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Sample records for mixture ii sedimentation

  1. Heat transfer from a high temperature condensable mixture. II. Sedimentation of fog condensate

    SciTech Connect

    Condiff, D.W.; Cho, D.H.; Chan, S.H.

    1985-01-01

    A kinematic wave analysis of fog sedimentation is employed to relate growth of a fog condensate deposit layer to radiation generated fog formation rates. The increase of surface radiation absorptivity with deposit layer thickness promotes a feedback mechanism for higher growth rates, which is evaluated in detail.

  2. Identification and evaluation of pyrethroid insecticide mixtures in urban sediments.

    PubMed

    Trimble, Andrew J; Weston, Donald P; Belden, Jason B; Lydy, Michael J

    2009-08-01

    Organochlorine, organophosphorous, and pyrethroid insecticides frequently have been detected together as mixtures in stream sediments. To simplify mixture analyses, additive toxic responses usually are assumed but rarely are confirmed, especially for compounds with similar modes of action. The first objective of the present study was to screen a database of 24 different pesticides and 94 urban-stream sediment samples collected throughout central and northern California (USA) to identify compounds and partial mixtures that dominated sample toxicity to Hyalella azteca. Pyrethroids and chlorpyrifos were the most toxicologically relevant compounds in terms of detection frequency, contribution to overall sample toxicity, and co-occurrence in the most common mixture patterns. Organochlorine insecticides were the least toxicologically relevant compounds, with only a small percentage of samples exceeding predefined screening values. The second objective was to confirm that mixtures of type I and type II pyrethroids display additive responses. Ten-day sediment toxicity tests of binary pesticide mixtures were conducted using H. azteca as the test organism. Observed dose-response curves were compared to those predicted from concentration-addition and independent-action models. Model deviation ratios (MDRs) were calculated at the median effect level to quantify the magnitudes of deviation between observed and predicted curves. Whereas the concentration-addition model adequately predicted toxicity for all the pyrethroid mixtures (MDRs within a factor of two), dose-response values deviated from additivity enough to warrant further investigation. PMID:19245272

  3. Electrical properties of methane hydrate + sediment mixtures

    USGS Publications Warehouse

    Du Frane, Wyatt L.; Stern, Laura A.; Weitemeyer, Karen A.; Constable, Steven; Roberts, Jeffery J.

    2011-01-01

    As part of our DOE-funded proposal to characterize gas hydrate in the Gulf of Mexico using marine electromagnetic methods, a collaboration between SIO, LLNL, and USGS with the goal of measuring the electrical properties of lab-created methane (CH4) hydrate and sediment mixtures was formed. We examined samples with known characteristics to better relate electrical properties measured in the field to specific gas hydrate concentration and distribution patterns. Here we discuss first-ever electrical conductivity (σ) measurements on unmixed CH4 hydrate (Du Frane et al., 2011): 6 x 10-5 S/m at 5 °C, which is ~5 orders of magnitude lower than seawater. This difference allows electromagnetic (EM) techniques to distinguish highly resistive gas hydrate deposits from conductive water saturated sediments in EM field surveys. More recently, we performed measurements on CH4 hydrate mixed with sediment and we also discuss those initial findings here. Our results on samples free of liquid water are important for predicting conductivity of sediments with pores highly saturated with gas hydrate, and are an essential starting point for comprehensive mixing models.

  4. Electrical properties of methane hydrate + sediment mixtures

    NASA Astrophysics Data System (ADS)

    Du Frane, Wyatt L.; Stern, Laura A.; Constable, Steven; Weitemeyer, Karen A.; Smith, Megan M.; Roberts, Jeffery J.

    2015-07-01

    Knowledge of the electrical properties of multicomponent systems with gas hydrate, sediments, and pore water is needed to help relate electromagnetic (EM) measurements to specific gas hydrate concentration and distribution patterns in nature. Toward this goal, we built a pressure cell capable of measuring in situ electrical properties of multicomponent systems such that the effects of individual components and mixing relations can be assessed. We first established the temperature-dependent electrical conductivity (σ) of pure, single-phase methane hydrate to be ~5 orders of magnitude lower than seawater, a substantial contrast that can help differentiate hydrate deposits from significantly more conductive water-saturated sediments in EM field surveys. Here we report σ measurements of two-component systems in which methane hydrate is mixed with variable amounts of quartz sand or glass beads. Sand by itself has low σ but is found to increase the overall σ of mixtures with well-connected methane hydrate. Alternatively, the overall σ decreases when sand concentrations are high enough to cause gas hydrate to be poorly connected, indicating that hydrate grains provide the primary conduction path. Our measurements suggest that impurities from sand induce chemical interactions and/or doping effects that result in higher electrical conductivity with lower temperature dependence. These results can be used in the modeling of massive or two-phase gas-hydrate-bearing systems devoid of conductive pore water. Further experiments that include a free water phase are the necessary next steps toward developing complex models relevant to most natural systems.

  5. Toxicity and photoactivation of PAH mixtures in marine sediment

    SciTech Connect

    Swartz, R.; Ferraro, S.; Lamberson, J.; Cole, F.; Ozretich, R.; Boese, B.; Schults, D.; Behrenfeld, M.; Ankley, G.

    1995-12-31

    The toxicity and toxicological photoactivation of mixtures of sediment-associated fluoranthene, phenanthrene, pyrene, and acenaphthene were determined using standard 10 d sediment toxicity tests with the marine amphipod, Rhepoxynius abronius. The four PAHs were spiked into sediment in a concentration series of either single compounds or an equitoxic mixture. Spiked sediment was stored at 4 C for 28 d before testing. Toxicity tests were conducted under fluorescent lighting. Survivors after 10 d in PAH-contaminated sediment were exposed for 1 h to UV light in the absence of sediment and then tested for their ability to bury in clean sediment. The 10 d LC50s for single PAHs were 3.3, 2.2, 2.8, and 2.3 mg/g oc for fluoranthene, phenanthrene, pyrene, and acenaphthene, respectively. These LC50s were used to calculate the sum of toxic units ({Sigma}TU) of the four PAHs in the equitoxic mixture treatments. The {Sigma}TU LC50 was then calculated for the mixture treatments. If the toxicological interaction of the four PAHs in the mixture was additive, the {Sigma}TU LC50 should equal 1.0. The observed {Sigma}TU LC50 in the mixture was 1.55, indicating the interaction was slightly less than additive. UV enhancement of toxic effects of individual PAHs was correctly predicted by photophysical properties, i.e. pyrene and fluoranthene were photoactivated and phenanthrene and acenaphthene were not. UV effects in the mixture of four PAHs can be explained by the photoactivation of pyrene and fluoranthene alone.

  6. Consensus sediment quality guidelines for polycyclic aromatic hydrocarbon mixtures

    SciTech Connect

    Swartz, R.C.

    1999-04-01

    Sediment quality guidelines (SQGs) for polycyclic aromatic hydrocarbons (PAHs) have been derived from a variety of laboratory, field, and theoretical foundations. They include the screening level concentration, effects ranges-low and -median, equilibrium partitioning concentrations, apparent effects threshold, {Sigma}PAH model, and threshold and probable effects levels. The resolution of controversial differences among the PAH SQGs lies in an understanding of the effects of mixtures. Polycyclic aromatic hydrocarbons virtually always occur in field-collected sediment as a complex mixture of covarying compounds. When expressed as a mixture concentration, that is, total PAH (TPAH), the guidelines form three clusters that were intended in their original derivations to represent threshold (TEC = 290 {micro}g/g organic carbon [OC]), median (MEC = 1,800 {micro}g/g OC), and extreme (EEC = 10,000 {micro}g/g OC) effects concentrations. The TEC/MEC/EEC consensus guidelines provide a unifying synthesis of other SQGs, reflect causal rather than correlative effects, account for mixtures, and predict sediment toxicity and benthic community perturbations at sites of PAH contamination. The TEC offers the most useful SQG because PAH mixtures are unlikely to cause adverse effects on benthic ecosystems below the TEC.

  7. Sediment Mixture Controls on Morphodynamics of Experimental Deltas

    NASA Astrophysics Data System (ADS)

    Cheshier, N. R.; van de Lageweg, W. I.; van Dijk, W. M.; Hoyal, D. C.; Kleinhans, M. G.; Postma, G.

    2010-12-01

    The creation of small scale deltas in the laboratory has proven challenging but significant progress has been made in several labs in recent years. Various types of river and fan deltas have been created, ranging from fine- to coarse-grained, non-cohesive to cohesive sediment, and from sheet flow dominated to strongly channelised. These experiments have elucidated a number of important factors and autogenic behaviours under constant boundary conditions, such as channelisation and mouth bar formation and backsedimentation leading to avulsion. However, there has been very little systematic investigation of scale effects (Kleinhans et al., this conference) and of experimental parameter space, particularly the link between the sediment mixture and autogenic delta behaviour. Here we describe systematic pilot experiments designed to investigate the link between sediment mixture properties, such as grain size, sorting, addition of fines or polymers, and delta morphodynamics, described by channel dimensions, network pattern, planform delta shape, and bifurcation mechanisms. These experiments were designed to be small, fast and repeatable, so that large quantities of data can be collected for different mixtures. They are run in conjunction with other small-scale tests on the same sediment mixtures to quantify the link between the mechanical properties of delta substrate, such as bank erodibility, and delta organisation. Discharge and sediment feed rate were kept constant and the same in all experiments. Delta evolution was recorded by high-resolution time-lapse photography, emphasising the channels by coloured flow and showing sorting patterns in cases with sediment mixtures. Topography was measured at sub-mm resolution at a few time steps for each delta. For sediment we used various combinations of well-sorted fine sand or poorly sorted sand with some fine gravel, and silica flour and/or polymer with benthonite. The uniform fine sand invariably exhibited sheet flow or

  8. Comparing catchment sediment fingerprinting procedures using an auto-evaluation approach with virtual sample mixtures.

    PubMed

    Palazón, Leticia; Latorre, Borja; Gaspar, Leticia; Blake, William H; Smith, Hugh G; Navas, Ana

    2015-11-01

    Information on sediment sources in river catchments is required for effective sediment control strategies, to understand sediment, nutrient and pollutant transport, and for developing soil erosion management plans. Sediment fingerprinting procedures are employed to quantify sediment source contributions and have become a widely used tool. As fingerprinting procedures are naturally variable and locally dependant, there are different applications of the procedure. Here, the auto-evaluation of different fingerprinting procedures using virtual sample mixtures is proposed to support the selection of the fingerprinting procedure with the best capacity for source discrimination and apportionment. Surface samples from four land uses from a Central Spanish Pyrenean catchment were used i) as sources to generate the virtual sample mixtures and ii) to characterise the sources for the fingerprinting procedures. The auto-evaluation approach involved comparing fingerprinting procedures based on four optimum composite fingerprints selected by three statistical tests, three source characterisations (mean, median and corrected mean) and two types of objective functions for the mixing model. A total of 24 fingerprinting procedures were assessed by this new approach which were solved by Monte Carlo simulations and compared using the root mean squared error (RMSE) between known and assessed source ascriptions for the virtual sample mixtures. It was found that the source ascriptions with the highest accuracy were achieved using the corrected mean source characterisations for the composite fingerprints selected by the Kruskal Wallis H-test and principal components analysis. Based on the RMSE results, high goodness of fit (GOF) values were not always indicative of accurate source apportionment results, and care should be taken when using GOF to assess mixing model performance. The proposed approach to test different fingerprinting procedures using virtual sample mixtures provides an

  9. Electrical properties of methane hydrate + sediment mixtures

    USGS Publications Warehouse

    Du Frane, Wyatt L.; Stern, Laura A.; Constable, Steven; Weitemeyer, Karen A.; Smith, Megan M; Roberts, Jeffery J.

    2015-01-01

    Knowledge of the electrical properties of multicomponent systems with gas hydrate, sediments, and pore water is needed to help relate electromagnetic (EM) measurements to specific gas hydrate concentration and distribution patterns in nature. Toward this goal, we built a pressure cell capable of measuring in situ electrical properties of multicomponent systems such that the effects of individual components and mixing relations can be assessed. We first established the temperature-dependent electrical conductivity (σ) of pure, single-phase methane hydrate to be ~5 orders of magnitude lower than seawater, a substantial contrast that can help differentiate hydrate deposits from significantly more conductive water-saturated sediments in EM field surveys. Here we report σ measurements of two-component systems in which methane hydrate is mixed with variable amounts of quartz sand or glass beads. Sand by itself has low σ but is found to increase the overall σ of mixtures with well-connected methane hydrate. Alternatively, the overall σ decreases when sand concentrations are high enough to cause gas hydrate to be poorly connected, indicating that hydrate grains provide the primary conduction path. Our measurements suggest that impurities from sand induce chemical interactions and/or doping effects that result in higher electrical conductivity with lower temperature dependence. These results can be used in the modeling of massive or two-phase gas-hydrate-bearing systems devoid of conductive pore water. Further experiments that include a free water phase are the necessary next steps toward developing complex models relevant to most natural systems.

  10. Mixture design and treatment methods for recycling contaminated sediment.

    PubMed

    Wang, Lei; Kwok, June S H; Tsang, Daniel C W; Poon, Chi-Sun

    2015-01-01

    Conventional marine disposal of contaminated sediment presents significant financial and environmental burden. This study aimed to recycle the contaminated sediment by assessing the roles and integration of binder formulation, sediment pretreatment, curing method, and waste inclusion in stabilization/solidification. The results demonstrated that the 28-d compressive strength of sediment blocks produced with coal fly ash and lime partially replacing cement at a binder-to-sediment ratio of 3:7 could be used as fill materials for construction. The X-ray diffraction analysis revealed that hydration products (calcium hydroxide) were difficult to form at high sediment content. Thermal pretreatment of sediment removed 90% of indigenous organic matter, significantly increased the compressive strength, and enabled reuse as non-load-bearing masonry units. Besides, 2-h CO2 curing accelerated early-stage carbonation inside the porous structure, sequestered 5.6% of CO2 (by weight) in the sediment blocks, and acquired strength comparable to 7-d curing. Thermogravimetric analysis indicated substantial weight loss corresponding to decomposition of poorly and well crystalline calcium carbonate. Moreover, partial replacement of contaminated sediment by various granular waste materials notably augmented the strength of sediment blocks. The metal leachability of sediment blocks was minimal and acceptable for reuse. These results suggest that contaminated sediment should be viewed as useful resources. PMID:25464304

  11. Assessing the risk of metal mixtures in contaminated sediments on Chironomus riparius based on cytosolic accumulation.

    PubMed

    Péry, Alexandre R R; Geffard, Alain; Conrad, Arnaud; Mons, Raphaël; Garric, Jeanne

    2008-11-01

    Sediments usually contain mixtures of trace metals introduced via natural geochemical processes and anthropogenic activities. Kinetics and effects of these metals are strongly dependent both on the composition of the mixture and on the physico-chemical characteristics of the sediment. Relating effects to metal concentration may consequently be advised. However, total accumulation may be a poor predictor of metal toxicity for Chironomus riparius exposed to contaminated field sediments. As an alternative, we proposed to relate effects on Chironomus growth with cytosolic metal accumulation, measured in larvae after a short exposure period. Dose-response relationships were derived for zinc, copper, and cadmium through single-metal exposure data analysed with toxicokinetics and toxicodynamics models. They permitted, on the basis of cytosolic accumulation measures, to predict successfully the effects of mixtures of cadmium, zinc, and copper on the growth of larvae exposed to spiked sediments, as well as to field sediments in which zinc and copper were assumed to be predominant. PMID:18514899

  12. Mathematical model of the component mixture distribution in the molten cast iron during centrifugation (sedimentation)

    NASA Astrophysics Data System (ADS)

    Bikulov, R. A.; Kotlyar, L. M.

    2014-12-01

    For the development and management of the manufacturing processes of axisymmetric articles with compositional structure by centrifugal casting method [1,2,3,4] is necessary to create a generalized mathematical model of the dynamics of component mixture in the molten cast iron during centrifugation. In article. based on the analysis of the dynamics of two-component mixture at sedimentation, a method of successive approximations to determine the distribution of a multicomponent mixture by centrifugation in a parabolic crucible is developed.

  13. CHROMATOGRAPHIC ALTERATION OF A NONIONIC SURFACTANT MIXTURE DURING TRANSPORT IN DENSE NONAQUEOUS PHASE LIQUID CONTAMINATED SEDIMENT (R826650)

    EPA Science Inventory

    Chromatographic alteration of a nonionic surfactant mixture during transport through DNAPL-contaminated aquifer sediment may occur due to differential loss of oligomers to sediment and to dense nonaqueous phase liquid (DNAPL). These losses may significantly alter the solubilizing...

  14. PROCEDURES FOR THE DERIVATION OF EQUILIBRIUM PARTITIONING SEDIMENT BENCHMARKS (ESBS) FOR THE PROTECTION OF BENTHIC ORGANISMS: PAH MIXTURES

    EPA Science Inventory

    This equilibrium partitioning sediment benchmark (ESB) document describes procedures to derive concentrations of PAH mixtures in sediment which are protective of the presence of benthic organisms. The equilibrium partitioning (EqP) approach was chosen because it accounts for the ...

  15. Sedimentation stacking diagrams of binary mixtures of thick and thin hard rods.

    PubMed

    Drwenski, Tara; Hooijer, Patrick; van Roij, René

    2016-06-29

    We use Onsager theory and the local density approximation to study sedimentation-diffusion equilibrium density profiles of binary mixtures of thick and thin hard rods. We construct stacking diagrams for three diameter ratios, and find that even a simple spindle-shaped phase diagram with only isotropic-nematic demixing can lead to counter-intuitive stacking sequences such as an isotropic phase sandwiched between two nematic phases. For the most complex phase diagram considered here, we find sixteen distinct stacking sequences, including several with five sedimented layers. By adding sedimentation paths to composition-pressure and density-density phase diagrams and calculating density and composition profiles, we show that conclusions about bulk phase diagrams of binary mixtures on the basis of sedimentation-diffusion equilibria should be drawn warily. PMID:27279434

  16. Toxicity and bioavailability of heavy metal mixtures in natural and synthetic sediments

    SciTech Connect

    Frugis, M.; Clements, W.H.

    1994-12-31

    Toxicity tests were conducted to compare differences in bioavailability of a metal mixture (zinc, copper, cadmium and lead) in natural and synthetic sediments to Chironomus tentans and Ceriodaphnia dubia. Preliminary tests were conducted with sediment collected at five stations from the Arkansas River (Leadville, CO) and one from the La Cache Poudre River (Fort Collins, CO). After seven days of exposure, mortality on C. tentans in sediment from the most contaminated station (AR3) was significantly different from the reference station (PDR). Bioaccumulation in these insects showed significant correlation with abiotic factors: particle size, organic matter, total carbon and cation exchange capacity. During a second experiment, particle size and carbon contents of synthetic sediment were modified to reflect composition of natural sediment. Two types of artificial sediments were spiked with 0X, 0.085X, 0.175X and 0.35X of metal mixture measured in AR3. After ten days, mortality of C. tentans in the 0.35X and AR3 treatments were similar. In a final experiment, synthetic and natural sediments were spiked at 0X, 0.175X, 0.35X, and 0.70X. Again, mortality of contents in 0.35X and AR3 were not significantly different. A 48hrs-acute test conducted with C. dubia showed that interstitial water from AR3 and AR5 stations had higher toxicity than other stations. In addition, toxicity of interstitial water from synthetic sediment was greater than from spiked natural sediment or sediments collected from the Arkansas River. These results indicate that heavy metals are more bioavailable in synthetic sediments than in natural substrates.

  17. Photoactivation and toxicity of mixtures of polycyclic aromatic hydrocarbon compounds in marine sediment

    SciTech Connect

    Swartz, R.C.; Ferraro, S.P.; Lamberson, J.O.; Cole, F.A.; Ozretich, R.J.; Boese, B.L.; Schults, D.W.; Behrenfeld, M.; Ankley, G.T.

    1997-10-01

    The direct toxicity and photoinduced toxicity of sediment-associated acenaphthene, phenanthrene, fluoranthene, and pyrene were determined for the marine amphipod Rhepoxynius abronius. The four polycyclic aromatic hydrocarbons (PAHs) were spiked into sediment in a concentration series of either single compounds or as approximately equitoxic mixtures of all four compounds. Standard 10-d sediment toxicity tests were conducted under fluorescent lighting. After 10 d, survivors were exposed for 1 h to ultraviolet (UV) radiation in the absence of sediment and then tested for their ability to bury in uncontaminated sediment. The 10-d median lethal concentrations (LC50s) were 2.31 mg acenaphthene/g organic carbon (OC), 2.22 mg phenanthrene/g OC, 3.31 mg fluoranthene/g OC, and 2.81 mg pyrene/g OC. These LC50s were used to calculate the sum of toxic units ({Sigma}TU) of the four PAHs in the approximately equitoxic mixtures. The {Sigma}TU LC50 was then calculated for the mixture treatments. If the toxicologic interaction of a mixture of contaminants is additive, {Sigma}TU LC50 = 1.0. The observed LC50 (1.55 {Sigma}TU) was slightly, but significantly, greater than unity, indicating that the interaction of PAHs in the mixture was less than additive. Exposure to UV radiation enhanced the toxic effects of fluoranthene and pyrene, but did not affect the toxicity of acenaphthene and phenanthrene. Effects of UV radiation on the toxicity of the mixture of four PAHs could be explained by the photoactivation of fluoranthene and pyrene alone. These results are consistent with predictions based on photophysical properties of PAH compounds.

  18. Glass polymorphism in glycerol–water mixtures: II. Experimental studies

    PubMed Central

    Bachler, Johannes; Fuentes-Landete, Violeta; Jahn, David A.; Wong, Jessina; Giovambattista, Nicolas

    2016-01-01

    We report a detailed experimental study of (i) pressure-induced transformations in glycerol–water mixtures at T = 77 K and P = 0–1.8 GPa, and (ii) heating-induced transformations of glycerol–water mixtures recovered at 1 atm and T = 77 K. Our samples are prepared by cooling the solutions at ambient pressure at various cooling rates (100 K s–1–10 K h–1) and for the whole range of glycerol mole fractions, χ g. Depending on concentration and cooling rates, cooling leads to samples containing amorphous ice (χ g ≥ 0.20), ice (χ g ≤ 0.32), and/or “distorted ice” (0 < χ g ≤ 0.38). Upon compression, we find that (a) fully vitrified samples at χ g ≥ 0.20 do not show glass polymorphism, in agreement with previous works; (b) samples containing ice show pressure-induced amorphization (PIA) leading to the formation of high-density amorphous ice (HDA). PIA of ice domains within the glycerol–water mixtures is shown to be possible only up to χ g ≈ 0.32 (T = 77 K). This is rather surprising since it has been known that at χ g < 0.38, cooling leads to phase-separated samples with ice and maximally freeze-concentrated solution of χ g ≈ 0.38. Accordingly, in the range 0.32 < χ g < 0.38, we suggest that the water domains freeze into an interfacial ice, i.e., a highly-distorted form of layered ice, which is unable to transform to HDA upon compression. Upon heating samples recovered at 1 atm, we observe a rich phase behavior. Differential scanning calorimetry indicates that only at χ g ≤ 0.15, the water domains within the sample exhibit polyamorphism, i.e., the HDA-to-LDA (low-density amorphous ice) transformation. At 0.15 < χ g ≤ 0.38, samples contain ice, interfacial ice, and/or HDA domains. All samples (χ g ≤ 0.38) show: the crystallization of amorphous ice domains, followed by the glass transition of the vitrified glycerol–water domains and, finally, the melting of ice at high temperatures. Our work exemplifies the complex

  19. Glass polymorphism in glycerol-water mixtures: II. Experimental studies.

    PubMed

    Bachler, Johannes; Fuentes-Landete, Violeta; Jahn, David A; Wong, Jessina; Giovambattista, Nicolas; Loerting, Thomas

    2016-04-20

    We report a detailed experimental study of (i) pressure-induced transformations in glycerol-water mixtures at T = 77 K and P = 0-1.8 GPa, and (ii) heating-induced transformations of glycerol-water mixtures recovered at 1 atm and T = 77 K. Our samples are prepared by cooling the solutions at ambient pressure at various cooling rates (100 K s(-1)-10 K h(-1)) and for the whole range of glycerol mole fractions, χg. Depending on concentration and cooling rates, cooling leads to samples containing amorphous ice (χg ≥ 0.20), ice (χg ≤ 0.32), and/or "distorted ice" (0 < χg ≤ 0.38). Upon compression, we find that (a) fully vitrified samples at χg ≥ 0.20 do not show glass polymorphism, in agreement with previous works; (b) samples containing ice show pressure-induced amorphization (PIA) leading to the formation of high-density amorphous ice (HDA). PIA of ice domains within the glycerol-water mixtures is shown to be possible only up to χg ≈ 0.32 (T = 77 K). This is rather surprising since it has been known that at χg < 0.38, cooling leads to phase-separated samples with ice and maximally freeze-concentrated solution of χg ≈ 0.38. Accordingly, in the range 0.32 < χg < 0.38, we suggest that the water domains freeze into an interfacial ice, i.e., a highly-distorted form of layered ice, which is unable to transform to HDA upon compression. Upon heating samples recovered at 1 atm, we observe a rich phase behavior. Differential scanning calorimetry indicates that only at χg ≤ 0.15, the water domains within the sample exhibit polyamorphism, i.e., the HDA-to-LDA (low-density amorphous ice) transformation. At 0.15 < χg ≤ 0.38, samples contain ice, interfacial ice, and/or HDA domains. All samples (χg ≤ 0.38) show: the crystallization of amorphous ice domains, followed by the glass transition of the vitrified glycerol-water domains and, finally, the melting of ice at high temperatures. Our work exemplifies the complex "phase" behavior of glassy binary

  20. Polymer-Induced Depletion Interaction and Its Effect on Colloidal Sedimentation in Colloid-Polymer Mixtures

    NASA Technical Reports Server (NTRS)

    Tong, Penger

    1996-01-01

    In this paper we focus on the polymer-induced depletion attraction and its effect on colloidal sedimentation in colloid-polymer mixtures. We first report a small angle neutron scattering (SANS) study of the depletion effect in a mixture of hard-sphere-like colloid and non-adsorbing polymer. Then we present results of our recent sedimentation measurements in the same colloid-polymer mixture. A key parameter in controlling the sedimentation of heavy colloidal particles is the interparticle potential U(tau), which is the work required to bring two colloidal particles from infinity to a distance tau under a give solvent condition. This potential is known to affect the average settling velocity of the particles and experimentally one needs to have a way to continuously vary U(tau) in order to test the theory. The interaction potential U(tau) can be altered by adding polymer molecules into the colloidal suspension. In a mixture of colloid and non-adsorbing polymer, the potential U(tau) can develop an attractive well because of the depletion effect, in that the polymer chains are expelled from the region between two colloidal particles when their surface separation becomes smaller than the size of the polymer chains. The exclusion of polymer molecules from the space between the colloidal particles leads to an unbalanced osmotic pressure difference pushing the colloidal particles together, which results in an effective attraction between the two colloidal particles. The polymer-induced depletion attraction controls the phase stability of many colloid-polymer mixtures, which are directly of interest to industry.

  1. Reductive debromination of the commercial polybrominated biphenyl mixture firemaster BP6 by anaerobic microorganisms from sediments

    SciTech Connect

    Morris, P.J.; Quensen, J.F. III; Tiedje, J.M.; Boyd, S.A. )

    1992-10-01

    Anaerobic microorganisms eluted from three sediments, one contaminated with polybrominated biphenyls (PBBs) and two contaminated with polychlorinated biphenyls, were compared for their ability to debrominate the commercial PBB mixture Firemaster. These microorganisms were incubated with reduced anaerobic mineral medium and noncontaminated sediment amended with Firemaster. Firemaster averages six bromines per biphenyl molecule; four of the bromines are substituted in the meta or para position. The inocula from all three sources were able to debrominate the meta and para positions. Microorganisms from the Pine River (St. Louis, Mich.) contaminated with Firemaster, the Hudson River (Hudson Falls, N.Y.) contaminated with Aroclor 1242, and Silver Lake (Pittsfield, Mass.) contaminated with Aroclor 1260 removed 32, 12, and 3% of the meta plus para bromines, respectively, after 32 weeks of incubation. This suggests that previous environmental exposure to PBBs enhances the debromination capability of the sediment microbial community through selection for different strains of microorganisms. The Pine River inoculum removed an average of 1.25 bromines per biphenyl molecule during a 32-week incubation period, resulting in a mixture potentially more accessible to aerobic degradation processes. No ortho bromine removal was observed. However, when Firemaster was incubated with Hudson River microorganisms that had been repeatedly transferred on a pyruvate medium amended with Aroclor 1242, 17% of the meta and para bromines were removed after 16 weeks of incubation and additional debromination products, including 2-bromobiphenyl and biphenyl, were detected.

  2. An interlaboratory study of TEX86 and BIT analysis of sediments, extracts, and standard mixtures

    NASA Astrophysics Data System (ADS)

    Schouten, Stefan; Hopmans, Ellen C.; Rosell-Melé, Antoni; Pearson, Ann; Adam, Pierre; Bauersachs, Thorsten; Bard, Edouard; Bernasconi, Stefano M.; Bianchi, Thomas S.; Brocks, Jochen J.; Carlson, Laura Truxal; Castañeda, Isla S.; Derenne, Sylvie; Selver, Ayça. Doǧrul; Dutta, Koushik; Eglinton, Timothy; Fosse, Celine; Galy, Valier; Grice, Kliti; Hinrichs, Kai-Uwe; Huang, Yongsong; Huguet, Arnaud; Huguet, Carme; Hurley, Sarah; Ingalls, Anitra; Jia, Guodong; Keely, Brendan; Knappy, Chris; Kondo, Miyuki; Krishnan, Srinath; Lincoln, Sara; Lipp, Julius; Mangelsdorf, Kai; Martínez-García, Alfredo; Ménot, Guillemette; Mets, Anchelique; Mollenhauer, Gesine; Ohkouchi, Naohiko; Ossebaar, Jort; Pagani, Mark; Pancost, Richard D.; Pearson, Emma J.; Peterse, Francien; Reichart, Gert-Jan; Schaeffer, Philippe; Schmitt, Gaby; Schwark, Lorenz; Shah, Sunita R.; Smith, Richard W.; Smittenberg, Rienk H.; Summons, Roger E.; Takano, Yoshinori; Talbot, Helen M.; Taylor, Kyle W. R.; Tarozo, Rafael; Uchida, Masao; Dongen, Bart E.; Mooy, Benjamin A. S.; Wang, Jinxiang; Warren, Courtney; Weijers, Johan W. H.; Werne, Josef P.; Woltering, Martijn; Xie, Shucheng; Yamamoto, Masanobu; Yang, Huan; Zhang, Chuanlun L.; Zhang, Yige; Zhao, Meixun; Damsté, Jaap S. Sinninghe

    2013-12-01

    Two commonly used proxies based on the distribution of glycerol dialkyl glycerol tetraethers (GDGTs) are the TEX86 (TetraEther indeX of 86 carbon atoms) paleothermometer for sea surface temperature reconstructions and the BIT (Branched Isoprenoid Tetraether) index for reconstructing soil organic matter input to the ocean. An initial round-robin study of two sediment extracts, in which 15 laboratories participated, showed relatively consistent TEX86 values (reproducibility ±3-4°C when translated to temperature) but a large spread in BIT measurements (reproducibility ±0.41 on a scale of 0-1). Here we report results of a second round-robin study with 35 laboratories in which three sediments, one sediment extract, and two mixtures of pure, isolated GDGTs were analyzed. The results for TEX86 and BIT index showed improvement compared to the previous round-robin study. The reproducibility, indicating interlaboratory variation, of TEX86 values ranged from 1.3 to 3.0°C when translated to temperature. These results are similar to those of other temperature proxies used in paleoceanography. Comparison of the results obtained from one of the three sediments showed that TEX86 and BIT indices are not significantly affected by interlaboratory differences in sediment extraction techniques. BIT values of the sediments and extracts were at the extremes of the index with values close to 0 or 1, and showed good reproducibility (ranging from 0.013 to 0.042). However, the measured BIT values for the two GDGT mixtures, with known molar ratios of crenarchaeol and branched GDGTs, had intermediate BIT values and showed poor reproducibility and a large overestimation of the "true" (i.e., molar-based) BIT index. The latter is likely due to, among other factors, the higher mass spectrometric response of branched GDGTs compared to crenarchaeol, which also varies among mass spectrometers. Correction for this different mass spectrometric response showed a considerable improvement in the

  3. An Extended Equation of State Modeling Method II. Mixtures

    NASA Astrophysics Data System (ADS)

    Scalabrin, G.; Marchi, P.; Stringari, P.; Richon, D.

    2006-09-01

    This work is the extension of previous work dedicated to pure fluids. The same method is extended to the representation of thermodynamic properties of a mixture through a fundamental equation of state in terms of the Helmholtz energy. The proposed technique exploits the extended corresponding-states concept of distorting the independent variables of a dedicated equation of state for a reference fluid using suitable scale factor functions to adapt the equation to experimental data of a target system. An existing equation of state for the target mixture is used instead of an equation for the reference fluid, completely avoiding the need for a reference fluid. In particular, a Soave-Redlich-Kwong cubic equation with van der Waals mixing rules is chosen. The scale factors, which are functions of temperature, density, and mole fraction of the target mixture, are expressed in the form of a multilayer feedforward neural network, whose coefficients are regressed by minimizing a suitable objective function involving different kinds of mixture thermodynamic data. As a preliminary test, the model is applied to five binary and two ternary haloalkane mixtures, using data generated from existing dedicated equations of state for the selected mixtures. The results show that the method is robust and straightforward for the effective development of a mixture- specific equation of state directly from experimental data.

  4. Dechlorination of four commercial polychlorinated biphenyl mixtures (Aroclors) by anaerobic microorganisms from sediments

    SciTech Connect

    Quensen, J.F. III; Boyd, S.A.; Tiedje, J.M. )

    1990-08-01

    The rate, extent, and pattern of dechlorination of four Aroclors by inocula prepared from two polychlorinated biphenyl (PCB)-contaminated sediments were compared. The four mixtures used, Aroclors 1242, 1248, 1254, and 1260, average approximately three, four, five, and six chlorines, respectively, per biphenyl molecule. All four Aroclors were dechlorinated with the loss of meta plus para chlorines ranging from 15 to 85%. Microorganisms from an Aroclor 1242-contaminated site in the upper Hudson River dechlorinated Aroclor 1242 to a greater extent than did microorganisms from Aroclor 1260-contaminated sediments from Silver Lake, Mass. The Silver Lake inoculum dechlorinated Aroclor 1260 more rapidly than the Hudson River inoculum did and showed a preferential removal of meta chlorines. For each inoculum the rate and extent of dechlorination tended to decrease as the degree of chlorination of the Aroclor increased, especially for Aroclor 1260. The maximal observed dechlorination rates were 0.3, 0.3, and 0.2 {mu}g-atoms of Cl removed per g of sediment per week for Aroclors 1242, 1248, and 1254, respectively. The maximal observed dechlorination rates for Hudson River and Silver Lake organisms for Aroclor 1260 were 0.04 and 0.21 {mu}g-atoms of Cl removed per g of sediment per week, respectively. The dechlorination patterns obtained suggested that the Hudson River microorganisms were more capable than the Silver Lake organisms of removing the last para chlorine.

  5. Electrical properties of methane hydrate + sediment mixtures: The σ of CH4 Hydrate + Sediment

    SciTech Connect

    Du Frane, Wyatt L.; Stern, Laura A.; Constable, Steven; Weitemeyer, Karen A.; Smith, Megan M.; Roberts, Jeffery J.

    2015-07-30

    Knowledge of the electrical properties of multicomponent systems with gas hydrate, sediments, and pore water is needed to help relate electromagnetic (EM) measurements to specific gas hydrate concentration and distribution patterns in nature. We built a pressure cell capable of measuring in situ electrical properties of multicomponent systems such that the effects of individual components and mixing relations can be assessed. We first established the temperature-dependent electrical conductivity (σ) of pure, single-phase methane hydrate to be ~5 orders of magnitude lower than seawater, a substantial contrast that can help differentiate hydrate deposits from significantly more conductive water-saturated sediments in EM field surveys. We report σ measurements of two-component systems in which methane hydrate is mixed with variable amounts of quartz sand or glass beads. Sand by itself has low σ but is found to increase the overall σ of mixtures with well-connected methane hydrate. Alternatively, the overall σ decreases when sand concentrations are high enough to cause gas hydrate to be poorly connected, indicating that hydrate grains provide the primary conduction path. Our measurements suggest that impurities from sand induce chemical interactions and/or doping effects that result in higher electrical conductivity with lower temperature dependence. Finally, these results can be used in the modeling of massive or two-phase gas-hydrate-bearing systems devoid of conductive pore water. Further experiments that include a free water phase are the necessary next steps toward developing complex models relevant to most natural systems.

  6. PROCEDURES FOR DERIVING EQUILIBRIUM PARTITIONING SEDIMENT BENCHMARKS (ESBS) FOR THE PROTECTION OF BENTHIC ORGANISMS: METALS MIXTURES (CADMIUM, COPPER, LEAD, NICKEL, SILVER, AND ZINC)

    EPA Science Inventory

    This equilibrium partitioning sediment benchmark (ESB) document describes procedures to derive concentrations of metal mixtures in sediment which are protective of the presence of benthic organisms. The equilibrium partitioning (EqP) approach was chosen because it accounts for t...

  7. CRITICAL BODY RESIDUES FOR FRESHWATER AND SALTWATER AMPHIPODS EXPOSED TO SEDIMENT CONTAINING A MIXTURE OF HIGH KOW PAHS

    EPA Science Inventory

    Sediments were spiked with a mixture of 13 high log Kow (5.4-6.8) PAH compounds to determine critical body residues (CBR) in Hyalella azteca and Leptocheirus plumulosus. Hyalella were exposed for 28 d in a intermittent flow test and for 10 d in a static test to compare PAH uptake...

  8. Evaluation of an extraction method for a mixture of endocrine disrupters in sediment using chemical and in vitro biological analyses.

    PubMed

    Creusot, Nicolas; Dévier, Marie-Hélène; Budzinski, Hélène; Aït-Aïssa, Selim

    2016-06-01

    Aquatic sediments are contaminated by a wide diversity of organic pollutants such as endocrine-disrupting chemicals (EDCs) which encompass a broad range of chemical classes having natural and anthropogenic origins. The use of in vitro bioassays is now widely accepted as an alternative method for their detection in complex samples. However, based on the diversity of EDC chemical properties, their common extraction is difficult and comprehensive validation of extraction methods for a bioanalysis purpose is still weakly documented. In this study, we compared the performance of several organic solvents, i.e., acetone, methanol, dichloromethane, heptane, dichloromethane/acetone (50:50, v/v), dichloromethane/methanol (50:50, v/v), heptane/acetone (50:50, v/v), and heptane/methanol (50:50, v/v), to extract a diversity of active chemicals from a spiked sediment matrix using pressurized liquid extraction. For this purpose, we defined a mixture of 12 EDCs with a wide range of polarity (2 < log Kow < 8) (i.e., estrone, 17β-estradiol, bisphenol A, o,p'DDT, 4-tert-octylphenol, fenofibrate, triphenyl phosphate, clotrimazole, PCB-126, 2,3,7,8 TCDD, benzo[k]fluoranthene, and dibenzo[a,h]anthracene). Working concentrations of each individual compound in the mixture were determined as equipotent concentrations on the basis of the concentration-addition (CA) model applied to in vitro estrogenic, dioxin-like, and pregnane X receptor (PXR)-like activities. Extraction efficiencies based on both chemical and biological analyses were assessed in triplicate in artificial blank sediment spiked with this mixture and in natural sediment contaminated by native EDCs. In both spiked and natural sediment, MeOH/DCM yields the best recovery while heptane was the least efficient solvent. Our study provided the validation of a sediment extraction methodology for EDC bioanalysis purposes, which can be used for comprehensive environmental contamination characterization. PMID:26832862

  9. Toxicity and bioaccumulation of a mixture of heavy metals in Chironomus tentans (Diptera: Chironomidae) in synthetic sediment

    SciTech Connect

    Harrahy, E.A.; Clements, W.H.

    1997-02-01

    This research investigated toxicity and bioaccumulation of a mixture of Cd, Cu, Pb, and Zn in Chironomus tentans in synthetic sediment, and compared predicted to measured steady-state bioaccumulation factors (BAFs). In a toxicity test, C. tentans were exposed to various dilutions of a base concentration (1.0 X) of a mixture of the four metals (5 {micro}g/g Cd. 10 {micro}g/g Cu. 70 {micro}g/g Pb, and 300 {micro}g/g Zn) in synthetic sediment. Mortality ranged from 17 to 100%. To measure bioaccumulation of the metals, C. tentans were exposed to 0.35 X the base concentration for a period of up to 14 d in two uptake tests. Bioaccumulation of all four metals increased over the 14-d uptake phases. Concentrations of metals in chironomids were significantly correlated with exposure time in the uptake phases. Only concentrations of copper approached background levels after 7 d depuration. Uptake rate coefficients and elimination rate constants were determined for each metal. Bioaccumulation factors were highest for Cd and lowest for Pb. With the exception of Pb, steady-state BAFs were within a factor of about two of those calculated using the first-order kinetic model. The high BAFs calculated may indicate greater bioavailability in synthetic sediment. Studies comparing toxicity and bioaccumulation of natural and synthetic sediments are necessary before the use of synthetic sediments is widely adopted.

  10. PHOTOACTIVATION AND TOXICITY OF MIXTURES OF POLYCYCLIC AROMATIC HYDROCARBON COMPOUNDS IN MARINE SEDIMENT

    EPA Science Inventory

    The direct toxicity and photoinduced toxicity of sediment-associated acenaphthene, phenanthrene, fluoranthene, and pyrene were determined for the marine amphipod Rhepoxynius abronius. The four polycyclic aromatic hydrocarbons (PAHs) were spiked into sediment in a concentration se...

  11. Laboratory experiments on dam-break flow of water-sediment mixtures

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dams induce sedimentation and store significant amounts of sediment as they age; therefore, dam failures often involve the release of sediment-laden water to the downstream floodplain. In particular, tailings dams, which are constructed to impound mining wastes, can cause devastating damage when the...

  12. Investigation of detachment and transport processes of sediment using different sand mixtures in high precision rainfall simulations

    NASA Astrophysics Data System (ADS)

    Fister, Wolfgang; Mayer, Marius; Reichle, Elisabeth; Kinnell, Peter I. A.; Kuhn, Nikolaus J.

    2016-04-01

    Detachment and transport of sediment in the landscape are controlled by many different factors. Beside environmental factors such as soil surface properties, land management and vegetation cover, the dominant ones are rainfall and surface flow characteristics. In order to be able to investigate the change of sediment properties over transport distance and time, it is, therefore, necessary to understand the basic interactions between rainfall kinetic energy and amount, particle size and density as well as flow depth and velocity. So far, the mechanistic understanding of these principal physical interactions is mostly of empirical nature, obtained either under natural, highly complex and uncontrollable conditions, or with rainfall experiments that weren't able to control the conditions with high enough precision. The aim of this study was, therefore, to fill this gap of knowledge in our mechanical process understanding by conducting rainfall experiments on different sand mixtures. In this bottom-up approach, the highly controlled experimental conditions and the use of stable sand ensured that the number of variable factors was kept to a minimum. Thus, specific relations between sand-sizes, drop kinetic energy, force of flow, and resulting erosion rates could be obtained. Although the results are very promising and could lead to a better understanding of the erosion processes in the future, they clearly show that already straightforward sand mixtures behave in a very complex way. Further experiments with simple grain mixtures are, therefore, needed before experiments on more complex, instable sediments can or should be investigated.

