Science.gov

Sample records for clay pore water

  1. Pore characteristics and their emergent effect on water adsorption and transport in clays using small-angle neutron scattering with contrast variation

    NASA Astrophysics Data System (ADS)

    Ding, M.; Hartl, M.; Wang, Y.; Hjelm, R.

    2013-12-01

    In nuclear waste management, clays are canonical materials in the construction of engineered barriers. They are also naturally occurring reactive minerals which play an important role in retention and colloidal facilitated reactive transport in subsurface systems. Knowledge of total and accessible porosity in clays is crucial in determining fluids transport behavior in clays. It will provide fundamental insight on the performance efficiency of specific clays as a barrier material and their role in regulating radionuclide transport in subsurface environments. The aim of the present work is to experimentally investigate the change in pore characteristics of clays as function of moisture content, and to determine their pore character in relation to their water retention capacity. Recent developments in small-angle neutron scattering (SANS) techniques allow quantitative measurement of pore morphology and size distribution of various materials in their pristine state under various sample environments (exposure to solution, high temperature, and so on). Furthermore, due to dramatic different neutron scattering properties of hydrogen and deuterium, one can readily use contrast variation, which is the isotopic labeling with various ratios of H and D (e.g. mixture of H2O/D2O) to highlight or suppress features of the sample. This is particularly useful in the study of complex pore system such as clays. In this study, we have characterized the pore structures for a number of clays including clay minerals and field samples which are relevant to high-level waste systems under various sample environments (e.g., humidity, temperature and pressure) using SANS. Our results suggest that different clays show unique pore features under various sample environments. To distinguish between accessible/non-accessible pores and the nature of pore filling (e.g. the quantity of H2O adsorbed by clays, and the distribution of H2O in relation to pore character) to water, clays were exposed for

  2. Non-disturbing characterization of natural organic matter (NOM) contained in clay rock pore water by mass spectrometry using electrospray and atmospheric pressure chemical ionization modes.

    PubMed

    Huclier-Markai, Sandrine; Landesman, Catherine; Rogniaux, Hélène; Monteau, Fabrice; Vinsot, Agnes; Grambow, Bernd

    2010-01-01

    We have investigated the composition of the mobile natural organic matter (NOM) present in Callovo-Oxfodian pore water using electrospray ionization mass spectrometry (ESI-MS), atmospheric pressure chemical ionization mass spectrometry (APCI-MS) and emission-excitation matrix (EEM) spectroscopy. The generation of knowledge of the composition, structure and size of mobile NOM is necessary if one wants to understand the interactions of these compounds with heavy metals/radionuclides, in the context of environmental studies, and particularly how the mobility of these trace elements is affected by mobile NOM. The proposed methodology is very sensitive in unambiguously identifying the in situ composition of dissolved NOM in water even at very low NOM concentration, due to innovative non-disturbing water sampling and ionization (ESI/APCI-MS) techniques. It was possible to analyze a quite exhaustive inventory of the small organic compounds of clay pore water without proceeding to any chemical treatment at naturally occurring concentration levels. The structural features observed were mainly acidic compounds and fatty acids as well as aldehydes and amino acids. PMID:20013952

  3. Calcium-ammonium exchange experiments on clay minerals using a (45)Ca tracer technique in marine pore water.

    PubMed

    Ockert, Charlotte; Wehrmann, Laura M; Kaufhold, Stephan; Ferdelman, Tim G; Teichert, Barbara M A; Gussone, Nikolaus

    2014-01-01

    Understanding cation exchange processes is important for evaluating early diagenetic and synsedimentary processes taking place in marine sediments. To quantify calcium (Ca) exchange and Ca-ammonium exchange in a seawater environment, we performed experiments with a radioactive (45)Ca tracer on clay mineral standards (Fithian illite, montmorillonite and kaolinite) and marine sediments from the North Atlantic Integrated Ocean Drilling Program Site U1306A in artificial seawater (ASW). The results show that equilibrium during the initial attachment of Ca as well as the exchange of Ca by [Formula: see text] is attained in less than 2 min. On average 8-20% of the exchangeable sites of the clay minerals were occupied by Ca in a seawater medium. The conditional selectivity coefficient, describing the [Formula: see text] exchange in ASW is mineral specific and it was determined to be 0.07 for montmorillonite, 0.05 for a natural marine sediment and 0.013 for Fithian illite. PMID:24437731

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

    USGS Publications Warehouse

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

    2006-01-01

    Pore water was extracted from clay-silt core samples collected from a borehole at Ocean View, west of Sea Isle City, in northeastern Cape May County, New Jersey. The borehole intersects the lower Miocene Kirkwood Formation, which includes a thick sand and gravel unit between two clay-silt units. The sand and gravel unit forms a major confined aquifer in the region, known as the Atlantic City 800-foot sand, the major source of potable water along the Atlantic Coast of southern New Jersey. The pore water from the core is of interest because the borehole intersects the aquifer in an area where the ground water is sodium-rich and sulfidic. Locally in the aquifer in central and southern Cape May County, sodium concentrations are near the New Jersey secondary drinking-water standard of 50 mg/L (milligrams per liter), and typically are greater than 30 mg/L, but chloride and sulfate do not approach their respective secondary drinking-water standards except in southernmost Cape May County. Pore waters from the confining units are suspected to be a source of sodium, sulfur, and chloride to the aquifer. Constituent concentrations in filtered pore-water samples were determined using the inductively coupled plasma-mass spectrometry analytical technique to facilitate the determination of low-level concentrations of many trace constituents. Calcium-sodium-sulfate-bicarbonate, calcium-chloride-sulfate, calcium-sulfate, and sodium-sulfate-chloride-bicarbonate type waters characterize samples from the deepest part of the confining unit directly overlying the aquifer (termed the 'lower' confining unit). A sodium-chloride-sulfate type water is dominant in the composite confining unit below the aquifer. Sodium, chloride, and sulfate became increasingly dominant with depth. Pore water from the deepest sample recovered (1,390 ft (feet) below land surface) was brackish, with concentrations of sodium, chloride, and sulfate of 5,930, 8,400, and 5,070 mg/L, respectively. Pore-water samples

  5. Clay Mineralogy And Pore Water Geochemistry Of Mud From Baratang Mud Volcanoes From Andamans, India And Great Boiling Springs, Nevada, USA: Linking Mud Mineralogy Using XRD And XRF To Extrusion Mechanisms

    NASA Astrophysics Data System (ADS)

    Datta, S.; Socki, R. A.; Niles, P.; Rekhi, S.; Cernatescu, I.; Sutton, P.; Litteer, B.

    2009-12-01

    The Andaman mud volcanic chain on the Indian Ocean is a major outlet for released fluids, resulting in a high background temperature gradient that triggers mineralogical transformations and geochemical reactions at shallow depths. These tectonic structures have provided escape pathways for overpressured material and fluids or have favoured upward fluid movement along the sedimentary column and eventually the build up of mud volcanoes. Baratang Islands of Middle Andamans, India is one such spot currently under study. We compare the mineralogy of the Andaman mud volcano with another mud diapiric site, Great Boiling Springs (GBS), near Gerlach, NV, situated within the Great Basin of N. America. In July, 2009 frequent explosions were witnessed and samples were collected at GBS. Powder X-ray Diffraction and XRF analyses of bulk mud samples from Baratang were performed to identify the complete suite of minerals, in addition to the clay minerals in each case. The x-ray results on the clay separates from these mud samples (Baratang) has helped in understanding the consequence of the transformation of hydrated clays, the crystallochemical characterisation of lattice layered silicates, illite, chlorite illite-montmorillonite and kaolinite that can be an indicator of depth of the origin of fluid. A lower content of the fine materials in the Baratang might suggest a mixing during upward transit. Smectite-montmorillonite transformation to illite and concurrent release of intracrystalline water indicates pore water freshening in surface sediments. The pore water analysis of the Baratang mud indicate hypersaline fluids with analyses of Na with salinity, B, K and Mg. Correlation of dissolved inorganic carbon (DIC) and B enrichment in ascending fluids indicate fermentation and B desorption from clays can occur concurrently during the fluid formation and advection. The most probable mechanism in Andamans involves the re-hydration of shales by both hydrocarbons and a geochemically

  6. Verifying accelerated physical modeling of reactive solute transport: the long term development of pore water solute profiles in a thick clay till.

    NASA Astrophysics Data System (ADS)

    Timms, W.; Hendry, J.

    2003-04-01

    Accelerated physical modeling, using a geotechnical centrifuge, is yet to be verified for reactive solute transport in very low permeability geologic materials. Whilst scaling relationships between the centrifuge model and corresponding prototype are established for physical parameters, scaling of chemical reactions requires special consideration. Centrifuge modeling was carried out on duplicate core samples of unoxidised clay rich till obtained from a research site in southern Saskatchewan, Canada. At this site, naturally occurring solutes, principally comprised of Na and SO4, concentrated at ˜70,000 mg/L TDS in the oxidized zone, have diffused downwards over the past 2-10 k years to background concentrations of 3,200 mg/L TDS. Data from new (N=9) and existing piezometers (N>7) were used to identify solute fronts between 12-22 m depth, revealing the K, Sr, Mg and Na were slightly retarded relative to Cl, δ2H and δ18O. Despite the very low hydraulic conductivity of the samples (1.2 ×10-11 m/s), approximately ˜20 k years of solute transport were simulated within 3 months of centrifuge modeling at ˜330×g. Stresses at the base of the samples were less than in situ preconsolidation pressure (550 kPa), yet centrifuge speed was sufficiently high that the Peclet number, based on measured flow rate and porosity, indicated advective and diffusive transport components. Over 4 pore volumes of NaCl, with a concentration equivalent to that at the top of the unoxidised zone (I=0.5) permeated the cores. Breakthrough of Na was significantly retarded and characterized by a lengthy tail below C0. The loss of Na from solution was accounted for by an increase of Ca and Mg due to cation exchange. The scaled prototype indicated retardation of Na by ion exchange over a period of thousands of years, similar to that observed at the field site. To account for minor scale differences, additional centrifuge models and PHREEQC geochemical models of 1D reactive solute transport are in

  7. Physical properties and mechanical behavior of clays with saline pore fluid

    SciTech Connect

    Shimizu, Masayoshi

    1995-12-31

    The sample of which the pore fluid is the sea water was prepared by remolding a powdered clay soil with the natural sea water. Physical and mechanical properties of this sample were compared to those of the sample prepared with distilled water. Results of consistency limits tests, CIU triaxial compression tests and oedometer tests are shown. Effects of the salinity on the effective stress and strain behavior in the states of normal and over consolidation and on the compressibility and consolidation behavior are shown. Discussion is made on the basis of the concept of aggregates of soil grains.

  8. Pore space analysis of NAPL distribution in sand-clay media

    USGS Publications Warehouse

    Matmon, D.; Hayden, N.J.

    2003-01-01

    This paper introduces a conceptual model of clays and non-aqueous phase liquids (NAPLs) at the pore scale that has been developed from a mathematical unit cell model, and direct micromodel observation and measurement of clay-containing porous media. The mathematical model uses a unit cell concept with uniform spherical grains for simulating the sand in the sand-clay matrix (???10% clay). Micromodels made with glass slides and including different clay-containing porous media were used to investigate the two clays (kaolinite and montmorillonite) and NAPL distribution within the pore space. The results were used to understand the distribution of NAPL advancing into initially saturated sand and sand-clay media, and provided a detailed analysis of the pore-scale geometry, pore size distribution, NAPL entry pressures, and the effect of clay on this geometry. Interesting NAPL saturation profiles were observed as a result of the complexity of the pore space geometry with the different packing angles and the presence of clays. The unit cell approach has applications for enhancing the mechanistic understanding and conceptualization, both visually and mathematically, of pore-scale processes such as NAPL and clay distribution. ?? 2003 Elsevier Science Ltd. All rights reserved.

  9. A robust model for pore-water chemistry of clayrock

    NASA Astrophysics Data System (ADS)

    Gaucher, E. C.; Tournassat, C.; Pearson, F. J.; Blanc, P.; Crouzet, C.; Lerouge, C.; Altmann, S.

    2009-11-01

    The chemistry of pore water is an important property of clayrocks being considered as host rocks for long-term storage of radioactive waste. It may be difficult, if not impossible, to obtain water samples for chemical analysis from such rocks because of their low hydraulic conductivity. This paper presents an approach for calculating the pore-water compositions of clayrocks from laboratory-measured properties of core samples, including their leachable Cl and SO 4 concentrations and analysed exchangeable cations, and from mineral and cation exchange equilibria based on the formation mineralogy. New core sampling and analysis procedures are presented that reduce or quantify side reactions such as sample oxidation (e.g. pyrite) and soluble mineral dissolution (celestite, SrSO 4) that affect measured SO 4 concentrations and exchangeable cation distributions. The model considers phase equilibria only with minerals that are observed in the formation including the principal clay phases. The model has been used to calculate the composition of mobile pore water in the Callovo-Oxfordian clayrock and validated against measurements of water chemistry made in an underground research laboratory in that formation. The model reproduces the measured, in situ pore-water composition without any estimated parameters. All required parameters can be obtained from core sample analysis. We highlight the need to consider only those mineral phases which can be shown to be in equilibrium with contacting pore water. The consequence of this is that some conceptual models available in the literature appear not to be appropriate for modelling clayrocks, particularly those considering high temperature and/or high pressure detrital phases as chemical buffers of pore water. The robustness of our model with respect to uncertainties in the log K values of clay phases is also demonstrated. Large uncertainties in log K values for clay minerals have relatively small effects on modelled pore-water

  10. Organically modified clay removes oil from water

    SciTech Connect

    Alther, G.R.

    1995-12-31

    When bentonite or other clays and zeolite are modified with quaternary amines, they become organophilic. Such modified bentonites are used to remove mechanically emulsified oil and grease, and other sparingly soluble organics. Types of oil found in water can include fats, lubricants, cutting fluids, heavy hydrocarbons such as tars, grease, crude oil, diesel oils; and light hydrocarbons such as kerosene, jet fuel, and gasoline. If the organoclay is granulated, it is placed into a liquid phase carbon filter vessel to remove FOGs (Free Oil and Grease) and chlorinated hydrocarbons. In this application the clay is mixed with anthrazite to prevent early plugging of the filter by oil or grease droplets. In batch systems a powdered organoclay is employed. Organoclay removes mechanically emulsified oil and grease at 5--7 times the rate of activated carbon, or 50% of its dry weight. Oil and grease and other large sparingly soluble chlorinated hydrocarbons and NOMs (Natural Organic Matter) blind the pores of activated carbon (and ion-exchange resins), reducing its effectiveness significantly. It is therefore economically advantageous for the end user to prepolish the water before it enters carbon vessels. Operating costs can often be reduced by 50% or more.

  11. Micro and nano-size pores of clay minerals in shale reservoirs: Implication for the accumulation of shale gas

    NASA Astrophysics Data System (ADS)

    Chen, Shangbin; Han, Yufu; Fu, Changqin; Zhang, han; Zhu, Yanming; Zuo, Zhaoxi

    2016-08-01

    A pore is an essential component of shale gas reservoirs. Clay minerals are the adsorption carrier second only to organic matter. This paper uses the organic maturity test, Field-Emission Scanning Electron Microscopy (FE-SEM), and X-ray Diffraction (XRD) to study the structure and effect of clay minerals on storing gas in shales. Results show the depositional environment and organic maturity influence the content and types of clay minerals as well as their structure in the three types of sedimentary facies in China. Clay minerals develop multi-size pores which shrink to micro- and nano-size by close compaction during diagenesis. Micro- and nano-pores can be divided into six types: 1) interlayer, 2) intergranular, 3) pore and fracture in contact with organic matter, 4) pore and fracture in contact with other types of minerals, 5) dissolved and, 6) micro-cracks. The contribution of clay minerals to the presence of pores in shale is evident and the clay plane porosity can even reach 16%, close to the contribution of organic matter. The amount of clay minerals and pores displays a positive correlation. Clay minerals possess a strong adsorption which is affected by moisture and reservoir maturity. Different pore levels of clay minerals are mutually arranged, thus essentially producing distinct reservoir adsorption effects. Understanding the structural characteristics of micro- and nano-pores in clay minerals can provide a tool for the exploration and development of shale gas reservoirs.

  12. Adsorption and Desorption of Nitrogen and Water Vapor by clay

    NASA Astrophysics Data System (ADS)

    Cui, Deshan; Chen, Qiong; Xiang, Wei; Huang, Wei

    2015-04-01

    Adsorption and desorption of nitrogen and water vapor by clay has a significant impact on unsaturated soil physical and mechanical properties. In order to study the adsorption and desorption characteristics of nitrogen and water vapor by montmorillonite, kaolin and sliding zone soils, the Autosorb-iQ specific surface area and pore size analyzer instrument of United State was taken to carry out the analysis test. The adsorption and desorption of nitrogen at 77K and water vapor at 293K on clay sample were conducted. The theories of BET, FHH and hydration energy were taken to calculate the specific surface, surface fractal dimension and adsorption energy. The results show that the calculated specific surface of water vapor by clay is bigger than nitrogen adsorption test because clay can adsorb more water vapor molecule than nitrogen. Smaller and polar water vapor molecule can access the micropore and then adsorb on the mineral surface and mineral intralayer, which make the mineral surface cations hydrate and the mineral surface smoother. Bigger and nonpolar nitrogen molecule can not enter into the micropore as water vapor molecule and has weak interaction with clay surface.

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

    NASA Astrophysics Data System (ADS)

    Cui, D.; Xiang, W.

    2011-12-01

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

  14. Water sites at a clay interface

    SciTech Connect

    Grandjean, J.

    1997-01-15

    Aqueous suspensions of swelling clays (smectites) find uses in many industrial applications including drilling fluids, suspending agents and water treatment. {sup 2}H NMR quadrupolar splittings of clay suspensions monitor the orientation of water molecules near the solid surface. Two limiting water interfacial sites explain the results on montmorillonite, hectorite, and saponite suspensions. The location of cation isomorphous substitution and the Ca{sup 2+}/Na{sup +} molar ratio of exchangeable cations modulate their relative importance. With beidellite suspensions, water orientation at the clay surface cannot be described within the above scheme.

  15. The effect of pore water pressure on debris flow dynamics

    NASA Astrophysics Data System (ADS)

    Okura, Y.; Parker, G.; Marr, J. G.; Yu, B.; Ochiai, H.

    2003-12-01

    Pore-water likely plays an important role to reduce shear force in debris flow. In experiments, we observed pore-water pressure during flow to clarify the relationship between the flow speed and pore water pressure which would be affected by flow depth and particle size distribution. Soil materials were prepared with mixing materials of sand, silt and clay. Pore-water pressure on the flume bed, flow depth, velocity and run out distance was observed, and the following results were quantitatively obtained in this series of experiments. 1. A positive relation was observed between strain rate and pore-water pressure ratio in the flow. The strain rate and pressure ratio were dimensionless parameters of the ratios of surface velocity to flow depth and pore-water pressure head to flow depth, respectively. This relationship indicated that shear resistance decreased as the pressure potential leading to acceleration of flow velocity increased. 2. A positive relation was also observed between flow depth and pore-water pressure ratio. This indicated that the pore pressure diffusion became increasingly obstructed as the flow depth increased. 3. The pore-water pressure ratio tended to increase with the uniformity coefficient of debris flow materials. The reason for this might have been that smaller particles suspended in the flow increased pore-water pressure, and the wider range of particle distribution effectively prevented pore-water pressure diffusion. 4. There was an apparently negative correlation between the equivalent coefficient of frictions and the pressure ratios. Equivalent friction is apparent friction during flow. The most likely reason for this is that shear resistance would decrease and run out distance increase as the pressure ratio increased. These results indicated that the effect of pore water fluctuations should be one of the most important factors affecting the shear resistance in debris flows. This work was supported by the National Science Foundation

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

    PubMed

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

    2014-10-01

    Today, clay bricks are facing technological challenges and are uncompetitive compared to materials such as concrete. Their performance must be improved if they are to stand up to the competition. Increasing environmental concerns over the accumulation of unmanaged wastes from agricultural or industrial productions have made these good candidates for incorporation into building materials to improve their performance. This process leads to the formation of pores in the bricks, producing lightweight and sustainable building materials. This paper reviews the different pore-forming agents from renewable or mineral resources as described in the literature. It also presents the impact of pore-forming agents on the physical, mechanical and thermal properties of clay bricks. PMID:24908498

  17. Pore water colloid properties in argillaceous sedimentary rocks.

    PubMed

    Degueldre, Claude; Cloet, Veerle

    2016-11-01

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

  18. Thermal behavior of water confined in micro porous of clay mineral at additional pressure.

    NASA Astrophysics Data System (ADS)

    Ito, Y.; Takemura, T.; Fujimori, H.; Nagoe, A.; Sugimoto, T.

    2014-12-01

    Water is the most familiar substance. However water has specific properties that has a crystal structure of a dozen and density of that is maximum at 277.15 K. Therefore it understands various natural phenomena to study physical properties of water. Oodo et al study physical properties of water confined in silica gel [1]. They indicate that melting point of water confined in silica gel decrease with decreasing pore size of silica gel. Also in case that pore size is less than 2 nm, water confined in silica gel is unfreezing water at low temperature. It is considered that effect of pore size prevent crystal growth of water. Therefore we are interested in water confined in clay minerals. Clay minerals have a number of water conditions. Also it is thought that water confined in clay minerals show different physical behavior to exist the domain where change with various effect. Therefore we studied a thermal properties and phase behavior of absorption water in clay minerals. In addition, we analyzed the changes in the thermal behavior of absorption water due to the effect of earth pressure that was an environmental factor in the ground. [1] Oodo & Fujimori, J. Non-Cryst. Solids, 357 (2011) 683.

  19. The Mobility of Organic Contaminants in Water and Clays

    NASA Astrophysics Data System (ADS)

    Lock, P. A.; Skipper, N. T.; Mirza, Z.; Fernandez-Alonso, F.; Adams, M.; Howells, S.; Swenson, J.

    2005-12-01

    The interlayer pores of swelling clays provide an ideal environment in which to study confined fluids, and are the site of many important hydrological and petrological processes. Swelling clays, such as vermiculites, are layered minerals, widespread in soils and sedimentary rocks and are an important sink/source of many toxic organic chemicals. Knowledge of diffusion of organics through clay-rich materials is therefore highly relevant to environmental issues. Experimental studies of solvation structure in aqueous systems show that charged groups can co-ordinate the surrounding water molecules quite strongly, but their is less certainty about the effect of polar and apolar groups. There is currently interest in bulk water-alcohol systems since these are known to aggregate at the nanometer scale. Our hypothesis is that the property of the interlayer fluids in clays arises from the very subtle balance of forces between the interactions of water, cations, clay and organic species. Quasi Elastic Neutron Scattering (QENS) has been used to probe the dynamics of fluids trapped inside clays and reveal the first detailed picture of confined methanol, phenol and glycol in aqueous solution. The picture that emerges is that these model contaminant molecules are surprisingly mobile. Successive QENS broadening for methanol in Na-Vermiculite over 150-330K was measured. The progressive broadening of the energy signal was accompanied by decrease in amplitude with rise in temperature. This is indicative of an overall increase in rotational and translational freedom. Methanol exhibits a Fickian diffusion mechanism as an unconfined fluid, characterised by a linear dependence of broadening of the energy signal with the scattering vector. Inside Na-Vermiculite clay however, the same fluid produces a signal broadening that becomes non-linear indicating a jump activated motion to be present. Glycol and phenol are also of fundamental interest, the former as a clay-swelling inhibitor of

  20. Displacement of soil pore water by trichloroethylene

    USGS Publications Warehouse

    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.

  1. Organically modified clay removes oil from water

    SciTech Connect

    Alther, G.R.

    1995-12-31

    When bentonite or other clays and zeolites are modified with quaternary amines, they become organophilic. Such modified bentonites are used to remove mechanically emulsified oil and grease, and other sparingly soluble organics. If the organoclay is granulated, it is placed into a liquid phase carbon filter vessel to remove FOG`s and chlorinated hydrocarbons. In this application the clay is mixed with anthrazite to prevent early plugging of the filter by oil or grease droplets. In batch systems a powered organoclay is employed. Types of oil found in water can include fats, lubricants, cutting fluids, heavy hydrocarbons such as tars, grease, crude oil, diesel oils; and light hydrocarbons such as kerosene, jet fuel, and gasoline.

  2. On the application of focused ion beam nanotomography in characterizing the 3D pore space geometry of Opalinus clay

    NASA Astrophysics Data System (ADS)

    Keller, Lukas M.; Holzer, Lorenz; Wepf, Roger; Gasser, Philippe; Münch, Beat; Marschall, Paul

    The evaluation and optimization of radioactive disposal systems requires a comprehensive understanding of mass transport processes. Among others, mass transport in porous geomaterials depends crucially on the topology and geometry of the pore space. Thus, understanding the mechanism of mass transport processes ultimately requires a 3D characterization of the pore structure. Here, we demonstrate the potential of focused ion beam nanotomography (FIB-nT) in characterizing the 3D geometry of pore space in clay rocks, i.e. Opalinus clay. In order to preserve the microstructure and to reduce sample preparation artefacts we used high pressure freezing and subsequent freeze drying to prepare the samples. Resolution limitations placed the lower limit in pore radii that can be analyzed by FIB-nT to about 10-15 nm. Image analysis and the calculation of pore size distribution revealed that pores with radii larger than 15 nm are related to a porosity of about 3 vol.%. To validate the method, we compared the pores size distribution obtained by FIB-nT with the one obtained by N 2 adsorption analysis. The latter yielded a porosity of about 13 vol.%. This means that FIB-nT can describe around 20-30% of the total pore space. For pore radii larger than 15 nm the pore size distribution obtained by FIB-nT and N 2 adsorption analysis were in good agreement. This suggests that FIB-nT can provide representative data on the spatial distribution of pores for pore sizes in the range of about 10-100 nm. Based on the spatial analysis of 3D data we extracted information on the spatial distribution of pore space geometrical properties.

  3. Dynamics of Water Confined in Synthetic Saponite Clays

    SciTech Connect

    Prabhudesai, S. A.; Sharma, V. K.; Mitra, S.; Mukhopadhyay, R.; Chakrabarty, D.; Vicente, Miguel A.

    2011-07-15

    The dynamics of water in two synthetic saponite clays (treated by microwave) with different interlayer spacing has been studied using the quasielastic neutron scattering technique. A model in which the molecules undergo random jump diffusion describes the dynamics of water in both clays. The dynamics of water confined in both saponite clays considered here is found to be hindered in comparison to the bulk phase. It is found that diffusivity increases for samples having higher interlayer spacing.

  4. Silver speciation in wastewater effluent, surface waters, and pore waters

    SciTech Connect

    Adams, N.W.H.; Kramer, J.R.

    1999-12-01

    Silver, inorganic sulfide, and thiol compounds were measured in municipal wastewater effluent, receiving waters, and pore waters from an anoxic lake sediment in order to predict silver speciation in these systems. The authors found submicromolar concentrations of inorganic sulfide even in fully oxic surface water. This inorganic sulfide is likely to exist in the form of colloidal metal sulfides, which have been shown to be stable under oxidizing conditions for periods of several hours. Inorganic sulfide in both the wastewater effluent and receiving waters was found to be 200 to 300 times in excess of silver concentrations, whereas inorganic sulfide in pore waters was 1,000 to 15,000 times in excess of silver concentrations. With sulfide in excess of silver, the authors predict silver sulfide complexes to dominate silver speciation. Thiols were present at low nanomolar levels in pore waters but were not detectable in wastewater effluent or receiving waters. Thiols do not appear to be important to silver speciation in these freshwater systems. Partitioning of silver into particular, colloidal, and dissolved size fractions showed that a significant proportion of silver is in the colloidal and dissolved phases. Dissolved phase concentrations were relatively constant in the treatment plant effluent and receiving waters, suggesting that silver in the <10-kDa size fraction is strongly complexed by ligands that are not significantly affected by aggregation or sorption processes.

  5. Clay-catalyzed reactions of coagulant polymers during water chlorination

    USGS Publications Warehouse

    Lee, J.-F.; Liao, P.-M.; Lee, C.-K.; Chao, H.-P.; Peng, C.-L.; Chiou, C.T.

    2004-01-01

    The influence of suspended clay/solid particles on organic-coagulant reactions during water chlorination was investigated by analyses of total product formation potential (TPFP) and disinfection by-product (DBP) distribution as a function of exchanged clay cation, coagulant organic polymer, and reaction time. Montmorillonite clays appeared to act as a catalytic center where the reaction between adsorbed polymer and disinfectant (chlorine) was mediated closely by the exchanged clay cation. The transition-metal cations in clays catalyzed more effectively than other cations the reactions between a coagulant polymer and chlorine, forming a large number of volatile DBPs. The relative catalytic effects of clays/solids followed the order Ti-Mont > Fe-Mont > Cu-Mont > Mn-Mont > Ca-Mont > Na-Mont > quartz > talc. The effects of coagulant polymers on TPFP follow the order nonionic polymer > anionic polymer > cationic polymer. The catalytic role of the clay cation was further confirmed by the observed inhibition in DBP formation when strong chelating agents (o-phenanthroline and ethylenediamine) were added to the clay suspension. Moreover, in the presence of clays, total DBPs increased appreciably when either the reaction time or the amount of the added clay or coagulant polymer increased. For volatile DBPs, the formation of halogenated methanes was usually time-dependent, with chloroform and dichloromethane showing the greatest dependence. ?? 2003 Elsevier Inc. All rights reserved.

  6. Eutrophication in the northern Adriatic Sea: Pore water and sediment studies

    SciTech Connect

    Hammond, D.E.; Berelson, W.M. ); Giordani, P.; Langone, L.; Frignani, M.; Ravaioli, M. )

    1990-01-09

    The northern Adriatic Sea has been plagued by problems of eutrophication. This area is relatively shallow (maximum depth = 60m), becoming stratified during the summer months which inhibits oxygen transport to bottom waters. Anthropogenic nutrient loading in rivers entering the northern Adriatic (Po River being the largest) has increased nutrient input to this system and stimulated algal growth. Cores were collected for studies of pore water and solid phase chemistry at 6 stations in this region. [sup 210]Pb was used to constrain sediment accumulation rates and a range of 0-0.5 cm/yr was determined at different stations. Excess [sup 234]Th was only found in the upper 1-2 cm, suggesting that bioturbation is largely restricted to shallow depths. Pore water profiles show evidence of irrigation, and mean diffusive fluxes for oxygen, silica phosphate and ammonia are generally 20-90% of the fluxes obtained from benthic chamber measurements. This is consistent with previous work in this area in which studies of radon fluxes indicated that irrigation plays an important role in sediment-water exchange. Pore water profiles in the northern portion of the study area (near the Po River Delta) were markedly different than profiles in the south; sediments in the north are substantially more acidic and have high concentrations of dissolved iron and phosphate. From the alkalinity vs. TCO[sub 2] relationship in sediment pore waters it appears that differences in reactions involving the reduction of iron oxides and the exchange of magnesium for iron in clays are responsible for this regional difference in pore water properties. Sediments close to the Po apparently undergo more iron-magnesium exchange, while more distal sediments are limited in their ability to do so. Other pore water observations are limited in their ability to do so. Other pore water observations and trends regarding the shape of the silica profiles (which show shallow maxima) will be discussed.

  7. Electrical properties of water in clay and silty soils

    NASA Astrophysics Data System (ADS)

    Saarenketo, Timo

    1998-10-01

    In order to better understand ground penetrating radar (GPR) results obtained in road surveys and site investigations, the dielectric properties and electrical conductivity of four silt and clay soils were measured at different densities and moisture contents ranging from oven dry material to the plastic state. The real parts K' and imaginary parts K″ of the relative dielectric permittivity values of the soils were measured with an HP Surface Network Analyzer over a frequency range from 30 MHz to 3.0 GHz. A dielectric and electrical conductivity meter produced by Adek was also used. The results suggest that water in soils can be classified according to its electrical properties as: (1) an adsorption water layer, also known as the hygroscopic water layer; (2) a viscous or capillary water layer; and (3) free water. The measurements also showed that the adsorption water layer can be divided into inner and outer layers in accordance with the electrical double layer theory. The imaginary part of the dielectric value of the material is formed mainly in the outer layer and partly in the viscous (capillary) water layer, which also has two layers with differing electrical properties. The measurements also clearly showed that if the Cation Exchange Capacity (CEC) of a material is low, the water molecules are orderly arranged around the soil particles and the dielectric values of the bound water layers remain almost independent of frequency. If the CEC increases, the molecular structure of the bound water layers is disturbed and the water molecules more easily follow the changing AC field so that the dielectric value is higher. These materials are also highly dielectrically dispersive, especially at GPR frequencies below 400 MHz. Increasing CEC correlates well with increasing imaginary part of the adsorption water layer. Measured ohmic electrical conductivities were low at low moisture content and increased as the outer viscous water layer developed with higher moisture

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  9. PORE STRUCTURE MODEL OF CEMENT HYDRATES CONSIDERING PORE WATER CONTENT AND REACTION PROCESS UNDER ARBITRARY HUMIDITY

    NASA Astrophysics Data System (ADS)

    Fujikura, Yusuke; Oshita, Hideki

    A simulation model to estimate the pore structure of cement hydrates by curing in arbitrary relative humidity is presented. This paper describes procedures for predicting phase compositions based on the classical hydration model of Portland cement, calculating the particle size distribution of constituent phases and evaluating the pore size distribution by stereological and statistical considerations. And to estimate the water content in pore structure under any relative humidity, we proposed the simulation model of adsorption isotherm model based on the pore structure. To evaluate the effectiveness of this model, simulation results were compared with experimental results of the pore size distribution measured by mercury porosimetry. As a result, it was found that the experimental and simulated results were in close agreement, and the simulated results indicated characterization of the po re structure of cement hydrates.

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

    USGS Publications Warehouse

    Chiou, C.T.; Rutherford, D.W.

    1997-01-01

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

  11. Mechanical dispersion of clay from soil into water: readily-dispersed and spontaneously-dispersed clay

    NASA Astrophysics Data System (ADS)

    Czyż, Ewa A.; Dexter, Anthony R.

    2015-01-01

    A method for the experimental determination of the amount of clay dispersed from soil into water is described. The method was evaluated using soil samples from agricultural fields in 18 locations in Poland. Soil particle size distributions, contents of organic matter and exchangeable cations were measured by standard methods. Sub-samples were placed in distilled water and were subjected to four different energy inputs obtained by different numbers of inversions (end-over-end movements). The amounts of clay that dispersed into suspension were measured by light scattering (turbidimetry). An empirical equation was developed that provided an approximate fit to the experimental data for turbidity as a function of number of inversions. It is suggested that extrapolation of the fitted equation to zero inversions enables the amount of spontaneously-dispersed clay to be estimated. This method introduces the possibility of replacing the existing subjective, qualitative method of determining spontaneously-dispersed clay with a quantitative, objective method. Even though the dispersed clay is measured under saturated conditions, soil samples retain a `memory' of the water contents at which they have been stored.

  12. Fouling Study of Silicon Oxide Pores Exposed to Tap Water

    SciTech Connect

    Nilsson, J.; Bourcier, W.L.; Lee, J.R.I.; Letant, S.E.; /LLNL, Livermore

    2007-07-12

    We report on the fouling of Focused Ion Beam (FIB)-fabricated silicon oxide nanopores after exposure to tap water for two weeks. Pore clogging was monitored by Scanning Electron Microscopy (SEM) on both bare silicon oxide and chemically functionalized nanopores. While fouling occurred on hydrophilic silicon oxide pore walls, the hydrophobic nature of alkane chains prevented clogging on the chemically functionalized pore walls. These results have implications for nanopore sensing platform design.

  13. The dielectric properties of water within model transbilayer pores.

    PubMed Central

    Sansom, M S; Smith, G R; Adcock, C; Biggin, P C

    1997-01-01

    Ion channels contain extended columns of water molecules within their transbilayer pores. The dynamic properties of such intrapore water have been shown to differ from those of water in its bulk state. In previous molecular dynamics simulations of two classes of model pore (parallel bundles of Ala20 alpha-helices and antiparallel barrels of Ala10 beta-strands), a substantially reduced translational and rotational mobility of waters was observed within the pore relative to bulk water. Molecular dynamics simulations in the presence of a transpore electrostatic field (i.e., a voltage drop along the pore axis) have been used to estimate the resultant polarization (due to reorientation) of the intrapore water, and hence to determine the local dielectric behavior within the pore. It is shown that the local dielectric constant of water within a pore is reduced for models formed by parallel alpha-helix bundles, but not by those formed by beta-barrels. This result is discussed in the context of electrostatics calculations of ion permeation through channels, and the effect of the local dielectric of water within a helix bundle pore is illustrated with a simple Poisson-Boltzmann calculation. Images FIGURE 1 PMID:9370434

  14. Extending electromagnetic methods to map coastal pore water salinities

    USGS Publications Warehouse

    Greenwood, Wm. J.; Kruse, S.; Swarzenski, P.

    2006-01-01

    The feasibility of mapping pore water salinity based on surface electromagnetic (EM) methods over land and shallow marine water is examined in a coastal wetland on Tampa Bay, Florida. Forward models predict that useful information on seabed conductivity can be obtained through <1.5 m of saline water, using floating EM-31 and EM-34 instruments from Geonics Ltd. The EM-31 functioned as predicted when compared against resistivity soundings and pore water samples and proved valuable for profiling in otherwise inaccessible terrain due to its relatively small size. Experiments with the EM-34 in marine water, however, did not reproduce the theoretical instrument response. The most effective technique for predicting pore water conductivities based on EM data entailed (1) computing formation factors from resistivity surveys and pore water samples at representative sites and (2) combining these formation factors with onshore and offshore EM-31 readings for broader spatial coverage. This method proved successful for imaging zones of elevated pore water conductivities/ salinities associated with mangrove forests, presumably caused by salt water exclusion by mangrove roots. These zones extend 5 to 10 m seaward from mangrove trunks fringing Tampa Bay. Modeling indicates that EM-31 measurements lack the resolution necessary to image the subtle pore water conductivity variations expected in association with diffuse submarine ground water discharge of fresher water in the marine water of Tampa Bay. The technique has potential for locating high-contrast zones and other pore water salinity anomalies in areas not accessible to conventional marine- or land-based resistivity arrays and hence may be useful for studies of coastal-wetland ecosystems. Copyright ?? 2005 National Ground Water Association.

  15. The effect of switchable water additives on clay settling.

    PubMed

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

    2013-01-01

    The recycling of process water from strip mining extractions is a very relevant task both industrially and environmentally. The sedimentation of fine tailings during such processes, however, can often require long periods of time and/or the addition of flocculants which make later water recycling difficult. We propose the use of switchable water additives as reversible flocculants for clay/water suspensions. Switchable water additives are compounds such as diamines that make it possible to reversibly control the ionic strength of an aqueous solution. Addition of CO(2) to such an aqueous solution causes the ionic strength to rise dramatically, and the change is reversed upon removal of the CO(2). These additives, while in the presence of CO(2), promote the aggregation of clay tailings, reduce settling times, and greatly increase the clarity of the liberated water. The removal of CO(2) from the liberated water regenerates a low ionic strength solution that does not promote clay aggregation and settling until CO(2) is added again. Such reversible behavior would be useful in applications such as oil sands separations in which the recycled water must not promote aggregation. When added to kaolinite and montmorillonite clay suspensions, switchable water provided process waters of lower turbidity than those additives from inorganic salts or by CO(2)-treatment alone. When recollected, the switchable water supernatant was shown to be recyclable over three cycles for enhanced settling of kaolinite. PMID:22945593

  16. Mangrove pore water exchange across a latitudinal gradient

    NASA Astrophysics Data System (ADS)

    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.

  17. Do conservative solutes migrate at average pore-water velocity?

    PubMed

    Rovey, Charles W; Niemann, William L

    2005-01-01

    According to common understanding, the advective velocity of a conservative solute equals the average linear pore-water velocity. Yet direct monitoring indicates that the two velocities may be different in heterogeneous media. For example, at the Camp Dodge, Iowa, site the advective velocity of discrete Cl- plumes was less than one tenth of the average pore-water velocity calculated from Darcy's law using the measured hydraulic gradient, effective porosity, and hydraulic conductivity (K) from large-scale three-dimensional (3D) techniques, e.g., pumping tests. Possibly, this difference reflects the influence of different pore systems, if the K relevant to transient solute flux is influenced more by lower-K heterogeneity than a steady or quasi-steady water flux. To test this idea, tracer tests were conducted under controlled laboratory conditions. Under one-dimensional flow conditions, the advective velocity of discrete conservative solutes equaled the average pore-water velocity determined from volumetric flow rates and Darcy's law. In a larger 3D flow system, however, the same solutes migrated at approximately 65% of the average pore-water velocity. These results, coupled with direct observation of dye tracers and their velocities as they migrated through both homogeneous and heterogeneous sections of the same model, demonstrate that heterogeneity can slow the advective velocity of discrete solute plumes relative to the average pore-water velocity within heterogeneous 3D flow sytems. PMID:15726924

  18. Pore Water Collection, Analysis and Evolution: The Need for Standardization.

    PubMed

    Gruzalski, Jacob G; Markwiese, James T; Carriker, Neil E; Rogers, William J; Vitale, Rock J; Thal, David I

    2016-01-01

    Investigating the ecological impacts of contaminants released into the environment requires integration of multiple lines of evidence. Collection and analysis of interstitial water is an often-used line of evidence for developing benthic exposure estimates in aquatic ecosystems. It is a well-established principle that chemical and toxicity data on interstitial water samples should represent in-situ conditions; i.e., sample integrity must be maintained throughout the sample collection process to avoid alteration of the in-situ geochemical conditions. Unfortunately, collection and processing of pore water is not standardized to address possible geochemical transformations introduced by atmospheric exposure. Furthermore, there are no suitable benchmarks (ecological or human health) against which to evaluate adverse effects from chemicals in pore water; i.e., empirical data is lacking on the toxicity of inorganic contaminants in sediment interstitial water. It is clear that pore water data is best evaluated by considering the bioavailability of trace elements and the partitioning of contaminants between the aqueous and solid phases. It is also evident that there is a need for sediment researchers and regulatory agencies to collaborate in developing a standardized approach for sediment/pore water collection and data evaluation. Without such guidelines, the number of different pore water collection and extraction techniques will continue to expand, and investigators will continue to evaluate potentially questionable data by comparison to inappropriate criteria. PMID:26613987

  19. High level nuclear waste glass corrosion in synthetic clay pore solution and retention of actinides in secondary phases

    NASA Astrophysics Data System (ADS)

    Bosbach, D.; Luckscheiter, B.; Brendebach, B.; Denecke, M. A.; Finck, N.

    2009-03-01

    The corrosion of the simulated high level waste glass GP WAK1 in synthetic clay pore solution was studied in batch-type experiments at 323 and 363 K with special focus on the effect of high carbonate concentration in solution. The corrosion rate after 130 days was <10-4g m-2 d-1 - no significant effect of the carbonate was identified. During glass corrosion, crystalline secondary phases (powellite, barite, calcite, anhydrite and clay-like Mg(Ca,Fe)-silicates) were formed. To obtain a molecular level picture of radionuclide speciation within the alteration layer, spectroscopic methods have been applied including grazing incidence X-ray absorption spectroscopy (XAS) to study the structural changes in the coordination of uranyl upon alteration layer formation. The number of equatorial oxygen atoms increases from 4 in the bulk glass to 5 in the alteration layer. Furthermore, reduced coordination symmetry was found. Hectorite, a frequently observed secondary clay mineral within the glass alteration layer, was synthesized in the presence of trivalent f-elements (e.g. Eu) and structurally characterized using time-resolved laser fluorescence spectroscopy. Structural incorporation into the octahedral layer is indicated.

  20. Pore-water chemistry explains zinc phytotoxicity in soil.

    PubMed

    Kader, Mohammed; Lamb, Dane T; Correll, Ray; Megharaj, Mallavarapu; Naidu, Ravi

    2015-12-01

    Zinc (Zn) is a widespread soil contaminant arising from a numerous anthropogenic sources. However, adequately predicting toxicity of Zn to ecological receptors remains difficult due to the complexity of soil characteristics. In this study, we examined solid-solution partitioning using pore-water data and toxicity of Zn to cucumber (Cucumis sativus L.) in spiked soils. Pore-water effective concentration (ECx, x=10%, 20% and 50% reduction) values were negatively related to pH, indicating lower Zn pore water concentration were needed to cause phytotoxicity at high pH soils. Total dissolved zinc (Znpw) and free zinc (Zn(2+)) in soil-pore water successfully described 78% and 80.3% of the variation in relative growth (%) in the full dataset. When the complete data set was used (10 soils), the estimated EC50pw was 450 and 79.2 µM for Znpw and Zn(2+), respectively. Total added Zn, soil pore water pH (pHpw) and dissolve organic carbon (DOC) were the best predictors of Znpw and Zn(2+) in pore-water. The EC10 (total loading) values ranged from 179 to 5214 mg/kg, depending on soil type. Only pH measurements in soil were related to ECx total Zn data. The strongest relationship to ECx overall was pHca, although pHw and pHpw were in general related to Zn ECx. Similarly, when a solution-only model was used to predict Zn in shoot, DOC was negatively related to Zn in shoot, indicating a reduction in uptake/ translocation of Zn from solution with increasing DOC. PMID:26283289

  1. Benthic invertebrate bioassays with toxic sediment and pore water

    USGS Publications Warehouse

    Giesy, John P.; Rosiu, Cornell J.; Graney, Robert L.; Henry, Mary G.

    1990-01-01

    The relative sensitivities of bioassays to determine the toxicity of sediments were investigated and three methods of making the sample dilutions required to generate dose-response relationships were compared. The assays studied were: (a) Microtox®, a 15-min assay ofPhotobacterium phosphoreum bioluminescence inhibition by pore water; (b) 48-h Daphnia magnalethality test in pore water; (c) 10-d subchronic assay of lethality to and reduction of weight gain by Chironomus tentans performed in either whole sediment or pore water; (d) 168-h acute lethality assay of Hexagenia limbata in either whole sediment or pore water. The three methods of diluting sediments were: (a) extracting pore water from the toxic location and dilution with pore water from the control station; (b) diluting whole sediment from the toxic location with control whole sediment from a reference location, then extracting pore water; and (c) diluting toxic, whole sediment with whole sediment from a reference location, then using the whole sediment in bioassays. Based on lethality, H. limbata was the most sensitive organism to the toxicity of Detroit River sediment. Lethality of D. magna in pore water was similar to that of H. limbata in whole sediment and can be used to predict effects of whole sediment toxicity to H. limbata. The concentration required to cause a 50% reduction in C. tentans growth (10-d EC50) was approximately that which caused 50% lethality of D. magna (48-h LC50) and was similar to the toxicity that restricts benthic invertebrate colonization of contaminated sediments. While the three dilution techniques gave similar results with some assays, they gave very different results in other assays. The dose-response relationships determined by the three dilution techniques would be expected to vary with sediment, toxicant and bioassay type, and the dose-response relationship derived from each technique needs to be interpreted accordingly.

  2. Testing geochemical models of bentonite pore water evolution against laboratory experimental data

    NASA Astrophysics Data System (ADS)

    Savage, David; Arthur, Randy; Watson, Claire; Wilson, James; Strömberg, Bo

    The determination of a bentonite pore water composition and understanding its evolution with time underpins many radioactive waste disposal issues, such as buffer erosion, canister corrosion, and radionuclide solubility, sorption, and diffusion, inter alia. Previous modelling approaches have tended to ignore clay dissolution-precipitation reactions, a consequence of which is that montmorillonite is theoretically preserved indefinitely in the repository system. Here, we investigate the applicability of an alternative clay pore fluid evolution model, that incorporates clay dissolution-precipitation reactions as an integral component and test it against well-characterised laboratory experimental data, where key geochemical parameters, Eh and pH, have been measured directly in compacted bentonite. Simulations have been conducted using different computer codes (Geochemist’s Workbench, PHREEQC, and QPAC) to test the applicability of this model. Thermodynamic data for the Gibb’s free energy of formation of MX-80 smectite used in the calculations were estimated using two different methods (‘Polymer’ and ‘Vieillard’ Models). Simulations of ‘end-point’ pH measurements in batch bentonite-water slurry experiments showed different pH values according to the complexity of the system studied. The most complete system investigated revealed pH values were a strong function of partial pressure of carbon dioxide, with pH increasing with decreasing PCO 2 (with log PCO 2 values ranging from -3.5 to -7.5 bars produced pH values ranging from 7.9 to 9.6). A second set of calculations investigated disequilibrium between clay and pore fluid in laboratory squeezing cell tests involving pure water (pH = 9.0) or a 1 M NaOH solution (pH = 12.1). Simulations carried out for 100 days (the same timescale as the experiments) showed that smectite remained far from equilibrium throughout, and that the lowering of pH due to smectite hydrolysis was trivial. However, extending the

  3. Unstable Pore-Water Flow in Intertidal Wetlands

    NASA Astrophysics Data System (ADS)

    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

  4. Diagenesis and pore water evolution in the Keuper reservoir, Paris Basin (France)

    SciTech Connect

    Spotl, C.; Matter, A. . Geologisches Inst.); Brevart, O. . Centre Scientifique et Technique Jean Feger)

    1993-09-01

    Keuper (Upper Triassic) fluvial sandstones and nonmarine carbonate rocks form a major oil reservoir in the western Paris Basin at burial depths of [approximately] 2km. Early-diagenetic processes comprise red-bed-type diagenesis and extensive dolocrete formation both in fluvial channels and in fine-grained over-bank sediments. Locally significant paleokarst created vuggy dissolution porosity in the carbonate units and probably also caused leaching of detrital alkali feldspar grains. Oxygen, carbon, and strontium isotope analyses of various eogenetic cements indicate a nonmarine pore-water composition. Ferroan carbonates, authigenic albite and potassium feldspar, quartz, sulfates, sulfides, and clay minerals formed subsequent to major mechanical compaction. Their isotopic compositions record significant changes in the chemistry of the parent pore water. Cl-Br relationships of the present-day pore water reveal that fluids saturated with respect to halite flushed the reservoir during burial. Based on radiogenic dating of illite cements, influx of warm brines into the reservoir most likely occurred during the earliest Cretaceous. The authors suggest that uplift of the Vosges crustal block created a hydraulic head in the eastern part of the basin and established a gravity-driven fluid flow system, displacing interstitial brines from the Keuper evaporites from the eastern part towards the western part of the basin. A second gravity-driven fluid flow system was established during the Oligocene by major uplift, and freshwater flushed the Keuper reservoir, causing brine dilution. The present-day pore water in the study area is still saline and mass-balance calculations indicate that the ratio of basinal brines to Tertiary meteoric water is about 1:2.

  5. Water swellable clay composition and method to maintain stability in salt contaminated water

    SciTech Connect

    Alexander, W.

    1987-01-06

    A method is described of drilling comprising contacting an earthen formation with a rotary drilling bit to form a salt contaminated drill hole and circulating a drilling fluid in the drill hole to cool and lubricate the drill bit during rotation and to lift drill cuttings of the drill hole. The drilling fluid becomes contaminated with salt contaminated water. The improvement described here comprises adding a water swellable montmorillonite clay composition to the drilling fluid. The composition comprises a water swellable montmorillonite clay, xanthan gum in an amount of 0.1% to 20% based on the weight of water swellable montmorillonite clay, and at least one other, water soluble gum selected from the group consisting of guar gum, dextran gum, locust bean gum, and mixtures thereof in an amount of 4.0% to 10% based on the weight of water swellable clay.

  6. Pore water testing and analysis: the good, the bad, and the ugly.

    PubMed

    Chapman, Peter M; Wang, Feiyue; Germano, Joseph D; Batley, Graeme

    2002-05-01

    The increasingly common practice of collecting and assessing sediment pore water as a primary measure of sediment quality is reviewed. Good features of this practice include: pore water is a key exposure route for some organisms associated with sediments; pore water testing eliminates particle size effects; pore water analyses and tests can provide useful information regarding contamination and pollution. Bad features include: pore water is not the only exposure route; pore water tests lack chemical or biological realism: their "sensitivity" relative to other tests may be meaningless due to manipulation and laboratory artifacts; many sediment and surface dwelling organisms are not directly influenced by pore water. Bad features can become ugly if: other exposure pathways are not considered (for toxicity or bioaccumulation); manipulation techniques are not appropriate; pore water tests are inappropriately linked to population-level effects. Pore water testing and analyses can be effective tools provided their limitations are well understood by researchers and managers. PMID:12146818

  7. A clay-vesicle system for water purification from organic pollutants.

    PubMed

    Undabeytia, Tomas; Nir, Shlomo; Sánchez-Verdejo, Trinidad; Villaverde, Jaime; Maqueda, Celia; Morillo, Esmeralda

    2008-02-01

    Vesicle-clay complexes in which positively charged vesicles composed of didodecyldimethylammonium bromide (DDAB) were adsorbed on montmorillonite removed efficiently anionic (sulfentrazone, imazaquin) and neutral (alachlor, atrazine) pollutants from water. These complexes (0.5% w:w) removed 92-100% of sulfentrazone, imazaquin and alachlor and 60% of atrazine from a solution containing 10mg/L of it. A synergistic effect on the adsorption of atrazine was observed when all pollutants were present simultaneously (30 mg/L each), its percentage of removal being 85.5. Column filters (18 cm) filled with a mixture of quartz sand and vesicle-clay (100:1, w:w) were tested. For the passage of 1L (25 pore volumes) of a solution including all the pollutants at 10mg/L each, removal was complete for sulfentrazone and imazaquin, 94% for alachlor and 53.1% for atrazine, whereas removal was significantly less efficient when using activated carbon. A similar advantage of the vesicle-clay filter was observed for the capacities of removal. PMID:17915281

  8. Active exchange of water and nutrients between seawater and shallow pore water in intertidal sandflats

    NASA Astrophysics Data System (ADS)

    Hwang, Dong-Woon; Kim, Guebuem; Yang, Han Soeb

    2008-12-01

    In order to determine the temporal and spatial variations of nutrient profiles in the shallow pore water columns (upper 30 cm depth) of intertidal sandflats, we measured the salinity and nutrient concentrations in pore water and seawater at various coastal environments along the southern coast of Korea. In the intertidal zone, salinity and nutrient concentrations in pore water showed marked vertical changes with depth, owing to the active exchange between the pore water and overlying seawater, while they are temporally more stable and vertically constant in the sublittoral zone. In some cases, the advective flow of fresh groundwater caused strong vertical gradients of salinity and nutrients in the upper 10 cm depth of surface sediments, indicating the active mixing of the fresher groundwater with overlying seawater. Such upper pore water column profiles clearly signified the temporal fluctuation of lower-salinity and higher-Si seawater intrusion into pore water in an intertidal sandflat near the mouth of an estuary. We also observed a semimonthly fluctuation of pore water nutrients due to spring-neap tide associated recirculation of seawater through the upper sediments. Our study shows that the exchange of water and nutrients between shallow pore water and overlying seawater is most active in the upper 20 cm layer of intertidal sandflats, due to physical forces such as tides, wave set-up, and density-thermal gradient.

  9. Enhanced submarine ground water discharge form mixing of pore water and estuarine water

    USGS Publications Warehouse

    Martin, Jonathan B.; Cable, Jaye E.; Swarzenski, Peter W.; Lindenberg, Mary K.

    2004-01-01

    Submarine ground water discharge is suggested to be an important pathway for contaminants from continents to coastal zones, but its significance depends on the volume of water and concentrations of contaminants that originate in continental aquifers. Ground water discharge to the Banana River Lagoon, Florida, was estimated by analyzing the temporal and spatial variations of Cl− concentration profiles in the upper 230 cm of pore waters and was measured directly by seepage meters. Total submarine ground water discharge consists of slow discharge at depths > ∼70 cm below seafloor (cmbsf) of largely marine water combined with rapid discharge of mixed pore water and estuarine water above ∼70 cmbsf. Cl− profiles indicate average linear velocities of ∼0.014 cm/d at depths > ∼70 cmbsf. In contrast, seepage meters indicate water discharges across the sediment-water interface at rates between 3.6 and 6.9 cm/d. The discrepancy appears to be caused by mixing in the shallow sediment, which may result from a combination of bioirrigation, wave and tidal pumping, and convection. Wave and tidal pumping and convection would be minor because the tidal range is small, the short fetch of the lagoon limits wave heights, and large density contacts are lacking between lagoon and pore water. Mixing occurs to ∼70 cmbsf, which represents depths greater than previously reported. Mixing of oxygenated water to these depths could be important for remineralization of organic matter.

  10. Pore connectivity, electrical conductivity, and partial water saturation: Network simulations

    NASA Astrophysics Data System (ADS)

    Li, M.; Tang, Y. B.; Bernabé, Y.; Zhao, J. Z.; Li, X. F.; Bai, X. Y.; Zhang, L. H.

    2015-06-01

    The electrical conductivity of brine-saturated rock is predominantly dependent on the geometry and topology of the pore space. When a resistive second phase (e.g., air in the vadose zone and oil/gas in hydrocarbon reservoirs) displaces the brine, the geometry and topology of the pore space occupied by the electrically conductive phase are changed. We investigated the effect of these changes on the electrical conductivity of rock partially saturated with brine. We simulated drainage and imbibition as invasion and bond percolation processes, respectively, in pipe networks assumed to be perfectly water-wet. The simulations included the formation of a water film in the pipes invaded by the nonwetting fluid. During simulated drainage/imbibition, we measured the changes in resistivity index as well as a number of relevant microstructural parameters describing the portion of the pore space saturated with water. Except Euler topological number, all quantities considered here showed a significant level of "universality," i.e., insensitivity to the type of lattice used (simple cubic, body-centered cubic, or face-centered cubic). Hence, the coordination number of the pore network appears to be a more effective measure of connectivity than Euler number. In general, the simulated resistivity index did not obey Archie's simple power law. In log-log scale, the resistivity index curves displayed a substantial downward or upward curvature depending on the presence or absence of a water film. Our network simulations compared relatively well with experimental data sets, which were obtained using experimental conditions and procedures consistent with the simulations. Finally, we verified that the connectivity/heterogeneity model proposed by Bernabé et al. (2011) could be extended to the partial brine saturation case when water films were not present.

  11. Submarine weathering of silicate minerals and the extent of pore water freshening at active continental margins

    NASA Astrophysics Data System (ADS)

    Scholz, Florian; Hensen, Christian; Schmidt, Mark; Geersen, Jacob

    2013-01-01

    In order to investigate how submarine weathering processes may affect the water balance of sediments at convergent plate margins, six sediment cores were retrieved off Central Chile at water depth between ˜800 and 4000 m. The sediment solid phase was analyzed for its major element composition and the pore fluids were analyzed for dissolved sulfate, sulfide, total alkalinity, major cations, chloride, bromide, iodide, hydrocarbons as well as the carbon isotopic composition of methane. Because of negligible weathering on land, surface sediments off Central Chile are rich in reactive silicate minerals and have a bulk composition similar to volcanic rocks in the adjacent Andes. Deep-sourced fluxes of alkalinity, cations and chloride indicate that silicate minerals are subject to weathering in the forearc during burial. Comparison of deep-sourced signals with data from nearby Ocean Drilling Program Sites reveals two different types of weathering processes: In shallow (tens of meters), methanic sediments of slope basins with high organic carbon burial rates, reactive silicate minerals undergo incongruent dissolution through reaction with CO2 from methanogenesis. At greater burial depth (hundreds of meters), silicate weathering is dominated by authigenic smectite formation. This process is accompanied by uptake of water into the clay interlayers thus leading to elevated salinities in the surrounding pore water. Deep-seated smectite formation is more widespread than shallow silicate dissolution, as it is independent from the availability of CO2 from methanogenesis. Although solute transport is not focused enough to form cold seeps in the proper sense, tectonically induced, diffuse fluid flow transfers the deep-seated signal of smectite formation into the shallow sediments. The temperature-controlled conversion of smectite to illite is considered the most important dehydration process in marine forearc environments (depth of kilometers). However, in agreement with other

  12. Hydrogeology and hydrodynamics of coral reef pore waters

    SciTech Connect

    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.

  13. Tunable water barrier properties of EVA by clay insertion?

    PubMed

    Wilson, R; Follain, N; Tenn, N; Kumar S, Anil; Thomas, S; Marais, S

    2015-07-15

    Organo-modified Cloisite clays at varying contents were incorporated into poly(ethylene-co-vinyl acetate) (EVA) by melt blending. Nanoclay dispersion in films was first evaluated. The water transport properties were investigated by pervaporation and sorption measurements. A decrease of the water permeation flux was obtained when incorporating nanoparticles. This barrier effect is usually attributed to the increase of the diffusion pathways due to nanoclay-induced tortuosity effects. However, the diffusion coefficient was found to be dependent on water concentration, which generally reflects a plasticization effect of water. Besides, at 7 wt% of loading, an unexpected increase of water diffusivity was measured with a time-scale shift of the permeation flux. This was correlated with the formation of preferential diffusion pathways along interfacial regions due to free volumes existing between the EVA matrix and nanoclays as well as the water affinity of microfillers. As a consequence, water mass gain was found to be increased. The water-induced plasticization of sorbed water molecules was also highlighted through sorption kinetics. Eventually, some applications to these films in which water barrier behaviour is required were discussed. PMID:26144216

  14. Oxygen Isotope Fractionation Effects in Soil Water via Cations Adsorbed to High-CEC Clays

    NASA Astrophysics Data System (ADS)

    Oerter, E.; Finstad, K.; Schaefer, J.; Goldsmith, G. R.; Dawson, T. E.; Amundson, R.

    2012-12-01

    In isotope-based approaches to hydrology, soil and sediment are implicitly considered to be an inert matrix in which water resides or moves. Yet, this assumption is inconsistent with the fact that soils contain a wide range of solutes, and highly variable concentrations of chemically reactive clay particles, all of which may react with bulk water and create pools of energetically differing water with varying isotope compositions. The empirical basis of this hypothesis is the work of Sofer and Gat (1972, EPSL, 15(3)), who showed that the formation of hydration spheres around cations in aqueous solutions fractionate oxygen isotopes of water in ways that appear to be dependent on the cation's ionic potential and concentration. Because soil solutions commonly have high solid to fluid ratios, the potential for solids to create substantial pools of low free energy water, with corresponding isotope fractionation of the free and low energy waters, may be a common process. The potential for this to create measurable isotopic effects would be most evident in soils with high Cation Exchange Capacity (CEC). In order to test this hypothesis, montmorillonite (CEC ≈ 100 meq/100g), kaolinite (CEC≈10) and quartz (CEC≈0) mineral powders were saturated with 3M MgCl2 and KCl solutions (separately), rinsed with methanol and dried to saturate all available CEC sites with either Mg or K cations. Triplicate sets of monominerallic-deionized water mixtures were created at 5, 25, 50, 75 and 95% gravimetric water content. Each set of samples was then subjected to one of three water extraction techniques designed to access specific "pools" of soil water: (1) direct equilibration with CO2 to sample the soil's "free water", i.e. water not adsorbed to cations via hydration spheres; (2) centrifugation to simulate permanent wilting point conditions, thereby yielding most micro-pore, macro-pore, and free water; and (3) cryogenic vacuum distillation to recover all the soil water (free, pore and

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

    PubMed

    Pourmohammadbagher, Amin; Shaw, John M

    2015-09-15

    Clays, in tailings, are a significant ongoing environmental concern in the mining and oilsands production industries, and clay rehabilitation following contamination poses challenges episodically. Understanding the fundamentals of clay behavior can lead to better environmental impact mitigation strategies. Systematic calorimetric measurements are shown to provide a framework for parsing the synergistic and antagonistic impacts of trace (i.e., parts per million level) components on the surface compositions of clays. The enthalpy of solution of as-received and "contaminated" clays, in as-received and "contaminated" organic solvents and water, at 60 °C and atmospheric pressure, provides important illustrative examples. Clay contamination included pre-saturation of clays with water and organic liquids. Solvent contamination included the addition of trace water to organic solvents and trace organic liquids to water. Enthalpy of solution outcomes are interpreted using a quantitative mass and energy balance modeling framework that isolates terms for solvent and trace contaminant sorption/desorption and surface energy effects. Underlying surface energies are shown to dominate the energetics of the solvent-clay interaction, and organic liquids as solvents or as trace contaminants are shown to displace water from as-received clay surfaces. This approach can be readily extended to include pH, salts, or other effects and is expected to provide mechanistic and quantitative insights underlying the stability of clays in tailings ponds and the behaviors of clays in diverse industrial and natural environments. PMID:26296102

  16. Water-Organic-Rock Reactions Recorded in Pores in Shales from the Marcellus and Rose Hill Formations (Invited)

    NASA Astrophysics Data System (ADS)

    Brantley, S. L.; Jin, L.; Rother, G.; Cole, D. R.; gu, X.; Balashov, V. N.

    2013-12-01

    The porosity of shales varies depending upon such attributes as the mineralogy, grain size, organic content, depth and duration of burial, and extent of water-rock reaction. Today, shales are being exploited when they contain significant natural gas, and the connectivity of pores are important toward controlling both recovery of gas after hydrofracking. In fact, the fine-scale nature of the pores controls aspects of release of natural gas and brines during hydrofracturing and gas exploitation. Despite the importance of shale as a source rock for natural gas and petroleum, it remains difficult to quantify and image porosity in shales because of their fine-scale nature. We are using neutron scattering, FIB SEM, CT microtomography, and other techniques to understand pores in a black (Marcellus) and a grey shale (Rose Hill formation) sampled in Pennsylvania. Samples were recovered both from outcrop and from depth in wellbores. We also report a new approach for investigating pores in shales by using neutron scattering before and after removal of organic matter. Pores in the two shales are observed to be isotropic (i.e. in the plane of bedding) or anisotropic (i.e. perpendicular to bedding), as expected for sediments that have been compacted after burial. Some nanometer-sized pores are observed in the organic matter of the Marcellus to be spherical; other pores are observed to be present in pyrite framboids and among silicate grains in that rock. We have no evidence that significant porosity is present in the organic matter in the Rose Hill formation, a relatively organic-poor shale, but pores are observed between and in clay particles. We also investigate how progressive water-rock reaction changes the primary porosity in the shales by investigating weathering samples. FIB SEM images document that organic matter is oxidized and removed significantly from the weathering Marcellus before the rock turns to soil, leaving behind porosity. Pyrite oxidation and dissolution

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

    NASA Astrophysics Data System (ADS)

    Takamoto, N.; Shimada, J.

    2014-12-01

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

  18. Processes in the pore waters of peat deposits

    SciTech Connect

    Levshenko, T.V.; Efremova, A.G.; Galkina, Z.M.; Surkova, T.E.; Tolstov, K.A.

    1983-01-01

    The composition of the waters of modern peat bogs that have developed in the intracontinental regions under the conditions of bogs of the high-moor, mixed, and lowmoor types have been investigated for the case of a number of peat deposits of the Smolensk, Volgorad, and Pskov provinces. During the work the pH of the deposits and the C1-, Alk, SO/sup 2/-, Ca/sup 2 +/, Mg/sup 2 +/, K- contents of the pore water of modern peat beds were studied. The thickness of the deposits studied amounted to 5-7 m. Samples were taken every 0.5 m in depth. The water was separated from the deposits by pressing out.

  19. Pore Water PAH Transport in Amended Sediment Caps

    NASA Astrophysics Data System (ADS)

    Gidley, P. T.; Kwon, S.; Ghosh, U.

    2009-05-01

    Capping is a common remediation strategy for contaminated sediments that creates a physical barrier between contaminated sediments and the water column. Diffusive flux of contaminants through a sediment cap is small. However, under certain hydrodynamic conditions such as groundwater potential and tidal pumping, groundwater advection can accelerate contaminant transport. Hydrophobic organic contaminants such as polycyclic aromatic hydrocarbons (PAHs) could be transported through the cap under advective conditions. To better understand PAH migration under these conditions, physical models of sediment caps were evaluated in the laboratory through direct measurement of pore water using solid phase micro-extraction with gas chromatography and mass spectrometry. Contaminated sediment and capping material was obtained from an existing Superfund site that was capped at Eagle Harbor, Washington. A PAH dissolution model linked to an advection-dispersion equation with retardation using published organic carbon-water partitioning coefficients (Koc) was compared to measured PAHs in the sediment and cap porewater of the physical model.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    Nano-scale processes on the solid-water interface of clay minerals control the mobility of metals in the environment. These processes can occur in confined pore spaces of clay buffers and barriers as well as in contaminated sediments and involve a combination of alteration, adsorption and nucleation processes of multiple species and phases. This study characterizes nano-scale processes on the interface between clay minerals and uranyl-bearing solution near neutral pH. Samples of clay minerals with a contact pH of ∼6.7 are collected from a U mill and mine tailings at Key Lake, Saskatchewan, Canada. The tailings material contains Cu-, As-, Co-, Mo-, Ni-, Se-bearing polymetallic phases and has been deposited with a surplus of Ca(OH)2 and Na2CO3 slaked lime. Small volumes of mill-process solutions containing sulfuric acid and U are occasionally discharged onto the surface of the tailings and are neutralized after discharge by reactions with the slaked lime. Transmission electron microscopy (TEM) in combination with the focused ion beam (FIB) technique and other analytical methods (SEM, XRD, XRF and ICP-OES) are used to characterize the chemical and mineralogical composition of phases within confined pore spaces of the clay minerals montmorillonite and kaolinite and in the surrounding tailings material. Alteration zones around the clay minerals are characterized by different generations of secondary silicates containing variable proportions of adsorbed uranyl- and arsenate-species and by the intergrowth of the silicates with the uranyl-minerals cuprosklodowskite, Cu[(UO2)2(SiO3OH)2](H2O)6 and metazeunerite, Cu[(UO2)(AsO4)2](H2O)8. The majority of alteration phases such as illite, illite-smectite, kaolinite and vermiculite have been most likely formed in the sedimentary basin of the U-ore deposit and contain low amounts of Fe (<5 at.%). Iron-enriched Al-silicates or illite-smectites (Fe >10 at.%) formed most likely in the limed tailings at high contact pH (∼10.5) and

  1. Flocculation of Clay and Organic Matter in Turbid Salt Water

    NASA Astrophysics Data System (ADS)

    Reed, A. H.; Yin, H.; Zhang, G.; Tan, X.; Furukawa, Y.

