WorldWideScience

Sample records for groundwater pore velocity

  1. Bacterial Chemotaxis Toward A NAPL Source Within A Pore-Scale Model Subject to A Range of Groundwater Flow Velocities

    Science.gov (United States)

    Wang, X.; Ford, R. M.

    2010-12-01

    Organic solvents such as toluene are the most widely distributed pollutants in groundwater. Biodegradation of these industrial pollutants requires that microorganisms in the aqueous phase are brought in contact with sources of contamination, which may be dispersed as pore-size organic-phase droplets within the saturated soil matrix. Chemotaxis toward chemical pollutants provides a mechanism for bacteria to migrate to locations of high contamination, which may not normally be accessible to bacteria carried along by groundwater flow, and thus it may improve the efficiency of bioremediation. A microfluidic device was designed to mimic the dissolution of an organic-phase contaminant from a single pore into a larger macropore representing a preferred pathway for microorganisms that are carried along by groundwater flow. The glass windows of the µ-chip allowed image analysis of bacterial distributions within the vicinity of the organic contaminant. Concentrations of chemotactic bacteria P. putida F1 near the organic/aqueous interface were 25% greater than those of a nonchemotactic mutant in the vicinity of toluene for a fluid velocity of 0.5 m/d. For E. coli responding to phenol, the bacterial concentrations were 60% greater than the controls, also at a velocity of 0.5 m/d. Velocities in the macropore were varied over a range that is typical of groundwater velocities from 0.5 to 10 m/d. The accumulation of chemotactic bacteria near the NAPL (nonaqueous phase liquid) chemoattractant source decreased as the fluid velocity increased. At the higher velocities, accumulation of chemotactic bacteria was comparable to the non-chemotactic control experiments. Computer-based simulation using finite element analysis software (COMSOL) was also performed to understand the effects of various model parameters on bacterial chemotaxis to NAPL. There was good agreement between the simulations (generated using reasonable values of the model parameters) and the experimental data for P

  2. Velocities in Solar Pores

    Science.gov (United States)

    Balasubramaniam, K. S.; Keil, S. L.; Smaldone, L. A.

    1996-05-01

    We investigate the three dimensional structure of solar pores and their surroundings using high spatial and spectral resolution data. We present evidence that surface velocities decrease around pores with a corresponding increase in the line-of-sight (LOS) velocities. LOS velocities in pores increase with the strength of the magnetic field. Surface velocities show convergence toward a weak downflow which appear to trace boundaries resembling meso-granular and super granular flows. The observed magnetic fields in the pores appear near these boundaries. We analyze the vertical velocity structure in pores and show that they generally have downflows decreasing exponentially with height, with a scale height of about 90 km. Evidence is also presented for the expanding nature of flux tubes. Finally we describe a phenomenological model for pores. This work was supported by AFOSR Task 2311G3. LAS was partially supported by the Progetto Nazionale Astrofisica e Fisica Cosmica of MURST and Scambi Internazionali of the Universita degli Studi di Napoli Frederico II. National Solar Observatory, NOAO, is operated for the National Science Foundation by AURA, Inc.

  3. Detailed Measurement of Horizontal Groundwater Velocities Without a Borehole

    Science.gov (United States)

    Bakker, M.; Calje, R.; Van der Made, K. J.; Schaars, F.

    2014-12-01

    A new methodology has been developed to measure horizontal groundwater velocities in unconsolidated aquifers. Groundwater velocities are measured with a heat tracer experiment. Temperature is measured along fiber optic cables using a Distributed Temperature Sensing (DTS) system. Fiber optic cables and a separate heating cable are pushed into the ground to depths of tens of meters. The groundwater is heated with the heating cable and the response is measured along several nearby fiber optic cables. The measured temperature responses are used to estimate the distribution of the magnitude and direction of the horizontal groundwater velocity over the entire depth of the cables. The methodology has been applied in a phreatic aquifer in the dune area along the Dutch coast. Significant variations of groundwater velocities with depth were observed even though the dune sand is relatively homogeneous. Major advantages of the new methodology are that the fiber optic cables are in direct contact with the groundwater and that the cables and installation are relatively cheap. No expensive boreholes are needed and consequently measurements are not affected by movement and mixing of water inside a borehole.

  4. Estimating groundwater velocity using apparent resistivity tomography: A sandbox experiment

    Science.gov (United States)

    Chen, J. L.; Chen, C. H.; Kuo, C. L.; Fen, C. S.; Wu, C. C.

    2016-08-01

    The electrical resistivity tomography (ERT) technique can estimate groundwater velocity to within 5% of the pre-set groundwater velocity. The apparent conductivity obtained by the ERT technique is linearly related to the groundwater conductivity, as described by Archie's law. Gaussian-like profiles of the tracer concentration were demonstrated with the ERT technique, and the estimated dispersion coefficient was between 0.0015 and 0.0051 cm2/sec. In terms of monitoring changes in groundwater conductivity, the ERT technique has two major advantages over monitoring wells: (1) it measures a larger area and provides more representative results; and, (2) it does not withdraw groundwater samples, and therefore does not affect the groundwater flow. The objective of this research is to measure groundwater velocity with the ERT technique using only one well. The experiments in this research were divided into two parts. The first part evaluated the accuracy and repeatability of the ERT technique using a dipole-dipole array, and the second part estimated the groundwater velocity in a sandbox using the ERT technique. The length, width, and height of the sandbox, which was made of acrylic, were 1.5, 5, and 1.0 m, respectively. The ERT sandbox was sequentially filled with 5-cm layers of the silica sand to a total height of 70 cm. A total of 32 electrodes spaced every 5-cm were installed in the center of the sandbox. Three monitoring wells were installed along the line of the electrodes. Both no-flow and constant flow (NaCl solution with electrical conductivity and concentration of 5,000 μs/cm and 2.456 g/L, respectively) tracer experiments were conducted.

  5. Pore Pressure Response to Groundwater Fluctuations in Saturated Double-Layered Soil

    Directory of Open Access Journals (Sweden)

    Hongwei Ying

    2015-01-01

    Full Text Available Analytical solutions are developed for one-dimensional consolidation of double-layered saturated soil subjected to groundwater fluctuations. The solutions are derived by an explicit mathematical procedure using Duhamel’s theorem in conjunction with a Fourier series, when groundwater fluctuation is described by a general time-dependent function and assumed to be the pore water pressure variations at the upper boundary. Taking as an example the harmonic groundwater fluctuation, the relevant response of the excess pore water pressure is discussed in detail, and the main influencing factors of the excess pore pressure distribution are analyzed. A dimensionless parameter θ has been introduced because it significantly affects the phase and the amplitude of excess pore pressures. The influences of the coefficients of permeability and compressibility of soil on the excess pore pressure distribution are different and cannot be incorporated into the coefficient of consolidation in double-layered soil. The relative permeability ratio of two clayey soils also plays an important role on the curves of the distributions of the excess pore pressures. The effects of the thickness of the soil layer on the excess pore pressure distribution should be considered together with the dimensionless parameter θ and the permeability and compressibility of the double-layered soil system.

  6. Inversion of Seismic Velocities to obtain the Crack and Pore Aspect Ratio Distribution

    Science.gov (United States)

    Zimmerman, R. W.; David, E. C.

    2010-12-01

    During a hydrostatic experiment, in the elastic regime, P and S elastic wave velocities measured on rock samples generally increase with pressure and reach asymptotic values at high pressures. This increase of seismic velocities with confining pressure is known to be caused by the closure of compliant pores, such as flat “cracks”, and therefore the high-pressure values of the velocities must reflect only the influence of stiff, “equant” pores. If the pores are assumed to be spheroids, the use of an effective medium theory, combined with a crack closure model, gives a model to relate the elastic properties to the microstructure at each pressure. Therefore, the pressure dependence of elastic velocities can be inverted to obtain the pore aspect ratio distribution. This is done more easily using data obtained in dry experiments, since pore fluids have a strong effect on velocities and to some extent mask the effect of the pore geometry. However, thus far most models have used restrictive assumptions, such as assuming that the stiff pores are spherical, or the interactions between inclusions can be neglected (such as Morlier’s method), which is unfortunately not realistic in most cases. Others methods, such as the one developed by Cheng and Toksoz (1979), assume that the rock contains a discrete distribution of crack aspect ratios, and are complicated to implement numerically. Moreover, in most work only the dry data have been inverted, or jointly the dry and wet data, but it seems that few works have tried to look in detail at a consistent pore model, that remains simple and is able to predict the dependence of Vp and Vs under saturated conditions, based on data collected on dry rocks. We assume that the rock contains a distribution of cracks with different aspect ratios, and two families of stiff pores, each with their own finite aspect ratio. We use this model to invert the wavespeeds to obtain aspect ratio distributions of some isotropic sandstones (Berea

  7. Pore water pressure variations in Subpermafrost groundwater : Numerical modeling compared with experimental modeling

    Science.gov (United States)

    Rivière, Agnès.; Goncalves, Julio; Jost, Anne; Font, Marianne

    2010-05-01

    Development and degradation of permafrost directly affect numerous hydrogeological processes such as thermal regime, exchange between river and groundwater, groundwater flows patterns and groundwater recharge (Michel, 1994). Groundwater in permafrost area is subdivided into two zones: suprapermafrost and subpermafrost which are separated by permafrost. As a result of the volumetric expansion of water upon freezing and assuming ice lenses and frost heave do not form freezing in a saturated aquifer, the progressive formation of permafrost leads to the pressurization of the subpermafrost groundwater (Wang, 2006). Therefore disappearance or aggradation of permafrost modifies the confined or unconfined state of subpermafrost groundwater. Our study focuses on modifications of pore water pressure of subpermafrost groundwater which could appear during thawing and freezing of soil. Numerical simulation allows elucidation of some of these processes. Our numerical model accounts for phase changes for coupled heat transport and variably saturated flow involving cycles of freezing and thawing. The flow model is a combination of a one-dimensional channel flow model which uses Manning-Strickler equation and a two-dimensional vertically groundwater flow model using Richards equation. Numerical simulation of heat transport consisted in a two dimensional model accounting for the effects of latent heat of phase change of water associated with melting/freezing cycles which incorporated the advection-diffusion equation describing heat-transfer in porous media. The change of hydraulic conductivity and thermal conductivity are considered by our numerical model. The model was evaluated by comparing predictions with data from laboratory freezing experiments. Experimental design was undertaken at the Laboratory M2C (Univesité de Caen-Basse Normandie, CNRS, France). The device consisted of a Plexiglas box insulated on all sides except on the top. Precipitation and ambient temperature are

  8. Estimation of the pore pressure distribution from three dimensional groundwater flow model at mine sites in Korea

    Science.gov (United States)

    Kang, Sangsoo; Jang, Myounghwan; Kim, Gyoungman; Kim, Donghui; Kim, Daehoon; Baek, Hwanjo

    2016-04-01

    Mining activities continually change the groundwater flow and associated pore pressure distributions within the rockmass around the mine openings or the open-pit bench during the operational periods. As the pore pressure distributions may substantially affect the mechanical behaviour or stability of the rockmass, it is important to monitor the variation of pore pressure incurred by mining operation. The pore pressure distributions within the rockmass can be derived using a two- or three-dimensional finite element groundwater flow model, adopted to simulate the groundwater flow. While the groundwater inflow at mines has generally been dealt with respect to the working environment, detailed case studies on the distribution of pore water pressure related to the stability analysis of mine openings have been relatively rare in Korea. Recently, however, as the health and safety problems are emerged for sustainable mining practice, these issues are of the major concerns for the mining industries. This study aims to establish a three dimensional groundwater flow model to estimate the pore pressure distributions in order to employ as an input parameter for numerical codes such as the FLAC 3D. Also, the groundwater flow simulated can be used for de-watering design at a mine site. The MINEDW code, a groundwater flow model code specifically developed to simulate the complicated hydro-geologic conditions related to mining, has mainly been used in this study. Based on the data collected from field surveys and literature reviews, a conceptual model was established and sensitivity analysis was performed.

  9. The effect of groundwater fluctuations on the velocity pattern of slow-moving landslides

    Directory of Open Access Journals (Sweden)

    Th. W. J. van Asch

    2009-05-01

    Full Text Available Slow-moving landslides show complex mechanical and fluid interactions. They show among others non linear intrinsic viscosity of the shear zone, undrained loading effects and the generation of excess pore water pressure. The parameterization of hydrological and geomechanical factors by field and laboratory tests to describe the movement pattern of these landslides is difficult. It is a challenge to simulate accurately the de- and acceleration of these landslides and particularly, to forecast catastrophic surges.

    In this paper the relation between groundwater fluctuation and landslide velocity for two deep-seated landslides of the Trièves Plateau (the Monestier-du-Percy landslide and the Saint-Guillaume landslide is analysed. Inclinometer measurements, showing the displacement in depth after 1–2 months periods, showed on both landslides shear band deformation within 1 m. At the Monestier-du-Percy landslide, depending on the position, the shear band depths vary between 25.0 m and 10.0 m. At the Saint-Guillaume landslide, the inclinometers detected several slip surfaces inside the clays, at respectively 37.0 m, 34.5 m, and 14.0 m depth. Two simple geomechanical models are developed to describe these displacements in depth in relation to measured groundwater fluctuations. Calibration of the models using the friction angle delivered no constant values for different measuring periods. It appeared that calibrated (apparent friction values increase with increasing groundwater levels. The paper discusses the possibility of the generation of negative excess pore water pressures as a feed back mechanism, which may explain the complex displacement pattern of these landslides developed in varved clays.

  10. On the importance of diffusion and compound-specific mixing for groundwater transport: an investigation from pore to field scale.

    Science.gov (United States)

    Rolle, Massimo; Chiogna, Gabriele; Hochstetler, David L; Kitanidis, Peter K

    2013-10-01

    Mixing processes significantly affect and limit contaminant transport and transformation rates in the subsurface. The correct quantification of mixing in groundwater systems must account for diffusion, local-scale dispersion and the flow variability in heterogeneous flow fields (e.g., flow-focusing in high-conductivity and de-focusing in low-conductivity zones). Recent results of multitracer laboratory experiments revealed the significant effect of compound-specific diffusive properties on the physical displacement of dissolved species across a representative range of groundwater flow velocities. The goal of this study is to investigate the role of diffusion and compound-specific mixing for solute transport across a range of scales including: (i) pore-scale (~10⁻² m), (ii) laboratory bench-scale (~10⁰ m) and (iii) field-scale (~10² m). We investigate both conservative and mixing-controlled reactive transport using pore-scale modeling, flow-through laboratory experiments and simulations, and field-scale numerical modeling of complex heterogeneous hydraulic conductivity fields with statistical properties similar to the ones reported for the extensively investigated Borden aquifer (Ontario, Canada) and Columbus aquifer (Mississippi, USA, also known as MADE site). We consider different steady-state and transient transport scenarios. For the conservative cases we use as a metric of mixing the exponential of the Shannon entropy to quantify solute dilution either in a given volume (dilution index) or in a given solute flux (flux-related dilution index). The decrease in the mass and the mass-flux of the contaminant plumes is evaluated to quantify reactive mixing. The results show that diffusive processes, occurring at the small-scale of a pore channel, strongly affect conservative and reactive solute transport at larger macroscopic scales. The outcomes of our study illustrate the need to consider and properly account for compound-specific diffusion and mixing

  11. Transport upscaling from pore- to Darcy-scale: Incorporating pore-scale Berea sandstone Lagrangian velocity statistics into a Darcy-scale transport CTRW model

    Science.gov (United States)

    Puyguiraud, Alexandre; Dentz, Marco; Gouze, Philippe

    2017-04-01

    For the past several years a lot of attention has been given to pore-scale flow in order to understand and model transport, mixing and reaction in porous media. Nevertheless we believe that an accurate study of spatial and temporal evolution of velocities could bring important additional information for the upscaling from pore to higher scales. To gather these pieces of information, we perform Stokes flow simulations on pore-scale digitized images of a Berea sandstone core. First, micro-tomography (XRMT) imaging and segmentation processes allow us to obtain 3D black and white images of the sample [1]. Then we used an OpenFoam solver to perform the Stokes flow simulations mentioned above, which gives us the velocities at the interfaces of a cubic mesh. Subsequently, we use a particle streamline reconstruction technique which uses the Eulerian velocity field previously obtained. This technique, based on a modified Pollock algorithm [2], enables us to make particle tracking simulations on the digitized sample. In order to build a stochastic pore-scale transport model, we analyze the Lagrangian velocity series in two different ways. First we investigate the velocity evolution by sampling isochronically (t-Lagrangian), and by studying its statistical properties in terms of one- and two-points statistics. Intermittent patterns can be observed. These are due to the persistance of low velocities over a characteristic space length. Other results are investigated, such as correlation functions and velocity PDFs, which permit us to study more deeply this persistence in the velocities and to compute the correlation times. However, with the second approach, doing these same analysis in space by computing the velocities equidistantly, enables us to remove the intermittency shown in the temporal evolution and to model these velocity series as a Markov process. This renders the stochastic particle dynamics into a CTRW [3]. [1] Gjetvaj, F., A. Russian, P. Gouze, and M. Dentz (2015

  12. Pore space characterization in carbonate rocks - Approach to combine nuclear magnetic resonance and elastic wave velocity measurements

    Science.gov (United States)

    Müller-Huber, Edith; Schön, Jürgen; Börner, Frank

    2016-04-01

    Pore space features influence petrophysical parameters such as porosity, permeability, elastic wave velocity or nuclear magnetic resonance (NMR). Therefore they are essential to describe the spatial distribution of petrophysical parameters in the subsurface, which is crucial for efficient reservoir characterization especially in carbonate rocks. While elastic wave velocity measurements respond to the properties of the solid rock matrix including pores or fractures, NMR measurements are sensitive to the distribution of pore-filling fluids controlled by rock properties such as the pore-surface-to-pore-volume ratio. Therefore a combination of both measurement principles helps to investigate carbonate pore space using complementary information. In this study, a workflow is presented that delivers a representative average semi-axis length of ellipsoidal pores in carbonate rocks based on the pore aspect ratio received from velocity interpretation and the pore-surface-to-pore-volume ratio Spor as input parameters combined with theoretical calculations for ellipsoidal inclusions. A novel method to calculate Spor from NMR data based on the ratio of capillary-bound to movable fluids and the thickness of the capillary-bound water film is used. To test the workflow, a comprehensive petrophysical database was compiled using micritic and oomoldic Lower Muschelkalk carbonates from Germany. The experimental data indicate that both mud-dominated and grain-dominated carbonates possess distinct ranges of petrophysical parameters. The agreement between the predicted and measured surface-to-volume ratio is satisfying for oomoldic and most micritic samples, while pyrite or significant sample heterogeneity may lead to deviations. Selected photo-micrographs and scanning electron microscope images support the validity of the estimated representative pore dimensions.

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

    Science.gov (United States)

    Zhou, BeiBei; Wang, QuanJiu

    2016-04-01

    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.

  14. The effects of pressure, temperature, and pore water on velocities in Westerly granite. [for seismic wave propagation

    Science.gov (United States)

    Spencer, J. W., Jr.; Nur, A. M.

    1976-01-01

    A description is presented of an experimental assembly which has been developed to conduct concurrent measurements of compressional and shear wave velocities in rocks at high temperatures and confining pressures and with independent control of the pore pressure. The apparatus was used in studies of the joint effects of temperature, external confining pressure, and internal pore water on sonic velocities in Westerly granite. It was found that at a given temperature, confining pressure has a larger accelerating effect on compressional waves in dry rock, whereas at a given confining pressure, temperature has a larger retarding effect on shear waves.

  15. Evaluation of multiple tracer methods to estimate low groundwater flow velocities.

    Science.gov (United States)

    Reimus, Paul W; Arnold, Bill W

    2017-04-01

    Four different tracer methods were used to estimate groundwater flow velocity at a multiple-well site in the saturated alluvium south of Yucca Mountain, Nevada: (1) two single-well tracer tests with different rest or "shut-in" periods, (2) a cross-hole tracer test with an extended flow interruption, (3) a comparison of two tracer decay curves in an injection borehole with and without pumping of a downgradient well, and (4) a natural-gradient tracer test. Such tracer methods are potentially very useful for estimating groundwater velocities when hydraulic gradients are flat (and hence uncertain) and also when water level and hydraulic conductivity data are sparse, both of which were the case at this test location. The purpose of the study was to evaluate the first three methods for their ability to provide reasonable estimates of relatively low groundwater flow velocities in such low-hydraulic-gradient environments. The natural-gradient method is generally considered to be the most robust and direct method, so it was used to provide a "ground truth" velocity estimate. However, this method usually requires several wells, so it is often not practical in systems with large depths to groundwater and correspondingly high well installation costs. The fact that a successful natural gradient test was conducted at the test location offered a unique opportunity to compare the flow velocity estimates obtained by the more easily deployed and lower risk methods with the ground-truth natural-gradient method. The groundwater flow velocity estimates from the four methods agreed very well with each other, suggesting that the first three methods all provided reasonably good estimates of groundwater flow velocity at the site. The advantages and disadvantages of the different methods, as well as some of the uncertainties associated with them are discussed. Published by Elsevier B.V.

  16. Equivalent pore radius and velocity of elastic waves in shale. Skjold Flank-1 Well, Danish North Sea

    DEFF Research Database (Denmark)

    Mbia, Ernest Ncha; Fabricius, Ida Lykke; Oji, Collins O.

    2013-01-01

    Equivalent pore radius links permeability and porosity of a porous medium. This property can be calculated from specific surface and porosity data measured in the laboratory. We can obtain porosity information from logging data but specific surface information can only be obtained from laboratory...... experiments on cuttings or core samples. In this study we demonstrate that elastic moduli as calculated from bulk density and velocity of elastic waves relate to equivalent pore radius of the studied shale intervals. This relationship establishes the possibility of calculating equivalent pore radius from...... and BET specific surface were obtained from these samples using kaolinite and smectite as reference. The cuttings samples were also characterized with respect to mineralogical composition, content of organic carbon and cation exchange capacity.Equivalent pore radius was calculated from porosity and BET...

  17. Evaluation of chloride mass balance of pore water as an indicator of groundwater recharge to the Monterrey Metropolitan Area, Mexico

    Science.gov (United States)

    Rosales-Lagarde, Laura; Pasten, Ernesto; Mora, Abrahan; Mahlknecht, Jürgen

    2016-04-01

    Monterrey Metropolitan Area in Nuevo Leon, Mexico, is the third largest metropolitan area and one of the most important industrial sites of Mexico. Groundwater constitutes 40% of the water supply to this urban area. This supply is under constant stress due to the population increase. The unsaturated zone at six sites along two cross-sections was characterized to evaluate the potential of chloride concentration as an indicator of recharge. The selected sites include the range of topographic elevations, vegetation, and annual precipitation of the study area. In each site, boreholes up to 5 m deep were drilled and soil was sampled every 0.5 m. The grain size of each soil sample was determined and pore water extracted to determine the water content percentage, and the chloride, sulfate and nitrate concentration of the pore water. The undersaturated zone consists of alluvial deposits with an average gravel and sand content greater than 60% for all but one of the sampling sites. The pore water content varies from 0.4 to 25% by weight with a decreasing trend as depth increases in areas with agriculture. Sulfate has the highest anion concentration in the pore waters, ranging from 42 to 45,000 mg/L and no apparent distribution pattern along the soil profile columns. Chloride concentration ranges from 8 to 3600 mg/L with an increase in concentration below 1.5 m depth in all the profiles. Chloride and sulfate concentrations with depth are directly correlated suggesting a common input, possibly dissolution-precipitation of evaporite minerals from nearby outcrops or an anthropogenic input. Hence, it is unlikely that chloride behaves as a conservative ion. As a result, its concentration is not likely to be a good indicator of groundwater recharge. Finally; the nitrate concentration ranges from 2 to 96 mg/L nitrate, without a clear pattern along the soil profiles. Low concentration of nitrate in the soil profiles below agricultural areas may suggest denitrification as suggested

  18. Influence of pore water velocity on the release of carbofuran and fenamiphos from commercial granulates embedded in a porous matrix

    Science.gov (United States)

    Paradelo, Marcos; Pérez-Rodríguez, Paula; Arias-Estévez, Manuel; López-Periago, J. Eugenio

    2012-11-01

    Pore water flow velocity can influence the processes involved in the contaminant transport between relative stagnant zones of porous media and their adjacent mobile zones. A particular case of special interest is the occurrence of high flow rates around the controlled release granules containing pesticides buried in soil. The release of the pesticides carbofuran and fenamiphos from commercial controlled release formulations (CRFs) was studied, comparing release tests in a finite volume of water with water flow release tests in saturated packed sand at different seepage velocities. For water release kinetics, the time taken for 50% of the pesticide to be released (T50) was 0.64 hours for carbofuran and 1.97 hours for fenamiphos. In general, the release rate was lower in the porous matrix than in the free water tests. The faster release rate for carbofuran was attributed to its higher water diffusivity. The seepage velocity has a strong influence on the pesticide release rate. The dominant release mechanism varies with the progress of release. The evolution of the mechanism is discussed on the basis of the successive steps that involve the moving boundary of the dissolution front of the pesticide inside the granule, the concentration gradient inside the granule and the flow boundary layer resistance to solute diffusion around the granule. The pore water velocity influences the overall release dynamics. Therefore, seepage velocity should be considered in pesticide release to evaluate the risk of pesticide leaching, especially in scenarios with fast infiltration.

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

    Science.gov (United States)

    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.

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

    KAUST Repository

    Gerke, Kirill

    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.

  1. A NEW NUMERICAL METHOD FOR GROUNDWATER FIOW AND SOLUTE TRANSPORT USING VELOCITY FIELD

    Institute of Scientific and Technical Information of China (English)

    ZHANG Qian-fei; LAN Shou-qi; WANG Yan-ming; XU Yong-fu

    2008-01-01

    A new numerical method for groundwater flow analysis was introduced to estimate simultaneously velocity vectors and water pressure head. The method could be employed to handle the vertical flow under variably saturated conditions and for horizontal flow as well. The method allows for better estimation of velocities at the element nodes which can be used as direct input to transport models. The advection-dispersion process was treated by the Eulerian-Lagrangian approach with particle tracking technique using the velocities at FEM nodes. The method was verified with the classical one dimensional model and applied to simulate contaminant transport process through a slurry wall as a barrier to prevent leachate pollution from a sanitary landfill.

  2. Mathematical model to predict the transport of dissolved arsenic in groundwater influenced by seepage velocity

    Directory of Open Access Journals (Sweden)

    Solomon Ndubuisi Eluozo

    2012-11-01

    Full Text Available Development of mathematical model to predict the transport of dissolved arsenic in groundwater influenced by seepage velocity has been carried out. This model was developed to monitor the rate of concentration at different period and depths. High and low concentrations were observed at different periods and depth as presented in the figures. These conditions can be attributed to soil stratification deposition in the study location and the influence of man-made activities. Based on these facts, it is recommended that risk assessment should be thoroughly done for soil and water and the predicted model should be applied in design and construction of groundwater system in the study area. 

  3. Optical measurements of pore geometry and fluid velocity in a bed of irregularly packed spheres

    Science.gov (United States)

    Huang, Alice Y. L.; Huang, Michelle Y. F.; Capart, Hervé; Chen, Rong-Her

    2008-08-01

    Imaging methods are proposed for the characterisation of liquid flows through transparent porous media of matched refractive index. The methods are based on the analysis of laser-illuminated slices, and specialized for the case in which the porous medium is composed of irregularly packed spheres. They include algorithms for the reconstruction of the three-dimensional (3D) sphere arrangement based on a laser scan of the packed bed, particle tracking velocimetry applied to the motions of micro-tracers in a laser-illuminated plane, and techniques for the co-registration of geometry and velocity measurements acquired from different slices. The methods are applied to a cylindrical flow cell filled with mono-sized spheres and operated at Reynolds number Re = 28. The data produced include the full 3D geometry of the packed spheres assembly, the 2D fluid velocity field in the axial centre-plane of the flow cell, and the corresponding porosity and velocity distributions.

  4. Determination of Groundwater Velocity and Dispersion Parameters by Borehole Wall Multielectrode Geoelectrics

    Science.gov (United States)

    Kessels, W.; Wuttke, M. W.

    2007-05-01

    A single well technique to determine groundwater flow values and transport parameters is presented. Multielectrode arrays are placed at the filtered casing depth by an inflatable packer or are installed on the borehole wall behind the casing.Tracer water with a higher or lower specific electrical conductivity (salinity) which is injected between the electrodes. This tracer plume then moves into the natural groundwater flow field. The observation of this movement by geoelectric logging enables the determination of the groundwater velocity and salinity. The transport parameters "effective porosity" and "dispersion length" can also be derived. The geoelectric logging uses n borehole electrodes and two grounding electrodes. Thus, either n independent two point measurements or n*(n-1)/2 pole-to-pole measurements can be conducted to obtain a full set of geoelectric measurements. This set is used to derive all electrode combinations by applying the law of superposition and reciprocity. The tracer distribution around the borehole during and after injection depends on the hydraulic and transport parameters of the aquifer and the filter sand. The transport parameter "porosity" plus the total injected tracer volume determines the tracer distribution around the borehole. The transport parameter "dispersivity" determines the abruptness of the tracer front. The method was tested by undertaking measurements in a lab aquifer filled with sand. The results are discussed and the limitations of the method are shown. Multielectrode installations behind casing were tested in situ in the two scientific boreholes CAT-LUD-1 and CAT- LUD-1A drilled in the northern part of Germany. A multielectrode packer system was designed, built and tested in these boreholes. The results are compared with colloid observations in the borehole and hydraulic triangulation in surrounded observation wells. Here, the interpretation of these in situ measurements is mainly restricted to two point geoelectric

  5. Groundwater flow and velocity in a 500 ka pre-Illinoian till, eastern Iowa

    Science.gov (United States)

    Schilling, K.E.; Tassier-Surine, S.

    2006-01-01

    Few hydrology studies have investigated glacial till older than Illinoian time (> 300,000 BP) despite these older tills overlying a large portion of North America. An 8- and 6-well monitoring well nest installed into a 31 m thick pre-Illinoian till sequence near Cedar Rapids, Iowa was characterized using traditional hydrologic methods and chemical tracers. The aquitard system consists of about 9 m of fine-grained oxidized pre-Illinoian till overlying 22 m of unoxidized till and Devonian dolomite bedrock. Hydraulic conductivity ranged from 10-7 m/s in oxidized till and 10-10 m/s in unoxidized till. Hydraulic head relations indicated downward groundwater flow through the till profile with hydraulic gradients steepest near the unoxidized till/bedrock interface. Tritium and nitrate concentrations indicated recent (groundwater velocity through the unoxidized till was estimated to range from 0.4 to 5.7 cm/year. The thickness of unoxidized pre-Illinoian till in Linn County was estimated from available records and contoured against vertical travel times to evaluate the effectiveness of pre-Illinoian till in preventing nitrate migration to underlying bedrock aquifers. ?? Springer-Verlag 2006.

  6. Groundwater.

    Science.gov (United States)

    Braids, Olin C.; Gillies, Nola P.

    1978-01-01

    Presents a literature review of groundwater quality covering publications of 1977. This review includes: (1) sources of groundwater contamination; and (2) management of groundwater. A list of 59 references is also presented. (HM)

  7. TO "LIMITATIONS OF ROI TESTING FOR VENTING DESIGN: DESCRIPTION OF AN ALTERNATIVE APPROACH BASED ON ATTAINMENT OF A CRITICAL PORE-GAS VELOCITY IN CONTAMINATED MEDIA

    Science.gov (United States)

    In this paper, we describe the limitations of radius of influence (ROI) evaluation for venting design in more detail than has been done previously and propose an alternative method based on specification and attainment of critical pore-gas velocities in contaminated subsurface me...

  8. Velocity Potential in Engineering Hydraulics versus Force Potential in Groundwater Dynamics

    Science.gov (United States)

    Weyer, K.

    2013-12-01

    Within engineering practice, the calculation of subsurface flow is dominated by the mathematical pseudo-physics of the engineer's adaptation of continuum methods to mechanics. Continuum mechanics rose to prominence in the 19th century in an successful attempt to solve practical engineering problems. To that end were put in place quite a number of simplifications in geometry and the properties of water and other fluids, as well as simplifications of Darcy's equation, in order to find reasonable answers to practical problems by making use of analytical equations. The proof of the correctness of the approach and its usefulness was in the practicability of results obtained. In the 1930s, a diametrically-opposed duality developed in the theoretical derivation of the laws of subsurface fluid flow between Muskat's (1937) velocity potential (engineering hydraulics) and Hubbert's (1940) force potential. The conflict between these authors lasted a lifetime. In the end Hubbert stated on one occasion that Muskat formulates a refined mathematics but does not know what it means in physical terms. In this author's opinion that can still be said about the application of continuum mechanics by engineers to date, as for example to CO2 sequestration, regional groundwater flow, oil sands work, and geothermal studies. To date, engineering hydraulics is best represented by Bear (1972) and de Marsily (1986). In their well-known textbooks, both authors refer to Hubbert's work as the proper way to deal with the physics of compressible fluids. Water is a compressible fluid. The authors then ignore, however, their own insights (de Marsily states so explicitly, Bear does not) and proceed to deal with water as an incompressible fluid. At places both authors assume the pressure gradients to be the main driving force for flow of fluids in the subsurface. That is not, however, the case. Instead the pressure potential forces are caused by compression initiated by unused gravitational energy not

  9. FORMULAE FOR AVERAGE VELOCITY OF GROUNDWATER FLOW AND EXPERIMENTAL EVIDENCE OF NON-DARCY'S FLOW THROUGH A SINGLE FRACTURE

    Institute of Scientific and Technical Information of China (English)

    Qian Jia-zhong; Wang Jia-quan; Li Ru-zhong; Liu Yong

    2003-01-01

    The formulae for average velocity of groundwater flow in a single fracture were derived based on the characteristics of fracture properties and hydraulic methods. The results show that the average velocity is proportional to the square root of the hydraulic gradient. In order to verify the results, a laboratory model was established, and the experimental data were analyzed. Experimental results indicate that the relation between the average velocity and hydraulic gradient is nonlinear, and can be fitted with power functions. And for both the unconfined and confined flows, the value of the exponent of power functions are close to 0.5. Thus the experimental results agree well with those from the theoretical analysis. By comparing the calculated and measured values of the average velocity under the same conditions, the formulae presented herein are more effective than the traditional formula based on Darcy's Law. These results provide the evidences of non-Darcy's flow in single fracture.

  10. The effect of groundwater fluctuations on the velocity pattern of slow-moving landslides

    NARCIS (Netherlands)

    Van Asch, T.W.J.; Malet, J.P.; Bogaard, T.A.

    2009-01-01

    Slow-moving landslides show complex mechanical and fluid interactions. They show among others non linear intrinsic viscosity of the shear zone, undrained loading effects and the generation of excess pore water pressure. The parameterization of hydrological and geomechanical factors by field and labo

  11. Hyporheic flow and dissolved oxygen distribution in fish nests: The effects of open channel velocity, permeability patterns, and groundwater upwelling

    Science.gov (United States)

    Cardenas, M. Bayani; Ford, Aimee E.; Kaufman, Matthew H.; Kessler, Adam J.; Cook, Perran L. M.

    2016-12-01

    Many fish lay their eggs in nests, or redds, which they construct in sediment. The viability of eggs depends on many factors, particularly their oxygenation. Because dissolved oxygen is typically saturated within the stream channel, the dissolved oxygen distribution within the redd depends on whether or not hyporheic flow and transport occur within the sediment. We conducted a series of flume and numerical flow and age transport modeling experiments with the aim of understanding the effects of salmonid redds on the hyporheic transport of young oxygenated water. Hyporheic flow was visualized directly through dye injections. Dissolved oxygen throughout the fish nest was measured using a planar optode. Experiments were conducted at various open channel flow velocities in order to understand their effect on dissolved oxygen, and computational simulations considered various sediment textures and ambient groundwater upwelling rates to add process-level insight. We found that, as also shown by previous studies, the redd topography induces multiscale hyporheic flow that effectively flushes the egg pocket location with younger presumably oxygenated water; older water upwells and forms anoxic zones. This pattern persists even at the lowest channel flow rates and at small upwelling velocities of older ambient groundwater which splits the multiscale hyporheic flow cells into isolated pockets. Large groundwater upwelling rates can shut down all the hyporheic flushing. The relatively coarse texture of the redd further promotes hyporheic flushing of the redd sediment with oxygenated water. Thus, redd morphology and sediment texture optimally combine to induce hyporheic exchange flow that delivers young oxygenated water to the egg pocket.

  12. Estimating regional pore pressure distribution using 3D seismic velocities in the Dutch Central North Sea Graben

    NARCIS (Netherlands)

    Winthaegen, P.L.A.; Verweij, J.M.

    2003-01-01

    The application of the empirical Eaton method to calibrated sonic well information and 3D seismic interval velocity data in the southeastern part of the Central North Sea Graben, using the Japsen (Glob. Planet. Change 24 (2000) 189) normal velocitydepth trend, resulted in the identification of an

  13. Estimating regional pore pressure distribution using 3D seismic velocities in the Dutch Central North Sea Graben

    NARCIS (Netherlands)

    Winthaegen, P.L.A.; Verweij, J.M.

    2003-01-01

    The application of the empirical Eaton method to calibrated sonic well information and 3D seismic interval velocity data in the southeastern part of the Central North Sea Graben, using the Japsen (Glob. Planet. Change 24 (2000) 189) normal velocitydepth trend, resulted in the identification of an un

  14. The effect of divalent ions on the elasticity and pore collapse of chalk evaluated from compressional wave velocity and low-field Nuclear Magnetic Resonance (NMR)

    DEFF Research Database (Denmark)

    Katika, Konstantina; Addassi, Mouadh; Alam, Mohammad Monzurul

    2015-01-01

    The effects of divalent ions on the elasticity and the pore collapse of chalk were studied through rock-mechanical testing and low-field Nuclear Magnetic Resonance (NMR) measurements. Chalk samples saturated with deionized water and brines containing sodium, magnesium, calcium and sulfate ions were...... subjected to petrophysical experiments, rock mechanical testing and low-field NMR spectroscopy. Petrophysical characterization involving ultrasonic elastic wave velocities in unconfined conditions, porosity and permeability measurements, specific surface and carbonate content determination and backscatter...... electron microscopy of the materials were conducted prior to the experiments. The iso-frame model was used to predict the bulk moduli in dry and saturated conditions from the compressional modulus of water-saturated rocks. The effective stress coefficient, as introduced by Biot, was also determined from...

  15. Characteristic Time Scales of Transport Processes for Chemotactic Bacteria in Groundwater: Analysis of Pore-scale to Field-scale Experimental Data

    Science.gov (United States)

    Ford, R. M.

    2010-12-01

    Many processes contribute to the transport of microorganisms in groundwater environments. One process of interest is chemotaxis, whereby motile bacteria are able to detect and swim toward increasing concentrations of industrial hydrocarbons that they perceive as food sources. By enabling bacteria to migrate to the sources of pollutants that they degrade, chemotaxis has the potential to enhance bioremediation efforts, especially in less permeable zones where contamination may persist. To determine the field conditions under which chemotaxis might be exploited in a bioremediation scheme requires an understanding of the characteristic time scales in the system. We defined a dimensionless chemotaxis number that compares the time over which a bacterial population is exposed to a chemical gradient to the time required for a bacterial population to migrate a significant distance in response to a chemical gradient. The exposure time and the response time are dependent upon the experimental conditions and properties of the bacteria and chemical attractant. Experimental data was analyzed for a range of groundwater flow rates over a wide scope of experimental systems including a single-pore with NAPL source, a microfluidic channel with and without a porous matrix, a laboratory column, a bench-scale microcosm and a field-scale study. Chemical gradients were created transverse to the flow direction. Distributions of chemotactic and nonchemotactic bacteria were compared to determine the extent of migration due to chemotaxis. Under some conditions at higher flow rates, the effect of chemotaxis was diminished to the point of not being detected. The goal of the study was to determine a critical value for the dimensionless chemotaxis number (which is independent of scale) that can be used as a design criterion to ascertain a priori the conditions under which a chemotactic response will impact bacterial transport relative to other processes such as advection and dispersion.

  16. [Groundwater].

    Science.gov (United States)

    González De Posada, Francisco

    2012-01-01

    From the perspective of Hydrogeology, the concept and an introductory general typology of groundwater are established. From the perspective of Geotechnical Engineering works, the physical and mathematical equations of the hydraulics of permeable materials, which are implemented, by electric analogical simulation, to two unique cases of global importance, are considered: the bailing during the construction of the dry dock of the "new shipyard of the Bahia de Cádiz" and the waterproofing of the "Hatillo dam" in the Dominican Republic. From a physical fundamental perspective, the theories which are the subset of "analogical physical theories of Fourier type transport" are related, among which the one constituted by the laws of Adolf Fick in physiology occupies a historic role of some relevance. And finally, as a philosophical abstraction of so much useful mathematical process, the one which is called "the Galilean principle of the mathematical design of the Nature" is dealt with.

  17. Solute transport into the Jiulong River estuary via pore water exchange and submarine groundwater discharge: New insights from 224Ra/228Th disequilibrium

    Science.gov (United States)

    Hong, Qingquan; Cai, Pinghe; Shi, Xiangming; Li, Qing; Wang, Guizhi

    2017-02-01

    Pore water exchange (PEX) and submarine groundwater discharge (SGD) represent two mechanisms for solute transport from the seabed into the coastal ocean. However, their relative importance remains to be assessed. In this study, we pursued the recently developed 224Ra/228Th disequilibrium approach to quantify PEX fluxes of 224Ra into the Jiulong River estuary, China. By constructing a full mass balance of water column 224Ra, we were allowed to put various source terms, i.e., SGD, diffusive and advective pore water flow (PEX), and river input in a single context. This led to the first quantitative assessment of the relative importance of PEX vs. SGD in the delivery of solutes into an estuary. We carried out two surveys in the Jiulong River estuary: one in January 2014 (winter survey), the other in August 2014 (summer survey). By virtue of a 1-D mass balance model of 224Ra in the sediment column, we demonstrated that PEX fluxes of 224Ra were highly variable, both temporally and spatially, and can change by 1-2 orders of magnitude in our study area. Moreover, we identified a strong correlation between 224Ra-based irrigation rate and 234Th-based sediment mixing rate. Our results highlighted irrigation as the predominant PEX process for solute transfer across the sediment-water interface. Total PEX flux of 224Ra (in 1010 dpm d-1) into the Jiulong River estuary was estimated to be 22.3 ± 3.0 and 33.7 ± 5.5 during the winter and summer surveys, respectively. In comparison, total SGD flux of 224Ra (in 1010 dpm d-1) was 11.3 ± 8.6 and 49.5 ± 16.3 in the respective seasons. By multiplying the PEX fluxes of 224Ra by the ratio of the concentration gradients of component/224Ra at the sediment-water interface, we quantified the total PEX fluxes of dissolved inorganic carbon (DIC) and nutrients (NH4+, NO3-, and H4SiO4) into the Jiulong River estuary. In the meantime, net export of DIC and nutrients via SGD were estimated by multiplying the SGD fluxes of 224Ra by the DIC

  18. Fast calculation of groundwater exfiltration salinity in a lowland catchment using a lumped celerity/velocity approach

    NARCIS (Netherlands)

    Delsman, Joost R.; De Louw, Perry G.B.; De Lange, Wim; Oude Essink, G.H.P.

    2017-01-01

    To support operational water management of freshwater resources in coastal lowlands, a need exists for a rapid, well-identifiable model to simulate salinity dynamics of exfiltrating groundwater. This paper presents the lumped Rapid Saline Groundwater Exfiltration Model (RSGEM). RSGEM simulates groun

  19. 粒径和流速对大肠杆菌在饱和多孔介质中迁移的影响%Effects of particle size and pore water velocity on transport of Escherichia coli in saturated porous media

    Institute of Scientific and Technical Information of China (English)

    姚舜译; 袁雪梅; 杨新瑶; 邓仕槐

    2016-01-01

    采用室内柱迁移实验,研究了在不同离子强度下多孔介质粒径和孔隙水流速对大肠杆菌在饱和石英砂柱中沉积与释放行为的影响。结果表明,介质粒径和孔隙水流速均能影响大肠杆菌在石英砂中的迁移过程。介质粒径的减小可增强大肠杆菌在多孔介质中的筛滤效应,增加其沉积率和滞留率,减小水化学扰动引起的释放效应;流速的降低有利于提高大肠杆菌的沉积率和滞留率。离子强度的高低可改变粒径和流速对大肠杆菌迁移影响的大小,在较高离子强度条件下,减小介质粒径和孔隙水流速对提高大肠杆菌的沉积率和滞留率的作用增强。由于自然环境的复杂性,今后的研究应注重真实地下水环境中多因素对大肠杆菌迁移行为的复合影响,以便更加准确地掌握大肠杆菌在多孔介质中迁移的规律。%The transport of pathogenic microbes in porous media is critical to groundwater quality. This study investigated the combined ef-fects of particle size and pore water velocity on the deposition and release behavior of Escherichia coli(E. coli)in saturated quartz sands at different ionic strengths. Results showed that both particle size and pore water velocity affected the transport of E. coli in porous media. De-creasing particle size increased straining effect, deposition and thus retention rates of E. coli. Moreover, the enhanced straining effect result-ed in lower releases of E. coli from the smaller particles. Reducing pore water velocity tended to increase deposition and retention rates of E. coli. At greater ionic strength, decreases in both particle size and pore water velocity further enhanced deposition and retention rates of E. coli. These results would improve our understanding of releases and transport of biocolloids under transient ionic strength.

  20. Thermal-plume fibre optic tracking (T-POT) test for flow velocity measurement in groundwater boreholes

    NARCIS (Netherlands)

    Read, T.; Bense, V.F.; Hochreutener, R.; Bour, O.; Borgne, Le T.; Lavenant, N.; Selker, J.S.

    2015-01-01

    We develop an approach for measuring in-well fluid velocities using point electrical heating combined with spatially and temporally continuous temperature monitoring using distributed temperature sensing (DTS). The method uses a point heater to warm a discrete volume of water. The rate of advection

  1. Thermal-Plume fibre Optic Tracking (T-POT test for flow velocity measurement in groundwater boreholes

    Directory of Open Access Journals (Sweden)

    T. Read

    2015-06-01

    Full Text Available We develop an approach for measuring in-well fluid velocities using point electrical heating combined with spatially and temporally continuous temperature monitoring using Distributed Temperature Sensing (DTS. The method uses a point heater to warm a discrete volume of water. The rate of advection of this plume, once the heating is stopped, equates to the average flow velocity in the well. We conducted Thermal-Plume fibre Optic Tracking (T-POT tests in a borehole in a fractured rock aquifer with the heater at the same depth and multiple pumping rates. Tracking of the thermal plume peak allowed the spatially varying velocity to be estimated up to 50 m downstream from the heating point, depending on the pumping rate. The T-POT technique can be used to estimate the velocity throughout long intervals provided that thermal dilution due to inflows, dispersion, or cooling by conduction do not render the thermal pulse unresolvable with DTS. A complete flow log may be obtained by deploying the heater at multiple depths, or with multiple point heaters.

  2. Pushpoint sampling for defining spatial and temporal variations in contaminant concentrations in sediment pore water near the ground-water / surface-water interface

    Science.gov (United States)

    Zimmerman, Marc J.; Massey, Andrew J.; Campo, Kimberly W.

    2005-01-01

    During four periods from April 2002 to June 2003, pore-water samples were taken from river sediment within a gaining reach (Mill Pond) of the Sudbury River in Ashland, Massachusetts, with a temporary pushpoint sampler to determine whether this device is an effective tool for measuring small-scale spatial variations in concentrations of volatile organic compounds and selected field parameters (specific conductance and dissolved oxygen concentration). The pore waters sampled were within a subsurface plume of volatile organic compounds extending from the nearby Nyanza Chemical Waste Dump Superfund site to the river. Samples were collected from depths of 10, 30, and 60 centimeters below the sediment surface along two 10-meter-long, parallel transects extending into the river. Twenty-five volatile organic compounds were detected at concentrations ranging from less than 1 microgram per liter to hundreds of micrograms per liter (for example, 1,2-dichlorobenzene, 490 micrograms per liter; cis-1,2-dichloroethene, 290 micrograms per liter). The most frequently detected compounds were either chlorobenzenes or chlorinated ethenes. Many of the compounds were detected only infrequently. Quality-control sampling indicated a low incidence of trace concentrations of contaminants. Additional samples collected with passive-water-diffusion-bag samplers yielded results comparable to those collected with the pushpoint sampler and to samples collected in previous studies at the site. The results demonstrate that the pushpoint sampler can yield distinct samples from sites in close proximity; in this case, sampling sites were 1 meter apart horizontally and 20 or 30 centimeters apart vertically. Moreover, the pushpoint sampler was able to draw pore water when inserted to depths as shallow as 10 centimeters below the sediment surface without entraining surface water. The simplicity of collecting numerous samples in a short time period (routinely, 20 to 30 per day) validates the use of a

  3. Comparison of Pore Water Chemical Extracted by Different Forces with In-situ Properties

    Science.gov (United States)

    Ito, N.; Machida, I.; Marui, A.; Scheytt, T.; Hebig, K. H.

    2010-12-01

    Due to the difficulty involved for in-situ sampling of groundwater, pore water was extracted from rock core samples for chemical analysis. Available literature indicated that, the chemical constituents of pore water are affected by large extraction force. This study is therefore aimed at discussing the reason behind the change in pore water chemistry when samples are subjected to different extraction forces. The process involved extraction of pore water from sandstone core samples at different pF values by centrifuge method. The pF expresses the tension of water, retained in soil. It is the base 10 logarithm of tension, which is measured as a head of water head in centimeters. The samples of lengths 100 m each were obtained from three locations. Tracer test using Iodine was also conducted to remove pore water polluted by drilling water. Pore water was extracted from a total of 63 samples at three different values of pF (low: up to pF 2.3, medium: pF 2.3 - 3.9, high: pF 3.9 - 4.3). For each pF range the pore water was analyzed for major anions and cations. Results showed variation of ionic concentrations with pF and depth. The average concentrations rose with increase of pF in all ions except for potassium. Based on the concentration distribution of Ca2+, three zones could be defined: (1) Ca2+ concentration, which does not depend on pF, (2) Ca2+ concentration, which increases with the value of pF and (3) Ca2+ showing the same value for medium and high pF values. It is thus concluded that, water chemistry of deep pore water is likely to have reached equilibrium due to almost stagnant flow conditions, whereas shallow water is likely to participate in chemical interactions due to the relatively high flow velocity. The depths of the interfaces of these three zones are almost consistent with geological boundaries of weathered and fine sandstone and there is evidence of a relationship between pore water chemistry and physical rock properties. Using this knowledge, we

  4. Groundwater Eruption in China Triggered By the 2004 Sumatra Earthquake

    Science.gov (United States)

    Shi, Z.; Wang, D.; Manga, M.; Wang, C. Y.; Wang, G.

    2014-12-01

    The 2004 Mw9.3 Sumatra earthquake initiated a large, sustained groundwater eruption in Guangdong, China, 3200 km away from the epicenter. The erupted water column reached a height of ~60 m above the ground surface when it was first sighted and the eruption lasted about 10 days. Estimated seismic energy density at the eruption site is only 0.046 J.m-3; thus it is surprising that the earthquake caused such an intense response. A field survey showed that a large amount of gaseous CO2 was released from groundwater during the eruption and suggested that the eruption was caused by the exsolution of CO2 from groundwater. In this study, we use numerical simulation to explore the mechanism of the well eruption. We apply tidal analysis to water level data from 2003 to 2006 to estimate the aquifer parameters before and after the earthquake; the hydraulic diffusivity inferred this way is 0.423 m2/s and 1.371 m2/s before and after the earthquake, respectively. Based on these parameters, we use TOUGH2, a widely used numerical program for simulating two-phase hydrothermal processes, to simulate the evolution of CO2 saturation, the velocity of erupted groundwater and pressure in the well-aquifer system after Sumatra earthquake. The simulations show that the earthquake may have triggered bubbles to nucleate from the CO2-rich groundwater and enhanced the aquifer permeability, leading to increased groundwater discharge to the well. Decreased pore-pressure in the aquifer caused greater exsolution of CO2 and greater discharge, leading to groundwater eruption. Exsolution of CO2 extends radially away from the wellbore as a function of time and the continued exsolution of CO2 sustained the eruption until pressure in the aquifer drops below hydrostatic, which is marked by a ~9 m drop in groundwater level from that before the earthquake. That earthquake trigger eruption and CO2 exsolution has implications for CO2 sequestration.

  5. Genesis of economic relevant fresh groundwater resources in Pleistocene/ Neogene aquifers in Nam Dinh (Red River Delta, Vietnam).

    Science.gov (United States)

    Wagner, F.; Ludwig, R. R.; Noell, U.; Hoang, H. V.; Pham, N. Q.; Larsen, F.; Lindenmaier, F.

    2012-04-01

    Holocene sediments. Consequently, 14C groundwater age dating suggests increasing groundwater ages from fresh to saline pore water in Pleistocene and Neogene up to 14 ka, presuming that contamination with dead carbon is neglectable. Highest 14C ages of low saline water has been observed in the center of the exploited fresh water lens reaching up to 10 ka, reflecting low groundwater flux and recharge rates. Due to the overexploitation, the natural coastward directed groundwater flow has turned towards the centre of the abstraction cone with horizontal apparent velocities of up to 0.6 m/a. This suggests, that brackish and higher saline groundwater from the Red River area (East Nam Dinh) and offshore migrates towards the fresh water lens. Thus, more sustainable exploitation strategies urgently must be implemented to reduce overexploitation of limited and valuable fresh groundwater resources in Nam Dinh Province. Reference: Hoan H., Pham Q. N., Larsen F. Tran L. V., Wagner F., Christiansen A.V. (2010): Processes Controlling High Saline Groundwater in the Nam Dinh Province, Vietnam. 2nd Asia-Pacific Coastal Aquifer Management Meeting (ACAMM), October 18-21, 2011, Jeju Island, Korea.

  6. SPECIFIC SOLUTIONS GROUNDWATER FLOW EQUATION

    OpenAIRE

    Syahruddin, Muhammad Hamzah

    2014-01-01

    Geophysic publication Groundwater flow under surface, its usually slow moving, so that in laminer flow condition can find analisys using the Darcy???s law. The combination between Darcy law and continuity equation can find differential Laplace equation as general equation groundwater flow in sub surface. Based on Differential Laplace Equation is the equation that can be used to describe hydraulic head and velocity flow distribution in porous media as groundwater. In the modeling Laplace e...

  7. Enhanced Retention of Chemotactic Bacteria in a Pore Network with Residual NAPL Contamination.

    Science.gov (United States)

    Wang, Xiaopu; Lanning, Larry M; Ford, Roseanne M

    2016-01-01

    Nonaqueous-phase liquid (NAPL) contaminants are difficult to eliminate from natural aquifers due, in part, to the heterogeneous structure of the soil. Chemotaxis enhances the mixing of bacteria with contaminant sources in low-permeability regions, which may not be readily accessible by advection and dispersion alone. A microfluidic device was designed to mimic heterogeneous features of a contaminated groundwater aquifer. NAPL droplets (toluene) were trapped within a fine pore network, and bacteria were injected through a highly conductive adjacent macrochannel. Chemotactic bacteria (Pseudomonas putida F1) exhibited greater accumulation near the pore network at 0.5 m/day than both the nonchemotactic control and the chemotactic bacteria at a higher groundwater velocity of 5 m/day. Chemotactic bacteria accumulated in the vicinity of NAPL droplets, and the accumulation was 15% greater than a nonchemotactic mutant. Indirect evidence showed that chemotactic bacteria were retained within the contaminated low-permeability region longer than nonchemotactic bacteria at 0.25 m/day. This retention was diminished at 5 m/day. Numerical solutions of the bacterial-transport equations were consistent with the experimental results. Because toluene is degraded by P. putida F1, the accumulation of chemotactic bacteria around NAPL sources is expected to increase contaminant consumption and improve the efficiency of bioremediation.

  8. Enhanced Retention of Chemotactic Bacteria in a Pore Network with Residual NAPL Contamination

    Science.gov (United States)

    Ford, R.; Wang, X.

    2013-12-01

    Nonaqueous phase liquid (NAPL) contaminants are difficult to eliminate from natural aquifers due, in part, to the heterogeneous structure of the soil matrix. Residual NAPL ganglia remain trapped in regions where the hydraulic conductivity is relatively low. Bioremediation processes depend on adequate mixing of microbial populations and the groundwater contaminants that they degrade. The ability of bacteria to sense a chemical gradient and swim preferentially toward locations of higher concentration, known as chemotaxis, can enhance the mixing of bacteria with contaminant sources that may not be readily accessible by advection and dispersion alone. The impact of chemotaxis on bacterial abundance within a low conductivity NAPL-contaminated region of a well-characterized porous matrix was investigated. A microfluidic device was designed to mimic heterogeneous features of a contaminated groundwater system. NAPL ganglia (toluene) were trapped within a fine pore network, and bacteria were injected into the system through a highly conductive adjacent channel. Chemotactic bacteria (P. putida F1) migrated preferentially towards and accumulated in the vicinity of NAPL contaminant sources. The accumulation of chemotactic bacteria was 15% greater in comparison to a nonchemotactic mutant (P. putida F1 CheA). Bacteria in the microfluidic device were subjected to different flow velocities from 0.25 to 5 m/d encompassing the range of typical groundwater flow rates. Chemotactic bacteria exhibited greater accumulation near the intersection between the macrochannel and the porous network at a flow velocity of 0.5 m/d than both the nonchemotactic mutant control and the chemotactic bacteria at a higher flow velocity of 5 m/d. Breakthrough curves observed at the outlet provided indirect evidence that chemotactic bacteria were retained within the contaminated low permeable region for a longer time than the nonchemotactic bacteria at a flow velocity of 0.25 m/d. This retention was

  9. Dilated pore of winer

    Directory of Open Access Journals (Sweden)

    Mittal R

    2002-01-01

    Full Text Available Two cases of dilated pore of Winer were observed. First case had single defined black papule with well defined margin, central pore and discharge of black powdery material from nose since 3 years. The second case had one 9mm, black well-defined papule with central pore discharging black powdery material on right forearm since 9 months and 9 similar smaller papules were seen on forearm and lower abdomen. Histopathologically both revealed greatly dilated infundibulum lined by acanthotic epidermis and atrophic subinfundibular hair structures thus confirming diagnosis of dilated pore of Winer

  10. Fingerprint pores extractor

    CSIR Research Space (South Africa)

    Mngenge, NA

    2012-11-01

    Full Text Available alone. Sweat pores have been less utilized in the past due to constraints imposed by fingerprint scanning devices and resolution standards. Recently, progress has been made on both scanning devices and resolution standards to support the use of pores...

  11. Pore size distribution mapping

    OpenAIRE

    Strange, John H.; J. Beau W. WEBBER; Schmidt, S.D.

    1996-01-01

    Pore size distribution mapping has been demonstrated using NMR cryoporometry\\ud in the presence of a magnetic field gradient, This novel method is extendable to 2D and 3D mapping. It offers a unique nondestructive method of obtaining full pore-size distributions in the range 3 to 100 nm at any point within a bulk sample. \\ud

  12. Relationship between elastic moduli and pore radius in clay aggregates

    DEFF Research Database (Denmark)

    Fabricius, Ida Lykke

    2011-01-01

    Available experimental data on elastic velocities of clay-air mixtures and clay-brine mixtures as a function of porosity are re-interpreted. Pore radius as calculated from porosity and specific surface measured by BET seems to be the factor controlling stiffness of these un-cemented sediments....... For each of the two pore fluids: air or brine smectitic clay and kaolinitic clay seem to have similar power law relationships between a given elastic modulus and pore radius. These results indicate that pore radius and thus permeability of shale in the depth interval of mechanical compaction may...

  13. Velocity field calculation for non-orthogonal numerical grids

    Energy Technology Data Exchange (ETDEWEB)

    Flach, G. P. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-03-01

    Computational grids containing cell faces that do not align with an orthogonal (e.g. Cartesian, cylindrical) coordinate system are routinely encountered in porous-medium numerical simulations. Such grids are referred to in this study as non-orthogonal grids because some cell faces are not orthogonal to a coordinate system plane (e.g. xy, yz or xz plane in Cartesian coordinates). Non-orthogonal grids are routinely encountered at the Savannah River Site in porous-medium flow simulations for Performance Assessments and groundwater flow modeling. Examples include grid lines that conform to the sloping roof of a waste tank or disposal unit in a 2D Performance Assessment simulation, and grid surfaces that conform to undulating stratigraphic surfaces in a 3D groundwater flow model. Particle tracking is routinely performed after a porous-medium numerical flow simulation to better understand the dynamics of the flow field and/or as an approximate indication of the trajectory and timing of advective solute transport. Particle tracks are computed by integrating the velocity field from cell to cell starting from designated seed (starting) positions. An accurate velocity field is required to attain accurate particle tracks. However, many numerical simulation codes report only the volumetric flowrate (e.g. PORFLOW) and/or flux (flowrate divided by area) crossing cell faces. For an orthogonal grid, the normal flux at a cell face is a component of the Darcy velocity vector in the coordinate system, and the pore velocity for particle tracking is attained by dividing by water content. For a non-orthogonal grid, the flux normal to a cell face that lies outside a coordinate plane is not a true component of velocity with respect to the coordinate system. Nonetheless, normal fluxes are often taken as Darcy velocity components, either naively or with accepted approximation. To enable accurate particle tracking or otherwise present an accurate depiction of the velocity field for a non

  14. Performance of slotted pores in particle manufacture using rotating membrane emulsification

    Institute of Scientific and Technical Information of China (English)

    Qingchun Yuan; Nita Aryanti; Ruozhou Hou; Richard A.Williams

    2009-01-01

    This paper addresses the use of different slotted pores in rotating membrane emulsification technology.Pores of square and rectangular shapes were studied to understand the effect of aspect ratio (1-3.5) and their orientation on oil droplet formation.Increasing the membrane rotation speed decreased the droplet size,and the oil droplets produced were more uniform using slotted pores as compared to circular geometry.At a given rotation speed,the droplet size was mainly determined by the pore size and the fluid velocity of oil through the pore (pore fluid velocity).The ratio of droplet diameter to the equivalent diameter of the slotted pore increased with the pore fluid velocity.At a given pore fluid velocity and rotation speed,pore orientation significantly influences the droplet formation rate: horizontally disposed pores (with their longer side perpendicular to the membrane axis) generate droplets at double the rate of vertically disposed pores.This work indicates practical benefits in the use of slotted membranes over conventional methods.

  15. Energy velocity and group velocity

    Institute of Scientific and Technical Information of China (English)

    陈宇

    1995-01-01

    A new Lagrangian method for studying the relationship between the energy velocity and the group velocity is described. It is proved that under the usual quasistatic electric field, the energy velocity is identical to the group velocity for acoustic waves in anisotropic piezoelectric (or non-piezoelectric) media.

  16. Analysis of a spatially deconvolved solar pore

    Science.gov (United States)

    Quintero Noda, C.; Shimizu, T.; Ruiz Cobo, B.; Suematsu, Y.; Katsukawa, Y.; Ichimoto, K.

    2016-08-01

    Solar pores are active regions with large magnetic field strengths and apparent simple magnetic configurations. Their properties resemble the ones found for the sunspot umbra although pores do not show penumbra. Therefore, solar pores present themselves as an intriguing phenomenon that is not completely understood. We examine in this work a solar pore observed with Hinode/SP using two state of the art techniques. The first one is the spatial deconvolution of the spectropolarimetric data that allows removing the stray light contamination induced by the spatial point spread function of the telescope. The second one is the inversion of the Stokes profiles assuming local thermodynamic equilibrium that let us to infer the atmospheric physical parameters. After applying these techniques, we found that the spatial deconvolution method does not introduce artefacts, even at the edges of the magnetic structure, where large horizontal gradients are detected on the atmospheric parameters. Moreover, we also describe the physical properties of the magnetic structure at different heights finding that, in the inner part of the solar pore, the temperature is lower than outside, the magnetic field strength is larger than 2 kG and unipolar, and the line-of-sight velocity is almost null. At neighbouring pixels, we found low magnetic field strengths of same polarity and strong downward motions that only occur at the low photosphere, below the continuum optical depth log τ = -1. Finally, we studied the spatial relation between different atmospheric parameters at different heights corroborating the physical properties described before.

  17. Properties of solar pores

    NARCIS (Netherlands)

    Sütterlin, Peter

    2001-01-01

    We present the results of an extensive investigation of the properties of solar pores. Spectra of all 4 Stokes parameters of several magnetic sensitive absorption lines as well as Stokes I only spectra of lines with low or vanishing Landéfactor have been observed. An inversion code based on the Leve

  18. Displacement of soil pore water by trichloroethylene

    Science.gov (United States)

    Wershaw, R. L.; Aiken, G.R.; Imbrigiotta, T.E.; Goldberg, M.C.

    1994-01-01

    Dense nonaqueous phase liquids (DNAPLS) are important pollutants because of their widespread use as chemical and industrial solvents. An example of the pollution caused by the discharge of DNAPLs is found at the Picatinny Arsenal, New Jersey, where trichloroethylene (TCE) has been discharged directly into the unsaturated zone. This discharge has resulted in the formation of a plume of TCE-contaminated water in the aquifer downgradient of the discharge. A zone of dark-colored groundwater containing a high dissolved organic C content has been found near the point of discharge of the TCE. The colored-water plume extends from the point of discharge at least 30 m (100 feet) downgradient. Fulvic acids isolated from the colored-waters plume, from water from a background well that has not been affected by the discharge of chlorinated solvents, and from soil pore water collected in a lysimeter installed at an uncontaminated site upgradient of the study area have been compared. Nuclear magnetic resonance spectra of the fulvic acids from the colored waters and from the lysimeter are very similar, but are markedly different from the nuclear magnetic resonance spectrum of the fulvic acid from the background well. The three-dimensional fluorescence spectrum and the DOC fractionation profile of the colored groundwater and the soil pore water are very similar to each other, but quite different from those of the background water. It is proposed from these observations that this colored water is soil pore water that has been displaced by a separate DNAPL liquid phase downward to the saturated zone.

  19. Measurements of pore-scale flow through apertures.

    Energy Technology Data Exchange (ETDEWEB)

    Chojnicki, Kirsten

    2017-09-01

    Pore-scale aperture effects on flow in pore networks was studied in the laboratory to provide a parameterization for use in transport models. Four cases were considered: regular and irregular pillar/pore alignment with and without an aperture. The velocity field of each case was measured and simulated, providing quantitatively comparable results. Two aperture effect parameterizations were considered: permeability and transmission. Permeability values varied by an order of magnitude between the cases with and without apertures. However, transmission did not correlate with permeability. Despite having much greater permeability the regular aperture case permitted less transmission than the regular case. Moreover, both irregular cases had greater transmission than the regular cases, a difference not supported by the permeabilities. Overall, these findings suggest that pore-scale aperture effects on flow though a pore-network may not be adequately captured by properties such as permeability for applications that are interested in determining particle transport volume and timing.

  20. The pore space scramble

    Science.gov (United States)

    Gormally, Alexandra; Bentham, Michelle; Vermeylen, Saskia; Markusson, Nils

    2015-04-01

    Climate change and energy security continue to be the context of the transition to a secure, affordable and low carbon energy future, both in the UK and beyond. This is reflected in for example, binding climate policy targets at the EU level, the introduction of renewable energy targets, and has also led to an increasing interest in Carbon Capture and Storage (CCS) technology with its potential to help mitigate against the effects of CO2 emissions from fossil fuel burning. The UK has proposed a three phase strategy to integrate CCS into its energy system in the long term focussing on off-shore subsurface storage (DECC, 2014). The potential of CCS therefore, raises a number of challenging questions and issues surrounding the long-term storage of CO2 captured and injected into underground spaces and, alongside other novel uses of the subsurface, contributes to opening a new field for discussion on the governance of the subsurface. Such 'novel' uses of the subsurface have lead to it becoming an increasingly contested space in terms of its governance, with issues emerging around the role of ownership, liability and property rights of subsurface pore space. For instance, questions over the legal ownership of pore space have arisen with ambiguity over the legal standpoint of the surface owner and those wanting to utilise the pore space for gas storage, and suggestions of whether there are depths at which legal 'ownership' becomes obsolete (Barton, 2014). Here we propose to discuss this 'pore space scramble' and provide examples of the competing trajectories of different stakeholders, particularly in the off-shore context given its priority in the UK. We also propose to highlight the current ambiguity around property law of pore space in the UK with reference to approaches currently taken in different national contexts. Ultimately we delineate contrasting models of governance to illustrate the choices we face and consider the ethics of these models for the common good

  1. Adsorption capacity of chosen sandy ground with respect to contaminants relocating with groundwater

    Directory of Open Access Journals (Sweden)

    Aniszewski Andrzej

    2017-03-01

    Full Text Available One of the most important problems concerning contaminant transport in the ground is the problem related to the definition of parameters characterizing the adsorption capacity of ground for the chosen contaminants relocating with groundwater. In this paper, for chloride and sulfate indicators relocating in sandy ground, the numerical values of retardation factors (Ra (treated as average values and pore groundwater velocities with adsorption (ux/Ra (in micro-pore ground spaces are taken into consideration. Based on 2D transport equation the maximal dimensionless concentration values (C*max c in the chosen ground cross-sections were calculated. All the presented numerical calculations are related to the unpublished measurement series which was marked in this paper as: October 1982. For this measurement series the calculated concentration values are compared to the measured concentration ones (C*max m given recently to the author of this paper. In final part of this paper the parameters characterizing adsorption capacity (Ra, ux/Ra are also compared to the same parameters calculated for the two earlier measurement series. Such comparison also allowed for the estimation of a gradual in time depletion of adsorption capacity for the chosen sandy ground.