  13. Separation of gas mixtures using Co(II) carborane-based porous coordination polymers

    SciTech Connect

    Bae, Youn-Sang; Spokoyny, Alexander M.; Farha, Omar K.; Snurr, Randall Q.; Hupp, Joseph T.; Mirkin, Chad A.

    2010-01-01

    Separations of CO{sub 2}/CH{sub 4}, CO{sub 2}/N{sub 2}, and O{sub 2}/N{sub 2} mixtures were studied in three porous coordination polymers made of the same carborane ligand and Co(II) nodes. High selectivities for CO{sub 2} over CH{sub 4} (~47) and CO{sub 2} over N{sub 2} (~95) were obtained, especially in the material with coordinated pyridine. Unusual selectivity for O{sub 2} over N{sub 2} (as high as 6.5) was demonstrated in the materials with open Co(II) sites.

  14. Calorimetric and spectroscopic studies of solutions of copper(II) and nickel(II) nitrates in water-carbamide mixtures at 298.15 K

    NASA Astrophysics Data System (ADS)

    Vandyshev, V. N.

    2008-06-01

    The heat effects of mixing aqueous solutions of copper(II) and nickel(II) nitrates with water-carbamide mixtures were measured on an isothermic-shell calorimeter in the amide concentration region. An increase in the concentration of carbamide strengthened solvation in copper(II) salt solutions to a greater extent. The electronic absorption spectra were recorded at fixed concentrations of the electrolytes to find that the solvation of copper(II) and nickel(II) nitrates in water-carbamide mixtures involved intrasphere and predominantly outer-sphere cation-solvent interactions, respectively.

  15. Variable Field Analytical Ultracentrifugation: II. Gravitational Sweep Sedimentation Velocity.

    PubMed

    Ma, Jia; Zhao, Huaying; Sandmaier, Julia; Alexander Liddle, J; Schuck, Peter

    2016-01-01

    Sedimentation velocity (SV) analytical ultracentrifugation is a classical biophysical technique for the determination of the size-distribution of macromolecules, macromolecular complexes, and nanoparticles. SV has traditionally been carried out at a constant rotor speed, which limits the range of sedimentation coefficients that can be detected in a single experiment. Recently we have introduced methods to implement experiments with variable rotor speeds, in combination with variable field solutions to the Lamm equation, with the application to expedite the approach to sedimentation equilibrium. Here, we describe the use of variable-field sedimentation analysis to increase the size-range covered in SV experiments by ∼100-fold with a quasi-continuous increase of rotor speed during the experiment. Such a gravitational-sweep sedimentation approach has previously been shown to be very effective in the study of nanoparticles with large size ranges. In the past, diffusion processes were not accounted for, thereby posing a lower limit of particle sizes and limiting the accuracy of the size distribution. In this work, we combine variable field solutions to the Lamm equation with diffusion-deconvoluted sedimentation coefficient distributions c(s), which further extend the macromolecular size range that can be observed in a single SV experiment while maintaining accuracy and resolution. In this way, approximately five orders of magnitude of sedimentation coefficients, or eight orders of magnitude of particle mass, can be probed in a single experiment. This can be useful, for example, in the study of proteins forming large assemblies, as in fibrillation process or capsid self-assembly, in studies of the interaction between very dissimilar-sized macromolecular species, or in the study of broadly distributed nanoparticles. PMID:26745414

  16. ACUTE TOXICITY OF FIVE SEDIMENT-ASSOCIATED METALS, INDIVIDUALLY AND IN A MIXTURE, TO THE ESTUARINE MEIOBENTHIC HARPACTICOID COPEPOD AMPHIASCUS TENUIREMIS. (R825279)

    EPA Science Inventory

    Abstract

    The acute effects of many individual, seawater-solubilized metals on meiobenthic copepods and nematodes are well known. In sediments, however, metals most often occur as mixtures, and it is not known whether such mixtures exhibit simple additive toxicity to me...

  17. Abiotic U(VI) Reduction by Sorbed Fe(II) on Natural Sediments

    SciTech Connect

    Fox, Patricia M.; Davis, James A.; Kukkadapu, Ravi K.; Singer, David M.; Bargar, John R.; Williams, Kenneth H.

    2013-09-15

    Laboratory experiments were performed as a function of aqueous Fe(II) concentration to determine the uptake and oxidation of Fe(II), and Fe(II)-mediated abiotic reduction of U(VI) by aquifer sediments from the Rifle IFRC field site in Colorado, USA. Mössbauer analysis of the sediments spiked with aqueous 57Fe(II) showed that 57Fe(II) was oxidized on the mineral surfaces to 57Fe(III) and most likely formed a nano-particulate Fe(III)-oxide or ferrihydrite-like phase. The extent of 57Fe oxidation decreased with increasing 57Fe(II) uptake, such that 100 % was oxidized at 7.3 μmol/g Fe and 52 % at 39.6 μmol/g Fe, indicating that the sediments had a finite capacity for oxidation of Fe(II). Abiotic U(VI) reduction was observed by XANES spectroscopy only when the Fe(II) uptake was greater than approximately 20 μmol/g and surface-bound Fe(II) was present. The level of U(VI) reduction increased with increasing Fe(II)- loading above this level to a maximum of 18 and 36 % U(IV) at pH 7.2 (40.7 μmol/g Fe) and 8.3 (56.1 μmol/g Fe), respectively in the presence of 400 ppm CO2. Greater U(VI) reduction was observed in CO2 free systems [up to 44 and 54 % at pH 7.2 (17.3 μmol/g Fe) and 8.3 (54.8 μmol/g Fe), respectively] compared to 400 ppm CO2 systems, presumably due to differences in aqueous U(VI) speciation. While pH affects the amount of Fe(II) uptake onto the solid phase, with greater Fe(II) uptake at higher pH, similar amounts of U(VI) reduction were observed at pH 7.2 and 8.3 for a similar Fe(II) uptake. Thus, it appears that abiotic U(VI) reduction is controlled primarily by Fe(II) concentration and aqueous U(VI) speciation. The range of Fe(II) loadings tested in this study are within the range observed in bioreduced sediments, suggesting that Fe(II)-mediated abiotic U(VI) reduction may indeed play a role in field settings.

  18. Evaluating the Type II error rate in a sediment toxicity classification using the Reference Condition Approach.

    PubMed

    Rodriguez, Pilar; Maestre, Zuriñe; Martinez-Madrid, Maite; Reynoldson, Trefor B

    2011-01-17

    Sediments from 71 river sites in Northern Spain were tested using the oligochaete Tubifex tubifex (Annelida, Clitellata) chronic bioassay. 47 sediments were identified as reference primarily from macroinvertebrate community characteristics. The data for the toxicological endpoints were examined using non-metric MDS. Probability ellipses were constructed around the reference sites in multidimensional space to establish a classification for assessing test-sediments into one of three categories (Non Toxic, Potentially Toxic, and Toxic). The construction of such probability ellipses sets the Type I error rate. However, we also wished to include in the decision process for identifying pass-fail boundaries the degree of disturbance required to be detected, and the likelihood of being wrong in detecting that disturbance (i.e. the Type II error). Setting the ellipse size to use based on Type I error does not include any consideration of the probability of Type II error. To do this, the toxicological response observed in the reference sediments was manipulated by simulating different degrees of disturbance (simpacted sediments), and measuring the Type II error rate for each set of the simpacted sediments. From this procedure, the frequency at each probability ellipse of identifying impairment using sediments with known level of disturbance is quantified. Thirteen levels of disturbance and seven probability ellipses were tested. Based on the results the decision boundary for Non Toxic and Potentially Toxic was set at the 80% probability ellipse, and the boundary for Potentially Toxic and Toxic at the 95% probability ellipse. Using this approach, 9 test sediments were classified as Toxic, 2 as Potentially Toxic, and 13 as Non Toxic. PMID:20980065

  19. Viruses-to-mobile genetic elements skew in the deep Atlantis II brine pool sediments.

    PubMed

    Adel, Mustafa; Elbehery, Ali H A; Aziz, Sherry K; Aziz, Ramy K; Grossart, Hans-Peter; Siam, Rania

    2016-01-01

    The central rift of the Red Sea has 25 brine pools with different physical and geochemical characteristics. Atlantis II (ATIID), Discovery Deeps (DD) and Chain Deep (CD) are characterized by high salinity, temperature and metal content. Several studies reported microbial communities in these brine pools, but few studies addressed the brine pool sediments. Therefore, sediment cores were collected from ATIID, DD, CD brine pools and an adjacent brine-influenced site. Sixteen different lithologic sediment sections were subjected to shotgun DNA pyrosequencing to generate 1.47 billion base pairs (1.47 × 10(9) bp). We generated sediment-specific reads and attempted to annotate all reads. We report the phylogenetic and biochemical uniqueness of the deepest ATIID sulfur-rich brine pool sediments. In contrary to all other sediment sections, bacteria dominate the deepest ATIID sulfur-rich brine pool sediments. This decrease in virus-to-bacteria ratio in selected sections and depth coincided with an overrepresentation of mobile genetic elements. Skewing in the composition of viruses-to-mobile genetic elements may uniquely contribute to the distinct microbial consortium in sediments in proximity to hydrothermally active vents of the Red Sea and possibly in their surroundings, through differential horizontal gene transfer. PMID:27596223

  20. Viruses-to-mobile genetic elements skew in the deep Atlantis II brine pool sediments

    PubMed Central

    Adel, Mustafa; Elbehery, Ali H. A.; Aziz, Sherry K.; Aziz, Ramy K.; Grossart, Hans-Peter; Siam, Rania

    2016-01-01

    The central rift of the Red Sea has 25 brine pools with different physical and geochemical characteristics. Atlantis II (ATIID), Discovery Deeps (DD) and Chain Deep (CD) are characterized by high salinity, temperature and metal content. Several studies reported microbial communities in these brine pools, but few studies addressed the brine pool sediments. Therefore, sediment cores were collected from ATIID, DD, CD brine pools and an adjacent brine-influenced site. Sixteen different lithologic sediment sections were subjected to shotgun DNA pyrosequencing to generate 1.47 billion base pairs (1.47 × 109 bp). We generated sediment-specific reads and attempted to annotate all reads. We report the phylogenetic and biochemical uniqueness of the deepest ATIID sulfur-rich brine pool sediments. In contrary to all other sediment sections, bacteria dominate the deepest ATIID sulfur-rich brine pool sediments. This decrease in virus-to-bacteria ratio in selected sections and depth coincided with an overrepresentation of mobile genetic elements. Skewing in the composition of viruses-to-mobile genetic elements may uniquely contribute to the distinct microbial consortium in sediments in proximity to hydrothermally active vents of the Red Sea and possibly in their surroundings, through differential horizontal gene transfer. PMID:27596223

  1. Abiotic U(VI) reduction by sorbed Fe(II) on natural sediments

    NASA Astrophysics Data System (ADS)

    Fox, Patricia M.; Davis, James A.; Kukkadapu, Ravi; Singer, David M.; Bargar, John; Williams, Kenneth H.

    2013-09-01

    Laboratory experiments were performed as a function of aqueous Fe(II) concentration to determine the uptake and oxidation of Fe(II), and Fe(II)-mediated abiotic reduction of U(VI) by aquifer sediments from the DOE Rifle field research site in Colorado, USA. Mössbauer analysis of the sediments spiked with aqueous 57Fe(II) showed that 57Fe(II) was oxidized on the mineral surfaces to 57Fe(III) and most likely formed a nano-particulate Fe(III)-oxide or ferrihydrite-like phase. The extent of 57Fe oxidation decreased with increasing 57Fe(II) uptake, such that 98% was oxidized at 7.3 μmol/g Fe and 41% at 39.6 μmol/g Fe, indicating that the sediments had a limited capacity for oxidation of Fe(II). Abiotic U(VI) reduction was observed by XANES spectroscopy only when the Fe(II) uptake was greater than approximately 20 μmol/g and surface-bound Fe(II) was present, possibly as oligomeric Fe(II) surface species. The degree of U(VI) reduction increased with increasing Fe(II)-loading above this level to a maximum of 18% and 36% U(IV) at pH 7.2 (40.7 μmol/g Fe) and 8.3 (56.1 μmol/g Fe), respectively in the presence of 400 ppm CO2. Greater U(VI) reduction was observed in CO2-free systems [up to 44% and 54% at pH 7.2 (17.3 μmol/g Fe) and 8.3 (54.8 μmol/g Fe), respectively] compared to 400 ppm CO2 systems, presumably due to differences in aqueous U(VI) speciation. While pH affects the amount of Fe(II) uptake onto the solid phase, with greater Fe(II) uptake at higher pH, similar amounts of U(VI) reduction were observed at pH 7.2 and 8.3 for a similar Fe(II) uptake. Thus, it appears that abiotic U(VI) reduction is controlled primarily by sorbed Fe(II) concentration and aqueous U(VI) speciation. The range of Fe(II) loadings tested in this study are within the range observed in biostimulation experiments at the Rifle site, suggesting that Fe(II)-mediated abiotic U(VI) reduction could play a significant role in field settings.

  2. Developmental toxicity of PAH mixtures in fish early life stages. Part II: adverse effects in Japanese medaka.

    PubMed

    Le Bihanic, Florane; Clérandeau, Christelle; Le Menach, Karyn; Morin, Bénédicte; Budzinski, Hélène; Cousin, Xavier; Cachot, Jérôme

    2014-12-01

    In aquatic environments, polycyclic aromatic hydrocarbons (PAHs) mostly occur as complex mixtures, for which risk assessment remains problematic. To better understand the effects of PAH mixture toxicity on fish early life stages, this study compared the developmental toxicity of three PAH complex mixtures. These mixtures were extracted from a PAH-contaminated sediment (Seine estuary, France) and two oils (Arabian Light and Erika). For each fraction, artificial sediment was spiked at three different environmental concentrations roughly equivalent to 0.5, 4, and 10 μg total PAH g(-1) dw. Japanese medaka embryos were incubated on these PAH-spiked sediments throughout their development, right up until hatching. Several endpoints were recorded at different developmental stages, including acute endpoints, morphological abnormalities, larvae locomotion, and genotoxicity (comet and micronucleus assays). The three PAH fractions delayed hatching, induced developmental abnormalities, disrupted larvae swimming activity, and damaged DNA at environmental concentrations. Differences in toxicity levels, likely related to differences in PAH proportions, were highlighted between fractions. The Arabian Light and Erika petrogenic fractions, containing a high proportion of alkylated PAHs and low molecular weight PAHs, were more toxic to Japanese medaka early life stages than the pyrolytic fraction. This was not supported by the toxic equivalency approach, which appeared unsuitable for assessing the toxicity of the three PAH fractions to fish early life stages. This study highlights the potential risks posed by environmental mixtures of alkylated and low molecular weight PAHs to early stages of fish development. PMID:24595754

  3. Evidence for dose-additive effects of a type II pyrethroid mixture. In vitro assessment.

    PubMed

    Romero, A; Ares, I; Ramos, E; Castellano, V; Martínez, M; Martínez-Larrañaga, M R; Anadón, A; Martínez, M A

    2015-04-01

    Despite the widespread use of pyrethroid insecticides that led to common exposure in the population, few studies have been conducted to quantitatively assess dose-additive effects of pyrethroids using a funcional measure involved in the common toxic mode of action. The aim of this study was to evaluate the potency and efficacy of 6 Type II pyretroids (α-cypermethrin, cyfluthrin, λ-cyhalothrin, deltamethrin, cyphenothrin and esfenvalerate) to evoke induction of both nitric oxide and lipid peroxides levels measured as malondialdehyde in three in vitro models (SH-SY5Y, HepG2 and Caco-2 human cells) as well as to test the hypothesis of dose additivity for mixtures of these same 6 pyrethroids. Concentration-responses for 6 pyrethroids were determined as well as the response to mixtures of all 6 pyrethroids. Additivity was tested assuming a dose-additive model. The human neuroblastoma SH-SY5Y cell line was the most sensitive in vitro model. The rank order of potency for cell SH-SY5Y viability MTT assay was deltamethrin>cyphenothrin>λ-cyhalothrin>cyfluthrin>esfenvalerate>α-cypermethrin. When 6 pyrethroids were present in the mixture at an equitoxic mixing ratio, the action on nitric oxide (NO) and lipid peroxides measured as malondialdehyde (MDA) production was consistent with a dose-additive model. The results of the present study are consistent with previous reports of additivity of pyrethroids in vivo e in vitro. PMID:25688004

  4. Low temperature hydrothermal maturation of organic matter in sediments from the Atlantis II Deep, Red Sea

    NASA Technical Reports Server (NTRS)

    Simoneit, Bernd R. T.; Grimalt, Joan O.; Hayes, J. M.; Hartman, Hyman

    1987-01-01

    Hydrocarbons and bulk organic matter of two sediment cores within the Atlantis II Deep are analyzed, and microbial inputs and minor terrestrial sources are found to represent the major sedimentary organic material. Results show that extensive acid-catalyzed reactions are occurring in the sediments, and the Atlantis II Deep is found to exhibit a lower degree of thermal maturation than other hydrothermal or intrusive systems. The lack of carbon number preference noted among the n-alkanes suggests that the organic matter of these sediments has undergone some degree of catagenesis, though yields of hydrocarbons are much lower than those found in other hydrothermal areas, probably due to the effect of lower temperature and poor source-rock characteristics.

  5. Manganese(II)-Oxidizing Bacillus Spores in Guaymas Basin Hydrothermal Sediments and Plumes

    PubMed Central

    Dick, Gregory J.; Lee, Yifan E.; Tebo, Bradley M.

    2006-01-01

    Microbial oxidation and precipitation of manganese at deep-sea hydrothermal vents are important oceanic biogeochemical processes, yet nothing is known about the types of microorganisms or mechanisms involved. Here we report isolation of a number of diverse spore-forming Mn(II)-oxidizing Bacillus species from Guaymas Basin, a deep-sea hydrothermal vent environment in the Gulf of California, where rapid microbially mediated Mn(II) oxidation was previously observed. mnxG multicopper oxidase genes involved in Mn(II) oxidation were amplified from all Mn(II)-oxidizing Bacillus spores isolated, suggesting that a copper-mediated mechanism of Mn(II) oxidation could be important at deep-sea hydrothermal vents. Phylogenetic analysis of 16S rRNA and mnxG genes revealed that while many of the deep-sea Mn(II)-oxidizing Bacillus species are very closely related to previously recognized isolates from coastal sediments, other organisms represent novel strains and clusters. The growth and Mn(II) oxidation properties of these Bacillus species suggest that in hydrothermal sediments they are likely present as spores that are active in oxidizing Mn(II) as it emerges from the seafloor. PMID:16672456

  6. The structures of the crystalline phase and columnar mesophase of rhodium (II) heptanoate and of its binary mixture with copper (II) heptanoate probed by EXAFS

    NASA Astrophysics Data System (ADS)

    Inb-Elhaj, M.; Guillon, D.; Skoulios, A.; Maldivi, P.; Giroud-Godquin, A. M.; Marchon, J.-C.

    1992-12-01

    EXAFS was used to investigate the local structure of the polar spines of rhodium (II) soaps in the columnar liquid crystalline state. It was also used to ascertain the degree of blending of the cores in binary mixtures of rhodium (II) and copper (II) soaps. For the pure rhodium soaps, the columns are shown to result from the stacking of binuclear metal-metal bonded dirhodium tetracarboxylate units bonded to one another by apical ligation of the metal atom of each complex with one of the oxygen atoms of the adjacent molecule. Mixtures of rhodium (II) and copper (II) soaps give a hexagonal columnar mesophase in which pure rhodium and pure copper columns are randomly distributed.

  7. Reduction of TcO4- by sediment-associated biogenic Fe(II)

    SciTech Connect

    Fredrickson, Jim K.; Zachara, John M.; Kennedy, David W.; Kukkadapu, Ravi K.; McKinley, James P.; Heald, Steve M.; Liu, Chongxuan; Plymale, Andrew E.

    2004-08-01

    The potential for reduction of {sup 99}TcO{sub 4}{sup -}{sub aq} to poorly soluble {sup 99}TcO{sub 2} {center_dot} nH{sub 2}O{sub (s)} by biogenic sediment-associated Fe(II) was investigated with three Fe(III)-oxide containing subsurface materials and the dissimilatory metal-reducing subsurface bacterium Shewanella putrefaciens CN32. Two of the subsurface materials from the U.S. Department of Energy's Hanford and Oak Ridge sites contained significant amounts of Mn(III,IV) oxides and net bioreduction of Fe(III) to Fe(II) was not observed until essentially all of the hydroxylamine HCl-extractable Mn was reduced. In anoxic, unreduced sediment or where Mn oxide bioreduction was incomplete, exogenous biogenic TcO{sub 2} {center_dot} nH{sub 2}O{sub (s)} was slowly oxidized over a period of weeks. Subsurface materials that were bioreduced to varying degrees and then pasteurized to eliminate biological activity, reduced TcO{sub 4}{sup -}{sub (aq)} at rates that generally increased with increasing concentrations of 0.5 N HCl-extractable Fe(II). Two of the sediments showed a common relationship between extractable Fe(II) concentration (in mM) and the first-order reduction rate (in h{sup -1}), whereas the third demonstrated a markedly different trend. A combination of chemical extractions and {sup 57}Fe Moessbauer spectroscopy were used to characterize the Fe(III) and Fe(II) phases. There was little evidence of the formation of secondary Fe(II) biominerals as a result of bioreduction, suggesting that the reactive forms of Fe(II) were predominantly surface complexes of different forms. The reduction rates of Tc(VII)O{sub 4}{sup -} were slowest in the sediment that contained plentiful layer silicates (illite, vermiculite, and smectite), suggesting that Fe(II) sorption complexes on these phases were least reactive toward pertechnetate. These results suggest that the in situ microbial reduction of sediment-associated Fe(III), either naturally or via redox manipulation, may be

  8. Reduction of TcO 4- by sediment-associated biogenic Fe(II)

    NASA Astrophysics Data System (ADS)

    Fredrickson, James K.; Zachara, John M.; Kennedy, David W.; Kukkadapu, Ravi K.; McKinley, James P.; Heald, Steve M.; Liu, Chongxuan; Plymale, Andrew E.

    2004-08-01

    The potential for reduction of 99TcO 4-(aq) to poorly soluble 99TcO 2 · nH 2O (s) by biogenic sediment-associated Fe(II) was investigated with three Fe(III)-oxide containing subsurface materials and the dissimilatory metal-reducing subsurface bacterium Shewanella putrefaciens CN32. Two of the subsurface materials from the U.S. Department of Energy's Hanford and Oak Ridge sites contained significant amounts of Mn(III,IV) oxides and net bioreduction of Fe(III) to Fe(II) was not observed until essentially all of the hydroxylamine HCl-extractable Mn was reduced. In anoxic, unreduced sediment or where Mn oxide bioreduction was incomplete, exogenous biogenic TcO 2 · nH 2O (s) was slowly oxidized over a period of weeks. Subsurface materials that were bioreduced to varying degrees and then pasteurized to eliminate biological activity, reduced TcO 4-(aq) at rates that generally increased with increasing concentrations of 0.5 N HCl-extractable Fe(II). Two of the sediments showed a common relationship between extractable Fe(II) concentration (in mM) and the first-order reduction rate (in h -1), whereas the third demonstrated a markedly different trend. A combination of chemical extractions and 57Fe Mössbauer spectroscopy were used to characterize the Fe(III) and Fe(II) phases. There was little evidence of the formation of secondary Fe(II) biominerals as a result of bioreduction, suggesting that the reactive forms of Fe(II) were predominantly surface complexes of different forms. The reduction rates of Tc(VII)O 4- were slowest in the sediment that contained plentiful layer silicates (illite, vermiculite, and smectite), suggesting that Fe(II) sorption complexes on these phases were least reactive toward pertechnetate. These results suggest that the in situ microbial reduction of sediment-associated Fe(III), either naturally or via redox manipulation, may be effective at immobilizing TcO 4-(aq) associated with groundwater contaminant plumes.

  9. Desorption of organochlorine pesticides from historically contaminated sediments into water-biofuel mixtures

    NASA Astrophysics Data System (ADS)

    Otero-Diaz, M.; Demond, A. H.

    2014-12-01

    Gasoline spills in surface waters generally volatilize due to their low miscibility and high volatility. However, biofuel blends may contain ethanol, a compound completely miscible in water. As hazardous components of gasoline are more soluble in ethanol than in water, the presence of ethanol increases the solubilization of these components, such as benzene, toluene, ethylbenzene, and xylenes (BTEX), in surface water. Furthermore, many of these spills may occur in water bodies that have sediments that are historically contaminated with persistent organic contaminants such as organochlorine pesticides. High concentrations of ethanol in the water column, along with solubilized components of gasoline, may increase the desorption of organochlorine pesticides from the sediment. Thus spills of ethanol/gasoline fuel blends have the potential of increasing concentrations of hazardous compounds in rivers and lakes, resulting in increased risk for human and ecological exposure. Using UNIFAC to calculate activity coefficients, one can predict the enhancement of the solubility of pesticides in the aqueous phase as the ethanol fraction increases. Moreover, by predicting the solubility of pesticides in both the aqueous phase and an organic liquid phase, one can construct ternary phase diagrams that show the partitioning behavior of pesticides as a function of ethanol fraction. Such information is useful in estimating the amount of desorption from contaminated sediments that may occur in the presence of biofuel spills. In order to confirm the predicted values, experiments have been conducted to measure the impact of ethanol on the partitioning coefficients of pesticides.

  10. Surface complexation modeling of Cu(II) adsorption on mixtures of hydrous ferric oxide and kaolinite

    PubMed Central

    Lund, Tracy J; Koretsky, Carla M; Landry, Christopher J; Schaller, Melinda S; Das, Soumya

    2008-01-01

    Background The application of surface complexation models (SCMs) to natural sediments and soils is hindered by a lack of consistent models and data for large suites of metals and minerals of interest. Furthermore, the surface complexation approach has mostly been developed and tested for single solid systems. Few studies have extended the SCM approach to systems containing multiple solids. Results Cu adsorption was measured on pure hydrous ferric oxide (HFO), pure kaolinite (from two sources) and in systems containing mixtures of HFO and kaolinite over a wide range of pH, ionic strength, sorbate/sorbent ratios and, for the mixed solid systems, using a range of kaolinite/HFO ratios. Cu adsorption data measured for the HFO and kaolinite systems was used to derive diffuse layer surface complexation models (DLMs) describing Cu adsorption. Cu adsorption on HFO is reasonably well described using a 1-site or 2-site DLM. Adsorption of Cu on kaolinite could be described using a simple 1-site DLM with formation of a monodentate Cu complex on a variable charge surface site. However, for consistency with models derived for weaker sorbing cations, a 2-site DLM with a variable charge and a permanent charge site was also developed. Conclusion Component additivity predictions of speciation in mixed mineral systems based on DLM parameters derived for the pure mineral systems were in good agreement with measured data. Discrepancies between the model predictions and measured data were similar to those observed for the calibrated pure mineral systems. The results suggest that quantifying specific interactions between HFO and kaolinite in speciation models may not be necessary. However, before the component additivity approach can be applied to natural sediments and soils, the effects of aging must be further studied and methods must be developed to estimate reactive surface areas of solid constituents in natural samples. PMID:18783619

  11. Crystallization of the oxygen-evolving reaction centre of photosystem II in nine different detergent mixtures.

    PubMed

    Adir, N

    1999-04-01

    Oxygen-evolving photosystem II reaction centres (RCII) isolated from both spinach and pea have been crystallized. A single crystal form grew from RCII monomers in the presence of nine different three-component mixtures of non-ionic detergents and heptane-1,2, 3-triol. The crystals grew as hexagonal rods with dimensions of up to 1 x 0.3 x 0.3 mm. The crystals diffracted to a maximum resolution of 6.5 A and belong to a hexagonal space group with unit-cell parameters a = 495, b = 495, c = 115 A, alpha = beta = 90, gamma = 120 degrees. The growth of a single crystal form in the presence of such a large variety of detergents suggests a very limited range of crystal lattice formation sites in the RCII complex. PMID:10089326

  12. Transformation of PBDE mixtures during sediment transport and resuspension in marine environments (Gulf of Lion, NW Mediterranean Sea).

    PubMed

    Salvadó, Joan A; Grimalt, Joan O; López, Jordi F; Durrieu de Madron, Xavier; Heussner, Serge; Canals, Miquel

    2012-09-01

    Polybromodiphenyl ethers (PBDEs) in superficial sediments from the Gulf of Lion were studied. They were largely predominated by BDE 209 (98.7% of all PBDEs) indicating that the main source of these pollutants was the commercial mixture deca-BDE. This compound and the less brominated BDE exhibited a southwestward decreasing concentration gradient following the dominant marine currents and bottom relief, e.g. the Mud Belt, the submarine canyons and the Open Continental Slope. All PBDEs exhibited statistically significant correlations confirming the common origin. However, a progressive transformation of the dumped BDE 209 was identified showing a depletion paralleled by increases of the less brominated BDEs (from 8.6% to 22%). These less brominated compounds were accumulated at about 100-140 km away from the Rhone prodelta, e.g., at the end of the submarine canyons, evidencing that these transformation compounds can be accumulated at long distances from the dumping sites in the marine system. PMID:22595764

  13. Network-scale dynamics of sediment mixtures: how do tectonics affect surface bed texture and channel slope?

    NASA Astrophysics Data System (ADS)

    Gasparini, N. M.; Bras, R. L.; Tucker, G. E.

    2003-04-01

    An alluvial channel's slope and bed texture are intimately linked. Along with fluvial discharge, these variables are the key players in setting alluvial transport rates. We know that both channel slope and mean grain size usually decrease downstream, but how sensitive are these variables to tectonic changes? Are basin concavity and downstream fining drastically disrupted during transitions from one tectonic regime to another? We explore these questions using the CHILD numerical landscape evolution model to generate alluvial networks composed of a sand and gravel mixture. The steady-state and transient patterns of both channel slope and sediment texture are investigated. The steady-state patterns in slope and sediment texture are verified independently by solving the erosion equations under equilibrium conditions, i.e. the case when the erosion rate is equal to the uplift rate across the entire landscape. The inclusion of surface texture as a free parameter (as opposed to just channel slope) leads to some surprising results. In all cases, an increase in uplift rate results in channel beds which are finer at equilibrium (for a given drainage area). Higher uplift rates imply larger equilibrium transport rates; this leads to finer channels that have a smaller critical shear stress to entrain material, and therefore more material can be transported for a given discharge (and channel slope). Changes in equilibrium slopes are less intuitive. An increase in uplift rates can cause channel slopes to increase, remain the same, or decrease, depending on model parameter values. In the surprising case in which equilibrium channel slopes decrease with increasing uplift rates, we suggest that surface texture changes more than compensate for the required increase in transport rates, causing channel slopes to decrease. These results highlight the important role of sediment grain size in determining transport rates and caution us against ignoring this important variable in fluvial

  14. Effect of fluoride, chloride, bromide, and thiocynate on potentiometric titrations of iron(II)-tin(II) mixtures with cerium(IV)

    SciTech Connect

    Kwok, Y.M.

    1980-07-31

    A two-step curve is expected in the potentiometric titration of Fe(II)-Sn(II) mixtures with Ce(IV) in H/sub 2/SO/sub 4/. Each end point should indicate the respective oxidation of Sn(II) and Fe(II). However, experimentally only one end point was found; it corresponded to the total oxidation of Sn(II) and Fe(II). When this oxidation-reduction reaction was carried out in the presence of Cl/sup -/, the theoretical behavior was observed. The present study was done to ascertain if monovalent anions other than Cl/sup -/ have a similar effect on this oxidation-reduction system. The monovalent species F/sup -/, Br/sup -/, and SCN/sup -/ were selected for this study, and the results indicate that each affects the rate of reaction relative to the ease of oxidation of the individual ions.

  15. [Molluscacide activity of a mixture of 6-n-alkyl salicylic acids (anacardic acid) and 2 of its complexes with copper (II) and lead (II)].

    PubMed

    Mendes, N M; de Oliveira, A B; Guimarães, J E; Pereira, J P; Katz, N

    1990-01-01

    The molluscicide activity of hexanic extract from Anacardium occidentale L. (cashew) nut shell, of copper (II) complex, of lead (II) complex and anacardic acid has been compared in the laboratory in an attempt to obtain better stability than anacardic acid. This was obtained from the hexanic extract of the cashew nut shell by precipitation with lead (II) hydroxide or cupric sulfate plus sodium hydroxide or (II) cupric hydroxide followed by treatment of lead (II) complex with a diluted solution of sulfuric acid. Ten products of the mixture obtained were tested on adults snails of Biomphalaria glabrata at 1 to 10 ppm. The most active products were copper (II) complex, obtained by cupric sulfate plus sodium hydroxide, and anacardic acid (sodium hydroxide) which presented activity at 4 ppm. The anacardic acid's lead content was above the limits accepted by the United States standards. PMID:2133588

  16. Slow desorption mechanisms of volatile organic chemical mixtures in soil and sediment micropores.

    PubMed

    Li, Jun; Werth, Charles J

    2004-01-15

    Desorption profiles of trichloroethylene (TCE), tetrachloroethylene (PCE), and a TCE-PCE mixture were measured for three natural solids and four zeolites. Initial sorbed mass (Mi) in slow desorbing sites of natural solids and in micropores of zeolites were obtained from desorption profiles. In natural solids, Mi increases with recalcitrant organic matter content. In zeolites, Mi generally increases with decreasing micropore width and increasing micropore hydrophobicity, but the effect of hydrophobicity is stronger. In both natural solids and zeolites, competition between TCE and PCE causes Mi for each sorbate in the mixture to be less than or similar to that for each sorbate alone. Zeolite results indicate that micropore width affects this competition more than micropore hydrophobicity for the solids examined. Desorption in all solids was simulated with the radial diffusion model, either alone or coupled with the advection-dispersion equation when necessary; diffusion rate constants (D/R2) were obtained. In natural solids, mean values of D/R2 increase with decreasing recalcitrant organic matter content. In zeolites, values of D/R2 generally increase with increasing micropore width, while they are a weak function of hydrophobicity. In both natural solids and zeolites, competition between TCE and PCE causes D/R2 for each sorbate in the mixture to generally be larger than that for each sorbate alone. Zeolite results indicate that the effects of competition on D/R2 generally decrease with decreasing micropore width for the solids examined; a trend with micropore hydrophobicity is not apparent. For the three natural solids and four zeolites examined in this study, the similar effects of competition between TCE and PCE on values of Mi and D/R2 and the overlapping range of D/R2 values support the hypothesis that diffusion through hydrophobic micropores affects and may control slow mass transfer processes in the recalcitrant organic matter of natural solids. These results

  17. Microbial Iron(II) Oxidation in Littoral Freshwater Lake Sediment: The Potential for Competition between Phototrophic vs. Nitrate-Reducing Iron(II)-Oxidizers

    PubMed Central

    Melton, E. D.; Schmidt, C.; Kappler, A.

    2012-01-01

    The distribution of neutrophilic microbial iron oxidation is mainly determined by local gradients of oxygen, light, nitrate and ferrous iron. In the anoxic top part of littoral freshwater lake sediment, nitrate-reducing and phototrophic Fe(II)-oxidizers compete for the same e− donor; reduced iron. It is not yet understood how these microbes co-exist in the sediment and what role they play in the Fe cycle. We show that both metabolic types of anaerobic Fe(II)-oxidizing microorganisms are present in the same sediment layer directly beneath the oxic-anoxic sediment interface. The photoferrotrophic most probable number counted 3.4·105 cells·g−1 and the autotrophic and mixotrophic nitrate-reducing Fe(II)-oxidizers totaled 1.8·104 and 4.5·104 cells·g−1 dry weight sediment, respectively. To distinguish between the two microbial Fe(II) oxidation processes and assess their individual contribution to the sedimentary Fe cycle, littoral lake sediment was incubated in microcosm experiments. Nitrate-reducing Fe(II)-oxidizing bacteria exhibited a higher maximum Fe(II) oxidation rate per cell, in both pure cultures and microcosms, than photoferrotrophs. In microcosms, photoferrotrophs instantly started oxidizing Fe(II), whilst nitrate-reducing Fe(II)-oxidizers showed a significant lag-phase during which they probably use organics as e− donor before initiating Fe(II) oxidation. This suggests that they will be outcompeted by phototrophic Fe(II)-oxidizers during optimal light conditions; as phototrophs deplete Fe(II) before nitrate-reducing Fe(II)-oxidizers start Fe(II) oxidation. Thus, the co-existence of the two anaerobic Fe(II)-oxidizers may be possible due to a niche space separation in time by the day-night cycle, where nitrate-reducing Fe(II)-oxidizers oxidize Fe(II) during darkness and phototrophs play a dominant role in Fe(II) oxidation during daylight. Furthermore, metabolic flexibility of Fe(II)-oxidizing microbes may play a paramount role in the

  18. RESIS-II: An Updated Version of the Original Reservoir Sedimentation Survey Information System (RESIS) Database

    USGS Publications Warehouse

    Ackerman, Katherine V.; Mixon, David M.; Sundquist, Eric T.; Stallard, Robert F.; Schwarz, Gregory E.; Stewart, David W.

    2009-01-01

    The Reservoir Sedimentation Survey Information System (RESIS) database, originally compiled by the Soil Conservation Service (now the Natural Resources Conservation Service) in collaboration with the Texas Agricultural Experiment Station, is the most comprehensive compilation of data from reservoir sedimentation surveys throughout the conterminous United States (U.S.). The database is a cumulative historical archive that includes data from as early as 1755 and as late as 1993. The 1,823 reservoirs included in the database range in size from farm ponds to the largest U.S. reservoirs (such as Lake Mead). Results from 6,617 bathymetric surveys are available in the database. This Data Series provides an improved version of the original RESIS database, termed RESIS-II, and a report describing RESIS-II. The RESIS-II relational database is stored in Microsoft Access and includes more precise location coordinates for most of the reservoirs than the original database but excludes information on reservoir ownership. RESIS-II is anticipated to be a template for further improvements in the database.

  19. Isotopic studies of epigenetic features in metalliferous sediment, Atlantis II Deep, Red Sea

    USGS Publications Warehouse

    Zierenberg, Robert A.; Shanks, Wayne C., III

    1988-01-01

    The unique depositional environment of the Atlantis II Deep brine pool in the Red Sea produces a stratiform metalliferous deposit of greater areal extent than deposits formed by buoyant-plume systems typical of the midocean ridges because of much more efficient metal entrapment. Isotopic analyses of strontium, sulfur, carbon, and oxygen from the metalliferous sediments indicate that three major sources contribute dissolved components to the hydrothermal system: seawater, Miocene evaporites, and rift-zone basalt. An areally restricted magnetite-hematite-pyroxene assemblage formed at high temperatures, possibly in response to hydrothermal convection initiated by intrusion of basalt into the metalliferous sediment. A correlation between smectite Fe/(Fe+Mg) ratios and oxygen isotope temperatures suggests that smectite is a potentially important chemical geothermometer, and confirms geochemical calculations indicating that Mg-rich smectite is more stable than Fe-rich smectite at elevated temperatures.

  20. Availability of polycyclic aromatic hydrocarbons to earthworms (Eisenia andrei, Oligochaeta) in field-polluted soils and soil-sediment mixtures.

    PubMed

    Jager, Tjalling; Baerselman, Rob; Dijkman, Ellen; de Groot, Arthur C; Hogendoorn, Elbert A; de Jong, Ad; Kruitbosch, Jantien A W; Peijnenburg, Willie J G M

    2003-04-01

    The bioavailability of polycyclic aromatic hydrocarbons (PAHs) for earthworms (Eisenia andrei) was experimentally determined in seven field-polluted soils and 15 soil-sediment mixtures. The pore-water concentration of most PAHs was higher than predicted. However, most of the compound was associated with dissolved organic carbon (DOC) and not directly available for uptake by earthworms. The apparent sorption could be reasonably predicted on the basis of interactions with DOC; however, the biota-soil accumulation factors (BSAFs) for earthworms were up to two orders of magnitude lower than predicted by equilibrium partitioning. The large variability between sites was not fully explained by differences in sorption. Experimental results indicate that the pool of freely dissolved PAHs in the pore water became partially depleted because of uptake by the earthworms and that bioaccumulation is thus also influenced by the kinetics of PAH desorption and mass transport. A pilot study with Lumbricus rubellus showed that steady-state body residues were well correlated to E. andrei. Current results show that depositing dredge spoil on land may lead to increased bioavailability of the lower-molecular-weight PAHs. However, risk assessment can conservatively rely on equilibrium partitioning, but accurate prediction requires quantification of the kinetics of bioavailability. PMID:12685711

  1. DEVELOPMENT AND AVAILABILITY OF EQUILIBRIUM PARTITIONING SEDIMENT GUIDELINES (ESGS) FOR NONIONIC ORGANIC CONTAMINANTS, METALS MIXTURES, AND POLYCYCLIC AROMATIC HYDROCARBON (PAH) MIXTURES

    EPA Science Inventory

    Collaborative efforts between EPA's Office of Water and Office of Research and Development have resulted in the development of sediment guidelines based on equilibrium partitioning theory (EqP). The guidance available includes a technical support document, describing the derivat...

  2. Sedimentation of a two-dimensional colloidal mixture exhibiting liquid-liquid and gas-liquid phase separation: a dynamical density functional theory study.

    PubMed

    Malijevský, Alexandr; Archer, Andrew J

    2013-10-14

    We present dynamical density functional theory results for the time evolution of the density distribution of a sedimenting model two-dimensional binary mixture of colloids. The interplay between the bulk phase behaviour of the mixture, its interfacial properties at the confining walls, and the gravitational field gives rise to a rich variety of equilibrium and non-equilibrium morphologies. In the fluid state, the system exhibits both liquid-liquid and gas-liquid phase separation. As the system sediments, the phase separation significantly affects the dynamics and we explore situations where the final state is a coexistence of up to three different phases. Solving the dynamical equations in two-dimensions, we find that in certain situations the final density profiles of the two species have a symmetry that is different from that of the external potentials, which is perhaps surprising, given the statistical mechanics origin of the theory. The paper concludes with a discussion on this. PMID:24116640

  3. How Grain Size Ratio and Fine Sediment Feed Concentration Influence Channel Slope Evolution Due to Grain Size Sorting in Bimodal Mixtures

    NASA Astrophysics Data System (ADS)

    Dudill, A. R.; Frey, P.; Church, M. A.; Hassan, M. A.