    2010-12-01

    Sediment transport and deposition in estuaries and tidal flats are often dominated by the aggregation of clay and organic matter into composite particles or “flocs”. The stability of the flocs is important in determining the distance over which the sediment is transported and the areas to which the sediment is deposited. During floc transport from riverine to oceanic environments, stability is determined by suspended sediment concentrations, sediment types, organic matter type, fluid flow rates and small scale turbulence. In a series of laboratory experiments, interactions between clay sediments and organic matter were evaluated within a flow column that was filled with saline water. The focus of this investigation was on changes in floc size, density and strength as flow velocities and turbulent stresses were altered. Significant changes in the floc shape, consolidation, density and behavior were determined for flow rates and Reynolds numbers that are common to riverine environments. The variability in floc composition was also shown to influence bulk sediment properties: heat transport, acoustic propagation and shear strength, while sediments were entrained in high-density suspensions and low-density deposits.

  2. Origin and transport of pore fluids in the Nankai accretionary prism inferred from chemical and isotopic compositions of pore water at cold seep sites off Kumano

    NASA Astrophysics Data System (ADS)

    Toki, Tomohiro; Higa, Ryosaku; Ijiri, Akira; Tsunogai, Urumu; Ashi, Juichiro

    2014-12-01

    We used push corers during manned submersible dives to obtain sediment samples of up to 30 cm from the subseafloor at the Oomine Ridge. The concentrations of B in pore water extracted from the sediment samples from cold seep sites were higher than could be explained by organic matter decomposition, suggesting that the seepage fluid at the site was influenced by B derived from smectite-illite alteration, which occurs between 50°C and 160°C. Although the negative δ18OH2O and δDH2O values of the pore fluids cannot be explained by freshwater derived from clay mineral dehydration (CMD), we considered the contribution of pore fluids in the shallow sediments of the accretionary prism, which showed negative δ18OH2O and δDH2O values according to the results obtained during Integrated Ocean Drilling Program (IODP) Expeditions 315 and 316. We calculated the mixing ratios based on a four-end-member mixing model including freshwater derived from CMD, pore fluids in the shallow (SPF) accretionary prism sediment, seawater (SW), and freshwater derived from methane hydrate (MH) dissociation. However, the Oomine seep fluids were unable to be explained without four end members, suggesting that deep-sourced fluids in the accretionary prism influenced the seeping fluids from this area. This finding presents the first evidence of deep-sourced fluids at cold seep sites in the Oomine Ridge, indicating that a megasplay fault is a potential pathway for the deep-sourced fluids.

  3. Retention and loss of water extractable carbon in soils: effect of clay properties.

    PubMed

    Nguyen, Trung-Ta; Marschner, Petra

    2014-02-01

    Clay sorption is important for organic carbon (C) sequestration in soils, but little is known about the effect of different clay properties on organic C sorption and release. To investigate the effect of clay content and properties on sorption, desorption and loss of water extractable organic C (WEOC), two experiments were conducted. In experiment 1, a loamy sand alone (native) or mixed with clay isolated from a surface or subsoil (78 and 96% clay) resulting in 90, 158 and 175 g clay kg(-1) soil. These soil treatments were leached with different WEOC concentrations, and then CO2 release was measured for 28 days followed by leaching with reverse osmosis water at the end of experiment. The second experiment was conducted to determine WEOC sorption and desorption of clays isolated from the loamy sand (native), surface soil and subsoil. Addition of clays isolated from surface and subsoil to sandy loam increased WEOC sorption and reduced C leaching and cumulative respiration in percentage of total organic C and WEOC added when expressed per g soil and per g clay. Compared to clays isolated from the surface and subsoil, the native clay had higher concentrations of illite and exchangeable Ca(2+), total organic C and a higher CEC but a lower extractable Fe/Al concentration. This indicates that compared to the clay isolated from the surface and the subsoil, the native clay had fewer potential WEOC binding sites because it had lower Fe/Al content thus lower number of binding sites and the existing binding sites are already occupied native organic matter. The results of this study suggest that in the soils used here, the impact of clay on WEOC sorption and loss is dependent on its indigenous organic carbon and Fe and/or Al concentrations whereas clay mineralogy, CEC, exchangeable Ca(2+) and surface area are less important. PMID:24144942

  4. Water Retention and Structure Stability in Smectitic or Kaolinitic Loam and Clay Soils Affected by Polyacrylamide Addition

    NASA Astrophysics Data System (ADS)

    Mamedov, Amirakh; Levy, Guy

    2015-04-01

    Studying the effects of polyacrylamide (PAM) on soil aggregate and structure stability is important in developing effective soil and water conservation practices and in sustaining soil and water quality. Five concentrations of an anionic PAM (0, 25, 50, 100 and 200 mg L-1) with a high molecular weight were tested on loam and clay soils having either a predominant smectitic or kaolinitic clay mineralogy. The effects of the PAM and of soil texture on soil water retention at near saturation and on aggregate and structure stability were investigated using the high energy moisture characteristic (HEMC) method. The S-shaped water retention curves obtained by the HEMC method were characterized by the modified van Genuchten (1980) model that provided: (i) the model parameters α and n, which represent the location of the inflection point and the steepness of the water retention curve, respectively; and (ii) the soil structure index, SI =VDP/MS, where VDP is the volume of drainable pores, an indicator of the quantity of water released by a soil over the range of applied suctions (0-5 J kg-1), and MS is the modal suction representing the most frequent pore sizes (> 60 μm). In general, the treatments tested (clay mineralogy, soil type and PAM concentration) resulted in: (i) a considerable modification of the shape of the water retention curves as indicated by the changes in the α and n values; and; (ii) substantial effects on the stability indices and other model parameters. The contribution of PAM concentration to soil structure stability depended on the clay mineralogy, being more effective in the smectitic soils than in the kaolinitic ones. Although kaolinitic soils are usually more stable than smectitic soils, when the latter were treated with PAM (25-200 mg L-1) the opposite trend was observed. In the loam soils, increasing the PAM concentration notably decreased the differences between values of the stability indices of the smectitic and kaolinitic samples. The

  5. Effects of a nearshore wastewater discharge: Water column and sediment pore water toxicity

    SciTech Connect

    Krause, P.R.; Carr, R.S.

    1995-12-31

    The relationship between water column and sediment pore water toxicity was investigated near a municipal-industrial wastewater discharge in southern Texas. Toxicity associated with effluent distributions in the water column are known to vary in both time and space. Toxicity of sediment, however, is often more stable over time. Sediment can serve as a long-term integrator of toxicity in areas subject to chronic exposure of effluents. This study addressed the relationship between water column toxicity and that found in the sediments on both spatial and temporal scales. Four 2 Km transacts were established around a nearshore wastewater outfall. Eight stations along each transact were sampled for both surface waters and sediment pore water toxicity. Toxicity was determined using a modified sea urchin fertilization test. Surface waters were sampled and tested for eight consecutive months, while sediment pore waters were sampled on three occasions over the length of this study. Results have shown that toxicity in receiving waters was a good indicator to trace movements of the highly variable effluent plume. The distribution of effluent in the water column, and hence water column toxicity, was primarily driven by local wind conditions. Toxicity in sediment porewater was, much less variable and more evenly distributed over the study site. Sediment pore water toxicity was also a good predictor of the distribution of benthic infaunal invertebrates over much of the study site.

  6. Rheological properties of purified illite clays in glycerol/water suspensions

    NASA Astrophysics Data System (ADS)

    Dusenkova, I.; Malers, J.; Berzina-Cimdina, L.

    2015-04-01

    There are many studies about rheological properties of clay-water suspensions, but no published investigations about clay-glycerol suspensions. In this work apparent viscosity of previously purified illite containing clay fraction < 2 μm and glycerol/water suspensions were investigated. Carbonates were removed by dissolution in hydrochloric and citric acids and other non-clay minerals were almost totally removed by centrifugation. All obtained suspensions behaved as shear-thinning fluids with multiple times higher viscosity than pure glycerol/water solutions. Reduction of clay fraction concentration by 5% decreased the apparent viscosity of 50% glycerol/water suspensions approximately 5 times. There was basically no difference in apparent viscosity between all four 50% glycerol/water suspensions, but in 90% glycerol/water suspensions samples from Iecava deposit showed slightly higher apparent viscosity, which could be affected by the particle size distribution.

  7. Contact micromechanics in granular media with clay

    SciTech Connect

    Ita, S.L.

    1994-08-01

    Many granular materials, including sedimentary rocks and soils, contain clay particles in the pores, grain contacts, or matrix. The amount and location of the clays and fluids can influence the mechanical and hydraulic properties of the granular material. This research investigated the mechanical effects of clay at grain-to-grain contacts in the presence of different fluids. Laboratory seismic wave propagation tests were conducted at ultrasonic frequencies using spherical glass beads coated with Montmorillonite clay (SWy-1) onto which different fluids were adsorbed. For all bead samples, seismic velocity increased and attenuation decreased as the contact stiffnesses increased with increasing stress demonstrating that grain contacts control seismic transmission in poorly consolidated and unconsolidated granular material. Coating the beads with clay added stiffness and introduced viscosity to the mechanical contact properties that increased the velocity and attenuation of the propagating seismic wave. Clay-fluid interactions were studied by allowing the clay coating to absorb water, ethyl alcohol, and hexadecane. Increasing water amounts initially increased seismic attenuation due to clay swelling at the contacts. Attenuation decreased for higher water amounts where the clay exceeded the plastic limit and was forced from the contact areas into the surrounding open pore space during sample consolidation. This work investigates how clay located at grain contacts affects the micromechanical, particularly seismic, behavior of granular materials. The need for this work is shown by a review of the effects of clays on seismic wave propagation, laboratory measurements of attenuation in granular media, and proposed mechanisms for attenuation in granular media.

  8. The Effect of Pore Connectivity on Water Adsorption Isotherms in Non-activated Graphitic Nanopores

    SciTech Connect

    StrioloDr., A; Gubbins, Dr. K. E.; Chialvo, Ariel A; Cummings, Peter T

    2005-01-01

    The adsorption of water in graphitic carbons is usually simulated via a weighted average of the adsorption isotherms simulated in carbon-slit pore of different widths. By following this procedure, details about pore morphology and pore connectivity may be overlooked. Towards a better match between virtual and real experiments, we present simulated adsorption isotherms for SPC/E model water in porous carbons composed by interconnected carbon-slit pores. The pores are separated from each other by one graphene layer. Imperfections (lack of carbon atoms) in the graphene layers result in interconnections between pores. The grand canonical Monte Carlo algorithm is used here to simulate water adsorption. Our results show that while the qualitative features obtained in the simulation of independent slit-shaped pores are reproduced when interconnected pores are considered, the adsorption isotherms rise more gradually and the adsorption/desorption hysteresis loops are narrower in the latter case.

  9. Transient streaming potentials under varying pore-water ionic strength

    NASA Astrophysics Data System (ADS)

    Malama, B.

    2014-12-01

    Streaming potentials (SP) are generated when polar fluids such as groundwater flow through porous media that have charged mineral surfaces. This is due to the flow-shearing of the diffuse layer of the electric double layer (EDL), which is known to form in the fluid phase at the fluid-rock interface. Previous works have suggested that the EDL vanishes at high pore-fluid ionic strengths resulting in vanishing SP signals. However, recent observations in sea-water intrusion applications by Jackson and coworkers indicate that measurable SP signals are obtainable in flows of fluids with high ionic strengths through silica sand. We demonstrate the repeatability of these observations through a series of laboratory flow experiments performed on 98% silica sand in a falling-head permeameter with brines of concentrations ranging from 0.001M to about 5 M NaCl. The results of the experiments, which clearly show measurable SP signals even at the highest concentration of 5 M NaCl, are reported. They are also used to estimate the hydraulic conductivity and electrokinetic coupling coefficient. The linearity assumption for the relation between pressure and SP differentials is evaluated for high pore-water NaCl concentrations. Additionally, displacement of one brine by another of different NaCl concentration yields dramatic transient SP responses that may be harnessed in the development of early-detection/warning technologies for sea-water intrusion applications. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. This research is funded by WIPP programs administered by the Office of Environmental Management (EM) of the U.S Department of Energy.

  10. Toxicity of ammonia in pore-water and in the water column to freshwater benthic invertebrates

    SciTech Connect

    Whiteman, F.W.; Kahl, M.D.; Rau, D.M.; Balcer, M.D.; Ankley, G.T.

    1994-12-31

    Ammonia has been mentioned as both a primary toxicant and a factor that can produce false positive results in laboratory sediment tests using benthic invertebrates. This study developed a sediment dosing system that percolates an ammonia solution through sediment to achieve target porewater ammonia concentrations that remain stable over four and ten day spiked sediment tests. Ten day flow-through water-only tests and ten day spiked sediment tests were used to determine the toxicity of ammonia in the water column and in the sediment pore-water to the oligochaete Lumbriculus variegatus and the midge Chironomus tentans. Four-day tests were run with the amphipod Hyalella azteca. The relationship between water column ammonia toxicity and sediment pore-water ammonia toxicity is influenced by the organism`s association with the sediment. For Lumbriculus variegatus and Chironomus tentans that burrow into the sediment and are in direct contact with the porewater, the pore-water LC50 for ammonia is 30--40% higher than the water-only LC50 for each species. Hyalella azteca is epibenthic and avoids ammonia spiked sediment, thus ammonia in the water column is considerably more toxic than the pore-water ammonia with the porewater LC50 about 800% higher than the water only LC50.

  11. Variations of marine pore water salinity and chlorinity in Gulf of Alaska sediments (IODP Expedition 341)

    NASA Astrophysics Data System (ADS)

    März, Christian; Mix, Alan C.; McClymont, Erin; Nakamura, Atsunori; Berbel, Glaucia; Gulick, Sean; Jaeger, John; Schneider (LeVay), Leah

    2014-05-01

    Pore waters of marine sediments usually have salinities and chlorinities similar to the overlying sea water, ranging around 34-35 psu (Practical Salinity Units) and around 550 mM Cl-, respectively. This is because these parameters are conservative in the sense that they do not significantly participate in biogeochemical cycles. However, pore water studies carried out in the frame of the International Ocean Discovery Program (IODP) and its predecessors have shown that salinities and chlorinities of marine pore waters can substantially deviate from the modern bottom water composition in a number of environmental settings, and various processes have been suggested to explain these phenomena. Also during the recent IODP Expedition 341 that drilled five sites in the Gulf of Alaska (Northeast Pacific Ocean) from the deep Surveyor Fan across the continental slope to the glaciomarine shelf deposits, several occurrences of pore waters with salinities and chlorinities significantly different from respective bottom waters were encountered during shipboard analyses. At the pelagic Sites U1417 and U1418 (~4,200 and ~3,700 m water depth, respectively), salinity and chlorinity maxima occur around 20-50 m sediment depth, but values gradually decrease with increasing drilling depths (down to 30 psu in ~600 m sediment depth). While the pore water freshening at depth is most likely an effect of clay mineral dehydration due to increasing burial depth, the shallow salinity and chlorinity maxima are interpreted as relicts of more saline bottom waters that existed in the North Pacific during the Last Glacial Maximum (Adkins et al., 2002). In contrast, the glaciomarine slope and shelf deposits at Site U1419 to U1421 (~200 to 1,000 m water depth) are characterised by unexpectedly low salinitiy and chlorinity values (as low as 16 psu and 295 mM Cl-, respectively) already in very shallow sediment depths (~10 m), and their records do not show systematic trends with sediment depth. Freshening

  12. Fate and transport of oil sand process-affected water into the underlying clay till: a field study.

    PubMed

    Abolfazlzadehdoshanbehbazari, Mostafa; Birks, S Jean; Moncur, Michael C; Ulrich, Ania C

    2013-08-01

    The South Tailings Pond (STP) is a ~2300-ha tailing pond operated by Suncor Energy Inc. that has received oil sand process-affected (PA) water and mature fine tailings since 2006. The STP is underlain by a clay till, which is in turn underlain by the Wood Creek Sand Channel (WCSC). The sandy deposits of the WCSC provide greater geotechnical stability but could act as a potential flow pathway for PA water to migrate off site and into the Athabasca River. Preliminary modeling of the STP suggests that PA water from the pond will infiltrate into the underlying sand channel, but the extent and development of this impact is still poorly understood. Suncor Energy Inc. built interception wells and a cut-off-wall to control any potential seepage. Here we present the results of an investigation of the fate and transport of PA water in clay till underlying a 10 m × 10 m infiltration pond that was constructed on the southeastern portion of the STP. The geochemistry of pore water in the till underlying the infiltration pond was determined prior to filling with process-affected water (2008) and two years after the infiltration pond was filled with PA waters (2010). Pore water was analyzed for metals, cations, anions, and isotopes ((2)H and (18)O). The distribution of conservative tracers ((18)O and chloride) indicated migration of the PA waters to approximately 0.9 m, but the migrations of major ions and metals were significantly delayed relative to this depth. Uptake of Na and Mo and release of Ca, Mg, Mn, Ba, and Sr suggest that adsorption and ion exchange reactions are the foremost attenuation processes controlling inorganic solutes transport. PMID:23752067

  13. Modeling virgin compression of reconstituted clay at different initial water contents

    NASA Astrophysics Data System (ADS)

    Bian, Xia; Qian, Sen; Ding, Jian-wen

    2015-10-01

    The observations on compressibility of reconstituted clays show that the compression line with a higher initial water content lies above the compression line with a lower initial water content for a given clay. Hence there exists additional void ratio due to initial water contents among virgin compression lines (VCLs) of reconstituted clays. In this paper, the difference in void ratio caused by different initial water contents is investigated based on the empirical equation proposed by Liu and Carter (2000) for describing the differential void ratio at the same stress between natural and reconstituted clays. The mechanism of compressibility of reconstituted clays, when the stress level is larger than the remolded yield stress, is also discussed.

  14. Excess pore water pressure due to ground surface erosion

    NASA Astrophysics Data System (ADS)

    Llewellyn Smith, Stefan; Gagniere, Steven

    2015-11-01

    Erosional unloading is the process whereby surface rocks and soil are removed by external processes, resulting in changes to water pressure within the underlying aquifer. We consider a mathematical model of changes in excess pore water pressure as a result of erosional unloading. Neuzil and Pollock (1983) studied this process in the case where the water table initially coincides with the surface. In contrast, we analyze an ideal aquifer which is initially separated from the ground surface by an unsaturated zone. The model is solved using Laplace Transform methods in conjunction with a boost operator derived by King (1985). The boost operator is used to boost the solution (in the Laplace domain) to a frame of reference moving at constant velocity with respect to the original frame. We use our solution to analyze the evolution of the pressure during erosion of the aquifer itself for small and large erosion rates. We also examine the flux at the upper boundary as a function of time and present a quasi-steady approximation valid for very small erosion rates in the appendix.

  15. METHODS FOR PORE WATER EXTRACTION FROM UNSATURATED ZONE TUFF, YUCCA MOUNTAIN, NEVADA

    SciTech Connect

    K.M. SCOFIELD

    2006-03-22

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

  16. Clay hydration/dehydration in dry to water-saturated supercritical CO2: Implications for caprock integrity

    SciTech Connect

    Loring, John S.; Schaef, Herbert T.; Thompson, Christopher J.; Turcu, Romulus VF; Miller, Quin R.; Chen, Jeffrey; Hu, Jian Z.; Hoyt, David W.; Martin, Paul F.; Ilton, Eugene S.; Felmy, Andrew R.; Rosso, Kevin M.

    2013-01-01

    Injection of supercritical CO2 (scCO2) for the geologic storage of carbon dioxide will displace formation water, and the pore space adjacent to overlying caprocks could eventually be dominated by dry to water-saturated scCO2. Wet scCO2 is highly reactive and capable of carbonating and hydrating certain minerals, whereas anhydrous scCO2 can dehydrate water-containing minerals. Because these geochemical processes affect solid volume and thus porosity and permeability, they have the potential to affect the long-term integrity of the caprock seal. In this study, we investigate the swelling and shrinkage of an expandable clay found in caprock formations, montmorillonite (Ca-STx-1), when exposed to variable water-content scCO2 at 50 °C and 90 bar using a combination of in situ probes, including X-ray diffraction (XRD), in situ magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR), and in situ attenuated total reflection infrared spectroscopy (ATR-IR). We show that the extent of montmorillonite clay swelling/shrinkage is dependent not only on water hydration/dehydration, but also on CO2 intercalation reactions. Our results also suggest a competition between water and CO2 for interlayer residency where increasing concentrations of intercalated water lead to decreasing concentrations of intercalated CO2. Overall, this paper demonstrates the types of measurements required to develop fundamental knowledge that will enhance modeling efforts and reduce risks associated with subsurface storage of CO2.

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  18. Influence of Water Table Depth on Pore Water Chemistry and Trihalomethane Formation Potential in Peatlands.

    PubMed

    Gough, Rachel; Holliman, Peter J; Fenner, Nathalie; Peacock, Mike; Freeman, Christopher

    2016-02-01

    Drained peatland catchments are reported to produce more colored, dissolved organic carbon (DOC)-rich water, presenting problems for potable water treatment. The blocking of peatland drainage ditches to restore the water table is increasingly being considered as a strategy to address this deterioration in water quality. However, the effect of ditch blocking on the potential of DOC to form trihalomethanes (THMs) has not been assessed. In this study, the effect of peat rewetting on pore water DOC concentration and characteristics (including THM formation potential [THMFP]) was assessed over 12 months using peat cores collected from two drained peatland sites. The data show little evidence of differences in DOC concentration or characteristics between the different treatments. The absence of any difference in the THMFP of pore water between treatments suggests that, in the short term at least, ditch blocking may not have an effect on the THMFP of waters draining peatland catchments. PMID:26803099

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  20. The one-dimensional compression method for extraction of pore water from unsaturated tuff and effects on pore-water chemistry

    SciTech Connect

    Higgins, J.D.; Burger, P.A.; Yang, L.C.

    1997-12-31

    Study of the hydrologic system at Yucca Mountain, Nevada, requires extraction of pore-water samples from unsaturated tuff bedrock. Two generations of compression cells have been designed and tested for extracting representative, unaltered pore-water samples from unsaturated tuff cores. The one-dimensional compression cell has a maximum compressive stress rating of 552 MPa. Results from 86 tests show that the minimum degree of saturation for successful extraction of pore water was about 14% for non welded tuff and about 61% for densely welded tuff. The high-pressure, one-dimensional compression cell has a maximum compressive stress rating of 827 MPa. Results from 109 tests show that the minimum degree of saturation for successful extraction of pore water was about 7.5% for non welded tuff and about 34% for densely welded tuff. Geochemical analyses show that, in general, there is a decrease in ion concentration of pore waters as extraction pressures increase. Only small changes in pore-water composition occur during the one-dimensional extraction test.

  1. Extrusion of transmitter, water and ions generates forces to close fusion pore.

    PubMed

    Tajparast, M; Glavinović, M I

    2009-05-01

    During exocytosis the fusion pore opens rapidly, then dilates gradually, and may subsequently close completely, but what controls its dynamics is not well understood. In this study we focus our attention on forces acting on the pore wall, and which are generated solely by the passage of transmitter, ions and water through the open fusion pore. The transport through the charged cylindrical nano-size pore is simulated using a coupled system of Poisson-Nernst-Planck and Navier-Stokes equations and the forces that act radially on the wall of the fusion pore are then estimated. Four forces are considered: a) inertial force, b) pressure, c) viscotic force, and d) electrostatic force. The inertial and viscotic forces are small, but the electrostatic force and the pressure are typically significant. High vesicular pressure tends to open the fusion pore, but the pressure induced by the transport of charged particles (glutamate, ions), which is predominant when the pore wall charge density is high tends to close the pore. The electrostatic force, which also depends on the charge density on the pore wall, is weakly repulsive before the pore dilates, but becomes attractive and pronounced as the pore dilates. Given that the vesicular concentration of free transmitter can change rapidly due to the release, or owing to the dissociation from the gel matrix, we evaluated how much and how rapidly a change of the vesicular K(+)-glutamate(-) concentration affects the concentration of glutamate(-) and ions in the pore and how such changes alter the radial force on the wall of the fusion pore. A step-like rise of the vesicular K(+)-glutamate(-) concentration leads to a chain of events. Pore concentration (and efflux) of both K(+) and glutamate(-) rise reaching their new steady-state values in less than 100 ns. Interestingly within a similar time interval the pore concentration of Na(+) also rises, whereas that of Cl(-) diminishes, although their extra-cellular concentration does not

  2. The Effects of Dry Density and Pore-water Salinity on the Physical and Microbiological Characteristics of Compacted 100% Bentonite

    SciTech Connect

    Stroes-Gascoyne, S.; Hamon, C.J.; Dixon, D.A.; Kohle, C.L.; Maak, P.

    2007-07-01

    This study examined the conditions required to suppress microbial activity in compacted bentonite, such that microbially influenced corrosion (MIC) of copper waste containers, surrounded by compacted bentonite in a future deep geologic repository, would become insignificant. Experiments were carried out to determine the effects of dry density and pore-water salinity on swelling pressure, water activity (a{sub w}) and the culturable microbial community in compacted bentonite. A dry density {>=} 1.6 g/cm{sup 3} ensures that a{sub w} is < 0.96 and the swelling pressure > 2 MPa. Both conditions suppress microbial culturability below background levels (2.1 x 10{sup 2} Colony-Forming Units/g) in as-purchased bentonite. Under such conditions, cells likely survive as dormant cells or inactive spores, which greatly reduces the possibility of significant MIC. Observations in natural clay-rich environments support these findings. (authors)

  3. Sorption of high explosives to water-dispersible clay: influence of organic carbon, aluminosilicate clay, and extractable iron.

    PubMed

    Dontsova, Katerina M; Hayes, Charolett; Pennington, Judith C; Porter, Beth

    2009-01-01

    Explosives in soils can present environmental problems for military installations. Fine, mobile particles represent the most reactive fraction of the soil and, therefore, are expected to adsorb explosives and potentially facilitate their transport. The objective of this study was to determine the relative significance of phyllosilicate clay, organic matter, and two forms of extractable iron in adsorption of 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) by the colloidal water-dispersible clay (WDC) fraction of the soil. The WDC fraction of two mineral and one organic soil was separated and then treated to remove organic carbon (OC) and several forms of iron (Fe(o), oxalate extractable, and Fe(d), dithionite-citrate extractable). Adsorption coefficients were determined for whole soils, untreated, and treated WDC. For mineral soils, adsorption of TNT and RDX on the WDC was greater than on the whole soil. The presence of OC increased explosives sorption by WDC. When OC was removed, iron interfered with TNT sorption. In the presence of OC, removal of Fe(o) decreased RDX adsorption and increased TNT adsorption indicating different adsorption mechanisms. Organic carbon was a more significant indicator of explosives adsorption by WDC than clays or iron oxides and hydroxides. Therefore, OC is the most likely medium for facilitated transport of TNT and RDX. PMID:19465721

  4. On equilibration of pore water in column leaching tests.

    PubMed

    Grathwohl, Peter

    2014-05-01

    Column leaching tests are closer to natural conditions than batch shaking tests and in the last years have become more popular for assessing the release potential of pollutants from a variety of solids such as contaminated soils, waste, recycling and construction materials. Uncertainties still exist regarding equilibration of the percolating water with the solids, that might potentially lead to underestimation of contaminant concentrations in the effluent. The intention of this paper is to show that equilibration of pore water in a finite bath is fundamentally different from release of a certain fraction of the pollutant from a sample and that equilibrium is reached much faster at low liquid-to-solid ratios typical for column experiments (<0.25) than in batch tests with much higher liquid-to-solid ratios (e.g., 2-10). Two mass transfer mechanisms are elucidated: First-order type release (film diffusion) and intraparticle diffusion. For the latter, mass transfer slows down with time and sooner or later non-equilibrium conditions are observed at the column outlet after percolation has been started. Time scales of equilibrium leaching can be estimated based on a comparison of column length with the length of the mass transfer zone, which is equivalent to a Damköhler number approach. Mass transfer and diffusion coefficients used in this study apply to mass transfer mechanisms limited by diffusion in water, which is typical for release of organic compounds but also for dissolution of soluble minerals such as calcite, gypsum or similar. As a conclusion based on these theoretical considerations column tests (a) equilibrate much faster than batch leaching tests and (b) the equilibrium concentrations are maintained in the column effluent even for slow intraparticle diffusion limited desorption for extended periods of time (>days). Since for equilibration the specific surface area is crucial, the harmonic mean of the grain size is relevant (small grain sizes result in high

  5. Soil-Water Characteristic Curves of Red Clay treated by Ionic Soil Stabilizer

    NASA Astrophysics Data System (ADS)

    Cui, D.; Xiang, W.

    2009-12-01

    The relationship of red clay particle with water is an important factor to produce geological disaster and environmental damage. In order to reduce the role of adsorbed water of red clay in WuHan, Ionic Soil Stabilizer (ISS) was used to treat the red clay. Soil Moisture Equipment made in U.S.A was used to measure soil-water characteristic curve of red clay both in natural and stabilized conditions in the suction range of 0-500kPa. The SWCC results were used to interpret the red clay behavior due to stabilizer treatment. In addition, relationship were compared between the basic soil and stabilizer properties such as water content, dry density, liquid limit, plastic limit, moisture absorption rate and stabilizer dosages. The analysis showed that the particle density and specific surface area increase, the dehydration rate slows and the thickness of water film thins after treatment with Ionic Soil Stabilizer. After treatment with the ISS, the geological disasters caused by the adsorbed water of red clay can be effectively inhibited.

  6. Bottom sediments and pore waters near a hydrothermal vent in Lake Baikal (Frolikha Bay)

    USGS Publications Warehouse

    Granina, L.Z.; Klerkx, J.; Callender, E.; Leermakers, M.; Golobokova, L.P.

    2007-01-01

    We discuss the redox environments and the compositions of bottom sediments and sedimentary pore waters in the region of a hydrothermal vent in Frolikha Bay, Lake Baikal. According to our results, the submarine vent and its companion nearby spring on land originate from a common source. The most convincing evidence for their relation comes from the proximity of stable oxygen and hydrogen isotope compositions in pore waters and in the spring water. The isotope composition indicates a meteoric origin of pore waters, but their major- and minor-element chemistry bears imprint of deep water which may seep through permeable faulted crust. Although pore waters near the submarine vent have a specific enrichment in major and minor constituents, hydrothermal discharge at the Baikal bottom causes a minor impact on the lake water chemistry, unlike the case of freshwater geothermal lakes in the East-African Rift and North America. ?? 2007.

  7. Diffusive Release of Uranium from Contaminated Sediments into Capillary Fringe Pore Water

    SciTech Connect

    Rod, Kenton A.; Wellman, Dawn M.; Flury, Markus; Pierce, Eric M.; Harsh, James B.

    2012-09-13

    We investigated the dynamics of U release between pore water fractions, during river stage changes from two contaminated capillary fringe sediments. Samples were from 7.0 m and 7.6 m below ground surface (bgs) in the Hanford 300 area. Sediments were packed into columns and saturated with Hanford groundwater for three to 84 days. After specified times, > 48 µm radius (calculated) sediment pores were drained, followed by draining pores to 15 µm radius. U release in the first two weeks was similar between sediments and pore sizes with a range of 4.4 to 5.6 µM U in the 14 day sample. The 7.0 m bgs sediment U declined in the larger pores to 0.22 µM at day 84, whereas the small pores released U to 6.7 µM at day 84. The 7.6 m bgs sediment released 1.4 µM on day 84, in the large pores, but continuously released U from the smaller pores (13.2 uM on day 84). The continuous release of U has resulted in a diffusion gradient from the smaller to larger pores. The observed differences in U pore-water concentrations between the two sediment samples were attributed to co-precipitation of U with carbonates. A mineral phase in the sediments was also identified as an U-carbonate species, similar to rutherfordine [UO2(CO3)].

  8. Ball clay

    USGS Publications Warehouse

    Virta, R.L.

    2013-01-01

    Four companies — H.C. Spinks Clay Co., Inc., Imerys, Old Hickory Clay Co. and Unimin Corp. — mined ball clay in five U.S. states in 2012. Production, on the basis of preliminary data, was 900 kt (992,000 st), with an estimated value of $42.3 million. This was a slight increase in tonnage from 886 kt (977,000 st), with a value of $40.9 million in 2011. Tennessee was the leading ball clay producing state, with 63 percent of domestic production, followed by Texas, Mississippi, Kentucky and Indiana. Reported ball clay production from Indiana probably was fire clay rather than ball clay. About 69 percent of total ball clay production was airfloat, 20 percent was crude and 11 percent was water-slurried.

  9. Stirring the Waters: The Influence of Marie Clay.

    ERIC Educational Resources Information Center

    Gaffney, Janet S., Ed.; Askew, Billie J., Ed.

    Celebrating Marie Clay as a major theorist of child literacy acquisition, this book presents 15 essays by distinguished scholars that reflect on her contributions to the field of early literacy; early childhood, bilingual, and special education; developmental, cognitive, and school psychology; assessment; teacher education; professional…

  10. Relating pore-scale geometric controls on NMR and SIP parameters for improved petrophysical models of synthetic sand-clay mixtures

    NASA Astrophysics Data System (ADS)

    Osterman, G. K.; Keating, K.; Slater, L. D.; Binley, A. M.

    2013-12-01

    The microgeometry of porous geologic materials controls a wide range of key hydraulic parameters, such as permeability. Non-invasive geophysical methods have shown promise in mapping these properties in-situ over laterally extensive areas. Two near-surface geophysical techniques, nuclear magnetic resonance (NMR) and spectral induced polarization (SIP), demonstrate distinct relationships with porosity, grain size, and surface area. Permeability is also thought to be related to these physical properties suggesting that NMR and SIP can be used to estimate permeability. However, SIP lacks a universally accepted model and NMR is insensitive to anisotropy and pore-connectivity. Additionally, geochemical factors alter NMR and SIP measurements in non-unique manners. In this study, we performed a series of laboratory experiments on well-controlled sand-clay mixtures in order to constrain the geometric controls on measureable NMR and SIP responses in porous media. We combined the geophysical data to formulate better petrophysical models of key hydraulic parameters than would be possible using each method separately. NMR and SIP measurements were performed on different brine saturated mixtures of Ottawa sand and kaolin. Independent measurements were made to estimate the specific surface area, porosity, grain size distribution, and permeability for each sand-clay mixture. Additionally, the brine conductivity was varied in order to test the sensitivity of the NMR and SIP measurements to pore-fluid chemistry as well as determine the true electrical formation factor of the samples. Empirical relationships were first established between each physical property and the measured geophysical parameters using regression analysis. The resulting relationships form the foundation for future mechanistic permeability models that incorporate joint NMR and SIP measurements.

  11. The effects of pore structure on the behavior of water in lignite coal and activated carbon.

    PubMed

    Nwaka, Daniel; Tahmasebi, Arash; Tian, Lu; Yu, Jianglong

    2016-09-01

    The effects of physical structure (pore structure) on behavior of water in lignite coal and activated carbon (AC) samples were investigated by using Differential Scanning Calorimetry (DSC) and low-temperature X-ray diffraction (XRD) techniques. AC samples with different pore structures were prepared at 800°C in steam and the results were compared with that of parent lignite coal. The DSC results confirmed the presence of two types of freezable water that freeze at -8°C (free water) and -42°C (freezable bound water). A shift in peak position of free water (FW) towards lower temperature was observed in AC samples compared to the lignite coal with decreasing water loading. The amount of free water (FW) increased with increasing gasification conversion. The amounts of free and freezable bound water (FBW) in AC samples were calculated and correlated to pore volume and average pore size. The amount of FW in AC samples is well correlated to the pore volume and average pore size of the samples, while an opposite trend was observed for FBW. The low-temperature XRD analysis confirmed the existence of non-freezable water (NFW) in coal and AC with the boundary between the freezable and non-freezable water (NFW) determined. PMID:27254256

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

    NASA Astrophysics Data System (ADS)

    Moffett, Kevan B.; Gorelick, Steven M.

    2016-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  14. Quantification of Water Content Across a Cement-clay Interface Using High Resolution Neutron Radiography

    NASA Astrophysics Data System (ADS)

    Shafizadeh, A.; Gimmi, T.; Van Loon, L.; Kaestner, A.; Lehmann, E.; Maeder, U. K.; Churakov, S. V.

    In many designs for radioactive waste repositories, cement and clay will come into direct contact. The geochemical contrast between cement and clay will lead to mass fluxes across the interface, which consequently results in alteration of structural and transport properties of both materials that may affect the performance of the multi-barrier system. We present an experimental approach to study cement-clay interactions with a cell to accommodate small samples of cement and clay. The cell design allows both in situ measurement of water content across the sample using neutron radiography and measurement of transport parameters using through-diffusion tracer experiments. The aim of the high-resolution neutron radiography experiments was to monitor changes in water content (porosity) and their spatial extent. Neutron radiographs of several evolving cement-clay interfaces delivered quantitative data which allow resolving local water contents within the sample domain. In the present work we explored the uncertainties of the derived water contents with regard to various input parameters and with regard to the applied image correction procedures. Temporal variation of measurement conditions created absolute uncertainty of the water content in the order of ±0.1 (m3/m3), which could not be fully accounted for by correction procedures. Smaller relative changes in water content between two images can be derived by specific calibrations to two sample regions with different, invariant water contents.

  15. Three dimensional analysis of the pore space in fine-grained Boom Clay, using BIB-SEM (broad-ion beam scanning electron microscopy), combined with FIB (focused ion-beam) serial cross-sectioning, pore network modeling and Wood's metal injection

    NASA Astrophysics Data System (ADS)

    Hemes, Susanne; Klaver, Jop; Desbois, Guillaume; Urai, Janos

    2014-05-01

    The Boom Clay is, besides the Ypresian clays, one of the potential host rock materials for radioactive waste disposal in Belgium (Gens et al., 2003; Van Marcke & Laenen, 2005; Verhoef et al., 2011). To access parameters, which are relevant for the diffusion controlled transport of radionuclides in the material, such as porosity, pore connectivity and permeability, it is crucial to characterize the pore space at high resolution (nm-scale) and in 3D. Focused-ion-beam (FIB) serial cross-sectioning in combination with high resolution scanning electron microscopy (SEM), pore network modeling, Wood's metal injection and broad-ion-beam (BIB) milling, constitute a superior set of methods to characterize the 3D pore space in fine-grained, clayey materials, down to the nm-scale resolution. In the present study, we identified characteristic 3D pore space morphologies, determined the 3D volume porosity of the material and applied pore network extraction modeling (Dong and Blunt, 2009), to access the connectivity of the pore space and to discriminate between pore bodies and pore throats. Moreover, we used Wood's metal injection (WMI) in combination with BIB-SEM imaging to assess the pore connectivity at a larger scale and even higher resolution. The FIB-SEM results show a highly (~ 90 %) interconnected pore space in Boom Clay, down to the resolution of ~ 3E+03 nm³ (voxel-size), with a total volume porosity of ~ 20 %. Pore morphologies of large (> 5E+08 nm³), highly interconnected pores are complex, with high surface area to volume ratios (shape factors G ~ 0.01), whereas small (< 1E+06 nm³), often isolated pores are much more compact and show higher shape factors (G) up to 0.03. WMI in combination with BIB-SEM, down to a resolution of ~ 50 nm² pixel-size, indicates an interconnected porosity fraction of ~ 80 %, of a total measured 2D porosity of ~ 20 %. Determining and distinguishing between pore bodies and pore throats enables us to compare 3D FIB-SEM pore

  16. Pore Water Circulation in Isolated Wetlands: Implications to Internal Nutrient Loading.

    NASA Astrophysics Data System (ADS)

    Bhadha, J. H.; Perkins, D. B.; Jawitz, J. W.

    2005-12-01

    The potential of wetland soils to accumulate and release pollutants including nutrients has been the motivation for numerous studies related to measuring the concentration, fate, and transport mechanisms of these substances in soils. While external nutrient loading from anthropogenic sources such as agricultural and cattle areas can be addressed through the implementation of Best Management Practices (BMPs), and interception strategies such as construction of storm-water treatment areas (STAs) in Florida, internal loading through shallow sediments has prevented the rapid improvement of water quality in numerous watersheds in South Florida, including the Lake Okeechobee drainage basin. The internal release of nutrients can occur via two different yet equally important mechanisms: advection and diffusion. These processes may mix the pore water not only within the sediment but also with the overlying water column over short periods of time (e.g., days or weeks). This provides sufficient time for diagenesis to alter the reactive chemical components of nutrients that may ultimately increase the nutrient fluxes to the overlying water column. The objectives of this research are to present a plausible and testable technique to collect pore water samples from saturated wetland soils, and to evaluate the importance of pore water circulation as a mechanism for mobilizing nutrients into the water column from within shallow sediments in isolated wetlands. Pore water sampling can be a difficult task to perform in low permeable wetland soils using standard sampling devices such as pore water equilibrators (peepers) and mechanical vises (Rheeburg squeezers). However, our attempt at using Multisamplers, which is in fact a multi-level piezometer capable of collecting up to ten pore water samples to a depth of 110 cm below the soil-water interface in a single deployment, proved to be a success. The ability to collect samples from multiple depths from a single location is an important

  17. Bioremediating oil spills in nutrient poor ocean waters using fertilized clay mineral flakes: some experimental constraints.

    PubMed

    Warr, Laurence N; Friese, André; Schwarz, Florian; Schauer, Frieder; Portier, Ralph J; Basirico, Laura M; Olson, Gregory M

    2013-01-01

    Much oil spill research has focused on fertilizing hydrocarbon oxidising bacteria, but a primary limitation is the rapid dilution of additives in open waters. A new technique is presented for bioremediation by adding nutrient amendments to the oil spill using thin filmed minerals comprised largely of Fullers Earth clay. Together with adsorbed N and P fertilizers, filming additives, and organoclay, clay flakes can be engineered to float on seawater, attach to the oil, and slowly release contained nutrients. Our laboratory experiments of microbial activity on weathered source oil from the Deepwater Horizon spill in the Gulf of Mexico show fertilized clay treatment significantly enhanced bacterial respiration and consumption of alkanes compared to untreated oil-in-water conditions and reacted faster than straight fertilization. Whereas a major portion (up to 98%) of the alkane content was removed during the 1 month period of experimentation by fertilized clay flake interaction; the reduced concentration of polyaromatic hydrocarbons was not significantly different from the non-clay bearing samples. Such clay flake treatment could offer a way to more effectively apply the fertilizer to the spill in open nutrient poor waters and thus significantly reduce the extent and duration of marine oil spills, but this method is not expected to impact hydrocarbon toxicity. PMID:23864952

  18. Dynamics of water in the amphiphilic pore of amyloid β fibrils

    NASA Astrophysics Data System (ADS)

    GhattyVenkataKrishna, Pavan K.; Mostofian, Barmak

    2013-09-01

    Alzheimers disease related amyloid peptide, Aβ, forms a fibrillar structure through aggregation. The aggregate is stabilized by a salt bridge that is responsible for the formation of an amphiphilic pore that can accommodate water molecules. None of the reported structures of Aβ, however, contain water. We present results from molecular dynamics simulations on dimeric Aβ fibrils solvated in water. Water penetrates and fills the amphiphilic pore increasing its volume. We observe a thick wire of water that is translationally and rotationally stiff in comparison to bulk water and may be essential for the stabilization of the amyloid Aβ protein.

  19. Water uptake of clay and desert dust aerosol particles at sub- and supersaturated water vapor conditions.

    PubMed

    Herich, Hanna; Tritscher, Torsten; Wiacek, Aldona; Gysel, Martin; Weingartner, Ernest; Lohmann, Ulrike; Baltensperger, Urs; Cziczo, Daniel J

    2009-09-28

    Airborne mineral dust particles serve as cloud condensation nuclei (CCN), thereby influencing the formation and properties of warm clouds. It is therefore of atmospheric interest how dust aerosols with different mineralogy behave when exposed to high relative humidity (RH) or supersaturation (SS) with respect to liquid water. In this study the subsaturated hygroscopic growth and the supersaturated cloud condensation nucleus activity of pure clays and real desert dust aerosols were determined using a hygroscopicity tandem differential mobility analyzer (HTDMA) and a cloud condensation nuclei counter (CCNC), respectively. Five different illite, montmorillonite and kaolinite clay samples as well as three desert dust samples (Saharan dust (SD), Chinese dust (CD) and Arizona test dust (ATD)) were investigated. Aerosols were generated both with a wet and a dry disperser. The water uptake was parameterized via the hygroscopicity parameter kappa. The hygroscopicity of dry generated dust aerosols was found to be negligible when compared to processed atmospheric aerosols, with CCNC derived kappa values between 0.00 and 0.02 (the latter corresponds to a particle consisting of 96.7% by volume insoluble material and approximately 3.3% ammonium sulfate). Pure clay aerosols were generally found to be less hygroscopic than natural desert dust particles. The illite and montmorillonite samples had kappa approximately 0.003. The kaolinite samples were less hygroscopic and had kappa=0.001. SD (kappa=0.023) was found to be the most hygroscopic dry-generated desert dust followed by CD (kappa=0.007) and ATD (kappa=0.003). Wet-generated dust showed an increased water uptake when compared to dry-generated samples. This is considered to be an artifact introduced by redistribution of soluble material between the particles. Thus, the generation method is critically important when presenting such data. These results indicate any atmospheric processing of a fresh mineral dust particle which

  20. Dynamics of confined reactive water in Smectic clay-zeolite composites.

    SciTech Connect

    Pitman, Michael C.; Van Duin, Adri C. T.

    2012-01-01

    The dynamics of water confined to mesoporous regions in minerals such as swelling clays and zeolites is fundamental to a wide range of resource management issues impacting many processes on a global scale, including radioactive waste containment, desalination, and enhanced oil recovery. Large-scale atomic models of freely diffusing multilayer smectite particles at low hydration confined in a silicalite cage are used to investigate water dynamics in the composite environment with the ReaxFF reactive force field over a temperature range of 300 647 K. The reactive capability of the force field enabled a range of relevant surface chemistry to emerge, including acid/base equilibria in the interlayer calcium hydrates and silanol formation on the edges of the clay and inner surface of the zeolite housing. After annealing, the resulting clay models exhibit both mono- and bilayer hydration structures. Clay surface hydration redistributed markedly and yielded to silicalite water loading. We find that the absolute rates and temperature dependence of water dynamics compare well to neutron scattering data and pulse field gradient measures from relevant samples of Ca-montmorillonite and silicalite, respectively. Within an atomistic, reactive context, our results distinguish water dynamics in the interlayer Ca(OH)2 nH2O environment from water flowing over the clay surface, and from water diffusing within silicalite. We find that the diffusion of water when complexed to Ca hydrates is considerably slower than freely diffusing water over the clay surface, and the reduced mobility is well described by a difference in the Arrhenius pre-exponential factor rather than a change in activation energy.

  1. Dynamics of confined reactive water in smectite clay-zeolite composites

    SciTech Connect

    Pitman, Michael C.; Van Duin, Adri C. T.

    2012-01-01

    The dynamics of water confined to mesoporous regions in minerals such as swelling clays and zeolites is fundamental to a wide range of resource management issues impacting many processes on a global scale, including radioactive waste containment, desalination, and enhanced oil recovery. Large-scale atomic models of freely diffusing multilayer smectite particles at low hydration confined in a silicalite cage are used to investigate water dynamics in the composite environment with the ReaxFF reactive force field over a temperature range of 300 647 K. The reactive capability of the force field enabled a range of relevant surface chemistry to emerge, including acid/base equilibria in the interlayer calcium hydrates and silanol formation on the edges of the clay and inner surface of the zeolite housing. After annealing, the resulting clay models exhibit both mono- and bilayer hydration structures. Clay surface hydration redistributed markedly and yielded to silicalite water loading. We find that the absolute rates and temperature dependence of water dynamics compare well to neutron scattering data and pulse field gradient measures from relevant samples of Ca-montmorillonite and silicalite, respectively. Within an atomistic, reactive context, our results distinguish water dynamics in the interlayer Ca(OH)2 nH2O environment from water flowing over the clay surface, and from water diffusing within silicalite. We find that the diffusion of water when complexed to Ca hydrates is considerably slower than freely diffusing water over the clay surface, and the reduced mobility is well described by a difference in the Arrhenius pre-exponential factor rather than a change in activation energy.

  2. Pore-Water Extraction Scale-Up Study for the SX Tank Farm

    SciTech Connect

    Truex, Michael J.; Oostrom, Martinus; Wietsma, Thomas W.; Last, George V.; Lanigan, David C.

    2013-01-15

    The phenomena related to pore-water extraction from unsaturated sediments have been previously examined with limited laboratory experiments and numerical modeling. However, key scale-up issues have not yet been addressed. Laboratory experiments and numerical modeling were conducted to specifically examine pore-water extraction for sediment conditions relevant to the vadose zone beneath the SX Tank Farm at Hanford Site in southeastern Washington State. Available SX Tank Farm data were evaluated to generate a conceptual model of the subsurface for a targeted pore-water extraction application in areas with elevated moisture and Tc-99 concentration. The hydraulic properties of the types of porous media representative of the SX Tank Farm target application were determined using sediment mixtures prepared in the laboratory based on available borehole sediment particle size data. Numerical modeling was used as an evaluation tool for scale-up of pore-water extraction for targeted field applications.

  3. Influence of Water Content on the Mechanical Behaviour of Limestone: Role of the Clay Minerals Content

    NASA Astrophysics Data System (ADS)

    Cherblanc, F.; Berthonneau, J.; Bromblet, P.; Huon, V.

    2016-06-01

    The mechanical characteristics of various sedimentary stones significantly depend on the water content, where 70 % loss of their mechanical strengths can be observed when saturated by water. Furthermore, the clay fraction has been shown to be a key factor of their hydro-mechanical behaviour since it governs for instance the hydric dilation. This work aims at investigating the correlations between the clay mineral content and the mechanical weakening experienced by limestones when interacting with water. The experimental characterization focuses on five different limestones that exhibit very different micro-structures. For each of them, we present the determination of clay mineral composition, the sorption isotherm curve and the dependences of tensile and compressive strengths on the water content. It emerges from these results that, first, the sorption behaviour is mainly governed by the amount of smectite layers which exhibit the larger specific area and, second, the rate of mechanical strength loss depends linearly on the sorption capacity. Indeed, the clay fraction plays the role of a retardation factor that delays the appearance of capillary bridges as well as the mechanical weakening of stones. However, no correlation was evidenced between the clay content and the amplitude of weakening. Since the mechanisms whereby the strength decreases with water content are not clearly established, these results would help to discriminate between various hypothesis proposed in the literature.

  4. Experimental investigation of human adenovirus cotransport with clay colloids and TiO2 nanoparticles in water saturated porous media

    NASA Astrophysics Data System (ADS)

    Syngouna, Vasiliki I.; Kokkinos, Petros; Tselepi, Maria A.; Kartoudis, Alexis; Vantarakis, Apostolos; Chrysikopoulos, Constantinos V.

    2016-04-01

    Particles such as clay colloids (e.g. kaolinite and montmorillonite) and metal oxides (e.g. TiO2) have great potential for controlling the fate and transport of viruses in the subsurface. Although human adenoviruses (hAdVs) are used worldwide to indicate human fecal pollution in groundwater, their transport behavior in the subsurface environment is not fully understood. This study focuses on the effects of both clay colloids (kaolinite, KGa-1b and montmorillonite, STx-1b), and TiO2 nanoparticles (NPs), on hAdV transport and retention in porous media. Laboratory-scale cotransport experiments were conducted in columns packed with glass beads, at three pore water velocities (0.38, 0.74, and 1.21 cm/min). The experimental results suggested that the presence of KGa-1b, STx-1b, and TiO2 NPs increased the attachment and inactivation of hAdVs, mainly due to the contribution of additional attachment sites. Retention of hAdVs by the packed column was shown to be highest in the presence of TiO2 NPs and lowest in the presence of KGa-1b. Moreover, the mass recovery values of both clay colloids and TiO2 NPs were affected by the presence of hAdVs, under all of the experimental conditions examined in this study. However, no distinct relationship between mass recovery and water velocity could be established from the present experimental cotransport results.

  5. Cryptic clues as to how water-soluble protein toxins form pores in membranes.

    PubMed

    Parker, Michael W

    2003-07-01

    Pore-forming protein toxins possess the remarkable property that they can exist either in a stable water-soluble state or as an integral membrane pore. In order to convert from the water-soluble to the membrane state, the toxin must undergo large conformational changes. Recent work on a class of pore-forming toxins that are rich in beta-sheet content suggests a common mechanism of membrane insertion may exist despite these toxins possessing very different primary, tertiary and quaternary structures. PMID:12893054

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

    NASA Astrophysics Data System (ADS)

    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.

  7. Dissolved organic matter in anoxic pore waters from Mangrove Lake, Bermuda

    USGS Publications Warehouse

    Orem, W.H.; Hatcher, P.G.; Spiker, E. C.; Szeverenyi, N.M.; Maciel, G.E.

    1986-01-01

    Dissolved organic matter and dissolved inorganic chemical species in anoxic pore water from Mangrove Lake, Bermuda sediments were studied to evaluate the role of pore water in the early diagenesis of organic matter. Dissolved sulphate, titration alkalinity, phosphate, and ammonia concentration versus depth profiles were typical of many nearshore clastic sediments and indicated sulphate reduction in the upper 100 cm of sediment. The dissolved organic matter in the pore water was made up predominantly of large molecules, was concentrated from large quantities of pore water by using ultrafiltration and was extensively tudied by using elemental and stable carbon isotope analysis and high-resolution, solid state 13C nuclear magnetic resonance and infrared spectroscopy. The results indicate that this material has a predominantly polysaccharide-like structure and in addition contains a large amount of oxygen-containing functional groups (e.g., carboxyl groups). The 13C nulcear magnetic resonance spectra of the high-molecular-weight dissolved organic matter resemble those of the organic matter in the surface sediments of Mangrove Lake. We propose that this high-molecular-weight organic matter in pore waters represents the partially degraded, labile organic components of the sedimentary organic matter and that pore waters serve as a conduit for removal of these labile organic components from the sediments. The more refractory components are, thus, selectively preserved in the sediments as humic substances (primarily humin). ?? 1986.

  8. A vacuum-operated pore-water extractor for estuarine and freshwater sediments

    USGS Publications Warehouse

    Winger, P.V.; Lasier, P.J.

    1991-01-01

    A vacuum-operated pore-water extractor for estuarine and freshwater sediments was developed and constructed from a fused-glass air stone attached with aquarium airline tubing to a 30 or 60 cc polypropylene syringe. Pore water is extracted by inserting the air stone into the sediment and creating a vacuum by retracting and bracing the syringe plunger. A hand-operated vacuum pump attached to a filtration flask was also evaluated as an alternative vacuum source. The volume and time to extract pore water varies with the number of devices and the sediment particle size. Extraction time is longer for fine sediments than for sandy sediments. Four liters of sediment generally yield between 500 and 1,500 mL of pore water. The sediment that surrounds and accumulates on the air stone acts as a filter, and, except for the first few milliliters, the collected pore water is clear. Because there is no exposure to air or avenue for escape, volatile compounds andin situ characteristics are retained in the extracted pore water.

  9. Cotransport of viruses and clay particles in water saturated and unsaturated porous media

    NASA Astrophysics Data System (ADS)

    Chrysikopoulos, C. V.; Syngouna, V. I.

    2014-12-01

    This experimental study examines the effects of clay colloids on the transport of viruses in variably saturated porous media. All cotransport experiments were conducted in both saturated and partially saturated columns packed with glass beads, using bacteriophages MS2 and ΦΧ174 as model viruses, and kaolinite (KGa-1b) and montmorillonite (STx-1b) as model clay colloids. The various experimental collision efficiencies were determined using the classical colloid filtration theory. The experimental data indicated that the mass recovery of viruses and clay colloids decreased as the water saturation decreased. Temporal moments of the various breakthrough concentrations collected, suggested that the presence of clays significantly influenced virus transport and irreversible deposition onto glass beads. The mass recovery of both viruses, based on total effluent virus concentrations, was shown to reduce in the presence of suspended clay particles. Furthermore, the transport of suspended virus and clay-virus particles was retarded, compared to the conservative tracer. Under unsaturated conditions both clay particles hindered the transport of the two viruses considered in this work. Moreover, the surface properties of viruses, clays and glass beads were employed for the construction of classical DLVO and capillary potential energy profiles, and the results suggested that capillary forces play a significant role on colloid retention. It was estimated that the capillary potential energy of MS2 is lower than that of ΦΧ174, and the capillary potential energy ofKGa-1b is lower than that of STx-1b, assuming that the protrusion distance through the water filmis the same for each pair of particles. Moreover, the capillary potential energy is several orders of magnitude greater than the DLVO energy potential. Figure 1Schematic illustration of the various concentrations involved in the cotransport experiments for: (a) saturated and (b) unsaturated porous media.

  10. Pore-size dependence and characteristics of water diffusion in slitlike micropores

    SciTech Connect

    Diallo, S. O.

    2015-07-16

    The temperature dependence of the dynamics of water inside microporous activated carbon fibers (ACF) is investigated by means of incoherent elastic and quasielastic neutron-scattering techniques. The aim is to evaluate the effect of increasing pore size on the water dynamics in these primarily hydrophobic slit-shaped channels. Using two different micropore sizes (similar to 12 and 18 angstrom, denoted, respectively, ACF-10 and ACF-20), a clear suppression of the mobility of the water molecules is observed as the pore gap or temperature decreases. Suppression, we found, is accompanied by a systematic dependence of the average translational diffusion coefficient D-r and relaxation time [tau(0)] of the restricted water on pore size and temperature. We observed D-r values and tested against a proposed scaling law, in which the translational diffusion coefficient D-r of water within a porous matrix was found to depend solely on two single parameters, a temperature-independent translational diffusion coefficient D-c associated with the water bound to the pore walls and the ratio theta of this strictly confined water to the total water inside the pore, yielding unique characteristic parameters for water transport in these carbon channels across the investigated temperature range.

  11. Pore-size dependence and characteristics of water diffusion in slitlike micropores

    DOE PAGESBeta

    Diallo, S. O.

    2015-07-16

    The temperature dependence of the dynamics of water inside microporous activated carbon fibers (ACF) is investigated by means of incoherent elastic and quasielastic neutron-scattering techniques. The aim is to evaluate the effect of increasing pore size on the water dynamics in these primarily hydrophobic slit-shaped channels. Using two different micropore sizes (similar to 12 and 18 angstrom, denoted, respectively, ACF-10 and ACF-20), a clear suppression of the mobility of the water molecules is observed as the pore gap or temperature decreases. Suppression, we found, is accompanied by a systematic dependence of the average translational diffusion coefficient D-r and relaxation timemore » [tau(0)] of the restricted water on pore size and temperature. We observed D-r values and tested against a proposed scaling law, in which the translational diffusion coefficient D-r of water within a porous matrix was found to depend solely on two single parameters, a temperature-independent translational diffusion coefficient D-c associated with the water bound to the pore walls and the ratio theta of this strictly confined water to the total water inside the pore, yielding unique characteristic parameters for water transport in these carbon channels across the investigated temperature range.« less

  12. Pore-size dependence and characteristics of water diffusion in slitlike micropores

    NASA Astrophysics Data System (ADS)

    Diallo, S. O.

    2015-07-01

    The temperature dependence of the dynamics of water inside microporous activated carbon fibers (ACF) is investigated by means of incoherent elastic and quasielastic neutron-scattering techniques. The aim is to evaluate the effect of increasing pore size on the water dynamics in these primarily hydrophobic slit-shaped channels. Using two different micropore sizes (˜12 and 18 Å, denoted, respectively, ACF-10 and ACF-20), a clear suppression of the mobility of the water molecules is observed as the pore gap or temperature decreases. This suppression is accompanied by a systematic dependence of the average translational diffusion coefficient Dr and relaxation time <τ0> of the restricted water on pore size and temperature. The observed Dr values are tested against a proposed scaling law, in which the translational diffusion coefficient Dr of water within a porous matrix was found to depend solely on two single parameters, a temperature-independent translational diffusion coefficient Dc associated with the water bound to the pore walls and the ratio θ of this strictly confined water to the total water inside the pore, yielding unique characteristic parameters for water transport in these carbon channels across the investigated temperature range.

  13. Subsurface water and clay mineral formation during the early history of Mars.

    PubMed

    Ehlmann, Bethany L; Mustard, John F; Murchie, Scott L; Bibring, Jean-Pierre; Meunier, Alain; Fraeman, Abigail A; Langevin, Yves

    2011-11-01

    Clay minerals, recently discovered to be widespread in Mars's Noachian terrains, indicate long-duration interaction between water and rock over 3.7 billion years ago. Analysis of how they formed should indicate what environmental conditions prevailed on early Mars. If clays formed near the surface by weathering, as is common on Earth, their presence would indicate past surface conditions warmer and wetter than at present. However, available data instead indicate substantial Martian clay formation by hydrothermal groundwater circulation and a Noachian rock record dominated by evidence of subsurface waters. Cold, arid conditions with only transient surface water may have characterized Mars's surface for over 4 billion years, since the early-Noachian period, and the longest-duration aqueous, potentially habitable environments may have been in the subsurface. PMID:22051674

  14. Wettability and spontaneous penetration of a water drop into hydrophobic pores.

    PubMed

    Choi, Hyunho; Liang, Hong

    2016-09-01

    The penetration of a water drop into hydrophobic pores reflects its instability on a porous surface. To understand the mechanism of penetration and to predict the behavior of such a drop, an investigation was conducted through experimental study combined theoretical analysis. Water drops with volumes from 0.5 to 15μL were examined on Polydimethylsiloxane (PDMS) substrates containing pores of 800μm and less in diameter. Results showed a critical condition at which a drop starts to penetrate into a certain sized pore. The critical condition presents a parabolic relationship between the volume of a water drop and the size of a hydrophobic pore. This behavior was due to a net force resulting from Laplace pressure, and capillary pressure. This force was found to be affected by the porosity, wetting angle, and there after the critical condition. The finding of this research will be beneficial for future design of structured surfaces. PMID:27267040

  15. Adsorption of As(V) inside the pores of porous hematite in water.

    PubMed

    Dai, Min; Xia, Ling; Song, Shaoxian; Peng, Changsheng; Lopez-Valdivieso, Alejandro

    2016-04-15

    As(V) adsorption inside the pores of porous hematite in water has been studied in this work. This study was performed on nonporous hematite and porous hematite prepared from the thermal decomposition of goethite and siderite through the measurements of adsorption isotherm, SEM-EDX, XRD and BET. The results demonstrated that the As(V) adsorption was difficult to be realized inside pores if they were too small. This observation might be due to that the pore entrances were blocked by the adsorbed ions and thus the inside surfaces became invalid for the adsorption. Only if the pore size is large enough, the effective surface area inside pores would be close to that on non-porous hematite for As(V) adsorption. In addition, it was found that siderite is better than goethite for preparing porous hematite with thermal decomposition as adsorbent for arsenic removal. PMID:26799222

  16. Dynamics of supercooled water in highly compacted clays studied by neutron scattering

    NASA Astrophysics Data System (ADS)

    González Sánchez, Fátima; Jurányi, Fanni; Gimmi, Thomas; Van Loon, Luc; Seydel, Tilo; Unruh, Tobias

    2008-10-01

    The freezing behavior of water confined in compacted charged and uncharged clays (montmorillonite in Na- and Ca-forms, illite in Na- and Ca-forms, kaolinite and pyrophyllite) was investigated by neutron scattering. Firstly, the amount of frozen (immobile) water was measured as a function of temperature at the IN16 backscattering spectrometer, Institute Laue-Langevin (ILL). Water in uncharged, partly hydrophobic (kaolinite) and fully hydrophobic (pyrophyllite) clays exhibited a similar freezing and melting behavior to that of bulk water. In contrast, water in charged clays which are hydrophilic could be significantly supercooled. To observe the water dynamics in these clays, further experiments were performed using quasielastic neutron scattering. At temperatures of 250, 260 and 270 K the diffusive motion of water could still be observed, but with a strong reduction in the water mobility as compared with the values obtained above 273 K. The diffusion coefficients followed a non-Arrhenius temperature dependence well described by the Vogel-Fulcher-Tammann and the fractional power relations. The fits revealed that Na- and Ca-montmorillonite and Ca-illite have similar Vogel-Fulcher-Tammann temperatures (TVFT, often referred to as the glass transition temperature) of ~120 K and similar temperatures at which the water undergoes the 'strong-fragile' transition, Ts~210 K. On the other hand, Na-illite had significantly larger values of TVFT~180 K and Ts~240 K. Surprisingly, Ca-illite has a similar freezing behavior of water to that of montmorillonites, even though it has a rather different structure. We attribute this to the stronger hydration of Ca ions as compared with the Na ions occurring in the illite clays.

  17. Mechanisms of water interaction with pore systems of hydrochar and pyrochar from poplar forestry waste.

    PubMed

    Conte, Pellegrino; Hanke, Ulrich M; Marsala, Valentina; Cimò, Giulia; Alonzo, Giuseppe; Glaser, Bruno

    2014-05-28

    The aim of this study was to understand the water-surface interactions of two chars obtained by gasification (pyrochar) and hydrothermal carbonization (hydrochar) of a poplar biomass. The two samples revealed different chemical compositions as evidenced by solid state (13)C NMR spectroscopy. In fact, hydrochar resulted in a lignin-like material still containing oxygenated functionalities. Pyrochar was a polyaromatic system in which no heteronuclei were detected. After saturation with water, hydrochar and pyrochar were analyzed by fast field cycling (FFC) NMR relaxometry. Results showed that water movement in hydrochar was mainly confined in very small pores. Conversely, water movement in pyrochar led to the conclusion that a larger number of transitional and very large pores were present. These results were confirmed by porosity evaluation derived from gas adsorption. Variable-temperature FFC NMR experiments confirmed a slow-motion regime due to a preferential diffusion of water on the solid surface. Conversely, the higher number of large pores in pyrochar allowed slow movement only up to 50 °C. As the temperature was raised to 80 °C, water interactions with the pore surface became weaker, thereby allowing a three-dimensional water exchange with the bulk liquid. This paper has shown that pore size distribution was more important than chemical composition in affecting water movement in two chemically different charred systems. PMID:24814907

  18. Water purification from organic pollutants by optimized micelle-clay systems.

    PubMed

    Polubesova, Tamara; Nir, Shlomo; Zadaka, Dikla; Rabinovitz, Onn; Serban, Carina; Groisman, Ludmila; Rubin, Baruch

    2005-04-01

    Removal of anionic pollutants (imazaquin, sulfentrazone, sulfosulfuron) and neutral pollutants (alachlor, acetochlor, chlorotoluron, bromacil) from water by micelles preadsorbed on montmorillonite was studied. Micelles of octadecyltrimethylammonium and benzyldimethylhexadecylammonium (BDMHDA) were used. The micelle-clay systems (1% w/w) removed 87-99% of the pollutants from their water solutions containing 1-33 mg/L of herbicide. The nature of the headgroup of the organic cation, which forms the micelles, is critical. Desorption of imazaquin and acetochlor from 0.3% (w/w) suspension of BDMHDA-clay complex after 24 h was around 7% in the range of adsorbed amounts from 0.6 to 15.3 mg/g. These results indicate rather slow rates and small extents of release of pollutants from micelle-clay complexes. Column filters (25 cm) made of a mixture of quartz sand and BDMHDA micelle-clay complex at 100:1 w/w ratio removed at least 99% of above pollutants from initial solutions containing 10 mg/L; 99.5 and 97% of sulfosulfuron and alachlor were removed from their initial solutions containing 200 and 5 microg/L, respectively. These data indicate that micelle-clay complexes are very efficient for water purification from organic contaminants. PMID:15871274

  19. Paleo-hydrological history in pore water extracted from sedimentary rocks in the coastal area

    NASA Astrophysics Data System (ADS)

    Ikawa, R.; Machida, I.; Koshigai, M.; Nishizaki, S.; Marui, A.; Yoshizawa, T.; Ito, N.

    2010-12-01

    Over the past decade, new utilization methods of underground space development such as geological disposal of high level radioactive waste (HLW) and carbon capture and storage (CCS) have been important issues under discussion in Japan. Coastal areas have been identified as suitable candidate sites for such projects. A good understanding of the structure of seawater/freshwater interface and fault is important due to the fact that it serves as a preferential pathway through which radionuclide can be transported by means of groundwater. There is, however, little available information worldwide on deep groundwater studies in coastal areas. There is also virtually no study has been conducted on the behavior of groundwater and pore water in coastal impermeable sedimentary rocks. In this study, large scale core drilling (1000m depth) has been carried out in coastal area at Hamasato in the Horonobe area of Hokkaido, Japan in order to investigate the geological structure and deep groundwater flow system with the residence time. Pore water with various adsorptivity from drilling core samples was gradually collected by centrifugation and squeezing methods and analyzed for water chemistry. This is aimed at estimating the paleo-hydrological history of the coastal environment by geochemical information from the pore water. Lithoface in the study area consists of sandy r and alternate (sandy and silty) layers intercalations up to 250m deep. Below 250m, shows sand and silt layers. Pore water volume collected in the sand layers by centrifugation method was almost same, contrary to that in the silt layers which decreased with depth. On the other hand, the ratio of pore water with high adsorpivity in silt layers increased with depth. Except the surface layer (<50m), electric conductivity (EC) and Cl values in pore water samples increased with depth below 300m. In this study, we report on the characteristics of seawater/freshwater interface and deep groundwater flow system based on

  20. The representativeness of pore water samples collected from the unsaturated zone using pressure-vacuum lysimeters

    USGS Publications Warehouse

    Peters, C.A.; Healy, R.W.

    1988-01-01

    Studies have indicated that the chemistry of water samples may be altered by the collection technique, creating concern about the representativeness of the pore water samples obtained. A study using soil water pressure-vacuum lysimeters in outwash sand and glacial till deposits demonstrates that for non-dilute-solution samples the effect of pH of sampling with lysimeters is minimal, and that measured major cation and anion concentrations are representative of the natural pore water; trace-metal concentrations can be significantly altered by collection procedures at low concentrations. -from Authors

  1. Pore Water Geochemistry of IODP Exp 315 and 316: The NanTroSEIZE Transect

    NASA Astrophysics Data System (ADS)

    Wheat, C. G.; Hulme, S.; Tomaru, H.; Liljedahl, L. C.; Solomon, E.