  2. Effect of pore structure on seismic rock-physics characteristics of dense carbonates

    Institute of Scientific and Technical Information of China (English)

    Pan Jian-Guo; Wang Hong-Bin; Li Chuang; Zhao Jian-Guo

    2015-01-01

    The Ordovician carbonate rocks of the Yingshan formation in the Tarim Basin have a complex pore structure owing to diagenetic and secondary structures. Seismic elastic parameters (e.g., wave velocity) depend on porosity and pore structure. We estimated the average specific surface, average pore-throat radius, pore roundness, and average aspect ratio of carbonate rocks from the Tazhong area. High P-wave velocity samples have small average specific surface, small average pore-throat radius, and large average aspect ratio. Differences in the pore structure of dense carbonate samples lead to fluid-related velocity variability. However, the relation between velocity dispersion and average specifi c surface, or the average aspect ratio, is not linear. For large or small average specifi c surface, the pore structure of the rock samples becomes uniform, which weakens squirtfl ow and minimizes the residuals of ultrasonic data and predictions with the Gassmann equation. When rigid dissolved (casting mold) pores coexist with less rigid microcracks, there are significant P-wave velocity differences between measurements and predictions.

  3. A Microfluidic Pore Network Approach to Investigate Water Transport in Fuel Cell Porous Transport Layers

    CERN Document Server

    Bazylak, A; Markicevic, B; Sinton, D; Djilali, N

    2008-01-01

    Pore network modelling has traditionally been used to study displacement processes in idealized porous media related to geological flows, with applications ranging from groundwater hydrology to enhanced oil recovery. Very recently, pore network modelling has been applied to model the gas diffusion layer (GDL) of a polymer electrolyte membrane (PEM) fuel cell. Discrete pore network models have the potential to elucidate transport phenomena in the GDL with high computational efficiency, in contrast to continuum or molecular dynamics modelling that require extensive computational resources. However, the challenge in studying the GDL with pore network modelling lies in defining the network parameters that accurately describe the porous media as well as the conditions of fluid invasion that represent realistic transport processes. In this work, we discuss the first stage of developing and validating a GDL-representative pore network model. We begin with a two-dimensional pore network model with a single mobile pha...

  4. Pore dynamics in lipid membranes

    Science.gov (United States)

    Gozen, I.; Dommersnes, P.

    2014-09-01

    Transient circular pores can open in plasma membrane of cells due to mechanical stress, and failure to repair such pores lead to cell death. Similar pores in the form of defects also exist among smectic membranes, such as in myelin sheaths or mitochondrial membranes. The formation and growth of membrane defects are associated with diseases, for example multiple sclerosis. A deeper understanding of membrane pore dynamics can provide a more refined picture of membrane integrity-related disease development, and possibly also treatment options and strategies. Pore dynamics is also of great importance regarding healthcare applications such as drug delivery, gene or as recently been implied, cancer therapy. The dynamics of pores significantly differ in stacks which are confined in 2D compared to those in cells or vesicles. In this short review, we will summarize the dynamics of different types of pores that can be observed in biological membranes, which include circular transient, fusion and hemi-fusion pores. We will dedicate a section to floral and fractal pores which were discovered a few years ago and have highly peculiar characteristics. Finally, we will discuss the repair mechanisms of large area pores in conjunction with the current cell membrane repair hypotheses.

  5. groundwater contribution to crop water requirement groundwater ...

    African Journals Online (AJOL)

    eobe

    Keywords: Groundwater, water table, capillary rise, soil type, waterleaf, ... GROUNDWATER CONTRIBUTION TO WATERLEAF (TALINUM TRIANGULARE) IN OXISOLS, I. J. ... Nutritionally, ... information to facilitate increased crop production,.

  6. Soils, Pores, and NMR

    Science.gov (United States)

    Pohlmeier, Andreas; Haber-Pohlmeier, Sabina; Haber, Agnes; Sucre, Oscar; Stingaciu, Laura; Stapf, Siegfried; Blümich, Bernhard

    2010-05-01

    Within Cluster A, Partial Project A1, the pore space exploration by means of Nuclear Magnetic Resonance (NMR) plays a central role. NMR is especially convenient since it probes directly the state and dynamics of the substance of interest: water. First, NMR is applied as relaxometry, where the degree of saturation but also the pore geometry controls the NMR signature of natural porous systems. Examples are presented where soil samples from the Selhausen, Merzenhausen (silt loams), and Kaldenkirchen (sandy loam) test sites are investigated by means of Fast Field Cycling Relaxometry at different degrees of saturation. From the change of the relaxation time distributions with decreasing water content and by comparison with conventional water retention curves we conclude that the fraction of immobile water is characterized by T1 samples (Haber-Pohlmeier et al. 2010). Third, relaxometric information forms the basis of understanding magnetic resonance imaging (MRI) results. The general difficulty of imaging in soils are the inherent fast T2 relaxation times due to i) the small pore sizes, ii) presence of paramagnetic ions in the solid matrix, and iii) diffusion in internal gradients. The last point is important, since echo times can not set shorter than about 1ms for imaging purposes. The way out is either the usage of low fields for imaging in soils or special ultra-short pulse sequences, which do not create echoes. In this presentation we will give examples on conventional imaging of macropore fluxes in soil cores (Haber-Pohlmeier et al. 2010), and the combination with relaxometric imaging, as well as the advantages and drawbacks of low-field and ultra-fast pulse imaging. Also first results on the imaging of soil columns measured by SIP in Project A3 are given. Haber-Pohlmeier, S., S. Stapf, et al. (2010). "Waterflow Monitored by Tracer Transport in Natural Porous Media Using MRI." Vadose Zone J.: submitted. Haber-Pohlmeier, S., S. Stapf, et al. (2010). "Relaxation in a

  7. 含不同孔隙流体的砂岩地震波速度随压力变化的实验研究%A laboratory study of seismic wave velocity in sandstone bearing differential pore fluids at different pressures

    Institute of Scientific and Technical Information of China (English)

    乔二伟; 赵卫华; 龙长兴

    2012-01-01

    岩石的地震波性质是区域构造研究和浅部地震勘探应用的基础.延长油田是我国重要的油气生产基地之一,但目前仍缺乏地震波性质方面的基础资料.作者利用Autolab2000多功能岩石物性自动测试设备,在0~180MPa及饱含不同孔隙流体(干燥、饱水及饱油)条件下,研究了三种来自延长油田砂岩岩芯的纵波、横波速度.结果表明:三种砂岩的Vp、Vs1和Vs2均随压力增加(或降低)而基本呈对数曲线增大(或减小);干燥、饱水和饱油三种波速间的关系因砂岩类型不同而不同,这主要取决于岩石的有效弹性模量、孔隙流体性质以及岩石的内部结构等;含同种孔隙流体的不同类型砂岩,其Vp、Vs1和Vs2随压力变化的规律主要受岩石孔隙度和粒度的影响;而含不同孔隙流体的同种砂岩,其Vp、Vs1和Vs2随压力变化的规律则主要受控于岩石的有效弹性模量和流体密度.另外,含水或含油饱和度的变化对Vs1和Vs2基本没有影响.实验结果可以为该地区地震资料的解释及与声波测井之间的对比提供重要的基础数据和参考依据.%Seismic properties of rock have a wide range of applications in regional tectonic research and shallow seismic exploration. The Yanchang oilfield is one of the important production bases for oil and gas in China, but there is no data of seismic wave. This paper applied the AutoLab 2000 computer-controlled servo hydraulic triaxial test system to obtain accurate P-and S-wave velocity data at pressures up to 180MPa on three kinds of core samples of sandstone in dry, water and oil-saturated conditions from the Yanchang oilfield. The results show the wave velocities Vp, Vs1 and Va for the three kinds of samples of sandstone change basically logarithmically with increasing or decreasing pressure? the relationship between wave velocities in dry, water and oil saturated conditios indicates obvious differences for three kinds of

  8. Influence of pore roughness on high-frequency permeability

    NARCIS (Netherlands)

    Cortis, A.; Smeulders, D.M.J.; Guermond, J.L.; Lafarge, D.

    2003-01-01

    The high-frequency behavior of the fluid velocity patterns for smooth and corrugated pore channels is studied. The classical approach of Johnson et al. [J. Fluid Mech. 176, 379 (1987)] for smooth geometries is obtained in different manners, thus clarifying differences with Sheng and Zhou [Phys. Rev.

  9. A pore water conductivity sensor

    NARCIS (Netherlands)

    Hilhorst, M.A.

    2001-01-01

    The electrical permittivity and conductivity of the bulk soil are a function of the permittivity and conductivity of the pore water. For soil water contents higher than 0.10 both functions are equal, facilitating in situ conductivity measurements of the pore water. A novel method is described, based

  10. Ion transport across transmembrane pores

    NARCIS (Netherlands)

    Leontiadou, Hari; Mark, Alan E.; Marrink, Siewert-Jan

    2007-01-01

    To study the pore-mediated transport of ionic species across a lipid membrane, a series of molecular dynamics simulations have been performed of a dipalmitoyl-phosphatidyl-choline bilayer containing a preformed water pore in the presence of sodium and chloride ions. It is found that the stability of

  11. Direct numerical simulation of pore-scale flow in a bead pack: Comparison with magnetic resonance imaging observations

    Science.gov (United States)

    Yang, Xiaofan; Scheibe, Timothy D.; Richmond, Marshall C.; Perkins, William A.; Vogt, Sarah J.; Codd, Sarah L.; Seymour, Joseph D.; McKinley, Matthew I.

    2013-04-01

    A significant body of current research is aimed at developing methods for numerical simulation of flow and transport in porous media that explicitly resolve complex pore and solid geometries, and at utilizing such models to study the relationships between fundamental pore-scale processes and macroscopic manifestations at larger (i.e., Darcy) scales. A number of different numerical methods for pore-scale simulation have been developed, and have been extensively tested and validated for simplified geometries. However, validation of pore-scale simulations of fluid velocity for complex, three-dimensional (3D) pore geometries that are representative of natural porous media is challenging due to our limited ability to measure pore-scale velocity in such systems. Recent advances in magnetic resonance imaging (MRI) offer the opportunity to measure not only the pore geometry, but also local fluid velocities under steady-state flow conditions in 3D and with high spatial resolution. In this paper, we present a 3D velocity field measured at sub-pore resolution (tens of micrometers) over a centimeter-scale 3D domain using MRI methods. We have utilized the measured pore geometry to perform 3D simulations of Navier-Stokes flow over the same domain using direct numerical simulation techniques. We present a comparison of the numerical simulation results with the measured velocity field. It is shown that the numerical results match the observed velocity patterns well overall except for a variance and small systematic scaling which can be attributed to the known experimental uncertainty in the MRI measurements. The comparisons presented here provide strong validation of the pore-scale simulation methods and new insights for interpretation of uncertainty in MRI measurements of pore-scale velocity. This study also provides a potential benchmark for future comparison of other pore-scale simulation methods. 2012 Elsevier Science.

  12. Pore network and pore scale modeling of reactive transport in porous media

    Science.gov (United States)

    Adler, P. M.; Vu, T. M.; Varloteaux, C.; Bekri, S.

    2012-12-01

    The study of the evolution of a porous medium where a reactive fluid flows is conditioned by the accurate determination of three macroscopic parameters governing the solute displacement, namely the solute velocity, dispersion and mean reaction rate. Of course, a possible application of such studies is CO2 sequestration. This presentation proposes to approach the determination of these parameters by two different ways and to compare them; both are on the pore scale. In the first one called PNM (for pore-network model), a pore-network is extracted from micro tomography images of a real porous medium. This network is composed of spherical pores joined by circular tubes; it is used to calculate transport macroscopic parameters and porosity-permeability evolution during the reactive transport flow as functions of dimensionless numbers representing the reaction and flow rate regimes. The flow is calculated by using Kirchhoff laws. Transport is determined in the asymptotic regime where the solute concentration undergoes an exponential evolution with time. In the second approach called PSM (for pore scale model), the pore-network model is used as a three dimensional medium which is discretized by the Level Set Method. The Stokes equations are solved in order to determine the local flow field and the corresponding permeability. The solute concentration is obtained by solving the local convection-diffusion equation in the 3D pore-network; numerical dispersion is reduced by a Flux Limiting Scheme. Two different geometries of porous media are addressed by both numerical codes. The first pore-network geometry is used to validate the PNM assumptions, whereas the second pore-network is defined for a better understanding of the dominant solute distribution. One of the main results obtained with the first pore-network is the dependence of the concentration profile on the Péclet number Pe in the pore-bodies. When this number increases, one has to switch from an assumption of

  13. Assessment of pore pressures and specific storage within sedimentary strata overlying underground mines

    Science.gov (United States)

    Timms, W.; David, K.; Barbour, L. S.

    2016-12-01

    Realistic values of specific storage (Ss) for groundwater systems are important to determine the spatial extent and timing of c pore pressure changes when the groundwater system is stressed. However, numerical groundwater models of underground excavations typically assume constant literature values of Ss. One part of our research program utilised high frequency pore pressure data to evaluate variability and changes in Ss within sedimentary strata overlying a longwall coal mine. Pore pressure data from a vertical series of 6 vibrating wire piezometers (50 to 278 m depth) recording at hourly intervals were compared with barometric pressure data over a period of several years, including data before and during mining. The site was located near the centre of a longwall panel that extracted 3 m of coal at a depth of 330 m. The data was processed to calculate loading efficiency and Ss values by multi-method analyses of barometric and earth tide responses. In situ Ss results varied over one to two orders of magnitude and indicated that Ss changed before and after excavation of underlying coal seams. The vertical leakage of groundwater within the constrained zone ( 10 to 150 m depth) was found to be limited, although some degree of vertical hydraulic connectivity was observed. Depressurization was evident in the fractured zone directly overlying the coal seam, and Ss changes at 250 m depth indicated this confined aquifer may have become unconfined. Our results demonstrate that high frequency pore pressure data can provide realistic Ss values. In situ Ss values were an order of magnitude lower than Ss measured by geomechnical tests of cores, and were significantly different to textbook values set in most local groundwater models. The timing and extent of groundwater level drawdown predicted by models may therefore be underestimated. We have shown, for the first time, that variability of Ss can be significant, and that these changes can provide important insights into how

  14. Groundwater Waters

    Directory of Open Access Journals (Sweden)

    Ramón Llamas

    1999-10-01

    Full Text Available The groundwaters released through springs constituted a basic element for the survival and progressive development of human beings. Man came to learn how to take better advantage of these waters by digging wells, irrigation channels, and galleries. Nevertheless, these activities do not require cooperation nor the collective agreement of relatively large groups of people, as in the case of creating the necessary structures to take advantage of the resources of surfacewaters. The construction and operation of these structures was a powerful factor in the birth of an urban or civil society – the designated water civilizations. The difference between people taking advantage of groundwater, quasi-individually, and those of surface water, where people work in a group, has continued to the present day. Whereas earlier, this difference did not bring about any special problems, the technological advances of this century, especially theturbine pump, have led to a spectacular increase in the use of roundwater. This advance has significantly contributed to reducing hunger in the world and has provided potable water in developing countries. However, the almost generalized lack of planning and control in the exploitation of these groundwaters reflects that they are little or badly understood by the managers of water policy in almost every country. As such, problems have occurred which have often become exaggerated, giving rise to water-myths. These problems, though, should be addressed if the aim is the sustainable usage of surface water as well as groundwater. To counter any misconceptions and to seek solutions to the problems, distinct plans of action can be highlighted: educating the public; fomenting a system of participative management and decisive support for the communities of users of subterranean waters; integrating a sufficient number of experts in hydrology in the various water management organizations;and assuring transparency of the data on

  15. Hydrogeology and hydrodynamics of coral reef pore waters

    Energy Technology Data Exchange (ETDEWEB)

    Buddemeier, R.W.; Oberdorfer, J.A.

    1988-06-29

    A wide variety of forces can produce head gradients that drive the flow and advective mixing of internal coral reef pore waters. Oscillatory gradients that produce mixing result from wave and tide action. Sustained gradients result from wave and tide-induced setup and ponding, from currents impinging on the reef structure, from groundwater heads, and from density differenced (temperature or salinity gradients). These gradients and the permeabilities and porosities of reef sediments are such that most macropore environments are dominated by advection rather than diffusion. The various driving forces must be analyzed to determine the individual and combined magnitudes of their effects on a specific reef pore-water system. Pore-water movement controls sediment diagenesis, the exchange of nutrients between sediments and benthos, and coastal/island groundwater resources. Because of the complexity of forcing functions, their interactions with specific local reef environments, experimental studies require careful incorporation of these considerations into their design and interpretation. 8 refs., 3 figs., 1 tab.

  16. Groundwater and security

    NARCIS (Netherlands)

    Conti, K.I.; Kukurić, N.; Gupta, J.; Pahl-Wostl, C.; Bhaduri, A.; Gupta, J.

    2016-01-01

    Humans abstract two hundred times more groundwater than oil, annually. Ironically, the role of groundwater in water management and supply is underappreciated, partially due to its invisibility. By conducting a literature survey and investigating groundwater information databases, this chapter answer

  17. Groundwater Pollution from Underground Coal Gasification

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In situ coal gasification poses a potential environmental risk to groundwater pollution although it depends mainly on local hydrogeological conditions.In our investigation, the possible processes of groundwater pollution originating from underground coal gasification (UCG) were analyzed.Typical pollutants were identified and pollution control measures are proposed.Groundwater pollution is caused by the diffusion and penetration of contaminants generated by underground gasification processes towards surrounding strata and the possible leaching of underground residue by natural groundwater flow after gasification.Typical organic pollutants include phenols, benzene, minor components such as PAHs and heterocyclics.Inorganic pollutants involve cations and anions.The natural groundwater flow after gasification through the seam is attributable to the migration of contaminants, which can be predicted by mathematical modeling.The extent and concentration of the groundwater pollution plume depend primarily on groundwater flow velocity, the degree of dispersion and the adsorption and reactions of the various contaminants.The adsorption function of coal and surrounding strata make a big contribution to the decrease of the contaminants over time and with the distance from the burn cavity.Possible pollution control measures regarding UCG include identifying a permanently, unsuitable zone, setting a hydraulic barrier and pumping contaminated water out for surface disposal.Mitigation measures during gasification processes and groundwater remediation after gasification are also proposed.

  18. Is Submarine Groundwater Discharge a Gas Hydrate Formation Mechanism on the Circum-Arctic Shelf?

    Science.gov (United States)

    Frederick, J. M.; Buffett, B. A.

    2015-12-01

    Methane hydrate is an ice-like solid that can sequester large quantities of methane gas in marine sediments along most continental margins where thermodynamic conditions permit its formation. Along the circum-Arctic shelf, relict permafrost-associated methane hydrate deposits formed when non-glaciated portions of the shelf experienced subaerial exposure during ocean transgressions. Gas hydrate stability and the permeability of circum-Arctic shelf sediments to gas migration is closely linked with relict submarine permafrost. Heat flow observations on the Alaskan North Slope and Canadian Beaufort Shelf suggest the movement of groundwater offshore, but direct observations of groundwater flow do not exist. Submarine discharge, an offshore flow of fresh, terrestrial groundwater, can affect the temperature and salinity field in shelf sediments, and may be an important factor in submarine permafrost and gas hydrate evolution on the Arctic continental shelf. Submarine groundwater discharge may also enhance the transport of organic matter for methanogenesis within marine sediments. Because it is buoyancy-driven, the velocity field contains regions with a vertical (upward) component as groundwater flows offshore. This combination of factors makes submarine groundwater discharge a potential mechanism controlling permafrost-associated gas hydrate evolution on the Arctic continental shelf. In this study, we quantitatively investigate the feasibility of submarine groundwater discharge as a control on permafrost-associated gas hydrate formation on the Arctic continental shelf, using the Canadian Beaufort Shelf as an example. We have developed a shelf-scale, two-dimensional numerical model based on the finite volume method for two-phase flow of pore fluid and methane gas within Arctic shelf sediments. The model tracks the evolution of the pressure, temperature, salinity, methane gas, methane hydrate, and permafrost fields given imposed boundary conditions, with latent heat of

  19. Induced charge electrophoresis of a conducting cylinder in a nonconducting cylindrical pore and its micromotoring application

    Science.gov (United States)

    Feng, Huicheng; Wong, Teck Neng; Che, Zhizhao

    2016-08-01

    Induced charge electrophoresis of a conducting cylinder suspended in a nonconducting cylindrical pore is theoretically analyzed and a micromotor is proposed that utilizes the cylinder rotation. The cylinder velocities are analytically obtained in the Dirichlet and the Neumann boundary conditions of the electric field on the cylindrical pore. The results show that the cylinder not only translates but also rotates when it is eccentric with respect to the cylindrical pore. The influences of a number of parameters on the cylinder velocities are characterized in detail. The cylinder trajectories show that the cylinder approaches and becomes stationary at certain positions within the cylindrical pore. The proposed micromotor is capable of working under a heavy load with a high rotational velocity when the eccentricity is large and the applied electric field is strong.

  20. Microfluidic Experiments Studying Pore Scale Interactions of Microbes and Geochemistry

    Science.gov (United States)

    Chen, M.; Kocar, B. D.

    2016-12-01

    Understanding how physical phenomena, chemical reactions, and microbial behavior interact at the pore-scale is crucial to understanding larger scale trends in groundwater chemistry. Recent studies illustrate the utility of microfluidic devices for illuminating pore-scale physical-biogeochemical processes and their control(s) on the cycling of iron, uranium, and other important elements 1-3. These experimental systems are ideal for examining geochemical reactions mediated by microbes, which include processes governed by complex biological phenomenon (e.g. biofilm formation, etc.)4. We present results of microfluidic experiments using a model metal reducing bacteria and varying pore geometries, exploring the limitations of the microorganisms' ability to access tight pore spaces, and examining coupled biogeochemical-physical controls on the cycling of redox sensitive metals. Experimental results will provide an enhanced understanding of coupled physical-biogeochemical processes transpiring at the pore-scale, and will constrain and compliment continuum models used to predict and describe the subsurface cycling of redox-sensitive elements5. 1. Vrionis, H. A. et al. Microbiological and geochemical heterogeneity in an in situ uranium bioremediation field site. Appl. Environ. Microbiol. 71, 6308-6318 (2005). 2. Pearce, C. I. et al. Pore-scale characterization of biogeochemical controls on iron and uranium speciation under flow conditions. Environ. Sci. Technol. 46, 7992-8000 (2012). 3. Zhang, C., Liu, C. & Shi, Z. Micromodel investigation of transport effect on the kinetics of reductive dissolution of hematite. Environ. Sci. Technol. 47, 4131-4139 (2013). 4. Ginn, T. R. et al. Processes in microbial transport in the natural subsurface. Adv. Water Resour. 25, 1017-1042 (2002). 5. Scheibe, T. D. et al. Coupling a genome-scale metabolic model with a reactive transport model to describe in situ uranium bioremediation. Microb. Biotechnol. 2, 274-286 (2009).

  1. Benchmark Study of 3D Pore-scale Flow and Solute Transport Simulation Methods

    Science.gov (United States)

    Scheibe, T. D.; Yang, X.; Mehmani, Y.; Perkins, W. A.; Pasquali, A.; Schoenherr, M.; Kim, K.; Perego, M.; Parks, M. L.; Trask, N.; Balhoff, M.; Richmond, M. C.; Geier, M.; Krafczyk, M.; Luo, L. S.; Tartakovsky, A. M.

    2015-12-01

    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 standard finite volume method (FVM), against magnetic resonance velocimetry (MRV) measurements of pore-scale velocities. Here we expand that benchmark study to include additional models of the first type based on the immersed-boundary method (IMB), lattice Boltzmann method (LBM), and smoothed particle hydrodynamics (SPH), as well as a model of the second type, a pore-network model (PNM). While the PNM approach is computationally much less demanding than direct numerical simulation methods, the effect of conceptualizing complex three-dimensional pore geometries in the manner of PNMs has not been fully determined. We apply all five approaches (FVM-based CFD, IMB, LBM, SPH and PNM) to simulate pore-scale velocity distributions and 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 benchmark study 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.

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

    Science.gov (United States)

    Yang, Xiaofan; Mehmani, Yashar; Perkins, William A.; Pasquali, Andrea; Schönherr, Martin; Kim, Kyungjoo; Perego, Mauro; Parks, Michael L.; Trask, Nathaniel; Balhoff, Matthew T.; Richmond, Marshall C.; Geier, Martin; Krafczyk, Manfred; Luo, Li-Shi; Tartakovsky, Alexandre M.; Scheibe, Timothy D.

    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 on 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

  3. Persistence of uranium groundwater plumes: Contrasting mechanisms at two DOE sites in the groundwater-river interaction zone

    Energy Technology Data Exchange (ETDEWEB)

    Zachara, John M.; Long, Philip E.; Bargar, John; Davis, James A.; Fox, Patricia M.; Fredrickson, Jim K.; Freshley, Mark D.; Konopka, Allan; Liu, Chongxuan; McKinley, James P.; Rockhold, Mark L.; Williams, Kenneth H.; Yabusaki, Steven B.

    2013-04-01

    We examine subsurface uranium (U) plumes at two U.S. Department of Energy sites that are located near large river systems and that are influenced by groundwater-river hydrologic interaction. Following surface excavation of contaminated materials, both sites were projected to naturally flush remnant uranium contamination to levels below regulatory limits (e.g., 30 µg/L or 0.126 µmol/L; U.S. EPA drinking water standard), with 10 years projected for the Hanford 300 Area (Columbia River) and 12 years for the Rifle site (Colorado River). The rate of observed uranium decrease was much lower than expected at both sites. While uncertainty remains, a comparison of current understanding suggests that the two sites have common, but also different mechanisms controlling plume persistence. At the Hanford 300 A, the persistent source is adsorbed U(VI) in the vadose zone that is released to the aquifer during spring water table excursions. The release of U(VI) from the vadose zone and its transport within the oxic, coarse-textured aquifer sediments is dominated by kinetically-limited surface complexation. Modeling implies that annual plume discharge volumes to the Columbia River are small (< one pore volume). At the Rifle site, slow oxidation of naturally reduced, contaminant U(IV) in the saturated zone and a continuous influx of U(VI) from natural, up-gradient sources influences plume persistence. Rate-limited mass transfer and surface complexation also control U(VI) migration velocity in the sub-oxic Rifle groundwater. Flux of U(VI) from the vadose zone at the Rifle site may be locally important, but it is not the dominant process that sustains the plume. A wide range in microbiologic functional diversity exists at both sites. Strains of Geobacter and other metal reducing bacteria are present at low natural abundance that are capable of enzymatic U(VI) reduction in localized zones of accumulated detrital organic carbon or after organic carbon amendment. Major differences

  4. PolyA Single Strand DNA Translocation Through an Alpha-Hemolysin Pore Stem

    Science.gov (United States)

    OKeeffe, James; Cozmuta, Ioana; Stolc, Viktor

    2003-01-01

    A new model for the polymer-pore interaction energy is introduced, based on an atomic-scale description of coulombic polymer-pore interaction. The enhanced drift velocity, experimentally observed for short polymers, is successfully accounted for, using this interaction energy model. For R/R(sub 0)>4 (R(sub 0)=7 angstroms) the translocation velocity approaches the free space drift velocity v(sub 0). This motivates the need to appropriately derivatize artificial nanopores, where R>R(sub 0).

  5. Seepage water flow velocity in hydromorphic acid brown earth in northeast Germany - {sup 15}N studies in groundwater lysimeters; Sickerwassergeschwindigkeit in Hydromorphen Sauerbraunerden Nordostdeutschlands - {sup 15}N-Untersuchungen in Grundwasserlysimetern

    Energy Technology Data Exchange (ETDEWEB)

    Behrendt, A.; Hoelzel, D.; Schalitz, G. [ZALF Muencheberg, Paulinenaue (Germany). Forschungstation; Merbach, W. [ZALF Muencheberg, Paulinenaue (Germany). Inst. fuer Rhizosphaerenforschung und Pflanzenernaehrung

    1999-02-01

    Sandy soils occur widely in Brandenburg. These soils are usually characterised by a high permeability. In low-lying areas such the Havellaendische Luch their proximity to groundwater can pose problems, especially when nutrients such as nitrate are not fully absorbed by the plants and are leached into the ground. Lysimeter studies with stable isotope tracers are especially well suited for estimating the leaching loss attributable to mineral fertilisation. For one thing, lateral flow can largely be excluded in the closed system of a lysimeter. For another, one can reasonably suppose that the marked nitrogen does not behave essentially differently from normal nitrogen. [Deutsch] In Brandenburg kommen verbreitet sandige Boeden vor. Diese Boeden zeichnen sich meist durch hohe Durchlaessigkeiten aus. Dadurch kann in Niederungsgebieten, wie dem Havellaendischen Luch, die Grundwassernaehe zum Problem werden, insbesondere wenn Naehrstoffe wie Nitrat nicht vollstaendig von den Pflanzen aufgenommen werden und der Auswaschung anheimfallen. Zur Abschaetzung der Auswaschungsverluste, die tatsaechlich aus der Mineralduengung stammen, eignen sich besonders Lysimeteruntersuchungen mit stabilisotopen Tracern. Einerseits lassen sich hier, im geschlossenen System, laterale Stroemungen weitgehend ausschliessen, andererseits kann man davon ausgehen, dass sich der makierte Stickstoff im System Boden-Pflanze nicht grundsaetzlich anders verhaelt als herkoemmlicher Stickstoff. (orig.)

  6. Experiment Analysis on Impact of Ground Vegetation and Soil Pores for Surface Runoff%地表植被覆盖与土壤大孔隙对地表径流影响实验分析

    Institute of Scientific and Technical Information of China (English)

    舒茂; 何国清

    2015-01-01

    There are two important factors to impact surface runoff. One is ground vegetation,another is soil pores. Vegetation can reduce the speed and flow of runoff,which make a strong impact to erodibility. The existence of soil pores improves the infiltration rate of the rainfall. The rain which enters into the soil bypasses most of the soil matrix and speeds up the response speed of groundwater. Groundwater was added before soil water has not yet reached to the field capacity. Thereby distribution of surface runoff was changed and velocity and flow of the surface runoff were both controlled. In this paper,we did the experiment of indoor soil box: made soil pores,artificial rainfall and planted vegetation on the surface. We analyzed the impact of ground vegetation and soil pores to surface runoff according to velocity,flow,subsurface flow and ground water formation. Then we get a further understanding that surface vegetation and soil pores play an important role in soil and water conservation.%地表植被与土壤大孔隙均为影响地表径流的重要因素,植被能够降低径流速度和流量,将对侵蚀程度有很大影响;大孔隙的存在,提高了降雨进入土壤的入渗率,而进入土壤中的水就绕过大部分土壤基质,加快了地下水的响应速度,地下水在土壤水还未达到田间持水量时就得到补充,改变了地表径流分配,对地表径流流速、流量均起到了抑制作用。文章采用室内土槽实验的方法人造大孔隙,在地表种植植被,通过人工降雨,从地表径流流量、流速及壤中流、地下水产生方式分析地表植被与土壤大孔隙对地表径流的影响程度,进一步认识地表植被及土壤大孔隙对水土保持的作用。

  7. Hydrocarbon saturation determination using acoustic velocities obtained through casing

    Science.gov (United States)

    Moos, Daniel

    2010-03-09

    Compressional and shear velocities of earth formations are measured through casing. The determined compressional and shear velocities are used in a two component mixing model to provides improved quantitative values for the solid, the dry frame, and the pore compressibility. These are used in determination of hydrocarbon saturation.

  8. Experimental Study on Pore Distribution Characters and Convert Rate of CaO

    Institute of Scientific and Technical Information of China (English)

    Li JIA; Yanyan ZENG; Tao ZHANG

    2005-01-01

    During the reaction between calcium sorbents and SO2, calcium sorbents are first calcined and converted into CaO. CaO can be obtained by calcining Ca(OH)2 or CaCO3. The porosity of the sorbent is increased because of calcination and is decreased because of sulfurization. In the calcination process H2O or CO2 is escaped from the particles and pores are formed in particles. The reaction or convert rate of CaO is influenced strongly by the pore structure characters. From Ca(OH)2 to CaO the escape velocity of H2O or its mass transfer is one of the key factors influencing the pore forming. During calcination process different heating velocity, different heating time and temperature were suggested. The temperature rising rate and calcining temperature play important role to the pore structure. The convert rates of CaO obtained through different calcining conditions were investigated experimentally. Some interesting results were showed that the calcium utilization of CaO particles is determined not only by the special surface area and total pore volume, but also by pore-size distribution. The main factor influencing the sulfation is the pore diameter distribution at lower sulfation temperature. For higher reaction temperature specific volume is the important reason. But pore-size distribution is strongly influenced by heat flux and temperature in the calcining process.

  9. Effects of pore-scale precipitation on permeability and flow

    Science.gov (United States)

    Noiriel, Catherine; Steefel, Carl I.; Yang, Li; Bernard, Dominique

    2016-09-01

    The effects of calcite precipitation on porous media permeability and flow were evaluated with a combined experimental and modeling approach. X-ray microtomography images of two columns packed with glass beads and calcite (spar crystals) or aragonite (Bahamas ooids) injected with a supersaturated solution (log Ω = 1.42) were processed in order to calculate rates of calcite precipitation with a spatial resolution of 4.46 μm. Identification and localization of the newly precipitated crystals on the 3D images was performed and results used to calculate the crystal growth rates and velocities. The effects of carbonate precipitation were also evaluated in terms of the integrated precipitation rate over the length of the column, crystal shape, surface area and pore roughness changes. While growth was epitaxial on calcite spar, calcite rhombohedra formed on glass beads and clusters of polyhedrons formed on aragonite ooids. Near the column inlet, calcite precipitation occurred preferentially on carbonate grains compared to glass beads, with almost 100% of calcite spar surface area covered by new crystals versus 92% in the case of aragonite and 11% in the case of glass beads. Although the experimental chemistry and flow boundary conditions in the two columns were similar, their porosity-permeability evolution was different because the nucleation and subsequent crystal growth on the two substrates (i.e., calcite spar and aragonite ooids) was very different. The impact of mineral precipitation on pore-scale flow and permeability was evaluated using a pore-scale Stokes solver that accounted for the changes in pore geometry. For similar magnitude reductions in porosity, the decrease in permeability was highest within the sample that experienced the greatest increase in pore roughness. Various porous media models were generated to show the impact of different crystal growth patterns and pore roughness changes on flow and permeability-porosity relationship. Under constant flow

  10. Effect of Low Energy Waves on the Accumulation and Transport of Fecal Indicator Bacteria in Sand and Pore Water at Freshwater Beaches.

    Science.gov (United States)

    Wu, Ming Zhi; O'Carroll, Denis M; Vogel, Laura J; Robinson, Clare E

    2017-02-24

    Elevated fecal indicator bacteria (FIB) in beach sand and pore water represent an important nonpoint source of contamination to surface waters. This study examines the physical processes governing the accumulation and distribution of FIB in a beach aquifer. Field data indicate E. coli and enterococci can be transported 1 and 2 m, respectively, below the water table. Data were used to calibrate a numerical model whereby FIB are delivered to a beach aquifer by wave-induced infiltration across the beach face. Simulations indicate FIB rapidly accumulate in a beach aquifer with FIB primarily associated with sand rather than freely residing in the pore water. Simulated transport of E. coli in a beach aquifer is complex and does not correlate with conservative tracer transport. Beaches with higher wave-induced infiltration rate and vertical infiltration velocity (i.e., beaches with higher beach slope and wave height, and lower terrestrial groundwater discharge) had greater E. coli accumulation and E. coli was transported deeper below the beach face. For certain beach conditions, the amount of FIB accumulated in sand over 5-6 days was found to be sufficient to trigger a beach advisory if eroded to surface water.

  11. Groundwater recharge: Accurately representing evapotranspiration

    CSIR Research Space (South Africa)

    Bugan, Richard DH

    2011-09-01

    Full Text Available Groundwater recharge is the basis for accurate estimation of groundwater resources, for determining the modes of water allocation and groundwater resource susceptibility to climate change. Accurate estimations of groundwater recharge with models...

  12. Groundwater dating for understanding nitrogen in groundwater systems - Time lag, fate, and detailed flow path ways

    Science.gov (United States)

    Morgenstern, Uwe; Hadfield, John; Stenger, Roland

    2014-05-01

    on nitrate fluxes it is insufficient to consider only the spatial distribution of oxic and anoxic zones; the flow through these zones needs to be quantified. If the majority of groundwater passes through the oxic zones rather the anoxic zones, insignificant N attenuation must be expected. Our results indicate about an order of magnitude lower vertical flow velocity and flux through anoxic zones compared to oxic zones. The age distribution of the groundwater allows identification of groundwater flow path ways, which in the Lake Taupo catchment is characterised by high piston flow, indicating groundwater flow between widely connected impermeable layers, probably paleosol layers. Groundwater dating has become an important tool for management of nitrate contamination.

  13. Pore-scale modeling of competitive adsorption in porous media.

    Science.gov (United States)

    Ryan, Emily M; Tartakovsky, Alexandre M; Amon, Cristina

    2011-03-01

    In this paper we present a smoothed particle hydrodynamics (SPH) pore-scale multicomponent reactive transport model with competitive adsorption. SPH is a Lagrangian, particle based modeling method which uses the particles as interpolation points to discretize and solve flow and transport equations. The theory and details of the SPH pore-scale model are presented along with a novel method for handling surface reactions, the continuum surface reaction (CSR) model. The numerical accuracy of the CSR model is validated with analytical and finite difference solutions, and the effects of spatial and temporal resolution on the accuracy of the model are also discussed. The pore-scale model is used to study competitive adsorption for different Damköhler and Peclet numbers in a binary system where a plume of species B is introduced into a system which initially contains species A. The pore-scale model results are compared with a Darcy-scale model to investigate the accuracy of a Darcy-scale reactive transport model for a wide range of Damköhler and Peclet numbers. The comparison shows that the Darcy model over estimates the mass fraction of aqueous and adsorbed species B and underestimates the mass fractions of species A. The Darcy-scale model also predicts faster transport of species A and B through the system than the pore-scale model. The overestimation of the advective velocity and the extent of reactions by the Darcy-scale model are due to incomplete pore-scale mixing. As the degree of the solute mixing decreases with increasing Peclet and Damköhler numbers, so does the accuracy of the Darcy-scale model. Copyright © 2010 Elsevier B.V. All rights reserved.

  14. Dynamics of the solar atmosphere above a pore with a light bridge

    CERN Document Server

    Sobotka, M; Jurcak, J; Heinzel, P; Del Moro, D; Berrilli, F

    2013-01-01

    Context: Solar pores are small sunspots lacking penumbra with prevailing vertical magnetic field component. They can include light bridges at places with locally reduced magnetic field. Like sunspots, they exhibit a wide range of oscillatory phenomena. Aims: A large isolated pore with a light bridge (NOAA 11005) is studied to obtain characteristics of a chromospheric filamentary structure around the pore, to analyse oscillations and waves in and around the pore, and to understand the structure and brightness of the light bridge. Methods: Spectral imaging observations in the line Ca II 854.2 nm and a complementary spectropolarimetry in Fe I lines, obtained with the DST/IBIS spectrometer and HINODE/SOT spectropolarimeter, are used to measure photospheric and chromospheric velocity fields, oscillations, waves, magnetic field in the photosphere, and acoustic energy flux and radiative losses in the chromosphere. Results: The chromospheric filamentary structure around the pore has all important characteristics of a...

  15. Groundwater Managment Districts

    Data.gov (United States)

    Kansas Data Access and Support Center — This dataset outlines the location of the five Groundwater Management Districts in Kansas. GMDs are locally formed and elected boards for regional groundwater...

  16. Origin and assessment of deep groundwater inflow in the Ca' Lita landslide using hydrochemistry and in situ monitoring

    NARCIS (Netherlands)

    Cervi, F.; Ronchetti, F.; Martinelli, G.; Bogaard, T.A.; Corsini, A.

    2012-01-01

    Changes in soil water content, groundwater flow and a rise in pore water pressure are well-known causal or triggering factors for hillslope instability. Rainfall and snowmelt are generally assumed as the main sources of groundwater recharge. This assumption neglects the role of deep water inflow in

  17. Origin and assessment of deep groundwater inflow in the Ca' Lita landslide using hydrochemistry and in situ monitoring

    NARCIS (Netherlands)

    Cervi, F.; Ronchetti, F.; Martinelli, G.; Bogaard, T.A.; Corsini, A.

    2012-01-01

    Changes in soil water content, groundwater flow and a rise in pore water pressure are well-known causal or triggering factors for hillslope instability. Rainfall and snowmelt are generally assumed as the main sources of groundwater recharge. This assumption neglects the role of deep water inflow in

  18. Future research needs involving pathogens in groundwater

    Science.gov (United States)

    Bradford, Scott A.; Harvey, Ronald W.

    2017-01-01

    Contamination of groundwater by enteric pathogens has commonly been associated with disease outbreaks. Proper management and treatment of pathogen sources are important prerequisites for preventing groundwater contamination. However, non-point sources of pathogen contamination are frequently difficult to identify, and existing approaches for pathogen detection are costly and only provide semi-quantitative information. Microbial indicators that are readily quantified often do not correlate with the presence of pathogens. Pathogens of emerging concern and increasing detections of antibiotic resistance among bacterial pathogens in groundwater are topics of growing concern. Adequate removal of pathogens during soil passage is therefore critical for safe groundwater extraction. Processes that enhance pathogen transport (e.g., high velocity zones and preferential flow) and diminish pathogen removal (e.g., reversible retention and enhanced survival) are of special concern because they increase the risk of groundwater contamination, but are still incompletely understood. Improved theory and modeling tools are needed to analyze experimental data, test hypotheses, understand coupled processes and controlling mechanisms, predict spatial and/or temporal variability in model parameters and uncertainty in pathogen concentrations, assess risk, and develop mitigation and best management approaches to protect groundwater.

  19. Future research needs involving pathogens in groundwater

    Science.gov (United States)

    Bradford, Scott A.; Harvey, Ronald W.

    2016-12-01

    Contamination of groundwater by enteric pathogens has commonly been associated with disease outbreaks. Proper management and treatment of pathogen sources are important prerequisites for preventing groundwater contamination. However, non-point sources of pathogen contamination are frequently difficult to identify, and existing approaches for pathogen detection are costly and only provide semi-quantitative information. Microbial indicators that are readily quantified often do not correlate with the presence of pathogens. Pathogens of emerging concern and increasing detections of antibiotic resistance among bacterial pathogens in groundwater are topics of growing concern. Adequate removal of pathogens during soil passage is therefore critical for safe groundwater extraction. Processes that enhance pathogen transport (e.g., high velocity zones and preferential flow) and diminish pathogen removal (e.g., reversible retention and enhanced survival) are of special concern because they increase the risk of groundwater contamination, but are still incompletely understood. Improved theory and modeling tools are needed to analyze experimental data, test hypotheses, understand coupled processes and controlling mechanisms, predict spatial and/or temporal variability in model parameters and uncertainty in pathogen concentrations, assess risk, and develop mitigation and best management approaches to protect groundwater.

  20. Future research needs involving pathogens in groundwater

    Science.gov (United States)

    Bradford, Scott A.; Harvey, Ronald W.

    2017-06-01

    Contamination of groundwater by enteric pathogens has commonly been associated with disease outbreaks. Proper management and treatment of pathogen sources are important prerequisites for preventing groundwater contamination. However, non-point sources of pathogen contamination are frequently difficult to identify, and existing approaches for pathogen detection are costly and only provide semi-quantitative information. Microbial indicators that are readily quantified often do not correlate with the presence of pathogens. Pathogens of emerging concern and increasing detections of antibiotic resistance among bacterial pathogens in groundwater are topics of growing concern. Adequate removal of pathogens during soil passage is therefore critical for safe groundwater extraction. Processes that enhance pathogen transport (e.g., high velocity zones and preferential flow) and diminish pathogen removal (e.g., reversible retention and enhanced survival) are of special concern because they increase the risk of groundwater contamination, but are still incompletely understood. Improved theory and modeling tools are needed to analyze experimental data, test hypotheses, understand coupled processes and controlling mechanisms, predict spatial and/or temporal variability in model parameters and uncertainty in pathogen concentrations, assess risk, and develop mitigation and best management approaches to protect groundwater.

  1. DESIGN INFORMATION ON FINE PORE AERATION SYSTEMS

    Science.gov (United States)

    Field studies were conducted over several years at municipal wastewater treatment plants employing line pore diffused aeration systems. These studies were designed to produce reliable information on the performance and operational requirements of fine pore devices under process ...

  2. Real-time monitoring of nitrate transport in the deep vadose zone under a crop field - implications for groundwater protection

    Science.gov (United States)

    Turkeltaub, Tuvia; Kurtzman, Daniel; Dahan, Ofer

    2016-08-01

    Nitrate is considered the most common non-point pollutant in groundwater. It is often attributed to agricultural management, when excess application of nitrogen fertilizer leaches below the root zone and is eventually transported as nitrate through the unsaturated zone to the water table. A lag time of years to decades between processes occurring in the root zone and their final imprint on groundwater quality prevents proper decision-making on land use and groundwater-resource management. This study implemented the vadose-zone monitoring system (VMS) under a commercial crop field. Data obtained by the VMS for 6 years allowed, for the first time known to us, a unique detailed tracking of water percolation and nitrate migration from the surface through the entire vadose zone to the water table at 18.5 m depth. A nitrate concentration time series, which varied with time and depth, revealed - in real time - a major pulse of nitrate mass propagating down through the vadose zone from the root zone toward the water table. Analysis of stable nitrate isotopes indicated that manure is the prevalent source of nitrate in the deep vadose zone and that nitrogen transformation processes have little effect on nitrate isotopic signature. The total nitrogen mass calculations emphasized the nitrate mass migration towards the water table. Furthermore, the simulated pore-water velocity through analytical solution of the convection-dispersion equation shows that nitrate migration time from land surface to groundwater is relatively rapid, approximately 5.9 years. Ultimately, agricultural land uses, which are constrained to high nitrogen application rates and coarse soil texture, are prone to inducing substantial nitrate leaching.

  3. A pore scale study on turbulent combustion in porous media

    Science.gov (United States)

    Jouybari, N. F.; Maerefat, M.; Nimvari, M. E.

    2016-02-01

    This paper presents pore scale simulation of turbulent combustion of air/methane mixture in porous media to investigate the effects of multidimensionality and turbulence on the flame within the pores of porous media. In order to investigate combustion in the pores of porous medium, a simple but often used porous medium consisting of a staggered arrangement of square cylinders is considered in the present study. Results of turbulent kinetic energy, turbulent viscosity ratio, temperature, flame speed, convective heat transfer and thermal conductivity are presented and compared for laminar and turbulent simulations. It is shown that the turbulent kinetic energy increases from the inlet of burner, because of turbulence created by the solid matrix with a sudden jump or reduction at the flame front due to increase in temperature and velocity. Also, the pore scale simulation revealed that the laminarization of flow occurs after flame front in the combustion zone and turbulence effects are important mainly in the preheat zone. It is shown that turbulence enhances the diffusion processes in the preheat zone, but it is not enough to affect the maximum flame speed, temperature distribution and convective heat transfer in the porous burner. The dimensionless parameters associated with the Borghi-Peters diagram of turbulent combustion have been analyzed for the case of combustion in porous media and it is found that the combustion in the porous burner considered in the present study concerns the range of well stirred reactor very close to the laminar flame region.

  4. Evolution of Unsteady Groundwater Flow Systems

    Science.gov (United States)

    Liang, Xing; Jin, Menggui; Niu, Hong

    2016-04-01

    Natural groundwater flow is usually transient, especially in long time scale. A theoretical approach on unsteady groundwater flow systems was adopted to highlight some of the knowledge gaps in the evolution of groundwater flow systems. The specific consideration was focused on evolution of groundwater flow systems from unsteady to steady under natural and mining conditions. Two analytical solutions were developed, using segregation variable method to calculate the hydraulic head under steady and unsteady flow conditions. The impact of anisotropy ratio, hydraulic conductivity (K) and specific yield (μs) on the flow patterns were analyzed. The results showed that the area of the equal velocity region increased and the penetrating depth of the flow system decreased while the anisotropy ratio (ɛ = °Kx-/Kz--) increased. Stagnant zones were found in the flow field where the directions of streamlines were opposite. These stagnant zones moved up when the horizontal hydraulic conductivity increased. The results of the study on transient flow indicated a positive impact on hydraulic head with an increase of hydraulic conductivity, while a negative effect on hydraulic head was observed when the specific yield was enhanced. An unsteady numerical model of groundwater flow systems with annual periodic recharge was developed using MODFLOW. It was observed that the transient groundwater flow patterns were different from that developed in the steady flow under the same recharge intensity. The water table fluctuated when the recharge intensity altered. The monitoring of hydraulic head and concentration migration revealed that the unsteady recharge affected the shallow local flow system more than the deep regional flow system. The groundwater flow systems fluctuated with the action of one or more pumping wells. The comparison of steady and unsteady groundwater flow observation indicated that the unsteady flow patterns cannot be simulated by the steady model when the condition

  5. Quantification of long-term wastewater fluxes at the surface water/groundwater-interface: An integrative model perspective using stable isotopes and acesulfame

    Energy Technology Data Exchange (ETDEWEB)

    Engelhardt, I., E-mail: i.engelhardt@fz-juelich.de [Forschungszentrum Jülich, Institute of Bio- and Geosciences, Agrosphere — IBG-3 (Germany); Technical University of Darmstadt, Institute of Applied Geosciences (Germany); Barth, J.A.C. [GeoZentrum Nordbayern, University of Erlangen-Nuremberg (Germany); Bol, R. [Forschungszentrum Jülich, Institute of Bio- and Geosciences, Agrosphere — IBG-3 (Germany); Schulz, M.; Ternes, T.A. [Federal Institute of Hydrology (BfG) (Germany); Schüth, C. [Technical University of Darmstadt, Institute of Applied Geosciences (Germany); van Geldern, R. [GeoZentrum Nordbayern, University of Erlangen-Nuremberg (Germany)

    2014-01-01

    The suitability of acesulfame to trace wastewater-related surface water fluxes from streams into the hyporheic and riparian zones over long-term periods was investigated. The transport behavior of acesulfame was compared with the transport of water stable isotopes (δ{sup 18}O or δ{sup 2}H). A calibrated model based on a joint inversion of temperature, acesulfame, and piezometric pressure heads was employed in a model validation using data sets of acesulfame and water stable isotopes collected over 5 months in a stream and groundwater. The spatial distribution of fresh water within the groundwater resulting from surface water infiltration was estimated by computing groundwater ages and compared with the predicted acesulfame plume obtained after 153 day simulation time. Both, surface water ratios calculated with a mixing equation from water stable isotopes and simulated acesulfame mass fluxes, were investigated for their ability to estimate the contribution of wastewater-related surface water inflow within groundwater. The results of this study point to limitations for the application of acesulfame to trace surface water–groundwater interactions properly. Acesulfame completely missed the wastewater-related surface water volumes that still remained in the hyporheic zone under stream-gaining conditions. In contrast, under stream-losing conditions, which developed after periods of stagnating hydraulic exchange, acesulfame based predictions lead to an overestimation of the surface water volume of up to 25% in the riparian zone. If slow seepage velocities prevail a proportion of acesulfame might be stored in smaller pores, while when released under fast flowing water conditions it will travel further downstream with the groundwater flow direction. Therefore, under such conditions acesulfame can be a less-ideal tracer in the hyporheic and riparian zones and additional monitoring with other environmental tracers such as water stable isotopes is highly recommended

  6. Unlocking the Physiochemical Controls on Organic Carbon Dynamics from the Soil Pore- to Core-Scale

    Science.gov (United States)

    Smith, A. P.; Tfaily, M. M.; Bond-Lamberty, B. P.; Todd-Brown, K. E.; Bailey, V. L.

    2015-12-01

    The physical organization of soil includes pore networks of varying size and connectivity. These networks control microbial access to soil organic carbon (C) by spatially separating microorganisms and C by both distance and size exclusion. The extent to which this spatially isolated C is vulnerable to microbial transformation under hydrologically dynamic conditions is unknown, and limits our ability to predict the source and sink capacity of soils. We investigated the effects of shifting hydrologic connectivity and soil structure on greenhouse gas C emissions from surface soils collected from the Disney Wilderness Preserve (Florida, USA). We subjected intact soil cores and re-packed homogenized soil cores to simulated groundwater rise or precipitation, monitoring their CO2 and CH4 emissions over 24 hours. Soil pore water was then extracted from each core using different suctions to sample water retained by pore throats of different sizes and then characterized by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. Greater respiration rates were observed from homogenized cores compared to intact cores, and from soils wet from below, in which the wetting front is driven by capillary forces, filling fine pores first. This suggests that C located in fine pores may turn over via diffusion processes that lead to the colocation of this C with other resources and microorganisms. Both the complexity and concentration of soluble-C increased with decreasing pore size domains. Pore water extracted from homogenized cores had greater C concentrations than from intact cores, with the greatest concentrations in pore waters sampled from very fine pores, highlighting the importance of soil structure in physically protecting C. These results suggest that the spatial separation of decomposers from C is a key mechanism stabilizing C in these soils. Further research is ongoing to accurately represent this protection mechanism, and the conditions under which it breaks

  7. Geochemistry of Clayey Aquitard Pore Water as Archive of Paleo-Environment, Western Bohai Bay

    Institute of Scientific and Technical Information of China (English)

    Jing Li; Xing Liang; Menggui Jin; Guoqiang Xiao; Jishan He; Yandong Pei

    2015-01-01

    The record of paleo-environment in clayey aquitard pore water is much more effective relative to aquifer groundwater owing to the low permeability of clayey aquitard. Oxygen-18 (18O), deuterium (D), and chemical patterns were determined in pore water samples extracted from two 500 m depth boreholes, G1 and G2, in western Bohai Bay, China. Shallow pore water samples (depth<102 m) are saline water, with the TDS (total dissolved solids) of 3.69–30.75 g/L, and deeper ones (depth=102–500 m) are fresh water, with the TDS<1 g/L. Content of major ions (i.e., Cl-, Na+, K+, Mg2+, SO42-, Ca2+) is high in marine sediment pore water samples and gradually decrease towards to terre-strial sediment pore water, together with the Cl/Br and Sr/Ba ratios changing significantly in different sedimentary facies along the study profile, indicating that pore water may be paleo-sedimentary water and not replaced by modern water.δ18O profile and positive correlation betweenδ18O and Cl-of shal-low saline pore water indicated diffusion as the main transport mechanism, and distinguished four transgressive layers since Late Quaternary (i.e., Holocene marine unit, two Late Pleistocene marine units and Middle Pleistocene marine unit), further supporting the finding that pore water retained the feature of paleo-sedimentary water. Climate was identified as the main influence on the isotopic signa-ture of aquitard pore water and four climate periods were determined byδ18O profile.

  8. Unstable Pore-Water Flow in Intertidal Wetlands

    Science.gov (United States)

    Barry, D. A.; Shen, C.; Li, L.

    2014-12-01

    Salt marshes are important intertidal wetlands strongly influenced by interactions between surface water and groundwater. Bordered by coastal water, the marsh system undergoes cycles of inundation and exposure driven by the tide. This leads to dynamic, complex pore-water flow and solute transport in the marsh soil. Pore-water circulations occur over vastly different spatial and temporal scales with strong link to the marsh topography. These circulations control solute transport between the marsh soil and the tidal creek, and ultimately affect the overall nutrient exchange between the marsh and coastal water. The pore-water flows also dictate the soil condition, particularly aeration, which influences the marsh plant growth. Numerous studies have been carried out to examine the pore-water flow process in the marsh soil driven by tides, focusing on stable flow with the assumption of homogeneity in soil and fluid properties. This assumption, however, is questionable given the actual inhomogeneous conditions in the field. For example, the salinity of surface water in the tidal creek varies temporally and spatially due to the influence of rainfall and evapotranspiration as well as the freshwater input from upland areas to the estuary, creating density gradients across the marsh surface and within the marsh soil. Many marshes possess soil stratigraphy with low-permeability mud typically overlying high-permeability sandy deposits. Macropores such as crab burrows are commonly distributed in salt marsh sediments. All these conditions are prone to the development of non-uniform, unstable preferential pore-water flow in the marsh soil, for example, funnelling and fingering. Here we present results from laboratory experiments and numerical simulations to explore such unstable flow. In particular, the analysis aims to address how the unstable flow modifies patterns of local pore-water movement and solute transport, as well as the overall exchange between the marsh soil and

  9. Kinematics in a slowly drying porous medium: Reconciliation of pore network simulations and continuum modeling

    Science.gov (United States)

    Attari Moghaddam, Alireza; Kharaghani, Abdolreza; Tsotsas, Evangelos; Prat, Marc

    2017-02-01

    We study the velocity field in the liquid phase during the drying of a porous medium in the capillarity-dominated regime with evaporation from the top surface. A simple mass balance in the continuum framework leads to a linear variation of the filtration velocity across the sample. By contrast, the instantaneous slice-averaged velocity field determined from pore network simulations leads to step velocity profiles. The vertical velocity profile is almost constant near the evaporative top surface and zero close to the bottom of the sample. The relative extent of the two regions with constant velocity is dictated by the position of the most unstable meniscus. It is shown that the continuum and pore network results can be reconciled by averaging the velocity field obtained from the pore network simulations over time. This opens up interesting prospects regarding the transport of dissolved species during drying. Also, the study reveals the existence of an edge effect, which is not taken into account in the classical continuum models of drying.

  10. Induced charge electrophoresis of a conducting cylinder in a non-conducting cylindrical pore and its micromotoring application

    CERN Document Server

    Feng, Huicheng; Che, Zhizhao

    2016-01-01

    Induced charge electrophoresis of a conducting cylinder suspended in a non-conducting cylindrical pore is theoretically analyzed, and a micromotor is proposed utilizing the cylinder rotation. The cylinder velocities are analytically obtained in the Dirichlet and the Neumann boundary conditions of the electric field on the cylindrical pore. The results show that the cylinder not only translates but also rotates when it is eccentric with respect to the cylindrical pore. The influences of a number of parameters on the cylinder velocities are characterized in detail. The cylinder trajectories show that the cylinder approaches and rests at certain positions within the cylindrical pore. The analysis reveals that the Dirichlet boundary condition predicts more reasonable cylinder behaviors than the Neumann boundary condition. The proposed micromotor is capable of working under a heavy load with a high rotational velocity when the eccentricity is large and the applied electric field is strong.

  11. Pore formation by Cry toxins.

    Science.gov (United States)

    Soberón, Mario; Pardo, Liliana; Muñóz-Garay, Carlos; Sánchez, Jorge; Gómez, Isabel; Porta, Helena; Bravo, Alejandra

    2010-01-01

    Bacillus thuringiensis (Bt) bacteria produce insecticidal Cry and Cyt proteins used in the biological control of different insect pests. In this review, we will focus on the 3d-Cry toxins that represent the biggest group of Cry proteins and also on Cyt toxins. The 3d-Cry toxins are pore-forming toxins that induce cell death by forming ionic pores into the membrane of the midgut epithelial cells in their target insect. The initial steps in the mode of action include ingestion of the protoxin, activation by midgut proteases to produce the toxin fragment and the interaction with the primary cadherin receptor. The interaction of the monomeric CrylA toxin with the cadherin receptor promotes an extra proteolytic cleavage, where helix alpha-1 of domain I is eliminated and the toxin oligomerization is induced, forming a structure of 250 kDa. The oligomeric structure binds to a secondary receptor, aminopeptidase N or alkaline phosphatase. The secondary receptor drives the toxin into detergent resistant membrane microdomains formingpores that cause osmotic shock, burst of the midgut cells and insect death. Regarding to Cyt toxins, these proteins have a synergistic effect on the toxicity of some Cry toxins. Cyt proteins are also proteolytic activated in the midgut lumen of their target, they bind to some phospholipids present in the mosquito midgut cells. The proposed mechanism of synergism between Cry and Cyt toxins is that Cyt1Aa function as a receptor for Cry toxins. The Cyt1A inserts into midgut epithelium membrane and exposes protein regions that are recognized by Cry11Aa. It was demonstrated that this interaction facilitates the oligomerization of Cry11Aa and also its pore formation activity.

  12. Investigation of the Biodegradation of Chlorinated Ethenes at the Pore-Scale Using Silicon- Based Micromodels

    Science.gov (United States)

    Nambi, I. M.; Werth, C. J.; Sanford, R. A.

    2001-05-01

    Groundwater contamination by chlorinated ethenes is a matter of serious concern in industrialized countries due to the hazardous nature of these solvents. Biodegradation of these contaminants has proved to be the most cost-effective remediation technology to solve this problem. One of the most common degradation pathways is anaerobic reductive dechlorination, in which chlorinated ethenes are successively reduced from PCE to TCE to DCE to Vinyl chloride and finally to ethene, an environmentally benign substance. The success rates of this degradation with batch cultures are not often repeatable in column or field scale experiments due to the complexities associated with the heterogeneous porous medium. Hence it is important to understand degradation phenomena at the pore-scale in order to devise successful remediation techniques at a larger scale. In this study, 1 cm2 silicon based micromodels were used to simulate the subsurface at the pore-scale. The microbial culture used was Dehalospirillum multivorans. A solution of PCE (0.2 mM) and lactate (1 mM) was fed continuously into the micromodel at a rate of 0.001ml/min, which translated to a Darcy velocity in the porous matrix of 9.6m/day. Micromodels were observed with epi-fluorescence and DIC microscopy with a microscope equipped with an automated stage, CCD camera and an image analysis system. Activity within the micromodel was verified by the presence of cis-DCE in the effluent, which indicated that 95% of the PCE had been degraded. Visible biomass was also observed within a few weeks of starting PCE feeding both by DIC and fluorescence microscopy. The active and inactive zones of degradation were identified by the use of pH sensitive fluorescent dyes. The aggregates of cell biomass were quantified based on their area and perimeter in the images. These measurements indicated that after a few weeks, the biomass had reached a steady-state with new cells growing at the same rate as the sloughing of old biomass. This

  13. The role of different grain shapes in modifying intra-pore flow and transport phenomena

    Science.gov (United States)

    Chaudhary, K.; Cardenas, B.; Bennett, P.; Ketcham, R. A.

    2010-12-01

    Intra-pore (10 -100 µm) fluid flow and mass transport depend on pore geometry. This has implication on microbial and biogeochemical processes within pores and residual trapping of Supercritical CO2. Since effects of grain size and grain sorting are already known, we investigate the effect of grain shapes in modifying intra-pore fluid flow and mass transport both inside and between pores and stagnant zones. Numerical simulations are carried out by solving the Navier-Stokes equations on idealized 2-D domains representing grain shapes such as squares and circles. We conduct a sensitivity study by varying grain angularity and imposing different Reynolds numbers flows to analyze their influence on permeability and distribution of vortices, also known as recirculation zones. We observe that the coupled effects of pore geometries and vortices lead to large variation in the fluid velocity, which consequently leads to non-Fickian transport even though flow can still be described by a continuum-scale Darcy equation. We find that the permeability increases and vorticity decreases with decreasing angularity of the grains. The flow velocities in the stagnant zone increases linearly with higher Reynolds number flows, with the rate of increase largest among the angular grains. The mass transfer mechanism between main pores and stagnant zones is mainly molecular diffusion, but the concentration gradient between the main pore and the stagnant zone is significantly influenced by the mixing effect associated with vortices. The overall effect of an increase in vorticity manifests itself as an increase in the global dispersion of the solute, which results both in an early arrival and a prolonged tail of a solute’s break-through curve. We find that the related effects of grain shapes and vortices are important in understanding pore scale flow and transport processes and may have significant implication on the issues of contaminant transport in aquifers and the geological storage of

  14. USING A NEW FINITE SLIT PORE MODEL FOR NLDFT ANALYSIS OF CARBON PORE STRUCTURE

    Energy Technology Data Exchange (ETDEWEB)

    Jagiello, Jacek [Micromeritics Instrument Corporation; Kenvin, Jeffrey [Micromeritics Instrument Corporation; Oliver, James P [Micromeritics Instrument Corporation; Lupini, Andrew R [ORNL; Contescu, Cristian I [ORNL

    2011-01-01

    In this work, we present a model for analyzing activated carbon micropore structures based on graphene sheet walls of finite thickness and extent. This is a two-dimensional modification of the widely used infinite slit pore model that assumes graphite-like infinitely extended pore walls. The proposed model has two versions: (1) a strip pore constructed with graphene strip walls that have finite length L in the x direction and are infinite in the y direction. Strip pores are open on both sides in the x direction. (2) A channel pore is a strip pore partially closed along one edge by a perpendicularly oriented graphene wall. This more realistic model allows pore termination via both physical pore entrances and pore blockage. The model consequently introduces heterogeneity of the adsorption potential that is reduced near pore entrances and enhanced near corners of pore walls. These energetically heterogeneous structures fill with adsorbate more gradually than homogeneous pores of the same width. As a result, the calculated adsorption isotherms are smoother and less steep for the finite versus the infinite pore model. In the application of this model for carbon characterization it is necessary to make an assumption about the pore length. In this work we made this assumption based on the high resolution scanning transmission electron microscopy (STEM) results. We find the agreement between the experiment and the model significantly better for the finite than for the infinite pore model.

  15. Velocity anticipation in the optimal velocity model

    Institute of Scientific and Technical Information of China (English)

    DONG Li-yun; WENG Xu-dan; LI Qing-ding

    2009-01-01

    In this paper,the velocity anticipation in the optimal velocity model (OVM) is investigated.The driver adjusts the velocity of his vehicle by the desired headway,which depends on both instantaneous headway and relative velocity.The effect of relative velocity is measured by a sensitivity function.A specific form of the sensitivity function is supposed and the involved parameters are determined by the both numerical simulation and empirical data.It is shown that inclusion of velocity anticipation enhances the stability of traffic flow.Numerical simulations show a good agreement with empirical data.This model provides a better description of real traffic,including the acceleration process from standing states and the deceleration process approaching a stopped car.

  16. DYNAMICS OF AGRICULTURAL GROUNDWATER EXTRACTION

    OpenAIRE

    Hellegers, Petra J.G.J.; Zilberman, David; van Ierland, Ekko C.

    2001-01-01

    Agricultural shallow groundwater extraction can result in desiccation of neighbouring nature reserves and degradation of groundwater quality in the Netherlands, whereas both externalities are often not considered when agricultural groundwater extraction patterns are being determined. A model is developed to study socially optimal agricultural shallow groundwater extraction patterns. It shows the importance of stock size to slow down changes in groundwater quality.

  17. DYNAMICS OF AGRICULTURAL GROUNDWATER EXTRACTION

    OpenAIRE

    Hellegers, Petra J.G.J.; Zilberman, David; van Ierland, Ekko C.

    2001-01-01

    Agricultural shallow groundwater extraction can result in desiccation of neighbouring nature reserves and degradation of groundwater quality in the Netherlands, whereas both externalities are often not considered when agricultural groundwater extraction patterns are being determined. A model is developed to study socially optimal agricultural shallow groundwater extraction patterns. It shows the importance of stock size to slow down changes in groundwater quality.

  18. Field demonstration of rapid turnaround, multilevel groundwater screening

    Energy Technology Data Exchange (ETDEWEB)

    Tingle, A.R. [Analysas Corp., Oak Ridge, TN (United States); Baker, L. [Automated Sciences Group, Inc., Oak Ridge, TN (United States); Long, D.D. [Martin Marietta Energy Systems, Inc., Oak Ridge, TN (United States). Hazardous Waste Remedial Actions Program; Miracle, M. [Advanced Sciences, Inc., Oak Ridge, TN (United States)

    1994-09-01

    A combined technology approach to rapidly characterizing source area and downgradient groundwater associated with a past fuel spill has been field tested. The purpose of this investigation was to determine the presence and extent of fuel-related compounds or indications of their biodegradation in groundwater. The distance from the source area to be investigated was established by calculating the potential extent of a plume based only on groundwater flow velocities. To accomplish this objective, commercially available technologies were combined and used to rapidly assess the source area and downgradient groundwater associated with the fuel discharge. The source of contamination that was investigated overlies glacial sand and gravel outwash deposits. Historical data suggest that from 1955 to 1970 as many as 1 to 6 million pi of aviation gasoline (AVGAS) were god at the study area. Although the remedial investigation (RI) for this study area indicated fuel-related groundwater contamination at the source area, fuel-related contamination was not detected in downgradient monitoring wells. Rapid horizontal groundwater velocities and the 24-year time span from the last reported spill farther suggest that a plume of contaminated groundwater could extend several thousand feet downgradient. The lack of contamination downgradient from the source suggests two possibilities: (1) monitoring wells installed during the RI did not intersect the plume or (2) fuel-related compounds had naturally degraded.