    2014-12-01

    It is essential that understanding of grain size sorting and its influence upon sediment transport in gravel-bed rivers is deepened due to implications for channel stability, ecology and stratigraphy. Previous work has shown how the addition of finer material to a coarse channel bed can enhance the mobility of the coarser sediment due to a reduced entrainment threshold. This enhanced mobility has been indexed using the change in equilibrium slope within the channel. However, it is not yet known how variations in the grain size ratio (diameter of coarse/diameter of fine), along with the concentration of fine material, influences this behavior. New experiments undertaken with bimodal mixtures of spherical glass particles in a relatively narrow sediment-feed flume permit observation of the individual and bulk particle motion. These experiments demonstrate that degradation can occur when fine sediment is added to a coarse bed (Figure 1), and show the grain size ratios and fine sediment feed concentrations at which this arises. The research also shows that under certain conditions, aggradation can also occur due to the addition of finer sediment to a coarse channel bed. The amount of degradation and aggradation under varying conditions is quantified using the change in equilibrium bed slope. Figure 1: Channel degradation (flow from right to left)

  4. Sediment Toxicity Identification and Evaluation (TIE) Phases I, II and III Guidance Document

    EPA Science Inventory

    This presentation summarizes the sediment toxicity identification evaluation (TIE) techniques that allow researchers to characterize and identify chemical causes of acute toxicity in sediments that can be applied using the 10-d solid-phase sediment toxicity tests.

  5. New insights into the mineralogy of the Atlantis II Deep metalliferous sediments, Red Sea

    NASA Astrophysics Data System (ADS)

    Laurila, Tea E.; Hannington, Mark D.; Leybourne, Matthew; Petersen, Sven; Devey, Colin W.; Garbe-Schönberg, Dieter

    2015-12-01

    The Atlantis II Deep of the Red Sea hosts the largest known hydrothermal ore deposit on the ocean floor and the only modern analog of brine pool-type metal deposition. The deposit consists mainly of chemical-clastic sediments with input from basin-scale hydrothermal and detrital sources. A characteristic feature is the millimeter-scale layering of the sediments, which bears a strong resemblance to banded iron formation (BIF). Quantitative assessment of the mineralogy based on relogging of archived cores, detailed petrography, and sequential leaching experiments shows that Fe-(oxy)hydroxides, hydrothermal carbonates, sulfides, and authigenic clays are the main "ore" minerals. Mn-oxides were mainly deposited when the brine pool was more oxidized than it is today, but detailed logging shows that Fe-deposition and Mn-deposition also alternated at the scale of individual laminae, reflecting short-term fluctuations in the Lower Brine. Previous studies underestimated the importance of nonsulfide metal-bearing components, which formed by metal adsorption onto poorly crystalline Si-Fe-OOH particles. During diagenesis, the crystallinity of all phases increased, and the fine layering of the sediment was enhanced. Within a few meters of burial (corresponding to a few thousand years of deposition), biogenic (Ca)-carbonate was dissolved, manganosiderite formed, and metals originally in poorly crystalline phases or in pore water were incorporated into diagenetic sulfides, clays, and Fe-oxides. Permeable layers with abundant radiolarian tests were the focus for late-stage hydrothermal alteration and replacement, including deposition of amorphous silica and enrichment in elements such as Ba and Au.

  6. Mycobacterial Lipid II Is Composed of a Complex Mixture of Modified Muramyl and Peptide Moieties Linked to Decaprenyl Phosphate†

    PubMed Central

    Mahapatra, Sebabrata; Yagi, Tetsuya; Belisle, John T.; Espinosa, Benjamin J.; Hill, Preston J.; McNeil, Michael R.; Brennan, Patrick J.; Crick, Dean C.

    2005-01-01

    Structural analysis of compounds identified as lipid I and II from Mycobacterium smegmatis demonstrated that the lipid moiety is decaprenyl phosphate; thus, M. smegmatis is the first bacterium reported to utilize a prenyl phosphate other than undecaprenyl phosphate as the lipid carrier involved in peptidoglycan synthesis. In addition, mass spectrometry showed that the muropeptides from lipid I are predominantly N-acetylmuramyl-l-alanine-d-glutamate-meso-diaminopimelic acid-d-alanyl-d-alanine, whereas those isolated from lipid II form an unexpectedly complex mixture in which the muramyl residue and the pentapeptide are modified singly and in combination. The muramyl residue is present as N-acetylmuramic acid, N-glycolylmuramic acid, and muramic acid. The carboxylic functions of the peptide side-chains of lipid II showed three types of modification, with the dominant one being amidation. The preferred site for amidation is the free carboxyl group of the meso-diaminopimelic acid residue. Diamidated species were also observed. The carboxylic function of the terminal d-alanine of some molecules is methylated, as are all three carboxylic acid functions of other molecules. This study represents the first structural analysis of mycobacterial lipid I and II and the first report of extensive modifications of these molecules. The observation that lipid I was unmodified strongly suggests that the lipid II intermediates of M. smegmatis are substrates for a variety of enzymes that introduce modifications to the sugar and amino acid residues prior to the synthesis of peptidoglycan. PMID:15805521

  7. A nifedipine coground mixture with sodium deoxycholate. II. Dissolution characteristics and stability.

    PubMed

    Suzuki, H; Ogawa, M; Hironaka, K; Ito, K; Sunada, H

    2001-10-01

    Nifedipine is a poorly water soluble drug that demonstrates low bioavailability. In a previous study, a coground mixture of nifedipine with sodium deoxycholate (DCNa), a bile salt, immediately produced colloidal particles when dispersed in water. In this study, the effect of the weight fraction of DCNa, grinding time, dissolution media, and storage conditions on colloidal particle formation in solution was investigated. The coground mixture was prepared with a vibration rod mill, and its solid state was characterized using powder X-ray diffraction. A laser diffraction particle size analyzer was used to determine the particle size distribution curve in water. The size of particles formed in solution decreased with an increase in the weight fraction of DCNa and grinding time. A nifedipine-DCNa (1:2 w/w) mixture coground for 30 min was used in the experiments. Colloidal particle formation from the coground mixture was also observed in dissolution media of water and a pH 6.8 buffer solution at 37 degrees C. Most precipitates passed through a filter with a pore size of 0.8 microm, but the particle size distribution in water was different from that in the pH 6.8 buffer solution. DCNa exhibited not only micellar solubilization for drug crystals, but also a retarding effect on drug crystal growth in a supersaturated solution. The latter effect could serve to form colloidal particles in solution. When stored under 75% relative humidity at 40 degrees C for 1 month, the amorphous coground mixture crystallized, and the particle size in water markedly increased. Therefore, the weight fraction of DCNa, grinding time, dissolution media, and humidity during storage influence the dissolution characteristics of nifedipine from a coground mixture. PMID:11763473

  8. Undergraduate experiment in critical phenomena. II. The coexistence curve of a binary fluid mixture

    NASA Astrophysics Data System (ADS)

    Ngubane, S. B.; Jacobs, D. T.

    1986-06-01

    An undergraduate experiment is described that uses meniscus heights to determine the coexistence curve of a binary fluid mixture. The data can be obtained with a minimum of equipment and yield results that are easily interpreted by the theory also presented. Data taken on the binary liquid mixture methanol-isooctane are presented and analyzed. The critical temperature and composition were found to be (42.5±0.5) °C and (67.3±0.2)% by volume isooctane, respectively.

  9. Speciation of organic phosphorus in a sediment profile of Lake Taihu. II. Molecular species and their depth attenuation.

    PubMed

    Ding, Shiming; Di, Xu; Bai, Xiuling; Yao, Shuchun; Fan, Chengxin; Zhang, Chaosheng

    2013-05-01

    The understanding of organic phosphorus (P) dynamics in sediments requires information on their species at the molecular level, but such information in sediment profiles is scarce. A sediment profile was selected from a large eutrophic lake, Lake Taihu (China), and organic P species in the sediments were detected using solution phosphorus-31 nuclear magnetic resonance spectroscopy (31P NMR) following extraction of the sediments with a mixture of 0.25 mol/L NaOH and 50 mmol/L EDTA (NaOH-EDTA) solution. The results showed that P in the NaOH-EDTA extracts was mainly composed of orthophosphate, orthophosphate monoesters, phospholipids, DNA, and pyrophosphate. Concentrations of the major organic P compound groups and pyrophosphate showed a decreasing trend with the increase of depth. Their half-life times varied from 3 to 27 years, following the order of orthophosphate monoesters > phospholipids > or = DNA > pyrophosphate. Principal component analysis revealed that the detected organic P species had binding phases similar to those of humic acid-associated organic P (NaOH-NRP(HA)), a labile organic P pool that tends to transform to recalcitrant organic P pools as the early diagenetic processes proceed. This demonstrated that the depth attenuation of the organic P species could be partly attributed to their increasing immobilization by the sediment solids, while their degradation rates should be significantly lower than what were suggested in previous studies. PMID:24218822

  10. Cell surface energy, contact angles and phase partition. II. Bacterial cells in biphasic aqueous mixtures.

    PubMed

    Gerson, D F; Akit, J

    1980-11-01

    Partition coefficients in biphasic mixtures of poly(ethylene glycol) and Dextran are compared to cell surface energies obtained from contact angles of each liquid phase on cell layers. Linear relationships are observed between these two independent measurements for a variety of bacterial cells. The results demonstrate the importance of interfacial phenomena and contact angles in the phase-partition process. PMID:6159003

  11. Dissipation of a commercial mixture of polyoxyethylene amine surfactants in aquatic outdoor microcosms: Effect of water depth and sediment organic carbon.

    PubMed

    Rodriguez-Gil, Jose Luis; Lissemore, Linda; Solomon, Keith; Hanson, Mark

    2016-04-15

    This study optimized existing analytical approaches and characterized the effect of sediment total organic carbon (0.05-2.05% TOC), and water depth (15, 30, and 90cm) on the fate of MON 0818, a commercial mixture of polyoxyethylene amine surfactants (POEAs), in outdoor microcosms. Mixtures of POEAs are commonly used as adjuvants in commercial herbicide formulations containing glyphosate. Until recently, analytical methods sensitive enough to monitor environmental concentrations of POEAs in aquatic systems were not available. After optimizing recently developed analytical methods, we found that the combined use of accelerated solvent extraction (ASE) and liquid chromatography-tandem mass spectrometry provided a reliable approach for determining the concentration of sediment-adsorbed POEAs. The surfactant showed strong affinity for sediment materials, with low maximum recoveries by ASE of 52%. Under microcosm conditions, water depth or sediment characteristics did not significantly affect the water-column half-life of POEA, which ranged from 3.2 to 5.3h. Binding of POEAs to suspended solids was observed, which dissipated via one- or two-phase exponential decay; when two-phase decay occurred, fast phase half-life values ranged from 0.71 to 1.3h and slow-phase values ranged from 18 to 44h. Concentrations of POEA increased in sediment shortly after application and decreased over the study period with a half-life of 5.8 to 71d. The concentrations of POEAs in the sediment of the shallow (15cm) ponds dissipated following a two-phase exponential decay model with an initial fast-phase half-life of 1.1 to 8.9d and a slower second-phase half-life of 21d. Our results suggest that aquatic organisms are unlikely to be exposed to POEAs in aqueous phase for periods of more than a few hours following an over-water application, and that sediment is a significant sink for POEAs in aquatic systems. PMID:26845181

  12. A gel probe equilibrium sampler for measuring arsenic porewater profiles and sorption gradients in sediments: II. Field application to Haiwee reservoir sediment

    USGS Publications Warehouse

    Campbell, K.M.; Root, R.; O'Day, P. A.; Hering, J.G.

    2008-01-01

    Arsenic (As) geochemistry and sorption behavior were measured in As- and iron (Fe)-rich sediments of Haiwee Reservoir by deploying undoped (clear) polyacrylamide gels and hydrous ferric oxide (HFO)-doped gels in a gel probe equilibrium sampler, which is a novel technique for directly measuring the effects of porewater composition on As adsorption to Fe oxides phases in situ. Arsenic is deposited at the sediment surface as As(V) and is reduced to As(III) in the upper layers of the sediment (0-8 cm), but the reduction of As(V) does not cause mobilization into the porewater. Dissolved As and Fe concentrations increased at depth in the sediment column driven by the reductive dissolution of amorphous Fe(III) oxyhydroxides and conversion to a mixed Fe(II, III) green rust-type phase. Adsorption of As and phosphorous (P) onto HFO-doped gels was inhibited at intermediate depths (10-20 cm), possibly due to dissolved organic or inorganic carbon, indicating that dissolved As concentrations were at least partially controlled by porewater composition rather than surface site availability. In sediments that had been recently exposed to air, the region of sorption inhibition was not observed, suggesting that prior exposure to air affected the extent of reductive dissolution, porewater chemistry, and As adsorption behavior. Arsenic adsorption onto the HFO-doped gels increased at depths >20 cm, and the extent of adsorption was most likely controlled by the competitive effects of dissolved phosphate. Sediment As adsorption capacity appeared to be controlled by changes in porewater composition and competitive effects at shallower depths, and by reductive dissolution and availability of sorption sites at greater burial depths. ?? 2008 American Chemical Society.

  13. Relativistic entrainment matrix of a superfluid nucleon-hyperon mixture. II. Effect of finite temperatures

    SciTech Connect

    Gusakov, Mikhail E.; Kantor, Elena M.; Haensel, Pawel

    2009-07-15

    We calculate the important quantity of superfluid hydrodynamics, the relativistic entrainment matrix for a nucleon-hyperon mixture at arbitrary temperature. In the nonrelativistic limit this matrix is also termed the Andreev-Bashkin or mass-density matrix. Our results can be useful for modeling the pulsations of massive neutron stars with superfluid nucleon-hyperon cores and for studies of the kinetic properties of superfluid baryon matter.

  14. Invasion of drilling mud into gas-hydrate-bearing sediments. Part II: Effects of geophysical properties of sediments

    NASA Astrophysics Data System (ADS)

    Ning, Fulong; Wu, Nengyou; Yu, Yibing; Zhang, Keni; Jiang, Guosheng; Zhang, Ling; Sun, Jiaxin; Zheng, Mingming

    2013-06-01

    This study examines the dynamic behaviour of drilling-mud invasion into gas-hydrate-bearing sediment (GHBS) and the effects of such an invasion on wellbore stability and the reliability of well logging. The effects of mud properties on mud invasion into the GHBS are detailed in Part I. Here, we discuss the effects of sediment properties on mud invasion by considering the Chinese first gas-hydrate-drilling expedition in the South China Sea and other hydrate projects. Our simulation results further show that mud-invasion coupling hydrate dissociation and reformation is the main unique characteristic observed during mud invasion in GHBS compared with conventional oil/gas sediments. The appearance of a high-saturation hydrate ring during mud-invasion process is related to not only mud density, temperature and salinity but also sediment properties. On the whole, the effective permeability and initial hydrate saturation plays a critical role in mud invasion in GHBS. The effect of initial hydrate saturation, which corresponds to effective permeability and porosity on the mud invasion in SH7 is pronounced because initial hydrate saturations vary greatly. For pore-filling GHBS without fractures, well-logging results in high-saturation hydrate intervals are more reliable and accurate than those in low-saturation hydrate intervals. The log results at the interbeds with low-saturation hydrates are easily distorted by mud invasion.

  15. Excess protons in water-acetone mixtures. II. A conductivity study.

    PubMed

    Semino, Rocío; Longinotti, M Paula

    2013-10-28

    In the present work we complement a previous simulation study [R. Semino and D. Laria, J. Chem. Phys. 136, 194503 (2012)] on the disruption of the proton transfer mechanism in water by the addition of an aprotic solvent, such as acetone. We provide experimental measurements of the mobility of protons in aqueous-acetone mixtures in a wide composition range, for water molar fractions, xw, between 0.05 and 1.00. Furthermore, new molecular dynamics simulation results are presented for rich acetone mixtures, which provide further insight into the proton transport mechanism in water-non-protic solvent mixtures. The proton mobility was analyzed between xw 0.05 and 1.00 and compared to molecular dynamics simulation data. Results show two qualitative changes in the proton transport composition dependence at xw ∼ 0.25 and 0.8. At xw < 0.25 the ratio of the infinite dilution molar conductivities of HCl and LiCl, Λ(0)(HCl).Λ(0)(LiCl)(-1), is approximately constant and equal to one, since the proton diffusion is vehicular and equal to that of Li(+). At xw ∼ 0.25, proton mobility starts to differ from that of Li(+) indicating that above this concentration the Grotthuss transport mechanism starts to be possible. Molecular dynamics simulation results showed that at this threshold concentration the probability of interconversion between two Eigen structures starts to be non-negligible. At xw ∼ 0.8, the infinite molar conductivity of HCl concentration dependence qualitatively changes. This result is in excellent agreement with the analysis presented in the previous simulation work and it has been ascribed to the interchange of water and acetone molecules in the second solvation shell of the hydronium ion. PMID:24182052

  16. Spinodal decomposition in mixtures containing nematogens. II. Kinetics of spinodal decomposition

    NASA Astrophysics Data System (ADS)

    Dorgan, J. R.

    1993-06-01

    The problem of simultaneous phase separation and ordering kinetics in mixtures containing a nematic component is addressed through the introduction of a time-dependent Landau-Ginzburg model. Dynamic equations for the time evolution of orientation and concentration fluctuations are given; the solution to these equations leads to explicit expressions for the structure factors for concentration and orientation. It is shown that the theory shares some salient features with the Cahn theory of spinodal decomposition. A simulation of a quenching experiment is performed and the time evolution of the structure factors during spinodal decomposition is calculated. Relevant small angle light scattering experiments which could be used to test the model are discussed.

  17. Unique Prokaryotic Consortia in Geochemically Distinct Sediments from Red Sea Atlantis II and Discovery Deep Brine Pools

    PubMed Central

    Siam, Rania; Mustafa, Ghada A.; Sharaf, Hazem; Moustafa, Ahmed; Ramadan, Adham R.; Antunes, Andre; Bajic, Vladimir B.; Stingl, Uli; Marsis, Nardine G. R.; Coolen, Marco J. L.; Sogin, Mitchell; Ferreira, Ari J. S.; Dorry, Hamza El

    2012-01-01

    The seafloor is a unique environment, which allows insights into how geochemical processes affect the diversity of biological life. Among its diverse ecosystems are deep-sea brine pools - water bodies characterized by a unique combination of extreme conditions. The ‘polyextremophiles’ that constitute the microbial assemblage of these deep hot brines have not been comprehensively studied. We report a comparative taxonomic analysis of the prokaryotic communities of the sediments directly below the Red Sea brine pools, namely, Atlantis II, Discovery, Chain Deep, and an adjacent brine-influenced site. Analyses of sediment samples and high-throughput pyrosequencing of PCR-amplified environmental 16S ribosomal RNA genes (16S rDNA) revealed that one sulfur (S)-rich Atlantis II and one nitrogen (N)-rich Discovery Deep section contained distinct microbial populations that differed from those found in the other sediment samples examined. Proteobacteria, Actinobacteria, Cyanobacteria, Deferribacteres, and Euryarchaeota were the most abundant bacterial and archaeal phyla in both the S- and N-rich sections. Relative abundance-based hierarchical clustering of the 16S rDNA pyrotags assigned to major taxonomic groups allowed us to categorize the archaeal and bacterial communities into three major and distinct groups; group I was unique to the S-rich Atlantis II section (ATII-1), group II was characteristic for the N-rich Discovery sample (DD-1), and group III reflected the composition of the remaining sediments. Many of the groups detected in the S-rich Atlantis II section are likely to play a dominant role in the cycling of methane and sulfur due to their phylogenetic affiliations with bacteria and archaea involved in anaerobic methane oxidation and sulfate reduction. PMID:22916172

  18. The stability constants of copper(II) complexes with some alpha-amino acids in dioxan-water mixtures.

    PubMed

    Doğan, A; Köseoğlu, F; Kiliç, E

    2001-08-15

    In this study, the overall stability constants of copper(II) complexes with some alpha-amino acids (glycine, dl-alanine, dl-valine, l-leucine, l-asparagine, l-glutamine) were determined by potentiometric titration in water, 25% dioxan-75% water, 35% dioxan-65% water, 50% dioxan-50% water, and 60% dioxan-40% water. The titrations were performed at 25 degrees C, under nitrogen atmosphere, and the ionic strength of the medium was maintained at 0.10 M by using sodium perchlorate. The formation curves of their complexes (n-p[L]) were obtained by means of the titration data. Then the stability constants were determined in relation to these curves. The mol ratio of copper(II) to alpha-amino acid was also determined and it was found that the complexes were CuL(2) type. Another important result obtained was that the tendency of amino acids to form complexes with copper(II) was greater in dioxan-water mixtures compared to water. PMID:11488627

  19. SEDIMENT TOXICITY IDENTIFICATION EVALUATION (TIE)PHASE I,II,III GUIDANCE DOCUMENT

    EPA Science Inventory

    Sediment contamination in the United States has been amply documented and, in order to comply with the 1972 Clean Water Act, the U.S. Environmental Protection Agency must address the issue of toxic sediments. Contaminated sediments from a number of freshwater and marine sites hav...

  20. Instability in evaporative binary mixtures. II. The effect of Rayleigh convection

    NASA Astrophysics Data System (ADS)

    Uguz, K. E.; Narayanan, R.

    2012-09-01

    Multi-component mixtures undergoing phase change in the presence of gravity depict instabilities whose physical origins depend upon the heating arrangement. Calculations on evaporative instability in closed systems using the example of low weight alcohols predict that cellular patterns would occur when the system is heated from above provided that the liquid depths are small compared to the vapor depths. The cellular patterns give way to long wavelength modes when the liquid depths are large because the solutal convection is dominant. When heated from below, cellular patterns can always be obtained regardless of the phase depths. Moreover, for this heating arrangement the physics shows thermal dominance at large wave numbers and solutal dominance at small wave numbers.

  1. Strong Acid Mixture and Sequential Geochemical Arsenic Extractions in Surface Sediments from the Santa Maria La Reforma Coastal Lagoon, Mexico: A Bioavailability Assessment.

    PubMed

    Rivera-Hernández, José R; Green-Ruiz, Carlos

    2016-02-01

    Thirty-three sediment samples were collected from the Santa Maria La Reforma coastal lagoon and digested by way of a strong acid mixture and sequential arsenic (As)-extraction method to determine the arsenic (As) content and bioavailability. The As content was determined by atomic fluorescence spectrometry. In addition, grain-size analyses were performed, and organic carbon, carbonate, and iron (Fe) and manganese (Mn) concentrations were determined. Fe and Mn determination was performed by atomic absorption spectroscopy. A Pearson correlation matrix and As enrichment factors were calculated. Sediment concentrations from Santa Maria La Reforma ranged from 3.6 to 25 µg As g(-1) with an average of 13.4 ± 7.6 µg As g(-1). The highest values were observed in the northern (Playa Colorada), north-central (Mocorito River discharge zone), and southern zones ("El Tule" agricultural drain). Most samples were classified as exhibiting no or minor As enrichment and were lower than the threshold effect level (TEL; 7.24 µg g(-1)) for biota (MacDonald et al. in Ecotoxicology 5:253-278, 1996). Low bioavailable As values (<3 %) were measured in the majority of the sediment. The highest As percentages were associated with the oxyhydroxide fraction (F5). The results indicate that As bioavailability is negligible. PMID:26743199

  2. The effect of biogenic Fe(II) on the stability and sorption of Co(II)EDTA{sup 2{minus}} to goethite and a subsurface sediment

    SciTech Connect

    Zachara, J.M.; Smith, S.C.; Fredrickson, J.K.

    2000-04-01

    Laboratory experiments were conducted with suspensions of goethite ({alpha}-FeOOH) and a subsurface sediment to assess the influence of bacterial iron reduction on the fate of Co(II)EDTA{sup 2{minus}}, a representative metal-ligand complex of intermediate stability (log K{sub Co(II)EDTA} = 17.97). The goethite was synthetic (ca. 55 m{sup 2}/g) and the sediment was a Pleistocene age, Fe(III) oxide-containing material from the Atlantic coastal plain (Milford). Shewanella alga strain BrY, a dissimulatory iron reducing bacterium (DIRB), was used to promote Fe(III) oxide reduction. Sorption isotherms and pH adsorption edges were measured for Co{sup 2+}, Fe{sup 2+}, Co(II)EDTA{sup 2{minus}}, and Fe(II)EDTA{sup 2{minus}} on the two sorbents in 0.001 mol/L Ca(ClO{sub 4}){sub 2} to aid in experiment interpretation. It is concluded that cationic radionuclides such as {sup 60}Co or {sup 239/240}Pu, which may be mobilized from disposed wastes by complexation with EDTA{sup 4{minus}}, may become immobilized in groundwater zones where dissimilatory bacterial iron reduction is operative.

  3. Survey of Lake Ontario bottom sediment off Rochester, New York, to define the extent of jettisoned World War II material and its potential for sediment contamination

    USGS Publications Warehouse

    Kennedy, Gregory; Kappel, William M.

    2000-01-01

    Military-type mat??riel was recovered from the bottom of Lake Ontario near Rochester, N.Y., during bottom-trawl, fish-stock surveys at depths of 75 to 180 feet each year from 1978 through 1996. The recovered mat??riel included many shell-detonator nose cones (2 inches in diameter by about 3.5 inches long); several electronic components; one corroded box of detonators; a corrugated container of mercury-filled capsules; and corroded batteries. Most of the recovered mat??riel has been identified as defective components of shell detonators (proximity-fuze assemblies) that were jettisoned in the lake to protect them from discovery during World War II. Side-scan SONAR, metal-detector, and ROV (remotely-operated-vehicle) surveys found no evidence of any large piles of mat??riel containing potentially hazardous, toxic, or polluting materials within the 17-square-mile study site. Many scattered magnetic anomalies were detected in this area, but chemical analysis of bottom sediment and of zebra- and quagga-mussel (Dreissena spp.) tissue indicate that the concentrations of mercury and other heavy metals are within the previously documented ranges for Lake Ontario sediment. The failure of ROV videos and of SCUBA-diver surveys and probes of the lake bottom to locate any debris indicates that most, if not all, of the debris is scattered and buried under a layer of fine-grained sediment and, possibly, mussels.

  4. [Sesame seed (Sesamum indicum, L.). II. Use of sesame flour in protein mixtures].

    PubMed

    Salgado, J M; Gonçalves, C M

    1988-06-01

    The results obtained in the first part of this study demonstrated that the sesame flour protein is of reasonable quality and can be utilized, although it has a low lysine content and is rich in sulfur amino acids. Based on the initial data, the sesame flour was supplemented with other meals: "carioca" beans, pigeon pea, and soybean. Nine diets were prepared and the best combination was that of 50% sesame flour protein and 50% pigeon pea, the PER of which was 2.28. Breads were made with these systems, as follows: 100% sesame flour, 100% wheat flour, 50% sesame flour + 50% wheat flour; 30% sesame flour + 70% wheat flour; 30% sesame flour + 30% soybean flour + 40% wheat flour. These were evaluated through sensory analysis by a grading system. Good acceptance was obtained with the bread prepared with 30% sesame flour + 70% wheat flour. Its external and internal appearance, as well as its organoleptic characteristics were close to the bread, with 100% wheat flour. Sesame flour at the 50% proportion gave a bread of medium quality. The protein mixtures of sesame flour and soybean flour were well accepted. Some of the panel members reported that it had a taste somewhat like integral bread. PMID:3154072

  5. Highly sensitive extractive spectrophotometric determination of palladium(II) in synthetic mixtures and hydrogenation catalysts using benzildithiosemicarbazone.

    PubMed

    Reddy, B Krishna; Reddy, K Janardhan; Kumar, J Rajesh; Kumar, A Kiran; Reddy, A Varada

    2004-06-01

    A simple and highly sensitive method was developed for the extractive-spectrophotometric determination of palladium with benzilidithiosemicarbazone. The metal ion formed a reddish brown complex with benzildithiosemicarbazone in a potassium chloride-hydrochloric acid buffer of pH 2.5, which was easily extractable into methyl isobutyl ketone. The 1:1 complex showed the maximum absorbance at 395 nm with a Beer's law range of 0.25-3.5 ppm. The molar absorptivity and Sandell's sensitivity were found to be 3.018 x 10(4) dm3 mol(-1) cm(-1) and 0.0035 microg cm(-2), respectively. The correlation coefficient of the Pd(II)-BDTSC complex was 0.998, which indicated an excellent linearity between the two variables. The repeatability of the method was checked by finding the relative standard deviation (RSD) (n = 10), which was 0.46%. The instability constant of the complex calculated from Edmond and Birnbaum's method was 2.41 x 10(-5), that of Asmus' method is 2.53 x 10(-5) at room temperature. The interfering effects of various cations and anions were studied. The proposed method was successfully applied to the determination of palladium(II) in synthetic mixtures and hydrogenation catalysts. The validity of the method was tested by comparing the results with those obtained using an atomic absorption spectrophotometer. PMID:15228112

  6. Capturing Bioavailable Organic Contaminants for Phase II Whole Sediment Toxicity Identification Evaluations

    EPA Science Inventory

    In Phase I of whole sediment TIEs, causes of toxicity to freshwater and marine organisms are characterized into broad toxicant classes including ammonia, metals and organic chemicals. In the whole sediment Phase I TIEs performed so far, organic chemicals have been shown to be t...

  7. Settling velocities in batch sedimentation. [Mixtures containing one and two sizes of resin beads, 44 and 62. mu. m in diameter

    SciTech Connect

    Fricke, A.M.; Thompson, B.E.

    1982-10-01

    The sedimentation of mixtures containing one and two sizes of spherical particles (44 and 62 ..mu..m in diameter) was studied. Radioactive tracing with /sup 57/Co was used to measure the settling velocities. The ratio of the settling velocity U of uniformly sized particles to the velocity predicted to Stokes' law U/sub 0/ was correlated to an expression of the form U/U/sub 0/ = epsilon/sup ..cap alpha../, where epsilon is the liquid volume fraction and ..cap alpha.. is an empirical constant, determined experimentally to be 4.85. No effect of viscosity on the ratio U/U/sub 0/ was observed as the viscosity of the liquid medium was varied from 1x10/sup -3/ to 5x10/sup -3/ Pa.s. The settling velocities of particles in a bimodal mixture were fit by the same correlation; the ratio U/U/sub 0/ was independent of the concentrations of different-sized particles.

  8. Polydopamine imprinted magnetic nanoparticles as a method to purify and detect class II hydrophobins from heterogeneous mixtures.

    PubMed

    Riveros G, D; Cordova, K; Michiels, C; Verachtert, H; Derdelinckx, G

    2016-11-01

    Hydrophobins are one of the most active surface active proteins in nature, with an amphiphilic nature and the ability to self-assembly in elastic monolayers, the possible applications in industry are continuously increasing. However, production and purification of these proteins still remains a tedious process. We introduce here the use of polydopamine as imprinter polymer to create specific magnetic nanoparticles for the recognition of Hydrophobin HFBII from Trichoderma reesei. The protein was molecularly imprinted to magnetic nanoparticles to facilitate its specific detection and purification from liquids or carbonated beverages in the presence of other proteins. The resulting magnetic nanoparticles were successfully imprinted adsorbing till 77,4µg of HFBII hydrophobin per miligram of nanoparticles. The adsorption capacity of the imprinted nanoparticles was also tested for specificity using a mixture of five different proteins and peptides. A slight cross interaction was observed when proteins of similar molecular weight to HFBII were used. With larger proteins and peptides the interaction was very low. with other class II Hydrophobins the interaction was very similar as to HFBII. PMID:27591673

  9. Carotenoid diagenesis in recent marine sediments: II. Degradation of fucoxanthin to loliolide

    NASA Astrophysics Data System (ADS)

    Repeta, Daniel J.

    1989-03-01

    The quantitative distributions of loliolide and the major phytoplankton carotenoids: fucoxanthin, diadinochrome, diatoxanthin, and β-carotene in two cores of anoxic marine sediment recovered from the Peru continental shelf are reported. Our results demonstrate that the rapid degradation of carotenoids in sediments is not a result of their high degree of unsaturation as has been previously suggested. Instead, carotenoids exhibit a wide range of degradation rates that are proportional to the ability of specific pigments to form unstable bicyclic furanoxides. Carotenoid furanoxides undergo subsequent fragmentation to loliolide, isololiolide, dihydroactinidiolide and other, as yet undetermined, low molecular weight products. This degradation pathway accounts for the relative rates of removal for specific carotenoids (fucoxanthin = fucoxanthinol > diadinoxanthin > diatoxanthin = carotene), the distribution of carotenoids reported by Wpatts and Maxwell (1977) and C ARDOSOet al. (1978) in ancient sediments, the occurrence of novel carotenoid transformation products in surface sediments reported by r pidout et al. (1984), and the distribution of loliolides in recent sediments recovered from the Namibian shelf reported by k plok et al. (1984a,b). We predict that loliolide and isololiolide will inherit a specific stereochemistry from their carotenoid precursors, but that dihydroactinidiolide will be racemic. For every μmole of fucoxanthin degraded in Peru sediments, 0.7-1.1 μmole of loliolide is produced. Summation of fucoxanthin and loliolide at each subsurface horizon yields an estimate of the total deposition of fucoxanthin at t = 0. Throughout the 0-20 cm depth of our samples, this parameter is remarkably constant to ±16%. Individual horizons exhibit excursions which may reflect changes in surface productivity. Extrapolation of our measurements to deeper sediments may therefore be of some value in deciphering questions on environmental conditions of deposition and

  10. Role of reef fauna in sediment transport and distribution - Studies from Tektite I and II

    USGS Publications Warehouse

    Clifton, H.E.

    1973-01-01

    1. Reef organisms may play a major role in the transport and distribution of sediment on the sea floor adjacent to coral reefs. 2. Some fish such as Malacanthus plumieri (Bloch) selectively transport and collect certain types of sediment (such as larger coral and shell fragments). 3. The random movement of crawling or burrowing organisms may cause a large amount of sediment to be shifted laterally on the sea floor. On slopes, a net downhill displacement may result. 4. The surface configuration and internal structure of the sediment is rapidly changed by faunal mixing. Ripple marks formed by waves or currents are obliterated by the activity of organisms in only a few weeks in the environment studied. Internal structure (bedding) near the sediment-water interface is similarly destroyed in a short period of time. 5. Larger clasts (including empty shells) on the sea floor tend to be buried by faunal undermining. The rate of burial depends primarily on the grain size of the substrate. 6. The random movement of fauna on the sea floor may produce a predominantly concave-up orientation of pelecypod shells and shell fragments on the sea floor - the opposite of that produced by the activity of waves or currents. ?? 1973 Biologischen Anstalt Helgoland.

  11. Coexistence of Microaerophilic, Nitrate-Reducing, and Phototrophic Fe(II) Oxidizers and Fe(III) Reducers in Coastal Marine Sediment.

    PubMed

    Laufer, Katja; Nordhoff, Mark; Røy, Hans; Schmidt, Caroline; Behrens, Sebastian; Jørgensen, Bo Barker; Kappler, Andreas

    2015-01-01

    Iron is abundant in sediments, where it can be biogeochemically cycled between its divalent and trivalent redox states. The neutrophilic microbiological Fe cycle involves Fe(III)-reducing and three different physiological groups of Fe(II)-oxidizing microorganisms, i.e., microaerophilic, anoxygenic phototrophic, and nitrate-reducing Fe(II) oxidizers. However, it is unknown whether all three groups coexist in one habitat and how they are spatially distributed in relation to gradients of O2, light, nitrate, and Fe(II). We examined two coastal marine sediments in Aarhus Bay, Denmark, by cultivation and most probable number (MPN) studies for Fe(II) oxidizers and Fe(III) reducers and by quantitative-PCR (qPCR) assays for microaerophilic Fe(II) oxidizers. Our results demonstrate the coexistence of all three metabolic types of Fe(II) oxidizers and Fe(III) reducers. In qPCR, microaerophilic Fe(II) oxidizers (Zetaproteobacteria) were present with up to 3.2 × 10(6) cells g dry sediment(-1). In MPNs, nitrate-reducing Fe(II) oxidizers, anoxygenic phototrophic Fe(II) oxidizers, and Fe(III) reducers reached cell numbers of up to 3.5 × 10(4), 3.1 × 10(2), and 4.4 × 10(4) g dry sediment(-1), respectively. O2 and light penetrated only a few millimeters, but the depth distribution of the different iron metabolizers did not correlate with the profile of O2, Fe(II), or light. Instead, abundances were homogeneous within the upper 3 cm of the sediment, probably due to wave-induced sediment reworking and bioturbation. In microaerophilic Fe(II)-oxidizing enrichment cultures, strains belonging to the Zetaproteobacteria were identified. Photoferrotrophic enrichments contained strains related to Chlorobium and Rhodobacter; the nitrate-reducing Fe(II) enrichments contained strains related to Hoeflea and Denitromonas. This study shows the coexistence of all three types of Fe(II) oxidizers in two near-shore marine environments and the potential for competition and interrelationships between

  12. Microbial production of isotopically light iron(II) in a modern chemically precipitated sediment and implications for isotopic variations in ancient rocks

    USGS Publications Warehouse

    Tangalos, G.E.; Beard, B.L.; Johnson, C.M.; Alpers, C.N.; Shelobolina, E.S.; Xu, H.; Konishi, H.; Roden, E.E.

    2012-01-01

    The inventories and Fe isotope composition of aqueous Fe(II) and solid-phase Fe compounds were quantified in neutral-pH, chemically precipitated sediments downstream of the Iron Mountain acid mine drainage site in northern California, USA. The sediments contain high concentrations of amorphous Fe(III) oxyhydroxides [Fe(III)am] that allow dissimilatory iron reduction (DIR) to predominate over Fe–S interactions in Fe redox transformation, as indicated by the very low abundance of Cr(II)-extractable reduced inorganic sulfur compared with dilute HCl-extractable Fe. δ56Fe values for bulk HCl- and HF-extractable Fe were ≈ 0. These near-zero bulk δ56Fe values, together with the very low abundance of dissolved Fe in the overlying water column, suggest that the pyrite Fe source had near-zero δ56Fe values, and that complete oxidation of Fe(II) took place prior to deposition of the Fe(III) oxide-rich sediment. Sediment core analyses and incubation experiments demonstrated the production of millimolar quantities of isotopically light (δ56Fe ≈ -1.5 to -0.5‰) aqueous Fe(II) coupled to partial reduction of Fe(III)am by DIR. Trends in the Fe isotope composition of solid-associated Fe(II) and residual Fe(III)am are consistent with experiments with synthetic Fe(III) oxides, and collectively suggest an equilibrium Fe isotope fractionation between aqueous Fe(II) and Fe(III)am of approximately -2‰. These Fe(III) oxide-rich sediments provide a model for early diagenetic processes that are likely to have taken place in Archean and Paleoproterozoic marine sediments that served as precursors for banded iron formations. Our results suggest pathways whereby DIR could have led to the formation of large quantities of low-δ56Fe minerals during BIF genesis.

  13. The organic geochemistry of Peru margin surface sediments: II. Paleoenvironmental implications of hydrocarbon and alcohol profiles

    SciTech Connect

    McCaffrey, M.A.; Farrington, J.W.; Repeta, D.J. )

    1991-02-01

    The authors assess the utility of sedimentary hydrocarbons and alcohols as indicators of short-term changes in depositional conditions in the coastal Peruvian upwelling regime at 15{degree}S. The distribution of 35 lipids in a 1 m dated core from 253 m water depth are interpreted by (1) a principal components analysis and (2) a consideration of individual source- specific biomarkers. profiles of odd-carbon-number n-alkanes (C{sub 25}-C{sub 33}) and even carbon-number n-alkanols (C{sub 24}-C{sub 28}) reflect changes in the contribution of terrigenous sediment relative to marine sediment during deposition, as indicated by the correlations between these lipids and inorganic indicators of terrigenous clastic debris. The n-alkane carbon preference index (CPI) provides a less-sensitive record of fluctuations in the terrestrial input than the concentration profiles of the individual n-alkanes and n-alkanols, and these lipids are not well-correlated with the historical El Nino record. The similarity of all the stenol profiles measured and the lack of concordance between these profiles and inorganic indicators of terrigenous input suggest that any fluctuations in the abundance of higher-plant stenols are obscured by the larger marine contribution of these compounds. Similarities between the profiles of total organic carbon (TOC) and cholestanol/cholesterol are consistent with stenol hydrogenation being influenced by the sediment redox conditions.

  14. Comparison of Propofol and Ketamine-Propofol Mixture (Ketofol) on Laryngeal Tube-Suction II Conditions and Hemodynamics: A Randomized, Prospective, Double-Blind Trial☆

    PubMed Central

    Ozgul, Ulku; Begec, Zekine; Karahan, Kalender; Ali Erdogan, Mehmet; Said Aydogan, Mustafa; Colak, Cemil; Durmus, Mahmut; Ozcan Ersoy, M.

    2013-01-01

    Objective The aim of our study is to compare the effect of ketamine–propofol mixture (ketofol) and propofol on the laryngeal tube-Suction II (LTS II) insertion conditions and hemodynamics. Methods Eighty American Society of Anesthesiologists class 1 and 2 patients were divided into 2 random groups to receive either 1 µg/kg remifentanil and propofol 2 mg/kg in Group P (n = 40), or 1 µg/kg remifentanil and ketofol (using a 1:1 single syringe mixture of 5 mg/mL ketamine and 5 mg/mL propofol) in Group K (n = 40) before induction of anesthesia. After induction, LTS II was inserted. Heart rate and noninvasive blood pressure were recorded before induction of anesthesia (t0); immediately following induction (t1); immediately after LTS II insertion (t2); and 3 minutes (t3), 5 minutes (t4), and 10 (t5) minutes after LTS II insertion. Conditions of insertion of LTS II were assessed and scored 1 to 3 using 6 variables as follows: mouth opening, swallowing, coughing, head and body movements, laryngospasm, and ease of LTS II insertion by the same experienced anesthesiologist who did not know the agents. LTS II insertion summed score was prepared depending upon these variables. Results In regard to LTS II insertion summed score, Group K was more favorable than Group P (P < 0.05). Apnea duration was longer in Group P (385.0 seconds [range = 195.0–840.0 seconds]) compared with Group K (325.50 seconds [range = 60.0–840.0 seconds]) but this was not statically significant. The heart rate values were significantly lower at all measurement intervals in both groups compared with the baseline values (P < 0.05). There was no difference in heart rate between Group P and Group K. The mean arterial pressure values were significantly lower at all measurement intervals in Group P compared with baseline values (P < 0.05). In Group K, the mean arterial pressure values were significantly lower at all measurement intervals compared with the baseline values, except t2 (P < 0.05). There was a

  15. Harvesting energy from the marine sediment-water interface II. Kinetic activity of anode materials.

    PubMed

    Lowy, Daniel A; Tender, Leonard M; Zeikus, J Gregory; Park, Doo Hyun; Lovley, Derek R

    2006-05-15

    Here, we report a comparative study on the kinetic activity of various anodes of a recently described microbial fuel cell consisting of an anode imbedded in marine sediment and a cathode in overlying seawater. Using plain graphite anodes, it was demonstrated that a significant portion of the anodic current results from oxidation of sediment organic matter catalyzed by microorganisms colonizing the anode and capable of directly reducing the anode without added exogenous electron-transfer mediators. Here, graphite anodes incorporating microbial oxidants are evaluated in the laboratory relative to plain graphite with the goal of increasing power density by increasing current density. Anodes evaluated include graphite modified by adsorption of anthraquinone-1,6-disulfonic acid (AQDS) or 1,4-naphthoquinone (NQ), a graphite-ceramic composite containing Mn2+ and Ni2+, and graphite modified with a graphite paste containing Fe3O4 or Fe3O4 and Ni2+. It was found that these anodes possess between 1.5- and 2.2-fold greater kinetic activity than plain graphite. Fuel cells were deployed in a coastal site near Tuckerton, NJ (USA) that utilized two of these anodes. These fuel cells generated ca. 5-fold greater current density than a previously characterized fuel cell equipped with a plain graphite anode, and operated at the same site. PMID:16574400

  16. Coexistence of Microaerophilic, Nitrate-Reducing, and Phototrophic Fe(II) Oxidizers and Fe(III) Reducers in Coastal Marine Sediment

    PubMed Central

    Laufer, Katja; Nordhoff, Mark; Røy, Hans; Schmidt, Caroline; Behrens, Sebastian; Jørgensen, Bo Barker

    2015-01-01

    Iron is abundant in sediments, where it can be biogeochemically cycled between its divalent and trivalent redox states. The neutrophilic microbiological Fe cycle involves Fe(III)-reducing and three different physiological groups of Fe(II)-oxidizing microorganisms, i.e., microaerophilic, anoxygenic phototrophic, and nitrate-reducing Fe(II) oxidizers. However, it is unknown whether all three groups coexist in one habitat and how they are spatially distributed in relation to gradients of O2, light, nitrate, and Fe(II). We examined two coastal marine sediments in Aarhus Bay, Denmark, by cultivation and most probable number (MPN) studies for Fe(II) oxidizers and Fe(III) reducers and by quantitative-PCR (qPCR) assays for microaerophilic Fe(II) oxidizers. Our results demonstrate the coexistence of all three metabolic types of Fe(II) oxidizers and Fe(III) reducers. In qPCR, microaerophilic Fe(II) oxidizers (Zetaproteobacteria) were present with up to 3.2 × 106 cells g dry sediment−1. In MPNs, nitrate-reducing Fe(II) oxidizers, anoxygenic phototrophic Fe(II) oxidizers, and Fe(III) reducers reached cell numbers of up to 3.5 × 104, 3.1 × 102, and 4.4 × 104 g dry sediment−1, respectively. O2 and light penetrated only a few millimeters, but the depth distribution of the different iron metabolizers did not correlate with the profile of O2, Fe(II), or light. Instead, abundances were homogeneous within the upper 3 cm of the sediment, probably due to wave-induced sediment reworking and bioturbation. In microaerophilic Fe(II)-oxidizing enrichment cultures, strains belonging to the Zetaproteobacteria were identified. Photoferrotrophic enrichments contained strains related to Chlorobium and Rhodobacter; the nitrate-reducing Fe(II) enrichments contained strains related to Hoeflea and Denitromonas. This study shows the coexistence of all three types of Fe(II) oxidizers in two near-shore marine environments and the potential for competition and interrelationships between them

  17. Sediment movement along the U.S. east coast continental shelf-II. Modelling suspended sediment concentration and transport rate during storms

    USGS Publications Warehouse

    Lyne, V.D.; Butman, B.; Grant, W.D.