    2008-12-01

    IODP Exp 315 and 316 drilled six sites as part of the first stage of NanTroSEIZE, an international, multi-year endeavor to elucidate earthquake-related processes. These six sites form a transect southeast of the Kumano Basin, Japan with boreholes that penetrated the Kumano forarc basin (C0002), the megasplay fault region (C0001, C0004, and C0008) and the frontal thrust including sediment from the subducting plate (C0006 and C0007). One element of this drilling is to evaluate the relationship between pore fluid behavior and slip and deformation in the crust. To help address this relationship 322 pore water samples were extracted from sediment whole rounds. Each of the whole rounds was scanned (CT) before it was processed within a nitrogen-filled glove bag and squeezed to express the pore fluid. In addition, 15 samples from C0002 underwent the GRIND technique to gather baseline pore water chemical data for future deep drilling where highly indurated sediments likely exist. Each of these pore water samples underwent a range of analytical procedures at sea. Additional procedures were conducted ashore. Combined, these procedures resulted in data for 30 chemical species including the stable isotopic composition of O and H in water. These data provide the most thorough preliminary reports tables in the history of DSDP, ODP and IODP, and ongoing measurements include a range of isotopic (e.g., I, B, Sr, Li, C), ionic (e.g., REE), and organic measurements. We will present all of the data that appear in the preliminary reports including GRIND samples for comparison to squeezed samples. Our presentation will highlight changes in pore water composition along the transect of boreholes, putting individual site-related pore water chemical profiles in a broader context. Pore water profiles in the upper about 30 m of the sediment column are dominated by microbially mediated reactions with a highly defined sulfate-methane transition. Deeper within the sediment the dissociation of gas

  2. Modeling the diffusion of Na+ in compacted water-saturated Na-bentonite as a function of pore water ionic strength

    SciTech Connect

    Bourg, I.C.; Sposito, G.; Bourg, A.C.M.

    2008-08-15

    Assessments of bentonite barrier performance in waste management scenarios require an accurate description of the diffusion of water and solutes through the barrier. A two-compartment macropore/nanopore model (on which smectite interlayer nanopores are treated as a distinct compartment of the overall pore space) was applied to describe the diffusion of {sup 22}Na{sup +} in compacted, water-saturated Na-bentonites and then compared with the well-known surface diffusion model. The two-compartment model successfully predicted the observed weak ionic strength dependence of the apparent diffusion coefficient (D{sub a}) of Na{sup +}, whereas the surface diffusion model did not, thus confirming previous research indicating the strong influence of interlayer nanopores on the properties of smectite clay barriers. Since bentonite mechanical properties and pore water chemistry have been described successfully with two-compartment models, the results in the present study represent an important contribution toward the construction of a comprehensive two-compartment model of compacted bentonite barriers.

  3. Confined Water Determines Transport Properties of Guest Molecules in Narrow Pores.

    PubMed

    Phan, Anh; Cole, David R; Weiß, R Gregor; Dzubiella, Joachim; Striolo, Alberto

    2016-08-23

    We computed the transport of methane through 1 nm wide slit-shaped pores carved out of solid substrates. Models for silica, magnesium oxide, and alumina were used as solid substrates. The pores were filled with water. The results show that the methane permeability through the hydrated pores is strongly dependent on the solid substrate. Detailed analysis of the simulated systems reveals that local properties of confined water, including its structure, and more importantly, evolution of solvation free energy and hydrogen bond structure are responsible for the pronounced differences observed. The simulations are extended to multicomponent systems representative of natural gas, containing methane, ethane, and H2S. The results show that all pores considered have high affinity for H2S, moderate affinity for methane, and low affinity for ethane. The H2S/methane transport selectivity through the hydrated alumina pore is comparable, or superior, to that reported for existing commercial membranes. A multiscale approach was then implemented to demonstrate that a Smoluchowski one-dimensional model is able to reproduce the molecular-level results for short pores when appropriate values for the local self-diffusion coefficients are used as input parameters. We propose that the model can be extended to predict methane transport through uniform hydrated pores of macroscopic length. When verified by experiments, our simulation results could have important implications in applications such as natural gas sweetening and predictions of methane migration through hydraulically fractured shale formations. PMID:27490280

  4. Water saturation of hydrothermal smectite-rich clay might have promoted slope instability prior to the 1998 debris avalanche at Casita volcano, Nicaragua

    NASA Astrophysics Data System (ADS)

    Delmelle, P.; Opfergelt, S.; Boivin, P.; Delvaux, B.

    2006-12-01

    In October 1998, a relatively small collapse (1 600 000 cubic meters) of a pre-existing scarp occurred on the southern flank of the dormant Casita volcano, Nicaragua. It resulted in a debris avalanche, which quickly transformed into a disastrous debris flow that destroyed two towns and killed more than 2500 people. The failure was shown to be triggered by an excess pore water pressure within highly fractured rocks, following prolonged seasonal rains and precipitations from Hurricane Mitch. This pressure was linked to the water saturation of a hydrothermally-altered clay bedrock impeding in-depth infiltration. Yet, the nature and amounts of the clay material involved in the slope failure were still unknown. Here we report on physical, chemical and mineralogical investigations aimed at quantifying the clay content, and identifying the layer silicates of the hydrothermally-altered clays uncovered by the 1998 debris avalanche. The fine clay material was exceptionally rich in smectite (up to 50 wt. percent), which swells upon wetting and shrinks during dry conditions (Opfergelt et al., 2006, Geophys. Res. Lett., 33 (15), L15305). The smectite belonged to the beidellite-montmorillonite series. The pervasive presence of water-saturated smectitic clay strongly reduced the permeability in depth, and also altered the rheological and mechanical properties of both the pre-failure rock mass and flow materials. The shrink-swell behavior progressively decreased the rock's shear strength, and gradually destabilized the overlying rock mass in the decades and centuries before the landslide, thereby contributing to slope instability. Prolonged intense rainfall led to the formation of incipient weak failure surfaces in the superficial rock mass. As provoked by water saturation, this process was likely favored by the rapid change of the mechanical properties of smectite-rich clays deposited in fracture, joint and gouge interfaces. We suggest that hazard assessments associated with

  5. Pore-Water Extraction Intermediate-Scale Laboratory Experiments and Numerical Simulations

    SciTech Connect

    Oostrom, Martinus; Freedman, Vicky L.; Wietsma, Thomas W.; Truex, Michael J.

    2011-06-30

    A series of flow cell experiments was conducted to demonstrate the process of water removal through pore-water extraction in unsaturated systems. In this process, a vacuum (negative pressure) is applied at the extraction well establishing gas and water pressure gradients towards the well. The gradient may force water and dissolved contaminants, such as 99Tc, to move towards the well. The tested flow cell configurations consist of packings, with or without fine-grained well pack material, representing, in terms of particle size distribution, subsurface sediments at the SX tank farm. A pore water extraction process should not be considered to be equal to soil vapor extraction because during soil vapor extraction, the main goal may be to maximize gas removal. For pore water extraction systems, pressure gradients in both the gas and water phases need to be considered while for soil vapor extraction purposes, gas phase flow is the only concern. In general, based on the limited set (six) of flow experiments that were conducted, it can be concluded that pore water extraction rates and cumulative outflow are related to water content, the applied vacuum, and the dimensions of the sediment layer providing the extracted water. In particular, it was observed that application of a 100-cm vacuum (negative pressure) in a controlled manner leads to pore-water extraction until the water pressure gradients towards the well approach zero. Increased cumulative outflow was obtained with an increase in initial water content from 0.11 to 0.18, an increase in the applied vacuum to 200 cm, and when the water-supplying sediment was not limited. The experimental matrix was not sufficiently large to come to conclusions regarding maximizing cumulative outflow.

  6. Dynamics of pore-water and salt in estuarine marshes subjected to tide and evaporation

    NASA Astrophysics Data System (ADS)

    Zhang, C.; Shen, C.; Li, L.; Lockington, D. A.

    2015-12-01

    Salt dynamics in estuarine tidal marshes are strongly associated with their intrinsic hydrological processes and ecological behaviors, which are not well understood. Numerical simulations were carried out to investigate the transport and distribution of pore water and salt in a vertical cross section perpendicular to the tidal creek that subjects to spring-neap tide and evaporation. Vaporizing pore water from unsaturated soil surface with salt left in soils, the time-variant actual evaporation is affected by aerodynamic factors as well as soil conditions, including pore-water saturation, solute concentration and the thickness of salt precipitation above the soil surface (efflorescence). Different simulation cases were performed by adjusting the tidal signal, marsh platform slope and soil properties. The simulation analysis indicates that, the tide-averaged soil salinity increases with the reduction of inundation period in a spring-neap tide cycle. As the salt accumulated by evaporation could leave soil from seepage back to seawater during ebbtide, the pore-water salinity at the surface within the tidal range remains close to that of seawater. With the presence of hyper-saline soil and efflorescence, salt flat develops only in the area where capillary connection between evaporating surface and water-saturated soil is maintained while tidal inundation absent. On the contrary, the sandy supratidal marsh where hydrological connections are disrupted keeps a relatively low soil salinity (40-60 ppt) and pore-water saturation as evaporation remains low throughout the tidal cycles.

  7. Water uptake of clay and desert dust aerosol particles at sub- and supersaturated water vapor conditions

    SciTech Connect

    Herich, Hanna; Tritscher, Torsten; Wiacek, Aldona; Gysel, Martin; Weingartner, E.; Lohmann, U.; Baltensperger, Urs; Cziczo, Daniel J.

    2009-11-01

    Airborne mineral dust particles serve as cloud condensation nuclei (CCN), thereby influencing the formation and properties of warm clouds. It is therefore of particular interest how dust aerosols with different mineralogy behave when exposed to high relative humidity (RH) or supersaturation with respect to liquid water similar to atmospheric conditions. In this study the sub-saturated hygroscopic growth and the supersaturated cloud condensation nucleus activity of pure clays and real desert dust aerosols was determined using a hygroscopicity tandem differential mobility analyzer (HTDMA) and a cloud condensation nuclei counter (CCNC), respectively. Five different illite, montmorillonite and kaolinite clay samples as well as three desert dust samples (Saharan dust (SD), Chinese dust (CD) and Arizona test dust (ATD)) were used. Aerosols were generated both with a wet and a dry disperser and the water uptake was parameterized via the hygroscopicity parameter, κ. The hygroscopicity of dry generated dust aerosols was found to be negligible when compared to processed atmospheric aerosols, with CCNC derived κ values between 0.00 and 0.02. The latter value can be idealized as a particle consisting of 96.7% (by volume) insoluble material and ~3.3% ammonium sulfate. Pure clay aerosols were found to be generally less hygroscopic than real desert dust particles. All illite and montmorillonite samples had κ~0.003, kaolinites were least hygroscopic and had κ=0.001. SD (κ=0.023) was found to be the most hygroscopic dry-generated desert dust followed by CD (κ=0.007) and ATD (κ=0.003). Wet-generated dust showed an increased water uptake when compared to dry-generated samples. This is considered to be an artifact introduced by redistribution of soluble material between the particles while immersed in an aqueous medium during atomization, thus indicating that specification of the generation method is critically important when presenting such data. Any atmospheric processing of

  8. Supercomputer simulation of clay-water-chemical interactions, Phase 3

    SciTech Connect

    Cushman, J.H.

    1991-01-01

    This report contains sections describing: Monte Carlo Calculation of Chemical Potential of a Stockmayer Fluid, Fractional Brownian Diffusion in Molecularly Thin Films, On Spectral Measure and Monte Carlo Approaches to Flow in Heterogeneous Media, Shear Melting of Molecularly-Thin Confined Films, Nonlocal Diffusion and Strain-Induced Liquification at Particulate Media, Hierarchical Problems: Some conceptual Difficulties in the Development of Transport Equations, Application of Multiple-Angle-of-Incidence Ellipsometry to the Study of Thin Films Adsorbed on Surfaces, On Adsorption and Diffusion at Rough Surfaces: A Comparison of Statistical Mechanic, Molecular Dynamics and Kinetic Theory, Fluids in Micropores: Self-Diffusion in a Slit-Pore with Hard Rough Walls, and Nonlocal Transport Theories for Media with Microstructure.

  9. Mapping the fluid flow of the Mariana Mounds ridge flank hydrothermal system: Pore water chemical tracers

    NASA Astrophysics Data System (ADS)

    Wheat, C. Geoffrey; McDuff, Russell E.

    1995-01-01

    We present a conceptual model of fluid circulation in a ridge flank hydrothermal system, the Mariana Mounds. The model is based on chemical data from pore waters extracted from piston cores and from push cores collected by deep-sea research vessel Alvin in small, meter-sized mounds situated on a local topographic high. These mounds are located within a region of heat flow exceeding that calculated from a conductive model and are zones of strong pore water upflow. We have interpreted the chemical data with time-dependent transport-reaction models to estimate pore water velocities. In the mounds themselves pore water velocities reach several meters per year to kilometers per year. Within about 100 m from these zones of focused upflow velocities decrease to several centimeters per year up to tens of centimeters per year. A larger area of low heat flow surrounds these heat flow and topographic highs, with upwelling pore water velocities less than 2 cm/yr. In some nearby cores, downwelling of bottom seawater is evident but at speeds less than 2 cm/yr. Downwelling through the sediments appears to be a minor source of seawater recharge to the basaltic basement. We conclude that the principal source of seawater recharge to basement is where basement outcrops exist, most likely a scarp about 2-4 km to the east and southeast of the study area.

  10. Sediment Core Sectioning and Extraction of Pore Waters under Anoxic Conditions.

    PubMed

    Keimowitz, Alison R; Zheng, Yan; Lee, Ming-Kuo; Natter, Michael; Keevan, Jeffrey

    2016-01-01

    We demonstrate a method for sectioning sediment cores and extracting pore waters while maintaining oxygen-free conditions. A simple, inexpensive system is built and can be transported to a temporary work space close to field sampling site(s) to facilitate rapid analysis. Cores are extruded into a portable glove bag, where they are sectioned and each 1-3 cm thick section (depending on core diameter) is sealed into 50 ml centrifuge tubes. Pore waters are separated with centrifugation outside of the glove bag and then returned to the glove bag for separation from the sediment. These extracted pore water samples can be analyzed immediately. Immediate analyses of redox sensitive species, such as sulfide, iron speciation, and arsenic speciation indicate that oxidation of pore waters is minimal; some samples show approximately 100% of the reduced species, e.g. 100% Fe(II) with no detectable Fe(III). Both sediment and pore water samples can be preserved to maintain chemical species for further analysis upon return to the laboratory. PMID:27023267

  11. Mapping the fluid flow of the Mariana Mounds ridge flank hydrothermal system: Pore water chemical tracers

    SciTech Connect

    Wheat, C.G.; McDuff, R.E.

    1995-05-10

    The authors present a conceptual model of fluid circulation in a ridge flank hydrothermal system, the Mariana Mounds. The model is based on chemical data from pore waters extracted from piston cores and from push cores collected by deep-sea research vessel Alvin in small, meter-sized mounds situated on a local topographic high. These mounds are located within a region of heat flow exceeding that calculated from a conductive model and are zones of strong pore water upflow. The authors have interpreted the chemical data with time-dependent transport-reaction models to estimate pore water velocities. In the mounds themselves pore water velocities reach several meters per year to kilometers per year. Within about 100 m from these zones of focused upflow velocities decrease to several centimeters per year up to tens of centimeters per year. A large area of low heat flow surrounds these heat flow and topographic highs, with upwelling pore water velocities less than 2 cm/yr. In some nearby cores, downwelling of bottom seawater is evident but at speeds less than 2 cm/yr. Downwelling through the sediments appears to be a minor source of seawater recharge to the basaltic basement. The authors conclude that the principal source of seawater recharge to basement is where basement outcrops exist, most likely a scarpt about 2-4 km to the east and southeast of the study area. 71 refs., 14 figs., 3 tabs.

  12. EFFECTS OF BENTONITE CLAY SOLIDS ON POLIOVIRUS CONCENTRATION FROM WATER BY MICROPOROUS FILTER METHODS

    EPA Science Inventory

    In order to determine if suspended solids interfere with enteric virus recovery from water by microporous filter methods, the effects of bentonite clay solids at a concentration of 10 NTU on the recovery of poliovirus type 1 from seeded, activated carbon-treated, filtered tap wat...

  13. ABIOTIC REDOX TRANSFORMATION OF ORGANIC COMPOUNDS AT THE CLAY-WATER INTERFACE

    EPA Science Inventory

    The interactions of clay, water and organic compounds considerably modify the structural and physico-chemical properties of all components and create a unique domain for biological and chemical species in environments. Previous research indicates that the nature and properties of...

  14. Rare earth element geochemistry in cold-seep pore waters of Hydrate Ridge, northeast Pacific Ocean

    NASA Astrophysics Data System (ADS)

    Himmler, Tobias; Haley, Brian A.; Torres, Marta E.; Klinkhammer, Gary P.; Bohrmann, Gerhard; Peckmann, Jörn

    2013-07-01

    The concentrations of rare earth elements (REEs), sulphate, hydrogen sulphide, total alkalinity, calcium, magnesium and phosphate were measured in shallow (<12 cm below seafloor) pore waters from cold-seep sediments on the northern and southern summits of Hydrate Ridge, offshore Oregon. Downward-decreasing sulphate and coevally increasing sulphide concentrations reveal sulphate reduction as dominant early diagenetic process from ~2 cm depth downwards. A strong increase of total dissolved REE (∑REE) concentrations is evident immediately below the sediment-water interface, which can be related to early diagenetic release of REEs into pore water resulting from the re-mineralization of particulate organic matter. The highest pore water ∑REE concentrations were measured close to the sediment-water interface at ~2 cm depth. Distinct shale-normalized REE patterns point to particulate organic matter and iron oxides as main REE sources in the upper ~2-cm depth interval. In general, the pore waters have shale-normalized patterns reflecting heavy REE (HREE) enrichment, which suggests preferential complexation of HREEs with carbonate ions. Below ~2 cm depth, a downward decrease in ∑REE correlates with a decrease in pore water calcium concentrations. At this depth, the anaerobic oxidation of methane (AOM) coupled to sulphate reduction increases carbonate alkalinity through the production of bicarbonate, which results in the precipitation of carbonate minerals. It seems therefore likely that the REEs and calcium are consumed during vast AOM-induced precipitation of carbonate in shallow Hydrate Ridge sediments. The analysis of pore waters from Hydrate Ridge shed new light on early diagenetic processes at cold seeps, corroborating the great potential of REEs to identify geochemical processes and to constrain environmental conditions.

  15. Pore-size dependent THz absorption of nano-confined water.

    PubMed

    Sun, Chi-Kuang; You, Borwen; Huang, Yu-Ru; Liu, Kao-Hsiang; Sato, Shusaku; Irisawa, Akiyoshi; Imamura, Motoki; Mou, Chung-Yuan

    2015-06-15

    We performed a THz absorption spectroscopy study on liquid water confined in mesoporous silica materials, MCM-41-S-18 and MCM-41-S-21, of two different pore sizes at room temperatures. We found that stronger confinement with a smaller pore size causes reduced THz absorption, indicating reduced water mobility due to confinement. Combined with recent theoretical studies showing that the microscopic structure of water inside the nanopores can be separated into a core water region and an interfacial water region, our spectroscopy analysis further reveals a bulk-water-like THz absorption behavior in the core water region and a solid-like THz absorption behavior in the interfacial water region. PMID:26076248

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

    PubMed

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

    2015-01-01

    Tailings produced during bitumen extraction from surface-mined oil sands ores (tar sands) comprise an aqueous suspension of clay particles that remain dispersed for decades in tailings ponds. Slow consolidation of the clays hinders water recovery for reuse and retards volume reduction, thereby increasing the environmental footprint of tailings ponds. We investigated mechanisms of tailings consolidation and revealed that indigenous anaerobic microorganisms altered porewater chemistry by producing CO and CH during metabolism of acetate added as a labile carbon amendment. Entrapped biogenic CO decreased tailings pH, thereby increasing calcium (Ca) and magnesium (Mg) cations and bicarbonate (HCO) concentrations in the porewater through dissolution of carbonate minerals. Soluble ions increased the porewater ionic strength, which, with higher exchangeable Ca and Mg, decreased the diffuse double layer of clays and increased consolidation of tailings compared with unamended tailings in which little microbial activity was observed. These results are relevant to effective tailings pond management strategies. PMID:25602329

  17. Effect of the hydroaffinity and topology of pore walls on the structure and dynamics of confined water

    SciTech Connect

    Harrach, Michael F. Klameth, Felix; Drossel, Barbara; Vogel, Michael

    2015-01-21

    We perform molecular dynamics simulations to observe the structure and dynamics of SPC/E water in amorphous silica pores and amorphous ice pores with radii slightly larger than 10 Å. In addition to atomically rough pores, we construct completely smooth pores such that the potential felt at a given distance from the pore wall is an averaged atomic potential. As compared to rough walls, smooth walls induce stronger distortions of water structure for both silica and ice confinements. On the other hand, unlike the smooth pores, the rough pores strongly slow down water dynamics at the pore wall. The slowdown vanishes when reducing the atomic charges in the wall, i.e., when varying the hydroaffinity, while keeping the surface topology, indicating that it is not a geometric effect. Rather, it is due to the fact that the wall atoms provide a static energy landscape along the surface, e.g., fixed anchor-points for hydrogen bonds, to which the water molecules need to adapt, blocking channels for structural rearrangement. In the smooth pores, water dynamics can be faster than in the bulk liquid not only at the pore wall but also in the pore center. Changes in the tetrahedral order rather than in the local density are identified as the main cause for this change of the dynamical behavior in the center of smooth pores.

  18. Stable water isotopes in pore water of Jurassic argillaceous rocks as tracers for solute transport over large spatial and temporal scales

    NASA Astrophysics Data System (ADS)

    Gimmi, T.; Waber, H. N.; Gautschi, A.; Rübel, A.

    2007-04-01

    In order to characterize the large-scale transport properties of the Opalinus Clay formation, the pore water isotope composition (δ18O and δ2H) was determined on samples from the deep borehole Benken (northeastern Switzerland) across Jurassic argillaceous rocks. The sequence of claystones and marls, delimited by two aquifers, is located at depth from about 400 to 700 m and exhibits very low hydraulic conductivities (below 10-13 m s-1). The isotope data of the pore water were obtained from core samples by diffusive vapor equilibration, vacuum distillation, and squeezing. Compared with the other methods, vacuum distillation led to too low values. To evaluate the large-scale transport properties of the formation, we performed a series of advective-dispersive model calculations and compared them with the experimental data. In accordance with the hydrogeological history, we varied initial and boundary conditions as well as model parameters. The main results can be summarized as follows: (1) Molecular diffusion to the underlying aquifer can explain the general features of the isotope profiles, (2) no signatures of advective flow could be detected, (3) the evolution time is of the order of 0.5-1 Ma (relying on laboratory diffusion coefficients) with a possible range of about 0.2-2 Ma, which is geologically plausible, and (4) parameters measured on small scales (centimeters or meters and months) are also plausible at the formation scale (tens of meters and millions of years) for the sediments investigated.

  19. Stable Isotope Anomalies and Low Chloride Concentrations in Pore Water of CH4-Rich Sediments at the Tanegashima Mud Volcano, Japan

    NASA Astrophysics Data System (ADS)

    Nakayama, N.; Tsunogai, U.; Ashi, J.; Gamo, T.

    2004-12-01

    Pore water from sediments collected at a Tanegashima mud volcano was analyzed for δ 13C (PDB) of dissolved CH4 together with other chemical components, Cl- and SO42-, and the δ 18O and δ D (SMOW). The Tanegashima mud volcanoes are located at the water depths from 1400 m to 1800 m, off Tanegashima island between Ryukyu trench and Ryukyu arc of Japan. It is situated at the end of south-western convergent plate boundary on Nankai-trough, which forms a part of Philippine Sea plate subducting under Eurasian plate. This cruise was conducted as a part of the JNOC (Japan National Oil Corporation) geochemical survey by R/V Hakurei-maru II. The concentrations of CH4 were generally higher than 100 micro-mol/kg. Its highest concentration (715 micro-mol/kg) was found in the crest core of a mud volcano. The δ 13C values ranged from -32 to -50 ‰ . C2H6 was detected only in the pore waters collected from the vicinity of the crest of the mud volcano. The highest δ 13C (around -22 ‰ ) and low C1/C2 concentration ratios (less than 100) were measured at the crest site, supporting the thermogenical production of methane. Other geochemical anomalies were also observed in the crest pore water. The concentrations of Cl- in the pore water at this site were extremely depleted to a minimum of 350 mmol/kg. The Cl- anomaly has not been previously reported for pore water from mud volcanoes around Japan. An endmember of isotopic composition of the fluid is estimated to be +12 ‰ for δ 18O and -40 ‰ for δ D. From these results we conclude that the most likely process to reduce pore water salinity is primarily the mixing of clay mineral dehydration water with seawater. The thermogenic methane found in the crest pore waters of the Tanegashima mud volcano may be brought from the depths of sediments due to the migration of fluid evolved by mineral the dehydration process.

  20. Pleistocene meteoric pore water in dated marine sediment cores off Callao, Peru

    NASA Astrophysics Data System (ADS)

    Kriete, Cornelia; Suckow, Axel; Harazim, Bodo

    2004-03-01

    During cruise SO 147 of the German research vessel SONNE, a large decrease in salinity with depth was found in the pore water at a site about 10 sea miles off Callao, Lima, Peru. The origin of this freshening was investigated in a multidisciplinary approach using geochemical, geochronological and isotope hydrological methods. The methodology applied is a possible strategy to deal with anomalous pore water freshenings and if necessary to put them into the general framework of submarine groundwater discharge. Concentrations of the major and conservative elements (e.g., Na, K, Cl, B, Br) decrease at the same ratios. Deuterium ( δD) and oxygen-18 ( δ18O) data reveal the meteoric origin of the fresh water end member, indicating a mixture of 30% seawater and 70% fresh water at a depth in sediment of about 10 m. 210Pb and 137Cs sedimentation rates determined by gamma spectrometry range between 2 and 4.5 mm/y for the last century whereas values derived from AMS 14C for the last millennia give mean rates smaller than 1 mm/y. This indicates strongly varying sedimentation conditions. Nevertheless, from the geochronological data it can be concluded that the origin of the fresh water end member is situated in sediments of Pleistocene age. Literature data of the isotope signature of modern water in the nearby Lima aquifer are clearly different from the calculated values for the fresh water end member in the pore waters. On the basis of the isotopic altitude effect described in the literature, the isotopic signature of the fresh pore water end member can be explained as rain water directly infiltrated into the Lima aquifer. In contrast, this infiltration is negligible there under present-day arid climatic conditions. Theoretical considerations on pore water advective and diffusive transport give further indications that the fresh pore water end member is entrapped paleowater of Pleistocene origin. The observed pore water freshening and the geochemical and geochronological data

  1. A simple pore water hydrogen diffusion syringe sampler

    USGS Publications Warehouse

    Vroblesky, D.A.; Chapelle, F.H.; Bradley, P.M.

    2007-01-01

    Molecular hydrogen (H2) is an important intermediate product and electron donor in microbial metabolism. Concentrations of dissolved H 2 are often diagnostic of the predominant terminal electron-accepting processes in ground water systems or aquatic sediments. H2 concentrations are routinely measured in ground water monitoring wells but are rarely measured in saturated aquatic sediments due to a lack of simple and practical sampling methods. This report describes the design and development (including laboratory and field testing) of a simple, syringe-based H 2 sampler in (1) saturated, riparian sediments, (2) surface water bed sediments, and (3) packed intervals of a fractured bedrock borehole that are inaccessible by standard pumped methods. ?? 2007 National Ground Water Association.

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

    USGS Publications Warehouse

    Smith, J.A.

    1990-01-01

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

  3. Characterizing pore sizes and water structure in stimuli-responsive hydrogels

    SciTech Connect

    Hoffman, A.S.; Antonsen, K.P.; Ashida, T.; Bohnert, J.L.; Dong, L.C.; Nabeshima, Y.; Nagamatsu, S.; Park, T.G.; Sheu, M.S.; Wu, X.S.; Yan, Q.

    1993-12-31

    Hydrogels have been extensively investigated as potential matrices for drug delivery. In particular, hydrogels responsive to pH and temperature changes have been of greatest interest most recently. Proteins and peptide drugs are especially relevant for delivery from such hydrogel matrices due to the relatively {open_quotes}passive{close_quotes} and biocompatible microenvironment which should exist within the hydrogel aqueous pores. The large molecular size of many proteins requires an interconnected large pore structure. Furthermore, the gel pore {open_quotes}walls{close_quotes} should not provide hydrophobic sites for strong interactions with proteins. In the special case of ion exchange release the protein would be attracted by opposite charges on the polymer backbones. Therefore, it is important both to control and to characterize the pore structure and the water character within a hydrogel to be used or protein or peptide drug delivery. This talk will critically review techniques for estimating these two key parameters in hydrogels.

  4. Dynamics of water in synthetic saponite clays: effect of trivalent ion substitution.

    PubMed

    Mitra, S; Prabhudesai, S A; Chakrabarty, D; Sharma, V K; Vicente, M A; Embs, J P; Mukhopadhyay, R

    2013-06-01

    Saponite clay belongs to the phyllosilicate family and is comprised of layers of Si(IV) tetrahedra and Al(III) or Mg(II) octahedra with definite interlayer spacing. In these systems, the trivalent ion substitutions in the tetrahedral layers lead to negative charge on the layers. Here we report the dynamics of water contained in [Si(6.97)Al(1.03)][Ni(6.00)]O(20)(OH)(4)[Na(1.03)]·28H(2)O (SAP-1) and [Si(7.13)Fe(0.86)][Ni(6.00)]O(20)(OH)(4)[Na(0.86)]·14H(2)O (SAP-2) saponite clays in the temperature range 200-310 K as studied by quasielastic neutron scattering technique. Particularly the effect of the ion substitution towards the dynamics of water is addressed here. Data analysis is carried out using the relaxing cage model. The existence of distribution in relaxation times indicated that the water molecules in saponite clay have a different local environment which leads to complex diffusion behavior. It is found that water exists in a supercooled state in the temperature range up to 235 K. However, some of the water molecules are found to be immobile in the temperature range 240-285 K. The fraction of immobile water decreases with increase in temperature. At higher temperatures, some of the water molecules in the hydration shells or those near the surface start participating in the diffusion process and at 293 K, almost all water molecules contribute to the dynamics. Diffusivity of water in both SAP-1 and SAP-2 are found to be lower in comparison to the bulk, and within the two samples of saponite clay diffusivity in SAP-1 is found to be lower compared to SAP-2; this has been explained on the basis of the charge on the tetrahedral layers and the charge balancing cations in the interlayer spacing. PMID:23848685

  5. Dynamics of water in synthetic saponite clays: Effect of trivalent ion substitution

    NASA Astrophysics Data System (ADS)

    Mitra, S.; Prabhudesai, S. A.; Chakrabarty, D.; Sharma, V. K.; Vicente, M. A.; Embs, J. P.; Mukhopadhyay, R.

    2013-06-01

    Saponite clay belongs to the phyllosilicate family and is comprised of layers of Si(IV) tetrahedra and Al(III) or Mg(II) octahedra with definite interlayer spacing. In these systems, the trivalent ion substitutions in the tetrahedral layers lead to negative charge on the layers. Here we report the dynamics of water contained in [Si6.97Al1.03][Ni6.00]O20(OH)4[Na1.03]·28H2O (SAP-1) and [Si7.13Fe0.86][Ni6.00]O20(OH)4[Na0.86]·14H2O (SAP-2) saponite clays in the temperature range 200-310 K as studied by quasielastic neutron scattering technique. Particularly the effect of the ion substitution towards the dynamics of water is addressed here. Data analysis is carried out using the relaxing cage model. The existence of distribution in relaxation times indicated that the water molecules in saponite clay have a different local environment which leads to complex diffusion behavior. It is found that water exists in a supercooled state in the temperature range up to 235 K. However, some of the water molecules are found to be immobile in the temperature range 240-285 K. The fraction of immobile water decreases with increase in temperature. At higher temperatures, some of the water molecules in the hydration shells or those near the surface start participating in the diffusion process and at 293 K, almost all water molecules contribute to the dynamics. Diffusivity of water in both SAP-1 and SAP-2 are found to be lower in comparison to the bulk, and within the two samples of saponite clay diffusivity in SAP-1 is found to be lower compared to SAP-2; this has been explained on the basis of the charge on the tetrahedral layers and the charge balancing cations in the interlayer spacing.

  6. Effects of macro-pores on water flow in coastal subsurface drainage systems

    NASA Astrophysics Data System (ADS)

    Xin, Pei; Yu, Xiayang; Lu, Chunhui; Li, Ling

    2016-01-01

    Leaching through subsurface drainage systems has been widely adopted to ameliorate saline soils. The application of this method to remove salt from reclaimed lands in the coastal zone, however, may be impacted by macro-pores such as crab burrows, which are commonly distributed in the soils. We developed a three-dimensional model to investigate water flow in subsurface drainage systems affected by macro-pores distributed deterministically and randomly through Monte Carlo simulations. The results showed that, for subsurface drainage systems under the condition of continuous surface ponding, macro-pores increased the hydraulic head in the deep soil, which in turn reduced the hydraulic gradient between the surface and deep soil. As a consequence, water infiltration across the soil surface was inhibited. Since salt transport in the soil is dominated by advection, the flow simulation results indicated that macro-pores decreased the efficiency of salt leaching by one order of magnitude, in terms of both the elapsed time and the amount of water required to remove salt over the designed soil leaching depth (0.6 m). The reduction of the leaching efficiency was even greater in drainage systems with a layered soil stratigraphy. Sensitivity analyses demonstrated that with an increased penetration depth or density of macro-pores, the leaching efficiency decreased further. The revealed impact of macro-pores on water flow represents a significant shortcoming of the salt leaching technique when applied to coastal saline soils. Future designs of soil amelioration schemes in the coastal zone should consider and aim to minimize the bypassing effect caused by macro-pores.

  7. Development of porous clay-based composites for the sorption of lead from water.

    PubMed

    Ake, C L; Mayura, K; Huebner, H; Bratton, G R; Phillips, T D

    2001-07-20

    Lead contamination of water is a major health hazard, as illustrated by the fact that exposure to this metal has been associated with death and disease in humans, birds, and animals. The present research was aimed at the development of a porous, solid-phase sorbent that can be used in the remediation of lead-contaminated water. A suitable sorbent was identified by screening various clays and other materials for their ability to effectively bind lead. The clay was adhered to a solid support using an aqueous solution of carboxymethyl cellulose. The binary composite was then tested for its ability to bind lead from solution, while providing void volume, increased surface area, and considerably enhanced hydraulic conductivity. The results suggested that a combination of sodium montmorillonite clay and carbon exhibited enhanced sorption of lead compared to carbon alone, and also supported the potential application of various combinations of sorbent materials. This value-added combination of clay, solid support, and adhesive will allow for the construction of column filtration systems that are multifunctional and capable of purifying large volumes of contaminated water. PMID:11482800

  8. Structural Investigation of Alkali Activated Clay Minerals for Application in Water Treatment Systems

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    Alkali activation technology can be applied for a wide range of alumo-silicates to produce innovative materials with various areas of application. Most researches focuse on the application of alumo-silicate materials in building industry as cement binder replacement to produce mortar and concrete [1]. However, alkali activation technology offers high potential also in biotechnologies [2]. In the processes where certain pH level, especially alkaline environment, must be ensured, alkali activated materials can be applied. One of such fields is water treatment systems where high level pH (up to pH 10.5) ensures efficient removal of water pollutants such as manganese [3]. Previous investigations had shown that alkali activation technology can be applied to calcined clay powder and aluminium scrap recycling waste as a foam forming agent to create porous alkali activated materials. This investigation focuses on the structural investigation of calcined kaolin and illite clay alkali activation processes. Chemical and mineralogical composition of both clays were determined and structural investigation of alkali activated materials was made by using XRD, DTA, FTIR analysis; the microstructure of hardened specimens was observed by SEM. Physical properties of the obtained material were determined. Investigation indicates the essential role of chemical composition of the clay used in the alkali activation process, and potential use of the obtained material in water treatment systems.

  9. Effect of Water on Elastic and Creep Properties of Self-Standing Clay Films.

    PubMed

    Carrier, Benoit; Vandamme, Matthieu; Pellenq, Roland J-M; Bornert, Michel; Ferrage, Eric; Hubert, Fabien; Van Damme, Henri

    2016-02-01

    We characterized experimentally the elastic and creep properties of thin self-standing clay films, and how their mechanical properties evolved with relative humidity and water content. The films were made of clay montmorillonite SWy-2, obtained by evaporation of a clay suspension. Three types of films were manufactured, which differed by their interlayer cation: sodium, calcium, or a mixture of sodium with calcium. The orientational order of the films was characterized by X-ray diffractometry. The films were mechanically solicited in tension, the resulting strains being measured by digital image correlation. We measured the Young's modulus and the creep over a variety of relative humidities, on a full cycle of adsorption-desorption for what concerns the Young's modulus. Increasing relative humidity made the films less stiff and made them creep more. Both the elastic and creep properties depended significantly on the interlayer cation. For the Young's modulus, this dependence must originate from a scale greater than the scale of the clay layer. Also, hysteresis disappeared when plotting the Young's modulus versus water content instead of relative humidity. Independent of interlayer cation and of relative humidity greater than 60%, after a transient period, the creep of the films was always a logarithmic function of time. The experimental data gathered on these mesoscale systems can be of value for modelers who aim at predicting the mechanical behavior of clay-based materials (e.g., shales) at the engineering macroscopic scale from the one at the atomistic scale, for them to validate the first steps of their upscaling scheme. They provide also valuable reference data for bioinspired clay-based hybrid materials. PMID:26752345

  10. Prediction of pore-water pressure response to rainfall using support vector regression

    NASA Astrophysics Data System (ADS)

    Babangida, Nuraddeen Muhammad; Mustafa, Muhammad Raza Ul; Yusuf, Khamaruzaman Wan; Isa, Mohamed Hasnain

    2016-05-01

    Nonlinear complex behavior of pore-water pressure responses to rainfall was modelled using support vector regression (SVR). Pore-water pressure can rise to disturbing levels that may result in slope failure during or after rainfall. Traditionally, monitoring slope pore-water pressure responses to rainfall is tedious and expensive, in that the slope must be instrumented with necessary monitors. Data on rainfall and corresponding responses of pore-water pressure were collected from such a monitoring program at a slope site in Malaysia and used to develop SVR models to predict pore-water pressure fluctuations. Three models, based on their different input configurations, were developed. SVR optimum meta-parameters were obtained using k-fold cross validation and a grid search. Model type 3 was adjudged the best among the models and was used to predict three other points on the slope. For each point, lag intervals of 30 min, 1 h and 2 h were used to make the predictions. The SVR model predictions were compared with predictions made by an artificial neural network model; overall, the SVR model showed slightly better results. Uncertainty quantification analysis was also performed for further model assessment. The uncertainty components were found to be low and tolerable, with d-factor of 0.14 and 74 % of observed data falling within the 95 % confidence bound. The study demonstrated that the SVR model is effective in providing an accurate and quick means of obtaining pore-water pressure response, which may be vital in systems where response information is urgently needed.

  11. Scaling Soil Microbe-Water Interactions from Pores to Ecosystems

    NASA Astrophysics Data System (ADS)

    Manzoni, S.; Katul, G. G.

    2014-12-01

    The spatial scales relevant to soil microbial activity are much finer than scales relevant to whole-ecosystem function and biogeochemical cycling. On the one hand, how to link such different scales and develop scale-aware biogeochemical and ecohydrological models remains a major challenge. On the other hand, resolving these linkages is becoming necessary for testing ecological hypotheses and resolving data-theory inconsistencies. Here, the relation between microbial respiration and soil moisture expressed in water potential is explored. Such relation mediates the water availability effects on ecosystem-level heterotrophic respiration and is of paramount importance for understanding CO2 emissions under increasingly variable rainfall regimes. Respiration has been shown to decline as the soil dries in a remarkably consistent way across climates and soil types (open triangles in Figure). Empirical models based on these respiration-moisture relations are routinely used in Earth System Models to predict moisture effects on ecosystem respiration. It has been hypothesized that this consistency in microbial respiration decline is due to breakage of water film continuity causing in turn solute diffusion limitations in dry conditions. However, this hypothesis appears to be at odds with what is known about soil hydraulic properties. Water film continuity estimated from soil water retention (SWR) measurements at the 'Darcy' scale breaks at far less negative water potential (<-0.1 MPa) levels than where microbial respiration ceases (approximately -15 MPa) as shown in the Figure (violet frequency distribution). Also, this threshold point inferred from SWR shows strong texture dependence, in contrast to the respiration curves. Employing theoretical tools from percolation theory, it is demonstrated that hydrological measurements can be spatially downscaled at a micro-level relevant to microbial activity. Such downscaling resolves the inconsistency between respiration thresholds and

  12. Water Imbibition into Rock as Affected by Sample Shape, Pore, Conductivity, and Antecedent Water Content

    SciTech Connect

    R.P. Ewing

    2005-08-29

    Infiltration is often presumed to follow Philip's equation, I = st{sup 1/2}, where I is cumulative infiltration, s is sorptivity, and t is time. This form of the equation is appropriate for short times, and/or for negligible gravitational effects. For a uniform soil, this equation describes a plot of log(mass imbibed) versus log(time), with a slope (imbibition exponent) of 1/2. The equation has also been applied to low-porosity rocks, where the extremely small pores render gravitational forces negligible. Experiments recently performed on a wide variety of rocks produced imbibition exponents from 0.2 to 0.5. Many rock types showed initial imbibition proceeding as I {approx} t{sup 1/4}, then later switched to ''normal'' (t{sup 1/2}) behavior. The distance to the wetting front that corresponds to this cross-over behavior was found to be related to the sample shape: tall thin samples are more likely to exhibit the exponent 1/4, and to cross over to 1/2-type behavior later, while short, squat samples are less likely to display the 1/4-type behavior at all. Additionally, the exponents are sensitive to antecedent water content, with initially wetter samples having smaller values. In this study, we present the experimental data, and provide a consistent and physically-based explanation using percolation theory. The analogy between imbibition and diffusion is used to model imbibition into samples with low pore connectivity, with the exponents and their crossover behavior emerging from a random walk process. All laboratory phenomena--different exponents, crossover behavior, and effects of sample shape and antecedent water content--are reproduced by the model, with similar patterns across experiment and simulation. We conclude both that diffusion is a useful and powerful conceptual model for understanding imbibition, and also that imbibition experiments, being simpler than diffusion measurements, can be used to examine diffusive behavior in rock.

  13. Water Retention Characteristics and State-Dependent Mechanical and Petro-Physical Properties of a Clay Shale

    NASA Astrophysics Data System (ADS)

    Wild, Katrin M.; Wymann, Linda P.; Zimmer, Sebastian; Thoeny, Reto; Amann, Florian

    2015-03-01

    A series of clay shale specimens in equilibrium with various humidity conditions were used to establish the water retention characteristics, the influence of suction on ultrasonic p-wave velocity and rock mechanical properties such as Young's modulus, Poisson's ratio, onset of dilatancy, unconfined compressive strength and Brazilian tensile strength. Opalinus Clay, a clay shale considered as host rock for the disposal of nuclear waste in Switzerland was utilized. The results showed that the p-wave velocity normal to bedding ( v p,n) dropped sharply upon desaturation until suction approached the air-entry value. The sharp decrease was associated with desiccation cracks solely oriented parallel to bedding. For suction in excess of the air-entry value, v p,n was constant, indicating no further desiccation damage. The suction at the shrinkage limit and at the air-entry point is similar in magnitude. The p-wave velocity parallel to bedding ( v p,p) remained constant in the entire range of suction investigated in this study. The constant v p,p with increasing suction might be associated with the disproportional decrease in the Poisson's ratio and Young's modulus and its opposing effect on p-wave velocity. An almost linear increase in unconfined compressive strength, Brazilian tensile strength, stress at the onset of dilatancy and Young's modulus with increasing suction was observed up to a suction of 56.6 MPa. For suction larger than 56.6 MPa, relatively constant strength and stiffness was observed. The increase is associated with the net contribution of suction to strength/stiffness, which decreases nonlinearly with decreasing volumetric water content. The rate of increase in tensile strength and unconfined compressive strength with increasing suction is different depending on the rock anisotropy. Compared to the strength values (Brazilian tensile and uniaxial compressive strength) obtained from specimens loaded parallel to bedding, the tensile strength parallel to

  14. Hydrogen and oxygen isotope exchange reactions between clay minerals and water

    USGS Publications Warehouse

    O'Neil, J.R.; Kharaka, Y.K.

    1976-01-01

    The extent of hydrogen and oxygen isotope exchange between clay minerals and water has been measured in the temperature range 100-350?? for bomb runs of up to almost 2 years. Hydrogen isotope exchange between water and the clays was demonstrable at 100??. Exchange rates were 3-5 times greater for montmorillonite than for kaolinite or illite and this is attributed to the presence of interlayer water in the montmorillonite structure. Negligible oxygen isotope exchange occurred at these low temperatures. The great disparity in D and O18 exchange rates observed in every experiment demonstrates that hydrogen isotope exchange occurred by a mechanism of proton exchange independent of the slower process of O18 exchange. At 350?? kaolinite reacted to form pyrophyllite and diaspore. This was accompanied by essentially complete D exchange but minor O18 exchange and implies that intact structural units in the pyrophyllite were inherited from the kaolinite precursor. ?? 1976.

  15. Field Test Design Simulations of Pore-Water Extraction for the SX Tank Farm

    SciTech Connect

    Truex, Michael J.; Oostrom, Martinus

    2013-09-01

    A proof of principle test of pore water extraction is being performed by Washington River Protection Solutions for the U.S. Department of Energy, Office of River Protection. This test is being conducted to meet the requirements of Hanford Federal Facility Agreement and Consent Order (HFFACO) (Ecology et al. 1989) Milestone M 045-20, and is described in RPP-PLAN-53808, 200 West Area Tank Farms Interim Measures Investigation Work Plan. To support design of this test, numerical simulations were conducted to help define equipment and operational parameters. The modeling effort builds from information collected in laboratory studies and from field characterization information collected at the test site near the Hanford Site 241-SX Tank Farm. Numerical simulations were used to evaluate pore-water extraction performance as a function of the test site properties and for the type of extraction well configuration that can be constructed using the direct-push installation technique. Output of simulations included rates of water and soil-gas production as a function of operational conditions for use in supporting field equipment design. The simulations also investigated the impact of subsurface heterogeneities in sediment properties and moisture distribution on pore-water extraction performance. Phenomena near the extraction well were also investigated because of their importance for pore-water extraction performance.

  16. Effects of soil stratigraphy on pore-water flow in a creek-marsh system

    NASA Astrophysics Data System (ADS)

    Xin, Pei; Kong, Jun; Li, Ling; Barry, D. A.

    2012-12-01

    SummaryIn coastal marshes, low-permeability mud is often found overlying high permeability sandy deposits. A recently developed 3D creek-marsh model was used to investigate the effects of soil stratigraphy (a mud layer overlying a sandy-loam layer) on pore-water flow in the marsh. Simulation results showed significant modifications of tide-induced pore-water flow due to the layered soil. The presence of the lower sandy-loam layer with a relatively high hydraulic conductivity not only increased the pore-water flow speed but also changed the flow direction, particularly in the upper mud layer where enhanced vertical flow dominated. Particle tracking revealed large changes in the overall pore-water circulation pattern, and associated particle travel path and time due to the influence of the soil stratigraphy. While the amount of water exchange between the marsh soil and tidal water increased, the residence time of particles in both soil layers was reduced. Sensitivity analysis showed the importance of soil compressibility, capillary rise and hydraulic conductivity contrast between the soil layers in modulating the effect of soil stratigraphy. In particular, the total net influx and efflux across the marsh surface (including the creek/channel bank and bed) increased proportionally with the square root of the lower layer's hydraulic conductivity. These results demonstrated the interplay of tides, marsh topography and soil stratigraphy in controlling the pore-water flow characteristics, which underpin solute transport and transformation as well as the aeration condition in the marsh soil.

  17. Polymerization and Functionalization of Membrane Pores for Water Related Applications

    PubMed Central

    2015-01-01

    Poly(vinylidene fluoride) (PVDF) was modified by chemical treatments in order to create active double bonds to obtain covalent grafting of poly(acrylic acid) (PAA) on membrane. The attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectrum confirms the formation of conjugated C=C double bonds with surface dehydrofluorination. The membrane morphology was studied by scanning electron microscopy (SEM). The surface composition was characterized by X-ray photoelectron spectroscopy (XPS). The thermal stability of the dehydrofluorinated membrane (Def-PVDF) and functionalized membranes were investigated by differential scanning calorimetry (DSC) analysis. The influence of covalently attached PAA on Def-PVDF membrane has been investigated to determine its effect on the transport of water and charged solute. Variations in the solution pH show an effect on both permeability and solute retention in a reversible fashion. Metal nanoparticles were also immobilized in the membrane for the degradation of toxic chlorinated organics from water. In addition, PVDF membranes with an asymmetric and sponge-like morphology were developed by immersion-precipitation phase-inversion methods in both lab-scale and large-scale. The new type of spongy PVDF membrane shows high surface area with higher yield of PAA functionalization. The ion-capacity with Ca2+ ions was also investigated. PMID:26074669

  18. A multi-level pore-water sampler for permeable sediments

    USGS Publications Warehouse

    Martin, J.B.; Hartl, K.M.; Corbett, D.R.; Swarzenski, P.W.; Cable, J.E.

    2003-01-01

    The construction and operation of a multi-level piezometer (multisampler) designed to collect pore water from permeable sediments up to 230 cm below the sediment-water interface is described. Multisamplers are constructed from 1 1/2 inch schedule 80 PVC pipe. One-quarter-inch flexible PVC tubing leads from eight ports at variable depths to a 1 1/2 inch tee fitting at the top of the PVC pipe. Multisamplers are driven into the sediments using standard fence-post drivers. Water is pumped from the PVC tubing with a peristaltic pump. Field tests in Banana River Lagoon, Florida, demonstrate the utility of multisamplers. These tests include collection of multiple samples from the permeable sediments and reveal mixing between shallow pore water and overlying lagoon water.

  19. Relating soil pore geometry to soil water content dynamics decomposed at multiple frequencies

    NASA Astrophysics Data System (ADS)

    Qin, Mingming; Gimenez, Daniel; Cooper, Miguel

    2016-04-01

    Soil structure is a critical factor determining the response of soil water content to meteorological inputs such as precipitation. Wavelet analysis can be used to filter a signal into several wavelet components, each characterizing a given frequency. The purpose of this research was to investigate relationships between the geometry of soil pore systems and the various wavelet components derived from soil water content dynamics. The two study sites investigated were located in the state of São Paulo, Brazil. Each site was comprised of five soil profiles, the first site was situated along a 300-meter transect with about 10% slope in a tropical semi-deciduous forest, while the second one spanned 230-meter over a Brazilian savanna with a slope of about 6%. For each profile, between two to four Water Content Reflectometer CS615 (Campbell Scientific, Inc.) probes were installed according to horizonation at depths varying between 0.1 m and 2.3 m. Bulk soil, three soil cores, and one undisturbed soil block were sampled from selected horizons for determining particle size distributions, water retention curves, and pore geometry, respectively. Pore shape and size were determined from binary images obtained from resin-impregnated blocks and used to characterize pore geometry. Soil water contents were recorded at a 20-minute interval over a 4-month period. The Mexican hat wavelet was used to decompose soil water content measurements into wavelet components. The responses of wavelet components to wetting and drying cycles were characterized by the median height of the peaks in each wavelet component and were correlated with particular pore shapes and sizes. For instance, large elongated and irregular pores, largely responsible for the transmission of water, were significantly correlated with wavelet components at high frequencies (40 minutes to 48 hours) while rounded pores, typically associated to water retention, were only significantly correlated to lower frequency ranges

  20. Evaporation of J13 and UZ pore waters at Yucca Mountain

    SciTech Connect

    Rosenberg, N D; Gdowski, G E; Knauss, K G

    2000-10-01

    This work is motivated by a need to characterize the chemistry of aqueous films that might form at elevated temperatures on engineered components at the potential high-level, nuclear-waste repository at Yucca Mountain, Nevada. Such aqueous films might form through evaporation of water that seeps into the drifts, or by water vapor absorption by hydroscopic salts directly deposited on these components (possibly from previous evaporation events or possibly from air-blown particles drawn into the drifts through a drift ventilation system). There is no consensus at this time on the chemical composition of water that might come in contact with engineered components at Yucca Mountain. Two possibilities have received the most attention: well J13 water and pore waters from the unsaturated zone (UZ) above the repository horizon. These waters represent the two major types of natural waters at Yucca Mountain. Well J13 water is a dilute Na-HCO{sub 3}-CO{sub 3} water, representative of regional perched water and groundwater. The UZ pore waters are Ca-Cl-SO{sub 4}-rich waters with a higher dissolved ion content. These waters are less well-characterized. We have studied the evaporative evolution of these two major types of waters through a series of open system laboratory experiments, with and without crushed repository-horizon tuff present, conducted at sub-boiling temperatures (75 C-85 C).

  1. Pore Distribution and Water Uptake in a Cenosphere-Cement Paste Composite Material

    NASA Astrophysics Data System (ADS)

    Baronins, J.; Setina, J.; Sahmenko, G.; Lagzdina, S.; Shishkin, A.

    2015-11-01

    Alumina silicate cenospheres (CS) is a significant waste material from power plants that use a coal. Use CS as Portland cement replacement material gives opportunity to control physical and mechanical properties and makes a product lighter and more cost-effective. In the frame of this study, Portland cement paste samples were produced by adding CS in the concentration range from 0 to 40 volume %. Water uptake of hardened samples was checked and pore size distribution by using the mercury porosimetry was determined. In a cold climate where the temperature often falls below 0 °C, it is important to avoid the amount of micrometer sized pores in the final structure and to decrease water absorption capacity of material. In winter conditions, water fills such pores and causes additional stresses to their walls by expansion while freezing. It was found that generally water uptake capacity for cement paste samples decreased up to 20% by increasing the concentration of CS up to 40 volume %, at the same time, the volume of micrometer sized opened pores increases.

  2. Development and deployment of a deep-sea Raman probe for measurement of pore water geochemistry

    NASA Astrophysics Data System (ADS)

    Zhang, Xin; Walz, Peter M.; Kirkwood, William J.; Hester, Keith C.; Ussler, William; Peltzer, Edward T.; Brewer, Peter G.

    2010-02-01

    We have developed, deployed, and tested a novel probe for study of the geochemistry of sediment pore waters based upon Raman spectroscopy. The Raman technique has already been used successfully for in situ measurements of targets of scientific interest including gas and hydrothermal vents and complex gas hydrates, but sediment geochemistry has so far been an intractable problem since the sediments themselves are strongly fluorescent and typically only very small sample volumes are obtainable. The 35 cm long probe extracts pore fluids through a 10 μm sintered metallic frit and draws the sample through a 2 mm diameter channel into a sapphire windowed optical cell within which the laser beam is focused and the spectrum recorded. The dead volume of the system is ˜1 ml and the instrument is ROV deployable with activation of probe insertion and sample withdrawal under direct operator control. The unique features of this mode of detection include observation of the sulfate gradient in marine pore waters as an indicator of diagenesis, direct measurement of the dissolved sulfide species H 2S and HS -, and measurement of dissolved methane; all of which are of primary geochemical interest. Quantitative analysis is achieved by area ratio to known water peaks and from standard calibration curves with a precision of ±5%. We find only very small fluorescence from pore waters measured in situ, but observe rapid increases in fluorescence from cores returned to the surface and exposed to oxygen.

  3. Pore-water pressures associated with clogging of soil pipes: Numerical analysis of laboratory experiments

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Clogging of soil pipes due to excessive internal erosion has been hypothesized to cause extreme erosion events such as landslides, debris flows, and gullies, but confirmation of this phenomenon has been lacking. Laboratory and field measurements have failed to measure pore water pressures within pip...

  4. EFFICIENCY OF SOIL CORE AND SOIL-PORE WATER SAMPLING SYSTEMS

    EPA Science Inventory

    A laboratory column and field lysimeter study were conducted to evaluate the efficiency of soil core and soil-pore water samples to detect the migration of the organic components of land treated wastes through soil. In the laboratory, column leaching studies were performed by pac...

  5. Estimating the combined toxicity of flufenacet and imazaquin to sorghum with pore water herbicide concentration.

    PubMed

    Wang, Donghong; Zhang, Qian; Zheng, Yuan; Lin, Dunli; Yu, Yunlong

    2016-03-01

    Combined toxicity of herbicides to non-target crops is usually resulted from their successive application. The present study was conducted to assess the combined toxicity of flufenacet (FLU) and imazaquin (IMA) to sorghum with their concentration in soil pore water. The concentrations that inhibited growth by 50% (IC50) of FLU and IMA individually and their combination estimated from the herbicide concentrations in soil pore water notably differed from those based on the amended concentrations, due to the decline in bioavailability resulting from adsorption of the herbicides onto soil. According to the amended concentrations, the combined effect of FLU and IMA in soil on sorghum growth was identified as additive action. Based on the concentration in soil pore water, however, it was determined to be antagonism, which was identical to that observed in a test using culture solution. The results revealed that pore water herbicide concentration might be an effective tool to assess the combined toxicity of herbicides in soil to rotational crops. PMID:26969061

  6. Assessment of metal toxicity in sediment pore water from Lake Macquarie, Australia.

    PubMed

    Doyle, C J; Pablo, F; Lim, R P; Hyne, R V

    2003-04-01

    Recent investigations into the level of heavy metal enrichment in the sediments of Lake Macquarie have indicated that significant contamination has occurred over the past 100 years, with elevated levels of lead, zinc, cadmium, copper, and selenium being observed in most parts of the lake. Pore water extracted from sediments showing the greatest contamination by these metals exhibited toxicity to the larval development of the sea urchin Heliocidaris tuberculata. However, an analysis of pore water metal concentrations revealed that the concentrations of these metals were too low to cause toxicity. Rather, pore water toxicity was highly correlated with manganese for the majority of sites sampled; subsequent spiking experiments confirmed manganese as a cause of toxicity. Current levels of manganese in the sediments of Lake Macquarie have arisen from natural sources and are not the result of anthropogenic activities. These results reiterate the importance of identifying the causes of toxicity in assessments of sediment contamination, particularly when testing sediment pore waters using sensitive early life stages. PMID:12712294

  7. Influence of silver nanoparticles on heavy metals of pore water in contaminated river sediments.

    PubMed

    Tao, Wei; Chen, Guiqiu; Zeng, Guangming; Yan, Ming; Chen, Anwei; Guo, Zhi; Huang, Zhenzhen; He, Kai; Hu, Liang; Wang, Lichao

    2016-11-01

    Despite the increasing knowledge on the discharge of silver nanoparticles (AgNPs) into the environment and their potential toxicity to microorganisms, the interaction of AgNPs with heavy metals remains poorly understood. This study focused on the effect of AgNPs on heavy metal concentration and form in sediment contaminated with heavy metals from the Xiangjiang River. The results showed that the concentration of Cu, Zn, Pb and Cd decreased and then increased with a change in form. The changes in form and concentrations of heavy metals in pore water suggested that Cu and Zn were more likely to be affected compared to Pb and Cd. The concentrations of Hg in sediment pore water in three AgNPs-dosed containers, increased greatly until they reached their peaks at 4.468 ± 0.133, 4.589 ± 0.235, and 5.083 ± 0.084 μg L(-1) in Bare AgNPs, Citrate AgNPs and Tween 80 AgNPs, respectively. The measurements of Hg concentrations in the sediment pore water, combined with SEM and EDX analysis, demonstrated that added AgNPs stabilized in pore water and formed an amalgam with Hg(0), which can affect Hg transportation over long distance. PMID:27494311

  8. Development and application of a marine sediment pore-water toxicity test using Ulva fasciata zoospores

    SciTech Connect

    Hooten, R.L.; Carr, R.S.

    1998-01-01

    An acute (96 h) pore-water toxicity test protocol using germination and growth of Ulva fasciata zoospores as endpoints was developed to test the toxicity of marine and estuarine sediment pore-water samples. Tests with an organic toxicant (sodium dodecyl sulfate; SDS), three metals (Cd, Cu, and Zn), and ammonia (NH{sub 3}) were conducted to determine zoospore sensitivity. Zoospore germination and gametophyte growth were as sensitive to SDS as sea urchin (Arbacia punctulata) fertilization and embryological development. Zoospore sensitivity to metals was greater than or comparable to that of adult macroalgae. Zoospores were less sensitive to NH{sub 3} than were other commonly used toxicity test organisms. Test results using this algal assay with sediment pore-water samples with high NH{sub 3} concentrations were compared with results from sea urchin fertilization and embryological development tests for the same samples. Ulva fasciata zoospore germination was not affected by samples with high NH{sub 3} concentrations that were toxic in both sea urchin tests. Zoospore tolerance of NH{sub 3} and sensitivity to other contaminants indicate that their response may be useful in toxicity identification evaluation studies with pore-water samples that contain high concentrations of unionized NH{sub 3}.

  9. Development and application of a marine sediment pore-water toxicity test using Ulva fasciata zoospores

    USGS Publications Warehouse

    Hooten, R.L.; Carr, R.S.

    1998-01-01

    An acute (96 h) pore-water toxicity test protocol using germination and growth of Ulva fasciata zoospores as endpoints was developed to test the toxicity of marine and estuarine sediment pore-water samples. Tests with an organic toxicant (sodium dodecyl sulfate; SDS), three metals (Cd, Cu, and Zn), and ammonia (NH3) were conducted to determine zoospore sensitivity. Zoospore germination and gametophyte growth were as sensitive to SDS as sea urchin (Arbacia punctulata) fertilization and embryological development. Zoospore sensitivity to metals was greater than or comparable to that of adult macroalgae. Zoospores were less sensitive to NH3 than were other commonly used toxicity test organisms. Test results using this algal assay with sediment pore-water samples with high NH3 concentrations were compared with results from sea urchin fertilization and embryological development tests for the same samples. Ulva fasciata zoospore germination was not affected by samples with high NH3 concentrations that were toxic in both sea urchin tests. Zoospore tolerance of NH3 and sensitivity to other contaminants indicate that their response may be useful in toxicity identification evaluation studies with pore-water samples that contain high concentrations of unionized NH3.

  10. Preliminary investigations on the defluoridation of water using fired clay chips

    NASA Astrophysics Data System (ADS)

    Moges, G.; Zewge, F.; Socher, M.

    1996-05-01

    The adsorption of fluoride ions on ground fired clay pot has been investigated. The maximum efficiency of the adsorbent for defluoridating 1-2 litres of water was found to be 200 mg fluoride kg -1 adsorbent. The investigation showed that 5-20 mg l -1 fluoride, from 1 litre of water, could be reduced to less than 1.5 mg l -1 using 120-240 g of the adsorbing medium. The effects of the dose of the medium, the pH, the contact time and the initial fluoride content were studied in relation to defluoridation efficiency. Comparison of fluoride removal capacity of the adsorbent was also made with those of fired brick, clay soil and red ash. The latter exhibited practically no adsorption. A packed column of the same ground clay pot was saturated with 285 mg fluoride kg -1 of adsorbent when 20 litres of water containing 10 mg l -1 F was allowed to pass through it. This column defluoridated 6 litres of tap water containing 10 ppm F - to below 1.5 mg l -1.

  11. Spectroscopic analyses of Fe and water in clays: A Martian surface weathering study

    NASA Technical Reports Server (NTRS)

    Bishop, J. L.; Pieters, Carle M.; Edwards, J. O.; Coyne, L. M.; Chang, S.

    1991-01-01

    Martian surface morphology suggests the presence of liquid H2O on Mars in the past. Reflectance spectra of the Martian surface include features which correspond to the crystal field transitions of iron, as well as features supporting the presence of ice and minerals containing structural OH and surface water. Researchers initiated further spectroscopic studies of surface iron and water and structural OH in clays in order to determine what remotely obtained spectra can indicate about the presence of clays on Mars based on a clearer understanding of the factors influencing the spectral features. Current technology allows researchers to better correlate the low frequency fundamental stretching and bending vibrations of O-H bonds with the diagnostic near infrared overtone and combination bands used in mineral characterization and identification.

  12. Water Desalination Using Nanoporous Single-Layer Graphene with Tunable Pore Size

    DOE PAGESBeta

    Surwade, Sumedh P.; Smirnov, Sergei N.; Vlassiouk, Ivan V.; Unocic, Raymond R.; Veith, Gabriel M.; Dai, Sheng; Mahurin, Shannon Mark

    2015-03-23

    Graphene has great potential to serve as a separation membrane due to its unique properties such as chemical and mechanical stability, flexibility and most importantly its one-atom thickness. In this study, we demonstrate first experimental evidence of the use of single-layer porous graphene as a desalination membrane. Nanometer-sized pores are introduced into single layer graphene using a convenient oxygen plasma etching process that permits tuning of the pore size. The resulting porous graphene membrane exhibited high rejection of salt ions and rapid water transport, thus functioning as an efficient water desalination membrane. Salt rejection selectivity of nearly 100% and exceptionallymore » high water fluxes exceeding 105 g m-2 s-1 at 40 C were measured using saturated water vapor as a driving force.« less

  13. Water Desalination Using Nanoporous Single-Layer Graphene with Tunable Pore Size

    SciTech Connect

    Surwade, Sumedh P.; Smirnov, Sergei N.; Vlassiouk, Ivan V.; Unocic, Raymond R.; Veith, Gabriel M.; Dai, Sheng; Mahurin, Shannon Mark

    2015-03-23

    Graphene has great potential to serve as a separation membrane due to its unique properties such as chemical and mechanical stability, flexibility and most importantly its one-atom thickness. In this study, we demonstrate first experimental evidence of the use of single-layer porous graphene as a desalination membrane. Nanometer-sized pores are introduced into single layer graphene using a convenient oxygen plasma etching process that permits tuning of the pore size. The resulting porous graphene membrane exhibited high rejection of salt ions and rapid water transport, thus functioning as an efficient water desalination membrane. Salt rejection selectivity of nearly 100% and exceptionally high water fluxes exceeding 105 g m-2 s-1 at 40 C were measured using saturated water vapor as a driving force.

  14. Clay microporosity in reservoir sandstones: An application of quantitative electron microscopy in petrophysical evaluation

    SciTech Connect

    Hurst, A.; Nadeau, P.H.

    1995-04-01

    Clay mineral microporosity in sandstones is measured using computer-assisted image analysis of back-scattered electron micrographs of petrographic sections. Diagenetic kaolinite has a variety of textures with microporosity values ranging from 15 to 61%. Diagenetic chlorite has a generally uniform grain-coating texture and microporosity of about 50%. Fibrous illitic clays are difficult to characterize by the same method (an average value of 63% microporosity was recorded), but analysis of stereo-pair micrographs from scanning-electron microscopy analyses reveals that illite commonly has microporosity of approximately 90%. Clay microporosity data are used to calculate effective pore volumes and volumes of clay-bound water for clay minerals in sandstones. Converting from weight percent clay to volume percent clay is important. Microporosity data are valuable input to V{sub shale} evaluation where water saturation is associated with clay mineral type, texture, and volume.

  15. Salt marsh pore water geochemistry does not correlate with microbial community structure

    NASA Astrophysics Data System (ADS)

    Koretsky, Carla M.; Van Cappellen, Philippe; DiChristina, Thomas J.; Kostka, Joel E.; Lowe, Kristi L.; Moore, Charles M.; Roychoudhury, Alakendra N.; Viollier, Eric

    2005-01-01

    Spatial and temporal trends in pore water geochemistry and sediment microbial community structure are compared at three intertidal sites of a saltmarsh on Sapelo Island, GA. The sites include a heavily bioturbated, unvegetated creek bank, a levee with dense growth of Spartina alterniflora, and a more sparsely vegetated ponded marsh site. The redox chemistry of the pore waters ranges from sulfide-dominated at the ponded marsh site to suboxic at the creek bank site. At the three sites, the vertical redox stratification of the pore waters is more compressed in summer than in winter. The trends in redox chemistry reflect opposing effects of sediment respiration and pore water irrigation. Intense and deep burrowing activity by fiddler crabs at the creek bank site results in the efficient oxidation of reduced byproducts of microbial metabolism and, hence, the persistence of suboxic conditions to depths of 50 cm below the sediment surface. Increased supply of labile organic substrates at the vegetated sites promotes microbial degradation processes, leading to sharper redox gradients. At the levee site, this is partly offset by the higher density and deeper penetration of roots and macrofaunal burrows. Surprisingly, the microbial community structure shows little correlation with the variable vertical redox zonation of the pore waters across the saltmarsh. At the three sites, the highest population densities of aerobic microorganisms, iron- plus manganese-reducing bacteria, and sulfate reducers coexist within the upper 10 cm of sediment. The absence of a clear vertical separation of these microorganisms is ascribed to the high supply of labile organic matter and intense mixing of the topmost sediment via bioturbation.

  16. Pore-water isotopic compositions and unsaturated-zone flow, Yucca Mountain, Nevada

    SciTech Connect

    Yang, In C.

    2001-04-29

    Isotopic compositions of core-water samples from boreholes USW SD-6 and USW WT-24 indicate that recent water has been introduced at depth. Tritium, carbon, oxygen, and deuterium isotopic compositions all support younger water at depth in the two boreholes. Peaks in tritium concentrations in pore-water samples, indicating younger water than the other samples, observed near the basal vitrophyre of the Topopah Spring Tuff and at the bottom of the CHF and the top of the PP in both boreholes SD-6 and WT-24. Larger {sup 14}C activities in two pore-water samples from WT-24 at the bottom of the CHF and the top of the PP indicate younger water than in other samples from WT-24. More positive {delta}{sup 18}O and {delta}D values indicate younger water in samples of pore water at the bottom of the CHF in boreholes SD-6 and WT-24. The isotopic compositions indicating younger water at depth in boreholes SD-6 and WT-24 occur at the basal vitrophyre zone of the Topopah Spring Tuff and the bottom of the CHF/upper part of the PP, probably from lateral preferential flow through connected fractures (fast-flow paths). The source of the young water at borehole WT-24 probably was recharge from The Prow to the north, which then flowed laterally southward through the highly fractured TSw. The source of the young water at borehole SD-6 probably was water flow from the Solitario Canyon fault to the west, which then flowed laterally through the TSw and CHF.