  19. Groundwater sustainability strategies

    Science.gov (United States)

    Gleeson, Tom; VanderSteen, Jonathan; Sophocleous, Marios A.; Taniguchi, Makoto; Alley, William M.; Allen, Diana M.; Zhou, Yangxiao

    2010-01-01

    Groundwater extraction has facilitated significant social development and economic growth, enhanced food security and alleviated drought in many farming regions. But groundwater development has also depressed water tables, degraded ecosystems and led to the deterioration of groundwater quality, as well as to conflict among water users. The effects are not evenly spread. In some areas of India, for example, groundwater depletion has preferentially affected the poor. Importantly, groundwater in some aquifers is renewed slowly, over decades to millennia, and coupled climate–aquifer models predict that the flux and/or timing of recharge to many aquifers will change under future climate scenarios. Here we argue that communities need to set multigenerational goals if groundwater is to be managed sustainably.

  20. Determination of small-scale flow directions and velocities in the hyporheic interstitial

    Science.gov (United States)

    Angermann, L.; Fleckenstein, J.; Nützmann, G.; Lewandowski, J.

    2009-04-01

    The hyporheic interstitial is a hydraulically dynamic and biogeochemical active interface between surface water and groundwater. Depending on the hydraulic boundary conditions and the connectivity with the adjacent aquifer, infiltrating and exfiltrating water pass through it. In addition to those larger scale flow patterns flow at the centimetre scale is influenced by streambed morphology, such as pool-ripple sequences, boulders and woody debris, and the hydrodynamics in the flowing water resulting in a very heterogeneous pattern of flow in the shallow sediment. Patterns of exchange at this scale control the supply of oxygen and nutrients to the sediments and are in turn crucial for biogeochemical turnover. To investigate flow velocity and flow direction in the hyporheic interstitial in situ, a method employing heat as a tracer was developed. The method was tested in a low gradient stream (mean slope of 1.8 0/00), with sandy streambed in Brandenburg, Germany (river Schlaube). The movement of a heat pulse emitted by a small point source is detected by temperature sensors attached to four rods (four sensors on each rod) that are vertically driven into the sediment in a concentric circle with a radius of 3 to 4.5 cm around the heat source. The resulting breakthrough-curves give evidence of flow velocities and flow directions in three dimensions, accounting for the local heterogeneities of the sediment. Patterns of flow direction were found to be quite heterogeneous even on small scales of a few decimetres. Interestingly at several locations flow in the sediment was directed opposite to surface flow. Measured flow velocities of up to 1.75 cm min-1 are several orders of magnitude larger than values previously reported in the literature. As this method is non-destructive it allows repetition of measurements and long-term investigations to assess the variability in time. Furthermore it is well suited for a combined application with sampling devices such as pore water

  1. Microlens arrays with integrated pores

    Directory of Open Access Journals (Sweden)

    Shu Yang

    2005-12-01

    Full Text Available Microlenses are important optical components that image, detect, and couple light. But most synthetic microlenses have fixed position and shape once they are fabricated, so their possible range of tunability and complexity is rather limited. By comparison, biology provides many varied, new paradigms for the development of adaptive optical networks. Here, we discuss inspirational examples of biological lenses and their synthetic analogs. We focus on the fabrication and characterization of biomimetic microlens arrays with integrated pores, whose appearance and function are similar to highly efficient optical elements formed by brittlestars. The complex design can be created by three-beam interference lithography. The synthetic lens has strong focusing ability for use as an adjustable lithographic mask and a tunable optical device coupled with the microfluidic system. Replacing rigid microlenses with soft hydrogels provides a way of changing the lens geometry and refractive index continuously in response to external stimuli, resulting in intelligent, multifunctional, tunable optics.

  2. Atomic Structure of Graphene Subnanometer Pores.

    Science.gov (United States)

    Robertson, Alex W; Lee, Gun-Do; He, Kuang; Gong, Chuncheng; Chen, Qu; Yoon, Euijoon; Kirkland, Angus I; Warner, Jamie H

    2015-12-22

    The atomic structure of subnanometer pores in graphene, of interest due to graphene's potential as a desalination and gas filtration membrane, is demonstrated by atomic resolution aberration corrected transmission electron microscopy. High temperatures of 500 °C and over are used to prevent self-healing of the pores, permitting the successful imaging of open pore geometries consisting of between -4 to -13 atoms, all exhibiting subnanometer diameters. Picometer resolution bond length measurements are used to confirm reconstruction of five-membered ring projections that often decorate the pore perimeter, knowledge which is used to explore the viability of completely self-passivated subnanometer pore structures; bonding configurations where the pore would not require external passivation by, for example, hydrogen to be chemically inert.

  3. Some specifics of influence of pore pressure on physical properties of deformable rocks

    Science.gov (United States)

    Sobolev, G. A.; Stakhovskaya, Z. I.; Mikayelyan, A. O.

    1984-07-01

    A study was made of a range of problems related to the physical and mechanical properties of limestones from the region of the Ingura hydroelectric powerplant under hydrostatic pore pressure with additional axial pressure. The purpose was to estimate the significance and effect of pore pressure on physical properties in rocks as a function of the stressed state under conditions of hydrostatic pressure and hydrostatic pressure with additional axial loading. The P wave velocity, resistivity and longitudinal deformation were measured under pressure with specimens which had been carefully dried and saturated under vacuum conditions with a 2 n solution of NaCl. Cyclical variations of pore pressure were found to cause compaction of the rock. Cyclical variations of pore pressure under complex stress conditions facilitate fracture and strength loss of the rock.

  4. Velocity measurements of low Reynolds number tube flow using fiber-optic technology

    Energy Technology Data Exchange (ETDEWEB)

    Bianchi, J.C.

    1993-03-01

    In 1988 Nielsen started work to measure the spatial variability of the mass flux vector being transported in a porous medium. To measure the spatial variability of the mass flux vector, the spatial variability of its components(velocity, concentration) must be measured. Nielsen was successful in measuring the pore level concentration at many different pores and in verifying the assumption that a nonuniform concentration field exists within the mixing zone between two miscible fluids. However, Nielsen was unable to conduct the necessary pore level velocity measurements needed. Nielsen's work is being continued and a probe is being developed that will measure both velocity and concentration components at pore level. The probe is essentially the same probe used to make the pore level concentration measurements with added capabilities needed to make the velocity measurements. This probe has several design variables, dealing primarily with the velocity component, that need further investigation. The research presented in this thesis investigates these parameters by performing experiments in a capillary tube. The tube is a controlled system where the velocity of the fluid can be determined from the volumetric flow rate using Poiseuille's solution for viscous flow. Also, a statistically based relationship between the velocity measured with the probe and the velocity determined from the volumetric flow rate has been developed.

  5. Velocity measurements of low Reynolds number tube flow using fiber-optic technology

    Energy Technology Data Exchange (ETDEWEB)

    Bianchi, J. Christopher [Univ. of Vermont, Burlington, VT (United States)

    1993-03-01

    In 1988 Nielsen started work to measure the spatial variability of the mass flux vector being transported in a porous medium. To measure the spatial variability of the mass flux vector, the spatial variability of its components(velocity, concentration) must be measured. Nielsen was successful in measuring the pore level concentration at many different pores and in verifying the assumption that a nonuniform concentration field exists within the mixing zone between two miscible fluids. However, Nielsen was unable to conduct the necessary pore level velocity measurements needed. Nielsen`s work is being continued and a probe is being developed that will measure both velocity and concentration components at pore level. The probe is essentially the same probe used to make the pore level concentration measurements with added capabilities needed to make the velocity measurements. This probe has several design variables, dealing primarily with the velocity component, that need further investigation. The research presented in this thesis investigates these parameters by performing experiments in a capillary tube. The tube is a controlled system where the velocity of the fluid can be determined from the volumetric flow rate using Poiseuille`s solution for viscous flow. Also, a statistically based relationship between the velocity measured with the probe and the velocity determined from the volumetric flow rate has been developed.

  6. Dynamics of Agricultural Groundwater Extraction

    NARCIS (Netherlands)

    Hellegers, P.J.G.J.; Zilberman, D.; Ierland, van E.C.

    2001-01-01

    Agricultural shallow groundwater extraction can result in desiccation of neighbouring nature reserves and degradation of groundwater quality in the Netherlands, whereas both externalities are often not considered when agricultural groundwater extraction patterns are being determined. A model is

  7. Chemistry and dissolved gases of matrix pore water and fluid inclusions in Olkiluoto bedrock from drillhole ONK-PH9

    Energy Technology Data Exchange (ETDEWEB)

    Eichinger, F.; Haemmerli, J.; Waber, H.N.; Diamond, L.W. [Univ. of Bern (Switzerland). Inst. of Geological Sciences; Smellie, J.A.T. [Conterra AB, Stockholm (Sweden)

    2013-05-15

    Matrix pore water and gas dissolved in matrix pore water in drillcore samples from drillhole ONK-PH9 have been successfully characterised for their chemical and isotopic composition. Based on the comparison of natural tracers in matrix pore water and adjacent fracture groundwater, conclusions about the palaeohydrogeological history of the encountered system are drawn. The investigations are based on naturally saturated core samples from the subhorizontal drillhole ONK-PH9 which was drilled from the ONKALO access tunnel at a vertical depth of 306 m into the bedrock intersecting the water-conducting hydrogeological zone HZ20B. Pore water samples were taken from this highly transmissive water-conducting zone and the adjacent low transmissive bedrock along a continuous eleven metre long profile. Additional samples have been collected at intervals between five and ten metres until 100 m drillhole length (DHL)

  8. Groundwater impact on geothermal systems; Impacto del agua subterranea en los sistemas geotermicos

    Energy Technology Data Exchange (ETDEWEB)

    Katzenbach, R.; Wagner, I. M.

    2009-07-01

    Thermal behavior of geothermal systems is influenced by the presence and the velocity of the groundwater. The impact has to be accounted for during the dimensioning as well as during the construction. it is shown that the impact on the interference with neigh bored installation has to be controlled, especially in case of groundwater flow. (Author) 9 refs.

  9. Human health and groundwater

    Science.gov (United States)

    The high quality of most groundwaters, consequent upon the self-purification capacity of subsurface strata, has long been a key factor in human health and wellbeing. More than 50% of the world’s population now rely on groundwater for their supply of drinking water – and in most circumstances a prope...

  10. Groundwater and Distribution Workbook.

    Science.gov (United States)

    Ekman, John E.

    Presented is a student manual designed for the Wisconsin Vocational, Technical and Adult Education Groundwater and Distribution Training Course. This program introduces waterworks operators-in-training to basic skills and knowledge required for the operation of a groundwater distribution waterworks facility. Arranged according to the general order…

  11. The dynamic nature of crystal growth in pores

    Science.gov (United States)

    Godinho, Jose R. A.; Gerke, Kirill M.; Stack, Andrew G.; Lee, Peter D.

    2016-09-01

    The kinetics of crystal growth in porous media controls a variety of natural processes such as ore genesis and crystallization induced fracturing that can trigger earthquakes and weathering, as well as, sequestration of CO2 and toxic metals into geological formations. Progress on understanding those processes has been limited by experimental difficulties of dynamically studying the reactive surface area and permeability during pore occlusion. Here, we show that these variables cause a time-dependency of barite growth rates in microporous silica. The rate is approximately constant and similar to that observed on free surfaces if fast flow velocities predominate and if the time-dependent reactive surface area is accounted for. As the narrower flow paths clog, local flow velocities decrease, which causes the progressive slowing of growth rates. We conclude that mineral growth in a microporous media can be estimated based on free surface studies when a) the growth rate is normalized to the time-dependent surface area of the growing crystals, and b) the local flow velocities are above the limit at which growth is transport-limited. Accounting for the dynamic relation between microstructure, flow velocity and growth rate is shown to be crucial towards understanding and predicting precipitation in porous rocks.

  12. Pore Water Pressure Contribution to Debris Flow Mobility

    Directory of Open Access Journals (Sweden)

    Chiara Deangeli

    2009-01-01

    Full Text Available Problem statement: Debris flows are very to extremely rapid flows of saturated granular soils. Two main types of debris flow are generally recognized: Open slope debris flows and channelized debris flows. The former is the results of some form of slope failures, the latter can develop along preexisting stream courses by the mobilization of previously deposited debris blanket. The problem to be addressed is the influence of the mode of initiation on the subsequent mechanism of propagation. In particular the role of pore water pressure on debris flow mobility in both types was debated. Approach: Laboratory flume experiments were set up in order to analyze the behavior of debris flows generated by model sand slope failures. Failures were induced in sand slopes by raising the water level by seepage from a drain located at the top end of the flume, and by rainfall supplied by a set of pierced plastic pipes placed above the flume. Video recordings of the tests were performed to analyze debris flow characteristics. Results: In all the tests the sand water mixture flows were unsteady and non uniform and sand deposition along the channel bed was a relevant phenomenon. The flows were characterized by a behavioral stratification of the sand water mixture along the flow depth. Back analyzed pore water pressure were just in excess to the hydrostatic condition. The reliability of the experimental results was checked by comparison with other flume experiment data. Conclusion: Debris flow behavior was influenced by the mode of initiation, the inclination of the channel and grain size of the soils. These factors affected the attained velocities and the pore water pressure values. The mobility of debris flows was not always enhanced by high excess pore water pressure values.

  13. Effects of salinity variations on pore water flow in salt marshes

    Science.gov (United States)

    Shen, Chengji; Jin, Guangqiu; Xin, Pei; Kong, Jun; Li, Ling

    2015-06-01

    Spatial and temporal salinity variations in surface water and pore water commonly exist in salt marshes under the combined influence of tidal inundation, precipitation, evapotranspiration, and inland freshwater input. Laboratory experiments and numerical simulations were conducted to investigate how density gradients associated with salinity variations affect pore water flow in the salt marsh system. The results showed that upward salinity (density) gradients could lead to flow instability and the formation of salt fingers. These fingers, varying in size with the distance from the creek, modified significantly the pore water flow field, especially in the marsh interior. While the flow instability enhanced local salt transport and mixing considerably, the net effect was small, causing only a slight increase in the overall mass exchange across the marsh surface. In contrast, downward salinity gradients exerted less influence on the pore water flow in the marsh soil and slightly weakened the surface water and groundwater exchange across the marsh surface. Numerical simulations revealed similar density effects on pore water flow at the field scale under realistic conditions. These findings have important implications for studies of marsh soil conditions concerning plant growth as well as nutrient exchange between the marsh and coastal marine system.

  14. Porosity and pore size distribution in a sedimentary rock: Implications for the distribution of chlorinated solvents

    Science.gov (United States)

    Shapiro, Allen M.; Evans, Chrsitopher E.; Hayes, Erin C.

    2017-01-01

    Characterizing properties of the rock matrix that control retention and release of chlorinated solvents is essential in evaluating the extent of contamination and the application of remediation technologies in fractured rock. Core samples from seven closely spaced boreholes in a mudstone subject to trichloroethene (TCE) contamination were analyzed using Mercury Intrusion Porosimetry to investigate porosity and pore size distribution as a function of mudstone characteristics, and depth and lateral extent in the aquifer; organic carbon content was also evaluated to identify the potential for adsorption. Porosity and retardation factor varied over two orders of magnitude, with the largest porosities and largest retardation factors associated with carbon-rich mudstone layers. Larger porosities were also measured in the shallow rock that has been subject to enhanced groundwater flow. Porosity also varied over more than an order of magnitude in spatially continuous mudstone layers. The analyses of the rock cores indicated that the largest pore diameters may be accessible to entry of the nonaqueous form of TCE. Although the porosity associated with the largest pore diameters is small (~ 0.1%), that volume of TCE can significantly affect the total TCE that is retained in the rock matrix. The dimensions of the largest pore diameters may also be accessible to microbes responsible for reductive dechlorination; however, the small percentage of the pore space that can accommodate microbes may limit the extent of reductive dechlorination in the rock matrix.

  15. Porosity and pore size distribution in a sedimentary rock: Implications for the distribution of chlorinated solvents.

    Science.gov (United States)

    Shapiro, Allen M; Evans, Christopher E; Hayes, Erin C

    2017-08-01

    Characterizing properties of the rock matrix that control retention and release of chlorinated solvents is essential in evaluating the extent of contamination and the application of remediation technologies in fractured rock. Core samples from seven closely spaced boreholes in a mudstone subject to trichloroethene (TCE) contamination were analyzed using Mercury Intrusion Porosimetry to investigate porosity and pore size distribution as a function of mudstone characteristics, and depth and lateral extent in the aquifer; organic carbon content was also evaluated to identify the potential for adsorption. Porosity and retardation factor varied over two orders of magnitude, with the largest porosities and largest retardation factors associated with carbon-rich mudstone layers. Larger porosities were also measured in the shallow rock that has been subject to enhanced groundwater flow. Porosity also varied over more than an order of magnitude in spatially continuous mudstone layers. The analyses of the rock cores indicated that the largest pore diameters may be accessible to entry of the nonaqueous form of TCE. Although the porosity associated with the largest pore diameters is small (~0.1%), that volume of TCE can significantly affect the total TCE that is retained in the rock matrix. The dimensions of the largest pore diameters may also be accessible to microbes responsible for reductive dechlorination; however, the small percentage of the pore space that can accommodate microbes may limit the extent of reductive dechlorination in the rock matrix. Published by Elsevier B.V.

  16. Intermittent Lagrangian velocities and accelerations in three-dimensional porous medium flow.

    Science.gov (United States)

    Holzner, M; Morales, V L; Willmann, M; Dentz, M

    2015-07-01

    Intermittency of Lagrangian velocity and acceleration is a key to understanding transport in complex systems ranging from fluid turbulence to flow in porous media. High-resolution optical particle tracking in a three-dimensional (3D) porous medium provides detailed 3D information on Lagrangian velocities and accelerations. We find sharp transitions close to pore throats, and low flow variability in the pore bodies, which gives rise to stretched exponential Lagrangian velocity and acceleration distributions characterized by a sharp peak at low velocity, superlinear evolution of particle dispersion, and double-peak behavior in the propagators. The velocity distribution is quantified in terms of pore geometry and flow connectivity, which forms the basis for a continuous-time random-walk model that sheds light on the observed Lagrangian flow and transport behaviors.

  17. Gas transport and subsoil pore characteristics

    DEFF Research Database (Denmark)

    Berisso, Feto Esimo; Schjønning, Per; Keller, Thomas

    2013-01-01

    Arrangements of elementary soil particles during soil deposition and subsequent biological and physical processes in long-term pedogenesis are expected to lead to anisotropy of the non-tilled subsoil pore system. Soil compaction by agricultural machinery is known to affect soil pore characteristi...

  18. Cavitation and pore blocking in nanoporous glasses.

    Science.gov (United States)

    Reichenbach, C; Kalies, G; Enke, D; Klank, D

    2011-09-06

    In gas adsorption studies, porous glasses are frequently referred to as model materials for highly disordered mesopore systems. Numerous works suggest that an accurate interpretation of physisorption isotherms requires a complete understanding of network effects upon adsorption and desorption, respectively. The present article deals with nitrogen and argon adsorption at different temperatures (77 and 87 K) performed on a series of novel nanoporous glasses (NPG) with different mean pore widths. NPG samples contain smaller mesopores and significantly higher microporosity than porous Vycor glass or controlled pore glass. Since the mean pore width of NPG can be tuned sensitively, the evolution of adsorption characteristics with respect to a broadening pore network can be investigated starting from the narrowest nanopore width. With an increasing mean pore width, a H2-type hysteresis develops gradually which finally transforms into a H1-type. In this connection, a transition from a cavitation-induced desorption toward desorption controlled by pore blocking can be observed. Furthermore, we find concrete hints for a pore size dependence of the relative pressure of cavitation in highly disordered pore systems. By comparing nitrogen and argon adsorption, a comprehensive insight into adsorption mechanisms in novel disordered materials is provided.

  19. Coating of silicon pore optics

    DEFF Research Database (Denmark)

    Cooper-Jensen, Carsten P.; Ackermann, M.; Christensen, Finn Erland

    2009-01-01

    For the International X-ray observatory (IXO), a mirror module with an effective area of 3 m2 at 1.25 keV and at least 0.65 m2 at 6 keV has to be realized. To achieve this goal, coated silicon pore optics has been developed over the last years. One of the challenges is to coat the Si plates...... and still to realize Si-Si bonding. It has been demonstrated that ribbed silicon plates can be produced and assembled into stacks. All previously work has been done using uncoated Si plates. In this paper we describe how to coat the ribbed Si plates with an Ir coating and a top C coating through a mask so...... that there will be coating only between the ribs and not in the area where bonding takes place. The paper includes description of the mounting jig and how to align the mask on top of the plate. We will also present energy scans from Si plates coated through a mask....

  20. Particle diffusion in complex nanoscale pore networks

    DEFF Research Database (Denmark)

    Müter, Dirk; Sørensen, Henning Osholm; Bock, H.

    2015-01-01

    decreased to as much as 60% when particle size increased from 1% to 35% of the average pore diameter. When particles were attracted to the pore surfaces, even very small particles, diffusion was drastically inhibited, by as much as a factor of 100. Thus, the size of particles and their interaction......We studied the diffusion of particles in the highly irregular pore networks of chalk, a very fine-grained rock, by combining three-dimensional X-ray imaging and dissipative particle dynamics (DPD) simulations. X-ray imaging data were collected at 25 nm voxel dimension for two chalk samples...... with very different porosities (4% and 26%). The three-dimensional pore systems derived from the tomograms were imported into DPD simulations and filled with spherical particles of variable diameter and with an optional attractive interaction to the pore surfaces. We found that diffusion significantly...

  1. FINGERPRINT MATCHING BASED ON PORE CENTROIDS

    Directory of Open Access Journals (Sweden)

    S. Malathi

    2011-05-01

    Full Text Available In recent years there has been exponential growth in the use of bio- metrics for user authentication applications. Automated Fingerprint Identification systems have become popular tool in many security and law enforcement applications. Most of these systems rely on minutiae (ridge ending and bifurcation features. With the advancement in sensor technology, high resolution fingerprint images (1000 dpi pro- vide micro level of features (pores that have proven to be useful fea- tures for identification. In this paper, we propose a new strategy for fingerprint matching based on pores by reliably extracting the pore features The extraction of pores is done by Marker Controlled Wa- tershed segmentation method and the centroids of each pore are con- sidered as feature vectors for matching of two fingerprint images. Experimental results shows that the proposed method has better per- formance with lower false rates and higher accuracy.

  2. Carbonate reservoir characterization with pore type inversion using differential effective medium (DEM) model at "X" field, East Java

    Science.gov (United States)

    Rosid, M. S.; Wahyuni, S. D.; Haidar, M. W.

    2017-07-01

    Pore system in the carbonate reservoirs is very complex than in clastic rocks. There are three types of classification of pore types in carbonate rocks: interparticle, stiff, and crack. The complexity of the pore types can cause changes in P-wave velocity by 40 %, as well as create a carbonate reservoir characterization becomes difficult when the S wave estimation is done only with the type of dominant pore (interparticle). Therefore, modeling the elastic moduli of rocks become essential to solve the problem of complexity of pore types in carbonate rocks. Differential Effective Medium (DEM) is a method of modeling the elastic moduli of rocks that takes into account the heterogeneity of types of pores in carbonate rocks by adding pore-type inclusions little by little into the parent material (host material) until the proportion of the material is reached. In addition, to the elastic moduli which have taken into account the heterogeneity of pore type. The inversion result shows that carbonate reservoir at "X" field is dominated by crack pore type and the relation between S wave and P wave is expressed by VS=-0.05 VP2+VP-1.1 and not in linear correlation.

  3. High-velocity clouds

    NARCIS (Netherlands)

    Wakker, BP; vanWoerden, H

    1997-01-01

    High-velocity clouds (HVCs) consist of neutral hydrogen (HI) at velocities incompatible with a simple model of differential galactic rotation; in practice one uses \\v(LSR)\\ greater than or equal to 90 km/s to define HVCs. This review describes the main features of the sky and velocity distributions,

  4. Transverse Spectral Velocity Estimation

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt

    2014-01-01

    A transverse oscillation (TO)-based method for calculating the velocity spectrum for fully transverse flow is described. Current methods yield the mean velocity at one position, whereas the new method reveals the transverse velocity spectrum as a function of time at one spatial location. A convex...

  5. Trends in groundwater quality in relation to groundwater age

    NARCIS (Netherlands)

    Visser, A.

    2009-01-01

    Groundwater is a valuable natural resource and as such should be protected from chemical pollution. Because of the long travel times of pollutants through groundwater bodies, early detection of groundwater quality deterioration is necessary to efficiently protect groundwater bodies. The aim of this

  6. Trends in groundwater quality in relation to groundwater age

    NARCIS (Netherlands)

    Visser, A.

    2009-01-01

    Groundwater is a valuable natural resource and as such should be protected from chemical pollution. Because of the long travel times of pollutants through groundwater bodies, early detection of groundwater quality deterioration is necessary to efficiently protect groundwater bodies. The aim of this

  7. ANALYSIS AND CALCULATION OF REGULATED WATER RESOURCES OF GROUNDWATER RESERVOIR

    Institute of Scientific and Technical Information of China (English)

    DAI Chang-lei; CHI Bao-ming; GAO Shu-qin

    2005-01-01

    Groundwater reservoir is a kind of important engineering, which can optimize water resources arran-gement by means of artificial regulation. Regulated water is the blood and value performance of groundwater reser-voir. To resolve the problem of real-time quantification of regulated water, the paper analyzed sources and composi-tions of regulated water in detail. Then, under the conditions of satisfying water demand inside research area, the pa-per analyzed quantity available and regulation coefficient of different regulated water and established a formula tocalculate regulated water. At last, based on a pore groundwater reservoir in the middle reaches of the Yinma River,Jilin Province, the paper calculated regulated water with the formula and the result shows that the method is feasible.With some constraint conditions, the formula can be adopted in other similar areas.

  8. Smart Fluids in Hydrology: Use of Non-Newtonian Fluids for Pore Structure Characterization

    Science.gov (United States)

    Abou Najm, M. R.; Atallah, N. M.; Selker, J. S.; Roques, C.; Stewart, R. D.; Rupp, D. E.; Saad, G.; El-Fadel, M.

    2015-12-01

    Classic porous media characterization relies on typical infiltration experiments with Newtonian fluids (i.e., water) to estimate hydraulic conductivity. However, such experiments are generally not able to discern important characteristics such as pore size distribution or pore structure. We show that introducing non-Newtonian fluids provides additional unique flow signatures that can be used for improved pore structure characterization while still representing the functional hydraulic behavior of real porous media. We present a new method for experimentally estimating the pore structure of porous media using a combination of Newtonian and non-Newtonian fluids. The proposed method transforms results of N infiltration experiments using water and N-1 non-Newtonian solutions into a system of equations that yields N representative radii (Ri) and their corresponding percent contribution to flow (wi). This method allows for estimating the soil retention curve using only saturated experiments. Experimental and numerical validation comparing the functional flow behavior of different soils to their modeled flow with N representative radii revealed the ability of the proposed method to represent the water retention and infiltration behavior of real soils. The experimental results showed the ability of such fluids to outsmart Newtonian fluids and infer pore size distribution and unsaturated behavior using simple saturated experiments. Specifically, we demonstrate using synthetic porous media that the use of different non-Newtonian fluids enables the definition of the radii and corresponding percent contribution to flow of multiple representative pores, thus improving the ability of pore-scale models to mimic the functional behavior of real porous media in terms of flow and porosity. The results advance the knowledge towards conceptualizing the complexity of porous media and can potentially impact applications in fields like irrigation efficiencies, vadose zone hydrology, soil

  9. Hydrochemical reactions and origin of offshore relatively fresh pore water from core samples in Hong Kong

    Science.gov (United States)

    Kwong, Hiu Tung; Jiao, Jiu Jimmy

    2016-06-01

    The existence of relatively fresh pore water offshore has been well recognised over the globe but studies on the chemistry of the pore water from offshore geological formations are extremely limited. This study aims to characterize the hydrochemistry of the submarine groundwater body in Hong Kong. It looks into the major ion concentrations and the stable isotopic compositions of pore water extracted from core samples from an offshore 42.30-m vibrocore in the southwestern Hong Kong waters. A minimum Cl- level of about one-third of that in typical seawater was noted in the terrestrial sediments, suggesting the presence of offshore relatively fresh water. Unexpectedly high NH4+ levels are attributed to organic matter decomposition in the terrestrial sediments. The leaching of shells due to exposure of marine sediments at sea-level low stands raises the Mg2+ and Ca2+ concentrations. Base Exchange Indices show weak cation exchange reactions in which Na+ and K+ are released while Mg2+ and Ca2+ are adsorbed. Isotopic compositions of pore water reveal that the low-salinity water is probably the relic water sequestered in fluvial systems during relative sea-level low stands. Cores properly stored in a freezer for a long time has been used to study the pore water chemistry. For the first time, this study introduces an approach to correct the measured data by considering the possible evaporation effect during the transportation and storage of the samples. Corrections for evaporation were applied to the major ion concentrations and the stable isotopic compositions of pore water measured. It is found that the corrections determined by the Cl- mass balance approach are more reliable. The corrected measurements give more reasonable observations and hence allow sensible conclusions on the hydrochemical reactions and the origin of pore water.

  10. Transient pore pressure response to confining stress excursions in Berea sandstone flooded with an aqueous solution of CO2

    Science.gov (United States)

    Crews, Jackson B.; Cooper, Clay A.

    2014-06-01

    We measured the pore pressure response due to carbon dioxide (CO2) gas bubble nucleation and growth in a Berea sandstone core flooded with an initially subsaturated aqueous solution of CO2, in response to a rapid drop in confining stress, under conditions representative of a confined aquifer. A portion of the CO2 in the Earth's crust, derived from volcanic, magmatic, and biogenic sources, dissolves in groundwater. Sudden reductions in confining stress in the Earth's crust occur due to dilational strain generated by the propagation of seismic Rayleigh and P waves, or aseismic slip in the near field of earthquakes. A drop in confining stress produces a proportional drop in pore fluid pressure. When the pore fluid contains dissolved CO2, the pore pressure responds to a drop in confining stress like it does in the dissolved gas-free case, until the pore pressure falls below the bubble pressure. Gas bubble nucleation and diffusive growth in the pore space trigger spontaneous, transient buildup of the pore fluid pressure, and reduction of effective stress. We measured the rate of pore fluid pressure buildup in the 100 s immediately following the confining stress drop, as a function of the saturation with respect to CO2 at the lowest pore pressure realized during the confining stress drop, using five different CO2 partial pressures. The rate scales with the saturation with respect to dissolved CO2, from 10 kPa/min at 1.25 to 166 kPa/min at 1.8. The net pore pressure rise was as large as 0.7 MPa (100 psi) over 5 h.

  11. Global depletion of groundwater resources

    NARCIS (Netherlands)

    Wada, Y.; Beek, L.P.H. van; van Kempen, C.M.; Reckman, J.W.T.M.; Vasak, S.; Bierkens, M.F.P.

    2010-01-01

    In regions with frequent water stress and large aquifer systems groundwater is often used as an additional water source. If groundwater abstraction exceeds the natural groundwater recharge for extensive areas and long times, overexploitation or persistent groundwater depletion occurs. Here we provid

  12. Using Independent Components Analysis to diminish the response of groundwater in borehole strainmeter

    Science.gov (United States)

    Chen, Chih-Yen; Hu, Jyr-Ching

    2017-04-01

    With designed feather, borehole strainmeter can not only record minor signals of tectonic movements, but also broad environmental signs such as barometry, rainfall and groundwater. Among these external factor, groundwater will influence the observation of borehole strainmeter mostly. According to essential observation, groundwater will cause much bigger response than the target tectonic strain change. We use co-sited piezometer to record pore pressure of groundwater in the rock formation in order to obtain the relationship of stain change and pore pressure. But there still exist some puzzle that can not be solved. First, due to instrument limitation, we could not set the pore pressure transducer in the same aquifer as strainmeter did. In this case, the response due to pore pressure change might be not fully correct. Furthermore, through pore-pressure transducers were set in most observatory, problem of electricity and connectivity will cause the record lack and lost. Therefore, it is necessary to find out a better and more stable method to diminish the groundwater response of strainmeter data.Strain transducer with different orientation can observe the groundwater response in different scale. If we can extract out groundwater signal from each independent strain transducer and estimate its original source. That will significantly rise signal strength and lower noise level. The case belongs some kind of blind-signal-separation (BSS) problem. The procedure of BSS extract or rebuild signal that can't be observed directly in many mixed sources and Independent-Component-Analysis (ICA) is one method adopted broadly. ICA is an analysis to find out parts which have statistics independence and non-Gaussian factor in complex signals. We use FastICA developed by to figure out the groundwater response strain in original strain data, and try to diminish it to rise the signal strength. We preceded strain data previously, then using ICA to separate data into serval independent

  13. Effect of pore pressure on deformation and unstable snap-back for shear band and elastic rock system

    Institute of Scientific and Technical Information of China (English)

    WANG Xue-bin

    2007-01-01

    Fast Lagrangian analysis of continua(FLAC) was used to study the influence of pore pressure on the mechanical behavior of rock specimen in plane strain direct shear, the distribution of yielded elements, the distribution of displacement and velocity across shear band as well as the snap-back (elastic rebound) instability. The effective stress law was used to represent the weakening of rock containing pore fluid under pressure. Numerical results show that rock specimen becomes soft (lower strength and hardening modulus) as pore pressure increases, leading to higher displacement skip across shear band. Higher pore pressure results in larger area of plastic zone, higher concentration of shear strain, more apparent precursor to snap-back (unstable failure) and slower snap-back. For higher pore pressure, the formation of shear band-elastic body system and the snap-back are earlier; the distance of snap-back decreases; the capacity of snap-back decreases, leading to lower elastic strain energy liberated beyond the instability and lower earthquake or rockburst magnitude. In the process of snap-back, the velocity skip across shear band is lower for rock specimen at higher pore pressure, showing the slower velocity of snap-back.

  14. A multicriterion approach to groundwater management

    Science.gov (United States)

    El Magnouni, Samir; Treichel, Wiktor

    1994-06-01

    A new approach to groundwater quantity (hydraulic) management, based on a multicriterion decision aid methodology, is presented. The method couples a hydrodynamic groundwater flow simulation model with the decision aid one. It takes into account multiple criteria used by the decision maker (DM) in evaluating a management scenario as well as the hydrodynamic behavior of the groundwater system. The finite element and embedding methods are used to integrate the groundwater flow model into a multiobjective linear programming (LP) problem. Constraints on head, pumping rates, hydraulic gradient and velocity vector may be included in the management model. The piecewise linear utility function is assessed for modeling the DM's preferences. The best compromise solution is determined from the continuous Pareto set by solving a piecewise LP problem. User friendly software was developed to realize this methodology which is able to treat real scale problems. An illustrative example of an unconfined aquifer management is presented. Nonlinearities resulting from functional dependence of aquifer parameters on hydraulic head are handled iteratively.

  15. Eddy correlation measurements of submarine groundwater discharge

    Science.gov (United States)

    Crusius, J.; Berg, P.; Koopmans, D.J.; Erban, L.

    2008-01-01

    This paper presents a new, non-invasive means of quantifying groundwater discharge into marine waters using an eddy correlation approach. The method takes advantage of the fact that, in virtually all aquatic environments, the dominant mode of vertical transport near the sediment-water interface is turbulent mixing. The technique thus relies on measuring simultaneously the fluctuating vertical velocity using an acoustic Doppler velocimeter and the fluctuating salinity and/or temperature using rapid-response conductivity and/or temperature sensors. The measurements are typically done at a height of 5-15??cm above the sediment surface, at a frequency of 16 to 64??Hz, and for a period of 15 to 60??min. If the groundwater salinity and/or temperature differ from that of the water column, the groundwater specific discharge (cm d- 1) can be quantified from either a heat or salt balance. Groundwater discharge was estimated with this new approach in Salt Pond, a small estuary on Cape Cod (MA, USA). Estimates agreed well with previous estimates of discharge measured using seepage meters and 222Rn as a tracer. The eddy correlation technique has several desirable characteristics: 1) discharge is quantified under in-situ hydrodynamic conditions; 2) salinity and temperature can serve as two semi-independent tracers of discharge; 3) discharge can be quantified at high temporal resolution, and 4) long-term records of discharge may be possible, due to the low power requirements of the instrumentation. ?? 2007 Elsevier B.V. All rights reserved.

  16. Designing Nonwovens to Meet Pore Size Specifications

    Directory of Open Access Journals (Sweden)

    Glen E. Simmonds

    2007-04-01

    Full Text Available New nonwovens applications in areas such as filtration require a media designed to particular pore size specifications in the 3 to 20 micron range. The purpose of this work was to develop a basis by which to design and construct a fabric with given pore size specifications. While doing so we have provided a validation for two different mathematical models. We have also found that bicomponent spunbonded islands-in-the-sea nonwoven fabrics can be designed very precisely to achieve target pore diameters and porosity. Mathematical models can be used to develop fabric specifications in the standard manufacturing terms of basis weight and fiber diameter. Measured mean flow pore diameters for the test fabrics showed excellent correlation to targeted mean flow pore diameters for both models. The experimental fit to the Bryner model is the better of the two, but requires specification of fabric thickness in addition to basis weight and fiber diameter to achieve actual mean pore diameters that closely match target values. Experimental validation of the influence of fabric thickness on the mean flow pore diameter at constant basis weight and fiber diameter remains open for further investigation. In addition, achieving complete separation of the island and sea polymers along with unbundling of the island fibers remain areas for improvement.

  17. Groundwater data network interoperability

    Science.gov (United States)

    Brodaric, Boyan; Booth, Nathaniel; Boisvert, Eric; Lucido, Jessica M.

    2016-01-01

    Water data networks are increasingly being integrated to answer complex scientific questions that often span large geographical areas and cross political borders. Data heterogeneity is a major obstacle that impedes interoperability within and between such networks. It is resolved here for groundwater data at five levels of interoperability, within a Spatial Data Infrastructure architecture. The result is a pair of distinct national groundwater data networks for the United States and Canada, and a combined data network in which they are interoperable. This combined data network enables, for the first time, transparent public access to harmonized groundwater data from both sides of the shared international border.

  18. Groundwater contamination in Japan

    Energy Technology Data Exchange (ETDEWEB)

    Tase, Norio [Univ. of Tsukuba, Ibaraki (Japan)

    1992-07-01

    Problems on groundwater contamination in Japan are briefly summarized in this paper. Although normal physical conditions in Japan restrict the possibilities of groundwater contamination, human activities are threatening groundwater resources. A survey by the Environment Agency of Japan showed nationwide spreading of organic substances, such as trichloroethylene as well as nitrogen compounds. Synthetic detergents have also been detected even in rural areas and in deep confined aquifers, although their concentrations are not as high. Public awareness of agrichemical or pesticides abuse, especially from golf courses, is apparent. Other problems such as nitrate-nitrogen, leachate from landfills, and the leaking of underground storage tanks are also discussed. 9 refs., 3 figs., 4 tabs.

  19. Groundwater contamination in Japan

    Science.gov (United States)

    Tase, Norio

    1992-07-01

    Problems on groundwater contamination in Japan are briefly summarized in this paper. Although normal physical conditions in Japan restrict the possibilities of groundwater contamination, human activities are threatening groundwater resources. A survey by the Environment Agency of Japan showed nationwide spreading of organic substances, such as trichloroethylene as well as nitrogen compounds. Synthetic detergents have also been detected even in rural areas and in deep confined aquifers, although their concentrations are not as high. Public awareness of agrichemical or pesticides abuse, especially from golf courses, is apparent. Other problems such as nitrate-nitrogen, leachate from landfills, and the leaking of underground storage tanks are also discussed.

  20. NON-LCL AND TRACER TEST FOR GROUNDWATER FLOW IN A SINGLE FRACTURE

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The validity of Local Cubic Law (LCL) is an important issue to study groundwater flow and transport in fractured media. According to laboratory simulaion tests, the average velocity with a lower gradient in a single fracture is calculated by the LCL, which is compared with the measured average velocity. Then dye tracer test is designed and completed. The evidence for non-LCL is drawn from the results of the simulation tests and the dye tracer tests. Then the Reynolds number of groundwater is calculated, the critical value of Re for laminar flow is discussed in a single fracture under different conditions. The motion types for groundwater flow have been discussed.

  1. Control of pore size in epoxy systems.

    Energy Technology Data Exchange (ETDEWEB)

    Sawyer, Patricia Sue; Lenhart, Joseph Ludlow (North Dakota State University, Fargo, ND); Lee, Elizabeth (North Dakota State University, Fargo, ND); Kallam, Alekhya (North Dakota State University, Fargo, ND); Majumdar, Partha (North Dakota State University, Fargo, ND); Dirk, Shawn M.; Gubbins, Nathan; Chisholm, Bret J. (North Dakota State University, Fargo, ND); Celina, Mathias Christopher; Bahr, James (North Dakota State University, Fargo, ND); Klein, Robert J.

    2009-01-01

    Both conventional and combinatorial approaches were used to study the pore formation process in epoxy based polymer systems. Sandia National Laboratories conducted the initial work and collaborated with North Dakota State University (NDSU) using a combinatorial research approach to produce a library of novel monomers and crosslinkers capable of forming porous polymers. The library was screened to determine the physical factors that control porosity, such as porogen loading, polymer-porogen interactions, and polymer crosslink density. We have identified the physical and chemical factors that control the average porosity, pore size, and pore size distribution within epoxy based systems.

  2. Analytical applications for pore-forming proteins.

    Science.gov (United States)

    Kasianowicz, John J; Balijepalli, Arvind K; Ettedgui, Jessica; Forstater, Jacob H; Wang, Haiyan; Zhang, Huisheng; Robertson, Joseph W F

    2016-03-01

    Proteinaceous nanometer-scale pores are ubiquitous in biology. The canonical ionic channels (e.g., those that transport Na(+), K(+), Ca(2+), and Cl(-) across cell membranes) play key roles in many cellular processes, including nerve and muscle activity. Another class of channels includes bacterial pore-forming toxins, which disrupt cell function, and can lead to cell death. We describe here the recent development of these toxins for a wide range of biological sensing applications. This article is part of a Special Issue entitled: Pore-Forming Toxins edited by Mauro Dalla Serra and Franco Gambale.

  3. Experimental Design for One Dimensional Electrolytic Reactive Barrier for Remediation of Munition Constituent in Groundwater

    Science.gov (United States)

    Gent, David B.; Wani, Altaf; Alshawabkeh, Akram N.

    2012-01-01

    A combination of direct electrochemical reduction and in-situ alkaline hydrolysis has been proposed to decompose energetic contaminants such as 1,3,5-Trinitroperhydro- 1,3,5-triazine and 2,4,6-Trinitrotoluene (RDX) in deep aquifers. This process utilizes natural groundwater convection to carry hydroxide produced by an upstream cathode to remove the contaminant at the cathode as well as in the pore water downstream as it migrates toward the anode. Laboratory evaluation incorporated fundamental principles of column design coupled with reactive contaminant modeling including electrokinetics transport. Batch and horizontal sand-packed column experiments included both alkaline hydrolysis and electrochemical treatment to determine RDX decomposition reaction rate coefficients. The sand packed columns simulated flow through a contaminated aquifer with a seepage velocity of 30.5 cm/day. Techniques to monitor and record the transient electric potential, hydroxide transport and contaminant concentration within the column were developed. The average reaction rate coefficients for both the alkaline batch (0.0487 hr−1) and sand column (0.0466 hr−1) experiments estimated the distance between the cathode and anode required to decompose 0.5 mg/L RDX to the USEPA drinking water lifetime Health Advisory level of 0.002 mg/L to be 145 and 152 cm. PMID:23472044

  4. Experimental Design for One Dimensional Electrolytic Reactive Barrier for Remediation of Munition Constituent in Groundwater.

    Science.gov (United States)

    Gent, David B; Wani, Altaf; Alshawabkeh, Akram N

    2012-12-30

    A combination of direct electrochemical reduction and in-situ alkaline hydrolysis has been proposed to decompose energetic contaminants such as 1,3,5-Trinitroperhydro- 1,3,5-triazine and 2,4,6-Trinitrotoluene (RDX) in deep aquifers. This process utilizes natural groundwater convection to carry hydroxide produced by an upstream cathode to remove the contaminant at the cathode as well as in the pore water downstream as it migrates toward the anode. Laboratory evaluation incorporated fundamental principles of column design coupled with reactive contaminant modeling including electrokinetics transport. Batch and horizontal sand-packed column experiments included both alkaline hydrolysis and electrochemical treatment to determine RDX decomposition reaction rate coefficients. The sand packed columns simulated flow through a contaminated aquifer with a seepage velocity of 30.5 cm/day. Techniques to monitor and record the transient electric potential, hydroxide transport and contaminant concentration within the column were developed. The average reaction rate coefficients for both the alkaline batch (0.0487 hr(-1)) and sand column (0.0466 hr(-1)) experiments estimated the distance between the cathode and anode required to decompose 0.5 mg/L RDX to the USEPA drinking water lifetime Health Advisory level of 0.002 mg/L to be 145 and 152 cm.

  5. Canada's groundwater resources

    National Research Council Canada - National Science Library

    Rivera, Alfonso

    2014-01-01

    Groundwater is essential for life in arid and semiarid region. It is also important in humid regions, and is one of the fundamental requirements for the maintenance of natural landscapes and aquatic ecosystem...

  6. Groundwater Capture Zones

    Data.gov (United States)

    Iowa State University GIS Support and Research Facility — Source water protection areas are delineated for each groundwater-based public water supply system using available geologic and hydrogeologic information to...

  7. A fast Laplace solver approach to pore scale permeability

    Science.gov (United States)

    Arns, Christoph; Adler, Pierre

    2017-04-01

    The permeability of a porous medium can be derived by solving the Stokes equations in the pore space with no slip at the walls. The resulting velocity averaged over the pore volume yields the permeability KS by application of the Darcy law. The Stokes equations can be solved by a number of different techniques such as finite differences, finite volume, Lattice Boltzmann, but whatever the technique it remains a heavy task since there are four unknowns at each node (the three velocity components and the pressure) which necessitate the solution of four equations (the projection of Newton's law on each axis and mass conservation). By comparison, the Laplace equation is scalar with a single unknown at each node. The objective of this work is to replace the Stokes equations by an elliptical equation with a space dependent permeability. More precisely, the local permeability k is supposed to be proportional to (r-alpha)**2 where r is the distance of the voxel to the closest wall, and alpha a constant; k is zero in the solid phase. The elliptical equation is div(k gradp)=0. A macroscopic pressure gradient is assumed to be exerted on the medium and again the resulting velocity averaged over space yields a permeability K_L. In order to validate this method, systematic calculations have been performed. First, elementary shapes (plane channel, circular pipe, rectangular channels) were studied for which flow occurs along parallel lines in which case KL is the arithmetic average of the k's. KL was calculated for various discretizations of the pore space and various values of alpha. For alpha=0.5, the agreement with the exact analytical value of KS is excellent for the plane and rectangular channels while it is only approximate for circular pipes. Second, the permeability KL of channels with sinusoidal walls was calculated and compared with analytical results and numerical ones provided by a Lattice Boltzmann algorithm. Generally speaking, the discrepancy does not exceed 25% when

  8. High-fluoride groundwater.

    Science.gov (United States)

    Rao, N Subba

    2011-05-01

    Fluoride (F(-)) is essential for normal bone growth, but its higher concentration in the drinking water poses great health problems and fluorosis is common in many parts of India. The present paper deals with the aim of establishment of facts of the chemical characteristics responsible for the higher concentration of F(-) in the groundwater, after understanding the chemical behavior of F(-) in relation to pH, total alkalinity (TA), total hardness (TH), carbonate hardness (CH), non-carbonate hardness (NCH), and excess alkalinity (EA) in the groundwater observed from the known areas of endemic fluorosis zones of Andhra Pradesh that have abundant sources of F(-)-bearing minerals of the Precambrians. The chemical data of the groundwater shows that the pH increases with increase F(-); the concentration of TH is more than the concentration of TA at low F(-) groundwater, the resulting water is represented by NCH; the TH has less concentration compared to TA at high F(-) groundwater, causing the water that is characterized by EA; and the water of both low and high concentrations of F(-) has CH. As a result, the F(-) has a positive relation with pH and TA, and a negative relation with TH. The operating mechanism derived from these observations is that the F(-) is released from the source into the groundwater by geochemical reactions and that the groundwater in its flowpath is subjected to evapotranspiration due to the influence of dry climate, which accelerates a precipitation of CaCO(3) and a reduction of TH, and thereby a dissolution of F(-). Furthermore, the EA in the water activates the alkalinity in the areas of alkaline soils, leading to enrichment of F(-). Therefore, the alkaline condition, with high pH and EA, and low TH, is a more conducive environment for the higher concentration of F(-) in the groundwater.

  9. Straight Pore Microfilter with Efficient Regeneration Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This Small Business Innovation Research Phase II project is directed toward development of a novel microfiltration filter that has distinctively narrow pore size...

  10. Straight Pore Microfilter with Efficient Regeneration Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This Small Business Innovation Research Phase I project is directed toward development of a novel microfiltration filter that has distinctively narrow pore size...

  11. A Potential Model for Cylindrical Pores

    Institute of Scientific and Technical Information of China (English)

    张现仁; 汪文川

    2001-01-01

    An analytical potential for cylindrical pores has been derived by introducing a variational method into the integration for the calculation of the interaction energy between the wall molecules and a test molecule, all of which are represented by Lennard-Jones potential. The model proposed gives good fit to the results from the cylindrical surface model and the pseudoatom model. To test the potential proposed rigorously, we have carried out grand canonical ensemble Monte Carlo(GCMC) simulation of nitrogen in the MCM-41 pore at 77 K, and compared the simulated adsorption isotherm with the experimental data reported in the literature. The simulated isotherm from our model is in almost qualitative agreement with experiment. Consequently, the model proposed provides an explicit and accurate description of cylindrical pores represented by the Lennard-Jones potential. Moreover, the model can be easily applied to a variety of cylindrical pores, ranging from cylindrical surface to finite thickness walls, in both theoretical studies and computer simulations.

  12. Pore structure in blended cement pastes

    DEFF Research Database (Denmark)

    Canut, Mariana Moreira Cavalcanti

    Supplementary cementitious materials (SCMs), such as slag and fly ash, are increasingly used as a substitute for Portland cement in the interests of improvement of engineering properties and sustainability of concrete. According to studies improvement of engineering properties can be explained...... supplement each other. Cement pastes (w/b=0.4) with and without slag and fly ash cured at two moisture (sealed and saturated) and temperature (20 and 55ºC) conditions were used to investigate the combined impact of SCMs addition and curing on the pore structure of pastes cured up to two years. Also...... volume and threshold pore size were found when comparing with plain cement paste at the same curing conditions. The porosity methods MIP, LTC and SEM have been shown to be suitable to characterise pore parameters of the pastes. MIP is a simple and fast method which covers a large range of pore sizes...

  13. Analysis of a spatially deconvolved solar pore

    CERN Document Server

    Noda, C Quintero; Cobo, B Ruiz; Suematsu, Y; Katsukawa, Y; Ichimoto, K

    2016-01-01

    Solar pores are active regions with large magnetic field strengths and apparent simple magnetic configurations. Their properties resemble the ones found for the sunspot umbra although pores do not show penumbra. Therefore, solar pores present themselves as an intriguing phenomenon that is not completely understood. We examine in this work a solar pore observed with Hinode/SP using two state of the art techniques. The first one is the spatial deconvolution of the spectropolarimetric data that allows removing the stray light contamination induced by the spatial point spread function of the telescope. The second one is the inversion of the Stokes profiles assuming local thermodynamic equilibrium that let us to infer the atmospheric physical parameters. After applying these techniques, we found that the spatial deconvolution method does not introduce artefacts, even at the edges of the magnetic structure, where large horizontal gradients are detected on the atmospheric parameters. Moreover, we also describe the p...

  14. Velocity selective optical pumping

    OpenAIRE

    Aminoff, C. G.; Pinard, M.

    1982-01-01

    We consider optical pumping with a quasi monochromatic tunable light beam, in the low intensity limit where a rate equation regime is obtained The velocity selective optical pumping (V.S.O.P.) introduces a correlation between atomic velocity and internal variables in the ground (or metastable) state. The aim of this article is to evaluate these atomic observables (orientation, alignment, population) as a function of velocity, using a phenomenological description of the relaxation effect of co...

  15. Pore-scale and Continuum Simulations of Solute Transport Micromodel Benchmark Experiments

    Energy Technology Data Exchange (ETDEWEB)

    Oostrom, Martinus; Mehmani, Yashar; Romero Gomez, Pedro DJ; Tang, Y.; Liu, H.; Yoon, Hongkyu; Kang, Qinjun; Joekar Niasar, Vahid; Balhoff, Matthew; Dewers, T.; Tartakovsky, Guzel D.; Leist, Emily AE; Hess, Nancy J.; Perkins, William A.; Rakowski, Cynthia L.; Richmond, Marshall C.; Serkowski, John A.; Werth, Charles J.; Valocchi, Albert J.; Wietsma, Thomas W.; Zhang, Changyong

    2016-08-01

    Four sets of micromodel nonreactive solute transport experiments were conducted with flow velocity, grain diameter, pore-aspect ratio, and flow focusing heterogeneity as the variables. The data sets were offered to pore-scale modeling groups to test their simulators. Each set consisted of two learning experiments, for which all results was made available, and a challenge experiment, for which only the experimental description and base input parameters were provided. The experimental results showed a nonlinear dependence of the dispersion coefficient on the Peclet number, a negligible effect of the pore-aspect ratio on transverse mixing, and considerably enhanced mixing due to flow focusing. Five pore-scale models and one continuum-scale model were used to simulate the experiments. Of the pore-scale models, two used a pore-network (PN) method, two others are based on a lattice-Boltzmann (LB) approach, and one employed a computational fluid dynamics (CFD) technique. The learning experiments were used by the PN models to modify the standard perfect mixing approach in pore bodies into approaches to simulate the observed incomplete mixing. The LB and CFD models used these experiments to appropriately discretize the grid representations. The continuum model use published non-linear relations between transverse dispersion coefficients and Peclet numbers to compute the required dispersivity input values. Comparisons between experimental and numerical results for the four challenge experiments show that all pore-scale models were all able to satisfactorily simulate the experiments. The continuum model underestimated the required dispersivity values and, resulting in less dispersion. The PN models were able to complete the simulations in a few minutes, whereas the direct models needed up to several days on supercomputers to resolve the more complex problems.

  16. Visualization of enzyme activities inside earthworm pores

    Science.gov (United States)

    Hoang, Duyen; Razavi, Bahar S.

    2015-04-01

    In extremely dynamic microhabitats as bio-pores made by earthworm, the in situ enzyme activities are assumed as a footprint of complex biotic interactions. Our study focused on the effect of earthworm on the enzyme activities inside bio-pores and visualizing the differences between bio-pores and earthworm-free soil by zymography technique (Spohn and Kuzyakov, 2013). For the first time, we aimed at quantitative imaging of enzyme activities in bio-pores. Lumbricus terrestris L. was placed into transparent box (15×20×15cm). After two weeks when bio-pore systems were formed by earthworms, we visualized in situ enzyme activities of five hydrolytic enzymes (β-glucosidase, cellobiohydrolase, chitinase, xylanase, leucine-aminopeptidase, and phosphatase. Zymography showed higher activity of β-glucosidase, chitinase, xylanase and phosphatase in biopores comparing to bulk soil. However, the differences in activity of cellobiohydrolase and leucine aminopeptidase between bio-pore and bulk soil were less pronounced. This demonstrated an applicability of zymography approach to monitor and to distinguish the in situ activity of hydrolytic enzymes in soil biopores.

  17. An Experimental and Modeling Study on the Response to Varying Pore Pressure and Reservoir Fluids in the Morrow A Sandstone

    Directory of Open Access Journals (Sweden)

    Aaron V. Wandler

    2012-01-01

    Full Text Available In mature oil fields undergoing enhanced oil recovery methods, such as CO2 injection, monitoring the reservoir changes becomes important. To understand how reservoir changes influence compressional wave (P and shear wave (S velocities, we conducted laboratory core experiments on five core samples taken from the Morrow A sandstone at Postle Field, Oklahoma. The laboratory experiments measured P- and S-wave velocities as a function of confining pressure, pore pressure, and fluid type (which included CO2 in the gas and supercritical phase. P-wave velocity shows a response that is sensitive to both pore pressure and fluid saturation. However, S-wave velocity is primarily sensitive to changes in pore pressure. We use the fluid and pore pressure response measured from the core samples to modify velocity well logs through a log facies model correlation. The modified well logs simulate the brine- and CO2-saturated cases at minimum and maximum reservoir pressure and are inputs for full waveform seismic modeling. Modeling shows how P- and S-waves have a different time-lapse amplitude response with offset. The results from the laboratory experiments and modeling show the advantages of combining P- and S-wave attributes in recognizing the mechanism responsible for time-lapse changes due to CO2 injection.

  18. Relation of deformation behavior with precipitation and groundwater of the Babaoshan fault in Beijing

    Institute of Scientific and Technical Information of China (English)

    HUANG Fu-qiong; CHEN Yong; BAI Chang-qing; ZHANG Jing; YAN Rui; YANG Ming-bo; LAN Cong-xin; ZHANG Xiao-dong; JIANG Zai-sen

    2005-01-01

    We discuss the influence of precipitation and groundwater on the deformation behavior of the Babaoshan fault of Beijing by using long-term observation data from Dahuichang station during 1970~2003. The results show that a)the pore pressure on fault zone as well as the fault deformation behavior exhibited periodically variation as precipitation changed steadily and periodically; b) the periodicity of the pore pressure of fault zones disappeared and the manner of fault deformation behavior changed when precipitation was small and/or was in aberrance. This implies that rainfall plays a key role in fault deformation behavior through changing the pore pressure of fault zones. Combining the existing results about the Babaoshan fault, it is concluded that precipitation and groundwater may adjust the stress/strain field by controlling the deformation behavior of the fault, which can provide direct observation evidence for the interaction of fluid and solid in shallow crust of the Earth.

  19. Limits to global groundwater consumption

    Science.gov (United States)

    de Graaf, I.; Van Beek, L. P.; Sutanudjaja, E.; Wada, Y.; Bierkens, M. F.

    2016-12-01

    Groundwater is the largest accessible freshwater resource worldwide and is of critical importance for irrigation, and so for global food security. For many regions of the world where groundwater abstraction exceeds groundwater recharge, persistent groundwater depletion occurs. A direct consequence of depletion is falling groundwater levels, reducing baseflows to rivers, harming ecosystems. Also, pumping costs increase, wells dry up and land subsidence can occur. Water demands are expected to increase further due to growing population, economic development and climate change, posing the urgent question how sustainable current water abstractions are worldwide and where and when these abstractions approach conceivable limits with all the associated problems. Here, we estimated past and future trends (1960-2050) in groundwater levels resulting from changes in abstractions and climate and predicted when limits of groundwater consumption are reached. We explored these limits by predicting where and when groundwater levels drop that low that groundwater becomes unattainable for abstractions and how river flows are affected. Water availabilities, abstractions, and lateral groundwater flows are simulated (5 arcmin. resolution) using a coupled version of the global hydrological model PCR-GLOBWB and a groundwater model based on MODFLOW. The groundwater model includes a parameterization of the worlds confined and unconfined aquifer systems, needed for a realistic simulation of groundwater head dynamics. Results show that, next to the existing regions experiencing groundwater depletion (like India, Pakistan, Central Valley) new regions will develop, e.g. Southern Europe, the Middle East, and Africa. Using a limit that reflects present-day feasibility of groundwater abstraction, we estimate that in 2050 groundwater becomes unattainable for 20% of the global population, mainly in the developing countries and pumping cost will increase significantly. Largest impacts are found

  20. Pore REconstruction and Segmentation (PORES) method for improved porosity quantification of nanoporous materials

    Energy Technology Data Exchange (ETDEWEB)

    Van Eyndhoven, G., E-mail: geert.vaneyndhoven@uantwerpen.be [iMinds-Vision Lab, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk (Belgium); Kurttepeli, M. [EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp (Belgium); Van Oers, C.J.; Cool, P. [Laboratory of Adsorption and Catalysis, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk (Belgium); Bals, S. [EMAT, University of Antwerp, Groenenborgerlaan 171, B-2020 Antwerp (Belgium); Batenburg, K.J. [iMinds-Vision Lab, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk (Belgium); Centrum Wiskunde and Informatica, Science Park 123, NL-1090 GB Amsterdam (Netherlands); Mathematical Institute, Universiteit Leiden, Niels Bohrweg 1, NL-2333 CA Leiden (Netherlands); Sijbers, J. [iMinds-Vision Lab, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk (Belgium)

    2015-01-15

    Electron tomography is currently a versatile tool to investigate the connection between the structure and properties of nanomaterials. However, a quantitative interpretation of electron tomography results is still far from straightforward. Especially accurate quantification of pore-space is hampered by artifacts introduced in all steps of the processing chain, i.e., acquisition, reconstruction, segmentation and quantification. Furthermore, most common approaches require subjective manual user input. In this paper, the PORES algorithm “POre REconstruction and Segmentation” is introduced; it is a tailor-made, integral approach, for the reconstruction, segmentation, and quantification of porous nanomaterials. The PORES processing chain starts by calculating a reconstruction with a nanoporous-specific reconstruction algorithm: the Simultaneous Update of Pore Pixels by iterative REconstruction and Simple Segmentation algorithm (SUPPRESS). It classifies the interior region to the pores during reconstruction, while reconstructing the remaining region by reducing the error with respect to the acquired electron microscopy data. The SUPPRESS reconstruction can be directly plugged into the remaining processing chain of the PORES algorithm, resulting in accurate individual pore quantification and full sample pore statistics. The proposed approach was extensively validated on both simulated and experimental data, indicating its ability to generate accurate statistics of nanoporous materials. - Highlights: • An electron tomography reconstruction/segmentation method for nanoporous materials. • The method exploits the porous nature of the scanned material. • Validated extensively on both simulation and real data experiments. • Results in increased image resolution and improved porosity quantification.

  1. Estimation of vector velocity

    DEFF Research Database (Denmark)

    2000-01-01

    Using a pulsed ultrasound field, the two-dimensional velocity vector can be determined with the invention. The method uses a transversally modulated ultrasound field for probing the moving medium under investigation. A modified autocorrelation approach is used in the velocity estimation. The new...

  2. Estimation of vector velocity

    DEFF Research Database (Denmark)

    2000-01-01

    Using a pulsed ultrasound field, the two-dimensional velocity vector can be determined with the invention. The method uses a transversally modulated ultrasound field for probing the moving medium under investigation. A modified autocorrelation approach is used in the velocity estimation. The new...

  3. Low Pore Connectivity in Natural Rock

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Qinhong; Ewing, Robert P.; Dultz, Stefan

    2012-05-15

    As repositories for CO₂ and radioactive waste, as oil and gas reservoirs, and as contaminated sites needing remediation, rock formations play a central role in energy and environmental management. The connectivity of the rock's porespace strongly affects fluid flow and solute transport. This work examines pore connectivity and its implications for fluid flow and chemical transport. Three experimental approaches (imbibition, tracer concentration profiles, and imaging) were used in combination with network modeling. In the imbibition results, three types of imbibition slope [log (cumulative imbibition) vs. log (imbibition time)] were found: the classical 0.5, plus 0.26, and 0.26 transitioning to 0.5. The imbibition slope of 0.26 seen in Indiana sandstone, metagraywacke, and Barnett shale indicates low pore connectivity, in contrast to the slope of 0.5 seen in the well-connected Berea sandstone. In the tracer profile work, rocks exhibited different distances to the plateau porosity, consistent with the pore connectivity from the imbibition tests. Injection of a molten metal into connected pore spaces, followed by 2-D imaging of the solidified alloy in polished thin sections, allowed direct assessment of pore structure and lateral connection in the rock samples. Pore-scale network modeling gave results consistent with measurements, confirming pore connectivity as the underlying cause of both anomalous behaviors: imbibition slope not having the classical value of 0.5, and accessible porosity being a function of distance from the edge. A poorly connected porespace will exhibit anomalous behavior in fluid flow and chemical transport, such as a lower imbibition slope (in air–water system) and diffusion rate than expected from classical behavior.

  4. Low pore connectivity in natural rock.

    Science.gov (United States)

    Hu, Qinhong; Ewing, Robert P; Dultz, Stefan

    2012-05-15

    As repositories for CO(2) and radioactive waste, as oil and gas reservoirs, and as contaminated sites needing remediation, rock formations play a central role in energy and environmental management. The connectivity of the rock's porespace strongly affects fluid flow and solute transport. This work examines pore connectivity and its implications for fluid flow and chemical transport. Three experimental approaches (imbibition, tracer concentration profiles, and imaging) were used in combination with network modeling. In the imbibition results, three types of imbibition slope [log (cumulative imbibition) vs. log (imbibition time)] were found: the classical 0.5, plus 0.26, and 0.26 transitioning to 0.5. The imbibition slope of 0.26 seen in Indiana sandstone, metagraywacke, and Barnett shale indicates low pore connectivity, in contrast to the slope of 0.5 seen in the well-connected Berea sandstone. In the tracer profile work, rocks exhibited different distances to the plateau porosity, consistent with the pore connectivity from the imbibition tests. Injection of a molten metal into connected pore spaces, followed by 2-D imaging of the solidified alloy in polished thin sections, allowed direct assessment of pore structure and lateral connection in the rock samples. Pore-scale network modeling gave results consistent with measurements, confirming pore connectivity as the underlying cause of both anomalous behaviors: imbibition slope not having the classical value of 0.5, and accessible porosity being a function of distance from the edge. A poorly connected porespace will exhibit anomalous behavior in fluid flow and chemical transport, such as a lower imbibition slope (in air-water system) and diffusion rate than expected from classical behavior.

  5. Fort Ord Groundwater Remediation Studies, 2002 - 2005

    Science.gov (United States)

    2006-08-01

    water Velocity at OU 1, Former Fort Ord, California. Su, G.W., B.M. Freifeld , C.M. Oldenburg, P.D. Jordan and P.F. Daley. 2005. Lawrence Berkeley...138. Oldenburg, C. M., P. F. Daley, B. M. Freifeld , J. Hinds, and P. D. Jordan, 2002. Three- Dimensional Groundwater Flow, Aquifer Response, and...U.S. Geological Survey Contract Number 1434-95-C-40232, 29 pp. Su, G.W., B.M. Freifeld , C.M. Oldenburg, P.D. Jordan, and P.F. Daley, 2005. Data

  6. Geohydrological control on radon availability in groundwater

    Energy Technology Data Exchange (ETDEWEB)

    Prasad, Yogesh; Prasad, Ganesh [Department of Physics, H. N. B. Garhwal University, Badshahi Thaul Campus, Tehri Garhwal 249 199 (India); Choubey, V.M. [Wadia Institute of Himalayan Geology, Dehradun 248001 (India); Ramola, R.C. [Department of Physics, H. N. B. Garhwal University, Badshahi Thaul Campus, Tehri Garhwal 249 199 (India)], E-mail: rcramola@gmail.com

    2009-01-15

    The radon content in groundwater sources depends on the radium concentration in the rock of the aquifer. Radon was measured in water in many parts of the world, mostly for the risk assessment due to consumption of drinking water. The exposure to radon through drinking water is largely by inhalation and ingestion. Airborne radon can be released during normal household activities and can pose a greater potential health risk than radon ingested with water. Transport of radon through soil and bedrock by water depends mainly on the percolation of water through the pores and along fractured planes of bedrock. In this study, radon concentration in springs and hand pumps of Kumaun and Garhwal Himalaya, India was measured using radon emanometry technique. The study shows that radon concentration in springs and hand pumps is controlled by geohydrological characteristics, which in turn is also governed by tectonic processes.