    1990-01-01

    Long-term near-bottom wave and current observations and a one-dimensional sediment transport model are used to calculate the concentration and transport of sediment during winter storms at 60-80 m water depth along the southern flank of Georges Bank and in the Mid-Atlantic Bight. Calculations are presented for five stations, separated by more than 600 km alongshelf, that have different bottom sediment texture, bedforms and current conditions. A modified version of the sediment transport model presented by Grant and Glenn (1983, Technical Report to the American Gas Association), Glenn (1983, D.Sc. Thesis, M.I.T.), and Glenn and Grant (1987, Journal of Geophysical Research, 92, 8244-8264) is used to examine the influence of wave-current interaction, sediment stratification, and limitations on the erodibility of the bottom sediments on the concentration of sediment in the water column and on transport. Predicted suspended sediment concentrations are higher than observed, based on beam transmissometer measurements, unless an erosion limit of order a few millimeters for sediments finer than 94 ??m is imposed. The agreement between predicted and measured beam attenuation is better at stations that have significant amounts of silt plus clay in the surficial sediments than for stations with sandy sediments. Sediment concentrations during storms estimated by Moody et al. (1987, Continental Shelf Research, 7, 609-628) are within 50% of the model predictions. Sediment transport rates for sediments 94 ??m and finer are determined largely by the concentrations in the surficial sediment and the erosion depth limit. Large alongshelf transports in the direction of storm-driven currents are inferred for stations in the Mid-Atlantic Bight. During a 115-day period in winter 1979-1980, the net transport of sediment along the shelf was westward; benthic storms (defined as periods when the bottom wave stress exceeded the current stress by 2 dyn cm-2) occurred between 23 and 73% of the

  18. Sedimentation equilibria of ferrofluids: II. Experimental osmotic equations of state of magnetite colloids.

    PubMed

    Luigjes, Bob; Thies-Weesie, Dominique M E; Erné, Ben H; Philipse, Albert P

    2012-06-20

    The first experimental osmotic equation of state is reported for well-defined magnetic colloids that interact via a dipolar hard-sphere potential. The osmotic pressures are determined from the sedimentation equilibrium concentration profiles in ultrathin capillaries using a low-velocity analytical centrifuge, which is the subject of the accompanying paper I. The pressures of the magnetic colloids, measured accurately to values as low as a few pascals, obey Van 't Hoff's law at low concentrations, whereas at increasing colloid densities non-ideality appears in the form of a negative second virial coefficient. This virial coefficient corresponds to a dipolar coupling constant that agrees with the coupling constant obtained via independent magnetization measurements. The coupling constant manifests an attractive potential of mean force that is significant but yet not quite strong enough to induce dipolar chain formation. Our results disprove van der Waals-like phase behavior of dipolar particles for reasons that are explained. PMID:22617544

  19. How to overcome inter-electrode variability and instability to quantify dissolved oxygen, Fe(II), mn(II), and S(−II) in undisturbed soils and sediments using voltammetry

    PubMed Central

    2012-01-01

    Background Although uniquely capable of measuring multiple redox constituents nearly simultaneously with no or minimal sample pretreatment, voltammetry is currently underutilized in characterizing redox conditions in aquatic and terrestrial systems. Investigation of undisturbed media such as pore water requires a solid-state electrode, and such electrodes can be difficult to fabricate reproducibly. An approach to determine the concentrations of electroactive constituents using indirectly calibrated electrodes has been developed, but the protocol for and accuracy of this approach—the pilot ion method—has not been documented in detail. Results A detailed procedure for testing electrode quality is provided, and the application and limitations of the pilot ion method have been documented. To quantify Fe(II) and Mn(II), subtraction of non-linear baseline functions from voltammetric signals produced better calibration curves than did linear baselines, enabled lower detection limits and reliable deconvolution of overlapping signals, and was successfully applied to sediment pore water signals. We observed that electrode sensitivities often vary by tens of percent, and that the sensitivity declines over time. The ratio of calibration slopes of Mn(II) to Fe(II) varied by no more than 11% from one Hg/Au electrode to another and Fe(II) concentrations predicted by the Mn(II) pilot ion were, on average, 13% different from their actual values. However, concentration predictions by the pilot ion method were worse for less than 15 μM Fe(II) (46% different on average). The ratio of calibration slopes of Mn(II) to S(−II) varied by almost 20% from one Hg/Au electrode to another, and S(−II) predicted concentrations were as much as 58% different from their actual values. These predictions of Fe(II) and S(−II) concentrations indicate that the accuracy of the pilot ion method depends on how independent calibration slope ratios are from the electrode used. At medium

  20. Coastal circulation and sediment dynamics in Hanalei Bay, Kaua'i, Hawaii: Part II: tracking recent fluvial sedimentation; isotope stratigraphy obtained in Summer 2005

    USGS Publications Warehouse

    Draut, Amy E.; Field, Michael E.; Bothner, Michael H.; Logan, Joshua B.; Casso, Michael A.; Baldwin, Sandra M.; Storlazzi, Curt D.

    2006-01-01

    Delivery and dispersal of fluvial sediment in Hanalei Bay, Kaua’i, Hawaii, have important implications for the health of local coral reefs. The reef community in Hanalei Bay represents a relatively healthy ecosystem. However, the reefs are periodically stressed by storm waves, and increases in sediment and dissolved substances from the Hanalei River have the potential to cause additional stress. Increased turbidity and sedimentation on corals during Hanalei River floods that occur in seasons of low wave energy, when sediment would not be readily remobilized and advected out of the bay, could affect the health and sustainability of coral reefs and the many associated species. Measurements of short-lived isotopes 7Be and 137Cs in sediment cores have been used to trace the thickness and distribution of terrestrial sediment in Hanalei Bay, in order to assess spatial and temporal patterns of sediment deposition and remobilization relative to coral-reef locations. A third isotope, 210Pb, derived primarily from seawater, provides additional information about recent sedimentary history. Isotope profiles and observations of sedimentary facies from cores collected at multiple locations in June 2005, and again in August 2005, indicate the presence of recent fluvial sediment and organic debris in the east part of the bay near the mouth of the Hanalei River. Away from the immediate vicinity of the river mouth, sediment in the uppermost 1 m below the sea floor had not retained a significant quantity of fluvial sediment within the eight months prior to either sampling effort. During the study interval in summer 2005 the Hanalei River had no major floods and there was relatively little sediment input to the bay. Sediment away from the river mouth was dominated by carbonate sand, although some terrestrial sediment was present in sub-sea-floor horizons. Sedimentary facies and isotope inventories throughout the bay showed substantial spatial heterogeneity. Sediment cores will be

  1. Tier II Analysis of Vadose Zone Sediments from UPRS 200-E-81 and 200-E-86

    SciTech Connect

    Valenta, Michelle M.; Geiszler, Keith N.; Bjornstad, Bruce N.; Schaef, Herbert T.; Brown, Christopher F.

    2009-04-01

    The overall goals of the Tank Farm Vadose Zone Project, led by Washington River Protection Solutions, are to define risks from past and future single-shell tank farm activities; identify and evaluate the efficacy of interim measures; and aid, via collection of geochemical information and data, the future decisions that must be made by the U.S. Department of Energy (DOE) regarding the near-term operations, future waste retrieval, and final closure activities for the single-shell tank waste management areas (WMAs). To meet the investigative goals of the Tank Farm Vadose Zone Project, the Environmental Sciences Laboratory performed geochemical analyses on vadose zone sediments collected within Waste Management Area C. Tier one analyses of UPR-200-E-86, which includes direct push probe holes C5952, C5958 and C5960, were performed between 3/25/08 and 4/14/08. Preliminary results were presented to CH2M Hill Hanford Group on 6/5/08. As a result of the tier one investigations, further tier two analyses were requested. Tier two investigations include particle size and mineralogy analyses on samples collected between 80 to 120 feet below ground surface that were found to contain high concentrations of chloride and sulfate. Tier one analyses on sediments retrieved near UPR-200-E-81, direct push probe hole C6394, were performed between 6/20/08 and 7/22/08. Preliminary results of the tier one analyses were presented on 8/15/08. As a result of the tier one investigations, further tier two analyses were requested. Tier two analyses include determining whether U-236 exists in samples at approximately 42 feet below the ground surface. Confirmation of U-236 will determine whether the U-238 seen in the leaches performed on samples at that depth is a result of contamination and not from leaching natural uranium. Using the water and acid extract U-238 concentrations from the tier one analysis, equilibrium Kd values were requested to be calculated. Additional tier two analysis includes

  2. Toxicology studies of a chemical mixture of 25 groundwater contaminants. II. Immunosuppression in B6C3F1 mice

    SciTech Connect

    Germolec, D.R.; Yang, R.S.; Ackermann, M.F.; Rosenthal, G.J.; Boorman, G.A.; Blair, P.; Luster, M.I. )

    1989-10-01

    Concern over the potential adverse health effects of chemically contaminated groundwater has existed for many years. In general, these studies have focused on retrospective epidemiological studies for cancer risk. In the present studies, immune function was monitored in female B6C3F1 mice exposed to a chemical mixture in drinking water for either 14 or 90 days. The mixture consisted of 25 common groundwater contaminants frequently found near toxic waste dumps, as determined by EPA surveys. None of the animals developed overt signs of toxicity such as body or liver weight changes. Mice exposed to the highest dose of this mixture for 14 or 90 days showed immune function changes which could be related to rapidly proliferating cells, including suppression of hematopoietic stem cells and of antigen-induced antibody-forming cells. Some of these responses, e.g., granulocyte-macrophage colony formation, were also suppressed at lower concentrations of the chemical mixture. There were no effects on T cell function or T and B cell numbers in any of the treatment groups. Altered resistance to challenge with an infectious agent also occurred in mice given the highest concentration, which correlated with the immune function changes. Paired-water studies indicated that the immune effects were related to chemical exposure and not to decreased water intake. These results suggest that long-term exposure to contaminated groundwater may represent a risk to the immune system in humans.

  3. The Quantitative Resolution of a Mixture of Group II Metal Ions by Thermometric Titration with EDTA. An Analytical Chemistry Experiment.

    ERIC Educational Resources Information Center

    Smith, Robert L.; Popham, Ronald E.

    1983-01-01

    Presents an experiment in thermometric titration used in an analytic chemistry-chemical instrumentation course, consisting of two titrations, one a mixture of calcium and magnesium, the other of calcium, magnesium, and barium ions. Provides equipment and solutions list/specifications, graphs, and discussion of results. (JM)

  4. Novel triterpene-derived hydrocarbons of the arborane/fernane series in sediments: Part II

    NASA Astrophysics Data System (ADS)

    Hauke, Verena; Graff, Roland; Wehrung, Patrick; Trendel, Jean M.; Albrecht, Pierre; Riva, Angelo; Hopfgartner, Gerard; Gülaçar, Fazil O.; Buchs, Armand; Eakin, Paul A.

    1992-09-01

    Two ring-B aromatized triterpenes related to the arborane/fernane series were isolated from an Italian Triassic black shale ( 4 and 7) and a French Jurassic laminated bituminous limestone (7). They were identified by MS and NMR spectroscopy. These compounds, 25-norferna-5,7,9-triene 7 (C 29) and 22,25,29,30-tetranor-18β-ferna-5,7,9-triene 4 (C 26), in the case of the Italian sediment, belong to a family which extends to at least C 32 as shown by GC-MS. The presence of higher homologs and ring-A methylated structures in the Italian Triassic shale is analogous with the hopane series, which together with carbon isotopic data obtained by gas chromatography-isotope ratio mass spectrometry (GC-IRMS), strongly support a bacterial origin for most of these compounds. This suggests that 4 and 7 may result from a yet unrecognized rearrangement of sedimentary hopenes which have subsequently undergone ring-B aromatization. As an alternative, the C 29 compound 7 could arise from C 30 precursors not necessarily of bacterial origin (fernenes?). This hypothesis would apply particularly to the case of the Jurassic limestone, which does not show any trace of 4 nor of compounds with an extended side chain or a methyl group on ring A. Related structures also bearing an isopropyl group could derive by microbiological transformations from the corresponding fernen-3β-ols or isoarborinol as can be deduced from the occurrence of ring-A degraded monoaromatic hydrocarbons 3 and 5.

  5. Early depositional history of metalliferous sediments in the Atlantis II Deep of the Red Sea: Evidence from rare earth element geochemistry

    NASA Astrophysics Data System (ADS)

    Laurila, Tea E.; Hannington, Mark D.; Petersen, Sven; Garbe-Schönberg, Dieter

    2014-02-01

    The Atlantis II Deep is a brine-filled depression on the slowly spreading Red Sea rift axis. It is by far the largest deposit of hydrothermally precipitated metals on the present ocean floor and the only known modern deposit that is analogous to laminated Fe-rich chemical sediments, such as banded iron formation (BIF). The brine pool at the bottom of the Atlantis II Deep creates an environment where most of the hydrothermally sourced elements can be dispersed and deposited over an area of ˜60 km2. We analyzed the rare earth element concentrations in 100 small-volume samples from 9 cores in different parts of the Atlantis II Deep to better understand the origins of different types of metalliferous sediments (detrital, proximal hydrothermal and distal hydrothermal). Our results agree with earlier studies based on larger bulk samples that show the composition of the major depositional units is related to major changes in the location and intensity of hydrothermal activity and the amount of hydrothermal versus background sedimentation. In this paper, we address the origins of chemically distinct laminae (down to sub-millimeter) that correspond to ˜annual deposition. REE patterns clearly reflect 3 different sources (e.g., detrital, scavenging, direct hydrothermal input). Detrital REE that are delivered to the Deep from outside account for most of the REE in the sediments of the Atlantis II Deep, similar to BIF, and are unaffected by fractionation due to hydrothermal processes during deposition and diagenesis. Fe- and Mn-(oxy)hydroxides that form at the anoxic-oxic boundary scavenge REE from the brine pool as they settle. The Fe-(oxy)hydroxides contain a larger proportion of REE from seawater than any other sediment-type and also scavenge REE from pore waters after deposition. In contrast, the Mn-(oxy)hydroxides dissolve before deposition and thus function as transporting agents between seawater and the brine. However, there is little evidence for direct seawater

  6. Evaluation of the Polyethylene Reverse Sampler as a Dosing System in Marine Phase II Whole Sediment Toxicity Identification Evaluations (TIEs)

    EPA Science Inventory

    Contaminated marine sediments can cause acute and chronic impairments to benthic organisms. Nonionic organic contaminants (NOCs) are often a primary cause of impairment. Toxicity Identification Evaluations (TIEs) are used to identify chemicals causing toxicity in sediments. Ph...

  7. Fe(II)- and Sulfide-Facilitated Reduction of 99Tc(VII)O4- in Microbially Reduced Hyporheic Zone Sediments

    SciTech Connect

    Lee, Ji-Hoon; Zachara, John M.; Fredrickson, Jim K.; Heald, Steve M.; McKinley, James P.; Plymale, Andrew E.; Resch, Charles T.; Moore, Dean A.

    2014-07-01

    Redox-reactive, biogeochemical phases generated by reductive microbial activity in hyporheic zone sediments from a dynamic groundwater-river interaction zone were evaluated for their ability to reduce soluble pertechnetate [99Tc(VII)O4-] to less soluble Tc(IV). The sediments were bioreduced by indigenous microorganisms that were stimulated by organic substrate addition in synthetic groundwater with or without sulfate. In most treatments, 20 µmol L-1 initial aqueous Tc(VII) was reduced to near or below detection (3.82×10-9 mol L-1) over periods of days to months in suspensions of variable solids concentrations. Native sediments containing significant lithogenic Fe(II) in various phases were, in contrast, unreactive with Tc(VII). The reduction rates in the bioreduced sediments increased with increases in sediment mass, in proportion to weak acid-extractable Fe(II) and sediment-associated sulfide (AVS). The rate of Tc(VII) reduction was first order with respect to both aqueous Tc(VII) concentration and sediment mass, but correlations between specific reductant concentrations and reaction rate were not found. X-ray microprobe measurements revealed a strong correlation between Tc hot spots and Fe-containing mineral particles in the sediment. However, only a portion of Fe-containing particles were Tc-hosts. The Tc-hot spots displayed a chemical signature (by EDXRF) similar to pyroxene. The application of autoradiography and electron microprobe allowed further isolation of Tc-containing particles that were invariably found to be ca 100 µm aggregates of primary mineral material embedded within a fine-grained phyllosilicate matrix. EXAFS spectroscopy revealed that the Tc(IV) within these were a combination of a Tc(IV)O2-like phase and Tc(IV)-Fe surface clusters, with a significant fraction of a TcSx-like phase in sediments incubated with SO42-. AVS was implicated as a more selective reductant at low solids concentration even though its concentration was below that

  8. Development and Evaluation of Reverse Polyethylene Samplers for Marine Phase II Whole-Sediment Toxicity Identification Evaluation

    EPA Science Inventory

    Marine and estuarine sediments accumulate contaminants and act as a sink for a wide range of toxic chemicals. As a result, the sediments themselves can become a source of contamination. At sufficient levels, contaminated sediments can cause benthic impairments and toxicity to mar...

  9. Development and Evaluation of Polychaete Reverse Samplers for Marine Phase II Whole Sediment Toxicitiy Identification Evaluations (TIE)

    EPA Science Inventory

    Marine and estuarine sediments accumulate contaminants and act as a sink for a wide range of toxic chemicals. As a result, the sediments themselves can become a source of contamination. At sufficient levels, contaminated sediments can cause benthic impairments and toxicity to m...

  10. Watershed sediment source fingerprinting: a view under the hood

    NASA Astrophysics Data System (ADS)

    Smith, H.

    2015-12-01

    Sediment source fingerprinting procedures involve the discrimination of sediment sources based on physical and chemical properties and estimation of the contributions from those sources to mixtures of fine-grained sediment transported within watersheds. Sources of sediment widely considered include agricultural land uses, channel banks and geological zones. There has been a tendency in the literature for sediment fingerprinting to be presented as a technique that can deliver accurate and precise information on source contributions to sediment across a range of environments. However, recent research indicates that such a view of sediment fingerprinting cannot presently be supported. Furthermore, many past papers lack transparency in data processing and presentation that prevents the critical assessment of results and hinders wider uptake of the technique. Therefore, this contribution aims to delve 'under the hood' of sediment fingerprinting to promote further discussion and debate over future research needs and method limitations. It draws on important developments from the last two years concerning the effect of (i) tracer selection, (ii) tracer behaviour during transport, (iii) corrections to tracer datasets and (iv) the choice of mixing model on predictions of sediment source contributions. Sediment fingerprinting has the potential to make a very significant contribution to the measurement of contemporary sediment sources in watersheds, but cannot be viewed as an 'off-the-shelf' technique for widespread application until important challenges have been addressed.

  11. A Bacillus sp. isolated from sediments of the Sarno River mouth, Gulf of Naples (Italy) produces a biofilm biosorbing Pb(II).

    PubMed

    Pepi, Milva; Borra, Marco; Tamburrino, Stella; Saggiomo, Maria; Viola, Alfio; Biffali, Elio; Balestra, Cecilia; Sprovieri, Mario; Casotti, Raffaella

    2016-08-15

    A Pb-resistant bacterial strain (named hereinafter Pb15) has been isolated from highly polluted marine sediments at the Sarno River mouth, Italy, using an enrichment culture to which Pb(II) 0.48mmoll(-1) were added. 16S rRNA gene sequencing (Sanger) allowed assignment of the isolate to the genus Bacillus, with Bacillus pumilus as the closest species. The isolate is resistant to Pb(II) with a minimum inhibitory concentration (MIC) of 4.8mmoll(-1) and is also resistant to Cd(II) and Mn(II) with MIC of 2.22mmoll(-1) and 18.20mmoll(-1), respectively. Inductively coupled plasma atomic emission spectrometry (ICP-AES) showed that Pb inoculated in the growth medium is absorbed by the bacterial cells at removal efficiencies of 31.02% and 28.21% in the presence of 0.48mmoll(-1) or 1.20mmoll(-1) Pb(II), respectively. Strain Pb15 forms a brown and compact biofilm when grown in presence of Pb(II). Scanning Electron Microscopy (SEM) coupled with Energy Dispersive X-ray Spectroscopy (SEM-EDS) confirm that the biofilm contains Pb, suggesting an active biosorption of this metal by the bacterial cells, sequestering 14% of inoculated Pb as evidenced by microscopic analyses. Altogether, these observations support evidence that strain Pb15 has potentials for being used in bioremediation of its native polluted sediments, with engineering solutions to be found in order to eliminate the adsorbed Pb before replacement of sediments in situ. PMID:27110973

  12. Imaging of Bioreduced Sediment: Tc(IV/VII) and Fe(II/III) redox kinetics and DTPA as a conservative tracer

    NASA Astrophysics Data System (ADS)

    Vandehey, N. T.; O'Neil, J. P.; Buchko, R.; Druhan, J. L.; Moses, W. W.; Nico, P. S.

    2011-12-01

    Microbially mediated reduction of sediment bound iron from Fe(III) to Fe(II) following electron donor augmentation holds great promise for the sequestration of environmental contaminants including technetium, uranium, and chromium. We have used gamma camera imaging to measure soluble 99mTc concentrations in microcosm experiments; tracking the rate of reduction of 99mTc(IV)-pertechnetate, evaluating 99mTc-DTPA as a conservative hydrologic flow tracer, and examining the dynamics of redox cycling of both Fe(II)/Fe(III) and Tc(IV)/Tc(VII) in sediment from the DOE-IRFC site at Rifle, CO. Eleven experiments were performed on 4 water/sediment microcosms over 4 weeks, before and after microcosms were augmented with 6mM acetate to stimulate microbially mediated reduction of Fe(III) to Fe(II). A summary of the experiments' data is given in the Figure 1. Data analysis methods of fitting concentration curves of 99mTc(VII) in solution to a dual exponential function gives a quantitative index Tc(VII) to Tc(IV) reduction rate in the presence of Fe(II). Following acetate amendment, the rate of Tc(VII) reduction progressively increased with time. A reoxidation experiment showed that oxygenating the microcosms oxidized Fe(II) to Fe(III), subsequently preventing Tc(VII) reduction, but with a return to anoxic conditions, bioreduction of Fe(III) occurred faster than before oxygenation, an observation that is particularly relevant to field-scale work. Another reoxygenation experiment showed that when in reducing conditions, sediment-bound Tc(IV) is rapidly resolublized to Tc(VII) with an increase in dissolved oxygen. 99mTc-DTPA proves to be a conservative tracer, showing little interaction with sediment in both Fe(III)-reducing and non-reducing conditions. These experiments show the utility of nuclear medicine tools and readily available radiotracers for non-invasive monitoring of sediment geochemistry and hydrologic properties during reactive transport.

  13. Sources and timing of anthropogenic pollution in the Ensenada de San Simon (inner Ria de Vigo), Galicia, NW Spain: an application of mixture-modelling and nonlinear optimization to recent sedimentation.

    PubMed

    Howarth, Richard J; Evans, Graham; Croudace, Ian W; Cundy, Andrew B

    2005-03-20

    The Ensenada de San Simon is the inner part of the Ria de Vigo, one of the major mesotidal rias of the Galician coast, NW Spain. The geochemistry of its bottom sediments can be accounted for in terms of both natural and anthropogenic sources. Mixture-modelling enables much of the Cr, Ni, V, Cu, Pb and Zn concentrations of the bottom and subaqueous sediments to be explained by sediment input from the river systems and faecal matter from manmade mussel rafts. The compositions and relative contributions of additional, unknown, sources of anomalous heavy-metal concentrations are quantified using constrained nonlinear optimization. The pattern of metal enrichment is attributed to: material carried in solution and suspension in marine water entering the Ensenada from the polluted industrial areas of the adjacent Ria de Vigo; wind-borne urban dusts and/or vehicular emissions from the surrounding network of roads and a motorway road-bridge over the Estrecho de Rande; industrial and agricultural pollution from the R. Redondela; and waste from a former ceramics factory near the mouth of the combined R. Oitaben and R. Verdugo. Using (137)Cs dating, it is suggested that heavy metal build-up in the sediments since the late 1970s followed development of inshore fisheries and introduction of the mussel rafts (ca. 1960) and increasing industrialisation. PMID:15752499

  14. Microscopic observation of ordered colloids in sedimentation equilibrium and important role of Debye-screening length. VI. Organic solvent aqueous mixtures for heavy and monodisperse spheres (specific gravity=1.50)

    NASA Astrophysics Data System (ADS)

    Okubo, Tsuneo

    1988-02-01

    A metallurgical microscope is used to directly observe the ordered structures of heavy and monodisperse polystyrene-type spheres (specific gravity=1.50) in sedimentation equilibrium and in organic solvent aqueous mixtures. Eight kinds of water miscible organic solvents, i.e., methanol, ethanol, propanol, 1,4-dioxane, ethylene glycol, propylene glycol, N-methylformamide (NMF), and N-methylacetamide (NMA) are used. The center-to-center interparticle distances (D) in the hexagonal ordering increase by the addition of organic solvents of dielectric constants lower than that of water, whereas D decreases in the presence of NMF or NMA, which has a dielectric constant higher than that of water. Young's modulus for the ordered lattices is estimated to be from 0.44 to 1.5 Pa in methanol (0 to 30 vol %) aqueous mixtures. These results show that electrostatic interparticle repulsion and the elongated Debye-screening length around the spheres are essential for the ordering.

  15. Representative measurement of two-dimensional reactive phosphate distributions and co-distributed iron(II) and sulfide in seagrass sediment porewaters.

    PubMed

    Pagès, Anaïs; Teasdale, Peter R; Robertson, David; Bennett, William W; Schäfer, Jörg; Welsh, David T

    2011-11-01

    The high degree of heterogeneity within sediments can make interpreting one-dimensional measurements difficult. The recent development and use of in situ techniques that measure two-dimensional distributions of porewater solutes have facilitated investigation of the role of spatial heterogeneity in sediment biogeochemistry. A colourimetric diffusive equilibration in thin films method has been developed that allows two-dimensional, high-resolution measurement of reactive phosphate in sediment porewaters. A method detection limit of 0.22 μM, an effective upper limit of ~1000 μM and relative standard deviations typically below 5% were achieved. This method was evaluated by deployment in seagrass (Zostera capricorni) colonised sediments, as part of combined probes with similar colourimetric methods for sulfide and iron(II). The two-dimensional, high resolution distributions obtained provide a highly representative measurement of the co-distributions of porewater solutes, allowing heterogeneous features and biogeochemical processes to be observed and interpreted. Microniches of high phosphate concentration >100 μM were observed throughout the distributions and were interpreted to be due to localised zones of rapid organic matter mineralisation, possibly using electron acceptors other than iron(III) oxyhydroxides (e.g. aerobic respiration) as often they did not correspond with microniches of higher Fe(II) concentration. PMID:21855104

  16. Selective recognition of D-tryptophan from d/l-tryptophan mixtures in the presence of Cu(II) by electropolymerized L-lysine film.

    PubMed

    Wang, Fang; Gong, Wencheng; Wang, Lili; Chen, Zilin

    2016-01-01

    Selective recognition of D-tryptophan (D-Trp) in the presence of Cu(II) was investigated at poly-L-lysine (p-l-Lys) film using electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV). p-l-Lys film was immobilized on a glassy carbon electrode (GCE) by cyclic voltammetry between 0.0 and 1.9 V in 20 mM phosphate buffer solution (pH 8.6). After the p-l-Lys/GCE electrode was incubated with D-Trp solution containing Cu(II) ions, obvious enhancement of electron transfer resistance and decrease of voltammetric current could be observed. If D-Trp was replaced by L-tryptophan (l-Trp), there was no apparent resistance and current changes. Moreover, no resistance and current changes could be found in the absence of Cu(II). It may be due to the formation of Cu complex with L-lysine and D-tryptophan. Finally, this method was successfully applied to monitoring enantiomeric composition of the D-Trp and l-Trp mixtures. PMID:26364949

  17. Investigation of simultaneous biosorption of copper(II) and chromium(VI) on dried Chlorella vulgaris from binary metal mixtures: Application of multicomponent adsorption isotherms

    SciTech Connect

    Aksu, Z.; Acikel, U.; Kutsal, T.

    1999-02-01

    Although the biosorption of single metal ions to various kinds of microorganisms has been extensively studied and the adsorption isotherms have been developed for only the single metal ion situation, very little attention has been given to the bioremoval and expression of adsorption isotherms of multimetal ions systems. In this study the simultaneous biosorption of copper(II) and chromium(VI) to Chlorella vulgaris from a binary metal mixture was studied and compared with the single metal ion situation in a batch stirred system. The effects of pH and single- and dual-metal ion concentrations on the equilibrium uptakes were investigated. In previous studies the optimum biosorption pH had been determined as 4.0 for copper(II) and as 2.0 for chromium(VI). Multimetal ion biosorption studies were performed at these two pH values. It was observed that the equilibrium uptakes of copper(II) or chromium(VI) ions were changed due to the biosorption pH and the presence of other metal ions. Adsorption isotherms were developed for both single- and dual-metal ions systems at these two pH values, and expressed by the mono- and multicomponent Langmuir and Freundlich adsorption models. Model parameters were estimated by nonlinear regression. It was seen that the adsorption equilibrium data fitted very well to the competitive Freundlich model in the concentration ranges studied.

  18. Methodological considerations regarding the use of inorganic 197Hg(II) radiotracer to assess mercury methylation potential rates in lake sediment

    USGS Publications Warehouse

    Perez, Catan S.; Guevara, S.R.; Marvin-DiPasquale, M.; Magnavacca, C.; Cohen, I.M.; Arribere, M.

    2007-01-01

    Methodological considerations on the determination of benthic methyl-mercury (CH3Hg) production potentials were investigated on lake sediment, using 197Hg radiotracer. Three methods to arrest bacterial activity were compared: flash freezing, thermal sterilization, and ??-irradiation. Flash freezing showed similar CH3Hg recoveries as thermal sterilization, which was both 50% higher than the recoveries obtained with ??-ray irradiation. No additional radiolabel was recovered in kill-control samples after an additional 24 or 65 h of incubation, suggesting that all treatments were effective at arresting Hg(II)-methylating bacterial activity, and that the initial recoveries are likely due to non-methylated 197Hg(II) carry-over in the organic extraction and/or [197Hg]CH3Hg produced via abiotic reactions. Two CH3Hg extraction methods from sediment were compared: (a) direct extraction into toluene after sediment leaching with CuSO4 and HCl and (b) the same extraction with an additional back-extraction step to thiosulphate. Similar information was obtained with both methods, but the low efficiency observed and the extra work associated with the back-extraction procedure represent significant disadvantages, even tough the direct extraction involves higher Hg(II) carry over. ?? 2007 Elsevier Ltd. All rights reserved.

  19. Enhancement of iron(II)-dependent reduction of nitrite to nitric oxide by thiocyanate and accumulation of iron(II)/thiocyanate/nitric oxide complex under conditions simulating the mixture of saliva and gastric juice.

    PubMed

    Takahama, Umeo; Hirota, Sachiko

    2012-01-13

    Iron(III) ingested as a food component or supplement for iron deficiencies can react with salivary SCN(-) to produce Fe(SCN)(2+) and can be reduced to iron(II) by ascorbic acid in the stomach. Iron(II) generated in the stomach can react with salivary nitrite and SCN(-) to produce nitric oxide (NO) and FeSCN(+), respectively. The purpose of this investigation is to make clear the reactions among nitrite, SCN(-), iron ions, and ascorbic acid under conditions simulating the mixture of saliva and gastric juice. Iron(II)-dependent reduction of nitrite to NO was enhanced by SCN(-) in acidic buffer solutions, and the oxidation product of iron(II) reacted with SCN(-) to produce Fe(SCN)(2+). Almost all of the NO produced was autoxidized to N(2)O(3) under aerobic conditions. Iron(II)-dependent production of NO was also observed in acidified saliva. Under anaerobic conditions, NO transformed Fe(SCN)(2+) and FeSCN(+) to Fe(SCN)NO(+) in acidic buffer solutions. Fe(SCN)NO(+) was also formed under aerobic conditions when excess ascorbic acid was added to iron(II)/nitrite/SCN(-) systems in acidic buffer solutions and acidified saliva. The Fe(SCN)NO(+) formed was transformed to Fe(SCN)(2+) and iron(III) at pH 2.0 and pH 7.4, respectively, by O(2). Salivary glycoproteins could complex with iron(III) in the stomach preventing the formation of Fe(SCN)(2+). Ascorbic acid reduced iron(III) to iron(II) to react with nitrite and SCN(-) as described above. The above results suggest (i) that iron(II) can have toxic effects on the stomach through the formation of reactive nitrogen oxide species from NO when supplemented without ascorbic acid and through the formation of both reactive nitrogen oxide species and Fe(SCN)NO(+) when supplemented with ascorbic acid, and (ii) that the toxic effects of iron(III) seemed to be smaller than and similar to those of iron(II) when supplemented without and with ascorbic acid, respectively. Possible mechanisms that cause oxidative stress on the stomach

  20. Proton/metal-ligand stability constants of complexes of Ni(II), Cu(II), and Co(II) with diethyl 4-(substituted-phenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate in 70% dioxane-water mixture

    NASA Astrophysics Data System (ADS)

    Tekade, Pradip V.; Bajaj, Sonal D.; Thool, Seemita

    2015-12-01

    Physico-chemical properties viz proton-ligand and metal-ligand stability constants of complexes of diethyl 4-(substituted-phenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate with Ni(II), Cu(II), and Co(II) were determined in mixed solvents (70% dioxane). Presence of OH/NH group(s) in these compounds was confirmed at 0.1 M ionic strength in 70% dioxane-water mixture pH-metrically. It is observed that Ni(II), Cu(II), and Co(II) metal ions formed 1: 1 and 1: 2 complex with all the three ligands. The results show that the ratio of log K 1/log K 2 is positive in all cases. This implies that there is little or no steric hindrance to the addition of secondary molecules.

  1. Raman spectroscopic characterization of gas mixtures. II. Quantitative composition and pressure determination of the CO2-CH4 system

    USGS Publications Warehouse

    Seitz, J.C.; Pasteris, J.D.; Chou, I.-Ming

    1996-01-01

    Raman spectral parameters were determined for the v1 band of CH4 and the v1 and 2v2 bands (Fermi diad) of CO2 in pure CO2 and CO2-CH4 mixtures at pressures up to 700 bars and room temperature. Peak position, area, height, and width were investigated as functions of pressure and composition. The peak positions of the CH4 and CO2 bands shift to lower relative wavenumbers as fluid pressure is increased. The peak position of the lower-wavenumber member of the Fermi diad for CO2 is sensitive to fluid composition, whereas the peak positions of the CH4 band and the upper Fermi diad member for CO2 are relatively insensitive in the CO2-CH4 system. The magnitude of the shifts in each of the three peak positions (as a function of pressure) is sufficient to be useful as a monitor of fluid pressure. The relative molar proportions in a CO2-CH4 mixture may be determined from the peak areas: the ratio of the peak areas of the CH4 band and the CO2 upper Fermi diad member is very sensitive to composition, whereas above about 100 bars, it is insensitive to pressure. Likewise, the peak height ratio is very sensitive to composition but also to fluid pressure. The individual peak widths of CO2 and CH4, as well as the ratios of the widths of the CH4 peak to the CO2 peaks are a sensitive function of pressure and, to a lesser extent, composition. Thus, upon determination of fluid composition, the peak width ratios may be used as a monitor of fluid pressure. The application of these spectral parameters to a suite of natural CO2-CH4 inclusions has yielded internally-consistent, quantitative determinations of the fluid composition and density.

  2. Zyflamend, a polyherbal mixture, down regulates class I and class II histone deacetylases and increases p21 levels in castrate-resistant prostate cancer cells

    PubMed Central

    2014-01-01

    Background Zyflamend, a mixture containing extracts of ten herbs, has shown promise in a variety of preclinical cancer models, including prostate cancer. The current experiments were designed to investigate the effects of Zyflamend on the expression of class I and II histone deacetylases, a family of enzymes known to be over expressed in a variety of cancers. Methods CWR22Rv1 cells, a castrate-resistant prostate cancer cell line, were treated with Zyflamend and the expression of class I and II histone deacetylases, along with their downstream target the tumor suppressor gene p21, was investigated. Involvement of p21 was confirmed with siRNA knockdown and over expression experiments. Results Zyflamend down-regulated the expression of all class I and II histone deacetylases where Chinese goldthread and baikal skullcap (two of its components) appear to be primarily responsible for these results. In addition, Zyflamend up regulated the histone acetyl transferase complex CBP/p300, potentially contributing to the increase in histone 3 acetylation. Expression of the tumor suppressor gene p21, a known downstream target of histone deacetylases and CBP/p300, was increased by Zyflamend treatment and the effect on p21 was, in part, mediated through Erk1/2. Knockdown of p21 with siRNA technology attenuated Zyflamend-induced growth inhibition. Over expression of p21 inhibited cell growth and concomitant treatment with Zyflamend enhanced this effect. Conclusions Our results suggest that the extracts of this polyherbal combination increase histone 3 acetylation, inhibit the expression of class I and class II histone deacetylases, increase the activation of CBP/p300 and inhibit cell proliferation, in part, by up regulating p21 expression. PMID:24555771

  3. INCIDENCE OF STRESS IN BENTHIC COMMUNITIES ALONG THE U.S. ATLANTIC AND GULF OF MEXICO COASTS WITHIN DIFFERENT RANGES OF SEDIMENT CONTAMINATION FROM CHEMICAL MIXTURES

    EPA Science Inventory

    Synoptic data on concentrations of sediment-associated chemical contaminants and benthic macroinfaunal community structure were collected from 1,389 stations in estuaries along the U.S. Atlantic and Gulf of Mexico coasts as part of the nationwide Environmental Monitoring and Asse...

  4. INCIDENCE OF STRESS IN BENTHIC COMMUNITIES ALONG U.S. ATLANTIC AND GULF OF MEXICO COASTS WITHIN DIFFERENT RANGES OF SEDIMENT CONTAMINATION FROM CHEMICAL MIXTURES

    EPA Science Inventory

    Synoptic data on concentrations of sediment-associated chemical contaminants and benthic macroinfaunal community structure were collected from 1,389 stations in estuaries along the U.S. Atlantic and Gulf of Mexico coasts as part of the nationwide Environmental Monitoring and Asse...

  5. Abundance, Distribution, and Activity of Fe(II)-Oxidizing and Fe(III)-Reducing Microorganisms in Hypersaline Sediments of Lake Kasin, Southern Russia

    PubMed Central

    Emmerich, Maren; Bhansali, Ankita; Lösekann-Behrens, Tina; Schröder, Christian; Kappler, Andreas

    2012-01-01

    The extreme osmotic conditions prevailing in hypersaline environments result in decreasing metabolic diversity with increasing salinity. Various microbial metabolisms have been shown to occur even at high salinity, including photosynthesis as well as sulfate and nitrate reduction. However, information about anaerobic microbial iron metabolism in hypersaline environments is scarce. We studied the phylogenetic diversity, distribution, and metabolic activity of iron(II)-oxidizing and iron(III)-reducing Bacteria and Archaea in pH-neutral, iron-rich salt lake sediments (Lake Kasin, southern Russia; salinity, 348.6 g liter−1) using a combination of culture-dependent and -independent techniques. 16S rRNA gene clone libraries for Bacteria and Archaea revealed a microbial community composition typical for hypersaline sediments. Most-probable-number counts confirmed the presence of 4.26 × 102 to 8.32 × 103 iron(II)-oxidizing Bacteria and 4.16 × 102 to 2.13 × 103 iron(III)-reducing microorganisms per gram dry sediment. Microbial iron(III) reduction was detected in the presence of 5 M NaCl, extending the natural habitat boundaries for this important microbial process. Quantitative real-time PCR showed that 16S rRNA gene copy numbers of total Bacteria, total Archaea, and species dominating the iron(III)-reducing enrichment cultures (relatives of Halobaculum gomorrense, Desulfosporosinus lacus, and members of the Bacilli) were highest in an iron oxide-rich sediment layer. Combined with the presented geochemical and mineralogical data, our findings suggest the presence of an active microbial iron cycle at salt concentrations close to the solubility limit of NaCl. PMID:22504804

  6. Ultralayered Co3O4 as a new adsorbent for preconcentration of Pb(II) from water, food, sediment and tobacco samples.

    PubMed

    Yavuz, Emre; Tokalıoğlu, Serife; Sahan, Halil; Patat, Saban

    2013-10-15

    In this study, ultralayered Co3O4 adsorbent was synthesized and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The surface area of the solid material was found to be 75.5m(2)g(-1) by BET method. The ultralayered Co3O4 was used for the first time as an effective adsorbent for the preconcentration of the Pb(II) ions in various samples prior to flame atomic absorption detection. Analytical parameters affecting the solid phase extraction of Pb(II) such as pH, adsorption and elution contact time, eluent volume and concentration, sample volume and common matrix ions were investigated. The recovery values for Pb(II) were found to be ≥ 92% even in the presence of 75,000 mg L(-1) Na(I), 75,000 mg L(-1) K(I), and 75,000 mg L(-1) Ca(II) ions. 10s vortexing time was enough for both adsorption and elution contact times. The elution was easily made with 2 mL of 2.0 mol L(-1) HNO3. The reusability (170 cycles) and adsorption capacity (35.5 mg g(-1)) of ultralayered Co3O4 were excellent. The preconcentration factor of the method and detection limit were found to be 175 and 0.72 µg L(-1), respectively. The described method was validated with certified reference material (RM 8704 Buffalo River Sediment, BCR-482 Licken and SPS-WW1 Batch 111-Wastewater) and spiked real samples. It was also applied for the preconcentration of Pb(II) ions in various water (well water, mineral water, waste water and sea water), food (cauliflower and barley), street sediment and tobacco samples. PMID:24054654

  7. Multielement chemical and statistical analyses from a uranium hydrogeochemical and stream-sediment survey in and near the Elkhorn Mountains, Jefferson County, Montana; Part II, Stream sediments

    USGS Publications Warehouse

    Suits, V.J.; Wenrich, K.J.