  17. A method for estimating pore water drainage from marsh soils using rainfall and well records

    NASA Astrophysics Data System (ADS)

    Gardner, Leonard Robert; Gaines, Emily F.

    2008-08-01

    Rainfall events during low tide exposure cause the water table in marshes to rise. If one has long time series of both rain events and water levels in wells along transects from creek bank to marsh interior, one can correlate well response with rain amount. In cases examined so far the well response is found to be a linear function of rain amount. As it is reasonable to assume that the amount of tidal infiltration required to restore the water table to the elevation of the marsh surface is equal to the amount of rain that would be required to do so, one can estimate the annual drainage of pore water from a well site by dividing the mean drawdown of the water table at low tide by the slope of the response versus rain regression and then multiplying the result by the number of tidal drawdowns in a year. Integration of such results along the transect then gives an estimate of the total annual drainage. An example of the use of this method is given for two well transects in a Typha and a Spartina marsh at the Plum Island Estuary Long Term Ecological Research (PIE-LTER) site in Massachusetts, USA. Both transects yielded pore water drainage rates of about 160 m 3 year -1 per meter of channel length. Although the annual volume of pore water drainage is small compared to the annual volume of the tidal prism, its impact on nutrient budgets in the estuary could be large because of the high concentrations of nutrients in marsh pore waters. We also discuss the possible effects of the capillary fringe, air entrapment and tidal forcing during rain events on these results.

  18. Dating very old pore waters in impermeable rocks by noble gas isotopes

    SciTech Connect

    Osenbrueck, K.; Lippmann, J.; Sonntag, C.

    1998-09-01

    The {sup 4}He, {sup 40}Ar, and {sup 136}Xe content dissolved in the pore water of sedimentary rock samples was measured on samples from borehole cores near the repository for nuclear waste in Morsleben, Germany. Due to the very low permeabilities of the rock formations, conventional groundwater sampling was almost impossible. Hence, the authors developed a new sampling method for noble gases in the pore water of freshly drilled rock cores. This method provides vertical noble gas profiles in high depth resolution, even in impermeable rocks. By application of the new technique quantitative age information of groundwater and pore water have been derived. The authors find palaeowaters from the last glaciation depleted in {delta}D and {delta}{sup 18}O with a {sup 4}He age of about 55 kyr. The high saline pore solutions below are at least 6 Mio years old. This has been concluded from the profiles of radiogenic {sup 4}He and {sup 40}Ar close to diffusion in steady-state and from xenon isotopes produced by spontaneous fission of {sup 238}U in the rocks. A {sup 4}He flux of 2 {center_dot} 10{sup {minus}7} cc STP/cm{sup 2} yr is derived from the profile, which is due to local {sup 4}He production within the investigated sediments.

  19. Clays causing adhesion with tool surfaces during mechanical tunnel driving

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

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

  20. Advective pore water input of nutrients to the Satilla River Estuary, Georgia, USA

    NASA Astrophysics Data System (ADS)

    Jahnke, R. A.; Alexander, C. R.; Kostka, J. E.

    2003-03-01

    In situ benthic flux measurements, pore water nutrient profiles, water column nutrient distributions, sediment grain size distributions and side-scan sonar observations suggest that advective transport of pore waters may be a major input pathway of nutrients into the Satilla River Estuary (coastal Georgia, USA). In situ benthic chamber incubations demonstrate the occurrence of highly variable, but occasionally very large sea floor fluxes of silicate, phosphate, and ammonium. Locally occurring benthic microbial mineralization of organic matter, as estimated by S 35-sulphate reduction rate measurements, is insufficient to support these large fluxes. We hypothesize that the observed interlayering of permeable, sandy sediments with fine-grained, organic-rich sediments in the estuary provides conduits for advective transport of pore water constituents out of the sediments. Because permeable layers may extend significant distances beneath the salt marsh, the large fluxes observed may be supported by remineralization occurring over large areas adjacent to the estuary. Advective transport may be induced by pressure gradients generated by a variety of processes, including landward recharge by meteoric or rain waters if sand layers extend far enough into the maritime coastal lands. Alternatively, tidal variations across the salt marsh sediment surface may hydraulically pump water through the sediment system. Because these fluxes appear to be concentrated into small layers, this source may be a significant input of nutrients to the estuary even if permeable, sandy layers comprise a very small proportion of the seabed.

  1. A Lattice Boltzmann model for simulating water flow at pore scale in unsaturated soils

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoxian; Crawford, John W.; Young, Iain M.

    2016-07-01

    The Lattice Boltzmann (LB) method is an established prominent model for simulating water flow at pore scale in saturated porous media. However, its application in unsaturated soil is less satisfactory because of the difficulties associated with most two-phase LB models in simulating immiscible fluids, such as water and air, which have contrasting densities and viscosities. While progress has been made in developing LB models for fluids with high density ratio, they are still prone to numerical instability and cannot accurately describe the interfacial friction on water-air interface in unsaturated media. Considering that one important application of the LB model in porous materials is to calculate their hydraulic properties when flow is at steady state, we develop a simple LB model to simulate steady water flow at pore scale in unsaturated soils. The method consists of two steps. The first one is to determine water distribution within the soil structure using a morphological model; once the water distribution is known, its interfaces with air are fixed. The second step is to use a single-phase LB model to simulate water flow by treating the water-air interfaces as free-flow boundaries where the shear resistance of air to water flow is assumed to be negligible. We propose a method to solve such free-flow boundaries, and validate the model against analytical solutions of flows of water film over non-slip walls in both two and three dimensions. We then apply the model to calculate water retention and hydraulic properties of a medium acquired using X-ray computed tomography at resolution of 6 μm. The model is quasi-static, similar to the porous network model, but is an improvement as it directly simulates water flow in the pore geometries acquired by tomography without making any further simplifications.

  2. Pore-Water Extraction from Unsaturated Porous Media: Intermediate-Scale Laboratory

    SciTech Connect

    Oostrom, Martinus; Truex, Michael J.; Wietsma, Thomas W.; Tartakovsky, Guzel D.

    2014-08-15

    As a remedial approach, vacuum-induced pore-water extraction offers the possibility of contaminant and water removal from the vadose zone, which may be beneficial in reducing the flux of vadose zone contaminants to groundwater. Vadose zone water extraction is being considered at the Hanford Site in Washington State as a means to remove technetium-99 contamination from low permeability sediments with relatively high water contents. A series of intermediate-scale laboratory experiments have been conducted to improve the fundamental understanding and limitations of the technique. Column experiments were designed to investigate the relations between imposed suctions, water saturations, and water production. Flow cell experiments were conducted to investigate the effects of high-permeability layers and near-well compaction on pore-water extraction efficiency. Results show that water extraction from unsaturated systems can be achieved in low permeability sediments, provided that the initial water saturations are relatively high. The presence of a high-permeability layer decreased the yield, and compaction near the well screen had a limited effect on overall performance. In all experiments, large pressure gradients were observed near the extraction screen. Minimum requirements for water extraction include an imposed vacuum-induced suction larger than the initial sediment capillary pressure, in combination with a fully saturated seepage-face boundary. A numerical multiphase simulator with a coupled seepage-face boundary conditions was used to simulate the experiments. Reasonable matches were obtained between measured and simulated results for both water extraction and capillary pressures, suggesting that numerical simulations may be used as a design tool for field-scale applications of pore-water extraction.

  3. Estimating flow and transport parameters in the unsaturated zone with pore water stable isotopes

    NASA Astrophysics Data System (ADS)

    Sprenger, M.; Volkmann, T. H. M.; Blume, T.; Weiler, M.

    2014-10-01

    Determining the soil hydraulic properties is a prerequisite to physically model transient water flow and solute transport in the vadose zone. Estimating these properties by inverse modelling techniques has become more common within the last two decades. While these inverse approaches usually fit simulations to hydrometric data, we expanded the methodology by using independent information about the stable isotope composition of the soil pore water depth profile as a single or additional optimization target. To demonstrate the potential and limits of this approach, we compared the results of three inverse modelling strategies where the fitting targets were (a) pore water isotope concentrations, (b) a combination of pore water isotope concentrations and soil moisture time series, and (c) a two-step approach using first soil moisture data to determine water flow parameters and then the pore water stable isotope concentrations to estimate the solute transport parameters. The analyses were conducted at three study sites with different soil properties and vegetation. The transient unsaturated water flow was simulated by numerically solving the Richards equation with the finite-element code of Hydrus-1D. The transport of deuterium was simulated with the advection-dispersion equation, and the Hydrus code was modified to allow for deuterium loss during evaporation. The Mualem-van Genuchten and the longitudinal dispersivity parameters were determined for two major soil horizons at each site. The results show that approach (a) using only the pore water isotope content cannot substitute hydrometric information to derive parameter sets that reflect the observed soil moisture dynamics, but gives comparable results when the parameter space is constrained by pedotransfer functions. Approaches (b) and (c) using both, the isotope profiles and the soil moisture time series resulted in satisfying model performances and good parameter identifiability. However, approach (b) has the

  4. Anisotropy on the collective dynamics of water confined in swelling clay minerals.

    PubMed

    Jiménez-Ruiz, M; Ferrage, E; Delville, A; Michot, L J

    2012-03-15

    Collective excitations of water confined in the interlayer space of swelling clay minerals were studied by means of inelastic neutron scattering. The effect of bidimensional confinement on the dynamics of the interlayer water was investigated by using a synthetic Na-saponite sample with a general formula of Si(7.3)Al(0.7)Mg(6)O(20)(OH)(4)Na(0.7) in a bilayer hydration state. Experimental results reveal two inelastic signals, different from those described for bulk water with a clear anisotropy on the low-energy excitation of the collective dynamics of interlayer water, this difference being stronger in the perpendicular direction. Results obtained for the parallel direction follow the same trend as bulk water, and the effect of the confinement is mainly manifested from the fact that clay interlayer water is more structured than bulk water. Data obtained in the perpendicular direction display a nondispersive behavior below a cutoff wavenumber value, Q(c), indicating a nonpropagative excitation below that value. Molecular dynamics simulations results agree qualitatively with the experimental results. PMID:22324768

  5. Impact cratering in sandstone: The MEMIN pilot study on the effect of pore water

    NASA Astrophysics Data System (ADS)

    Kenkmann, Thomas; Wünnemann, Kai; Deutsch, Alexander; Poelchau, Michael H.; Schäfer, Frank; Thoma, Klaus

    2011-06-01

    Planetary surfaces are subjected to meteorite bombardment and crater formation. Rocks forming these surfaces are often porous and contain fluids. To understand the role of both parameters on impact cratering, we conducted laboratory experiments with dry and wet sandstone blocks impacted by centimeter-sized steel spheres. We utilized a 40 m two-stage light-gas gun to achieve impact velocities of up to 5.4 km s-1. Cratering efficiency, ejection velocities, and spall volume are enhanced if the pore space of the sandstone is filled with water. In addition, the crater morphologies differ substantially from wet to dry targets, i.e., craters in wet targets are larger, but shallower. We report on the effects of pore water on the excavation flow field and the degree of target damage. We suggest that vaporization of water upon pressure release significantly contributes to the impact process.

  6. Isotopic data of pore water extracted from unsaturated-zone cores at Yucca Mountain, Nevada

    SciTech Connect

    Yang, I.C.

    1997-12-01

    Isotopic compositions of unsaturated-zone (UZ) ground water ({delta}{sup 18}O, {delta}D, {delta}{sup 13}C and {sup 14}C) at Yucca Mountain, Nevada, the site of a potential permanent national nuclear waste repository, can be used to infer the origins of water, residence times of the water, water flux, climatic and evaporative history of water, flow paths and velocities. These data can also be used as indicators of transport properties or water-rock interaction. The lack of long-term direct measurements of infiltration requires proxy indicators of water movement through the unsaturated zone to extend the record into the past. This report will discuss {delta}D and {delta}{sup 18}O data obtained from pore water, along with the {delta}{sup 13}C and {sup 14}C data of gas and water obtained from four boreholes dry-drilled through all UZ lithologic units to infer the existence of nonvertical flowpaths through the mountain and residence times of pore water.

  7. Cycling of trace metals (Mn, Fe, Mo, U, V, Cr) in deep pore waters of intertidal flat sediments

    NASA Astrophysics Data System (ADS)

    Beck, Melanie; Dellwig, Olaf; Schnetger, Bernhard; Brumsack, Hans-Jürgen

    2008-06-01

    Trace metals (Mn, Fe, Mo, U, Cr, V) were studied in pore waters of an intertidal flat located in the German Wadden Sea. The study system is an example of a permeable tidal flat system where pore water exchange is affected by tidal driven pressure gradients besides diffusion. Permanently installed in situ samplers were used to extract pore waters down to 5 m depth throughout one year. The samplers were either located close to the tidal flat margin or in central parts of the tidal flat. Despite dynamic sedimentological and hydrological conditions, the general trends with depth in deep tidal flat pore waters are remarkably similar to those observed in deep sea environments. Rates of trace metal cycling must be comparably large in order to maintain the observed pore water profiles. Trace metals further show similar general trends with depth close to the margin and in central parts of the tidal flat. Seasonal sampling revealed that V and Cr vary concurrent with seasonal changes in dissolved organic carbon (DOC) concentration. This effect is most notable close to the tidal flat margin where sulphate, DOC, and nutrients vary with season down to some metres depth. Seasonal variations of Mn, Fe, Mo, and U are by contrast limited to the upper decimetres of the sediment. Their seasonal patterns depend on organic matter supply, redox stratification, and particulate matter deposited on sediment surfaces. Pore water sampling within one tidal cycle provides evidence for pore water advection in margin sediments. During low tide pore water flow towards the creekbank is generated by a hydraulic gradient suggesting that deep pore waters may be seeping out of creekbank sediments. Owing to the enrichment of specific elements like Mn in pore water compared to sea water, seeping pore waters may have an impact on the chemistry of the open water column. Mass balance calculations reveal that the impact of deep pore waters on the Mn budget in the open water column is below 4%. Mn deep pore

  8. Temporal and Spatial Pore Water Pressure Distribution Surrounding a Vertical Landfill Leachate Recirculation Well

    PubMed Central

    Kadambala, Ravi; Townsend, Timothy G.; Jain, Pradeep; Singh, Karamjit

    2011-01-01

    Addition of liquids into landfilled waste can result in an increase in pore water pressure, and this in turn may increase concerns with respect to geotechnical stability of the landfilled waste mass. While the impact of vertical well leachate recirculation on landfill pore water pressures has been mathematically modeled, measurements of these systems in operating landfills have not been reported. Pressure readings from vibrating wire piezometers placed in the waste surrounding a liquids addition well at a full-scale operating landfill in Florida were recorded over a 2-year period. Prior to the addition of liquids, measured pore pressures were found to increase with landfill depth, an indication of gas pressure increase and decreasing waste permeability with depth. When liquid addition commenced, piezometers located closer to either the leachate injection well or the landfill surface responded more rapidly to leachate addition relative to those far from the well and those at deeper locations. After liquid addition stopped, measured pore pressures did not immediately drop, but slowly decreased with time. Despite the large pressures present at the bottom of the liquid addition well, much smaller pressures were measured in the surrounding waste. The spatial variation of the pressures recorded in this study suggests that waste permeability is anisotropic and decreases with depth. PMID:21655145

  9. Temporal and spatial pore water pressure distribution surrounding a vertical landfill leachate recirculation well.

    PubMed

    Kadambala, Ravi; Townsend, Timothy G; Jain, Pradeep; Singh, Karamjit

    2011-05-01

    Addition of liquids into landfilled waste can result in an increase in pore water pressure, and this in turn may increase concerns with respect to geotechnical stability of the landfilled waste mass. While the impact of vertical well leachate recirculation on landfill pore water pressures has been mathematically modeled, measurements of these systems in operating landfills have not been reported. Pressure readings from vibrating wire piezometers placed in the waste surrounding a liquids addition well at a full-scale operating landfill in Florida were recorded over a 2-year period. Prior to the addition of liquids, measured pore pressures were found to increase with landfill depth, an indication of gas pressure increase and decreasing waste permeability with depth. When liquid addition commenced, piezometers located closer to either the leachate injection well or the landfill surface responded more rapidly to leachate addition relative to those far from the well and those at deeper locations. After liquid addition stopped, measured pore pressures did not immediately drop, but slowly decreased with time. Despite the large pressures present at the bottom of the liquid addition well, much smaller pressures were measured in the surrounding waste. The spatial variation of the pressures recorded in this study suggests that waste permeability is anisotropic and decreases with depth. PMID:21655145

  10. Seasonal variations in pore water and sediment geochemistry of littoral lake sediments (Asylum Lake, MI, USA)

    PubMed Central

    Koretsky, Carla M; Haas, Johnson R; Miller, Douglas; Ndenga, Noah T

    2006-01-01

    Background Seasonal changes in pore water and sediment redox geochemistry have been observed in many near-surface sediments. Such changes have the potential to strongly influence trace metal distribution and thus create seasonal fluctuations in metal mobility and bioavailability. Results Seasonal trends in pore water and sediment geochemistry are assessed in the upper 50 cm of littoral kettle lake sediments. Pore waters are always redox stratified, with the least compressed redox stratification observed during fall and the most compressed redox stratification observed during summer. A 2-step sequential sediment extraction yields much more Fe in the first step, targeted at amorphous Fe(III) (hydr)oxides (AEF), then in the second step, which targets Fe(II) monosulfides. Fe extracted in the second step is relatively invariant with depth or season. In contrast, AEF decreases with sediment depth, and is seasonally variable, in agreement with changes in redox stratification inferred from pore water profiles. A 5-step Tessier extraction scheme was used to assess metal association with operationally-defined exchangeable, carbonate, iron and manganese oxide (FMO), organic/sulfide and microwave-digestible residual fractions in cores collected during winter and spring. Distribution of metals in these two seasons is similar. Co, As, Cd, and U concentrations approach detection limits. Fe, Cu and Pb are mostly associated with the organics/sulfides fraction. Cr and Zn are mostly associated with FMO. Mn is primarily associated with carbonates, and Co is nearly equally distributed between the FMO and organics/sulfide fractions. Conclusion This study clearly demonstrates that near-surface lake sediment pore water redox stratification and associated solid phase geochemistry vary significantly with season. This has important ramifications for seasonal changes in the bioavailability and mobility of trace elements. Without rate measurements, it is not possible to quantify the

  11. Methanotrophy potential versus methane supply by pore water diffusion in peatlands

    NASA Astrophysics Data System (ADS)

    Hornibrook, E. R. C.; Bowes, H. L.; Culbert, A.; Gallego-Sala, A. V.

    2008-06-01

    Low affinity methanotrophic bacteria consume a significant quantity of methane in wetland soils in the vicinity of plant roots and at the oxic-anoxic interface. Estimates of the efficiency of methanotrophy in peat soils vary widely in part because of differences in approaches employed to quantify methane cycling. High resolution profiles of dissolved methane abundance measured during the summer of 2003 were used to quantify rates of upward methane flux in four peatlands situated in Wales, UK. Aerobic incubations of peat from a minerotrophic and an ombrogenous mire were used to determine depth distributions of kinetic parameters associated with methane oxidation. The capacity for methanotrophy in a 3 cm thick zone immediately beneath the depth of nil methane abundance in pore water was significantly greater than the rate of upward diffusion of methane in all four peatlands. Rates of methane diffusion in pore water at the minerotrophic peatlands were small (<10%) compared to surface emissions during June to August. The proportions were notably greater in the ombrogenous bogs because of their typically low methane emission rates. Methanotrophy appears to consume entirely methane transported by pore water diffusion in the four peatlands with the exception of 4 of the 33 gas profiles sampled. Flux rates to the atmosphere regardless are high because of gas transport through vascular flora, in particular, at the minerotrophic sites. Cumulative rainfall amount 3-days prior to sampling correlated well with the distance between the water table level and the depth of 0 μmol l-1 methane, indicating that precipitation events can impact methane distributions in pore water. Further work is needed to characterise the kinetics of methane oxidation spatially and temporally in different wetland types in order to determine generalized relationships for methanotrophy in peatlands that can be incorporated into process-based models of methane cycling in peat soils.

  12. Penetration Behavior of a Water Droplet into a Cylindrical Hydrophobic Pore.

    PubMed

    Nonomura, Yoshimune; Tanaka, Tomoya; Mayama, Hiroyuki

    2016-06-28

    Understanding the dynamics with which a water droplet penetrates a pore is important because of its relationship with transfer phenomena in plants and animals. Using a high-speed camera, we observe the penetration processes of a water droplet into a cylindrical pore on a silicone substrate. The force on the water droplet is generated by dropping the substrate plus water droplet from a height of several centimeters onto an acrylic resin substrate. The penetration characteristics depend on pore size Dp, height of release of a drop h, and the viscosity of the droplet liquid and are classified into the following patterns: spreading, penetration, and breaking. During the process of relaxation to the steady state, various interesting deformation or oscillation phenomena occur. Based on high-speed images, we estimate the interfacial energy ΔG during the intermediate states and find an energy barrier ΔG = 1 × 10(-7) J when Dp = 1.0 mm and h = 15 mm for the spreading pattern and ΔG = 0.7 × 10(-7) J when Dp = 1.0 mm and h = 10 mm for the penetration pattern. Finally, based on a theoretical model considering the driving and suppression factors, we explain the experimentally obtained phase diagram including the separation, penetration, and breaking patterns. PMID:27249319

  13. Evaporative Evolution of Carbonate-Rich Brines from Synthetic Topopah Spring Tuff Pore Water, Yucca Mountain

    SciTech Connect

    Sutton, M; Alai, M; Carroll, S A

    2004-04-14

    The evaporation of a range of synthetic pore water solutions representative of the potential high-level-nuclear-waste repository at Yucca Mountain, NV is being investigated. The motivation of this work is to understand and predict the range of brine compositions that may contact the waste containers from evaporation of pore waters, because these brines could form corrosive thin films on the containers and impact their long-term integrity. A relatively complex synthetic Topopah Spring Tuff pore water was progressively concentrated by evaporation in a closed vessel, heated to 95 C in a series of sequential experiments. Periodic samples of the evaporating solution were taken to determine the evolving water chemistry. According to chemical divide theory at 25 C and 95 C our starting solution should evolve towards a high pH carbonate brine. Results at 95 C show that this solution evolves towards a complex brine that contains about 99 mol% Na{sup +} for the cations, and 71 mol% Cl{sup -}, 18 mol% {Sigma}CO{sub 2}(aq), 9 mol%SO{sub 4}{sup 2-} for the anions. Initial modeling of the evaporating solution indicates precipitation of aragonite, halite, silica, sulfate and fluoride phases. The experiments have been used to benchmark the use of the EQ3/6 geochemical code in predicting the evolution of carbonate-rich brines during evaporation.

  14. Estimating methane production rates in bogs and landfills by deuterium enrichment of pore water

    USGS Publications Warehouse

    Siegel, D.I.; Chanton, J.P.; Glaser, P.H.; Chasar, L.S.; Rosenberry, D.O.

    2001-01-01

    Raised bogs and municipal waste landfills harbor large populations of methanogens within their domed deposits of anoxic organic matter. Although the methane emissions from these sites have been estimated by various methods, limited data exist on the activity of the methanogens at depth. We therefore analyzed the stable isotopic signature of the pore waters in two raised bogs from northern Minnesota to identify depth intervals in the peat profile where methanogenic metabolism occurs. Methanogenesis enriched the deuterium (2H) content of the deep peat pore waters by as much as +11% (Vienna Standard Mean Sea Water), which compares to a much greater enrichment factor of +70% in leachate from New York City's Fresh Kills landfill. The bog pore waters were isotopically dated by tritium (3H) to be about 35 years old at 1.5 m depth, whereas the landfill leachate was estimated as ~ 17 years old from Darcy flow calculations. According to an isotopic mass balance the observed deuterium enrichment indicates that about 1.2 g of CH4m-3 d-1 were produced within the deeper peat, compared to about 2.8 g CH4 m-3 d-1 in the landfill. The values for methane production in the bog peat are substantially higher than the flux rates measured at the surface of the bogs or at the landfill, indicating that deeper methane production may be much higher than was previously assumed.

  15. Inelastic neutron scattering and molecular simulation of the dynamics of interlayer water in smectite clay minerals

    DOE PAGESBeta

    Cygan, Randall T.; Daemen, Luke L.; Ilgen, Anastasia G.; Krumhansl, James L.; Nenoff, Tina M.

    2015-11-16

    The study of mineral–water interfaces is of great importance to a variety of applications including oil and gas extraction, gas subsurface storage, environmental contaminant treatment, and nuclear waste repositories. Understanding the fundamentals of that interface is key to the success of those applications. Confinement of water in the interlayer of smectite clay minerals provides a unique environment to examine the interactions among water molecules, interlayer cations, and clay mineral surfaces. Smectite minerals are characterized by a relatively low layer charge that allows the clay to swell with increasing water content. Montmorillonite and beidellite varieties of smectite were investigated to comparemore » the impact of the location of layer charge on the interlayer structure and dynamics. Inelastic neutron scattering of hydrated and dehydrated cation-exchanged smectites was used to probe the dynamics of the interlayer water (200–900 cm–1 spectral region) and identify the shift in the librational edge as a function of the interlayer cation. Molecular dynamics simulations of equivalent phases and power spectra, derived from the resulting molecular trajectories, indicate a general shift in the librational behavior with interlayer cation that is generally consistent with the neutron scattering results for the monolayer hydrates. Both neutron scattering and power spectra exhibit librational structures affected by the location of layer charge and by the charge of the interlayer cation. Furthermore, divalent cations (Ba2+ and Mg2+) characterized by large hydration enthalpies typically exhibit multiple broad librational peaks compared to monovalent cations (Cs+ and Na+), which have relatively small hydration enthalpies.« less

  16. Inelastic neutron scattering and molecular simulation of the dynamics of interlayer water in smectite clay minerals

    SciTech Connect

    Cygan, Randall T.; Daemen, Luke L.; Ilgen, Anastasia G.; Krumhansl, James L.; Nenoff, Tina M.

    2015-11-16

    The study of mineral–water interfaces is of great importance to a variety of applications including oil and gas extraction, gas subsurface storage, environmental contaminant treatment, and nuclear waste repositories. Understanding the fundamentals of that interface is key to the success of those applications. Confinement of water in the interlayer of smectite clay minerals provides a unique environment to examine the interactions among water molecules, interlayer cations, and clay mineral surfaces. Smectite minerals are characterized by a relatively low layer charge that allows the clay to swell with increasing water content. Montmorillonite and beidellite varieties of smectite were investigated to compare the impact of the location of layer charge on the interlayer structure and dynamics. Inelastic neutron scattering of hydrated and dehydrated cation-exchanged smectites was used to probe the dynamics of the interlayer water (200–900 cm–1 spectral region) and identify the shift in the librational edge as a function of the interlayer cation. Molecular dynamics simulations of equivalent phases and power spectra, derived from the resulting molecular trajectories, indicate a general shift in the librational behavior with interlayer cation that is generally consistent with the neutron scattering results for the monolayer hydrates. Both neutron scattering and power spectra exhibit librational structures affected by the location of layer charge and by the charge of the interlayer cation. Furthermore, divalent cations (Ba2+ and Mg2+) characterized by large hydration enthalpies typically exhibit multiple broad librational peaks compared to monovalent cations (Cs+ and Na+), which have relatively small hydration enthalpies.

  17. Water dynamics in hectorite clays: influence of temperature studied by coupling neutron spin echo and molecular dynamics.

    PubMed

    Marry, Virginie; Dubois, Emmanuelle; Malikova, Natalie; Durand-Vidal, Serge; Longeville, Stéphane; Breu, Josef

    2011-04-01

    Within the wider context of water behavior in soils, and with a particular emphasis on clays surrounding underground radioactive waste packages, we present here the translational dynamics of water in clays in low hydrated states as studied by coupling molecular dynamics (MD) simulations and quasielastic neutron scattering experiments by neutron spin echo (NSE). A natural montmorillonite clay of interest is modeled by a synthetic clay which allows us to understand the determining parameters from MD simulations by comparison with the experimental values. We focus on temperatures between 300 and 350 K, i.e., the range relevant to the highlighted application. The activation energy Ea experimentally determined is 6.6 kJ/mol higher than that for bulk water. Simulations are in good agreement with experiments for the relevant set of conditions, and they give more insight into the origin of the observed dynamics. PMID:21381672

  18. Strontium isotope evolution of pore water and calcite in the Topopah Spring Tuff, Yucca Mountain, Nevada

    SciTech Connect

    Marshall, Brian D.; Futa, Kiyoto

    2001-04-29

    Pore water in the Topopah Spring Tuff has a narrow range of {delta}{sup 87}Sr values that can be calculated from the {delta}{sup 87}Sr values of the rock considering advection through and reaction with the overlying nonwelded tuffs of the PTn. This model can be extended to estimate the variation of {delta}{sup 87}Sr in the pore water through time; this approximates the variation of {delta}{sup 87}Sr measured in calcite fracture coatings. In samples of calcite where no silica can be dated by other methods, strontium isotope data may be the only method to determine ages. In addition, other Sr-bearing minerals in the calcite and opal coatings, such as fluorite, may be dated using the same model.

  19. Major Cation, Carbon System and Trace Element Chemistry in Pore Waters from a Depth Transect of Cores on the Iberian Margin: Implications for Paleoproxies.

    NASA Astrophysics Data System (ADS)

    Greaves, M.; Elderfield, H.; Hodell, D. A.; Skinner, L. C.; Sevilgen, D.; Grauel, A. L.; de la Fuente, M.; Misra, S.

    2014-12-01

    A significant body of work exists on the chemistry of pore waters from DSDP and ODP drilling cores (e.g. Gieskes 1975; Sayles 1981) showing large gradients in sea salt cations and anions interpreted in terms of diagenetic reactions such as the formation of Mg-rich clays and dolomite formation (Higgins and Schrag, 2010). Another class of diagenetic reactions involves the breakdown of organic matter and trace element behaviour (Froelich et al., 1979). The translation of chemical gradients into fluxes requires estimates of pore water chemistry across the sea water - sediment surface boundary. Additionally, the use of the chemistry of benthic foraminiferal calcite for seawater paleochemistry requires estimation of the chemistry of pore waters which may differ from that of bottom seawater because of diagenetic reactions. In this work we have collected multi core samples from 10 core sites on cruise RRS James Cook JC089 on the southwest Iberian continental margin. Pore waters were extracted from the core surface and at 1 cm depth intervals down core (typically to ~40 cm depth) using Rhizon samplers and analysed for Alkalinity, DIC, ∂13C and Na, K, Mg, Ca, Li, Mn, Fe, Ba, B, Sr by atomic emission spectrophotometry as well as O2 penetration and pH by microelectrodes. This has allowed us to inspect chemical behavior at the bottom water - sediment interface. Some examples of results are a large gradient in ∂13C of DIC, the similarity of zero O2 penetration followed by an increase in Mn concentration and then decrease to zero, the similarity of Li to Mn and, in contrast to much DSDP/ODP work, Ca2+ and Mg2+both decrease with depth in pore waters near the sediment surface. References: Gieskes J.M. Annu. Rev. Earth Planet. Sci. 3, 433 (1975). Sayles F. L. Geochim. Cosmochim. Acta45, 1061 (1981). Higgins J.A. and D.P. Schrag. Geochim. Cosmochim. Acta.74, 5039 (2010). Froelich, P.N., et al., Geochim. Cosmochim. Acta. 43, 1075 (1979).

  20. Mercury cycling in stream ecosystems. 2. Benthic methylmercury production and bed sediment - Pore water partitioning

    USGS Publications Warehouse

    Marvin-DiPasquale, M.; Lutz, M.A.; Brigham, M.E.; Krabbenhoft, D.P.; Aiken, G.R.; Orem, W.H.; Hall, B.D.

    2009-01-01

    Mercury speciation, controls on methylmercury (MeHg) production, and bed sediment - pore water partitioning of total Hg (THg) and MeHg were examined in bed sediment from eight geochemically diverse streams where atmospheric deposition was the predominant Hg input. Across all streams, sediment THg concentrations were best described as a combined function of sediment percent fines (%fines; particles < 63 ??m) and organic content. MeHg concentrations were best described as a combined function of organic content and the activity of the Hg(II)-methylating microbial community and were comparable to MeHg concentrations in streams with Hg inputs from industrial and mining sources. Whole sediment tin-reducible inorganic reactive Hg (Hg(II)R) was used as a proxy measure for the Hg(II) pool available for microbial methylation. In conjunction with radiotracer-derived rate constants of 203Hg(II) methylation, Hg(II)R was used to calculate MeHg production potential rates and to explain the spatial variability in MeHg concentration. The %Hg(II)R (of THg) was low (2.1 ?? 5.7%) and was inversely related to both microbial sulfate reduction rates and sediment total reduced sulfur concentration. While sediment THg concentrations were higher in urban streams, %MeHg and %Hg(II)R were higher in nonurban streams. Sediment pore water distribution coefficients (log Kd's) for both THg and MeHg were inversely related to the log-transformed ratio of pore water dissolved organic carbon (DOC) to bed sediment %fines. The stream with the highest drainage basin wetland density also had the highest pore water DOC ?? 2009 American Chemical Society.

  1. Mechanisms associated with the high adsorption of dibenzo-p-dioxin from water by smectite clays.

    PubMed

    Liu, Cun; Li, Hui; Teppen, Brian J; Johnston, Cliff T; Boyd, Stephen A

    2009-04-15

    Clay minerals may be an important unrecognized sorptive phase for dioxins in soils and clay deposits. Smectites, especially Cs-saponite, effectively adsorbed dibenzo-p-dioxin (DD) from water, reaching 0.8% (wt/wt). Adsorption was promoted by exchangeable cations with low hydration energies, and negative charge in the smectite arising from the tetrahedral siloxane sheets. X-ray diffraction measurements revealed that as DD loading increased to > or =8000 mg/kg the clay basal spacing increased abruptly from 12.3 to 15.2 A demonstrating DD intercalation. The 12.3 A spacing provides an interlayer distance that closely matches the molecular thickness of DD. In this configuration DD is essentially dehydrated as it interacts with the opposing hydrophobic siloxane sheets and with coplanar Cs+ via one of the dioxin ring oxygens. Ab initio calculations suggest that geometrical structures form at higher loadings in which intercalated DD molecules adopt a butterfly geometry sandwiched between dehydrated interlayer Cs+ and the siloxane surface, consistent with the 15.2 A spacing, wherein Cs+ interacts with dioxin ring oxygens and benzene ring pi-electrons. Fourier transformation infrared measurements confirm that adsorbed DD is present in orientations that are not parallel with the interlayer planar siloxane surfaces of smectite. PMID:19475949

  2. NSWE. BAS: BASIC program for determining effective water saturation in shaly sands using percentage of clay-bound water-filled microporosity

    SciTech Connect

    Asquith, G.B. )

    1990-06-01

    Reservoirs with microporosity present significant exploration opportunities as well as new exploitation potential. In sandstones with clay or shale, clay microporosity may distort a number of log-calculated parameters that form the basis for estimating producible reserves. Since reservoirs with microporosity often appear water-productive, the author concludes that producible hydrocarbons in such zones often may be overlooked. Standard formation evaluation approaches that correct for the presence of shale or clay are hampered by the lack of accurate methods for determining volume of clay (Vcl), total shale porosity ({phi}tsh), bound water resistivity (Rb), and resistivity of dispersed clay (Rcl) or by the lack of laboratory-determined values for cation exchange capacity (CEC). In addition some shaly sand corrections (Fertl and Dispersed Clay) can be unreliable in shaly sands with large formation water resistivities (Rw). This paper proposes a microporosity approach which does not require values for Vcl, {phi}tsh, Rcl, Rb, or CEC, and is based on the observation that CEC is related to specific surface area of clays, and specific surface area is related to the amount of clay-bound water-filled microporosity. Without the limitations imposed on other approaches the microporosity method has broad application.

  3. The marine geochemistry of actinium-227: Evidence for its migration through sediment pore water

    SciTech Connect

    Nozaki, Yoshiyuki; Yamada, Masatoshi ); Nikaido, Hirofumi )

    1990-10-01

    {sup 227}Ac with a half life of 21.8 years has a potential utility as a tracer of deep water circulation and mixing studies on time scales less than 100 years. Here the authors present the first measurement of {sup 227}Ac profile in the pore water of Northwest Pacific deep-sea sediment and in the {approximately}10,000 m long water column of Izu-Ogasawara Trench. The results clearly show that {sup 227}Ac is supplied from the sediment to the overlying water through migration in the pore water. The model calculation indicates that the molecular diffusion alone through sediment porewater can support only a half of the standing crop of excess {sup 227}Ac in the water column and the enhanced supply of {sup 227}Ac by particle mixing is necessary to account for the remainder. Thus, bioturbation in the deep sea plays an important role in controlling the flux of some short-lived radionuclides such as {sup 227}Ac and {sup 228}Ra across the sediment-water interface.

  4. Sulfide controls on mercury speciation and bioavailability to methylating bacteria in sediment pore waters

    SciTech Connect

    Benoit, J.M.; Gilmour, C.C.; Heyes, A.; Mason, R.P.

    1999-03-15

    A chemical equilibrium model for Hg complexation in sediments with sulfidic pore waters is presented. The purpose of the model was to explain observed relationships between pore water sulfide, dissolved inorganic Hg (Hg{sub D}), and bulk methylmercury (MeHg) in surficial sediments of two biogeochemically different ecosystems, the Florida Everglades and Patuxent River, MD. The model was constructed to test the hypothesis that the availability of Hg for methylation in sediments is a function of the concentration of neutral dissolved Hg complexes rather than Hg{sup 2+} or total Hg{sub D}. The model included interaction of mercury with solids containing one or two sulfide groups, and it was able to reproduce observed Hg{sub D} and bulk MeHg trends in the two ecosystems. The model is consistent with HgS{sup 0} as the dominant neutral Hg complex and the form of Hg accumulated by methylating bacteria in sulfidic pore waters. The model-estimated decline in HgS{sup 0} with increasing sulfide was consistent with the observed decline in bulk sediments MeHg. Since bacterial Hg uptake rate is one of the factors affecting methylation rate, Hg complexation models such as the one presented are helpful in understanding the factors that control MeHg production and accumulation in aquatic ecosystems.

  5. Characteristics of fluoride in pore-water at accidental hydrofluoric acid spillage site, Gumi, Korea

    NASA Astrophysics Data System (ADS)

    Kwon, E. H.; Lee, H. A.; Lee, J.; Kim, D.; Lee, S.; Yoon, H. O.

    2015-12-01

    A leakage accident of hydrofluoric acid (HF) occurred in Gumi, South Korea at Sep. 2012. The study site is located in the borderline between a large-scale industrial complex and a rural area. The HF plume was made immediately, and moved toward the rural area through air. After the accident, 212 ha of farm land were influenced and most of crops were withered. To recover the soil, CaO was applied after six months. Although several studies have done to estimate the extension and movement of HF plume in the air and to assess the impact on human health or plant after the incident, the long-term fate of fluoride (F) in the affected soils is not identified clearly. Thus, this study aimed to understand the behavior of F in the soil after HF releasing from accident site through chemical analysis and geochemical modeling. Within the radius of 1 km of accident site, 16 pore-water and soil samples were collected. The semi-quantitative soil composition (i.e., Al, Ca, Fe, K, Mg, Mn, Na, P, Si, Ti), total F, total P, OM contents in soil, and soil pH have already been measured, and pore-water compositions are also identified. From these experimental and modeling data, we could be evaluate if impact of accident exists until now, and also could be select and identify existing form of fluoride in soil and pore-water.

  6. Development of Layered Sediment Structure and its Effects on Pore Water Transport and Hyporheic Exchange

    SciTech Connect

    Packman, Aaron I.; Marion, Andrea; Zaramella, Mattia; Chen, Cheng; Gaillard, Jean-François; Keane, Denis T.

    2008-04-15

    Hyporheic exchange is known to provide an important control on nutrient and contaminant fluxes across the stream-subsurface interface. Similar processes also mediate interfacial transport in other permeable sediments. Recent research has focused on understanding the mechanics of these exchange processes and improving estimation of exchange rates in natural systems. While the structure of sediment beds obviously influences pore water flow rates and patterns, little is known about the interplay of typical sedimentary structures, hyporheic exchange, and other transport processes in fluvial/alluvial sediments. Here we discuss several processes that contribute to local-scale sediment heterogeneity and present results that illustrate the interaction of overlying flow conditions, the development of sediment structure, pore water transport, and stream-subsurface exchange. Layered structures are shown to develop at several scales within sediment beds. Surface sampling is used to analyze the development of an armor layer in a sand-and-gravel bed, while innovative synchrotron-based X-ray microtomography is used to observe patterns of grain sorting within sand bedforms. We show that layered bed structures involving coarsening of the bed surface increase interfacial solute flux but produce an effective anisotropy that favors horizontal pore water transport while limiting vertical penetration.

  7. Ecological impacts of lead mining on Ozark streams: Toxicity of sediment and pore water

    USGS Publications Warehouse

    Besser, J.M.; Brumbaugh, W.G.; Allert, A.L.; Poulton, B.C.; Schmitt, C.J.; Ingersoll, C.G.

    2009-01-01

    We studied the toxicity of sediments downstream of lead-zinc mining areas in southeast Missouri, using chronic sediment toxicity tests with the amphipod, Hyalella azteca, and pore-water toxicity tests with the daphnid, Ceriodaphnia dubia. Tests conducted in 2002 documented reduced survival of amphipods in stream sediments collected near mining areas and reduced survival and reproduction of daphnids in most pore waters tested. Additional amphipod tests conducted in 2004 documented significant toxic effects of sediments from three streams downstream of mining areas: Strother Creek, West Fork Black River, and Bee Fork. Greatest toxicity occurred in sediments from a 6-km reach of upper Strother Creek, but significant toxic effects occurred in sediments collected at least 14 km downstream of mining in all three watersheds. Toxic effects were significantly correlated with metal concentrations (nickel, zinc, cadmium, and lead) in sediments and pore waters and were generally consistent with predictions of metal toxicity risks based on sediment quality guidelines, although ammonia and manganese may also have contributed to toxicity at a few sites. Responses of amphipods in sediment toxicity tests were significantly correlated with characteristics of benthic invertebrate communities in study streams. These results indicate that toxicity of metals associated with sediments contributes to adverse ecological effects in streams draining the Viburnum Trend mining district.

  8. Mapping of accumulated nitrogen in the sediment pore water of a eutrophic lake in Iowa, USA

    USGS Publications Warehouse

    Iqbal, M.Z.; Fields, C.L.

    2009-01-01

    A large pool of nitrogen in the sediment pore fluid of a eutrophic lake in Iowa, USA, was mapped in this study. Previously, the lake had supported fishing and boating, but today it no longer supports its designated uses as a recreational water body. In the top 5 cm of the lake bottom, the pore water nitrogen ranges between 3.1 and 1,250 ??g/cm3 of sediments, with an average of 160.3 ??g/cm3. Vertically, nitrate concentrations were measured as 153 ??g/cm3 at 0-10 cm, 162 ??g/cm3 at 10-20 cm, and 32 ??g/cm3 at 20-30 cm. Nitrate mass distribution was quantified as 3.67 ?? 103 kg (65%) in the bottom sediments, 172 kg (3%) in suspended particulates, and 1.83 ?? 103 kg (32%) in the dissolved phase. Soil runoff nutrients arrive at the lake from the heavily fertilized lands in the watershed. Upon sedimentation, a large mass of nitrogen desorbs from mineral particles to the relatively immobile pore fluid. Under favorable conditions, this nitrogen diffuses back into the water column, thereby dramatically limiting the lake's capability to process incoming nutrients from farmlands. Consequently, a condition of oxygen deficiency disrupts the post-season biological activities in the lake. ?? 2008 Springer-Verlag.

  9. Pore Water Extraction Test Near 241-SX Tank Farm at the Hanford Site, Washington, USA

    SciTech Connect

    Eberlein, Susan J.; Parker, Danny L.; Tabor, Cynthia L.; Holm, Melissa J.

    2013-11-11

    A proof-of-principle test is underway near the Hanford Site 241-SX Tank Farm. The test will evaluate a potential remediation technology that will use tank farm-deployable equipment to remove contaminated pore water from vadose zone soils. The test system was designed and built to address the constraints of working within a tank farm. Due to radioactive soil contamination and limitations in drilling near tanks, small-diameter direct push drilling techniques applicable to tank farms are being utilized for well placement. To address space and weight limitations in working around tanks and obstacles within tank farms, the above ground portions of the test system have been constructed to allow deployment flexibility. The test system utilizes low vacuum over a sealed well screen to establish flow into an extraction well. Extracted pore water is collected in a well sump,and then pumped to the surface using a small-diameter bladder pump.If pore water extraction using this system can be successfully demonstrated, it may be possible to target local contamination in the vadose zone around underground storage tanks. It is anticipated that the results of this proof-of-principle test will support future decision making regarding interim and final actions for soil contamination within the tank farms.

  10. Diffusive release of uranium from contaminated sediments into capillary fringe pore water

    SciTech Connect

    Rod, Kenton A.; Wellman, Dawn M.; Flury, Markus; Pierce, Eric M.; Harsh, James B.

    2012-10-01

    Despite remediation efforts at the former nuclear weapons facility at the Hanford site (Washington State), leaching of uranium (U) from contaminated sediments to the ground water persists at the Hanford 300 Area. Flooding of contaminated capillary fringe sediments due to seasonal changes in the Columbia River stage has been identified as a reason of continued U supply to ground water. We investigated the release of U from Hanford capillary fringe sediments to pore water. Contaminated Hanford sediments were packed into reservoirs of centrifugal filter devices and saturated with Columbia River water for 3 to 84 days at varying solution-to-solid ratios (1:3, 1:1, 5:1, 10:1, 25:1 mL:g). After specified times, samples were centrifuged to a gravimetric water content of 0.11 ± 0.06 g g-1. Within the first three days, there was an initial rapid release of 6-9% of total U from the sediments into the pore water, independent of the solution-to-solid ratio. After 14 days of reaction, however, the experiments with the narrowest solution-to-solid ratios (1:3 and 1:1 mL:g) showed a decline in dissolved U concentrations. The removal of U from the solution phase was accompanied by removal of Ca and HCO3-. Geochemist workbench simulations, conducted using measured solution concentrations from experiments, indicated that calcite could precipitate in the 1:3 solution-to-solid ratio experiment. After the rapid initial release in the first three days for the 5:1, 10:1, and 25:1 solution-to-solid ratio experiments, there was sustained release of U into the pore water. Up to 22% of total U was released on day 84 for the 25:1 solution-to-solid ratio reaction. This sustained release of U from the sediments had diffusion-limited kinetics.

  11. Burial diagenesis, hydraulic conductivity and pore water chemistry in the Marshall Sandstone regional aquifer, Michigan Basin

    SciTech Connect

    Zacharias, K.F.; Sibley, D.F.; Long, D.T. . Dept. of Geological Sciences)

    1992-01-01

    The Marshall Sandstone (MS) is a regional aquifer and local natural-gas reservoir in the Michigan basin. Hydraulic conductivities measured of sandstone cores range from 10[sup [minus]4] to 10[sup [minus]9] cm/s. Low hydraulic conductivities were measured in samples with abundant kaolinite, chlorite and illite; quartz and carbonate cemented sandstones have consistently higher values. Dissolved solids concentrations of the water from the MS range from 260 to 418, 169 mg/l. Geochemical modeling of pore water elemental composition and stable isotopes indicates mixing between meteoric water and evaporated seawater. The authors analyzed cements precipitated in the MS to determine whether or not they reflect this mixture of brine and meteoric water. Chlorite is a pre- to syn-compaction cement. Dolomite-ankerite is a syn- to post-compaction cement. Kaolinite and illite are post-compaction cements. Kaolinite overlies and therefore post-dates the carbonate cements. Illite overlies and therefore post-dates the kaolinite. Cement stable isotopes and a mineral paragenesis are consistent with carbonate and phyllosilicate precipitation during burial diagenesis at approximately 50--120 C in brine similar to the brine in the saline portion of the aquifer today. Cements occur throughout the basin, regardless of present pore water composition. Also, secondary porosity due to feldspar and carbonate dissolution occurs throughout the basin. Solid phase analyses and pore water analyses indicate that mixing of meteoric water and brine may have caused some carbonate cement dissolution but otherwise has not influenced mineral paragenesis or hydraulic properties.

  12. Estimating flow and transport parameters in the unsaturated zone with pore water stable isotopes

    NASA Astrophysics Data System (ADS)

    Sprenger, M.; Volkmann, T. H. M.; Blume, T.; Weiler, M.

    2015-06-01

    Determining the soil hydraulic properties is a prerequisite to physically model transient water flow and solute transport in the vadose zone. Estimating these properties by inverse modelling techniques has become more common within the last 2 decades. While these inverse approaches usually fit simulations to hydrometric data, we expanded the methodology by using independent information about the stable isotope composition of the soil pore water depth profile as a single or additional optimization target. To demonstrate the potential and limits of this approach, we compared the results of three inverse modelling strategies where the fitting targets were (a) pore water isotope concentrations, (b) a combination of pore water isotope concentrations and soil moisture time series, and (c) a two-step approach using first soil moisture data to determine water flow parameters and then the pore water stable isotope concentrations to estimate the solute transport parameters. The analyses were conducted at three study sites with different soil properties and vegetation. The transient unsaturated water flow was simulated by solving the Richards equation numerically with the finite-element code of HYDRUS-1D. The transport of deuterium was simulated with the advection-dispersion equation, and a modified version of HYDRUS was used, allowing deuterium loss during evaporation. The Mualem-van Genuchten and the longitudinal dispersivity parameters were determined for two major soil horizons at each site. The results show that approach (a), using only the pore water isotope content, cannot substitute hydrometric information to derive parameter sets that reflect the observed soil moisture dynamics but gives comparable results when the parameter space is constrained by pedotransfer functions. Approaches (b) and (c), using both the isotope profiles and the soil moisture time series, resulted in good simulation results with regard to the Kling-Gupta efficiency and good parameter

  13. Elucidating the mechanical effects of pore water pressure increase on the stability of unsaturated soil slopes

    NASA Astrophysics Data System (ADS)

    Buscarnera, G.

    2012-12-01

    The increase of the pore water pressure due to rain infiltration can be a dominant component in the activation of slope failures. This paper shows an application of the theory of material stability to the triggering analysis of this important class of natural hazards. The goal is to identify the mechanisms through which the process of suction removal promotes the initiation of mechanical instabilities. The interplay between increase in pore water pressure, and failure mechanisms is investigated at material point level. In order to account for multiple failure mechanisms, the second-order work criterion is used and different stability indices are devised. The paper shows that the theory of material stability can assess the risk of shear failure and static liquefaction in both saturated and unsaturated contexts. It is shown that the combined use of an enhanced definition of second-order work for unsaturated porous media and a hydro-mechanical constitutive framework enables to retrieve bifurcation conditions for water-infiltration processes in unsaturated deposits. This finding discloses the importance of the coupling terms that incorporate the interaction between the solid skeleton and the pore fluids. As a consequence, these theoretical results suggest that some material properties that are not directly associated with the shearing resistance (e.g., the potential for wetting compaction) can play an important role in the initiation of slope failures. According to the proposed interpretation, the process of pore pressure increase can be understood as a trigger of uncontrolled strains, which at material point level are reflected by the onset of bifurcation conditions.

  14. Distribution of Dissolved Hydrogen in Pore Water at Cold Seep Site

    NASA Astrophysics Data System (ADS)

    Toki, T.; Maegawa, K.; Tsunogai, U.; Ashi, J.; Kinoshita, M.; Gamo, T.

    2005-12-01

    White patches have been observed at the Oomine Ridge (33°7.32'N, 136°28.75'E) on the Nankai accretionary prism. During the KY04-11 cruise (2004. 9. 5 ~ 2004. 10. 2) of the R/V Kaiyo (JAMSTEC), a sediment sample was obtained with a piston corer from the seafloor at the Oomine Ridge. The recovered sediment was 268.5 cm long. Subsampled sediments for gas analysis were taken and were treated for the extraction of dissolved gas in the pore water. The gas samples were measured for CH4, δ13C(CH4), CO2, δ13C(CO2), and H2. The other subsamples for pore water analysis were taken from the residual sediment in the corer. The retrieved pore water samples were analyzed for NH4+, Cl-, SO42-, CH4, δ13C(CH4), CO2, δ13C(CO2), δ18O(H2O), and δD(H2O). Chloride concentrations and both isotopic signatures (δ18O and δD) of the pore water decreased with depth, suggesting that the pore water in this site was affected by seeping fluid characterized by Cl, δ18O, and δD-depleted. Sulfate concentrations rapidly decreased within 2 m, indicating that sulfate consumption occurred in the surface sediments and/or sulfate-free fluid flowing upward. Ammonium concentrations increased with depth even after sulfate was completely reduced, which indicates that there are processes of organic matter decomposition that are capable of producing ammonium after sulfate reduction is complete. Methane concentrations showed concave-upward depth profile and carbon isotopic compositions of methane were as low as _E0 ‰PDB, indicating that methane is derived from microbial production in sediments. We observed a significant H2 peak reaching 500 μmol/kg at the deepest sample, which would be produced as an intermediate during processes of organic matter decomposition in oxide-free environments.

  15. Data Qualification Report: Pore Water Data for Use on the Yucca Mountain Project

    SciTech Connect

    H. Miller; R. Monks; C. Warren; W. Wowak

    2000-06-09

    Pore water data associated with Data Tracking Number (DTN) No.LL990702804244.100 are referenced in the Analysis and Model Reports (AMRs) prepared to support the Site Recommendation in determining the suitability of the Yucca Mountain, Nevada as a repository for high-level nuclear waste. It has been determined, in accordance with procedure AP-3.15Q Rev. 1, ICN 1, ''Managing Technical Product Inputs'', Attachment 6 , that the DTN-referenced data are used in AMRs that provide a direct calculation of ''Principal Factors'' for the Post-closure Safety Case or Potentially Disruptive Processes or Events. Therefore, in accordance with the requirements of procedure AP-SIII.2Q, Rev 0, ICN 2, ''Qualification of Unqualified Data and the Documentation of Rationale for Accepted Data'', Section 5.3.1 .a, a Data Qualification Report has been prepared for submittal to the Assistant Manager, Office of Project Execution for concurrence. This report summarizes the findings of the Data Qualification Team assembled to evaluate unqualified ''pore water data'' represented by DTN No. LL990702804244.100. This DTN is currently used in the following AMRs: Drift-Scale Coupled Processes (DST and THC Seepage) Models (CRWMS M&O 2000a), Environment of the Surfaces of the Drip Shield and Waste Package Outer Barrier (CRWMS M&O 2000b), and Engineered Barrier System: Physical and Chemical Environment Model (CRWMS M&O 2000c). Mineral composition of pore water submitted to the Technical Data Management System (TDMS) using the subject DTN were acquired data from the analysis pore water samples sent to Lawrence Livermore National Laboratory's (LLNL) by UFA Ventures, Inc. and analyzed by LLNL's Analytical Sciences/Analytical and Nuclear Chemistry Division (ASD). The purpose and scope of the AMRs that reference the subject DTN and the potential application of pore water data is described below. These AMRs use only that data associated with the specific samples: ESF-HD-PERM-1, ESF-HD-PERM-2, and ESF-HD-PERM-3

  16. Deciphering the science behind electrocoagulation to remove suspended clay particles from water.

    PubMed

    Holt, P K; Barton, G W; Mitchell, C A

    2004-01-01

    Electrocoagulation removes pollutant material from water by a combination of coagulant delivered from a sacrificial aluminium anode and hydrogen bubbles evolved at an inert cathode. Rates of clay particle flotation and settling were experimentally determined in a 7 L batch reactor over a range of currents (0.25-2.0 A) and pollutant loadings (0.1-1.7 g/L). Sedimentation and flotation are the dominant removal mechanism at low and high currents, respectively. This shift in separation mode can be explained by analysing the reactor in terms of a published dissolved air flotation model. PMID:15686019

  17. Deep-water fossorial shrimps from the Oligocene Kiscell Clay of Hungary: Taxonomy and palaeoecology

    PubMed Central

    HYŽNÝ, MATÚŠ; DULAI, ALFRÉD

    2015-01-01

    We describe deep-water ghost shrimp assemblages from the otherwise well known Oligocene Kiscell Clay in Hungary. The described fossorial shrimps (Decapoda: Callianassidae and Ctenochelidae) include: Ctenocheles rupeliensis (younger synonym Callianassa nuda) and Lepidophthalmus crateriferus (younger synonym Callianassa brevimanus). The fossil material of the former species is assigned to Ctenocheles based on the morphology of the major cheliped, particularly the pectinate fingers, bulbous propodus, cup-shaped carpus and elongated merus. Lepidophthalmus crateriferus from the Oligocene of Hungary is the first unequivocal fossil record of the genus, which is distinguished in the fossil record on the basis of the presence of a meral blade and meral hook on the major cheliped. Lepidophthalmus is today known exclusively from shallow-water environments. The finding of a deep-water fossil representative of Lepidophthalmus therefore appears to be a reverse of the common pattern of groups shifting environments from onshore to offshore over geological time, as seen in many taxa. The presence of Lepidophthalmus crateriferus comb. nov. in the Kiscell Clay therefore suggests different ecological requirements for at least some populations of this genus in the geological past. PMID:25908897

  18. Confined water in controlled pore glass CPG-10-120 studied by positron annihilation lifetime spectroscopy and differential scanning calorimetry

    NASA Astrophysics Data System (ADS)

    Šauša, O.; Mat'ko, I.; Illeková, E.; Macová, E.; Berek, D.

    2015-06-01

    The solidification and melting of water confined in the controlled pore glass (CPG) with average pore size 12.6 nm has been studied by differential scanning calorimetry (DSC) and positron annihilation lifetime spectroscopy (PALS). The fully-filled sample of CPG by water as well as the samples of CPG with different content of water were used. The measurements show the presence of amorphous and crystalline phases of water in this type and size of pores, freezing point depression of a confined liquid and presence of certain transitions at lower temperatures, which could be detected only for cooling regime. The localization of confined water in the partially filled pores of CPG at room temperature was studied.

  19. A USANS/SANS study of the accessibility of pores in the Barnett Shale to methane and water

    USGS Publications Warehouse

    Ruppert, Leslie F.; Sakurovs, Richard; Blach, Tomasz P.; He, Lilin; Melnichenko, Yuri B.; Mildner, David F.; Alcantar-Lopez, Leo

    2013-01-01

    Shale is an increasingly important source of natural gas in the United States. The gas is held in fine pores that need to be accessed by horizontal drilling and hydrofracturing techniques. Understanding the nature of the pores may provide clues to making gas extraction more efficient. We have investigated two Mississippian Barnett Shale samples, combining small-angle neutron scattering (SANS) and ultrasmall-angle neutron scattering (USANS) to determine the pore size distribution of the shale over the size range 10 nm to 10 μm. By adding deuterated methane (CD4) and, separately, deuterated water (D2O) to the shale, we have identified the fraction of pores that are accessible to these compounds over this size range. The total pore size distribution is essentially identical for the two samples. At pore sizes >250 nm, >85% of the pores in both samples are accessible to both CD4 and D2O. However, differences in accessibility to CD4 are observed in the smaller pore sizes (~25 nm). In one sample, CD4 penetrated the smallest pores as effectively as it did the larger ones. In the other sample, less than 70% of the smallest pores (4, but they were still largely penetrable by water, suggesting that small-scale heterogeneities in methane accessibility occur in the shale samples even though the total porosity does not differ. An additional study investigating the dependence of scattered intensity with pressure of CD4 allows for an accurate estimation of the pressure at which the scattered intensity is at a minimum. This study provides information about the composition of the material immediately surrounding the pores. Most of the accessible (open) pores in the 25 nm size range can be associated with either mineral matter or high reflectance organic material. However, a complementary scanning electron microscopy investigation shows that most of the pores in these shale samples are contained in the organic components. The neutron scattering results indicate that the pores are

  20. Accumulation of Nitrogen in the Pore Water of Anoxic Lake Sediments

    NASA Astrophysics Data System (ADS)

    Iqbal, M. Z.; Fields, C. L.

    2005-05-01

    The impact of soil runoff nitrogen on the Silver Lake of Iowa was assessed in this study. Currently, the lake cannot support its designated uses as a recreational water body. Extensive algal blooms characterize the lake in late summer, lowering the dissolved oxygen content in water (< 2.0 mg/L). The goal of this study was to map the buildup of nitrogen in the pore water of lake sediments and come up with recommendations for restoration strategies. Sediment cores were taken from 20 sites along 5 transects in the lake. In the top 5 cm of the sediments, the pore water nitrogen ranges between 1.8 and 733.1 micro-gm of nitrate per gm of sediments. The average concentration is 94 micro-g/gm. Vertically, nitrate concentrations were measured at 90 micro-g/gm at 0-10 cm, 95 micro-g/gm at 10-20 cm, and 19 micro-g/gm at 20-30 cm. The sharp decline in nitrate below the 20 cm depth in the sediment is attributed to biochemical reduction of nitrate through denitrification in relatively older, much anoxic sediments. The above results indicate that sediments in Silver Lake are heavily contaminated with N trapped in the pore water. The primary sources of N are the surrounding croplands and an active hog lot on the southeastern lakeshore. The average rate of sedimentation in the lake has been 1 cm/year in the last 32 years. Upon sedimentation, the pore water N is slowly released to the lake water, thereby dramatically limiting the lake's capability to process incoming nutrients. The mass distribution of N in the lake was estimated as 3.66 x 103 kg (65%) in bottom sediments, 172 kg (3%) in suspended particulates, and 1.83 x 103 kg (32%) in the dissolved phase. Some of the recommendations made through this study include dredging the top 25 cm of lake sediments, applying buffer strips along the lake's northern and eastern shorelines, and reducing the application of N and P-based fertilizers.

  1. Diagenetic facies controls on pore structure and rock electrical parameters in tight gas sandstone

    NASA Astrophysics Data System (ADS)

    Liu, Hongping; Zhao, Yanchao; Luo, Yang; Chen, Zhaoyou; He, Sheng

    2015-08-01

    Rock electrical parameters of tight gas sandstone show large variations in the T2 member in Dingbei Block, Ordos Basin, China. Applying the same rock electrical parameters in water saturation calculations would lead to large errors. Based on casting thin sections, x-ray diffraction, scanning electron microscopy (SEM), cathode luminescence, porosity and permeability, image analysis, and high-pressure mercury intrusion/withdrawal method, identification of the diagenetic facies are first conducted, and then their pore structure and their relationship with rock electrical parameters are investigated. Five diagenetic facies (A-E), which are identified based mainly on pore types and authigenic minerals, have different pore structure and rock electrical parameters. Conceptual models that incorporate the rock properties of each diagenetic facies have been built, before applying the electrical efficiency theory to explain the values of cementation exponent (m) and saturation exponent (n). A conventional network model, a shunt pore model, a netted pore model, and a dotted line model are utilized to mimic the intergranular pores, authigenic kaolinite intercrystal pores, carbonate-cement dissolution pores, and clay-matrix intercrystal pores, respectively. A decrease of the contents of large pores increases electrical efficiency and therefore reduces m. The saturation exponent, which depends on the distribution of water and gas, can be better understood by applying the different pore models. In the shunt and netted pore models, gas displacement starts from the larger pores and smaller pores provide alternative conduction pathways, hence sustaining electrical efficiency and decreasing n. Clay-matrix intercrystal pores are mainly micropores, since the brine in the rocks are isolated after gas displacement, reducing overall electrical efficiency and dramatically increasing the value of n in the diagenetic facies, which is dominated by clay-matrix intercrystal pores.

  2. Removal of organic pollutants in model water and thermal wastewater using clay minerals.

    PubMed

    Szabó, Emese; Vajda, Krisztina; Veréb, Gábor; Dombi, András; Mogyorósi, Károly; Ábrahám, Imre; Májer, Marcell

    2011-01-01

    Water treatment method was developed for the removal of different anionic dyes such as methyl orange and indigo carmine, and also for thymol applying sodium bentonite and cationic surfactant - hexadecyltrimethylammonium bromide (HTAB) - or polyelectrolytes (polydiallyldimethylammonium chloride, poly-DADMAC and poly-amines). The removal efficiency of these model substrates was examined in model water using UV-Vis spectrophotometry, HPLC and TOC analysis. The clay mineral and HTAB were added in one step to the polluted model water in Jar-test experiments. The influence of the cation exchange capacity (CEC) of the applied clay mineral and the presence of polyaluminium chloride coagulant (BOPAC) were also tested for the water treatment process. The structures of the in situ produced and pre-prepared organoclay composites were compared by XRD analysis. The rapid formation of organoclay adsorbents provided very efficient removal of the dyes (65-90 % in 3-10 mg/L TOC(0) range) with 200 mg/L sodium bentonite dose, however thymol was less efficiently separated. Adsorption efficiencies of the composites were compared at different levels of ion exchange such as at 40, 60 and 100 %. In the case of thymol, the elimination of inorganic carbon from the model water before the TOC analysis resulted in some loss of the analysed volatile compound therefore the HPLC analysis was found to be the most suitable tool for the evaluation of the process. This one-step adsorption method using in situ formed organoclay was better performing than the conventional process in which the montmorillonite-surfactant composite is pre-preapared and subsequently added to the polluted water. The purification performance of this method was also evaluated on raw and artificially polluted thermal wastewater samples containing added thymol. PMID:21929471

  3. Adsorption of cobalt ions from waste water on activated Saudi clays

    NASA Astrophysics Data System (ADS)

    Al-Jlil, Saad A.

    2014-11-01

    The aim of this work was to remove the Cobalt ions from wastewater by three types of Saudi clay. These were collected from Tabbuk city (Tabbuk clay), Khiber city (Khiber clay), and Bahhah city (Bahhah clay). The paper also examined the effect of different activators on the enhancement of adsorption capacity of clays for cobalt ions. The results showed minor enhancement in the adsorption capacities of cobalt ions on three types of clays activated by acid treatment. The adsorption capacity of clays improved particularly for Tabbuk clay when treated with hydrogen peroxide as an activator. The adsorption capacity increased from 3.94 to 12.9 mg/g for the untreated and treated Tabbuk clay, respectively. Also, the adsorption capacity of Bahhah clay increased by activating with sodium chloride from 3.44 to 12.55 mg/g for untreated and treated sample, respectively. The equilibrium adsorption data were correlated using five equilibrium equations, namely, Langmuir, Freundlich, Langmuir-Freundlich, BET, and Toth isotherm equations. Langmuir isotherm agreed well with the experimental data of Khiber and Bahhah clay, while Freundlich model and Langmuir-Freundlich model fitted well with the experimental data of Tabbuk and Bahhah clay activated by NaCl. The results showed that Freundlich model fitted well with the experimental data of Tabbuk clay when activated by H2O2 and H2SO4. Finally, the BET model did not describe the experimental data well for the three types of clay after activation.

  4. Evidence for excess pore pressures in southwest Indian Ocean sediments

    SciTech Connect

    Abbott, D.; Menke, W.; Hobart, M.; Anderson, R.

    1981-03-10

    Brown clay cores from the Madagascar and Crozet basins show the following evidence of excess pore pressures: large amounts of flow-in, increasing average sedimentation rate with age, and nonlinear temperature gradients. Additionally, many hilltops in these basins have no visible sediment cover. The bare hilltops may result from periodic slumping caused by excess pore pressures. Calculated excess pore pressures which equal or exceed the overburden pressure were inferred from water fluxes predicted by nonlinear temperature gradients and laboratory permeability measurements by using Darcy's law. Since pore pressures which exceed the overburden pressure are unreasonable, we attribute this discrepancy to laboratory measures which underestimate the in situ permeability. The widespread presence of overpressured sediments in areas of irregular topography provides a process for resuspension of clay-sized particles. This mechanism does not require high current velocities for the erosion of clay and therefore can be applied to many areas where no strong currents are evident. Carbonate-rich sediments from the Madagascar Ridge, the Mozambique Ridge, and the Agulhas Plateau had almost no flow-in and occurred in areas where all topography was thickly draped with sediment, Since the age and tectonic location of the ridges and plateaus preclude water circulation in the basement, we attribute these differences between the brown clay and the carbonate-rich material to an absence of significant excess pore pressures in the plateau and ridge sediments.

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

    SciTech Connect

    B.D. Marshall; K. Futa

    2001-02-07

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

  6. Transgenic nematodes as biosensors for metal stress in soil pore water samples.

    PubMed

    Anbalagan, Charumathi; Lafayette, Ivan; Antoniou-Kourounioti, Melissa; Haque, Mainul; King, John; Johnsen, Bob; Baillie, David; Gutierrez, Carmen; Martin, Jose A Rodriguez; de Pomerai, David

    2012-03-01

    Caenorhabditis elegans strains carrying stress-reporter green fluorescent protein transgenes were used to explore patterns of response to metals. Multiple stress pathways were induced at high doses by most metals tested, including members of the heat shock, oxidative stress, metallothionein (mtl) and xenobiotic response gene families. A mathematical model (to be published separately) of the gene regulatory circuit controlling mtl production predicted that chemically similar divalent metals (classic inducers) should show additive effects on mtl gene induction, whereas chemically dissimilar metals should show interference. These predictions were verified experimentally; thus cadmium and mercury showed additive effects, whereas ferric iron (a weak inducer) significantly reduced the effect of mercury. We applied a similar battery of tests to diluted samples of soil pore water extracted centrifugally after mixing 20% w/w ultrapure water with air-dried soil from an abandoned lead/zinc mine in the Murcia region of Spain. In addition, metal contents of both soil and soil pore water were determined by ICP-MS, and simplified mixtures of soluble metal salts were tested at equivalent final concentrations. The effects of extracted soil pore water (after tenfold dilution) were closely mimicked by mixtures of its principal component ions, and even by the single most prevalent contaminant (zinc) alone, though other metals modulated its effects both positively and negatively. In general, mixtures containing similar (divalent) metal ions exhibited mainly additive effects, whereas admixture of dissimilar (e.g. trivalent) ions often resulted in interference, reducing overall levels of stress-gene induction. These findings were also consistent with model predictions. PMID:22037694

  7. Triaxial- and uniaxial-compression testing methods developed for extraction of pore water from unsaturated tuff, Yucca Mountain, Nevada

    SciTech Connect

    Mower, T.E.; Higgins, J.D.; Yang, I.C.