  7. Inertial forces affect fluid front displacement dynamics in a pore-throat network model.

    Science.gov (United States)

    Moebius, Franziska; Or, Dani

    2014-08-01

    The seemingly regular and continuous motion of fluid displacement fronts in porous media at the macroscopic scale is propelled by numerous (largely invisible) pore-scale abrupt interfacial jumps and pressure bursts. Fluid fronts in porous media are characterized by sharp phase discontinuities and by rapid pore-scale dynamics that underlie their motion; both attributes challenge standard continuum theories of these flow processes. Moreover, details of pore-scale dynamics affect front morphology and subsequent phase entrapment behind a front and thereby shape key macroscopic transport properties of the unsaturated zone. The study presents a pore-throat network model that focuses on quantifying interfacial dynamics and interactions along fluid displacement fronts. The porous medium is represented by a lattice of connected pore throats capable of detaining menisci and giving rise to fluid-fluid interfacial jumps (the study focuses on flow rate controlled drainage). For each meniscus along the displacement front we formulate a local inertial, capillary, viscous, and hydrostatic force balance that is then solved simultaneously for the entire front. The model enables systematic evaluation of the role of inertia and boundary conditions. Results show that while displacement patterns are affected by inertial forces mainly by invasion of throats with higher capillary resistance, phase entrapment (residual saturation) is largely unaffected by inertia, limiting inertial effects on hydrological properties behind a front. Interfacial jump velocities are often an order of magnitude larger than mean front velocity, are strongly dependent on geometrical throat dimensions, and become less predictable (more scattered) when inertia is considered. Model simulations of the distributions of capillary pressure fluctuations and waiting times between invasion events follow an exponential distribution and are in good agreement with experimental results. The modeling approach provides insights

  8. Characterization of the intragranular water regime within subsurface sediments: Pore volume, surface area, and mass transfer limitations

    Science.gov (United States)

    Hay, Michael B.; Stoliker, Deborah L.; Davis, James A.; Zachara, John M.

    2011-10-01

    Although "intragranular" pore space within grain aggregates, grain fractures, and mineral surface coatings may contain a relatively small fraction of the total porosity within a porous medium, it often contains a significant fraction of the reactive surface area, and can thus strongly affect the transport of sorbing solutes. In this work, we demonstrate a batch experiment procedure using tritiated water as a high-resolution diffusive tracer to characterize the intragranular pore space. The method was tested using uranium-contaminated sediments from the vadose and capillary fringe zones beneath the former 300A process ponds at the Hanford site (Washington). Sediments were contacted with tracers in artificial groundwater, followed by a replacement of bulk solution with tracer-free groundwater and the monitoring of tracer release. From these data, intragranular pore volumes were calculated and mass transfer rates were quantified using a multirate first-order mass transfer model. Tritium-hydrogen exchange on surface hydroxyls was accounted for by conducting additional tracer experiments on sediment that was vacuum dried after reaction. The complementary ("wet" and "dry") techniques allowed for the simultaneous determination of intragranular porosity and surface area using tritium. The Hanford 300A samples exhibited intragranular pore volumes of ˜1% of the solid volume and intragranular surface areas of ˜20%-35% of the total surface area. Analogous experiments using bromide ion as a tracer yielded very different results, suggesting very little penetration of bromide into the intragranular porosity.

  9. Characterization of the intragranular water regime within subsurface sediments: pore volume, surface area, and mass transfer limitations

    Science.gov (United States)

    Hay, Michael B.; Stoliker, Deborah L.; Davis, James A.; Zachara, John M.

    2011-01-01

    Although "intragranular" pore space within grain aggregates, grain fractures, and mineral surface coatings may contain a relatively small fraction of the total porosity within a porous medium, it often contains a significant fraction of the reactive surface area, and can thus strongly affect the transport of sorbing solutes. In this work, we demonstrate a batch experiment procedure using tritiated water as a high-resolution diffusive tracer to characterize the intragranular pore space. The method was tested using uranium-contaminated sediments from the vadose and capillary fringe zones beneath the former 300A process ponds at the Hanford site (Washington). Sediments were contacted with tracers in artificial groundwater, followed by a replacement of bulk solution with tracer-free groundwater and the monitoring of tracer release. From these data, intragranular pore volumes were calculated and mass transfer rates were quantified using a multirate first-order mass transfer model. Tritium-hydrogen exchange on surface hydroxyls was accounted for by conducting additional tracer experiments on sediment that was vacuum dried after reaction. The complementary ("wet" and "dry") techniques allowed for the simultaneous determination of intragranular porosity and surface area using tritium. The Hanford 300A samples exhibited intragranular pore volumes of ~1% of the solid volume and intragranular surface areas of ~20%–35% of the total surface area. Analogous experiments using bromide ion as a tracer yielded very different results, suggesting very little penetration of bromide into the intragranular porosity.

  10. Limits to Global Groundwater Consumption

    Science.gov (United States)

    Graaf, I. D.; Van Beek, R.; Sutanudjaja, E.; Wada, Y.; Bierkens, M. F.

    2015-12-01

    In regions with frequent water stress and large aquifer systems, groundwater is often used as an additional fresh water source. For many regions of the world groundwater abstraction exceeds groundwater recharge and persistent groundwater depletion occurs. The most direct effect of groundwater depletion is declining of water tables, leading to reduced groundwater discharge needed to sustain base-flow to e.g. rivers. Next to that, pumping costs increase, wells dry up and land subsidence occurs. These problems are expected to increase in the near future due to growing population and climate changes. This poses the urgent question of what the limits are of groundwater consumption worldwide. We simulate global water availability (5 arc-minute resolution, for 1960-2050) using the hydrological model PCR-GLOBWB (van Beek et al. 2011), coupled to a groundwater model based on MODFLOW (de Graaf et al. 2015), allowing for groundwater - surface water interactions. The groundwater model includes a parameterization of world's confined and unconfined aquifer systems needed for a realistic simulation of groundwater head dynamics. Water demands are included (from Wada et al. 2014). We study the limits to water consumption, focusing on locally attainable groundwater and groundwater levels critical to rivers to sustain low flows. We show an increasing trend (1960-2050) in groundwater head declines, due to increase in groundwater demand. Also, stream flow will decrease and low flow conditions will occur more frequent and will be longer in duration in the near future, especially for irrigated areas. Next to that, we provide a global overview of the years it takes until groundwater gets unattainable for e.g. a local farmer (100 m below land-surface used as a proxy), and estimate the increase in pumping cost for the near future. The results show where and when limits of groundwater consumption are reached globally.

  11. Pore Structure Characterization of Indiana Limestone and Pink Dolomite from Pore Network Reconstructions

    Directory of Open Access Journals (Sweden)

    Freire-Gormaly Marina

    2016-05-01

    Full Text Available Carbon sequestration in deep underground saline aquifers holds significant promise for reducing atmospheric carbon dioxide emissions (CO2. However, challenges remain in predicting the long term migration of injected CO2. Addressing these challenges requires an understanding of pore-scale transport of CO2 within existing brine-filled geological reservoirs. Studies on the transport of fluids through geological porous media have predominantly focused on oil-bearing formations such as sandstone. However, few studies have considered pore-scale transport within limestone and other carbonate formations, which are found in potential storage sites. In this work, high-resolution micro-Computed Tomography (microCT was used to obtain pore-scale structural information of two model carbonates: Indiana Limestone and Pink Dolomite. A modified watershed algorithm was applied to extract pore network from the reconstructed microCT volumetric images of rock samples and compile a list of pore-scale characteristics from the extracted networks. These include statistical distributions of pore size and radius, pore-pore separation, throat radius, and network coordination. Finally, invasion percolation algorithms were applied to determine saturation-pressure curves for the rock samples. The statistical distributions were comparable to literature values for the Indiana Limestone. This served as validation for the network extraction approach for Pink Dolomite, which has not been considered previously. Based on the connectivity and the pore-pore separation, formations such as Pink Dolomite may present suitable storage sites for carbon storage. The pore structural distributions and saturation curves obtained in this study can be used to inform core- and reservoir-scale modeling and experimental studies of sequestration feasibility.

  12. Furthering Chemical and Geophysical Computations: Analysis of SACROC SEM and CT images to obtain pore percentage, size, and connectivity data

    Science.gov (United States)

    Mur, A. J.; Purcell, C. C.; Harbert, W. P.; Soong, Y.; Kutchko, B. G.; Kennedy, S.; McIntryre, D.

    2009-12-01

    The National Energy Technology Laboratory of the United States Department of Energy, in collaboration with the Bureau of Economic Geology in Austin, Texas has been involved in an extensive study of the many aspects involved in the injection of CO2 into the 2042 meter deep Permian reef structure at the SACROC field. Subsamples of reef limestone cores used for seismic velocity measurements were obtained. XRD determined the sample to be ~99% Calcite and ~1% Dolomite with a small amount of impurities. Preliminary petrographic slides revealed a vuggy porosity. We acquired CT scans of a SACROC limestone core at the Morgantown NETL site. We also acquired a high pixel resolution (112 MB) SEM secondary electron image of the reef limestone at RJ Lee Group. By using ArcMap , we created a tool that groups grayscale ranges into three categories, cleans boundaries between groups, and produces a polygon map of the macropores, micropores, and matrix. The darkest areas in the SEM image were cavern-like pores and were thus called macropores. Micropores, the brightest regions, are textured micrite faces that create many, small pore spaces. Using ImageJ, the CT and Arc pore maps were analyzed to reveal pore shape statistics. Average pore perimeter, average pore area, and pore connectivity is essential for chemistry experiments that will emulate time exposure of CO2 to limestone. Further, ImageJ allows us to obtain pore orientation information. This is important in understanding the anisotropic conditions that may or may not affect seismic data. The image is 10240x11264 pixels which correspond to ~ 8890.00x9780.00 micrometers. Micro- and macropores combined, there were 613744 pores mapped. Differing statistical methods revealed differing results. For example, the average pore perimeter was ~28 microns while the average pore area was perimeter. The lower estimate was formulated by using the maximum pore perimeter as the average pore size. By using the 13% porosity model and assuming

  13. Freeze-cast alumina pore networks: Effects of freezing conditions and dispersion medium

    Energy Technology Data Exchange (ETDEWEB)

    Miller, S. M.; Xiao, X.; Faber, K. T.

    2015-11-01

    Alumina ceramics were freeze-cast from water- and camphene-based slurries under varying freezing conditions and examined using X-ray computed tomography (XCT). Pore network characteristics, i.e., porosity, pore size, geometric surface area, and tortuosity, were measured from XCT reconstructions and the data were used to develop a model to predict feature size from processing conditions. Classical solidification theory was used to examine relationships between pore size, temperature gradients, and freezing front velocity. Freezing front velocity was subsequently predicted from casting conditions via the two-phase Stefan problem. Resulting models for water-based samples agreed with solidification-based theories predicting lamellar spacing of binary eutectic alloys, and models for camphene-based samples concurred with those for dendritic growth. Relationships between freezing conditions and geometric surface area were also modeled by considering the inverse relationship between pore size and surface area. Tortuosity was determined to be dependent primarily on the type of dispersion medium. (C) 2015 Elsevier Ltd. All rights reserved.

  14. Modeling branching pore structures in membrane filters

    Science.gov (United States)

    Sanaei, Pejman; Cummings, Linda J.

    2016-11-01

    Membrane filters are in widespread industrial use, and mathematical models to predict their efficacy are potentially very useful, as such models can suggest design modifications to improve filter performance and lifetime. Many models have been proposed to describe particle capture by membrane filters and the associated fluid dynamics, but most such models are based on a very simple structure in which the pores of the membrane are assumed to be simple circularly-cylindrical tubes spanning the depth of the membrane. Real membranes used in applications usually have much more complex geometry, with interconnected pores which may branch and bifurcate. Pores are also typically larger on the upstream side of the membrane than on the downstream side. We present an idealized mathematical model, in which a membrane consists of a series of bifurcating pores, which decrease in size as the membrane is traversed. Feed solution is forced through the membrane by applied pressure, and particles are removed from the feed either by sieving, or by particle adsorption within pores (which shrinks them). Thus the membrane's permeability decreases as the filtration progresses, ultimately falling to zero. We discuss how filtration efficiency depends on the characteristics of the branching structure. Partial support from NSF DMS 1261596 is gratefully acknowledged.

  15. Performance of Small Pore Microchannel Plates

    Science.gov (United States)

    Siegmund, O. H. W.; Gummin, M. A.; Ravinett, T.; Jelinsky, S. R.; Edgar, M.

    1995-01-01

    Small pore size microchannel plates (MCP's) are needed to satisfy the requirements for future high resolution small and large format detectors for astronomy. MCP's with pore sizes in the range 5 micron to 8 micron are now being manufactured, but they are of limited availability and are of small size. We have obtained sets of Galileo 8 micron and 6.5 micron MCP's, and Philips 6 micron and 7 micron pore MCP's, and compared them to our larger pore MCP Z stacks. We have tested back to back MCP stacks of four of these MCP's and achieved gains greater than 2 x 1O(exp 7) with pulse height distributions of less than 40% FWHM, and background rates of less than 0.3 events sec(exp -1) cm(exp -2). Local counting rates up to approx. 100 events/pore/sec have been attained with little drop of the MCP gain. The bare MCP quantum efficiencies are somewhat lower than those expected, however. Flat field images are characterized by an absence of MCP fixed pattern noise.

  16. Modeling Tissue Growth Within Nonwoven Scaffolds Pores

    Science.gov (United States)

    Church, Jeffrey S.; Alexander, David L.J.; Russell, Stephen J.; Ingham, Eileen; Ramshaw, John A.M.; Werkmeister, Jerome A.

    2011-01-01

    In this study we present a novel approach for predicting tissue growth within the pores of fibrous tissue engineering scaffolds. Thin nonwoven polyethylene terephthalate scaffolds were prepared to characterize tissue growth within scaffold pores, by mouse NR6 fibroblast cells. On the basis of measurements of tissue lengths at fiber crossovers and along fiber segments, mathematical models were determined during the proliferative phase of cell growth. Tissue growth at fiber crossovers decreased with increasing interfiber angle, with exponential relationships determined on day 6 and 10 of culture. Analysis of tissue growth along fiber segments determined two growth profiles, one with enhanced growth as a result of increased tissue lengths near the fiber crossover, achieved in the latter stage of culture. Derived mathematical models were used in the development of a software program to visualize predicted tissue growth within a pore. This study identifies key pore parameters that contribute toward tissue growth, and suggests models for predicting this growth, based on fibroblast cells. Such models may be used in aiding scaffold design, for optimum pore infiltration during the tissue engineering process. PMID:20687775

  17. Hydrogeological modeling for improving groundwater monitoring network and strategies

    Science.gov (United States)

    Thakur, Jay Krishna

    2016-09-01

    The research aimed to investigate a new approach for spatiotemporal groundwater monitoring network optimization using hydrogeological modeling to improve monitoring strategies. Unmonitored concentrations were incorporated at different potential monitoring locations into the groundwater monitoring optimization method. The proposed method was applied in the contaminated megasite, Bitterfeld/Wolfen, Germany. Based on an existing 3-D geological model, 3-D groundwater flow was obtained from flow velocity simulation using initial and boundary conditions. The 3-D groundwater transport model was used to simulate transport of α-HCH with an initial ideal concentration of 100 mg/L injected at various hydrogeological layers in the model. Particle tracking for contaminant and groundwater flow velocity realizations were made. The spatial optimization result suggested that 30 out of 462 wells in the Quaternary aquifer (6.49 %) and 14 out of 357 wells in the Tertiary aquifer (3.92 %) were redundant. With a gradual increase in the width of the particle track path line, from 0 to 100 m, the number of redundant wells remarkably increased, in both aquifers. The results of temporal optimization showed different sampling frequencies for monitoring wells. The groundwater and contaminant flow direction resulting from particle tracks obtained from hydrogeological modeling was verified by the variogram modeling through α-HCH data from 2003 to 2009. Groundwater monitoring strategies can be substantially improved by removing the existing spatio-temporal redundancy as well as incorporating unmonitored network along with sampling at recommended interval of time. However, the use of this model-based method is only recommended in the areas along with site-specific experts' knowledge.

  18. DS796 California Groundwater Units

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — The California Groundwater Units dataset classifies and delineates the State into one of three groundwater based polygon units: (1) those areas defined as alluvial...

  19. TIG Dressing Effects on Weld Pores and Pore Cracking of Titanium Weldments

    Directory of Open Access Journals (Sweden)

    Hui-Jun Yi

    2016-10-01

    Full Text Available Weld pores redistribution, the effectiveness of using tungsten inert gas (TIG dressing to remove weld pores, and changes in the mechanical properties due to the TIG dressing of Ti-3Al-2.5V weldments were studied. Moreover, weld cracks due to pores were investigated. The results show that weld pores less than 300 μm in size are redistributed or removed via remelting due to TIG dressing. Regardless of the temperature condition, TIG dressing welding showed ductility, and there was a loss of 7% tensile strength of the weldments. Additionally, it was considered that porosity redistribution by TIG dressing was due to fluid flow during the remelting of the weld pool. Weld cracks in titanium weldment create branch cracks around pores that propagate via the intragranular fracture, and oxygen is dispersed around the pores. It is suggested that the pore locations around the LBZ (local brittle zone and stress concentration due to the pores have significant effects on crack initiation and propagation.

  20. Chromatographic performance of large-pore versus small-pore columns in micellar liquid chromatography.

    Science.gov (United States)

    McCormick, Timothy J; Foley, Joe P; Lloyd, David K

    2003-02-25

    Micellar liquid chromatography (MLC) is useful in bioanalysis because proteinaceous biofluids can be directly injected onto the column. The technique has been limited in part because of the apparently weak eluting power of micellar mobile phases. It has recently been shown [Anal. Chem. 72 (2000) 294] that this may be overcome by the use of large pore size stationary phases. In this work, large-pore (1000 A) C(18) stationary phases were evaluated relative to conventional small-pore (100 A) C(18) stationary phases for the direct sample injection of drugs in plasma. Furthermore, the difference between the large and small pore phases in gradient elution separations of mixtures of widely varying hydrophobicities was investigated. Large-pore stationary phases were found to be very effective for eluting moderately to highly hydrophobic compounds such as ibuprofen, crotamiton, propranolol, and dodecanophenone, which were highly retained on the small-pore stationary phases typically used in MLC. The advantages of direct introduction of biological samples (drugs in plasma) and rapid column re-equilibration after gradient elution in MLC were maintained with large-pore phases. Finally, recoveries, precision, linearity, and detection limits for the determination of quinidine and DPC 961 in spiked bovine plasma were somewhat better using MLC with wide pore phases.

  1. Modeling of N2 adsorption in MCM-41 materials: hexagonal pores versus cylindrical pores.

    Science.gov (United States)

    Ustinov, Eugene A

    2009-07-07

    Low-temperature nitrogen adsorption in hexagonal pores and equivalent cylindrical pores is analyzed using nonlocal density functional theory extended to amorphous solids (NLDFT-AS). It is found that, despite significant difference of the density distribution over the cross-section of the pore, the capillary condensation/evaporation pressure is not considerably affected by the pore shape being slightly lower in the case of hexagonal geometry. However, the condensation/evaporation step in the hexagonal pore is slightly larger than that in the equivalent cylindrical pore because in the latter case the pore wall surface area and, hence, the amount adsorbed at pressures below the evaporation pressure are underestimated by 5%. We show that a dimensionless parameter defined as the ratio of the condensation/evaporation step and the upper value of the amount adsorbed at the condensation/evaporation pressure can be used as an additional criterion of the correct choice of the gas-solid molecular parameters along with the dependence of condensation/evaporation pressure on the pore diameter. Application of the criteria to experimental data on nitrogen adsorption on a series of MCM-41 silica at 77 K corroborates some evidence that the capillary condensation occurs at equilibrium conditions.

  2. Changes in groundwater chemistry before two consecutive earthquakes in Iceland

    KAUST Repository

    Skelton, Alasdair

    2014-09-21

    Groundwater chemistry has been observed to change before earthquakes and is proposed as a precursor signal. Such changes include variations in radon count rates1, 2, concentrations of dissolved elements3, 4, 5 and stable isotope ratios4, 5. Changes in seismic wave velocities6, water levels in boreholes7, micro-seismicity8 and shear wave splitting9 are also thought to precede earthquakes. Precursor activity has been attributed to expansion of rock volume7, 10, 11. However, most studies of precursory phenomena lack sufficient data to rule out other explanations unrelated to earthquakes12. For example, reproducibility of a precursor signal has seldom been shown and few precursors have been evaluated statistically. Here we analyse the stable isotope ratios and dissolved element concentrations of groundwater taken from a borehole in northern Iceland between 2008 and 2013. We find that the chemistry of the groundwater changed four to six months before two greater than magnitude 5 earthquakes that occurred in October 2012 and April 2013. Statistical analyses indicate that the changes in groundwater chemistry were associated with the earthquakes. We suggest that the changes were caused by crustal dilation associated with stress build-up before each earthquake, which caused different groundwater components to mix. Although the changes we detect are specific for the site in Iceland, we infer that similar processes may be active elsewhere, and that groundwater chemistry is a promising target for future studies on the predictability of earthquakes.

  3. Tehran Groundwater Chemical Pollution

    Directory of Open Access Journals (Sweden)

    M- Shariatpanahi

    1990-06-01

    Full Text Available Seventy eight wells water sample of Tehran plain were examined to determine r its groundwaters chemical pollution. Tehran s groundwaters are slightly acidic and their total dissolved solids are high and are in the hard water category."nThe nitrate concentration of wells water of west region is less than per¬missible level of W.H.O. standard, whereas, the nitrate concentration of some of the other regions wells exceed W.H.O. standard which is indication of pollution"nwith municipal wastewaters. The concentration of toxic elements Cr, Cd, As, Hg and"ni Pb of some of the west, east and south regions wells of Tehran is more than per¬missible level of W.H.O. standard, whereas, the concentration of Cu, Zn,Mn and detergents is below W.H.O. standard."n1"nIn general, the amount of dissolved materials of Tehran s groundwaters and also"ni the potential of their contamination with nitrate is increased as Tehran s ground-"nwaters move further to the south, and even though, Tehran s groundwaters contamination with toxic elements is limited to the industrial west district, industrial-residential east and south districts, but»with regard to the disposal methods of"nt municipal and industrial wastewaters, if Tehran s groundwaters pollution continues,"nlocal contamination of groundwaters is likely to spread. So that finally their quality changes in such a way that this water source may become unfit for most domestic, industrial and agricultural uses. This survey shows the necessity of collection and treatment of Tehran s wastewaters and Prevention of the disposal of untreated wastewaters into the environment.

  4. The thermal impact of subsurface building structures on urban groundwater resources - A paradigmatic example.

    Science.gov (United States)

    Epting, Jannis; Scheidler, Stefan; Affolter, Annette; Borer, Paul; Mueller, Matthias H; Egli, Lukas; García-Gil, Alejandro; Huggenberger, Peter

    2017-10-15

    Shallow subsurface thermal regimes in urban areas are increasingly impacted by anthropogenic activities, which include infrastructure development like underground traffic lines as well as industrial and residential subsurface buildings. In combination with the progressive use of shallow geothermal energy systems, this results in the so-called subsurface urban heat island effect. This article emphasizes the importance of considering the thermal impact of subsurface structures, which commonly is underestimated due to missing information and of reliable subsurface temperature data. Based on synthetic heat-transport models different settings of the urban environment were investigated, including: (1) hydraulic gradients and conductivities, which result in different groundwater flow velocities; (2) aquifer properties like groundwater thickness to aquitard and depth to water table; and (3) constructional features, such as building depths and thermal properties of building structures. Our results demonstrate that with rising groundwater flow velocities, the heat-load from building structures increase, whereas down-gradient groundwater temperatures decrease. Thermal impacts on subsurface resources therefore have to be related to the permeability of aquifers and hydraulic boundary conditions. In regard to the urban settings of Basel, Switzerland, flow velocities of around 1 md(-1) delineate a marker where either down-gradient temperature deviations or heat-loads into the subsurface are more relevant. Furthermore, no direct thermal influence on groundwater resources should be expected for aquifers with groundwater thicknesses larger 10m and when the distance of the building structure to the groundwater table is higher than around 10m. We demonstrate that measuring temperature changes down-gradient of subsurface structures is insufficient overall to assess thermal impacts, particularly in urban areas. Moreover, in areas which are densely urbanized, and where groundwater flow

  5. Pore to Core Scale Simulation of the Mass Transfer with Mineral Reaction in Porous Media

    Directory of Open Access Journals (Sweden)

    Bekri S.

    2015-04-01

    Full Text Available Pore Network Model (PNM is used to simulate mass transfer with mineral reaction in a single phase flow through porous medium which is here a sandstone sample from the reservoir formation of the Pakoslaw gas field. The void space of the porous medium is represented by an idealized geometry of pore-bodies joined by pore-throats. Parameters defining the pore-bodies and the pore-throats distribution are determined by an optimization process aiming to match the experimental Mercury Intrusion Capillary Pressure (MICP curve and petrophysical properties of the rock such as intrinsic permeability and formation factor. The generated network is used first to simulate the multiphase flow by solving Kirchhoff’s laws. The capillary pressure and relative permeability curves are derived. Then, reactive transport is addressed under asymptotic regime where the solute concentration undergoes an exponential evolution with time. The porosity/permeability relationship and the three phenomenological coefficients of transport, namely the solute velocity, the dispersion and the mean reaction rate are determined as functions of Peclet and Peclet-Damköhler dimensionless numbers. Finally, the role of the dimensionless numbers on the reactive flow properties is highlighted.

  6. A Pore-Centric Model for Combined Shrinkage and Gas Porosity in Alloy Solidification

    Science.gov (United States)

    Khalajzadeh, Vahid; Carlson, Kent D.; Backman, Daniel G.; Beckermann, Christoph

    2017-04-01

    A unified model has been developed for combined gas- and shrinkage-induced pore formation during solidification of metal alloys. The model is based on a pore-centric approach, in which the temporal evolution of the pore radius is calculated as a function of cooling rate, thermal gradient, gas diffusion, and shrinkage. It accounts for the effect of porosity formation on the liquid velocity within the mushy zone. Simulations for an aluminum alloy show that the porosity transitions smoothly from shrinkage-induced to gas-induced as the Niyama value is increased. A Blake (cavitation) instability is observed to occur when the porosity is both gas- and shrinkage-driven. A revised dimensionless Niyama curve for pure shrinkage is presented. The experimentally observed gas porosity trend that the pore volume decreases with increasing cooling rate is well predicted. The pore-centric formulation allows the present model to be solved locally, at any point in a casting, during a regular casting simulation.

  7. Moving Magnetic Features around a Pore

    CERN Document Server

    Kaithakkal, A J; Solanki, S K; Lagg, A; Barthol, P; Gandorfer, A; Gizon, L; Hirzberger, J; vanNoort, M; Rodríguez, J Blanco; Iniesta, J C Del Toro; Suárez, D Orozco; Schmidt, W; Pillet, V Martínez; Knölker, M

    2016-01-01

    Spectropolarimetric observations from Sunrise II/IMaX obtained in June 2013 are used for a statistical analysis to determine the physical properties of moving magnetic features (MMFs) observed near a pore. MMFs of the same and opposite polarity with respect to the pore are found to stream from its border at an average speed of 1.3 km s$^{-1}$ and 1.2 km s$^{-1}$ respectively, with mainly same-polarity MMFs found further away from the pore. MMFs of both polarities are found to harbor rather weak, inclined magnetic fields. Opposite-polarity MMFs are blue-shifted, while same-polarity MMFs do not show any preference for up- or downflows. Most of the MMFs are found to be of sub-arcsecond size and carry a mean flux of $\\sim$ 1.2$\\times 10^{17}$ Mx.

  8. Optical detection of pores in adipocyte membrane

    Science.gov (United States)

    Yanina, I. Yu.; Doubrovski, V. A.; Tuchin, V. V.

    2013-08-01

    Structures that can be interpreted as cytoplasm droplets leaking through the membrane are experimentally detected on the membranes of adipocytes using optical digital microscopy. The effect of an aqueous alcohol solution of brilliant green on the amount and sizes of structures is studied. It is demonstrated that the optical irradiation of the adipocytes that are sensitized with the aid of the brilliant green leads to an increase in the amount of structures (pores) after the irradiation. The experimental results confirm the existence of an earlier-proposed effect of photochemical action on the sensitized cells of adipose tissue that involves additional formation of pores in the membrane of the sensitized cell under selective optical irradiation. The proposed method for the detection of micropores in the membrane of adipose tissue based on the detection of the cytoplasm droplets leaking from the cell can be considered as a method for the optical detection of nanosized pores.

  9. In situ groundwater bioremediation

    Energy Technology Data Exchange (ETDEWEB)

    Hazen, Terry C.

    2009-02-01

    In situ groundwater bioremediation of hydrocarbons has been used for more than 40 years. Most strategies involve biostimulation; however, recently bioaugmentation have been used for dehalorespiration. Aquifer and contaminant profiles are critical to determining the feasibility and strategy for in situ groundwater bioremediation. Hydraulic conductivity and redox conditions, including concentrations of terminal electron acceptors are critical to determine the feasibility and strategy for potential bioremediation applications. Conceptual models followed by characterization and subsequent numerical models are critical for efficient and cost effective bioremediation. Critical research needs in this area include better modeling and integration of remediation strategies with natural attenuation.

  10. Groundwater recharge in the tropics: a pan-African analysis of observations

    Science.gov (United States)

    Taylor, R. G.

    2015-12-01

    Groundwater is a vital source of freshwater in sub-Saharan Africa where rainfall and river discharge are unreliable and per-capita reservoir storage is among the lowest in the world. Groundwater is widely considered a distributed, low-cost and climate-resilient option to meet rapidly growing freshwater demand and alleviate endemic poverty by expanding access to safe water and improving food security through irrigation. Recent research indicates that groundwater storage in Africa is about 100 times greater than annual river discharge yet major uncertainties remain in the magnitude and nature of replenishment through recharge as well as the impacts of land-use and climate change. Here, we present newly compiled, multi-decadal observations of groundwater levels from 5 countries (Benin, Burkina Faso, Niger, Tanzania, Uganda) and paired measurements of stable isotope ratios of O and H in precipitation and groundwater at 11 locations. These data reveal both a distinct bias in groundwater recharge to intensive rainfall and rapid recharge pathways (e.g. focused, macropore flow) that are inconsistent with conventional recharge models assuming pore-matrix flow defined by the Darcy-Richards equation. Further the records highlight the substantial influence of land-use change (e.g. conversion of natural, perennial cover to croplands) on groundwater recharge. The compiled observations also provide, for the first time, a pan-African baseline to evaluate the performance of large-scale hydrological models and Land-Surface Models incorporating groundwater in this region. Our results suggest that the intensification of precipitation brought about by global warming favours groundwater replenishment in sub-Saharan Africa. As such, groundwater may prove to be a climate-resilient source of freshwater in the tropics, enabling adaptive strategies such as groundwater-fed irrigation and sustaining domestic and industrial water supplies.

  11. Groundwater: A Community Action Guide.

    Science.gov (United States)

    Boyd, Susan, Ed.; And Others

    Designed to be a guide for community action, this booklet examines issues and trends related to groundwater contamination. Basic concepts about groundwater and information about problems affecting it are covered under the categories of (1) what is groundwater? (2) availability and depletion; (3) quality and contamination; (4) public health…

  12. Groundwater: A Community Action Guide.

    Science.gov (United States)

    Boyd, Susan, Ed.; And Others

    Designed to be a guide for community action, this booklet examines issues and trends related to groundwater contamination. Basic concepts about groundwater and information about problems affecting it are covered under the categories of (1) what is groundwater? (2) availability and depletion; (3) quality and contamination; (4) public health…

  13. Limitations of fibre optic distributed temperature sensing for quantifying surface water groundwater interactions

    Directory of Open Access Journals (Sweden)

    H. Roshan

    2014-07-01

    Full Text Available Studies of surface water–groundwater interactions using fiber optic distributed temperature sensing (FO-DTS has increased in recent years. However, only a few studies to date have explored the limitations of FO-DTS in detecting groundwater discharge to streams. A FO_DTS system was therefore tested in a flume under controlled laboratory conditions for its ability to accurately measure the discharge of hot or cold groundwater into a simulated surface water flow. In the experiment the surface water (SW and groundwater (GW velocities, expressed as ratios (vgw/vsw, were varied from 0.21% to 61.7%; temperature difference between SW-GW were varied from 2 to 10 °C; the direction of temperature gradient were varied with both cold and-hot water injection; and two different bed materials were used to investigate their effects on FO_DTS's detection limit of groundwater discharge. The ability of the FO_DTS system to detect the discharge of groundwater of a different temperature in the laboratory environment was found to be mainly dependent upon the surface and groundwater flow velocities and their temperature difference. A correlation was proposed to estimate the groundwater discharge from temperature. The correlation is valid when the ratio of the apparent temperature response to the source temperature difference is above 0.02.

  14. Superluminal Recession Velocities

    CERN Document Server

    Davis, T M; Davis, Tamara M.; Lineweaver, Charles H.

    2000-01-01

    Hubble's Law, v=HD (recession velocity is proportional to distance), is a theoretical result derived from the Friedmann-Robertson-Walker metric. v=HD applies at least as far as the particle horizon and in principle for all distances. Thus, galaxies with distances greater than D=c/H are receding from us with velocities greater than the speed of light and superluminal recession is a fundamental part of the general relativistic description of the expanding universe. This apparent contradiction of special relativity (SR) is often mistakenly remedied by converting redshift to velocity using SR. Here we show that galaxies with recession velocities faster than the speed of light are observable and that in all viable cosmological models, galaxies above a redshift of three are receding superluminally.

  15. Pore Pressure Measurements Inside Rubble Mound Breakwaters

    DEFF Research Database (Denmark)

    Helgason, Einar; Burcharth, H. F.; Grüne, Joachim

    2004-01-01

    The present paper presents pore pressure measurements from large scale model tests performed at the Large Wave Channel, Hannover, Germany and small scale model test performed at the Hydraulic & Coastal Engineering Laboratory, Aalborg University, Denmark. Information on pore pressure attenuation......, and compared to a damping model presented by Burcharth et al. (1999). Reasonable agreement is found when considering the difference in the grading and uniformity of the model core materials. Comparison between results obtained from small and large scale model tests showed no clear evidence of scale effects....

  16. Porous media fluid transport and pore structure

    CERN Document Server

    Dullien, F A L

    1992-01-01

    This book examines the relationship between transport properties and pore structure of porous material. Models of pore structure are presented with a discussion of how such models can be used to predict the transport properties of porous media. Portions of the book are devoted to interpretations of experimental results in this area and directions for future research. Practical applications are given where applicable, and are expected to be useful for a large number of different fields, including reservoir engineering, geology, hydrogeology, soil science, chemical process engineering, biomedica

  17. Active Pore Volume in Danish Peat Soils

    DEFF Research Database (Denmark)

    Forsmann, Ditte M.; Kjærgaard, Charlotte

    2012-01-01

    Phosphorus release within the soil matrix caused by the changed redox conditions due to re-establishment of a riparian wetland can be critical for the aquatic environment. However, phosphorous released in the soil will not always result in an immediate contribution to this loss to the aquatic...... is not actively transported out of the system, but is only transported via diffusion, which is a very slow process. Thus it is interesting to investigate the size of the active pore volume in peat soils. The hypothesis of this study is that the active pores volume of a peat soil can be expressed using bulk...

  18. Conservation agriculture effects on soil pore characteristics

    DEFF Research Database (Denmark)

    Munkholm, Lars Juhl; Abdollahi, Lotfollah

    of quantitative knowledge to support this statement. This study examines the long-term effects of crop rotations, residue management and tillage on soil pore characteristics of two sandy loam soils in Denmark. Results are reported from a split plot field experiment rotation as main plot factor and tillage...... air permeability and pore continuity index. Generally, residue input, especially when combined with direct drilling at the Foulum site, decreased bulk density and the volume of blocked air porosity, and increased air-filled porosity, volumetric water content, air permeability and gas diffusivity. Our...

  19. Extreme Velocity Wind Sensor

    Science.gov (United States)

    Perotti, Jose; Voska, Ned (Technical Monitor)

    2002-01-01

    This presentation provides an overview of the development of new hurricane wind sensor (Extreme Velocity Wind Sensor) for the Kennedy Space Center (KSC) which is designed to withstand winds of up to three hundred miles an hour. The proposed Extreme Velocity Wind Sensor contains no moveable components that would be exposed to extreme wind conditions. Topics covered include: need for new hurricane wind sensor, conceptual design, software applications, computational fluid dynamic simulations of design concept, preliminary performance tests, and project status.

  20. Acceleration of groundwater remediation by deep sweeps and vortex ejections induced by rapidly pulsed pumping

    Science.gov (United States)

    Kahler, David M.; Kabala, Zbigniew J.

    2016-05-01

    One key limiting factor to groundwater remediation is contaminant sequestered in pores whose contents do not mix well with the bulk flow. Mixing between well-connected (pores whose volume is flushed as water flows through the aquifer) and poorly connected pores (pores whose volume does not exchange readily when water flows through the aquifer) is of primary concern. Under steady flow, contaminants are effectively trapped in the poorly connected pores and are transferred only by molecular diffusion. This slow mixing process between pore types is a bottleneck to remediation. We present a novel rapidly pulsed pumping method that increases the mixing between these pore types. We do it in the context of pump-and-treat remediation because it is the most common remediation practice. In rapidly pulsed pumping, the increase in flow causes a deep sweep, which pushes the flow into poorly connected pores and sweeps out sequestered contaminants. The decrease in flow causes a vortex ejection, which causes the vortex within the poorly connected pore to emerge with contaminant. These actions are modeled with computational fluid mechanics to elucidate the individual mechanisms and determine how they function and interact. Cleanup of single and multiple poorly connected pore systems were simulated and show the acceleration possible. This technique can decrease the time and cost needed to remediate contaminated aquifers, which in the United States has been estimated to exceed $1 trillion. Since our rapidly pulsed pumping method enhances mixing between well-connected and poorly connected pores, it can be applied to other remediation schemes such as in situ methods.

  1. Selection of Dispersivity in Groundwater Risk Assessment

    Institute of Scientific and Technical Information of China (English)

    武晓峰; 唐杰

    2004-01-01

    The Domenico model is used in combination with ASTM E 1739 in a Tier 2 risk assessment of chlorinated organic solvents contaminated groundwater sites to predict potential contaminant concentration in groundwater down-gradient from the point of exposure (POE). A knowledge of the dispersivity parameters is necessary for carrying out this calculation. A constant longitudinal dispersivity of 10 m is often used in analytical and numerical calculation. However, because of the scale effect of dispersion, two other main approaches are currently often used. From the viewpoint of conservative principle in risk assessment, it is necessary to determine which dispersivity data will give a higher predicted concentration, corresponding to a more conservative risk calculation. Generally, it is considered that a smaller dispersivity leads to a higher predicted concentration. This assumption is correct when dispersion is the only natural attenuation factor. However, degradation of commonly encountered chlorinated organic solvents in environment under natural condition has been widely reported. Calculations given in this paper of several representative cases show that a general consideration of the influence of dispersivity on concentration prediction is not always correct when a degradation term is included in the calculation. To give a conservative risk calculation, the scale effect of dispersion is considered. Calculations also show that the dispersivity parameters need to be determined by considering the POE distance from the source, the groundwater velocity, and the degradation rate of the contaminant.

  2. Groundwater contamination from an inactive uranium mill tailings pile: 1. Application of a chemical mixing model

    Science.gov (United States)

    White, A. F.; Delany, J. M.; Narasimhan, T. N.; Smith, A.

    1984-11-01

    Low-pH process waters contained in a number of inactive and abandoned uranium mill tailings in the United States represent potential sources of radionuclide and trace metal contamination of groundwater. Detailed investigations at a typical site at Riverton, Wyoming, indicate that chemical transport occurs from initial dewatering of the tailings, downward infiltration due to precipitation, and groundwater intrusion into the base of the tailings pile. Except for elevated uranium and molybdenum concentrations, current radionuclide and trace metal transport is limited by the near-neutral pH conditions of the groundwater. Significant reactions include the dissolution of calcite, production of CO2, and precipitation of gypsum and the hydroxides of iron and aluminum. A geochemical mixing model employing the PHREEQE computer code is used to estimate current rates of the groundwater contamination by tailings water. A maximum mixing of 1.7% of pore water is a factor of 2 less than steady state estimates based on hydraulic parameters.

  3. Groundwater level deterioration issues and suggested solution for the water curtain cultivation area in South Korea

    Science.gov (United States)

    Kim, Yongcheol; Lee, Bongju; Ha, Kucheol; Yoon, Yunyeol; Moon, Sangho; Cho, Suyoung; Kim, Seongyun

    2013-04-01

    Protected water curtain cultivation system is an energy saving technique for winter season by splashing groundwater on the inner roof of the green house. But the issue is that the method results in groundwater level deterioration because it disposes the used groundwater to nearby stream. Reuse of the groundwater for water curtain cultivation is important Groundwater level, steam level, and groundwater usage rate are investigated at the five green house concentrated areas such as Cheongwon, Namyangju, Choongju, Namwon, Jinju. Groundwater usage rate is estimated using a ultrasonic flowmeter for a specific well and using the combination of pressure sensor and propeller type velocity counting equipment at a water disposal channel from November to April which is water curtain cultivating season. Groundwater usage rate ranges from 46.9m3/d to 108.0m3/d for a 10a greenhouse. Groundwater level change is strongly influenced by seasonal variation of rainfall and concentrated pumping activities in winter but the level is lower than stream level all year long resulting in all year around losing stream at Cheongwon, Namyangju, Jinju. At Nanwon, the stream is converted from losing one in winter to gaining one in summer. Groundwater level deterioration at concentrated water curtain cultivation area is found to be severe for some area where circulating water curtain cultivation system is need to be applied for groundwater restoration and sustainable cultivation in winter. Circulating water curtain cultivation system can restore the groundwater level by recharging the used groundwater through injection well and then pumping out from pumping well.

  4. VelProbePE: An automated spreadsheet program for interpreting point velocity probe breakthrough curves

    Science.gov (United States)

    Schillig, P. C.

    2012-02-01

    Groundwater velocity is an important parameter for determining the fate and transport of contaminants. Recently developed point velocity probes (PVPs) were designed to provide centimeter-scale measurements of the direction and magnitude of groundwater velocity based on the injection and electrical detection of a small, saline tracer. The code reported here for velocity probe parameter estimation (VelProbePE) was designed using Visual Basic for Applications (VBA) in Microsoft Excel for processing and interpreting tracer breakthrough curves specifically for PVP applications. VelProbePE contains multiple, autoinitializing user forms that guide the user through the data-processing steps. The program allows for the rapid processing and editing of up to 16 detector signals in a single workbook. VelProbePE uses simplex optimization to calculate the intermediate parameters required for the estimation of velocity magnitude and direction.

  5. Numerical Simulation of Changes in Groundwater-Level Induced by Earthquakes

    Science.gov (United States)

    Liu, Ching-Yi; Chia, Yeeping; Zheng, Ding-Qian

    2016-04-01

    Changes in groundwater level induced by earthquakes have been recorded worldwide. Sustained groundwater-level changes during earthquakes, primarily induced by the co-seismic strain due to fault displacement, are often observed in the confined aquifer. In the unconfined aquifer, sustained co-seismic changes can hardly be observed due to the rapid recovery of pore pressure change. In this study, field observation of co-seismic groundwater-level changes are showed. Also, the finite element software ABAQUS is used to simulate two-dimensional time-dependent pore pressure change in the aquifer due to fault displacement during earthquakes. Different physical properties are used to represent different types of aquifer. We adopted the 3-step method to simulate how earthquakes affect pore pressure in the 3 models, unconfined aquifer, confined aquifer and over-pressured confined layers. Results from the simulation gives us more details of how co-seismic and post-seismic pore pressure temporal changes are processed in different aquifers.

  6. Smart Fluids in Hydrology: Use of Non-Newtonian Fluids for Pore Structure Characterization

    Science.gov (United States)

    Abou Najm, Majdi; Atallah, Nabil; Selker, John; Roques, Clément; Stewart, Ryan; Rupp, David; Saad, George; El-Fadel, Mutasem

    2016-04-01

    Classic porous media characterization relies on typical infiltration experiments with Newtonian fluids (i.e., water) to estimate hydraulic conductivity. However, such experiments are generally not able to discern important characteristics such as pore size distribution or pore structure. We show that introducing non-Newtonian fluids provides additional unique flow signatures that can be used for improved pore structure characterization. We present a new method that transforms results of N infiltration experiments using water and N-1 non-Newtonian solutions into a system of equations that yields N representative radii (Ri) and their corresponding percent contribution to flow (wi). Those radii and weights are optimized in terms of flow and porosity to represent the functional hydraulic behavior of real porous media. The method also allows for estimating the soil retention curve using only saturated experiments. Experimental and numerical validation revealed the ability of the proposed method to represent the water retention and functional infiltration behavior of real soils. The experimental results showed the ability of such fluids to outsmart Newtonian fluids and infer pore size distribution and unsaturated behavior using simple saturated experiments. Specifically, we demonstrate using synthetic porous media composed of different combinations of sizes and numbers of capillary tubes that the use of different non-Newtonian fluids enables the prediction of the pore structure. The results advance the knowledge towards conceptualizing the complexity of porous media and can potentially impact applications in fields like irrigation efficiencies, vadose zone hydrology, soil-root-plant continuum, carbon sequestration into geologic formations, soil remediation, petroleum reservoir engineering, oil exploration and groundwater modeling.

  7. Chalk porosity and sonic velocity versus burial depth

    DEFF Research Database (Denmark)

    Fabricius, Ida Lykke; Gommesen, Lars; Krogsbøll, Anette Susanne

    2008-01-01

    that porosity and sonic velocity follow the most consistent depth trends when fluid pressure and pore-volume compressibility are considered. Quartz content up to 10% has no marked effect, but more than 5% clay causes lower porosity and velocity. The mineralogical effect differs between P-wave and shear velocity...... for fluid pressure because the cementing ions originate from stylolites, which are mechanically similar to fractures. We find that cementation occurs over a relatively short depth interval.......Seventy chalk samples from four formations in the overpressured Danish central North Sea have been analyzed to investigate how correlations of porosity and sonic velocity with burial depth are affected by varying mineralogy, fluid pressure, and early introduction of petroleum. The results show...

  8. PATHS groundwater hydrologic model

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, R.W.; Schur, J.A.

    1980-04-01

    A preliminary evaluation capability for two-dimensional groundwater pollution problems was developed as part of the Transport Modeling Task for the Waste Isolation Safety Assessment Program (WISAP). Our approach was to use the data limitations as a guide in setting the level of modeling detail. PATHS Groundwater Hydrologic Model is the first level (simplest) idealized hybrid analytical/numerical model for two-dimensional, saturated groundwater flow and single component transport; homogeneous geology. This document consists of the description of the PATHS groundwater hydrologic model. The preliminary evaluation capability prepared for WISAP, including the enhancements that were made because of the authors' experience using the earlier capability is described. Appendixes A through D supplement the report as follows: complete derivations of the background equations are provided in Appendix A. Appendix B is a comprehensive set of instructions for users of PATHS. It is written for users who have little or no experience with computers. Appendix C is for the programmer. It contains information on how input parameters are passed between programs in the system. It also contains program listings and test case listing. Appendix D is a definition of terms.

  9. GROUNDWATER RECHARGE AND CHEMICAL ...

    Science.gov (United States)

    The existing knowledge base regarding the presence and significance of chemicals foreign to the subsurface environment is large and growing -the papers in this volume serving as recent testament. But complex questions with few answers surround the unknowns regarding the potential for environmental or human health effects from trace levels of xenobiotics in groundwater, especially groundwater augmented with treated wastewater. Public acceptance for direct or indirect groundwater recharge using treated municipal wastewater ( especially sewage) spans the spectrum from unquestioned embrace to outright rejection. In this article, I detour around the issues most commonly discussed for groundwater recharge and instead focus on some of the less-recognized issues- those that emanate from the mysteries created at the many literal and virtual interfaces involved with the subsurface world. My major objective is to catalyze discussion that advances our understanding of the barriers to public acceptance of wastewater reuse -with its ultimate culmination in direct reuse for drinking. I pose what could be a key question as to whether much of the public's frustration or ambivalence in its decision making process for accepting or rejecting water reuse (for various purposes including personal use) emanates from fundamental inaccuracies, misrepresentation, or oversimplification of what water 'is' and how it functions in the environment -just what exactly is the 'water cyc

  10. Regulating groundwater use

    NARCIS (Netherlands)

    Hoogesteger van Dijk, Jaime; Wester, Flip

    2017-01-01

    Around the world it has proven very difficult to develop policies and interventions that ensure socio-environmentally sustainable groundwater use and exploitation. In the state of Guanajuato, Central Mexico, both the national government and the decentralized state government have pursued to regulate

  11. Seismic Anisotropy and Velocity-Porosity Relationships in the Seafloor.

    Science.gov (United States)

    Berge, Patricia A.

    In this dissertation, I investigate the structure and composition of marine sediments and the upper oceanic crust using seismic data and rock physics theories. Common marine sediments such as silty clays exhibit anisotropy because they are made up of thin sub-parallel lamellae of contrasting mineralogical composition and differing elastic properties. In 1986, Rondout Associates, Inc. and Woods Hole Oceanographic Institution recorded direct shear waves in shallow marine sediments in 21-m-deep water by using a newly developed ocean-bottom shear source and a multicomponent on-bottom receiver. A nearby drill hole showed that the sediments are interbedded silty clays, clays, and sands. I used an anisotropic reflectivity program written by Geo-Pacific Corporation to produce synthetic seismograms to estimate the five independent elastic stiffnesses necessary for describing transverse isotropy, the form of anisotropy found in these sediments. The synthetics fit the vertical and two horizontal components for two intersecting profiles, 150 and 200 m long. The data require low shear velocities (theories to modeling the oceanic crust. Seismic velocities are controlled by the porosity, typically 20-30% for the top of layer 2. Most rock physics theories that relate seismic velocities to porosities are invalid for such high porosities. I combined elements of the self-consistent and noninteraction approaches to extend some rock physics theories for porosities up to at least 30-35%. Since the oceanic crust contains pores and cracks of many shapes, an appropriate theory must model round pores as well as flat cracks. I present examples of how layer 2A of the oceanic crust might be represented using an extended version of the Kuster-Toksoz theory. Alteration processes modify the pore structure of the oceanic crust. Currently, alteration is measured primarily from ocean drilling results. By developing a realistic relationship between seismic velocities and the age-dependent pore

  12. Groundwater ages from the freshwater zone of the Edwards aquifer, Uvalde County, Texas—Insights into groundwater flow and recharge

    Science.gov (United States)

    Hunt, Andrew G.; Landis, Gary P.; Faith, Jason R.

    2016-02-23

    Tritium–helium-3 groundwater ages of the Edwards aquifer in south-central Texas were determined as part of a long-term study of groundwater flow and recharge in the Edwards and Trinity aquifers. These ages help to define groundwater residence times and to provide constraints for calibration of groundwater flow models. A suite of 17 samples from public and private supply wells within Uvalde County were collected for active and noble gases, and for tritium–helium-3 analyses from the confined and unconfined parts of the Edwards aquifer. Samples were collected from monitoring wells at discrete depths in open boreholes as well as from integrated pumped well-head samples. The data indicate a fairly uniform groundwater flow system within an otherwise structurally complex geologic environment comprised of regionally and locally faulted rock units, igneous intrusions, and karst features within carbonate rocks. Apparent ages show moderate, downward average, linear velocities in the Uvalde area with increasing age to the east along a regional groundwater flow path. Though the apparent age data show a fairly consistent distribution across the study area, many apparent ages indicate mixing of both modern (less than 60 years) and premodern (greater than 60 years) waters. This mixing is most evident along the “bad water” line, an arbitrary delineation of 1,000 milligrams per liter dissolved solids that separates the freshwater zone of the Edwards aquifer from the downdip saline water zone. Mixing of modern and premodern waters also is indicated within the unconfined zone of the aquifer by high excess helium concentrations in young waters. Excess helium anomalies in the unconfined aquifer are consistent with possible subsurface discharge of premodern groundwater from the underlying Trinity aquifer into the younger groundwater of the Edwards aquifer.

  13. Fluctuations of a fluid inside a pore

    NARCIS (Netherlands)

    Zvelindovsky, AV; Zatovsky, AV

    The correlation theory of the thermal hydrodynamic fluctuations of compressible viscous fluids within a spherical pore has been developed. The fluctuation motions ape described by the linearized Navier-Stokes and heat transfer equations, containing spontaneous viscous stresses and heat fluxes. The

  14. Induction of nano pore in Agrobacterial hemoglobin

    Directory of Open Access Journals (Sweden)

    Mojtaba Tousheh

    2014-01-01

    Full Text Available Introduction: A variety of oxygen-transport and -binding proteins exist in organisms including bacteria, protozoans, and fungi all have hemoglobin-like proteins. In addition to dealing with transport and sensing of oxygen, they may also deal with NO2, CO2, sulfide compounds, and even O2 scavenging in environments. Also they detoxified chlorinated materials like P450 enzymes and peroxidases and use as a detector of nitrate and hydrogen peroxide. Pore-forming bacterial globins are interested for filtration. Materials and methods: Although there are data for bacterial toxin as a filter, here we used Agrobacterial hem to induce nano pore in the heme structure using point mutation. Results: Investigations showed that three amino acids leucine 76, alanine 83 and histidine 80 are important for pore formation in Agrobacterium hemoglobin. A point mutation on leucine 76 to glycine, histidine 80 to asparagine and alanine 83 to lysine step by step led to create the nano pore 0.7- 0.8 nm in the globin. Discussion and conclusion: These mutations in bacterial hemoglobin increase the stability when mutation is with it’s at pH7. This mutation decreases the aliphatic index however increase the stability index.

  15. Particle diffusion in complex nanoscale pore networks

    DEFF Research Database (Denmark)

    Müter, Dirk; Sørensen, Henning Osholm; Bock, H.;

    2015-01-01

    We studied the diffusion of particles in the highly irregular pore networks of chalk, a very fine-grained rock, by combining three-dimensional X-ray imaging and dissipative particle dynamics (DPD) simulations. X-ray imaging data were collected at 25 nm voxel dimension for two chalk samples with v...

  16. Maximal pore size in UF membranes

    NARCIS (Netherlands)

    Arkhangelsky, E.; Duek, A.; Gitis, V.

    2012-01-01

    The ultrafiltration membrane rejection capability is most often characterized by molecular weight cutoff (MWCO). The value is found by rejection of organic solutes and the evaluation of particle retention requires a conversion of either MWCO to pore size or particle diameter to molecular weight. The

  17. Silicon Pore Optics development for ATHENA

    DEFF Research Database (Denmark)

    Collon, Maximilien J.; Vacanti, Giuseppe; Guenther, Ramses

    2015-01-01

    ) to meet the science requirements of large effective area (1-2 m(2) at a few keV) at a focal length of 12 m. To meet the high angular resolution (5 arc seconds) requirement the X-ray lens will also need to be very accurate. Silicon Pore Optics (SPO) technology has been invented to enable building...

  18. Observations of sausage modes in magnetic pores

    CERN Document Server

    Morton, R J; Jess, D B; Mathioudakis, M

    2010-01-01

    We present here evidence for the observation of the magneto-hydrodynamic (MHD) sausage modes in magnetic pores in the solar photosphere. Further evidence for the omnipresent nature of acoustic global modes is also found. The empirical decomposition method of wave analysis is used to identify the oscillations detected through a 4170 {\\AA} 'blue continuum' filter observed with the Rapid Oscillations in the Solar Atmosphere (ROSA) instrument. Out of phase, periodic behavior in pore size and intensity is used as an indicator of the presence of magneto-acoustic sausage oscillations. Multiple signatures of the magneto-acoustic sausage mode are found in a number of pores. The periods range from as short as 30 s up to 450 s. A number of the magneto-acoustic sausage mode oscillations found have periods of 3 and 5 minutes, similar to the acoustic global modes of the solar interior. It is proposed that these global oscillations could be the driver of the sausage type magneto-acoustic MHD wave modes in pores.

  19. Fluctuations of a fluid inside a pore

    NARCIS (Netherlands)

    Zvelindovsky, AV; Zatovsky, AV

    1997-01-01

    The correlation theory of the thermal hydrodynamic fluctuations of compressible viscous fluids within a spherical pore has been developed. The fluctuation motions ape described by the linearized Navier-Stokes and heat transfer equations, containing spontaneous viscous stresses and heat fluxes. The e

  20. Fluctuations of a fluid inside a pore

    NARCIS (Netherlands)

    Zvelindovsky, AV; Zatovsky, AV

    1997-01-01

    The correlation theory of the thermal hydrodynamic fluctuations of compressible viscous fluids within a spherical pore has been developed. The fluctuation motions ape described by the linearized Navier-Stokes and heat transfer equations, containing spontaneous viscous stresses and heat fluxes. The e

  1. Pore-Forming Toxins Trigger the Purge.

    Science.gov (United States)

    Bonfini, Alessandro; Buchon, Nicolas

    2016-12-14

    The intestinal epithelium responds to pathogens by coordinating microbial elimination with tissue repair, both required to survive an infection. In this issue of Cell Host & Microbe, Lee et al. (2016) discover a rapid and evolutionarily conserved response to pore-forming toxins in the gut, involving cytoplasm ejection and enterocyte regrowth.

  2. Silicon Pore Optics development for ATHENA

    DEFF Research Database (Denmark)

    Collon, Maximilien J.; Vacanti, Giuseppe; Guenther, Ramses;

    2015-01-01

    ) to meet the science requirements of large effective area (1-2 m(2) at a few keV) at a focal length of 12 m. To meet the high angular resolution (5 arc seconds) requirement the X-ray lens will also need to be very accurate. Silicon Pore Optics (SPO) technology has been invented to enable building...

  3. Facial skin pores: a multiethnic study

    Science.gov (United States)

    Flament, Frederic; Francois, Ghislain; Qiu, Huixia; Ye, Chengda; Hanaya, Tomoo; Batisse, Dominique; Cointereau-Chardon, Suzy; Seixas, Mirela Donato Gianeti; Dal Belo, Susi Elaine; Bazin, Roland

    2015-01-01

    Skin pores (SP), as they are called by laymen, are common and benign features mostly located on the face (nose, cheeks, etc) that generate many aesthetic concerns or complaints. Despite the prevalence of skin pores, related literature is scarce. With the aim of describing the prevalence of skin pores and anatomic features among ethnic groups, a dermatoscopic instrument, using polarized lighting, coupled to a digital camera recorded the major features of skin pores (size, density, coverage) on the cheeks of 2,585 women in different countries and continents. A detection threshold of 250 μm, correlated to clinical scorings by experts, was input into a specific software to further allow for automatic counting of the SP density (N/cm2) and determination of their respective sizes in mm2. Integrating both criteria also led to establishing the relative part of the skin surface (as a percentage) that is actually covered by SP on cheeks. The results showed that the values of respective sizes, densities, and skin coverage: 1) were recorded in all studied subjects; 2) varied greatly with ethnicity; 3) plateaued with age in most cases; and 4) globally refected self-assessment by subjects, in particular those who self-declare having “enlarged pores” like Brazilian women. Inversely, Chinese women were clearly distinct from other ethnicities in having very low density and sizes. Analyzing the present results suggests that facial skin pore’s morphology as perceived by human eye less result from functional criteria of associated appendages such as sebaceous glands. To what extent skin pores may be viewed as additional criteria of a photo-altered skin is an issue to be further addressed. PMID:25733918

  4. Carbon-14 as a tracer of groundwater discharge to streams

    Science.gov (United States)

    Bourke, Sarah; Harrington, Glenn; Cook, Peter; Post, Vincent; Dogramaci, Shawan

    2014-05-01

    The provenance of groundwater discharge to a stream can be determined by measuring the response of multiple groundwater age tracers within the stream across the discharge zone. The sampling interval required to detect groundwater discharge is limited by the rate of equilibration with the atmosphere downstream of the discharge zone, which is determined by the gas transfer velocity. Carbon-14 (14C) equilibration is driven by CO2 exchange, which is a small component of the dissolved inorganic carbon in most stream systems, and therefore the rate of equilibration is slower than for other gaseous age tracers. In this paper we use a step-wise approach to develop and demonstrate the use of 14C as a tracer in streams receiving groundwater discharge. Excess carbon dioxide (CO2) in the emerging groundwater degasses until equilibrium with atmospheric CO2 is reached; increasing pH and enriching the residual 14C by fractionation. In addition, the 14C gradient between groundwater and the atmosphere drives a slower process of isotopic equilibration. We have measured the rates of this chemical and isotopic equilibration experimentally by exposing 250 L of old groundwater to the atmosphere in an evaporation pan. Chemical equilibrium was achieved within 2 days, during which the 14C increased from 6 to 16 pMC. The influence of fractionation during the initial CO2 degassing on isotopic equilibrium rates was negligible. Isotopic equilibrium took over 2 months, with 14C in the evaporation pan increasing to 108 pMC over 71 days. This increase in 14C was simulated using a mass balance model with an effective 14C gas transfer velocity of 0.013 m d-1. Field testing of the method was conducted at two sites. Firstly, we measured the evolution of 14C in dewatering discharge as it flows along an ephemeral creek channel in the Pilbara, Western Australia. Measured 14C increased from 11 to 31 pMC along the 10km reach, which corresponds to a travel time of about 2 days. The measured increase was

  5. Simulation for the development of the continuous groundwater flow measurement technology

    Science.gov (United States)

    Kobayashi, Kaoru; Kumagai, Koki; Fujima, Ritsuko; Chikahisa, Hiroshi

    The flow of groundwater varies with time due to rainfall, atmospheric pressure change, tidal change, melting of snow during seasonal change, underground construction works etc. Therefore, to increase the precision of assessing in-situ groundwater flow characteristics, it is important to measure continuously the direction and velocity of the flow, in addition to obtaining accurate data for the afore mentioned environmental changes. The first part of this paper describes the development of a new device for measuring the direction and velocity of groundwater flow. The device was composed of a unique floating sensor with a hinge end at the bottom, which enabled continuous measurement of groundwater flow based on image data processing technique. In the second part, discussion is focused on clarifying the optimum cross-section shape and the behavior of the float sensor in saltwater and freshwater using numerical analysis.

  6. Pore Structure of Cement Pastes Blended with Volcanic Rock

    Institute of Scientific and Technical Information of China (English)

    YU Lehua; ZHOU Shuangxi; LI Liling

    2016-01-01

    The pore parameters of cement pastes blended with volcanic rock at the curing age of 1, 28 and 90 d were de-termined by a mercury intrusion porosimetry. The pore structure of the pastes was characterized through the analysis of porosity, average pore diameter, the most probable pore aperture, pore size distribution, as well as total pore volume. For the improvement of mechanical property and durability of cement-based material, the correlation of the formed pore structure with hydration time and replacement level of volcanic rock for cement was revealed. The results indicate that volcanic rock can diminish porosity and reduce pore size in cement paste when curing time prolongs, which is particu-larly prominent with replacement level of less than 20% in late period. The more harmful pores (i.e., capillary pore) are gradually transformed into harmless pore (i.e., gel pores or micropore), even fully filled and disappeared when hydration products increase. The pore structure of the cement paste is thus refined. The beneficial effect of volcanic rock on the pore structure of cement paste could enhance the mechanical property and durability of cement-based material.

  7. Quantitative velocity modulation spectroscopy

    Science.gov (United States)

    Hodges, James N.; McCall, Benjamin J.

    2016-05-01

    Velocity Modulation Spectroscopy (VMS) is arguably the most important development in the 20th century for spectroscopic study of molecular ions. For decades, interpretation of VMS lineshapes has presented challenges due to the intrinsic covariance of fit parameters including velocity modulation amplitude, linewidth, and intensity. This limitation has stifled the growth of this technique into the quantitative realm. In this work, we show that subtle changes in the lineshape can be used to help address this complexity. This allows for determination of the linewidth, intensity relative to other transitions, velocity modulation amplitude, and electric field strength in the positive column of a glow discharge. Additionally, we explain the large homogeneous component of the linewidth that has been previously described. Using this component, the ion mobility can be determined.

  8. The Prescribed Velocity Method

    DEFF Research Database (Denmark)

    Nielsen, Peter Vilhelm

    The- velocity level in a room ventilated by jet ventilation is strongly influenced by the supply conditions. The momentum flow in the supply jets controls the air movement in the room and, therefore, it is very important that the inlet conditions and the numerical method can generate a satisfactory...... description of this momentum flow. The Prescribed Velocity Method is a practical method for the description of an Air Terminal Device which will save grid points close to the opening and ensure the right level of the momentum flow....

  9. Cirrus Crystal Terminal Velocities.

    Science.gov (United States)

    Heymsfield, Andrew J.; Iaquinta, Jean

    2000-04-01

    Cirrus crystal terminal velocities are of primary importance in determining the rate of transport of condensate from upper- to middle-tropospheric levels and profoundly influence the earth's radiation balance through their effect on the rate of buildup or decay of cirrus clouds. In this study, laboratory and field-based cirrus crystal drag coefficient data, as well as analytical descriptions of cirrus crystal shapes, are used to derive more physically based expressions for the velocities of cirrus crystals than have been available in the past.Polycrystals-often bullet rosettes-are shown to be the dominant crystal types in synoptically generated cirrus, with columns present in varying but relatively large percentages, depending on the cloud. The two critical parameters needed to calculate terminal velocity are the drag coefficient and the ratio of mass to cross-sectional area normal to their fall direction. Using measurements and calculations, it is shown that drag coefficients from theory and laboratory studies are applicable to crystals of the types found in cirrus. The ratio of the mass to area, which is shown to be relatively independent of the number of bullets in the rosette, is derived from an analytic model that represents bullet rosettes containing one to eight bullets in 19 primary geometric configurations. The ratio is also derived for columns. Using this information, a general set of equations is developed to calculate the terminal velocities and masses in terms of the aspect ratio (width divided by length), ice density, and rosette maximum dimension. Simple expressions for terminal velocity and mass as a function of bullet rosette maximum dimension are developed by incorporating new information on bullet aspect ratios.The general terminal velocity and mass relations are then applied to a case from the First International Satellite Cloud Climatology Project (ISCCP) Research Experiment (FIRE) 2, when size spectra from a balloon-borne ice crystal

  10. Radionuclide inventories for the F- and H-area seepage basin groundwater plumes

    Energy Technology Data Exchange (ETDEWEB)

    Hiergesell, Robert A [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Kubilius, Walter P. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2016-05-01

    Within the General Separations Areas (GSA) at the Savannah River Site (SRS), significant inventories of radionuclides exist within two major groundwater contamination plumes that are emanating from the F- and H-Area seepage basins. These radionuclides are moving slowly with groundwater migration, albeit more slowly due to interaction with the soil and aquifer matrix material. The purpose of this investigation is to quantify the activity of radionuclides associated with the pore water component of the groundwater plumes. The scope of this effort included evaluation of all groundwater sample analyses obtained from the wells that have been established by the Environmental Compliance & Area Completion Projects (EC&ACP) Department at SRS to monitor groundwater contamination emanating from the F- and H-Area Seepage Basins. Using this data, generalized groundwater plume maps for the radionuclides that occur in elevated concentrations (Am-241, Cm-243/244, Cs-137, I-129, Ni-63, Ra-226/228, Sr-90, Tc-99, U-233/234, U-235 and U-238) were generated and utilized to calculate both the volume of contaminated groundwater and the representative concentration of each radionuclide associated with different plume concentration zones.

  11. Holocene estuarine sediments as a source of arsenic in Pleistocene groundwater in suburbs of Hanoi, Vietnam

    Science.gov (United States)

    Kuroda, Keisuke; Hayashi, Takeshi; Funabiki, Ayako; Do, An Thuan; Canh, Vu Duc; Nga, Tran Thi Viet; Takizawa, Satoshi

    2017-06-01

    Groundwater pollution by arsenic is a major health threat in suburban areas of Hanoi, Vietnam. The present study evaluates the effect of the sedimentary environments of the Pleistocene and Holocene deposits, and the recharge systems, on the groundwater arsenic pollution in Hanoi suburbs distant from the Red River. At two study sites (Linh Dam and Tai Mo communes), undisturbed soil cores identified a Pleistocene confined aquifer (PCA) and Holocene unconfined aquifer (HUA) as major aquifers, and Holocene estuarine and deltaic sediments as an aquitard layer between the two aquifers. The Holocene estuarine sediments (approximately 25-40 m depth, 9.6-4.8 cal ka BP) contained notably high concentrations of arsenic and organic matter, both likely to have been accumulated by mangroves during the Holocene sea-level highstand. The pore waters in these particular sediments exhibited elevated levels of arsenic and dissolved organic carbon. Arsenic in groundwater was higher in the PCA (25-94 μg/L) than in the HUA (5.2-42 μg/L), in both the monitoring wells and neighboring household tubewells. Elevated arsenic concentration in the PCA groundwater was likely due to vertical infiltration through the arsenic-rich and organic-matter-rich overlying Holocene estuarine sediments, caused by massive groundwater abstraction from the PCA. Countermeasures to prevent arsenic pollution of the PCA groundwater may include seeking alternative water resources, reducing water consumption, and/or appropriate choice of aquifers for groundwater supply.

