency, it is also decreases permeability and allows diffusive transport to dominate. It appears difficult for ultrafiltration to generate brines as speculated, but widespread and less extreme ultrafiltration effects in the subsurface could be unrecognized. Conditions needed for ultrafiltration are present in settings that include topographically-driven flow systems, confined aquifer systems subjected to injection or withdrawal, compacting basins, and accretionary complexes.

Reexamining ultrafiltration and solute transport in groundwater

USGS Publications Warehouse

Neuzil, Christopher E.; Person, Mark

2017-01-01

Geologic ultrafiltration—slowing of solutes with respect to flowing groundwater—poses a conundrum: it is consistently observed experimentally in clay-rich lithologies, but has been difficult to identify in subsurface data. Resolving this could be important for clarifying clay and shale transport properties at large scales as well as interpreting solute and isotope patterns for applications ranging from nuclear waste repository siting to understanding fluid transport in tectonically active environments. Simulations of one-dimensional NaCl transport across ultrafiltering clay membrane strata constrained by emerging data on geologic membrane properties showed different ultrafiltration effects than have often been envisioned. In relatively high-permeability advection-dominated regimes, salinity increases occurred mostly within membrane units while their effluent salinity initially fell and then rose to match solute delivery. In relatively low-permeability diffusion-dominated regimes, salinity peaked at the membrane upstream boundary and effluent salinity remained low. In both scenarios, however, only modest salinity changes (up to ∼3 g L−1) occurred because of self-limiting tendencies; membrane efficiency declines as salinity rises, and although sediment compaction increases efficiency, it is also decreases permeability and allows diffusive transport to dominate. It appears difficult for ultrafiltration to generate brines as speculated, but widespread and less extreme ultrafiltration effects in the subsurface could be unrecognized. Conditions needed for ultrafiltration are present in settings that include topographically-driven flow systems, confined aquifer systems subjected to injection or withdrawal, compacting basins, and accretionary complexes.

Surface area effects on the reduction of U VI in the presence of synthetic montmorillonite

DOE PAGES

Boyanov, Maxim I.; Latta, Drew E.; Scherer, Michelle M.; ...

2016-12-14

Here, the redox transformations that affect the environmental mobility of metal or radionuclide contaminants typically take place in the presence of mineral or biological surfaces. Adsorption can alter the speciation and free energy of a dissolved ion and can thus change the occurrence, rate, or products of redox reactions relative to those expected in homogenous solution. Here, we investigated the effect of SYn-1, a redox-inactive synthetic montomorillonite clay mineral, on the reduction of U VI by dihydroanthraquinone-2,6 disulfonate (AH 2QDS, the reduced form of the soluble electron shuttle AQDS). We varied the surface:U ratio in a circumneutral bicarbonate solution andmore » measured the valence and atomic coordination of U in the solids using X-ray absorption spectroscopy (XANES and EXAFS). The spectra show that U IV was the predominant product both in the presence or absence of the clay mineral, indicating that adsorption of U VI to clay mineral surface sites does not affect its ability to be reduced by AH 2QDS. In the absence of the clay mineral and at low-to-intermediate surface:U ratios the predominant UIV product was nanoparticulate uraninite, UO 2. At the highest surface:U ratio tested (100 g/L clay mineral and 50 μM U) we observe a decrease in the proportion of uraninite down to 50%, with the remaining U IV present as adsorbed, non-uraninite species. These results are similar to previous findings with magnetite and rutile, where adsorbed U IV were the predominant species below a specific surface coverage and U in excess of this coverage was precipitated as uraninite. The threshold coverage determined here for the SYn-1 clay mineral is 10-100 × lower than that determined for magnetite and rutile, suggesting that clay mineral surfaces may be less important than metal oxides for stabilizing non-uraninite U IV species in natural sediments.« less