    1989-12-31

    To support the study of hydrologic system in the unsaturated zone at Yucca Mountain, Nevada, two extraction methods were examined to obtain representative, uncontaminated pore-water samples from unsaturated tuff. Results indicate that triaxial compression, which uses a standard cell, can remove pore water from nonwelded tuff that has an initial moisture content greater than 11% by weight; uniaxial compression, which uses a specifically fabricated cell, can extract pore water from nonwelded tuff that has an initial moisture content greater than 8% and from welded tuff that has an initial moisture content greater than 6.5%. For the ambient moisture conditions of Yucca Mountain tuffs, uniaxial compression is the most efficient method of pore-water extraction. 12 refs., 7 figs., 2 tabs.

  8. PORE-WATER ISOTOPIC COMPOSITION AND UNSATURATED-ZONE FLOW, YUCCA MOUNTAIN, NEVADA

    SciTech Connect

    C. Yang

    2000-10-23

    Site characterization at Yucca Mountain, Nevada, the site of a potential high-level radioactive waste repository, has included studies of recharge, flow paths, percolation flux, perched water bodies, and chemical compositions of the water in the thick unsaturated zone (UZ). Samples of pore water from cores of two recently drilled boreholes, USW SD-6 near the ridge top of Yucca Mountain and USW WT-24 north of Yucca mountain, were analyzed for isotopic compositions as part of a study by the US Geological Survey (USGS), in cooperation with the US Department of Energy, under Interagency Agreement DE-AI08-97NV12033. The purpose of this report is to interpret {sup 14}C, {delta}{sup 13}C, {sup 3}H, {delta}D and {delta}{sup 18}O isotopic compositions of pore water from the core of boreholes USW SD-6 and USW WT-24 in relation to sources of recharge and flow paths in the UZ at Yucca Mountain. Borehole designation USW SD-6 and USW WT-24 subsequently will be referred to as SD-6 and WT-24. The sources of recharge and flow paths are important parameters that can be used in a UZ flow model, total system performance assessment (TSPA), and the license application (LA) for the potential repository at Yucca Mountain.

  9. The radiocarbon age of calcite dissolving at the sea floor: Estimates from pore water data

    SciTech Connect

    Martin, W.R.; McNichol, A.P.; McCorkle, D.C.

    2000-04-01

    The authors measured the radiocarbon content and stable isotopic composition of pore water and bottom water {Sigma}CO{sub 2}, sedimentary organic carbon, and CaCO{sub 3} at two sites on the Ceara Rise, one underlying bottom water that is supersaturated with respect to calcite (Site B), the other underlying under saturated bottom water (Site G). The results were combined with pore water O{sub 2}, {Sigma}CO{sub 2}, and Ca{sup 2+} profiles (Martin and Sayles, 1996) to estimate the radiocarbon content of the CaCO{sub 3} that is dissolving in the sediment mixed layer. At Site G, the CaCO{sub 3} that is dissolving in the upper 2 cm of the sediments is clearly younger (richer in {sup 14}C) than the bulk sedimentary CaCO{sub 3}, indicating that nonhomogeneous CaCO{sub 3} dissolution occurs there. The case for nonhomogeneous dissolution is much weaker at the site underlying supersaturated bottom water. The results indicate that nonhomogeneous dissolution occurs in sediments underlying under saturated bottom water, that the dissolution is rapid relative to the rate of homogenization of the CaCO{sub 3} in the mixed layer by bioturbation, and that the dissolution rate of CaCO{sub 3} decreases as it ages in the sediment mixed layer. The results support the hypothesis, based on solid phase analyses, that the preferential dissolution of young (i.e., radiocarbon-rich) CaCO{sub 3} leads to a pattern of increasing radiocarbon age of mixed-layer CaCO{sub 3} as the degree of under saturation of bottom water increases (Keir, 1984; Broecker et al., 1991).

  10. Geochemistry of Lake Van pore water and sediment, or How to distinguish climatic from diagenetic signals?

    NASA Astrophysics Data System (ADS)

    Kwiecien, Ola; Tomonaga, Yama; Brennwald, Matthias S.; Randlett, Marie-Eve; Peterse, Francien; Bechtel, Achim; van der Meer, Marcel; Stockhecke, Mona; Bucher, Stefan; Anselmetti, Flavio; Litt, Thomas; Schubert, Carsten J.; Kipfer, Rolf

    2014-05-01

    Lake Van is a terminal soda lake located in a semiarid region (eastern Anatolia, Turkey). Its geographical setting makes Lake Van a superb archive of paleoenvironmental changes. One of the aims of the ICDP PALEOVAN project is the reconstruction of the hydrological and climatic variability in the eastern Mediterranean region and the Near East on glacial/interglacial and millennial time scales. We applied a multi-proxy approach to distinguish the environmental synsedimentary imprint and the postsedimentary diagenetic changes. Microfaunal evidence, carbonate isotopic composition (d18O, d13C), molecular proxies (BIT, ACE) and isotopic composition of lipid biomarkers (dD) are matched with isotopic and elemental composition (d18O, dD, Mg, Ca, Sr, Cl, salinity) of sediment pore-water. An excellent correspondence between these proxies indicates that the elemental composition of pore water in Lake Van does not result from diagenetic changes, but, unlike in many cases known from marine environment, represents to some extent relicts of 'paleolake-water'. On the contrary, the stable isotopic composition of the pore water (d18O, dD) seems to reflect more recent hydrological regime dominated by precipitation/evaporation changes. As salinity and chlorine concentration changes mimic the isotopic composition of biomarkers for the last 140 ka, we use pore-water data to quantify changes in the lake level. Our reconstruction (Tomonaga et al., in review) is in line with previous studies on lake terraces (Kuzucuoglu et al., 2010) and seismic surveys (Cukur et al., 2012) showing a major transgression of up to 105 m with respect to the current lake level during the last interglacial (MIS5e), and a major regression of ~145 m at ~30 ka BP during the last glacial. Kuzucuoglu et al. (2010) Formation of the Upper Pleistocene terraces of Lake Van (Turkey). Journal of Quaternary Science 25, 1124-1137. Cukur et al. (2012) Sedimentary evolution of Lake Van (Eastern Turkey) reconstructed from high

  11. Aeration effects on the partitioning of a PCB to anoxic estuarine sediment pore water dissolved organic matter

    SciTech Connect

    Pedersen, J.A.; Gabelich, C.J.; Lin, C.H.; Suffet, I.H.

    1999-05-01

    Pore water dissolved organic matter (DOM) plays an important role in the distribution, mobility, and bioavailability of hydrophobic organic chemicals (HOCs) in sediment environments. The effect of aeration on the partitioning of 2,2{prime},4,4{prime}-tetrachlorobiphenyl (TeCB) to anoxic pore water DOM from three estuarine sites was investigated. Pore water DOM was fractionated into molecular size and polarity fractions by ultrafiltration and XAD-8 resin chromatography. Total organic carbon analysis was utilized to determine shifts in molecular size and polarity distributions. Changes in functional groups and aromaticity were evaluated for whole and fractionated pore waters by specific UV absorbance at 254 nm (SUVA{sub 254}). The solubility enhancement method was used to determine the partitioning of TeCB to whole and fractionated pore water DOM. At two sites, the overall TeCB-DOM distribution coefficient decreased by an order of magnitude after aeration. The higher molecular size and all polarity fractions exhibited a decrease in partitioning behavior upon aeration. The aromaticity and TeCB-DOM distribution coefficient of the lowest molecular size fraction decreased upon aeration. The highest and lowest molecular size fractions contributed the most to overall partitioning. The observed aeration effects in anoxic estuarine sediment pore waters differed significantly from those previously reported in freshwater systems.

  12. Pore water chemistry reveals gradients in mineral transformation across a model basaltic hillslope

    NASA Astrophysics Data System (ADS)

    Pohlmann, Michael; Dontsova, Katerina; Root, Robert; Ruiz, Joaquin; Troch, Peter; Chorover, Jon

    2016-06-01

    The extent of weathering incongruency during soil formation from rock controls local carbon and nutrient cycling in ecosystems, as well as the evolution of hydrologic flow paths. Prior studies of basalt weathering, including those that have quantified the dynamics of well-mixed, bench-scale laboratory reactors or characterized the structure and integrated response of field systems, indicate a strong influence of system scale on weathering rate and trajectory. For example, integrated catchment response tends to produce lower weathering rates than do well mixed reactors, but the mechanisms underlying these disparities remain unclear. Here we present pore water geochemistry and physical sensor data gathered during two controlled rainfall-runoff events on a large-scale convergent model hillslope mantled with 1 m uniform depth of granular basaltic porous media. The dense sampler and sensor array (1488 samplers and sensors embedded in 330 m3 of basalt) showed that rainfall-induced dissolution of basaltic glass produced supersaturation of pore waters with respect to multiple secondary solids including allophane, gibbsite, ferrihydrite, birnessite and calcite. The spatial distribution of saturation state was heterogeneous, suggesting an accumulation of solutes leading to precipitation of secondary solids along hydrologic flow paths. Rapid dissolution of primary silicates was widespread throughout the entire hillslope, irrespective of up-gradient flowpath length. However, coherent spatial variations in solution chemistry and saturation indices were observed in depth profiles and between distinct topographic regions of the hillslope. Colloids (110-2000 nm) enriched in iron (Fe), aluminum (Al), and phosphorus (P) were mobile in soil pore waters.

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

    SciTech Connect

    Greathouse, Jeffery A.; Hart, David; Bowers, Geoffrey M.; Kirkpatrick, R. James; Cygan, Randall Timothy

    2015-07-20

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

  14. Controls on soil pore water solutes: An approach for distinguishing between biogenic and lithogenic processes

    USGS Publications Warehouse

    White, A.F.; Schulz, M.S.; Vivit, D.V.; Blum, A.E.; Stonestrom, D.A.

    2006-01-01

    Spatial and temporal variations in pore water compositions are characterized for a deep regolith profile developed on a marine terrace chronosequence near Santa Cruz California. Variations are resolved in terms of the dominance of either a lithogenic process, i.e. chemical weathering, or a biogenic process, i.e. plant nutrient cycling. The concept of elemental fractionation is introduced describing the extent that specific elements are mobilized and cycled as a result of these processes. ?? 2005 Elsevier B.V. All rights reserved.

  15. Upwelling of hydrothermal solutions through ridge flank sediments shown by pore water profiles

    SciTech Connect

    Maris, C.R.P.; Bender, M.L.

    1982-05-07

    High calcium ion and low magnesium ion concentrations in sediment pore waters in cores from the Galapagos Mounds Hydrothermal Field on the flank of the Galapagos Spreading Center are believed to be due to a calcium-magnesium exchange reaction between circulating seawater and basement basalt. The nonlinearity of the calcium ions and magnesium ion gradients indicates that these discharging hydrothermal solutions on the ridge flank are upwelling at the rate of about 1 centimeter per year through the pelagic sediments of the Mounds Field and at about 20 centimeters per year through the hydrothermal mounds themselves.

  16. Liquid CO2 displacement of water in a dual-permeability pore network micromodel.

    PubMed

    Zhang, Changyong; Oostrom, Mart; Grate, Jay W; Wietsma, Thomas W; Warner, Marvin G

    2011-09-01

    Permeability contrasts exist in multilayer geological formations under consideration for carbon sequestration. To improve our understanding of heterogeneous pore-scale displacements, liquid CO(2) (LCO(2))-water displacement was evaluated in a pore network micromodel with two distinct permeability zones. Due to the low viscosity ratio (logM = -1.1), unstable displacement occurred at all injection rates over 2 orders of magnitude. LCO(2) displaced water only in the high permeability zone at low injection rates with the mechanism shifting from capillary fingering to viscous fingering with increasing flow rate. At high injection rates, LCO(2) displaced water in the low permeability zone with capillary fingering as the dominant mechanism. LCO(2) saturation (S(LCO2)) as a function of injection rate was quantified using fluorescent microscopy. In all experiments, more than 50% of LCO(2) resided in the active flowpaths, and this fraction increased as displacement transitioned from capillary to viscous fingering. A continuum-scale two-phase flow model with independently determined fluid and hydraulic parameters was used to predict S(LCO2) in the dual-permeability field. Agreement with the micromodel experiments was obtained for low injection rates. However, the numerical model does not account for the unstable viscous fingering processes observed experimentally at higher rates and hence overestimated S(LCO2). PMID:21774502

  17. Sequestration of priority pollutant PAHs from sediment pore water employing semipermeable membrane devices.

    PubMed

    Williamson, Kelly S; Petty, Jimmie D; Huckins, James N; Lebo, Jon A; Kaiser, Edwin M

    2002-11-01

    Semipermeable membrane devices (SPMDs) were employed to sample sediment pore water in static exposure studies under controlled laboratory conditions using (control pond and formulated) sediments fortified with 15 priority pollutant polycyclic aromatic hydrocarbons (PPPAHs). The sediment fortification level of 750 ng/g was selected on the basis of what might be detected in a sediment sample from a contaminated area. The sampling interval consisted of 0, 4, 7, 14, and 28 days for each study. The analytical methodologies, as well as the extraction and sample cleanup procedures used in the isolation, characterization, and quantitation of 15 PPPAHs at different fortification levels in SPMDs, water, and sediment were reported previously (Williamson, M.S. Thesis, University of Missouri-Columbia, USA; Williamson et al., Chemosphere (This issue--PII: S0045-6535(02)00394-6)) and used for this project. Average (mean) extraction recoveries for each PPPAH congener in each matrix are reported and discussed. No procedural blank extracts (controls) were found to contain any PPPAH residues above the method quantitation limit, therefore, no matrix interferences were detected. The focus of this publication is to demonstrate the ability to sequester environmental contaminants, specifically PPPAHs, from sediment pore water using SPMDs and two different types of fortified sediment. PMID:12431008

  18. Measuring pyrethroids in sediment pore water using matrix-solid phase microextraction.

    PubMed

    Hunter, Wesley; Yang, Yu; Reichenberg, Fredrik; Mayer, Philipp; Gan, Jianying

    2009-01-01

    Pyrethroids are hydrophobic insecticides commonly used in both agricultural and urban environments. Their high toxicity to aquatic organisms, including benthic invertebrates, and detection in the sediment at many locations in California, U.S.A., have spawned interest in understanding their bioavailability in bed sediments. A recent study showed good correlation between uptake of 14C-permethrin in Chironomus tentans and solid-phase microextraction (SPME) fibers in sediments. The present study was directed at the development of an SPME technique applicable to trace levels of nonlabeled pyrethroids in sediment. Disposable polydimethylsiloxane fibers were used to detect freely dissolved pore-water concentrations of bifenthrin, fenpropathrin, cis-permethrin, trans-permethrin, cyfluthrin, cypermethrin, and esfenvalerate under agitated and static conditions. Partition equilibrium between fiber and sediment was reached in <5 d when the samples were agitated on a shaker at low speed, while much longer times (>23 d) were needed without agitation. Polydimethylsiloxane to water partition ratios (K(PDMS)) of the seven pyrethroids were measured separately and ranged from 2.83 x 10(5) to 1.89 x 10(6). When applied to field-contaminated sediments, agitated matrix-SPME was able to detect pore-water concentrations as low as 0.1 ng/L. The method developed in the present study may be coupled with bioassays to gain mechanistic understanding of factors affecting pyrethroid toxicities, and applied to field samples to better predict sediment toxicities from pyrethroid contamination. PMID:18712946

  19. Sequestration of priority pollutant PAHs from sediment pore water employing semipermeable membrane devices

    USGS Publications Warehouse

    Williamson, K.S.; Petty, J.D.; Huckins, J.N.; Lebo, J.A.; Kaiser, E.M.

    2002-01-01

    Semipermeable membrane devices (SPMDs) were employed to sample sediment pore water in static exposure studies under controlled laboratory conditions using (control pond and formulated) sediments fortified with 15 priority pollutant polycyclic aromatic hydrocarbons (PPPAHs). The sediment fortification level of 750 ng/g was selected on the basis of what might be detected in a sediment sample from a contaminated area. The sampling interval consisted of 0, 4, 7, 14, and 28 days for each study. The analytical methodologies, as well as the extraction and sample cleanup procedures used in the isolation, characterization, and quantitation of 15 PPPAHs at different fortification levels in SPMDs, water, and sediment were reported previously (Williamson, M.S. Thesis, University of Missouri - Columbia, USA; Williamson et al., Chemosphere (This issue - PII: S0045-6535(02)00394-6)) and used for this project. Average (mean) extraction recoveries for each PPPAH congener in each matrix are reported and discussed. No procedural blank extracts (controls) were found to contain any PPPAH residues above the method quantitation limit, therefore, no matrix interferences were detected. The focus of this publication is to demonstrate the ability to sequester environmental contaminants, specifically PPPAHs, from sediment pore water using SPMDs and two different types of fortified sediment.

  20. Accounting for pore water pressure and confined aquifers in assessing the stability of slopes: a Limit Equilibrium analysis carried out through the Minimum Lithostatic Deviation method

    NASA Astrophysics Data System (ADS)

    Ausilia Paparo, Maria; Tinti, Stefano

    2015-04-01

    The model we introduce is an implementation of the Minimum Lithostatic Deviation (MLD) method, developed by Tinti and Manucci (Tinti and Manucci 2006; 2008), that makes use of the limit equilibrium (LE) theory to estimate the stability of a slope. The main purpose here is to analyse the role of a confined aquifer on the value of the Safety Factor (F), the parameter that in the LE is used to determine if a slope is stable or unstable. The classical LE methods treat unconfined aquifers by including the water pore pressure in the Mohr-Coulomb failure formula: since the water decreases the friction shear strength, the soil above the sliding surface turns out to be more prone to instability. In case of a confined aquifer, however, due to a presence of impermeable layers, the water is not free to flow into the matrix of the overlying soil. We consider here the assumption of a permeable soil sliding over an impermeable layer, which is an occurrence that is found in several known landslide cases (e.g. Person, 2008; Strout and Tjeltja, 2008; Morgan et al., 2010 for offshore slides; and Palladino and Peck, 1972; Miller and Sias, 1998; Jiao et al. 2005; Paparo et al., 2013 for slopes in proximity of artificial or natural water basins) where clay beds form the potential sliding surface: the water, confined below, pushes along these layers and acts on the sliding body as an external bottom load. We modify the MLD method equations in order to take into account the load due to a confined aquifer and apply the new model to the Vajont case, where many have hypothesised the contribution of a confined aquifer to the failure. Our calculations show that the rain load i) infiltrating directly into the soil body and ii) penetrating into the confined aquifer below the clay layers, in addition with the lowering of the reservoir level, were key factors of destabilization of the Mt Toc flank and caused the disastrous landslide.

  1. Ball clay

    USGS Publications Warehouse

    Virta, R.L.

    2012-01-01

    Four companies — H.C. Spinks Clay Co., Inc., Imerys Group, Old Hickory Clay Co., and Unimin Corp. — mined ball clay in four states in 2011. Production, on the basis of preliminary data, was 940 kt (1.04 million st) with an estimated value of $44.2 million. This is a 3-percent increase in tonnage from 912 kt (1.01 million st) with a value of $41.3 million that was produced in 2010. Tennessee was the leading producing state with 63 percent of domestic production, followed by Texas, Mississippi and Kentucky. About 69 percent of production was airfloat, 20 percent was crude and 11 percent was water-slurried.

  2. The influence of water and supercritical CO2 on the frictional strength and velocity dependence of swelling (montmorillonite and saponite) and non-swelling (muscovite and illite) clays and the potential for fault zone reactivation in CO2 storage reservoirs

    NASA Astrophysics Data System (ADS)

    Samuelson, J. E.

    2012-12-01

    Recent research indicates that CO2 is capable of inducing swelling in clay minerals in a similar fashion to water, though to a more modest extent. It is therefore of importance for feasibility studies of the geological storage of CO2 to understand if the addition of CO2 to clay rich fault zones has the potential to cause significant frictional weakening, similar to that associated with water. We conduct velocity-stepping direct shear experiments on pre-pressed plates (49 mm long x 35 mm wide x ~1 mm thick), of montmorillonite and saponite, both known swelling clays, as well as plates of illite and muscovite also important phyllosilicate minerals in faults, though non-swelling. An effective normal stress of 35 MPa is used in all experiments, which is roughly equivalent to the effective overburden stress expected in many storage projects. Temperature was held constant at ~ 48 °C, consistent with previous experiments which indicated CO2 induced swelling in montmorillonite. Pore fluid conditions are the main variable in this suite of experiments, in which the frictional strength of each clay mineral is analyzed dry (open to atmospheric conditions), saturated with deionized (DI) water, and saturated with supercritical CO2. Pore pressure is maintained at 15 MPa for the water and CO2 saturated experiments (σn=50 MPa, PH20/CO2=15 MPa). Shearing velocity is varied systematically from approximately 11 μm/s to 0.2, 1.1, 11, 1.1, and 0.2 μm/s in order to determine the rate and state friction parameters, a, b, and DC. Additionally, microstructural analysis of the post-shear clay gouges is conducted in an effort to understand the rheology behind changes observed in frictional properties. Initial experiments on montmorillonite show an overconsolidation peak at strains of approximately 0.3 for each of the dry and water and CO2 saturated experiments. Peak friction (μP) for dry montmorillonite is 0.18, decaying to a steady state friction (μss) of 0.13. For DI

  3. Water vapor weathering of Taurus-Littrow orange soil - A pore-structure analysis

    NASA Technical Reports Server (NTRS)

    Cadenhead, D. A.; Mikhail, R. S.

    1975-01-01

    A pore-volume analysis was performed on water vapor adsorption data previously obtained on a fresh sample of Taurus-Littrow orange soil, and the analysis was repeated on the same sample after its exposure to moist air for a period of approximately six months. The results indicate that exposure of an outgassed sample to high relative pressures of water vapor can result in the formation of substantial micropore structure, the precise amount being dependent on the sample pretreatment, particularly the outgassing temperature. Micropore formation is explained in terms of water penetration into surface defects. In contrast, long-term exposure to moist air at low relative pressures appears to reverse the process with the elimination of micropores and enlargement of mesopores possibly through surface diffusion of metastable adsorbent material. The results are considered with reference to the storage of lunar samples.

  4. Pore water nutrient characteristics and the fluxes across the sediment in the Pearl River estuary and adjacent waters, China

    NASA Astrophysics Data System (ADS)

    Zhang, Ling; Wang, Lu; Yin, Kedong; Lü, Ying; Zhang, Derong; Yang, Yongqiang; Huang, Xiaoping

    2013-11-01

    Spatio-temporal distribution of pore water nutrients and the fluxes at the sediment-water interface (SWI) were investigated to probe into the geochemical behavior of nutrients associated with early diagenesis of organic matter (OM), and to study the accumulation and transformation processes of nutrients at the SWI, as well as to discuss the impact of riverine inputs on nutrients in the Pearl River estuary (PRE) and adjacent offshore areas. Nutrient concentrations decreased from the upper to the lower reaches of the estuary, suggesting that there was a high input of anthropogenic nutrients and the estuary was acting as a nutrient sink. Dissolved inorganic nitrogen (DIN: the sum of NH4-N, NO3-N and NO2-N) concentrations in the water column and the pore water were higher in the estuary than at offshore areas due to the riverine discharge and the high accumulation rate in the estuary. NO3-N concentration was the highest of the three forms of DIN in the overlying water and showed a sharp decrease from the surficial sediment with increasing sediment depth, indicating that there was strong denitrification at the SWI. NH4-N, mainly deriving from the anaerobic degradation of OM, was the main form of DIN in the pore water and increased with depth. Negative NO3-N fluxes (into the sediment) and positive NH4-N fluxes (from the sediment) were commonly observed from incubation experiments, indicating the denitrification occurred at the SWI. DIN flux suggested that the sediment was a sink of DIN in spring, however, the sediment was the source of DIN in summer and winter. Nutrients dominantly diffused out of the sediment, suggesting that the sediment was the source of nutrients in spring at adjacent offshore areas. The fluxes directed that PO4-P mainly diffused into the sediment while SiO4-Si mainly diffused out of the sediment.

  5. Structure and Dynamics of Confined Water and CO2 in Clays under Supercritical Conditions

    NASA Astrophysics Data System (ADS)

    Glezakou, V.; Lee, M.; Schaef, T.; Loring, J.; Davidson, C.; McGrail, P.

    2013-12-01

    Carbon dioxide (CO2) driven enhanced gas recovery (EGR) from depleted fractured shale gas reservoirs has the potential for producing economic benefits and providing long term storage options for anthropogenic derived CO2 emissions. However key scientific processes related to CO2:CH4 exchange rates, mineral volume changes, organic mobility, and mineral stability in the presence of acid gas injections are not well understood. In this paper, we conduct atomistic simulations to examine interactions occurring between model clay minerals and supercritical CO2 equilibrated with water or brines to identify parameters controlling adsorption and desorption of gases. Integrated within these simulations are results derived from a set of newly developed experimental techniques designed to characterize physico-chemical reactions at reservoir conditions. In a series of cell optimizations under pressures relevant to sequestration scenarios, molecular simulations within the NVT and NPT ensembles with varying water/CO2 ratios showed a range of interlayer expansion for specific cation-saturated smectites. In conjunction with experimental in situ high pressure x-ray diffraction (HXRD), semi-quantitative concentrations of interlayer H2O and CO2 were established. For example, Ca saturated smectites maintaining sub-single to single hydration states (<1W to 1W), expand approximately 1.7-2.0 Å when exposed to anhydrous supercritical CO2. In contrast, for single to double hydration states (1W-2W), the simulations indicate formation of a quasi-single, metastable state, leading to a reduced interlayer spacing. Partial dehydration of the interlayer spacing while in contact with CO2 is due to a reduction of the interlayer cation coordination number. Structural analysis of the intercalated species shows an increase in the hydrogen bonding between waters during CO2 intercalation coincident with a decrease in the coordination population around the cations. Power spectra reveal rotationally

  6. Glass transition and relaxation dynamics of propylene glycol-water solutions confined in clay.

    PubMed

    Elamin, Khalid; Björklund, Jimmy; Nyhlén, Fredrik; Yttergren, Madeleine; Mårtensson, Lena; Swenson, Jan

    2014-07-21

    The molecular dynamics of aqueous solutions of propylene glycol (PG) and propylene glycol methylether (PGME) confined in a two-dimensional layer-structured Na-vermiculite clay has been studied by broadband dielectric spectroscopy and differential scanning calorimetry. As typical for liquids in confined geometries the intensity of the cooperative α-relaxation becomes considerably more suppressed than the more local β-like relaxation processes. In fact, at high water contents the calorimetric glass transition and related structural α-relaxation cannot even be observed, due to the confinement. Thus, the intensity of the viscosity related α-relaxation is dramatically reduced, but its time scale as well as the related glass transition temperature Tg are for both systems only weakly influenced by the confinement. In the case of the PGME-water solutions it is an important finding since in the corresponding bulk system a pronounced non-monotonic concentration dependence of the glass transition related dynamics has been observed due to the growth of hydrogen bonded relaxing entities of water bridging between PGME molecules [J. Sjöström, J. Mattsson, R. Bergman, and J. Swenson, Phys. Chem. B 115, 10013 (2011)]. The present results suggest that the same type of structural entities are formed in the quasi-two-dimensional space between the clay platelets. It is also observed that the main water relaxation cannot be distinguished from the β-relaxation of PG or PGME in the concentration range up to intermediate water contents. This suggests that these two processes are coupled and that the water molecules affect the time scale of the β-relaxation. However, this is most likely true also for the corresponding bulk solutions, which exhibit similar time scales of this combined relaxation process below Tg. Finally, it is found that at higher water contents the water relaxation does not merge with, or follow, the α-relaxation above Tg, but instead crosses the

  7. Glass transition and relaxation dynamics of propylene glycol-water solutions confined in clay

    NASA Astrophysics Data System (ADS)

    Elamin, Khalid; Björklund, Jimmy; Nyhlén, Fredrik; Yttergren, Madeleine; Mârtensson, Lena; Swenson, Jan

    2014-07-01

    The molecular dynamics of aqueous solutions of propylene glycol (PG) and propylene glycol methylether (PGME) confined in a two-dimensional layer-structured Na-vermiculite clay has been studied by broadband dielectric spectroscopy and differential scanning calorimetry. As typical for liquids in confined geometries the intensity of the cooperative α-relaxation becomes considerably more suppressed than the more local β-like relaxation processes. In fact, at high water contents the calorimetric glass transition and related structural α-relaxation cannot even be observed, due to the confinement. Thus, the intensity of the viscosity related α-relaxation is dramatically reduced, but its time scale as well as the related glass transition temperature Tg are for both systems only weakly influenced by the confinement. In the case of the PGME-water solutions it is an important finding since in the corresponding bulk system a pronounced non-monotonic concentration dependence of the glass transition related dynamics has been observed due to the growth of hydrogen bonded relaxing entities of water bridging between PGME molecules [J. Sjöström, J. Mattsson, R. Bergman, and J. Swenson, Phys. Chem. B 115, 10013 (2011)]. The present results suggest that the same type of structural entities are formed in the quasi-two-dimensional space between the clay platelets. It is also observed that the main water relaxation cannot be distinguished from the β-relaxation of PG or PGME in the concentration range up to intermediate water contents. This suggests that these two processes are coupled and that the water molecules affect the time scale of the β-relaxation. However, this is most likely true also for the corresponding bulk solutions, which exhibit similar time scales of this combined relaxation process below Tg. Finally, it is found that at higher water contents the water relaxation does not merge with, or follow, the α-relaxation above Tg, but instead crosses the

  8. Deuterium nuclear magnetic resonance unambiguously quantifies pore and collagen-bound water in cortical bone

    PubMed Central

    Ong, Henry H.; Wright, Alexander C.; Wehrli, Felix W.

    2012-01-01

    Bone water (BW) plays a pivotal role in nutrient transport and conferring bone with its viscoelastic mechanical properties. BW is partitioned between the pore spaces of the Haversian and lacuno-canalicular system, and water predominantly bound to the matrix proteins (essentially collagen). The general model of BW is that the former predominantly experiences fast isotropic molecular reorientation, whereas water in the bone matrix undergoes slower anisotropic rotational diffusion. Here, we provide direct evidence for the correctness of this model and show that unambiguous quantification in situ of these two functionally and dynamically different BW fractions is possible. The approach chosen relies on nuclear magnetic resonance (NMR) of deuterium (2H) that unambiguously separates and quantifies the two fractions on the basis of their distinguishing microdynamic properties. Twenty-four specimens of the human tibial cortex from six donors (3 male, 3 female, ages 27-83 years) were cored and 2H spectra recorded at 62 MHz (9.4 Tesla) on a Bruker Instruments DMX 400 spectrometer after exchange of native BW with 2H2O. Spectra consisted of a doublet signal resulting from quadrupole interaction of water bound to collagen. Doublet splittings were found to depend on the orientation of the osteonal axis with respect to the magnetic field direction (8.2 and 4.3 kHz for parallel and perpendicular orientation, respectively). In contrast, the isotropically reorienting pore-resident water yielded a single resonance line superimposed on the doublet. Nulling of the singlet resonance allowed separation of the two fractions. The results indicate that in human cortical bone 60-80% of detectable BW is collagen-bound. Porosity determined as the difference between total BW and collagen bound water fraction was found to strongly parallel μCT based measurements (R2 = 0.91). Our method provides means for direct validation of emerging relaxation-based measurements of cortical bone porosity by

  9. Monitoring water content in Opalinus Clay within the FE-Experiment: Test application of dielectric water content sensors

    NASA Astrophysics Data System (ADS)

    Sakaki, T.; Vogt, T.; Komatsu, M.; Müller, H. R.

    2013-12-01

    The spatiotemporal variation of water content in the near field rock around repository tunnels for radioactive waste in clay formations is one of the essential quantities to be monitored for safety assessment in many waste disposal programs. Reliable measurements of water content are important not only for the understanding and prediction of coupled hydraulic-mechanic processes that occur during tunnel construction and ventilation phase, but also for the understanding of coupled thermal-hydraulic-mechanical (THM) processes that take place in the host rock during the post closure phase of a repository tunnel for spent fuel and high level radioactive waste (SF/HLW). The host rock of the Swiss disposal concept for SF/HLW is the Opalinus Clay formation (age of approx. 175 Million years). To better understand the THM effects in a full-scale heater-engineered barrier-rock system in Opalinus Clay, a full-scale heater test, namely the Full-Scale Emplacement (FE) experiment, was initiated in 2010 at the Mont Terri underground rock laboratory in north-western Switzerland. The experiment is designed to simulate the THM evolution of a SF/HLW repository tunnel based on the Swiss disposal concept in a realistic manner during the construction, emplacement, backfilling, and post-closure phases. The entire experiment implementation (in a 50 m long gallery with approx. 3 m diameter) as well as the post-closure THM evolution will be monitored using a network of several hundred sensors. The sensors will be distributed in the host rock, the tunnel lining, the engineered barrier, which consists of bentonite pellets and blocks, and on the heaters. The excavation is completed and the tunnel is currently being ventilated. Measuring water content in partially saturated clay-rich high-salinity rock with a deformable grain skeleton is challenging. Therefore, we use the ventilation phase (before backfilling and heating) to examine the applicability of commercial water content sensors and to

  10. Movement of diuron and hexazinone in clay soil and infiltrated pond water.

    PubMed

    Prichard, Terry; Troiano, John; Marade, Joe; Guo, Fengmao; Canevari, Mick

    2005-01-01

    Pre-emergence herbicide residues were detected in domestic wells sampled near Tracy, CA. This study sought to determine the source of contamination by comparing soil distribution of diuron [N'-(3,4-dichlorophenyl)-N,N-dimethylurea] and hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione] in an agricultural field where the soil was a cracking clay to infiltration of residues in water captured by an adjacent holding pond. Diuron and hexazinone were applied in December to a 3-yr-old alfalfa (Medicago sativa L.) crop. Water content of soil taken after major rainfall but before irrigation at 106 d after application was elevated at the lowest depth sampled centered at 953 mm, indicating water was available for percolation. Herbicide residues (reporting limit 8 microg kg(-1)) were confined above the 152 mm soil depth, even after subsequent application of two border-check surface irrigations. The pattern of distribution and concentration of residues in the soil were similar to results obtained from the LEACHM model, suggesting that macropore flow was limited to a shallow depth of soil. Herbicide residues were measured in runoff water at the first irrigation at 20 microg L(-1) for diuron and 1 microg L(-1) for hexazinone. Runoff water captured in the pond rapidly infiltrated into the subsurface soil, causing a concomitant rise in ground water elevation near the pond. Herbicide residues were also detected in the sampled ground water. We concluded that the pond was the predominant source for movement to ground water. Since addition of a surfactant to the spray mixture did not reduce concentrations in runoff water, mitigation methods will focus on minimizing infiltration of water from the pond. PMID:16221820

  11. Determining the stable isotope composition of pore water from saturated and unsaturated zone core: improvements to the direct vapour equilibration laser spectrometry method

    NASA Astrophysics Data System (ADS)

    Hendry, M. J.; Schmeling, E.; Wassenaar, L. I.; Barbour, S. L.; Pratt, D.

    2015-11-01

    A method to measure the δ2H and δ18O composition of pore waters in saturated and unsaturated geologic core samples using direct vapour equilibration and laser spectrometry (DVE-LS) was first described in 2008, and has since been rapidly adopted. Here, we describe a number of important methodological improvements and limitations encountered in routine application of DVE-LS over several years. Generally, good comparative agreement, as well as accuracy, is obtained between core pore water isotopic data obtained using DVE-LS and that measured on water squeezed from the same core. In complex hydrogeologic settings, high-resolution DVE-LS depth profiles provide greater spatial resolution of isotopic profiles compared to long-screened or nested piezometers. When fluid is used during drilling and coring (e.g. water rotary or wet sonic drill methods), spiking the drill fluid with 2H can be conducted to identify core contamination. DVE-LS analyses yield accurate formational isotopic data for fine-textured core (e.g. clay, shale) samples, but are less effective for cores obtained from saturated permeable (e.g. sand, gravels) geologic media or on chip samples that are easily contaminated by wet rotary drilling fluid. Data obtained from DVE-LS analyses of core samples collected using wet (contamination by drill water) and dry sonic (water loss by heating) methods were also problematic. Accurate DVE-LS results can be obtained on core samples with gravimetric water contents > 5 % by increasing the sample size tested. Inexpensive Ziploc™ gas-sampling bags were determined to be as good as, if not better than, other, more expensive specialty bags. Sample storage in sample bags provides acceptable results for up to 10 days of storage; however, measurable water loss, as well as evaporitic isotopic enrichment, occurs for samples stored for up to 6 months. With appropriate care taken during sample collection and storage, the DVE-LS approach for obtaining high-resolution pore water

  12. Determining the stable isotope composition of pore water from saturated and unsaturated zone core: improvements to the direct vapor equilibration laser spectroscopy method

    NASA Astrophysics Data System (ADS)

    Hendry, M. J.; Schmeling, E.; Wassenaar, L. I.; Barbour, S. L.; Pratt, D.

    2015-06-01

    A method to measure the δ2H and δ18O composition of pore waters in saturated and unsaturated geologic core samples using direct vapor equilibration and laser spectroscopy (DVE-LS) was first described in 2008, and has since been widely adopted by others. Here, we describe a number of important methodological improvements and limitations encountered in routine application of DVE-LS over several years. Generally, good comparative agreement and accuracy is obtained between core pore water isotopic data obtained using DVE-LS and that measured on water squeezed from the same core. In complex hydrogeologic settings, high-resolution DVE-LS depth profiles provide greater spatial resolution of isotopic profiles compared to long-screened or nested piezometers. When fluid is used during drilling and coring (e.g., water rotary or wet sonic drill methods), spiking the drill fluid with 2H can be conducted to identify core contamination. DVE-LS analyses yield accurate formational isotopic data for fine-textured core (e.g., clay, shale) samples, but are less effective for cores obtained from saturated permeable (e.g., sand, gravels) geologic media or on chip samples that are easily contaminated by wet rotary drilling fluid. Data obtained from DVE-LS analyses of core samples collected using wet (contamination by drill water) and dry sonic (water loss by heating) methods were also problematic. Accurate DVE-LS results can be obtained on core samples with gravimetric water contents < 5 % by increasing the sample size tested. Inexpensive Ziploc™ gas sampling bags were determined to be as good as, if not better, than other, more expensive bags. Sample storage in gas tight sample bags provides acceptable results for up to 10 days of storage; however, measureable water loss and evaporitic isotopic enrichment occurs for samples stored for up to 6 months. With appropriate care taken during sample collection and storage, the DVE-LS approach for obtaining high resolution pore water

  13. Occurrence and significance of polychlorinated biphenyls in water, sediment pore water and surface sediments of Umgeni River, KwaZulu-Natal, South Africa.

    PubMed

    Gakuba, Emmanuel; Moodley, Brenda; Ndungu, Patrick; Birungi, Grace

    2015-09-01

    The Umgeni River is one of the main sources of water in KwaZulu-Natal, South Africa; however; there is currently a lack of information on the presence and distribution of polychlorinated biphenyls (PCBs) in its sediment, sediment pore water and surface water. This study aims to determine the occurrence and significance of selected PCBs in the surface water, sediment pore water and surface sediment samples from the Umgeni River. Liquid-liquid and soxhlet extractions were used for water or pore water, and sediments, respectively. Extracts were cleaned up using a florisil column and analysed by gas chromatography-mass spectrometry. The total concentrations of eight polychlorinated biphenyls were 6.91-21.69 ng/mL, 40.67-252.30 ng/mL and 102.60-427.80 ng/g (dry weight), in unfiltered surface water, unfiltered sediment pore water and surface sediments, respectively. The percentage contributions of various matrices were 4, 36 and 60 % for unfiltered surface water, unfiltered pore water and sediment, respectively. The highest concentrations of PCBs were found in water, pore water and sediment collected from sampling sites close to the Northern Wastewater Treatment Works. The highest chlorinated biphenyl, PCB 180, was the most abundant at almost all sampling sites. To our knowledge, this is the first report on occurrence of polychlorinated biphenyls in the Umgeni River water, pore water and sediment system and our results provide valuable information regarding the partitioning of the PCBs between the water and sediment systems as well as the organic chemical quality of the water. PMID:26266899

  14. Relative role of pore water versus ingested sediment in bioavailability of organic contaminants in marine sediments

    SciTech Connect

    Forbes, T.L.; Hansen, R.; Kure, L.K.; Forbes, V.E.; Giessing, A. |

    1998-12-01

    Experimental data for fluoranthene and feeding selectivity in combination with reaction-diffusion modeling suggest that ingestion of contaminated sediment may often be the dominant uptake pathway for deposit-feeding invertebrates in sediments. A dietary absorption efficiency of 56% and accompanying forage ratio of 2.4 were measured using natural sediment that had been dual-labeled ({sup 14}C:{sup 51}Cr) with fluoranthene and fed to the marine deposit-feeding polychaete Capitella species I. Only 3 to 4% of the total absorption could be accounted for by desorption during gut passage. These data were then used as input into a reaction-diffusion model to calculate the importance of uptake from ingested sediment relative to pore-water exposure. The calculations predict a fluoranthene dietary uptake flux that is 20 to 30 times greater than that due to pore water. Factors that act to modify or control the formation of local chemical gradients, boundary layers, or dietary absorption rates including particle selection or burrow construction will be important in determining the relative importance of potential exposure pathways. From a chemical perspective, the kinetics of the adsorption and desorption process are especially important as they will strongly influence the boundary layer immediately surrounding burrowing animals or irrigated tubes. The most important biological factors likely include irrigation behavior and burrow density and size.

  15. Predicting copper phytotoxicity based on pore-water pCu.

    PubMed

    Kader, Mohammed; Lamb, Dane T; Wang, Liang; Megharaj, Mallavarapu; Naidu, Ravi

    2016-04-01

    The free ion activity and "biotic ligand" models predict that the free metal ion and other pore-water parameters describe terrestrial phytotoxicity. In this study, pore-water chemistry and measured Cu(2+) was used to describe phytotoxicity of cucumber (Cucumis sativa L) in 10 contrasting soils at different soil Cu loadings. Both soil solution Cu (Cu(pw)) and Cu(2+) successfully described the response variable for all ten soils with R(2) values of 0.73 and 0.66, respectively. Separation of soils as acid and alkaline and fitting separately showed that there was a strongly significant fit for both log Cu(2+) and log Cu(pw) in acidic soils (R(2) = 0.92 and 0.86, respectively) but weakly significant fit for alkaline soils. The pCu EC50 and EC10 values in all acidic soils for cucumber were 5.83 (6.03-5.63) and 7.53 (8.27-7.00), respectively. In our dataset alkaline soils need to be treated individually. In addition, pCu could be predicted based on pH and total concentration alone. Despite only 12 weeks 'ageing' there was quantitative agreement between pCu model from this study and predicted pCu from Sauvé et al. This agreement from studies performed independently indicates that, at least in the case of Cu(2+), the difference in an ageing period of ≥10 years appears minimal. PMID:26738879

  16. Toxicity identification evaluation of metal-contaminated sediments using an artificial pore water containing dissolved organic carbons

    SciTech Connect

    Boucher, A.M.; Watzin, M.C.

    1999-03-01

    Recent investigations of sediment-associated pollutants in Lake Champlain indicated significant contamination with As, Mn, and Ni in Outer Malletts Bay, Vermont, US. Ceriodaphnia dubia exposed to sediment pore water from several sites in Outer Malletts Bay showed repeatable, acute mortality at only one site. A toxicity identification evaluation (TIE) was conducted on pore water to determine the contaminants causing mortality at this site. Unlike most TIE applications, the dilution water used in these tests was formulated to match the hardness, alkalinity, pH, conductivity, and dissolved organic carbon content of the pore water. Results from phase 1 of the TIE indicated that divalent metals may be responsible for toxicity. Phase 2 results revealed levels of Mn above LC50 values. Spiking experiments employed in phase 3 confirmed Mn as the principal toxicant in sediment pore water. The formulated pore water worked well and helped ensure that toxicant behavior was influenced primarily by each TIE manipulation and not by physical and chemical differences between the dilution and site water. Although the Mn toxicity at this site may be the result of its unique geomorphology, this situation underscores the need to look broadly for potential toxicants when evaluating contaminated sites.

  17. Measurement and conceptual modelling of herbicide transport to field drains in a heavy clay soil with implications for catchment-scale water quality management.

    PubMed

    Tediosi, A; Whelan, M J; Rushton, K R; Thompson, T R E; Gandolfi, C; Pullan, S P

    2012-11-01

    Propyzamide and carbetamide are essential for blackgrass control in oilseed rape production. However, both of these compounds can contaminate surface waters and pose compliance problems for water utilities. The transport of propyzamide and carbetamide to an instrumented field drain in a small clay headwater tributary of the Upper Cherwell catchment was monitored over a winter season. Despite having very different sorption and dissipation properties, both herbicides were transported rapidly to the drain outlet in the first storm event after application, although carbetamide was leached more readily than propyzamide. A simple conceptual model was constructed to represent solute displacement from mobile pore water and preferential flow to drains. The model was able to reproduce the timing and magnitude of herbicide losses well, lending support to its conceptual basis. Measured losses in drainflow in the month following application were 1.1 and 8.1%, respectively, for propyzamide and carbetamide. Differences were due to a combination of differences in herbicide mobility and due to the fact that the monitoring period for carbetamide was hydrologically more active. For both compounds, losses were greater than those typically reported elsewhere for other herbicides. The data suggest that drainflow is the dominant pathway for the transfer of these herbicides to the catchment outlet, where water is abstracted for municipal supply. This imposes considerable constraints on the management options available to reduce surface water concentrations of herbicides in this catchment. PMID:22982449

  18. SeamountFlux: Pore water geochemistry and sediment characteristics (Guatemala Basin, East Pacific)

    NASA Astrophysics Data System (ADS)

    Pichler, T.; Poonchai, W.; Schmidt-Schierhorn, F.; Villinger, H. W.

    2011-12-01

    The scientific goal of the project "SeamountFlux" is to study a process, which can possibly contribute significantly to large scale cooling of the oceanic crust. The focus of the study is to investigate the exchange of matter and energy between the ocean and the upper young oceanic crust in the vicinity of unexplained circular depressions in the sedimentary cover, which are widely spread in the equatorial Pacific. A possible model for the formation of these so-called "hydrothermal pits" is the dissolution of calcium carbonate (CaCO3) minerals by upward flowing warm fluids, which are under-saturated in CaCO3. Seamounts are suspected to act as an entrance point for cold seawater, which then equilibrates with the basaltic oceanic crust prior to exiting through the pits. Such a process should affect the thermal structure in and around the pits as well as the geochemistry of the pore water. During cruise SO207 (June/July 2010 on the German RV Sonne) in the vicinity of ODP/IODP Site 1256 and ODP site 844 (Guatemala Basin, eastern equatorial Pacific) we collected 24 gravity cores varying in length between 3.3 m and 10.6 m from 3 distinct working areas. The cores were generally taken along a transect, starting in the center of a pit, across the pit slope to the surrounding seafloor. From these cores a total of 451 pore water samples were collected and analyzed onboard (pH, Eh, Fe, NH4 and alkalinity), as well as in the laboratory (Cl, SO4, Na, Mg, K, Ca, Sr and Mn). First results do not show any obvious evidence for the "hydrothermal" hypotheses. Pore water profiles were more or less identical, whether collected from within or from outside a pit. Chloride, SO4, Na, Mg, K, Ca, and Sr concentrations were identical to those in seawater. Particularly higher Ca and Sr concentrations were to be expected if calcium carbonate dissolution took place within the sediments. With respect to sediment composition and physico-chemical conditions in the pore waters, we observed larger

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

    NASA Astrophysics Data System (ADS)

    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

  20. Microstructural analysis of Iberian expanded clay aggregates.

    PubMed

    Bogas, J Alexandre; Mauricio, António; Pereira, M F C

    2012-10-01

    This article presents a detailed study of the microstructure of Iberian expanded clay lightweight aggregates (LWA). Other than more commonly used mercury porosimetry (MP) and water absorption methods, the experimental study involves optical microscopy, scanning electron microscopy (SEM), and microtomography (μ-CT). Pore connectivity and how it is deployed are shown to some degree, and the pore size spectrum is estimated. LWA are in general characterized by a dense outer shell up to 200 μm thick, encasing an inner cellular structure of 10-100 times bigger pore size. Aggregate pore sizes may span from some hundreds of nanometers up to over 1 mm, though the range of 1-25 μm is more typical. A noteworthy fraction of these pores is closed, and they are mainly up to 1 μm. It is also shown that macropore spatial arrangement is affected by the manufacturing process. A step forward is given to understanding how the outer shell and the inner pore network influence the mechanical and physical LWA properties, particularly the density and water absorption. The joint consideration of μ-CT and SEM seems to be the most appropriate methodology to study LWA microstructure. MP analysis is likely to distort LWA pore spectrum assessment. PMID:23031601

  1. Pore-Filling Ice Diffusively Derived From Atmospheric Water Vapor Under Mars Conditions

    NASA Astrophysics Data System (ADS)

    Hudson, T. L.; Aharonson, O.; Oslund, K.; Siegler, M.; Schorghofer, N.

    2007-12-01

    Conditions during previous climate epochs on Mars may have allowed subsurface ice to form via diffusion from a moist atmosphere. The deposition and recharge of such reservoirs is driven by subsurface humidity gradients; an atmospheric frostpoint greater than that of the subsurface results in a net influx of vapor which deposits in pore space as ice. Observations of the hydrogen distribution by Mars Odyssey indicate that the ice content of some high-latitude regions (e.g. Olympia Undae) exceeds 70% by volume. Reconciliation of this concentration with typically lower porosities of soils demands a process of ice segregation (lensing) and mechanical expansion, or direct precipitation. We investigate the possibility and consequences of volumetrically significant subsurface ice derived from the Mars atmosphere by vapor diffusion, at present and in the past. Experiments conducted at the Mars Simulation and Ice Laboratory at Caltech demonstrate that diffusion processes produce significant pore-filling ice under controlled lab conditions. Atmospherically derived water vapor is deposited within an initially dry porous medium subject to a strong (~15~K/cm) temperature gradient forcing a humidity gradient. This mimics the humidity gradient caused by time varying temperatures in the shallow subsurface of Mars with a static experimental setup. The vertical profile of water content is determined at the end of the experiment by gravimetric analysis and the thermal conductivity of the ice-bearing sample is calculated. Pore filling fractions up to 100% have been measured. Profiles with a marked transition in ice content at the frostpoint depth are observed corresponding to a subsurface ice table. The data enable calculation of time-varying diffusion coefficients which exhibit a reduction of up to an order of magnitude with respect to ice-free regolith. These are compared to numerical models of vapor diffusion incorporating ice deposition and pore constriction. Formation theories of

  2. Partitioning of PAHs in pore water from mangrove wetlands in Shantou, China.

    PubMed

    Cao, Qi min; Wang, Hua; Qin, Jian qiao; Chen, Gui zhu; Zhang, Yong bei

    2015-01-01

    To investigate the trend of selected polycyclic aromatic hydrocarbons (PAHs) partitioning, fifteen pore water samples collected from the sediments of three mangrove wetlands were analyzed, and the partition coefficients and the partition model for the PAHs were determined by the correlation between K(oc) and octanol-water partition coefficient (K(ow)). The results revealed that the mean Kp values in inner mangrove wetlands were between 143 and 1031 L /Kg; the particulate organic carbon (POC) could strongly adsorb low-ring PAHs; the PAHs partitioning was on a obvious trend transported to particle phase. We suggest that the classic equilibrium model of organic carbon normalized (K(p)=K(oc)f(oc)) may be used to predict the trend of the selected PAHs partitioning. PMID:25450913

  3. Changes in14c activity over time during vacuum distillation of carbon from rock pore water

    USGS Publications Warehouse

    Davidson, G.R.; Yang, I.C.

    1999-01-01

    The radiocarbon activity of carbon collected by vacuum distillation from a single partially saturated tuff began to decline after approximately 60% of the water and carbon had been extracted. Disproportionate changes in 14C activity and ??13C during distillation rule out simple isotopic fractionation as a causative explanation. Additional phenomena such as matrix diffusion and ion exclusion in micropores may play a role in altering the isotopic value of extracted carbon, but neither can fully account for the observed changes. The most plausible explanation is that distillation recovers carbon from an adsorbed phase that is depleted in 14C relative to DIC in the bulk pore water. ?? 1999 by the Arizona Board of Regents on behalf of the University of Arizona.

  4. Synthesis and characterization of a PbO{sub 2}-clay nanocomposite: Removal of lead from water using montmorillonite

    SciTech Connect

    Aroui, L.; Zerroual, L.; Boutahala, M.

    2012-02-15

    Graphical abstract: The replacement of Na by Pb in the interlayer space of the smectite leads to a decrease in the intensity of the the (0 0 1) reflection as the concentration of lead nitrate increases. A significant restructuring at the particle scale is observed leading probably to the exfoliation of the caly. In addition, the thermal behaviour of the montmorillonite samples with regard to their dehydration and dehydroxilation capacities is significantly influenced. This leads to a lowering of the water content and a decrease in the ionic conductivity of the clay. Highlights: Black-Right-Pointing-Pointer In the clay, Pb replaces Na ions and a significant restructuring at the particle scale is observed. Black-Right-Pointing-Pointer Pb influenced significantly the thermal behaviour of the clay with regard to its dehydration. Black-Right-Pointing-Pointer In the interlayer space, the exchange of Na by Pb leads to a decrease in the protonic conductivity. Black-Right-Pointing-Pointer A PbO{sub 2}-clay nanocomposite material with good conductivity is synthesized. -- Abstract: The aim of this paper is to present the results obtained with Pb(II) sorption on an Algerian Clay. The experiments were carried out using a batch process. Powder X-rays diffraction patterns (PXRD) prove that in the montmorillonite Pb replaces Na ions. A significant restructuring at the particle scale is observed leading to the disappearance of the d{sub 001} reflection of the clay at high concentrations of lead. The replacement of hydrated Na with Pb ions influenced significantly the thermal behaviour of the montmorillonite samples with regard to their dehydration and dehydroxilation capacities with a lowering of the water content. A PbO{sub 2}-clay composite material with good electrical conductivity is synthesized.

  5. Phosphates in some missouri refractory clays

    USGS Publications Warehouse

    Hall, R.B.; Foord, E.E.; Keller, D.J.; Keller, W.D.

    1997-01-01

    This paper describes in detail phosphate minerals occurring in refractory clays of Missouri and their effect on the refractory degree of the clays. The minerals identified include carbonate-fluorapatite (francolite), crandallite, goyazite, wavellite, variscite and strengite. It is emphasized that these phosphates occur only in local isolated concentrations, and not generally in Missouri refractory clays. The Missouri fireclay region comprises 2 districts, northern and southern, separated by the Missouri River In this region, clay constitutes a major part of the Lower Pennsylvanian Cheltenham Formation. The original Cheltenham mud was an argillic residue derived from leaching and dissolution of pre-Pennsylvanian carbonates. The mud accumulated on a karstic erosion surface truncating the pre-Cheltenham rocks. Fireclays of the northern district consist mainly of poorly ordered kaolinite, with variable but minor amounts of illite, chlorite and fine-grained detrital quartz. Clays of the southern district were subjected to extreme leaching that produced well-ordered kaolinite flint clays. Local desilication formed pockets of diaspora, or more commonly, kaolinite, with oolite-like nubs or burls of diaspore ("burley" clay). The phosphate-bearing materials have been studied by X-ray diffraction (XRD), scanning electron microscopy-energy dispersive spectral analysis (SEM-EDS) and chemical analysis. Calcian goyazite was identified in a sample of diaspore, and francolite in a sample of flint clay. A veinlet of wavellite occurs in flint clay at one locality, and a veinlet of variscite-strengite at another locality. The Missouri flint-clay-hosted francolite could not have formed in the same manner as marine francolite The evidence suggests that the Cheltenham francolite precipitated from ion complexes in pore water nearly simultaneously with crystallization of kaolinite flint clay from an alumina-silica gel. Calcian goyazite is an early diagenetic addition to its diaspore host

  6. Low Pore Connectivity Increases Bacterial Diversity in Soil▿

    PubMed Central

    Carson, Jennifer K.; Gonzalez-Quiñones, Vanesa; Murphy, Daniel V.; Hinz, Christoph; Shaw, Jeremy A.; Gleeson, Deirdre B.

    2010-01-01

    One of soil microbiology's most intriguing puzzles is how so many different bacterial species can coexist in small volumes of soil when competition theory predicts that less competitive species should decline and eventually disappear. We provide evidence supporting the theory that low pore connectivity caused by low water potential (and therefore low water content) increases the diversity of a complex bacterial community in soil. We altered the pore connectivity of a soil by decreasing water potential and increasing the content of silt- and clay-sized particles. Two textures were created, without altering the chemical properties or mineral composition of the soil, by adding silt- and clay-sized particles of quartz to a quartz-based sandy soil at rates of 0% (sand) or 10% (silt+clay). Both textures were incubated at several water potentials, and the effect on the active bacterial communities was measured using terminal restriction fragment length polymorphism (TRFLP) of bacterial 16S rRNA. Bacterial richness and diversity increased as water potential decreased and soil became drier (P < 0.012), but they were not affected by texture (P > 0.553). Bacterial diversity increased at water potentials of ≤2.5 kPa in sand and ≤4.0 kPa in silt+clay, equivalent to ≤56% water-filled pore space (WFPS) in both textures. The bacterial community structure in soil was affected by both water potential and texture (P < 0.001) and was correlated with WFPS (sum of squared correlations [δ2] = 0.88, P < 0.001). These findings suggest that low pore connectivity is commonly experienced by soil bacteria under field conditions and that the theory of pore connectivity may provide a fundamental principle to explain the high diversity of bacteria in soil. PMID:20418420

  7. Organic geochemistry and pore water chemistry of sediments from Mangrove Lake, Bermuda

    USGS Publications Warehouse

    Hatcher, P.G.; Simoneit, B.R.T.; MacKenzie, F.T.; Neumann, A.C.; Thorstenson, D.C.; Gerchakov, S.M.

    1982-01-01

    Mangrove Lake, Bermuda, is a small coastal, brackish-water lake that has accumulated 14 m of banded, gelatinous, sapropelic sediments in less than 104 yr. Stratigraphic evidence indicates that Mangrove Lake's sedimentary environment has undergone three major depositional changes (peat, freshwater gel, brackish-water gel) as a result of sea level changes. The deposits were examined geochemically in an effort to delineate sedimentological and diagenetic changes. Gas and pore water studies include measurements of sulfides, ammonia, methane, nitrogen gas, calcium, magnesium, chloride, alkalinity, and pH. Results indicate that sulfate reduction is complete, and some evidence is presented for bacterial denitrification and metal sulfide precipitation. The organic-rich sapropel is predominantly algal in origin, composed mostly of carbohydrates and insoluble macromolecular organic matter called humin with minor amounts of proteins, lipids, and humic acids. Carbohydrates and proteins undergo hydrolysis with depth in the marine sapropel but tend to be preserved in the freshwater sapropel. The humin, which has a predominantly aliphatic structure, increases linearly with depth and composes the greatest fraction of the organic matter. Humic acids are minor components and are more like polysaccharides than typical marine humic acids. Fatty acid distributions reveal that the lipids are of an algal and/or terrestrial plant source. Normal alkanes with a total concentration of 75 ppm exhibit two distribution maxima. One is centered about n-C22 with no odd/even predominance, suggestive of a degraded algal source. The other is centered at n-C31 with a distinct odd/even predominance indicative of a vascular plant origin. Stratigraphic changes in the sediment correlate to observed changes in the gas and pore water chemistry and the organic geochemistry. ?? 1982.

  8. Investigation of Two Novel Approaches for Detection of Sulfate Ion and Methane Dissolved in Sediment Pore Water Using Raman Spectroscopy

    PubMed Central

    Du, Zengfeng; Chen, Jing; Ye, Wangquan; Guo, Jinjia; Zhang, Xin; Zheng, Ronger

    2015-01-01

    The levels of dissolved sulfate and methane are crucial indicators in the geochemical analysis of pore water. Compositional analysis of pore water samples obtained from sea trials was conducted using Raman spectroscopy. It was found that the concentration of SO42− in pore water samples decreases as the depth increases, while the expected Raman signal of methane has not been observed. A possible reason for this is that the methane escaped after sampling and the remaining concentration of methane is too low to be detected. To find more effective ways to analyze the composition of pore water, two novel approaches are proposed. One is based on Liquid Core Optical Fiber (LCOF) for detection of SO42−. The other one is an enrichment process for the detection of CH4. With the aid of LCOF, the Raman signal of SO42− is found to be enhanced over 10 times compared to that obtained by a conventional Raman setup. The enrichment process is also found to be effective in the investigation to the prepared sample of methane dissolved in water. By CCl4 extraction, methane at a concentration below 1.14 mmol/L has been detected by conventional Raman spectroscopy. All the obtained results suggest that the approach proposed in this paper has great potential to be developed as a sensor for SO42− and CH4 detection in pore water. PMID:26016919

  9. Unexpected Arsenate/Arsenite Gradients in Pore-Water Profiles From a Shallow-Water Hydrothermal System

    NASA Astrophysics Data System (ADS)

    Price, R. E.; Pichler, T.; Amend, J. P.

    2005-12-01

    The shallow-water submarine hot-springs near Ambitle Island in eastern Papua New Guinea provide us with the exceptional opportunity to study the biogeochemistry of arsenic (As) along a horizontal and a vertical gradient. Hydrothermal venting occurs as discharge of a clear, two-phase fluid from discrete orifices, 10-15 cm in diameter, with minor phase separation (boiling) at the sea floor. In addition diffuse seepage of the same fluid, but without phase separation occurs throughout the area. Fluid temperatures for individual springs range from 89 to 98/degC, while diffuse seepage temperatures are generally lower. The hydrothermal fluids contain up to 1000 μg/L As, which is exclusively present as the trivalent species arsenite (As(III)). Stepping away to a distance of 300 m from the area of focused venting, we collected 10 pore-water profiles down to a depth of 1 m in 10-cm intervals. The profiles were collected with a 10-port sampler by simultaneously filling 10 syringes to reduce vertical flow. In those samples 10 cm below the seawater-sediment interface, total As concentrations decreased from 900 μg/L closest to the vents to 6 μg/L at 300 m away. The 6 μg/L at 300 m is still 3-times the expected value for seawater, thus indicating the potential extension of hydrothermal influence. As(V)/As(III) ratios were determined to investigate the transport and fate of As(III) and to evaluate horizontal and vertical redox gradients. Surprisingly, As in the vertical pore-water profiles occurs predominantly as the oxidized form, As(V), with As(V)/As(III) ratios ranging from 0.05 to 0.1, whereas vertical pore-water profiles from a "non-hydrothermal" control site show a redox gradient with a ratio ranging from 0.5 to 1.0. Along the horizontal gradient the 10 cm pore-water samples show an increase in the As(V)/As(III) ratio, from 0.07 near the vents to 1.75 at 300 m away. These unexpected ratios suggest that microbes may be catalyzing the oxidation of hydrothermal As(III) to

  10. Treatment with coated layer double hydroxide clays decreases the toxicity of copper-contaminated water.

    PubMed

    Blake, Deanne; Nar, Mangesh; D'Souza, Nandika Anne; Glenn, J Brad; Klaine, Stephen J; Roberts, Aaron P

    2014-05-01

    Copper is a common pollutant found in watersheds that exerts toxic effects on both invertebrates and vertebrates. Layer double hydroxide (LDH) clays are able to adsorb a wide range of contaminants through ion-exchange mechanisms. Coating LDH clays with various materials alters the aggregation of clay particles into the nano-size range, thus increasing relative surface area and offering great potential for contaminant remediation. The goal of this study was to determine if treatment with coated LDH clays decreases the toxicity of copper-containing solutions to Daphnia magna. Four LDH clays with different coatings used to alter hydrophobicity were as follows: used: Na(+) montmorillonite, Zn-Al LDH-nitrate, Zn-Al LDH-stearate, and Zn-Al LDH-carbonate. It was determined that coated LDH clays decreased copper toxicity by decreasing bioavailability and that smaller aggregate sizes decreased bioavailability the most. 96 h LC50 values increased by as much as 4.2 times with the treatment of the solutions with 100 mg/L LDH clay. Copper analysis of the clay and solutions indicated that the clays work by decreasing copper bioavailability by way of a binding mechanism. Coated LDH clays hold promise as a small-scale remediation tool or as an innovative tool for toxicity identification and evaluation characterization of metals. PMID:24442186

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

    NASA Astrophysics Data System (ADS)

    Zhou, BeiBei; Wang, QuanJiu

    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.

  12. Permeability of Clay Concretes

    NASA Astrophysics Data System (ADS)

    Solomon, F.; Ekolu, S. O.

    2015-11-01

    This paper presents an investigation on the effect of clay addition on water permeability and air permeability of concretes. Clay concrete mixes consisted of 0 to 40% clay content incorporated as cement replacement. Flow methods using triaxial cells and air permeameters were used for measuring the injected water and air flows under pressure. It was found that the higher the clay content in the mixture, the greater the permeability. At higher water-cement ratios (w/c), the paste matrix is less dense and easily allows water to ingress into concrete. But at high clay contents of 30 to 40% clay, the variation in permeability was significantly diminished among different concrete mixtures. It was confirmed that air permeability results were higher than the corresponding water permeability values when all permeability coefficients were converted to intrinsic permeability values.

  13. Monitoring water transport between pores and voids in aerated gypsum using two-dimensional nuclear magnetic resonance exchange measurements

    NASA Astrophysics Data System (ADS)

    Song, Kyung-Min; Mitchell, Jonathan; Jaffel, Hamouda; Gladden, Lynn F.

    2012-03-01

    We investigate the connectivity between aeration voids (radius 200-300 µm) and pores (radius 20 µm) in aerated gypsum plaster using two-dimensional (2D) nuclear magnetic resonance T2-T2 relaxation time exchange experiments. These measurements provide an estimate of diffusive exchange rates for water molecules moving between environments differentiated by relaxation time. Aerated gypsum is a lightweight material manufactured by the inclusion of voids to reduce the bulk density. Such materials exhibit a multi-modal distribution of pore and void sizes and are associated with novel water imbibition processes. Here, we use T2-T2 exchange experiments to characterize the extent of fluid communication between the voids and pores to better understand the structure-transport relationships in these systems. In turn, this will aid the design of gypsum plasters with improved physical and mechanical properties. Utilizing an analytical model based on diffusion-driven exchange, we extract exchange times and hence diffusive length-scales, which are equivalent to the pore diameter. Overall, we conclude that the voids and pores are well connected. This confirms our previous hypothesis that water uptake occurs via capillary-driven imbibition through a continuum of voids and pores in aerated gypsum.

  14. Release of Escherichia coli from Foreshore Sand and Pore Water during Intensified Wave Conditions at a Recreational Beach.

    PubMed

    Vogel, Laura J; O'Carroll, Denis M; Edge, Thomas A; Robinson, Clare E

    2016-06-01

    Foreshore beach sands and pore water may act as a reservoir and nonpoint source of fecal indicator bacteria (FIB) to surface waters. This paper presents data collected at a fine sand beach on Lake Huron, Canada over three field events. The data show that foreshore sand erosion as wave height increases results in elevated Escherichia coli concentrations in surface water, as well as depletion of E. coli from the foreshore sand and pore water. E. coli initially attached to foreshore sand rather than initially residing in the pore water was found to be the main contributor to elevated surface water concentrations. Surface water E. coli concentrations were a function of not only wave height (and associated sand erosion) but also the time elapsed since a preceding period of high wave intensity. This finding is important for statistical regression models used to predict beach advisories. While calculations suggest that foreshore sand erosion may be the dominant mechanism for releasing E. coli to surface water during intensified wave conditions at a fine sand beach, comparative characterization of the E. coli distribution at a coarse sand-cobble beach suggests that interstitial pore water flow and discharge may be more important for coarser sand beaches. PMID:27120087

  15. Active Sampling Device for Determining Pollutants in Surface and Pore Water - the In Situ Sampler for Biphasic Water Monitoring.

    PubMed

    Supowit, Samuel D; Roll, Isaac B; Dang, Viet D; Kroll, Kevin J; Denslow, Nancy D; Halden, Rolf U

    2016-01-01

    We designed and evaluated an active sampling device, using as analytical targets a family of pesticides purported to contribute to honeybee colony collapse disorder. Simultaneous sampling of bulk water and pore water was accomplished using a low-flow, multi-channel pump to deliver water to an array of solid-phase extraction cartridges. Analytes were separated using either liquid or gas chromatography, and analysis was performed using tandem mass spectrometry (MS/MS). Achieved recoveries of fipronil and degradates in water spiked to nominal concentrations of 0.1, 1, and 10 ng/L ranged from 77 ± 12 to 110 ± 18%. Method detection limits (MDLs) were as low as 0.040-0.8 ng/L. Extraction and quantitation of total fiproles at a wastewater-receiving wetland yielded concentrations in surface water and pore water ranging from 9.9 ± 4.6 to 18.1 ± 4.6 ng/L and 9.1 ± 3.0 to 12.6 ± 2.1 ng/L, respectively. Detected concentrations were statistically indistinguishable from those determined by conventional, more laborious techniques (p > 0.2 for the three most abundant fiproles). Aside from offering time-averaged sampling capabilities for two phases simultaneously with picogram-per-liter MDLs, the novel methodology eliminates the need for water and sediment transport via in situ solid phase extraction. PMID:26905924

  16. Active Sampling Device for Determining Pollutants in Surface and Pore Water - the In Situ Sampler for Biphasic Water Monitoring

    NASA Astrophysics Data System (ADS)

    Supowit, Samuel D.; Roll, Isaac B.; Dang, Viet D.; Kroll, Kevin J.; Denslow, Nancy D.; Halden, Rolf U.