    1982-01-01

    Fifty-two stream-sediment samples, collected from an area south of Helena, Jefferson County, Montana, were sieved into two size fractions (50 ppm for the fine fraction) were encountered in samples from the Warm Springs Creek drainage area, along Prickly Pear Creek near Welmer and Golconda Creeks and along Muskrat Creek. All groups showed a significant correlation at the 99 percent confidence level (r between 0.73 and 0.77) between U and Th. Uranium was found to correlate significantly only with Th (as mentioned above) and with -Ni in the fine fraction of the volcanics group. U correlates significantly with -Al2O3, Ba, organic C, -K2O, -Sr and Y in both size fractions for the Boulder batholith. Correlations between U and each of several elements differ for the fine and coarse fractions of the Boulder batholith group, suggesting that the U distribution in these stream sediments is in large part controlled by grain size. Correlations were found between U and CaO, Cr, Fe203, -Na2O, Sc, -SiO2, TiO2, Yb and Zr in the coarse fraction but not in the fine fraction. U correlates weakly (to the 90% confidence level, crc<.37) with -Co and -Cu in the fine but not the coarse fraction. These results are compared to a previous study in the northern Absaroka mountains. Correlation coefficients between all other elements determined from these samples are also shown in Tables 12 to 15.

  8. Oil residues in Baltic sediment, mussel and fish. II. Study of the Finnish Archipelago 1979-81

    SciTech Connect

    Paasivirta, J.; Kaariainen, H.; Lahtipera, M.; Pellinen, J.; Sinkkonen, S.

    1982-01-01

    Aliphatic hydrocarbons and non-polar aromatic compounds have been analyzed after a spill of crude oil at Baltic Sea 1979 from drifting weathered oil glumps, sediment and sediment trap samples and bivalves at five areas of the Finnish Archipelago Sea. Mytilus and flounder muscles and flounder livers were analyzed 1980 and 1981 from three of the previous five areas. The glumps were shown to be weathered crude oil. Sediment trap samples on the visibly contaminated area contained higher amounts of oil residues and in different ratios than the bottom sediments at the same areas. Extra local aliphatic hydrocarbon pollution was detected from the sediment traps at the reference area. Bivalves contained high amounts of oil residues at visibly polluted but in some visibly non-polluted areas also 1979. Any significant decontamination was not detected at summer 1979 but next year the Mytilus samples contained only traces if any and 1981 no detectable levels of aromatic oil residues. Aliphatic hydrocarbon residues in flounders showed no regional differences and no significant change of levels between 1980 and 1981. In contrary, the aromatic oil residues decreased to the non-detectable level in flounder muscles and to a significantly lower level in flounder livers 1981 related to 1980. Linear correlations of the analysis results are discussed.

  9. Natural attenuation of contaminated marine sediments from an old floating dock Part II: changes of sediment microbial community structure and its relationship with environmental variables.

    PubMed

    Wang, Ya-Fen; Tam, Nora Fung-Yee

    2012-04-15

    Changes of microbial community structure and its relationship with various environmental variables in surface marine sediments were examined for a one-year period after the removal of an old floating dock in Hong Kong SAR, South China. Temporal variations in the microbial community structure were clearly revealed by principal component analysis (PCA) of the microbial ester-linked fatty acid methyl ester (EL-FAME) profiles. The most obvious shift in microbial community structure was detected 6 months after the removal of the dock, although no significant decline in the levels of pollutants could be detected. As determined by EL-FAME profiles, the microbial diversity recovered and the predominance of gram-negative bacteria was gradually replaced by gram-positive bacteria and fungi in the impacted stations. With redundancy analysis (RDA), the concentration of total polycyclic aromatic hydrocarbons (PAHs) was found to be the second important determinant of microbial community structure, next to Time. The relative abundance of 18:1ω9c and hydroxyl fatty acids enriched in the PAH hot spots, whereas 16:1ω9 and 18:1ω9t were negatively correlated to total PAH concentration. The significant relationships observed between microbial EL-FAME profiles and pollutants, exampled by PAHs in the present study, suggested the potential of microbial community analysis in the assessment of the natural attenuation process in contaminated environments. PMID:22417882

  10. Use of vegetated drainage ditches and low-grade weirs for aquaculture effluent mitigation: II. Suspended sediment

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Total suspended solids are a priority pollutant under the Clean Water Act and a point of concern for aquaculture facilities. The use of ubiquitous vegetated ditches on the aquaculture landscape may serve as an environmentally and economically sustainable practice for reducing suspended sediment cont...

  11. Organic geochemistry of sediments from the continental margin off southern New England, U.S.A.--Part II. Lipids

    NASA Technical Reports Server (NTRS)

    Venkatesan, M. I.; Ruth, E.; Steinberg, S.; Kaplan, I. R.

    1987-01-01

    Organic geochemical measurements of the lipid fraction, comparing saturated and aromatic hydrocarbons, fatty acids, alcohols and sterols, have been carried out on six sediments cores collected from the Atlantic shelf, slope and the rise areas to evaluate the cross-shelf transport of the organic carbon. The concentration of most of the organic compound classes studied is correlated with the total organic carbon, which decreases from the shelf through slope to the rise. Terrigenous carbon is recognizable even in the slope and rise sediments, but terrestrial influx decreases relative to marine generated lipids in the slope and rise organic matter. We estimate that approximately 50% of the shelf organic matter is exported to the slope. Data of sediment trap material collected at 1200 m from 1250 m water depth are discussed and compared with that of surface sediment from 1280 m water depth (slope). Fluxes for specific organic compound classes have been computed. The fluxes are of the same magnitude as for equatorial North Atlantic trap particulates at comparable water depth, studied by other investigations.

  12. From dihydrated iron(III) phosphate to monohydrated ammonium-iron(II) phosphate: Solvothermal reaction mediated by acetone-urea mixtures

    SciTech Connect

    Alfonso, Belen F.; Pique, Carmen; Blanco, Jesus A.

    2012-12-15

    By reaction between synthetic phosphosiderite FePO{sub 4}{center_dot}2H{sub 2}O, urea (NH{sub 2}){sub 2}CO, and acetone (CH{sub 3}){sub 2}CO, we report a novel solvothermal synthesis of polycrystalline NH{sub 4}FePO{sub 4}{center_dot}H{sub 2}O. The preparation of other two individual phases, NH{sub 4}Fe{sub 2}(OH)(PO{sub 4}){sub 2}{center_dot}2H{sub 2}O and NH{sub 4}Fe{sub 2}(PO{sub 4}){sub 2}, is also described. The obtained product is a function of the reaction time and the N/P molar ratio in the reagent mixture, and the existence of structural memory in the dissolution-precipitation processes is discussed. Below 25 K, NH{sub 4}FePO{sub 4}{center_dot}H{sub 2}O behaves magnetically in a complex way, because both ferromagnetic and antiferromagnetic signals are superimposed, suggesting the existence of a canting of iron(II) magnetic moments. - Graphical abstract: Solvothermal synthesis of polycrystalline NH{sub 4}FePO{sub 4}{center_dot}H{sub 2}O is presented. The preparation of other two individual phases, NH{sub 4}Fe{sub 2}(OH)(PO{sub 4}){sub 2}{center_dot}2H{sub 2}O and NH{sub 4}Fe{sub 2}(PO{sub 4}){sub 2} as a function of the N/P molar ratio in the reagent mixture and the reaction time, is also described. Highlights: Black-Right-Pointing-Pointer Solvothermal synthesis of NH{sub 4}FePO{sub 4}{center_dot}H{sub 2}O from an Fe(III) phosphate: reduction process. Black-Right-Pointing-Pointer Formation of two intermediate metastable phases: phase diagram. Black-Right-Pointing-Pointer Thermal decomposition in two steps: mass loss of both water and ammonia. Black-Right-Pointing-Pointer Magnetic behaviour: AF+constant spontaneous magnetization.

  13. Development of Surface Complexation Models of Cr(VI) Adsorption on Soils, Sediments and Model Mixtures of Kaolinite, Montmorillonite, γ-Alumina, Hydrous Manganese and Ferric Oxides and Goethite

    SciTech Connect

    Koretsky, Carla

    2013-11-29

    Hexavalent chromium is a highly toxic contaminant that has been introduced into aquifers and shallow sediments and soils via many anthropogenic activities. Hexavalent chromium contamination is a problem or potential problem in the shallow subsurface at several DOE sites, including Hanford, Idaho National Laboratory, Los Alamos National Laboratory and the Oak Ridge Reservation (DOE, 2008). To accurately quantify the fate and transport of hexavalent chromium at DOE and other contaminated sites, robust geochemical models, capable of correctly predicting changes in chromium chemical form resulting from chemical reactions occurring in subsurface environments are needed. One important chemical reaction that may greatly impact the bioavailability and mobility of hexavalent chromium in the subsurface is chemical binding to the surfaces of particulates, termed adsorption or surface complexation. Quantitative thermodynamic surface complexation models have been derived that can correctly calculate hexavalent chromium adsorption on well-characterized materials over ranges in subsurface conditions, such pH and salinity. However, models have not yet been developed for hexavalent chromium adsorption on many important constituents of natural soils and sediments, such as clay minerals. Furthermore, most of the existing thermodynamic models have been developed for relatively simple, single solid systems and have rarely been tested for the complex mixtures of solids present in real sediments and soils. In this study, the adsorption of hexavalent chromium was measured as a function of pH (3-10), salinity (0.001 to 0.1 M NaNO3), and partial pressure of carbon dioxide(0-5%) on a suite of naturally-occurring solids including goethite (FeOOH), hydrous manganese oxide (MnOOH), hydrous ferric oxide (Fe(OH)3), γ-alumina (Al2O3), kaolinite (Al2Si2O5(OH)4), and montmorillonite (Na3(Al, Mg)2Si4O10(OH)2-nH2O). The results show that all of these materials can bind substantial quantities of

  14. Co-precipitation of Ni, Cr, Mn, Pb and Zn in industrial wastewater and sediment samples with copper(II) cyclo-hexylmethyldithiocarbamate for their flame atomic absorption spectrometric determination.

    PubMed

    Ipeaiyeda, Ayodele Rotimi; Odola, Adekunle Johnson

    2012-01-01

    A co-precipitation technique for nickel(II), chromium(II), manganese(II), lead(II) and zinc(II) with the aid of copper(II) cyclo-hexylmethyldithiocarbamate was established. The influences of some analytical parameters such as pH, sample volume, amounts of cyclo-hexylmethyldithiocarbamate and copper(II) on the recovery of metal ions were investigated. The heavy metals in the precipitate were determined by flame atomic absorption spectrophotometry. The range of detection limits for the heavy metals was 0.003-0.005 mg/L. The atomic spectrometric technique with co-precipitation procedure was successfully applied for the determination of Ni, Cr, Mn, Pb and Zn in industrial wastewater and sediment samples from Ladipo stream in Lagos, Nigeria. The mean concentrations for these metals using co-precipitation procedure were not significantly different from corresponding concentrations obtained using spectrometric techniques without co-precipitation procedure. PMID:22678206

  15. [Product development on the basis of cereal and leguminous flours to coeliac disease in children aged 6-24 months; II: properties of the mixtures].

    PubMed

    Cerezal Mezquita, P; Urtuvia Gatica, V; Ramírez Quintanilla, V; Arcos Zavala, R

    2011-01-01

    The nutritional formulations of high protein content, provided by a flour mixture from two Andean cultures, quinua (Chenopodium quinua Willd) and lupino (Lupinus albus L), with two traditional cereals, maize (Zea mays L.) and rice (Oryza sativa L.), entailed to the preparation of a "sweet mixture" for the elaboration of "queques" and another "dessert mixture" flavoured with banana, that can be prepared with water or milk, constituted a good alternative as food supplement for the nutrition of children aged 6-24 months who suffer from celiac disease, since they contribute to the quality improvement of the protein, by essential amino acids compensation, they are of low cost and allow an increase in availability of products for gluten-intolerant children. Some physical, chemical, rheological, mechanical and fluidity properties, as well as the color of these mixtures for a period of conservation of 90 days were evaluated. At the end of the storage, the sweet mixture turned out to be of "little flow" and the dessert mixture changed from "little flow" to "easy flow". Viscosity for the dessert mixture, with its two types of dilutions, water and milk, presented a behavior of pseudoplastic fluid. It was possible to guess that the time of shelf life of the mixtures would be of 9 months before achieving the rancidity limit (10 mEq of oxigen/kg of fat, which would disqualify the product for consumption). The CIEL*a*b* color coordinates did not show significant differences keeping the colour in "a beige" tonality. PMID:21519743

  16. Anaerobic oxidation of methane (AOM) in marine sediments from the Skagerrak (Denmark): II. Reaction-transport modeling

    NASA Astrophysics Data System (ADS)

    Dale, A. W.; Regnier, P.; Knab, N. J.; Jørgensen, B. B.; Van Cappellen, P.

    2008-06-01

    A steady-state reaction-transport model is applied to sediments retrieved by gravity core from two stations (S10 and S13) in the Skagerrak to determine the main kinetic and thermodynamic controls on anaerobic oxidation of methane (AOM). The model considers an extended biomass-implicit reaction network for organic carbon degradation, which includes extracellular hydrolysis of macromolecular organic matter, fermentation, sulfate reduction, methanogenesis, AOM, acetogenesis and acetotrophy. Catabolic reaction rates are determined using a modified Monod rate expression that explicitly accounts for limitation by the in situ catabolic energy yields. The fraction of total sulfate reduction due to AOM in the sulfate-methane transition zone (SMTZ) at each site is calculated. The model provides an explanation for the methane tailing phenomenon which is observed here and in other marine sediments, whereby methane diffuses up from the SMTZ to the top of the core without being consumed. The tailing is due to bioenergetic limitation of AOM in the sulfate reduction zone, because the methane concentration is too low to engender favorable thermodynamic drive. AOM is also bioenergetically inhibited below the SMTZ at both sites because of high hydrogen concentrations (∼3-6 nM). The model results imply there is no straightforward relationship between pore water concentrations and the minimum catabolic energy needed to support life because of the highly coupled nature of the reaction network. Best model fits are obtained with a minimum energy for AOM of ∼11 kJ mol-1, which is within the range reported in the literature for anaerobic processes.

  17. 900-m high gas plumes rising from marine sediments containing structure II hydrates at Vestnesa Ridge, offshore W-Svalbard

    NASA Astrophysics Data System (ADS)

    Smith, Andrew J.; Mienert, Jürgen; Bünz, Stefan; Greinert, Jens; Rasmussen, Tine L.

    2013-04-01

    We study an arctic sediment drift in ~1200 m water depth at Vestnesa Ridge, offshore western Svalbard. The ridge is spotted with pockmarks that range in size from a few meters to hundreds of meters in diameter and centimeters to tens of meters in height (e.g. Vogt et al., 1994). There is a strong negative-polarity seismic reflection below the ridge that is interpreted to record a negative impedance contrast marking the boundary between gas hydrate and water above and free gas and water below: it is the bottom-simulating reflector (BSR). Seismically transparent zones, interpreted as gas chimneys, extend from pockmarks at the seafloor to depths below the BSR (180-220 meters below the seafloor) (Bünz et al., 2012). Gas flares, gas hydrate, and methane-seep-specific biological communities (pogonphora and begiatoa bacterial mats) have been observed adjacent to pockmarks at the ridge (Bünz et al., 2012). We present new single-beam echosounding data that were acquired during 2010 and 2012 cruises on the R/V Helmer Hanssen at Vestnesa Ridge using a Simrad EK60 system that operates at frequencies of 18 and 38 kHz. During both cruises which lasted 3-5 days, we detected continuous bubble release from 4 separate pockmarks in 2010 and 6 separate pockmarks in 2012. There were no noticeable, short-term (hourly or daily) variations in the bubble release from the pockmarks, indicating that the venting from the pockmarks does not undergo rapid changes. Plumes from the pockmarks rise between 875 to 925m above the seafloor to a final water depth of 325 to 275m, respectively. This depth is in excellent agreement with the top of the hydrate stability zone (275 meters below sea level) for the gas composition of hydrate sampled at the ridge (96.31% C1; 3.36% C2; 0.21% C3; 0.11% IC4; 0.01% NC4). This suggests that hydrate skins are forming around the gas bubbles, inhibiting the dissolution of gas, and allowing the bubbles to rise to such great heights in the water column. Our results

  18. Cloud point extraction of Cu(II) using a mixture of Triton X-100 and dithizone with a salting-out effect and its application to visual determination.

    PubMed

    Sato, Nobuko; Mori, Masanobu; Itabashi, Hideyuki

    2013-12-15

    A method for the separation and concentration of trace copper(II) ion (Cu(II)) via cloud point extraction (CPE) using a nonionic surfactant with a salting-out effect was developed and applied as a technique for the visual determination of Cu(II). Triton X-100 (TX-100), which has a cloud point at 64-67 °C in aqueous solutions, was used as the nonionic surfactant for the CPE of Cu(II). Although CPE with TX-100 requires heating of the solution to separate the surfactant-rich phase from the aqueous phase, the new method achieves phase separation at 15-30 °C owing to the addition of a large amount of salt to the solution, which lowers the cloud point. The compound 1,5-diphenylthiocarbazone (dithizone) was selected as the chelating agent for complexation and transfer of Cu(II) to the surfactant-rich phase. The extractability of Cu(II) (initial concentration: 10 μM) was 96.6±2.1% when Na2SO4 was added to a 20% TX-100/4 μM dithizone solution (pH 2). Using this method, the visual determination of Cu(II) was possible for concentrations ranging from 0.01 to 10 μM. In addition, the extraction system was successfully applied to the visual determination of Cu(II) in a river water sample. PMID:24209356

  19. Person Heterogeneity of the BDI-II-C and Its Effects on Dimensionality and Construct Validity: Using Mixture Item Response Models

    ERIC Educational Resources Information Center

    Wu, Pei-Chen; Huang, Tsai-Wei

    2010-01-01

    This study was to apply the mixed Rasch model to investigate person heterogeneity of Beck Depression Inventory-II-Chinese version (BDI-II-C) and its effects on dimensionality and construct validity. Person heterogeneity was reflected by two latent classes that differ qualitatively. Additionally, person heterogeneity adversely affected the…

  20. How to overcome inter-electrode variability and instability to quantify dissolved oxygen, Fe(II), mn(II), and S(−II) in undisturbed soils and sediments using voltammetry

    USGS Publications Warehouse

    Slowey, Aaron J.; Marvin-DiPasquale, Mark

    2012-01-01

    Conclusions - Despite their intrinsic variability, Hg/Au electrodes fabricated by hand can be used to quantify O2, S(−II), Fe(II), and Mn(II) without calibrating every electrode for every constituent of interest. The pilot ion method can achieve accuracies to within 20% or less, provided that the underlying principle—the independence of slope ratios—is demonstrated for all voltammetric techniques used, and effects of the physicochemical properties of the system on voltammetric signals are addressed through baseline subtraction.

  1. Consequences of contaminant mixture on the dynamics and functional diversity of bacterioplankton in a southwestern Mediterranean coastal ecosystem.

    PubMed

    Pringault, Olivier; Lafabrie, Céline; Avezac, Murielle; Bancon-Montigny, Chrystelle; Carre, Claire; Chalghaf, Mohamed; Delpoux, Sophie; Duvivier, Adrien; Elbaz-Poulichet, Françoise; Gonzalez, Catherine; Got, Patrice; Leboulanger, Christophe; Spinelli, Sylvie; Hlaili, Asma Sakka; Bouvy, Marc

    2016-02-01

    Contamination of coastal environments is often due to a complex mixture of pollutants, sometimes in trace levels, that may have significant effects on diversity and function of organisms. The aim of this study was to evaluate the short-term dynamics of bacterioplankton exposed to natural and artificial mixtures of contaminants. Bacterial communities from a southwestern Mediterranean ecosystem, lagoon and the bay (offshore) of Bizerte were exposed to i) elutriate from resuspension of contaminated sediment, and ii) an artificial mixture of metals and herbicides mimicking the contamination observed during sediment resuspension. Elutriate incubation as well as artificial spiking induced strong enrichments in nutrients (up to 18 times), metals (up to six times) and herbicides (up to 20 times) relative to the in situ concentrations in the offshore station, whereas the increases in contaminants were less marked in the lagoon station. In the offshore waters, the artificial mixture of pollutants provoked a strong inhibition of bacterial abundance, production and respiration and significant modifications of the potential functional diversity of bacterioplankton with a strong decrease of the carbohydrate utilization. In contrast, incubation with elutriate resulted in a stimulation of bacterial activities and abundances, suggesting that the toxic effects of pollutants were modified by the increase in nutrient and DOM concentrations due to the sediment resuspension. The effects of elutriate and the artificial mixture of pollutants on bacterial dynamics and the functional diversity were less marked in the lagoon waters, than in offshore waters, suggesting a relative tolerance of lagoon bacteria against contaminants. PMID:26451655

  2. Measurement of methyl mercury (I) and mercury (II) in fish tissues and sediments by HPLC-ICPMS and HPLC-HGAAS.

    PubMed

    Jagtap, Rajani; Krikowa, Frank; Maher, William; Foster, Simon; Ellwood, Michael

    2011-07-15

    A procedure for the extraction and determination of methyl mercury and mercury (II) in fish muscle tissues and sediment samples is presented. The procedure involves extraction with 5% (v/v) 2-mercaptoethanol, separation and determination of mercury species by HPLC-ICPMS using a Perkin-Elmer 3 μm C8 (33 mm×3 mm) column and a mobile phase 3 containing 0.5% (v/v) 2-mercaptoethanol and 5% (v/v) CH(3)OH (pH 5.5) at a flow rate 1.5 ml min(-1) and a temperature of 25°C. Calibration curves for methyl mercury (I) and mercury (II) standards were linear in the range of 0-100 μgl(-1) (r(2)=0.9990 and r(2)=0.9995 respectively). The lowest measurable mercury was 0.4 μgl(-1) which corresponds to 0.01 μgg(-1) in fish tissues and sediments. Methyl mercury concentrations measured in biological certified reference materials, NRCC DORM - 2 Dogfish muscle (4.4±0.8 μgg(-1)), NRCC Dolt - 3 Dogfish liver (1.55±0.09 μgg(-1)), NIST RM 50 Albacore Tuna (0.89±0.08 μgg(-1)) and IRMM IMEP-20 Tuna fish (3.6±0.6 μgg(-1)) were in agreement with the certified value (4.47±0.32μgg(-1), 1.59±0.12 μgg(-1), 0.87±0.03 μgg(-1), 4.24±0.27 μgg(-1) respectively). For the sediment reference material ERM CC 580, a methyl mercury concentration of 0.070±0.002 μgg(-1) was measured which corresponds to an extraction efficiency of 92±3% of certified values (0.076±0.04 μgg(-1)) but within the range of published values (0.040-0.084 μgg(-1); mean±s.d.: 0.073±0.05 μgg(-1), n=40) for this material. The extraction procedure for the fish tissues was also compared against an enzymatic extraction using Protease type XIV that has been previously published and similar results were obtained. The use of HPLC-HGAAS with a Phenomenox 5 μm Luna C18 (250 mm×4.6 mm) column and a mobile phase containing 0.06 moll(-1) ammonium acetate (Merck Pty Limited, Australia) in 5% (v/v) methanol and 0.1% (w/v) l-cysteine at 25°C was evaluated as a complementary alternative to HPLC-ICPMS for the measurement of

  3. Fission-fragment excited xenon/rare gas mixtures. II. Small signal gain of the 2. 03 [mu]m xenon transition

    SciTech Connect

    Hebner, G.A.; Hays, G.N. )

    1993-04-15

    The results of small signal gain measurements of the 2.03 [mu]m (5[ital d][3/2][sub 1][minus]6[ital p][3/2][sub 1]) xenon transition in fission-fragment excited Ar/Xe, He/Ar/Xe, Ne/Ar/Xe, and He/Ne/Ar/Xe gas mixtures is presented. Time resolved small signal gain was probed using a cw He/Xe discharge laser as a function of total pressure, xenon concentration, pump power, He/Ne/Ar buffer ratio, and impurity concentration. Small signal gains of up to 6%/cm were observed for pump rates of 15 W/cm[sup 3]. Addition of helium and/or neon to the argon buffer increased the width of the laser gain and reduced the absorption observed under some experimental conditions. Experimentally determined gain scaling laws for several gas mixtures are presented.

  4. Assessment of heavy metals and arsenic contamination in the sediments of the Moulouya River and the Hassan II Dam downstream of the abandoned mine Zeïda (High Moulouya, Morocco)

    NASA Astrophysics Data System (ADS)

    El Azhari, Abdellah; Rhoujjati, Ali; EL Hachimi, Moulay Laârabi

    2016-07-01

    To evaluate the sediment contamination level near the abandoned (PbZn) mine Zeïda, heavy metal concentrations were determined in sediment samples from the Moulouya River, the Ansegmir tributary and the Hassan II Dam located downstream of the abandoned mine. These samples were analysed for their geochemical properties: mineralogy by XRD, carbonate content, pH, particle size and the total concentrations of Pb, Zn, As and Cu elements by ICP-AES. The assessment of the sediment pollution extent was performed by using the multiple pollution indices: contamination factor (CF), pollution load index (PLI) and the geoaccumulation index (Igeo). The Highest CF values (>6) of Pb that have been observed downstream of the tailings promote a high Pb contamination in that specific area. The PLIs results showed that all stations, except for those upstream of the tailings and on the Hassan II Dam, have been found moderately to highly contaminated. The Igeo results confirmed the Pb high contamination but also the extreme As contamination. The potential ecological risk factor results and the comparison with the sediment quality guidelines revealed that the Pb and As levels are potentially toxic to the sediment-dwelling organisms. Based on the multivariate statistical analysis results and the spatial distribution of the sediment contamination level, the pollution of Pb and As have different sources. Pb contamination is located exclusively near and downstream of the tailings. These latter's may be considered as an important point source of Pb into the Moulouya River. The As contamination is derived from a larger scale input sources which can be related to anthropogenic and/or lithogenic effects.

  5. Solvent effects on the vibrational structure of the ultraviolet spectra of cyanoaromatics. The influence of electron—donor—acceptor (EDA) interactions—II. Studies in binary solvent mixtures

    NASA Astrophysics Data System (ADS)

    Toselli, Nancy B.; Silber, Juana J.; Anunziata, Jorge D.

    The concept of preferential solvation has been used to detect and quantify specific interactions, particularly electron—donor—acceptor (EDA) interactions for the solutes 1-cyanonaphthalene and 1,2-dicyanobenzene which can act as π electron acceptors. These acceptors have been studied in binary solvent mixtures, in which one of the solvents can act as an electron donor while the other is an "inert" cosolvent. Thus we analysed the preferential solvation of the aromatic compounds in the following mixtures: cyclohexane—diethylether, cyclohexane—diethylamine, diethylamine—diethylether, cyclohexane-diisopropylamine, cyclohexane—diisopropylether and diisopropylamine—diisopropylether. The evaluation of the degree of preferential solvation was performed by an analysis of the intensity enhancements of the vibronic absorption spectral bands of the acceptors in the binary mixtures. This method seems to be a useful approach to observing preferential solvation, is proposed as a method to detect EDA interaction, for systems where no new bands are observed such as in complexes between cyanoaromatics and aliphatic amines.

  6. Oral exposure of mice to cadmium (II), chromium (VI) and their mixture induce oxidative- and endoplasmic reticulum-stress mediated apoptosis in the livers.

    PubMed

    Jin, Yuanxiang; Zhang, Songbin; Tao, Runhua; Huang, Jie; He, Xingzhi; Qu, Lanya; Fu, Zhengwei

    2016-06-01

    Health concerns regarding the environmental heavy metals in wildlife and humans have increased in recent years. We evaluated the effects of exposure of mice to low doses of cadmium (Cd), chromium (Cr) and their mixtures on oxidative- and ER-stress. Male adult mice were orally exposed to Cd (0.5 and 2 mg kg(-1) ), Cr (1 and 4 mg kg(-1) ) and binary Cd+Cr mixtures (0.25 + 05 and 1 + 2 mg kg(-1) ) daily for 36 days. We observed that the bioaccumulation of Cd and Cr in the liver in a dose-dependent manner, and the Cd and Cr contents in the 2 mg kg(-1) Cd and 4 mg kg(-1) Cr treated groups reached 2.43 and 3.46 µg g(-1) liver weight. In addition, treatments with 2 mg kg(-1) Cd, 4 mg kg(-1) Cr or their mixture (1 + 2 mg kg(-1) ) significantly decreased body and liver weights, increased the levels of reactive oxygen species (ROS), malondialdehyde (MDA) and activities of catalase (CAT) and glutathione peroxidase (GPX) in the liver. Moreover, Cd and Cr exposures also elevated the transcription of the oxidative- and endoplasmic reticulum (ER)-stress related genes including Cat, Gpx, heme oxygenase 1 (Ho-1), regulated protein 78 (Grp78), activating transcription factor 6 (Atf6) and proaoptotic CCAAT/-enhancer-binding protein homologous protein (Chop) in a dose dependent manner in the liver. And hepatic cytochrome c levels increased in all Cd, Cr or their mixture treated groups. Furthermore, the transcriptional status and the activities of Caspase 9 and Caspase 3 were increased significantly in the liver when exposed to high doses of Cd, Cr or their mixture. These results suggested that a long period exposure of mice to Cd or Cr has the potential to elicit oxidative- and ER-stress mediated apoptosis in their livers. © 2014 Wiley Periodicals, Inc. Environ Toxicol 31: 693-705, 2016. PMID:25409916

  7. Multi-level assessment of chronic toxicity of estuarine sediments with the amphipod Gammarus locusta: II. Organism and population-level endpoints.

    PubMed

    Costa, Filipe O; Neuparth, Teresa; Correia, Ana D; Costa, Maria Helena

    2005-07-01

    This study aimed to test the performance of the amphipod Gammarus locusta (L.) in chronic sediment toxicity tests. It constitutes part of a multi-level assessment of chronic toxicity of estuarine sediments, integrating organism and population-level endpoints with biochemical markers responses. Here we account for organism and population-level effects, while biomarker responses were reported in a companion article. Five moderately contaminated sediments from Sado and Tagus estuaries were tested, comprising 3 muddy and 2 sandy sediments. These sediments either did not show acute toxicity or were diluted with control sediment as much as required to remove acute toxicity. Subsequent chronic tests consisted of 28-day exposures with survival, individual growth and reproductive traits as endpoints. Two of the muddy sediments induced higher growth rates in the amphipods, and improved reproductive traits. This was understood to be a consequence of the amount of organic matter in the sediment, which was nutritionally beneficial to the amphipods, while concurrently decreasing contaminant bioavailability. Biomarker responses did not reveal toxicant-induced stress in amphipods exposed to these sediments. One of the sandy sediments was acutely toxic at 50% dilution, but in contrast stimulated amphipod growth when diluted 75%. This was presumed to be an indication of a hormetic response. Finally the two remaining contaminated sediments showed pronounced chronic toxicity, affecting survival and reproduction. The sex ratio of survivors was highly biased towards females, and offspring production was severely impaired. The particulars of the responses of this amphipod were examined, as well as strengths versus limitations of the sediment test. This study illustrates the utility of this chronic test for toxicity assessment of contaminated estuarine sediments, with potential application all along Atlantic Europe. PMID:15649529

  8. Nano sponge Mn₂O ₃ as a new adsorbent for the preconcentration of Pd(II) and Rh(III) ions in sea water, wastewater, rock, street sediment and catalytic converter samples prior to FAAS determinations.

    PubMed

    Yavuz, Emre; Tokalıoğlu, Serife; Sahan, Halil; Patat, Saban

    2014-10-01

    In this study, a nano sponge Mn2O3 adsorbent was synthesized and was used for the first time. Various parameters affecting the recovery values of Pd(II) and Rh(III) were examined. The tolerance limits (≥ 90 %) for both Pd(II) and Rh(III) ions were found to be 75,000 mg L(-1) Na(I), 75,000 mg L(-1) K(I), 50,000 mg L(-1) Mg(II) and 50,000 mg L(-1) Ca(II). A 30s contact time was enough for both adsorption and elution. A preconcentration factor of 100 was obtained by using 100mg of the nano sponge Mn2O3. The reusability of the adsorbent was 120 times. Adsorption capacities for Pd(II) and Rh(III) were found to be 42 and 6.2 mg g(-1), respectively. The detection limits were 1.0 µg L(-1) for Pd(II) and 0.37 µg L(-1) for Rh(III) and the relative standard deviations (RSD, %) were found to be ≤ 2.5%. The method was validated by analyzing the standard reference material, SRM 2556 (Used Auto Catalyst Pellets) and spiked real samples. The optimized method was applied for the preconcentration of Pd(II) and Rh(III) ions in water (sea water and wastewater), rock, street sediment and catalytic converter samples. PMID:25059126

  9. Origin and depositional environment of fine-grained sediments since the last glacial maximum in the southeastern Yellow Sea: evidence from rare earth elements

    NASA Astrophysics Data System (ADS)

    Um, In Kwon; Choi, Man Sik; Lee, Gwang Soo; Chang, Tae Soo

    2015-12-01

    Despite the well-reconstructed seismic stratigraphy of the Holocene mud deposit in the southeastern Yellow Sea, known as the Heuksan mud belt (HMB), the provenances of these sediments and their depositional environments are unclear, especially for the fine-grained sediments. According to seismic data (extracted from another article in this special issue), the HMB comprises several sedimentary units deposited since the last glacial maximum. Based on analytical results on rare earth elements, fine-grained sediments in all sedimentary units can be interpreted as mixtures of sediments discharged from Chinese and Korean rivers. The proportions of fine-grained sediments from Chinese rivers (74.5 to 80.0%) were constant and higher than those from Korean rivers in all units. This fact demonstrates that all units have the same fine-grained sediment provenance: units III-b and III-a, located in the middle and northern parts of the HMB and directly deposited from Chinese rivers during the sea-level lowstand, could be the sediment source for units II-b and II-a. Unit I, while ambiguous, is of mixed origin combining reworked sediments from nearby mud deposits and Changjiang River-borne material with those of the Keum River. The results of this study indicate that at least 18.6% of bulk sediments in the HMB clearly originate from Chinese rivers, despite its location close to the southwestern coast of Korea.

  10. Predicting bedforms and primary current stratification in cohesive mixtures of mud and sand

    NASA Astrophysics Data System (ADS)

    Best, J.; Jaco, B.; Peakall, J.

    2015-12-01

    The use of sedimentary structures as indicators of flow and sediment morphodynamics in ancient sediments is essential for reconstruction of formative flow conditions generated in a wide range of grain sizes and sedimentary environments. Yet, the vast majority of past research has concerned bedforms generated in essentially cohesionless sediments that lack the presence of mud within the flow and within the sediment bed itself. However, most sedimentary environments possess fine-grained sediments, with recent work demonstrating how the presence of such fine sediment may substantially modify the fluid dynamics of such flows. It is thus increasingly evident that the influence of mud, and the presence of cohesive forces, is essential to permit a fuller interpretation and understanding of many modern and ancient sedimentary successions. In this paper, we summarize on the fluid dynamics of turbulence modulation generated by the presence of fine suspended sediment, and use this knowledge to propose a new extended bedform phase diagram for bedforms generated in mixtures of sand and mud under rapidly decelerated flows. This diagram provides a phase space using the variables of yield strength and grain mobility as the abscissa and ordinate axes, respectively, and defines the stability fields of a range of bedforms generated under flows that have modified fluid dynamics due to the presence of suspended sediment within the flow. We also show data on a range of bedforms generated in such flows, from laboratory experiments and examples from ancient sediments, including: i) heterolithic stratification, comprising alternating laminae or layers of sand and mud; ii) the preservation of low amplitude bed-waves, large current ripples, and bed scours with intrascour composite bedforms; iii) low angle cross-lamination and long lenses and streaks of sand and mud formed by bed-waves; iv) complex stacking of reverse bedforms, mud layers and low-angle cross-lamination on the upstream face of

  11. Application of hierarchical Bayesian unmixing models in river sediment source apportionment

    NASA Astrophysics Data System (ADS)

    Blake, Will; Smith, Hugh; Navas, Ana; Bodé, Samuel; Goddard, Rupert; Zou Kuzyk, Zou; Lennard, Amy; Lobb, David; Owens, Phil; Palazon, Leticia; Petticrew, Ellen; Gaspar, Leticia; Stock, Brian; Boeckx, Pacsal; Semmens, Brice

    2016-04-01

    Fingerprinting and unmixing concepts are used widely across environmental disciplines for forensic evaluation of pollutant sources. In aquatic and marine systems, this includes tracking the source of organic and inorganic pollutants in water and linking problem sediment to soil erosion and land use sources. It is, however, the particular complexity of ecological systems that has driven creation of the most sophisticated mixing models, primarily to (i) evaluate diet composition in complex ecological food webs, (ii) inform population structure and (iii) explore animal movement. In the context of the new hierarchical Bayesian unmixing model, MIXSIAR, developed to characterise intra-population niche variation in ecological systems, we evaluate the linkage between ecological 'prey' and 'consumer' concepts and river basin sediment 'source' and sediment 'mixtures' to exemplify the value of ecological modelling tools to river basin science. Recent studies have outlined advantages presented by Bayesian unmixing approaches in handling complex source and mixture datasets while dealing appropriately with uncertainty in parameter probability distributions. MixSIAR is unique in that it allows individual fixed and random effects associated with mixture hierarchy, i.e. factors that might exert an influence on model outcome for mixture groups, to be explored within the source-receptor framework. This offers new and powerful ways of interpreting river basin apportionment data. In this contribution, key components of the model are evaluated in the context of common experimental designs for sediment fingerprinting studies namely simple, nested and distributed catchment sampling programmes. Illustrative examples using geochemical and compound specific stable isotope datasets are presented and used to discuss best practice with specific attention to (1) the tracer selection process, (2) incorporation of fixed effects relating to sample timeframe and sediment type in the modelling

  12. Accurate lacustrine and wetland sediment accumulation rates determined from 14c activity of bulk sediment fractions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In the absence of identifiable macrofossils in lacustrine sediments, 14C dating must rely on pollen or bulk sediment fractions. Bulk sediment fractions are not generally preferred because they contain an unknown mixture of organic material of variable age, they may contain dead carbon such as ligni...

  13. An exchange-Coulomb model potential energy surface for the Ne-CO interaction. II. Molecular beam scattering and bulk gas phenomena in Ne-CO mixtures.

    PubMed

    Dham, Ashok K; McBane, George C; McCourt, Frederick R W; Meath, William J

    2010-01-14

    Four potential energy surfaces are of current interest for the Ne-CO interaction. Two are high-level fully ab initio surfaces obtained a decade ago using symmetry-adapted perturbation theory and supermolecule coupled-cluster methods. The other two are very recent exchange-Coulomb (XC) model potential energy surfaces constructed by using ab initio Heitler-London interaction energies and literature long range dispersion and induction energies, followed by the determination of a small number of adjustable parameters to reproduce a selected subset of pure rotational transition frequencies for the (20)Ne-(12)C(16)O van der Waals cluster. Testing of the four potential energy surfaces against a wide range of available experimental microwave, millimeter-wave, and mid-infrared Ne-CO transition frequencies indicated that the XC potential energy surfaces gave results that were generally far superior to the earlier fully ab initio surfaces. In this paper, two XC model surfaces and the two fully ab initio surfaces are tested for their abilities to reproduce experiment for a wide range of nonspectroscopic Ne-CO gas mixture properties. The properties considered here are relative integral cross sections and the angle dependence of rotational state-to-state differential cross sections, rotational relaxation rate constants for CO(v=2) in Ne-CO mixtures at T=296 K, pressure broadening of two pure rotational lines and of the rovibrational lines in the CO fundamental and first overtone transitions at 300 K, and the temperature and, where appropriate, mole fraction dependencies of the interaction second virial coefficient, the binary diffusion coefficient, the interaction viscosity, the mixture shear viscosity and thermal conductivity coefficients, and the thermal diffusion factor. The XC model potential energy surfaces give results that lie within or very nearly within the experimental uncertainties for all properties considered, while the coupled-cluster ab initio surface gives

  14. Electrochemical and spectroscopic study of Zn(ii) coordination and Zn electrodeposition in three ionic liquids with the trifluoromethylsulfonate anion, different imidazolium ions and their mixtures with water.