  12. Holocene estuarine sediments as a source of arsenic in Pleistocene groundwater in suburbs of Hanoi, Vietnam

    Science.gov (United States)

    Kuroda, Keisuke; Hayashi, Takeshi; Funabiki, Ayako; Do, An Thuan; Canh, Vu Duc; Nga, Tran Thi Viet; Takizawa, Satoshi

    2017-01-01

    Groundwater pollution by arsenic is a major health threat in suburban areas of Hanoi, Vietnam. The present study evaluates the effect of the sedimentary environments of the Pleistocene and Holocene deposits, and the recharge systems, on the groundwater arsenic pollution in Hanoi suburbs distant from the Red River. At two study sites (Linh Dam and Tai Mo communes), undisturbed soil cores identified a Pleistocene confined aquifer (PCA) and Holocene unconfined aquifer (HUA) as major aquifers, and Holocene estuarine and deltaic sediments as an aquitard layer between the two aquifers. The Holocene estuarine sediments (approximately 25-40 m depth, 9.6-4.8 cal ka uc(BP)) contained notably high concentrations of arsenic and organic matter, both likely to have been accumulated by mangroves during the Holocene sea-level highstand. The pore waters in these particular sediments exhibited elevated levels of arsenic and dissolved organic carbon. Arsenic in groundwater was higher in the PCA (25-94 μg/L) than in the HUA (5.2-42 μg/L), in both the monitoring wells and neighboring household tubewells. Elevated arsenic concentration in the PCA groundwater was likely due to vertical infiltration through the arsenic-rich and organic-matter-rich overlying Holocene estuarine sediments, caused by massive groundwater abstraction from the PCA. Countermeasures to prevent arsenic pollution of the PCA groundwater may include seeking alternative water resources, reducing water consumption, and/or appropriate choice of aquifers for groundwater supply.

  13. Study of pores produced in underwater wet welding

    Institute of Scientific and Technical Information of China (English)

    Shen Xiaoqin; Liu Shiming

    2006-01-01

    This paper deals with the effect of water depth in the range of 10 m to 80 m upon the formation of pores produced during underwater wet welding. The results show that it is easy for the inner pores to occur owing to the particularity of the molten metal solidification that the outer pores begin to appear when the water depth increases to about 60 m, that the porosity increases and pore grows up as the water depth increases, and that pores are all hydrogen-cont aining ones through the examination of the variation of number of pores with the residual hydrogen and oxygen content in the weld metal.

  14. Spectral Induced Polarization monitoring of the groundwater physico-chemical parameters daily variations for stream-groundwater interactions

    Science.gov (United States)

    Jougnot, Damien; Camerlynck, Christian; Robain, Henri; Tallec, Gaëlle; Ribolzi, Olivier; Gaillardet, Jérôme

    2017-04-01

    During the last decades, geophysical methods have been attracting an increasing interest in hydrology and environmental sciences given their sensitivity to parameters of interests and their non-intrusive nature. The Spectral Induced Polarization (SIP) is a low frequency electro-magnetic method that allows the characterization of the subsurface through its complex electrical conductivity. It reports the modulus of the conductivity and the phase between an injected current and a measured voltage over a rather large frequency range (from few millihertz to few tens of kilohertz). The real part of the conductivity is sensitive to lithological (porosity, specific surface area) and hydrological (water saturation, water salinity) parameters, while the imaginary part is linked to electrochemical polarizations, that have been shown to be largely influenced by the chemistry of the pore water. In the present contribution, we aim at better characterizing the exchanges between a stream and the surrounding groundwater using the SIP method and its sensitivity to pore water changes over time. Two sites from the OZCAR Research Infrastructure (French Critical Zone observatories) have been chosen for this study: the Houay Pano catchment (Laos) and the Orgeval catchment (France). These two sites have a good existing infrastructure and have been already studied extensively in terms of hydrology, geophysics, and hydrochemistry. They constitute perfect experimental sites to develop novel methodologies for the assessment of stream-groundwater exchanges. We propose to obtain a vertical description of the changes in complex electrical conductivity with depth based on SIP soundings undertaken with the multi-channel system SIP Fuchs III. We conducted a high-frequency monitoring close to a river stream (one vertical profiles every 30 min). In parallel, a high frequency monitoring of the physico-chemical parameters (temperature, conductivity, ionic concentrations) in the river stream has been

  15. Intermittent Filtration of Bacteria and Colloids at Pore and Column Scales

    Science.gov (United States)

    Auset, M.; Keller, A. A.; Brissaud, F.; Lazarova, V.

    2004-12-01

    Intermittent sand filters used for water and wastewater treatment can achieve high disinfection performance if properly designed and operated. Soil filtration can also play a significant role in pathogen removal. In order to help predict removal of pathogenic bacteria in sand filters and natural porous media, the effects of cyclic infiltration and draining events (transient unsaturated flow) on microorganism fate were investigated. We visualized bacterial transport in unsaturated porous media at the pore scale using micromodels. Column experiments provided quantitative measurements of the phenomena observed at the pore scale. Escherichia coli and a conservative tracer (NaI) were applied once in a pulse to a 1.5 m sand column. Outflow concentrations during subsequent tracer-free pulses were monitored for 4 days. The reproducibility of the breakthrough curve was established in five repeated experiments. We observed earlier breakthrough of bacteria compared to the dissolved tracer, as predicted from pore scale studies. Transport of bacteria and tracer was influenced by the temporal variations in pore water velocity and moisture content. Advancement of the wetting front remobilized bacteria either attached to the air-water interface (AWI) or entrapped in stagnant pore water between gas bubbles. Remobilization leads to successive concentration peaks of bacteria and tracer in the effluent. Overall microbial retention rate was high, 99.972 %. Observations at the pore-scale showed that bacteria retention was due to reversible bacteria entrapment in stagnant regions and sorption onto the AWI and essentially irreversible attachment onto solid-water interface (SWI). Bacterial detachment from the AWI was only observed during complete gas bubble dissolution or if bubble interface stress occurred during the dissolution process.

  16. Groundwater hydrology instructional system

    Science.gov (United States)

    Schmidt, Ronald G.

    Wright State University, Dayton, Ohio, is preparing for its third cycle of the Interactive Remote Instructional System (IRIS) in groundwater hydrology, beginning January 15, 1986. The first cycle finished with an impressive completion ratio for registered participants, and the second cycle has currently been underway since July. This comprehensive hydrogeology program was originally developed for the Soil Conservation Service (of the U.S. Department of Agriculture) to prepare their personnel for professional practice work. Since its evolution into IRIS, an 80% participant completion rate has been recorded for the first cycle, which is a significant departure from success rates traditionally recorded by correspondence courses. This excellent rate of success is the result of 2 years of refinement and demonstrates the progressive nature of the program. IRIS has met the needs of participants by developing a curriculum that reflects current trends in the groundwater industry and has provided a unique educational approach that ensures maximum interaction between the instructional staff and participants.

  17. Modeling Terminal Velocity

    Science.gov (United States)

    Brand, Neal; Quintanilla, John A.

    2013-01-01

    Using a simultaneously falling softball as a stopwatch, the terminal velocity of a whiffle ball can be obtained to surprisingly high accuracy with only common household equipment. This classroom activity engages students in an apparently daunting task that nevertheless is tractable, using a simple model and mathematical techniques at their…

  18. Contain contaminated groundwater

    Energy Technology Data Exchange (ETDEWEB)

    Mutch, R.D. Jr.; Caputi, J.R. [Eckenfelder, Inc., Mahwah, NJ (United States); Ash, R.E. IV [Eckenfelder Inc., Nashville, TN (United States)

    1997-05-01

    Despite recent progress in innovative treatment technologies, many problems with contaminated groundwater still require the use of barrier walls, typically in combination with extraction and treatment systems. New technologies for subsurface barrier walls, mostly based on geomembranes, advancements in self-hardening slurries and permeation grouts with materials such as colloidal silica gel and montan wax emulsions, are being developed at an unprecedented pace. The paper discusses deep soil mixing, jet grouting, slurry trenches, and permeation grouting.

  19. An Estimation of Groundwater Fuxes Induced by Topography Structure at Basin Scale

    Science.gov (United States)

    Caruso, A.; Boano, F.; Ridolfi, L.

    2016-12-01

    Water exchange between surface water bodies and aquifers influences biogeochemical processes, playing a crucial role for nutrient cycling and contaminant transport. In this picture, hyporheic exchange has been recognized as a key process for the biochemical and ecological conditions of the stream ecosystem. It has widely recognized that hyporheic exchange is strongly affected by the local morphology of the streambed and the flow conditions. The objective of this work is to investigate the role of basin topography complexity on river-aquifer interactions to analyze how gaining flow conditions affect the hyporheic fluxes and the spatial distribution of the flow paths which feed the river. By using a mathematical model, we determine the spatial structure of the ambient groundwater upwelling along the stream network and investigate the effect of large-scale groundwater flow on hyporheic flow velocity. The evaluation of the groundwater velocity field allows us to identify down- and upwelling areas and to assess the origin and the transit times of groundwater fluxes, which have important implications for water quality. Indeed, determining where groundwater is discharging into the river and where attenuation of groundwater pollutants at the groundwater-surface water interface occurs is very useful to cope with water quality problems. We consider a benchmark case study and show how the complex topographic conformation determines a substantial spatial variability of the aquifer-river exchange. The fragmentation of the hyporeic zone induced by groundwater discharge at the basin scale is evidenced. Our results highlight that the topographic structure of a basin contributes to determine the spatial complexity of the groundwater flow field together with the geomorphological river configuration. This complexity reflects on the depth and the intensity of the hyporheic exchange since the hyporheic zone is confined by groundwater upwelling.

  20. Mineral dissolution kinetics at the pore scale

    Energy Technology Data Exchange (ETDEWEB)

    Li, L.; Steefel, C.I.; Yang, L.

    2007-05-24

    Mineral dissolution rates in the field have been reported to be orders of magnitude slower than those measured in the laboratory, an unresolved discrepancy that severely limits our ability to develop scientifically defensible predictive or even interpretive models for many geochemical processes in the earth and environmental sciences. One suggestion links this discrepancy to the role of physical and chemical heterogeneities typically found in subsurface soils and aquifers in producing scale-dependent rates where concentration gradients develop. In this paper, we examine the possibility that scale-dependent mineral dissolution rates can develop even at the single pore and fracture scale, the smallest and most fundamental building block of porous media. To do so, we develop two models to analyze mineral dissolution kinetics at the single pore scale: (1) a Poiseuille Flow model that applies laboratory-measured dissolution kinetics at the pore or fracture wall and couples this to a rigorous treatment of both advective and diffusive transport, and (2) a Well-Mixed Reactor model that assumes complete mixing within the pore, while maintaining the same reactive surface area, average flow rate, and geometry as the Poiseuille Flow model. For a fracture, a 1D Plug Flow Reactor model is considered in addition to quantify the effects of longitudinal versus transverse mixing. The comparison of averaged dissolution rates under various conditions of flow, pore size, and fracture length from the three models is used as a means to quantify the extent to which concentration gradients at the single pore and fracture scale can develop and render rates scale-dependent. Three important minerals that dissolve at widely different rates, calcite, plagioclase, and iron hydroxide, are considered. The modeling indicates that rate discrepancies arise primarily where concentration gradients develop due to comparable rates of reaction and advective transport, and incomplete mixing via molecular

  1. Evolution of Pore Size Distribution and Mean Pore Size in Lotus-type Porous Magnesium Fabricated with Gasar Process

    Institute of Scientific and Technical Information of China (English)

    Yuan LIU; Yanxiang LI; Huawei ZHANG; Jiang WAN

    2006-01-01

    The effect of gas pressures on the mean pore size, the porosity and the pore size distribution of lotus-type porous magnesium fabricated with Gasar process were investigated. The theoretical analysis and the experimental results all indicate that there exists an optimal ratio of the partial pressures of hydrogen pH2 to argon pAr for producing lotus-type structures with narrower pore size distribution and smaller pore size. The effect of solidification mode on the pore size distribution and pore size was also discussed.

  2. Induction of nano pore in Agrobacterial hemoglobin

    OpenAIRE

    Mojtaba Tousheh; Giti Emtiazi; Peyman Derikvand

    2014-01-01

    Introduction: A variety of oxygen-transport and -binding proteins exist in organisms including bacteria, protozoans, and fungi all have hemoglobin-like proteins. In addition to dealing with transport and sensing of oxygen, they may also deal with NO2, CO2, sulfide compounds, and even O2 scavenging in environments. Also they detoxified chlorinated materials like P450 enzymes and peroxidases and use as a detector of nitrate and hydrogen peroxide. Pore-forming bacterial globins are interested fo...

  3. Biomimetic collagen scaffolds with anisotropic pore architecture.

    Science.gov (United States)

    Davidenko, N; Gibb, T; Schuster, C; Best, S M; Campbell, J J; Watson, C J; Cameron, R E

    2012-02-01

    Sponge-like matrices with a specific three-dimensional structural design resembling the actual extracellular matrix of a particular tissue show significant potential for the regeneration and repair of a broad range of damaged anisotropic tissues. The manipulation of the structure of collagen scaffolds using a freeze-drying technique was explored in this work as an intrinsically biocompatible way of tailoring the inner architecture of the scaffold. The research focused on the influence of temperature gradients, imposed during the phase of crystallisation of collagen suspensions, upon the degree of anisotropy in the microstructures of the scaffolds produced. Moulding technology was employed to achieve differences in heat transfer rates during the freezing processes. For this purpose various moulds with different configurations were developed with a view to producing uniaxial and multi-directional temperature gradients across the sample during this process. Scanning electron microscopy analysis of different cross-sections (longitudinal and horizontal) of scaffolds revealed that highly aligned matrices with axially directed pore architectures were obtained where single unidirectional temperature gradients were induced. Altering the freezing conditions by the introduction of multiple temperature gradients allowed collagen scaffolds to be produced with complex pore orientations, and anisotropy in pore size and alignment.

  4. Pore morphology study of silica aerogels

    Energy Technology Data Exchange (ETDEWEB)

    Hua, D.W.; Anderson, J.; Haereid, S.; Smith, D.M. [UNM/NSF Center for Micro-Engineered Ceramics, Albuquerque, NM (United States); Beaucage, G. [Sandia National Labs., Albuquerque, NM (United States)

    1994-12-31

    Silica aerogels have numerous properties which suggest applications such as ultra high efficiency thermal insulation. These properties relate directly to the aerogel`s pore size distribution. The micro and meso pore size ranges can be investigated by normal small angle x-ray scattering and possibly, nitrogen adsorption. However, the measurement of larger pores (> 250 {angstrom}) is more difficult. Due to their limited mechanical strength, mercury porosimetry and nitrogen condensation can disrupt the gel structure and electron microscopy provides only limited large scale structure information. The use of small angle light scattering techniques seems to have promise, the only hurdle is that aerogels exhibit significant multiple scattering. This can be avoided if one observes the gels in the wet stage since the structure of the aerogel should be very similar to the wet gel (as the result of supercritical drying). Thus, if one can match the refractive index, the morphology can be probed. The combination of certain alcoholic solvents fit this index matching criteria. Preliminary results for the gel network (micron range) and primary particle structure (manometer) are reported by using small angle light scattering and ultra-small angle x-ray scattering. The effects on structure over the length scale range of <1 nm to >5 {mu}m under different conditions (precursors, pH, etc.) are presented. The change in structure of an aerogel during isostatic compaction to 228 MPa (to simulate drying from wetting solvents) are also discussed.

  5. INVESTIGATIONS INTO BIOFOULING PHENOMENA IN FINE PORE AERATION DEVICES

    Science.gov (United States)

    Microbiologically-based procedures were used to describe biofouling phenomena on fine pore aeration devices and to determine whether biofilm characteristics could be related to diffuser process performance parameters. Fine pore diffusers were obtained from five municipal wastewa...

  6. GROUNDWATER PROTECTION MANAGEMENT PROGRAM DESCRIPTION.

    Energy Technology Data Exchange (ETDEWEB)

    PAQUETTE,D.E.; BENNETT,D.B.; DORSCH,W.R.; GOODE,G.A.; LEE,R.J.; KLAUS,K.; HOWE,R.F.; GEIGER,K.

    2002-05-31

    THE DEPARTMENT OF ENERGY ORDER 5400.1, GENERAL ENVIRONMENTAL PROTECTION PROGRAM, REQUIRES THE DEVELOPMENT AND IMPLEMENTATION OF A GROUNDWATER PROTECTION PROGRAM. THE BNL GROUNDWATER PROTECTION MANAGEMENT PROGRAM DESCRIPTION PROVIDES AN OVERVIEW OF HOW THE LABORATORY ENSURES THAT PLANS FOR GROUNDWATER PROTECTION, MONITORING, AND RESTORATION ARE FULLY DEFINED, INTEGRATED, AND MANAGED IN A COST EFFECTIVE MANNER THAT IS CONSISTENT WITH FEDERAL, STATE, AND LOCAL REGULATIONS.

  7. Groundwater types in Southeast Srem

    Directory of Open Access Journals (Sweden)

    Gregorić Enike

    2009-01-01

    Full Text Available The region of Southeast Srem is rich in ground waters, which is of great significance to agricultural production. The objective of this paper was to designate the zones of different groundwater types from the aspect of recharge, based on the analysis of groundwater regimes in the study area. A very complex groundwater regime in Southeast Srem, which depends on a great number of natural and some anthropogenic factors, makes it difficult to designate clearly the zones of the three main types of groundwater regime. Still, the boundaries of the zones of groundwater regime types were defined based on the results of correlation analysis of the basic factors affecting the groundwater regime. Zone I includes the climatic type of groundwater. Its fluctuation corresponds to the vertical factors of water balance (precipitation and evaporation and it is not affected by the river water level. This zone extends North and East of the line Putinci, Golubinci, Stara Pazova, Batajnica, Dobanovci, mainly in the area of the loess plateau. Within the zone, groundwater is at a relatively great depth. Only exceptionally, in the valleys, it appears almost on the surface. Zone II includes the climatic-hydrological groundwater type, which is the transition between the climatic type and the hydrological type. The fluctuation of groundwater regime is affected both by the effect of vertical balance factors, and by the effect of watercourses. Climatic-hydrological groundwater type covers the central and the lowest part of the study area and the South part of the middle terrace. Zone III is classified as the hydrological groundwater type and it covers the riparian areas along the Sava and the Danube. The aquifer is hydraulically connected with the river Sava.

  8. Minimum requirements for predictive pore-network modeling of solute transport in micromodels

    Science.gov (United States)

    Mehmani, Yashar; Tchelepi, Hamdi A.

    2017-10-01

    Pore-scale models are now an integral part of analyzing fluid dynamics in porous materials (e.g., rocks, soils, fuel cells). Pore network models (PNM) are particularly attractive due to their computational efficiency. However, quantitative predictions with PNM have not always been successful. We focus on single-phase transport of a passive tracer under advection-dominated regimes and compare PNM with high-fidelity direct numerical simulations (DNS) for a range of micromodel heterogeneities. We identify the minimum requirements for predictive PNM of transport. They are: (a) flow-based network extraction, i.e., discretizing the pore space based on the underlying velocity field, (b) a Lagrangian (particle tracking) simulation framework, and (c) accurate transfer of particles from one pore throat to the next. We develop novel network extraction and particle tracking PNM methods that meet these requirements. Moreover, we show that certain established PNM practices in the literature can result in first-order errors in modeling advection-dominated transport. They include: all Eulerian PNMs, networks extracted based on geometric metrics only, and flux-based nodal transfer probabilities. Preliminary results for a 3D sphere pack are also presented. The simulation inputs for this work are made public to serve as a benchmark for the research community.

  9. Wave propagation and group velocity

    CERN Document Server

    Brillouin, Léon

    1960-01-01

    Wave Propagation and Group Velocity contains papers on group velocity which were published during the First World War and are missing in many libraries. It introduces three different definitions of velocities: the group velocity of Lord Rayleigh, the signal velocity of Sommerfeld, and the velocity of energy transfer, which yields the rate of energy flow through a continuous wave and is strongly related to the characteristic impedance. These three velocities are identical for nonabsorbing media, but they differ considerably in an absorption band. Some examples are discussed in the last chapter

  10. Pore-Scale Investigation of Micron-Size Polyacrylamide Elastic Microspheres (MPEMs) Transport and Retention in Saturated Porous Media

    KAUST Repository

    Yao, Chuanjin

    2014-05-06

    Knowledge of micrometer-size polyacrylamide elastic microsphere (MPEM) transport and retention mechanisms in porous media is essential for the application of MPEMs as a smart sweep improvement and profile modification agent in improving oil recovery. A transparent micromodel packed with translucent quartz sand was constructed and used to investigate the pore-scale transport, surface deposition-release, and plugging deposition-remigration mechanisms of MPEMs in porous media. The results indicate that the combination of colloidal and hydrodynamic forces controls the deposition and release of MPEMs on pore-surfaces; the reduction of fluid salinity and the increase of Darcy velocity are beneficial to the MPEM release from pore-surfaces; the hydrodynamic forces also influence the remigration of MPEMs in pore-throats. MPEMs can plug pore-throats through the mechanisms of capture-plugging, superposition-plugging, and bridge-plugging, which produces resistance to water flow; the interception with MPEM particulate filters occurring in the interior of porous media can enhance the plugging effect of MPEMs; while the interception with MPEM particulate filters occurring at the surface of low-permeability layer can prevent the low-permeability layer from being damaged by MPEMs. MPEMs can remigrate in pore-throats depending on their elasticity through four steps of capture-plugging, elastic deformation, steady migration, and deformation recovery. © 2014 American Chemical Society.

  11. An Integrated Approach on Groundwater Flow and Heat/Solute Transport for Sustainable Groundwater Source Heat Pump (GWHP) System Operation

    Science.gov (United States)

    Park, D. K.; Bae, G. O.; Joun, W.; Park, B. H.; Park, J.; Park, I.; Lee, K. K.

    2015-12-01

    The GWHP system uses a stable temperature of groundwater for cooling and heating in buildings and thus has been known as one of the most energy-saving and cost-efficient renewable energy techniques. A GWHP facility was installed at an island located at the confluence of North Han and South Han rivers, Korea. Because of well-developed alluvium, the aquifer is suitable for application of this system, extracting and injecting a large amount of groundwater. However, the numerical experiments under various operational conditions showed that it could be vulnerable to thermal interference due to the highly permeable gravel layer, as a preferential path of thermal plume migration, and limited space for well installation. Thus, regional groundwater flow must be an important factor of consideration for the efficient operation under these conditions but was found to be not simple in this site. While the groundwater level in this site totally depends on the river stage control of Paldang dam, the direction and velocity of the regional groundwater flow, observed using the colloidal borescope, have been changed hour by hour with the combined flows of both the rivers. During the pumping and injection tests, the water discharges in Cheongpyeong dam affected their respective results. Moreover, the measured NO3-N concentrations might imply the effect of agricultural activities around the facility on the groundwater quality along the regional flow. It is obvious that the extraction and injection of groundwater during the facility operation will affect the fate of the agricultural contaminants. Particularly, the gravel layer must also be a main path for contaminant migration. The simulations for contaminant transport during the facility operation showed that the operation strategy for only thermal efficiency could be unsafe and unstable in respect of groundwater quality. All these results concluded that the integrated approach on groundwater flow and heat/solute transport is necessary

  12. New ultrasonic technique for the study of the pore shape of track-etched pores in polymer films

    Energy Technology Data Exchange (ETDEWEB)

    Gomez Alvarez-Arenas, T.E., E-mail: tgomez@ia.cetef.csic.e [Instituto de Acustica, CSIC, Serrano 144, 28006 Madrid (Spain); Apel, P.Yu.; Orelovitch, O.L. [Flerov Lab. of Nuclear Reactions, JINR, Dubna (Russian Federation); Munoz, M. [Institute of Applied Physics, CSIC, Serrano 144, Madrid (Spain)

    2009-10-15

    A new technique for the study of the pore shape of track-etched pores in polymer films is presented. This technique is based on the use of air-coupled ultrasounds and phase and magnitude spectral analysis. Transmission of ultrasounds through these membranes is made up of two contributions: propagation through the solid part and propagation along the pore channels. A time-domain procedure to separate these to contributions is presented. Sensitivity of ultrasounds propagation in the pore channels to variations of pore shape is studied. Membranes with similar properties (gas flow rate values) but slight differences in the pore shape are studied. The proposed technique reveals to be sensitive to such differences; unlike other techniques, it is capable to provide information in a separate way about pore aperture at the surface and pore diameter inside the membrane, in addition the technique is non-destructive.

  13. Radial Velocities with PARAS

    Science.gov (United States)

    Roy, Arpita; Mahadevan, S.; Chakraborty, A.; Pathan, F. M.; Anandarao, B. G.

    2010-01-01

    The Physical Research Laboratory Advanced Radial-velocity All-sky Search (PARAS) is an efficient fiber-fed cross-dispersed high-resolution echelle spectrograph that will see first light in early 2010. This instrument is being built at the Physical Research laboratory (PRL) and will be attached to the 1.2m telescope at Gurushikhar Observatory at Mt. Abu, India. PARAS has a single-shot wavelength coverage of 370nm to 850nm at a spectral resolution of R 70000 and will be housed in a vacuum chamber (at 1x10-2 mbar pressure) in a highly temperature controlled environment. This renders the spectrograph extremely suitable for exoplanet searches with high velocity precision using the simultaneous Thorium-Argon wavelength calibration method. We are in the process of developing an automated data analysis pipeline for echelle data reduction and precise radial velocity extraction based on the REDUCE package of Piskunov & Valenti (2002), which is especially careful in dealing with CCD defects, extraneous noise, and cosmic ray spikes. Here we discuss the current status of the PARAS project and details and tests of the data analysis procedure, as well as results from ongoing PARAS commissioning activities.

  14. The groundwater subsidy to vegetation: groundwater exchanges between landcover patches

    Science.gov (United States)

    Steven, L. I.; Gimenez, R.; Jobbagy, E. G.

    2015-12-01

    The Gran Chaco is a hot, dry plain, that spans over 60 million hectares across Bolivia, Paraguay, Brazil and Argentina. It supports high biodiversity in its dry forest and savannahs, but is rapidly being converted to agriculture in response to growing soy demand and technology including genetic modification and zero-till, that has made cultivation in drier landscapes more viable. Under natural conditions, the deep-rooted, native vegetation of the Chaco effectively captured all rainfall for evapotranspiration resulting in near zero groundwater recharge under the dry forest. Conversion to shallower rooted soy and corn, combined with the fallow period prior to the growing season, reduces evapotranspiration and allows some water to percolate through the root zone and recharge the groundwater system. When this groundwater recharge occurs, it creates groundwater mounding and a hydraulic gradient that drives flow to adjacent landcover patches where recharge does not occur. As the watertable rises, groundwater becomes available to the deep-rooted, dry forest vegetation. We develop a soil and groundwater flow model to simulate infiltration, percolation, evaporation, rootwater uptake, groundwater recharge and the lateral transfer of water between adjacent landcover patches to quantify this groundwater subsidy from converted agricultural lands to remnant patches of dry forest.

  15. A novel approach for direct estimation of fresh groundwater discharge to an estuary

    Science.gov (United States)

    Ganju, Neil K.

    2011-01-01

    Coastal groundwater discharge is an important source of freshwater and nutrients to coastal and estuarine systems. Directly quantifying the spatially integrated discharge of fresh groundwater over a coastline is difficult due to spatial variability and limited observational methods. In this study, I applied a novel approach to estimate net freshwater discharge from a groundwater-fed tidal creek over a spring-neap cycle, with high temporal resolution. Acoustic velocity instruments measured tidal water fluxes while other sensors measured vertical and lateral salinity to estimate cross-sectionally averaged salinity. These measurements were used in a time-dependent version of Knudsen's salt balance calculation to estimate the fresh groundwater contribution to the tidal creek. The time-series of fresh groundwater discharge shows the dependence of fresh groundwater discharge on tidal pumping, and the large difference between monthly mean discharge and instantaneous discharge over shorter timescales. The approach developed here can be implemented over timescales from days to years, in any size estuary with dominant groundwater inputs and well-defined cross-sections. The approach also directly links delivery of groundwater from the watershed with fluxes to the coastal environment. Copyright. Published in 2011 by the American Geophysical Union.

  16. Pore Water Arsenic Dynamics in Rice Paddies Under Projected Future Climates

    Science.gov (United States)

    Plaganas, M.; Wang, T.; Muehe, E. M.; Fendorf, S. E.

    2016-12-01

    Rice is one of the staple crops in the world, with 50% of the global population eating rice daily. Many rice-producing regions of the world are irrigated with groundwater contaminated with arsenic (As), and in particular South and Southeast Asia, where geogenic As is leached into the groundwater. Use of groundwater pervasively high in As leads to subsequent accumulation in paddy soils. Arsenic, a toxic metalloid, also decreases rice productivity and further jeopardizes food security. Hence, rice agriculture is concerned with its productivity in a climate change impacted future and the particular impacts of arsenic on yields. However, past studies do not address the prevalence of As in paddy soils or its fate in the rhizosphere and ultimate impact on the plant. The objective of our study was to determine changes in pore water As dynamics in the rhizosphere of rice plants grown on As-contaminated paddy soil under climate conditions projected for the end of the century. In order to address this objective, we designed greenhouse chambers with today's climate and projected climate conditions for the year 2100, specifically 5°C increase in temperature and doubled concentration of atmospheric CO2. We hypothesize that the effects of climate change with these conditions will increase the mobility of As in the rhizosphere, and thus, decrease rice growth in As-bearing paddies more than, so far, expected. We examined pore water geochemistry including pH and As concentrations, and correlate that to the height of the plants. Furthermore, the dynamics of other elements in the pore water such as carbon, iron, sulfur, manganese, and silica are further evaluated for their effects on rice growth. Arsenic will have an impact on rice production and conditions induced by future climatic conditions need to be considered for food security. Considering that climate change will decrease the global agricultural output, we should urgently consider adapting our agricultural practices to aid

  17. Effects of alongshore morphology on groundwater flow and solute transport in a nearshore aquifer

    Science.gov (United States)

    Zhang, Ying; Li, Ling; Erler, Dirk V.; Santos, Isaac; Lockington, David

    2016-02-01

    Variations of beach morphology in both the cross-shore and alongshore directions, associated with tidal creeks, are common at natural coasts, as observed at a field site on the east coast of Rarotonga, Cook Islands. Field investigations and three-dimensional (3-D) numerical simulations were conducted to study the nearshore groundwater flow and solute transport in such a system. The results show that the beach morphology, combined with tides, induced a significant alongshore flow and modified local pore water circulation and salt transport in the intertidal zone substantially. The bathymetry and hydraulic head of the creek enabled further and more rapid landward intrusion of seawater along the creek than in the aquifer, which created alongshore hydraulic gradient and solute concentration gradient to drive pore water flow and salt transport in the alongshore direction within the aquifer. The effects of the creek led to the formation of a saltwater plume in groundwater at an intermediate depth between fresher water zones on a cross-shore transect. The 3-D pore water flow in the nearshore zone was also complicated by the landward hydraulic head condition, resulting in freshwater drainage across the inland section of the creek while seawater infiltrating the seaward section. These results provided new insights into the complexity, intensity, and time scales of mixing among fresh groundwater, recirculating seawater and creek water in three dimensions. The 3-D characteristics of nearshore pore water flow and solute transport have important implications for studies of submarine groundwater discharge and associated chemical input to the coastal sea, and for evaluation of the beach habitat conditions.

  18. Anisotropic rock physics models for interpreting pore structures in carbonate reservoirs

    Institute of Scientific and Technical Information of China (English)

    Li Sheng-Jie; Shao Yu; Chen Xu-Qiang

    2016-01-01

    We developed an anisotropic effective theoretical model for modeling the elastic behavior of anisotropic carbonate reservoirs by combining the anisotropic self-consistent approximation and differential effective medium models. By analyzing the measured data from carbonate samples in the TL area, a carbonate pore-structure model for estimating the elastic parameters of carbonate rocks is proposed, which is a prerequisite in the analysis of carbonate reservoirs. A workfl ow for determining elastic properties of carbonate reservoirs is established in terms of the anisotropic effective theoretical model and the pore-structure model. We performed numerical experiments and compared the theoretical prediction and measured data. The result of the comparison suggests that the proposed anisotropic effective theoretical model can account for the relation between velocity and porosity in carbonate reservoirs. The model forms the basis for developing new tools for predicting and evaluating the properties of carbonate reservoirs.%♦Corresponding author: Li Sheng-Jie (Email: Richard@cup.edu.cn)

  19. Thick and hard anodized aluminum film with large pores for surface composites

    Institute of Scientific and Technical Information of China (English)

    WANG Hui; WANG Hao-wei

    2004-01-01

    Al-base surface self-lubricating composites need thick and hard alumina membranes with large pores to add lubricants easily. This kind of porous alumina layer was fabricated in additive-containing, phosphoric acid-based solution. The effects of additive containing organic carboxylic acid and Ce salt on the properties of the oxide film and mechanism were investigated in detail with SEM and EDAX analyses. The results show that the pore diameter is about 100 nm, the film thickness increases by 4 -5 times, and the Vickers hardness improves by about 50% through adding some amount of organic carboxylic acid and Ce salt. Such an improvement in properties is explained in terms of a lower film dissolving velocity and better film quality in compound solution.

  20. Soil Pore Network Visualisation and Quantification using ImageJ

    DEFF Research Database (Denmark)

    Garbout, Amin; Pajor, Radoslaw; Otten, Wilfred

    Computed Tomography data. We used ImageJ to analyze images of pore geometries in soils generated by X-ray micro Computed Tomography. Soil samples were scanned at 30 μm resolution, and we produced replicated samples with different pore geometries by packing different sized soil aggregates at pre......-defined densities. First, scanned grayscale data of soil volumes were thresholded to separate solid and pore phases. Then, pore networks were extracted with the Skeletonize3D plug-in (Ignacio Arganda-Carreras), exploiting an ITK algorithm: binary thinning was used for finding the centerlines (”skeleton”) of pores...

  1. Energy conversion device with support member having pore channels

    Science.gov (United States)

    Routkevitch, Dmitri [Longmont, CO; Wind, Rikard A [Johnstown, CO

    2014-01-07

    Energy devices such as energy conversion devices and energy storage devices and methods for the manufacture of such devices. The devices include a support member having an array of pore channels having a small average pore channel diameter and having a pore channel length. Material layers that may include energy conversion materials and conductive materials are coaxially disposed within the pore channels to form material rods having a relatively small cross-section and a relatively long length. By varying the structure of the materials in the pore channels, various energy devices can be fabricated, such as photovoltaic (PV) devices, radiation detectors, capacitors, batteries and the like.

  2. Solutions Remediate Contaminated Groundwater

    Science.gov (United States)

    2010-01-01

    During the Apollo Program, NASA workers used chlorinated solvents to clean rocket engine components at launch sites. These solvents, known as dense non-aqueous phase liquids, had contaminated launch facilities to the point of near-irreparability. Dr. Jacqueline Quinn and Dr. Kathleen Brooks Loftin of Kennedy Space Center partnered with researchers from the University of Central Florida's chemistry and engineering programs to develop technology capable of remediating the area without great cost or further environmental damage. They called the new invention Emulsified Zero-Valent Iron (EZVI). The groundwater remediation compound is cleaning up polluted areas all around the world and is, to date, NASA's most licensed technology.

  3. Tracer attenuation in groundwater

    Science.gov (United States)

    Cvetkovic, Vladimir

    2011-12-01

    The self-purifying capacity of aquifers strongly depends on the attenuation of waterborne contaminants, i.e., irreversible loss of contaminant mass on a given scale as a result of coupled transport and transformation processes. A general formulation of tracer attenuation in groundwater is presented. Basic sensitivities of attenuation to macrodispersion and retention are illustrated for a few typical retention mechanisms. Tracer recovery is suggested as an experimental proxy for attenuation. Unique experimental data of tracer recovery in crystalline rock compare favorably with the theoretical model that is based on diffusion-controlled retention. Non-Fickian hydrodynamic transport has potentially a large impact on field-scale attenuation of dissolved contaminants.

  4. Determination of an equivalent pore size from acoustic flow measurements

    Science.gov (United States)

    Clark, Linde; Liu, Jin; Garrett, Steven

    2005-09-01

    The hydraulic radius, rh, is defined as the ratio of a channel's cross-sectional area to its perimeter. This parameter is important for specification of the performance of a porous medium that can be used as a regenerator in a Stirling engine or refrigerator. It is easy to calculate rh for pores of regular geometry, but difficult in more complex media. Two techniques which use oscillating flow to determine this parameter will be presented and compared. One technique extracts rh by finding the low velocity limit of the standard expression for viscous pressure drop in the Poiseuille flow regime. The other involves a plot of the nondimensional viscous flow resistance, Δpvis/Δxωρu, versus the reciprocal of the viscous penetration depth, 1/δν, in the laminar flow regime. When rhflow behavior is frequency independent and the dynamics is characterized by rh only. When rh>δν, the flow resistance is frequency dependent and the dynamics is characterized by both rh and δν. It is possible to identify an effective hydraulic radius by equating it to the value of δν where that transition occurs. [Work supported by ONR.

  5. Measurement and modeling of energetic-material mass transfer to soil-pore water - Project CP-1227 final technical report.

    Energy Technology Data Exchange (ETDEWEB)

    Stein, Joshua S.; Sallaberry, Cedric M.; Webb, Stephen Walter; Phelan, James M.; Hadgu, Teklu

    2006-05-01

    Military test and training ranges operate with live-fire engagements to provide realism important to the maintenance of key tactical skills. Ordnance detonations during these operations typically produce minute residues of parent explosive chemical compounds. Occasional low-order detonations also disperse solid-phase energetic material onto the surface soil. These detonation remnants are implicated in chemical contamination impacts to groundwater on a limited set of ranges where environmental characterization projects have occurred. Key questions arise regarding how these residues and the environmental conditions (e.g., weather and geostratigraphy) contribute to groundwater pollution. This final report documents the results of experimental and simulation model development for evaluating mass transfer processes from solid-phase energetics to soil-pore water.

  6. Numerical Analysis of Velocity Dispersion in Multi-Phase Fluid-Saturated Porous Rocks

    Science.gov (United States)

    Chen, Xuehua; Zhong, Wenli; Gao, Gang; Zou, Wen; He, Zhenhua

    2017-03-01

    Seismic waves are subject to velocity dispersion when they propagate in fluid-saturated porous media. In this work, we explore the velocity dispersion behavior of P- and SV-waves in multi-phase fluid-saturated porous reservoirs while taking into account the effects of multi-phase pore fluids on the effective viscosities that control the wave-induced fluid flow. The effective viscosities associated with the hydrocarbon saturation of a synthetic sandstone reservoir saturated with different pore fluid mixtures are calculated using the Refutas model. We then analyze the frequency-dependent velocity, dispersion variation rate and characteristic frequency for different fluid saturation cases by employing Chapman's dynamic equivalent-medium theory. The results demonstrate that the hydrocarbon proportions and types in multi-phase mixed pore fluids significantly affect the magnitude and characteristic frequencies of velocity dispersion features for both the P- and S-waves. The dispersion anomalies of SV-waves are in general larger than those of the P-waves. This indicates that the velocity dispersion anomalies of SV-waves are equally sensitive to fluid saturation as the P-waves and should not be neglected. The velocities at lower frequencies (e.g., 10 and 100 Hz) within the seismic frequency range show a more remarkable decrease with increasing hydrocarbon proportion than those at higher frequency (1000 Hz). The numerical examples help to improve the understanding of the frequency-dependent AVO inversion from seismic reflection data.

  7. Numerical Analysis of Velocity Dispersion in Multi-Phase Fluid-Saturated Porous Rocks

    Science.gov (United States)

    Chen, Xuehua; Zhong, Wenli; Gao, Gang; Zou, Wen; He, Zhenhua

    2016-12-01

    Seismic waves are subject to velocity dispersion when they propagate in fluid-saturated porous media. In this work, we explore the velocity dispersion behavior of P- and SV-waves in multi-phase fluid-saturated porous reservoirs while taking into account the effects of multi-phase pore fluids on the effective viscosities that control the wave-induced fluid flow. The effective viscosities associated with the hydrocarbon saturation of a synthetic sandstone reservoir saturated with different pore fluid mixtures are calculated using the Refutas model. We then analyze the frequency-dependent velocity, dispersion variation rate and characteristic frequency for different fluid saturation cases by employing Chapman's dynamic equivalent-medium theory. The results demonstrate that the hydrocarbon proportions and types in multi-phase mixed pore fluids significantly affect the magnitude and characteristic frequencies of velocity dispersion features for both the P- and S-waves. The dispersion anomalies of SV-waves are in general larger than those of the P-waves. This indicates that the velocity dispersion anomalies of SV-waves are equally sensitive to fluid saturation as the P-waves and should not be neglected. The velocities at lower frequencies (e.g., 10 and 100 Hz) within the seismic frequency range show a more remarkable decrease with increasing hydrocarbon proportion than those at higher frequency (1000 Hz). The numerical examples help to improve the understanding of the frequency-dependent AVO inversion from seismic reflection data.

  8. Transverse velocity shifts in protostellar jets: rotation or velocity asymmetries?

    CERN Document Server

    De Colle, Fabio; Riera, Angels

    2016-01-01

    Observations of several protostellar jets show systematic differences in radial velocity transverse to the jet propagation direction, which have been interpreted as evidence of rotation in the jets. In this paper we discuss the origin of these velocity shifts, and show that they could be originated by rotation in the flow, or by side to side asymmetries in the shock velocity, which could be due to asymmetries in the jet ejection velocity/density or in the ambient medium. For typical poloidal jet velocities (~ 100-200 km/s), an asymmetry >~ 10% can produce velocity shifts comparable to those observed. We also present three dimensional numerical simulations of rotating, precessing and asymmetric jets, and show that, even though for a given jet there is a clear degeneracy between these effects, a statistical analysis of jets with different inclination angles can help to distinguish between the alternative origins of transverse velocity shifts. Our analysis indicate that side to side velocities asymmetries could ...

  9. Effect of Initial Hydraulic Conditions on Capillary Rise in a Porous Medium: Pore-Network Modeling

    KAUST Repository

    Joekar-Niasar, V.

    2012-01-01

    The dynamics of capillary rise in a porous medium have been mostly studied in initially dry systems. As initial saturation and initial hydraulic conditions in many natural and industrial porous media can be variable, it is important to investigate the influence of initial conditions on the dynamics of the process. In this study, using dynamic pore-network modeling, we simulated capillary rise in a porous medium for different initial saturations (and consequently initial capillary pressures). Furthermore, the effect of hydraulic connectivity of the wetting phase in corners on the height and velocity of the wetting front was studied. Our simulation results show that there is a trade-off between capillary forces and trapping due to snap-off, which leads to a nonlinear dependence of wetting front velocity on initial saturation at the pore scale. This analysis may provide a possible answer to the experimental observations in the literature showing a non-monotonic dependency between initial saturation and the macroscopic front velocity. © Soil Science Society of America.

  10. Silicon pore optics developments and status

    DEFF Research Database (Denmark)

    Bavdaz, Marcos; Wille, Eric; Wallace, Kotska;

    2012-01-01

    Silicon Pore Optics (SPO) is a lightweight high performance X-ray optics technology being developed in Europe, driven by applications in observatory class high energy astrophysics missions. An example of such application is the former ESA science mission candidate ATHENA (Advanced Telescope...... of the SPO technology. The technology development programme has succeeded in maturing the SPO further and achieving important milestones, in each of the main activity streams: environmental compatibility, industrial production and optical performance. In order to accurately characterise the increasing...... performance of this innovative optical technology, the associated X-ray test facilities and beam-lines have been refined and upgraded. © 2012 SPIE....

  11. Viral Subversion of the Nuclear Pore Complex

    Directory of Open Access Journals (Sweden)

    Valerie Le Sage

    2013-08-01

    Full Text Available The nuclear pore complex (NPC acts as a selective barrier between the nucleus and the cytoplasm and is responsible for mediating communication by regulating the transport of RNA and proteins. Numerous viral pathogens have evolved different mechanisms to hijack the NPC in order to regulate trafficking of viral proteins, genomes and even capsids into and out of the nucleus thus promoting virus replication. The present review examines the different strategies and the specific nucleoporins utilized during viral infections as a means of promoting their life cycle and inhibiting host viral defenses.

  12. Sustainable groundwater management in California

    Science.gov (United States)

    Phillips, Steven P.; Rogers, Laurel Lynn; Faunt, Claudia

    2015-12-01

    The U.S. Geological Survey (USGS) uses data collection, modeling tools, and scientific analysis to help water managers plan for, and assess, hydrologic issues that can cause “undesirable results” associated with groundwater use. This information helps managers understand trends and investigate and predict effects of different groundwater-management strategies.

  13. Promoting local management in groundwater

    Science.gov (United States)

    van Steenbergen, Frank

    2006-03-01

    There is a strong case for making greater effort to promote local groundwater management—in addition to other measures that regulate groundwater use. Though scattered, there are several examples—from India, Pakistan, Yemen and Egypt—where groundwater users effectively self-imposed restrictions on the use of groundwater. There are a number of recurrent themes in such spontaneously-developed examples of local regulation: the importance of not excluding potential users; the importance of simple, low transaction cost rules; the power of correct and accessible hydrogeological information; the possibility of making more use of demand and supply management strategies; and the important supportive role of local governments. The case is made, using examples, for actively promoting local groundwater management as an important element in balancing groundwater uses. Two programmes for promoting local groundwater management in South India are described—one focussing on participatory hydrological monitoring, and one focussing on micro-resource planning and training. In both cases the response was very positive and the conclusion is that promoting local groundwater regulation is not difficult, costly or sensitive and can reach the necessary scale quickly.

  14. Analysis of quantitative pore features based on mathematical morphology

    Institute of Scientific and Technical Information of China (English)

    QI Heng-nian; CHEN Feng-nong; WANG Hang-jun

    2008-01-01

    Wood identification is a basic technique of wood science and industry. Pore features are among the most important identification features for hardwoods. We have used a method based on an analysis of quantitative pore feature, which differs from traditional qualitative methods. We applies mathematical morphology methods such as dilation and erosion, open and close transformation of wood cross-sections, image repairing, noise filtering and edge detection to segment the pores from their background. Then the mean square errors (MSE) of pores were computed to describe the distribution of pores. Our experiment shows that it is easy to classift the pore features into three basic types, just as in traditional qualitative methods, but with the use of MSE of pores. This quantitative method improves wood identification considerably.

  15. Quantifying similarity of pore-geometry in nanoporous materials

    Science.gov (United States)

    Lee, Yongjin; Barthel, Senja D.; Dłotko, Paweł; Moosavi, S. Mohamad; Hess, Kathryn; Smit, Berend

    2017-05-01

    In most applications of nanoporous materials the pore structure is as important as the chemical composition as a determinant of performance. For example, one can alter performance in applications like carbon capture or methane storage by orders of magnitude by only modifying the pore structure. For these applications it is therefore important to identify the optimal pore geometry and use this information to find similar materials. However, the mathematical language and tools to identify materials with similar pore structures, but different composition, has been lacking. We develop a pore recognition approach to quantify similarity of pore structures and classify them using topological data analysis. This allows us to identify materials with similar pore geometries, and to screen for materials that are similar to given top-performing structures. Using methane storage as a case study, we also show that materials can be divided into topologically distinct classes requiring different optimization strategies.

  16. Using radon-222 to study coastal groundwater/surface-water interaction in the Crau coastal aquifer (southeastern France)

    Science.gov (United States)

    Mayer, Adriano; Nguyen, Bach Thao; Banton, Olivier

    2016-11-01

    Radon has been used to determine groundwater velocity and groundwater discharge into wetlands at the southern downstream boundary of the Crau aquifer, southeastern France. This aquifer constitutes an important high-quality freshwater resource exploited for agriculture, industry and human consumption. An increase in salinity occurs close to the sea, highlighting the need to investigate the water balance and groundwater behavior. Darcy velocity was estimated using radon activities in well waters according to the Hamada "single-well method" (involving comparison with radon in groundwater in the aquifer itself). Measurements done at three depths (7, 15 and 21 m) provided velocity ranging from a few mm/day to more than 20 cm/day, with highest velocities observed at the 15-m depth. Resulting hydraulic conductivities agree with the known geology. Waters showing high radon activity and high salinity were found near the presumed shoreline at 3,000 years BP, highlighting the presence of ancient saltwater. Radon activity has also been measured in canals, rivers and ponds, to trace groundwater discharges and evaluate water balance. A model of the radon spatial evolution explains the observed radon activities. Groundwater discharge to surface water is low in pond waters (4 % of total inputs) but significant in canals (55 l/m2/day).

  17. Decadal variations in groundwater quality

    DEFF Research Database (Denmark)

    Jessen, Søren; Postma, Dieke; Thorling, Lærke

    2017-01-01

    Twenty-five years of groundwater quality monitoring in a sandy aquifer beneath agricultural fields showed large temporal and spatial variations in major ion groundwater chemistry, which were linked closely to the nitrate (NO3) content of agricultural recharge. Between 1988 and 2013, the NO3 content...... loading. Agriculture thus is an important determinant of major ion groundwater chemistry. Temporal and spatial variations in the groundwater quality were simulated using a 2D reactive transport model, which combined effects of the historical NO3 leaching and denitrification, with dispersive mixing...... into the pristine groundwater residing deeper in the aquifer. Reactant-to-product ratios across reaction fronts are altered by dispersive mixing and transience in reactant input functions. Modelling therefore allowed a direct comparison of observed and simulated ratios of concentrations of NO3 (reactant...

  18. Dark Matter Velocity Spectroscopy.

    Science.gov (United States)

    Speckhard, Eric G; Ng, Kenny C Y; Beacom, John F; Laha, Ranjan

    2016-01-22

    Dark matter decays or annihilations that produce linelike spectra may be smoking-gun signals. However, even such distinctive signatures can be mimicked by astrophysical or instrumental causes. We show that velocity spectroscopy-the measurement of energy shifts induced by relative motion of source and observer-can separate these three causes with minimal theoretical uncertainties. The principal obstacle has been energy resolution, but upcoming experiments will have the precision needed. As an example, we show that the imminent Astro-H mission can use Milky Way observations to separate possible causes of the 3.5-keV line. We discuss other applications.

  19. Minimum Length - Maximum Velocity

    CERN Document Server

    Panes, Boris

    2011-01-01

    We study a framework where the hypothesis of a minimum length in space-time is complemented with the notion of reference frame invariance. It turns out natural to interpret the action of the obtained reference frame transformations in the context of doubly special relativity. As a consequence of this formalism we find interesting connections between the minimum length properties and the modified velocity-energy relation for ultra-relativistic particles. For example we can predict the ratio between the minimum lengths in space and time using the results from OPERA about superluminal neutrinos.

  20. Dark Matter Velocity Spectroscopy

    CERN Document Server

    Speckhard, Eric G; Beacom, John F; Laha, Ranjan

    2016-01-01

    Dark matter decays or annihilations that produce line-like spectra may be smoking-gun signals. However, even such distinctive signatures can be mimicked by astrophysical or instrumental causes. We show that velocity spectroscopy-the measurement of energy shifts induced by relative motion of source and observer-can separate these three causes with minimal theoretical uncertainties. The principal obstacle has been energy resolution, but upcoming and proposed experiments will make significant improvements. As an example, we show that the imminent Astro-H mission can use Milky Way observations to separate possible causes of the 3.5-keV line. We discuss other applications.

  1. Effects of crossflow velocity and transmembrane pressure on microfiltration of oil-in-water emulsions

    CERN Document Server

    Darvishzadeh, Tohid

    2012-01-01

    This study addresses the issue of oil removal from water using hydrophilic porous membranes. The effective separation of oil-in-water dispersions involves high flux of water through the membrane and, at the same time, high rejection rate of the oil phase. The effects of transmembrane pressure and crossflow velocity on rejection of oil droplets and thin oil films by pores of different cross-section are investigated numerically by solving the Navier-Stokes equation. We found that in the absence of crossflow, the critical transmembrane pressure, which is required for the oil droplet entry into a circular pore of a given surface hydrophilicity, agrees well with analytical predictions based on the Young-Laplace equation. With increasing crossflow velocity, the shape of the oil droplet is strongly deformed near the pore entrance and the critical pressure of permeation increases. We determined numerically the phase diagram for the droplet rejection, permeation, and breakup depending of the transmembrane pressure and...

  2. Seismic velocities for hydrate-bearing sediments using weighted equation

    Science.gov (United States)

    Lee, M.W.; Hutchinson, D.R.; Collett, T.S.; Dillon, William P.

    1996-01-01

    A weighted equation based on the three-phase time-average and Wood equations is applied to derive a relationship between the compressional wave (P wave) velocity and the amount of hydrates filling the pore space. The proposed theory predicts accurate P wave velocities of marine sediments in the porosity range of 40-80% and provides a practical means of estimating the amount of in situ hydrate using seismic velocity. The shear (S) wave velocity is derived under the assumption that the P to S wave velocity ratio of the hydrated sediments is proportional to the weighted average of the P to S wave velocity ratios of the constituent components of the sediment. In the case that all constituent components are known, a weighted equation using multiphase time-average and Wood equations is possible. However, this study showed that a three-phase equation with modified matrix velocity, compensated for the clay content, is sufficient to accurately predict the compressional wave velocities for the marine sediments. This theory was applied to the laboratory measurements of the P and S wave velocities in permafrost samples to infer the amount of ice in the unconsolidated sediment. The results are comparable to the results obtained by repeatedly applying the two-phase wave scattering theory. The theory predicts that the Poisson's ratio of the hydrated sediments decreases as the hydrate concentration increases and the porosity decreases. In consequence, the amplitude versus offset (AVO) data for the bottom-simulating reflections may reveal positive, negative, or no AVO anomalies depending on the concentration of hydrates in the sediments.

  3. Groundwater Temperature in the Limmat Valley Aquifer, Zurich

    Science.gov (United States)

    Jung, Martin; Rivera, Jaime; Blum, Philipp; Bayer, Peter

    2014-05-01

    dominant role of advective heat transport. However, this is different at locations where hydraulic conductivity is small, and accordingly groundwater flow velocity is only minor. We find increasing temperatures towards the ground surface, showing that here heat is accumulated. This leads to maximum groundwater temperatures of 27°C at certain wells. These observations point out that there is a strong coherence between hydrogeological parameters and subsurface temperature in Zurich.

  4. Pore-scaling Modeling of Physical Property Changes During CO2 Injection into Sandstone

    Science.gov (United States)

    Keehm, Y.; Yoo, G.

    2009-12-01

    Carbon dioxide is a green-house gas and is believed to be an important factor in global warming and climate change. Many countries around the world are working on reducing and sequestrating CO2 to follow international regulations. One of promising area for CO2 sequestration is the storage in geological formation. To accurately determine the performance of geological injection and storage, quantification and monitoring of the physical property changes are essential. In this paper, we are presenting a new approach for the monitoring of CO2 sequestration in sandstone using pore-scale simulation techniques. The method consists of three steps: 1) acquisition of high-resolution pore microstructures by X-ray micro-tomography; 2) CO2 injection simulation using lattice-Boltzmann (LB) two-phase flow simulation; and 3) FEM property simulations (electrical and elastic) at different CO2 saturations during the injection. We use three different sandstone samples: sand-pack, Berea sandstone, and B2 sandstone from offshore of Korea. The porosity of the sand-pack is 42% and that of two sandstone samples is around 17%. The digital pore structures were obtained by X-ray micro-tomography with a spatial resolution of 2 micron. The LB two-phase flow simulation is then conducted by injecting CO2 into fully water-saturated samples and gives a realistic movement of CO2 in the pore structure. At each CO2 saturation, electrical and elastic properties are determined by pore-scale FEM simulation techniques. The electrical conductivity decreases almost linearly as CO2 saturations increases; however, the P-wave velocity decrease more rapidly at the low CO2 saturation (up to 30%), than at higher saturation. S-wave velocity does not show any significant changes. The higher porosity rock shows more sensitivity to saturation changes. The modeling shows that we can have quantitative relations between physical properties and CO2 saturation, which can be used to determine injection performance and

  5. Artificial recharge of groundwater

    Science.gov (United States)

    The Task Committee on Guidelines for Artificial Recharge of Groundwater, of the American Society of Civil Engineers' (ASCE) Irrigation and Drainage Division, sponsored an International Symposium on Artificial Recharge of Groundwater at the Inn-at-the-Park Hotel in Anaheim, Calif., August 23-27, 1988. Cosponsors were the U.S. Geological Survey, California Department of Water Resources, University of California Water Resources Center, Metropolitan Water District of Southern California, with cooperation from the U.S. Bureau of Reclamation, International Association of Hydrological Sciences, American Water Resources Association, U.S. Agency for International Development, World Bank, United Nations Department of Technical Cooperation for Development, and a number of local and state organizations.Because of the worldwide interest in artificial recharge and the need to develop efficient recharge facilities, the Anaheim symposium brought together an interdisciplinary group of engineers and scientists to provide a forum for many professional disciplines to exchange experiences and findings related to various types of artificial recharge; learn from both successful and unsuccessful case histories; promote technology transfer between the various disciplines; provide an education resource for communication with those who are not water scientists, such as planners, lawyers, regulators, and the public in general; and indicate directions by which cities or other entities can save funds by having reasonable technical guidelines for implementation of a recharge project.

  6. Unraveling complexities of velocity dependent retention and release parameters for E. coli in saturated porous media

    Science.gov (United States)

    Escherichia coli transport and release experiments were conducted to investigate the pore-water velocity (v) dependency of the sticking efficiency (a), the fraction of the solid surface area that contributed to retention (Sf), the percentage of injected cells that were irreversibly retained (Mirr), ...

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

    Science.gov (United States)

    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.

  8. Temperature induced pore fluid pressurization in geomaterials

    CERN Document Server

    Ghabezloo, Siavash

    2010-01-01

    The theoretical basis of the thermal response of the fluid-saturated porous materials in undrained condition is presented. It has been demonstrated that the thermal pressurization phenomenon is controlled by the discrepancy between the thermal expansion of the pore fluid and of the solid phase, the stress-dependency of the compressibility and the non-elastic volume changes of the porous material. For evaluation of the undrained thermo-poro-elastic properties of saturated porous materials in conventional triaxial cells, it is important to take into account the effect of the dead volume of the drainage system. A simple correction method is presented to correct the measured pore pressure change and also the measured volumetric strain during an undrained heating test. It is shown that the porosity of the tested material, its drained compressibility and the ratio of the volume of the drainage system to the one of the tested sample, are the key parameters which influence the most the error induced on the measuremen...

  9. Atmosphere above a large solar pore

    CERN Document Server

    Sobotka, M; Jurcak, J; Heinzel, P; Del Moro, D

    2013-01-01

    A large solar pore with a granular light bridge was observed on October 15, 2008 with the IBIS spectrometer at the Dunn Solar Telescope and a 69-min long time series of spectral scans in the lines Ca II 854.2 nm and Fe I 617.3 nm was obtained. The intensity and Doppler signals in the Ca II line were separated. This line samples the middle chromosphere in the core and the middle photosphere in the wings. Although no indication of a penumbra is seen in the photosphere, an extended filamentary structure, both in intensity and Doppler signals, is observed in the Ca II line core. An analysis of morphological and dynamical properties of the structure shows a close similarity to a superpenumbra of a sunspot with developed penumbra. A special attention is paid to the light bridge, which is the brightest feature in the pore seen in the Ca II line centre and shows an enhanced power of chromospheric oscillations at 3-5 mHz. Although the acoustic power flux in the light bridge is five times higher than in the "quiet" chr...

  10. Molecular dynamics simulation of flow in pores

    Science.gov (United States)

    Blömer, Jan

    2001-08-01

    The gaseous flow in nano-scale pores is of wide interest for many today's industrial applications, e.g., in microelectronics, nano-mechanical devices (Knudsen compressor) and reaction and adsorption at porous surfaces. This can be seen from a variety of papers of recent RGD Symposia. Furthermore it is possible to separate gases by porous membranes. Although the fundamental problem of all these applications is same, namely the important role of the gas-surface interaction in such small structures, we will primarily concentrate on the separation of different gas species by porous membranes. These membranes are typically very robust (temperature, chemical resistance) because they are made from ceramics which offers new application fields. Porous flow can roughly be divided in several flow regimes by the Knudsen number: From viscous flow to Knudsen diffusion to surface diffusion and up to capillary condensation. A Molecular Dynamics (MD) model for the gas as well as the surface is formulated to investigate the interaction of gas atoms or molecules with internal degrees of freedom and the pore. The MD method seems to be well suited to study these phenomena because it can deal with the high density and the many-body-interactions, which occur during the multilayer adsorption and condensation at the surface, although it is clear that it is limited to a small physical space because of its high computational consumption.

  11. Simulation of groundwater and nuclide transport in the near-field of the high-level radioactive waste repository with TOUGHREACT

    Institute of Scientific and Technical Information of China (English)

    LI Xun; YANG Zeping; ZHENG Zhihong; WU Hongmei

    2008-01-01

    In order to know the mechanism of groundwater transport and the variation of ion concentrations in the near-field of the high-level radioactive waste repository, the whole process was simulated by EOS3 module of TOUGHREACT. Generally, the pH and cation concentrations vary obviously in the near-field saturated zone due to interaction between groundwater and bentonite. Moreover, the simulated results showed that calcite precipitation could not cause obvious variations in the porosity of media in the near-filed if the chemical components and their concentrations of groundwater and bentonite pore water are similar to those used in this study.

  12. An Analytical Method for Groundwater Inflow into a Drained Circular Tunnel.

    Science.gov (United States)

    Su, Kai; Zhou, Yafeng; Wu, Hegao; Shi, Changzheng; Zhou, Li

    2017-09-01

    Groundwater inflow estimation is essential for the design and construction of tunnel and the assessment of the environmental impacts. Analytical solutions used in current engineering practice do not adequately account for the effect of the excavation-induced drawdown, which leads to significant change in pore water pressure distribution and reductions of the water level beyond tunnel. Based on the numerical analysis results, this article proposes semianalytical method to predict the height of lowered water level and groundwater tunnel inflow. The tunnel problem is conceptualized as two-dimensional flow in a plane perpendicular to the tunnel axis. The analytical formula, considering the effect of the excavation-induced drawdown, provides a better prediction of the tunnel inflow compared to the existing analytical formulas, even for the cases with inclined groundwater level. © 2017, National Ground Water Association.

  13. Pore formation in lipid membrane I: Continuous reversible trajectory from intact bilayer through hydrophobic defect to transversal pore.

    Science.gov (United States)

    Akimov, Sergey A; Volynsky, Pavel E; Galimzyanov, Timur R; Kuzmin, Peter I; Pavlov, Konstantin V; Batishchev, Oleg V

    2017-09-22

    Lipid membranes serve as effective barriers allowing cells to maintain internal composition differing from that of extracellular medium. Membrane permeation, both natural and artificial, can take place via appearance of transversal pores. The rearrangements of lipids leading to pore formation in the intact membrane are not yet understood in details. We applied continuum elasticity theory to obtain continuous trajectory of pore formation and closure, and analyzed molecular dynamics trajectories of pre-formed pore reseal. We hypothesized that a transversal pore is preceded by a hydrophobic defect: intermediate structure spanning through the membrane, the side walls of which are partially aligned by lipid tails. This prediction was confirmed by our molecular dynamics simulations. Conversion of the hydrophobic defect into the hydrophilic pore required surmounting some energy barrier. A metastable state was found for the hydrophilic pore at the radius of a few nanometers. The dependence of the energy on radius was approximately quadratic for hydrophobic defect and small hydrophilic pore, while for large radii it depended on the radius linearly. The pore energy related to its perimeter, line tension, thus depends of the pore radius. Calculated values of the line tension for large pores were in quantitative agreement with available experimental data.

  14. Development and Evaluation of an Ultrasonic Groundwater Seepage Meter

    Science.gov (United States)

    Paulsen, R. J.; Smith, C. F.; O'Rourke, D.; Wong, T.; Bokuniewicz, H.

    2001-05-01

    Submarine groundwater discharge can influence significantly the near-shore transport and flux of chemicals into the oceans. Quantification of the sources and rates of such discharge requires a groundwater seepage meter that provides continuous measurements at high resolution over an extended period of time. An ultrasonic flow meter has been adapted for such measurements in the submarine environment. Connected to a steel collection funnel, the meter houses two piezoelectric transducers mounted at opposite ends of a cylindrical flow tube. By monitoring the perturbations of fluid flow on the propagation of sound waves inside the flow tube, the ultrasonic meter can measure both forward and reverse fluid flows in real time. Laboratory and field calibrations show that the ultrasonic meter can resolve groundwater discharges on the order of 0.1 μ m/s, and it is sufficiently robust for deployment in the field for several days. Data from West Neck Bay, Shelter Island, New York elucidate the temporal and spatial heterogeneity of submarine groundwater discharge and its interplay with tidal loading. A negative correlation between the discharge and tidal elevation was generally observed. A methodology was also developed whereby data for the sound velocity as a function of temperature can be used to infer the salinity and source of the submarine discharge. Independent measurements of electrical conductance were performed to validate this methodology. This meter has also been deployed as part of an international groundwater seepage intercomparison experiment with Scientific Committee on Oceanic Research (SCOR) / Land-Ocean Interaction in the Coastal Zone (LOICZ) Working Group 112. Results are in good agreement with other methodologies developed to quantify submarine groundwater discharge.

  15. An emerging pore-making strategy: confined swelling-induced pore generation in block copolymer materials.

    Science.gov (United States)

    Wang, Yong; Li, Fengbin

    2011-05-17

    Block copolymers (BCPs) composed of two or more thermodynamically incompatible homopolymers self-assemble into periodic microdomains. Exposing self-assembled BCPs with solvents selective to one block causes a swelling of the domains composed of this block. Strong swelling in the confinement imposed by the matrix of the other glassy block leads to well-defined porous structures via morphology reconstruction. This confined swelling-induced pore-making process has emerged recently as a new strategy to produce porous materials due to synergic advantages that include extreme simplicity, high pore regularity, involvement of no chemical reactions, no weight loss, reversibility of the pore forming process, etc. The mechanism, kinetics, morphology, and governing parameters of the confined swelling-induced pore-making process in BCP thin films are discussed, and the main applications of nanoporous thin films in the fields of template synthesis, surface patterning, and guidance for the areal arrangements of nanomaterials and biomolecules are summarized. Recent, promising results of extending this mechanism to produce BCP nanofibers or nanotubes and bulk materials with well-defined porosity, which makes this strategy also attractive to researchers outside the nanocommunity, are also presented. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Computational modeling of electrokinetic transport in random networks of micro-pores and nano-pores

    Science.gov (United States)

    Alizadeh, Shima; Mani, Ali

    2014-11-01

    A reduced order model has been developed to study the nonlinear electrokinetic behaviors emerging in the transport of ionic species through micro-scale and nano-scale porous media. In this approach a porous structure is modeled as a network of long and thin pores. By assuming transport equilibrium in the thin dimensions for each pore, a 1D transport equation is developed in the longitudinal direction covering a wide range of conditions including extreme limits of thick and thin electric double layers. This 1D model includes transport via diffusion, electromigration and wide range of advection mechanisms including pressure driven flow, electroosmosis, and diffusion osmosis. The area-averaged equations governing the axial transport from different pores are coupled at the pore intersections using the proper conservation laws. Moreover, an asymptotic treatment has been included in order to remove singularities in the limit of small concentration. The proposed method provides an efficient framework for insightful simulations of porous electrokinetic systems with applications in water desalination and energy storage. PhD student in Mechanical Engineering, Stanford University. She received her Master's degree in Mechanical Engineering from Stanford at 2013. Her research interests include CFD, high performance computing, and optimization.

  17. Reconstruction of groundwater depletion using a global scale groundwater model

    Science.gov (United States)

    de Graaf, Inge; van Beek, Rens; Sutanudjaja, Edwin; Wada, Yoshi; Bierkens, Marc

    2015-04-01

    Groundwater forms an integral part of the global hydrological cycle and is the world's largest accessible source of fresh water to satisfy human water needs. It buffers variable recharge rates over time, thereby effectively sustaining river flows in times of drought as well as evaporation in areas with shallow water tables. Moreover, although lateral groundwater flows are often slow, they cross topographic and administrative boundaries at appreciable rates. Despite the importance of groundwater, most global scale hydrological models do not consider surface water-groundwater interactions or include a lateral groundwater flow component. The main reason of this omission is the lack of consistent global-scale hydrogeological information needed to arrive at a more realistic representation of the groundwater system, i.e. including information on aquifer depths and the presence of confining layers. The latter holds vital information on the accessibility and quality of the global groundwater resource. In this study we developed a high resolution (5 arc-minutes) global scale transient groundwater model comprising confined and unconfined aquifers. This model is based on MODFLOW (McDonald and Harbaugh, 1988) and coupled with the land-surface model PCR GLOBWB (van Beek et al., 2011) via recharge and surface water levels. Aquifers properties were based on newly derived estimates of aquifer depths (de Graaf et al., 2014b) and thickness of confining layers from an integration of lithological and topographical information. They were further parameterized using available global datasets on lithology (Hartmann and Moosdorf, 2011) and permeability (Gleeson et al., 2014). In a sensitivity analysis the model was run with various hydrogeological parameter settings, under natural recharge only. Scenarios of past groundwater abstractions and corresponding recharge (Wada et al., 2012, de Graaf et al. 2014a) were evaluated. The resulting estimates of groundwater depletion are lower than

  18. Structure and mechanism of peptide-induced membrane pores

    Science.gov (United States)

    Qian, Shuo

    This thesis reports the studies of the structure and mechanism of peptide-induced membrane pores by antimicrobial peptide alamethicin and by a peptide named Baxalpha5, which is derived from Bax protein. Alamethicin is one of best known antimicrobial peptides, which are ubiquitous throughout the biological world. Bax-alpha5 peptide is the pore-forming domain of apoptosis regulator protein Bax, which activates pore formation on outer mitochondrial membrane to release cytochrome c to initiate programmed cell death. Both peptides as well as many other pore-forming peptides, induce pores in membrane, however the structure and mechanism of the pore formation were unknown. By utilizing grazing angle x-ray diffraction, I was able to reconstruct the electron density profile of the membrane pores induced by both peptides. The fully hydrated multiple bilayers of peptide-lipid mixture on solid substrate were prepared in the condition that pores were present, as established previously by neutron in-plane scattering and oriented circular dichroism. At dehydrated conditions, the inter bilayer distance of the sample shortened and the interactions between bilayers caused the membrane pores to become long-ranged correlated and formed a periodically ordered lattice of rhombohedral symmetry, so that x-ray diffraction can be applied. To help solving the phase problem of diffraction, a brominated lipid was used and multi-wavelength anomalous diffraction was performed below the bromine K-edge. The reconstructed electron density profiles unambiguously revealed that the alamethicin-induced membrane pore is of barrel-stave type, while the Bax-alpha5 induced pore is of lipidic toroidal (wormhole) type. The underlying mechanism of pore formation was resolved by observing the time-dependent process of pore formation in vesicles exposed to Bax-alpha5 solutions, as well as the membrane thinning experiment. This demonstrated that Bax-alpha5 exhibited the same sigmoidal concentration dependence as

  19. Assessing deep-seated landslide susceptibility using 3-D groundwater and slope-stability analyses, southwestern Seattle, Washington

    Science.gov (United States)

    Brien, Dianne L.; Reid, Mark E.