    2016-02-01

    We designed and evaluated an active sampling device, using as analytical targets a family of pesticides purported to contribute to honeybee colony collapse disorder. Simultaneous sampling of bulk water and pore water was accomplished using a low-flow, multi-channel pump to deliver water to an array of solid-phase extraction cartridges. Analytes were separated using either liquid or gas chromatography, and analysis was performed using tandem mass spectrometry (MS/MS). Achieved recoveries of fipronil and degradates in water spiked to nominal concentrations of 0.1, 1, and 10 ng/L ranged from 77 ± 12 to 110 ± 18%. Method detection limits (MDLs) were as low as 0.040-0.8 ng/L. Extraction and quantitation of total fiproles at a wastewater-receiving wetland yielded concentrations in surface water and pore water ranging from 9.9 ± 4.6 to 18.1 ± 4.6 ng/L and 9.1 ± 3.0 to 12.6 ± 2.1 ng/L, respectively. Detected concentrations were statistically indistinguishable from those determined by conventional, more laborious techniques (p > 0.2 for the three most abundant fiproles). Aside from offering time-averaged sampling capabilities for two phases simultaneously with picogram-per-liter MDLs, the novel methodology eliminates the need for water and sediment transport via in situ solid phase extraction.

  17. Active Sampling Device for Determining Pollutants in Surface and Pore Water – the In Situ Sampler for Biphasic Water Monitoring

    PubMed Central

    Supowit, Samuel D.; Roll, Isaac B.; Dang, Viet D.; Kroll, Kevin J.; Denslow, Nancy D.; Halden, Rolf U.

    2016-01-01

    We designed and evaluated an active sampling device, using as analytical targets a family of pesticides purported to contribute to honeybee colony collapse disorder. Simultaneous sampling of bulk water and pore water was accomplished using a low-flow, multi-channel pump to deliver water to an array of solid-phase extraction cartridges. Analytes were separated using either liquid or gas chromatography, and analysis was performed using tandem mass spectrometry (MS/MS). Achieved recoveries of fipronil and degradates in water spiked to nominal concentrations of 0.1, 1, and 10 ng/L ranged from 77 ± 12 to 110 ± 18%. Method detection limits (MDLs) were as low as 0.040–0.8 ng/L. Extraction and quantitation of total fiproles at a wastewater-receiving wetland yielded concentrations in surface water and pore water ranging from 9.9 ± 4.6 to 18.1 ± 4.6 ng/L and 9.1 ± 3.0 to 12.6 ± 2.1 ng/L, respectively. Detected concentrations were statistically indistinguishable from those determined by conventional, more laborious techniques (p > 0.2 for the three most abundant fiproles). Aside from offering time-averaged sampling capabilities for two phases simultaneously with picogram-per-liter MDLs, the novel methodology eliminates the need for water and sediment transport via in situ solid phase extraction. PMID:26905924

  18. Dissolved N2/Ar Ratios in Sedimentary Pore Waters: A New Twist in Marine Nitrogen Cycle

    NASA Astrophysics Data System (ADS)

    Berelson, W.; Prokopenko, M. G.; Sigman, D. M.; Hammond, D.

    2008-12-01

    The nitrogen cycle is comprised predominantly of biologically mediated pathways, leading to a series of negative feedbacks that stabilize the cycle. Sedimentary denitrification, the major sink in the nitrogen budget, is regulated by the rate of organic carbon rain to the sea floor, as well as oxygen concentrations in overlying bottom waters. The sensitivity of sedimentary denitrification as a negative feedback can be expressed as a ratio between total denitrification (including nitrification sub-cycle) rates integrated over depth (fluxes) and fluxes of remineralized organic carbon out of the sediments, Ndenitr/Coxid_total. We have investigated benthic nitrogen cycling in three, semi-enclosed basins of the California Borderlands: Santa Monica, San Pedro and Santa Barbara located in the regime of seasonal coastal upwelling. Deep water in these basins is separated from the open ocean by sills of various depths, contributing to the low [O2], <1 to10 uM. In this study, we developed a method to sample pore waters for dissolved gas analysis. Ratios between O2, Ar and N2 were determined on extracted pore waters with 1) offline cryogenic extraction and subsequent analysis on Finnigan Delta Plus IRMS with 8 collectors; 2) Membrane Inlet Mass Spectrometery (MIMS). Vertical profiles of pore water N2/Ar in the three basins indicate N2 production at depth horizons which exceed by a factor of 5 to 20 the depth of nitrate penetration supported solely by diffusive flux. At depths of maximum subsurface N2 production, we discovered large pools of intracellular nitrate. The relationship between δ15N and δ18O of nitrate are consistent with the activity of a membrane-bound nitrate reductase affecting the measured isotopic composition of the nitrate pool (Granger et al., 2008, in press). In addition, increases in δ15N of pore water NH4 at this depth suggests that at least some of the nitrate might be used for anaerobic ammonium oxidation. Our model estimates up to 25 % of the measured

  19. Mercury cycling in boreal ecosystems: The long-term effect of acid rain constituents on peatland pore water methylmercury concentrations

    NASA Astrophysics Data System (ADS)

    Branfireun, Brian A.; Bishop, Kevin; Roulet, Nigel T.; Granberg, Gunnar; Nilsson, Mats

    Sulphate-reducing bacteria have been identified as primary methylators of mercury (Hg) in the laboratory and in field investigations. However, no studies have investigated the effect of long-term deposition of sulphate on methylmercury (MeHg) dynamics in peatlands, which are known to be significant sources of MeHg to downstream waters in the boreal forest zone. As an ancillary experiment to a larger project investigating the effects of acid rain constituents on peatland carbon dynamics, the influence of experimentally elevated Na2SO4 and/or NH4NO3 deposition on peat pore water MeHg concentrations was determined using a simple mesocosm experimental design. After three years, additions of S in amounts equivalent to the 1980s dry and wet deposition in Southern Sweden resulted in peat pore water MeHg concentrations up to six times above background levels. Elevated N loads had no effect on pore water MeHg concentrations.

  20. Mineralogy and pore water chemistry of a boiler ash from a MSW fluidized-bed incinerator

    SciTech Connect

    Bodenan, F.; Guyonnet, D.; Piantone, P.; Blanc, P.

    2010-07-15

    This paper presents an investigation of the mineralogy and pore water chemistry of a boiler ash sampled from a municipal solid waste fluidized-bed incinerator, subject to 18 months of dynamic leaching in a large percolation column experiment. A particular focus is on the redox behaviour of Cr(VI) in relation to metal aluminium Al{sup 0}, as chromium may represent an environmental or health hazard. The leaching behaviour and interaction between Cr(VI) and Al{sup 0} are interpreted on the basis of mineralogical evolutions observed over the 18-month period and of saturation indices calculated with the geochemical code PhreeqC and reviewed thermodynamic data. Results of mineralogical analyses show in particular the alteration of mineral phases during leaching (e.g. quartz and metal aluminium grains), while geochemical calculations suggest equilibria of percolating fluids with respect to specific mineral phases (e.g. monohydrocalcite and aluminium hydroxide). The combination of leaching data on a large scale and mineralogical analyses document the coupled leaching behaviour of aluminium and chromium, with chromium appearing in the pore fluids in its hexavalent and mobile state once metal aluminium is no longer available for chromium reduction.

  1. Mineralogy and pore water chemistry of a boiler ash from a MSW fluidized-bed incinerator.

    PubMed

    Bodénan, F; Guyonnet, D; Piantone, P; Blanc, P

    2010-07-01

    This paper presents an investigation of the mineralogy and pore water chemistry of a boiler ash sampled from a municipal solid waste fluidized-bed incinerator, subject to 18 months of dynamic leaching in a large percolation column experiment. A particular focus is on the redox behaviour of Cr(VI) in relation to metal aluminium Al(0), as chromium may represent an environmental or health hazard. The leaching behaviour and interaction between Cr(VI) and Al(0) are interpreted on the basis of mineralogical evolutions observed over the 18-month period and of saturation indices calculated with the geochemical code PhreeqC and reviewed thermodynamic data. Results of mineralogical analyses show in particular the alteration of mineral phases during leaching (e.g. quartz and metal aluminium grains), while geochemical calculations suggest equilibria of percolating fluids with respect to specific mineral phases (e.g. monohydrocalcite and aluminium hydroxide). The combination of leaching data on a large scale and mineralogical analyses document the coupled leaching behaviour of aluminium and chromium, with chromium appearing in the pore fluids in its hexavalent and mobile state once metal aluminium is no longer available for chromium reduction. PMID:20153161

  2. Solid-state 13C NMR studies of dissolved organic matter in pore waters from different depositional environments

    USGS Publications Warehouse

    Orem, W.H.; Hatcher, P.G.

    1987-01-01

    Dissolved organic matter (DOM) in pore waters from sediments of a number of different depositional environments was isolated by ultrafiltration using membranes with a nominal molecular weight cutoff of 500. This > 500 molecular weight DOM represents 70-98% of the total DOM in these pore waters. We determined the gross chemical structure of this material using both solid-state 13C nuclear magnetic resonance spectroscopy and elemental analysis. Our results show that the DOM in these pore waters appears to exist as two major types: one type dominated by carbohydrates and paraffinic structures and the second dominated by paraffinic and aromatic structures. We suggest that the dominance of one or the other structural type of DOM in the pore water depends on the relative oxidizing/reducing nature of the sediments as well as the source of the detrital organic matter. Under dominantly anaerobic conditions carbohydrates in the sediments are degraded by bacteria and accumulate in the pore water as DOM. However, little or no degradation of lignin occurs under these conditions. In contrast, sediments thought to be predominantly aerobic in character have DOM with diminished carbohydrate and enhanced aromatic character. The aromatic structures in the DOM from these sediments are thought to arise from the degradation of lignin. The large amounts of paraffinic structures in both types of DOM may be due to the degradation of unidentified paraffinic materials in algal or bacterial remains. ?? 1987.

  3. Evidence and characteristics of a diverse and metabolically active microbial community in deep subsurface clay borehole water.

    PubMed

    Wouters, Katinka; Moors, Hugo; Boven, Patrick; Leys, Natalie

    2013-12-01

    The Boom Clay in Belgium is investigated in the context of geological nuclear waste disposal, making use of the High Activity Disposal Experimental Site (HADES) underground research facility. This facility, located in the Boom Clay at a depth of 225 m below the surface, offers a unique access to a microbial community in an environment, of which all geological and geochemical characteristics are being thoroughly studied. This study presents the first elaborate description of a microbial community in water samples retrieved from a Boom Clay piezometer (borehole water). Using an integrated approach of microscopy, metagenomics, activity screening and cultivation, the presence and activity of this community are disclosed. Despite the presumed low-energy environment, microscopy and molecular analyses show a large bacterial diversity and richness, tending to correlate positively with the organic matter content of the environment. Among 10 borehole water samples, a core bacterial community comprising seven bacterial phyla is defined, including both aerobic and anaerobic genera with a range of metabolic preferences. In addition, a corresponding large fraction of this community is found cultivable and active. In conclusion, this study shows the possibility of a microbial community of relative complexity to persist in subsurface Boom Clay borehole water. PMID:23802615

  4. Pilot-scale in situ bioremediation of HMX and RDX in soil pore water in Hawaii.

    PubMed

    Payne, Zachary M; Lamichhane, Krishna M; Babcock, Roger W; Turnbull, Stephen J

    2013-10-01

    A nine-month in situ bioremediation study was conducted in Makua Military Reservation (MMR) in Oahu, Hawaii (USA) to evaluate the potential of molasses to enhance biodegradation of royal demolition explosive (RDX) and high-melting explosive (HMX) contaminated soil below the root zone. MMR has been in operation since the 1940's resulting in subsurface contamination that in some locations exceeds USEPA preliminary remediation goals for these chemicals. A molasses-water mixture (1 : 40 dilution) was applied to a treatment plot and clean water was applied to a control plot via seven flood irrigation events. Pore water samples were collected from 12 lysimeters installed at different depths in 3 boreholes in each test plot. The difference in mean concentrations of RDX in pore water samples from the two test plots was very highly significant (p < 0.001). The concentrations differences with depth were also very highly significant (p < 0.001) and degradation was greatly enhanced at depths from 5 to 13.5 ft. biodegradation was modeled as first order and the rate constant was 0.063 per day at 5 ft and decreased to 0.023 per day at 11 ft to 13.5 ft depth. Enhanced biodegradation of HMX was also observed in molasses treated plot samples but only at a depth of 5 ft. The difference in mean TOC concentration (surrogate for molasses) was highly significant with depth (p = 0.003) and very highly significant with treatment (p < 0.001). Mean total nitrogen concentrations also differed significantly with treatment (p < 0.001) and depth (p = 0.059). The molasses water mixture had a similar infiltration rate to that of plain water (average 4.12 ft per day) and reached the deepest sensor (31 ft) within 5 days of application. Most of the molasses was consumed by soil microorganisms by about 13.5 feet below ground surface and treatment of deeper depths may require greater molasses concentrations and/or more frequent flood irrigation. Use of the bioremediation method described herein

  5. Sediment-pore water interactions controlling cementation in the NanTroSEIZE drilling transects

    NASA Astrophysics Data System (ADS)

    Hong, W.; Spinelli, G. A.; Torres, M. E.

    2012-12-01

    One goal of the Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) is to understand how changes in subducting sediment control the transition from aseismic to seismogenic behavior in subduction zones. In the sediment entering the Nankai subduction zone, dramatic changes in physical and chemical properties occur across a diagenetic boundary; they are thought to affect sediment strength and deformation. The dissolution of disseminated volcanic ash and precipitation of silica cement may be responsible for these changes in physical properties, but the mechanism controlling cementation was unclear (Spinelli et al., 2007). In this study, we used CrunchFlow (Steefel, 2009) to simulate chemical reactions and fluid flow through 1-D sediment columns at Integrated Ocean Drilling Program (IODP) sites on the incoming plate in Nankai Trough. The simulations include the thermodynamics and kinetics of sediment-water interactions, advection of pore water and sediment due to compaction, and multi-component diffusion in an accumulating sediment column. Key reactions in the simulations are: ash dissolution, amorphous silica precipitation and dissolution, and zeolite precipitation. The rate of ash decomposition was constrained using Sr isotope data of Joseph et al. (2012). Our model reproduces the distinct diagenetic boundary observed in sediment and pore water chemistry, which defines two zones. Above this boundary (zone 1), dissolved and amorphous silicate contents are high and the potassium concentration remains near seawater values or gradually decreases toward the boundary. Below the boundary, both dissolved and amorphous silicate content drop rapidly, concomitant with a decrease in dissolved potassium. Our model shows that these changes in the system are driven by formation of clinoptilolite in response to changes in pore fluid pH. The low pH values (<7.6) above the diagenetic boundary accelerate ash decomposition and maintain clinoptilolite slightly undersaturated. The

  6. Sorption of cadmium and lead by clays from municipal incinerator ash- water suspensions

    USGS Publications Warehouse

    Roy, W.R.; Krapac, I.G.; Steele, J.D.

    1993-01-01

    The effect of Cl complexation in extracts of a flue gas-scrubber incinerator fly ash sample on the sorption of Cd and Pb by kaolinite and illite was investigated using batch-sorption methods. In the pH range of 5 to 9, Cl complexation may reduce sorption and thus increase the mobility of these metals. When an ash-water suspension was acidified to pH 6.85, the dissolution of Cl and Ca essentially eliminated Cd sorption because of complexation and cationic competition. Cadmium would be considered as either mobile or very mobile under these conditions. Lead was not soluble in the pH- 6.85 suspension. At pH 12, the approximate pH of water in contact with flue gas-scrubber fly ash, Cd was essentially insoluble and Pb occurred as anionic Pb hydroxide. Anionic Pb was sorbed by the two clays, and the extent of sorption was not influenced by Cl or carbonate complexation. Sorption constants, derived from isotherms, suggested that Pb would be relatively immobile in saturated soil-water systems. The recent concern that highly alkaline, flue gas-scrubber fly ash may release environmentally significant concentrations of mobile Pb when placed in an ash-disposal site with a soil liner should be reevaluated in light of this study.

  7. Stable isotope geochemistry of pore waters from the New Jersey shelf - No evidence for Pleistocene melt water

    NASA Astrophysics Data System (ADS)

    van Geldern, Robert; Hayashi, Takeshi; Böttcher, Michael E.; Mottl, Michael J.; Barth, Johannes A. C.; Stadler, Susanne

    2013-04-01

    Scientific drillings in the 1970s revealed the presence of a large fresh water lens below the New Jersey Shelf. The origin and age of this fresh water body is still under debate. Groundwater flow models suggest that the water mainly originates from glacial melt water that entered the ground below large continental ice sheets during the last glacial maximum (LGM), whereas other studies suggest an age up to late Miocene. In this study, interstitial water was sampled during the Integrated Ocean Drilling Program (IODP) expedition 313 "New Jersey Shallow Shelf" (Mountain et al., 2010) and analyzed for water chemistry and stable isotope ratios (van Geldern et al, 2013). The pore fluid stable isotope values define a mixing line with end members that have oxygen and hydrogen isotope values of -7.0‰ and -41‰ for fresh water, and -0.8‰ and -6‰ for saltwater, respectively. The analyses revealed the following sources of fluids beneath the shelf: (1) modern rainwater, (2) modern seawater, and (3) a brine that ascends from deep sediments. The stable isotope composition of the water samples indicates modern meteoric recharge from New Jersey onshore aquifers as the fresh-water end member. This contradicts earlier views on the formation of the New Jersey fresh water lens, as it does not support the ice-age-origin theory. The salt-water end member is identical to modern New Jersey shelf seawater. Lower core parts of the drilling sites are characterized by mixing with a brine that originates from evaporites in the deep underground and that ascends via faults into the overlying sediments. The geochemical data from this study may provide the basis for an approach to construct a transect across the New Jersey shallow shelf since they fill a missing link in the shelf's geochemical profile. They also lay foundations for future research on hardly explored near-shore freshwater resources. References Mountain, G. and the Expedition 313 Scientists, 2010, Proceedings of the Integrated

  8. Hydrologic inferences from strontium isotopes in pore water from the unsaturated zone at Yucca Mountain, Nevada

    SciTech Connect

    Marshall, B.D.; Futa, K.; Peterman, Z.E.

    1997-12-31

    Calcite is ubiquitous at Yucca Mountain, occurring in the soils and as fracture and cavity coatings within the volcanic tuff section. Strontium is a trace element in calcite, generally at the tens to hundreds of ppm level. Because calcite contains very little rubidium and the half-life of the {sup 87}Rb parent is billions of years, the {sup 87}Sr/{sup 86}Sr ratios of the calcite record the ratio in the water from which the calcite precipitated. Dissolution and reprecipitation does not alter these compositions so that, in the absence of other sources of strontium, one would expect the strontium ratios along a flow path to preserve variations inherited from strontium in the soil zone. Strontium isotope compositions of calcites from various settings in the Yucca Mountain region have contributed to the understanding of the unsaturated zone (UZ), especially in distinguishing unsaturated zone calcite from saturated zone calcite. Different populations of calcite have been compared, either to group them together or distinguish them from each other in terms of their strontium isotope compositions. Ground water and perched water have also been analyzed; this paper presents strontium isotope data obtained on pore water.

  9. Diffusive release of uranium from contaminated sediments into capillary fringe pore water

    SciTech Connect

    Rod, Kenton A.; Wellman, Dawn M.; Flury, Markus; Pierce, Eric M; Harsh, James B.

    2012-01-01

    Despite remediation efforts at the former nuclear weapons facility, leaching of uranium (U) from contaminated sediments to the ground water persists at the Hanford site 300 Area. Flooding of contaminated capillary fringe sediments due to seasonal changes in the Columbia River stage has been identified as a source for U supply to ground water. We investigated U release from Hanford capillary fringe sediments by packing sediments into reservoirs of centrifugal filter devices and saturated with Columbia River water for 3 to 84 days at varying solution-to-solid ratios. After specified times, samples were centrifuged. Within the first three days, there was an initial rapid release of 6-9% of total U, independent of the solution-to-solid ratio. After 14 days of reaction, however, the experiments with the narrowest solution-to-solid ratios showed a decline in dissolved U concentrations. The removal of U from the solution phase was accompanied by removal of Ca and HCO3-. Geochemical modeling indicated that calcite could precipitate in the narrowest solution-to-solid ratio experiment. After the rapid initial release in the first three days for the wide solution-to-solid ratio experiments, there was sustained release of U into the pore water. This sustained release of U from the sediments had diffusion-limited kinetics.

  10. Pore water chemistry of an alkaline rift valley lake: Lake Turkana, Kenya

    SciTech Connect

    Cerling, T.E.; Johnson, T.C.; Halfman, J.D.; Lister, G.

    1985-01-01

    Lake Turkana is the largest closed basin lake in the African rift system. It has evolved through the past 5000 years to become a moderately alkaline lake. Previous mass balance argument suggest that sulfate is removed from the lake by sulfate reduction in the sediments, and that the lake is accumulating in chloride, sodium, and alkalinity. Studies of pore water from 12 meter cores collected in November 1984 show that sulfate is reduced in the sediment column with a net production of alkalinity. Some sodium is lost from the lake and diffuses into the sediment to maintain charge balance. At several meters depth, organic matter is destroyed by methanogenic bacteria, as shown by the high delta /sup 13/C values for dissolved inorganic carbon. Magnesium and calcium molar ratios change with depth; chloride, sodium, and alkalinity also change with depth.

  11. Microanalysis of dissolved iron and phosphate in pore waters of hypersaline sediment

    NASA Technical Reports Server (NTRS)

    Haddad, R.; Shaw, T.

    1985-01-01

    Diurnal fluctuations of reduced iron concentrations, expected to occur in reduced sediments in the photic zone, were studied. Iron concentration was compared to O2-H2S, a microcanalysis of sulfate reduction was performed, as well as an examination of diurnal concentration of dissolved phosphate and changes in interstitial CO2. The iron profiles suggest a strong correlation between iron remobilization and processes occurring in the light. Phosphate profiles suggest the removal of phosphate is strongly correlated with precipitation of oxidized iron in the upper 2 mm to 5 mm of the sediments. Pore water CO2 concentrations and carbon isotope ratios are presented. These data are from the analyses of minisediment cores collected from the 42 per mil salt pond and incubated in the laboratory under light and dark conditions.

  12. SWRC fit - a nonlinear fitting program with a water retention curve for soils having unimodal and bimodal pore structure

    NASA Astrophysics Data System (ADS)

    Seki, K.

    2007-02-01

    The soil hydraulic parameters for analyzing soil water movement can be determined by fitting a soil water retention curve to a certain function, i.e., a soil hydraulic model. For this purpose, the program "SWRC Fit," which performs nonlinear fitting of soil water retention curves to 5 models by Levenberg-Marquardt method, was developed. The five models are the Brooks and Corey model, the van Genuchten model, Kosugi's log-normal pore-size distribution model, Durner's bimodal pore-size distribution model, and a bimodal log-normal pore-size distribution model propose in this study. This program automatically determines all the necessary conditions for the nonlinear fitting, such as the initial estimate of the parameters, and, therefore, users can simply input the soil water retention data to obtain the necessary parameters. The program can be executed directly from a web page at http://purl.org/net/swrc/; a client version of the software written in numeric calculation language GNU Octave is included in the electronic supplement of this paper. The program was used for determining the soil hydraulic parameters of 420 soils in UNSODA database. After comparing the root mean square error of the unimodal models, the van Genuchten and Kosugi's models were better than the Brooks and Corey model. The bimodal log-normal pore-size distribution model had similar fitting performance to Durner's bimodal pore-size distribution model.

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

    NASA Astrophysics Data System (ADS)

    West, L. J.; Handley, K.

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

  14. Micron-pore-sized metallic filter tube membranes for filtration of particulates and water purification

    SciTech Connect

    Phelps, Tommy Joe; Palumbo, Anthony Vito; Fagan, Lisa Anne; Bischoff, Brian L; Miller, Curtis Jack; Drake, Meghan M; Judkins, Roddie Reagan

    2008-01-01

    Robust filtering techniques capable of efficiently removing particulates and biological agents from water or air suffer from plugging, poor rejuvenation, low permeance, and high backpressure. Operational characteristics of pressure-driven separations are in part controlled by the membrane pore size, charge of particulates, transmembrane pressure and the requirement for sufficient water flux to overcome fouling. With long term use filters decline in permeance due to filter-cake plugging of pores, fouling, or filter deterioration. Though metallic filter tube development at ORNL has focused almost exclusively on gas separations, a small study examined the applicability of these membranes for tangential filtering of aqueous suspensions of bacterial-sized particles. A mixture of fluorescent polystyrene microspheres ranging in size from 0.5 to 6 {micro}m in diameter simulated microorganisms in filtration studies. Compared to a commercial filter, the ORNL 0.6 {micro}m filter averaged approximately 10-fold greater filtration efficiency of the small particles, several-fold greater permeance after considerable use and it returned to approximately 85% of the initial flow upon backflushing versus 30% for the commercial filter. After filtering several liters of the particle-containing suspension, the ORNL composite filter still exhibited greater than 50% of its initial permeance while the commercial filter had decreased to less than 20%. When considering a greater filtration efficiency, greater permeance per unit mass, greater percentage of rejuvenation upon backflushing (up to 3-fold), and likely greater performance with extended use, the ORNL 0.6 {micro}m filters can potentially outperform the commercial filter by factors of 100-1000 fold.

  15. Ball clay

    USGS Publications Warehouse

    Virta, Robert L.

    2010-01-01

    The article reports on the global market performance of ball clay in 2009 and presents an outlook for its 2010 performance. Several companies mined ball call in the country including Old Hickey Clay Co., Kentucky-Tennessee Clay Co., and H.C. Spinks Clay Co. Information on the decline in ball clay imports and exports is also presented.

  16. Rare earth elements in pore waters from Cabo Friós western boundary upwelling system

    NASA Astrophysics Data System (ADS)

    Smoak, J. M.; Silva-Filho, E. V.; Rousseau, T.; Albuquerque, A. L.; Caldeira, P. P.; Moreira, M.

    2015-12-01

    Rare earth elements (REE) are a group of reactive trace elements in aqueous media, they have a coherent chemical behavior with however a subtle and gradual shift in physicochemical properties allowing their use as tracers of sources and processes. Uncertainties on their oceanic inputs and outputs still remains [Arsouze et al., 2009; Siddall et al., 2008; Tachikawa et al., 2003]. The water-sediment interface were early on identified as a relevant REE source due to the high distribution coefficient between sediments and pore waters [Elderfield and Sholkovitz, 1987] and substantially higher concentration then the water column [Abbott et al., 2015; Haley et al., 2004; Sholkovitz et al., 1989; Soyol-Erdene and Huh, 2013]. Here we present a cross shelf transect of 4 short pore waters REE profiles on a 680 km2 mud bank located in the region of Cabo Frio, Brazil. This study reveals similar trends at the four sites: a REE production zone reflected by a maximum in concentration at the top of the sediment evolving with depth toward a REE consumption zone reflected by a minimum in REE concentrations. PAAS normalized patterns shows 1) a progressive depletion in LREE with depth with HREE/LREE ratios comprised between 1.1 and 1.6 in the 2 first centimeters evolving gradually to ratios comprised between 2.8 and 4.7 above 7 cm 2) A sharp gradient in negative Ce anomaly with Ce/Ce* values reaching 0.3. With maximum Nd concentrations comprised between 780 and 1200 pmol.kg and considering that seawater Nd concentrations of Brazilian shelf bottom waters are comprised between 24 and 50 pmol.Kg-1 we apply the Fick´s First Law of diffusion and estimate that 340 +/- 90 nmol. m-2 Y-1 of Nd is released in the Cabo frio´s mudbank. This flux is in the same order of magnitude of recent estimates by [Abbott et al., 2015] in the slope of Oregon´s margin. Unraveling processes responsible for the REE production zone will help to refine the global REE fluxes estimates.

  17. The Water Permeability and Pore Entrance Structure of Aquaporin-4 Depend on Lipid Bilayer Thickness.

    PubMed

    Tong, Jihong; Wu, Zhe; Briggs, Margaret M; Schulten, Klaus; McIntosh, Thomas J

    2016-07-12

    Aquaporin-4 (AQP4), the primary water channel in glial cells of the mammalian brain, plays a critical role in water transport in the central nervous system. Previous experiments have shown that the water permeability of AQP4 depends on the cholesterol content in the lipid bilayer, but it was not clear whether changes in permeability were due to direct cholesterol-AQP4 interactions or to indirect effects caused by cholesterol-induced changes in bilayer elasticity or bilayer thickness. To determine the effects resulting only from bilayer thickness, here we use a combination of experiments and simulations to analyze AQP4 in cholesterol-free phospholipid bilayers with similar elastic properties but different hydrocarbon core thicknesses previously determined by x-ray diffraction. The channel (unit) water permeabilities of AQP4 measured by osmotic-gradient experiments were 3.5 ± 0.2 × 10(-13) cm(3)/s (mean ± SE), 3.0 ± 0.3 × 10(-13) cm(3)/s, 2.5 ± 0.2 × 10(-13) cm(3)/s, and 0.9 ± 0.1 × 10(-13) cm(3)/s in bilayers containing (C22:1)(C22:1)PC, (C20:1)(C20:1)PC, (C16:0)(C18:1)PC, and (C13:0)(C13:0)PC, respectively. Channel permeabilities obtained by molecular dynamics (MD) simulations were 3.3 ± 0.1 × 10(-13) cm(3)/s and 2.5 ± 0.1 × 10(-13) cm(3)/s in (C22:1)(C22:1)PC and (C14:0)(C14:0)PC bilayers, respectively. Both the osmotic-gradient and MD-simulation results indicated that AQP4 channel permeability decreased with decreasing bilayer hydrocarbon thickness. The MD simulations also suggested structural modifications in AQP4 in response to changes in bilayer thickness. Although the simulations showed no appreciable changes to the radius of the pore located in the hydrocarbon region of the bilayers, the simulations indicated that there were changes in both pore length and α-helix organization near the cytoplasmic vestibule of the channel. These structural changes, caused by mismatch between the hydrophobic length of AQP4 and the bilayer hydrocarbon

  18. Assessing sulfate reduction and methane cycling in a high salinity pore water system in the northern Gulf of Mexico

    USGS Publications Warehouse

    Pohlman, J.W.; Ruppel, C.; Hutchinson, D.R.; Downer, R.; Coffin, R.B.

    2008-01-01

    Pore waters extracted from 18 piston cores obtained on and near a salt-cored bathymetric high in Keathley Canyon lease block 151 in the northern Gulf of Mexico contain elevated concentrations of chloride (up to 838 mM) and have pore water chemical concentration profiles that exhibit extensive departures (concavity) from steady-state (linear) diffusive equilibrium with depth. Minimum ??13C dissolved inorganic carbon (DIC) values of -55.9??? to -64.8??? at the sulfate-methane transition (SMT) strongly suggest active anaerobic oxidation of methane (AOM) throughout the study region. However, the nonlinear pore water chemistry-depth profiles make it impossible to determine the vertical extent of active AOM or the potential role of alternate sulfate reduction pathways. Here we utilize the conservative (non-reactive) nature of dissolved chloride to differentiate the effects of biogeochemical activity (e.g., AOM and/or organoclastic sulfate reduction) relative to physical mixing in high salinity Keathley Canyon sediments. In most cases, the DIC and sulfate concentrations in pore waters are consistent with a conservative mixing model that uses chloride concentrations at the seafloor and the SMT as endmembers. Conservative mixing of pore water constituents implies that an undetermined physical process is primarily responsible for the nonlinearity of the pore water-depth profiles. In limited cases where the sulfate and DIC concentrations deviated from conservative mixing between the seafloor and SMT, the ??13C-DIC mixing diagrams suggest that the excess DIC is produced from a 13C-depleted source that could only be accounted for by microbial methane, the dominant form of methane identified during this study. We conclude that AOM is the most prevalent sink for sulfate and that it occurs primarily at the SMT at this Keathley Canyon site.

  19. Determination of acute Zn toxicity in pore water from soils previously treated with sewage sludge using bioluminescence assays

    SciTech Connect

    Chaudri, A.M.; Knight, B.P.; Barbosa-Jefferson, V.L.

    1999-06-01

    The effects of increasing concentrations of Zn and Cu in soil pore water from soils of a long-term sewage sludge field experiment on microbial bioluminescence were investigated. Concentrations of total soluble Zn, free Zn{sup 2+}, and soluble Cu increased sharply in soil pore water with increasing total soil metal concentrations above 140 mg of Zn kg{sup {minus}1} or 100 mg of Cu kg{sup {minus}1}. Two luminescence bioassays were tested, based on two bacteria (Escherichia coli and Pseudomonas fluorescens) with the lux genes encoding bacterial luminescence inserted into them. The bioluminescence response of the two microorganisms declined as total soil Zn, soil pore water soluble Zn, and soil pore water free Zn{sup 2+} concentrations increased. The EC{sub 25} values for E. coli and P. fluorescens were 1.3 {+-} 0.2 and 4.3 {+-} 0.5 mg L{sup {minus}1} on a free Zn{sup 2+} basis, respectively. The EC{sub 50} values were 2.5 {+-} 0.2 and 9.6 {+-} 0.9 mg of free Zn{sup 2+} L{sup {minus}1}, respectively. Copper had no significant effect on bioluminescence in the two assays, even at the largest soil pore water concentration of about 620 {micro}g L{sup {minus}1}, corresponding to a total Cu concentration in bulk soil of about 350 mg kg{sup {minus}1}. Thus, the decline in bioluminescence of the two assays was ascribed to increasing soil pore water free Zn{sup 2+} and not soluble Cu.

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

    DOE PAGESBeta

    Greathouse, Jeffery A.; Hart, David; Bowers, Geoffrey M.; Kirkpatrick, R. James; Cygan, Randall Timothy

    2015-07-20

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

  1. Multiphase Reactive Transport modeling of Stable Isotope Fractionation of Infiltrating Unsaturated Zone Pore Water and Vapor Using TOUGHREACT

    SciTech Connect

    Singleton, Michael J.; Sonnenthal, Eric L.; Conrad, Mark E.; DePaolo, Donald J.

    2003-08-28

    Numerical simulations of transport and isotope fractionation provide a method to quantitatively interpret vadose zone pore water stable isotope depth profiles based on soil properties, climatic conditions, and infiltration. We incorporate the temperature-dependent equilibration of stable isotopic species between water and water vapor, and their differing diffusive transport properties into the thermodynamic database of the reactive transport code TOUGHREACT. These simulations are used to illustrate the evolution of stable isotope profiles in semiarid regions where recharge during wet seasons disturbs the drying profile traditionally associated with vadose zone pore waters. Alternating wet and dry seasons lead to annual fluctuations in moisture content, capillary pressure, and stable isotope compositions in the vadose zone. Periodic infiltration models capture the effects of seasonal increases in precipitation and predict stable isotope profiles that are distinct from those observed under drying (zero infiltration) conditions. After infiltration, evaporation causes a shift to higher 18O and D values, which are preserved in the deeper pore waters. The magnitude of the isotopic composition shift preserved in deep vadose zone pore waters varies inversely with the rate of infiltration.

  2. MONITORING OF PORE WATER PRESSURE AND WATER CONTENT AROUND A HORIZONTAL DRIFT THROUGH EXCAVATION - MEASUREMENT AT THE 140m GALLERY IN THE HORONOBE URL -

    NASA Astrophysics Data System (ADS)

    Yabuuchi, Satoshi; Kunimaru, Takanori; Kishi, Atsuyasu; Komatsu, Mitsuru

    Japan Atomic Energy Agency has been conducting the Horonobe Underground Research Laboratory (URL) project in Horonobe, Hokkaido, as a part of the research and development program on geological disposal of high-level radioactive waste. Pore water pressure and water content around a horizontal drift in the URL have been monitored for over 18 months since before the drift excavation was started. During the drift excavation, both pore water pressure and water content were decreasing. Pore water pressure has been still positive though it continued to decrease with its gradient gradually smaller after excavation, while water content turned to increase about 6 months after the completion of the excavation. It turned to fall again about 5 months later. An unsaturated zone containing gases which were dissolved in groundwater may have been formed around the horizontal drift.

  3. Error Analysis of Clay-Rock Water Content Estimation with Broadband High-Frequency Electromagnetic Sensors—Air Gap Effect

    PubMed Central

    Bore, Thierry; Wagner, Norman; Delepine Lesoille, Sylvie; Taillade, Frederic; Six, Gonzague; Daout, Franck; Placko, Dominique

    2016-01-01

    Broadband electromagnetic frequency or time domain sensor techniques present high potential for quantitative water content monitoring in porous media. Prior to in situ application, the impact of the relationship between the broadband electromagnetic properties of the porous material (clay-rock) and the water content on the frequency or time domain sensor response is required. For this purpose, dielectric properties of intact clay rock samples experimental determined in the frequency range from 1 MHz to 10 GHz were used as input data in 3-D numerical frequency domain finite element field calculations to model the one port broadband frequency or time domain transfer function for a three rods based sensor embedded in the clay-rock. The sensor response in terms of the reflection factor was analyzed in time domain with classical travel time analysis in combination with an empirical model according to Topp equation, as well as the theoretical Lichtenecker and Rother model (LRM) to estimate the volumetric water content. The mixture equation considering the appropriate porosity of the investigated material provide a practical and efficient approach for water content estimation based on classical travel time analysis with the onset-method. The inflection method is not recommended for water content estimation in electrical dispersive and absorptive material. Moreover, the results clearly indicate that effects due to coupling of the sensor to the material cannot be neglected. Coupling problems caused by an air gap lead to dramatic effects on water content estimation, even for submillimeter gaps. Thus, the quantitative determination of the in situ water content requires careful sensor installation in order to reach a perfect probe clay rock coupling. PMID:27096865

  4. Error Analysis of Clay-Rock Water Content Estimation with Broadband High-Frequency Electromagnetic Sensors--Air Gap Effect.

    PubMed

    Bore, Thierry; Wagner, Norman; Lesoille, Sylvie Delepine; Taillade, Frederic; Six, Gonzague; Daout, Franck; Placko, Dominique

    2016-01-01

    Broadband electromagnetic frequency or time domain sensor techniques present high potential for quantitative water content monitoring in porous media. Prior to in situ application, the impact of the relationship between the broadband electromagnetic properties of the porous material (clay-rock) and the water content on the frequency or time domain sensor response is required. For this purpose, dielectric properties of intact clay rock samples experimental determined in the frequency range from 1 MHz to 10 GHz were used as input data in 3-D numerical frequency domain finite element field calculations to model the one port broadband frequency or time domain transfer function for a three rods based sensor embedded in the clay-rock. The sensor response in terms of the reflection factor was analyzed in time domain with classical travel time analysis in combination with an empirical model according to Topp equation, as well as the theoretical Lichtenecker and Rother model (LRM) to estimate the volumetric water content. The mixture equation considering the appropriate porosity of the investigated material provide a practical and efficient approach for water content estimation based on classical travel time analysis with the onset-method. The inflection method is not recommended for water content estimation in electrical dispersive and absorptive material. Moreover, the results clearly indicate that effects due to coupling of the sensor to the material cannot be neglected. Coupling problems caused by an air gap lead to dramatic effects on water content estimation, even for submillimeter gaps. Thus, the quantitative determination of the in situ water content requires careful sensor installation in order to reach a perfect probe clay rock coupling. PMID:27096865

  5. Clays, specialty

    USGS Publications Warehouse

    Virta, R.L.

    1998-01-01

    Part of a special section on the state of industrial minerals in 1997. The state of the specialty clay industry worldwide for 1997 is discussed. The specialty clays mined in the U.S. are ball clay, fuller's earth, bentonite, fire clay, and kaolin. Sales of specialty clays in the U.S. were around 17 Mt in 1997. Approximately 53 kt of specialty clays were imported.

  6. Ball clay

    USGS Publications Warehouse

    Virta, R.L.

    2006-01-01

    In 2005, four companies including H.C. Spinks Clay, Kentucky-Tennessee Clay, Old Hickory Clay and Unimin mined ball clay in four states. Based on a preliminary survey of the ball clay industry, production reached 1.32 Mt valued at $53.3 million. Tennessee was the leading ball clay producer state with 61% of domestic production, followed by Texas, Mississippi and Kentucky.

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

    NASA Astrophysics Data System (ADS)

    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

  8. Pore-Scale Investigation of CO2 Exsolution from Carbonated Water in Sedimentary Rocks

    NASA Astrophysics Data System (ADS)

    Zuo, L.; Zhang, C. Y.; Falta, R. W.; Benson, S. M.

    2012-04-01

    Geologic sequestration of supercritical CO2 in saline aquifers and depleted oil and gas fields will cause large volumes of brine to become saturated with dissolved CO2 at concentrations of 50 g/L or more due to the high CO2 solubility in brine at elevated pressure and temperature. While dissolution of CO2 improves storage security by removing buoyancy forces, risks still exist if CO2 saturated brine escapes from the reservoir as the solubility of CO2 decreases with hydrostatic pressure. The CO2, released from solution, would expand or even form a separate phase at shallower depths after being transported through caprocks or seals. Previous studies (Zuo et al., 2011) have shown that exsolution results in a separate CO2 phase with very low mobility. We hypothesized that the low mobility resulted from the dispersed morphology of CO2 bubbles. The objective of this study is to understand the dynamics of CO2 exsolution and the effects on reservoir flows at a microscope scale. In this study, a silicon-glass micromodel was fabricated based on images of a thin section of a Mount Simon sandstone from Illinois, USA. The micromodel mimics the complexity of pore structures existing in real porous media in two dimensions and has a minimum aperture of 3um. Carbon dioxide exsolution was created by slowly extracting fluids from the micromodel, which was initially saturated with carbonated water under reservoir conditions (9MPa and 45C). An optical microscope was used to monitor and record the entire process. Instantaneous nucleation was observed in the micromodel at a constant pressure drop rate of 1MPa/h, followed by a rapid process of bubble expansion and cluster growth. Carbon dioxide bubbles were highly dispersed and poorly interconnected, even when the gas saturation reached as high as 53%. Compared to a drainage process in the same micromodel, at the same gas saturation, exsolution resulted in a greater number of bubbles, but with a smaller average size. Forty to sixty

  9. Oxygen isotope fractionation effects in soil water via interaction with cations (Mg, Ca, K, Na) adsorbed to phyllosilicate clay minerals

    NASA Astrophysics Data System (ADS)

    Oerter, Erik; Finstad, Kari; Schaefer, Justin; Goldsmith, Gregory R.; Dawson, Todd; Amundson, Ronald

    2014-07-01

    In isotope-enabled hydrology, soil and vadose zone sediments have been generally considered to be isotopically inert with respect to the water they host. This is inconsistent with knowledge that clay particles possessing an electronegative surface charge and resulting cation exchange capacity (CEC) interact with a wide range of solutes which, in the absence of clays, have been shown to exhibit δ18O isotope effects that vary in relation to the ionic strength of the solutions. To investigate the isotope effects caused by high CEC clays in mineral-water systems, we created a series of monominerallic-water mixtures at gravimetric water contents ranging from 5% to 32%, consisting of pure deionized water of known isotopic composition with homoionic (Mg, Ca, Na, K) montmorillonite. Similar mixtures were also created with quartz to determine the isotope effect of non-, or very minimally-, charged mineral surfaces. The δ18O value of the water in these monominerallic soil analogs was then measured by isotope ratio mass spectrometry (IRMS) after direct headspace CO2 equilibration. Mg- and Ca-exchanged homoionic montmorillonite depleted measured δ18O values up to 1.55‰ relative to pure water at 5% water content, declining to 0.49‰ depletion at 30% water content. K-montmorillonite enriched measured δ18O values up to 0.86‰ at 5% water content, declining to 0.11‰ enrichment at 30% water. Na-montmorillonite produces no measureable isotope effect. The isotope effects observed in these experiments may be present in natural, high-clay soils and sediments. These findings have relevance to the interpretation of results of direct CO2-water equilibration approaches to the measurement of the δ18O value of soil water. The adsorbed cation isotope effect may bear consideration in studies of pedogenic carbonate, plant-soil water use and soil-atmosphere interaction. Finally, the observed isotope effects may prove useful as molecular scale probes of the nature of mineral-water

  10. A mini drivepoint sampler for measuring pore water solute concentrations in the hyporheic zone of sand-bottom streams

    USGS Publications Warehouse

    Duff, J.H.; Murphy, F.; Fuller, C.C.; Triska, F.J.

    1998-01-01

    A new method for collecting pore-water samples in sand and gravel streambeds is presented. We developed a mini drivepoint solution sampling (MINIPOINT) technique to collect pore-water samples at 2.5-cm vertical resolution. The sampler consisted of six small-diameter stainless steel drivepoints arranged in a 10-cm-diameter circular array. In a simple procedure, the sampler was installed in the streambed to preset drivepoint depths of 2.5, 5.0, 7.5, 10.0, 12.5, and 15.0 cm. Sampler performance was evaluated in the Shingobee River, Minnesota, and Pinal Creek, Arizona, by measuring the vertical gradient of chloride concentration in pore water beneath the streambed that was established by the uninterrupted injection to the stream for 3 d. Pore-water samples were withdrawn from all drivepoints simultaneously. In the first evaluation, the vertical chloride gradient was unchanged at withdrawal rates between 0.3 and 4.0 ml min-1 but was disturbed at higher rates. In the second evaluation, up to 70 ml of pore water was withdrawn from each drivepoint at a withdrawal rate of 2.5 ml min-1 without disturbing the vertical chloride gradient. Background concentrations of other solutes were also determined with MINIPOINT sampling. Steep vertical gradients were present for biologically reactive solutes such as DO, NH4/+, NO3/-, and dissolved organic C in the top 20 cm of the streambed. These detailed solute profiles in the hyporheic zone could not have been determined without a method for close interval vertical sampling that does not disturb natural hydrologic mixing between stream water and groundwater.

  11. Concentrations, diffusive fluxes and toxicity of heavy metals in pore water of the Fuyang River, Haihe Basin.

    PubMed

    Tang, Wenzhong; Duan, Shenghui; Shan, Baoqing; Zhang, Hong; Zhang, Wenqiang; Zhao, Yu; Zhang, Chao

    2016-05-01

    While the concentrations of heavy metals in pore water provide important information about their bioavailability, to date few studies have focused on this topic. In this study, pore water in river sediments collected from nine sampling sites (S1-S9) was examined to determine the concentrations, fluxes, and toxicity of heavy metals in the Fuyang River. The results showed that the average concentrations of Cr, Ni, Cu, As, Zn, and Pb in pore water were 17.06, 15.97, 20.93, 19.08, 43.72, and 0.56μgL(-1), respectively; these concentrations varied as the pore water depth increased. The diffusive fluxes of Cr, Ni, Cu, As, Zn, and Pb were in the following range: (-0.37) to 3.17, (-1.37) to 2.63, (-4.61) to 3.44, 0.17-6.02, (-180.26) to 7.51, and (-0.92) to (-0.29)μg(m(2)day)(-1), respectively. There was a potential risk of toxicity from Cu to aquatic organisms, as indicated by a value of the Interstitial Water Criteria Toxic Units that exceeded 1.0. Values of the Nemeraw Index were 2.06, 0.48, 0.11, 0.20, 1.11, 1.03, 0.99, 0.88, and 0.89 from S1 to S9, respectively. Only S1 was moderately polluted by heavy metals in pore water. PMID:26802565

  12. Electron transfer at the mineral/water interface: Selenium reduction by ferrous iron sorbed on clay

    NASA Astrophysics Data System (ADS)

    Charlet, L.; Scheinost, A. C.; Tournassat, C.; Greneche, J. M.; Géhin, A.; Fernández-Martínez, A.; Coudert, S.; Tisserand, D.; Brendle, J.

    2007-12-01

    surface H 2 species, and are then available for the later Se(IV) reduction. The slow reaction rate indicates a diffusion controlled process. Homogeneous precipitation of an iron selenite was thermodynamically predicted and experimentally observed only in the absence of clay. Interestingly, half of Fe was oxidized in this precipitate (Mössbauer). Since DFT calculations predicted the oxidation of Fe at the water-FeSe solid interface only and not in the bulk phase, we derived an average particle size of this precipitate which does not exceed 2 nm. A comparison with the Mössbauer and XAS spectra of the clay samples demonstrates that such homogenous precipitation can be excluded as a mechanism for the observed slow Se reduction, emphasizing the role of abiotic, heterogeneous precipitation and reduction for the removal of Se from subsurface waters.

  13. Clay honeycomb monoliths for water purification: Modulating methylene blue adsorption through controlled activation via natural coal templating

    NASA Astrophysics Data System (ADS)

    Gatica, José M.; Gómez, Diana M.; Harti, Sanae; Vidal, Hilario

    2013-07-01

    Texturally modified clay honeycomb monoliths were prepared for use as filters to remove pollutants from water solutions. An easy, economical, "green chemistry" activation route was employed during the preparation to enhance the adsorption capacity of the honeycombs. The method involves mixing the clay before its extrusion with a natural coal that is subsequently eliminated from the monolith by heating it under air at the lowest possible temperature (440 °C according to a thermogravimetric study). The size of the coal particles used as a template was intentionally modified by adjusting the milling process (dry or wet) and its duration (1-120 min) to modulate the porosity induced in the clay monoliths after their further burning. N2 physisorption, mercury porosimetry, granulometry and SEM were used to investigate the influence of the above preparative variables on the textural properties of the clay, significant effects being found in the macropore range. Methylene blue adsorption tests under dynamic conditions suggest that there is a correlation between pollutant removal and the macropore structure generated. FTIR spectroscopy indicates that the differences observed in cationic dye adsorption over the monoliths must be related to their different texture rather than to differences in the nature of their surface hydroxyl groups.

  14. Use of pore-water composition to reconstruct past dissolved inorganic carbon concentration and alkalinity in Pacific bottom water

    NASA Astrophysics Data System (ADS)

    Sauvage, J. F.; Spivack, A. J.; D'Hondt, S. L.; Integrated Ocean Drilling Program Expedition 329 shipboard scientific party

    2011-12-01

    The carbonate system is a crucial component in controlling the pH of the world's oceans and the distribution of CO2 within the ocean, as well as between the ocean and atmosphere. Consequently, dissolved inorganic carbon (DIC) and alkalinity reconstructions bear lots of promise for improving understanding of the ocean's role in the global carbon cycle and climate. We propose and test a method to quantify in situ concentrations of deep-sea carbonate-system components (DIC, alkalinity, CO32-, Ca2+, and minor component concentrations) in pore fluid of deep-sea sediment cores. These concentrations can in turn be used to reconstruct deep-sea carbonate-system chemistry of the geologic past. Alkalinity, DIC and Ca2+ concentrations measured on research vessels differ from in situ values because temperature and pressure changes during core recovery, storage and extraction induce calcium carbonate precipitation and in this way alter the original composition. To reconstruct in situ values, we developed a method that takes advantage of the mathematically over-determined state of the system if three components are measured, given that CaCO3 is saturated and the dissolved carbonate system is at equilibrium in situ. As a result, based on the measured alkalinity, DIC and Ca2+ concentrations, in situ CO2aq, HCO3-, CO32-, and minor species concentrations are calculated by applying an iteration process. This approach allows us to calculate the amount of CaCO3 precipitated during sediment recovery from the seafloor, and hence in situ carbonate system components. We apply our model to pore-water data from two SPG sites rich in calcium carbonate and drilled by Integrated Ocean Drilling Program Expedition 329 (Sites 1367 and 1368). We compared two sample types for this study, (i) samples squeezed and processed within minutes of recovery (rapidly processed) and (ii) samples processed in the following hours/days, and as consequence prone to some substantial alteration (slowly processed

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

    NASA Technical Reports Server (NTRS)

    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.

  16. Novel Anionic Clay Adsorbents for Boiler-Blow-Down Waters Reclaim and Reuse

    SciTech Connect

    Muhammad Sahimi; Theodore Tsotsis

    2010-01-08

    Arsenic (As) and Selenium (Se) are found in water in the form of oxyanions. Relatively high concentrations of As and Se have been reported both in power plant discharges, as well as, in fresh water supplies. The International Agency for Research on Cancer currently classifies As as a group 1 chemical, that is considered to be carcinogenic to humans. In Phase I of this project we studied the adsorption of As and Se by uncalcined and calcined layered double hydroxide (LDH). The focus of the present work is a systematic study of the adsorption of As and Se by conditioned LDH adsorbents. Conditioning the adsorbent significantly reduced the Mg and Al dissolution observed with uncalcined and calcined LDH. The adsorption rates and isotherms have been investigated in batch experiments using particles of four different particle size ranges. As(V) adsorption is shown to follow a Sips-type adsorption isotherm. The As(V) adsorption rate on conditioned LDH increases with decreasing adsorbent particle size; the adsorption capacity, on the other hand, is independent of the particle size. A homogeneous surface diffusion model (HSDM) and a bi-disperse pore model (BPM) - the latter viewing the LDH particles as assemblages of microparticles and taking into account bulk diffusion in the intraparticle pore space, and surface diffusion within the microparticles themselves - were used to fit the experimental kinetic data. The HSDM estimated diffusivity values dependent on the particle size, whereas the BPM predicted an intracrystalline diffusivity, which is fairly invariant with particle size. The removal of As(V) on conditioned LDH adsorbents was also investigated in flow columns, where the impact of important solution and operational parameters such as influent As concentration, pH, sorbent particle size and flow rate were studied. An early breakthrough and saturation was observed at higher flow rates and at higher influent concentrations, whereas a decrease in the sorbent particle

  17. Clay Play

    ERIC Educational Resources Information Center

    Rogers, Liz; Steffan, Dana

    2009-01-01

    This article describes how to use clay as a potential material for young children to explore. As teachers, the authors find that their dialogue about the potential of clay as a learning medium raises many questions: (1) What makes clay so enticing? (2) Why are teachers noticing different play and conversation around the clay table as compared to…

  18. Ball clay

    USGS Publications Warehouse

    Virta, R.L.

    2001-01-01

    Part of the 2000 annual review of the industrial minerals sector. A general overview of the ball clay industry is provided. In 2000, sales of ball clay reached record levels, with sanitary ware and tile applications accounting for the largest sales. Ball clay production, consumption, prices, foreign trade, and industry news are summarized. The outlook for the ball clay industry is also outlined.

  19. Carbonation of Clay Minerals Exposed to scCO2/Water at 200 degrees and 250 degrees C

    SciTech Connect

    Sugama, T.; Ecker, L.; Gill, S.; Butcher, T.; Bour, D.

    2010-11-01

    To clarify the mechanisms of carbonation of clay minerals, such as bentonite, kaolinite, and soft clay, we exposed them to supercritical carbon dioxide (scCO2)/water at temperatures of 200 and 250 C and pressures of 1500 and 2000 psi for 72- and 107-hours. Bentonite, comprising three crystalline phases, montmorillonite (MMT), anorthoclase-type albite, and quartz was susceptible to reactions with ionic carbonic acid yielded by the interactions between scCO2 and water, particularly MMT and anorthoclase-type albite phases. For MMT, the cation-exchangeable ions, such as Na+ and Ca2+, present in its basal interplanar space, were replaced by proton, H+, from ionic carbonic acid; thereafter, the cations leaching from MMT directly reacted with CO32- as a counter ion of H+ to form carbonate compounds. Such in-situ carbonation process in basal space caused the shrinkage and breakage of the spacing structure within MMT. In contrast, the wet carbonation of anorthoclase-type albite, categorized as rock minerals, entailed the formation of three amorphous by-products, such as carbonates, kaolinite-like compounds, and silicon dioxide. Together, these two different carbonations caused the disintegration and corruption of bentonite. Kaolinite clay containing the amorphous carbonates and silicon dioxide was inert to wet carbonation. We noted only a gain in weight due to its water uptake, suggesting that kaolinite-like by-products generated by the wet carbonation of rock minerals might remain unchanged even during extended exposure. Soft clay consisting of two crystalline phases, dolomite and silicon dioxide, also was unaltered by wet carbonation, despite the uptake of water.

  20. Chemical analyses of pore water from boreholes USW SD-6 and USW WT-24, Yucca Mountain, Nevada.

    PubMed

    Yang, In C; Peterman, Zell E; Scofield, Kevin M

    2003-01-01

    Analyses of pore water extracted from cores of boreholes USW SD-6 in the central part and USW WT-24 in the northern part of Yucca Mountain, Nevada, show significant vertical and lateral variations in dissolved-ion concentrations. Analyses of samples of only a few milliliters of pore water extracted by uniaxial or triaxial compression and by ultracentrifugation methods from adjacent core samples are generally in agreement, within the analytical error of 10% to 15%. However, the values of silica for water obtained by ultracentrifugation are consistently lower than values for water obtained by compression. The larger concentrations probably are due to localized pressure solution of silicate minerals during compression. The shallower water from core in borehole USW SD-6 was extracted from nonwelded units collectively referred to as the Paintbrush Tuff nonwelded (PTn). The deeper water was from core in both boreholes USW SD-6 and USW WT-24 in the nonwelded units referred to as the Calico Hills nonwelded (CHn). Significant differences in mean dissolved-ion concentrations in pore water between the PTn and CHn are (1) decreases in Ca, Mg, SO(4), and NO(3) and (2) increases in HCO(3) and (Na+K)/(Ca+Mg) ratios. The decrease in NO(3) and the increase in HCO(3) could be the result of denitrification through the oxidation of organic matter. The decrease in Ca and associated increase in (Na+K)/(Ca+Mg) is the result of ion exchange with zeolites in the CHn in borehole USW WT-24. This effect is not nearly as pronounced in borehole USW SD-6, probably reflecting a smaller amount of zeolitization of the CHn in USW SD-6. Geochemical calculations using the PHREEQC code indicate that the pore water from both boreholes USW SD-6 and USW WT-24 is uniformly undersaturated in anhydrite, gypsum, and amorphous silica, but supersaturated in quartz and chalcedony. The saturation of calcite, aragonite, sepiolite, and dolomite is more variable from sample to sample. PMID:12714300

  1. Specific features of soil water exchange and chemistry of pore and ground waters

    NASA Astrophysics Data System (ADS)

    Muromtsev, N. A.; Pylenok, P. I.; Semenov, N. A.; Anisimov, K. B.

    2015-07-01

    The regularities of water infiltration and evaporation of groundwater at different depths of the groundwater table were established for soddy-podzolic and dark gray forest soils. The recharge of the soils with moisture from the groundwater decreased with a lowering of its table, and the infiltration increased. At the high groundwater table (70 cm from the surface), the moisture recharge of the soddy-podzolic soil amounted to 86 mm and the infiltration amounted to 17 mm; at the groundwater table of 145 cm, these values were 13 and 51 mm, respectively. The concentrations of chemical elements in the lysimeters with the high groundwater table were 2-4 times greater than those in the lysimeters with the low groundwater table.

  2. Measuring Temporal Variability of Methylmercury and Methane in the Pore Waters of a Chesapeake Bay Tidal Marsh

    NASA Astrophysics Data System (ADS)

    Martin, K. R.; Oster, J.; Lapham, L.; Heyes, A.

    2015-12-01

    This study assesses the use of OsmoSampler technology to monitor methylmercury production in a tidal marsh and examines temporal variability of methylmercury in relation to controlling factors. We collected pore water samples in a Chesapeake Bay marsh using continuous pore-fluid sampling devices called OsmoSamplers. OsmoSampler technology has not previously been used to investigate mercury cycling. We designed systems using OsmoSamplers to collect pore water samples for methylmercury, methane, chloride, and sulfate analysis, sampling in a vegetated area and an area devegetated by clipping. Samples were collected over a 27 day period and stored in coils to create a temporal data set of in situ concentrations. This time series allows us to explore the methane-methylmercury connection and the effects of vegetation removal on methylmercury production. Some methanogens are known to methylate mercury, but the relative importance of the methane community in mercury methylation is not well understood. We hypothesized a positive correlation between methane and methylmercury production and a decrease in methylmercury production corresponding to vegetation removal. We also sought to demonstrate the feasibility of using OsmoSamplers to look at methylmercury flux in relation to these controls on mercury methylation. This study is a preliminary exploration of this technology in a marsh environment. Using our system we have successfully collected pore water samples. We present the temporal variability of measured concentrations with a discussion of adjustments for future long-term deployment.

  3. Level and degradation of Deepwater Horizon spilled oil in coastal marsh sediments and pore-water.

    PubMed

    Natter, Michael; Keevan, Jeff; Wang, Yang; Keimowitz, Alison R; Okeke, Benedict C; Son, Ahjeong; Lee, Ming-Kuo

    2012-06-01

    This research investigates the level and degradation of oil at ten selected Gulf saltmarsh sites months after the 2010 BP Macondo-1 well oil spill. Very high levels (10-28%) of organic carbon within the heavily oiled sediments are clearly distinguished from those in pristine sediments (<3%). Dissolved organic carbon in contaminated pore-waters, ranging up to hundreds of mg/kg, are 1 to 2 orders of magnitude higher than those at pristine sites. Heavily oiled sediments are characterized by very high sulfide concentrations (up to 80 mg/kg) and abundance of sulfate reducing bacteria. Geochemical biomarkers and stable carbon isotope analyses fingerprint the presence of oils in sediments. Ratios of selected parameters calculated from the gas chromatograph spectra are in a remarkable narrow range among spilled oils and initial BP crude. At oiled sites dominated by C(4) plants, δ(13)C values of sediments (-20.8 ± 2.0‰) have been shifted significantly lower compared to marsh plants (-14.8 ± 0.6‰) due to the inflow of isotopically lighter oil (-27 ± 0.2‰). Our results show that (1) lighter compounds of oil are quickly degraded by microbes while the heavier fractions of oil still remain and (2) higher inputs of organic matter from the oil spill enhance the key microbial processes associated with sulfate reducing bacteria. PMID:22571231

  4. Inorganic and organic sulfur cycling in salt-marsh pore waters

    SciTech Connect

    Luther, G.W. III; Church, T.M.; Scudlark, J.R.; Cosman, M.

    1986-05-09

    Sulfur species in pore waters of the Great Marsh, Delaware, were analyzed seasonally by polarographic methods. The species determined (and their concentrations in micromoles per liter) included inorganic sulfides (less than or equal to3360), polysulfides (less than or equal to326), thiosulfate (less than or equal to104), tetrathionate (less than or equal to302), organic thiols (less than or equal to2411), and organic disulfides (less than or equal to139). Anticipated were bisulfide increases with depth due to sulfate reduction and subsurface sulfate excesses and pH minima, the result of a seasonal redox cycle. Unanticipated was the pervasive presence of thiols (for example, glutathione), particularly during periods of biological production. Salt marshes appear to be unique among marine systems in producing high concentrations of thiols. Polysulfides, thiosulfate, and tetrathionate also exhibited seasonal subsurface maxima. These results suggest a dynamic seasonal cycling of sulfur in salt marshes involving abiological and biological reactions and dissolved and solid sulfur species. The chemosynthetic turnover of pyrite to organic sulfur is a likely pathway for this sulfur cycling. Thus, material, chemical, and energy cycles in wetlands appear to be optimally synergistic.

  5. Ball clay

    USGS Publications Warehouse

    Virta, R.L.

    2007-01-01

    The article offers information on ball clay. Among the companies that mine ball clay in the U.S. are H.C. Spinks Clay, Kentucky-Tennessee Clay and Old Hickory Clay. In 2006, an estimated 1.2 million tons of the mineral was sold or used domestically and exported. Forty-percent of the total sales is accounted for ceramic floor and wall tile followed by sanitaryware and miscellaneous ceramics. Its average value was $ 45 per ton in 2006.

  6. Ball clay

    USGS Publications Warehouse

    Virta, R.L.

    2011-01-01

    The article discusses the latest developments in the global ball clay mining industry, particularly in the U.S., as of June 2011. It cites several firms that are involved in ball clay mining in the U.S., including HC Spins Clay Co. Inc., the Imerys Group and Old Hickory Clay Co. Among the products made from ball clay are ceramic tiles, sanitaryware, as well as fillers, extenders and binders.

  7. Estimation of water saturated permeability of soils, using 3D soil tomographic images and pore-level transport phenomena modelling

    NASA Astrophysics Data System (ADS)

    Lamorski, Krzysztof; Sławiński, Cezary; Barna, Gyöngyi

    2014-05-01

    There are some important macroscopic properties of the soil porous media such as: saturated permeability and water retention characteristics. These soil characteristics are very important as they determine soil transport processes and are commonly used as a parameters of general models of soil transport processes used extensively for scientific developments and engineering practise. These characteristics are usually measured or estimated using some statistical or phenomenological modelling, i.e. pedotransfer functions. On the physical basis, saturated soil permeability arises from physical transport processes occurring at the pore level. Current progress in modelling techniques, computational methods and X-ray micro-tomographic technology gives opportunity to use direct methods of physical modelling for pore level transport processes. Physically valid description of transport processes at micro-scale based on Navier-Stokes type modelling approach gives chance to recover macroscopic porous medium characteristics from micro-flow modelling. Water microflow transport processes occurring at the pore level are dependent on the microstructure of porous body and interactions between the fluid and the medium. In case of soils, i.e. the medium there exist relatively big pores in which water can move easily but also finer pores are present in which water transport processes are dominated by strong interactions between the medium and the fluid - full physical description of these phenomena is a challenge. Ten samples of different soils were scanned using X-ray computational microtomograph. The diameter of samples was 5 mm. The voxel resolution of CT scan was 2.5 µm. Resulting 3D soil samples images were used for reconstruction of the pore space for further modelling. 3D image threshholding was made to determine the soil grain surface. This surface was triangulated and used for computational mesh construction for the pore space. Numerical modelling of water flow through the

  8. Pore Water Composition at Gas Seeps in the Northern Gulf of Mexico: Understanding Flow Regime and Chemical Processes

    NASA Astrophysics Data System (ADS)

    Hubbard, L. A.; Dugan, B.; Dickens, G. R.

    2006-12-01

    Cold seeps on continental slopes discharge large quantities of gas and fluid to the ocean. The expulsion rate and composition of seep fluids can vary significantly in space and time, which can affect local biological and chemical processes. The factors influencing variability in flux and composition, however, are not fully documented. For this study, we have collected and analyzed pore fluids at four sites in the northern Gulf of Mexico: Atwater Valley (AV), Mississippi Canyon (MC), Garden Banks (GB) and Keathley Canyon (KC). The magnitude of fluid discharge is likely highest at the GB and MC sites where active mounds are comparatively larger in size, high heat flux exists across the mounds, and recent mudflow deposits flank the mounds. The AV site samples characterize a smaller mound that may still be growing. Fluxes at the KC site are diffusive and methane-charged, but no mound exists. A comparison of the major ions and trace metals in the pore fluids shows large differences in composition. Pore water barium (Ba2+) values demonstrate the most variation between sites. The maximum Ba2+ values at the GB and MC sites reach 7,800 μM and 12,000 μM. This is two orders of magnitude greater than maximum values at the AV (176 μM) and KC (31 μM) sites. Other components, such as salinity, calcium (Ca2+) and strontium (Sr2+) also record differences in composition between the sites. Pore water salinity values measured at the MC and GB sites reach a maximum of 130 ‰, which is at least 2 times greater than values measured at the AV and KC sites. Differences in pore water Ca2+ and Sr2+ are similar to salinity; in general, maximum values are two times greater at GB and MC than at Atwater Valley and Keathley Canyon. The observed differences in pore water composition are the result of the seep fluid source and the chemical processes (e.g., dissolution and precipitation) that occur during migration. Fluid sources and reaction pathways will be evaluated by integrating pore water

  9. Interaction of Ammonia Gas with Sediments and Pore Water and Induced Uranium Immobilization under Vadose Zone Conditions

    NASA Astrophysics Data System (ADS)

    Zhong, L.; Szecsody, J. E.; Truex, M. J.

    2014-12-01

    Preliminary studies have demonstrated the potential of ammonia gas (NH3) treatment on contaminated sediment as a vadose zone uranium remediation approach. In this work, we conducted batch, column, and flow wedge experiments to study the ammonia gas transport and interaction with sediments and pore water. The uranium immobilization effectiveness of the ammonia gas treatment technology was also evaluated. Ammonia gas quickly partitions into sediment pore water and significantly increases the pH (up to ~13.2) and the electrical conductivity (EC). The rate and range of the increase in both pH and EC are dependent on the ammonia concentration in the gas and the pore water content and chemistry. The pH and EC changes follow a similar pattern. During an ammonia gas injection into a heterogeneous system, it was observed that the NH3 front proceeded faster in layers of lower water content compared to the same sediment layers of higher water content. Elevated pH values (11 to 13.2) initially resulted from the NH3 gas partitioning into the pore water was buffered down to ~ 9 after 7 months of sediment exposure to the air. The rate of NH3 diffusion in sediment is a function of the water content in the sediment. Higher cation/anion concentrations during the ammonia gas treatment indicated mineral dissolution due to pH increase, while lower ionic concentrations after the pH buffering revealed significant mineral precipitation. This precipitation incorporates uranium into mineral structures or provides a coating to uranium minerals, therefore achieving uranium immobilization. Treatment with 5% v/v NH3 gas for one week followed by three weeks buffering resulted in a 75% reduction in the mobile uranium mass. After 2 to 12 months of treatment, the immobile phase of uranium mass increased by up to 2.3 times.

  10. Use of swelling clays to reduce permeability and its potential application to nuclear waste repository sealing

    NASA Astrophysics Data System (ADS)

    Moore, D. E.; Morrow, C. A.; Byerlee, J. D.

    1982-09-01

    The injection of swelling-clay slurries into joints or faults at a deep-burial nuclear waste disposal site may result in significant permeability reductions for the effective containment of radioactive wastes. In an experiment conducted to illustrate the permeability change accompanying clay swelling, a coarse stone with interconnected pore spaces was injected with a clay-electrolyte slurry, modelling the pressure-grouting of a fractured repository rock. Subsequently, solutions with lower electrolyte concentrations were driven through the clay-filled stone, corresponding to migration of lower salinity ground-waters through the clay-grouted fracture. The initial injection procedure reduced the permeability of the stone from 1-10 darcies to 700 nanodarcies; the changes in solution composition decreased permeability by more than 2 additional orders of magnitude to 3 nanodarcies. For application at a nuclear waste repository, the electrolyte concentration of the injected clay slurry should be made higher than that of the ground-water in the host rock. Subsequent interaction of the ground-water with the clays would initiate swelling and create the additional, post-injection permeability reductions that may be important in preventing the escape of buried radioactive wastes. The measured permeability of the clay filling is considerably lower than that of cement tested for borehole plugging. Clays also have the advantage over cement and chemical grouts in that they are geologically stable at relatively low temperatures and have a high capacity for radionuclide adsorption.