    PubMed

    Liu, Zhen; El Abedin, Sherif Zein; Endres, Frank

    2015-06-28

    In this paper we report on the use of three ionic liquids, 1-methylimidazolium trifluoromethylsulfonate ([MIm]TfO), 1-ethyl-3-methylimidazolium trifluoromethylsulfonate ([EMIm]TfO) and 1-ethyl-2,3-dimethylimidazolium trifluoromethylsulfonate ([EMMIm]TfO) containing zinc trifluoromethylsulfonate as electrolytes for zinc electrodeposition. By varying the cations from [MIm](+)via [EMIm](+) to [EMMIm](+), the vibrational band in the Far-IR spectra below 200 cm(-1), characterizing the cation-anion interaction, is shifted to lower wavenumbers, which suggests that the interaction between cations and anions is arranged in order of [MIm]TfO > [EMIm]TfO > [EMMIm]TfO. The coordination of Zn(2+) ions in these electrolytes was investigated by Raman spectroscopy. The Raman spectra show obvious differences in terms of the solvation of Zn(2+) ions in the dried electrolytes. The average number of TfO(-) anions bound to each Zn(2+) ion is lower in [MIm]TfO than in [EMIm]TfO and in [EMMIm]TfO, respectively. In ionic liquid-water mixtures, aqueous zinc species were formed in all cases. The differences in zinc species present in the electrolytes should have an influence on their electrochemical behavior and on the morphology of the deposits. In dried ionic liquids, the cyclic voltammograms reveal that the potentials for the deposition of zinc were shifted to more negative values by varying the cations, while in ionic liquid-water mixtures, the deposition of zinc occurs at almost the same potential. The SEM and XRD results show that the surface morphology, crystal shape and size as well as crystallographic orientation of the deposits are markedly affected by varying the cations of the ionic liquids. PMID:26027842

  15. Toxicity of sediment-bound pollutants in the Seine estuary, France, using a Eurytemora affinis larval bioassay.

    PubMed

    Lesueur, Teddy; Boulangé-Lecomte, Céline; Restoux, Gwendal; Deloffre, Julien; Xuereb, Benoît; Le Menach, Karyn; Budzinski, Hélène; Petrucciani, Nathalie; Marie, Sabine; Petit, Fabienne; Forget-Leray, Joëlle

    2015-03-01

    Coastal urbanisation exposes surrounding estuarine environments to urban-related contaminants such as polycyclic aromatic hydrocarbons (PAHs), polychlorobiphenyls (PCBs) and pesticide mixtures. Hydrophobic contaminants can adsorb on estuarine sediments. They can subsequently be released on a massive scale in the aquatic environment due to artificial or natural phenomena (e.g. dredging, tides), thereby threatening living organisms. The contamination of sediment is a significant ecological issue in the Seine estuary, France. However, few relevant methods have been developed to assess sediment toxicity and its ecological impacts in a cost-effective way. In this context, we aimed to assess the toxicity of natural sediments from the Seine estuary on the development of the calanoid copepod Eurytemora affinis using a previously developed larval bioassay. This assay involves direct exposure of nauplii to elutriates of sediments for six days. Sediments were collected along the Seine estuary from six polluted sites and one reference site. Pollutants in this estuary included PAHs, PCBs and OCPs (organochlorine pesticides). Nauplius survival was significantly more affected by exposure to all contaminated sediment elutriates, than by exposure to sediment from Yville-sur-Seine (the reference site), whereas nauplius growth was significantly reduced after exposure to contaminated sediment elutriates from four of the six contaminated sites. We identified two distinct site clusters, one including both the sand-rich and the least polluted sediments (Oissel, Quillebeuf-sur-Seine, Caudebec-en-Caux) and the other including both the clay- and silt-rich, and the most polluted sediments (La Bouille, Poses, Pont de Normandie). As expected, survival was significantly more impacted after exposure to elutriates from the second cluster than from the first. This work enables (i) assessment of the toxicity of natural sediments in the Seine estuary and (ii) validation of the larval bioassay

  16. Speciation of copper(II) complexes in an ionic liquid based on choline chloride and in choline chloride/water mixtures.

    PubMed

    De Vreese, Peter; Brooks, Neil R; Van Hecke, Kristof; Van Meervelt, Luc; Matthijs, Edward; Binnemans, Koen; Van Deun, Rik

    2012-05-01

    A deep-eutectic solvent with the properties of an ionic liquid is formed when choline chloride is mixed with copper(II) chloride dihydrate in a 1:2 molar ratio. EXAFS and UV-vis-near-IR optical absorption spectroscopy have been used to compare the coordination sphere of the cupric ion in this ionic liquid with that of the cupric ion in solutions of 0.1 M of CuCl(2)·2H(2)O in solvents with varying molar ratios of choline chloride and water. The EXAFS data show that species with three chloride ions and one water molecule coordinated to the cupric ion as well as species with two chloride molecules and two water molecules coordinated to the cupric ion are present in the ionic liquid. On the other hand, a fully hydrated copper(II) ion is formed in an aqueous solution free of choline chloride, and the tetrachlorocuprate(II) complex forms in aqueous choline chloride solutions with more than 50 wt % of choline chloride. In solutions with between 0 and 50 wt % of choline chloride, mixed chloro-aquo complexes occur. Upon standing at room temperature, crystals of CuCl(2)·2H(2)O and of Cu(choline)Cl(3) formed in the ionic liquid. Cu(choline)Cl(3) is the first example of a choline cation coordinating to a transition-metal ion. Crystals of [choline](3)[CuCl(4)][Cl] and of [choline](4)[Cu(4)Cl(10)O] were also synthesized from molecular or ionic liquid solvents, and their crystal structures were determined. PMID:22524435

  17. Comparison of surface vacuum ultraviolet emissions with resonance level number densities. II. Rare-gas plasmas and Ar-molecular gas mixtures

    SciTech Connect

    Boffard, John B. Lin, Chun C.; Wang, Shicong; Wendt, Amy E.; Culver, Cody; Radovanov, Svetlana; Persing, Harold

    2015-03-15

    Vacuum ultraviolet (VUV) emissions from excited plasma species can play a variety of roles in processing plasmas, including damaging the surface properties of materials used in semiconductor processing. Depending on their wavelength, VUV photons can easily transmit thin upper dielectric layers and affect the electrical characteristics of the devices. Despite their importance, measuring VUV fluxes is complicated by the fact that few materials transmit at VUV wavelengths, and both detectors and windows are easily damaged by plasma exposure. The authors have previously reported on measuring VUV fluxes in pure argon plasmas by monitoring the concentrations of Ar(3p{sup 5}4s) resonance atoms that produce the VUV emissions using noninvasive optical emission spectroscopy in the visible/near-infrared wavelength range [Boffard et al., J. Vac. Sci. Technol., A 32, 021304 (2014)]. Here, the authors extend this technique to other rare-gases (Ne, Kr, and Xe) and argon-molecular gas plasmas (Ar/H{sub 2}, Ar/O{sub 2}, and Ar/N{sub 2}). Results of a model for VUV emissions that couples radiation trapping and the measured rare-gas resonance level densities are compared to measurements made with both a calibrated VUV photodiode and a sodium salicylate fluorescence detection scheme. In these more complicated gas mixtures, VUV emissions from a variety of sources beyond the principal resonance levels of the rare gases are found to contribute to the total VUV flux.

  18. Two-Phase Calorimetry. II. Studies on the Thermodynamics of Cesium and Strontium Extraction by Mixtures of H+CCD- and PEG-400 in FS-13

    SciTech Connect

    Zalupski, Peter R.; Herbst, R. S.; Delmau, Laetitia Helene; Martin, L. R.; Peterman, D. R.; Nash, Ken L

    2010-01-01

    Thermochemical characterization of the partitioning of cesium and strontium from nitric acid solutions into mixtures of the acid form of chlorinated cobalt dicarbollide (H+CCD-) and polyethylene glycol (PEG-400) in FS-13 diluent has been completed using isothermal titration microcalorimetry and radiotracer distribution methods. The phase transfer reaction for Cs+ is a straightforward (H+ for Cs+) cation exchange reaction. In contrast, the extraction of Sr2+ does not proceed in the absence of the co-solvent molecule PEG-400. This molecule is believed to facilitate the dehydration of the Sr2+ aquo cation to overcome its resistance to partitioning. The phase transfer reactions for both Cs+ and Sr2+ are enthalpy driven (exothermic), but partially compensated by an unfavorable entropy. The results of the calorimetry studies suggest that the PEG-400 functions as a stoichiometric phase transfer reagent rather than acting simply as a phase transfer catalyst or phase modifier. The calorimetry results also demonstrate that the extraction of Sr2+ is complex, including evidence for both the partitioning of Sr(NO3)+ and endothermic ion pairing interactions in the organic phase that contribute to the net enthalpic effect. The thermodynamics of the liquid-liquid distribution equilibria are discussed mainly considering the basic features of the ion solvation thermochemistry.

  19. PROCEDURES FOR DERIVING EQUILIBRIUM PARTITIONING BENCHMARKS (ESBS) FOR THE PROTECTION OF BENTHIC ORGANISM: PAH MIXTURES

    EPA Science Inventory

    This equilibrium partitioning sediment benchmark (ESB) document describes procedures to derive concentrations of PAH mixtures in sediment which are protective of the presence of benthic organisms. The equilibrium partitioning (EqP) approach was chosen because it accounts for t...

  20. Anaerobic Redox Cycling of Iron by Freshwater Sediment Microorganisms

    SciTech Connect

    Weber, Karrie A.; Urrutia, Matilde M.; Churchill, Perry F.; Kukkadapu, Ravi K.; Roden, Eric E.

    2006-01-01

    The potential for microbially-mediated anaerobic redox cycling of iron (Fe) was examined in a first-generation enrichment culture of freshwater wetland sediment microorganisms. MPN enumerations revealed the presence of significant populations of Fe(III)-reducing (ca. 108 cells mL-1) and Fe(II)-oxidizing, nitrate-reducing organisms (ca. 105 cells mL-1) in the sediment used to inoculate the enrichment cultures. Nitrate reduction commenced immediately following inoculation of acetate-containing (ca. 1 mM) medium with a small quantity (1% vol/vol) of wetland sediment, and resulted in the transient accumulation of NO2- and production of a mixture of end-products including NH4+. Fe(III) oxide (high surface area goethite) reduction took place - after NO3- was depleted and continued until all the acetate was utilized. Addition of NO3 after Fe(III) reduction ceased resulted in the immediate oxidation of Fe(II) coupled to reduction of + NO3-to NH4 . No significant NO2- accumulation was observed during nitrate-dependent Fe(II) oxidation. No Fe(II) oxidation occurred in pasteurized controls. Microbial community structure in the enrichment was monitored by DGGE analysis of PCR amplified 16s rDNA and RT-PCR amplified 16S rRNA, as well as by construction of 16S rDNA clone libraries for four different time points during the experiment. Strong similarities in dominant members of the microbial community were observed in the Fe(III) reduction and nitrate-dependent Fe(II) oxidation phases of the experiment, specifically the common presence of organisms closely related (= 95% sequence similarity) to the genera Geobacter and Dechloromonas. These results indicate that the wetland sediments contained organisms such as Geobacter sp. which are capable of both + dissimilatory Fe(III) reduction and oxidation of Fe(II) with reduction of NO3-reduction to NH4 . Our findings suggest that microbially-catalyzed nitrate-dependent Fe(II) oxidation has the potential to contribute to a dynamic

  1. Analytical Ultracentrifugation: Sedimentation Velocity and Sedimentation Equilibrium

    PubMed Central

    Cole, James L.; Lary, Jeffrey W.; Moody, Thomas; Laue, Thomas M.

    2009-01-01

    Analytical ultracentrifugation (AUC) is a versatile and powerful method for the quantitative analysis of macromolecules in solution. AUC has broad applications for the study of biomacromolecules in a wide range of solvents and over a wide range of solute concentrations. Three optical systems are available for the analytical ultracentrifuge (absorbance, interference and fluorescence) that permit precise and selective observation of sedimentation in real time. In particular, the fluorescence system provides a new way to extend the scope of AUC to probe the behavior of biological molecules in complex mixtures and at high solute concentrations. In sedimentation velocity, the movement of solutes in high centrifugal fields is interpreted using hydrodynamic theory to define the size, shape and interactions of macromolecules. Sedimentation equilibrium is a thermodynamic method where equilibrium concentration gradients at lower centrifugal fields are analyzed to define molecule mass, assembly stoichiometry, association constants and solution nonideality. Using specialized sample cells and modern analysis software, researchers can use sedimentation velocity to determine the homogeneity of a sample and define whether it undergoes concentration-dependent association reactions. Subsequently, more thorough model-dependent analysis of velocity and equilibrium experiments can provide a detailed picture of the nature of the species present in solution and their interactions. PMID:17964931

  2. Aquatic Sediments.

    ERIC Educational Resources Information Center

    Sanville, W. D.; And Others

    1978-01-01

    Presents a literature review of aquatic sediments and its effect upon water quality, covering publications of 1976-77. This review includes: (1) sediment water interchange; (2) chemical and physical characterization; and (3) heavy water in sediments. A list of 129 references is also presented. (HM)

  3. Pesticide pressure and fish farming in barrage pond in Northeastern France. Part II: residues of 13 pesticides in water, sediments, edible fish and their relationships.

    PubMed

    Lazartigues, Angélique; Thomas, Marielle; Cren-Olivé, Cécile; Brun-Bellut, Jean; Le Roux, Yves; Banas, Damien; Feidt, Cyril

    2013-01-01

    Residues of pesticides in fish farming productions from barrage ponds are seldom studied in spite of increasing health questionings and environmental concerns. The purpose of this study is to establish the pesticide contamination profiles of sediments and edible fish from five ponds in Northeastern France. Multi-residues method and liquid chromatography-tandem mass spectrometry analysis were used to quantify 13 pesticides (azoxystrobin, carbendazim, clomazone, diflufenican, dimethachlor, fluroxypyr, iprodion, isoproturon, mesosulfuron-methyl, metazachlor, napropamid, quizalofop and thifensulfuron-methyl). Ten sediments and 143 muscles samples were analysed, corresponding to two successive fishing campaigns (first fishing date and second fishing date (P2), about 1 year later) on five sites (noted C-0, C-25, C-45, C-75 and C-85 to express the increasing gradient of crop area). Isoproturon was present in all sediments samples (1.8-56.4 μg/kg dry weight). During P2 period, carbendazim was quantified in the fish of site C-0 (0.09 ± 0.02, 0.2 ± 0.1 and 0.17 ± 0.06 μg/kg wet weight (ww) for roach, carp and perch, respectively). Metazachlor was only quantified in perch of the site C-25 (0.13 ± 0.02 μg/kg ww). Concentrations of isoproturon were similar for the sites C-45 and C-75 with 0.4 ± 0.1 and 0.75 ± 0.06 μg/kg ww for carp and perch, respectively. Contamination of fish reflected generally concentrations in surroundings. Isoproturon was the most concentrated and its main source was water for perch while carp was exposed through both water and sediments, highlighting their life strategies in pond. PMID:22961490

  4. Mineralogy and Mobility of Fe and As in Meghna River Sediments in Bangladesh

    NASA Astrophysics Data System (ADS)

    Datta, S.; Mallioux, B.; Jung, H.; Dhar, R.; Stute, M.; Hoque, M.; Assaf-Anid, N.; Ahmed, K.; Zheng, Y.

    2005-12-01

    It is now accepted that elevated concentrations of arsenic prevalent in the Holocene shallow aquifers found in the river deltaic systems of Ganges-Brahmaputra-Meghna can be attributed to natural As present in the aquifer sediments. The mobility of sedimentary As has only recently been more carefully evaluated, with a fraction of sediment As that is extractable by a near neutral phosphate solution known as "mobilizable" As. However, questions remain how sediment As becomes mobilizable. In addition, groundwater As concentrations are found to increase with groundwater age determined by 3H/3He dating. This suggests that at the point of discharge, reducing, As-enriched groundwater will likely to sorb onto oxides in sediment that is under more oxic conditions. In January 2003, a transect of 14, 2-m long sediment push cores and 14, 0.5-m sediment auger samples were obtained in the upstream (major tributary to the northern most point of Meghan River, n=5), mid-stream (southward to the confluence, n=3) and down stream (confluence to the coast, n=6). Except for the shallowest samples (depths 10cm - 50cm) that are gray with high Fe(II)/Fe ratios, river sediments at depths tend to be oxidized with low Fe(II)/Fe ratios of < 0.5. Mineralogy of Fe determined by EXAFS confirm that downstream and midstream samples are mostly of magnetite with a mixed Fe(II) and Fe(III), with two upstream samples showing characteristic spectrum of goethite. The most surprising finding was that many sediments samples (8 of 14) contained 237-1300 mg/kg phosphate-extractable As and 249-23,000 mg/kg HCl-extractable As. Much of P-extractable As was determined as arsenite by voltammetry immediately following anaerobic extraction. Analysis using XANES confirms that the downstream samples are mostly arsenite while the upstream and midstream samples are mixture of arsenite and arsenate. When 6-stream sediment samples were incubated, a significant amount of As was released in the presence of acetate. Our

  5. Concentration fluctuations in fluid mixtures. II.

    PubMed

    Mazo, Robert M; Matteoli, Enrico; Smith, Paul E

    2009-06-21

    The method developed in a previous paper [R. Mazo, J. Chem. Phys. 129, 154101 (2008)] for extracting information on the size of relative fluctuations in multicomponent systems is tested on ten binary systems and one ternary system. For the binary systems, it is found that the approximation works well for mole fractions in the range of 0.15-0.85 in most cases. For the ternary case, the method inherently yields less information and is valid only over a more restricted range for the case studied (chloroform-methanol-acetone). It is found that the predicted ratio of number fluctuations is approximately equal to the ratio of molar volumes of the components. PMID:19548740

  6. Human impact on the Middle and Late Holocene floodplain sediment characteristics along the River Rhine

    NASA Astrophysics Data System (ADS)

    Erkens, G.; Prins, M.; Toonen, W.

    2012-04-01

    The Rhine catchment has an extensive history of human land use. Deforestation to create arable land started as early as 6300 cal BP, at the onset of the Late Neolithic. This caused increased erosion and sediment production on the hillslopes in the upstream part of the fluvial system. Recent studies show that this human-induced erosion also increased the suspended load sedimentation rates in the Rhine trunk valley and delta from approximately 3000 years ago. Besides such changes in the quantity of fine sediment, it is hypothesised that human land use may also change the source of the sediment supplied to the fluvial system. Sediment released by erosion during agricultural practises may be different than the sediments that erode under conditions of forest cover. If this is true, the Late Holocene floodplain sediments have different characteristics in terms of grain size and texture than older floodplain deposits (Middle Holocene). To test this, we collected 15 cores from three large stretches along the trunk Rhine River: the Upper Rhine Graben, the Lower Rhine Valley, and the Rhine Delta. Using detailed palaeogeographic reconstructions of the area, the cores were carefully selected in order to (i) to obtain the longest possible record (preferably up to 5000 years), and (ii) to have a continuous sedimentation record as much as possible. Cores are taken from residual channels, and distal flood basin and plains, although very distal sites were avoided to minimise the amount of peat or soil formation. Individual age-depth models are derived from radiocarbon dates taken in the cores, correlation of the regional deposits with a known age, and by using groundwater models (in the delta). Grain size characteristics of the siliciclastic sediment fraction were analysed every 2-5 cm, which yielded a record of grain size variations of the floodplains depositions in time. Using the end-member modelling algorithm EMMA it was possible to distinguish different groups of sediment

  7. Dispersion of interface waves in sediments with power-law shear speed profiles. II. Experimental observations and seismo-acoustic inversions.

    PubMed

    Chapman, D M; Godin, O A

    2001-10-01

    The propagation of seismic interface waves is investigated in soft marine sediments in which the density is constant, the shear modulus is small, and the profile of shear speed c(s) versus depth z is of the power-law form c(s) (z) = c0z(v), in which c0 and v are constants (0< v < 1). Both the phase speed V and the group speed U of interface waves scale with frequency as f(v/(v -1)) and they obey the simple relation U= (1 - v) V. These relations are derived in a simple way using ray theory and the WKB method; a companion paper [O. A. Godin and D. M. F. Chapman, J. Acoust. Soc. Am. 110, 1890 (2001)] rigorously derives the same result from the solutions to the equations of motion. The frequency scaling is shown to exist in experimental data sets of interface wave phase speed and group speed. Approximate analytical formulas for the dispersion relations (phase and group speed versus frequency) enable direct inversion of the profile parameters c0 and v from the experimental data. In cases for which there is multi-mode dispersion data, the water-sediment density ratio can be determined as well. The theory applies to vertically polarized (P-SV) modes as well as to horizontally polarized (SH) modes (that is, Love waves). PMID:11681371

  8. Mackinawite (FeS) Reduces Mercury(II) under Sulfidic Conditions

    PubMed Central

    2015-01-01

    Mercury (Hg) is a toxicant of global concern that accumulates in organisms as methyl Hg. The production of methyl Hg by anaerobic bacteria may be limited in anoxic sediments by the sequestration of divalent Hg [Hg(II)] into a solid phase or by the formation of elemental Hg [Hg(0)]. We tested the hypothesis that nanocrystalline mackinawite (tetragonal FeS), which is abundant in sediments where Hg is methylated, both sorbs and reduces Hg(II). Mackinawite suspensions were equilibrated with dissolved Hg(II) in batch reactors. Examination of the solid phase using Hg LIII-edge extended X-ray absorption fine structure (EXAFS) spectroscopy showed that Hg(II) was indeed reduced in FeS suspensions. Measurement of purgeable Hg using cold vapor atomic fluorescence spectrometry (CVAFS) from FeS suspensions and control solutions corroborated the production of Hg(0) that was observed spectroscopically. However, a fraction of the Hg(II) initially added to the suspensions remained in the divalent state, likely in the form of β-HgS-like clusters associated with the FeS surface or as a mixture of β-HgS and surface-associated species. Complexation by dissolved S(-II) in anoxic sediments hinders Hg(0) formation, but, by contrast, Hg(II)–S(-II) species are reduced in the presence of mackinawite, producing Hg(0) after only 1 h of reaction time. The results of our work support the idea that Hg(0) accounts for a significant fraction of the total Hg in wetland and estuarine sediments. PMID:25180562

  9. Crayfish and fish as bioturbators of streambed sediments: Assessing joint effects of species with different mechanistic abilities

    NASA Astrophysics Data System (ADS)

    Statzner, Bernhard; Sagnes, Pierre

    2008-01-01

    Many studies illustrate that bioturbating animal species individually affect aquatic sediments through diverse mechanistic abilities, whereas assessments of joint effects of such species on sediments are relatively rare. Such joint effects have implications for real systems, in which different bioturbators coexist, but are difficult to predict for two reasons. First, they can be additive (being the sum of the individual effects of each species) or they can be positive or negative interactive (being greater or smaller than the sum of the individual effects). Second, if interactive, they can depend on biotic interactions that affect the bioturbating activities of the species and/or they can depend on physical interactions among bioturbator-induced sediment modifications. Using experimental streams, we assessed such joint effects on gravel-sand sediments for flow and sediment conditions preferred by barbel ( Barbus barbus) but also used by gudgeon ( Gobio gobio) and, in a second experiment, for flow and sediment conditions preferred by both male crayfish ( Orconectes limosus) and gudgeon. These species have different mechanistic abilities to affect gravel and/or sand in stream beds. In each experiment, we measured (i) the transport of gravel and sand at baseflow (during 12 experimental days); (ii) four sediment surface characteristics (after 12 d); and (iii) the critical shear stress ( τc) causing incipient gravel and sand motion during experimental floods (after 12 d). Gudgeon contributed differently to the joint effects in the two experiments, which related to its individual weight, prevailing baseflow shear stress, sediment particle weight, and sediment mixture (availability of surface sand). Overall, the species pairs had predominantly negative interactive joint effects on the sediment variables assessed by us. Both a literature survey and observations during the experiments provided no evidence for direct biotic interactions between barbel and gudgeon or

  10. Alteration of organic matter during infaunal polychaete gut passage and links to sediment organic geochemistry. Part II: Fatty acids and aldoses

    NASA Astrophysics Data System (ADS)

    Woulds, Clare; Middelburg, Jack J.; Cowie, Greg L.

    2014-07-01

    The activities of sediment-dwelling fauna are known to influence the rates of and pathways through which organic matter is cycled in marine sediments, and thus to influence eventual organic carbon burial or decay. However, due to methodological constraints, the role of faunal gut passage in determining the subsequent composition and thus degradability of organic matter is relatively little studied. Previous studies of organic matter digestion by benthic fauna have been unable to detect uptake and retention of specific biochemicals in faunal tissues, and have been of durations too short to fit digestion into the context of longer-term sedimentary degradation processes. Therefore this study aimed to investigate the aldose and fatty acid compositional alterations occurring to organic matter during gut passage by the abundant and ubiquitous polychaetes Hediste diversicolor and Arenicola marina, and to link these to longer-term changes typically observed during organic matter decay. This aim was approached through microcosm experiments in which selected polychaetes were fed with 13C-labelled algal detritus, and organisms, sediments, and faecal pellets were sampled at three timepoints over ∼6 weeks. Samples were analysed for their 13C-labelled aldose and fatty acid contents using GC-MS and GC-IRMS. Compound-selective net accumulation of biochemicals in polychaete tissues was observed for both aldoses and fatty acids, and the patterns of this were taxon-specific. The dominant patterns included an overall loss of glucose and polyunsaturated fatty acids; and preferential preservation or production of arabinose, microbial compounds (rhamnose, fucose and microbial fatty acids), and animal-synthesised fatty acids. These patterns may have been driven by fatty acid essentiality, preferential metabolism of glucose, and A. marina grazing on bacteria. Fatty acid suites in sediments from faunated microcosms showed greater proportions of saturated fatty acids and bacterial markers

  11. Determination of organoarsenic warfare agents in sediment samples from Skagerrak by gas chromatography-mass spectrometry.

    PubMed

    Tørnes, John Aasulf; Opstad, Aase Mari; Johnsen, Bjørn Arne

    2006-03-01

    In 1945 the Norwegian authorities gave permission to scuttle ships loaded with captured chemical ammunition on board in an area approximately 14x4 km in size, 25 nautical miles south-east of Arendal. An investigation was carried out in 2002 to inspect four wrecks by using a remote-operated vehicle with video cameras. The Norwegian Defence Research Establishment (Forsvarets forskningsinstitutt, FFI) carried out the project on behalf of the Norwegian Pollution Control Authority (SFT). Sediment samples were collected at eight positions around each wreck. One of the wrecks was broken up into several smaller parts. Here sediments were collected at one additional position close to one of the parts. From each position, at least two sediment cores were taken up to the surface. One of the cores from each position was sliced into three parts that were immediately frozen. The other whole cores were frozen on board the ship and transported back to the laboratory in a freezer. In total, sediment samples from 33 different locations were collected and analysed for organoarsenic warfare agents and some of their decomposition products by gas chromatography-mass spectrometry (GC-MS) after derivatisation with 1-propanethiol. Most of the identified organoarsenic compounds found in the sediment samples are parts of the arsine oil mixture produced by Germany during World War II. The compounds were found both close to the wreck and at a somewhat longer distance from the wrecks. The highest concentrations were found in a sediment sample collected close to a bomb seen on the seabed. The organoarsenic warfare agents adamsite or lewisite were not found in any of the samples. Lewisite is not reported to have been produced during World War II, but was nevertheless looked for in the samples. PMID:15993928

  12. I. Cognitive and instructional factors relating to students' development of personal models of chemical systems in the general chemistry laboratory II. Solvation in supercritical carbon dioxide/ethanol mixtures studied by molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Anthony, Seth

    likely to appear in students' post-laboratory refined models. These discussions during the laboratory period are primarily prompted by factors external to the students or their laboratory groups such as questions posed by the instructor or laboratory materials. Part II. Solvation of polar molecules within non-polar supercritical carbon dioxide is often facilitated by the introduction of polar cosolvents as entrainers, which are believed to preferentially surround solute molecules. Molecular dynamics simulations of supercritical carbon dioxide/ethanol mixtures reveal that ethanol molecules form hydrogen-bonded aggregates of varying sizes and structures, with cyclic tetramers and pentamers being unusually prevalent. The dynamics of ethanol molecules within these mixtures at a range of thermodynamic conditions can largely be explained by differences in size and structure in these aggregates. Simulations that include solute molecules reveal enhancement of the polar cosolvent around hydrogen-bonding sites on the solute molecules, corroborating and helping to explain previously reported experimental trends in solute mobility.

  13. Investigation of natural and anthropogenic hydrocarbon inputs in sediments using geochemical markers. II. Sao Sebastião, SP--Brazil.

    PubMed

    Medeiros, Patricia Matheus; Bícego, Márcia Caruso

    2004-12-01

    The São Sebastião Channel, NE São Paulo State, Brazil, is an area of environmental interest of that state not only because of the tourism, but also because of the presence of the most important oil terminal of Brazil, the PETROBRAS Maritime Terminal (DTCS). Sediment samples were collected at 15 sites in the channel, extracted and analyzed by GC/FID and GC/MS for composition and levels of the following organic geochemical markers: aliphatic hydrocarbons (normal and isoprenoid alkanes), petroleum biomarkers, linear alkylbenzenes (LABs) and polycyclic aromatic hydrocarbons (PAHs). The total concentrations varied from 0.04 to 8.53 micorg g(-1) for aliphatics, from 51.1 to 422.0 ng g(-1) for petroleum biomarkers, from 12.6 to 27.7 ng g(-1) for LABs and from 20.4 to 200.3 ng g(-1) for PAHs. The PETROBRAS Maritime Terminal (DTCS), Sao Sebastião Harbor and sewage outfalls along the area had clear influences on the geochemical marker concentrations, especially at locales in the central and north parts of the channel. PMID:15556173

  14. Permissive tracts for sediment-hosted lead-zinc-silver deposits in Mauritania (phase V, deliverable 72): Chapter J1 in Second projet de renforcement institutionnel du secteur minier de la République Islamique de Mauritanie (PRISM-II)

    USGS Publications Warehouse

    Mauk, Jeffrey L.; Horton, John D.

    2012-01-01

    This report contains the USGS results of the PRISM-II Mauritania Minerals Project and is presented in cooperation with the Ministry of Petroleum, Energy, and Mines of the Islamic Republic of Mauritania. The Report is composed of separate chapters consisting of multidisciplinary interpretive reports with accompanying plates on the geology, structure, geochronology, geophysics, hydrogeology, geochemistry, remote sensing (Landsat TM and ASTER), and SRTM and ASTER digital elevation models of Mauritania. The syntheses of these multidisciplinary data formed the basis for additional chapters containing interpretive reports on 12 different commodities and deposit types known to occur in Mauritania, accompanied by countrywide mineral resource potential maps of each commodity/deposit type. The commodities and deposit types represented include: (1) Ni, Cu, PGE, and Cr deposits hosted in ultramafic rocks; (2) orogenic, Carlin-like, and epithermal gold deposits; (3) polymetallic Pb-Zn-Cu vein deposits; (4) sediment-hosted Pb-Zn-Ag deposits of the SEDEX and Mississippi Valley-type; (5) sediment-hosted copper deposits; ( 6) volcanogenic massive sulfide deposits; (7) iron oxide copper-gold deposits; (8) uranium deposits; (9) Algoma-, Superior-, and oolitic-type iron deposits; (10) shoreline Ti-Zr placer deposits; (11) incompatible element deposits hosted in pegmatites, alkaline rocks, and carbonatites, and; (12) industrial mineral deposits. Additional chapters include the Mauritanian National Mineral Deposits Database are accompanied by an explanatory text and the Mauritania Minerals Project GIS that contains all of the interpretive layers created by USGS scientists. Raw data not in the public domain may be obtained from the Ministry of Petroleum, Energy, and Mines in Nouakchott, Mauritania.

  15. Permissive tracts for sediment-hosted copper deposits in Mauritania (phase V, deliverable 74): Chapter K1 in Second projet de renforcement institutionnel du secteur minier de la République Islamique de Mauritanie (PRISM-II)

    USGS Publications Warehouse

    Taylor, Cliff D.; Horton, John D.

    2012-01-01

    This report contains the USGS results of the PRISM-II Mauritania Minerals Project and is presented in cooperation with the Ministry of Petroleum, Energy, and Mines of the Islamic Republic of Mauritania. The Report is composed of separate chapters consisting of multidisciplinary interpretive reports with accompanying plates on the geology, structure, geochronology, geophysics, hydrogeology, geochemistry, remote sensing (Landsat TM and ASTER), and SRTM and ASTER digital elevation models of Mauritania. The syntheses of these multidisciplinary data formed the basis for additional chapters containing interpretive reports on 12 different commodities and deposit types known to occur in Mauritania, accompanied by countrywide mineral resource potential maps of each commodity/deposit type. The commodities and deposit types represented include: (1) Ni, Cu, PGE, and Cr deposits hosted in ultramafic rocks; (2) orogenic, Carlin-like, and epithermal gold deposits; (3) polymetallic Pb-Zn-Cu vein deposits; (4) sediment-hosted Pb-Zn-Ag deposits of the SEDEX and Mississippi Valley-type; (5) sediment-hosted copper deposits; ( 6) volcanogenic massive sulfide deposits; (7) iron oxide copper-gold deposits; (8) uranium deposits; (9) Algoma-, Superior-, and oolitic-type iron deposits; (10) shoreline Ti-Zr placer deposits; (11) incompatible element deposits hosted in pegmatites, alkaline rocks, and carbonatites, and; (12) industrial mineral deposits. Additional chapters include the Mauritanian National Mineral Deposits Database are accompanied by an explanatory text and the Mauritania Minerals Project GIS that contains all of the interpretive layers created by USGS scientists. Raw data not in the public domain may be obtained from the Ministry of Petroleum, Energy, and Mines in Nouakchott, Mauritania.

  16. Targeting sediment management strategies using sediment quantification and fingerprinting methods

    NASA Astrophysics Data System (ADS)

    Sherriff, Sophie; Rowan, John; Fenton, Owen; Jordan, Phil; hUallacháin, Daire Ó.

    2016-04-01

    Cost-effective sediment management is required to reduce excessive delivery of fine sediment due to intensive land uses such as agriculture, resulting in the degradation of aquatic ecosystems. Prioritising measures to mitigate dominant sediment sources is, however, challenging, as sediment loss risk is spatially and temporally variable between and within catchments. Fluctuations in sediment supply from potential sources result from variations in land uses resulting in increased erodibility where ground cover is low (e.g., cultivated, poached and compacted soils), and physical catchment characteristics controlling hydrological connectivity and transport pathways (surface and/or sub-surface). Sediment fingerprinting is an evidence-based management tool to identify sources of in-stream sediments at the catchment scale. Potential sediment sources are related to a river sediment sample, comprising a mixture of source sediments, using natural physico-chemical characteristics (or 'tracers'), and contributions are statistically un-mixed. Suspended sediment data were collected over two years at the outlet of three intensive agricultural catchments (approximately 10 km2) in Ireland. Dominant catchment characteristics were grassland on poorly-drained soils, arable on well-drained soils and arable on moderately-drained soils. High-resolution (10-min) calibrated turbidity-based suspended sediment and discharge data were combined to quantify yield. In-stream sediment samples (for fingerprinting analysis) were collected at six to twelve week intervals, using time-integrated sediment samplers. Potential sources, including stream channel banks, ditches, arable and grassland field topsoils, damaged road verges and tracks were sampled, oven-dried (<40oC) and sieved (125 microns). Soil and sediment samples were analysed for mineral magnetics, geochemistry and radionuclide tracers, particle size distribution and soil organic carbon. Tracer data were corrected to account for particle

  17. Determination of molecular structure of kerogens using 13C NMR spectroscopy: II. The effects of thermal maturation on kerogens from marine sediments

    NASA Astrophysics Data System (ADS)

    Patience, R. L.; Mann, A. L.; Poplett, I. J. F.

    1992-07-01

    Solid state 13C nuclear magnetic resonance (NMR) spectrometry has been used to analyse kerogens isolated from marine sediments, to obtain information about relative changes in average molecular structures with increases in thermal maturity. Three suites of samples, all of which vary from immature to mature with respect to petroleum generation, were investigated: (a) seven samples of the Cretaceous Brown Limestone Formation (BLF), Gulf of Suez; (b) six from the Miocene Monterey Formation (MF), California; (c) seven from the Upper Jurassic to Lower Cretaceous Kimmeridge Clay Formation (KCF), UK continental shelf (UKCS). Each NMR spectrum has been quantified in terms of fourteen different carbon types. The immature KCF samples have a somewhat higher initial aromaticity (f a) than immature representatives of the other two suites, perhaps due to a slightly greater terrestrial organic input. With increasing maturity, only a modest increase in f a occurs in all three suites, until petroleum generation commences. The latter results in a sharp increase in f a, because alkyl carbon types are progressively lost from kerogen. No preferential loss of particular alkyl carbon types is seen within the resolution of the method. The percentage of heteroatom-bonded carbon (to O or S) declines consistently with increasing maturation and prior to the onset of petroleum generation. The distribution of aromatic carbon types changes substantially with increasing maturity, in that the relative abundances of bridgehead (ring junction) and protonated aromatic carbons increase, whereas phenolic and alkylated aromatic carbon decline or remain roughly constant, respectively. The data acquired have been used to monitor the hydrogen budget during maturation. Firstly, aromatisation reactions seem to occur during petroleum generation (increasing aromaticity is not simply a concentration of existing aromatic carbon) and, secondly, sufficient or excess hydrogen is liberated during these reactions to

  18. Determination of sediment provenance by unmixing the mineralogy of source-area sediments: The "SedUnMix" program

    USGS Publications Warehouse

    Andrews, John T.; Eberl, D.D.

    2012-01-01

    Along the margins of areas such as Greenland and Baffin Bay, sediment composition reflects a complex mixture of sources associated with the transport of sediment in sea ice, icebergs, melt-water and turbidite plumes. Similar situations arise in many contexts associated with sediment transport and with the mixing of sediments from different source areas. The question is: can contributions from discrete sediment (bedrock) sources be distinguished in a mixed sediment by using mineralogy, and, if so, how accurately? To solve this problem, four end-member source sediments were mixed in various proportions to form eleven artificial mixtures. Two of the end-member sediments are felsic, and the other two have more mafic compositions. End member and mixed sediment mineralogies were measured for the < 2. mm sediment fractions by quantitative X-ray diffraction (qXRD). The proportions of source sediments in the mixtures then were calculated using an Excel macro program named SedUnMix, and the results were evaluated to determine the robustness of the algorithm. The program permits the unmixing of up to six end members, each of which can be represented by up to 5 alternative compositions, so as to better simulate variability within each source region. The results indicate that we can track the relative percentages of the four end members in the mixtures. We recommend, prior to applying the technique to down-core or to other provenance problems, that a suite of known, artificial mixtures of sediments from probable source areas be prepared, scanned, analyzed for quantitative mineralogy, and then analyzed by SedUnMix to check the sensitivity of the method for each specific unmixing problem. ?? 2011 Elsevier B.V..

  19. Sedimentation models

    SciTech Connect

    Rector, D.R.; Bunker, B.C.

    1995-09-01

    The nuclear wastes currently stored in tanks at the Hanford site contain complex mixtures of insoluble sludge particles, salts, and supernatant liquids. Treatment and ultimate disposal of these tank wastes will require that the complex solid-liquid mixtures be dispersed in aqueous solutions for retrieval and transport. The mixtures will then require pretreatment steps that will ultimately require the isolation of insoluble particles from supernatant liquids via solid-liquid separation steps such as settle-decant operations, centrifugation, or filtration. There is a perception that sludge treatment in general, and solid-liquid separations in particular, are relatively trivial operations that can easily be transferred to private industry to initiate tank cleanup. Experiences gained over the past few years at Hanford suggest that waste processing is not as trivial as it seems.

  20. METHOD FOR TESTING THE AQUATIC TOXICITY OF SEDIMENT EXTRACTS FOR USE IN IDENTIFYING ORGANIC TOXICANTS IN SEDIMENTS

    EPA Science Inventory

    Biologically-directed fractionation techniques are a fundamental tool for identifying the cause of toxicity in environmental samples, but few are available for studying mixtures of organic chemicals in aquatic sediments. This paper describes a method for extracting organic chemic...

  1. Fluvial sediments a summary of source, transportation, deposition, and measurement of sediment discharge

    USGS Publications Warehouse

    Colby, B.R.

    1963-01-01

    continuously at about the velocity of the flow, and even low flows can transport large amounts of fine sediment. Hence, the discharge of fine sediments, being largely dependent on the availability of fine sediment upstream rather than on the properties of the sediment and of the flow at a cross section, can seldom be computed from properties, other than concentrations based directly on samples, that can be observed at the cross section. Sediment particles continually change their positions in the flow; some fall to the streambed, and others are removed from the bed. Sediment deposits form locally or over large areas if the volume rate at which particles settle to the bed exceeds the volume rate at which particles are removed from the bed. In general, large particles are deposited more readily than small particles, whether the point of deposition is behind a rock, on a flood plain, within a stream channel, or at the entrance to a reservoir, a lake, or the ocean. Most samplers used for sediment observations collect a water-sediment mixture from the water surface to within a few tenths of a foot of the streambed. They thus sample most of the suspended sediment, especially if the flow is deep or if the sediment is mostly fine; but they exclude the bedload and some of the suspended sediment in a layer near the streambed where the suspended-sediment concentrations are highest. Measured sediment discharges are usually based on concentrations that are averages of several individual sediment samples for a cross section. If enough average concentrations for a cross section have been determined, the measured sediment discharge can be computed by interpolating sediment concentrations between sampling times. If only occasional samples were collected, an average relation between sediment discharge and flow can be used with a flow-duration curve to compute roughly the average or the total sediment discharges for any periods of time for which the flow-duration c

  2. Development of a reference artificial sediment for chemical testing adapted to the MELA sediment contact assay.

    PubMed

    Le Bihanic, Florane; Perrichon, Prescilla; Landi, Laure; Clérandeau, Christelle; Le Menach, Karyn; Budzinski, Hélène; Cousin, Xavier; Cachot, Jérôme

    2014-12-01

    Most persistent organic pollutants, due to their hydrophobic properties, accumulate in aquatic sediments and represent a high risk for sediment quality. To assess the toxicity of hydrophobic pollutants, a novel approach was recently proposed as an alternative to replace, refine and reduce animal experimentation: the medaka embryo-larval sediment contact assay (MELAc). This assay is performed with Japanese medaka embryos incubated on a natural sediment spiked with the compound being tested. With the aim of improving this assay, our study developed a reference exposure protocol with an artificial sediment specifically designed to limit natural sediment composition uncertainties and preparation variability. The optimum composition of the new artificial sediment was tested using a model polycyclic aromatic hydrocarbon (PAH), fluoranthene. The sediment was then validated with two other model PAHs, benz[a]anthracene and benzo[a]pyrene. Various developmental end points were recorded, including survival, embryonic heartbeat, hatching delay, hatching success, larval biometry and abnormalities. The final artificial sediment composition was set at 2.5 % dry weight (dw) Sphagnum peat, 5 % dw kaolin clay and 92.5 % dw silica of 0.2- to 0.5-mm grain size. In contrast with natural sediments, the chemical components of this artificial matrix are fully defined and readily identifiable. It is totally safe for fish embryos and presents relatively high sorption capacities for hydrophobic compounds. Studies with other hydrophobic and metallic contaminants and mixtures should be performed to further validate this artificial sediment. PMID:24526399

  3. Oxygen isotope ratios (18O/16O) of hemicellulose-derived sugar biomarkers in plants, soils and sediments as paleoclimate proxy II: Insight from a climate transect study

    NASA Astrophysics Data System (ADS)

    Tuthorn, Mario; Zech, Michael; Ruppenthal, Marc; Oelmann, Yvonne; Kahmen, Ansgar; Valle, Héctor Francisco del; Wilcke, Wolfgang; Glaser, Bruno

    2014-02-01

    The oxygen isotopic composition of precipitation (δ18Oprec) is well known to be a valuable (paleo-)climate proxy. Paleosols and sediments and hemicelluloses therein have the potential to serve as archives recording the isotopic composition of paleoprecipitation. In a companion paper (Zech et al., 2014) we investigated δ18Ohemicellulose values of plants grown under different climatic conditions in a climate chamber experiment. Here we present results of compound-specific δ18O analyses of arabinose, fucose and xylose extracted from modern topsoils (n = 56) along a large humid-arid climate transect in Argentina in order to answer the question whether hemicellulose biomarkers in soils reflect δ18Oprec. The results from the field replications indicate that the homogeneity of topsoils with regard to δ18Ohemicellulose is very high for most of the 20 sampling sites. Standard deviations for the field replications are 1.5‰, 2.2‰ and 1.7‰, for arabinose, fucose and xylose, respectively. Furthermore, all three hemicellulose biomarkers reveal systematic and similar trends along the climate gradient. However, the δ18Ohemicellulose values (mean of the three sugars) do not correlate positively with δ18Oprec (r = -0.54, p < 0.014, n = 20). By using a Péclet-modified Craig-Gordon (PMCG) model it can be shown that the δ18Ohemicellulose values correlate highly significantly with modeled δ18Oleaf water values (r = 0.81, p < 0.001, n = 20). This finding suggests that hemicellulose biomarkers in (paleo-)soils do not simply reflect δ18Oprec but rather δ18Oprec altered by evaporative 18O enrichment of leaf water due to evapotranspiration. According to the modeling results, evaporative 18O enrichment of leaf water is relatively low (˜10‰) in the humid northern part of the Argentinian transect and much higher (up to 19‰) in the arid middle and southern part of the transect. Model sensitivity tests corroborate that changes in relative air humidity exert a dominant

  4. Oxygen isotope ratios (18O/16O) of hemicellulose-derived sugar biomarkers in plants, soils and sediments as paleoclimate proxy II: Insight from a climate transect study

    NASA Astrophysics Data System (ADS)

    Tuthorn, Mario; Zech, Michael; Ruppenthal, Marc; Oelmann, Yvonne; Kahmen, Ansgar; Valle, Héctor Francisco del; Wilcke, Wolfgang; Glaser, Bruno

    2014-02-01

    The oxygen isotopic composition of precipitation (δ18Oprec) is well known to be a valuable (paleo-)climate proxy. Paleosols and sediments and hemicelluloses therein have the potential to serve as archives recording the isotopic composition of paleoprecipitation. In a companion paper (Zech et al., 2014) we investigated δ18Ohemicellulose values of plants grown under different climatic conditions in a climate chamber experiment. Here we present results of compound-specific δ18O analyses of arabinose, fucose and xylose extracted from modern topsoils (n = 56) along a large humid-arid climate transect in Argentina in order to answer the question whether hemicellulose biomarkers in soils reflect δ18Oprec. The results from the field replications indicate that the homogeneity of topsoils with regard to δ18Ohemicellulose is very high for most of the 20 sampling sites. Standard deviations for the field replications are 1.5‰, 2.2‰ and 1.7‰, for arabinose, fucose and xylose, respectively. Furthermore, all three hemicellulose biomarkers reveal systematic and similar trends along the climate gradient. However, the δ18Ohemicellulose values (mean of the three sugars) do not correlate positively with δ18Oprec (r = -0.54, p < 0.014, n = 20). By using a Péclet-modified Craig-Gordon (PMCG) model it can be shown that the δ18Ohemicellulose values correlate highly significantly with modeled δ18Oleaf water values (r = 0.81, p < 0.001, n = 20). This finding suggests that hemicellulose biomarkers in (paleo-)soils do not simply reflect δ18Oprec but rather δ18Oprec altered by evaporative 18O enrichment of leaf water due to evapotranspiration. According to the modeling results, evaporative 18O enrichment of leaf water is relatively low (˜10‰) in the humid northern part of the Argentinian transect and much higher (up to 19‰) in the arid middle and southern part of the transect. Model sensitivity tests corroborate that changes in relative air humidity exert a dominant

  5. Coastal sediment dynamics in Spitsbergen

    NASA Astrophysics Data System (ADS)

    Deloffre, J.; Lafite, R.; Baltzer, A.; Marlin, C.; Delangle, E.; Dethleff, D.; Petit, F.