    2008-01-01

    In Seattle, Washington, deep-seated landslides on bluffs along Puget Sound have historically caused extensive damage to land and structures. These large failures are controlled by three-dimensional (3-D) variations in strength and pore-water pressures. We assess the slope stability of part of southwestern Seattle using a 3-D limit-equilibrium analysis coupled with a 3-D groundwater flow model. Our analyses use a high-resolution digital elevation model (DEM) combined with assignment of strength and hydraulic properties based on geologic units. The hydrogeology of the Seattle area consists of a layer of permeable glacial outwash sand that overlies less permeable glacial lacustrine silty clay. Using a 3-D groundwater model, MODFLOW-2000, we simulate a water table above the less permeable units and calibrate the model to observed conditions. The simulated pore-pressure distribution is then used in a 3-D slope-stability analysis, SCOOPS, to quantify the stability of the coastal bluffs. For wet winter conditions, our analyses predict that the least stable areas are steep hillslopes above Puget Sound, where pore pressures are elevated in the outwash sand. Groundwater flow converges in coastal reentrants, resulting in elevated pore pressures and destabilization of slopes. Regions predicted to be least stable include the areas in or adjacent to three mapped historically active deep-seated landslides. The results of our 3-D analyses differ significantly from a slope map or results from one-dimensional (1-D) analyses.

  20. Velocity centroids as tracers of the turbulent velocity statistics

    CERN Document Server

    Lazarian, A E A

    2004-01-01

    We use the results of magnetohydrodynamic (MHD) simulations to emulate spectroscopic observations, and produce maps of variations of velocity centroids to study their scaling properties. We compare them with those of the underlying velocity field, and analytic predictions presented in a previous paper (Lazarian & Esquivel 2003). We tested, with success, a criteria for recovering velocity statistics from velocity centroids derived in our previous work. That is, if >> (where S is a 2D map of ``unnormalized'', v velocity, and I integrated intensity map -column density-), then the structure function of the centroids is dominated by the structure function of velocity. We show that it is possible to extract the velocity statistics using centroids for subsonic and mildly supersonic turbulence (e.g. Mach numbers ~2.5). While, towards higher Mach numbers other effects could affect significantly the statistics of centroids.

  1. Statistics of Velocity from Spectral Data Modified Velocity Centroids

    CERN Document Server

    Lazarian, A

    2003-01-01

    We address the problem of studying interstellar (ISM) turbulence using spectral line data. We construct a measure that we term modified velocity centroids (MVCs) and derive an analytical solution that relates the 2D spectra of the modified centroids with the underlying 3D velocity spectrum. We test our results using synthetic maps constructed with data obtained through simulations of compressible MHD turbulence. We prove that the MVCs are able to restore the underlying spectrum of turbulent velocity. We show that the modified velocity centroids (MVCs) are complementary to the the Velocity Channel Analysis (VCA) technique that we introduced earlier. Employed together they make determining of the velocity spectral index more reliable. At the same time we show that MVCs allow to determine velocity spectra when the underlying statistics is not a power law and/or the turbulence is subsonic.

  2. Analysis of dispersion and absorption characteristics of shear waves in sinusoidally corrugated elastic medium with void pores

    Science.gov (United States)

    Pandit, Deepak Kr.; Kundu, Santimoy; Gupta, Shishir

    2017-02-01

    This theoretical work reports the dispersion and absorption characteristics of horizontally polarized shear wave (SH-wave) in a corrugated medium with void pores sandwiched between two dissimilar half-spaces. The dispersion and absorption equations have been derived in a closed form using the method of separation of variables. It has been established that there are two different kinds of wavefronts propagating in the proposed media. One of the wavefronts depends on the modulus of rigidity of elastic matrix of the medium and satisfies the dispersion equation of SH-waves. The second wavefront depends on the changes in volume fraction of the pores. Numerical computation of the obtained relations has been performed and the results are depicted graphically. The influence of corrugation, sandiness on the phase velocity and the damped velocity of SH-wave has been studied extensively.

  3. Predicting S-wave velocities for unconsolidated sediments at low effective pressure

    Science.gov (United States)

    Lee, Myung W.

    2010-01-01

    Accurate S-wave velocities for shallow sediments are important in performing a reliable elastic inversion for gas hydrate-bearing sediments and in evaluating velocity models for predicting S-wave velocities, but few S-wave velocities are measured at low effective pressure. Predicting S-wave velocities by using conventional methods based on the Biot-Gassmann theory appears to be inaccurate for laboratory-measured velocities at effective pressures less than about 4-5 megapascals (MPa). Measured laboratory and well log velocities show two distinct trends for S-wave velocities with respect to P-wave velocity: one for the S-wave velocity less than about 0.6 kilometer per second (km/s) which approximately corresponds to effective pressure of about 4-5 MPa, and the other for S-wave velocities greater than 0.6 km/s. To accurately predict S-wave velocities at low effective pressure less than about 4-5 MPa, a pressure-dependent parameter that relates the consolidation parameter to shear modulus of the sediments at low effective pressure is proposed. The proposed method in predicting S-wave velocity at low effective pressure worked well for velocities of water-saturated sands measured in the laboratory. However, this method underestimates the well-log S-wave velocities measured in the Gulf of Mexico, whereas the conventional method performs well for the well log velocities. The P-wave velocity dispersion due to fluid in the pore spaces, which is more pronounced at high frequency with low effective pressures less than about 4 MPa, is probably a cause for this discrepancy.

  4. Virus-sized colloid transport in a single pore: Model development and sensitivity analysis

    Science.gov (United States)

    Seetha, N.; Mohan Kumar, M. S.; Majid Hassanizadeh, S.; Raoof, Amir

    2014-08-01

    A mathematical model is developed to simulate the transport and deposition of virus-sized colloids in a cylindrical pore throat considering various processes such as advection, diffusion, colloid-collector surface interactions and hydrodynamic wall effects. The pore space is divided into three different regions, namely, bulk, diffusion and potential regions, based on the dominant processes acting in each of these regions. In the bulk region, colloid transport is governed by advection and diffusion whereas in the diffusion region, colloid mobility due to diffusion is retarded by hydrodynamic wall effects. Colloid-collector interaction forces dominate the transport in the potential region where colloid deposition occurs. The governing equations are non-dimensionalized and solved numerically. A sensitivity analysis indicates that the virus-sized colloid transport and deposition is significantly affected by various pore-scale parameters such as the surface potentials on colloid and collector, ionic strength of the solution, flow velocity, pore size and colloid size. The adsorbed concentration and hence, the favorability of the surface for adsorption increases with: (i) decreasing magnitude and ratio of surface potentials on colloid and collector, (ii) increasing ionic strength and (iii) increasing pore radius. The adsorbed concentration increases with increasing Pe, reaching a maximum value at Pe = 0.1 and then decreases thereafter. Also, the colloid size significantly affects particle deposition with the adsorbed concentration increasing with increasing particle radius, reaching a maximum value at a particle radius of 100 nm and then decreasing with increasing radius. System hydrodynamics is found to have a greater effect on larger particles than on smaller ones. The secondary minimum contribution to particle deposition has been found to increase as the favorability of the surface for adsorption decreases. The sensitivity of the model to a given parameter will be high

  5. Determination of the elastic wave velocities in porous rocks with the change of overburden pressure and its universal significance

    Institute of Scientific and Technical Information of China (English)

    史謌; 杨东全

    2002-01-01

    Typical rock samples with different lithologic characteristics were collected from exploring wells drilled in sandstone-conglomerate sedimental reservoirs with positive rhythm. In different pore fluid states (fully saturated with gas, water and oil), the velocities of compressional and shear waves (Vp, Vs) were measured under different overburden pressure in laboratory. The effects of pore fluid and different fluid types on the velocities were analyzed. The velocities (Vp, Vs) of the samples fully saturated with water were calculated by use of Gassmann's formula that is suitable for low frequency. The calculated values were compared with the experimental values obtained at high frequency. The result shows that Gassmann's theory can be used to calculate elastic wave velocities in porous rocks saturated with fluid. By this result, the change of elastic velocities with the change of fluid can be predicted. The error is allowable in petroleum engineering. This conclusion is useful for sonic logging interpretation and seismic datum processing.

  6. Investigating riparian groundwater flow close to a losing river using diurnal temperature oscillations at high vertical resolution

    Directory of Open Access Journals (Sweden)

    T. Vogt

    2012-02-01

    Full Text Available River-water infiltration is of high relevance for hyporheic and riparian groundwater ecology as well as for drinking water supply by river-bank filtration. Heat has become a popular natural tracer to estimate exchange rates between rivers and groundwater. However, quantifying flow patterns and velocities is impeded by spatial and temporal variations of exchange fluxes, insufficient sensors spacing during field investigations, or simplifying assumptions for analysis or modeling such as uniform flow. The objective of this study is to investigate lateral shallow groundwater flow upon river-water infiltration at the shoreline of the riverbed and in the adjacent riparian zone of the River Thur in northeast Switzerland. Here we have applied distributed temperature sensing (DTS along optical fibers wrapped around tubes to measure high-resolution vertical temperature profiles of the unsaturated zone and shallow riparian groundwater. Diurnal temperature oscillations were tracked in the subsurface and analyzed by means of dynamic harmonic regression to extract amplitudes and phase angles. Subsequent calculations of amplitude attenuation and time shift relative to the river signal show in detail vertical and temporal variations of heat transport in shallow riparian groundwater. In addition, we apply a numerical two-dimensional heat transport model for the unsaturated zone and shallow groundwater to obtain a better understanding of the observed heat transport processes in shallow riparian groundwater and to estimate the groundwater flow velocity. Our results show that the observed riparian groundwater temperature distribution cannot be described by uniform flow, but rather by horizontal groundwater flow velocities varying over depth. In addition, heat transfer of diurnal temperature oscillations from the losing river through shallow groundwater is influenced by thermal exchange with the unsaturated zone. Neglecting the influence of the unsaturated zone

  7. Groundwater Pollution and Vulnerability Assessment.

    Science.gov (United States)

    Kurwadkar, Sudarshan

    2017-10-01

    Groundwater is a critical resource that serve as a source of drinking water to large human population and, provide long-term water for irrigation purposes. In recent years; however, this precious resource being increasingly threatened, due to natural and anthropogenic activities. A variety of contaminants of emerging concern such as pharmaceuticals and personal care products, perfluorinated compounds, endocrine disruptors, and biological agents detected in the groundwater sources of both developing and developed nations. In this review paper, various studies have been included that documented instances of groundwater pollution and vulnerability to emerging contaminants of concern, pesticides, heavy metals, and leaching potential of various organic and inorganic contaminants from poorly managed residual waste products (biosolids, landfills, latrines, and septic tanks etc.). Understanding vulnerability of groundwater to pollution is critical to maintain the integrity of groundwater. A section on managed artificial recharge studies is included to highlight the sustainable approaches to groundwater conservation, replenishment and sustainability. This review paper is the synthesis of studies published in last one year that either documented the pollution problems or evaluated the vulnerability of groundwater pollution.

  8. A Stereolithography Pore-Throat Model

    Science.gov (United States)

    Crandall, D.; Ahmadi, G.; Ferer, M.; Smith, D. H.

    2007-12-01

    A new experimental, heterogeneous pore-throat model has been designed and fabricated using stereolithography (SL). In SL production, a laser cures a thin layer of photo-sensitive resin on the surface of a vat of liquid resin; a moveable platform then submerges the cured layer and a new layer is cured on top of the previous one, creating a physical model from a computer generated model. This layered fabrication of a computer generated model has enabled the production of an experimental porous medium with improved fluid resistance properties, as compared to previously studied, constant-height etched cells. A uniform distribution of throat widths was randomly placed throughout the pore-throat matrix and the throat height of each throat was assigned to increase the range of viscous and capillary resistances within the physical model. This variation in both throat height and width generated a porous medium with fairly low porosity (43%), permeability (~400 D), and wide range of geometric resistance properties. Experimental, two-phase immiscible drainage studies in the porous flowcell were performed. Analysis of the captured images was performed with open-source image processing software. These analysis techniques utilized the capability of both ImageJ and the Gnu Image Manipulation Program to be customized with ancillary codes. This enabled batch procedures to be created that converted the original grey-scale bitmaps to binary data sets, which were then analyzed with in-house codes. The fractal dimension, Df, (measured with box-counting) and percent saturation of these experiments were calculated and shown to compare favorably to fractal predictions and previous flowcell studies. Additionally, using the computer generated pore-throat geometry, a computational fluid dynamics model of two- phase flow through the porous medium was created. This model was created using FLUENT code and the Volume of Fluid method. The percent saturation of the less-viscous invading fluid

  9. Radioactive Seepage through Groundwater Flow from the Uranium Mines, Namibia

    Directory of Open Access Journals (Sweden)

    Tamiru Abiye

    2017-02-01

    Full Text Available The study focused on the seepage of uranium from unlined tailing dams into the alluvial aquifer in the Gawib River floodplain in Namibia where the region solely relies on groundwater for its economic activities as a result of arid climatic condition. The study reviewed previous works besides water sample collection and analyses for major ions, metals and environmental isotopes in addition to field tests on physico-chemical parameters (pH, Electrical Conductivity, Redox and T. Estimation of seepage velocity (true velocity of groundwater flow has been conducted in order to understand the extent of radioactive plume transport. The hydrochemistry, stable isotopes and tritium results show that there is uranium contamination from the unlined uranium tailings in the Gawib shallow aquifer system which suggests high permeability of the alluvial aquifer facilitating groundwater flow in the arid region. The radioactive contaminants could spread into the deeper aquifer system through the major structures such as joints and faults. The contamination plume could also spread downstream into the Swakop River unless serious interventions are employed. There is also a very high risk of the plume to reach the Atlantic Ocean through seasonal flash floods that occurs in the area.

  10. Minimal information in velocity space

    CERN Document Server

    Evrard, Guillaume

    1995-01-01

    Jaynes' transformation group principle is used to derive the objective prior for the velocity of a non-zero rest-mass particle. In the case of classical mechanics, invariance under the classical law of addition of velocities, leads to an improper constant prior over the unbounded velocity space of classical mechanics. The application of the relativistic law of addition of velocities leads to a less simple prior. It can however be rewritten as a uniform volumetric distribution if the relativistic velocity space is given a non-trivial metric.

  11. Bioremediation of contaminated groundwater

    Science.gov (United States)

    Hazen, Terry C.; Fliermans, Carl B.

    1995-01-01

    An apparatus and method for in situ remediation of contaminated subsurface soil or groundwater contaminated by chlorinated hydrocarbons. A nutrient fluid is selected to stimulate the growth and reproduction of indigenous subsurface microorganisms that are capable of degrading the contaminants; an oxygenated fluid is selected to create a generally aerobic environment for these microorganisms to degrade the contaminants, leaving only pockets that are anaerobic. The nutrient fluid is injected periodically while the oxygenated fluid is injected continuously and both are extracted so that both are drawn across the plume. The nutrient fluid stimulates microbial colony growth; withholding it periodicially forces the larger, healthy colony of microbes to degrade the contaminants. Treatment is continued until the subsurface concentration of contaminants is reduced to an acceptable, preselected level. The nutrient fluid can be methane and the oxygenated fluid air for stimulating production of methanotrophs to break down chlorohydrocarbons, especially trichloroethylene (TCE) and tetrachloroethylene.

  12. Groundwater and Terrestrial Water Storage

    Science.gov (United States)

    Rodell, Matthew; Chambers, Don P.; Famiglietti, James S.

    2012-01-01

    Groundwater is a vital resource and also a dynamic component of the water cycle. Unconfined aquifer storage is less responsive to short term weather conditions than the near surface terrestrial water storage (TWS) components (soil moisture, surface water, and snow). However, save for the permanently frozen regions, it typically exhibits a larger range of variability over multi-annual periods than the other components. Groundwater is poorly monitored at the global scale, but terrestrial water storage (TWS) change data from the Gravity Recovery and Climate Experiment (GRACE) satellite mission are a reasonable proxy for unconfined groundwater at climatic scales.

  13. Use of a mixing model to investigate groundwater-surface water mixing and nitrogen biogeochemistry in the bed of a groundwater-fed river

    Science.gov (United States)

    Lansdown, Katrina; Heppell, Kate; Ullah, Sami; Heathwaite, A. Louise; Trimmer, Mark; Binley, Andrew; Heaton, Tim; Zhang, Hao

    2010-05-01

    The dynamics of groundwater and surface water mixing and associated nitrogen transformations in the hyporheic zone have been investigated within a gaining reach of a groundwater-fed river (River Leith, Cumbria, UK). The regional aquifer consists of Permo-Triassic sandstone, which is overlain by varying depths of glaciofluvial sediments (~15 to 50 cm) to form the river bed. The reach investigated (~250m long) consists of a series of riffle and pool sequences (Käser et al. 2009), with other geomorphic features such as vegetated islands and marginal bars also present. A network of 17 piezometers, each with six depth-distributed pore water samplers based on the design of Rivett et al. (2008), was installed in the river bed in June 2009. An additional 18 piezometers with a single pore water sampler were installed in the riparian zone along the study reach. Water samples were collected from the pore water samplers on three occasions during summer 2009, a period of low flow. The zone of groundwater-surface water mixing within the river bed sediments was inferred from depth profiles (0 to 100 cm) of conservative chemical species and isotopes of water with the collected samples. Sediment cores collected during piezometer installation also enabled characterisation of grain size within the hyporheic zone. A multi-component mixing model was developed to quantify the relative contributions of different water sources (surface water, groundwater and bank exfiltration) to the hyporheic zone. Depth profiles of ‘predicted' nitrate concentration were constructed using the relative contribution of each water source to the hyporheic and the nitrate concentration of the end members. This approach assumes that the mixing of different sources of water is the only factor controlling the nitrate concentration of pore water in the river bed sediments. Comparison of predicted nitrate concentrations (which assume only mixing of waters with different nitrate concentrations) with actual

  14. Pore-scale observation and 3D simulation of wettability effects on supercritical CO2 - brine immiscible displacement in drainage

    Science.gov (United States)

    Hu, R.; Wan, J.; Chen, Y.

    2016-12-01

    Wettability is a factor controlling the fluid-fluid displacement pattern in porous media and significantly affects the flow and transport of supercritical (sc) CO2 in geologic carbon sequestration. Using a high-pressure micromodel-microscopy system, we performed drainage experiments of scCO2 invasion into brine-saturated water-wet and intermediate-wet micromodels; we visualized the scCO2 invasion morphology at pore-scale under reservoir conditions. We also performed pore-scale numerical simulations of the Navier-Stokes equations to obtain 3D details of fluid-fluid displacement processes. Simulation results are qualitatively consistent with the experiments, showing wider scCO2 fingering, higher percentage of scCO2 and more compact displacement pattern in intermediate-wet micromodel. Through quantitative analysis based on pore-scale simulation, we found that the reduced wettability reduces the displacement front velocity, promotes the pore-filling events in the longitudinal direction, delays the breakthrough time of invading fluid, and then increases the displacement efficiency. Simulated results also show that the fluid-fluid interface area follows a unified power-law relation with scCO2 saturation, and show smaller interface area in intermediate-wet case which suppresses the mass transfer between the phases. These pore-scale results provide insights for the wettability effects on CO2 - brine immiscible displacement in geologic carbon sequestration.

  15. Visual control of walking velocity.

    Science.gov (United States)

    François, Matthieu; Morice, Antoine H P; Bootsma, Reinoud J; Montagne, Gilles

    2011-06-01

    Even if optical correlates of self-motion velocity have already been identified, their contribution to the control of displacement velocity remains to be established. In this study, we used a virtual reality set-up coupled to a treadmill to test the role of both Global Optic Flow Rate (GOFR) and Edge Rate (ER) in the regulation of walking velocity. Participants were required to walk at a constant velocity, corresponding to their preferred walking velocity, while eye height and texture density were manipulated. This manipulation perturbed the natural relationship between the actual walking velocity and its optical specification by GOFR and ER, respectively. Results revealed that both these sources of information are indeed used by participants to control walking speed, as demonstrated by a slowing down of actual walking velocity when the optical specification of velocity by either GOFR or ER gives rise to an overestimation of actual velocity, and vice versa. Gait analyses showed that these walking velocity adjustments result from simultaneous adaptations in both step length and step duration. The role of visual information in the control of self-motion velocity is discussed in relation with other factors.

  16. The thin section rock physics: Modeling and measurement of seismic wave velocity on the slice of carbonates

    Energy Technology Data Exchange (ETDEWEB)

    Wardaya, P. D., E-mail: pongga.wardaya@utp.edu.my; Noh, K. A. B. M., E-mail: pongga.wardaya@utp.edu.my; Yusoff, W. I. B. W., E-mail: pongga.wardaya@utp.edu.my [Petroleum Geosciences Department, Universiti Teknologi PETRONAS, Tronoh, Perak, 31750 (Malaysia); Ridha, S. [Petroleum Engineering Department, Universiti Teknologi PETRONAS, Tronoh, Perak, 31750 (Malaysia); Nurhandoko, B. E. B. [Wave Inversion and Subsurface Fluid Imaging Research Laboratory (WISFIR), Dept. of Physics, Institute of Technology Bandung, Bandung, Indonesia and Rock Fluid Imaging Lab, Bandung (Indonesia)

    2014-09-25

    This paper discusses a new approach for investigating the seismic wave velocity of rock, specifically carbonates, as affected by their pore structures. While the conventional routine of seismic velocity measurement highly depends on the extensive laboratory experiment, the proposed approach utilizes the digital rock physics view which lies on the numerical experiment. Thus, instead of using core sample, we use the thin section image of carbonate rock to measure the effective seismic wave velocity when travelling on it. In the numerical experiment, thin section images act as the medium on which wave propagation will be simulated. For the modeling, an advanced technique based on artificial neural network was employed for building the velocity and density profile, replacing image's RGB pixel value with the seismic velocity and density of each rock constituent. Then, ultrasonic wave was simulated to propagate in the thin section image by using finite difference time domain method, based on assumption of an acoustic-isotropic medium. Effective velocities were drawn from the recorded signal and being compared to the velocity modeling from Wyllie time average model and Kuster-Toksoz rock physics model. To perform the modeling, image analysis routines were undertaken for quantifying the pore aspect ratio that is assumed to represent the rocks pore structure. In addition, porosity and mineral fraction required for velocity modeling were also quantified by using integrated neural network and image analysis technique. It was found that the Kuster-Toksoz gives the closer prediction to the measured velocity as compared to the Wyllie time average model. We also conclude that Wyllie time average that does not incorporate the pore structure parameter deviates significantly for samples having more than 40% porosity. Utilizing this approach we found a good agreement between numerical experiment and theoretically derived rock physics model for estimating the effective seismic

  17. Viruses as groundwater tracers: using ecohydrology to characterize short travel times in aquifers

    Science.gov (United States)

    Hunt, Randall J.; Borchardt, Mark A.; Bradbury, Kenneth R.

    2014-01-01

    Viruses are attractive tracers of short (travel times in aquifers because they have unique genetic signatures, are detectable in trace quantities, and are mobile in groundwater. Virus “snaphots” result from infection and disappearance in a population over time; therefore, the virus snapshot shed in the fecal wastes of an infected population at a specific point in time can serve as a marker for tracking virus and groundwater movement. The virus tracing approach and an example application are described to illustrate their ability to characterize travel times in high-groundwater velocity settings, and provide insight unavailable from standard hydrogeologic approaches. Although characterization of preferential flowpaths does not usually characterize the majority of other travel times occurring in the groundwater system (e.g., center of plume mass; tail of the breakthrough curve), virus approaches can trace very short times of transport, and thus can fill an important gap in our current hydrogeology toolbox.

  18. Viruses as groundwater tracers: using ecohydrology to characterize short travel times in aquifers.

    Science.gov (United States)

    Hunt, Randall J; Borchardt, Mark A; Bradbury, Kenneth R

    2014-01-01

    Viruses are attractive tracers of short (aquifers because they have unique genetic signatures, are detectable in trace quantities, and are mobile in groundwater. Virus "snaphots" result from infection and disappearance in a population over time; therefore, the virus snapshot shed in the fecal wastes of an infected population at a specific point in time can serve as a marker for tracking virus and groundwater movement. The virus tracing approach and an example application are described to illustrate their ability to characterize travel times in high-groundwater velocity settings, and provide insight unavailable from standard hydrogeologic approaches. Although characterization of preferential flowpaths does not usually characterize the majority of other travel times occurring in the groundwater system (e.g., center of plume mass; tail of the breakthrough curve), virus approaches can trace very short times of transport, and thus can fill an important gap in our current hydrogeology toolbox.

  19. Pore size matters for potassium channel conductance

    Science.gov (United States)

    Moldenhauer, Hans; Pincuntureo, Matías

    2016-01-01

    Ion channels are membrane proteins that mediate efficient ion transport across the hydrophobic core of cell membranes, an unlikely process in their absence. K+ channels discriminate K+ over cations with similar radii with extraordinary selectivity and display a wide diversity of ion transport rates, covering differences of two orders of magnitude in unitary conductance. The pore domains of large- and small-conductance K+ channels share a general architectural design comprising a conserved narrow selectivity filter, which forms intimate interactions with permeant ions, flanked by two wider vestibules toward the internal and external openings. In large-conductance K+ channels, the inner vestibule is wide, whereas in small-conductance channels it is narrow. Here we raise the idea that the physical dimensions of the hydrophobic internal vestibule limit ion transport in K+ channels, accounting for their diversity in unitary conductance. PMID:27619418

  20. Silicon pore optics development for ATHENA

    Science.gov (United States)

    Collon, Maximilien J.; Vacanti, Giuseppe; Günther, Ramses; Yanson, Alex; Barrière, Nicolas; Landgraf, Boris; Vervest, Mark; Chatbi, Abdelhakim; Beijersbergen, Marco W.; Bavdaz, Marcos; Wille, Eric; Haneveld, Jeroen; Koelewijn, Arenda; Leenstra, Anne; Wijnperle, Maurice; van Baren, Coen; Müller, Peter; Krumrey, Michael; Burwitz, Vadim; Pareschi, Giovanni; Conconi, Paolo; Christensen, Finn E.

    2015-09-01

    The ATHENA mission, a European large (L) class X-ray observatory to be launched in 2028, will essentially consist of an X-ray lens and two focal plane instruments. The lens, based on a Wolter-I type double reflection grazing incidence angle design, will be very large (~ 3 m in diameter) to meet the science requirements of large effective area (1-2 m2 at a few keV) at a focal length of 12 m. To meet the high angular resolution (5 arc seconds) requirement the X-ray lens will also need to be very accurate. Silicon Pore Optics (SPO) technology has been invented to enable building such a lens and thus enabling the ATHENA mission. We will report in this paper on the latest status of the development, including details of X-ray test campaigns.

  1. Silicon pore optics for the ATHENA telescope

    Science.gov (United States)

    Collon, Maximilien J.; Vacanti, Giuseppe; Günther, Ramses; Yanson, Alex; Barriere, Nicolas; Landgraf, Boris; Vervest, Mark; Chatbi, Abdelhakim; van der Hoeven, Roy; Beijersbergen, Marco W.; Bavdaz, Marcos; Wille, Eric; Shortt, Brian; Haneveld, Jeroen; Koelewijn, Arenda; van Baren, Coen; Eigenraam, Alexander; Müller, Peter; Krumrey, Michael; Burwitz, Vadim; Pareschi, Giovanni; Conconi, Paolo; Massahi, Sonny; Christensen, Finn E.; Valsecchi, Giuseppe

    2016-07-01

    Silicon Pore Optics is a high-energy optics technology, invented to enable the next generation of high-resolution, large area X-ray telescopes such as the ATHENA observatory, a European large (L) class mission with a launch date of 2028. The technology development is carried out by a consortium of industrial and academic partners and focuses on building an optics with a focal length of 12 m that shall achieve an angular resolution better than 5". So far we have built optics with a focal length of 50 m and 20 m. This paper presents details of the work carried out to build silicon stacks for a 12 m optics and to integrate them into mirror modules. It will also present results of x-ray tests taking place at PTB's XPBF with synchrotron radiation and the PANTER test facility.

  2. Distributed Pore Chemistry in Porous Organic Polymers

    Science.gov (United States)

    Koontz, Steven L. (Inventor)

    1999-01-01

    A method for making a biocompatible polymer article using a uniform atomic oxygen treatment is disclosed. The substrate may be subsequently optionally grated with a compatibilizing compound. Compatibilizing compounds may include proteins, phosphorylcholine groups, platelet adhesion preventing polymers, albumin adhesion promoters, and the like. The compatibilized substrate may also have a living cell layer adhered thereto. The atomic oxygen is preferably produced by a flowing afterglow microwave discharge. wherein the substrate resides in a sidearm out of the plasma. Also, methods for culturing cells for various purposes using the various membranes are disclosed as well. Also disclosed are porous organic polymers having a distributed pore chemistry (DPC) comprising hydrophilic and hydrophobic regions. and a method for making the DPC by exposing the polymer to atomic oxygen wherein the rate of hydrophilization is greater than the rate of mass loss.

  3. Evaluating transport in irregular pore networks

    CERN Document Server

    Klimenko, Dimitri A; Klimenko, Alexander Y; 10.1103/PhysRevE.86.011112

    2012-01-01

    A general approach for investigating transport phenomena in porous media is presented. This approach has the capacity to represent various kinds of irregularity in porous media without the need for excessive detail or computational effort. The overall method combines a generalized Effective Medium Approximation (EMA) with a macroscopic continuum model in order to derive a transport equation with explicit analytical expressions for the transport coefficients. The proposed form of the EMA is an anisotropic and heterogeneous extension of Kirkpatrick's EMA [Rev. Mod. Phys. 45, 574 (1973)] which allows the overall model to account for microscopic alterations in connectivity (with the locations of the pores and the orientation and length of the throat) as well as macroscopic variations in transport properties. A comparison to numerical results for randomly generated networks with different properties is given, indicating the potential for this methodology to handle cases that would pose significant difficulties to ...

  4. Factors Determining the Pore Shape in Polycarbonate Track Membranes

    CERN Document Server

    Apel, P Yu; Orelovich, O L; Akimenko, S N; Sartowska, B; Dmitriev, S N

    2004-01-01

    The process of pore formation in ion-irradiated polycarbonate films on treatment with alkali solutions in the presence of a surfactant is studied. It is found that the pore shape depends on both the structure of the initial films and the peculiarities of the interaction of the surfactant with the polymer surface and the transport of the surfactant into tracks. Due to heterogeneity of the films the cross-section of a track pore channel changes along its length. The presence of the surfactant results in a further effect. Surfactant molecules adsorb on the polymer surface at the pore entries and reduce the etch rate which leads to formation of cigar-like pore channels. The use of surfactant as a component of chemical etchant enables one to control the pore shape in track membranes thus optimizing their retention and permeation characteristics.

  5. Experimental study on pore water pressure dissipation of mucky soil

    Institute of Scientific and Technical Information of China (English)

    Xianwei ZHANG; Changming WANG; Junxia LI; Bin WANG

    2008-01-01

    Pore water pressure has an important influence on mechanical properties of soil. The authors studied the characteristics of pore water pressure dissipating of mucky soil under consolidated-drained condition by using refitted triaxial instrument and analyzed the variation of pore pressure coefficient with consolidation pressure. The results show that the dissipating of pore water pressure behaves in different ways depends on different styles of loading. What is more, the pore water pressure coefficient of mucky soil is less than 1. As the compactness of soil increases and moisture content reduces, the value of B reduces. There is a staggered dissipating in the process of consolidation, in which it is a mutate point when U/P is 80%. It is helpful to establish the pore water pressure model and study the strength-deformation of soil in process of consolidation.

  6. Geological factors controlling radon hazardous concentration in groundwater

    Science.gov (United States)

    Przylibski, T. A.

    2009-04-01

    Radon waters are classified as waters containing more than 100 Bq/L of Rn-222. In many regions radon groundwaters are commonly used as a tap waters. Exploitation of radon groundwater without removing radon out of water in the intake may be hazardous for the consumers. Radon removing is relatively simple and cheap, and may be achieved trough the degassing of tapped water. The following factors are crucial for the genesis of radon (Rn-222) and changes in its concentration in groundwaters: the content of parent Ra-226 in the reservoir rock, the emanation coefficient of the reservoir rock, mixing of various groundwater components. Simplifying the geochemical characterisctics of Ra-226, one can say that the highest radium contents outside uranium deposits could be expected above all in crystalline rocks such as granites, ryolites and gneisses, and among sedimentary rocks - in fine-grained rocks - mudstones and clay rocks. Therefore the highest content of Rn-222 is characteristic of groundwaters flowing through the abovementioned rocks. What is very important for the genesis of groundwater dissolved Rn-222 is not only the total content of Ra-226 in the aquifer, but also the distribution of this isotope's atoms in relation to the surface of mineral grains (crystals) and crack surfaces. Only if Ra-226 atoms lie in the outer zone of grains (crystals), they can be the source of Rn-222 atoms released directly or indirectly into pores and fissures. If the pores and fissures are filled with free groundwater, then the radon dissolved in this water can migrate with it. Therefore particularly high Rn-222 concentration values can be expected in groundwaters circulating in zones of strongly cracked reservoir rocks, i.e. in the weathering zone, reaching the depth of several dozen meters below ground surface, as well as in zones of brittle tectonic deformations. The number of Rn-222 atoms formed in groundwater as a result of the decay of Ra-226 ion (Ra2+) dissolved in this water

  7. Groundwater Contamination with NO3-N in a Wheat-Corn Cropping System in the North China Plain

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The North China Plain, where summer corn (Zea mays L.) and winter wheat (Triticum aestivum L.) are the major crops grown, is a major agricultural area in China. Permeable soils make the region susceptible to groundwater pollution by NO3-N, which is applied to fields in large amounts of more than 400 kg NO3-N ha-1 as fertilizer. A field experiment was established in 2002 to examine the relationship among N fertilization rate, soil NO3-N, and NO3-N groundwater contamination. Two adjacent fields were fertilized with local farmers' N fertilization rate (LN) and double the normal application rate (HN), respectively, and managed under otherwise identical conditions. The fields were under a traditional summer corn/winter wheat rotation. Over a 22-month period, we monitored NO3-N concentrations in both bulk soil and soil pore water in 20-40 cm increments up to 180 cm depth. We also monitored NO3-N concentrations in groundwater and the depth of the groundwater table. No significant differences in soil NO3-N were observed between the LN and HN treatment. We identified NO3-N plumes moving downward through the soil profile. The HN treatment resulted in significantly higher groundwater NO3-N, relative to the LN treatment, with groundwater NO3-N consistently exceeding the maximum safe level of 10 mg L-1, but groundwater NO3-N above the maximum safe level was also observed in the LN treatment after heavy rain. Heavy rain in June, July, and August 2003 caused increased NO3-N leaching through the soil and elevated NO3-N concentrations in the groundwater. Concurrent rise of the groundwater table into NO3-N-rich soil layers also contributed to the increased NO3-N concentrations in the groundwater. Our results indicate that under conditions of average rainfall, soil NO3-N was accumulated in the soil profile. The subsequent significantly higherthan-average rainfalls continuously flushed the soil NO3-N into deeper layers and raised the groundwater table, which caused continuous

  8. Vapor intrusion in soils with multimodal pore-size distribution

    OpenAIRE

    Alfaro Soto Miguel; Hung Kiang Chang

    2016-01-01

    The Johnson and Ettinger [1] model and its extensions are at this time the most widely used algorithms for estimating subsurface vapor intrusion into buildings (API [2]). The functions which describe capillary pressure curves are utilized in quantitative analyses, although these are applicable for porous media with a unimodal or lognormal pore-size distribution. However, unaltered soils may have a heterogeneous pore distribution and consequently a multimodal pore-size distribution [3], which ...

  9. Using pore-scale imaging and modeling to provide new insights in multi-phase flow, transport and reaction phenomena in porous media (Invited)

    Science.gov (United States)

    Bijeljic, B.; Andrew, M. G.; Menke, H. P.; Blunt, M. J.

    2013-12-01

    Advances in X ray imaging techniques made it possible not only to accurately describe solid and fluid(s) distributions in the pore space but also to study dynamics of multi-phase flow and reactive transport in-situ. This has opened up a range of new opportunities to better understand fundamental physics at the pore scale by experiment, and test and validate theoretical models in order to develop predictive tools at the pore scale and use it for upscaling. Firstly, we illustrate this concept by describing a new methodology for predicting non-Fickian transport in millimeter-sized three-dimensional micro-CT images of a beadpack, a sandstone, and a carbonate, representing porous media with an increasing degree of pore-scale complexity. The key strategy is to retain the full information on flow and transport signature of a porous medium by using probability distribution functions (PDFs) of voxel velocities for flow, and both PDFs of particle displacements and PDFs of particle transit times between voxels for transport. For this purpose, direct-simulation flow and transport model is used to analyse the relationship between pore structure, velocity, and the dynamics of the evolving plume. The model predictions for PDFs of particle displacements obtained by the model are in excellent agreement with those measured on similar cores in nuclear magnetic resonance experiments. A key determinant for non-Fickian transport is the spread in velocity distribution in the pore space. Further, we present micro-CT imaging of capillary trapping of scCO2 at reservoir conditions in a range of carbonates and sandstones having different pore structure and demonstrate that substantial quantities of scCO2 can be trapped in the pore space. Higher residual scCO2 saturations are found in sandstones compared to carbonates. The trapped ganglia exhibit different distribution of size, related to the inherent structure of pore space. Pore structures with large, open pores that are well connected lead

  10. Pore structure modification of cement concretes by impregnation with sulfur-containing compounds

    Directory of Open Access Journals (Sweden)

    YANAKHMETOV Marat Rafisovich

    2015-02-01

    Full Text Available The authors study how the impregnation with sulfur-containing compounds changes the concrete pore structure and how it influences on the water absorption and watertightness. The results of this research indicate that impregnation of cement concrete with water-based solution of polysulphide modifies pore structure of cement concrete in such a way that it decreases total and effective porosity, reduces water absorption and increases watertightness. The proposed impregnation based on mineral helps to protect for a long time the most vulnerable parts of buildings – basements, foundations, as well as places on the facades of buildings exposed to rain, snow and groundwater. Application of the new product in the construction industry can increase the durability of materials, preventing the destruction processes caused by weathering, remove excess moisture in damp basements. The surfaces treated by protective compounds acquire antisoiling properties for a long time, and due to reduced thermal conductivity the cost of heating buildings is decreased. The effectiveness of the actions and the relatively low cost of proposed hydrophobizator makes it possible to spread widely the proposed protection method for building structures.

  11. Carbon and nitrogen stoichiometry regulates the magnitude and temporal dynamics of nitrogenous nutrient regeneration in sandy beach pore water

    Science.gov (United States)

    Goodridge, B. M.; Melack, J. M.

    2013-12-01

    Sandy beaches are located at the interface of terrestrial and marine ecosystems, lining about 70% of the world's ice-free coastline. They can be conduits for fresh groundwater delivery of dissolved inorganic nitrogen (DIN), a vital and often limiting nutrient source, to oceans along coastlines where a hydrologic connection exists with shallow coastal aquifers. However, even along such coastlines, the majority of water within beach sands is recirculated seawater (i.e., pore water), and the regeneration of DIN from the mineralization of marine organic matter (OM) is considered the dominant source of DIN in beach pore water and flux to coastal oceans. The biogeochemical mechanisms regulating the magnitude of and temporal changes in DIN regeneration in saline beach pore water are therefore of prime importance in assessing the role of beaches in coastal marine nitrogen cycling. We assessed the potential stoichiometric control of resource carbon to nitrogen (C:N) on pore water DIN regeneration at four sandy beach study locations, and temporal evolution of pore water C:N at two of the four study locations, along the Santa Barbara, California coastline during synoptic sampling events over the course of a year. We identified pore water dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) as the resources most likely available to microbial heterotrophic metabolism (i.e., C:N), the dominant catalyst of DIN regeneration in marine sediments, finding a negative exponential correlation of DIN with DOC:TDN ratios (673 × 173 e-1.05 × 0.30(DOC:TDN); R2 = 0.55, n = 123). DOC:TDN ratios also demonstrated a negative exponential correlation with residence time (10.0 × 1.7 e-1.08 × 0.48(RT) + 1.61 × 0.54; R2 = 0.79, n = 46), estimated using radon-222 as a pore water residence time tracer. Using model-derived DOC:TDN ratios as the independent variable in the DIN vs. DOC:TDN relationship, we explored temporal changes in DIN regeneration. The modeled DIN vs. residence time

  12. Correlation of electrical resistivity imaging, push-tool and groundwater electrical conductivity at a heterogeneous field site

    Energy Technology Data Exchange (ETDEWEB)

    Rayner, S.F.; Bentley, L.R.; Robillard, J.M. [Calgary Univ., AB (Canada)

    2003-07-01

    This paper describes the collection of data at a decommissioned sour gas plant, located on a topographic high in central Alberta. The information collected included: push-tool electrical conductivity (EC), three-dimensional electrical resistivity imaging (3D-ERI) and groundwater sample electrical conductivity. There was no correlation between the inverted ERI conductivity values and groundwater EC values, despite the existence of strong correlation between the inverted ERI conductivity values and upscaled push-tool EC. The most probable cause for the lack of correlation between the ERI and groundwater EC values is subsurface heterogeneity. There is a possibility that the EC of the mobile groundwater within the fractures and sand lenses are different than that of the relatively immobile matrix pore water, due to remediation activities. The entrance of the groundwater from piezometers is from high permeability zones (like sand lenses and fractures) within the screened interval. The ERI data mostly likely does not specifically identify the conductivity of the groundwater within these fractures and thin sand lenses. As a result, the manner in which ERI and groundwater data are interpreted in terms of subsurface geochemistry is affected. 4 refs., 4 figs.

  13. Inter-relationship between shallow and deep aquifers under the influence of deep groundwater exploitation in the North China Plain

    Science.gov (United States)

    Han, Dongmei; Cao, Guoliang; Love, Andrew J.

    2017-04-01

    In the North China Plain (NCP), the interaction between shallow and deep groundwater flow systems enhanced by groundwater extraction has been investigated using multi-isotopic and chemical tracers for understanding the mechanism of salt water transport, which has long been one of the major regional environmental hydrogeological problems in NCP. Information about the problem will be determined using multiple lines of evidence, including field surveys of drilling and water sampling, as well as laboratory experiments and physical and numerical simulations. A conceptual model of groundwater flow system along WE cross-section from piedmont area to coastal region (Shijiazhuang-Hengshui-Cangzhou) has been developed and verified by geochemical modeling. A combined hydrogeochemical and isotopic investigation using ion relationships such as Cl/Br ratios, and environment isotopes (δ 18O, δ 2H, δ 34SSO4-δ 18OSO4, δ 15NNO_3-δ 18ONO_3, δ 13C and 87Sr/86Sr) was reviewed and carried for determining the sources of aquifer recharge, the origin of solutes and the mixing processes in groundwater flow system under the anthropogenic pumping and pollution. Results indicate that hydrochemistry of groundwater is characterized by mixing between end-members coming directly from Piedmont recharge areas, saline groundwater formed during geohistorical transgression in the shallow aquifers of central plain, and to groundwater circulating in a deeply buried Quaternary sediments. We also reviewed the groundwater age (tritium contents, 14C ages, 3H-3He ages, basin-scale flow modeling ages of groundwater) to recognize the local distributed recharge in this strongly exploited aquifer system. Finally, combined with the 1-D Cl transport modeling for the pore water of clay-rich aquitard, we reveal that salt transport in the aquitard is primarily controlled by vertical diffusion on million years' time scale, and the observed the salinized groundwater in deep aquifer may be caused by passing

  14. Fusion Pore Diameter Regulation by Cations Modulating Local Membrane Anisotropy

    Directory of Open Access Journals (Sweden)

    Doron Kabaso

    2012-01-01

    Full Text Available The fusion pore is an aqueous channel that is formed upon the fusion of the vesicle membrane with the plasma membrane. Once the pore is open, it may close again (transient fusion or widen completely (full fusion to permit vesicle cargo discharge. While repetitive transient fusion pore openings of the vesicle with the plasma membrane have been observed in the absence of stimulation, their frequency can be further increased using a cAMP-increasing agent that drives the opening of nonspecific cation channels. Our model hypothesis is that the openings and closings of the fusion pore are driven by changes in the local concentration of cations in the connected vesicle. The proposed mechanism of fusion pore dynamics is considered as follows: when the fusion pore is closed or is extremely narrow, the accumulation of cations in the vesicle (increased cation concentration likely leads to lipid demixing at the fusion pore. This process may affect local membrane anisotropy, which reduces the spontaneous curvature and thus leads to the opening of the fusion pore. Based on the theory of membrane elasticity, we used a continuum model to explain the rhythmic opening and closing of the fusion pore.

  15. Enzyme screening with synthetic multifunctional pores: Focus on biopolymers

    Science.gov (United States)

    Sordé, Nathalie; Das, Gopal; Matile, Stefan

    2003-01-01

    This report demonstrates that a single set of identical synthetic multifunctional pores can detect the activity of many different enzymes. Enzymes catalyzing either synthesis or degradation of DNA (exonuclease III or polymerase I), RNA (RNase A), polysaccharides (heparinase I, hyaluronidase, and galactosyltransferase), and proteins (papain, ficin, elastase, subtilisin, and pronase) are selected to exemplify this key characteristic of synthetic multifunctional pore sensors. Because anionic, cationic, and neutral substrates can gain access to the interior of complementarily functionalized pores, such pores can be the basis for very user-friendly screening of a broad range of enzymes. PMID:14530413

  16. Pore-size-distribution of cationic polyacrylamide hydrogels. Progress report

    Energy Technology Data Exchange (ETDEWEB)

    Kremer, M.; Prausnitz, J.M.

    1992-06-01

    The pore size distribution of a AAm/MAPTAC (acrylamide copolymerized with (3-methacrylamidopropyl)trimethylammonium chloride) hydrogel was investigated using Kuga`s mixed-solute-exclusion method, taking into account the wall effect. A Brownian-motion model is also used. Results show the feasibility of determining pore-size distribution of porous materials using the mixed-solute-exclusion method in conjunction with solution of the Fredholm equation; good agreement was obtained with experiment, even for bimodal pore structures. However, different pore size distributions were calculated for the two different probe-solutes (Dextran and poly(ethylene glycol/oxide)). Future work is outlined. 32 figs, 25 refs.

  17. Pore-size-distribution of cationic polyacrylamide hydrogels

    Energy Technology Data Exchange (ETDEWEB)

    Kremer, M.; Prausnitz, J.M.

    1992-06-01

    The pore size distribution of a AAm/MAPTAC (acrylamide copolymerized with (3-methacrylamidopropyl)trimethylammonium chloride) hydrogel was investigated using Kuga's mixed-solute-exclusion method, taking into account the wall effect. A Brownian-motion model is also used. Results show the feasibility of determining pore-size distribution of porous materials using the mixed-solute-exclusion method in conjunction with solution of the Fredholm equation; good agreement was obtained with experiment, even for bimodal pore structures. However, different pore size distributions were calculated for the two different probe-solutes (Dextran and poly(ethylene glycol/oxide)). Future work is outlined. 32 figs, 25 refs.

  18. Ultrafast laser fabrication of submicrometer pores in borosilicate glass.

    Science.gov (United States)

    An, Ran; Uram, Jeffrey D; Yusko, Erik C; Ke, Kevin; Mayer, Michael; Hunt, Alan J

    2008-05-15

    We demonstrate rapid fabrication of submicrometer-diameter pores in borosilicate glass using femtosecond laser machining and subsequent wet-etch techniques. This approach allows direct and repeatable fabrication of high-quality pores with diameters of 400-800 nm. Such small pores coupled with the desirable electrical and chemical properties of glass enable sensitive resistive-pulse analysis to determine the size and concentration of macromolecules and nanoparticles. Plasma-enhanced chemical vapor deposition allows further reduction of pore diameters to below 300 nm.

  19. Tension-induced vesicle fusion: pathways and pore dynamics

    DEFF Research Database (Denmark)

    Shillcock, Julian C.

    2008-01-01

    and eventually opens a pore to complete the fusion process. In pathway II, at higher tension, a stalk is formed during the fusion process that is then transformed by transmembrane pore formation into a fusion pore. Whereas the latter pathway II resembles stalk pathways as observed in other simulation studies...... fusion time on membrane tension implies that the fusion process is completed by overcoming two energy barriers with scales of 13kBT and 11kBT. The fusion pore radius as a function of time has also been extracted from the simulations, and provides a quantitative measure of the fusion dynamics which...

  20. GROUNDWATER HYDROCHEMISTRY EVALUATION IN RURAL ...

    African Journals Online (AJOL)

    Osondu

    2012-10-09

    Oct 9, 2012 ... the quality of groundwater from domestic water supply boreholes across rural Botswana. Ionic ... quality limits the supply of potable fresh water. To utilize and protect valuable water ..... prescribed specification of World Health.

  1. Groundwater Vulnerability Regions of Iowa

    Data.gov (United States)

    Iowa State University GIS Support and Research Facility — The regions onThis map represent areas with similar hydrogeologic characteristics thought to represent similar potentials for contamination of groundwater and/or...

  2. INFLUENCE OF SEEPAGE FACE OBLIQUITY ON DISCHARGE OF GROUNDWATER AND ITS POLLUTANT INTO LAKE FROM A TYPICAL UNCONFINED AQUIFER

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Lab experiment and mathematical simulation Modular three dimensional finite difference groundwater (MODFLOW) were performed in a soil tank to simulate the hydrogeochemical interaction between lake and typical unconfined aquifer. Results show that the velocity decreases exponentially with the transect distance on seepage face. The maximal velocity occurs at the top point of seepage face. The obliquity of seepage face has a great influence on the maximum and distribution of seepage velocity. With the increase of the obliquity of seepage face, the maximal velocity decreases quickly and the velocity distribution becomes much more even. Most of groundwater flow and pollutant flux discharges through a narrow portion near the top of seepage face. The flow and mass concentrated in the narrow portion increase with the decrease of the obliquity of seepage face. These will benefit to design a reasonable and economical scenario to manage lakeshore and to control the pollution of lake water near lakeshore.

  3. Pore-scale visualization of the mobilization of a partially wetting droplet

    Science.gov (United States)

    Hsu, Shao-Yiu; Hilpert, Markus

    2016-09-01

    We experimentally investigated the mobilization process of a partially wetting droplet in a pore doublet model. The process, involving contact line movement, liquid film generation, and interface deformation, has not been fully understood and modeled. In equilibrium, the droplet sat in one of the capillary tubes of the pore doublet, and the contact lines of the droplet were pinned with nonzero contact angles. The droplet was subject to pressure differences that were generated by pumping the continuous liquid into the pore doublet at different flow rates. At low flow rates, the droplet moved with sliding contact lines, and the shapes of the droplet's menisci roughly resembled spherical caps. When the flow rate increased, the velocity of the droplet increased, and the shapes of the liquid-liquid interfaces changed dramatically forming finger-like structures and films. Once films form, the classical Young-Laplace equation, which assumes a spherical interface, is not sufficient to describe droplet mobilization and the corresponding pressure drops. The films ruptured as the droplet moved forward, and a certain amount of droplet liquid was left behind. When the flow rates reached a certain level, the droplet snapped off from the tube wall and rolled while being surrounded by thin films formed by the continuous liquid.

  4. Development of an optimal velocity selection method with velocity obstacle

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Min Geuk; Oh, Jun Ho [KAIST, Daejeon (Korea, Republic of)

    2015-08-15

    The Velocity obstacle (VO) method is one of the most well-known methods for local path planning, allowing consideration of dynamic obstacles and unexpected obstacles. Typical VO methods separate a velocity map into a collision area and a collision-free area. A robot can avoid collisions by selecting its velocity from within the collision-free area. However, if there are numerous obstacles near a robot, the robot will have very few velocity candidates. In this paper, a method for choosing optimal velocity components using the concept of pass-time and vertical clearance is proposed for the efficient movement of a robot. The pass-time is the time required for a robot to pass by an obstacle. By generating a latticized available velocity map for a robot, each velocity component can be evaluated using a cost function that considers the pass-time and other aspects. From the output of the cost function, even a velocity component that will cause a collision in the future can be chosen as a final velocity if the pass-time is sufficiently long enough.

  5. Rock Physics of Reservoir Rocks with Varying Pore Water Saturation and Pore Water Salinity

    DEFF Research Database (Denmark)

    Katika, Konstantina

    be performed on specific geological structures and why it is sometimes successful; has yet to be established. The presence of both oil and water in the pore space, several different ions present in the injected water that contact the pore walls, possible changes in the fluid wetting the surface of the grains......Advanced waterflooding (injection of water with selective ions in reservoirs) is a method of enhanced oil recovery (EOR) that has attracted the interest of oil and gas companies that exploit the Danish oil and gas reservoirs. This method has been applied successfully in oil reservoirs...... and in the Smart Water project performed in a laboratory scale in order to evaluate the EOR processes in selected core plugs. A major step towards this evaluation is to identify the composition of the injected water that leads to increased oil recovery in reservoirs and to define changes in the petrophysical...

  6. Entropy of Shortest Distance (ESD as Pore Detector and Pore-Shape Classifier

    Directory of Open Access Journals (Sweden)

    Klaudia Oleschko

    2013-06-01

    Full Text Available The entropy of shortest distance (ESD between geographic elements (“elliptical intrusions”, “lineaments”, “points” on a map, or between "vugs", "fractures" and "pores" in the macro- or microscopic images of triple porosity naturally fractured vuggy carbonates provides a powerful new tool for the digital processing, analysis, classification and space/time distribution prognostic of mineral resources as well as the void space in carbonates, and in other rocks. The procedure is applicable at all scales, from outcrop photos, FMI, UBI, USI (geophysical imaging techniques to micrographs, as we shall illustrate through some examples. Out of the possible applications of the ESD concept, we discuss in details the sliding window entropy filtering for nonlinear pore boundary enhancement, and propose this procedure as unbiased thresholding technique.

  7. Velocity dependant splash behaviour

    Science.gov (United States)

    Hamlett, C. A. E.; Shirtcliffe, N. J.; McHale, G.; Ahn, S.; Doerr, S. H.; Bryant, R.; Newton, M. I.

    2012-04-01

    Extreme soil water repellency can occur in nature via condensation of volatile organic compounds released during wildfires and can lead to increased erosion rate. Such extreme water repellent soil can be classified as superhydrophobic and shares similar chemical and topographical features to specifically designed superhydrophobic surfaces. Previous studies using high speed videography to investigate single droplet impact behaviour on artificial superhydrophobic have revealed three distinct modes of splash behaviour (rebound, pinned and fragmentation) which are dependent on the impact velocity of the droplet. In our studies, using high-speed videography, we show that such splash behaviour can be replicated on fixed 'model' water repellent soils (hydrophobic glass beads/particles). We show that the type of splash behaviour is dependent on both the size and chemical nature of the fixed particles. The particle shape also influences the splash behaviour as shown by drop impact experiments on fixed sand samples. We have also studied soil samples, as collected from the field, which shows that the type of droplet splash behaviour can lead to enhanced soil particle transport.

  8. Pore morphologies of root induced biopores from single pore to network scale investigated by XRCT

    Science.gov (United States)

    Peth, Stephan; Wittig, Marlen C.; Uteau Puschmann, Daniel; Pagenkemper, Sebastian; Haas, Christoph; Holthusen, Dörthe; Horn, Rainer

    2015-04-01

    Biopores are assumed to be an important factor for nutrient acquisition by providing biologically highly active soil-root interfaces to re-colonizing roots and controlling oxygen and water flows at the pedon scale and within the rhizosphere through the formation of branching channel networks which potentially enhance microbial turnover processes. Characteristic differences in pore morphologies are to be expected depending on the genesis of biopores which, for example, can be earthworm-induced or root-induced or subsequently modified by one of the two. Our understanding of biophysical interactions between plants and soil can be significantly improved by quantifying 3D biopore architectures across scales ranging from single biopores to pedon scale pore networks and linking pore morphologies to microscale measurements of transport processes (e.g. oxygen diffusion). While a few studies in the past have investigated biopore networks on a larger scale yet little is known on the micro-morphology of root-induces biopores and their associated rhizosphere. Also little data is available on lateral transport of oxygen through the rhizosphere which will strongly influence microbial turnover processes and consequently control the release and uptake of nutrients. This paper highlights results gathered within a research unit on nutrient acquisition from the subsoil. Here we focus on X-ray microtomography (XRCT) studies ranging from large soil columns (70 cm length and 20 cm diameter) to individual biopores and its surrounding rhizosphere. Samples were collected from sites with different preceding crops (fescue, chicory, alfalfa) and various cropping durations (1-3 years). We will present an approach for quantitative image analysis combined with micro-sensor measurements of oxygen diffusion and spatial gradients of O2 partial pressures to relate pore structure with transport functions. Implications of various biopore architectures for the accessibility of nutrient resources in

  9. Optimal and Sustainable Groundwater Extraction

    Directory of Open Access Journals (Sweden)

    Christopher A. Wada

    2010-08-01

    Full Text Available With climate change exacerbating over-exploitation, groundwater scarcity looms as an increasingly critical issue worldwide. Minimizing the adverse effects of scarcity requires optimal as well as sustainable patterns of groundwater management. We review the many sustainable paths for groundwater extraction from a coastal aquifer and show how to find the particular sustainable path that is welfare maximizing. In some cases the optimal path converges to the maximum sustainable yield. For sufficiently convex extraction costs, the extraction path converges to an internal steady state above the level of maximum sustainable yield. We describe the challenges facing groundwater managers faced with multiple aquifers, the prospect of using recycled water, and the interdependence with watershed management. The integrated water management thus described results in less water scarcity and higher total welfare gains from groundwater use. The framework also can be applied to climate-change specifications about the frequency, duration, and intensity of precipitation by comparing before and after optimal management. For the case of South Oahu in Hawaii, the prospect of climate change increases the gains of integrated groundwater management.

  10. Submarine ground-water discharge: nutrient loading and nitrogen transformations

    Science.gov (United States)

    Kroeger, Kevin D.; Swarzenski, Peter W.; Crusius, John; Bratton, John F.; Charette, Matthew A.

    2006-01-01

    Eutrophication of coastal waters due to nonpoint source land-derived nitrogen (N) loads is a worldwide phenomenon and perhaps the greatest agent of change altering coastal ecology (National Research Council, 2000; Howarth and others, 2000). Within the United States, a majority of estuaries have been determined to be moderately to severely impaired by eutrophication associated with increasing nutrient loads (Bricker and others, 1999).In coastal watersheds with soils of high hydraulic conductivity and permeable coastal sediments, ground water is a major route of transport of freshwater and its solutes from land to sea. Freshwater flowing downgradient from aquifers may either discharge from a seepage face near the intertidal zone, or flow directly into the sea as submarine ground-water discharge (SGD) (fig. 1). In the coastal aquifer, entrainment of saline pore water occurs prior to discharge, producing a gradient in ground-water salinity from land to sea, referred to as a subterranean estuary (Moore, 1999). In addition, processes including density-driven flow and tidal pumping create brackish and saline ground-water circulation. Hence, submarine ground-water discharge often consists of a substantial amount of recirculating seawater. Mixing of fresh and saline ground waters in the context of coastal sediments may alter the chemical composition of the discharging fluid. Depending on the biogeochemical setting, removal of fixed N due to processes leading to N2 (dinitrogen gas) production in the nearshore aquifer and subterranean estuary may significantly attenuate land-derived N loads; or, processes such as ion exchange and tidal pumping in the subterranean estuary may substantially accelerate the transport of both land-derived and sediment re-mineralized N to estuarine water columns.As emphasized by Burnett and others (2001, 2002), a fundamental problem in evaluating the importance of ground-water discharge in marine geochemical budgets is the difficulty of collecting

  11. Groundwater vulnerability mapping in Guadalajara aquifers system (Western Mexico)

    Science.gov (United States)

    Rizo-Decelis, L. David; Marín, Ana I.; Andreo, Bartolomé

    2016-04-01

    Groundwater vulnerability mapping is a practical tool to implement strategies for land-use planning and sustainable socioeconomic development coherent with groundwater protection. The objective of vulnerability mapping is to identify the most vulnerable zones of catchment areas and to provide criteria for protecting the groundwater used for drinking water supply. The delineation of protection zones in fractured aquifers is a challenging task due to the heterogeneity and anisotropy of hydraulic conductivities, which makes difficult prediction of groundwater flow organization and flow velocities. Different methods of intrinsic groundwater vulnerability mapping were applied in the Atemajac-Toluquilla groundwater body, an aquifers system that covers around 1300 km2. The aquifer supplies the 30% of urban water resources of the metropolitan area of Guadalajara (Mexico), where over 4.6 million people reside. Study area is located in a complex neotectonic active volcanic region in the Santiago River Basin (Western Mexico), which influences the aquifer system underneath the city. Previous works have defined the flow dynamics and identified the origin of recharge. In addition, the mixture of fresh groundwater with hydrothermal and polluted waters have been estimated. Two main aquifers compose the multilayer system. The upper aquifer is unconfined and consists of sediments and pyroclastic materials. Recharge of this aquifer comes from rainwater and ascending vertical fluids from the lower aquifer. The lower aquifer consists of fractured basalts of Pliocene age. Formerly, the main water source has been the upper unit, which is a porous and unconsolidated unit, which acts as a semi-isotropic aquifer. Intense groundwater usage has resulted in lowering the water table in the upper aquifer. Therefore, the current groundwater extraction is carried out from the deeper aquifer and underlying bedrock units, where fracture flow predominates. Pollution indicators have been reported in

  12. Aquifers and hyporheic zones: Towards an ecological understanding of groundwater

    Science.gov (United States)

    Hancock, Peter J.; Boulton, Andrew J.; Humphreys, William F.

    2005-03-01

    Ecological constraints in subsurface environments relate directly to groundwater flow, hydraulic conductivity, interstitial biogeochemistry, pore size, and hydrological linkages to adjacent aquifers and surface ecosystems. Groundwater ecology has evolved from a science describing the unique subterranean biota to its current form emphasising multidisciplinary studies that integrate hydrogeology and ecology. This multidisciplinary approach seeks to elucidate the function of groundwater ecosystems and their roles in maintaining subterranean and surface water quality. In aquifer-surface water ecotones, geochemical gradients and microbial biofilms mediate transformations of water chemistry. Subsurface fauna (stygofauna) graze biofilms, alter interstitial pore size through their movement, and physically transport material through the groundwater environment. Further, changes in their populations provide signals of declining water quality. Better integrating groundwater ecology, biogeochemistry, and hydrogeology will significantly advance our understanding of subterranean ecosystems, especially in terms of bioremediation of contaminated groundwaters, maintenance or improvement of surface water quality in groundwater-dependent ecosystems, and improved protection of groundwater habitats during the extraction of natural resources. Overall, this will lead to a better understanding of the implications of groundwater hydrology and aquifer geology to distributions of subsurface fauna and microbiota, ecological processes such as carbon cycling, and sustainable groundwater management. Les contraintes écologiques dans les environnements de subsurface sont en relation directe avec les écoulements des eaux souterraines, la conductivité hydraulique, la biogéochimie des milieux interstitiels, la taille des pores, et les liens hydrologiques avec les aquifères et les écosystèmes adjacents. L'écologie des eaux souterraines a évolué d'une science décrivant uniquement les

  13. Monitoring and Analysis of Transient Pore Water Pressures in Large Suspended Rock Slides near Poschiavo, CH

    Science.gov (United States)

    de Palézieux, Larissa; Loew, Simon; Zwahlen, Peter

    2016-04-01

    Many mountain slopes in the Alps exhibit large compound rock slides or Deep Seated Gravitational Slope Deformations. Due to the basal rupture plane geometry and the cumulative displacement magnitude such landslide bodies are often strongly deformed, highly fractured and - at least locally - very permeable. This can lead to high infiltration rates and low phreatic groundwater tables. This is also the situation in the studied mountain slopes southwest of Poschiavo, where large suspended rockslides occur, with very little surface runoff at high elevations, and torrents developing only at the elevation of the basal rupture planes. Below the landslide toes, at altitudes below ca. 1700 m a.s.l., groundwater appears forming spring lines or distributed spring clusters. Within the scope of the design of a hydropower pump storage plant in the Poschiavo valley by Lagobianco SA (Repower AG), numerous cored and deep boreholes (of 50 to 300 m depth) have been drilled along the planned pressure tunnel alignement at elevations ranging from 963 to 2538 m a.s.l. in the years 2010 and 2012. In several boreholes Lugeon and transient pressure tests were executed and pore water pressure sensors installed in short monitoring sections at various depths. Most of these boreholes intersect deep rockslides in crystalline rocks and limestones, showing highly fragmented rock masses and cohesionless cataclastic shear zones of several tens of meters thickness. This study explores these borehole observations in landslides and adjacent stable slopes and links them to the general hydrologic and hydrogeologic framework. The analysis of the pore water pressure data shows significant variability in seasonal trends and short-term events (from snow melt and summer rain storms) and remarkable pressure differences over short horizontal and vertical distances. This reflects rock mass damage within landslide bodies and important sealing horizons at their base. Based on water balances, the estimated effective

  14. 2D-Cell Experiment on Methyl Tert-Butyl Ether Transport in Saturated Zone of Groundwater

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    As an additive of gasoline, methyl tert-butyl ether (MTBE) has a higher solubility in water, which is about 20 times as high as that of benzene. This characteristic results in MTBE dissolving out of the gasoline into the soil and groundwater. Due to relative unique physicochemical behavior of MTBE it would be an ideal candidate for use in environmental forensic investigations. In order to study the transport and distribution of MTBE in saturated zone of ground water, a two-dimensional experimental cell was setup to simulate the real environment of the groundwater flow.The effects of soil and groundwater flow velocity on the MTBE transport were investigated. The results show that the mobile distance of MTBE in vertical direction was smaller than that in horizontal direction paralleling with the groundwater flow. Because the main dynamics of groundwater flow direction was convection and dispersion, the movement of MTBE is also diffusion in the vertical direction. In addition, the transport of MTBE was more quick in high permeability porous media, and the increase of groundwater flow velocity can accelerate the MTBE plume development, but the irregularity and randomness of the plume are enhanced synchronously. These research results can give some helps for the investigation of MTBE movement in the groundwater, also can make some references for other petroleum contamination behavior.

  15. Effects of supersaturation on pore shape in solid

    Science.gov (United States)

    Wei, P. S.; Hsiao, S. Y.

    2017-02-01

    The shape of a pore resulting from a bubble entrapped by a solidification front with different supersaturation ratios is predicted in this work. Supersaturation ratio, representing the ratio between solute concentration and saturation solute concentration, determines nucleation of a bubble and development of the pore shape in the early stage. Pore formation and its shape in solid influence contemporary issues of biology, engineering, foods, geophysics and climate change, etc. This work extends and combines previous models accounting for realistic mass and momentum transport, and physico-chemical equilibrium of solute gas across the bubble cap to self-consistently determine shape of the bubble cap beyond the solidification front and the pore shape in solid. The study also deal with that pore formation can be resulted from three different mechanisms, depending on the directions and magnitude of solute gas transport across the bubble cap. Case 1 is subject to solute transport from the pore across the cap into the surrounding liquid in the early stage. Cases 2a and 2b indicate opposite direction of solute transport. In contrast to Case 2b, the effect of solute transport on solute gas pressure in the pore in Case 2a is stronger than that of pore volume expansionin the last stage. The results find that an increase in supersaturation ratio decreases pore radius and time for bubble entrapment in Case 1. The bubble cannot be entrapped in Case 2. The predicted pore shape in solid agrees with experimental data. Understanding, prediction and control of the growth of the pore shape have therefore been obtained.