  11. Novel Anionic Clay Adsorbents for Boiler-Blow Down Waters Reclaim and Reuse

    SciTech Connect

    Muhammad Sahimi; Theodore T. Tsotsis

    2005-12-01

    Our goal in this study is to utilize novel anionic clay sorbents for treating and reclaiming/reusing power-plant effluents, in particular, boiler blow-down waters containing heavy metals, such as As and Se. Developing and using novel materials for such application is dictated by the challenge posed by reclaiming and recycling these too-clean-to-clean effluent streams, generated during electricity production, whose contaminant levels are in the ppm/ppb (or even less) trace levels. During the study model blow-down streams have been treated in batch experiments. Adsorption isotherms as a function of pH/temperature have been established for both As and Se. Adsorption rates have also measured as a function of concentration, temperature, pH, and space time. For both the equilibrium and rate measurements, we have studied the As/Se interaction, and competition from background anions. A homogeneous surface diffusion model is used to describe the experimental kinetic data. The estimated diffusivity values are shown to depend on the particle size. On the other hand, a model taking into account the polycrystalline nature of these adsorbent particles, and the presence of an intercrystallite porous region predicts correctly that the surface diffusivity is particle size independent. A mathematical model to describe flow experiments in packed-beds has also been developed during phase I of this project. The goal is to validate this model with flow experiments in packed-beds during the phase II of this project, to determine the adsorption capacity under flow conditions, and to compare it with the capacity estimated from the adsorption isotherms determined from the batch studies.

  12. Hierarchical modelling of solute diffusion in clays: From the molecular to the continuum scale

    NASA Astrophysics Data System (ADS)

    Gimmi, T.; Churakov, S.

    2009-04-01

    The diffusion properties of clays are most often investigated in laboratory small-scale experiments using uncharged, anionic, and cationic tracers. Typically, the flux of anions through clay samples is lower than that of water tracers like tritiated water. This is explained by anion exclusion effects, which push back anions from the charged clay surfaces towards the centre of the pores and thus reduce the anion accessible porosity to half or less of the water accessible porosity. The diffusion of cations is slowed down because of sorption to the negatively charged clay surfaces. In certain cases, however, the cation flux is larger than expected from the sorption capacity, which is often attributed to surface diffusion, that is, a diffusion of sorbed cations along the clay interlayers or along external surfaces. The consistent description of such phenomena like anion exclusion and surface diffusion with continuum-scale models is rather complicated and relies mostly on empirical parameters. A consistent prediction requires consideration of pore-scale processes, because the ion or tracer specific diffusion behaviour depends on the type and the precise arrangement of the clay phases within the sample. In this presentation, we report on our approach to upscale the specific transport behaviour of anions, cations, and water tracers from the molecular or pore scale to the continuum scale. We developed a random walk model that operates on a pore-scale description of the clay structure. Obtaining such a description for clays is itself a difficult task, because it is hardly possible to directly visualise the very small pores in the nanometre range. Instead, the description has to rely on a combination of mostly indirect methods. We then used the model to predict diffusion coefficients of water tracers, anions, and cations in a given clay. It is possible to obtain these coefficients in a consistent way for a single structural description, using input parameters derived from

  13. The Influence of Sulphate Deposition on the Seasonal Variation of Peat Pore Water Methyl Hg in a Boreal Mire

    PubMed Central

    Bergman, Inger; Bishop, Kevin; Tu, Qiang; Frech, Wolfgang; Åkerblom, Staffan; Nilsson, Mats

    2012-01-01

    In this paper we investigate the hypothesis that long-term sulphate (SO42−) deposition has made peatlands a larger source of methyl mercury (MeHg) to remote boreal lakes. This was done on experimental plots at a boreal, low sedge mire where the effect of long-term addition of SO42− on peat pore water MeHg concentrations was observed weekly throughout the snow-free portion of 1999. The additions of SO42− started in 1995. The seasonal mean of the pore water MeHg concentrations on the plots with 17 kg ha−1 yr−1 of sulphur (S) addition (1.3±0.08 ng L−1, SE; n = 44) was significantly (p<0.0001) higher than the mean MeHg concentration on the plots with 3 kg ha−1 yr−1 of ambient S deposition (0.6±0.02 ng L−1, SE; n = 44). The temporal variation in pore water MeHg concentrations during the snow free season was larger in the S-addition plots, with an amplitude of >2 ng L−1 compared to +/−0.5 ng L−1 in the ambient S deposition plots. The concentrations of pore water MeHg in the S-addition plots were positively correlated (r2 = 0.21; p = 0.001) to the groundwater level, with the lowest concentrations of MeHg during the period with the lowest groundwater levels. The pore water MeHg concentrations were not correlated to total Hg, DOC concentration or pH. The results from this study indicate that the persistently higher pore water concentrations of MeHg in the S-addition plots are caused by the long-term additions of SO42− to the mire surface. Since these waters are an important source of runoff, the results support the hypothesis that SO42− deposition has increased the contribution of peatlands to MeHg in downstream aquatic systems. This would mean that the increased deposition of SO42− in acid rain has contributed to the modern increase in the MeHg burdens of remote lakes hydrologically connected to peatlands. PMID:23029086

  14. The influence of sulphate deposition on the seasonal variation of peat pore water methyl Hg in a boreal mire.

    PubMed

    Bergman, Inger; Bishop, Kevin; Tu, Qiang; Frech, Wolfgang; Åkerblom, Staffan; Nilsson, Mats

    2012-01-01

    In this paper we investigate the hypothesis that long-term sulphate (SO(4) (2-)) deposition has made peatlands a larger source of methyl mercury (MeHg) to remote boreal lakes. This was done on experimental plots at a boreal, low sedge mire where the effect of long-term addition of SO(4) (2-) on peat pore water MeHg concentrations was observed weekly throughout the snow-free portion of 1999. The additions of SO(4) (2-) started in 1995. The seasonal mean of the pore water MeHg concentrations on the plots with 17 kg ha(-1) yr(-1) of sulphur (S) addition (1.3±0.08 ng L(-1), SE; n = 44) was significantly (p<0.0001) higher than the mean MeHg concentration on the plots with 3 kg ha(-1) yr(-1) of ambient S deposition (0.6±0.02 ng L(-1), SE; n = 44). The temporal variation in pore water MeHg concentrations during the snow free season was larger in the S-addition plots, with an amplitude of >2 ng L(-1) compared to +/-0.5 ng L(-1) in the ambient S deposition plots. The concentrations of pore water MeHg in the S-addition plots were positively correlated (r(2) = 0.21; p = 0.001) to the groundwater level, with the lowest concentrations of MeHg during the period with the lowest groundwater levels. The pore water MeHg concentrations were not correlated to total Hg, DOC concentration or pH. The results from this study indicate that the persistently higher pore water concentrations of MeHg in the S-addition plots are caused by the long-term additions of SO(4) (2-) to the mire surface. Since these waters are an important source of runoff, the results support the hypothesis that SO(4) (2-) deposition has increased the contribution of peatlands to MeHg in downstream aquatic systems. This would mean that the increased deposition of SO(4) (2-) in acid rain has contributed to the modern increase in the MeHg burdens of remote lakes hydrologically connected to peatlands. PMID:23029086

  15. Benthic response to shellfish farming in Thau lagoon: Pore water signature

    NASA Astrophysics Data System (ADS)

    Metzger, E.; Simonucci, C.; Viollier, E.; Sarazin, G.; Prévot, F.; Jézéquel, D.

    2007-04-01

    Vertical distributions of dissolved species across the sediment-water interface (SWI), including major cations (sodium, potassium, magnesium, calcium), minor cations (lithium, strontium, barium), redox sensitive species (dissolved manganese, iron, sulfate, sulfide, ammonium) and other chemical parameters (pH, alkalinity, soluble reactive phosphorous, dissolved silica) were studied in a Mediterranean lagoon used for intensive shellfish farming. In order to quantify the impact of this activity on diagenetic processes and the influence of seasonal changes, two stations contrasted with respect to organic carbon fluxes were sampled in Thau lagoon from March 2001 to August 2002 during four field campaigns in winter, spring, summer and fall. Well-defined layers enriched with redox sensitive species were observed following the conventional sequence of early diagenetic reactions. However, differences were observed between both stations in depths and thickness layers. Concentration gradients extended down to more than 92 cm depth at the central position of the lagoon (station C4 - 8 m depth) and down to 40 cm depth inside shellfish farming zones (station C5 - 9 m depth). Station C4 showed an unusual diagenetic signature: sharp dissolved oxygen, iron, nitrate and manganese gradients existed at the SWI but gradients of dissolved sulfide and alkalinity as well as other parameters (dissolved silica, Ba, etc.) were recorded only from 25 to 30 cm depth downward. Seasonal changes were observed in pore water composition as deep as 30-50 cm in station C4 (only 15 cm in station C5). The center of the lagoon is not directly subjected to biodeposits deriving from shellfish activity. Isotopic and bioturbation data allowed to rule out a reworking of the sediment deeper than a few centimeters. In addition to organic content of the sediment, physical parameters were likely to induce the 10-20 cm gap between dissolved iron and sulfide profile as well as the higher vertical extent of

  16. Bioavailability of PAHs in aluminum smelter affected sediments: evaluation through assessment of pore water concentrations and in vivo bioaccumulation.

    PubMed

    Ruus, Anders; Bøyum, Olav; Grung, Merete; Næs, Kristoffer

    2010-12-15

    Bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) from coal tar pitch polluted sediments was predicted by (1) a generic approach based on organic carbon-water partitioning and Gibbs linear free energy relationship (between K(OW) and K(OC)), and (2) measurements of freely dissolved concentrations of PAHs in the sediment pore water, using passive samplers and solid phase extraction. Results from these predictions were compared with those from in vivo bioaccumulation experiments using Nereis diversicolor (Polychaeta), Hinia reticulata (Gastropoda), and Nuculoma tenuis (Bivalvia). Measured sediment/water partition coefficients were higher than predicted by the generic approach. Furthermore, predicted biota-to-sediment accumulation factors (BSAFs) derived from measured pore water concentrations were more in agreement with the bioaccumulation observed for two of the three species. Discrepancies associated with the third species (N. tenuis) were likely a result of particles remaining in the intestine (as shown by microscopic evaluation). These results indicate the importance of conducting site-specific evaluations of pore water concentrations and/or bioaccumulation studies by direct measurements to accurately provide a basis for risk assessment and remediation plans. The importance of knowledge regarding specific characteristics of model organisms is emphasized. PMID:21077669

  17. Water permeability and chloride ion diffusion in portland cement mortars: Relationship to sand content and critical pore diameter

    SciTech Connect

    Halamickova, P.; Detwiler, R.J.; Bentz, D.P.; Garboczi, E.J.

    1995-05-01

    The pore structure of hydrated cement in mortar and concrete is quite different from that of neat cement paste. The porous transition zones formed at the aggregate-paste interfaces affect the pore size distribution. The effect of the sand content on the development of pore structure, the permeability to water, and the diffusivity of chloride ions was studied on portland cement mortars. Mortars of two water-to-cement ratios and three sand volume fractions were cast together with pastes and tested at degrees of hydration ranging from 45 to 70%. An electrically-accelerated concentration cell test was used to determine the coefficient of chloride ion diffusion while a high pressure permeability cell was employed to assess liquid permeability. The coefficient of chloride ion diffusion varied linearly with the critical pore radius as determined by mercury intrusion porosimetry while permeability was found to follow a power-law relationship vs. this critical radius. The data set provides an opportunity to directly examine the application of the Katz-Thompson relationship to cement-based materials.

  18. Pore-scale simulation of liquid CO2 displacement of water using a two-phase lattice Boltzmann model

    SciTech Connect

    Liu, Haihu; Valocchi, Albert J.; Werth, Charles J.; Kang, Oinjun; Oostrom, Martinus

    2014-11-01

    A lattice Boltzmann color-fluid model, which was recently proposed by Liu et al. [H. Liu, A.J. Valocchi, and Q. Kang. Three-dimensional lattice Boltzmann model for immiscible two-phase flow simulations. Phys. Rev. E, 85:046309, 2012.] based on a concept of continuum surface force, is improved to simulate immiscible two-phase flows in porous media. The new improvements allow the model to account for different kinematic viscosities of both fluids and to model fluid-solid interactions. The capability and accuracy of this model is first validated by two benchmark tests: a layered two-phase flow with a viscosity ratio, and a dynamic capillary intrusion. This model is then used to simulate liquid CO2 (LCO2) displacing water in a dual-permeability pore network. The extent and behavior of LCO2 preferential flow (i.e., fingering) is found to depend on the capillary number (Ca), and three different displacement patterns observed in previous micromodel experiments are reproduced. The predicted variation of LCO2 saturation with Ca, as well as variation of specific interfacial length with LCO2 saturation, are both in good agreement with the experimental observations. To understand the effect of heterogeneity on pore-scale displacement, we also simulate LCO2 displacing water in a randomly heterogeneous pore network, which has the same size and porosity as the dual-permeability pore network. In comparison to the dual-permeability case, the transition from capillary fingering to viscous fingering occurs at a higher Ca, and LCO2 saturation is higher at low Ca but lower at high Ca. In either pore network, the LCO2-water specific interfacial length is found to obey a power-law dependence on LCO2 saturation.

  19. Sediment pore-water toxicity test results and preliminary toxicity identification of post-landfall pore-water samples collected following the Deepwater Horizon oil release, Gulf of Mexico, 2010

    USGS Publications Warehouse

    Biedenbach, James M.; Carr, Robert S.

    2011-01-01

    Pore water from coastal beach and marsh sediments from the northern Gulf of Mexico, pre- and post-landfall of the Deepwater Horizon oil release, were collected and evaluated for toxicity with the sea urchin fertilization and embryological development assays. There were 17 pre-landfall samples and 49 post-landfall samples tested using both assays. Toxicity was determined in four pre-landfall sites and in seven post-landfall sites in one or both assays as compared to a known reference sediment pore-water sample collected in Aransas Bay, Texas. Further analysis and testing of five of the post-landfall toxic samples utilizing Toxicity Identification Evaluation techniques indicated that ammonia, and to a lesser extent metals, contributed to most, if not all, of the observed toxicity in four of the five samples. Results of one sample (MS-39) indicated evidence that ammonia, metals, and non-ionic organics were contributing to the observed toxicity.

  20. Authigenic molybdenum formation in marine sediments: A link to pore water sulfide in the Santa Barbara Basin

    USGS Publications Warehouse

    Zheng, Yen; Anderson, Robert F.; VanGeen, A.; Kuwabara, J.

    2000-01-01

    Pore water and sediment Mo concentrations were measured in a suite of multicores collected at four sites along the northeastern flank of the Santa Barbara Basin to examine the connection between authigenic Mo formation and pore water sulfide concentration. Only at the deepest site (580 m), where pore water sulfide concentrations rise to >0.1 ??M right below the sediment water interface, was there active authigenic Mo formation. At shallower sites (550,430, and 340 m), where pore water sulfide concentrations were consistently <0.05 ??M, Mo precipitation was not occuring at the time of sampling. A sulfide concentration of ???0.1 ??M appears to be a threshold for the onset of Mo-Fe-S co-precipitation. A second threshold sulfide concentration of ???100 ??M is required for Mo precipitation without Fe, possibly as Mo-S or as particle-bound Mo. Mass budgets for Mo were constructed by combining pore water and sediment results for Mo with analyses of sediment trap material from Santa Barbara Basin as well as sediment accumulation rates derived from 210Pb. The calculations show that most of the authigenic Mo in the sediment at the deepest site is supplied by diffusion from overlying bottom waters. There is, however, a non-lithogenic particulate Mo associated with sinking particles that contributes ???15% to the total authigenic Mo accumulation. Analysis of sediment trap samples and supernant brine solutions indicates the presence of non-lithogenic particulate Mo, a large fraction of which is easily remobilized and, perhaps, associated with Mn-oxides. Our observations show that even with the very high flux of organic carbon reaching the sediment of Santa Barbara Basin, active formation of sedimentary authigenic Mo requires a bottom water oxygen concentration below 3 ??M. However, small but measurable rates of authigenic Mo accumulation were observed at sites where bottom water oxygen ranged between 5 and 23 ??M, indicating that the formation of authigenic Mo occured in the

  1. Geochemical changes in pore water and reservoir rock due to CO2 injection

    NASA Astrophysics Data System (ADS)

    Huq, Farhana; Blum, Philipp; Nowak, Marcus; Haderlein, Stefan; Grathwohl, Peter

    2010-05-01

    In response to current global warming, carbon capture and storage has been identified as one of the promising option. Thus, it can be an interim solution that is indeed a bridge to the future renewable energy without altering the present mode of energy consumption. Although large natural CO2 sinks are terrestrial eco-system and oceans, geological media or more specifically large sedimentary basins are now the most feasible options for carbon sequestration. At the study site, a former gas field (Altmark), which is located in the South of the Northeast German Basin, CO2 is planned to be injected into the reservoir with high pressure (> 50 bar) and temperature (125°C). Afterwards, CO2 dissolves into the pore water leading to acidification and follow up reactions such as dissolution/precipitation, which potentially change the porosity-permeability of the reservoir and the wetting properties of the mineral surfaces. The Altmark site was chosen due to its large storage capacity, well explored reservoir, high seal integrity due to the presence of massive salt layer (cap rock) and existing infrastructure required for enhanced gas recovery. The main objective of the current study is to quantify the CO2 trapping in aqueous solution under in situ reservoir condition. Therefore, it is necessary to investigate the geochemical changes in fluid composition due to dissolution of minerals under controlled laboratory conditions and to quantify the concentrations of complexing agents that might influence the concentration of total dissolved CO2 in aqueous solution over time. To observe these geochemical and hydraulic changes due to the injection of CO2, a closed system (batch system) technique is developed to study the influence of salinity, temperature, pressure and kinetics on mineral reactions. In addition to the closed system, a flow through (open) autoclave system was constructed. Water saturated sedimentary rock cores (e.g. from the Altmark site; 5cm long, 3cm diameter) are

  2. A possible role of fluctuating clay-water systems in the production of ordered prebiotic oligomers

    NASA Technical Reports Server (NTRS)

    Lahav, N.; White, D. H.

    1980-01-01

    A model is proposed for the intermediate stages of prebiotic evolution, based on the characteristics of the adsorption and condensation of amino acids and nucleotides on the surface area of clay minerals in a fluctuating environment. Template replication and translation of adsorbed oligonucleotides and catalytic effects by peptide products on further condensation are proposed, due to specific properties of hypohydrous clay surfaces as well as the biomolecules themselves. Experimental evidence supports some of the proposed interactions, and all of them can be tested experimentally.

  3. Clay with Desiccation Cracks is an Advection Dominated Environment

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  4. Rapid toxicity screening of sediment pore waters using physiological and biochemical biomarkers of Daphnia magna

    SciTech Connect

    Coen, W.M. De; Janssen, C.R.; Persoone, G.

    1995-12-31

    Two new rapid toxicity tests, based on ingestion activity and digestive enzyme activity of D. magna, were developed and evaluated. The ingestion activity was measured using fluorescent latex micro-beads and an automated microplate fluorimeter allowing a sensitive quantification of the feeding activity of the organisms. The activity of the digestive enzymes, 6-galactosidase, esterase and trypsin, was determined in test organism homogenates using the following fluorogenic{sup 1} and chromogenic{sup 2} substrates: 4-methylumbelliferyl-{beta}-D galactoside{sup 1}, fluorescin diacetate{sup 1} and N-Benzoyl-L-arginine-4-nitroanilide{sup 2}. Both biomarker techniques were developed to allow rapid toxicity screening on a routine basis. The toxicity of the pore waters of eight contaminated samples was assessed with the aid of the developed biomarker assays. Comparison of the conventional 24h EC50 values with the EC50 values obtained with the 1.5h ingestion test and the threshold concentrations of the 2h digestive enzyme tests revealed a positive correlation between the different effect concentrations. A similar correlation (r{sup 2} = 0.87) between the conventional 24h EC50 values and 1.5h EC50 values was observed in toxicity tests with pure compounds. Correlation coefficients for the relationships between the 3 enzyme effect concentrations and the 24h EC50 values ranged from 0.95 to 0.98, The positive correlations between the conventional and biomarker effect criteria, observed for both environmental samples and pure compounds, demonstrate the potential use of the developed methods as rapid toxicity screening tools.

  5. Pore water geochemistry at two seismogenic areas in the Sea of Marmara

    NASA Astrophysics Data System (ADS)

    Ruffine, Livio; Germain, Yoan; Polonia, Alina; de Prunelé, Alexis; Croguennec, Claire; Donval, Jean-Pierre; Pitel-Roudaut, Mathilde; Ponzevera, Emmanuel; Caprais, Jean-Claude; Brandily, Christophe; Grall, Céline; Bollinger, Claire; Géli, Louis; Gasperini, Luca

    2015-07-01

    Within the Sea of Marmara, the highly active North Anatolian Fault (NAF) is responsible for major earthquakes (Mw ≥ 7), and acts as a pathway for fluid migration from deep sources to the seafloor. This work reports on pore water geochemistry from three sediment cores collected in the Gulfs of Izmit and Gemlik, along the Northern and the Middle strands of the NAF, respectively. The resulting data set shows that anaerobic oxidation of methane (AOM) is the major process responsible for sulfate depletion in the shallow sediment. In the Gulf of Gemlik, depth concentration profiles of both sulfate and alkalinity exhibit a kink-type profile. The Sulfate Methane Transition Zone (SMTZ) is located at moderate depth in the area. In the Gulf of Izmit, the low concentrations observed near the seawater-sediment interface for sulfate, calcium, strontium, and magnesium result from rapid geochemical processes, AOM, and carbonate precipitation, occurring in the uppermost part of the sedimentary column and sustained by free methane accumulation. Barite dissolution and carbonate recrystallization have also been identified at deeper depth at the easternmost basin of the Gulf of Izmit. This is supported by the profile of the strontium isotope ratios (87Sr/86Sr) as a function of depth which exhibits negative anomalies compared to the modern seawater value. The strontium isotopic signature also shows that these carbonates had precipitated during the reconnection of the Sea of Marmara with the Mediterranean Sea. Finally, a first attempt to interpret the sulfate profiles observed in the light of the seismic activity at both sites is presented. We propose the hypothesis that seismic activity in the areas is responsible for the transient sulfate profile, and that the very shallow SMTZ depths observed in the Gulf of Izmit is likely due to episodic release of significant amount of methane.

  6. [High resolution measurement of concentrations and fluxes of heavy metals in pore waters by DGT].

    PubMed

    Fan, Ying-hong; Lin, Chun-ye; He, Meng-chang; Zhou, Yu-xiang; Yang, Zhi-feng

    2007-12-01

    Three sediment cores were collected from the Daliao River system in May 2006. The physico-chemical characteristics and heavy metal contents of sediment cores were analyzed. The vertical profiles of metals in pore water were measured by diffusive gradient in thin films (DGT) and centrifugal methods separately. The sequence of the concentrations of Cd, Co, Cr and Cu in sediment is Cr > Cu > Co > Cd. The concentrations measured by DGT were lower than that measured by centrifugal method. The average ratios of DGT measured concentrations (cDGT) to the concentrations measured by centrifugal method of Cd, Co, Cr and Cu were 0.389, 0.328, 0.863 and 0.403, respectively. This suggested that the release rates of these metals from solid phase to solution followed the sequence of Cr > Cu > Cd > Co. The fluxes of Cd, Co Cr and Cu were 1.12 x 10(-7) - 3.28 x 10(-7) nmol/(cm2 x s), 2.48 x 10(-7) - 10.40 x 10(-7) nmol/(cm2 x s), 8.80 x 10(-6) - 12.65 x 10(-6) nmol/(cm2 x s) and 6.14 x 10(-6) - 13.93 x 10(-6) nmol/(cm2 x s), respectively. The result showed that the release of Cd and Cu was mainly influenced by organic matter (OM), while Fe oxides, Mn oxides and OM were major factors controlling the transfer of Cr. The redox potential may be the major factor influencing the release of Co element. PMID:18290432

  7. Comparison of Experimental and Model Data for the Evaporation of a Synthetic Topopah Spring Tuff Pore Water, Yucca Mountain, NV

    SciTech Connect

    Alai, M; Sutton, M; Carroll, S

    2003-10-14

    The evaporation of a range of synthetic pore water solutions representative of the potential high-level-nuclear-waste repository at Yucca Mountain, NV is being investigated. The motivation of this work is to understand and predict the range of brine compositions that may contact the waste containers from evaporation of pore waters, because these brines could form corrosive thin films on the containers and impact their long-term integrity. A relatively complex synthetic Topopah Spring Tuff pore water was progressively concentrated by evaporation in a closed vessel, heated to 95 C in a series of sequential experiments. Periodic samples of the evaporating solution were taken to determine the evolving water chemistry. According to chemical divide theory at 25 C and 95 C our starting solution should evolve towards a high pH carbonate brine. Results at 95 C show that this solution evolves towards a complex brine that contains about 99 mol% Na{sup +} for the cations, and 71 mol% Cl{sup -}, 18 mol% {Sigma}CO{sub 2}(aq), 9 mol% SO{sub 4}{sup 2-} for the anions. Initial modeling of the evaporating solution indicates precipitation of aragonite, halite, silica, sulfate and fluoride phases. The experiments have been used to benchmark the use of the EQ3/6 geochemical code in predicting the evolution of carbonate-rich brines during evaporation.

  8. Behaviour of pharmaceuticals and personal care products in constructed wetland compartments: Influent, effluent, pore water, substrate and plant roots.

    PubMed

    Hijosa-Valsero, María; Reyes-Contreras, Carolina; Domínguez, Carmen; Bécares, Eloy; Bayona, Josep M

    2016-02-01

    Seven mesocosm-scale constructed wetlands (CWs) with different design configurations, dealing with primary-treated urban wastewater, were assessed for the concentration, distribution and fate of ten pharmaceutical and personal care products (PPCPs) [ibuprofen, ketoprofen, naproxen, diclofenac, salicylic acid, caffeine, carbamazepine, methyl dihydrojasmonate, galaxolide and tonalide] and eight of their transformation products (TPs). Apart from influent and effluent, various CW compartments were analysed, namely, substrate, plant roots and pore water. PPCP content in pore water depended on the specific CW configuration. Macrophytes can take up PPCPs through their roots. Ibuprofen, salicylic acid, caffeine, methyl dihydrojasmonate, galaxolide and tonalide were present on the root surface with a predominance of galaxolide and caffeine in all the planted systems. Naproxen, ibuprofen, salicylic acid, methyl dihydrojasmonate, galaxolide and tonalide were uptaken by the roots. In order to better understand the removal processes, biomass measurement and biodegradability studies through the characterization of internal-external isomeric linear alkylbenzenes present on the gravel bed were performed. Three TPs namely, ibuprofen-amide, 3-ethylbenzophenone and 4-hydroxy-diclofenac were identified for the first time in wetland pore water and effluent water, which suggests de novo formation (they were not present in the influent). Conversely, O-desmethyl-naproxen was degraded through the wetland passage since it was detected in the influent but not in the subsequent treatment stages. Biodegradation pathways are therefore suggested for most of the studied PPCPs in the assessed CWs. PMID:26702554

  9. Geochemistry of pore waters from Shell Oil Company drill holes on the continental slope of the northern Gulf of Mexico

    USGS Publications Warehouse

    Manheim, F. T.; Bischoff, J.L.

    1969-01-01

    Pore waters were analyzed from 6 holes drilled from M.V. "Eureka" as a part of the Shell Oil Co. deeper offshore study. The holes were drilled in water depths of 600-3,000 ft. (approximately 180-550 m) and penetrated up to 1,000 ft. (300 m) of Pliocene-Recent clayey sediments. Salt and anhydrite caprock was encountered in one diapiric structure on the continental slope. Samples from holes drilled near diapiric structures showed systematic increases of pore-water salinity with depth, suggestive of salt diffusion from underlying salt plugs. Anomalous concentrations of K and Br indicate that at least one plug contains late-stage evaporite minerals. Salinities approaching halite saturation were observed. Samples from holes away from diapiric structures showed little change in pore-water chemistry, except for loss of SO4 and other variations attributable to early-stage diagenetic reactions with enclosing sediments. Thus, increased salt concentrations in even shallow sediments from this part of the Gulf appear to provide an indicator of salt masses at depth. ?? 1969.

  10. Radiogenic helium in shallow groundwater within a clay till, southwestern Ontario

    USGS Publications Warehouse

    Sheldon, A.L.; Solomon, D.K.; Poreda, R.J.; Hunt, A.

    2003-01-01

    Profiles of 4He in pore water were measured in clay aquitards in SW Ontario. The 4He distributions are consistent with groundwater velocities that are 70% of initial 4He for 50 to 60 kA prior to incorporation into the till.

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

    USGS Publications Warehouse

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

    2001-01-01

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

  12. MRI-derived bound and pore water concentrations as predictors of fracture resistance.

    PubMed

    Manhard, Mary Kate; Uppuganti, Sasidhar; Granke, Mathilde; Gochberg, Daniel F; Nyman, Jeffry S; Does, Mark D

    2016-06-01

    Accurately predicting fracture risk in the clinic is challenging because the determinants are multi-factorial. A common approach to fracture risk assessment is to combine X-ray-based imaging methods such as dual-energy X-ray absorptiometry (DXA) with an online Fracture Risk Assessment Tool (FRAX) that includes additional risk factors such as age, family history, and prior fracture incidents. This approach still does not adequately diagnose many individuals at risk, especially those with certain diseases like type 2 diabetes. As such, this study investigated bound water and pore water concentrations (Cbw and Cpw) from ultra-short echo time (UTE) magnetic resonance imaging (MRI) as new predictors of fracture risk. Ex vivo cadaveric arms were imaged with UTE MRI as well as with DXA and high-resolution micro-computed tomography (μCT), and imaging measures were compared to both whole-bone structural and material properties as determined by three-point bending tests of the distal-third radius. While DXA-derived areal bone mineral density (aBMD) and μCT-derived volumetric BMD correlated well with structural strength, they moderately correlated with the estimate material strength with gender being a significant covariate for aBMD. MRI-derived measures of Cbw and Cpw had a similar predictive ability of material strength as aBMD but did so independently of gender. In addition, Cbw was the only imaging parameter to significantly correlate with toughness, the energy dissipated during fracture. Notably, the strength of the correlations with the material properties of bone tended to be higher when a larger endosteal region was used to determine Cbw and Cpw. These results indicate that MRI measures of Cbw and Cpw have the ability to probe bone material properties independent of bone structure or subject gender. In particular, toughness is a property of fracture resistance that is not explained by X-ray based methods. Thus, these MRI-derived measures of Cbw and Cpw in cortical

  13. Effects of Different Factors on Water Flow and Solute Transport Investigated by Time Domain Reflectometry in Sandy Clay Loam Field Soil.

    PubMed

    Merdun, Hasan

    2012-09-01

    Factors affecting preferential flow and transport in the vadose zone need to be investigated by experiments and simulations to protect groundwater against surface applied chemicals. The objectives of this study were to investigate the effects of several factors (soil structure, initial soil water content (SWC), and application rate) and their interactions on the extent of preferential flow and transport in a sandy clay loam field soil using the time domain reflectometry (TDR) for measuring SWC and electrical conductivity (EC) in 12 treatments, modeling (by HYDRUS-1D and VS2DTI) the measured SWC and EC, and conducting statistical tests for comparing the means of the measured and modeled SWC and EC and solute transport parameters (pore water velocity and dispersion coefficient) obtained by inversely fitting in the CXTFIT program. The study results showed that the applied solution moved faster in the undisturbed, wet initial SWC, and higher application rate experimental conditions than in the disturbed, dry initial SWC, and lower application rate, respectively, based on the analysis of the changes in TDR measured SWC and EC with depth at 1, 2, 5, and 15 h of the experiments. However, the effects of interactive factors or treatments on water flow and solute transport were not clear enough. The modeling results showed that HYDRUS-1D was better than VS2DTI in the estimation of EC and especially SWC, but overall the models had relatively low performances in the simulations. Statistical test results also showed that the treatments had different flow and transport characteristics because they were divided into different groups in terms of the means of SWC and EC and solute transport parameters. These results suggest that similar experiments with more distinct interactions and modeling studies with different approaches need to be considered for better understanding the complex flow and transport processes in the vadose zone. PMID:23002311

  14. Sphagnum can 'filter' N deposition, but effects on the plant and pore water depend on the N form.

    PubMed

    Chiwa, Masaaki; Sheppard, Lucy J; Leith, Ian D; Leeson, Sarah R; Tang, Y Sim; Cape, J Neil

    2016-07-15

    The ability of Sphagnum moss to efficiently intercept atmospheric nitrogen (N) has been assumed to be vulnerable to increased N deposition. However, the proposed critical load (20kgNha(-1)yr(-1)) to exceed the capacity of the Sphagnum N filter has not been confirmed. A long-term (11years) and realistic N manipulation on Whim bog was used to study the N filter function of Sphagnum (Sphagnum capillifolium) in response to increased wet N deposition. On this ombrotrophic peatland where ambient deposition was 8kgNha(-1)yr(-1), an additional 8, 24, and 56kgNha(-1)yr(-1) of either ammonium (NH4(+)) or nitrate (NO3(-)) has been applied for 11years. Nutrient status of Sphagnum and pore water quality from the Sphagnum layer were assessed. The N filter function of Sphagnum was still active up to 32kgNha(-1)yr(-1) even after 11years. N saturation of Sphagnum and subsequent increases in dissolved inorganic N (DIN) concentration in pore water occurred only for 56kgNha(-1)yr(-1) of NH4(+) addition. These results indicate that the Sphagnum N filter is more resilient to wet N deposition than previously inferred. However, functionality will be more compromised when NH4(+) dominates wet deposition for high inputs (56kgNha(-1)yr(-1)). The N filter function in response to NO3(-) uptake increased the concentration of dissolved organic N (DON) and associated organic anions in pore water. NH4(+) uptake increased the concentration of base cations and hydrogen ions in pore water though ion exchange. The resilience of the Sphagnum N filter can explain the reported small magnitude of species change in the Whim bog ecosystem exposed to wet N deposition. However, changes in the leaching substances, arising from the assimilation of NO3(-) and NH4(+), may lead to species change. PMID:27058130

  15. Ion and water transport in a Nafion{reg_sign} membrane pore: A statistical mechanical model with molecular structure

    SciTech Connect

    Paddison, S.J.; Zawodzinski, T.A. Jr.; Paul, R.

    1998-12-31

    With the well established importance of the coupling of water and protons through electroosmotic drag in operating PEFCs the authors present here a derivation of a mathematical model that focuses on the computation of the mobility of an hydronium ion through an arbitrary cylindrical pore of a PEM with a non-uniform charge distribution on the walls of the pore. The total Hamiltonian is derived for the hydronium ion as it moves through the hydrated pore and is effected by the net potential due to interaction with the solvent molecules and the pendant side chains. The corresponding probability density is derived through solution of the Liouville equation. This probability density is then used to compute the friction tensor for the hydronium ion. The authors find two types of contributions: (a) due to the solvent-ion interactions for which they adopt the conventional continuum model; (b) due to the interaction between the pendant charges and the hydronium ion. The latter is a new result and displays the role of the non-uniform nature of the charge distribution on the pore wall.

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

    USGS Publications Warehouse

    Hay, M.B.; Stoliker, D.L.; Davis, J.A.; Zachara, J.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. Copyright 2011 by the American Geophysical Union.

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

    USGS Publications Warehouse

    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.

  18. Universal scaling of the formation factor in clays: Example from the Nankai Trough

    NASA Astrophysics Data System (ADS)

    Daigle, Hugh; Ghanbarian, Behzad; Henry, Pierre; Conin, Marianne

    2015-11-01

    Electrical conductivity is a fundamental characteristic describing how strongly a network opposes flow of electrical current. In fully water-saturated porous media the conductivity, represented by the formation factor, is mainly controlled by porosity, connectivity of the conducting phases, and the tortuosity of electrical current paths. Previous work has shown that universal scaling derived from percolation and effective medium theories accurately describes the relationship between formation factor and porosity when the percolation threshold is taken account, as well as the porosity value at which the scaling switches from percolation theory to effective medium theory. We determined the formation factor in clay-rich sediments based on cation exchange capacity measurements on samples from five scientific ocean drilling sites in the Nankai Trough. We then compared the results to predictions from universal scaling after determining the volume of clay-bound water and the percolation threshold. We found that the previously reported universal scaling relations hold in these clay-rich sediments once the corrections are made for the clay-bound water and that percolation scaling appears to be valid over the entire range of observed porosities, probably due to relatively broad pore size distributions or low pore system connectivity. Our results show that universal scaling can be applied to describe the porosity dependence of the formation factor in clay-rich sediments when appropriate corrections are made for the presence of clay-bound water.

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

    NASA Astrophysics Data System (ADS)

    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.

  20. Fire clay

    USGS Publications Warehouse

    Virta, R.L.

    2011-01-01

    The article discusses the latest developments in the fire clay industry, particularly in the U.S., as of June 2011. It claims that the leading fire clay producer in the U.S. is the state of Missouri. The other major producers include California, Texas and Washington. It reports that the use of heavy clay products made of fire clay like brick, cement and lightweight aggregate has increased slightly in 2010.

  1. Clays, common

    USGS Publications Warehouse

    Virta, R.L.

    1998-01-01

    Part of a special section on the state of industrial minerals in 1997. The state of the common clay industry worldwide for 1997 is discussed. Sales of common clay in the U.S. increased from 26.2 Mt in 1996 to an estimated 26.5 Mt in 1997. The amount of common clay and shale used to produce structural clay products in 1997 was estimated at 13.8 Mt.

  2. Bioavailability of metals and toxicity identification of the sediment pore waters from Plow Shop Pond, Fort Devens, Massachusetts

    SciTech Connect

    Jop, K.; Putt, A.; Shepherd, S.; Askew, A.; Bleiler, J.; Reed, S.; George, C.

    1995-12-31

    Plow Shop Pond is a shallow, 30-acre pond located at Fort Devens, Massachusetts. An ecological risk assessment was conducted at Plow Shop Pond as part of a remedial investigation. Preliminary analysis revealed high concentrations of arsenic, copper, chromium, lead, and mercury in the sediment. Therefore, a laboratory testing program was incorporated into this investigation to assess the toxicity of sediments to aquatic organisms. The screening testing program included short-term chronic exposure of Ceriodaphnia dubia to pore waters, 10-day exposures of Chironomus tentans and Hyalella azteca to bulk sediments and a bioaccumulation study with Lumbriculus variegatus. Survival and reproduction of C. dubia, growth of amphipods and reproduction of oligochaetes appeared to indicate sediment toxicity at some sites within the pond. Although high concentrations of arsenic, copper, mercury and lead were detected in the whole sediments and pore waters, the response could not be correlated to a particular element. Also, relatively low bioaccumulation of methyl mercury and high uptake of inorganic mercury was established for three sediment samples. To characterize and identify the source of toxicity, a toxicity identification evaluation program using sediments collected at several locations was performed. The pore water from these samples was used for fractionation coupled with a 10-day test using H. azteca. Survival and growth were evaluated as endpoints during the exposures. Partitioning of metals and their bioavailability was influenced primarily by organic carbon and AVS concentration. At least two constituents were responsible for the toxicity.

  3. Intercomparison and applicability of some dynamic and equilibrium approaches to determine methylated mercury species in pore water.

    PubMed

    Liu, Jinling; Feng, Xinbin; Qiu, Guangle; Yao, Heng; Shang, Lihai; Yan, Haiyu

    2011-08-01

    To assess adequately the impact of methylmercury (MeHg) on sensitive wetland ecosystems, accurate measurements of MeHg in pore water are required. In the present study, the feasibility of three methods for porewater sampling was investigated with respect to MeHg in sediments and rice paddy fields. The performance of dialysis samplers (peepers), sediment core sectioning followed by porewater separation by centrifugation (core), and the thin film diffusive samplers (DGT) were evaluated. These methods were intercompared in field experiments at two sites in Guizhou province, SW China disparately impacted by mercury pollution. All the methods report that the concentrations of MeHg in the soils of the Gouxi (GX) rice paddy near Wanshan were much higher than that in the sediment of the Hongjiadu Reservoir (HR), which is located within the Wujiang River basin. The three methods also report different MeHg profiles at the same site. However, these methods exhibit different temporal and spatial resolution scales, due to the differing operations involved with the sampling methods, may also reflect different states of MeHg in pore water. This corresponds to MeHg derived from diffusive flux, equilibrium concentration, and bulk concentration in pore water detected by DGT, peeper, and sediment core, respectively. The advantages and limits of the three methods are also presented. PMID:21538492

  4. Mechanism and kinetics of pore formation in membranes by water-soluble amphipathic peptides

    PubMed Central

    Lee, Ming-Tao; Hung, Wei-Chin; Chen, Fang-Yu; Huang, Huey W.

    2008-01-01

    How antimicrobial peptides form pores in membranes is of interest as a fundamental membrane process. However, the underlying molecular mechanism, which has potential applications in therapeutics, nonviral gene transfer, and drug delivery, has been in dispute. We have resolved this mechanism by observing the time-dependent process of pore formation in individual giant unilamellar vesicles (GUVs) exposed to a melittin solution. An individual GUV first expanded its surface area at constant volume and then suddenly reversed to expanding its volume at constant area. The area expansion, the volume expansion, and the point of reversal all match the results of equilibrium measurements performed on peptide–lipid mixtures. The mechanism includes a negative feedback that makes peptide-induced pores stable with a well defined size, contrary to the suggestion that peptides disintegrate the membrane in a detergent-like manner. PMID:18375755

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

    NASA Astrophysics Data System (ADS)

    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

  6. Clay Houses

    ERIC Educational Resources Information Center

    Pedro, Cathy

    2011-01-01

    In this article, the author describes a project designed for fourth-graders that involves making clay relief sculptures of houses. Knowing the clay houses will become a family heirloom makes this lesson even more worth the time. It takes three classes to plan and form the clay, and another two to underglaze and glaze the final products.

  7. River water quality of the River Cherwell: an agricultural clay-dominated catchment in the upper Thames Basin, southeastern England.

    PubMed

    Neal, Colin; Neal, Margaret; Hill, Linda; Wickham, Heather

    2006-05-01

    The water quality of the River Cherwell and a tributary of it, the Ray, are described in terms of point and diffuse sources of pollution, for this rural area of the upper Thames Basin. Point sources of pollution dominate at the critical ecological low flow periods of high biological activity. Although the surface geology is predominantly clay, base flow is partly supplied from springs in underlying carbonate-bearing strata, which influences the water quality particularly with regards to calcium and alkalinity. The hydrogeochemistry of the river is outlined and the overall importance of urban point sources even in what would normally be considered to be rural catchments is stressed in relation to the European Unions Water Framework Directive. Issues of phosphorus stripping at sewage treatment works are also considered: such stripping on the Cherwell has reduced phosphorus concentrations by about a factor of two, but this is insufficient for the needs of the Water Framework Directive. PMID:16253306

  8. Ion adsorption and diffusion in smectite: Molecular, pore, and continuum scale views

    NASA Astrophysics Data System (ADS)

    Tinnacher, Ruth M.; Holmboe, Michael; Tournassat, Christophe; Bourg, Ian C.; Davis, James A.

    2016-03-01

    Clay-rich media have been proposed as engineered barrier materials or host rocks for high level radioactive waste repositories in several countries. Hence, a detailed understanding of adsorption and diffusion in these materials is needed, not only for radioactive contaminants, but also for predominant earth metals, which can affect radionuclide speciation and diffusion. The prediction of adsorption and diffusion in clay-rich media, however, is complicated by the similarity between the width of clay nanopores and the thickness of the electrical double layer (EDL) at charged clay mineral-water interfaces. Because of this similarity, the distinction between 'bulk liquid' water and 'surface' water (i.e., EDL water) in clayey media can be ambiguous. Hence, the goal of this study was to examine the ability of existing pore scale conceptual models (single porosity models) to link molecular and macroscopic scale data on adsorption and diffusion in compacted smectite. Macroscopic scale measurements of the adsorption and diffusion of calcium, bromide, and tritiated water in Na-montmorillonite were modeled using a multi-component reactive transport approach while testing a variety of conceptual models of pore scale properties (adsorption and diffusion in individual pores). Molecular dynamics (MD) simulations were carried out under conditions similar to those of our macroscopic scale diffusion experiments to help constrain the pore scale models. Our results indicate that single porosity models cannot be simultaneously consistent with our MD simulation results and our macroscopic scale diffusion data. A dual porosity model, which allows for the existence of a significant fraction of bulk liquid water-even at conditions where the average pore width is only a few nanometers-may be required to describe both pore scale and macroscopic scale data.

  9. Differential equations governing slip-induced pore-pressure fluctuations in a water-saturated granular medium

    USGS Publications Warehouse

    Iverson, R.M.

    1993-01-01

    Macroscopic frictional slip in water-saturated granular media occurs commonly during landsliding, surface faulting, and intense bedload transport. A mathematical model of dynamic pore-pressure fluctuations that accompany and influence such sliding is derived here by both inductive and deductive methods. The inductive derivation shows how the governing differential equations represent the physics of the steadily sliding array of cylindrical fiberglass rods investigated experimentally by Iverson and LaHusen (1989). The deductive derivation shows how the same equations result from a novel application of Biot's (1956) dynamic mixture theory to macroscopic deformation. The model consists of two linear differential equations and five initial and boundary conditions that govern solid displacements and pore-water pressures. Solid displacements and water pressures are strongly coupled, in part through a boundary condition that ensures mass conservation during irreversible pore deformation that occurs along the bumpy slip surface. Feedback between this deformation and the pore-pressure field may yield complex system responses. The dual derivations of the model help explicate key assumptions. For example, the model requires that the dimensionless parameter B, defined here through normalization of Biot's equations, is much larger than one. This indicates that solid-fluid coupling forces are dominated by viscous rather than inertial effects. A tabulation of physical and kinematic variables for the rod-array experiments of Iverson and LaHusen and for various geologic phenomena shows that the model assumptions commonly are satisfied. A subsequent paper will describe model tests against experimental data. ?? 1993 International Association for Mathematical Geology.

  10. Characterization of colloidal phosphorus species in drainage waters from a clay soil using asymmetric flow field-flow fractionation.

    PubMed

    Regelink, Inge C; Koopmans, Gerwin F; van der Salm, Caroline; Weng, Liping; van Riemsdijk, Willem H

    2013-01-01

    Phosphorus transport from agricultural land contributes to eutrophication of surface waters. Pipe drain and trench waters from a grassland field on a heavy clay soil in the Netherlands were sampled before and after manure application. Phosphorus speciation was analyzed by physicochemical P fractionation, and the colloidal P fraction in the dissolved fraction (<0.45 μm) was analyzed by asymmetric flow field-flow fractionation (AF4) coupled to high-resolution inductively coupled plasma-mass spectrometry and ultraviolet diode array detector. When no manure was applied for almost 7 mo, total P (TP) concentrations were low (<21 μmol L), and TP was almost evenly distributed among dissolved reactive P (DRP), dissolved unreactive P (DUP), and particulate P (PP). Total P concentrations increased by a factor of 60 and 4 when rainfall followed shortly after application of cattle slurry or its solid fraction, respectively. Under these conditions, DRP contributed 50% or more to TP. The P speciation within the DUP and PP fractions varied among the different sampling times. Phosphorus associated with dissolved organic matter, probably via cation bridging, comprised a small fraction of DUP at all sampling times. Colloidal P coeluted with clay particles when P application was withheld for almost 7 mo and after application of the solid cattle slurry fraction. At these sampling times, PP correlated well with particulate Fe, Al, and Si, indicating that P is associated with colloidal clay particles. After cattle slurry application, part of DUP was probably present as phospholipids. Physicochemical fractionation combined with AF4 analysis is a promising tool to unravel the speciation of colloidal P in environmental water samples. PMID:23673839

  11. Pore Network Modeling and Synchrotron Imaging of Liquid Water in the Gas Diffusion Layer of Polymer Electrolyte Membrane Fuel Cells

    NASA Astrophysics Data System (ADS)

    Hinebaugh, James Thomas

    Polymer electrolyte membrane (PEM) fuel cells operate at levels of high humidity, leading to condensation throughout the cell components. The porous gas diffusion layer (GDL) must not become over-saturated with liquid water, due to its responsibility in providing diffusion pathways to and from the embedded catalyst sites. Due to the opaque and microscale nature of the GDL, a current challenge of the fuel cell industry is to identify the characteristics that make the GDL more or less robust against flooding. Modeling the system as a pore network is an attractive investigative strategy; however, for flooding simulations to provide meaningful material comparisons, accurate GDL topology and condensation distributions must be provided. The focus of this research is to provide the foundational tools with which to capture both of these requirements. The method of pore network modeling on topologically representative pore networks is demonstrated to describe flooding phenomena within GDL materials. A stochastic modeling algorithm is then developed to create pore spaces with the relevant features of GDL materials. Then, synchrotron based X-ray visualization experiments are developed and conducted to provide insight into condensation conditions. It was found that through-plane porosity distributions have significant effects on the GDL saturation levels. Some GDL manufacturing processes result in high porosity regions which are predicted to become heavily saturated with water if they are positioned between the condensation sites and the exhaust channels. Additionally, it was found that fiber diameter and the volume fraction of binding material applied to the GDL have significant impacts on the GDL heterogeneity and pore size distribution. Representative stochastic models must accurately describe these three material characteristics. In situ, dynamic liquid water behavior was visualized at the Canadian Light source, Inc. synchrotron using imaging and image processing

  12. A pore-scale model of two-phase flow in water-wet rock

    SciTech Connect

    Silin, Dmitriy; Patzek, Tad

    2009-02-01

    A finite-difference discretization of Stokes equations is used to simulate flow in the pore space of natural rocks. Numerical solutions are obtained using the method of artificial compressibility. In conjunction with Maximal Inscribed Spheres method, these computations produce relative permeability curves. The results of computations are in agreement with laboratory measurements.

  13. Fire clay

    USGS Publications Warehouse

    Virta, R.L.

    2013-01-01

    Four companies mined fire clay in three states in 2012. Production, based on a preliminary survey of the fire clay industry, was estimated to be 230 kt (254,000 st) valued at $6.98 million, an increase from 215 kt (237,000 st) valued at $6.15 million in 2011. Missouri was the leading producing state, followed by Colorado and Texas, in decreasing order by quantity. The number of companies mining fire clay declined in 2012 because several common clay producers that occasionally mine fire clay indicated that they did not do so in 2012.

  14. Chemical analyses of pore water from boreholes USW SD-6 and USW WT-24, Yucca Mountain, Nevada

    USGS Publications Warehouse

    Yang, I.C.; Peterman, Z.E.; Scofield, K.M.

    2003-01-01

    Analyses of pore water extracted from cores of boreholes USW SD-6 in the central part and USW WT-24 in the northern part of Yucca Mountain, Nevada, show significant vertical and lateral variations in dissolved-ion concentrations. Analyses of samples of only a few milliliters of pore water extracted by uniaxial or triaxial compression and by ultracentrifugation methods from adjacent core samples are generally in agreement, within the analytical error of 10% to 15%. However, the values of silica for water obtained by ultracentrifugation are consistently lower than values for water obtained by compression. The larger concentrations probably are due to localized pressure solution of silicate minerals during compression. The shallower water from core in borehole USW SD-6 was extracted from nonwelded units collectively referred to as the Paintbrush Tuff nonwelded (PTn). The deeper water was from core in both boreholes USW SD-6 and USW WT-24 in the nonwelded units referred to as the Calico Hills nonwelded (CHn). Significant differences in mean dissolved-ion concentrations in pore water between the PTn and CHn are (1) decreases in Ca, Mg, SO4, and NO3 and (2) increases in HCO3 and (Na+K)/(Ca+Mg) ratios. The decrease in NO3 and the increase in HCO3 could be the result of denitrification through the oxidation of organic matter. The decrease in Ca and associated increase in (Na+K)/(Ca+Mg) is the result of ion exchange with zeolites in the CHn in borehole USW WT-24. This effect is not nearly as pronounced in borehole USW SD-6, probably reflecting a smaller amount of zeolitization of the CHn in USW SD-6. Geochemical calculations using the PHREEQC code indicate that the pore water from both boreholes USW SD-6 and USW WT-24 is uniformly undersaturated in anhydrite, gypsum, and amorphous silica, but supersaturated in quartz and chalcedony. The saturation of calcite, aragonite, sepiolite, and dolomite is more variable from sample to sample. ?? 2002 Elsevier Science B.V. All rights

  15. Field experiments of Controlled Drainage of agricultural clay soils show positive effects on water quantity (retention, runoff) and water quality (nitrate leaching).

    NASA Astrophysics Data System (ADS)

    schipper, peter; stuyt, lodewijk; straat, van der, andre; schans, van der, martin

    2014-05-01

    Despite best management practices, agriculture is still facing major challenges to reduce nutrients leaching to the aquatic environment. In deltas, most of total nutrient losses from artificially drained agricultural soils are discharged via drains. Controlled drainage is a promising measure to prevent drainage of valuable nutrients, improve water quality and agricultural yield and adapt to climate change (reduce peak runoff, manage water scarcity and drought). In The Netherlands, this technique has attracted much attention by water managers and farmers alike, yet field studies to determine the expected (positive) effects for Dutch conditions were scarce. Recently, a field experiment was set up on clay soils. Research questions were: how does controlled, subsurface drainage perform on clay soils? Will deeper tile drains function just as well? What are the effects on drain water quality (especially with respect to nitrogen and salt) and crop yield? An agricultural field on clay soils was used to test different tile drainage configurations. Four types of tile drainage systems were installed, all in duplicate: eight plots in total. Each plot has its own outlet to a control box, where equipment was installed to control drain discharge and to measure the flow, concentrations of macro-ions, pH, nitrogen, N-isotopes and heavy metals. In each plot, groundwater observation wells and suction cups are installed in the saturated and vadose zones, at different depths, and crop yield is determined. Four plots discharge into a hydrologic isolated ditch, enabling the determination of water- and nutrient balances. Automatic drain water samplers and innovative nitrate sensors were installed in four plots. These enable identification and unravelling so-called first flush effects (changes in concentrations after a storm event). Water-, chloride- and nitrogen balances have been set up, and the interaction between groundwater and surface water has been quantified. The hydrological

  16. Recent spectroscopic findings concerning clay/water interactions at low humidity: Possible applications to models of Martian surface reactivity

    NASA Technical Reports Server (NTRS)

    Coyne, L.; Bishop, J.; Howard, L.; Scattergood, T. W.

    1991-01-01

    A feasibility study assessing the utility of the adaptation of near infrared correlation spectroscopy to quantifying iron and adsorbed water in some clay-based Mars soil analog materials (MarSAM's). The work was intended to constitute Phase 1 of an approach to identifying optical analytical wavelength regions, not only for important mineral classes, but for chemically active centers within them. Many of these centers are common to unrelated mineral classes and of disproportionate influence relative to the mineral structure as a whole in determining the surface reactivity of mineral surfaces. We previously reported linearity between reflectance and total iron and total moisture over a large range of both key variables. We also discovered interesting relationships between the intensity of iron bands and the relative humidity of the systems. These relationships were confirmed. We also show that, in the low humidity range, reflectance is linearly dependent on a different kind of water from that best representing the full humidity range (the kind of water associated, in clays, with surface acidity). These relationships and the sensitivity and capability of quantitation of near infrared data indicate high promise with the production of reactive surface intermediates of products of surface reactions.

  17. Strontium Isotopes in Pore Water as an Indicator of Water Flux at the Proposed High-Level Radioactive Waste Repository, Yucca Mountain, Nevada

    SciTech Connect

    B. Marshall; K. Futa

    2004-02-19

    The proposed high-level radioactive waste repository at Yucca Mountain, Nevada, would be constructed in the high-silica rhyolite (Tptp) member of the Miocene-age Topopah Spring Tuff, a mostly welded ash-flow tuff in the {approx}500-m-thick unsaturated zone. Strontium isotope compositions have been measured in pore water centrifuged from preserved core samples and in leachates of pore-water salts from dried core samples, both from boreholes in the Tptp. Strontium isotope ratios ({sup 87}Sr/{sup 86}Sr) vary systematically with depth in the surface-based boreholes. Ratios in pore water near the surface (0.7114 to 0.7124) reflect the range of ratios in soil carbonate (0.7112 to 0.7125) collected near the boreholes, but ratios in the Tptp (0.7122 to 0.7127) at depths of 150 to 370 m have a narrower range and are more radiogenic due to interaction with the volcanic rocks (primarily non-welded tuffs) above the Tptp. An advection-reaction model relates the rate of strontium dissolution from the rocks with flow velocity. The model results agree with the low transport velocity ({approx}2 cm per year) calculated from carbon-14 data by I.C. Yang (2002, App. Geochem., v. 17, no. 6, p. 807-817). Strontium isotope ratios in pore water from Tptp samples from horizontal boreholes collared in tunnels at the proposed repository horizon have a similar range (0.7121 to 0.7127), also indicating a low transport velocity. Strontium isotope compositions of pore water below the proposed repository in core samples from boreholes drilled vertically downward from tunnel floors are more varied, ranging from 0.7112 to 0.7127. The lower ratios (<0.7121) indicate that some of the pore water in these boreholes was replaced by tunnel construction water, which had an {sup 87}Sr/{sup 86}Sr of 0.7115. Ratios lower than 0.7115 likely reflect interaction of construction water with concrete in the tunnel inverts, which had an {sup 87}Sr/{sup 86}Sr < 0.709. These low Sr ratios indicate penetration of

  18. Strontium Isotopes in Pore Water as an Indicator of Water Flow at the Proposed High-Level Radioactive Waste Repository, Yucca Mountain, Nevada

    NASA Astrophysics Data System (ADS)

    Marshall, B. D.; Futa, K.

    2004-05-01

    The proposed high-level radioactive waste repository at Yucca Mountain, Nevada, would be constructed in the high-silica rhyolite (Tptp) member of the Miocene-age Topopah Spring Tuff, a mostly welded ash-flow tuff in the ~500-m-thick unsaturated zone. Strontium isotope compositions have been measured in pore water centrifuged from preserved core samples and in leachates of pore-water salts from dried core samples. Strontium isotope ratios (87}Sr/{86Sr) vary systematically with depth in the surface-based boreholes. Ratios in pore water near the surface (0.7114 to 0.7124) reflect the range of ratios in soil carbonate (0.7112 to 0.7125) collected near the boreholes, but ratios in the Tptp (0.7122 to 0.7127) at depths of 150 to 370 m have a narrower range and are more radiogenic due to interaction with the volcanic rocks (primarily non-welded tuffs) above the Tptp. An advection-reaction model relates the rate of strontium dissolution from the rocks with flow velocity. The model results agree with the low transport velocity (~2 cm per year) calculated from carbon-14 data by I.C. Yang (2002, App. Geochem., v. 17, no. 6, p. 807-817). Strontium isotope ratios in pore water from Tptp samples from horizontal boreholes collared in tunnels at the proposed repository horizon have a similar range (0.7121 to 0.7127), also indicating a low transport velocity. Strontium isotope compositions of pore water below the proposed repository in core samples from boreholes drilled vertically downward from tunnel floors are more varied, ranging from 0.7112 to 0.7127. The lower ratios (<0.7121) indicate that some of the pore water in these boreholes was replaced by tunnel construction water, which had an 87}Sr/{86Sr of 0.7115. Ratios lower than 0.7115 likely reflect interaction of construction water with concrete in the tunnel inverts, which had an 87}Sr/{86Sr <0.709. These low Sr ratios indicate penetration of construction water to depths of ~20 m below the tunnels within three years after

  19. Response of pore water Al, Fe and S concentrations to waterlogging in a boreal acid sulphate soil.

    PubMed

    Virtanen, Seija; Simojoki, Asko; Hartikainen, Helinä; Yli-Halla, Markku

    2014-07-01

    Environmental hazards caused by acid sulphate (AS) soils are of worldwide concern. Among various mitigation measures, waterlogging has mainly been studied in subtropical and tropical conditions. To assess the environmental relevance of waterlogging as a mitigation option in boreal AS soils, we arranged a 2.5-year experiment with monolithic lysimeters to monitor changes in the soil redox potential, pH and the concentrations of aluminium (Al), iron (Fe) and sulphur (S) in pore water in response to low and high groundwater levels in four AS soil horizons. The monoliths consisted of acidic oxidized B horizons and a reduced C horizon containing sulphidic material. Eight lysimeters were cropped (reed canary grass, Phalaris arundinacea) and two were bare without a crop. Waterlogging was conducive to reduction reactions causing a slight rise in pH, a substantial increase in Fe (Fepw) and a decrease in Al (Alpw) in the pore water. The increase in Fepw was decisively higher in the cropped waterlogged lysimeters than in the bare ones, which was attributable to the microbiologically catalysed reductive dissolution of poorly ordered iron oxides and secondary minerals. In contrast to warmer climates, Fepw concentrations remained high throughout the experiment, indicating that the reduction was poised in the iron range, while sulphate was not reduced to sulphide. Therefore, the precipitation of iron sulphide was negligible in the environment with a low pH and abundant with poorly ordered Fe oxides. Increased Fe in pore water counteracts the positive effects of waterlogging, when water is flushed from fields to watercourses, where re-oxidation of Fe causes acidity and oxygen depletion. However, waterlogging prevented further oxidation of sulphidic materials and decreased Alpw to one-tenth of the initial concentrations, and even to one-hundredth of the levels in the low water table lysimeters. PMID:24704964

  20. Hypoplastic model for simulation of compressibility characteristics of cement-admixed Bangkok soft clay at high water content

    NASA Astrophysics Data System (ADS)

    Chattonjai, Piyachat

    2016-06-01

    The developed hypoplastic model for simulation of compressibility characteristics of cement-admixed Bangkok soft clay at high water content was proposed in this paper. By using unique equation, the model is able to predict the relationship between void ratio and vertical effective stress of different water and cement content of soil cement. For practically convenient utilization and understanding, the parameters of Q1 which represented to initial cement bonding of soil (the initial value of structure tensor at time = 0) and C2 which effected to the model stiffness on isotropic consolidation direction, at 45° for loading and 225° for unloading of stress response envelope, were proposed as the function of cement and water content by comparing with dry weight of soil. By numerical integration that satisfied one-dimensional settlement, the simulation results were directly compared with fifteen experimental results to verify the accuracy of the proposed model.

  1. Pore-water chemistry from the ICDP-USGS coer hole in the Chesapeake Bay impact structure--Implications for paleohydrology, microbial habitat, and water resources

    USGS Publications Warehouse

    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.

  2. Electrical Resistivity Correlation to Vadose Zone Sediment and Pore-Water Composition for the BC Cribs and Trenches Area

    SciTech Connect

    Serne, R. Jeffrey; Ward, Anderson L.; Um, Wooyong; Bjornstad, Bruce N.; Rucker, Dale F.; Lanigan, David C.; Benecke, Mark W.

    2009-06-01

    This technical report documents the results of geochemical and soil resistivity characterization of sediment obtained from four boreholes drilled in the BC Cribs and Trench area. Vadose zone sediment samples were obtained at a frequency of about every 2.5 ft from approximately 5 ft bgs to borehole total depth. In total, 505 grab samples and 39 six-inch long cores were obtained for characterization. The pore-water chemical composition data, laboratory-scale soil resistivity and other ancillary physical and hydrologic measurements and analyses described in this report are designed to provide a crucial link between direct measurements on sediments and the surface-based electrical-resistivity information obtained via field surveys. A second goal of the sediment characterization was to measure the total and water-leachable concentrations of key contaminants of concern as a function of depth and distance from the footprints of inactive disposal facilities. The total and water-leachable concentrations of key contaminants will be used to update contaminant distribution conceptual models and to provide more data for improving base-line risk predictions and remedial alternative selections. The ERC “ground truthing” exercise for the individual boreholes showed mixed results. In general, the high concentrations of dissolved salts in the pore waters of sediments from C5923, C5924 and C4191 produced a low resistivity “target” in the processed resistivity field surveys, and variability could be seen in the resistivity data that could relate to the variability in pore- water concentrations but the correlations (regression R2 were mediocre ranging from 0.2 to 0.7 at best; where perfect correlation is 1.0). The field-based geophysical data also seemed to suffer from a sort of vertigo, where looking down from the ground surface, the target (e.g., maximum pore-water salt concentration) depth was difficult to resolve. The best correlations between the field electrical

  3. Pore water chemistry in a disturbed and an undisturbed peat forests in Brunei Darussalam: Nutrient and carbon contents

    NASA Astrophysics Data System (ADS)

    Gandois, L.; Cobb, A.; Abu Salim, K.; Chieng Hei, I.; Lim Biaw Leng, L.; Corlett, R.; Harvey, C.

    2010-12-01

    Tropical peat swamp forests in their natural state are important reservoir of biodiversity, carbon and water. However, they are rapidly vanishing due to agricultural conversion (mainly to oil palms), logging, drainage and fire. Peat swamp forests constitute an important contribution to global and regional biodiversity, providing an habitat to rare and threatened species. They encompass a sequence of forest types from the perimeter to the center of mildely elevated domes, and at our site in Brunei, are host to Shorea Albida trees (Anderson, 1983). They constitute a large terrestrial carbon reservoir (tropical peat soils contain up to 70 Pg C, which accounts for 20% of global peat soil carbon and 2% of the global soil carbon (Hirano et al., 2007)). In tropical peat swamp forests, the most important factors controling organic matter accumulation, as well as the biodiversity and structure of the forest, are hydrology and nutrients availability (Page et al., 1999). Study of pore water in peat swamp forest can provide key information on carbon cycle, including biomass production, organic matter decomposition and leaching of carbon in draining water. However, data on pore water chemistry and nutrient concentrations in pristine tropical peatlands, as well as the effect of forest exploitation are scarce. The study area is located in the Belait district in Brunei Darussalam in Borneo Island. Brunei is perhaps the best of the regional guardians of peat forest systems; potentially irreversible damage to peat forest ecosystems has been widespread elsewhere. Two sites, one pristine dome and a logging concession, are being investigated. In order to assess the chemical status of the peat soil, pore water is sampled at different depth along the dome radius. The chemistry of pore water, including pH, conductivity, dissolved oxygen, concentration of major elements, as well as organic carbon content and properties are analyzed. References: Anderson, 1983. The tropical peat swamp of

  4. The effects of Calluna cutting and burning on soil pore water DOC - are they only surface deep?

    NASA Astrophysics Data System (ADS)

    Qassim, Suzane; Dixon, Simon; Rowson, James; Worrall, Fred

    2013-04-01

    Dissolved organic carbon (DOC) is carbon lost from peatlands via the fluvial pathway and is the major component of water colour. It also is costly to remove during the water treatment process. Previous studies have found that the top ten centimetres of peatland soil pore water has the greatest association with surface water DOC concentration (DOCc). An important question of interest to peatland stakeholders is: can DOCc at the catchment scale be significantly affected by land management upstream? From this the question arises: do management effects manifest themselves differently in the upper ten centimetres of the peat than at greater depths? And further: are the effects observed in the top ten centimetres of the peat more strongly correlated to surface water DOCc than those from greater depths? The research presented in this poster, is on data gathered between, May 2008 - January 2013 in the Goyt Valley, Peak District National Park, UK. DOCc was investigated from sites subjected to differing Calluna vulgaris management techniques on both wet and dry heathlands. There are eight study sites with different treatments: control; managed burning; vegetation cutting and mulching; and, vegetation cutting and removal. There are six, replicate, one metre depth dipwells (apertures every ten centimetres), six surface water runoff traps and four ten centimetre sampling depth dipwells per site. Water table depth was monitored and samples were collected monthly from both the one metre dipwells and runoff traps over a four year period. As of May 2012 samples were also obtained from the ten centimetre depth dipwells as well. Monthly rainfall DOCc and daily surface water DOCc (in a nearby stream) were also measured to compare to the soil pore water DOCc gathered monthly. To address the aims of this study, data from the ten centimetre dipwells will be compared to those from the one metre dipwells. Across the four year period DOCc measured from the one meter dipwells, showed that

  5. Sulfide variation in the pore and surface waters of artificial salt-marsh ditches and a natural tidal creek

    SciTech Connect

    Rey, J.R.; Shaffer, J.; Kain, T.; Stahl, R.; Crossman, R. )

    1992-09-01

    Pore and surface water sulfide variation near artificial ditches and a natural creek are examined in salt marshes bordering the Indian River Lagoon in east-central Florida. Pore water sulfide concentrations ranged from 0 [mu]g-at l[sup [minus]1] to 1,640 [mu]g-at l[sup [minus]1]. On average, the natural creek had the lowest sulfide concentrations (mean < 1.0 [mu]g-at l[sup [minus]1]) and the perimeter ditch of a managed salt marsh impoundment the highest (436.5 [mu]g-at l[sup [minus]1]). There was a trend of increasing sulfide concentration in the summer, and sharp peaks in late fall-early winter which correspond with peak litter input into the sediments. Significant differences in sulfide concentration between sites are attributed to differences in water flow and in organic matter content. Delaying the seasonal opening of culverts (which connect impounded marshes with the lagoon) until lagoon water levels rise in fall may prevent massive fish kills that have been associated with high sulfide levels in the impoundment perimeter ditches. 35 refs., 7 figs., 5 tabs.

  6. Pore-water chemistry from the ICDP-USGS core hole in the Chesapeake Bay impact structure-Implications for paleohydrology, microbial habitat, and water resources

    USGS Publications Warehouse

    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. Vitamin B1 in marine sediments: pore water concentration gradient drives benthic flux with potential biological implications

    PubMed Central

    Monteverde, Danielle R.; Gómez-Consarnau, Laura; Cutter, Lynda; Chong, Lauren; Berelson, William; Sañudo-Wilhelmy, Sergio A.