    2010-12-01

    In arctic knowledge on coastal sediment dynamics and sedimentary processes is limited. The studied area is located in the microtidal Kongsfjorden glacial fjord on the North-western coast of Spitsbergen in the Artic Ocean (79°N). In this area sediment contributions to the coastal zone is provided by small temporary rivers that flows into the fjord. The objectives of this study are to (i) assess the origin and fate of fine-grained particles (<63µm) from the piedmont glacier to the coastal zone (0-30m depth), (ii) establish the role of this coastal zone in sediment transfer and (iii) identify the impact of sea ice cover on sediment dynamics. The sampling strategy is based on characterization of sediment and SPM (grain-size, X-rays diffraction, SEM images, carbonates and organic matter contents) from the glacier to the coastal zone completed by a bottom-sediment map on the nearshore using side-scan sonar validated with Ekman binge sampling. River inputs (i.e. river plumes) to the coastal zone were punctually followed using CTD (conductivity, temperature, depth and turbidity) profiles. OBS (water level, temperature and turbidity) operating at high-frequency and during at least 1 years (including under sea ice cover) was settled at the mouth of rivers at 10m depth. In the coastal zone the fine-grained sediment deposit is limited to mud patches located at river mouths that originate the piedmont glacier. However a significant amount of sediment originates the coastal glacier located in the eastern part of the fjord via two processes: direct transfer and ice-drop. Results from turbidity measurements show that the sediment dynamics is controlled by river inputs in particular during melting period. During winter sediment resuspension can occurs directly linked to significant wind-events. When the sea ice cover is present (January to April) no sediment dynamics is observed. Sediment processes in the coastal zone of arctic fjords is significant however only a small amount of

  6. Nitrogen cycling between sediment and the shallow-water column in the transition zone of the Potomac River and Estuary. II. The role of wind-driven resuspension and adsorbed ammonium

    NASA Astrophysics Data System (ADS)

    Simon, N. S.

    1989-05-01

    During periods of sediment resuspension, desorption of ammonium from sediment solids can be the major pathway for enriching the water column with the ammonium that is produced by bacterial degradation of organic matter in the bottom material. This hyopthesis is based on a three-year study of diffusive flux in the transition zone of the Potomac River at a site 35 m from the Virginia shore where the average water-column depth is approximately 1 m over sandy sediment. A diffusion-controlled sampler was used to collect water samples at the interface between the water column and sediment and at several tens of centimeters into the sediment. Interstitial water concentration gradients showed that diffusive flux of ammonium from the sandy shallow-water sediments was approximately 1% of the diffusive flux of ammonium from the silty channel sediments in the same zone of the Potomac River. Organic nitrogen and bound or adsorbed ammonium were the predominant nitrogen forms in the sediment. Adsorbed ammonium concentrations ranged from nondetectable to 3·7 μmol g -1 of sediment. Concentrations of adsorbed ammonium per gram of sediment were one to three orders of magnitude more than interstitial water ammonium concentrations. Desorption of ammonium from sediment solids appeared to be the controlling factor in the degree of water-column ammonium enrichment. In laboratory experiments that simulated sediment resuspension, 40-80% of the adsorbed ammonium predicted to desorb did so after approximately 30 min of mixing. Based on calculations for 1 m 2 to a depth of 4 cm, one resuspenion event lasting minutes could mix more ammonium into the water column from desorption of ammonium from sediment solids than could be delivered to the water column by diffusive flux from shallow-water sediments in 10-1000 days and would be comparable to enrichment by ammonium diffusive flux for 5-50 days from channel sediments in the same river zone.

  7. Nitrogen cycling between sediment and the shallow-water column in the transition zone of the Potomac River and Estuary. II. The role of wind-driven resuspension and adsorbed ammonium

    USGS Publications Warehouse

    Simon, N.S.

    1989-01-01

    During periods of sediment resuspension, desorption of ammonium from sediment solids can be the major pathway for enriching the water column with the ammonium that is produced by bacterial degradation of organic matter in the bottom material. This hyopthesis is based on a three-year study of diffusive flux in the transition zone of the Potomac River at a site 35 m from the Virginia shore where the average water-column depth is approximately 1 m over sandy sediment. A diffusion-controlled sampler was used to collect water samples at the interface between the water column and sediment and at several tens of centimeters into the sediment. Interstitial water concentration gradients showed that diffusive flux of ammonium from the sandy shallow-water sediments was approximately 1% of the diffusive flux of ammonium from the silty channel sediments in the same zone of the Potomac River. Organic nitrogen and bound or adsorbed ammonium were the predominant nitrogen forms in the sediment. Adsorbed ammonium concentrations ranged from nondetectable to 3??7 ??mol g-1 of sediment. Concentrations of adsorbed ammonium per gram of sediment were one to three orders of magnitude more than interstitial water ammonium concentrations. Desorption of ammonium from sediment solids appeared to be the controlling factor in the degree of water-column ammonium enrichment. In laboratory experiments that simulated sediment resuspension, 40-80% of the adsorbed ammonium predicted to desorb did so after approximately 30 min of mixing. Based on calculations for 1 m2 to a depth of 4 cm, one resuspenion event lasting minutes could mix more ammonium into the water column from desorption of ammonium from sediment solids than could be delivered to the water column by diffusive flux from shallow-water sediments in 10-1000 days and would be comparable to enrichment by ammonium diffusive flux for 5-50 days from channel sediments in the same river zone. ?? 1989.

  8. Near azeotropic mixture substitute

    NASA Technical Reports Server (NTRS)

    Jones, Jack A. (Inventor)

    1996-01-01

    The present invention comprises a refrigerant mixture consisting of a first mole fraction of 1,1,1,2-tetrafluoroethane (R134a) and a second mole fraction of a component selected from the group consisting of a mixture of CHClFCF.sub.3 (R124) and CH.sub.3 CClF.sub.2 (R142b); a mixture of CHF.sub.2 CH.sub.3 (R152a) and CHClFCF.sub.3 (R124); a mixture of CHF.sub.2 CH.sub.3 (R152a) and CH.sub.3 CClF.sub.2 (R142b); and a mixture of CHClFCF.sub.3 (R124), CH.sub.3 CClF.sub.2 (R142b) and CHF.sub.2 CH.sub.3 (R152a).

  9. Devices, systems, and methods for conducting assays with improved sensitivity using sedimentation

    DOEpatents

    Schaff, Ulrich Y.; Koh, Chung-Yan; Sommer, Gregory J.

    2016-04-05

    Embodiments of the present invention are directed toward devices, systems, and method for conducting assays using sedimentation. In one example, a method includes layering a mixture on a density medium, subjecting sedimentation particles in the mixture to sedimentation forces to cause the sedimentation particles to move to a detection area through a density medium, and detecting a target analyte in a detection region of the sedimentation channel. In some examples, the sedimentation particles and labeling agent may have like charges to reduce non-specific binding of labeling agent and sedimentation particles. In some examples, the density medium is provided with a separation layer for stabilizing the assay during storage and operation. In some examples, the sedimentation channel may be provided with a generally flat sedimentation chamber for dispersing the particle pellet over a larger surface area.

  10. Devices, systems, and methods for conducting assays with improved sensitivity using sedimentation

    DOEpatents

    Schaff, Ulrich Y; Koh, Chung-Yan; Sommer, Gregory J

    2015-02-24

    Embodiments of the present invention are directed toward devices, systems, and method for conducting assays using sedimentation. In one example, a method includes layering a mixture on a density medium, subjecting sedimentation particles in the mixture to sedimentation forces to cause the sedimentation particles to move to a detection area through a density medium, and detecting a target analyte in a detection region of the sedimentation channel. In some examples, the sedimentation particles and labeling agent may have like charges to reduce non-specific binding of labeling agent and sedimentation particles. In some examples, the density medium is provided with a separation layer for stabilizing the assay during storage and operation. In some examples, the sedimentation channel may be provided with a generally flat sedimentation chamber for dispersing the particle pellet over a larger surface area.

  11. Size of Suspended Sediment over Dunes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Samples of suspended sediment were collected at four elevations simultaneously over two-dimensional mobile dunes in two mixtures of 0.5 mm sand in a laboratory flume channel. A constant sampling position relative to the dunes was maintained by adjusting the translation rate of the sampling carriage...

  12. The algal lift: Buoyancy-mediated sediment transport

    NASA Astrophysics Data System (ADS)

    Mendoza-Lera, Clara; Federlein, Laura L.; Knie, Matthias; Mutz, Michael

    2016-01-01

    The role of benthic algae as biostabilizers of sediments is well-known, however, their potential to lift and transport sediments remains unclear. Under low-flow conditions, matured algal mats may detach from the bed and may lift up sediment, thereby causing disturbance to the uppermost streambed sediment. We tested the potential of algal mats to lift sediments in 12 indoor flumes filled with sand (0.2 - 0.8 mm), gravel (2 - 8 mm) or a sand-gravel mixture (25/75% mass). After four weeks, the algal mats covered about 50% of the flumes area. Due to the accumulation of oxygen gas bubbles in the mats, that developed from high primary production at 4.5 weeks, about half of the algal mats detached from the bed carrying entangled sediments. Both the area covered by algal mats and detached area were similar among sediment types, but the amount of sediment transported tended to be higher for sand and sand-gravel mixture compared to gravel. Our results reveal that biologically mediated sediment transport mainly depends on the development of a dense filamentous algal matrix, that traps gas bubbles, increasing the mats buoyancy. This novel mechanism of sediment transport will occur in shallow ecosystems during low-flow periods, with the highest impact for sandy sediments.

  13. Geo-chemical Characteristics of the Sediments in Southwest Indian Ridge

    NASA Astrophysics Data System (ADS)

    Huang, Dasong; Zhang, Xiaoyu; Yao, Lingling; Du, Yong; Jiang, Binbin

    2015-04-01

    Major elements,trace elements and rare earth elements measurements were carried out on twenty-one sediment samples taken from the Leg II and III in Chinese reasearch cruise DY-30 which explored in Southwest Indian Ridge. The results show that all of the samples can be divided into to two groups: Si-rich group and Ca-rich group. Similar to silicates/aluminosilicates, Si-rich group sediments enrich Si(SiO2:34% to 49.6%), Mg(MgO:4.92% to 27.5%),Fe (Fe2O3:7.78% to 10.65%)and Al(Al2O3:4.87% to 12.15%) , which are very different from Ca-rich group sediments that enrich Ca(CaO:39.7%~53.9%), LOI(29.32% to 42.98%) and Sr(972ppm to 1680ppm) that are similar to biogenetic carbonate. The variation range of ∑REE of Si-rich group sediments is 12.89ppm to 44.90ppm similar to Ca-rich group sediments that is 16.82ppm to 35.11ppm, while the ratio of LREE/HREE of Si-rich group sediments(1.03 to 1.83) is much less than Ca-rich group sediments(2.39 to 5.36). The normalized REEs with North American Shale Composite(NASC) in samples show N-MORB characteristics in Si-group sediments though the ∑REE are a bit lower, and slight negative Ce anomaly in both two groups(δCe: 0.80 to 0.43) while positive Eu anomaly is relatively distinctive in Si-group sediments(δEu: 1.14 to 1.60). Contens of CaO+LOI in Ca-rich group sediments are mostly higher than 80%(even 90%) indicate biodeposition is prominent in contrast to Si-rich group sediments(CaO+LOI: 11.33% to 46.68% ) that are concerned with the mixture of basalt, ultrabasic rocks and calcareous sediments. The good correlation coefficients for major elements (SiO2,Al2O3,MgO,TiO2 and LOI) corrected by CaO(for mitigating the effects of biodeposition) in Si-rich sediments with the comparison of the ∑REE-P2O5 among the Si-rich group sediment, Ca-rich group sediments and basalt in Southwest Indian Ridge also support the basalt is the main material source of Si-rich group sediment. Both of the δCe values and the U/Th-V/(V+Ni)plot show an oxide

  14. Oxic and Anoxic Regions of Subseafloor Sediment

    NASA Astrophysics Data System (ADS)

    D'Hondt, S.; Pockalny, R. A.; Spivack, A. J.; Inagaki, F.; Murray, R. W.; Adhikari, R. R.; Gribsholt, B.; Kallmeyer, J.; McKinley, C. C.; Morono, Y.; Røy, H.; Sauvage, J.; Ziebis, W.

    2015-12-01

    Dissolved oxygen content defines two broad categories of subseafloor sediment. In areas with high rates of microbial respiration, most of the sediment column is anoxic and active anaerobic microbial communities are present for hundreds of meters or more below the seafloor. In these regions, O2 and aerobic communities penetrate only millimeters to centimeters into the sediment from the sediment-water interface. In some areas of active fluid flow through the underlying basalt, O2 may also penetrate meters upward into the sediment from the basalt. In areas with low sedimentary respiration, O2 and aerobic communities penetrate tens of meters downward from the seafloor and may persist throughout the entire sediment column. IODP Expedition 329 showed that microbial cells and aerobic respiration persist through the entire sediment sequence (to depths of at least 75 meters below seafloor) in the South Pacific Gyre. Extrapolating from these results and a global relationship of O2 penetration depth to sedimentation rate and sediment thickness, we suggest that oxygen and aerobic communities occur throughout the entire sediment sequence in 15-44% of the Pacific and 9-37% of the global seafloor. Subduction of sediment from largely anoxic regions and subduction of sediment and basalt from fully oxic regions are respectively sources of reduced and oxidized material to the mantle. The balance between oxic and anoxic regions has presumably changed considerably throughout Earth history. Regions with largely anoxic sediment and regions with fully oxic sediment present fundamentally different opportunities for understanding of (i) paleoceanographic history and (ii) the nature of microbial life under extreme energy limitations.

  15. SEPARATION OF FLUID MIXTURES

    DOEpatents

    Lipscomb, R.; Craig, A.; Labrow, S.; Dunn, J.F.

    1958-10-28

    An apparatus is presented for separating gaseous mixtures by selectively freezing a constituent of the mixture and subsequently separating the frozen gas. The gas mixture is passed through a cylinder fltted with a cooling jacket, causing one gas to freeze on the walls of the cylinder. A set of scraper blades are provided in the interior of the cyllnder, and as the blades oscillate, the frozen gas is scraped to the bottom of the cylinder. Means are provided for the frozen material to pass into a heating chamber where it is vaporized and the product gas collected.

  16. Radiotracer Imaging of Sediment Columns

    NASA Astrophysics Data System (ADS)

    Moses, W. W.; O'Neil, J. P.; Boutchko, R.; Nico, P. S.; Druhan, J. L.; Vandehey, N. T.

    2010-12-01

    Nuclear medical PET and SPECT cameras routinely image radioactivity concentration of gamma ray emitting isotopes (PET - 511 keV; SPECT - 75-300 keV). We have used nuclear medical imaging technology to study contaminant transport in sediment columns. Specifically, we use Tc-99m (T1/2 = 6 h, Eγ = 140 keV) and a SPECT camera to image the bacteria mediated reduction of pertechnetate, [Tc(VII)O4]- + Fe(II) → Tc(IV)O2 + Fe(III). A 45 mL bolus of Tc-99m (32 mCi) labeled sodium pertechnetate was infused into a column (35cm x 10cm Ø) containing uranium-contaminated subsurface sediment from the Rifle, CO site. A flow rate of 1.25 ml/min of artificial groundwater was maintained in the column. Using a GE Millennium VG camera, we imaged the column for 12 hours, acquiring 44 frames. As the microbes in the sediment were inactive, we expected most of the iron to be Fe(III). The images were consistent with this hypothesis, and the Tc-99m pertechnetate acted like a conservative tracer. Virtually no binding of the Tc-99m was observed, and while the bolus of activity propagated fairly uniformly through the column, some inhomogeneity attributed to sediment packing was observed. We expect that after augmentation by acetate, the bacteria will metabolically reduce Fe(III) to Fe(II), leading to significant Tc-99m binding. Imaging sediment columns using nuclear medicine techniques has many attractive features. Trace quantities of the radiolabeled compounds are used (micro- to nano- molar) and the half-lives of many of these tracers are short (<1 day). This allows multiple measurements to be made on the same column and thus the sediment biology to be monitored non-invasively over time (i.e. after an augmentation has been introduced) and minimizes long-lived radioactive waste. Different parameters can be measured, depending on the tracer type and delivery. A constant infusion of a conservative tracer, such as the positron emitter Br-76 (T1/2= 16.2 hr), measures the exclusion fraction (as

  17. Kinematic separation of mixtures

    SciTech Connect

    Goldshtik, M.; Husain, H.S.; Hussain, F. )

    1992-06-15

    A phenomenon of spontaneous separation of components in an initially uniform fluid mixture is found experimentally. A qualitative explanation of the effect is proposed in terms of nonparallel streamlines in the medium.

  18. Condensate Mixtures and Tunneling

    SciTech Connect

    Timmermans, E.

    1998-09-14

    The experimental study of condensate mixtures is a particularly exciting application of the recently developed atomic-trap Bose-Einstein condensate (BEC) technology: such multiple condensates represent the first laboratory systems of distinguishable boson superfluid mixtures. In addition, as the authors point out in this paper, the possibility of inter-condensate tunneling greatly enhances the richness of the condensate mixture physics. Not only does tunneling give rise to the oscillating particle currents between condensates of different chemical potentials, such as those studied extensively in the condensed matter Josephson junction experiments, it also affects the near-equilibrium dynamics and stability of the condensate mixtures. In particular, the stabilizing influence of tunneling with respect to spatial separation (phase separation) could be of considerable practical importance to the atomic trap systems. Furthermore, the creation of mixtures of atomic and molecular condensates could introduce a novel type of tunneling process, involving the conversion of a pair of atomic condensate bosons into a single molecular condensate boson. The static description of condensate mixtures with such type of pair tunneling suggests the possibility of observing dilute condensates with the liquid-like property of a self-determined density.

  19. Determining the Porosity and Saturated Hydraulic Conductivity of Binary Mixtures

    SciTech Connect

    Zhang, Z. F.; Ward, Anderson L.; Keller, Jason M.

    2011-02-14

    Gravels and coarse sands make up significant portions of some environmentally important sediments, while the hydraulic properties of the sediments are typically obtained in the laboratory using only the fine fraction (e.g., <2 mm or 4.75 mm). Researchers have found that the content of gravel has significant impacts on the hydraulic properties of the bulk soils. Laboratory experiments were conducted to measure the porosity and the saturated hydraulic conductivity of binary mixtures with different fractions of coarse and fine components. We proposed a mixing-coefficient model to estimate the porosity and a power-averaging method to determine the effective particle diameter and further to predict the saturated hydraulic conductivity of binary mixtures. The proposed methods could well estimate the porosity and saturated hydraulic conductivity of the binary mixtures for the full range of gravel contents and was successfully applied to two data sets in the literature.

  20. Determining the Porosity and Saturated Hydraulic Conductivity of Binary Mixtures

    SciTech Connect

    Zhang, Z. F.; Ward, Anderson L.; Keller, Jason M.

    2009-09-27

    Gravels and coarse sands make up significant portions of some environmentally important sediments, while the hydraulic properties of the sediments are typically obtained in the laboratory using only the fine fraction (e.g., <2 mm or 4.75 mm). Researchers have found that the content of gravel has significant impacts on the hydraulic properties of the bulk soils. Laboratory experiments were conducted to measure the porosity and the saturated hydraulic conductivity of binary mixtures with different fractions of coarse and fine components. We proposed a mixing-coefficient model to estimate the porosity and a power-averaging method to determine the effective particle diameter and further to predict the saturated hydraulic conductivity of binary mixtures. The proposed methods could well estimate the porosity and saturated hydraulic conductivity of the binary mixtures for the full range of gravel contents and was successfully applied to two data sets in the literature.

  1. Formation of siliceous sediments in brandy after diatomite filtration.

    PubMed

    Gómez, J; Gil, M L A; de la Rosa-Fox, N; Alguacil, M

    2015-03-01

    Brandy is quite a stable spirit but sometimes light sediment appears. This sediment was separated and analysed by IR and SEM-EDX. It was revealed that the sediment is composed mostly of silica and residual organic matter. Silica was present as an amorphous phase and as microparticles. In an attempt to reproduce the formation of the sediment, a diatomite extract was prepared with an ethanol/water mixture (36% vol.) and a calcined diatomite similar to that used in brandy filtration. This extract was added to unfiltered brandy in different amounts. After 1 month, the Si concentration decreased in all samples and sediments with similar compositions and features to those found in the unstable brandy appeared. The amounts of sediment obtained were directly related to the decrease in Si concentration in solution. Consequently, it can be concluded that siliceous sediment in brandy originates from Si released during diatomite filtration. PMID:25306320

  2. Flocculation settling characteristics of mud: sand mixtures

    NASA Astrophysics Data System (ADS)

    Manning, Andrew J.; Baugh, John V.; Spearman, Jeremy R.; Whitehouse, Richard J. S.

    2010-04-01

    When natural muds become mixed with sandy sediments in estuaries, it has a direct effect on the flocculation process and resultant sediment transport regime. Much research has been completed on the erosion and consolidation of mud/sand mixtures, but very little is known quantitatively about how mixed sediments interact whilst in suspension, particularly in terms of flocculation. This paper presents the settling velocity findings from a recent laboratory study which examined the flocculation dynamics for three different mud/sand mixtures at different concentrations (0.2-5 g.l-1) and turbulent shear stresses (0.06-0.9 Pa) in a mini-annular flume. The low intrusive video-based Laboratory Spectral Flocculation Characteristics instrument was used to determine floc/aggregate properties (e.g., size, settling velocity, density and mass) for each population. Settling data was assessed in terms of macrofloc (>160 μm) and microfloc (<160 μm) settling parameters: Wsmacro and Wsmicro, respectively. For pure muds, the macroflocs are regarded as the most dominant contributors to the total depositional flux. The parameterised settling data indicates that by adding more sand to a mud/sand mixture, the fall velocity of the macrofloc fraction slows and the settling velocity of microflocs quickens. Generally, a mainly sandy suspension comprising 25% mud and 75% sand (25M:75S), will produce resultant Wsmacro which are slower than Wsmicro. The quickest Wsmicro appears to consistently occur at a higher level of turbulent shear stress (τ ˜ 0.6 Pa) than both the macrofloc and microfloc fractions from suspensions of pure natural muds. Flocculation within a more cohesively dominant muddy-sand suspension (i.e., 75M:25S) produced macroflocs which fell at similar speeds (±10%) to pure mud suspensions at both low (200 mg l-1) and intermediate (1 g l-1) concentrations at all shear stress increments. Also, low sand content suspensions produced Wsmacro values that were faster than the Wsmicro

  3. Estimating suspended sediment concentrations in surface waters of the Amazon River wetlands from Landsat images

    SciTech Connect

    Mertes, L.A.K.; Smith, M.O.; Adams, J.B. )

    1993-03-01

    A method has been developed, based on spectral mixture analysis, to estimate the concentration of suspended sediment in surface waters of the Amazon River wetlands from Landsat MSS and TM images. Endmembers were derived from laboratory reflectance measurements of water-sediment mixtures with a range of sediment concentrations. Using these references spectra, the authors applied a linear mixture analysis to multispectral images after accounting for instrument and atmosphere gains and offsets. Sediment concentrations were estimated for individual pixels from the mixture analysis results based on a nonlinear calibration curve relating laboratory sediment concentrations and reflectance to endmember fractions. The uncertainty in the sediment concentrations derived from this analysis for three Amazon images is predicted to be within [plus minus] 20 mg/L, and the concentrations fall within a range of concentrations of suspended sediment that were measured at several times and places in the field over the past 15 years. The emphasis of their work is to use the patterns of sediment concentrations to compute the approximate volumes of sediment that are transferred between the main channel and floodplain of the Amazon River. However, the methodology can be applied universally if the optical properties of water and sediment at the site are known, and it is, therefore, useful for the study of suspended sediment concentrations in surface waters of wetlands elsewhere.

  4. Mixture toxicity of the antiviral drug Tamiflu((R)) (oseltamivir ethylester) and its active metabolite oseltamivir acid.

    PubMed

    Escher, Beate I; Bramaz, Nadine; Lienert, Judit; Neuwoehner, Judith; Straub, Jürg Oliver

    2010-02-18

    Tamiflu (oseltamivir ethylester) is an antiviral agent for the treatment of influenza A and B. The pro-drug Tamiflu is converted in the human body to the pharmacologically active metabolite, oseltamivir acid, with a yield of 75%. Oseltamivir acid is indirectly photodegradable and slowly biodegradable in sewage works and sediment/water systems. A previous environmental risk assessment has concluded that there is no bioaccumulation potential of either of the compounds. However, little was known about the ecotoxicity of the metabolite. Ester hydrolysis typically reduces the hydrophobicity and thus the toxicity of a compound. In this case, a zwitterionic, but overall neutral species is formed from the charged parent compound. If the speciation and predicted partitioning into biological membranes is considered, the metabolite may have a relevant contribution to the overall toxicity. These theoretical considerations triggered a study to investigate the toxicity of oseltamivir acid (OA), alone and in binary mixtures with its parent compound oseltamivir ethylester (OE). OE and OA were found to be baseline toxicants in the bioluminescence inhibition test with Vibrio fischeri. Their mixture effect lay between predictions for concentration addition and independent action for the mixture ratio excreted in urine and nine additional mixture ratios of OE and OA. In contrast, OE was an order of magnitude more toxic than OA towards algae, with a more pronounced effect when the direct inhibition of photosystem II was used as toxicity endpoint opposed to the 24h growth rate endpoint. The binary mixtures in this assay yielded experimental mixture effects that agreed with predictions for independent action. This is consistent with the finding that OE exhibits slightly enhanced toxicity, while OA acts as baseline toxicant. Therefore, with respect to mixture classification, the two compounds can be considered as acting according to different modes of toxic action, although there are

  5. Relationship of Bacterial Richness to Organic Degradation Rate and Sediment Age in Subseafloor Sediment

    PubMed Central

    Walsh, Emily A.; Kirkpatrick, John B.; Pockalny, Robert; Sauvage, Justine; Spivack, Arthur J.; Murray, Richard W.; Sogin, Mitchell L.

    2016-01-01

    ABSTRACT Subseafloor sediment hosts a large, taxonomically rich, and metabolically diverse microbial ecosystem. However, the factors that control microbial diversity in subseafloor sediment have rarely been explored. Here, we show that bacterial richness varies with organic degradation rate and sediment age. At three open-ocean sites (in the Bering Sea and equatorial Pacific) and one continental margin site (Indian Ocean), richness decreases exponentially with increasing sediment depth. The rate of decrease in richness with increasing depth varies from site to site. The vertical succession of predominant terminal electron acceptors correlates with abundance-weighted community composition but does not drive the vertical decrease in richness. Vertical patterns of richness at the open-ocean sites closely match organic degradation rates; both properties are highest near the seafloor and decline together as sediment depth increases. This relationship suggests that (i) total catabolic activity and/or electron donor diversity exerts a primary influence on bacterial richness in marine sediment and (ii) many bacterial taxa that are poorly adapted for subseafloor sedimentary conditions are degraded in the geologically young sediment, where respiration rates are high. Richness consistently takes a few hundred thousand years to decline from near-seafloor values to much lower values in deep anoxic subseafloor sediment, regardless of sedimentation rate, predominant terminal electron acceptor, or oceanographic context. IMPORTANCE Subseafloor sediment provides a wonderful opportunity to investigate the drivers of microbial diversity in communities that may have been isolated for millions of years. Our paper shows the impact of in situ conditions on bacterial community structure in subseafloor sediment. Specifically, it shows that bacterial richness in subseafloor sediment declines exponentially with sediment age, and in parallel with organic-fueled oxidation rate. This result

  6. Check dams effects on sediment transport in steep slope flume

    NASA Astrophysics Data System (ADS)

    Piton, Guillaume; Recking, Alain

    2014-05-01

    Depending on many influences (geology, relief, hydrology, land use, etc.) some mountainous watershed are prone to cause casualties and facilities damages. Large amounts of sediments episodically released by torrents are often the biggest problem in torrent related hazard mitigation. Series of transversal structures as check dams and ground sills are often used in the panel of risk mitigation technics. A large literature exits on check dams and it mainly concerns engineering design, e.g. toe scouring, stability stress diagram, changes in upper and lower reaches equilibrium slopes. Check dams in steep slope rivers constitute fixed points in the bed profile and prevent general bed incision. However their influence on sediment transport once they are filled is not yet clear. Two flume test campaigns, synthetize in Table 1, were performed to investigate this question: Table 1 : experiment plan Run (duration) Ref1 (50h)CD1a (30h)CD1b (30h)Ref2 (92h)CD2 (18h) Solid feeding discharge (g.s^-1) 44 44 44 60 60 Number of check dams none 1 3 none 2 A nearly 5-m-long, 10-cm-wide and 12%-steep flume was used. The water discharge was set to 0,55 l/s in all runs. A mixture of poorly sorted natural sediments with diameters between 0.8 and 40 mm was used. An open solid-discharge-feeding circuit kept the inlet sediment flux constant during all experiments. As both feeding rates did not present variation, changes in outlet solid discharge were assumed to be due to bed variations in the bed storage. We observed strong fluctuations of solid flux and slope in each reaches of all runs between: (i) steep aggradating armoured bed and (ii) less steep and finer bed releasing bedload sheets during erosion events and inducing bedload pulses. All experiments showed consistent results: transported volume associated with erosion event decreased with the length between two subsequent check dams. Solid transversal structures shorten the upstream erosion-propagation and avoid downstream change in the

  7. Current Methods in Sedimentation Velocity and Sedimentation Equilibrium Analytical Ultracentrifugation

    PubMed Central

    Zhao, Huaying; Brautigam, Chad A.; Ghirlando, Rodolfo; Schuck, Peter

    2013-01-01

    Significant progress in the interpretation of analytical ultracentrifugation (AUC) data in the last decade has led to profound changes in the practice of AUC, both for sedimentation velocity (SV) and sedimentation equilibrium (SE). Modern computational strategies have allowed for the direct modeling of the sedimentation process of heterogeneous mixtures, resulting in SV size-distribution analyses with significantly improved detection limits and strongly enhanced resolution. These advances have transformed the practice of SV, rendering it the primary method of choice for most existing applications of AUC, such as the study of protein self- and hetero-association, the study of membrane proteins, and applications in biotechnology. New global multi-signal modeling and mass conservation approaches in SV and SE, in conjunction with the effective-particle framework for interpreting the sedimentation boundary structure of interacting systems, as well as tools for explicit modeling of the reaction/diffusion/sedimentation equations to experimental data, have led to more robust and more powerful strategies for the study of reversible protein interactions and multi-protein complexes. Furthermore, modern mathematical modeling capabilities have allowed for a detailed description of many experimental aspects of the acquired data, thus enabling novel experimental opportunities, with important implications for both sample preparation and data acquisition. The goal of the current commentary is to supplement previous AUC protocols, Current Protocols in Protein Science 20.3 (1999) and 20.7 (2003), and 7.12 (2008), and provide an update describing the current tools for the study of soluble proteins, detergent-solubilized membrane proteins and their interactions by SV and SE. PMID:23377850

  8. Floating nematic phase in colloidal platelet-sphere mixtures.

    PubMed

    de las Heras, Daniel; Doshi, Nisha; Cosgrove, Terence; Phipps, Jonathan; Gittins, David I; van Duijneveldt, Jeroen S; Schmidt, Matthias

    2012-01-01

    The phase behaviour of colloidal dispersions is interesting for fundamental reasons and for technological applications such as photonic crystals and electronic paper. Sedimentation, which in everyday life is relevant from blood analysis to the shelf life of paint, is a means to determine phase boundaries by observing distinct layers in samples that are in sedimentation-diffusion equilibrium. However, disentangling the effects due to interparticle interactions, which generate the bulk phase diagram, from those due to gravity is a complex task. Here we show that a line in the space of chemical potentials µ(i), where i labels the species, represents a sedimented sample and that each crossing of this sedimentation path with a binodal generates an interface under gravity. Complex phase stacks can result, such as the sandwich of a floating nematic layer between top and bottom isotropic phases that we observed in a mixture of silica spheres and gibbsite platelets. PMID:23145313

  9. Manganese inhibition of microbial iron reduction in anaerobic sediments

    USGS Publications Warehouse

    Lovley, D.R.; Phillips, E.J.P.

    1988-01-01

    Potential mechanisms for the lack of Fe(II) accumulation in Mn(IV)-containing anaerobic sediments were investigated. The addition of Mn(IV) to sediments in which Fe(II) reduction was the terminal electron-accepting process removed all the pore-water Fe(II), completely inhibited net Fe(III) reduction, and stimulated Mn(IV) reduction. Results demonstrate that preferential reduction of Mn(IV) by FE(III)-reducing bacteria cannot completely explain the lack of Fe(II) accumulation in anaerobic, Mn(IV)-containing sediments, and indicate that Mn(IV) oxidation of Fe(II) is the mechanism that ultimately prevents Fe(II) accumulation. -Authors

  10. MIXTURES FEASIBILITY STUDY

    EPA Science Inventory

    A number of studies have been conducted to address questions concerning the toxicity of "real world" mixtures of DBPs. These studies, which used either concentrates of drinking water or humic acid preparations treated with various disinfectants, were largely negative and had a nu...

  11. Mineral potential for sediment-hosted copper deposits in the Islamic Republic of Mauritania (phase V, deliverable 75): Chapter K in Second projet de renforcement institutionnel du secteur minier de la République Islamique de Mauritanie (PRISM-II)

    USGS Publications Warehouse

    Taylor, Cliff D.; Giles, Stuart A.

    2015-01-01

    Although mineral occurrence data and descriptive geological information are adequate to delineate areas favorable for sediment-hosted copper deposits, this review indicates that potential for this type of deposit in Mauritania is low.

  12. Mercury Methylation Rates in Prairie Wetland Sediments

    NASA Astrophysics Data System (ADS)

    Hoggarth, C.; Hall, B.

    2011-12-01

    The majority of methylmercury (MeHg) in aquatic ecosystems is likely produced through methylation of Hg(II) by sulfate-reducing and iron-reducing bacteria. Wetland sediments may be significant sites of MeHg production, due to the combination of anoxic conditions and availability of organic matter to support microbial activity. Methylmercury produced by methylation of inorganic mercury within wetland sediments may be transferred to the water column, allowing for bioaccumulation of neurotoxic MeHg in the aquatic food web. Little information is available on sediment MeHg and total mercury concentrations, mercury methylation rates, and MeHg flux to the water column in prairie wetlands. Sediment cores from the St. Denis National Wildlife Area (SDNWA), ~40 km east of Saskatoon in central Saskatchewan, Canada, will be collected to measure sediment mercury methylation rates, total mercury, and MeHg concentrations in prairie wetland sediments. The SDNWA has been a site of prairie wetland research since 1968 and is located near the northern boundary of the Prairie Pothole Region which supports 50-80% of North American waterfowl. Sediment MeHg production will be measured in 2011 through the injection of 201Hg stable isotope to sediment cores from 12 prairie wetlands located within and nearby the SDNWA. Amended sediment cores will be incubated in situ for four hours to allow methylation of a fraction of the inorganic mercury stable isotope to Me201Hg. Analysis of the incubated sediment cores will allow for measurement of MeHg production rates, MeHg, and total mercury concentrations. Additional sediment cores will be taken to determine sediment water content, organic content, and porosity. Water samples from sediment pore water and the wetland water column will be analyzed for MeHg, total mercury, DOC, sulphate, SUVA, and water chemistry. Methylmercury flux from sediment pore water to the overlying water column will be calculated. Sediment MeHg production rates in the 12

  13. Determining Relative Contributions of Eroded Landscape Sediment and Bank Sediment to the Suspended Load of Streams and Wetlands Using 7Be and 210Pbxs

    NASA Astrophysics Data System (ADS)

    Wilson, C.; Matisoff, G.; Whiting, P.; Kuhnle, R.

    2005-12-01

    The naturally occurring radionuclides, 7Be and 210Pbxs, have been used individually as tracers of sediment particles throughout watersheds. However, use of the two radionuclides together enables eliciting information regarding the major contributors of fine sediment to the suspended load of a stream or wetland. We report on a study that uses these radionuclides to quantify the relative proportion of eroded surface soils, bank material and resuspended bed sediment in the fine suspended sediment load of the Goodwin Creek, MS, and Old Woman Creek, OH watersheds. The eroded surface soil has a unique radionuclide signature relative to the bed sediments in Old Woman Creek and the bank material along Goodwin Creek that allows for the quantification of the relative proportions of the different sediments in the sediment load. In Old Woman Creek, the different signatures are controlled by the differential decay of the two radionuclides. In Goodwin Creek, the different signatures are due to different erosion processes controlling the sediment delivery to streams, namely sheet erosion and bank collapse. The eroded surface soils will have higher activities of the 7Be and 210Pbxs than bed/bank sediments. The fine suspended sediment, which is a mixture of eroded surface soils and resuspended bed sediment or collapsed bank sediment, will have an intermediate radionuclide signature quantified in terms of the relative proportion from both sediments. A simple two-end member mixing model is used to determine the relative proportions of both sediments to the total fine sediment load.

  14. Anisotropy of bituminous mixture in the linear viscoelastic domain

    NASA Astrophysics Data System (ADS)

    Di Benedetto, Hervé; Sauzéat, Cédric; Clec'h, Pauline

    2016-08-01

    Some anisotropic properties in the linear viscoelastic domain of bituminous mixtures compacted with a French LPC wheel compactor are highlighted in this paper. Bituminous mixture is generally considered as isotropic even if the compaction process on road or in laboratory induces anisotropic properties. Tension-compression complex modulus tests have been performed on parallelepipedic specimens in two directions: (i) direction of compactor wheel movement (direction I, which is horizontal) and (ii) direction of compaction (direction II, which is vertical). These tests consist in measuring sinusoidal axial and lateral strains as well as sinusoidal axial stress, when sinusoidal axial loading is applied on the specimen. Different loading frequencies and temperatures are applied. Two complex moduli, EI ^{*} and E_{II}^{*}, and four complex Poisson's ratios, ν_{{II-I}}^{*}, ν_{{III-I}}^{*}, ν_{{I-II}}^{*} and ν_{{III-II}}^{*}, were obtained. The vertical direction appears softer than the other ones for the highest frequencies. There are very few differences between the two directions I and II for parameters concerning viscous effects (phase angles φ(EI) and φ(E_{II}), and shift factors). The four Poisson's ratios reveal anisotropic properties but rheological tensor can be considered as symmetric when considering very similar values obtained for the two measured parameters (I-II and II-I)

  15. Biogeochemical Coupling of Fe and Tc Speciation in Subsurface Sediments: Implications to Long-Term Tc Immobilization

    SciTech Connect

    Zachara, John M.; Kukkadapu, Ravi K.; Heald, Steve M.; McKinley, James P.; Dohnalkova, Alice C.; Fredrickson, James K.; Byong-Hun Jeon

    2006-04-05

    The overall project has been investigating the reactivity of pertechnetate [Tc(VII)] with Fe(II) forms in model mineral and mineral-microbe systems, and with sediments from the Oak Ridge FRC and the Hanford site. Past project results with Hanford and Oak Ridge sediments have been published in Fredrickson et al., (2004) and Kukkadapu et al., (2006). This poster summarizes a series of model system experiments that investigates whether microbes or biogenic Fe(II) were more important in the reduction of Tc(VII) in an anoxic suspension of ferrihydrite, Shewanella oneidensis MR-1, Tc(VII), and electron donor. Ferrihydrite is used to represent a bioavailable Fe(III) oxide present in small amounts in Oak Ridge and Hanford sediments. In order to address this overall goal, Tc(VII) reduction rates and redox products were studied in less complex systems where individual abiotic and biotic reactions were isolated for rigorous characterization. The specific objectives of the individual experiments in the series were as follows: (1) Identify the rates and products of the reaction of Tc(VII) with aqueous Fe(II) at circumneutral pH values (homogeneous reduction). (2) Identify the rates and products of the reaction of Tc(VII) with surface complexed Fe(II) on goethite and hematite in the circumneutral pH range (heterogeneous reduction). (3) Identify the rates and products of the reaction of Tc(VII) with MR-1 under anoxic conditions individually with hydrogen and lactate as electron donors (biologic reduction). (4) Use insights from the above experiments to determine which of the three above, potentially parallel reactions determine the final speciation of Tc in a mixture of ferrihydrite, respiring MR-1, and Tc(VII).