  16. Examples of Vector Velocity Imaging

    DEFF Research Database (Denmark)

    Hansen, Peter M.; Pedersen, Mads M.; Hansen, Kristoffer L.

    2011-01-01

    To measure blood flow velocity in vessels with conventional ultrasound, the velocity is estimated along the direction of the emitted ultrasound wave. It is therefore impossible to obtain accurate information on blood flow velocity and direction, when the angle between blood flow and ultrasound wa...... with a 90° angle on the vessel. Moreover secondary flow in the abdominal aorta is illustrated by scanning on the transversal axis....

  17. A fiber matrix model for the filtration through fenestral pores in a compressible arterial intima.

    Science.gov (United States)

    Huang, Y; Rumschitzki, D; Chien, S; Weinbaum, S

    1997-04-01

    We advance a new hypothesis to explain the changes in hydraulic conductivity of an intact artery wall with transmural pressure previously observed by Tedgui and Lever [Am. J. Physiol. 247 (Heart Circ. Physiol. 16): H784-H791, 1984] and Baldwin and Wilson [Am. J. Physiol. 264 (Heart Circ. Physiol. 33): H26-H32, 1993]. This hypothesis suggests that compaction due to pressure loading of the proteoglycan matrix in the arterial intima near fenestral pores of the internal elastic lamina (IEL) leads to a narrowing of the pore entrance area and a large decrease in local intrinsic Darcy permeability of the matrix. To quantitatively assess the feasibility of this mechanism, a local two-dimensional model is proposed to study filtration flow in the vicinity of fenestral pores in a compressible intima. Using a heterogenous fiber matrix theory, we first predict the change in Darcy permeability with intimal thickness (Li). The model then calculates local velocity profiles and pressure distributions in the intima and media. The results show a marked nonlinear steepening of intimal pressure profiles near fenestral pores when the intima thins at higher luminal pressures. The predicted relative change in resistances of the IEL (with intima, R(I)) and of the media (Rm) shows a steep increase in R(I)/Rm when Li is <20% of its unstressed value. Numerical results also suggest that intimal compression has a limiting behavior in which the much stiffer collagen fibrils inhibit further compaction at high pressures after the proteoglycan matrix is maximally compressed. Predictions are also presented to show how different transmural pressures alter growth of an intimal horseradish peroxidase spot that derives from a localized (a single cell's boundary) endothelial leakage. Such a prediction is amenable to experimental verification.

  18. Reversible Self-Actuated Thermo-Responsive Pore Membrane

    Science.gov (United States)

    Park, Younggeun; Gutierrez, Maria Paz; Lee, Luke P.

    2016-12-01

    Smart membranes, which can selectively control the transfer of light, air, humidity and temperature, are important to achieve indoor climate regulation. Even though reversible self-actuation of smart membranes is desirable in large-scale, reversible self-regulation remains challenging. Specifically, reversible 100% opening/closing of pore actuation showing accurate responsiveness, reproducibility and structural flexibility, including uniform structure assembly, is currently very difficult. Here, we report a reversible, thermo-responsive self-activated pore membrane that achieves opening and closing of pores. The reversible, self-actuated thermo-responsive pore membrane was fabricated with hybrid materials of poly (N-isopropylacrylamide), (PNIPAM) within polytetrafluoroethylene (PTFE) to form a multi-dimensional pore array. Using Multiphysics simulation of heat transfer and structural mechanics based on finite element analysis, we demonstrated that pore opening and closing dynamics can be self-activated at environmentally relevant temperatures. Temperature cycle characterizations of the pore structure revealed 100% opening ratio at T = 40 °C and 0% opening ratio at T = 20 °C. The flexibility of the membrane showed an accurate temperature-responsive function at a maximum bending angle of 45°. Addressing the importance of self-regulation, this reversible self-actuated thermo-responsive pore membrane will advance the development of future large-scale smart membranes needed for sustainable indoor climate control.

  19. Hydrodemetallization of residue (Part 3). Influence of catalyst pore size

    Energy Technology Data Exchange (ETDEWEB)

    Hinuma, Yutaka; Kushiyama, Akira; Kobayashi, Satoru; Aizawa, Reiji; Inoue, Keiichi; Shimizu, Yoshikazu (National Research Inst. for Pollution and Resources, Tsukuba (Japan))

    1989-03-25

    Influence of catalyst pore size on hydrodemetallization of residues was studied, Starting oils were Khafji atmospheric residue and Morichal crude and two catalysts of alumina which have 93A and 160A mean pore diameters respectively and Mo was supported, were used. The rate at which asphaltene(A) was decomposed to maltene(M), related large to the demetallization of whole heavy oil and larger the pore diameter of catalyst, higher the demetallizing activity. But in the demetallization from A and M, the influence of pore size was different and vanadium(V) removal from A was preferable for larger pore size but was reverse from M. These were caused by the difference of diffusion in their pores. Ni was more difficult to remove than V. Catalyst of small pore size was preferable for simultaneous desulfurization, because sulfur compounds were composed of smaller molecular weight distribution. The decomposition of A started preferentially from part having large number of peripheral carbon in condensed aromatic ring or f{sub a} (aromaticity) and the catalyst of large pore size affected large on the structural change of A. 12 ref., 7 figs., 5 tabs.

  20. The Pore Structure of Direct Methanol Fuel Cell Electrodes

    DEFF Research Database (Denmark)

    Lund, Peter Brilner

    2005-01-01

    The pore structure and morphology of direct methanol fuel cell electrodes are characterized using mercury intrusion porosimetry and scanning electron microscopy. It is found that the pore size distributions of printed primer and catalyst layers are largely dictated by the powders used to make the...

  1. Reversible Self-Actuated Thermo-Responsive Pore Membrane.

    Science.gov (United States)

    Park, Younggeun; Gutierrez, Maria Paz; Lee, Luke P

    2016-12-19

    Smart membranes, which can selectively control the transfer of light, air, humidity and temperature, are important to achieve indoor climate regulation. Even though reversible self-actuation of smart membranes is desirable in large-scale, reversible self-regulation remains challenging. Specifically, reversible 100% opening/closing of pore actuation showing accurate responsiveness, reproducibility and structural flexibility, including uniform structure assembly, is currently very difficult. Here, we report a reversible, thermo-responsive self-activated pore membrane that achieves opening and closing of pores. The reversible, self-actuated thermo-responsive pore membrane was fabricated with hybrid materials of poly (N-isopropylacrylamide), (PNIPAM) within polytetrafluoroethylene (PTFE) to form a multi-dimensional pore array. Using Multiphysics simulation of heat transfer and structural mechanics based on finite element analysis, we demonstrated that pore opening and closing dynamics can be self-activated at environmentally relevant temperatures. Temperature cycle characterizations of the pore structure revealed 100% opening ratio at T = 40 °C and 0% opening ratio at T = 20 °C. The flexibility of the membrane showed an accurate temperature-responsive function at a maximum bending angle of 45°. Addressing the importance of self-regulation, this reversible self-actuated thermo-responsive pore membrane will advance the development of future large-scale smart membranes needed for sustainable indoor climate control.

  2. A FILTRATION METHOD AND APPARATUS INCLUDING A ROLLER WITH PORES

    DEFF Research Database (Denmark)

    2008-01-01

    The present invention offers a method for separating dry matter from a medium. A separation chamber is at least partly defined by a plurality of rollers (2,7) and is capable of being pressure regulated. At least one of the rollers is a pore roller (7) having a surface with pores allowing permeabi...

  3. Bacteriocins : mechanism of membrane insertion and pore formation

    NARCIS (Netherlands)

    Moll, Gert N.; Konings, Wil N.; Driessen, Arnold J.M.

    1999-01-01

    Lactic acid bacteria produce several types of pore forming peptides. Class I bacteriocins are lantibiotics that contain (methyl)lanthionine residues that may form intramolecular thioether rings. These peptides generally have a broad spectrum of activity and form unstable pores. Class II bacteriocins

  4. Pore size distribution in tablets measured with a morphological sieve

    NARCIS (Netherlands)

    Wu, Yu San; van Vliet, Lucas J.; Frijlink, Henderik W.; van der Voort Maarschalk, Kees

    2007-01-01

    Porosity and pore structure are important characteristics of tablets, since they influence mechanical strength and many other proper-ties. This paper proposes an alternative method for the characterization of pore structure based on image analysis of SEM micrographs. SEM images were made of sodium c

  5. Pore structure and growth kinetics in carbon materials

    Energy Technology Data Exchange (ETDEWEB)

    Bose, S.

    1978-04-01

    Pore structure of glassy carbon (GC) and pyrolytic graphite (PG) have been investigated. GC is one of the most impervious of solids finding applications in prosthetic devices and fuel cells while PG is used extensively in the aerospace industry. One third of the microstructure of GC consists of closed pores inaccessible to fluids. The microstructure of this material has been characterized using x-ray diffraction (XRD) and high resolution electron microscopy. Small angle x-ray scattering (SAXS) has been used to measure the angstrom sized pores and to follow the evolution of pore surface area as a function of heat treatment temperature (HTT) and heat treatment time (HTt) at constant temperature. From these measurements an analysis of the surface area kinetics was made to find out if rate processes are involved and to locate graphitization occurring at pore surfaces. PG on the other hand has been found to have larger sized pores that comprise five percent of its volume. In addition to being closed these pores are oriented. Some pore models are proposed for PG and the existing scattering theory from oriented ellipsoids is modified to include the proposed shapes.

  6. Bacteriocins : mechanism of membrane insertion and pore formation

    NARCIS (Netherlands)

    Moll, G.N.; Konings, W.N; Driessen, A.J.M.

    1999-01-01

    Lactic acid bacteria produce several types of pore forming peptides. Class I bacteriocins are lantibiotics that contain (methyl)lanthionine residues that may form intramolecular thioether rings. These peptides generally have a broad spectrum of activity and form unstable pores. Class II bacteriocins

  7. Letter to the editor: Diffusion under pore saturation conditions

    NARCIS (Netherlands)

    Krishna, R.; van Baten, J.M.

    2010-01-01

    In the article "Diffusion Under Pore Saturaton Conditions", Lettat et al. (1) presents a model to describe mixture diffusion in MFI zeolite under conditions of pore saturation. As a motivation for developing their model they remark ‘‘the classical adsorbed-phase diffusion models based on the Maxwell

  8. Groundwater potential zoning of a peri-urban wetland of south Bengal Basin, India.

    Science.gov (United States)

    Sahu, Paulami; Sikdar, Pradip K

    2011-03-01

    Demand for groundwater for drinking, agricultural, and industrial purposes has increased due to rapid increase in population. Therefore, it is imperative to assess the groundwater potential of different areas, especially in a fragile wetland ecosystem to select appropriate sites for developing well fields to minimize adverse environmental impacts of groundwater development. This study considers East Calcutta Wetlands (ECW)--a freshwater peri-urban inland wetland ecosystem located at the lower part of the deltaic alluvial plain of South Bengal Basin and east of Kolkata city. This wetland is well known over the world for its resource recovery systems developed by local people through ages, using wastewater of the city. The subsurface geology is completely blanketed by the Quaternary sediments comprising a succession of silty clay, sand of various grades, and sand mixed with occasional gravels and thin intercalations of silty clay. Groundwater occurs mostly under confined condition except in those places where the top aquitard has been obliterated due to scouring action of past channels. The groundwater in the study area is being over-extracted at the rate of 65 × 10(3) m(3)/day. Overlay analysis in Geographic Information System platform using multiple criteria such as water quality index, hydraulic conductivity, groundwater velocity, and depth to piezometric surface reveals that in and around ECW, there are five groundwater potential zones. About 74% of the aquifer of this area shows very poor to medium groundwater potential. Management options such as minimization of groundwater abstraction by introducing the treated surface water supply system and the implementation of rainwater harvesting and artificial recharge in high-rise buildings and industries are suggested for different potential zones.

  9. Analysis of the applicability of geophysical methods and computer modelling in determining groundwater level

    Science.gov (United States)

    Czaja, Klaudia; Matula, Rafal

    2014-05-01

    The paper presents analysis of the possibilities of application geophysical methods to investigation groundwater conditions. In this paper groundwater is defined as liquid water flowing through shallow aquifers. Groundwater conditions are described through the distribution of permeable layers (like sand, gravel, fractured rock) and impermeable or low-permeable layers (like clay, till, solid rock) in the subsurface. GPR (Ground Penetrating Radar), ERT(Electrical Resistivity Tomography), VES (Vertical Electric Soundings) and seismic reflection, refraction and MASW (Multichannel Analysis of Surface Waves) belong to non - invasive, surface, geophysical methods. Due to differences in physical parameters like dielectric constant, resistivity, density and elastic properties for saturated and saturated zones it is possible to use geophysical techniques for groundwater investigations. Few programmes for GPR, ERT, VES and seismic modelling were applied in order to verify and compare results. Models differ in values of physical parameters such as dielectric constant, electrical conductivity, P and S-wave velocity and the density, layers thickness and the depth of occurrence of the groundwater level. Obtained results for computer modelling for GPR and seismic methods and interpretation of test field measurements are presented. In all of this methods vertical resolution is the most important issue in groundwater investigations. This require proper measurement methodology e.g. antennas with frequencies high enough, Wenner array in electrical surveys, proper geometry for seismic studies. Seismic velocities of unconsolidated rocks like sand and gravel are strongly influenced by porosity and water saturation. No influence of water saturation degree on seismic velocities is observed below a value of about 90% water saturation. A further saturation increase leads to a strong increase of P-wave velocity and a slight decrease of S-wave velocity. But in case of few models only the

  10. Porous Boron Nitride with Tunable Pore Size.

    Science.gov (United States)

    Dai, Jun; Wu, Xiaojun; Yang, Jinlong; Zeng, Xiao Cheng

    2014-01-16

    On the basis of a global structural search and first-principles calculations, we predict two types of porous boron-nitride (BN) networks that can be built up with zigzag BN nanoribbons (BNNRs). The BNNRs are either directly connected with puckered B (N) atoms at the edge (type I) or connected with sp(3)-bonded BN chains (type II). Besides mechanical stability, these materials are predicted to be thermally stable at 1000 K. The porous BN materials entail large surface areas, ranging from 2800 to 4800 m(2)/g. In particular, type-II BN material with relatively large pores is highly favorable for hydrogen storage because the computed hydrogen adsorption energy (-0.18 eV) is very close to the optimal adsorption energy (-0.15 eV) suggested for reversible hydrogen storage at room temperature. Moreover, the type-II materials are semiconductors with width-dependent direct bandgaps, rendering the type-II BN materials promising not only for hydrogen storage but also for optoelectronic and photonic applications.

  11. Freezing of charged colloids in slit pores.

    Science.gov (United States)

    Grandner, Stefan; Klapp, Sabine H L

    2008-12-28

    Using Monte Carlo simulations in the grand canonical and isobaric ensembles we investigate freezing phenomena in a charged colloidal suspension confined to narrow slit pores. Our model involves only the macroions which interact via a Derjaguin-Landau-Verwey-Overbeek (DLVO) potential supplemented by a soft-sphere potential. We focus on DLVO parameters typical for moderately charged silica particles (with charges Z approximately 35) in solvents of low ionic strengths. The corresponding DLVO interactions are too weak to drive a (bulk) freezing transition. Nevertheless, for sufficiently small surface separations L(z) the confined systems display not only layering but also significant in-plane crystalline order at chemical potentials where the bulk system is a globally stable fluid (capillary freezing). At confinement conditions related to two-layer systems the observed in-plane structures are consistent with those detected in ground state calculations for perfect Yukawa bilayers [R. Messina and H. Lowen, Phys. Rev. Lett. 91, 146101 (2003)]. Here we additionally observe (at fixed L(z)) a compression-induced first-order phase transition from a two-layer to a three-layer system with different in-plane structure, in agreement with previous findings for pure hard spheres.

  12. Silicon pore optics developments and status

    Science.gov (United States)

    Bavdaz, Marcos; Wille, Eric; Wallace, Kotska; Shortt, Brian; Collon, Maximilien; Ackermann, Marcelo; Olde Riekerink, Mark; Haneveld, Jeroen; van Baren, Coen; Erhard, Markus; Christensen, Finn; Krumrey, Michael; Burwitz, Vadim

    2012-09-01

    Silicon Pore Optics (SPO) is a lightweight high performance X-ray optics technology being developed in Europe, driven by applications in observatory class high energy astrophysics missions. An example of such application is the former ESA science mission candidate ATHENA (Advanced Telescope for High Energy Astrophysics), which uses the SPO technology for its two telescopes, in order to provide an effective area exceeding 1 m2 at 1 keV, and 0.5 m2 at 6 keV, featuring an angular resolution of 10” or better [1 to 24]. This paper reports on the development activities led by ESA, and the status of the SPO technology. The technology development programme has succeeded in maturing the SPO further and achieving important milestones, in each of the main activity streams: environmental compatibility, industrial production and optical performance. In order to accurately characterise the increasing performance of this innovative optical technology, the associated X-ray test facilities and beam-lines have been refined and upgraded.

  13. Evaluating transport in irregular pore networks

    Science.gov (United States)

    Klimenko, Dimitri A.; Hooman, Kamel; Klimenko, Alexander Y.

    2012-07-01

    A general approach for investigating transport phenomena in porous media is presented. This approach has the capacity to represent various kinds of irregularity in porous media without the need for excessive detail or computational effort. The overall method combines a generalized effective medium approximation (EMA) with a macroscopic continuum model in order to derive a transport equation with explicit analytical expressions for the transport coefficients. The proposed form of the EMA is an anisotropic and heterogeneous extension of Kirkpatrick's EMA [Rev. Mod. Phys.RMPHAT0034-686110.1103/RevModPhys.45.574 45, 574 (1973)] which allows the overall model to account for microscopic alterations in connectivity (with the locations of the pores and the orientation and length of the throat) as well as macroscopic variations in transport properties. A comparison to numerical results for randomly generated networks with different properties is given, indicating the potential for this methodology to handle cases that would pose significant difficulties to many other analytical models.

  14. Sodium Velocity Maps on Mercury

    Science.gov (United States)

    Potter, A. E.; Killen, R. M.

    2011-01-01

    The objective of the current work was to measure two-dimensional maps of sodium velocities on the Mercury surface and examine the maps for evidence of sources or sinks of sodium on the surface. The McMath-Pierce Solar Telescope and the Stellar Spectrograph were used to measure Mercury spectra that were sampled at 7 milliAngstrom intervals. Observations were made each day during the period October 5-9, 2010. The dawn terminator was in view during that time. The velocity shift of the centroid of the Mercury emission line was measured relative to the solar sodium Fraunhofer line corrected for radial velocity of the Earth. The difference between the observed and calculated velocity shift was taken to be the velocity vector of the sodium relative to Earth. For each position of the spectrograph slit, a line of velocities across the planet was measured. Then, the spectrograph slit was stepped over the surface of Mercury at 1 arc second intervals. The position of Mercury was stabilized by an adaptive optics system. The collection of lines were assembled into an images of surface reflection, sodium emission intensities, and Earthward velocities over the surface of Mercury. The velocity map shows patches of higher velocity in the southern hemisphere, suggesting the existence of sodium sources there. The peak earthward velocity occurs in the equatorial region, and extends to the terminator. Since this was a dawn terminator, this might be an indication of dawn evaporation of sodium. Leblanc et al. (2008) have published a velocity map that is similar.

  15. Influence of pore structure on compressive strength of cement mortar.

    Science.gov (United States)

    Zhao, Haitao; Xiao, Qi; Huang, Donghui; Zhang, Shiping

    2014-01-01

    This paper describes an experimental investigation into the pore structure of cement mortar using mercury porosimeter. Ordinary Portland cement, manufactured sand, and natural sand were used. The porosity of the manufactured sand mortar is higher than that of natural sand at the same mix proportion; on the contrary, the probable pore size and threshold radius of manufactured sand mortar are finer. Besides, the probable pore size and threshold radius increased with increasing water to cement ratio and sand to cement ratio. In addition, the existing models of pore size distribution of cement-based materials have been reviewed and compared with test results in this paper. Finally, the extended Bhattacharjee model was built to examine the relationship between compressive strength and pore structure.

  16. Vapor intrusion in soils with multimodal pore-size distribution

    Directory of Open Access Journals (Sweden)

    Alfaro Soto Miguel

    2016-01-01

    Full Text Available The Johnson and Ettinger [1] model and its extensions are at this time the most widely used algorithms for estimating subsurface vapor intrusion into buildings (API [2]. The functions which describe capillary pressure curves are utilized in quantitative analyses, although these are applicable for porous media with a unimodal or lognormal pore-size distribution. However, unaltered soils may have a heterogeneous pore distribution and consequently a multimodal pore-size distribution [3], which may be the result of specific granulometry or the formation of secondary porosity related to genetic processes. The present paper was designed to present the application of the Vapor Intrusion Model (SVI_Model to unsaturated soils with multimodal pore-size distribution. Simulations with data from the literature show that the use of a multimodal model in soils with such pore distribution characteristics could provide more reliable results for indoor air concentration, rather than conventional models.

  17. Role of pore-forming toxins in neonatal sepsis.

    Science.gov (United States)

    Sonnen, Andreas F-P; Henneke, Philipp

    2013-01-01

    Protein toxins are important virulence factors contributing to neonatal sepsis. The major pathogens of neonatal sepsis, group B Streptococci, Escherichia coli, Listeria monocytogenes, and Staphylococcus aureus, secrete toxins of different molecular nature, which are key for defining the disease. Amongst these toxins are pore-forming exotoxins that are expressed as soluble monomers prior to engagement of the target cell membrane with subsequent formation of an aqueous membrane pore. Membrane pore formation is not only a means for immediate lysis of the targeted cell but also a general mechanism that contributes to penetration of epithelial barriers and evasion of the immune system, thus creating survival niches for the pathogens. Pore-forming toxins, however, can also contribute to the induction of inflammation and hence to the manifestation of sepsis. Clearly, pore-forming toxins are not the sole factors that drive sepsis progression, but they often act in concert with other bacterial effectors, especially in the initial stages of neonatal sepsis manifestation.

  18. Surface pore tension and adsorption characteristics of polluted sediment

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Most natural sediment particles have numerous pores and a complex surface texture which facilitates their adsorption of contaminants. Particle surface structure,therefore,is an important instrumental factor in the transport of contaminants,especially in water environments. This paper reports on the results of adsorption-desorption experiments to analyze polluted sediment surface pore tension characteristics performed on samples from the bottom of Guanting Reservoir. In our analysis,the Frenkel-Halsey-Hill(FHH) equation is applied to calculate the fractal dimensions of particles to quantify the surface roughness and pore tension characteristics. The results show that the surface fractal dimensions of sediment particle surfaces normally measure from 2.6 to 2.85. The volume of pores smaller than 10 nm changes significantly after being contaminated with pollutants and the fractal dimension decreases because the pores adsorb the contaminants.

  19. Pore capillary pressure and saturation of methane hydrate bearing sediments

    Institute of Scientific and Technical Information of China (English)

    SUN Shicai; LIU Changling; YE Yuguang; LIU Yufeng

    2014-01-01

    To better understand the relationship between the pore capillary pressure and hydrate saturation in sedi-ments, a new method was proposed. First, the phase equilibria of methane hydrate in fine-grained silica sands were measured. As to the equilibrium data, the pore capillary pressure and saturation of methane hydrate were calculated. The results showed that the phase equilibria of methane hydrates in fine-grained silica sands changed due to the depressed activity of pore water caused by the surface group and negatively charged characteristic of silica particles as well as the capillary pressure in small pores together. The capil-lary pressure increased with the increase of methane hydrate saturation due to the decrease of the available pore space. However, the capillary-saturation relationship could not yet be described quantitatively because of the stochastic habit of hydrate growth.

  20. Interaction between shallow groundwater, saline surface water and nutrient discharge in a seasonal estuary: the Swan-Canning system

    Science.gov (United States)

    Linderfelt, William R.; Turner, Jeffrey V.

    2001-09-01

    The Swan and Canning Rivers converge to form an estuary that is seasonally forced by wet winter and dry summer conditions. The estuary is also tidally forced due to its contact with the Indian Ocean. The perception that the occurrence of nuisance algal blooms has increased in frequency and severity in recent years has prompted the present investigation into the interaction of the shallow groundwater system with the Swan-Canning Estuary. The extent to which this interaction contributes to nutrient delivery to the river is a focus of the work.Groundwater interaction with the upper reaches of the Swan River is shown to occur at three length scales: (i) the scale of the river-bed sediments (i.e. 1000 m). Two-dimensional groundwater flow modelling in plan covering the regionally advected groundwater flow domain of the upper Swan River Estuary from the Causeway to Guildford shows that there is a net groundwater discharge to the Swan River of groundwater discharge of about 80 000 m3/day, or about 29 million m3/year. Between 1987 and 1996, the average surface tributary inflow to the Swan River was about 460 million m3/year. Thus groundwater discharge contributed approximately 6% of the total annual river flow. This percentage is clearly small in comparison to the total river flow. However, in the six months from November to April in summer, tributary flow into the Swan River declines sharply to an average total of approximately 12 million m3. Groundwater discharge during this six-month period is approximately 14 million m3 or about 55% of the surface tributary flow, and thus groundwater is a significant component of the total inflow to the Swan-Canning Estuary during this period. Nutrient concentrations, particularly ammonium, within the sediment pore fluids underlying the river are very high relative to concentrations in the river, such that groundwater discharge rates of this magnitude are capable of introducing significant nutrient loadings to the river. The nitrogen

  1. Contribution of seawater recirculation to submarine groundwater discharge and related nutrient fluxes in two tropical bays

    Science.gov (United States)

    Vautier, Camille; Dulaiova, Henrietta

    2017-04-01

    Hawaiian coastal waters suffer from excess terrestrial nutrient loading, most of which comes from submarine groundwater discharge (SGD). This study quantifies and distinguishes the role of the fresh terrestrial and tidally pumped salt water components of SGD into the nearshore zone of two reefs on the island of Oahu: Maunalua Bay and Kāneohe Bay. The two components of SGD are characterized using isotopic techniques, and the study mainly focuses on the less understood recirculation component. A two-step approach is implemented: first, a conceptual model of groundwater circulation is established; second, nutrient fluxes associated with seawater recirculation are quantified. Groundwater circulation through the beach berm is quantified and characterized using 222Rn and 224Ra activity measurements. Nutrient fluxes are obtained by coupling nutrient concentration measurements and discharge estimates. The isotopic signatures inform us about the influence of the tidal cycle on groundwater circulation. 222Rn, 224Ra, and δ18O isotopes are used to derive apparent ages of the infiltrated seawater and allow us to quantify recirculation rates. The method is also complemented with the use of silicate concentration as tracers of the recirculation process. The trends in apparent ages observed in pore water in Maunalua match previously published conceptual groundwater circulation models and show a sequentially aging pore water circulation loop. However, the ages obtained in Kāneohe suggest a different tidal pumping dynamic that lacks a circulation loop, perhaps resulting from the absence of freshwater discharge. Derived nutrient fluxes show that the autochthonous production of inorganic nitrogen and phosphorus that occurs during seawater recirculation has a significant impact on nutrient cycles in the nearshore areas of the bays. This result suggests that seawater recirculation should be taken into account in biogeochemical studies of coastal areas.

  2. Status of geochemical modeling of groundwater evolution at the Tono in-situ tests site, Japan

    Energy Technology Data Exchange (ETDEWEB)

    Sasamoto, Hiroshi; Yui, Mikazu [Japan Nuclear Cycle Development Inst., Tokai Works, Tokai, Ibaraki (Japan); Arthur, R.C. [Monitor Scientific, L.L.C., Denver, Colorado (United States)

    1999-12-01

    Hydrochemical investigation of Tertiary sedimentary rocks at JNC's Tono in-situ tests site indicate the groundwaters are: meteoric in origin, chemically reducing at depths greater than a few tens of meters in the sedimentary rock, relatively old [carbon-14 ages of groundwaters collected from the lower part of the sedimentary sequence range from 13,000 to 15,000 years BP (before present)]. Ca-Na-HCO{sub 3} type solutions near the surface, changing to Na-HCO{sub 3} type groundwaters with increasing depth. The chemical evolution of the groundwaters is modeled assuming local equilibrium for selected mineral-fluid reactions, taking into account the rainwater origin of these solutions. Results suggest it is possible to interpret approximately the 'real' groundwater chemistry (i.e., pH, Eh, total dissolved concentrations of Si, Na, Ca, K, Al, carbonate and sulfate) if the following assumptions are adopted: CO{sub 2} concentration in the gas phase contacting pore solutions in the overlying soil zone=10{sup -1} bar, minerals in the rock zone that control the solubility of respective elements in the groundwater include; chalcedony (Si), albite (Na), kaolinite (Al), calcite (Ca and carbonate), muscovite (K) and pyrite (Eh and sulfate). It is noted, however, that the available field data may not be sufficient to adequately constrain parameters in the groundwater evolution model. In particular, more detailed information characterizing certain site properties (e.g., the actual mineralogy of 'plagioclase', 'clay' and 'zeolite') are needed to improve the model. Alternative conceptual models of key reactions may also be necessary. For this reason, a model that accounts for ion-exchange reactions among clay minerals, and which is based on the results of laboratory experiments, has also been evaluated in the present study. Further improvements of model considering ion-exchange reactions are needed in future, however. (author)

  3. Biophysics, Pathophysiology and Pharmacology of Ion Channel Gating Pores

    Directory of Open Access Journals (Sweden)

    Adrien eMoreau

    2014-04-01

    Full Text Available Voltage sensor domain (VSDs are a feature of voltage gated ion channel (VGICs and voltage sensitive proteins. They are composed of four transmembrane (TM segments (S1 to S4. Currents leaking through VSDs are called omega or gating pore currents.Gating pores are caused by mutations of the highly conserved positively charged amino acids in the S4 segment that disrupt interactions between the S4 segment and the gating charge transfer center (GCTC. The GCTC separates the intracellular and extracellular water crevices. The disruption of S4–GCTC interactions allows these crevices to communicate and create a fast activating and non-inactivating alternative cation-selective permeation pathway of low conductance, or a gating pore.Gating pore currents have recently been shown to cause periodic paralysis phenotypes. There is also increasing evidence that gating pores are linked to several other familial diseases. For example, gating pores in Nav1.5 and Kv7.2 channels may underlie mixed arrhythmias associated with dilated cardiomyopathy (DCM phenotypes and peripheral nerve hyperexcitability (PNH respectively. There is little evidence for the existence of gating pore blockers. Moreover, it is known that a number of toxins bind to the VSD of a specific domain of Na+ channels. These toxins may thus modulate gating pore currents. This focus on the VSD motif opens up a new area of research centered on developing molecules to treat a number of cell excitability disorders such as epilepsy, cardiac arrhythmias, and pain.The purpose of the present review is to summarize existing knowledge of the pathophysiology, biophysics, and pharmacology of gating pore currents and to serve as a guide for future studies aimed at improving our understanding of gating pores and their pathophysiological roles.

  4. X-ray CT analysis of pore structure in sand

    Science.gov (United States)

    Mukunoki, Toshifumi; Miyata, Yoshihisa; Mikami, Kazuaki; Shiota, Erika

    2016-06-01

    The development of microfocused X-ray computed tomography (CT) devices enables digital imaging analysis at the pore scale. The applications of these devices are diverse in soil mechanics, geotechnical and geoenvironmental engineering, petroleum engineering, and agricultural engineering. In particular, the imaging of the pore space in porous media has contributed to numerical simulations for single-phase and multiphase flows or contaminant transport through the pore structure as three-dimensional image data. These obtained results are affected by the pore diameter; therefore, it is necessary to verify the image preprocessing for the image analysis and to validate the pore diameters obtained from the CT image data. Moreover, it is meaningful to produce the physical parameters in a representative element volume (REV) and significant to define the dimension of the REV. This paper describes the underlying method of image processing and analysis and discusses the physical properties of Toyoura sand for the verification of the image analysis based on the definition of the REV. On the basis of the obtained verification results, a pore-diameter analysis can be conducted and validated by a comparison with the experimental work and image analysis. The pore diameter is deduced from Young-Laplace's law and a water retention test for the drainage process. The results from previous study and perforated-pore diameter originally proposed in this study, called the voxel-percolation method (VPM), are compared in this paper. In addition, the limitations of the REV, the definition of the pore diameter, and the effectiveness of the VPM for an assessment of the pore diameter are discussed.

  5. Predicting salt advection in groundwater from saline aquaculture ponds

    Science.gov (United States)

    Verrall, D. P.; Read, W. W.; Narayan, K. A.

    2009-01-01

    SummaryThis paper predicts saltwater advection in groundwater from leaky aquaculture ponds. A closed form solution for the potential function, stream function and velocity field is derived via the series solutions method. Numerically integrating along different streamlines gives the location (or advection front) of saltwater throughout the domain for any predefined upper time limit. Extending this process produces a function which predicts advection front location against time. The models considered in this paper are easily modified given knowledge of the required physical parameters.

  6. Assessment and validation of groundwater vulnerability to nitrate based on a modified DRASTIC model: a case study in Jilin City of northeast China.

    Science.gov (United States)

    Huan, Huan; Wang, Jinsheng; Teng, Yanguo

    2012-12-01

    The assessment of groundwater vulnerability to pollution has become a useful tool for groundwater pollution prevention and control. Following the theory of overlay index method and with the aid of GIS technique and a statistical method, this study employed a modified DRASTIC model to assess the groundwater vulnerability to nitrate in Jilin City of northeast China. In order to reduce the subjectivity of the overlay index method, the model was optimized by rebuilding the index system, adjusting the rating scale of each index, reassigning the index weights and comparing grading methods for groundwater vulnerability to nitrate. The criteria for these optimizations were the correlation coefficient of each index with the nitrate concentration in groundwater. Net recharge (R), soil type (S), impact of vadose zone (I), groundwater velocity (V) and land use type (L) were picked up to compose the index system. And then the accuracy of vulnerability mapping was discussed by a group of integrated indicators, including the corresponding relationship between the extreme nitrate concentration and the vulnerability classes, F statistic and class difference between the groundwater vulnerability classification and concentration classification of NO(3)-N. The optimized model graded by geometrical interval method improved the correlation between vulnerability index and nitrate concentration to the order of 0.6698 which was 0.4098 higher than that by the DRASTIC model. By level difference calculation, the correct vulnerability regions accounted for 64.45% of the study area. Lastly, sensitivity analyses indicated that the soil media and groundwater velocity were the most critical factors affecting groundwater vulnerability to nitrate. In short, RSIVL model was suitable to assess the groundwater vulnerability to nitrate in the study area with readily available hydrogeological and hydrochemical data. Hence, the mapping of groundwater vulnerability to nitrate can be applied for sensible

  7. Correlation between permeability and groundwater flow patterns in carbonate rocks

    Science.gov (United States)

    Park, Y.; Lee, J.; Park, Y.; Keehm, Y.

    2011-12-01

    Groundwater flow in carbonate rocks is controlled by many factors such as degree of fracture and pore development, weathering and diagenesis. Among these factors, fracture is main factor and can form main flow path. Also, flow patterns in carbonate area are decided by these factors. This study was performed to understand factors controlling permeability and flow patterns in carbonate area and to evaluate correlation between permeability and flow patterns. Data used in this study were collected from many literatures and these data were analyzed and evaluated using graphic and statistical analysis. In many carbonate areas, branching conduit patterns were dominant. Of these areas, permeability was relatively high in areas where moving distance of flow was short and hydraulic gradient was steep. This work was supported by the Energy Resources R&D program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government Ministry of Knowledge Economy (No. 2009201030001A).

  8. Introduction to vector velocity imaging

    DEFF Research Database (Denmark)

    Jensen, Jørgen Arendt; Udesen, Jesper; Hansen, Kristoffer Lindskov;

    Current ultrasound scanners can only estimate the velocity along the ultrasound beam and this gives rise to the cos() factor on all velocity estimates. This is a major limitation as most vessels are close to perpendicular to the beam. Also the angle varies as a function of space and time making...

  9. Instantaneous Velocity Using Photogate Timers

    Science.gov (United States)

    Wolbeck, John

    2010-01-01

    Photogate timers are commonly used in physics laboratories to determine the velocity of a passing object. In this application a card attached to a moving object breaks the beam of the photogate timer providing the time for the card to pass. The length L of the passing card can then be divided by this time to yield the average velocity (or speed)…

  10. Kriging Interpolating Cosmic Velocity Field

    CERN Document Server

    Yu, Yu; Jing, Yipeng; Zhang, Pengjie

    2015-01-01

    [abridge] Volume-weighted statistics of large scale peculiar velocity is preferred by peculiar velocity cosmology, since it is free of uncertainties of galaxy density bias entangled in mass-weighted statistics. However, measuring the volume-weighted velocity statistics from galaxy (halo/simulation particle) velocity data is challenging. For the first time, we apply the Kriging interpolation to obtain the volume-weighted velocity field. Kriging is a minimum variance estimator. It predicts the most likely velocity for each place based on the velocity at other places. We test the performance of Kriging quantified by the E-mode velocity power spectrum from simulations. Dependences on the variogram prior used in Kriging, the number $n_k$ of the nearby particles to interpolate and the density $n_P$ of the observed sample are investigated. (1) We find that Kriging induces $1\\%$ and $3\\%$ systematics at $k\\sim 0.1h{\\rm Mpc}^{-1}$ when $n_P\\sim 6\\times 10^{-2} ({\\rm Mpc}/h)^{-3}$ and $n_P\\sim 6\\times 10^{-3} ({\\rm Mpc...

  11. Fault gouge rheology under confined, high-velocity conditions

    Science.gov (United States)

    Reches, Z.; Madden, A. S.; Chen, X.

    2012-12-01

    We recently developed the experimental capability to investigate the shear properties of fine-grain gouge under confined conditions and high-velocity. The experimental system includes a rotary apparatus that can apply large displacements of tens of meters, slip velocity of 0.001- 2.0 m/s, and normal stress of 35 MPa (Reches and Lockner, 2010). The key new component is a Confined ROtary Cell (CROC) that can shear a gouge layer either dry or under pore-pressure. The pore pressure is controlled by two syringe pumps. CROC includes a ring-shape gouge chamber of 62.5 mm inner diameter, 81.25 mm outer diameter, and up to 3 mm thick gouge sample. The lower, rotating part of CROC contains the sample chamber, and the upper, stationary part includes the loading, hollow cylinder and setting for temperature, and dilation measurements, and pore-pressure control. Each side of the gouge chamber has two pairs of industrial, spring-energized, self-lubricating, teflon-graphite seals, built for particle media and can work at temperature up to 250 ded C. The space between each of the two sets of seals is pressurized by nitrogen. This design generates 'zero-differential pressure' on the inner seal (which is in contact with the gouge powder), and prevents gouge leaks. For the preliminary dry experiments, we used ~2.0 mm thick layers of room-dry kaolinite powder. Total displacements were on the order of meters and normal stress up to 4 MPa. The initial shear was accommodated by multiple internal slip surfaces within the kaolinite layer accommodated as oriented Riedel shear structures. Later, the shear was localized within a thin, plate-parallel Y-surface. The kaolinite layer was compacted at a quasi-asymptotic rate, and displayed a steady-state friction coefficient of ~ 0.5 with no clear dependence on slip velocity up to 0.15 m/s. Further experiments with loose quartz sand (grain size ~ 125 micron) included both dry runs and pore-pressure (distilled water) controlled runs. The sand was

  12. Groundwater and Terrestrial Water Storage

    Science.gov (United States)

    Rodell, Matthew; Chambers, Don P.; Famiglietti, James S.

    2011-01-01

    Most people think of groundwater as a resource, but it is also a useful indicator of climate variability and human impacts on the environment. Groundwater storage varies slowly relative to other non-frozen components of the water cycle, encapsulating long period variations and trends in surface meteorology. On seasonal to interannual timescales, groundwater is as dynamic as soil moisture, and it has been shown that groundwater storage changes have contributed to sea level variations. Groundwater monitoring well measurements are too sporadic and poorly assembled outside of the United States and a few other nations to permit direct global assessment of groundwater variability. However, observational estimates of terrestrial water storage (TWS) variations from the GRACE satellites largely represent groundwater storage variations on an interannual basis, save for high latitude/altitude (dominated by snow and ice) and wet tropical (surface water) regions. A figure maps changes in mean annual TWS from 2009 to 2010, based on GRACE, reflecting hydroclimatic conditions in 2010. Severe droughts impacted Russia and the Amazon, and drier than normal weather also affected the Indochinese peninsula, parts of central and southern Africa, and western Australia. Groundwater depletion continued in northern India, while heavy rains in California helped to replenish aquifers that have been depleted by drought and withdrawals for irrigation, though they are still below normal levels. Droughts in northern Argentina and western China similarly abated. Wet weather raised aquifer levels broadly across western Europe. Rains in eastern Australia caused flooding to the north and helped to mitigate a decade long drought in the south. Significant reductions in TWS seen in the coast of Alaska and the Patagonian Andes represent ongoing glacier melt, not groundwater depletion. Figures plot time series of zonal mean and global GRACE derived non-seasonal TWS anomalies (deviation from the mean of

  13. An undulation theory for condensation in open end slit pores: critical hysteresis temperature & critical hysteresis pore size.

    Science.gov (United States)

    Fan, Chunyan; Zeng, Yonghong; Do, D D; Nicholson, D

    2014-06-28

    A new theory of condensation in an open end slit pore, based on the concept of temperature dependent undulation, at the interface separating the adsorbed phase and the gas-like region, is presented. The theory, describes, for the first time, the microscopic origin of the critical hysteresis temperature and the critical hysteresis pore size, properties which are not accessible to any classical theories.

  14. Investigating Hydrophilic Pores in Model Lipid Bilayers Using Molecular Simulations: Correlating Bilayer Properties with Pore-Formation Thermodynamics.

    Science.gov (United States)

    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.

  15. Virus removal vs. subsurface water velocity during slow sand filtration.

    Science.gov (United States)

    Dizer, Halim; Brackmann, Bernhard; Rahman, M Azizur; Szewzyk, Regine; Sprenger, Christoph; Holzbecher, Ekkehard; López-Pila, Juan M

    2015-06-01

    In an attempt to obtain a conservative estimate of virus removal during slow sand and river bank filtration, a somatic phage was isolated with slow decay and poor adsorption to coarse sand. We continuously fed a phage suspension to a 7-m infiltration path and measured the phage removal. In a second set of experiments, we fed the phage suspension to 1-m long columns run at different pore water velocities. Using the data obtained, a mathematical model was constructed describing removal vs. pore water velocity (PWV), assuming different statistical distributions of the adsorption coefficient λ. The bimodal distribution best fit the results for PWVs higher than 1 m/d. It predicted a removal of approximately 4 log10 after 50 days infiltration at 1 m/d. At PWVs below 1 m/d the model underestimated removal. Sand-bound phages dissociated slowly into the liquid phase, with a detachment constant kdet of 2.6 × 10⁻⁵. This low kdet suggests that river bank filtration plants should be intermittently operated when viral overload is suspected, e.g. during flooding events or at high water-marks in rivers, in order for viruses to become soil-associated during the periods of standstill. Resuming filtration will allow only a very slow virus release from the soil.

  16. A simple way to model the pressure dependency of rock velocity

    Science.gov (United States)

    Han, Tongcheng

    2016-04-01

    Modeling the pressure dependency of rock velocity is important for interpreting and comparing the seismic and earthquake data from different depths. This study develops a multicomponent differential effective medium model for the elastic properties of porous rocks with two types of pores in the grain background without mixing order. The developed model is applied to modeling the pressure dependent elastic velocity of porous rocks by incorporating the variation of stiff and compliant porosity as a function of pressure. The pressure dependent stiff and compliant porosity were inverted from the measured total porosity under pressure using a dual porosity model, and the unknown constant stiff and compliant pore aspect ratios were inverted by best fitting the modeled velocity to the measured data. Application of the approach to a low porosity granite and a medium porosity sandstone sample showed that the pressure dependency of rock velocity can be satisfactorily modeled by the developed model using the pressure dependent stiff and compliant porosity and carefully estimated stiff and compliant pore aspect ratio values.

  17. Groundwater recharge and agricultural contamination

    Science.gov (United States)

    Böhlke, J.K.

    2002-01-01

    Agriculture has had direct and indirect effects on the rates and compositions of groundwater recharge and aquifer biogeochemistry. Direct effects include dissolution and transport of excess quantities of fertilizers and associated materials and hydrologic alterations related to irrigation and drainage. Some indirect effects include changes in water-rock reactions in soils and aquifers caused by increased concentrations of dissolved oxidants, protons, and major ions. Agrilcultural activities have directly or indirectly affected the concentrations of a large number of inorganic chemicals in groundwater, for example NO3-, N2, Cl, SO42-, H+, P, C, K, Mg, Ca, Sr, Ba, Ra, and As, as well a wide variety of pesticides and other organic compounds. For reactive contaminants like NO3-, a combination of chemical, isotopic, and environmental-tracer analytical approaches might be required to resolve changing inputs from subsequent alterations as causes of concentration gradients in groundwater. Groundwater records derived from multi-component hydrostratigraphic data can be used to quantify recharge rates and residence times of water and dissolved contaminants, document past variations in recharging contaminant loads, and identify natural contaminant-remediation processes. These data indicate that many of the world's surficial aquifers contain transient records of changing agricultural contamination from the last half of the 20th century. The transient agricultural groundwater signal has important implications for long-term trends and spatial heterogeneity in discharge.

  18. Geochemical Investigations of Groundwater Stability

    Energy Technology Data Exchange (ETDEWEB)

    Bath, Adrian [Intellisci Ltd., Loughborough (United Kingdom)

    2006-05-15

    The report describes geochemical parameters and methods that provide information about the hydrodynamic stability of groundwaters in low permeability fractured rocks that are potential hosts for radioactive waste repositories. Hydrodynamic stability describes the propensity for changes in groundwater flows over long timescales, in terms of flow rates and flow directions. Hydrodynamic changes may also cause changes in water compositions, but the related issue of geochemical stability of a potential repository host rock system is outside the scope of this report. The main approaches to assessing groundwater stability are numerical modelling, measurement and interpretation of geochemical indicators in groundwater compositions, and analyses and interpretations of secondary minerals and fluid inclusions in these minerals. This report covers the latter two topics, with emphasis on geochemical indicators. The extent to which palaeohydrogeology and geochemical stability indicators have been used in past safety cases is reviewed. It has been very variable, both in terms of the scenarios considered, the stability indicators considered and the extent to which the information was explicitly or implicitly used in assessing FEPs and scenarios in the safety cases. Geochemical indicators of hydrodynamic stability provide various categories of information that are of hydrogeological relevance. Information about groundwater mixing, flows and water sources is potentially provided by the total salinity of groundwaters, their contents of specific non-reactive solutes (principally chloride) and possibly of other solutes, the stable isotopic ratio of water, and certain characteristics of secondary minerals and fluid inclusions. Information pertaining directly to groundwater ages and the timing of water and solute movements is provided by isotopic systems including tritium, carbon-14, chlorine-36, stable oxygen and hydrogen isotopes, uranium isotopes and dissolved mobile gases in

  19. Elastic wave velocities and Poisson`s ratio in reservoir rocks; Choryugan no danseiha sokudo to Poisson hi

    Energy Technology Data Exchange (ETDEWEB)

    Fujii, Y. [Japan National Oil Corp., Tokyo (Japan)

    1998-04-01

    This paper discusses the relationship between elastic wave velocities and physical properties of reservoir rocks. For sandstones, the elastic wave velocity decreases with increasing the porosity and the content of clay minerals. For rocks containing heavy oil, the P-wave velocity decreases with increasing the temperature. The P-wave velocity under dry condition is much more lower than that under water saturated condition. When there are a few percent of gas in pores against the water saturated condition, the P-wave velocity decreases rapidly. It is almost constant under the lower water saturation factor. The S-wave velocity is almost constant independent of the water saturation factor. Accordingly, the water saturation factor can not be estimated from the elastic wave velocity at the water saturation factor between 0% and 96%. The Poisson`s ratio also greatly decreases at the water saturation factor between 96% and 100%, but it is almost constant under the lower water saturation factor. The elastic wave velocity increases with increasing the pressure or increasing the depth. Since closure of cracks by pressure is inhibited due to high pore pressure, degree of increase in the elastic wave velocity is reduced. 14 refs., 6 figs.

  20. P-wave velocity changes in freezing hard low-porosity rocks: a laboratory-based time-average model

    Directory of Open Access Journals (Sweden)

    D. Draebing

    2012-02-01

    Full Text Available P-wave refraction seismics is a key method in permafrost research but its applicability to low-porosity rocks, that constitute alpine rock walls, has been denied in prior studies. These explain p-wave velocity changes in freezing rocks exclusively due to changing velocities of pore infill, i.e. water, air and ice. In existing models, no velocity increase is expected for low-porosity bedrock. We postulate, that mixing laws apply for high-porosity rocks, but freezing in confined space in low-porosity bedrock also alters physical rock matrix properties. In the laboratory, we measured p-wave velocities of 22 decimeter-large low-porosity (<6 % metamorphic, magmatic and sedimentary permafrost rock samples with a natural texture (>100 micro-fissures from 25 °C to –15 °C in 0.3 °C increments close to the freezing point. P-wave velocity increases by 7–78 % when freezing parallel to cleavage/bedding and matrix velocity increases from 5–59 % coincident to an anisotropy decrease in most samples. The expansion of rigid bedrock upon freezing is restricted and ice pressure will increase matrix velocity and decrease anisotropy while changing velocities of the pore infill are insignificant. Here, we present a modified Timur's 2-phase equation implementing changes in matrix velocity dependent on lithology and demonstrate the physical basis for refraction seismics in low-porosity bedrock.

  1. Diffraction imaging and velocity analysis using oriented velocity continuation

    KAUST Repository

    Decker, Luke

    2014-08-05

    We perform seismic diffraction imaging and velocity analysis by separating diffractions from specular reflections and decomposing them into slope components. We image slope components using extrapolation in migration velocity in time-space-slope coordinates. The extrapolation is described by a convection-type partial differential equation and implemented efficiently in the Fourier domain. Synthetic and field data experiments show that the proposed algorithm is able to detect accurate time-migration velocities by automatically measuring the flatness of events in dip-angle gathers.

  2. Pore Scale Dynamics of Microemulsion Formation.

    Science.gov (United States)

    Unsal, Evren; Broens, Marc; Armstrong, Ryan T

    2016-07-19

    Experiments in various porous media have shown that multiple parameters come into play when an oleic phase is displaced by an aqueous solution of surfactant. In general, the displacement efficiency is improved when the fluids become quasi-miscible. Understanding the phase behavior oil/water/surfactant systems is important because microemulsion has the ability to generate ultralow interfacial tension (formation and the resulting properties under equilibrium conditions. However, the majority of applications where microemulsion is present also involve flow, which has received relatively less attention. It is commonly assumed that the characteristics of an oil/water/surfactant system under flowing conditions are identical to the one under equilibrium conditions. Here, we show that this is not necessarily the case. We studied the equilibrium phase behavior of a model system consisting of n-decane and an aqueous solution of olefin sulfonate surfactant, which has practical applications for enhanced oil recovery. The salt content of the aqueous solution was varied to provide a range of different microemulsion compositions and oil-water interfacial tensions. We then performed microfluidic flow experiments to study the dynamic in situ formation of microemulsion by coinjecting bulk fluids of n-decane and surfactant solution into a T-junction capillary geometry. A solvatochromatic fluorescent dye was used to obtain spatially resolved compositional information. In this way, we visualized the microemulsion formation and the flow of it along with the excess phases. A complex interaction between the flow patterns and the microemulsion properties was observed. The formation of microemulsion influenced the flow regimes, and the flow regimes affected the characteristics of the microemulsion formation. In particular, at low flow rates, slug flow was observed, which had profound consequences on the pore scale mixing behavior and resulting microemulsion properties.

  3. Hydromechanical Rock Mass Fatigue in Deep-Seated Landslides Accompanying Seasonal Variations in Pore Pressures

    Science.gov (United States)

    Preisig, Giona; Eberhardt, Erik; Smithyman, Megan; Preh, Alexander; Bonzanigo, Luca

    2016-06-01

    The episodic movement of deep-seated landslides is often governed by the presence of high pore pressures and reduced effective stresses along active shear surfaces. Pore pressures are subject to cyclic fluctuation under seasonal variations of groundwater recharge, resulting in an intermittent movement characterized by acceleration-deceleration phases. However, it is not always clear why certain acceleration phases reach alarming levels without a clear trigger (i.e., in the absence of an exceptional pore pressure event). This paper presents a conceptual framework linking hydromechanical cycling, progressive failure and fatigue to investigate and explain the episodic behavior of deep-seated landslides using the Campo Vallemaggia landslide in Switzerland as a case study. A combination of monitoring data and advanced numerical modeling is used. The principal processes forcing the slope into a critical disequilibrium state are analyzed as a function of rock mass damage and fatigue. Modeling results suggest that during periods of slope acceleration, the rock slope experiences localized fatigue and gradual weakening through slip along pre-existing natural fractures and yield of critically stressed intact rock bridges. At certain intervals, pockets of critically weakened rock may produce a period of enhanced slope movement in response to a small pore pressure increase similar to those routinely experienced each year. Accordingly, the distribution and connectivity of pre-existing permeable planes of weakness play a central role. These structures are often related to the rock mass's tectonic history or initiate (and dilate) in response to stress changes that disturb the entire slope, such as glacial unloading or seismic loading via large earthquakes. The latter is discussed in detail in a companion paper to this (Gischig et al., Rock Mech Rock Eng, 2015). The results and framework presented further demonstrate that episodic movement and progressive failure of deep

  4. Organic Carbon Inventories and Vertical Fluxes Through the Vadose Zone into Groundwater at the Rifle, Colorado River Floodplain Site

    Science.gov (United States)

    Tokunaga, T. K.; Wan, J.; Dong, W.; Williams, K. H.; Robbins, M.; Kim, Y.; Faybishenko, B.; Conrad, M. E.; Christensen, J. N.; Gilbert, B.; Dayvault, R. D.; Long, P. E.; Hubbard, S. S.

    2013-12-01

    Understanding carbon inventories and fluxes within the vadose zone and groundwater of semi-arid regions is challenging because of their typically deep profiles, moderately low soil organic carbon (SOC) inventories, low dissolved organic carbon (DOC) fluxes, and slow changes in soil inorganic carbon (SIC) inventories. The remediated uranium/vanadium mill tailings site situated on a floodplain at Rifle, Colorado possesses a number of characteristics that facilitate investigation of subsurface carbon fluxes. These include locally derived fill soil having SOC and SIC concentrations representative of the region, established vegetation cover (perennial grasses and shrubs) on the fill, boundaries between the fill and underlying alluvium distinguishable through concentrations of SIC and other chemical components, predictable groundwater flow and interaction with the adjacent Colorado River, and a clearly delineated impermeable lower boundary (Wasatch Formation shale) at depths ranging from 6 to 7.5 m. Environmental characteristics of this site permit year-round sampling of both pore water and pore gas throughout most of the moderately deep (~ 3.5 m) vadose zone. Within this well-defined hydrological system, we recently installed a suite of tensiometers, pore water (vadose zone and groundwater) samplers, gas samplers, and neutron probe access tubes at three sites along a transect aligned with the groundwater flow direction in order to determine inventories and fluxes of water, carbon, and other components. The tensiometer and piezometer measurements are revealing impacts of infiltration and groundwater recharge events, evapotranspiration, and capillary fringe-groundwater interactions. The results of pore water analyses are showing relatively high concentrations of DOC (up to 4 mM) in the vadose zone, and particulate organic carbon (POC) mobile in the capillary fringe. Differences in DOC characteristics are being determined using a variety of analytical techniques. Hydraulic

  5. Pore-water chemistry from the ICDP-USGS coer hole in the Chesapeake Bay impact structure--Implications for paleohydrology, microbial habitat, and water resources

    Science.gov (United States)

    Sanford, Ward E.; Voytek, Mary A.; Powars, David S.; Jones, Blair F.; Cozzarelli, Isabelle M.; Eganhouse, Robert P.; Cockell, Charles S.

    2009-01-01

    We investigated the groundwater system of the Chesapeake Bay impact structure by analyzing the pore-water chemistry in cores taken from a 1766-m-deep drill hole 10 km north of Cape Charles, Virginia. Pore water was extracted using high-speed centrifuges from over 100 cores sampled from a 1300 m section of the drill hole. The pore-water samples were analyzed for major cations and anions, stable isotopes of water and sulfate, dissolved and total carbon, and bioavailable iron. The results reveal a broad transition between fresh and saline water from 100 to 500 m depth in the post-impact sediment section, and an underlying syn-impact section that is almost entirely filled with brine. The presence of brine in the lowermost post-impact section and the trend in the dissolved chloride with depth suggest a transport process dominated by molecular diffusion and slow, compaction-driven, upward flow. Major ion results indicate residual effects of diagenesis from heating, and a pre-impact origin for the brine. High levels of dissolved organic carbon (6-95 mg/L) and the distribution of electron acceptors indicate an environment that may be favorable for microbial activity throughout the drilled section. The concentration and extent of the brine is much greater than had previously been observed, suggesting its occurrence may be common in the inner crater. However, groundwater flow conditions in the structure may reduce the salt-water-intrusion hazard associated with the brine.

  6. Pore-water chemistry from the ICDP-USGS core hole in the Chesapeake Bay impact structure-Implications for paleohydrology, microbial habitat, and water resources

    Science.gov (United States)

    Sanford, W.E.; Voytek, M.A.; Powars, D.S.; Jones, B.F.; Cozzarelli, I.M.; Cockell, C.S.; Eganhouse, R.P.

    2009-01-01

    We investigated the groundwater system of the Chesapeake Bay impact structure by analyzing the pore-water chemistry in cores taken from a 1766-m-deep drill hole 10 km north of Cape Charles, Virginia. Pore water was extracted using high-speed centrifuges from over 100 cores sampled from a 1300 m section of the drill hole. The pore-water samples were analyzed for major cations and anions, stable isotopes of water and sulfate, dissolved and total carbon, and bioavailable iron. The results reveal a broad transition between freshwater and saline water from 100 to 500 m depth in the postimpact sediment section, and an underlying synimpact section that is almost entirely filled with brine. The presence of brine in the lowermost postimpact section and the trend in dissolved chloride with depth suggest a transport process dominated by molecular diffusion and slow, compaction-driven, upward flow. Major ion results indicate residual effects of diagenesis from heating, and a pre-impact origin for the brine. High levels of dissolved organic carbon (6-95 mg/L) and the distribution of electron acceptors indicate an environment that may be favorable for microbial activity throughout the drilled section. The concentration and extent of the brine is much greater than had previously been observed, suggesting that its occurrence may be common in the inner crater. However, groundwater-flow conditions in the structure may reduce the saltwater-intrusion hazard associated with the brine. ?? 2009 The Geological Society of America.

  7. Groundwater resource-directed measures software

    African Journals Online (AJOL)

    2006-07-21

    Jul 21, 2006 ... 1Institute for Groundwater Studies, University of the Free State, PO Box 339, Bloemfontein, 9300, South Africa ... In this paper the methods developed for the GRDM .... The geothermal gradient for groundwater, that is, the.

  8. ASSESSMENT OF GROUNDWATER QUALITY IN SHALLOW ...

    African Journals Online (AJOL)

    development of human societies. In Okrika Island ... abstraction of groundwater due to population increase in Port ... 298. Nwankwoala and Walter: Assessment of Groundwater Quality in Shallow Coastal Aquifers ..... and Tai-Eleme areas.

  9. Future research needs involving pathogens in groundwater

    Science.gov (United States)

    Contamination of groundwater by enteric pathogens has commonly been associated with disease outbreaks. Proper management and treatment of pathogen sources are important barriers to preventing groundwater contamination. However, non-point sources of pathogen contamination are frequently difficult to ...

  10. Valuing groundwater: A practical approach for integrating ...

    African Journals Online (AJOL)

    groundwater economic values into decision making ... The methodology incorporates a 2-tiered valuation approach. .... groundwater systems in Botswana (SADC, 2010). .... tion) can be investigated to support water resource management.

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

    Science.gov (United States)

    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

  12. INTEC Groundwater Monitoring Report 2006

    Energy Technology Data Exchange (ETDEWEB)

    J. R. Forbes

    2007-02-01

    This report summarizes 2006 perched water and groundwater monitoring activities at the Idaho Nuclear Technology and Engineering Center (INTEC) located at the Idaho National Laboratory (INL). During 2006, groundwater samples were collected from a total of 22 Snake River Plain Aquifer (SRPA) monitoring wells, plus six aquifer wells sampled for the Idaho CERCLA Disposal Facility (ICDF) monitoring program. In addition, perched water samples were collected from 21 perched wells and 19 suction lysimeters. Groundwater and perched water samples were analyzed for a suite of radionuclides and inorganic constituents. Laboratory results in this report are compared to drinking water maximum contaminant levels (MCLs). Such comparison is for reference only and it should be noted that the Operable Unit 3-13 Record of Decision does not require that perched water comply with drinking water standards.

  13. Groundwater arsenic contamination throughout China.

    Science.gov (United States)

    Rodríguez-Lado, Luis; Sun, Guifan; Berg, Michael; Zhang, Qiang; Xue, Hanbin; Zheng, Quanmei; Johnson, C Annette

    2013-08-23

    Arsenic-contaminated groundwater used for drinking in China is a health threat that was first recognized in the 1960s. However, because of the sheer size of the country, millions of groundwater wells remain to be tested in order to determine the magnitude of the problem. We developed a statistical risk model that classifies safe and unsafe areas with respect to geogenic arsenic contamination in China, using the threshold of 10 micrograms per liter, the World Health Organization guideline and current Chinese standard for drinking water. We estimate that 19.6 million people are at risk of being affected by the consumption of arsenic-contaminated groundwater. Although the results must be confirmed with additional field measurements, our risk model identifies numerous arsenic-affected areas and highlights the potential magnitude of this health threat in China.

  14. GENERALIZED UPWIND SCHEME WITH FRACTIONAL STEPS FOR 3-D PROBLEM OF CONVECTION DOMINATING GROUNDWATER TRANSPORT

    Institute of Scientific and Technical Information of China (English)

    姚磊华

    1997-01-01

    A generalized upwind scheme with fractional steps for 3-D mathematical models of convection dominating groundwater quality is suggested. The mass transport equation is split into a convection equation and a dispersive equation. The generalized upwind scheme is used to solve the convection equation and the finite element method is used to compute the dispersive equation. These procedures which not only overcome the phenomenon of the negative concentration and numerical dispersion appear frequently with normal FEM or FDM to solve models of convection dominating groundwater transport but also avoid the step for computing each node velocity give a more suitable method to calculate the concentrations of the well points.

  15. Pore geometry as a control on rock strength

    Science.gov (United States)

    Bubeck, A.; Walker, R. J.; Healy, D.; Dobbs, M.; Holwell, D. A.

    2017-01-01

    The strength of rocks in the subsurface is critically important across the geosciences, with implications for fluid flow, mineralisation, seismicity, and the deep biosphere. Most studies of porous rock strength consider the scalar quantity of porosity, in which strength shows a broadly inverse relationship with total porosity, but pore shape is not explicitly defined. Here we use a combination of uniaxial compressive strength measurements of isotropic and anisotropic porous lava samples, and numerical modelling to consider the influence of pore shape on rock strength. Micro computed tomography (CT) shows that pores range from sub-spherical to elongate and flat ellipsoids. Samples that contain flat pores are weaker if compression is applied parallel to the short axis (i.e. across the minimum curvature), compared to compression applied parallel to the long axis (i.e. across the maximum curvature). Numerical models for elliptical pores show that compression applied across the minimum curvature results in relatively broad amplification of stress, compared to compression applied across the maximum curvature. Certain pore shapes may be relatively stable and remain open in the upper crust under a given remote stress field, while others are inherently weak. Quantifying the shape, orientations, and statistical distributions of pores is therefore a critical step in strength testing of rocks.

  16. Impedance nanopore biosensor: influence of pore dimensions on biosensing performance.

    Science.gov (United States)

    Kant, Krishna; Yu, Jingxian; Priest, Craig; Shapter, Joe G; Losic, Dusan

    2014-03-07

    Knowledge about electrochemical and electrical properties of nanopore structures and the influence of pore dimensions on these properties is important for the development of nanopore biosensing devices. The aim of this study was to explore the influence of nanopore dimensions (diameter and length) on biosensing performance using non-faradic electrochemical impedance spectroscopy (EIS). Nanoporous alumina membranes (NPAMs) prepared by self-ordered electrochemical anodization of aluminium were used as model nanopore sensing platforms. NPAMs with different pore diameters (25-65 nm) and lengths (4-18 μm) were prepared and the internal pore surface chemistry was modified by covalently attaching streptavidin and biotin. The performance of this antibody nanopore biosensing platform was evaluated using various concentrations of biotin as a model analyte. EIS measurements of pore resistivity and conductivity were carried out for pores with different diameters and lengths. The results showed that smaller pore dimensions of 25 nm and pore lengths up to 10 μm provide better biosensing performance.

  17. Superplastically foaming method to make closed pores inclusive porous ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Kishimoto, Akira; Hayashi, Hidetaka, E-mail: kishim-a@cc.okayama-u.ac.jp [Division of Molecular and Material Science, Graduate School of Natural Science and Technology, Okayama University Okayama (Japan)

    2011-04-15

    Porous ceramics incorporates pores to improve several properties including thermal insulation maintaining inherenet ceramic properties such as corrosion resistance and large mechanical strength. Conventional porous ceramics is usually fabricated through an insufficient sintering. Since the sintering accompanies the exclusion of pores, it must be terminated at the early stage to maintain the high porosity, leading to degraded strength and durability. Contrary to this, we have innovated superplastically foaming method to make ceramic foams only in the solid state. In this method, the previously inserted foam agent evaporates after the full densification of matrix at around the sintering temperature. Closed pores expand utilizing the superplastic deformation driven by the evolved gas pressure. The typical features of this superplastically foaming method are listed as follows, 1. The pores are introduced after sintering the solid polycrystal. 2. Only closed pores are introduced, improving the insulation of gas and sound in addition to heat. 3. The pore walls are fully densified expecting a large mechanical strength. 4. Compared with the melt foaming method, this method is practical because the fabrication temperature is far below the melting point and it does not need molds. 5. The size and the location pores can be controlled by the amount and position of the foam agent.

  18. Clostridial pore-forming toxins: powerful virulence factors.

    Science.gov (United States)

    Popoff, Michel R

    2014-12-01

    Pore formation is a common mechanism of action for many bacterial toxins. More than one third of clostridial toxins are pore-forming toxins (PFTs) belonging to the β-PFT class. They are secreted as soluble monomers rich in β-strands, which recognize a specific receptor on target cells and assemble in oligomers. Then, they undergo a conformational change leading to the formation of a β-barrel, which inserts into the lipid bilayer forming functional pore. According to their structure, clostridial β-PFTs are divided into several families. Clostridial cholesterol-dependent cytolysins form large pores, which disrupt the plasma membrane integrity. They are potent virulence factors mainly involved in myonecrosis. Clostridial heptameric β-PFTs (aerolysin family and staphylococcal α-hemolysin family) induce small pores which trigger signaling cascades leading to different cell responses according to the cell types and toxins. They are mainly responsible for intestinal diseases, like necrotic enteritis, or systemic diseases/toxic shock from intestinal origin. Clostridial intracellularly active toxins exploit pore formation through the endosomal membrane to translocate the enzymatic component or domain into the cytosol. Single chain protein toxins, like botulinum and tetanus neurotoxins, use hydrophobic α-helices to form pores, whereas clostridial binary toxins encompass binding components, which are structurally and functionally related to β-PFTs, but which have acquired the specific activity to internalize their corresponding enzymatic components. Structural analysis suggests that β-PFTs and binding components share a common evolutionary origin.

  19. Nuclear Pore-Like Structures in a Compartmentalized Bacterium

    Science.gov (United States)

    Sagulenko, Evgeny; Green, Kathryn; Yee, Benjamin; Morgan, Garry; Leis, Andrew; Lee, Kuo-Chang; Butler, Margaret K.; Chia, Nicholas; Pham, Uyen Thi Phuong; Lindgreen, Stinus; Catchpole, Ryan; Poole, Anthony M.; Fuerst, John A.