    2015-01-01

    Vitamin B1, or thiamin, can limit primary productivity in marine environments, however the major marine environmental sources of this essential coenzyme remain largely unknown. Vitamin B1 can only be produced by organisms that possess its complete synthesis pathway, while other organisms meet their cellular B1 quota by scavenging the coenzyme from exogenous sources. Due to high bacterial cell density and diversity, marine sediments could represent some of the highest concentrations of putative B1 producers, yet these environments have received little attention as a possible source of B1 to the overlying water column. Here we report the first dissolved pore water profiles of B1 measured in cores collected in two consecutive years from Santa Monica Basin, CA. Vitamin B1 concentrations were fairly consistent between the two years ranging from 30 pM up to 770 pM. A consistent maximum at ~5 cm sediment depth covaried with dissolved concentrations of iron. Pore water concentrations were higher than water column levels and represented some of the highest known environmental concentrations of B1 measured to date, (over two times higher than maximum water column concentrations) suggesting increased rates of cellular production and release within the sediments. A one dimensional diffusion-transport model applied to the B1 profile was used to estimate a diffusive benthic flux of ~0.7 nmol m−2 d−1. This is an estimated flux across the sediment-water interface in a deep sea basin; if similar magnitude B-vitamin fluxes occur in shallow coastal waters, benthic input could prove to be a significant B1-source to the water column and may play an important role in supplying this organic growth factor to auxotrophic primary producers. PMID:26029181

  8. Composition of pore water in lake sediments, research site "B", Osage County, Oklahoma: Implications for lake water quality and benthic organisms

    USGS Publications Warehouse

    Zielinski, R.A.; Herkelrath, W.N.; Otton, J.K.

    2007-01-01

    Shallow ground water at US Geological Survey research site B in northeastern Oklahoma is contaminated with NaCl-rich brine from past and present oil production operations. Contaminated ground water provides a potential source of salts, metals, and hydrocarbons to sediment and water of adjacent Skiatook Lake. A former brine storage pit 10 m in diameter that is now submerged just offshore from site B provides an additional source of contamination. Cores of the upper 16-40 cm of lake sediment were taken at the submerged brine pit, near an offshore saline seep, and at a location containing relatively uncontaminated lake sediment. Pore waters from each 2-cm interval were separated by centrifugation and analyzed for dissolved anions, cations, and trace elements. High concentrations of dissolved Cl- in pore waters (200-5000 mg/L) provide the most direct evidence of contamination, and contrast sharply with an average value of only about 37 mg/L in Skiatook Lake. Chloride/Br- mass ratios of 220-240 in contaminated pore waters are comparable to values in contaminated well waters collected onshore. Dissolved concentrations of Se, Pb, Cu and Ni in Cl--rich pore waters exceed current US Environmental Protection Agency criteria for probable toxicity to aquatic life. At the submerged brine storage pit, the increase of Cl- concentration with depth is consistent with diffusion-dominant transport from deeper contaminated sediments. Near the offshore saline seep, pore water Cl- concentrations are consistently high and vary irregularly with depth, indicating probable Cl- transport by layer-directed advective flow. Estimated annual contributions of Cl- to the lake from the brine storage pit (???20 kg) and the offshore seep (???9 kg) can be applied to any number of similar sources. Generous estimates of the number of such sources at site B indicate minimal impact on water quality in the local inlet of Skiatook Lake. Similar methodologies can be applied at other sites of Na

  9. Gas hydrates (clathrates) causing pore-water freshening and oxygen isotope fractionation in deep-water sedimentary sections of terrigenous continental margins

    USGS Publications Warehouse

    Hesse, R.; Harrison, W.E.

    1981-01-01

    The occurrence of gas hydrates in deep-water sections of the continental margins predicted from anomalous acoustic reflectors on seismic profiles has been confirmed by recent deep-sea drilling results. On the Pacific continental slope off Guatemala gas hydrates were brought up for the first time from two holes (497, 498A) drilled during Leg 67 of the DSDP in water depths of 2360 and 5500 m, respectively. The hydrates occur in organic matter-rich Pleistocene to Miocene terrigenous sediments. In the hydrate-bearing zone a marked decrease in interstitial water chlorinities was observed starting at about 10-20 m subbottom depth. Pore waters at the bottom of the holes (near 400 m subbottom) have as little as half the chlorinity of seawater (i.e. 9???). Similar, but less pronounced, trends were observed during previous legs of the DSDP in other hydrate-prone segments of the continental margins where recharge of fresh water from the continent can be excluded (e.g. Leg 11). The crystallization of hydrates, like ice, excludes salt ions from the crystal structure. During burial the dissolved salts are separated from the solids. Subsidence results in a downward motion of the solids (including hydrates) relative to the pore fluids. Thawing of hydrates during recovery releases fresh water which is remixed with the pore fluid not involved in hydrate formation. The volume of the latter decreases downhole thus causing downward decreasing salinity (chlorinity). Hydrate formation is responsible for oxygen isotope fractionation with 18O-enrichment in the hydrate explaining increasingly more positive ??18O values in the pore fluids recovered (after hydrate dissociation) with depth. ?? 1981.

  10. Smectite diagenesis, pore-water freshening, and fluid flow at the toe of the Nankai wedge

    USGS Publications Warehouse

    Brown, K.M.; Saffer, D.M.; Bekins, B.A.

    2001-01-01

    The presence of low-chloride fluids in the lowermost sediments drilled at Ocean Drilling Program Site 808, at the Nankai accretionary wedge, has been considered as prime evidence for long-distance, lateral fluid flow from depth. Here, we re-evaluate the potential role of in situ reaction of smectite (S) to illite (I) in the genesis of this low chloride anomaly. This reaction is known to be occurring at Site 808, with both the S content and S to I ratio in the mixed layer clays decreasing substantially with depth. We show that the bulk of the chloride anomaly can generate by in situ clay dehydration, particularly if pre-reaction smectite abundances (Ai) approach ?? 10-15% of the bulk sediment. The Ai values, however, are not well constrained. At Ai values < 10-15%, an additional source of low-Cl fluid centered close to the de??collement could be required. Thus, there remains the important possibility that the observed low-Cl anomaly is a compound effect of both lateral flow and in situ smectite dehydration. ?? 2001 Elsevier Science B.V. All rights reserved.

  11. Fire clay

    USGS Publications Warehouse

    Virta, R.L.

    2006-01-01

    In 2005, six companies mined fire clay in Missouri, Ohio and South Carolina. Production was estimate to be 300 kt with a value of $8.3 million. Missouri was the leading producer state followed by Ohio and South Carolina. For the third consecutive year, sales and use of fire clays have been relatively unchanged. For the next few years, sales of fire clay is forecasted to remain around 300 kt/a.

  12. Adsorption of carbon dioxide, methane, and their mixtures in porous carbons: effect of surface chemistry, water content, and pore disorder.

    PubMed

    Billemont, Pierre; Coasne, Benoit; De Weireld, Guy

    2013-03-12

    The adsorption of carbon dioxide, methane, and their mixtures in nanoporous carbons in the presence of water is studied using experiments and molecular simulations. Both the experimental and numerical samples contain polar groups that account for their partially hydrophilicity. For small amounts of adsorbed water, although the shape of the adsorption isotherms remain similar, both the molecular simulations and experiments show a slight decrease in the CO2 and CH4 adsorption amounts. For large amounts of adsorbed water, the experimental data suggest the formation of methane or carbon dioxide clathrates in agreement with previous work. In contrast, the molecular simulations do not account for the formation of such clathrates. Another important difference between the simulated and experimental data concerns the number of water molecules that desorb upon increasing the pressure of carbon dioxide and methane. Although the experimental data indicate that water remains adsorbed upon carbon dioxide and methane adsorption, the molecular simulations suggest that 40 to 75% of the initial amount of adsorbed water desorbs with carbon dioxide or methane pressure. Such discrepancies show that differences between the simulated and experimental samples are crucial to account for the rich phase behavior of confined water-gas systems. Our simulations for carbon dioxide-methane coadsorption in the presence of water suggest that the pore filling is not affected by the presence of water and that adsorbed solution theory can be applied for pressures as high as 15 MPa. PMID:23346958

  13. Polar organic compounds in pore waters of the Chesapeake Bay impact structure, Eyreville core hole: Character of the dissolved organic carbon and comparison with drilling fluids

    USGS Publications Warehouse

    Rostad, C.E.; Sanford, W.E.

    2009-01-01

    Pore waters from the Chesapeake Bay impact structure cores recovered at Eyreville Farm, Northampton County, Virginia, were analyzed to characterize the dissolved organic carbon. After squeezing or centrifuging, a small volume of pore water, 100 ??L, was taken for analysis by electrospray ionization-mass spectrometry. Porewater samples were analyzed directly without filtration or fractionation, in positive and negative mode, for polar organic compounds. Spectra in both modes were dominated by low-molecular-weight ions. Negative mode had clusters of ions differing by -60 daltons, possibly due to increasing concentrations of inorganic salts. The numberaverage molecular weight and weight-average molecular weight values for the pore waters from the Chesapeake Bay impact structure are higher than those reported for other aquatic sources of natural dissolved organic carbon as determined by electrospray ionization-mass spectrometry. In order to address the question of whether drilling mud fluids may have contaminated the pore waters during sample collection, spectra from the pore waters were compared to spectra from drilling mud fluids. Ions indicative of drilling mud fluids were not found in spectra from the pore waters, indicating there was no detectable contamination, and highlighting the usefulness of this analytical technique for detecting potential contamination during sample collection. ?? 2009 The Geological Society of America.

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

    NASA Astrophysics Data System (ADS)

    Marcolli, C.

    2013-06-01

    Heterogeneous ice nucleation is an important mechanism for the glaciation of mixed phase clouds and may also be relevant for cloud formation and dehydration at the cirrus cloud level. It is thought to proceed through different mechanisms, namely contact, condensation, immersion and deposition nucleation. Supposedly, deposition nucleation is the only pathway which does not involve liquid water but occurs by direct water vapor deposition on a surface. This study challenges this classical view by putting forward the hypothesis that what is called deposition nucleation is in fact homogeneous or immersion nucleation occurring in pores and cavities that may form between aggregated primary particles and fill with water at relative humidity RHw < 100% because of the inverse Kelvin effect. Evidence for this hypothesis of pore condensation and freezing (PCF) originates from a number of only loosely connected scientific areas. The prime example for PCF is ice nucleation in clay minerals and mineral dusts, for which the data base is best. Studies on freezing in confinement carried out on mesoporous silica materials such as SBA-15, SBA-16, MCM-41, zeolites and KIT have shown that homogeneous ice nucleation occurs abruptly at T=230-235 K in pores with diameters (D) of 3.5-4 nm or larger but only gradually at T=210-230 K in pores with D=2.5-3.5 nm. Melting temperatures in pores are depressed by an amount that can be described by the Gibbs-Thomson equation. Water adsorption isotherms of MCM-41 show that pores with D=3.5-4 nm fill with water at RHw = 56-60% in accordance with an inverse Kelvin effect. Water in such pores should freeze homogeneously for T < 235 K even before relative humidity with respect to ice (RHi) reaches ice saturation. Ice crystal growth by water vapor deposition from the gas phase is therefore expected to set in as soon as RHw > 100%. Pores with D > 7.5 nm fill with water at RHi > 100% for T < 235 K and are likely to freeze homogeneously as soon as they are

  15. Experimental Study on the pH of Pore water in Compacted Bentonite under Reducing Conditions with Electromigration

    SciTech Connect

    Nessa, S.A.; Idemitsu, K.; Yamazaki, S.; Ikeuchi, H.; Inagaki, Y.; Arima, T.

    2008-07-01

    Compacted bentonite and carbon steel are considered a good buffer and over-pack materials in the repositories of high-level radioactive waste disposal. Sodium bentonite, Kunipia-F contains approximately 95 wt% of montmorillonite. Bentonites prominent properties of high swelling, sealing ability and cation exchange capacity provide retardation against the transport of radionuclides from the waste into the surrounding rocks in the repository and its properties determine the behavior of bentonite. In this regards, the pH of pore water in compacted bentonite is measured with pH test paper wrapped with semi-permeable membrane of collodion sheet under reducing conditions. On 30 days, the pH test paper in the experimental apparatus indicated that the pH of pore water in compacted bentonite is around 8.0 at saturated state. The carbon steel coupon is connected as the working electrode to the potentiostat and is held at a constant supplied potential between +300 and -300 mV vs. Ag/AgCl electrode for up to 7 days. During applying electromigration the pH of pore water in bentonite decreased and it reached 6.0{approx}6.0 on 7 days. The concentration of iron and sodium showed nearly complementary distribution in the bentonite specimen after electromigration. It is expected that iron could migrate as ferrous ion through the interlayer of montmorillonite replacing exchangeable sodium ions in the interlayer. Semi-permeable membrane of collodion sheet does not affect the color change of pH test paper during the experiment. (authors)

  16. Protein-fluctuation-induced water-pore formation in ion channel voltage-sensor translocation across a lipid bilayer membrane

    NASA Astrophysics Data System (ADS)

    Rajapaksha, Suneth P.; Pal, Nibedita; Zheng, Desheng; Lu, H. Peter

    2015-11-01

    We have applied a combined fluorescence microscopy and single-ion-channel electric current recording approach, correlating with molecular dynamics (MD) simulations, to study the mechanism of voltage-sensor domain translocation across a lipid bilayer. We use the colicin Ia ion channel as a model system, and our experimental and simulation results show the following: (1) The open-close activity of an activated colicin Ia is not necessarily sensitive to the amplitude of the applied cross-membrane voltage when the cross-membrane voltage is around the resting potential of excitable membranes; and (2) there is a significant probability that the activation of colicin Ia occurs by forming a transient and fluctuating water pore of ˜15 Å diameter in the lipid bilayer membrane. The location of the water-pore formation is nonrandom and highly specific, right at the insertion site of colicin Ia charged residues in the lipid bilayer membrane, and the formation is intrinsically associated with the polypeptide conformational fluctuations and solvation dynamics. Our results suggest an interesting mechanistic pathway for voltage-sensitive ion channel activation, and specifically for translocation of charged polypeptide chains across the lipid membrane under a transmembrane electric field: the charged polypeptide domain facilitates the formation of hydrophilic water pore in the membrane and diffuses through the hydrophilic pathway across the membrane; i.e., the charged polypeptide chain can cross a lipid membrane without entering into the hydrophobic core of the lipid membrane but entirely through the aqueous and hydrophilic environment to achieve a cross-membrane translocation. This mechanism sheds light on the intensive and fundamental debate on how a hydrophilic and charged peptide domain diffuses across the biologically inaccessible high-energy barrier of the hydrophobic core of a lipid bilayer: The peptide domain does not need to cross the hydrophobic core to move across a

  17. Ball clay

    USGS Publications Warehouse

    Virta, R.L.

    2000-01-01

    Part of the 1999 Industrial Minerals Review. The state of the ball clay industry in 1999 is presented. Record highs in the sales and use of ball clay were attained in 1999 due to the continued strength of the U.S. economy. U.S. production was estimated at 1.25 million st for the year, with more than half of that amount mined in Tennessee. Details of the consumption, price, imports, and exports of ball clay in 1999 and the outlook for ball clay over the next few years are provided.

  18. Composition of pore and spring waters from Baby Bare: global implications of geochemical fluxes from a ridge flank hydrothermal system

    NASA Astrophysics Data System (ADS)

    Wheat, C. Geoffrey; Mottl, Michael J.

    2000-02-01

    Warm hydrothermal springs were discovered on Baby Bare, which is an isolated basement outcrop on 3.5 Ma-old crust on the eastern flank of the Juan de Fuca Ridge. We have sampled these spring waters from a manned submersible, along with associated sediment pore waters from 48 gravity and piston cores. Systematic variations in the chemical composition of these waters indicate that hydrothermal reactions in basement at moderate temperatures (63°C in uppermost basement at this site) remove Na, K, Li, Rb, Mg, TCO 2, alkalinity, and phosphate from the circulating seawater and leach Ca, Sr, Si, B, and Mn from the oceanic crust; and that reactions with the turbidite sediment surrounding Baby Bare remove Na, Li, Mg, Ca, Sr, and sulfate from the pore water while producing ammonium and Si and both producing and consuming phosphate, nitrate, alkalinity, Mn, and Fe. K, Rb, and B are relatively unreactive in the sediment column. These data confirm the earlier inference that sediment pore waters from areas of upwelling can be used to estimate the composition of altered seawater in the underlying basement, even for those elements that are reactive in the sediment column or are affected by sampling artifacts. The composition of altered seawater in basement at Baby Bare is similar to the inferred composition of 58°C formation water from crust nearly twice as old (5.9 Ma) on the southern flank of the Costa Rica Rift. The Baby Bare fluids also exhibit the same directions of net elemental transfer between basalt and seawater as solutions produced in laboratory experiments at a similar temperature, and complement compositional changes from seawater observed in seafloor basalts altered at cool to moderate temperatures. The common parameter among the two ridge flanks and experiments is temperature, suggesting that the residence time of seawater in basement at the two ridge-flank sites is sufficiently long for the solutions to equilibrate with altered basalt. This conclusion is supported

  19. Temporal and vertical distribution of total ammonia nitrogen and un-ionized ammonia nitrogen in sediment pore water from the upper Mississippi River

    USGS Publications Warehouse

    Frazier, Bradley E.; Naimo, Teresa J.; Sandheinrich, Mark B.

    1996-01-01

    We examined the temporal and vertical distribution of total ammonia nitrogen (TAN) and un-ionized ammonia nitrogen (NH3-N) in sediment pore water and compared the temporal patterns of TAN and NH3-N concentrations in overlying surface water with those in pore water. Pore water was obtained by core extraction and subsequent centrifugation. We measured TAN concentrations and calculated NH3-N concentrations from February through October 1993 at four sites in Pool 8, upper Mississippi River, at depths of 0 to 4, 4 to 8, and 8 to 12 cm below the sediment-water interface. Total ammonia nitrogen and NH3-N concentrations were significantly different among sampling dates (p = 0.0001) and sediment depths (p = 0.0001). Concentrations of TAN and NH3-N in surface water were significantly less than those in pore water from all sediment depths (p < 0.05). Concentrations in pore water ranged from 0.07 to 4.0 mg TAN/L and less than 1 to 20 I?g NH3-N/L in winter, and from 0.07 to 10.0 mg TAN/L and 1 to 175 I?g NH3-N/L in summer; greatest concentrations were usually found in sediments 8 to 12 cm deep. Annual mean TAN concentrations were positively correlated with silt and volatile solids content and were negatively correlated with sand content. Because of the high variability of TAN and NH3-N concentrations in pore water, sediment toxicity studies should take into account the season and the depth at which sediments are obtained. The annual mean NH3-N concentration in pore water at one site (55 I?g/L) exceeded the concentration (30 I?g/L) demonstrated to inhibit growth of fingernail clams in laboratory studies. However, these concentrations apparently were not lethal, as evidenced by the presence of fingernail clams at this site.

  20. Bi-component T2 * analysis of bound and pore bone water fractions fails at high field strengths.

    PubMed

    Seifert, Alan C; Wehrli, Suzanne L; Wehrli, Felix W

    2015-07-01

    Osteoporosis involves the degradation of the bone's trabecular architecture, cortical thinning and enlargement of cortical pores. Increased cortical porosity is a major cause of the decreased strength of osteoporotic bone. The majority of cortical pores, however, are below the resolution limit of MRI. Recent work has shown that porosity can be evaluated by MRI-based quantification of bone water. Bi-exponential T2 * fitting and adiabatic inversion preparation are the two most common methods purported to distinguish bound and pore water in order to quantify matrix density and porosity. To assess the viability of T2 * bi-component analysis as a method for the quantification of bound and pore water fractions, we applied this method to human cortical bone at 1.5, 3, 7 and 9.4 T, and validated the resulting pool fractions against micro-computed tomography-derived porosity and gravimetrically determined bone densities. We also investigated alternative methods: two-dimensional T1 -T2 * bi-component fitting by incorporation of saturation recovery, one- and two-dimensional fitting of Carr-Purcell-Meiboom-Gill (CPMG) echo amplitudes, and deuterium inversion recovery. The short-T2 * pool fraction was moderately correlated with porosity (R(2)  = 0.70) and matrix density (R(2)  = 0.63) at 1.5 T, but the strengths of these associations were found to diminish rapidly as the field strength increased, falling below R(2)  = 0.5 at 3 T. The addition of the T1 dimension to bi-component analysis only slightly improved the strengths of these correlations. T2 *-based bi-component analysis should therefore be used with caution. The performance of deuterium inversion recovery at 9.4 T was also poor (R(2)  = 0.50 vs porosity and R(2)  = 0.46 vs matrix density). The CPMG-derived short-T2 fraction at 9.4 T, however, was highly correlated with porosity (R(2)  = 0.87) and matrix density (R(2)  = 0.88), confirming the utility of this method for independent

  1. Bi-Component T2* Analysis of Bound and Pore Bone Water Fractions Fails at High Field Strengths

    PubMed Central

    Seifert, Alan C.; Wehrli, Suzanne L.; Wehrli, Felix W.

    2015-01-01

    Osteoporosis involves degradation of bone’s trabecular architecture, cortical thinning, and enlargement of cortical pores. Increased cortical porosity is a major cause of the decreased strength of osteoporotic bone. The majority of cortical pores, however, are below the resolution limit of MRI. Recent work has shown that porosity can be evaluated by MRI-based quantification of bone water. Bi-exponential T2* fitting and adiabatic inversion preparation are the two most common methods purported to distinguish bound and pore water in order to quantify matrix density and porosity. To assess the viability of T2* bi-component analysis as a method for quantifying bound and pore water fractions, we have applied this method to human cortical bone at 1.5T, 3T, 7T, and 9.4T, and validated the resulting pool fractions against μCT-derived porosity and gravimetrically-determined bone densities. We also investigated alternative methods: 2D T1–T2* bi-component fitting by incorporating saturation-recovery, 1D and 2D fitting of CPMG echo amplitudes, and deuterium inversion recovery. Short-T2* pool fraction was moderately correlated with porosity (R2 = 0.70) and matrix density (R2 = 0.63) at 1.5T, but the strengths of these associations were found to diminish rapidly as field strength increases, falling below R2 = 0.5 at 3T. Addition of the T1 dimension to bi-component analysis only slightly improved the strengths of these correlations. T2*-based bi-component analysis should therefore be used with caution. Performance of deuterium inversion-recovery at 9.4T was also poor (R2 = 0.50 versus porosity and R2 = 0.46 versus matrix density). CPMG-derived short-T2 fraction at 9.4T, however, is highly correlated with porosity (R2 = 0.87) and matrix density (R2 = 0.88), confirming the utility of this method for independent validation of bone water pools. PMID:25981785

  2. Two-dimensional small-scale variability of pore water phosphate in freshwater lakes: results from a novel dialysis sampler.

    PubMed

    Lewandowski, Jorg; Rüter, Kristina; Hupfer, Michael

    2002-05-01

    Vertical concentration profiles of soluble reactive phosphorus (SRP) in the upper sedimentary zone of freshwater lakes are an important means for studying internal phosphorus (P) loading and to gain insight into early diagenetic processes. The interpretation of such pore water profiles generally neglects the occurrence of horizontal variability at a specific sampling site. To further examine this variability, we have designed a novel two-dimensional sampler (2D peeper) consisting of 2280 chambers at a spatial resolution of 9 mm providing a sampling area of 43 x 44 cm. This new device was deployed in three eutrophic lakes in north-eastern Germany. The resulting 2D images of the SRP concentrations, diffusive fluxes, and turnover rates revealed systematic vertical and horizontal structures with local niches of increased phosphorus release. Thus, the extrapolation of P flux calculations based on one-dimensional pore water profiles may lead to a considerable error. The observed small-scale horizontal heterogeneity, probably mainly caused by organisms, was larger in the biologically more active Lake Müllrose and Süsser See than in the deeper Arendsee where meio- and macrozoobenthos were missing. In all cases, the variability was highest at the sediment-water interface and diminished with sediment depth. PMID:12026990

  3. The 1.7- to 4.2-micron spectrum of asteroid 1 Ceres - Evidence for structural water in clay minerals

    NASA Technical Reports Server (NTRS)

    Lebofsky, L. A.; Feierberg, M. A.; Larson, H. P.; Johnson, J. R.; Tokunaga, A. T.

    1981-01-01

    A high-resolution Fourier spectrum (1.7-3.5 microns) and medium-resolution spectrophotometry (2.7-4.2 microns) were obtained for Asteroid 1 Ceres. The presence of the 3-micron absorption feature due to water of hydration was confirmed. The 3-micron feature is compared with the 3-micron bands due to water of hydration in clays and salts. It is concluded that the spectrum of Ceres shows a strong absorption at 2.7-2.8 microns due to structural OH groups in clay minerals. The dominant minerals on the surface of Ceres are therefore hydrated clay minerals structurally similar to terrestrial montmorillonites. There is also a narrow absorption feature at 3.1 microns which is attributable to a very small amount of water ice on Ceres. This is the first evidence for ice on the surface of an asteroid.

  4. Chemical data for bottom sediment, lake water, bottom-sediment pore water, and fish in Mountain Creek Lake, Dallas, Texas, 1994-96

    USGS Publications Warehouse

    Jones, S.A.; Van Metre, P.C.; Moring, J.B.; Braun, C.L.; Wilson, J.T.; Mahler, B.J.

    1997-01-01

    Mountain Creek Lake is a reservoir adjacent to two U.S. Department of the Navy facilities, the Naval Weapons Industrial Reserve Plant and the Naval Air Station in Dallas, Texas. A Resource Conservation and Recovery Act Facility Investigation found ground-water plumes containing chlorinated solvents on both facilities. These findings led to a U.S. Geological Survey study of Mountain Creek Lake adjacent to both facilities between June 1994 and August 1996. Bottom sediments, lake water, bottom-sediment pore water, and fish were collected for chemical analysis.

  5. In situ Determination of Pore-water pH in Reducing Sediments near Methane Seeps and Vents by Laser Raman Spectroscopy

    NASA Astrophysics Data System (ADS)

    Peltzer, E. T.; Walz, P. M.; Luna, M.; Zhang, X.; Brewer, P. G.

    2015-12-01

    Sediments near methane vents and seeps are often anoxic in nature due to the microbial oxidation of organic matter. When the pore-water oxygen is consumed, the microbial population resorts to using sulfate as the terminal electron receptor. For the anaerobic oxidation of methane, the net reaction is: CH4 + SO42- = HCO3- + HS- + H2O. Hydrogen sulfide produced by this reaction dissociates into bisulfide in proportion to the pore-water pH. Since the first pK of H2S is about 7 and close to the in situ pore-water pH, it satisfies the criteria for a useful pH indicating dye. Although the two forms of hydrogen sulfide are not visually discernable by the human eye, these two forms have distinct Raman spectra and thus can be easily quantified using an in situ spectrometer. The relative Raman cross-sections of the hydrogen sulfide species were determined in the laboratory across a range of relevant pH values and at the approximate salinity (ionic strength) and temperature of deep-sea pore waters. With this calibration, it is simple to compute the pore-water pH from the relative abundance of the two sulfide species: pH = pK1 + log10([HS-]/[H2S]). Pore-water profiles were investigated at several sites in the Santa Monica basin around methane mounds, gas vents and cold seeps. A titanium pore-water probe with a stainless steel frit was used to filter and collect pore-water samples at 5-10 cm intervals in the top 50-60 cm of sediment. Filtration and collection of the pore-water samples was usually accomplished in 5-10 minutes, with acquisition of the laser Raman spectra requiring only 2-4 minutes additional time. Vertical profiles of sulfate, total sulfide (H2S + HS-), methane and pH were collected simultaneously using the laser Raman spectrometer and pore-water profile sampler. Sulfate was observed to decrease from seawater concentrations to below detection limits while both methane and total sulfide increased proportionally to the sulfate loss. Once total sulfide concentrations

  6. Radar frequency dielectric dispersion in sandstone: Implications for determination of moisture and clay content

    NASA Astrophysics Data System (ADS)

    West, L. Jared; Handley, Kirk; Huang, Yi; Pokar, Magdeline

    2003-02-01

    The relationship between dielectric permittivity, water saturation, and clay content for the Sherwood Sandstone from NE England was characterized as part of a wider study of the vadose zone moisture dynamics and pollution vulnerability of this aquifer. Dielectric permittivity was measured over the full range of saturation levels, for various lithologies ranging from clean medium-grained sandstone to fine-grained sandstone containing up to 5% clay, using a specially constructed dielectric cell. Dielectric constant, Kr, is largely independent of frequency between 350 MHz and 1000 MHz. Below 350 MHz, Kr of fine-grained, clay-rich sandstone shows frequency dispersion. Tests on physical models of the sandstone consisting of a fine fraction of Ottawa Sand and montmorillonite clay indicate that the clay minerals within the sandstone are responsible for its frequency dispersive behavior. These tests also show that increasing pore fluid salinity increases dielectric dispersion at the lower end of the frequency range, which indicates that this arises from the interfacial Maxwell-Wagner mechanism associated with platy clay particles. Water saturated sand:clay mixtures show very low dielectric constants at high frequencies (over 650 MHz). This effect is independent of salinity and probably results from the layered geometric arrangement of solids, bound and free water within the swelling clay. The complex refractive index method (CRIM) with a mineral dielectric constant of about 5 provides a good match to the water saturation versus dielectric constant data for all Sherwood Sandstone lithologies at frequencies between 350 and 1000 MHz and for clay-poor sandstone at lower frequencies. Below 350 MHz the presence of a few percent of clay in some Sherwood Sandstone lithologies raises their CRIM best fit mineral dielectric constant substantially.

  7. Effects Of Bedrock Shape And Hillslope Gradient On The Pore-Water Pressure Development: Implication For Slope Stability

    NASA Astrophysics Data System (ADS)

    Lanni, Cristiano; McDonnell, Jeff

    2010-05-01

    Shallow Landslides are one of the most important causes of loss of human life and socio-economic damage related to the hydro-geological risk issues. The danger of these phenomena is related to their speed of development, the diffculty of foreseeing their location, and the high density of individual phenomena, whose downhill trajectories have a relevant probability of interfering with urbanized areas. Research activity on precipitation-induced landslides has focused mainly on developing predictive understanding of where and when landslides are likely to occur. Nevertheless, some major aspects that may be related to activation of landslides have been poorly investigated. For instance, landslide susceptibility zones are generally predicted assuming constant thickness of soil over an impervious bedrock layer. Nevertheless, recent studies showed subsurface topography could be a first order control for subsurface water-flow dynamics, because of the effects of its own irregular shape. Tromp-van Meerveld and McDonnell (2006) argued that connectivity of patches of transient saturation were a necessary prerequisite for exceeding the rainfall threshold necessary to drive lateral flow. Connectivity - "how the hillslope architecture controls the filling and spilling of isolated patches of saturation" (Hopp and McDonnell, 2009) - appears to be a possible unifying concept and theoretical platform for moving hillslope and watershed hydrology forward. Connectivity could also have important implications on triggering of shallow landslides, because the particular shape of bedrock may limit the water-flow downhill. Here we present a number of virtual numerical experiments performed to investigate the role of bedrock shape and hillslope gradient on pore-water pressure development. On this purpose, our test is represented by the subsurface topography of the Panola Experiment Hillslope (PEH). That is because scientific literature on PEH provides substantial documentation about the role

  8. Comparison between monitored and modeled pore water pressure and safety factor in a slope susceptible to shallow landslides

    NASA Astrophysics Data System (ADS)

    Bordoni, Massimiliano; Meisina, Claudia; Zizioli, Davide; Valentino, Roberto; Bittelli, Marco; Chersich, Silvia

    2014-05-01

    Shallow landslides can be defined as slope movements affecting superficial deposits of small thicknesses which are usually triggered due to extreme rainfall events, also very concentrated in time. Shallow landslides are hazardous phenomena: in particular, if they happen close to urbanized areas they could cause significant damages to cultivations, structures, infrastructures and, sometimes, human losses. The triggering mechanism of rainfall-induced shallow landslides is strictly linked with the hydrological and mechanical responses of usually unsaturated soils to rainfall events. For this reason, it is fundamental knowing the intrinsic hydro-mechanical properties of the soils in order to assess both susceptibility and hazard of shallow landslide and to develop early-warning systems at large scale. The hydrological data collected by a 20 months monitoring on a slope susceptible to shallow landslides in an area of the North -Eastern Oltrepo Pavese (Northern Apennines, Italy) were used to identify the hydrological behaviors of the investigated soils towards rainfall events. Field conditions under different rainfall trends have also been modeled by using both hydrological and physically-based stability models for the evaluation of the slope safety factor . The main objectives of this research are: (a) to compare the field measured pore water pressures at different depths with results of hydrological models, in order to evaluate the efficiency of the tested models and to determine how precipitations affect pore pressure development; (b) to compare the time trends of the safety factor that have been obtained by applying different stability models; (c) to evaluate, through a sensitivity analysis, the effects of soil hydrological properties on modeling pore water pressure and safety factor. The test site slope where field measurements were acquired is representative of other sites in Northern Apennines affected by shallow landslides and is characterized by medium

  9. Simultaneous removal of multiple pesticides from water: effect of organically modified clays as coagulant aid and adsorbent in coagulation-flocculation process.

    PubMed

    Shabeer, T P Ahammed; Saha, Ajoy; Gajbhiye, V T; Gupta, Suman; Manjaiah, K M; Varghese, Eldho

    2014-01-01

    Contamination of drinking water sources with agrochemical residues became a major concern in the twenty-first century. Coagulation-flocculation is the most widely used water-treatment process, but the efficiency to remove pesticides and other organic pollutants are limited compared to adsorption process. Thus, simultaneous action of adsorption on normal bentonite or organo-modified montmorillonite clays [modified with octadecylamine (ODA-M) and octadecylamine + amino-propyltriethoxysilane (ODAAPS-M)] followed by coagulation-flocculation by alum and poly aluminium chloride has been evaluated for removal of 10 different pesticides, namely atrazine, lindane, metribuzin, aldrin, chlorpyriphos, pendimethalin, alpha-endosulphan, beta-endosulphan, p,p'-DDT, cypermethrin and two of its metabolites, endosulphan sulphate and p,p'-DDE, from water. The coagulation without integration of adsorption was less effective (removal % varies from 12 to 49) than the adsorption-coagulation integrated system (removal % varies from 71 to 100). Further, coagulation integrated with adsorption was more effective when organically modified montmorillonite was used as adsorbent compared to normal bentonite. The removal efficiency of organic clay depends upon the concentration of pesticides, doses of clay minerals, and efficiency was more for ODAAPS-M as compared to ODA-M. The combination of ODAAPS-M-clay with coagulants was also used efficiently for the removal of pesticides from natural and fortified natural water collected and the results exhibit the usefulness of this remediation technique for application in water decontamination and in treatment of industrial and agricultural waste waters. PMID:25145219

  10. Zinc isotope investigation of surface and pore waters in a mountain watershed impacted by acid rock drainage.

    PubMed

    Aranda, Suzan; Borrok, David M; Wanty, Richard B; Balistrieri, Laurie S

    2012-03-15

    The pollution of natural waters with metals derived from the oxidation of sulfide minerals like pyrite is a global environmental problem. However, the metal loading pathways and transport mechanisms associated with acid rock drainage reactions are often difficult to characterize using bulk chemical data alone. In this study, we evaluated the use of zinc (Zn) isotopes to complement traditional geochemical tools in the investigation of contaminated waters at the former Waldorf mining site in the Rocky Mountains, Colorado, U.S.A. Geochemical signatures and statistical analysis helped in identifying two primary metal loading pathways at the Waldorf site. The first was characterized by a circumneutral pH, high alkalinity, and high Zn/Cd ratios. The second was characterized by acidic pHs and low Zn/Cd ratios. Zinc isotope signatures in surface water samples collected across the site were remarkably similar (the δ(66)Zn, relative to JMC 3-0749-L, for most samples ranged from 0.20 to 0.30‰±0.09‰ 2σ). This probably suggests that the ultimate source of Zn is consistent across the Waldorf site, regardless of the metal loading pathway. The δ(66)Zn of pore water samples collected within a nearby metal-impacted wetland area, however, were more variable, ranging from 0.20 to 0.80‰±0.09‰ 2σ. Here the Zn isotopes seemed to reflect differences in groundwater flow pathways. However, a host of secondary processes might also have impacted Zn isotopes, including adsorption of Zn onto soil components, complexation of Zn with dissolved organic matter, uptake of Zn into plants, and the precipitation of Zn during the formation of reduced sulfur species. Zinc isotope analysis proved useful in this study; however, the utility of this isotopic tool would improve considerably with the addition of a comprehensive experimental foundation for interpreting the complex isotopic relationships found in soil pore waters. PMID:22326318

  11. An evaluation of materials and methods for vapour measurement of the isotopic composition of pore water in deep, unsaturated zones.

    PubMed

    Pratt, Dyan L; Lu, Mengna; Lee Barbour, S; Jim Hendry, M

    2016-01-01

    The development of in situ vapour sampling methods to measure δ(2)H and δ(18)O in pore water of deep, unsaturated soil profiles, including mine tailings and waste rock, is required to improve our ability to track water migration through these deposits. To develop appropriate field sampling methods, a laboratory study was first undertaken to evaluate potential materials and sampling methods to collect and analyse vapour samples from unsaturated mine waste. Field methods were developed based on these findings and tested at two mine sites using either on-site analyses with a portable isotope laser spectrometer or sample collection and storage prior to laboratory analyses. The field sites included a series of deep (>50 m) multiport profiles within a coal waste rock dump and open wells installed in a sand tailings dyke at an oil sands mine. Laboratory results show that memory effects in sample bags and tubing require 3-5 pore volumes of vapour flushing prior to sample collection and sample storage times are limited to 24 h. Field sampling highlighted a number of challenges including the need to correct for sample humidity and in situ temperature. Best results were obtained when a portable laser spectrometer was used to measure vapour samples in situ. PMID:27002493

  12. Non-equilibrium passive sampling of hydrophobic organic contaminants in sediment pore-water: PCB exchange kinetics.

    PubMed

    Choi, Yongju; Wu, Yanwen; Luthy, Richard G; Kang, Seju

    2016-11-15

    This study investigates the isotropic exchange kinetics of PCBs for polyethylene (PE) passive samplers in quiescent sediment and develops a novel non-equilibrium passive sampling method using PE with multiple thicknesses. The release and uptake kinetics of PCBs in quiescent sediment are reproduced by a 1-D diffusion model using sediment diffusion parameters fitted with the data from actual measurements. From the sediment diffusion parameters observed for uptake and release kinetics, it is seen that the uptake kinetics are distinctly slower than the release kinetics, most likely because of the sorption-desorption hysteresis of PCBs in the study sediment. Despite the presence of the anisotropic PCB exchange kinetics, a performance reference compound (PRC)-based method, which is grounded on the assumption of isotropic exchange kinetics, estimated the freely dissolved aqueous concentrations (Cfree) of PCBs in sediment pore-water with less than a factor of two error for the study sediment. The novel method developed in this study using PE with multiple thicknesses also gives reasonable estimates of Cfree, demonstrating its potential as another option for non-equilibrium passive sampling for hydrophobic organic contaminants in sediment pore-water. PMID:27472074

  13. The electrical conductivity of CO2-bearing pore waters at elevated pressure and temperature: a laboratory study and its implications in CO2 storage monitoring and leakage detection

    NASA Astrophysics Data System (ADS)

    Börner, Jana H.; Herdegen, Volker; Repke, Jens-Uwe; Spitzer, Klaus

    2015-11-01

    The electrical rock conductivity is a sensitive indicator for carbon dioxide (CO2) injection and migration processes. For a reliable balancing of the free CO2 in pore space with petrophysical models such as Archie's law or for the detection of migrating CO2, detailed knowledge of the pore water conductivity during interaction with CO2 is essential but not available yet. Contrary to common assumptions, pore water conductivity cannot be assumed constant since CO2 is a reactive gas that dissolves into the pore water in large amounts and provides additional charge carriers due to the dissociation of carbonic acid. We consequently carried out systematic laboratory experiments to quantify and analyse the changes in saline pore water conductivity caused by CO2 at thermodynamic equilibrium. Electrical conductivity is measured on pore water samples for pressures up to 30 MPa and temperatures up to 80 °C. The parameter range covers the gaseous, liquid and supercritical state of the CO2 involved. Pore water salinities from 0.006 up to 57.27 g L-1 sodium chloride were investigated as well as selective other ion species. At the same time, the CO2 concentration in the salt solution was determined by a wet-chemical procedure. A two-regime behaviour appears: for small salinities, we observe an increase of up to more than factor 3 in the electrical pore water conductivity, which strongly depends on the solution salinity (low-salinity regime). This is an expected behaviour, since the additional ions originating from the dissociation of carbonic acid positively contribute to the solution conductivity. However, when increasing salinities are considered this effect is completely diminished. For highly saline solutions, the increased mutual impeding causes the mobility of all ions to decrease, which may result in a significant reduction of conductivity by up to 15 per cent despite the added CO2 (high-salinity regime). We present the data set covering the pressure, temperature, salinity

  14. Elastic Properties of Clay Minerals

    NASA Astrophysics Data System (ADS)

    Vanorio, T.; Prasad, M.; Nur, A.

    2001-12-01

    We present ultrasonic P- and S-waves velocity measurements on pure clay samples using three different experiment setups. These experiments provided petrophysical and acoustic properties of clay minerals as a function both of mineralogy and compaction. In the first experiment, acoustic measurements were performed on cold-pressed clay aggregates at ambient and at hydrostatic pressure conditions. Porosity and grain density values of the different clay mineralogy aggregates ranged from 4 to 43% and 2.13 to 2.83 g cm-3, respectively. In the second experiment, we measured P-wave velocity and attenuation in a kaolinite-water suspension in which clay concentration was increased up to 60%. In the third experiment, P- and S- wave velocities were measured during uniaxial stress compaction of clay powders. Results from all three experiments revealed low bulk (K) and shear (μ ) moduli for kaolinite, montmorillonite, and smectite; the values range between 6-12 GPa for K and 4-6 GPa for μ , respectively. Using these clay moduli values in effective medium and granular porous media models, velocity is predicted in saturated pure kaolinite samples, kaolinite suspension and shaly sandstones fairly well. Experimental results also showed that water interlayers play an important role in the compaction and strength of clay aggregates. Clay minerals carrying on water interlayers in their structure showed high compaction and strength. This study is relevant for a more reliable assessment of the seismic response in reservoirs and/or basins characterized by clay-bearing formations.

  15. Small pores in soils: Is the physico-chemical environment accurately reflected in biogeochemical models ?

    NASA Astrophysics Data System (ADS)

    Weber, Tobias K. D.; Riedel, Thomas

    2015-04-01

    Free water is a prerequesite to chemical reactions and biological activity in earth's upper crust essential to life. The void volume between the solid compounds provides space for water, air, and organisms that thrive on the consumption of minerals and organic matter thereby regulating soil carbon turnover. However, not all water in the pore space in soils and sediments is in its liquid state. This is a result of the adhesive forces which reduce the water activity in small pores and charged mineral surfaces. This water has a lower tendency to react chemically in solution as this additional binding energy lowers its activity. In this work, we estimated the amount of soil pore water that is thermodynamically different from a simple aqueous solution. The quantity of soil pore water with properties different to liquid water was found to systematically increase with increasing clay content. The significance of this is that the grain size and surface area apparently affects the thermodynamic state of water. This implies that current methods to determine the amount of water content, traditionally determined from bulk density or gravimetric water content after drying at 105°C overestimates the amount of free water in a soil especially at higher clay content. Our findings have consequences for biogeochemical processes in soils, e.g. nutrients may be contained in water which is not free which could enhance preservation. From water activity measurements on a set of various soils with 0 to 100 wt-% clay, we can show that 5 to 130 mg H2O per g of soil can generally be considered as unsuitable for microbial respiration. These results may therefore provide a unifying explanation for the grain size dependency of organic matter preservation in sedimentary environments and call for a revised view on the biogeochemical environment in soils and sediments. This could allow a different type of process oriented modelling.

  16. In situ Measurement of Pore-Water pH in Anoxic Sediments Using Laser Raman Spectrometry

    NASA Astrophysics Data System (ADS)

    Peltzer, E. T.; Luna, M.; Walz, P. M.; Zhang, X.; Brewer, P. G.

    2010-12-01

    Accurate measurement of the geochemical properties of sediment pore waters is of fundamental importance in ocean geochemistry and microbiology. Recent work has shown that the properties of pore waters can be measured rapidly in situ with a novel Raman based insertion probe (Zhang et al., 2010), and that data obtained from anoxic sediments on in situ dissolved methane concentrations are very different (~30x) than from recovered cores due the large scale degassing that occurs during core recovery (Zhang et al., submitted). Degassing of methane must carry with it via Henry’s Law partioning significant quantities of H2S, which is clearly detectable by smell during sample processing, and thus in situ measurement of H2S is also highly desirable. In practice, dissolved H2S is partitioned between the HS- and H2S species as a function of pH with pKa ~7 for the acid dissociation reaction. Since both species are Raman active full determination of the sulfide system is possible if the relative Raman cross sections are known. The diagenetic equations for these reactions are commonly summarized as: 2CH2O + SO4= ↔ 2HCO3- + H2S CH4 + SO4= ↔ HCO3- + HS- + H2O Three of the major components of these equations, CH4, SO4=, and H2S/HS-, are all observable directly by Raman spectroscopy; but the detection of HCO3- presents a challenge due to its low Raman cross section and thus poor sensitivity. We show that pore water pH, which is a good estimator of HCO3- if total CO2 or alkalinity are known, can be measured by observing the H2S / HS- ratio via the equation: pH = pKa + log([HS-]/[H2S]) thereby fully constraining these equations within a single measurement protocol. The Raman peak for HS- is at 2573 cm-1 and for H2S is at 2592 cm-1; thus the peaks are well separated and may easily be deconvoluted from the observed spectrum. We have determined the relative Raman cross sections by a series of laboratory measurements over a range of pH and by using the definition that when pH = p

  17. The Determination of Metals in Sediment Pore Waters and in 1N HCl-Extracted Sediments by ICP-MS

    USGS Publications Warehouse

    May, T.W.; Wiedmeyer, R.H.; Brumbaugh, W.G.; Schmitt, C.J.

    1997-01-01

    Concentrations of metals in sediment interstitial water (pore water) and those extractable from sediment with weak acids can provide important information about the bioavailability and toxicological effects of such contaminants. The highly variable nature of metal concentrations in these matrices requires instrumentation with the detection limit capability of graphite furnace atomic absorption and the wide dynamic linear range capability of ICP-OES. These criteria are satisfied with ICP-MS instrumentation. We investigated the performance of ICP-MS in the determination of certain metals from these matrices. The results for three metals were compared to those determined by graphite furnace atomic absorption spectroscopy. It was concluded that ICP-MS was an excellent instrumental approach for the determination of metals in these matrices.

  18. Pore-water extraction from unsaturated tuff by triaxial and one-dimensional compression methods, Nevada Test Site, Nevada

    SciTech Connect

    Mower, T.E.; Higgins, J.D.; Yang, In C.; Peters, C.A.

    1994-07-01

    The hydrologic system in the unsaturated tuff at Yucca Mountain, Nevada, is being evaluated for the US Department of Energy by the Yucca Mountain Project Branch of the US Geological Survey as a potential site for a high-level radioactive-waste repository. Part of this investigation includes a hydrochemical study that is being made to assess characteristics of the hydrologic system such as: traveltime, direction of flow, recharge and source relations, and types and magnitudes of chemical reactions in the unsaturated tuff. In addition, this hydrochemical information will be used in the study of the dispersive and corrosive effects of unsaturated-zone water on the radioactive-waste storage canisters. This report describes the design and validation of laboratory experimental procedures for extracting representative samples of uncontaminated pore water from welded and nonwelded, unsaturated tuffs from the Nevada Test Site.

  19. Comparative study of illite clay and illite-based geopolymer products

    NASA Astrophysics Data System (ADS)

    Sperberga, I.; Sedmale, G.; Stinkulis, G.; Zeila, K.; Ulme, D.

    2011-10-01

    Quaternary (Q-clay) clayey deposits are one of the dominating parts of mineral raw materials of the sedimentary cover at present area of Latvia. These clays can be characterised by illite content up to 75-80 %. Two ways for use of illite clays were studied: conventional and geopolymers method. Purpose of the second mentioned method was showing the influence of alkali (KOH) on the transformation of Q-clay/illite structure. Obtained products were investigated by IR-spectroscopy, DTA and XRD, pore size distribution was determined as well. Some ceramic properties and compressive strength were determined and compared. IR-spectrum showed the effect of alkali on the transformation of Q-clay/illite structure in three main absorption bands: 3620-3415 cm-1 which is related to the vibrational modes of adsorbed water between SiO4 and AlO6 layers; new stronger absorption bands at 1635 cm-1 and 1435 cm-1 indicate on the appearance of vibrations in Q-KOH and are related to the K-O-Si bonds; the most essential changes are vibrations at 850 cm-1 showing the changes in the coordination number of Al from 6 to 4 for Q-KOH. Investigations of the bulk density in dependence on temperature showed the small increase of bulk density for Q-clay while - the relatively remarkable decrease for Q-clay/KOH. Mentioned values correlate with the compressive strength of Q-clay and Q-KOH products.

  20. Effect of tidal flooding on metal distribution in pore waters of marsh sediments and its transport to water column (Tagus estuary, Portugal).

    PubMed

    Santos-Echeandía, Juan; Vale, Carlos; Caetano, Miguel; Pereira, Patrícia; Prego, Ricardo

    2010-12-01

    Sediment cores and flooding water were collected at 0, 5, 10 and 50 min of tidal inundation in two sites of the Rosário salt marsh located in the proximity of a heavy industrialised zone of Tagus estuary colonised by pure stands of Spartina maritima (low marsh) and Sarcocornia fruticosa (high marsh). The cores were sliced in 5 cm layers and sediment solids, pore water, and belowground biomass were separated in order to measure Fe, Mn, Zn, Cu, Pb and Cd. The pore waters and sediments colonised by S. fruticosa, as well as belowground biomass presented high concentrations of Zn, Cu, Pb and Cd. Belowground biomass exceeded in one order of magnitude the metal levels in sediments. Abundant belowground biomass and small dimension of S. fruticosa roots facilitates the root-sediment interactions and presumably the metal retention in the higher marsh. The novelty of this work is the result of tidal inundation on pore water concentrations of metals in salt marsh sediments and their exportation to the water column. Concentrations in pore waters varied at minute scales, but 50 min after inundation levels were comparable to the initial values. The metal levels in flooding water increased abruptly during the first 10-20 min of inundation. The concentration peaks (Fe = 60 μM, Mn = 7.5 μM, Zn = 1.7 μM, Cu = 550 nM, Pb = 100 nM, Cd = 1.7 nM) reached one to two orders of magnitude above the values found in subsequent periods of inundation. The advective transports during the 50 min inundation during two daily pulses of inundation were: Fe (9520 and 1640), Mn (24), Zn (220 and 82), Cu (74 and 16), Pb (13 and 15) and Cd (0.3 and 0.08) for S. maritima and S. fruticosa, respectively. These quantities exceeded three to four orders of magnitude of the corresponding predicted diffusive fluxes (Fick 1st law) on a daily basis. This work emphasizes the importance of tidal flooding over salt marsh sediments to the metal exportation to the water column. PMID:20727578

  1. Availability of water in the Floridan aquifer in southern Duval and northern Clay and St Johns counties, Florida

    USGS Publications Warehouse

    Fairchild, R.W.

    1976-01-01

    The Floridan aquifer within the area of investigation consists of 1,100 to 1,800 feet of soft, porous limestone interbedded with hard, dense limestone and dolomite overlain by several hundred feet of confining beds. From late 1948 to May 1972, water levels in wells tapping the Floridan aquifer declined as much as 14 feet in northern Clay and St. Johns Counties and more than 20 feet at Jacksonville in Duval County, Florida. These trends will probably continue as withdrawals from the aquifer increase. Water-level depressions exist at Green Cove Springs and Jacksonville because of natural discharge and large scale withdrawals. Withdrawals from wells could result in well interference unless the wells are spaced at least 1,000 ft apart. Two- to four-inch diameter wells drilled 100 ft or less into the aquifer yield 50 to 250 gal/min. Larger and deeper wells yield 1,000 gal/min or more. Hardness of water is generally less than 10 mg/liter. Quality of water from wells sampled over a span of 10 to 30 years has not changed noticeably. Principal recharge to the Floridan occurs southwest of the area in a lake region where rainfall percolates directly into the aquifer. (Woodard-USGS)

  2. Water and solute transport in agricultural soils predicted by volumetric clay and silt contents.

    PubMed

    Karup, Dan; Moldrup, Per; Paradelo, Marcos; Katuwal, Sheela; Norgaard, Trine; Greve, Mogens H; de Jonge, Lis W

    2016-09-01

    Solute transport through the soil matrix is non-uniform and greatly affected by soil texture, soil structure, and macropore networks. Attempts have been made in previous studies to use infiltration experiments to identify the degree of preferential flow, but these attempts have often been based on small datasets or data collected from literature with differing initial and boundary conditions. This study examined the relationship between tracer breakthrough characteristics, soil hydraulic properties, and basic soil properties. From six agricultural fields in Denmark, 193 intact surface soil columns 20cm in height and 20cm in diameter were collected. The soils exhibited a wide range in texture, with clay and organic carbon (OC) contents ranging from 0.03 to 0.41 and 0.01 to 0.08kgkg(-1), respectively. All experiments were carried out under the same initial and boundary conditions using tritium as a conservative tracer. The breakthrough characteristics ranged from being near normally distributed to gradually skewed to the right along with an increase in the content of the mineral fines (particles ≤50μm). The results showed that the mineral fines content was strongly correlated to functional soil structure and the derived tracer breakthrough curves (BTCs), whereas the OC content appeared less important for the shape of the BTC. Organic carbon was believed to support the stability of the soil structure rather than the actual formation of macropores causing preferential flow. The arrival times of 5% and up to 50% of the tracer mass were found to be strongly correlated with volumetric fines content. Predicted tracer concentration breakthrough points as a function of time up to 50% of applied tracer mass could be well fitted to an analytical solution to the classical advection-dispersion equation. Both cumulative tracer mass and concentration as a function of time were well predicted from the simple inputs of bulk density, clay and silt contents, and applied tracer mass

  3. Water and solute transport in agricultural soils predicted by volumetric clay and silt contents

    NASA Astrophysics Data System (ADS)

    Karup, Dan; Moldrup, Per; Paradelo, Marcos; Katuwal, Sheela; Norgaard, Trine; Greve, Mogens H.; de Jonge, Lis W.

    2016-09-01

    Solute transport through the soil matrix is non-uniform and greatly affected by soil texture, soil structure, and macropore networks. Attempts have been made in previous studies to use infiltration experiments to identify the degree of preferential flow, but these attempts have often been based on small datasets or data collected from literature with differing initial and boundary conditions. This study examined the relationship between tracer breakthrough characteristics, soil hydraulic properties, and basic soil properties. From six agricultural fields in Denmark, 193 intact surface soil columns 20 cm in height and 20 cm in diameter were collected. The soils exhibited a wide range in texture, with clay and organic carbon (OC) contents ranging from 0.03 to 0.41 and 0.01 to 0.08 kg kg- 1, respectively. All experiments were carried out under the same initial and boundary conditions using tritium as a conservative tracer. The breakthrough characteristics ranged from being near normally distributed to gradually skewed to the right along with an increase in the content of the mineral fines (particles ≤ 50 μm). The results showed that the mineral fines content was strongly correlated to functional soil structure and the derived tracer breakthrough curves (BTCs), whereas the OC content appeared less important for the shape of the BTC. Organic carbon was believed to support the stability of the soil structure rather than the actual formation of macropores causing preferential flow. The arrival times of 5% and up to 50% of the tracer mass were found to be strongly correlated with volumetric fines content. Predicted tracer concentration breakthrough points as a function of time up to 50% of applied tracer mass could be well fitted to an analytical solution to the classical advection-dispersion equation. Both cumulative tracer mass and concentration as a function of time were well predicted from the simple inputs of bulk density, clay and silt contents, and applied tracer

  4. In situ interaction between different concretes and Opalinus Clay

    NASA Astrophysics Data System (ADS)

    Jenni, A.; Mäder, U.; Lerouge, C.; Gaboreau, S.; Schwyn, B.

    Interactions between cementitious materials and claystone are driven by chemical gradients in pore water and might lead to mineralogical modifications in both materials. In the context of a radioactive waste repository, this alteration might influence safety-relevant clay properties like swelling pressure, permeability, or specific retention. In this study, interfaces of Opalinus Clay, a potential host-rock in Switzerland, and three concrete formulations emplaced in the Cement-Clay Interaction (CI) Experiment at the Mont Terri Underground Laboratory (St. Ursanne, Switzerland) were analysed after 2.2 years of interaction. Sampling techniques with interface stabilisation followed by inclined intersection drilling were developed. Element distribution maps of the concrete-clay interfaces show complex zonations like sulphur enrichment, zones depleted in Ca but enriched in Mg, strong Mg enrichment adjacent to the interface, or carbonation. Consistently, the carbonated zone shows a reduced porosity. Properties of the complex zonation strongly depend on cement properties like water content and pH (ordinary Portland cement vs. low-pH cement). An increased Ca or Mg content in the first 100 μm next to the interface is observed in Opalinus Clay. The cation occupancy of clay exchanger phases next to the ordinary Portland cement interface is depleted in Mg, but enriched in Na, whereas porosity shows no changes at all. The current data suggests migration of CO2/HCO3-, SO42-, and Mg species from clay into cement. pH decrease in the cement next to the interface leads to instability of ettringite, and the sulphate liberated diffuses towards higher pH regions (away from the interface), where additional ettringite can form.

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

    NASA Astrophysics Data System (ADS)

    Marcolli, C.

    2014-02-01

    Heterogeneous ice nucleation is an important mechanism for the glaciation of mixed phase clouds and may also be relevant for cloud formation and dehydration at the cirrus cloud level. It is thought to proceed through different mechanisms, namely contact, condensation, immersion and deposition nucleation. Conceptually, deposition nucleation is the only pathway that does not involve liquid water, but occurs by direct water vapor deposition onto a surface. This study challenges this classical view by putting forward the hypothesis that what is called deposition nucleation is in fact pore condensation and freezing (PCF) occurring in voids and cavities that may form between aggregated primary particles and host water at relative humidity RHw < 100% because of the inverse Kelvin effect. Homogeneous ice nucleation is expected to occur below 235 K when at least one pore is filled with water. Ice nucleation in pores may also happen in immersion mode but with a lower probability because it requires at least one active site in a water filled pore. Therefore a significant enhancement in ice nucleation efficiency is expected when temperature falls below 235 K. For a deposition nucleation process from water vapor no discontinuous change in ice nucleation efficiency should occur at T = 235 K because no liquid water is involved in this process. Studies on freezing in confinement carried out on mesoporous silica materials such as SBA-15, SBA-16, MCM-41, zeolites and KIT have shown that homogeneous ice nucleation occurs abruptly at T = 230-235 K in pores with diameters (D) of 3.5-4 nm or larger but only gradually at T = 210-230 K in pores with D = 2.5-3.5 nm. Pore analysis of clay minerals shows that kaolinites exhibit pore structures with pore diameters (Dp) of 20-50 nm. The mesoporosity of illites and montmorillonites is characterized by pores with Dp = 2-5 nm. The number and size of pores is distinctly increased in acid treated montmorillonites like K10. Water adsorption

  6. Determination of the pore size distribution and hydraulic properties from Nuclear Magnetic Resonance relaxometry

    NASA Astrophysics Data System (ADS)

    Stingaciu, Laura R.; Weihermüller, Lutz; Haber-Pohlmeier, Sabina; Stapf, Siegfried; Vereecken, Harry; Pohlmeier, Andreas

    2010-05-01

    Known pore size distributions can be directly linked to the water retention characteristic which is essential for the prognosis of water and solute movement through the material. In our study, we evaluated the feasibility to use Nuclear Magnetic Resonance (NMR) relaxometry measurements for the characterization of pore size distribution in four porous samples with different texture and composition. Therefore, NMR T2 and T1 relaxation measurements at 6.47 MHz were carried out for three model samples (medium sand; fine sand; and a homogenous sand / kaolin clay mixture) and a natural soil. To quantify the goodness of the approach, the NMR measurements were compared in terms of cumulated pore size distribution functions and mean pore diameter with the two classical techniques based on water retention and mercury porosimetry measurements. The results showed that T1 and T2 derived mean pore size diameters are in good agreement with each other but deviate from retention curve derived ones. This is especially the case for well sorted sands with n values > 2.7. For finer materials differences are less pronounced. A short study was performed to evaluate the influence of the variations observed in the pore diameter distributions on the hydraulic properties of the samples: θS, α, and n. In conclusion, NMR T1 and T2 relaxation measurements can be used to estimate pore size distribution, mean pore diameter, as well as the retention function and corresponding hydraulic properties.

  7. NMR and Electrochemical Investigation of the Transport Properties of Methanol and Water in Nafion and Clay-Nanocomposites Membranes for DMFCs

    PubMed Central

    Nicotera, Isabella; Angjeli, Kristina; Coppola, Luigi; Aricò, Antonino S.; Baglio, Vincenzo

    2012-01-01

    Water and methanol transport behavior, solvents adsorption and electrochemical properties of filler-free Nafion and nanocomposites based on two smectite clays, were investigated using impedance spectroscopy, DMFC tests and NMR methods, including spin-lattice relaxation and pulsed-gradient spin-echo (PGSE) diffusion under variable temperature conditions. Synthetic (Laponite) and natural (Swy-2) smectite clays, with different structural and physical parameters, were incorporated into the Nafion for the creation of exfoliated nanocomposites. Transport mechanism of water and methanol appears to be influenced from the dimensions of the dispersed platelike silicate layers as well as from their cation exchange capacity (CEC). The details of the NMR results and the effect of the methanol solution concentration are discussed. Clays particles, and in particular Swy-2, demonstrate to be a potential physical barrier for methanol cross-over, reducing the methanol diffusion with an evident blocking effect yet nevertheless ensuring a high water mobility up to 130 °C and for several hours, proving the exceptional water retention property of these materials and their possible use in the DMFCs applications. Electrochemical behavior is investigated by cell resistance and polarization measurements. From these analyses it is derived that the addition of clay materials to recast Nafion decreases the ohmic losses at high temperatures extending in this way the operating range of a direct methanol fuel cell. PMID:24958179

  8. Laboratory testing of salt samples for water content/loss of weight on heating, thermal fracture, insoluble residue, and clay and bulk mineralogy: Revision 1

    SciTech Connect

    Owen, L.B.; Schwendiman, L.

    1987-07-01

    This report presents the results of laboratory testing on salt samples from the Palo Duro Basin of the Texas Panhandle. Laboratory specimens were tested to determine water content by loss of weight on heating, temperature of thermal fracture, the amount of insoluble residue, and clay and bulk mineralogy. 7 refs., 3 figs., 8 tabs.

  9. Influence of Pore-Fluid Pressure on Elastic Wave Velocity and Electrical Conductivity in Water-Saturated Rocks

    NASA Astrophysics Data System (ADS)

    Higuchi, A.; Watanabe, T.

    2013-12-01

    Pore-fluid pressure in seismogenic zones can play a key role in the occurrence of earthquakes (e.g., Sibson, 2009). Its evaluation via geophysical observations can lead to a good understanding of seismic activities. The evaluation requires a thorough understanding of the influence of the pore-fluid pressure on geophysical observables like seismic velocity and electrical conductivity. We have studied the influence of pore-fluid pressure on elastic wave velocity and electrical conductivity in water-saturated rocks. Fine grained (100-500μm) biotite granite (Aji, Kagawa pref., Japan) was used as rock samples. The density is 2.658-2.668 g/cm3, and the porosity 0.68-0.87%. The sample is composed of 52.8% plagioclase, 36.0% Quartz, 3.0% K-feldspar, 8.2% biotite. SEM images show that a lot of grain boundaries are open. Few intracrystalline cracks were observed. Following the method proposed by David and Zimmerman (2012), the distribution function of crack aspect ratio was evaluated from the pressure dependence of compressional and shear wave velocities in a dry sample. Cylindrical sample has dimensions of 25 mm in diameter and 30 mm in length, and saturated with 0.01 mol/l KCl aqueous solution. Compressional and shear wave velocities were measured with the pulse transmission technique (PZT transducers, f=2 MHz), and electrical conductivity the two-electrode method (Ag-AgCl electrodes, f=1 Hz-100 kHz). Simultaneous measurements of velocities and conductivity were made using a 200 MPa hydrostatic pressure vessel, in which confining and pore-fluid pressures can be separately controlled. The pore-fluid is electrically insulated from the metal work of the pressure vessel by using a newly designed plastic device (Watanabe and Higuchi, 2013). The confining pressure was progressively increased up to 25 MPa, while the pore-fluid pressure was kept at 0.1 MPa. It took five days or longer for the electrical conductivity to become stationary after increasing the confining pressure

  10. Regulation of landslide motion by dilatancy and pore pressure feedback

    USGS Publications Warehouse

    Iverson, R.M.

    2005-01-01

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

  11. Linking local riverbed flow patterns and pore-water chemistry to hydrogeologic and geomorphic features across scales

    NASA Astrophysics Data System (ADS)

    Ibrahim, T. G.; Thornton, S.; Surridge, B.; Wainwright, J.

    2009-12-01

    The groundwater-surface water interface (GSI) is a critical environmental hotspot, a key area influencing the fate of carbon, nutrients and contaminants of surface and subsurface origin, and a zone of ecological importance. Policy seeking to mitigate issues relating to dissolved contaminants and to improve stream health, increasingly recognizes its significance, particularly in the context of integrated management of streams and aquifers. Techniques assessing riverbed flow and solute patterns are often limited to the local scale. When related to the multi-scale pattern of hydrogeologic and geomorphic features controlling stream, hyporheic and groundwater fluxes, they can improve larger scale predictions of flow and solute behaviour at the GSI. This study develops a conceptual model of riverbed flow and solute patterns, and tests it in a 4th order stream in the UK. It assesses the interaction between large scale subsurface flowpaths, driven by the distribution of bedrock outcrops, and the expansion and closure of alluvial deposits, and small-scale hyporheic flowpaths, driven by riffle-pool sequences. It uses two networks of riverbed mini-piezometers and multi-level samplers: network 1, across fifteen sites in a 7.2 km length of river in unconstrained (open alluvial valley), asymmetric (bedrock outcropping on one bank) and constrained (bedrock on both banks) contexts; and network 2, across six riffle-pool sequences in a 350-m reach, at the transition between asymmetric/unconstrained and constrained contexts. Subsurface flowpaths and stream-water infiltration were deduced by relating vertical exchange fluxes to stream and pore-water patterns of conservative natural tracers. Biogeochemical processes were highlighted using reactive natural tracers. At network 2, measurements of surface water profiles and riverbed coring were also undertaken, and dissolved metal concentrations in the first 15 cm of sediments assessed using gel probes. Network 1 was sampled twice. Monthly

  12. Fire clay

    USGS Publications Warehouse

    Virta, R.L.

    2012-01-01

    Five companies mined fire clay in four states in 2011. Production, based on a preliminary survey of the fire clay industry, was estimated to be 240 kt (265,000 st), valued at $7.68 million, an increase from 216 kt (238,000 st), valued at $6.12 million in 2010. Missouri was the leading producing state, followed by Texas, Washington and Ohio, in decreasing order by quantity.

  13. Composition of pore and spring waters from Baby Bare: Global implications of geochemical fluxes from a ridge flank hydrothermal system

    SciTech Connect

    Wheat, C.G.; Mottl, M.J.

    2000-02-01

    Warm hydrothermal springs were discovered on Baby Bare, which is an isolated basement outcrop on 3.5 Ma-old crust on the eastern flank of the Juan de Fuca Ridge. The authors have sampled these spring waters from a manned submersible, along with associated sediment pore waters from 48 gravity and piston cores. Systematic variations in the chemical composition of these waters indicate that hydrothermal reactions in basement at moderate temperatures remove Na, K, Li, Rb, Mg, TCO{sub 2}, alkalinity, and phosphate from the circulating seawater and leach Ca, Sr, Si, B, and Mn from the oceanic crust; and that reactions with the turbidite sediment surrounding Baby Bare remove Na, Li, Mg, Ca, Sr, and sulfate from the pore water while producing ammonium and Si and both producing and consuming phosphate, nitrate, alkalinity, Mn, and Fe. K, Rb, and B are relatively unreactive in the sediment column. The composition of altered seawater in basement at Baby Bare is similar to the inferred composition of 58 C formation water from crust nearly twice as old (5.9 Ma) on the southern flank of the Costa Rica Rift. The Baby Bare fluids also exhibit the same directions of net elemental transfer between basalt and seawater as solutions produced in laboratory experiments at a similar temperature, and complement compositional changes form seawater observed in seafloor basalts altered at cool to moderate temperatures. The common parameter among the two ridge flanks and experiments is temperature, suggesting that the residence time of seawater in the two ridge-flank sites is sufficiently long for the solutions to equilibrate with altered basalt. The authors use the Baby Bare spring water to estimate upper limits on the global fluxes of 14 elements at warm ridge-flank sites such as Baby Bare. Maximum calculated fluxes of Mg, Ca, sulfate, B, and K may equal or exceed 25% of the riverine flux, and such sites may represent the missing, high K/Rb sink required for the K budget.

  14. Estimating topsoil water content of clay soils with data from time-lapse electrical conductivity surveys

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Spatial estimation of soil water content (') at the field, hillslope, or catchment scale is required in numerous applications. Time-lapse electrical resistivity and electrical conductivity surveys were recognized as the useful source of information about both spatial variations in soil water conten...

  15. Comparing Sediment and Pore-water Measurements as Predictors of PCB Uptake by Oligochaetes from Sediments

    EPA Science Inventory

    There is an increasing amount of chemical and biological evidence that using sediment concentrations and commonly applied Koc values frequently overpredicts interstitial water concentrations of HOCs, and thereby overestimates uptake and/or effects of those chemicals on exposed or...

  16. Sorption and diffusion of chlorinated methanes in moist clay