  16. Enhanced selective metal adsorption on optimised agroforestry waste mixtures.

    PubMed

    Rosales, Emilio; Ferreira, Laura; Sanromán, M Ángeles; Tavares, Teresa; Pazos, Marta

    2015-04-01

    The aim of this work is to ascertain the potentials of different agroforestry wastes to be used as biosorbents in the removal of a mixture of heavy metals. Fern (FE), rice husk (RI) and oak leaves (OA) presented the best removal percentages for Cu(II) and Ni(II), Mn(II) and Zn(II) and Cr(VI), respectively. The performance of a mixture of these three biosorbents was evaluated, and an improvement of 10% in the overall removal was obtained (19.25mg/g). The optimum mixture proportions were determined using simplex-centroid mixture design method (FE:OA:RI=50:13.7:36.3). The adsorption kinetics and isotherms of the optimised mixture were fit by the pseudo-first order kinetic model and Langmuir isotherm. The adsorption mechanism was studied, and the effects of the carboxylic, hydroxyl and phenolic groups on metal-biomass binding were demonstrated. Finally, the recoveries of the metals using biomass were investigated, and cationic metal recoveries of 100% were achieved when acidic solutions were used. PMID:25681794

  17. Part II: temporal and spatial distribution of multiclass pesticide residues in lake sediments of northern Greece: application of an optimized MAE-LC-MS/MS pretreatment and analytical method.

    PubMed

    Kalogridi, Eleni-Chrysoula; Christophoridis, Christophoros; Bizani, Erasmia; Drimaropoulou, Garyfallia; Fytianos, Konstantinos

    2014-06-01

    The development and application of an analytical methodology for the pretreatment and determination of 253 multiclass pesticides, in lake sediment samples, using liquid chromatography coupled with mass spectrometry (LC-MS/MS) are described in this work. Sediments of lakes Volvi, Doirani, and Kerkini, located in northern Greece, were collected in two-time periods (fall/winter 2010 and spring/summer 2011) and analyzed, applying the developed analytical methodology. Microwave-assisted extraction (MAE) was applied to extract the pesticide residues from lake sediment samples. Analytical results were stored, categorized, and visualized using geographical information systems, in order to assess and observe spatial and temporal variations of the pollution. Main pesticides that were detected included the following: amitrole, tebuconazole, phoxim, diniconazole, sethoxydim, temephos, tetrachlorvinphos, pendimethalin, boscalid, disulfoton sulfone, lenacil, propiconazole, cycloxydim, pyridaben, and terbuthylazine. Amitrole, diniconazole, and tebuconazole were found to be common in all three lakes. Lakes Kerkini and Doirani exhibited increased concentrations during the first sampling period (winter 2010) with predominant pesticide classes, triazines/triazoles and organophosphates. Pollution is mainly located near the populated villages of the lakes and the nearby cultivations. During the second sampling period, pesticide concentrations appear lower and located in sediments near the center of the lake. Lake Volvi exhibits increased pesticide concentrations during the second sampling period, temporal and spatial variations and different pesticide profile pattern. Increased pollution occurs near the center of the lake during the first sampling period, mainly comprised by triazines/triazoles and organophosphates. During the second sampling period, the majority of the sediment samples demonstrated a different pesticide profile dominated by unclassified pesticides and triazines

  18. Combustion of Gaseous Mixtures

    NASA Technical Reports Server (NTRS)

    Duchene, R

    1932-01-01

    This report not only presents matters of practical importance in the classification of engine fuels, for which other means have proved inadequate, but also makes a few suggestions. It confirms the results of Withrow and Boyd which localize the explosive wave in the last portions of the mixture burned. This being the case, it may be assumed that the greater the normal combustion, the less the energy developed in the explosive form. In order to combat the detonation, it is therefore necessary to try to render the normal combustion swift and complete, as produced in carbureted mixtures containing benzene (benzol), in which the flame propagation, beginning at the spark, yields a progressive and pronounced darkening on the photographic film.

  19. Repetitively pulsed atmospheric pressure discharge treatment of rough polymer surfaces: II. Treatment of micro-beads in He/NH3/H2O and He/O2/H2O mixtures

    NASA Astrophysics Data System (ADS)

    Bhoj, Ananth N.; Kushner, Mark J.

    2008-08-01

    Plasmas are increasingly being used to functionalize the surface of polymers having complex shapes for biomedical applications such as tissue scaffolds and drug delivering micro-beads. The functionalization often requires affixation of amine (NH2) or O-containing groups. In this paper, results are discussed from a two-dimensional computational investigation of the atmospheric pressure plasma functionalization of non-planar and porous surfaces of polypropylene with NHx and O-containing groups. For the former, the discharge is sustained in He/NH3/H2O mixtures in a dielectric barrier-corona configuration. Significant microscopic non-uniformities arise due to competing pathways for reactive gas phase radicals such as OH and NH2, and on the surface by the availability of OH to initiate amine attachment. The treatment of inside surfaces of porous polymer micro-beads placed on an electrode is particularly sensitive to view angles to the discharge and pore size, and is ultimately controlled by the relative rates of radical transport and surface reactions deep into the pores. The functionalization of micro-beads suspended in He/O2/H2O discharges is rapid with comparable treatment of the outer and interior surfaces, but varies with the location of the micro-bead in the discharge volume.

  20. Reentrant network formation in patchy colloidal mixtures under gravity

    NASA Astrophysics Data System (ADS)

    de las Heras, Daniel; Treffenstädt, Lucas L.; Schmidt, Matthias

    2016-03-01

    We study a two-dimensional binary mixture of patchy colloids in sedimentation-diffusion equilibrium using Monte Carlo simulation and Wertheim's theory. By tuning the buoyant masses of the colloids we can control the gravity-induced sequence of fluid stacks of differing density and percolation properties. We find complex stacking sequences with up to four layers and reentrant network formation, consistently in simulations and theoretically using only the bulk phase diagram as input. Our theory applies to general patchy colloidal mixtures and is relevant to understanding experiments under gravity.

  1. Hydrodynamic gas mixture separation

    SciTech Connect

    Stolyarov, A.A.

    1982-02-10

    The separation of gas mixtures is the basis of many chemical, petrochemical, and gas processes. Classical separation methods (absorption, adsorption, condensation, and freezing) require cumbersome and complex equipment. No adequate solution is provided by the cheapening and simplification of gas-processing apparatus and separation methods by hydration and diffusion. For example, an apparatus for extracting helium from natural gas by diffusion has a throughput of gas containing 0.45% helium of 117,000 m/sup 3//h and in the first stage has teflon membranes working at a pressure difference of 63.3x10/sup 5/ Pa of area 79,000 m/sup 2/, and the specific cost of the apparatus was 8500 dollars per m/sup 3//h of helium. Therefore, vigorous studies are being conducted on new ways of efficient separation of gas mixtures that are cheaper and simpler. Here we consider a novel method of physically essentially reversible separation of gas mixtures, which involves some features of single-phase supersonic flows.

  2. Sedimentation of multisized particles in concentrated suspensions

    SciTech Connect

    Selim, M.S.; Kothari, A.C.; Turian, R.M.

    1983-11-01

    A model is developed for predicting the sedimentation velocity in suspensions of multisized nonflocculating solids, in which the retarding effect of the smaller particles on the setting velocities of the larger ones is taken into account. Tests of the model, and comparisons with other models, demonstrate that it provides improved prediction of data on suspensions comprising both discrete particle size mixtures and continuous size distributions, and that it is applicable to continuous countercurrent solid-liquid operations.

  3. Stream processes with heterogeneous bed sediment

    NASA Astrophysics Data System (ADS)

    Prestegaard, Karen L.

    The AGU Erosion and Sedimentation Committee sponsored a daylong session on sediment transport in channels with mixtures of sediment sizes on December 13, 1985, at the AGU Fall Meeting in San Francisco, Calif. The morning session contained an interesting set of related theoretical and empirical research on particle motion. Ned Andrews (U.S. Geological Survey (USGS), Denver, Colo.) began the session by presenting empirical evidence for critical shear stresses required to move bed particles in simple natural channels. He presented work that he has been working on for the past several years (along with Gary Parker of St. Anthony Falls Hydraulic Laboratory, Minneapolis, Minn., and other colleagues) that suggests that coarse and fine bed particles have essentially equal mobility because of the hiding of fine particles by larger particles. Pat Wiberg and Jim Smith (both of University of Washington, Seattle) presented a theoretical analysis of the movement of different-sized particles that supported the work presented by Andrews.

  4. Lipids of aquatic sediments, recent and ancient

    NASA Technical Reports Server (NTRS)

    Eglinton, G.; Hajibrahim, S. K.; Maxwell, J. R.; Quirke, J. M. E.; Shaw, G. J.; Volkman, J. K.; Wardroper, A. M. K.

    1979-01-01

    Computerized gas chromatography-mass spectrometry (GC-MS) is now an essential tool in the analysis of the complex mixtures of lipids (geolipids) encountered in aquatic sediments, both 'recent' (less than 1 million years old) and ancient. The application of MS, and particularly GC-MS, has been instrumental in the rapid development of organic geochemistry and environmental organic chemistry in recent years. The techniques used have resulted in the identification of numerous compounds of a variety of types in sediments. Most attention has been concentrated on molecules of limited size, mainly below 500 molecular mass, and of limited functionality, for examples, hydrocarbons, fatty acids and alcohols. Examples from recent studies (at Bristol) of contemporary, 'recent' and ancient sediments are presented and discussed.

  5. IRSL from fine-grained glacifluvial sediment

    NASA Astrophysics Data System (ADS)

    Gemmell, Alastair M. D.

    1999-02-01

    Samples of suspended sediment were obtained from the Dora di Ferret, a glacifluvial stream in the Italian Alps, over a period of 24 h. IRSL analysis of the sediment indicates that the residual ( INAT) signal is almost completely zeroed within 3 km of fluvial transport during daylight hours. In contrast, samples collected at night possess environmental doses ( DE) in excess of 100 Gy, probably the luminescence signal of the parent till from which the fine-grained suspended load has been derived. Quaternary deposits of glacifluvial sediment will contain a mixture of daylight and night transported mineral grains, the resulting complex behaviour accounting for difficulties in luminescence dating such materials. Adaptations of single-aliquot protocols and single-grain protocols appear to offer the best chance of dating glacifluvial deposits accurately.

  6. EXAMINATION OF DECHLORINATION PROCESSES AND PATHWAYS IN NEW BEDFORD HARBOR SEDIMENTS

    EPA Science Inventory

    Estuarine sediments from upper New Bedford Harbor, Massachusetts, which were heavily contaminated with polychlorinated biphenyls (PCBs), showed considerable compositional alterations of PCB residues relative to mixtures of Aroclor 1242 and 1254 standards, and PCB distributions pr...

  7. Contaminated aquatic sediments: Geochemical engineering solutions

    SciTech Connect

    Forstner, U.

    1995-12-31

    Risk assessment and management of contaminated sediments requires a holistic approach, i.e., the analytical and experimental parameters should always be related to the potential remediation options for a specific sediment problem. Particular emphasis should be posed on evaluation of redox-sensitive components. Regarding the potential release of metals from sediments changing of pH conditions are of prime importance. To incorporate new experience with non-linear and time-delayed processes, special emphasis should be put on the characteristics of the mineral and organic solid matrices, e.g., to capacity controlling properties, and in particular, the buffer capacity against pH-depression. There is a long retention time for sediments in larger catchment areas. Improvement at the source may need decades to become effective in the sediments at the tower reaches and harbors close to the river mouth. Remediation techniques on contaminated sediments generally are much more limited than for most other solid waste materials, except of mine wastes. The widely diverse contamination sources in larger catchment areas usually produces a mixture of pollutants, which is more difficult to treat than an industrial waste. Only a very small percentage of dredged sediments can undergo treatment in the closer sense -- solvent extraction, bioremediation, thermal desorption, vitrification, etc. Mechanical separation of less strongly contaminated fractions, however, may be an useful step prior to storage of the residues. For most sediments from maintenance dredging, there are more arguments in favor of disposal. Final storage conditions would imply that these materials should be deposited in a favorable geochemical environment. At the actual state of knowledge, this could only mean deposition under permanent anoxic conditions. Such conditions can be made artificially or be selected from natural environments.

  8. Contaminated Sediment Core Profiling

    EPA Science Inventory

    Evaluating the environmental risk of sites containing contaminated sediments often poses major challenges due in part to the absence of detailed information available for a given location. Sediment core profiling is often utilized during preliminary environmental investigations ...

  9. Sediment Toxicity Identification Evaluation

    EPA Science Inventory

    Approach combining chemical manipulations and aquatic toxicity testing, generally with whole organisms, to systematically characterize, identify and confirm toxic substances causing toxicity in whole sediments and sediment interstitial waters. The approach is divided into thre...

  10. Prediction of bedload sediment transport for heterogeneous sediments in shape

    NASA Astrophysics Data System (ADS)

    Durafour, Marine; Jarno, Armelle; Le Bot, Sophie; Lafite, Robert; Marin, François

    2015-04-01

    Key words: Particle shape, in-situ measurements, bedload transport, heterogeneous sediments Bedload sediment transport in the coastal area is a dynamic process mainly influenced by the type of hydrodynamic forcings involved (current and/or waves), the flow properties (velocity, viscosity, depth) and sediment heterogeneity (particle size, density, shape). Although particle shape is recognized to be a significant factor in the hydrodynamic behavior of grains, this parameter is not currently implemented in bedload transport formulations: firstly because the mechanisms of initiation of motion according to particle shape are still not fully understood, and secondly due to the difficulties in defining common shape parameters. In March 2011, a large panel of in-situ instruments was deployed on two sites in the Eastern English Channel, during the sea campaign MESFLUX11. Samples of the sediment cover available for transport are collected, during a slack period, per 2cm thick strata by divers and by using a Shipeck grab. Bedload discharges along a tidal cycle are also collected with a Delft Nile Sampler (DNS; Gaweesh and Van Rijn, 1992, 1994) on both sites. The first one is characterized by a sandy bed with a low size dispersion, while the other study area implies graded sediments from fine sands to granules. A detailed analysis of the data is performed to follow the evolution of in-situ bedload fluxes on the seabed for a single current. In-situ measurements are compared to existing formulations according to a single fraction approach, using the median diameter of the mixture, and a fractionwise approach, involving a discretization of the grading curve. Results emphasize the interest to oscillate between these two methods according to the dispersion in size of the site considered. The need to apply a hiding/exposure coefficient (Egiazaroff, 1965) and a hindrance factor (Kleinhans and Van Rijn, 2002) for size heterogeneous sediments is also clearly highlighted. A really good

  11. Evaluating Whole Chemical Mixtures and Sufficient Similarity

    EPA Science Inventory

    This powerpoint presentation supports apresentation describing dose-response assessment for complex chemical mixtures including deriving reference doses for mixtures evaluating sufficient similarity among chemical mixtures.

  12. Trend analyses with river sediment rating curves

    USGS Publications Warehouse

    Warrick, Jonathan A.

    2015-01-01

    Sediment rating curves, which are fitted relationships between river discharge (Q) and suspended-sediment concentration (C), are commonly used to assess patterns and trends in river water quality. In many of these studies it is assumed that rating curves have a power-law form (i.e., C = aQb, where a and b are fitted parameters). Two fundamental questions about the utility of these techniques are assessed in this paper: (i) How well to the parameters, a and b, characterize trends in the data? (ii) Are trends in rating curves diagnostic of changes to river water or sediment discharge? As noted in previous research, the offset parameter, a, is not an independent variable for most rivers, but rather strongly dependent on b and Q. Here it is shown that a is a poor metric for trends in the vertical offset of a rating curve, and a new parameter, â, as determined by the discharge-normalized power function [C = â (Q/QGM)b], where QGM is the geometric mean of the Q values sampled, provides a better characterization of trends. However, these techniques must be applied carefully, because curvature in the relationship between log(Q) and log(C), which exists for many rivers, can produce false trends in â and b. Also, it is shown that trends in â and b are not uniquely diagnostic of river water or sediment supply conditions. For example, an increase in â can be caused by an increase in sediment supply, a decrease in water supply, or a combination of these conditions. Large changes in water and sediment supplies can occur without any change in the parameters, â and b. Thus, trend analyses using sediment rating curves must include additional assessments of the time-dependent rates and trends of river water, sediment concentrations, and sediment discharge.

  13. Identifying and Quantifying Chemical Forms of Sediment-Bound Ferrous Iron.

    NASA Astrophysics Data System (ADS)

    Kohler, M.; Kent, D. B.; Bekins, B. A.; Cozzarelli, I.; Ng, G. H. C.

    2015-12-01

    Aqueous Fe(II) produced by dissimilatory iron reduction comprises only a small fraction of total biogenic Fe(II) within an aquifer. Most biogenic Fe(II) is bound to sediments on ion exchange sites; as surface complexes and, possibly, surface precipitates; or incorporated into solid phases (e.g., siderite, magnetite). Different chemical forms of sediment-bound Fe(II) have different reactivities (e.g., with dissolved oxygen) and their formation or destruction by sorption/desorption and precipitation/dissolution is coupled to different solutes (e.g., major cations, H+, carbonate). We are quantifying chemical forms of sediment-bound Fe(II) using previously published extractions, novel extractions, and experimental studies (e.g., Fe isotopic exchange). Sediments are from Bemidji, Minnesota, where biodegradation of hydrocarbons from a burst oil pipeline has driven extensive dissimilatory Fe(III) reduction, and sites potentially impacted by unconventional oil and gas development. Generally, minimal Fe(II) was mobilized from ion exchange sites (batch desorption with MgCl2 and repeated desorption with NH4Cl). A < 2mm sediment fraction from the iron-reducing zone at Bemidji had 1.8umol/g Fe(II) as surface complexes or carbonate phases (sodium acetate at pH 5) of which ca. 13% was present as surface complexes (FerroZine extractions). Total bioavailable Fe(III) and biogenic Fe(II) (HCl extractions) was 40-50 umole/g on both background and iron-reducing zone sediments . Approximately half of the HCl-extractable Fe from Fe-reducing zone sediments was Fe(II) whereas 12 - 15% of Fe extracted from background sediments was present as Fe(II). One-third to one-half of the total biogenic Fe(II) extracted from sediments collected from a Montana prairie pothole located downgradient from a produced-water disposal pit was present as surface-complexed Fe(II).

  14. The Reductive Immobilization of Pertechnetate by Bioreduced Sediments

    NASA Astrophysics Data System (ADS)

    McKinley, J. P.; Zachara, J. M.; Heald, S. M.; Fredrickson, J. K.

    2002-12-01

    Sediments from the Hanford Site, WA, and Oak Ridge, TN, were incubated for up to 60 d with Shewanella putrifaciens, washed and pasteurized, then contacted with 20 micromolar pertechnetate. The clastic Hanford sediment was fluviolacustrine in origin, and the Oak Ridge sediment was fine weathered shale. In Hanford sediment only 1% of the total Fe (8 wt. %) was reduced after 50 d incubation; in Oak Ridge sediment 18% of the total Fe (5 wt. %) was bioreduced. 72% of the Hanford Mn (1 wt. %), and all of the Oak Ridge Mn (0.2 wt. %) were bioreduced. Mn(III/IV) oxides buffered the sediment redox potential and inhibited Tc(VII) reduction. Examination by EMP and XMP showed the absence of discrete Mn(II) solids after bioreduction. Individual microXANES analyses of Hanford sediment indicated the presence of Mn(II) and Mn(III/IV), even after Mn bioreduction reached a terminal state after 23 d. In Hanford sediment Tc(IV) was associated with Fe-Mn oxides and weathered biotites including interlaminar Fe-Mn oxides. On the biotites, Tc(IV) was concentrated at grain boundaries, where Fe and Mn were most available to microbial reduction. In Oak Ridge sediment, Tc(IV) was associated with one of two morphotypes of weathered shale.

  15. Heavy metals retention capacity of a non-conventional sorbent developed from a mixture of industrial and agricultural wastes.

    PubMed

    Agouborde, Lina; Navia, Rodrigo

    2009-08-15

    Zinc and copper removal from aqueous solutions using brine sediments (industrial residue), sawdust (agricultural residue) and the mixture of both materials has been researched through batch and column tests. Brine sediments were found to be mainly constituted by halite and calcite, while its main cations exchangeable were sodium, calcium, magnesium and potassium. In sawdust the main exchangeable cations detected were calcium, magnesium, sodium and potassium. FT-IR spectra of sawdust and brine sediment-sawdust mixture showed that brine sediments produced important changes in carboxylic, alcoholic and phenolic groups present in the sawdust. The maximum zinc adsorption capacity was found to be 4.85, 2.58 and 5.59 mg/g using an adsorbent/solution ratio of 1/40, for brine sediments, sawdust and the mixture, respectively. For copper, the maximum adsorption capacity was found to be 4.69, 2.31 and 4.33 mg/g, using adsorbent/solution ratios of 1/40, for brine sediments, sawdust and the mixture, respectively. Maximum copper adsorption capacity of the mixture, on the contrary to zinc adsorption, was lightly inferior to maximum adsorption capacity obtained in brine sediments. Adsorption isotherms data adjusted better to the Langmuir model. Additionally, columns reached the saturation point at 690 min for zinc and 360 min for copper. The main mechanism involved in the removal of both metals may be the ionic exchange between sodium and calcium ions present in brine sediments and H(+) present in functional groups of sawdust. The use of brine sediments, sawdust and their mixture, presents an interesting option both, for wastewater decontamination (as a possible non-conventional sorbent for the removal of heavy metals) and as a waste recycling option. PMID:19188023

  16. Toxicological evaluation of chemical mixtures.

    PubMed

    Feron, V J; Groten, J P

    2002-06-01

    This paper addresses major developments in the safety evaluation of chemical mixtures during the past 15 years, reviews today's state of the art of mixture toxicology, and discusses challenges ahead. Well-thought-out tailor-made mechanistic and empirical designs for studying the toxicity of mixtures have gradually substituted trial-and-error approaches, improving the insight into the testability of joint action and interaction of constituents of mixtures. The acquired knowledge has successfully been used to evaluate the safety of combined exposures and complex mixtures such as, for example, the atmosphere at hazardous waste sites, drinking water disinfection by-products, natural flavouring complexes, and the combined intake of food additives. To consolidate the scientific foundation of mixture toxicology, studies are in progress to revisit the biological concepts and mathematics underlying formulas for low-dose extrapolation and risk assessment of chemical mixtures. Conspicuous developments include the production of new computer programs applicable to mixture research (CombiTool, BioMol, Reaction Network Modelling), the application of functional genomics and proteomics to mixture studies, the use of nano-optochemical sensors for in vivo imaging of physiological processes in cells, and the application of optical sensor micro- and nano-arrays for complex sample analysis. Clearly, the input of theoretical biologists, biomathematicians and bioengineers in mixture toxicology is essential for the development of this challenging branch of toxicology into a scientific subdiscipline of full value. PMID:11983277

  17. Toxicological approaches to complex mixtures.

    PubMed Central

    Mauderly, J L

    1993-01-01

    This paper reviews the role of toxicological studies in understanding the health effects of environmental exposures to mixtures. The approach taken is to review mixtures that have received the greatest emphasis from toxicology; major mixtures research programs; the toxicologist's view of mixtures and approaches to their study; and the complementary roles of toxicological, clinical, and epidemiological studies. Studies of tobacco smoke, engine exhaust, combustion products, and air pollutants comprise most of the past research on mixtures. Because of their great experimental control over subjects, exposures, and endpoints, toxicologists tend to consider a wider range of toxic interactions among mixture components and sequential exposures than is practical for human studies. The three fundamental experimental approaches used by toxicologists are integrative (studying the mixture as a whole), dissective (dissecting a mixture to determine causative constituents), and synthetic (studying interactions between agents in simple combinations). Toxicology provides information on potential hazards, mechanisms by which mixture constituents interact to cause effects, and exposure dose-effect relationships; but extrapolation from laboratory data to quantitative human health risks is problematic. Toxicological, clinical, and epidemiological approaches are complementary but are seldom coordinated. Fostering synergistic interactions among the disciplines in studying the risks from mixtures could be advantageous. PMID:7515806

  18. Intact polar and core glycerol dibiphytanyl glycerol tetraether lipids in the Arabian Sea oxygen minimum zone. Part II: Selective preservation and degradation in sediments and consequences for the TEX86

    NASA Astrophysics Data System (ADS)

    Lengger, Sabine K.; Hopmans, Ellen C.; Reichart, Gert-Jan; Nierop, Klaas G. J.; Sinninghe Damsté, Jaap S.; Schouten, Stefan

    2012-12-01

    The TEX86 is a proxy based on a ratio of pelagic archaeal glycerol dibiphytanyl glycerol tetraether lipids (GDGTs), and used for estimating past sea water temperatures. Concerns exist that in situ production of GDGTs lipids by sedimentary Archaea may affect its validity. In this study, we investigated the influence of benthic GDGT production on the TEX86 by analyzing the concentrations and distributions of GDGTs present as intact polar lipids (IPLs) and as core lipids (CLs) in three sediment cores deposited under contrasting redox conditions across a depth range from 900 to 3000 m below sea level in and below the Arabian Sea oxygen minimum zone (OMZ). Direct analysis of IPLs with crenarchaeol as CL via HPLC/ESI-MS2 revealed that surface sediments in the OMZ were relatively depleted in the phospholipid hexose, phosphohexose (HPH)-crenarchaeol compared to suspended particulate matter from the water column, suggesting preferential and rapid degradation of this IPL. In sediment cores recovered from deeper, more oxic environments, concentrations of HPH-crenarchaeol peaked at the surface, probably due to in situ production by ammonia-oxidizing Archaea, followed by a rapid decrease with increasing depth. No surface maximum was observed in the sediment core from within the OMZ. In contrast, the glycolipids, monohexose-crenarchaeol and dihexose-crenarchaeol, did not change in concentration with depth in the sediment, indicating that they were relatively well preserved and likely mostly derived from fossil pelagic GDGTs. These results suggest that phospholipids are more sensitive to degradation, while glycolipids might be preserved over longer time scales, in line with previous incubation and modeling studies. Furthermore, in situ produced IPL-GDGTs did not accumulate as IPLs, and did not influence the CL-TEX86. This suggests that in-situ produced GDGT lipids were more susceptible to degradation than fossil CL and IPL and did not accumulate as CL. In agreement, no

  19. Stabilizer for fuel mixtures

    SciTech Connect

    Abe, M.; Moriyama, N.; Yamamura, M.

    1981-02-24

    A stabilizer for fuel mixtures of finely divided coal and fuel oil is composed of an active ingredient, a non-ionic surface active agent consisting of a block copolymer represented by the following general formula (I): R/sub 1/O-(C/sub 2/H/sup 4/O)l-(C/sub 3/H/sup 6/O)m-(C/sub 2/H/sup 4/O)n-R/sub 2/ (I) wherein r/sub 1/ and r/sub 2/ stand for a hydrogen atom or an alklyl group having 1 to 6 carbon atoms, the mole number (L+n) of added ethylene oxide is in the range of from 30 to 300, the mole number (M) of added propylene oxide is in the range of from 15 to 80, and the content of ethylene oxide in the whole molecule is 40 to 85% by weight.

  20. Equilibrium passive sampling as a tool to study polycyclic aromatic hydrocarbons in Baltic Sea sediment pore-water systems.

    PubMed

    Lang, Susann-Cathrin; Hursthouse, Andrew; Mayer, Philipp; Kötke, Danjiela; Hand, Ines; Schulz-Bull, Detlef; Witt, Gesine

    2015-12-15

    Solid Phase Microextraction (SPME) was applied to provide the first large scale dataset of freely dissolved concentrations for 9 polycyclic aromatic hydrocarbons (PAHs) in Baltic Sea sediment cores. Polydimethylsiloxane (PDMS) coated glass fibers were used for ex-situ equilibrium sampling followed by automated thermal desorption and GC-MS analysis. From the PAH concentrations in the fiber coating we examined (i) spatially resolved freely dissolved PAH concentrations (Cfree); (ii) baseline toxicity potential on the basis of chemical activities (a); (iii) site specific mixture compositions; (iv) diffusion gradients at the sediment water interface and within the sediment cores and (v) site specific distribution ratios. Contamination levels were low in the northern Baltic Sea, moderate to elevated in the Baltic Proper and highest in the Gulf of Finland. Chemical activities were well below levels expected to cause narcosis to benthos organisms. The SPME method is a very sensitive tool that opens new possibilities for studying the PAHs at trace levels in marine environments. PMID:26593280

  1. Alternative method to trace sediment sources in a subtropical rural catchment of southern Brazil by using near-infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Tiecher, Tales; Caner, Laurent; Gomes Minella, Jean Paolo; Henrique Ciotti, Lucas; Antônio Bender, Marcos; dos Santos Rheinheimer, Danilo

    2014-05-01

    Conventional fingerprinting methods based on geochemical composition still require a time-consuming and critical preliminary sample preparation. Thus, fingerprinting characteristics that can be measured in a rapid and cheap way requiring a minimal sample preparation, such as spectroscopy methods, should be used. The present study aimed to evaluate the sediment sources contribution in a rural catchment by using conventional method based on geochemical composition and on an alternative method based on near-infrared spectroscopy. This study was carried out in a rural catchment with an area of 1,19 km2 located in southern Brazil. The sediment sources evaluated were crop fields (n=20), unpaved roads (n=10) and stream channels (n=10). Thirty suspended sediment samples were collected from eight significant storm runoff events between 2009 and 2011. Sources and sediment samples were dried at 50oC and sieved at 63 µm. The total concentration of Ag, As, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, K, La, Li, Mg, Mn, Mo, Na, Ni, P, Pb, Sb, Se, Sr, Ti, Tl, V and Zn were estimated by ICP-OES after microwave assisted digestion with concentrated HNO3 and HCl. Total organic carbon (TOC) was estimated by wet oxidation with K2Cr2O7 and H2SO4. The near-infrared spectra scan range was 4000 to 10000 cm-1 at a resolution of 2 cm-1, with 100 co added scans per spectrum. The steps used in the conventional method were: i) tracer selection based on Kruskal-Wallis test, ii) selection of the best set of tracers using discriminant analyses and finally iii) the use of a mixed linear model to calculate the sediment sources contribution. The steps used in the alternative method were i) principal component analyses to reduce the number of variables, ii) discriminant analyses to determine the tracer potential of the near-infrared spectroscopy, and finally iii) the use of past least square based on 48 mixtures of the sediment sources in various weight proportions to calculate the sediment sources

  2. Clinical studies of a vegetarian food diet mixture.

    PubMed

    Carter, J P; Bonney, G; Molnar, I G; Garces, N; Lulseged, S; Habte, D; Ryan, J; Allen, D

    1989-05-01

    A vegetarian food mixture when incorporated into a commercially prepared diet can be used as a supplement or in a vegetarian protein-sparing modified fast. A modification of this diet was given to protein-energy deficient malnourished children in Ethiopia, and it reversed their biochemical defects. The soluble or gel-forming fiber in the mixture also gives the product a favorable glycemic index and reduces glycemic excursion as well as fasting blood glucose and insulin levels. This accounts for the improvements seen in glucose tolerance in type II diabetic patients. These results, however, were preceded by a study of the effects of the mixture in improving glucose tolerance in diabetic rats. A clinical study among New Orleans police officers also suggests that this mixture helps people, without much self-motivation, to lose weight. PMID:2746679

  3. Clinical studies of a vegetarian food diet mixture.

    PubMed Central

    Carter, J. P.; Bonney, G.; Molnar, I. G.; Garces, N.; Lulseged, S.; Habte, D.; Ryan, J.; Allen, D.

    1989-01-01

    A vegetarian food mixture when incorporated into a commercially prepared diet can be used as a supplement or in a vegetarian protein-sparing modified fast. A modification of this diet was given to protein-energy deficient malnourished children in Ethiopia, and it reversed their biochemical defects. The soluble or gel-forming fiber in the mixture also gives the product a favorable glycemic index and reduces glycemic excursion as well as fasting blood glucose and insulin levels. This accounts for the improvements seen in glucose tolerance in type II diabetic patients. These results, however, were preceded by a study of the effects of the mixture in improving glucose tolerance in diabetic rats. A clinical study among New Orleans police officers also suggests that this mixture helps people, without much self-motivation, to lose weight. PMID:2746679

  4. Interactions Between Microbial Iron Reduction and Metal Geochemistry: Effect of Redox Cycling on Transition Metal Speciation in Iron Bearing Sediments

    SciTech Connect

    D. Craig Cooper; Flynn W. Picardal; Aaron J. Coby

    2006-02-01

    Microbial iron reduction is an important biogeochemical process that can affect metal geochemistry in sediments through direct and indirect mechanisms. With respect to Fe(III) (hydr)oxides bearing sorbed divalent metals, recent reports have indicated that (1) microbial reduction of goethite/ferrihydrite mixtures preferentially removes ferrihydrite, (2) this process can incorporate previously sorbed Zn(II) into an authigenic crystalline phase that is insoluble in 0.5 M HCl, (3) this new phase is probably goethite, and (4) the presence of nonreducible minerals can inhibit this transformation. This study demonstrates that a range of sorbed transition metals can be selectively sequestered into a 0.5 M HCl insoluble phase and that the process can be stimulated through sequential steps of microbial iron reduction and air oxidation. Microbial reduction experiments with divalent Cd, Co, Mn, Ni, Pb, and Zn indicate that all metals save Mn experienced some sequestration, with the degree of metal incorporation into the 0.5 M HCl insoluble phase correlating positively with crystalline ionic radius at coordination number = 6. Redox cycling experiments with Zn adsorbed to synthetic goethite/ferrihydrite or iron-bearing natural sediments indicate that redox cycling from iron reducing to iron oxidizing conditions sequesters more Zn within authigenic minerals than microbial iron reduction alone. In addition, the process is more effective in goethite/ferrihydrite mixtures than in iron-bearing natural sediments. Microbial reduction alone resulted in a ~3× increase in 0.5 M HCl insoluble Zn and increased aqueous Zn (Zn-aq) in goethite/ferrihydrite, but did not significantly affect Zn speciation in natural sediments. Redox cycling enhanced the Zn sequestration by ~12% in both goethite/ferrihydrite and natural sediments and reduced Zn-aq to levels equal to the uninoculated control in goethite/ferrihydrite and less than the uninoculated control in natural sediments. These data suggest

  5. Bitumen II from the Paleoproterozoic Here’s Your Chance Pb/Zn/Ag deposit: Implications for the analysis of depositional environment and thermal maturity of hydrothermally-altered sediments

    NASA Astrophysics Data System (ADS)

    Holman, Alex I.; Grice, Kliti; Jaraula, Caroline M. B.; Schimmelmann, Arndt

    2014-08-01

    The formation of sedimentary exhalative (SEDEX) Pb/Zn deposits is linked to ocean euxinia, but recent evidence suggests that ferruginous conditions may have dominated the deep ocean during the Middle Proterozoic, a maximum period for SEDEX distribution. Biomarkers of sulfate-reducing and sulfide-oxidising bacteria are valuable indicators of euxinic conditions in such settings. Organic matter (OM) from SEDEX deposits is often affected by alteration and/or migration, but OM entrapped within the kerogen/mineral matrix (Bitumen II) may be less affected than the freely-extractable OM (Bitumen I). We analysed Bitumen II from the Paleoproterozoic Here’s Your Chance (HYC) Pb/Zn/Ag deposit to find evidence of euxinic conditions in the depositional environment. n-Alkane distributions in Bitumen II are markedly distinct from previously-reported Bitumen I. Bitumen II contains long-chain n-alkanes (up to C36 or C38) and a strong even-over-odd distribution in a number of samples, which are 4‰ to 7‰ depleted in 13C compared to n-alkanes in Bitumen I and verified as indigenous by comparison with δ13C of isolated kerogen. These features are interpreted as evidence of sulfate-reducing and sulfide-oxidising bacteria, confirming that HYC was deposited under euxinic conditions. Bitumen II has the potential to reveal information from OM that is degraded and/or overprinted in Bitumen I. Commonly-used methylphenanthrene maturity ratios give conflicting information as to the relative maturity of Bitumens I and II. Bitumen I contains a far higher proportion of methylated phenanthrenes than Bitumen II. As Bitumen II is sequestered within the kerogen/mineral matrix it may have restricted access to the ‘methyl pool’ of organic compounds that can donate methyl groups to aromatic hydrocarbons. Parameters that include both phenanthrene and methylphenanthrenes do not appear suitable to compare the maturity of Bitumens I and II; hence there is no clear evidence that Bitumen II is of

  6. Paonia Reservoir Sediment Management

    NASA Astrophysics Data System (ADS)

    Kimbrel, S.; Collins, K.; Williams, C.

    2014-12-01

    Paonia Dam and Reservoir are located on Muddy Creek, a tributary of the North Fork Gunnison River in western Colorado. Since dam closure in 1962, the 2002 survey estimates an annual sedimentation rate of 153,000 m3/y, resulting in a 25% loss of total reservoir capacity. Long before sediment levels completely fill the reservoir, the outlet works have recently plugged with sediment and debris, adversely impacting operations, and emphasizing the urgency of formulating an effective sediment management plan. Starting in 2010-2011, operations were changed to lower the reservoir and flush sediment through the outlet works in early spring before filling the pool for irrigation. Even though the flushing strategy through the long, narrow reservoir (~5 km long and 0.3 km wide) has prevented outlet works plugging, a long term plan is needed to manage inflowing and deposited sediment more efficiently. Reclamation's Sedimentation and River Hydraulics Group is leading an effort to study the past and current sediment issues at Paonia Dam and Reservoir, evaluate feasible sediment management alternatives, and formulate a plan for future operations and monitoring. The study is building on previously collected data and the existing knowledge base to develop a comprehensive, sustainable sediment management plan. The study is being executed in three phases: Phase 1 consisted of an initial site visit to map and sample existing reservoir bottom sediments, a preliminary site evaluation upstream and downstream of the dam, and establishment of time-lapse photo sites and taking initial ground-based photos. Phase 2 includes a bathymetric survey of entire reservoir and 11 km of the river downstream of the dam, continuous suspended sediment monitoring upstream and downstream of the reservoir, and collection of additional core samples of reservoir bottom sediments. Phase 3 involves the evaluation of current and past operations and sediment management practices, evaluate feasible sediment

  7. Bioaccumulation kinetics of polybrominated diphenyl ethers from estuarine sediments to the marine polychaete, Nereis virens.

    PubMed

    Klosterhaus, Susan L; Dreis, Erin; Baker, Joel E

    2011-05-01

    Polybrominated diphenyl ethers (PBDEs) are flame-retardant chemicals that have become ubiquitous environmental contaminants. Polybrominated diphenyl ether no-uptake rates from estuarine or marine sediments to deposit-feeding organisms have not yet been reported. In the present study, the marine polychaete worm Nereis virens was exposed to field-contaminated and spiked sediments containing the penta- and deca-BDE commercial mixtures in a 28-d experiment to characterize the relative bioavailability of PBDE congeners from estuarine sediments. A time series sampling regimen was conducted to estimate uptake rate constants. In both field-collected and laboratory-spiked sediment exposures, worms selectively accumulated congeners in the penta-BDE mixture over BDE 209 and other components of the deca-BDE mixture, supporting the prevalence of these congeners in higher trophic level species. Brominated diphenyl ether 209 was not bioavailable to N. virens from field sediment and was only minimally detected in worms exposed to spiked sediments in which bioavailability was maximized. Chemical hydrophobicity was not a good predictor of bioavailability for congeners in the penta-BDE mixture. Direct comparison of bioavailability from the spiked and field sediments for the predominant congeners in the penta-BDE mixture was confounded by the considerable difference in exposure concentration between treatments. Biota-sediment accumulation factors (BSAFs) for N. virens after 28 d of exposure to the field sediment were lower than the BSAFs for Nereis succinea collected from the field site, indicating that 28-d bioaccumulation tests using N. virens may underestimate the in situ concentration of PBDEs in deposit-feeding species. The bioavailability of PBDEs to N. virens indicates that these chemicals can be remobilized from estuarine sediments and transferred to aquatic food webs. PMID:21337608

  8. SORPTION OF NONIONIC SURFACTANT OLIGOMERS TO SEDIMENT AND PCE DNAPL: EFFECTS ON PCE DISTRIBUTION BETWEEN WATER AND SEDIMENT. (R826650)

    EPA Science Inventory

    Introduction of surfactant mixtures to the subsurface for the purpose of
    surfactant-enhanced aquifer remediation requires consideration of the effects of
    surfactant sorption to sediment and nonaqueous phase liquids. These effects
    include alteration of the solubiliz...

  9. Continuous automated sensing of streamflow density as a surrogate for suspended-sediment concentration sampling

    USGS Publications Warehouse

    Larsen, Matthew C.; Figueroa Alamo, Carlos; Gray, John R.; Fletcher, William

    2001-01-01

    A newly refined technique for continuously and automatically sensing the density of a water-sediment mixture is being tested at a U.S. Geological Survey streamflow-gaging station in Puerto Rico. Originally developed to measure crude oil density, the double bubbler instrument measures fluid density by means of pressure transducers at two elevations in a vertical water column. By subtracting the density of water from the value measured for the density of the water-sediment mixture, the concentration of suspended sediment can be estimated. Preliminary tests of the double bubbler instrument show promise but are not yet conclusive.

  10. Flocculation and settling characteristics of mixed sediment suspensions

    NASA Astrophysics Data System (ADS)

    Samsami, Farzin; Cuthbertson, Alan J. S.

    2014-05-01

    Estuaries and nearshore coastal areas are amongst the most productive, dynamic and complex ecosystems in the world. Many of these estuaries and sheltered inshore waters (e.g. tidal inlets and embayments) have bed sediments consisting of mixtures of cohesive mud and non-cohesive sands. Whilst extensive studies have been conducted on transport processes associated with sand- or mud-only sediments, there remains limited knowledge on the physical behavior (e.g. flocculation and settling) of sand-mud mixtures. Because of important differences in cohesive and non-cohesive sediment behavior, it is essential to investigate the small-scale processes associated with mixed sediments, which typically occur under strongly time-dependent flow conditions and concentration gradients generated by tidal cycles and/or unsteady wave fields. The aim of this study is thus to quantify the fundamental dynamic processes for cohesive and non-cohesive sediment mixtures over a wide range of steady and unsteady (cyclic) turbulent flow conditions. The experimental studies are performed in a 2.1 m long by 0.25 m diameter settling column installation in the School of the Built and Environment at Heriot-Watt University, UK. Controlled and repeatable hydrodynamic forcing conditions (i.e. zero-mean shear turbulence) can be generated in the column through the oscillation of a fixed, regular array of grids. Within the experimental runs, pure kaolin clay and superfine, well-sorted silica sand are used to represent the cohesive and non-cohesive sediment fractions, respectively. Results are presented herein from a series of parametric experimental runs investigating temporal variations in the flocculation and settling characteristics for both purely cohesive sediment suspensions (i.e. kaolin clay) and cohesive and non-cohesive sediment mixtures (i.e. kaolin clay-sand). These results include physical descriptions of mixed sediment flocculation under steady and unsteady (cyclic) grid-generated turbulence