    2017-01-01

    Planctomycetes are distinguished from other Bacteria by compartmentalization of cells via internal membranes, interpretation of which has been subject to recent debate regarding potential relations to Gram-negative cell structure. In our interpretation of the available data, the planctomycete Gemmata obscuriglobus contains a nuclear body compartment, and thus possesses a type of cell organization with parallels to the eukaryote nucleus. Here we show that pore-like structures occur in internal membranes of G.obscuriglobus and that they have elements structurally similar to eukaryote nuclear pores, including a basket, ring-spoke structure, and eight-fold rotational symmetry. Bioinformatic analysis of proteomic data reveals that some of the G. obscuriglobus proteins associated with pore-containing membranes possess structural domains found in eukaryote nuclear pore complexes. Moreover, immunogold labelling demonstrates localization of one such protein, containing a β-propeller domain, specifically to the G. obscuriglobus pore-like structures. Finding bacterial pores within internal cell membranes and with structural similarities to eukaryote nuclear pore complexes raises the dual possibilities of either hitherto undetected homology or stunning evolutionary convergence. PMID:28146565

  20. Morphological Characterization of the Polyflux 210H Hemodialysis Filter Pores

    Directory of Open Access Journals (Sweden)

    A. Hedayat

    2012-01-01

    Full Text Available Background. Morphological characterization of hemodialysis membranes is necessary to improve pore design. Aim. To delineate membrane pore structure of a high flux filter, Polyflux 210H. Methods. We used a Joel JSM-6010LV scanning electron microscope (SEM and a SU6600 Hitachi field emission scanning electron microscope (FESEM to characterize the pore and fiber morphology. The maximal diameters of selected uremic toxins were calculated using the macromolecular modeling Crystallographic Object-Oriented Toolkit (COOT software. Results. The mean pore densities on the outermost and innermost surfaces of the membrane were 36.81% and 5.45%, respectively. The membrane exhibited a tortuous structure with poor connection between the inner and outer pores. The aperture’s width in the inner surface ranged between 34 and 45 nm, which is 8.76–11.60 times larger than the estimated maximum diameter of β2-microglobulin (3.88 nm. Conclusion. The results suggest that the diameter size of inner pore apertures is not a limiting factor to middle molecules clearance, the extremely diminished density is. Increasing inner pore density and improving channel structure are strategies to improve clearance of middle molecules.

  1. Size dependent pore size distribution of shales by gas physisorption

    Science.gov (United States)

    Roshan, Hamid; Andersen, Martin S.; Yu, Lu; Masoumi, Hossein; Arandian, Hamid

    2017-04-01

    Gas physisorption, in particular nitrogen adsorption-desorption, is a traditional technique for characterization of geomaterials including the organic rich shales. The low pressure nitrogen is used together with adsorption-desorption physical models to study the pore size distribution (PSD) and porosity of the porous samples. The samples are usually crushed to a certain fragment size to measure these properties however there is not yet a consistent standard size proposed for sample crushing. Crushing significantly increases the surface area of the fragments e.g. the created surface area is differentiated from that of pores using BET technique. In this study, we show that the smaller fragment sizes lead to higher cumulative pore volume and smaller pore diameters. It is also shown that some of the micro-pores are left unaccounted because of the correction of the external surface area. In order to illustrate this, the nitrogen physisorption is first conducted on the identical organic rich shale samples with different sizes: 20-25, 45-50 and 63-71 µm. We then show that such effects are not only a function of pore structure changes induced by crushing, but is linked to the inability of the physical models in differentiating between the external surface area (BET) and micro-pores for different crushing sizes at relatively low nitrogen pressure. We also discuss models currently used in nano-technology such as t-method to address this issue and their advantages and shortcoming for shale rock characterization.

  2. Airborne Thermal Remote Sensing for Estimation of Groundwater Discharge to a River.

    Science.gov (United States)

    Liu, Chuankun; Liu, Jie; Hu, Yue; Wang, Heshun; Zheng, Chunmiao

    2016-05-01

    Traditional methods for studying surface water and groundwater interactions have usually been limited to point measurements, such as geochemical sampling and seepage measurement. A new methodology is presented for quantifying groundwater discharge to a river, by using river surface temperature data obtained from airborne thermal infrared remote sensing technology. The Hot Spot Analysis toolkit in ArcGIS was used to calculate the percentage of groundwater discharge to a river relative to the total flow of the river. This methodology was evaluated in the midstream of the Heihe River in the arid and semiarid northwest China. The results show that the percentage of groundwater discharge relative to the total streamflow was as high as 28%, which is in good agreement with the results from previous geochemical studies. The data analysis methodology used in this study is based on the assumption that the river water is fully mixed except in the areas of extremely low flow velocity, which could lead to underestimation of the amount of groundwater discharge. Despite this limitation, this remote sensing-based approach provides an efficient means of quantifying the surface water and groundwater interactions on a regional scale.

  3. Food supply reliance on groundwater

    Science.gov (United States)

    Dalin, Carole; Puma, Michael; Wada, Yoshihide; Kastner, Thomas

    2016-04-01

    Water resources, essential to sustain human life, livelihoods and ecosystems, are under increasing pressure from population growth, socio-economic development and global climate change. As the largest freshwater resource on Earth, groundwater is key for human development and food security. Yet, excessive abstraction of groundwater for irrigation, driven by an increasing demand for food in recent decades, is leading to fast exhaustion of groundwater reserves in major agricultural areas of the world. Some of the highest depletion rates are observed in Pakistan, India, California Central Valley and the North China Plain aquifers. In addition, the growing economy and population of several countries, such as India and China, makes prospects of future available water and food worrisome. In this context, it is becoming particularly challenging to sustainably feed the world population, without exhausting our water resources. Besides, food production and consumption across the globe have become increasingly interconnected, with many areas' agricultural production destined to remote consumers. In this globalisation era, trade is crucial to the world's food system. As a transfer of water-intensive goods, across regions with varying levels of water productivity, food trade can save significant volumes of water resources globally. This situation makes it essential to address the issue of groundwater overuse for global food supply, accounting for international food trade. To do so, we quantify the current, global use of non-renewable groundwater for major crops, accounting for various water productivity and trade flows. This will highlight areas requiring quickest attention, exposing major exporters and importers of non-renewable groundwater, and thus help explore solutions to improve the sustainability of global food supply.

  4. Groundwater and climate change research scoping study

    OpenAIRE

    Jackson, C. R.; Cheetham, M.; Guha, P

    2006-01-01

    This scoping study has reviewed much of the published literature in the field of climate change and groundwater research. Whilst it is not exhaustive with regard to groundwater quality issues, most of the published literature relating to climate change and groundwater resources, particularly in the UK, is covered. Further work is required to identify current research needs relating to the effects of climate change on groundwater quality. The study of the effects of climate chan...

  5. Coseismic and postseismic velocity changes measured by repeating earthquakes

    Science.gov (United States)

    Schaff, David P.; Beroza, Gregory C.

    2004-10-01

    Repeating earthquakes that rupture approximately the same fault patch and have nearly identical waveforms are a useful tool for measuring temporal changes in wave propagation in the Earth's crust. Since source and path effects are common to all earthquakes in a repeating earthquake sequence (multiplet), differences in their waveforms can be attributed to changes in the characteristics of the medium. We have identified over 20 multiplets containing between 5 and 40 repeating events in the aftershock zones of the 1989 Loma Prieta and 1984 Morgan Hill, California, earthquakes. Postmain shock events reveal delays of phases in the early S wave coda of as much as 0.2 s relative to premain shock events. The delay amounts to a path-averaged coseismic velocity decrease of about 1.5% for P waves and 3.5% for S waves. Since most of the multiplets are aftershocks and follow Omori's law, we have excellent temporal sampling in the immediate postmain shock period. We find that the amplitude of the velocity decrease decays logarithmically in time following the main shock. In some cases it returns to the premain shock values, while in others it does not. Similar results are obtained for the Morgan Hill main shock. Because the fractional change in S wave velocity is greater than the fractional change in P wave velocity, it suggests that the opening or connection of fluid-filled fractures is the underlying cause. The magnitude of the velocity change implies that low effective pressures are present in the source region of the velocity change. Our results suggest that the changes are predominantly near the stations and shallow, but we cannot exclude the possibility that changes occur at greater depth as well. If the variations are shallow, we may be detecting the lingering effects of nonlinearity during main shock strong ground motion. If the variations are deep, it suggests that pore pressures at seismogenic depths are high, which would likely play a key role in the earthquake process.

  6. Novel Techniques to Characterize Pore Size of Porous Materials

    KAUST Repository

    Alabdulghani, Ali J.

    2016-04-24

    Porous materials are implemented in several industrial applications such as water desalination, gas separation and pharmaceutical care which they are mainly governed by the pore size and the PSD. Analyzing shale reservoirs are not excluded from these applications and numerous advantages can be gained by evaluating the PSD of a given shale reservoir. Because of the limitations of the conventional characterization techniques, novel methods for characterizing the PSD have to be proposed in order to obtain better characterization results for the porous materials, in general, and shale rocks in particular. Thus, permporosimetry and evapoporometry (EP) technologies were introduced, designed and utilized for evaluating the two key parameters, pore size and pore size distribution. The pore size and PSD profiles of different shale samples from Norway and Argentina were analyzed using these technologies and then confirmed by mercury intrusion porosimeter (MIP). Norway samples showed an average pore diameter of 12.94 nm and 19.22 nm with an average diameter of 13.77 nm and 23.23 nm for Argentina samples using permporosimetry and EP respectively. Both techniques are therefore indicative of the heterogeneity of the shales. The results from permporosimetry are in good agreement with those obtained from MIP technique, but EP for most part over-estimates the average pore size. The divergence of EP results compared to permporosimetry results is referred to the fact that the latter technique measures only the active pores which is not the case with the former technique. Overall, both techniques are complementary to each other which the results from both techniques seem reasonable and reliable and provide two simple techniques to estimate the pore size and pore size distributions for shale rocks.

  7. Complexed iron removal from groundwater

    Energy Technology Data Exchange (ETDEWEB)

    Munter, R.; Ojaste, H.; Sutt, J. [Tallinn Technical University, Tallinn (Estonia). Dept. of Environmental & Chemical Technology

    2005-07-01

    The paper demonstrates an intensive work carried out and results obtained on the pilot plant of the City of Kogalym Water Treatment Station (Tjumen, Siberia, Russian Federation) to elaborate on a contemporary nonreagent treatment technology for the local iron-rich groundwater. Several filter materials (Birm, Pyrolox, hydroanthracite, Everzit, granulated activated carbon) and chemical oxidants (ozone, chlorine, hydrogen peroxide, oxygen, and potassium permanganate) were tested to solve the problem with complexed iron removal from groundwater. The final elaborated technology consists of raw water intensive aeration in the gas-degas treatment unit followed by sequential filtration through hydroanthracite and the special anthracite Everzit.

  8. AUTOMATING GROUNDWATER SAMPLING AT HANFORD

    Energy Technology Data Exchange (ETDEWEB)

    CONNELL CW; HILDEBRAND RD; CONLEY SF; CUNNINGHAM DE

    2009-01-16

    Until this past October, Fluor Hanford managed Hanford's integrated groundwater program for the U.S. Department of Energy (DOE). With the new contract awards at the Site, however, the CH2M HILL Plateau Remediation Company (CHPRC) has assumed responsibility for the groundwater-monitoring programs at the 586-square-mile reservation in southeastern Washington State. These programs are regulated by the Resource Conservation and Recovery Act (RCRA) and the Comprehensive Environmental Response Compensation and Liability Act (CERCLA). The purpose of monitoring is to track existing groundwater contamination from past practices, as well as other potential contamination that might originate from RCRA treatment, storage, and disposal (TSD) facilities. An integral part of the groundwater-monitoring program involves taking samples of the groundwater and measuring the water levels in wells scattered across the site. More than 1,200 wells are sampled each year. Historically, field personnel or 'samplers' have been issued pre-printed forms that have information about the well(s) for a particular sampling evolution. This information is taken from the Hanford Well Information System (HWIS) and the Hanford Environmental Information System (HEIS)--official electronic databases. The samplers used these hardcopy forms to document the groundwater samples and well water-levels. After recording the entries in the field, the samplers turned the forms in at the end of the day and the collected information was posted onto a spreadsheet that was then printed and included in a log book. The log book was then used to make manual entries of the new information into the software application(s) for the HEIS and HWIS databases. This is a pilot project for automating this tedious process by providing an electronic tool for automating water-level measurements and groundwater field-sampling activities. The automation will eliminate the manual forms and associated data entry, improve the

  9. Groundwater and Terrestrial Water Storage

    Science.gov (United States)

    Rodell, Matthew; Chambers, Don P.; Famiglietti, James S.

    2014-01-01

    Terrestrial water storage (TWS) comprises groundwater, soil moisture, surface water, snow,and ice. Groundwater typically varies more slowly than the other TWS components because itis not in direct contact with the atmosphere, but often it has a larger range of variability onmultiannual timescales (Rodell and Famiglietti, 2001; Alley et al., 2002). In situ groundwaterdata are only archived and made available by a few countries. However, monthly TWSvariations observed by the Gravity Recovery and Climate Experiment (GRACE; Tapley et al.,2004) satellite mission, which launched in 2002, are a reasonable proxy for unconfinedgroundwater at climatic scales.

  10. Simple model of capillary condensation in cylindrical pores

    Science.gov (United States)

    Szybisz, Leszek; Urrutia, Ignacio

    2002-11-01

    A simple model based on an approximation of the dropletlike model is formulated for studying adsorption of fluids into cylindrical pores. This model yields a nearly universal description of capillary condensation transitions for noble gases confined by alkali metals. The system's thermodynamical behavior is predicted from the values of two dimensionless parameters: D* (the reduced asymptotic strength of the fluid-adsorber interaction, a function of temperature) and R* (the reduced radius of the pore). The phenomenon of hysteresis inherently related to capillary condensation is discussed. The connection to a previously proposed universality for cylindrical pores is also established.

  11. Pore structure of SWNTs with high hydrogen storage capacity

    Institute of Scientific and Technical Information of China (English)

    杨全红; 刘畅; 刘敏; 樊彦贞; 成会明; 王茂章

    2002-01-01

    This paper reveals, by analyses of nitrogen cryo-adsorption isotherm, the energetic and structural heterogeneity of single-walled carbon nanotubes (SWNTs) which has a high hydrogen storage capacity. It was found that SWNTs had manifold pore structures and distributed surface energy. By comparison of the pore structures and energy distributions of SWNTs before and after hydrogen adsorption, it is preliminarily indicated that hydrogen adsorption occurred in micropores and mesopores with smaller diameter, and that the pores of different diameters determined different hydrogen adsorption processes and underwent different structure changes during hydrogen adsorption.

  12. Numerical study of viscoelastic polymer flow in simplified pore structures using stabilised finite element model

    Energy Technology Data Exchange (ETDEWEB)

    Qi, M.; Wegner, J.; Ganzer, L. [Technische Univ. Clausthal, Clausthal-Zellerfeld (Germany). ITE

    2013-08-01

    Polymer flooding, as an EOR method, has become one of the most important driving forces after water flooding. The conventional believe is that polymer flooding can only improve sweep efficiency, but it has no contribution to residual oil saturation reduction. However, experimental studies indicated that polymer solution can also improve displacement efficiency and decrease residual oil saturation. To get a better understanding of the mechanism to increase the microscopic sweep efficiency and the displacement efficiency, theoretical studies are required. In this paper, we studied the viscoelasticity effect of polymer by using a numerical simulator, which is based on Finite Element Analysis. Since it is showed experimentally that the first normal stress difference of viscoelastic polymer solution is higher than the second stress difference, the Oldroyd-B model was selected as the constitutive equation in the simulation. Numerical modelling of Oldroyd-B viscoelastic fluids is notoriously difficult. Standard Galerkin finite element methods are prone to numerical oscillations, and there is no convergence as the elasticity of fluid increases. Therefore, we use a stabilised finite element model. In order to verify our model, we first built up a model with the same geometry and fluid properties as presented in literature and compared the results. Then, with the tested model we simulated the effect of viscoelastic polymer fluid on dead pores in three simplified pore structures, which are contraction structure, expansion structure and expansion-contraction structure. Correspondingly, the streamlines and velocity contours of polymer solution, with different Reynolds numbers (Re) and Weissenberg numbers (We), flowing in these three structures are showed. The simulation results indicate that the viscoelasticity of polymer solution is the main contribution to increase the micro-scale sweep efficiency. With higher elasticity, the velocity of polymer solution is getting bigger at

  13. Sensitivity analyses of the theoretical equations used in point velocity probe (PVP) data interpretation

    Science.gov (United States)

    Devlin, J. F.

    2016-09-01

    Point velocity probes (PVPs) are dedicated, relatively low-cost instruments for measuring groundwater speed and direction in non-cohesive, unconsolidated porous media aquifers. They have been used to evaluate groundwater velocity in groundwater treatment zones, glacial outwash aquifers, and within streambanks to assist with the assessment of groundwater-surfaced water exchanges. Empirical evidence of acceptable levels of uncertainty for these applications has come from both laboratory and field trials. This work extends previous assessments of the method by examining the inherent uncertainties arising from the equations used to interpret PVP datasets. PVPs operate by sensing tracer movement on the probe surface, producing apparent velocities from two detectors. Sensitivity equations were developed for the estimation of groundwater speed, v∞, and flow direction, α, as a function of the apparent velocities of water on the probe surface and the α angle itself. The resulting estimations of measurement uncertainty, which are inherent limitations of the method, apply to idealized, homogeneous porous media, which on the local scale of a PVP measurement may be approached. This work does not address experimental sources of error that may arise from the presence of cohesive sediments that prevent collapse around the probe, the effects of centimeter-scale aquifer heterogeneities, or other complications related to borehole integrity or operator error, which could greatly exceed the inherent sources of error. However, the findings reported here have been shown to be in agreement with the previous empirical work. On this basis, properly installed and functioning PVPs should be expected to produce estimates of groundwater speed with uncertainties less than ± 15%, with the most accurate values of groundwater speed expected when horizontal flow is incident on the probe surface at about 50° from the active injection port. Directions can be measured with uncertainties less than

  14. Mapping groundwater quality in the Netherlands

    NARCIS (Netherlands)

    Pebesma, Edzer Jan

    2001-01-01

    Groundwater quality is the suitability of groundwater for a certain purpose (e.g. for human consumption), and is mostly determined by its chemical composition. Pollution from agricultural and industrial origin threatens the groundwater quality in the Netherlands. Locally, this pollution is me

  15. Groundwater: Illinois' Buried Treasure. Education Activity Guide.

    Science.gov (United States)

    Environmental Education Association of Illinois, Chicago.

    Groundwater is an extremely valuable resource that many feel has been too long neglected and taken for granted. There is growing recognition in Illinois and throughout the United States that comprehensive groundwater protection measures are vital. Illinois embarked on a course in protecting groundwater resources with the passage of the Illinois…

  16. Geochemical modelling baseline compositions of groundwater

    DEFF Research Database (Denmark)

    Postma, Diederik Jan; Kjøller, Claus; Andersen, Martin Søgaard

    2008-01-01

    Reactive transport models, were developed to explore the evolution in groundwater chemistry along the flow path in three aquifers; the Triassic East Midland aquifer (UK), the Miocene aquifer at Valreas (F) and the Cretaceous aquifer near Aveiro (P). All three aquifers contain very old groundwaters...... of the evolution in natural baseline properties in groundwater....

  17. Groundwater: Illinois' Buried Treasure. Education Activity Guide.

    Science.gov (United States)

    Environmental Education Association of Illinois, Chicago.

    Groundwater is an extremely valuable resource that many feel has been too long neglected and taken for granted. There is growing recognition in Illinois and throughout the United States that comprehensive groundwater protection measures are vital. Illinois embarked on a course in protecting groundwater resources with the passage of the Illinois…

  18. Detection and Remediation of Groundwater Pollution

    Institute of Scientific and Technical Information of China (English)

    王杰

    2016-01-01

    Groundwater is an important part of the water cycle and is also widely used as sources of drinking water. With the increasing de?velopment of groundwater exploitation, the pollution is becoming more and more serious. This paper talks about the main research direc?tions of groundwater pollution, the detection, the remediation and some conclusions.

  19. Groundwater and geothermal: urban district heating applications

    Energy Technology Data Exchange (ETDEWEB)

    Mounts, R.; Frazier, A.; Wood, E.; Pyles, O.

    1982-01-01

    This report describes how several cities use groundwater and geothermal energy in district heating systems. It begins with groundwater, introducing the basic technology and techniques of development, and describing two case studies of cities with groundwater-based district heating systems. The second half of the report consists of three case studies of cities with district heating systems using higher temperature geothermal resources.

  20. State space modeling of groundwater fluctuations

    NARCIS (Netherlands)

    Berendrecht, W.L.

    2004-01-01

    Groundwater plays an important role in both urban and rural areas. It is therefore essential to monitor groundwater fluctuations. However, data that becomes available need to be analyzed further in order to extract specific information on the groundwater system. Until recently, simple linear time se

  1. Evolution of seismic velocities in heavy oil sand reservoirs during thermal recovery process

    CERN Document Server

    Nauroy, Jean-François; Guy, N; Baroni, Axelle; Delage, Pierre; Mainguy, Marc; 10.2516/ogst/2012027

    2013-01-01

    In thermally enhanced recovery processes like cyclic steam stimulation (CSS) or steam assisted gravity drainage (SAGD), continuous steam injection entails changes in pore fluid, pore pressure and temperature in the rock reservoir, that are most often unconsolidated or weakly consolidated sandstones. This in turn increases or decreases the effective stresses and changes the elastic properties of the rocks. Thermally enhanced recovery processes give rise to complex couplings. Numerical simulations have been carried out on a case study so as to provide an estimation of the evolution of pressure, temperature, pore fluid saturation, stress and strain in any zone located around the injector and producer wells. The approach of Ciz and Shapiro (2007) - an extension of the poroelastic theory of Biot-Gassmann applied to rock filled elastic material - has been used to model the velocity dispersion in the oil sand mass under different conditions of temperature and stress. A good agreement has been found between these pre...

  2. A small-diameter NMR logging tool for groundwater investigations.

    Science.gov (United States)

    Walsh, David; Turner, Peter; Grunewald, Elliot; Zhang, Hong; Butler, James J; Reboulet, Ed; Knobbe, Steve; Christy, Tom; Lane, John W; Johnson, Carole D; Munday, Tim; Fitzpatrick, Andrew

    2013-01-01

    A small-diameter nuclear magnetic resonance (NMR) logging tool has been developed and field tested at various sites in the United States and Australia. A novel design approach has produced relatively inexpensive, small-diameter probes that can be run in open or PVC-cased boreholes as small as 2 inches in diameter. The complete system, including surface electronics and various downhole probes, has been successfully tested in small-diameter monitoring wells in a range of hydrogeological settings. A variant of the probe that can be deployed by a direct-push machine has also been developed and tested in the field. The new NMR logging tool provides reliable, direct, and high-resolution information that is of importance for groundwater studies. Specifically, the technology provides direct measurement of total water content (total porosity in the saturated zone or moisture content in the unsaturated zone), and estimates of relative pore-size distribution (bound vs. mobile water content) and hydraulic conductivity. The NMR measurements show good agreement with ancillary data from lithologic logs, geophysical logs, and hydrogeologic measurements, and provide valuable information for groundwater investigations.

  3. Linking denitrification and infiltration rates during managed groundwater recharge.

    Science.gov (United States)

    Schmidt, Calla M; Fisher, Andrew T; Racz, Andrew J; Lockwood, Brian S; Huertos, Marc Los

    2011-11-15

    We quantify relations between rates of in situ denitrification and saturated infiltration through shallow, sandy soils during managed groundwater recharge. We used thermal methods to determine time series of point-specific flow rates, and chemical and isotopic methods to assess denitrification progress. Zero order denitrification rates between 3 and 300 μmol L(-1) d(-1) were measured during infiltration. Denitrification was not detected at times and locations where the infiltration rate exceeded a threshold of 0.7 ± 0.2 m d(-1). Pore water profiles of oxygen and nitrate concentration indicated a deepening of the redoxocline at high flow rates, which reduced the thickness of the zone favorable for denitrification. Denitrification rates were positively correlated with infiltration rates below the infiltration threshold, suggesting that for a given set of sediment characteristics, there is an optimal infiltration rate for achieving maximum nitrate load reduction and improvements to water supply during managed groundwater recharge. The extent to which results from this study may be extended to other managed and natural hydrologic settings remains to be determined, but the approach taken in this study should be broadly applicable, and provides a quantitative link between shallow hydrologic and biogeochemical processes.

  4. Application of hydrogeology and groundwater-age estimates to assess the travel time of groundwater at the site of a landfill to the Mahomet Aquifer, near Clinton, Illinois

    Science.gov (United States)

    Kay, Robert T.; Buszka, Paul M.

    2016-03-02

    .The piston-flow based age of recharge determined from the tritium concentration in the groundwater sample from monitoring well G53S yielded an estimated maximum vertical velocity from the land surface to the upper part of the Radnor Till Member of 0.85 feet per year or less. This velocity, ifassumed to apply to the remaining glacial till deposits above the Mahomet aquifer, indicates that recharge flows through the 170 feet of glacial deposits between the base of the proposed chemical waste unit and the top of the Mahomet aquifer in a minimum of 200 years or longer. Analysis of hydraulic data from the site, constrained by a tritium-age based maximum groundwater velocity estimate, computed minimum estimates of effective porosity that range from about 0.021 to 0.024 for the predominantly till deposits above the Mahomet aquifer.Estimated rates of transport of recharge from land surface to the Mahomet aquifer for the CLU#3 site computed using the Darcy velocity equation with site-specific data were about 260 years or longer. The Darcy velocity-based estimates were computed using values that were based on tritium data, estimates of vertical velocity and effective porosity and available site-specific data. Solution of the Darcy velocity equation indicated that maximum vertical groundwater velocities through the deposits above the aquifer were 0.41 or 0.61 feet per year, depending on the site-specific values of vertical hydraulic conductivity (laboratory triaxial test values) and effective porosity used for the computation. The resulting calculated minimum travel times for groundwater to flow from the top of the Berry Clay Member (at the base of the proposed chemical waste unit) to the top of the Mahomet aquifer ranged from about 260 to 370 years, depending on the velocity value used in the calculation. In comparison, plausible travel times calculated using vertical hydraulic conductivity values from a previously published regional groundwater flow model were either slightly less

  5. Pore-pressure sensitivities to dynamic strains: observations in active tectonic regions

    Science.gov (United States)

    Barbour, Andrew J.

    2015-01-01

    Triggered seismicity arising from dynamic stresses is often explained by the Mohr-Coulomb failure criterion, where elevated pore pressures reduce the effective strength of faults in fluid-saturated rock. The seismic response of a fluid-rock system naturally depends on its hydro-mechanical properties, but accurately assessing how pore-fluid pressure responds to applied stress over large scales in situ remains a challenging task; hence, spatial variations in response are not well understood, especially around active faults. Here I analyze previously unutilized records of dynamic strain and pore-pressure from regional and teleseismic earthquakes at Plate Boundary Observatory (PBO) stations from 2006 through 2012 to investigate variations in response along the Pacific/North American tectonic plate boundary. I find robust scaling-response coefficients between excess pore pressure and dynamic strain at each station that are spatially correlated: around the San Andreas and San Jacinto fault systems, the response is lowest in regions of the crust undergoing the highest rates of secular shear strain. PBO stations in the Parkfield instrument cluster are at comparable distances to the San Andreas fault (SAF), and spatial variations there follow patterns in dextral creep rates along the fault, with the highest response in the actively creeping section, which is consistent with a narrowing zone of strain accumulation seen in geodetic velocity profiles. At stations in the San Juan Bautista (SJB) and Anza instrument clusters, the response depends non-linearly on the inverse fault-perpendicular distance, with the response decreasing towards the fault; the SJB cluster is at the northern transition from creeping-to-locked behavior along the SAF, where creep rates are at moderate to low levels, and the Anza cluster is around the San Jacinto fault, where to date there have been no statistically significant creep rates observed at the surface. These results suggest that the strength

  6. Seismic wave velocity of rocks in the Oman ophiolite: constraints for petrological structure of oceanic crust

    Science.gov (United States)

    Saito, S.; Ishikawa, M.; Shibata, S.; Akizuki, R.; Arima, M.; Tatsumi, Y.; Arai, S.

    2010-12-01

    Evaluation of rock velocities and comparison with velocity profiles defined by seismic refraction experiments are a crucial approach for understanding the petrological structure of the crust. In this study, we calculated the seismic wave velocities of various types of rocks from the Oman ophiolite in order to constrain a petrological structure of the oceanic crust. Christensen & Smewing (1981, JGR) have reported experimental elastic velocities of rocks from the Oman ophiolite under oceanic crust-mantle conditions (6-430 MPa). However, in their relatively low-pressure experiments, internal pore-spaces might affect the velocity and resulted in lower values than the intrinsic velocity of sample. In this study we calculated the velocities of samples based on their modal proportions and chemical compositions of mineral constituents. Our calculated velocities represent the ‘pore-space-free’ intrinsic velocities of the sample. We calculated seismic velocities of rocks from the Oman ophiolite including pillow lavas, dolerites, plagiogranites, gabbros and peridotites at high-pressure-temperature conditions with an Excel macro (Hacker & Avers 2004, G-cubed). The minerals used for calculations for pillow lavas, dolerites and plagiogranites were Qtz, Pl, Prh, Pmp, Chl, Ep, Act, Hbl, Cpx and Mag. Pl, Hbl, Cpx, Opx and Ol were used for the calculations for gabbros and peridotites. Assuming thermal gradient of 20° C/km and pressure gradient of 25 MPa/km, the velocities were calculated in the ranges from the atmospheric pressure (0° C) to 200 MPa (160° C). The calculation yielded P-wave velocities (Vp) of 6.5-6.7 km/s for the pillow lavas, 6.6-6.8 km/s for the dolerites, 6.1-6.3 km/s for the plagiogranites, 6.9-7.5 km/s for the gabbros and 8.1-8.2 km/s for the peridotites. On the other hand, experimental results reported by Christensen & Smewing (1981, JGR) were 4.5-5.9 km/s for the pillow lavas, 5.5-6.3 km/s for the dolerites, 6.1-6.3 km/s for the plagiogranites, 6

  7. Use of rhodamine WT with XAD-7 resin for determining groundwater flow paths

    Science.gov (United States)

    Close, Murray E.; Stanton, Greg J.; Pang, Liping

    2002-06-01

    A passive sampling system for use with rhodamine WT (RWT) in groundwater tracing experiments was developed to assist in the characterisation of groundwater flow paths. Amberlite XAD-7 resin was found to be suitable for adsorption of RWT, which can then be extracted using an ethanol/water mix and analysed fluorometrically. Batch and column experiments showed that XAD-7 resin has a high RWT capacity. The adsorption was slightly dependent on pH, but was always above 75% under batch conditions. The resin had a high percentage mass recovery at flow velocities around 1.5 m/day, but this decreased with increasing flow velocities. Desorption of RWT off the resin in water is dependent on the flow velocity of water and the time after the peak RWT has passed. The mass of RWT extracted from the resin bags correlated very well with both the RWT mass flux in the water and the peak concentrations observed in the monitoring wells in a field experiment. The results of resin bags were reproducible in the field with a mean coefficient of variation equal to 16%. This method has been successfully applied to two field situations with different flow velocities to indicate groundwater flow paths.

  8. Neutrino Velocity and Neutrino Oscillations

    CERN Document Server

    Minakata, H

    2012-01-01

    We study distances of propagation and the group velocities of the muon neutrinos in the presence of mixing and oscillations assuming that Lorentz invariance holds. Oscillations lead to distortion of the $\

  9. Statistics of Centroids of Velocity

    CERN Document Server

    Esquivel, A

    2009-01-01

    We review the use of velocity centroids statistics to recover information of interstellar turbulence from observations. Velocity centroids have been used for a long time now to retrieve information about the scaling properties of the turbulent velocity field in the interstellar medium. We show that, while they are useful to study subsonic turbulence, they do not trace the statistics of velocity in supersonic turbulence, because they are highly influenced by fluctuations of density. We show also that for sub-Alfv\\'enic turbulence (both supersonic and subsonic) two-point statistics (e.g. correlation functions or power-spectra) are anisotropic. This anisotropy can be used to determine the direction of the mean magnetic field projected in the plane of the sky.

  10. A Black Hills-Madison Aquifer origin for Dakota Aquifer groundwater in northeastern Nebraska.

    Science.gov (United States)

    Stotler, Randy; Harvey, F Edwin; Gosselin, David C

    2010-01-01

    Previous studies of the Dakota Aquifer in South Dakota attributed elevated groundwater sulfate concentrations to Madison Aquifer recharge in the Black Hills with subsequent chemical evolution prior to upward migration into the Dakota Aquifer. This study examines the plausibility of a Madison Aquifer origin for groundwater in northeastern Nebraska. Dakota Aquifer water samples were collected for major ion chemistry and isotopic analysis ((18)O, (2)H, (3)H, (14)C, (13)C, (34)S, (18)O-SO(4), (87)Sr, (37)Cl). Results show that groundwater beneath the eastern, unconfined portion of the study area is distinctly different from groundwater sampled beneath the western, confined portion. In the east, groundwater is calcium-bicarbonate type, with delta(18)O values (-9.6 per thousand to -12.4 per thousand) similar to local, modern precipitation (-7.4 per thousand to -10 per thousand), and tritium values reflecting modern recharge. In the west, groundwater is calcium-sulfate type, having depleted delta(18)O values (-16 per thousand to -18 per thousand) relative to local, modern precipitation, and (14)C ages 32,000 to more than 47,000 years before present. Sulfate, delta(18)O, delta(2)H, delta(34)S, and delta(18)O-SO(4) concentrations are similar to those found in Madison Aquifer groundwater in South Dakota. Thus, it is proposed that Madison Aquifer source water is also present within the Dakota Aquifer beneath northeastern Nebraska. A simple Darcy equation estimate of groundwater velocities and travel times using reported physical parameters from the Madison and Dakota Aquifers suggests such a migration is plausible. However, discrepancies between (14)C and Darcy age estimates indicate that (14)C ages may not accurately reflect aquifer residence time, due to mixtures of varying aged water.

  11. Kriging interpolating cosmic velocity field

    Science.gov (United States)

    Yu, Yu; Zhang, Jun; Jing, Yipeng; Zhang, Pengjie

    2015-10-01

    Volume-weighted statistics of large-scale peculiar velocity is preferred by peculiar velocity cosmology, since it is free of the uncertainties of galaxy density bias entangled in observed number density-weighted statistics. However, measuring the volume-weighted velocity statistics from galaxy (halo/simulation particle) velocity data is challenging. Therefore, the exploration of velocity assignment methods with well-controlled sampling artifacts is of great importance. For the first time, we apply the Kriging interpolation to obtain the volume-weighted velocity field. Kriging is a minimum variance estimator. It predicts the most likely velocity for each place based on the velocity at other places. We test the performance of Kriging quantified by the E-mode velocity power spectrum from simulations. Dependences on the variogram prior used in Kriging, the number nk of the nearby particles to interpolate, and the density nP of the observed sample are investigated. First, we find that Kriging induces 1% and 3% systematics at k ˜0.1 h Mpc-1 when nP˜6 ×1 0-2(h-1 Mpc )-3 and nP˜6 ×1 0-3(h-1 Mpc )-3 , respectively. The deviation increases for decreasing nP and increasing k . When nP≲6 ×1 0-4(h-1 Mpc )-3 , a smoothing effect dominates small scales, causing significant underestimation of the velocity power spectrum. Second, increasing nk helps to recover small-scale power. However, for nP≲6 ×1 0-4(h-1 Mpc )-3 cases, the recovery is limited. Finally, Kriging is more sensitive to the variogram prior for a lower sample density. The most straightforward application of Kriging on the cosmic velocity field does not show obvious advantages over the nearest-particle method [Y. Zheng, P. Zhang, Y. Jing, W. Lin, and J. Pan, Phys. Rev. D 88, 103510 (2013)] and could not be directly applied to cosmology so far. However, whether potential improvements may be achieved by more delicate versions of Kriging is worth further investigation.

  12. Event Detection by Velocity Pyramid

    OpenAIRE

    2014-01-01

    In this paper, we propose velocity pyramid for multimediaevent detection. Recently, spatial pyramid matching is proposed to in-troduce coarse geometric information into Bag of Features framework,and is eective for static image recognition and detection. In video, notonly spatial information but also temporal information, which repre-sents its dynamic nature, is important. In order to fully utilize it, wepropose velocity pyramid where video frames are divided into motionalsub-regions. Our meth...

  13. Microfiltration of distillery stillage: Influence of membrane pore size

    Directory of Open Access Journals (Sweden)

    Vasić Vesna M.

    2012-01-01

    Full Text Available Stillage is one of the most polluted waste products of the food industry. Beside large volume, the stillage contains high amount of suspended solids, high values of chemical oxygen demand and biological oxygen demand, so it should not be discharged in the nature before previous purification. In this work, three ceramic membranes for microfiltration with different pore sizes were tested for stillage purification in order to find the most suitable membrane for the filtration process. Ceramic membranes with a nominal pore size of 200 nm, 450 nm and 800 nm were used for filtration. The influence of pore size on permeate flux and removal efficiency was investigated. A membrane with the pore size of 200 nm showed the best filtration performance so it was chosen for the microfiltration process.

  14. Nano pores evolution in hydroxyapatite microsphere during spark plasma sintering

    Directory of Open Access Journals (Sweden)

    Lin C.

    2011-01-01

    Full Text Available Micron-spherical granules of hydroxyapatite (HAp nanoparticles were prepared by powder granulation methods. Through subsequent sintering, porous HAp microspheres with tailored pore and grain framework structures were obtained. Detailed microstructure investigation by SEM and TEM revealed the correlation of the pore structure and the necking strength with the sintering profiles that determine the coalescence features of the nanoparticles. The partially sintered porous HAp microspheres containing more than 50% porosity consisting of pores and grains both in nano-scale are active in inducing the precipitation of HAp in simulated body fluid. The nano-porous HAp microspheres with an extensive surface and interconnecting pores thus demonstrate the potential of stimulating the formation of collagen and bone and the integration with the newly formed bones during physiological bone remodeling.

  15. Bilayer Deformation, Pores, and Micellation Induced by Oxidized Lipids.

    Science.gov (United States)

    Boonnoy, Phansiri; Jarerattanachat, Viwan; Karttunen, Mikko; Wong-Ekkabut, Jirasak

    2015-12-17

    The influence of different oxidized lipids on lipid bilayers was investigated with 16 individual 1 μs atomistic molecular dynamics (MD) simulations. Binary mixtures of lipid bilayers of 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphatidylcholine (PLPC) and its peroxide and aldehyde products were performed at different concentrations. In addition, an asymmetrical short chain lipid, 1-palmitoyl-2-decanoyl-sn-glycero-3-phosphatidylcholine (PDPC), was used to compare the effects of polar/apolar groups in the lipid tail on lipid bilayer. Although water defects occurred with both aldehyde and peroxide lipids, full pore formation was observed only for aldehyde lipids. At medium concentrations the pores were stable. At higher concentrations, however, the pores became unstable and micellation occurred. Data analysis shows that aldehyde lipids' propensity for pore formation is due to their shorter and highly mobile tail. The highly polar peroxide lipids are stabilized by strong hydrogen bonds with interfacial water.

  16. The Pore Structure and Hydration Performance of Sulphoaluminate MDF Cement

    Institute of Scientific and Technical Information of China (English)

    HUANG Cong-yun; YUAN Run-zhang; LONG Shi-zong

    2004-01-01

    The hydration and pore structure of sulphoaluminate MDF cement were studied by X-ray diffractometer ( XRD ), scanning electron microscope (SEM) and mercury intrusion porosimeter ( MIP ) etc. The ex-perimental results indicate that hydration products of the materials are entringites ( Aft ), aluminium hydroxide andCSH (Ⅰ) gel etc. Due to its very low water-cement ratio, hydration function is only confined to the surfaces of ce-ment grains, and there is a lot of sulphoaluminate cement in the hardenite which is unhydrated yet. Hydration re-action was rapidly carried under the condition of the heat-pressing. Therefore cement hydrates Aft, CSH (Ⅰ) andaluminium hydroxide gel fill in pores. The expansibility of Aft makes the porosity of MDF cement lower ( less than1 percent ) and the size of pore smaller (80 percent pore was less than 250A), and enhances its strength.

  17. Diffusion Pore Imaging by Hyperpolarized Xenon-129 Nuclear Magnetic Resonance

    CERN Document Server

    Kuder, Tristan Anselm; Windschuh, Johannes; Laun, Frederik Bernd

    2012-01-01

    Nuclear magnetic resonance (NMR) diffusion measurements are widely used to derive parameters indirectly related to the microstructure of biological tissues and porous media. However, a direct imaging of cell or pore shapes and sizes would be of high interest. For a long time, determining pore shapes by NMR diffusion acquisitions seemed impossible, because the necessary phase information could not be preserved. Here we demonstrate experimentally using the measurement technique which we have recently proposed theoretically that the shape of arbitrary closed pores can be imaged by diffusion acquisitions, which yield the phase information. For this purpose, we use hyperpolarized xenon gas in well-defined geometries. The signal can be collected from the whole sample which mainly eliminates the problem of vanishing signal at increasing resolution of conventional NMR imaging. This could be used to non-invasively gain structural information inaccessible so far such as pore or cell shapes, cell density or axon integri...

  18. Diffusion in the pore water of compacted crushed salt

    Energy Technology Data Exchange (ETDEWEB)

    Fluegge, Judith; Herr, Sebastian; Lauke, Thomas; Meleshyn, Artur; Miehe, Ruediger; Ruebel, Andre

    2016-07-15

    Diffusion of dissolved radionuclides in the pore water of compacted crushed salt in the long-term is the most relevant process for the release of radionuclides from a dedicated repository for high-level waste in a salt formation as has been shown in latest safety assessments and research projects /BUH 16/. So far, diffusion coefficients for free water have been applied for the diffusion in pore water in models for long-term safety assessments. This conservative assumption was used, because data on the diffusion coefficient of dissolved substances in crushed salt have been missing. Furthermore, the diffusion coefficient in the pore water was assumed to be constant and independent from the degree of compaction of the crushed salt. The work presented in this report was intended to contribute to fill this gap of knowledge about how the diffusion of radionuclides takes place in the compacted backfill of a repository in salt. For the first time, the pore diffusion coefficient as well as its dependence on the porosity of the crushed salt was determined experimentally by means of through-diffusion experiments using caesium as tracer. The results achieved in this project suggest that the diffusion in compacted crushed salt is not fully comparable to that in a homogeneous, temporally stable porous medium like sand or clay. The results obtained from four diffusion experiments show a remarkably different behaviour and all yield unique concentration versus time plots which includes highly temporal variable tracer fluxes with even full interruptions of the flux for longer periods of time. This effect cannot be explained by assuming a tracer transport by diffusion in a temporarily invariant pore space and / or under temporally invariant experimental conditions. From our point of view, a restructuring of the pore space seems to lead to closed areas of pore water in the sample which may open up again after some time, leading to a variable pore space and hence variable diffusive

  19. Global Groundwater related Risk Indicators: quantifying groundwater stress and groundwater table decline (1990-2010) at global scale

    Science.gov (United States)

    Faneca Sanchez, Marta; Sutanudjaja, Edwin; Kuijper, Marijn; Bierkens, Marc

    2016-04-01

    Groundwater is an invisible but indispensable resource for the economic development of many countries. Due to the need for this resource, in many cases it is exploited under severe pressure and the exploitation can become not sustainable. The non-sustainable exploitation of water is a well-known problem on both regional and global scales. However, most currently-available assessments on water stress still mostly focus on surface water and on water balances. In this work, we presented two global maps of groundwater risk indicators: an updated version of the groundwater stress (Gleeson et al., 2011, DOI: 10.1038/nature11295) and an indicator on groundwater table decline for the period 1990-2010. To calculate both indicators, we used the updated PCR-GLOBWB model output at 5 arcmin resolution (about 10 km at the equator), that is extended with an offline coupling to a global groundwater MODFLOW model. PCR-GLOBWB simulates daily river discharge and groundwater recharge, as well as surface water and groundwater abstraction rates. The latter are estimated internally within the model based on the simulation of their availabilities and water demands for irrigation and other sectors. The daily output of PCR-GLOBWB would then be aggregated to the monthly resolution and used to force the MODFLOW groundwater model resolving spatio-temporal groundwater table dynamics, incorporating the simulated groundwater abstraction of PCR-GLOBWB. Using the PCR-GLOBWB and MODFLOW simulation results from the period 1990-2010, we then quantified groundwater stress and assessed the groundwater table decline. Results are presented on four different spatial scales: 5 arcmin pixel, drainage/sub-catchment unit, state level, and major aquifer unit. The maps clearly show where groundwater is under stress, where there is a trend in the drop of the groundwater table, the slope of the drop and the significance of it.

  20. Subsurface hydrological information in rock-slide phenomena from groundwater spring monitoring.

    Science.gov (United States)

    Rochetti, Francesco; Corsini, Alessandro; Deiana, Manuela; Loche, Roberto; Mulas, Marco; Russo, Michele

    2016-04-01

    Frequently rock-slide phenomena are characterized by rough topography and high declivity of the slope. Due to these characteristics, the drilling of boreholes is not so common and in some circumstance expensive. Consequently, the exact information about depth of the sliding surface and about groundwater processes, groundwater levels or pore water pressure distribution are missing. Alternately, some information about the groundwater can be obtained from the physical-chemical monitoring of springs. The research highlights preliminary results, about the groundwater processes, obtained from the continuous flow-rate monitoring of a spring located in the active Piagneto rock-slide (northern Apennine). The spring has been monitored from Sept-2014 until Oct-2015 using a piezometer transducer (sampling frequency 1 h) and a triangular weir. The landslide was monitored in continuous since the 2009 using an automatic total station and some reflectors. The monitoring of the rock-slide displacements showed creep phenomena in the summer and acceleration phases from autumn to late spring, during periods characterized by high rainfall intensity; rainfall with intensity higher than 10 mm/d and duration less than 15 days can produce the acceleration of the sliding mass. Before 2014 any information about groundwater was collected. The successively spring monitoring shows the follow results: the spring flow rate is strongly variable in the time; only some rainfall events, with particular intensity and duration (generally total amount higher than 100 mm), are responsible of strong changes in the flow rate, and the flow rate starts to increase only after some hours; the snow melting events, also when there is a fast reduction of the snow thickness, don't produce high variation in the flow rate discharge; there is a strong correlation between the flow rate peaks and the rock-slide acceleration; an infiltration coefficient higher than 70% is estimated through the comparison between the

  1. Interaction of rare earth elements and components of the Horonobe deep groundwater.

    Science.gov (United States)

    Kirishima, Akira; Kuno, Atsushi; Amamiya, Hiroshi; Kubota, Takumi; Kimuro, Shingo; Amano, Yuki; Miyakawa, Kazuya; Iwatsuki, Teruki; Mizuno, Takashi; Sasaki, Takayuki; Sato, Nobuaki

    2017-02-01

    To better understand the migration behavior of minor actinides in deep groundwater, the interactions between doped rare earth elements (REEs) and components of Horonobe deep groundwater were investigated. Approximately 10 ppb of the REEs, i.e. Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, Tm, and Yb were doped into a groundwater sample collected from a packed section in a borehole drilled at 140 m depth in the experiment drift of Horonobe Underground Research Laboratory in Hokkaido, Japan. The groundwater sample was sequentially filtered with a 0.2 μm pore filter, and 10 kDa, 3 kDa and 1 kDa nominal molecular weight limit (NMWL) ultrafilters with conditions kept inert. Next, the filtrate solutions were analyzed with inductively coupled plasma mass spectrometry (ICP-MS) to determine the concentrations of the REEs retained in solution at each filtration step, while the used filters were analyzed through neutron activation analysis (NAA) and TOF-SIMS element mapping to determine the amounts and chemical species of the trapped fractions of REEs on each filter. A strong relationship between the ratios of REEs retained in the filtrate solutions and the ionic radii of the associated REEs was observed; i.e. smaller REEs occur in larger proportions dissolved in the solution phase under the conditions of the Horonobe groundwater. The NAA and TOF-SIMS analyses revealed that portions of the REEs were trapped by the 0.2 μm pore filter as REE phosphates, which correspond to the species predicted to be predominant by chemical equilibrium calculations for the conditions of the Horonobe groundwater. Additionally, small portions of colloidal REEs were trapped by the 10 kDa and 3 kDa NMWL ultrafilters. These results suggest that phosphate anions play an important role in the chemical behavior of REEs in saline (seawater-based) groundwater, which may be useful for predicting the migration behavior of trivalent actinides released from radioactive waste repositories in the far

  2. Groundwater regulation and integrated planning

    Science.gov (United States)

    Quevauviller, Philippe; Batelaan, Okke; Hunt, Randall J.

    2016-01-01

    The complex nature of groundwater and the diversity of uses and environmental interactions call for emerging groundwater problems to be addressed through integrated management and planning approaches. Planning requires different levels of integration dealing with: the hydrologic cycle (the physical process) including the temporal dimension; river basins and aquifers (spatial integration); socioeconomic considerations at regional, national and international levels; and scientific knowledge. The great natural variation in groundwater conditions obviously affects planning needs and options as well as perceptions from highly localised to regionally-based approaches. The scale at which planning is done therefore needs to be carefully evaluated against available policy choices and options in each particular setting. A solid planning approach is based on River Basin Management Planning (RBMP), which covers: (1) objectives that management planning are designed to address; (2) the way various types of measures fit into the overall management planning; and (3) the criteria against which the success or failure of specific strategies or interventions can be evaluated (e.g. compliance with environmental quality standards). A management planning framework is to be conceived as a “living” or iterated document that can be updated, refined and if necessary changed as information and experience are gained. This chapter discusses these aspects, providing an insight into European Union (EU), United States and Australia groundwater planning practices.

  3. Groundwater Resources: Investigation and Development

    Science.gov (United States)

    Anderson, Mary P.

    A glance through the table of contents of this volume might suggest that it is yet another introductory text on principles of groundwater hydrology. All of the usual basic topics are covered including definitions of terms and concepts, aquifer types, drilling methods, and pumping tests. But partly because this book is intended for practicing groundwater consultants rather than students, other less elementary topics such as environmental isotope techniques, geochemical methods, interpretation and utilization of spring flow, geophysical methods, and groundwater balances are also included.According to the preface, ‘practical applicability’ is stressed ‘to show how groundwater investigations should be conducted using a systematic, well-directed effort’ and to describe ‘… what to do, what to avoid, and what kind of results one can reasonably expect …’ While this book was published as part of a series of monographs on water pollution, it is more in the nature of a handbook than a true monograph. That is, it is not an in-depth treatment of a single topic but presents a broad introduction to the ways in

  4. Adsorptive Iron Removal from Groundwater

    NARCIS (Netherlands)

    Sharma, S.K.

    2001-01-01

    Iron is commonly present in groundwater worldwide. The presence of iron in drinking water is not harmful to human health, however it is undesirable because of the associated aesthetic and operational problems, namely: bad taste, colour, stains on laundry and plumbing fixtures, and aftergrowth in the

  5. Adsorptive iron removal from groundwater

    NARCIS (Netherlands)

    Sharma, S.K.

    2001-01-01

    Iron is commonly present in groundwater worldwide. The presence of iron in the water supply is not harmful to human health, however it is undesirable. Bad taste, discoloration, staining, deposition in the distribution system leading to aftergrowth, and incidences of high turbidity are some

  6. Determination of pore size distributions in capillary-channeled polymer fiber stationary phases by inverse size-exclusion chromatography and implications for fast protein separations.

    Science.gov (United States)

    Wang, Zhengxin; Marcus, R Kenneth

    2014-07-18

    Capillary-channeled polymer (C-CP) fibers have been utilized as liquid chromatography stationary phases, primarily for biomacromolecule separations on the analytical and preparative scales. The collinear packing of the eight-channeled C-CP fibers provides for very efficient flow, allowing operation at high linear velocity (u>100mm s(-1)) and low backpressure (transport properties, there must not be mass transfer limitations as would be imposed by having an appreciably porous phase, wherein solute diffusion limits the overall mass transport rates. To better understand the physical nano-/micro- structure of C-CP fibers, inverse size exclusion chromatography (iSEC) has been employed to determine the pore size distribution (PSD) within C-CP fibers. A diversity of test species (from metal ions to large proteins) was used as probes under non-retaining conditions to obtain a response curve reflecting the apparent partition coefficient (Kd) versus hydrodynamic radii (rm). A mean pore radius (rp) of 4.2nm with standard deviation (sp) of ±1.1nm was calculated by fitting the Kd versus rm data to model equations with a Gaussian pore size distribution, and a pore radius of 4.0±0.1nm was calculated based on a log-normal distribution. The derived mean pore radius is much smaller than traditional support materials, with the standard deviation showing a relatively uniform pore distribution. van Deemter plots were analyzed to provide practical confirmation of the structural implications. Large molecules (e.g., proteins) that are fully excluded from pores have no significant C-terms in the van Deemter plots whereas small molecules that can access the pore volumes display appreciable C-terms, as expected. Fitting of retention data to the Knox equation suggests that the columns operate with a characteristic particle diameter (dp) of ∼53μm.

  7. Origin and assessment of deep groundwater inflow in the Ca' Lita landslide using hydrochemistry and in situ monitoring

    Directory of Open Access Journals (Sweden)

    F. Cervi

    2012-06-01

    Full Text Available Changes in soil water content, groundwater flow and a rise in pore water pressure are well-known causal or triggering factors for hillslope instability. Rainfall and snowmelt are generally assumed as the only sources of groundwater recharge. This assumption neglects the role of deep water inflow in highly tectonized areas, a factor that can influence long-term pore-pressure regimes and play a role on local slope instability.

    This paper aims to assess the origin of groundwater in the Ca' Lita landslide (northern Italian Apennines and to qualify and quantify the aliquot attributable to deep water inflow. The research is essentially based on in situ monitoring and hydrochemical analyses. It involved 5 yr of continuous monitoring of groundwater levels, electrical conductivity and temperature, and with groundwater sampling followed by determination of major ions, tracers (such as Boron and Strontium, and isotopes (Oxygen, Deuterium, Tritium. Leaching experiments on soil samples and water recharge estimation were also carried out.

    Results show that the groundwater balance in the Ca' Lita landslide must take into account an inflow of highly mineralized Na-SO4 water (more than 9500 μS cm−1 with non-negligible amounts of Chloride (up to 800 mg l−1. The deep water inflow recharges the aquifer hosted in the bedrock underlying the sliding surface (at a rate of about 7800–17 500 m3 yr−1. It also partly recharges the landslide body, where the hydrochemical imprint of deep water mixed with rainfall and snowmelt water was observed. This points to a probable influence of deep water inflow on the mobility of the Ca' Lita landslide, a finding that could be applicable to other large landslides occurring in highly tectonized areas in the northern Apennines or in other mountain chains.

  8. Molecular biology and biophysical properties of ion channel gating pores.

    Science.gov (United States)

    Moreau, Adrien; Gosselin-Badaroudine, Pascal; Chahine, Mohamed

    2014-11-01

    The voltage sensitive domain (VSD) is a pivotal structure of voltage-gated ion channels (VGICs) and plays an essential role in the generation of electrochemical signals by neurons, striated muscle cells, and endocrine cells. The VSD is not unique to VGICs. Recent studies have shown that a VSD regulates a phosphatase. Similarly, Hv1, a voltage-sensitive protein that lacks an apparent pore domain, is a self-contained voltage sensor that operates as an H⁺ channel. VSDs are formed by four transmembrane helices (S1-S4). The S4 helix is positively charged due to the presence of arginine and lysine residues. It is surrounded by two water crevices that extend into the membrane from both the extracellular and intracellular milieus. A hydrophobic septum disrupts communication between these water crevices thus preventing the permeation of ions. The septum is maintained by interactions between the charged residues of the S4 segment and the gating charge transfer center. Mutating the charged residue of the S4 segment allows the water crevices to communicate and generate gating pore or omega pore. Gating pore currents have been reported to underlie several neuronal and striated muscle channelopathies. Depending on which charged residue on the S4 segment is mutated, gating pores are permeant either at depolarized or hyperpolarized voltages. Gating pores are cation selective and seem to converge toward Eisenmann's first or second selectivity sequences. Most gating pores are blocked by guanidine derivatives as well as trivalent and quadrivalent cations. Gating pores can be used to study the movement of the voltage sensor and could serve as targets for novel small therapeutic molecules.

  9. Relationship between pore structure and compressive strength of concrete: Experiments and statistical modeling

    Indian Academy of Sciences (India)

    J BU; Z TIAN

    2016-03-01

    Properties of concrete are strongly dependent on its pore structure features, porosity being an important one among them. This study deals with developing an understanding of the pore structure-compressive strength relationship in concrete. Several concrete mixtures with different pore structures are proportioned and subjected to static compressive tests. The pore structure features such as porosity, pore size distribution are extracted using mercury intrusion porosimetry technique. A statistical model is developed to relate thecompressive strength to relevant pore structure features.

  10. Porosity, Dispersivity, and Contaminant Transport in Groundwater

    Institute of Scientific and Technical Information of China (English)

    MOIWO Juana P.

    2001-01-01

    Porosity (n) and Dispersivity (D) were modeled in relation to Solute Transport Time (t) in a saturated, homogeneous, isotropic, unconfined aquifer using the MOC model. It was noted that n and D have an important influence on solute transport time t in groundwater, with a consistently strong and direct relationship between n, D, and t. In the case of porosity, the relationship was found to be directly related to t when other aquifer properties remained unchanged. This was also mathematically argued using a form of the flow equation put forward by Henry Darcy (1856). Dispersivity on the other hand had somehow the same relationship with solute transport time t as porosity, but with much less effect. That is, higher dispersions lead to longer solute transport time within the aquifer system. This was because as the individual solute particles set off from the average seepage velocity, they traversed through longer distances due to tortuosity, mechanical mixing, diffusion, and microscopic heterogeneity latent in the porous media. Also when n and D were co- treated over t, n was noted to be dominant over D with regard t. This follows that the effect of porosity on solute transport time far out shadowed that of dispersivity. Stated in other words, the dispersivity of a substance in any porous medium is to a large extent a function of the porosity of that medium.

  11. Distributed pore model for bio-molecule chromatography.

    Science.gov (United States)

    Coquebert de Neuville, Bertrand; Tarafder, Abhijit; Morbidelli, Massimo

    2013-07-12

    One of the main peculiarities in protein chromatography is that the adsorbing proteins and the adsorbent pores have comparable sizes. This has the consequence that the pore accessibility depends not only on the solute size but also on the loading conditions of the adsorbent because protein adsorption significantly reduces the size of the pores. A model that accounts for the pore size distribution of the stationary phase and for the pore shrinkage due to protein adsorption has been developed to describe mass transport and adsorption in the porous particles. This model has been shown to be equivalent to the general rate model (GRM) in the case of processes under highly diluted conditions with little adsorption. This implies that the model parameters determination follows the same procedure as for the classical GRM. The new pore model has been applied and compared to the GRM for the simulation of lysozyme breakthrough experiments and for the prediction of 5% dynamic binding capacity values solely based on static capacity measurements.

  12. Pore opening dynamics in the exocytosis of serotonin

    Science.gov (United States)

    Ramirez-Santiago, Guillermo; Cercos, Montserrat G.; Martinez-Valencia, Alejandro; Salinas Hernandez, Israel; Rodríguez-Sosa, Leonardo; de-Miguel, Francisco F.

    2015-03-01

    The current view of the exocytosis of transmitter molecules is that it starts with the formation of a fusion pore that connects the intravesicular and the extracellular spaces, and is completed by the release of the rest of the transmitter contained in the vesicle upon the full fusion and collapse of the vesicle with the plasma membrane. However, under certain circumstances, a rapid closure of the pore before the full vesicle fusion produces only a partial release of the transmitter. Here we show that whole release of the transmitter occurs through fusion pores that remain opened for tens of milliseconds without vesicle collapse. This was demonstrated through amperometric measurements of serotonin release from electrodense vesicles in the axon of leech Retzius neurons and mathematical modelling. By modeling transmitter release with a diffusion equation subjected to boundary conditions that are defined by the experiment, we showed that those pores with a fast half rise time constant remained opened and allowed the full quantum release without vesicle collapse, whereas pores with a slow rise time constant closed rapidly, thus producing partial release. We conclude that a full transmitter release may occur through the fusion pore in the absence of vesicle collapse. This work was founded by a DGAPA-UNAM grants IN200914 and IN118410 CONACYT GRANT 130031, and CONACyT doctoral fellowships.

  13. Mangrove pore water exchange across a latitudinal gradient

    Science.gov (United States)

    Tait, Douglas R.; Maher, Damien T.; Macklin, Paul A.; Santos, Isaac R.

    2016-04-01

    We combined observations of the natural tracer radon (222Rn) with hydrodynamic models across a broad latitudinal gradient covering several climate zones to estimate pore water exchange rates in mangroves. Pore water exchange ranged from 2.1 to 35.5 cm d-1 from temperate to tropical regions and averaged 16.3 ± 5.1 cm d-1. If upscaled to the global weighted mangrove area, pore water exchange in mangroves would recirculate the entire volume of water overlying the continental shelf in less than 153 years. Although pore water exchange (recirculated seawater) and river discharge represent different pathways for water entering the coastal ocean, the estimated global mangrove pore water exchange would be equal to approximately one third of annual global river discharge to the ocean (3.84 × 1013 m3 yr-1). Because biogeochemical processes in mangroves are largely dependent on pore water exchange, these large exchange rates have major implications for coastal nutrient, carbon, and greenhouse gas cycling in tropical marine systems.

  14. Patch-clamp detection of macromolecular translocation along nuclear pores

    Directory of Open Access Journals (Sweden)

    Bustamante J.O.

    1998-01-01

    Full Text Available The present paper reviews the application of patch-clamp principles to the detection and measurement of macromolecular translocation along the nuclear pores. We demonstrate that the tight-seal 'gigaseal' between the pipette tip and the nuclear membrane is possible in the presence of fully operational nuclear pores. We show that the ability to form a gigaseal in nucleus-attached configurations does not mean that only the activity of channels from the outer membrane of the nuclear envelope can be detected. Instead, we show that, in the presence of fully operational nuclear pores, it is likely that the large-conductance ion channel activity recorded derives from the nuclear pores. We conclude the technical section with the suggestion that the best way to demonstrate that the nuclear pores are responsible for ion channel activity is by showing with fluorescence microscopy the nuclear translocation of ions and small molecules and the exclusion of the same from the cisterna enclosed by the two membranes of the envelope. Since transcription factors and mRNAs, two major groups of nuclear macromolecules, use nuclear pores to enter and exit the nucleus and play essential roles in the control of gene activity and expression, this review should be useful to cell and molecular biologists interested in understanding how patch-clamp can be used to quantitate the translocation of such macromolecules into and out of the nucleus

  15. Pore growth in U-Mo/Al dispersion fuel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yeon Soo, E-mail: yskim@anl.gov [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Jeong, G.Y.; Sohn, D.-S. [Ulsan National Institute of Science and Technology, 50 UNIST-gil, Eonyang-eup, Ulju-gun, Ulsan, 689-798 (Korea, Republic of); Jamison, L.M. [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States)

    2016-09-15

    U-Mo/Al dispersion fuel is currently under development in the DOE’s Material Management and Minimization program to convert HEU-fueled research reactors to LEU-fueled reactors. In some demanding conditions in high-power and high-performance reactors, large pores form in the interaction layers between the U-Mo fuel particles and the Al matrix, which pose a potential to cause fuel failure. In this study, comprehension of the formation and growth of these pores was explored. As a product, a model to predict pore growth and porosity increase was developed. The model includes three major topics: fission gas release from the U-Mo and the IL to the pores, stress evolution in the fuel meat, and the effect of amorphous IL growth. Well-characterized in-pile data from reduced-size plates were used to fit the model parameters. A data set from full-sized plates, independent and distinctively different from those used to fit the model parameters, was used to examine the accuracy of the model. The model showed fair agreement with the measured data. The model suggested that the growth of the IL has a critical effect on pore growth, as both its material properties and energetics are favorable to pore formation. Therefore, one area of the current effort, focused on suppressing IL growth, appears to be on the right track to improve the performance of this fuel.

  16. Nonlinear electrokinetic transport in networks of microscale and nanoscale pores

    Science.gov (United States)

    Alizadeh, Shima; Andersen, Mathias B.; Mani, Ali

    2012-11-01

    The objective of this study is to develop the understanding of nonlinear electrohydrodynamic effects in a wide range of systems including lab-on-a-chip systems, electroosmotic pumps, and, in general, porous media with random or fabricated pore morphology. We present a continuum model in which these systems are described as massive networks of long and thin pores. The thickness of the pores can vary from nanoscale to microscale, corresponding to the highly overlapped electric double layers (EDL) to the thin double layer limit. Within each pore the transport in the wall-normal direction is assumed to be in equilibrium leading to a reduced order model for the axial transport of species in the form of a transient one-dimensional partial differential equation (PDE). PDEs from different pores are coupled through boundary conditions at the pore intersections by proper implementation of the conservation laws. We show that this model can capture important nonlinear dynamics, which are typically ignored in homogenized models. Specifically, our model captures concentration polarization shocks and flow recirculation zones respectively formed when micropores and nanopores are connected in series and in parallel. We present a comparison between our model and recent experiments in microfluidics, and will discuss applications in porous media modeling for energy storage and water purification systems.

  17. Accumulation of formamide in hydrothermal pores to form prebiotic nucleobases

    Science.gov (United States)

    Niether, Doreen; Afanasenkau, Dzmitry; Dhont, Jan K. G.

    2016-04-01

    Formamide is one of the important compounds from which prebiotic molecules can be synthesized, provided that its concentration is sufficiently high. For nucleotides and short DNA strands, it has been shown that a high degree of accumulation in hydrothermal pores occurs, so that temperature gradients might play a role in the origin of life [Baaske P, et al. (2007) Proc Natl Acad Sci USA 104(22):9346-9351]. We show that the same combination of thermophoresis and convection in hydrothermal pores leads to accumulation of formamide up to concentrations where nucleobases are formed. The thermophoretic properties of aqueous formamide solutions are studied by means of Infrared Thermal Diffusion Forced Rayleigh Scattering. These data are used in numerical finite element calculations in hydrothermal pores for various initial concentrations, ambient temperatures, and pore sizes. The high degree of formamide accumulation is due to an unusual temperature and concentration dependence of the thermophoretic behavior of formamide. The accumulation fold in part of the pores increases strongly with increasing aspect ratio of the pores, and saturates to highly concentrated aqueous formamide solutions of ˜85 wt% at large aspect ratios. Time-dependent studies show that these high concentrations are reached after 45-90 d, starting with an initial formamide weight fraction of 10-310-3 wt % that is typical for concentrations in shallow lakes on early Earth.

  18. Atomic structure of anthrax protective antigen pore elucidates toxin translocation.

    Science.gov (United States)

    Jiang, Jiansen; Pentelute, Bradley L; Collier, R John; Zhou, Z Hong

    2015-05-28

    Anthrax toxin, comprising protective antigen, lethal factor, and oedema factor, is the major virulence factor of Bacillus anthracis, an agent that causes high mortality in humans and animals. Protective antigen forms oligomeric prepores that undergo conversion to membrane-spanning pores by endosomal acidification, and these pores translocate the enzymes lethal factor and oedema factor into the cytosol of target cells. Protective antigen is not only a vaccine component and therapeutic target for anthrax infections but also an excellent model system for understanding the mechanism of protein translocation. On the basis of biochemical and electrophysiological results, researchers have proposed that a phi (Φ)-clamp composed of phenylalanine (Phe)427 residues of protective antigen catalyses protein translocation via a charge-state-dependent Brownian ratchet. Although atomic structures of protective antigen prepores are available, how protective antigen senses low pH, converts to active pore, and translocates lethal factor and oedema factor are not well defined without an atomic model of its pore. Here, by cryo-electron microscopy with direct electron counting, we determine the protective antigen pore structure at 2.9-Å resolution. The structure reveals the long-sought-after catalytic Φ-clamp and the membrane-spanning translocation channel, and supports the Brownian ratchet model for protein translocation. Comparisons of four structures reveal conformational changes in prepore to pore conversion that support a multi-step mechanism by which low pH is sensed and the membrane-spanning channel is formed.

  19. Pore Scale Analysis of Oil Shale/Sands Pyrolysis

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Chen-Luh [Univ. of Utah, Salt Lake City, UT (United States); Miller, Jan [Univ. of Utah, Salt Lake City, UT (United States)

    2011-03-01

    There are important questions concerning the quality and volume of pore space that is created when oil shale is pyrolyzed for the purpose of producing shale oil. In this report, 1.9 cm diameter cores of Mahogany oil shale were pyrolyzed at different temperatures and heating rates. Detailed 3D imaging of core samples was done using multiscale X-ray computed tomography (CT) before and after pyrolysis to establish the pore structure. The pore structure of the unreacted material was not clear. Selected images of a core pyrolyzed at 400oC were obtained at voxel resolutions from 39 microns (Οm) to 60 nanometers (nm). Some of the pore space created during pyrolysis was clearly visible at these resolutions and it was possible to distinguish between the reaction products and the host shale rock. The pore structure deduced from the images was used in Lattice Boltzmann simulations to calculate the permeability in the pore space. The permeabilities of the pyrolyzed sampl